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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
×
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
×
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
×
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
×
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
×
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Suggested Citation:"Final Report." National Academies of Sciences, Engineering, and Medicine. 2004. Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide. Washington, DC: The National Academies Press. doi: 10.17226/13766.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

FINAL REPORT

5CHAPTER 1 INTRODUCTION AND RESEARCH APPROACH Zinc and aluminum have been used as steel coatings since the early 1900s, with early application of thermally sprayed metal coatings (TSMCs) to bridge structures in the 1930s (1). TSMCs have been used widely in the European bridge indus- try, in the U.S. Navy, and on offshore oil exploration drill plat- forms for quite some time. TSMCs of zinc, aluminum, and their alloys can offer substantial advantages when compared with other coatings typically used to protect steel pilings. Organic coatings can fail prematurely as a result of corrosion progression from coating defects. Transportation, handling, installation, or simple long-term material deterioration may cause these defects. TSMCs offer advantages in generally higher mechanical damage resistance, low self-corrosion rates, and the ability to provide steel corrosion control via cathodic protection at coatings defects. The objective of this research was to develop a guide for highway agency personnel on the selection and use of TSMCs for highway pilings that would be suitable as an AASHTO reference. The Thermally Sprayed Metal Coating Guide, containing all of the information gath- ered from the literature, industry research, and laboratory test- ing, is the primary product of this research. The extensive body of information on TSMCs, including existing guides, was researched so as not to repeat basic research and development work or conflict with industry standards where those standards are applicable. Applicable portions of existing materials were used in the preparation of the Thermally Sprayed Metal Coating Guide. This study also sought to resolve any issues that were unclear concerning the use of TSMCs on steel pilings. ISSUES OF CONCERN Alloy Selection There are several TSMC alloys available. Most commonly used metals for the protection of steel are anodic to steel. This eliminates the need for a completely pinhole-free barrier because the TSMC provides sacrificial protection to the steel substrate (2). Zinc, aluminum, and alloys of the two metals are thus favored for the protection of steel. Ideally, the alloy should have a very low self-corrosion rate and be an efficient and effective sacrificial anode. Aluminum TSMCs have been found to protect steel well under seawater immersion condi- tions (3). The excellent barrier properties and low rate of self- corrosion for the aluminum coating make it attractive for sea- water exposure. Because TSMCs are porous, sealers are often specified to reduce the porosity and improve the service life of the coating. Common sealers include epoxies and vinyl coatings. Because of the advances in coating technology, part of this study was to investigate other sealer materials. Quality Assurance Requirements TSMC materials are sensitive to surface preparation and application conditions (4). Most specifications require sur- face preparation and application conditions that meet the Society for Protective Coatings Surface Preparation Specifi- cation 5 (SSPC-SP-5), “White Metal Blast Cleaning,” for application of a TSMC (5). This can be difficult to achieve in all conditions, especially if field coating is being considered rather than shop coating. Other parameters, such as abrasive type for surface preparation, required profile range, and accep- tance environmental conditions, can affect porosity, adhesion, and corrosion performance of the coating. Damage Tolerance of the Coating A key aspect of the coatings is their resistance to damage in transportation, handling, and installation. Regardless of whether shop or field coatings are used, there is a tendency for there to be impact and flexure damage to the coatings. The performance of the alternative alloys and application conditions must be qualified in these regards. RESEARCH PLAN The research plan consisted of eight tasks, briefly described below. Task 1—Collect and Review Domestic and Foreign Literature and Information The review of existing literature and other information included the following:

• Existing specifications and guides on coatings for steel pilings and for metallizing in general, • Published research studies of metallized coating perfor- mance in immersion environments, • Interviews with suppliers of metallizing materials and application equipment and review of their literature, • A visit by researchers to a coating fabrication shop where steel piles were being coated, • Laboratory studies to perform certain basic testing on TSMC, and • Interviews with coating applicators. Task 2—Evaluate and Summarize the Literature This consisted of the evaluation of information gathered in Task 1 to determine the completeness and relevance of exist- ing information. From this evaluation, a detailed work plan was developed that would provide the information necessary for the guide to TSMCs. Task 3—Develop a Detailed Experimental Work Plan The purpose of Task 3 was to develop an experimental work plan built around key issues related to TSMC perfor- mance. It was anticipated that the work plan would consist of laboratory tests designed to provide information to supple- ment the literature in the areas of surface preparation, seal- ers, and application parameters. Task 4—Interim Report The interim report presented the results of Tasks 1 through 3. As a result of the interim report, the panel determined that an expanded literature search was needed. The panel directed that a draft guide to TSMCs be prepared incorporating all of 6 the information available to date and delineating areas requir- ing further research. They also asked that a second interim report be prepared. Task 5—Work Plan Execution The work plan execution consisted of conducting laboratory tests to provide additional information about the effectiveness of sealers, different sealer materials, surface preparation mate- rials, and the application variables on performance. The tests consisted of both standard laboratory tests and seawater expo- sure tests. Researchers also intended to perform field inspec- tions of several TSMC structures, including some existing structures operated by the U.S. Army Corps of Engineers. The inability to access these structures without extensive dewa- tering procedures prevented this from occurring. Task 6—Final Guide to TSMCs This task consisted of preparing the final guide on the basis of the combined results of the literature search and laboratory tests. Task 7—Long-Term Validation Plan The objective of this task was to develop a long-term implementation plan for the use of TSMCs for pilings. The plan was to have the guide to TSMCs accepted as an AASHTO guide by demonstrating the usefulness and appli- cability of the guide and TSMCs to state DOT officials. Task 8—Final Report This report contains a discussion of all of the work described in Tasks 1 through 7.

7CHAPTER 2 FINDINGS COLLECT AND REVIEW DOMESTIC AND FOREIGN LITERATURE Literature Review A comprehensive information search was conducted to obtain and review information relevant to the design, speci- fication, and installation of coated steel pilings. Literature was obtained by using available government, university, and industry databases. The search included the following: • The Transportation Information Research Service (TRIS), • The National Technical Information Systems Database, • AASHTO Listings of Research in Progress, • The Current Technologies Index, • Engineered Materials Abstracts, • Federal Research in Progress, • International Conference Papers Abstracts, • The Federal Highway Administration, • The U.S. Army Corps of Engineers, • The Soil Conservation Service, • State DOTs, • The National Institute for Standards and Technology, • The American Society for Testing and Materials, • The National Association of Corrosion Engineers (NACE) International, • The Society for Protective Coatings (SSPC), • The American Welding Society (AWS), • The Materials Information Society (ASM), and • The Thermal Spray Society. This literature included performance data in technical papers and reports and specifications for the application of TSMCs. This literature was sorted, and the most relevant reports were reviewed. Of primary interest were data related to the per- formance of TSMCs in natural waters, application factors affecting the life of TSMCs, and appropriate quality assur- ance tests. Literature of significant value was abstracted and is included in the report appendixes. Although the literature identified several available thermal spray systems, the ones used most frequently were wire-arc spray and wire-flame spray. Also, these two systems are often the most practical application methods for TSMC on pilings. However, wire-arc spray techniques generally allow for hot- ter particles, faster output, and superior adhesion than do flame spray techniques (2, 6–12). Various thermal spray coating materials are available for use over steel. Table 1 lists and categorizes some of the mate- rials commonly used for metallizing, as well as typical wire gauges that are available. Zinc, aluminum, and their alloys are commonly used as TSMCs on steel in water immersion. The sacrificial corrosion protection that they offer, in combination with their relatively low corrosion rates, make them suitable for such harsh environments (2, 7, 9, 11, 13–19). Thus, zinc, aluminum, and an alloy of the two metals (8515 weight per- cent [wt%] zinc/aluminum) were selected for testing under this program. Table 2 lists some of the properties of these three TSMCs commonly used on steel in water immersion. Thermally sprayed zinc and aluminum coatings are com- monly used without sealers in mild environments. However, TSMCs inherently contain porosity that has a major effect on corrosion performance. When exposed to harsh environments, such as marine atmospheres and/or freshwater or saltwater immersion, the application of a sealer on top of the thermally sprayed coating is generally recommended (2, 7, 20–23). The purpose of the sealer is to mitigate corrosion caused by the penetration of moisture and corrosive ions through pores. Sealers are often used to enhance the appearance of the coated structure as well as to extend the life of the thermal spray coat- ing. Previous studies have involved dozens of different seal- ers, and the studies generally agree that an important property of the sealer is to adequately fill the pores in the thermally sprayed coating (2, 8, 9, 14, 16, 22, 24). Some of the more common sealers tested include vinyls, silicones, epoxies, ure- thanes, phenolic resins (may react with zinc [24]), and alu- minum pigmented silicone (for high temperature) (7, 8, 20). Previous studies have indicated that corrosion rates of steel in marine environments are lower in the immersed and inter- tidal zones than in the splash zone (25). The lower corrosion rates in the immersed and intertidal zones are believed to be, in part, the result of the attachments of various organisms and marine growth. Marine fouling is not as prominent in the splash zone. Because of this lack of fouling and the wet/dry cycling in the splash zone, corrosion rates tend to be highest in this area. Unprotected steel corrosion rates in the splash zone generally range from 4 to 10 mils (102 to 254 µm) per year. Corrosion of steel pilings in a marine environment may also be the result of exposure to variable oxygen concentrations.

Corrosion will be more severe at zones with low oxygen con- tent and lower at more aerated zones. Highly localized corro- sion known as macrocell corrosion, or oxygen concentration cell corrosion, can result. This phenomenon is believed to be the primary cause of corrosion of piles in heterogeneous soils (26). Other studies have also concluded that macrocell corro- sion is involved in the corrosion of steel in the tidal zone (25). In oxygen-deficient areas, excess metal dissolution occurs, and the local pH falls; in oxygen-rich areas, oxygen reduction of hydroxide ions occurs, and the local alkalinity increases. Severe concentrated corrosion can occur just below the low tide zone as a result of oxygen concentration cells. The edge retention of coating systems is a property that can affect the overall system performance. If the edges of a struc- ture are not coated well, the system may not be acceptable for complex shapes or assemblies. Edge retention is defined as the percentage of the flat surface film thickness that covers an edge of the substrate. As an example, if the nominal dry film 8 thickness (DFT) of a coating over an “I beam” were 10 mils (254 µm) and the minimum DFT over an edge of the beam were 5 mils (127 µm), then the edge retention would be 50 per- cent. Most liquid coatings tend to “pull back” or flow away from sharp edges during application. This further exagger- ates the low film thickness encountered at the edges of a part. Many coating specifications make up for this lower edge cov- erage by adding “stripe coats” over all edges and nonuniform surfaces (e.g., bolts and welds). TSMCs are applied via a “line-of-sight process” (very similar to conventional and air- less spray of liquid coatings) yet do not “flow” as many liq- uid coatings do. TSMC deposition only occurs when the metal particles collide with a surface. As a TSMC application gun is turned away from perpendicular to the surface, the deposi- tion efficiency decreases dramatically. Unlike spraying liq- uid coatings, in which the “wet” material may have more of a tendency to adhere from a severe angle or long spray dis- tance, TSMC relies on impact energy and a short molten Classification Materials/Wire Comments Anodic Al99.0%—11 and 14 gauge and 1/8-in. wire Zn 99.9%—11 and 14 gauge and 1/8-in. wire Aluminum and zinc are available pre-alloyed or can be pseudo alloyed with the proper metallizing system. These coatings offer sacrificial galvanic protection to a steel substrate. Corrosion Resistant Cu 99.8%—14 gauge Cu 9Al 1Fe—14 gauge Fe 13Cr 0.5Si 0.5Ni 0.5Mn 0.35C— 14 gauge Fe 18Cr 8.5Mn 5Ni 1Si 0.15C—14 gauge Fe 28Cr 5C 1Mn—14 gauge Ni 5Al—14 gauge Ni 5Mo 5.5A1—14 gauge Ni 5Mo 5.5A1—14 gauge Ni 18Cr 6A1—14 gauge Sn 7.5Sb 3.5Cu 0.25Pb—14 gauge C 276 Ni Alloy—14 gauge While these coating systems are considered corrosion resistant, they are all cathodic to steel and, thus, offer no sacrificial protection to a steel substrate at coating defects. Hard Coatings Chromium Tungsten-Carbides These TSMCs are generally used in applications where abrasion resistance is a desired property. NOTE: 1 in. = 2.54 cm. Al = aluminum, Zn = zinc, Cu = copper, Fe = iron, Cr = chromium, Si = silicon, Ni = nickel, Mn = manganese, C = carbon, Sn = tin, Sb = antimony, Pb = lead. TABLE 1 List of materials commonly available as TSMCs TSMC Metal Alloy Alloy Rational 1 99.9% pure Zn Excellent cathodic protection properties, harder than aluminum, life proportional to thickness, not for acidic environments or high temperatures. 2 99% pure Al Low self-corrosion rate, good seawater performance, high-temperature resistance, lightweight, acid (pollution) resistant. 3 85:15 wt% Zn- Al Harder than aluminum, has shown better atmospheric performance than zinc or aluminum. NOTE: Al = aluminum, Zn = zinc. TABLE 2 Properties of commonly used TSMC materials

phase for adhesion, so a TSMC particle has a greater ten- dency to “bounce” from the surface. Over an edge, where the angle of application will stray from perpendicular, a TSMC will deposit with less efficiency than on a flat surface, so a reduced thickness on the edge is expected. The sharpness of the edge will also affect TSMC deposition on the edge. A very sharp, 90-degree edge will retain less coating thickness than a chamfered or “broken” edge. While many liquid coating systems rely on stripe coatings to build the film thickness at edges, a TSMC that is anodic to steel may not need additional edge coverage because of the sacrificial protection offered by the other areas of TSMC. However, because piles often have several different edge configurations, edge retention was considered during the lab- oratory phase of the project. Although the literature identifies various coating systems for potential application in natural waters (predominately sea- water), there are three principal systems that have received the most consideration: commercially pure aluminum, commer- cially pure zinc, and 8515 wt% zinc-aluminum. Table 3 shows the TSMC materials of interest tested most frequently within the literature. Of these primary TSMC materials, the material most often suggested as having superior performance in seawater and freshwater environments is aluminum. Aluminum is listed as the outstanding candidate by the National Materials Advi- sory Board at the National Academy of Sciences in their report, Metallized Coatings for Corrosion Control of Naval Ship Structures and Components, in the American Welding Society (AWS) 19-year report on metallized coatings, and in several papers dealing with TSMC used in the offshore industry (i.e., used in seawater) (7, 8, 11, 12, 14, 22, 27–31). Other papers have also concluded that aluminum is an excel- lent performer in freshwater environments (12, 24, 28). From a material property standpoint, the corrosion rate of all the TSMCs is quite low. These general corrosion rates appear in the 0.1- to 0.4-mpy (2.5- to 10-µm/yr) range. The literature suggests corrosion rates of 0.13 mpy (3.3 µm/yr) for aluminum TSMC. The same literature suggests corrosion 9 rates of 0.31 mpy (7.8 µm/yr) for 8515 wt% zinc-aluminum. These corrosion rates agree quite well with measurements obtained as part of this program on samples from both the laboratory and the field. These data are discussed below. Such low corrosion rates are consistent with the findings of field exposure testing listed in the literature (i.e., 12-mil [300-µm] coatings lasting for 20 years with little to no base- metal deterioration). Several materials, as discussed above, exhibit the findings of low corrosion rate and extended service life. This extended service life is in the range of 20 years or more. Several sys- tems, properly applied, seem to be able to meet this criterion. Thus, inherent material corrosion rate is not a key issue for the better performing materials; the key issue becomes the coating process needed to obtain a coating that meets this performance expectation. This is a specification and quality assurance issue as opposed to a material selection issue. The most common defect cited in the deterioration of TSMCs is inter-coat “blistering” or delamination. In this process, significant section loss of the TSMC is observed. Extensive propagation of such delamination can impact the useful service life of the material. It appears that delamination may be related to inter-coat corrosion occurring at selected pores or defects in the coating. This may occur along oxide boundaries or, in the case of mixed-metal TSMC, at differ- ing alloy phases/compositions. On a visit to test piles at the North Carolina DOT test site at Ocracoke, North Carolina, defects in thermally sprayed aluminum (99.5%) coating were visible, as shown in Figure 1, after 2 years of service in a seawater piling application. The defect appears as a split in the coating at the bend in the sheet piling. Similar inter-coat defects with a slightly different con- figuration also appeared on an 8515 wt% zinc/aluminum piling treated with TSMC at the same site. A 7030 wt% zinc/ aluminum pseudo-alloy TSMC appeared in the best shape at Material Percent of Time Tested Pure Al 75 Pure Zn 60 85:15 wt% Zn-Al 25 65:35 wt% Zn-Al 5 55:45 wt% Zn-Al 5 90:10 wt% Al-Al2O3 10 95:5 wt% Al-Mg 10 60:40 wt% Zn-Fe 5 Al-Zn-In 5 NOTE: Al = aluminum, Zn = zinc, Al2O3 = aluminum oxide, Mg = magnesium, Fe = iron, In = indium. TABLE 3 Materials and frequency of testing Figure 1. Thermal spray aluminum (99.5 percent) coating in seawater after 2 years exposure.

the site, free of such delaminations through 2 years of ser- vice. Yet, some areas of the piling appeared to exhibit incip- ient blisters. Similar types of defects have often been the deciding factor in the ultimate rating of TSMCs. If the occur- rence of such defects can be related to specific application parameters, then the life of the coating can be extended con- siderably. Historically, appropriate sealer coats are often listed as reducing the tendency for these types of defects. Several thermal spray systems were reviewed for testing under this program. Some of these systems include wire-arc spray, wire-flame spray, powder flame spray, high-velocity oxygen-fuel (HVOF) spray, and plasma spray. Wire-arc spray generally provides faster output and superior adhesion when compared with flame spray techniques (8). Production rates of up to 90 and 300 lb (41 and 136 kg) per hour have been obtained for wire-arc sprayed aluminum and zinc, respec- tively (15). Various other thermal spray techniques, includ- ing HVOF and plasma spray, are also available. However, these alternative thermal spray systems, when compared with wire-arc spray, generally do not offer the same levels of out- put and cost-effectiveness. There are also reports in the literature that using a larger- diameter feed wire can increase productivity (32). How- ever, other technical papers suggest that as wire diameter is increased, porosity also increases (9). This may lead to more coating defects. Any such tradeoffs between productivity and coating performance need to be considered in testing. Surface preparation is considered the most important part of thermally sprayed coating application. Typical require- 10 ments include an SSPC-SP-10, “Near-White Blast Clean- ing,” or SSPC-SP-5, “White Metal Blast Cleaning,” produc- ing a 2- to 4-mil (25- to 102-µm) profile with angular grit. Testing under this program included variations in surface preparation quality to determine the influence of such factors as surface profile and surface contamination. Initial Testing and Field Surveys One of the initial laboratory tests was a galvanic current test in which polyvinyl chloride (PVC) panels were coated with thermally sprayed aluminum and zinc by wire-arc spray. These panels, which were 2 in. (5 cm) in diameter, were elec- trically coupled to bare steel panels (1/32 in. × 4 in. × 6 in. [0.079 cm × 10.2 cm × 15.2 cm]) and immersed in natural seawater. Current flow between the coated PVC panels and the bare steel panels was monitored and plotted as a function of time, as shown in Figure 2. The preliminary electrochem- ical data indicated that while zinc may be more active ini- tially, its corrosion rate gradually decreases to a level closer to that of aluminum. Visual observations indicated that the steel panel coupled to the aluminum coating exhibited sig- nificantly more corrosion (red rust) than did the panel cou- pled to the zinc coating. Figure 2 shows that the galvanic cur- rent flows from the aluminum- and zinc-coated panels were at the same level after 3 weeks of immersion. These data indi- cate that the corrosion rate of zinc, relative to aluminum, in long-term exposure, may not be as high as much of the liter- 0 1 2 3 4 5 6 7 0 20 40 60 80 100 120 TIME (days) Zinc Aluminum Figure 2. Galvanic current data for TSMC materials (zinc and aluminum) coupled to steel panels in seawater.

ature suggests. The conclusions in the literature that zinc will corrode at higher rates may be somewhat misleading because of the lack of data from long-term exposures. However, according to the AWS “Corrosion Test of Flame-Sprayed Coated Steel—19 Year Report,” unlike aluminum, the ser- vice life of zinc thermal spray coatings is dependent on coat- ing thickness (28). A test piling was set up outside of Corrpro’s Ocean City lab- oratory to evaluate corrosion mechanisms associated with a seawater environment. Seven steel segments were exposed to various zones in seawater—mud, immersion, tidal, and splash zones. Five of the segments were coated with zinc applied by wire-arc spray. Two segments, one below the mudline and one in seawater immersion, were bare steel. The five zinc- coated segments were electrically connected with the bare steel segment below the mudline. Current flow between the segments was monitored periodically. Current data indicated that the majority of the sacrificial protection to the bare steel segment came from the zinc-coated segment below the mud- line. One of the zinc-coated segments in the seawater immer- sion zone was consistently receiving protective current. This lack of uniform galvanic current flow is indicative of macro- cell corrosion effects. These results imply that, as a design agent, long-term local corrosion driven by the macrocell cor- rosion, as well as the general corrosion rate of the material, are corrosion mechanisms that need to be considered. The majority of long-term piling tests have focused on the visible corrosion at or above the water line. The segmented piling data imply that corrosion below the water line, via macrocell corrosion, may be a factor in determining the service life of a coated piling. These results lead to the question of whether the piling should be coated below the mudline to limit gal- vanic interaction. Corrpro personnel performed a field survey of existing test pilings installed in late 1997 by the North Carolina Depart- ment of Transportation (NCDOT) at the South Side Cape Hatteras Ferry Dock on Ocracoke Island in North Carolina. Five steel test pilings had been exposed for about 2 years at the time of the field survey. The test piles consisted of the fol- lowing TSMCs: • Arc-sprayed aluminum and sealer, • Arc-sprayed 7030 wt% aluminum-zinc and sealer, • Arc-sprayed 8515 wt% zinc/aluminum and sealer, • Inorganic zinc-rich paint, and • Bare steel. In addition, the propeller wash piling wall is coated with coal tar. The results of the field survey are summarized as follows: • Electrochemical data indicated that the uniform corrosion rates of the thermally sprayed coating materials were rel- atively low; however, visual observations indicated local- ized areas of deterioration. 11 • The primary source of coating deterioration was inter- coat cracking and delamination between the base metal and coating. • Deterioration occurred at rolled corners. • Electrochemical data confirmed that the seal coats were not effective electrical barriers. Seal coats are not intended to behave as full barrier coatings. • A 2-year exposure period is inadequate to extrapolate the coating performance over a 20-year period. Interviews with Coating Applicators Six thermal spray coating applicators were contacted. Of these, three were willing to discuss the TSMC procedures. Structural Coatings, Inc., was visited in July 1999, at the beginning of the project, to view some pipe piles being coated and to obtain some initial information. Structural Coatings, Inc., was visited again on February 20, 2001, and question- naires were submitted to the other two applicators. Informa- tion gathered included types of abrasive used, use of mixed abrasives, treatment of flame-cut edges, spray techniques used, types of application equipment, types of sealers used, qual- ity control procedures, and qualifications. The three applica- tors provided useful information, which helped to focus and reduce the amount of laboratory testing needed. The thermal spray applicators contacted were the following: Jupiter Painting Structural Coatings, Inc. 1500 River Rd. P.O. Box 334, Highway 70 E Croydon, PA 19020 Clayton, NC 25720 215-785-6920 919-553-3034 Contact: Paul Tsourous Contact: Ray Hails CSI Coatings 2102 5 Street Nisku, Alberta T9E7X3 Canada 780-955-2856 Contact: Wayne Duncan (CSI Coatings is a wholly owned subsidiary of Corrpro Companies, Inc.) As a result of the literature search and field and initial labo- ratory studies, the following focus was determined for follow- on research: • Further testing should be limited to the most commonly used alloys for corrosion control, that is, the anodic coat- ings of “pure” aluminum and zinc and the 8515 wt% zinc/aluminum alloy. Properly applied, these materials show every indication of being able to meet the intent of the program (i.e., to significantly extend the life of steel piling materials in immersion in natural waters). • As opposed to testing an increased variety of TSMC base materials, a significant testing focus should be appropriate

sealers and sealing techniques. This investigation should include the use of 100-percent solids materials with report- edly higher “pore-penetrating” abilities. This includes the newer classes of maintenance painting primers designed to penetrate cracked and aged organic coatings. • The study should examine the effect of abrasive mixes on TSMC performance. • The program should also focus on those application para- meters that may affect the occurrence of critical pore sizes, pore geometry, and alloy micro-segregation or inter-coat oxide formation that will impact performance. • The program should focus on wire-arc spray applications of the materials to obtain optimal application rates. The program should include some focused study of the effects of increased productivity on material performance. PROCEDURES USED IN LABORATORY TESTS Laboratory testing was designed to improve the usefulness of the guide to TSMCs in several basic areas. These were the following: • Tests on sealer materials, including high solids, high- penetration epoxies, and urethanes. • Testing of the effects of different abrasive mixes on the performance of TSMC to examine the effects of angu- larity on performance and to examine methods to mea- sure angularity in the field. • Evaluation of the spray parameters of standoff dis- tance and application angle on coating microstructure and performance. • Testing of the effects of the hardness of the steel sub- strate on surface preparation requirements. • Testing of the effects of high-strength, low-alloy steel versus carbon steel substrate on TSMC performance. 12 • Testing of the effects of edge geometry on coating reten- tion and TSMC performance. • Testing of the effects of coating defects on TSMC performance. • Testing of the effects of surface contamination (chlo- rides) on coating performance. Test Panel Preparation Test panels to evaluate adhesion, sealers, different abra- sive mixes, edge effects, and application parameters were prepared by CSI Coatings in Nisku, Canada, using Thermion Bridgemaster equipment. The steel used for the corrosion tests met the requirements of AASHTO M-270 Grade 36 or ASTM A-328. M/020 steel was used for the complex corro- sion test panels and had a nominal analysis of 0.17 to 0.24 car- bon (C), 0.25 to 0.56 manganese (Mn), 0.04 max phosphorus (P), and 0.05 max sulfur (S). Panels for the impact test were A36 steel with an actual analysis of 0.16 C, 0.84 Mn, 0.004 S, 0.010 P, 0.04 silicon (Si), 0.29 copper (Cu), 0.11 nickel (Ni), 0.08 chromium (Cr), 0.005 vanadium (V), 0.002 cobalt (Cb), 0.030 molybdenum (Mo), 0.032 aluminum (Al), and 0.034 titanium (Ti). Other test panels were made from ASTM A569 steel having an actual analysis of 0.07 C, 0.46 Mn, 0.007 P, 0.004 S, and 0.02 Cu. Test panels were prepared using a Metco wire-arc appa- ratus to evaluate surface contamination and alloy and hard- ness effects at Corrpro’s Ocean City, New Jersey (OC) lab- oratory facility. Grade A36 steel was used for most of the testing, and ASTM A572 Grade 50 steel was used in the hardness comparison tests between A36 and Grade 50. Figures 3 and 4 show the panels being prepared at both facilities. Figure 5 shows the complex test panel used in the corrosion testing. Aluminum TSMC Zinc TSMC Figure 3. TSMC application at CSI.

Surface Preparation Unless otherwise specified, the test panels for this study were prepared using 100-percent G-16 steel grit. In all cases, the surface finish was SSPC-SP-5 white metal with a target profile of 3 mils (76µm). This study also explored the effects of grit-to-shot ratio on surface profile and coating performance using aluminum and zinc TSMCs. This is important because most current stan- dards and guidance documents specify the use of “angular” abrasives to obtain the required surface profile; thus an angu- lar profile is expected. A high degree of angularity is impor- tant because most of the debonding stresses acting on the coating are shear forces, and an angular surface provides more surface area for the coating to adhere to. However, many steel fabricators employ recycled steel shot as the preferred (and economical) method of surface preparation and often use mixed shot and grit in order to reduce equipment wear. Vary- ing levels of angular profile may result. This work investi- 13 gated the impact of such practices by metallizing over various surface roughness conditions. The most common technique for determining angularity compares magnified images of the surface to standard photomicrographs. Part of this work included tests to try to identify a field-friendly method of quan- titatively measuring angularity. Table 4 lists the abrasive mixes tested using aluminum and zinc thermally sprayed coat- ings. The surfaces were prepared to an SSPC-SP-5 white metal finish. TSMC Application TSMC application was performed with wire-arc spray equipment using standard parameters for the application equipment. Test panels to evaluate adhesion, sealers, surface preparation parameters, edge effects, and application para- meters were prepared by CSI Coatings. Test panels prepared to evaluate surface contamination and alloy and hardness effects were prepared at Corrpro’s laboratory facility. Dur- ing this application, a target film thickness of 10 to 12 mils (254 to 305 µm) was specified. The standoff was nominally 8 to 10 in. (20 to 25 cm), and the gun angle was 90 degrees from the sample. Testing Program Table 5 shows the test plan and Table 6 shows the tests applied to the various objectives of the test program. Quality Assurance Testing After surface preparation, quality assurance testing was conducted on representative samples. This included visual Aluminum TSMC Zinc TSMC Figure 4. TSMC application at Corrpro’s laboratory. BOLT & WASHER (COMPLEX SHAPE, EDGES, CREVICE) SCRIBE CHANNEL, WELDED TO PANEL WELD EDGE TREATMENTS (SHARP + 3) Figure 5. Test coupon used for corrosion testing.

14 TABLE 4 Blast procedures investigated Grit/Shot Steel Shot Steel Grit Rationale Shot Blast 100% S-280 Negative Control. Grit Blast 100% G-16 Positive Control. Shot/Grit Mix 33% S-280 67% G-16 Observed in shop for TSMC project in North Carolina. Alternate Shot/Grit Mix 70% S-280 30% G-16 Test the profile provided by a “low- grit” mixture. Test Coupon Size1 Specification Reference Comments 1 Microstructure Analysis 1 in. x 3 in. x 0.125 in.2 ANSI/AWS A5.33- 98 Porosity, segregation, oxides, and sealer penetration. Tensile (Pull- Off) Adhesion 4 in. x 6 in. x 0.125 in. ASTM D4541 “Pull-Off Strength of Coatings Using Portable Adhesion Testers” Requires a 15–20 mil (375–500 µm) TSMC thickness to prevent adhesive from reaching substrate. Bend Adhesion 2 in. x 4 in. x 0.063 in. ANSI/AWS C2.18- 93 MIL-STD-2138A Coated coupons are deformed 180° around a 0.5-in. (13-mm) mandrel and inspected for cracking and delamination. Alternate Wet/Dry Seawater Immersion 4 in. x 6 in. x 0.125 in.3 Representative of splash and tidal zone exposure. Full Seawater Immersion 4 in. x 6 in. x 0.125 in. Representative of complete immersion conditions. Drop Weight Impact 6 in. x 12 in. x 0.25 in. Modified ASTM D2794, “Resistance of Organic Coatings to the Effects of Rapid Deformation (Impact)” A 16-lb spherical weight is dropped onto the panel. Height will be increased as necessary using a longer guide tube. This method has higher impact energy than ASTM D2794 provides. NOTE: 1 in. = 2.54 cm. 1 The tests will be replicated three times except for the corrosion tests, which will be replicated two times. 2 One sample from the beginning of the coating application run, one from the middle, and one from the end. 3 Special panel containing crevice, scribe, fastener, and edge treatments—see Figure 5. TABLE 5 General test matrix TEST Testing Objective Th ic kn es s Pr of ile B en d ad he sio n Te ns ile ad he sio n Co rro sio n D ro p w ei gh t im pa ct M ic ro - st ru ct ur e Sealers X X X X X X X Abrasive mixes X X X X X X Spray parameters X X X X X Effect of steel hardness X X X X HSLA1 steel v. carbon steel X X2 Edge geometry effects X X X X Coating defects X X X Surface contamination X X X X 1 HSLA = high-strength, low-alloy. 2 Existing coupons from a previous study and laboratory polarization tests used to evaluate. TABLE 6 Tests applied to the objectives

inspection, surface profile evaluation, and chloride contami- nation. Methods for these evaluations are discussed below. Visual Inspection for Surface Quality. Visual inspection of the surface was made in accordance with the Society for Pro- tective Coatings (SSPC) Standard VIS-1-89. The appearance of the prepared surface was compared to the visual standards to determine if it conformed to an SSPC-SP-5, “White Metal Blast Cleaning,” condition. Surface Profile Evaluation. The target surface profile was 3 mils (76 microns). Profile evaluation was performed on all samples for the 100-percent shot, 70/30-percent shot/grit, and 33/66-percent shot/grit abrasives. Selected 100-percent- grit abrasive samples were tested. Surface profile was evalu- ated using two methods. Initial measurements were made using Testex brand replica tape. This tape is placed over the blasted substrate and rubbed in place to create an impression of the surface profile. A micrometer is then used to determine the overall profile (peak-to-valley height) of the surface. This is the most commonly used field technique to evaluate sur- face profile. Figure 6 shows this measurement. The second method was the use of a surface profile gauge to determine the profile of the blasted surface. Two gauges were used on the basis of their availability during sample preparation. Samples prepared by CSI Coatings were evalu- ated using a Perthometer MP4 150 profilometer. Samples prepared at the Ocean City laboratory were evaluated using a Mitutoyo SJ-201 surface roughness gauge. Both models are field usable and capable of measuring various aspects of the profile, which are shown in Table 7. Figure 7 shows the two gauges used to evaluate the profile of these samples. Both surface profile gauges use a stylus on a linearly dis- placed moving head to measure surface profile characteris- tics. This stylus follows the contour of the substrate, mea- suring peak height, valley depth, and the variations of these. Both profilometers were calibrated before use, and the same individual performed the profile measurements at both loca- tions. Both instruments are relatively operator independent. These measurements and their statistical manipulation are used to calculate the values shown in Table 7. 15 Coating Thickness Measurements. DFT measurements were made on samples after preparation and cure (after cooling for TSMC samples and a minimum of 7 days after sealer coats were applied). Coating thickness measurements were made using an Elcometer 345 eddy current thickness gauge (SSPC-PA [paint application] Type 2 gauge). Before thick- ness measurements were made, the Elcometer 345 thickness gauge was calibrated for measurement over a blasted surface. Using a representative steel panel blasted to an SSPC-SP-5 condition and a 3-mil (76.2-µm) surface profile, calibration was performed using standard plastic “shims” of known thickness that bracketed the expected coating thickness. This calibration was performed daily. Calibration thickness measurements were made on each test sample. Typically five measurements per side were made on all test samples with the exception of the 4- × 6-in. (10.2- × 15.2-cm) complex samples (8 measurements per side and 16 measurements in total were made on these pan- els). Measurements were taken at consistent locations with each type of panel. The thickness ranges of the TSMCs applied by CSI coat- ings were 12.9 to 20.8 mils (327 to 528 µm) for zinc, 14.8 to 22.9 mils (376 to 582 µm) for aluminum, and 14.7 to 19.5 mils Figure 6. Testex tape to evaluate surface profile. NAME ABBREVIATION DESCRIPTION Arithmetic mean deviation RA The average of the absolute value of the height or depth for all measurements. Root-mean-square deviation RQ The square root of the average of the squared absolute height or depth value. Maximum profile height RY The sum of maximum height and depth over a given area. 10-point height irregularities RZ The sum of the mean of the five highest peaks and five lowest valleys over a given area. Peak count RPC The number of peaks above a specified threshold limit from the mean. TABLE 7 Surface profile characteristics

(373 to 495 µm) for zinc/aluminum. The thickness ranges of the TSMCs applied to the A36 and Grade 50 panels at Ocean City were 9.9 to 11.8 mils (251 to 300 µm) for zinc and 12.3 to 14.2 mils (312 to 361 µm) for aluminum. Tensile (Pull-Off) Adhesion. Pull-off adhesion testing was performed on selected test samples. Adhesion is commonly used to monitor coating quality. MIL-STD-2138A specifies that a “good” aluminum TSMC should have a minimum adhe- sion strength of 1,500 psi (10.3 MPa) for individual samples and 2,000-psi (13.8-MPa) average (MIL STD paragraph 5.3.3.3) (4). Adhesion testing measures the bond strength at the weakest point in a coating system, with both strength (stress per unit test area) and failure location reported. Adhesion testing was performed in accordance with ASTM D4541, “Standard Test Method for Pull-Off Strength of Coat- ings Using Portable Adhesion Testers.” Testing was per- formed using a Patti Jr. pneumatic adhesion tester. Aluminum pull stubs (dollies) were adhered to the topcoat surface (TSMC or sealer coat) using a two-part epoxy adhesive. Following complete cure (24 hours after adhesive application), the pull stub was mounted in the tester, and air pressure was used to disbond the stub from the test sample. This system uses an air bladder to apply an upward (nor- mal) force to the pull stub until disbondment or the limit of the apparatus is reached. This apparatus uses an approximate 401 ratio to apply a maximum upward force (normalized to pull-stub contact area) of approximately 4,000 psi (28 MPa) from a 100-psi (0.7-MPa) air source. Figure 8 shows a dia- gram of this apparatus. Once disbondment occurs, the air pressure is recorded along with the location of failure for comparative analysis. The air pressure is then converted into adhesion strength from tabulated values. The tensile adhesion strength of TSMC on a 100-percent grit-prepared surface was 895 psi (6.2 MPa) with a 36-psi 16 (0.25-MPa) standard deviation for zinc and 1,514 psi (10.4 MPa) with a 263-psi (1.81-MPa) standard deviation. Mandrel Bend Adhesion Test. Mandrel bend testing is used to determine the flexibility and adhesion of a coating mater- ial. For liquid coatings, mandrel bend results for a “good” coating typically have minimal or no cracking because of their inherent flexibility. However, TSMCs are more rigid. Because of this, mandrel bend test requirements are less stringent and allow some cracking of the coating. Figure 9 shows examples of passing and failure conditions for TSMCs. Mandrel bend testing was performed on the samples indi- cated in Table 5. Testing was conducted on the 2- × 4- × 1/16-in. (5- × 10- × 0.16-cm) samples, which were bent around a 1/2-in (1.27-cm)-diameter cylindrical mandrel. Samples were bent approximately 180 degrees around this mandrel, creating a “U” shape similar to that shown in Figure 9. Imme- diately after testing, samples were evaluated for cracking and disbondment. No disbondment was observed on zinc or alu- minum TSMCs prepared by grit blasting. Other Tests Additional tests were conducted in order to provide input to the objectives of the laboratory program. The specific tests used are listed below. Falling Weight Impact The falling weight impact test was performed to determine the ability of the coating to resist damage caused by rapid deformation (impact). Testing was performed both with and Perthometer Mitutoyo SJ-201 Figure 7. Surface profile gauges.

without a sealer on aluminum and zinc TSMCs. For the test, a 12.5-lb (5.67-kg) steel ball (weight) was dropped from suc- cessive heights under natural gravitational acceleration at sea level (32.2 ft/s [9.81 m/s]), through a 15-ft (4.6-m) guide tube, onto the test panel, which was place horizontally. During this test, the 12.5-lb (5.67-kg) weight was dropped from varying heights. After each impact, the panel was inspected for signs of coating (TSMC and/or sealer) penetra- tion. Testing was continued until the height of the drop (to the nearest 6 in. [15.2 cm]) at which the coating just resisted penetration by the weight was determined. Five replicate tests were performed at this height to confirm the failure end point. The total energy ft-lb (N-m) that the coating could withstand without penetration was reported. Figure 10 shows this test apparatus. 17 Microstructure Analysis (Metallography) Microstructure analysis was performed on untested and post-simulation test samples as identified in Table 5. This analysis was performed using visual microscopy (metallog- raphy) to determine • Porosity—size, distribution, geometry, and intercon- nection; • Compositional phases—number present; • Oxide inclusions—number, size, and distribution; and • Coating substrate interface characteristics—trapped grit, disbondment, and so forth (general evaluation on untested samples, local characteristics adjacent to the scribe on post-test samples). Lehigh Testing Laboratories, Inc. (New Castle, Delaware) performed the microstructure analysis. Data were generated using photomicrographs, visual observations, and the point- count method for porosity and oxide distributions. The samples were examined in their unetched state for porosity and oxide evaluation and in their chemically etched state to show the pres- ence of multiple phases. This did not identify the chemistry of such phases, but showed whether one or more different phases were present. Two samples from each test were examined. Corrosion Tests Laboratory tests consisting of alternate wet-dry seawater exposure and constant immersion were performed to evaluate Figure 8. Pneumatic adhesion test apparatus. Figure 9. TSMC mandrel bend pass/fail examples.

the sealers, surface preparation, and application variables in this program. On the basis of results from previous studies, it is recognized that a short-term exposure test may be inad- equate to differentiate the performance of TSMC/sealer sys- tems. Thermally sprayed coating systems may be exposed to harsh environments for several years without exhibiting sig- nificant levels of corrosion. Natural seawater immersion testing was used to evaluate the performance of TSMC and other preparation variables in nat- ural waters. Testing was conducted at Corrpro’s Ocean City, New Jersey, facility using natural seawater obtained from the Inland Intracoastal Waterway adjacent to Corrpro’s facility. Seawater is pumped through this facility in an open-loop, once-through system. There are provisions for the filtration of large debris and biological growth; otherwise, the seawater contains all chemicals naturally found at this location. Test samples were placed in a non-metallic (plastic) tank and held in place with plastic holders. Samples were oriented at 90 degrees from horizontal and completely submerged in the natural seawater environment. To avoid stagnation, the 18 seawater in this tank was continually refreshed using a trickle (quiescent) flow from the intake system. During this test, periodic inspections (nominally every 3 months) were made to evaluate performance. This included evaluations for substrate corrosion (rusting) in accordance with ASTM D610, coating blistering in accordance with ASTM D714, formation of corrosion products on the samples, and visible cutback from the intentional holidays. The test methods used for these evaluations are presented in Table 8. For analytical purposes, the ASTM D714 rating is converted to a composite blistering rating. On the basis of the size and density of the blisters, a numerical rating from 0 to 10 is given to the sample. Table 9 shows this composite blister index. Figure 5 illustrates the type of panel used. The scribe was a diagonal line cut through the metallized coating with a hardened steel tool with a sharp point to ensure that the steel substrate was exposed. The panel edges were used to exam- ine the effect of different edge treatments. After sample preparation and sealer cure, an intentional scribe (removal of all coating materials to the steel substrate) Sketch Test Apparatus Figure 10. Falling weight impact test apparatus. Evaluation Test Method Description Substrate corrosion ASTM D610 Evaluation of percent corrosion on a test sample by comparison with visual standards (0 to 10 scale, 10 = no corrosion). Coating blistering ASTM D714 Evaluation of blister size and frequency on a test sample by comparison with visual standards (0 to 10 for size, 10 = no blistering; for frequency, F = few, M = medium, MD = medium dense, D = dense). Corrosion products N/A Visual observation for corrosion at the intentional scribes, along edges, in crevices, at welds, general deterioration and other observations. Cutback from holidays Modified ASTM D1654 Measurement of visible coating (TSMC or sealer) disbondment from intentional holidays evidenced by disbondment, blistering, or rusting. Measurements made in millimeters. TABLE 8 Coating deterioration inspection techniques

was placed into the test samples. This was performed to create a known defect and measure the coating systems’ ability to resist additional corrosion damage at this location. This tech- nique is commonly used in laboratory testing to accelerate the natural degradation of samples. In addition to linear scribes, some samples also had circular holidays made through the TSMC. These holidays were 1.5 in. (3.81 cm) in diameter and were used to further stress the test samples. These relatively large holidays (compared with the linear scribes) were used to evaluate the “throwing power” of the TSMCs applied (alu- minum and zinc). This large-diameter holiday increases the anode-to-cathode surface area ratio, thus increasing the sacri- ficial protection requirements of the TSMC. These scribes rep- resent an order-of-magnitude increase in anode-to-cathode sur- face area of 48 to 0.18 square in. (scribed) to 48 to 1.8 square in. (circular holiday). Use of a larger-diameter holiday will emphasize performance differences between TSMCs. Fig- ure 11 shows examples of the intentional scribe and circular holidays used (holidays and scribes highlighted). Constant Seawater Immersion. The constant seawater immersion test is indicative of a fully immersed environment for metallized piles. Panels were immersed continuously except during evaluation periods. Alternate Wet-Dry Seawater Immersion. Alternate wet- dry (or cyclic) seawater immersion was similar to constant 19 immersion, except that immersion was intermittent. Test sam- ples exposed in this environment were immersed in natural seawater for approximately 15 minutes followed by 75 min- utes of exposure to a harsh marine environment. This cycle was used to simulate the tidal action of natural waters, which can accelerate the corrosion of structures with their wet-dry cyclic actions. This test was conducted in the same tank used for constant immersion, with test samples placed just above this environ- ment. An automated timer was used to cycle immersion and atmospheric exposure in this zone only (constant immersion samples were continually submerged in natural seawater). The presence of natural seawater in the lower half of this tank created an atmospheric environment similar to the environ- ment that might be expected during naturally occurring peri- ods of low tide. Similar to the constant immersion samples, cyclic samples were periodically (nominally every 3 months) inspected for deterioration. These samples were inspected for the same deterioration as constant immersion samples using the test methods described in Table 8, above. RESULTS OF THE LABORATORY TESTS Sealer Tests Sealers are usually specified to seal the pores in TSMCs to improve coating performance. The U.S. Army Corps of Engineers thermally sprayed coating guide lists vinyl, coal tar epoxy, aluminum-pigmented epoxy mastic, tung-oil phe- nolic aluminum, vinyl-butyral wash primer, aluminum sili- cone, and silicone alkyd. This test program tested three new sealers along with two standard sealers and unsealed metal- lized samples (controls). The sealers were tested on ther- mally sprayed aluminum-coated steel panels and zinc-coated steel panels. Unsealed metallized samples were also tested and served as controls. Table 10 lists the sealers tested. Two low-surface-energy, high-solids sealers were selected for testing because they are different formulations and because they are both recommended by the Virginia DOT, according to one of the applicators interviewed. Blister Size Dense Medium Dense Medium Few 1 0.00 1.00 2.00 3.00 2 0.35 1.65 2.60 3.78 3 0.55 2.10 3.20 4.56 4 0.75 2.50 3.80 5.33 5 0.90 3.00 4.40 6.11 6 1.10 3.70 5.00 6.89 7 1.60 4.60 6.25 7.67 8 3.50 6.00 7.50 8.44 9 4.80 8.00 8.75 9.22 10 10.0 10.0 10.0 10.0 TABLE 9 Composite blister index Scribe (4 x 6 in.) Scribe (4 x 6-in. complex) Circular Holiday (4 x 6 in.) Figure 11. Representative intentional holidays (1 in. = 2.54 cm).

The sealer coats were applied using air spray equipment. Application was performed in accordance with the manufac- turers’ recommendations for mixing and thinning. All systems were applied with a maximum target DFT of 1 mil (25.4 µm) or as specified by the manufacturer (if less). The samples were scribed as described above. Adhesion Comparison of tensile adhesion strength with each of the five sealers tested showed similar ranges as those observed for aluminum and zinc TSMC samples applied over a 100-percent grit-blasted substrate. However, the primary failure location for the sealed samples varied from substrate to adhesive fail- ures. This differs from the failures of the unsealed TSMCs; for unsealed samples, all primary failures occurred at the substrate. The change in failure location was observed to be primarily related to sealer although some variations were observed between the aluminum and zinc TSMCs. Table 11 shows the primary failure location and average strength for each sealer. The average tensile adhesion strengths fall within the range of values for unsealed 100-percent grit-blasted steel, which indicates that the use of these sealers does not reduce the overall strength of the coating system. The change in failure location for several of the sealers from substrate (complete) to adhesive (used to attach aluminum pull stubs) or intra-coat (between sealer and TSMC) failures suggests that some ben- efit is gained by using a sealer coat. In these cases, the adhe- sion bond between the TSMC and substrate is greater than the reported value. Figure 12 shows the results of the U-bend adhesion tests on the 100-percent grit-blasted sealed zinc panels. The results of the bend tests on the abrasive mix variations are given later 20 in this report. Cracking was observed on almost every sam- ple that was evaluated using this test procedure. However, disbondment was observed on only four of the five sealer coats over zinc (Xymax did not show any disbondment). No disbondment was observed on the sealed aluminum TSMC U-bend specimens. Falling Weight Impact Tests Results from this testing showed that without a sealer coat, all TSMCs had failures at 12.5 ft-lb (16.9 N-m), which was the lowest energy application possible with the test apparatus. The results of the drop weight impact tests showed that when a sealer coat was applied all samples had no failure at 187.5 ft-lb (254.2 N-m) (highest energy application possible with the test apparatus). This was determined by visual obser- vation, where marring of the coating occurred, but no pene- tration of the TSMC to the steel substrate was recorded. These results suggest that in high-impact or mechanical wear areas, a sealer coat would improve abrasion- and impact- resistance performance. Sealer Coverage and Penetration Several methods were investigated to attempt to quantify sealer coverage and penetration. Successes and limitations were encountered with each method, all of which are dis- cussed below. Chemical Indicator Solutions. Sealer coverage and pene- tration can be determined by using chemical solutions that react with specific metal alloys to indicate the presence of these metal alloys. The chemical solutions cannot be used GENERIC TYPE SUPPLIER Zinc chromate vinyl wash primer (control material) Elite 1380 Epoxy (coal tar epoxy or equivalent) Devoe BarRust 235 Low-surface-energy, high-solids sealer Devoe 167 Pre-prime Low-surface-energy, high-solids sealer Carboline Rustbond Low-viscosity penetrating urethane Xymax Monolock PP TABLE 10 Sealers tested Aluminum TSMC Zinc TSMC Sealer Strength, psi (MPa) Location Strength, psi (MPa) Location Elite 1380 1,575 (10.9) Substrate 1,126 (7.8) Substrate Devoe BarRust 235 1,507 (10.4) Adhesive 1,214 (8.4) Substrate Devoe 167 Pre-prime 2,167 (14.9) Adhesive 1,698 (11.7) Adhesive Carboline Rustbond 1,527 (10.5) Substrate 1,303 (9.0) Adhesive Xymax Monolock PP 1,330 (9.2) Intra-coat 1,276 (8.8) Intra-coat TABLE 11 Tensile adhesion results for sealed TSMC samples

to determine the thickness of the sealer. Reaction of the chemical solution with the TSMC (aluminum or zinc) would indicate inadequate or incomplete coverage by the sealer. Two chemical solutions were used to verify coverage of the aluminum and zinc TSMCs. These were sodium hydroxide (NaOH) and saturated copper sulfate (CuSO4) solutions. Sodium hydroxide is used to detect the presence of aluminum as evidenced by a foaming reaction. Copper sulfate is used to detect the presence of zinc, which changes color to black when copper sulfate is applied. These indicator solutions were applied to representative samples for each coating to determine if complete coverage of the TSMC was achieved. Solutions were applied using brush and roller techniques, and the samples were visually monitored for the above-described reactions. The percentage of the surface area not covered by the sealer was determined on the basis of these chemical reactions. Table 12 shows a list of the sealers and the estimated percentage of the surface area covered for each TSMC. For zinc TSMC, area estimation was more readily per- formed than with the aluminum TSMC samples. This was pri- marily because the chemical reaction—a change in color— 21 was easily observed. The reaction caused by the sodium hydroxide solution on the aluminum samples often obscured coated areas. Chemical indicator solutions are easily employed and can be implemented in field evaluations, but the reaction of the sodium hydroxide solution on the aluminum TSMC may prevent an accurate measurement of exposed metal. The data presented in Table 12 suggest that most sealers provided near complete coverage of the aluminum and zinc TSMCs, with the possible exception of Devoe 167 Pre- prime and Carboline Rustbond on the aluminum TSMC. The lower values are the result of the thin sealer coat (about 1 mil [25.4 µm]) and a rougher aluminum TSMC surface, which, of course, is the same situation encountered in the field. Metallographic Evaluation. Visual metallography was tested as a method to determine sealer thickness, coverage, and pen- etration on cut sections of test samples. Evaluation of these samples was difficult because the thin, lightly tinted sealers were not easily discernable from the TSMC. A second eval- uation of freshly cut samples was conducted with a thin black coating applied on top of the sealer coats. This was used as a contrasting color to distinguish between the TSMC and sealer 0 0.5 1 1.5 2 2.5 3 3.5 ELITE 1380 DEVOE BAR RUST 235 DEVOE PRE-PRIME 167 CARBOLINE RUSTBOND XYMAX MONOLOCK PP SEALER D IS BO ND M EN T (m m) N O NE O BS ER VE D Figure 12. Average U-bend disbondment results for grit-blasted sealed zinc TSMC panels. Sealer Surface Area, % Aluminum Surface Area, % Zinc Elite 1380 99.0 95.0 Devoe BarRust 235 98.0 100 Devoe 167 Pre-prime 45.0 100 Carboline Rustbond 75.0 97.0 Xymax Monolock PP 99.5 100 TABLE 12 Percent surface area covered by sealers as shown by chemical indicator solutions

coats. This also was used to prevent the sealer coat from dis- appearing into the background as can often occur when per- forming metallography on thin coatings. Despite these efforts, the sealer coats could still not be readily viewed using visual microscopic techniques. Optically Stimulated Electron Emission Evaluation. Opti- cally stimulated electron emission (OSEE) was tested to quan- tify the coverage of the sealer coats over aluminum and zinc TSMCs. This technique uses photon emission technology to measure coating quality. An ultraviolet light source is focused on a specific area of a conductive, coated substrate. The reflec- tion and absorption of photons is measured as a current value (OSEE value) to determine coating quality. Figure 13 shows a picture of this test apparatus. OSEE is a comparative technique, which can be used to determine the general coverage of material or substrate. Con- ductive coatings (such as TSMCs) will have a higher value, while tinted coatings will have a lower value. Voids, thin spots, or other coating anomalies will allow for increased pho- ton transmission and thus result in values closer to an unsealed TSMC. This technique returns a dimensionless value, which is used for comparison between sealer coats. The relative rank- ing of sealers using this method was compared with other test methods to determine if OSEE provides an accurate ranking of the sealers and which sealer provides optimal coverage. Figure 14 shows the average OSEE measured values for the sealers applied over aluminum and zinc TSMCs. The 95-percent confidence interval for the data was also calcu- lated and found to be very close to the averages shown in the 22 graph. In general, the addition of a sealer reduced the OSEE values by an order of magnitude. The average differences between the samples were minimal, and overlap of the con- fidence intervals suggests that these sealer coats have similar electron emission characteristics. Compared with the indica- tor solution results, similar electron emission characteristics might be explained by the relatively high percentage of sur- face area coverage (demonstrated by this visual technique). While the OSEE method can detect whether a sealer is pres- ent, further work is needed to determine if the method can be used to provide an estimation of sealer quality. 1 10 100 1,000 NONE ELITE BAR RUST PRE-PRIME CARBOLINE XYMAX SEALER AV ER AG E O SE E VA LU ES ZINC ALUMINUM Figure 13. OSEE test apparatus. Figure 14. Average OSEE measured values for the sealers applied over aluminum and zinc TSMCs.

Visual Evaluation. Visual evaluations were performed with the unaided eye and under 5x magnification to determine over- all sealer quality and coverage. During this inspection, the coatings were observed for apparent voids, cracking, check- ing, blistering, color, and uniformity. Variations in general appearance and coating quality were recorded. Visual evaluation techniques were not well suited for determining sealer coverage, especially when lightly tinted sealers were used. Here, the sealer coat was difficult to dis- tinguish from the rough TSMC surface. Although in most cases the presence of the sealer coat could be verified, com- plete coverage was difficult to determine. Corrosion Tests Comparing Sealers The results from constant immersion testing after 12 months suggest that the presence of a sealer coat is beneficial for reducing corrosion and blistering. The overall corrosion rat- ing for unsealed zinc TSMC was 8, and the rating for unsealed aluminum TSMC was 9. Overall corrosion ratings for sealed aluminum and zinc TSMCs were 9 to10. Composite blister ratings for unsealed zinc and aluminum TSMCs were 6.9 and 10, respectively. Composite blister ratings for the sealed TSMCs remained at 10 for both TSMCs except for Carboline Rustbond, for which the rating was 7.5. Zinc TSMC showed increased cutback with all but the Elite 1380 sealer. The amount of cutback ranged from about 0.03 in. (0.76 mm) to 0.12 in. (3 mm). Aluminum TSMC was not observed to have the same cutback issues and performed well both sealed and unsealed. For zinc TSMC, the optimum sealer for immersion service appears to be a conversion coating. Note that chro- mate conversion coatings use hexavalent chromium, which is regulated as a hazardous waste product. Its use may not be possible in all areas. Alternative conversion coatings are a suggested alternative, but their performance in these envi- ronments is untested. Aluminum appears unaffected by the use of a sealer. Following 12 months of exposure in a cyclic immersion environment, none of the sealed samples experienced any significant deterioration. Corrosion ratings for both zinc and aluminum TSMCs were an average of 9 (out of a possible 10) or higher for samples (including unsealed controls), and composite blister ratings were greater than 9.5 for all sealers (the control zinc average was below 5.5). Similarly, none of the samples experienced any cutback from the intentional scribe. In total, the results suggest that the presence of a sealer coat may be beneficial over zinc TSMC by reducing blistering in cyclic immersion service. The presence of a sealer coat did not appear to be beneficial or detrimental when applied over aluminum TSMC. The results after 12 months of exposure indicate that the performance of aluminum TSMC may not be improved by using a sealer, but that the performance of zinc TSMC might be improved. Differences were relatively small, however, 23 and the 12 months of exposure time does not afford enough time for a meaningful comparison of sealer materials. The plan is to keep all of the corrosion test panels in testing long enough for significant differences to be observed. Abrasive Mix Effects Adhesion Tests Figure 15 presents the surface profile measurements made using Testex replica tape on the samples prepared by CSI Coatings using different abrasive mixes (see Table 4). Figure 15 presents the average of the profile data and the confidence interval. The confidence interval was estimated using the Stu- dent t distribution, where the confidence interval is given by the following equation: where Mean = statistical mean of the data points, StdDev = Standard Deviation of the data points, t = the Student’s t variable at a 95-percent confidence and 3 degrees of freedom, and n = number of data points. Other graphs in this report showing a confidence interval were generated in the same fashion. The results show that the 100-percent grit and 67-percent grit mixtures produced deeper profiles than did the 100-percent shot or 70-percent shot mix- ture. The average profile produced on the 33-/67-percent shot/grit mix is deeper than the profile produced on the 100-percent grit, but there is overlap in the data. Figure 16 provides the tensile adhesion data for zinc and aluminum TSMCs on the panels prepared with different abra- sive mixes. The results show clearly that there is an increase in adhesion strength going from the shot blast profile to 100-percent grit blast profile. The results also show that the abrasive mixtures result in decreased adhesion strength, but they do not show whether this will reduce the effectiveness of the coating. The U-bend adhesion test specimens showed cracking on almost every sample that was evaluated using this test pro- cedure. However, disbondment was only observed on spe- cific samples. Disbondment occurred on aluminum and zinc TSMCs prepared with 100-percent shot and zinc TSMC pre- pared with grit/shot mixtures. No disbondment was observed on aluminum or zinc TSMCs applied to 100-percent grit- prepared coupons. Figure 17 shows a plot of average dis- bondment length for each surface preparation method. This figure demonstrates that zinc TSMC is more susceptible to disbondment on surfaces prepared with less angular abra- sives than 100-percent grit. Confidence Interval Mean t StdDev n = ± ×

24 2 2.5 3 3.5 4 100% SHOT 100% GRIT 33% SHOT/67% GRIT 70% SHOT/30% GRIT MEDIA UPPER CONF. LIMIT LOWER CONF. LIMIT AVERAGE PR O FI LE , M IL S 0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 100% Shot 100% Grit 33% Shot/ 67% Grit 70% Shot/ 30% Grit 100% Shot 100% Grit 33% Shot/ 67% Grit 70% Shot/ 30% Grit SURFACE PREPARATION AD H ES IO N, P SI UPPER CONF. LIMIT LOWER CONF. LIMIT AVERAGE ALUMINUMZINC Figure 15. Testex replica tape profile ranges (panels prepared by CSI). Figure 16. Tensile adhesion of zinc TSMC versus abrasive mix (panels prepared by CSI, 1 psi = 6.89 KPa).

Profile Measurements As described in the section on procedures, surface profile characteristics were measured with a profilometer for the val- ues of RA, RY, RZ and RQ (see Table 7 for the definitions of these values). Figure 18 shows the values of RA, RY, RZ and 25 RQ, and Figure 19 shows the values of RPC on the A36 steel panels prepared by CSI Coatings. Similar measurements were performed on the A36 and Grade 50 samples prepared at the Ocean City lab. The values of RA, RY, RQ, and RZ for the A36 and Grade 50 samples on the CSI-prepared panels all have significant overlaps in the confidence bands. No distinction 0 5 10 15 20 25 100% SHOT 100% GRIT 33% SHOT/67% GRIT 70% SHOT/30% GRIT SURFACE PREPARAT D IS BO ND M EN T (m m) ION ZINC ALUMINUM N O NE D ET EC TE D Figure 17. Average U-bend disbondment results for unsealed TSMC panels. 0 1 2 3 4 SH O T G RI T 33 /6 7 70 /3 0 SH O T G RI T 33 /6 7 70 /3 0 SH O T G RI T 33 /6 7 70 /3 0 SH O T G RI T 33 /6 7 70 /3 0 R A, R Y, R Z a n d RQ , m ils UPPER CONF. LIMIT LOW ER CONF. LIMIT AVERAGE RA RY RZ RQ Figure 18. Average values and 95-percent confidence ranges for RA, RY, RZ and RQ profilometer data on A36 panels prepared with different abrasive mixes (1 mil = 25.4 µm).

can be made between the abrasive mixes except that the shot- blasted panels have significantly lower values than the grit- blasted panels. The panels prepared by the Ocean City labo- ratory exhibited the same characteristics. For all profilometer data except peak count, definite increases in the RA, RY, RQ and RZ values are seen for abra- sive containing more angular grit. Figure 20 shows the graphs of RQ versus abrasive mix and applicator, and Figure 21 shows the similar graphs of RPC. Peak count on the panels prepared at CSI, as seen in Figure 21, showed significant overlap between the abrasive mixes used, and no definite distinction between mixes could be made. Interestingly, the values of RPC are generally higher and the values of RQ are lower on the panels prepared at Ocean City than are the values of RPC and RQ on panels prepared by CSI. Average RPC for the coated grit-blasted panels prepared at CSI is 113 peaks/in., and the average peak counts for the panels prepared at Ocean City are 173 and 176 peaks/in. for A36 and Grade 50 steel, respectively. Variables were abra- 26 sive equipment, abrasive source, profilometer instrument used, and steel, so which variable(s) are responsible for the differ- ences in RPC and RQ cannot be ascertained from the existing data. Comparison of the adhesion strength values along with their corresponding confidence intervals indicates that the adhesion strengths are higher for the panels with higher RPC values and lower RQ values. This holds true for the grit-blasted aluminum and 70-/30-percent shot/grit and 33-/67-percent shot/grit zinc TSMC panels, but not the grit-blasted zinc or shot-blasted panels. Figure 22 shows the tensile adhesion val- ues versus abrasive mix and applicator for A36 steel. The importance of peak count on coating performance has been emphasized by several authors (33–36). Generally, a higher peak count results in higher adhesion (as found in this study) as long as the coating can wet the prepared surface. The increase in adhesion strength occurs because the peaks and valleys cause the disbondment forces to change from tension to shear. However, if the coating bridges the valleys rather 70 80 90 100 110 120 130 SHOT GRIT 33/67 70/30 RP C , pe ak s pe r i nc h UPPER CONF. LIMIT LOWER CONF. LIMIT AVERAGE 0 0.2 0.4 0.6 0.8 1 1.2 SH O T G RI T 33 /6 7 70 /3 0 SH O T G RI T 33 /6 7 70 /3 0 SH O T G RI T 33 /6 7 70 /3 0 RQ UPPER CONF. LIMIT LOWER CONF. LIMIT AVERAGE CSI APPL. OC - A36 OC - A50 0 50 100 150 200 250 SH O T G RI T 33 /6 7 70 /3 0 SH O T G RI T 33 /6 7 70 /3 0 SH O T G RI T 33 /6 7 70 /3 0 RP C , pe ak s pe r i nc h UPPER CONF. LIMIT LOWER CONF. LIMIT AVERAGE CSI OC - A36 OC - A50 0 500 1,000 1,500 2,000 2,500 3,000 3,500 Sh ot G rit 33 /6 7 70 /3 0 Sh ot G rit 33 /6 7 70 /3 0 Sh ot G rit 33 /6 7 70 /3 0 Sh ot G rit 33 /6 7 70 /3 0 Ad he sio n, p si UPPER CONF. LIMIT LOWER CONF. LIMIT AVERAGE Zn OC Al OC Zn CSI Al CSI A36 STEEL Figure 19. Average values and 95-percent confidence ranges for RPC profilometer data on A36 panels prepared with different abrasive mixes (1 in. = 2.54 cm). Figure 20. Values of RQ versus abrasive mix and applicator. Figure 21. RPC versus abrasive mix and applicator (1 in. = 2.54 cm). Figure 22. Tensile adhesion for aluminum and zinc TSMCs on A36 steel versus abrasive mix and applicator (1 psi = 6.89 KPa).

than wetting the surface, the adhesion could be worse with a high-peak density than with a low-peak density. Data in the literature show that finer abrasive size (shot or grit) pro- duces higher peak counts (33), but optimum peak counts for TSMCs have not been found in the literature. The labora- tory data for this study seem to suggest that a peak density of about 175 peaks/in. increases adhesion; however, the data are far from consistent, and the confidence bands in both the RPC data and adhesion data are much larger for the samples prepared in Ocean City. RPC might have value as a field mea- surement for predicting TSMC adhesion performance. Addi- tional work is required to develop this concept and determine optimum values of RPC for TSMCs. All thermal spray guides and specifications call for the sur- face profile to be “angular,” but do not define acceptable angularity limits or methods of measuring angularity. Angu- larity is defined not only by the number of peaks per unit area but also by the rapidity, or sharpness, of how peaks and val- leys change shape. Part of this measurement can be obtained through the use of surface profilometers. RPC and RQ values have shown promise in this study as indicators of good “angularity.” Work reported recently by the U.S Army Corps of Engineers indicates that this profilometer data may not be adequate (37). Angularity can be quantified using scanning electron microscopy, but this is hardly a field-friendly method. It might be that the best measure of angularity is indirect— characterizing the abrasive used. A chart that compares the roundness of abrasive grains can be found in a 1994 article by Hansink (38). According to the results presented in the U.S. Army Corps of Engineers study mentioned above, very angular, angular, and subangular shapes produced similar adhesion strengths (37). Corrosion Tests Comparing Abrasive Mixes The aluminum TSMC in cyclic immersion tests appeared to be tolerant of the use of various shot/grit mixture ratios in the constant immersion test. The corrosion and blister ratings were 10 for all abrasive mixtures tested, and no cutback was observed. In the constant immersion tests, the corrosion and blister ratings were 9, and there was no cutback for all the abrasive mixes tested. The aluminum TSMC appears to be insensitive to the abrasive mixture, at least up to 12 months of exposure. The zinc TSMC in cyclic immersion tests had a corrosion rating of 9 for all abrasive mixes tested. Blistering of the zinc TSMC was observed for all shot/grit mixtures, and visual cut- back was observed for all mixtures except the 70-/30-percent shot/grit. The 100-percent shot mixture was the most sus- ceptible to attack, with a composite blister rating of 2 and an average cutback of 1 in. (25.4 cm). The 70-/30-percent shot/ grit and 100-percent grit mixtures were the best performers, having composite blister ratings of 4.6 and 5.3, respectively, and average cutback measurements of 0 and 0.25 in. (6.5 mm), respectively. 27 The zinc TSMC in constant immersion tests had a corrosion rating of 8 for the grit and shot/grit mixtures (no shot abrasive was tested for this coating). The blister ratings were 6.9 for grit, 10 for 70-/30-percent shot/grit, and 3 for 33-/67-percent shot/grit after 12 months. There was no cutback observed for the grit-blasted panel, 0.19 in. (4.8 mm) for the 70-/30-percent shot/grit mixture, and 0.38 in. (9.7 mm) for the 33-/67-percent shot/grit mixture. These tests show that at 12 months of exposure, the alu- minum TSMC is insensitive to the abrasive mixes used in these tests. On the other hand, the zinc TSMC performs better when a 100-percent grit or high-content grit mixture is used. Effects of Application Parameters on Metallurgical Characteristics and Performance Metallography Most TSMC guides and specifications for wire-arc spray call for the distance between the tip of the gun to be within 6 to 8 in. (15 to 20 cm) and the angle of the gun to the work sur- face to be 90 degrees (optimum) and 45 degrees (maximum). The extremes of distance and deposition angle (45 degrees) are situations that are expected to be encountered when coating difficult-to-reach surfaces such as the inside flange surfaces of H-piles. In order to test whether the extremes of these ranges are detrimental to TSMC performance, tests were con- ducted to evaluate porosity, oxide content, adhesion, and cor- rosion performance. Table 13 shows the application parame- ters tested. Table 14 shows the results of the metallographic exami- nation. Some studies (10, 39, 40) imply that greater spray distances and more acute angles of incidence between the metal spray and surface lead to more porosity and oxides in the coating. In our studies, the pore size in the zinc and zinc/ aluminum TSMC samples was slightly smaller at the 12-in. (30.5-cm) distance than at the 8-in. (20.3-cm) distance. The pore size for the zinc TSMC was larger at the 45-degree application angle than at the 90-degree application angle. The porosity distribution was a larger percentage of the coat- ing volume at the 8-in. (20.3-cm) distance. The degree of interconnection between pores was also larger at the 8-in. (20.3-cm) distance. Alloy Application Rate Wire Diameter Standoff Deposition Angle Aluminum (Al)* 20 lbs/hr 1/8 in. 8 in. 12 in. 45° 90° Zinc (Zn)* 80 lbs/hr 1/8 in. 8 in. 12 in. 45° 90° 85 Zn–15 Al 60 lbs/hr 1/8 in. 8 in. 12 in. 45° 90° * Commercial purity wire; 1 cm = 2.54 in., 453.5 g = 1 lb. TABLE 13 Test protocol for application parameter study

Adhesion Figure 23 shows the average tensile adhesion strength values measured for each of the application parameters. The adhesion of aluminum is seen to decrease at the 12-in. (30.5-cm) distance from the value at 8 in. (20.3 cm), but is not affected by the angle (45 or 90 degrees). The adhesion of zinc and zinc/aluminum appear to be unaffected by appli- 28 cation angle and gun-to-surface distance within the parame- ters tested. Recent research by the U.S. Army Corps of Engineers concluded that distance affected the variation in porosity and oxide levels of zinc and zinc/aluminum, but none of the param- eters affected the variation in oxide and porosity of alu- minum (39). That report recommended the following opti- mum angles and distances: Angle TSMC (degrees) Distance Zinc 90 6 in. (15.2 cm) Aluminum 90 6–11 in. (15.2–27.9 cm) Zinc/Aluminum 90 6–10 in. (15.2–25.4 cm) Corrosion Tests Comparing Application Parameters The aluminum TSMC in constant immersion displayed a corrosion rating and composite blister rating of 10 for all of the application parameter variables. No cutback was observed on any of the test panels in this test. In the cyclic immersion tests, the aluminum had an overall corrosion rating of 9, a blister rating of 10, and displayed no measurable cutback for all of the application parameters. The zinc coating in the constant immersion tests displayed corrosion ratings of 9 at 45 degrees, 8 in. (20.3 cm); 8 at ALLOY PARAMETER POROSITY OXIDES SUBSTRATE 45/90 degrees Max size Distribution Geometry Degree of Max size Geometry PHASES INTERFACE 8 in. or 12 in. in. % interconnection % in. Trapped Debond spacing Grit Zinc 45 deg 8 in. 0.004 20 irregular moderate ND N/A N/A 1 ND minor 0.002 20 irregular moderate 5 0.002 irregular 1 ND major 90 deg 8 in. 0.001 5 rounded minor ND N/A N/A 1 ND moderate 0.002 <5 irregular moderate <5 0.002 irregular 1 ND moderate 45 deg 12 in. 0.001 <5 irregular minor ND N/A N/A 1 ND minor 0.003 6 rounded minor <5 0.002 irregular 1 ND major 90 deg 12 in. 0.001 <5 rounded minor ND N/A N/A 1 ND minor 0.0003 <5 rounded minor ND N/A N/A 1 ND minor Aluminum 45 deg 8 in. 0.002 7 rounded minor ND N/A N/A 1 ND minor 0.002 5 rounded moderate <5 0.007 elongated 1 ND minor 90 deg 8 in. 0.001 5 rounded minor ND N/A N/A 1 ND minor 0.001 <5 rounded minor 30 0.006 irregular 1 ND minor 45 deg 12 in. 0.001 <5 rounded minor 10 0.005 irregular 1 ND moderate 0.001 <5 irregular minor 5 0.002 irregular 1 ND minor 90 deg 12 in. 0.001 <5 irregular minor 30 0.007 irregular 1 ND moderate 0.003 7 rounded minor ND N/A N/A 1 ND minor Zn/Al 45 deg 8 in. 0.001 <5 irregular minor <5 0.007 irregular 2 ND moderate 0.003 5 irregular moderate ND N/A N/A 2 ND major 90 deg 8 in. 0.003 6 irregular moderate ND N/A N/A 2 ND moderate 0.002 <5 rounded minor ND N/A N/A 2 ND major 45 deg 12 in. 0.001 <5 rounded minor ND N/A N/A 2 ND major 0.001 <5 rounded minor <5 0.007 elongated 2 ND minor 90 deg 12 in. 0.001 <5 rounded minor ND N/A N/A 2 ND minor 0.002 <5 rounded minor ND N/A N/A 2 ND minor NOTE: 1 in. = 2.54 cm, ND = not detected, N/A = not applicable, deg = degrees, Zn/Al = zinc/aluminum. TABLE 14 Effects of application parameters on TSMC metallurgy 0 500 1,000 1,500 2,000 2,500 45- deg, 8-in 90- deg, 8-in 45- deg, 12-in 90- deg, 12-in 45- deg, 8-in 90- deg, 8-in 45- deg, 12-in 90- deg, 12-in 45- deg, 8-in 90- deg, 8-in 45- deg, 12-in 90- deg, 12-in APPLICATION PARAMETER AD H ES IO N, P SI UPPER CONF. LIMIT LOWER CONF. LIMIT AVERAGE ZINC ALUMINUM ZINC/ALUM. Figure 23. Average adhesion strengths and confidence limits for the application parameters tested (1 psi = 6.89 KPa).

90 degrees, 8 in. (20.3 cm); 7 at 45 degrees, 12 in. (30.5 cm); and 8.5 at 90 degrees, 12 in. (30.5 cm). The composite blister rating was 10 for all application parameters except 45 degrees, 12 in. (30.5 cm), where it was 6.5. The cutback was 0.19 in. (4.8 mm) at both 45 degrees, 8 in. (20.3 cm), and at 90 degrees, 12 in. (30.5 cm), and it was 0.38 in. (9.7 mm) at 45 degrees, 12 in. (30.5 cm). The zinc TSMC in the cyclic immersion tests displayed an overall corrosion rating of 10 for all of the application parameters. The blister rating was 10 for the 90-degree angle at both spacings, but fell to 4.6 at 45 degrees, 8 in. (20.3 cm), and 5.2 at 45 degrees, 12 in. (30.5 cm). No measurable cutback was observed at any of the application parameters. The zinc/aluminum TSMC in the constant immersion tests had an overall corrosion rating of 10 for all application param- eters tested, and no cutback was observed. In the cyclic immersion tests, the zinc/aluminum coating displayed an over- all corrosion rating of 10 for all parameters. The composite blister rating was 5.2 at 45 degrees, 8 in. (20.3 cm); 4.6 at 90 degrees, 8 in. (20.3 cm), and 45 degrees, 12 in. (30.5 cm), and 3.9 at 90 degrees, 12 in. (30.5 cm). There was no mea- surable cutback at any of the application parameters. The results at 12 months of exposure time suggest that the aluminum and zinc/aluminum TSMCs are insensitive to the application parameters tested, but that the zinc TSMC is sen- sitive to shallow angles from gun to work surface. Effect of Carbon Steel Hardness The effects of small differences in hardness caused by dif- ferent steel alloys were addressed by measuring the surface profile and adhesion of TSMCs on ASTM A36 and ASTM A572 Grade 50 steel panels abrasive blasted in the same man- ner. The tensile strength of ASTM A36 steel can range from 58 to 80 ksi (400 to 550 MPa), and the tensile strength of ASTM A572 Grade 50 steel is specified as 65 ksi (450 MPa). Because this means that there can be overlap in the hardness between the two materials, we measured the hardness of the samples and found a Rockwell B (RB) hardness of 90.8 for the A36 material and 75 for the Grade 50 material. Figure 24 shows the surface profiles of the A36 and Grade 50 steel sam- ples as measured with Testex tape. The profiles appear to be the same for both alloys. Adhesion Figure 25 shows the adhesion strength of aluminum and zinc TSMCs on grit-blasted A36 and Grade 50 steel panels. The adhesion of the zinc TSMC was essentially the same on the A36 and Grade 50 panels. There is a considerable varia- tion in the aluminum adhesion strength; however, this wide variation was observed on both aluminum and zinc TSMC panels. No discernable difference was observed in the adhe- sion of the zinc or aluminum TSMCs on A36 and Grade 50 samples prepared by grit, shot, or the mixtures tested. 29 Corrosion Tests Comparing Steel Hardness In the constant immersion tests, the overall corrosion ratings of both alloys were similar, differing by less that 1 unit for all of the abrasive mixes used. The blister ratings were 6.8 for A36 steel, 8.7 for Grade 50 steel over a 100-percent shot/ prepared surface, and 10 for both steel alloys on 100-percent grit-prepared surfaces. For a 70-/30-percent shot/grit-prepared surface, the blister ratings were 10 for A36 steel and 8.4 for Grade 50 steel. Cutback was less than 0.05 in. (1.3 mm) for all panels except the Grade 50 on a 100-percent grit surface, where it was 0.11 in. (2.8 mm). In the cyclic immersion tests, the overall corrosion ratings were within 1 unit for both alloys and abrasive mixes, except the 70-/30-percent shot/grit mixture, where the A36 steel had 0 0.5 1 1.5 2 2.5 3 3.5 Shot Grit 70/30 33/67 SURFACE PREPARATION METHOD PR O FI LE , M IL S A36 A50 Figure 24. Surface profile of A36 and A50 steel samples using Testex tape (1 mil = 25.4 µm). 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 ZINC A36 ZINC A50 ALUMINUM A36 ALUMINUM A50 COATING - STEEL ALLOY AD H ES IO N, P SI UPPER CONF. LIMIT LOWER CONF. LIMIT AVERAGE Figure 25. Tensile adhesion of zinc and aluminum TSMCs on A36 and A50 grit-blasted steel panels (1 psi = 6.89 KPa).

a rating of 9.6, and the Grade 50 steel had a rating of 8.3. The composite blister ratings were all within 1 unit for each steel alloy and abrasive mix tested. The shot-prepared panels had the lowest blister ratings, 7.7 (Grade 50) and 7.9 (A36). The other panels had blister ratings between 9 and 10. The cut- backs for the shot-prepared surface were 0.06 in. (1.5 mm) for A36 and 0.36 in. (9.1 mm) for Grade 50. The cutbacks for the grit-prepared surfaces were 0 for A36 and 0.02 in. (0.51 mm) for Grade 50. The cutbacks for the 70-/30-percent shot/grit-prepared surfaces were 0.2 in. (0.51 mm) for A36 and 0.03 in. (0.76 mm) for Grade 50. The cutbacks for the 33-/67-percent shot/grit-prepared surfaces were 0 for A36 and 0.02 in. (0.51 mm) for Grade 50. The corrosion test data indicate that, with the exception of cutback at defects in cyclic immersion on shot-prepared sur- faces, the substrate hardness does not affect the performance of the TSMC. HSLA Steel versus Carbon Steel HSLA steels, such as ASTM A588, are designed to have better strength and atmospheric corrosion resistance than conventional carbon steel. The corrosion resistance of HSLA steels is due to small quantities of alloying elements such as chromium, nickel, manganese, copper, and molybdenum in the steel. Weathering steels, a type of HSLA steel, are some- times used as steel pilings because of their strength and cor- rosion resistance. The low alloy content of the steel might make it slightly nobler than carbon steel (41). This testing was designed to determine what effect, if any, that has on the performance of TSMCs allied to the HSLA steel. 30 Galvanic Behavior To determine the overall ability of aluminum and zinc to pro- vide sacrificial protection to Grades A36 and A588 steels, test- ing was conducted to measure current flow versus time in sev- eral aqueous environments. Sacrificial protection is provided by the TSMC to the steel substrate onto which it is applied. Intimate contact between the TSMC and the steel occurs dur- ing the application process, providing an electrical pathway for sacrificial protection, but it is impossible to measure the pro- tection current being provided to the substrate. However, by simulating such an exposure using temporary connections between a TSMC sample and a bare steel panel, a measure of the protective current provided by the TSMC was performed. A panel coated with aluminum TSMC and a panel coated with zinc TSMC, each with equal areas exposed in an elec- trochemical test apparatus, were used for testing. In tests, the coated panel was coupled to freshly blasted Grade 36 and Grade 588 steel panels through individual wire connections. Provisions were made to periodically monitor current flow between the TSMC panel and bare panels to determine if sac- rificial protection was being provided. Visual evaluations were also conducted to verify the mitigation of steel substrate corrosion mitigated and the presence of TSMC corrosion. Figure 26 shows a sketch of this test setup. By their very nature, aluminum and zinc TSMCs are not uniform and contain voids, pores, and other areas where elec- trical contact to the substrate and/or surrounding aluminum or zinc particles may be compromised. As such, the electrical current measurements are subject to variation, and time-based activation of the TSMC may occur unlike the behavior of an aluminum or zinc anode connected to a steel structure. How- ever, these measurements can be indicative of the presence NOTE: A = ammeter, V = voltmeter, SCE = saturated calomel electrode. Figure 26. Electrochemical sacrificial protection test cell (1 in. = 2.54 cm).

and relative level of sacrificial protection being provided. Figures 27 through 30 show plots of current versus time for aluminum and zinc TSMCs to A36 and A588 steel, using electrolytes of 25, 500, 1,000, and 5,000 ohm-cm. Sacrificial current flow monitoring has demonstrated that after 2 to 5 days in tests, a measurable sacrificial current is generated by both TSMC materials to protect the A36 and A588 bare steel panels. Current flow to these samples is mar- 31 ginally reduced for A588 steel compared with A36 steel, suggesting that this more corrosion-resistant alloy requires less sacrificial protection. Current flow is also shown to be inversely proportional to solution resistivity (i.e., low resistivity = higher current flow). This is as expected, because a higher resistivity electrolyte is typically considered less corrosive (without the presence of other factors). -2.00E-03 -1.00E-03 0.00E+00 1.00E-03 2.00E-03 3.00E-03 0 2 4 6 8 10 12 Elapsed Time (days) Cu rre nt (a mp ere s) 25 ohm-cm 500 ohm-cm 1,000 ohm-cm 5,000 ohm-cm -2.00E-03 -1.00E-03 0.00E+00 1.00E-03 2.00E-03 3.00E-03 0 2 4 6 8 10 12 Elapsed Time (days) 25 ohm-cm 500 ohm-cm 1,000 ohm-cm 5,000 ohm-cm Cu rre nt (a mp ere s) Figure 27. Galvanic current, zinc TSMC versus A36 steel. Figure 28. Galvanic current, zinc TSMC versus A588 steel.

In addition to electrical measurements, periodic visual eval- uations were made without disrupting exposure. After approx- imately 1 week of exposure, samples in seawater and lower- conductivity electrolytes began to show calcareous deposits on the bare steel surfaces. Calcareous deposits are a by-product of cathodic protection. The formation of calcareous deposits occurs at the cathode of a protected substrate (by either sac- rificial or impressed current cathodic protection). The forma- tion of these deposits suggests that some degree of cathodic protection is being provided. 32 Long-Term Marine Atmospheric Exposure Analysis In a past Federal Highway Administration project (“Environmentally Acceptable Materials for the Corrosion Protection of Steel Bridges,” Contract DTFH61-92-C- 00091), Corrpro evaluated TSMC for corrosion protection of steel at its Sea Isle City, New Jersey, marine atmos- pheric exposure facilities. Although this project is com- pleted, the panels have been continued in testing. The site -3.00E-03 -2.00E-03 -1.00E-03 0.00E+00 1.00E-03 2.00E-03 0 2 4 6 8 10 12 Elapsed Time (days) 25 ohm-cm 500 ohm-cm 1,000 ohm-cm 5,000 ohm-cm Cu rre nt (a mp ere s) -2.00E-03 -1.00E-03 0.00E+00 1.00E-03 2.00E-03 3.00E-03 0 2 4 6 8 10 12 Elapsed Time (days) 25 ohm-cm 500 ohm-cm 1,000 ohm-cm 5,000 ohm-cm Cu rre nt (a mp ere s) Figure 29. Galvanic current, aluminum TSMC versus A36 steel. Figure 30. Galvanic current, aluminum TSMC versus A588 steel.

is located approximately 100 yards from the Atlantic Ocean to the east and bordered by Ludlum’s Bay to the west. In 1989, several panels of A36 and A588 steel with aluminum, zinc, and zinc/aluminum (8515 wt%) ther- mally sprayed coatings were exposed at this test site. The panels were prepared by grit blasting with G16 steel grit to an SSPC-SP-10 finish and 4-mil (102-µm) profile. The TSMCs were applied by the flame spray wire technique. A vinyl chloride/vinylidene chloride copolymer was used to seal half the panels. These samples have been exposed to a harsh, natural marine environment for a period of 13 years. Evaluation of these samples is beneficial in determining the long-term atmospheric performance of a TSMC over low-alloy and weathering steel. The general condition of the TSMC samples did show minimal signs of deterioration. Panels coated with organic coatings (epoxy powder, electrostatic spray polyester, electrostatic spray epoxy powder with polyurethane, and acrylic topcoats), and also exposed for 13 years, showed severe deterioration. Figure 31 shows a photo of all TSMC and liquid-coating systems exposed as part of this previous program. Thickness measurements were taken on each of the zinc, aluminum, and zinc/aluminum panels. Some corrosion of the TSMC had occurred and was evidenced by the white corrosion products on the panel surface. A slight thickening 33 of the coating was measured, which is due to corrosion products. However, with the exception of the aluminum TSMC samples, no substrate corrosion was observed on these samples. Some substrate corrosion (red rust) occurred on two aluminum TSMC A36 panels (without sealer) at a scribe and at the edges of the welded channels indicating possible inadequate galvanic protection ability at exposed substrate defects. Localized corrosion (red rust) was also found on the back of two aluminum TSMC A588 panels (without sealer), which is due to a crevice between the panel and wood support. The sealers appeared to be eroded on the aluminum panels, but they are generally intact on the zinc and zinc/aluminum panels. The conclusion to these tests is that the TSMCs perform similarly on both carbon steel and HSLA steel substrates. Edge Geometry Effects Sheared, saw-cut, and flame-cut edges are common occurrences in sheet piles. Edge retention analysis was per- formed on cut sections of the complex panels prepared for corrosion testing (see Figure 5). Prior to the TSMC applica- tion, the edges of these samples were altered using a bench-top shop grinder. Some edges were chamfered (approximately 45 degrees), some were rounded (approximately semi- circular), and some were made flat (approximately 90 degrees from panel face). The chamfered and rounded edges simulate the “relief on an edge” used to promote coating adhesion and coverage. The flat edge provides a “sharp” edge, which has historically shown worse performance. These different edges were used to determine if the TSMCs are susceptible to edge retention issues, like liquid systems, and if sharp edges reduce corro- sion protection. Edge retention/characterization was performed by micro- scopic analysis. Sections of untested panels were cut, expos- ing the cross section of one of the four edges. This section was then mounted in an epoxy resin and polished using suc- cessively finer abrasives to evaluate TSMC thickness and microstructure. Visual metallography was used to examine these samples and compare them with flat sections of the same panel, with the following observations. Aluminum TSMC The use of a relieved edge (i.e., rounded or chamfered) appeared to promote adhesion of the TSMC as evidenced by more uniform coverage. Figure 32 shows aluminum TSMC applied to a chamfered edge. The aluminum TSMC adheres well along the chamfer and provides complete coverage. However, at the end of the chamfer (performed on approximately 1/2 the width of the edge) no TSMC is present. Figure 31. TSMC and paint systems, 13 years marine atmospheric exposure. (Panels shown in Columns 1, 3, and 5 are not sealed. Panels in Columns 1 and 2 have a zinc TSMC. Panels in Columns 3 and 4 have a zinc/aluminum TSMC, and panels in Columns 5 and 6 have an aluminum TSMC. Panels in Columns 2, 4, and 6 are sealed. Panels in Columns 7, 8, and 9 are powder-spray coated. Panels in Columns 10 to 14 are coated with organic materials. Panels in Rows A and B have a Grade 36 steel substrate. Panels in Rows C and D have a Grade A588 substrate.)

Figure 33 shows similar results for aluminum TSMC applied to a rounded edge, although to a lesser degree. The semi-circular treatment here covers most of the edge width and the TSMC appears to adhere more readily to this surface. The exception is where the edge and face of the panel meet, where a reduction in thickness is observed. Figure 34 shows the ground flat edge for the aluminum TSMC panels. This figure shows that at sharp corners there is notable thinning of the aluminum TSMC. The TSMC was also observed to have thin spots and voids along the flat edge. Zinc TSMC On a relieved (chamfered) edge, the zinc TSMC was observed to have a consistent thickness (see Figure 35). 34 However, at the end of the chamfer a notable thinning was observed. The end of the chamfer can create a sharp corner, as this is where the relieved and flat edges meet. The observed reduction in the zinc TSMC is consistent with the observations on the chamfered edge of the aluminum TSMC. Figure 36 shows the rounded edge for the zinc TSMC panels. This figure shows that the zinc TSMC has no visible thinning or voids when applied on this type of edge. This was also the best edge (with respect to TSMC integrity and reten- tion) for aluminum. Figure 37 shows the flat edge for the zinc TSMC panels. This figure shows that although the zinc TSMC could be applied consistently, there was a gap between the substrate and the thermally sprayed coating. The clean edge with which this coating disbonded, combined with the lack of visible Aluminum on Chamfer No Aluminum at End of Chamfer Figure 32. Aluminum TSMC photomicrographs, chamfered edge. Aluminum on Rounded Thin/Porous Aluminum at End Figure 33. Aluminum TSMC photomicrographs, rounded edge.

35 Thinning Aluminum at Sharp Corner Incomplete Coverage of Flat Edge Zinc on Chamfer Thinning Zinc and End of Chamfer Zinc on Rounded Edge Zinc at Apex of Rounded Edge Figure 34. Aluminum TSMC photomicrographs, flat edge. Figure 35. Zinc TSMC photomicrographs, chamfered edge. Figure 36. Zinc TSMC photomicrographs, rounded edge.

contamination at the interface, suggests that the zinc TSMC has poor adhesion over this type of edge. This disbondment probably occurred during application. On the basis of the conditions observed for both TSMC materials, the optimum edge for coating application would be achieved by rounding. A chamfered edge can help improve coating retention, but the edges can still be affected by thinning and/or lack of coating adhesion as observed above. Corrosion Tests Comparing Edge Geometry No differences in corrosion performance caused by edge geometry were observed after 12 months of testing. Coating Defects Several samples (with and without chloride contamina- tion) received a 3.8-cm- (1.5-in.-) diameter intentional holi- day prior to testing. These were used to test the “throwing power” of the TSMC materials. Following 6 months of con- stant immersion exposure, minimal deterioration of these TSMC materials has been observed. Some corrosion of the holiday area has occurred on most samples, suggesting that such large defects are not fully protected by the exposed TSMC surface area. Similar to the constant immersion samples above, mini- mal deterioration of the TSMC on the cyclic immersion samples has been observed. Some corrosion of the holiday area has occurred on most samples, suggesting that such large defects are not fully protected by the exposed TSMC surface area under conditions of cyclic immersion and drying. 36 Surface Contamination Surface contamination can decrease the performance of a coating system, liquid, or TSMC. However, some coatings are more tolerant of contamination, and their performance is not as significantly reduced. The U.S. Navy recommends a chloride contamination limit of 3 µg/cm2, and both higher and lower limits are found elsewhere for immersion service (42). The U.S. Army Corps of Engineers guide for thermal spray coating recommends a level of chloride contamination less than 7 µg/cm2. Experience suggests that performance degra- dation generally begins at chloride levels above 5 µg/cm2 and significantly affects coating performance at 10 µg/cm2. Some panels were purposefully contaminated using a sodium chloride solution to achieve chloride levels of 5 and 10 µg/cm2 to determine if the aluminum and zinc TSMCs are significantly affected. To contaminate the surface of the test samples, A36 steel panels that had been abrasive blasted using 100-percent steel grit were immersed in a sodium chlo- ride solution made using deionized water. To verify the con- tamination level, chloride measurements were made using the Bresle method. This method uses a latex rubber patch, which is adhesively backed for application to a steel sub- strate. During this test, an extraction fluid is injected into the area exposed to the steel substrate and massaged to dissolve the available chloride ions into solution. The extraction fluid is then removed, and a titration is performed to determine the presence of chloride ions. The 5-µg/cm2 panels had actual chloride levels of 5 to 7 µg/cm2 and the 10-µg/cm2 panels had actual chloride levels of 9 to 11 µg/cm2. Adhesion Figure 38 shows the results of the tensile adhesion tests on the contaminated panels compared with the measure- Zinc on Flat Edge, TSMC and Substrate Zinc on Edge, TSMC Only Figure 37. Zinc TSMC photomicrographs, flat edge.

ments on uncontaminated panels. The data indicate that the adhesion of the zinc TSMC is insensitive to chloride con- tamination at the levels tested. On the other hand, the alu- minum TSMC shows a definite decrease in adhesion val- ues at both levels of contamination tested. Corrosion Tests Comparing Surface Contamination The zinc TSMC in constant immersion tests exhibited a lower corrosion rating at the 10-µg/cm2 chloride level than at the 5-µg/cm2 level. The ratings at 5-µg/cm2 of chloride were 9.6 with a holiday and 9.2 without a holiday. The ratings at 10 µg/cm2 were 8 without a holiday and 7.7 with a holiday. The composite blister ratings were actually higher for the higher level of contamination: the values at 5 µg/cm2 were 6.9 with a holiday and 5.1 without a holiday. At 10 µg/cm2, the ratings were 8.7 with a holidayand 8.4 without a holiday. The corrosion ratings were independent of contamination levels, having a value of 10 across the board. In cyclic immersion tests, the zinc TSMC had a corrosion rating of 10 across the board. The composite blister ratings were 7.2 at 5 µg/cm2 with a holiday, 5.2 at 5 µg/cm2 without a holiday, 4.8 at 10 µg/cm2 with a holiday, and 4.5 at 10 µg/cm2 with- out a holiday. No significant cutback was observed under any condition in this particular test. The aluminum TSMC in constant immersion tests did not exhibit a trend in the corrosion ratings with contamination 37 level.The ratings at the 5-µg/cm2 level were 8.2 with a holiday and 7.3 without a holiday. The ratings at 10 µg/cm2 were 8 with a holiday and 6.7 without a holiday. The composite blister rat- ings were independent of contamination levels, having a value of 10 across the board. Negligible cutback was observed on all panels. In cyclic immersion tests, the aluminum TSMC had corrosion ratings of 9.3 at 5 µg/cm2 with a holiday, 7.7 at 5 µg/cm2 without a holiday, and 9 at 10 µg/cm2 with or without a holiday. The composite blister ratings for aluminum TSMC were 10 at 5 µg/cm2 with a holiday, 8.7 at 5 µg/cm2 without a holiday, 8.6 at 10 µg/cm2 with a holiday, and 10 at 10 µg/cm2 without a holiday. No significant cutback was observed under any condition in this particular test. In general, the zinc TSMC appeared to perform better than the aluminum coating with regard to overall corrosion rating, but worse than the aluminum with respect to blister rating. The performance of the TSMC materials in constant immersion varied depending on the metric being evalu- ated. The presence of holidays in the coating did not appear to affect performance, with holiday samples often having improved performance compared with the scribed samples. Negligible cutback was observed for all test samples. Overall, the aluminum TSMC appears to be more tolerant of surface contamination. In general, application of a TSMC over a contaminated substrate should be avoided. Figures 39 and 40 show typical panels (5 µg/cm2 chloride) with circular holidays and scribes after 6 months of expo- sure to cyclic seawater immersion. 0 500 1,000 1,500 2,000 2,500 NONE 5 10 NONE 5 10 CHLORIDE CONTAMINATION LEVEL, µg/cm2 AD H ES IO N, P SI UPPER CONF. LIMIT LOWER CONF. LIMIT AVERAGE ZINCALUMINUM Figure 38. Average tensile adhesion and confidence limits for zinc and aluminum TSMCs on chloride-contaminated substrates (1 psi = 6.89 KPa).

38 Figure 39. Cyclic (alternate) immersion panels with circular holidays after 6 months in test (zinc TSMC on left and aluminum TSMC on right). Figure 40. Cyclic (alternate) immersion panels with scribes after 6 months test (zinc TSMC on left and aluminum TSMC on right).

39 CHAPTER 3 INTERPRETATION, APPRAISAL, APPLICATION The research study provided several important facts con- cerning surface preparation and application of TSMCs. Many of these confirmed existing guidelines, but others suggested future research that might lead to improvements in TSMC performance. INTERPRETATION AND APPRAISAL Surface Preparation The use of 100-percent grit provides better adhesion than does 100-percent shot. Using a 100-percent grit abrasive also provides better adhesion than either of the shot/grit mixtures tested in this study. Shot/grit mixtures did provide better adhe- sion than 100-percent shot and might provide adequate corro- sion performance. Shot/grit mixtures are sometimes used to improve equipment life because the shot is not as aggressive toward the blasting equipment. However, these findings show that, in order to improve coating adhesion, shot or shot/grit mixtures can be used for initial cleaning, and 100-percent grit should be used for final surface preparation. The test results also show that not all 100-percent grit- prepared surfaces are the same and that improvements in coat- ing adhesion can be achieved with improved angularity in the surface profile. This can be achieved through the use of fine angular grit. Measuring angularity can be performed in the field using a profilometer; however, interpretation of the data can be a problem. This study found correlation between pro- filometer measurements using a field-friendly instrument of RPC (peak count) and RQ (root mean square deviation) and adhesion; however, other research in the literature has not. Research is suggested to study the role of grit size and shape on surface profile and coating performance. Better definition of the values of RPC and RQ should be researched. Mean- while, an indirect method of ensuring an angular profile is suggested using grit classified as very angular, angular, and subangular with respect to an American Geological Society grading system. Zinc TSMC should be considered for areas where salt con- tamination is present because of its relative insensitivity to salts. Where aluminum must be used, the surface preparation should include provisions for thorough washing of the sur- face to remove chlorides. Application The study found no differences among surface profile, adhesion, and performance of coatings applied over steel grades with differing hardness. Areas with extreme differ- ences in hardness, such as flame-cut edges, however, still require special attention in order to achieve satisfactory coat- ing performance. The study also found no differences in the performance of TSMCs when they were applied to carbon steel and HSLA steel. Even if surface preparation and coating application have been done properly, TSMC deterioration can occur at sharp edges and defects. The study confirmed that removing the sharpness of edges by slight curvature or grinding provides better coating coverage and adhesion. Although TSMCs are capable of protecting the substrate at narrow defects because of their ability to provide cathodic protection to the steel, larger defects present a problem. Coating defects larger than relatively narrow scratches should be repaired. LONG-TERM IMPLEMENTATION PLAN The ultimate goal of this program is to have a guide to TSMCs adopted by AASHTO. The keys to effective imple- mentation are (1) identification of the user community, (2) reports demonstrating and advocating the technical and cost benefits of this work, and (3) effective report and data distribution. The probable user community for the project is large. At a minimum, it extends to architects/engineers involved in bridge design, ferry terminal design, and DOT, FHWA, and transportation-authority engineers at headquarters, regional, or divisional levels. The user community also includes indus- try consultants and equipment manufacturers. The biggest impediment to implementation will be the higher cost of the TSMC materials in comparison with more traditional coatings. People will, at first, only see the increased material and application cost. The user community has to understand that the cost benefits of TSMC materials outweigh the increased initial costs. They also need to understand that the cost of the coating materials and application are not as sig- nificant as costs such as mobilization, containment, waste removal, and temporary removal of the structure from service for any repair work. Studies have shown that TSMCs do not

have to be replaced as often as liquid-applied coating. This can make them more economical to use. This research includes • Research conducted by the U.S. Army Corps of Engi- neers; • Research conducted by Rosbrook et al., Bhursari and Mitchener, Bland, Kain and Young, Kuroda and Take- moto, Tsourous, Kogler et al., and the Platt Brothers and Company (11, 14, 43–48); • The observations of the coatings at the North Carolina DOT test facility at Ocracoke Island, North Carolina, reported in this study (discussed in Chapter 2); and 40 • The test panels in continuous exposure at Corrpro’s Sea Isle City, New Jersey, test facility, reported on in this study (discussed in Chapter 2). It is recommended that the guide to TSMCs and associated articles on the benefits of TSMCs be presented in periodicals such as Roads and Bridges, Journal of Protective Coatings and Linings, Materials Performance, and at the TRB annual conference. It is further recommended that the Tri-Society (AWS/NACE/SSPC) Thermal Spray Committee on Corro- sion Protection of Steel be addressed to assist in the dissem- ination of the guide.

41 CHAPTER 4 CONCLUSIONS AND SUGGESTED RESEARCH CONCLUSIONS The results of the laboratory testing indicate the conclu- sions listed below. 1. The Effect of Sealers 1.1. The use of sealers has no detrimental effect on TSMCs and might actually improve the adhesion properties as measured by the tensile adhesion, U-bend, and impact tests. 1.2. Sealers appear to improve the performance of zinc TSMC, but do not appear to improve the performance of aluminum TSMC in the corrosion tests to date. 1.3. Based on the falling weight impact tests, the use of a sealer improves the impact resistance of the TSMC. 2. The Effect of Abrasive Mixes 2.1. Based on tensile adhesion and disbondment tests, 100-percent grit abrasive results in significantly better adhesion than does 100-percent shot. Also, 100-percent grit provides better adhesion than do either of the two shot/grit mixtures tested in this study; however, the shot/grit ratios used might pro- vide acceptable performance based on the corrosion tests completed to date. At this point, the TSMC Guide should specify the use of 100-percent grit as the optimum surface preparation finish. 2.2. The zinc TSMC showed better corrosion perfor- mance with 100-percent grit and the 70-/30-percent shot/grit mixture than with 100-percent shot or the 33-/67-percent shot/grit mixture. 2.3. The aluminum TSMC appeared to be insensitive to the abrasive mixes tested in this study based on the 12-month corrosion tests. 3. Angularity Measurements 3.1. A simple field-friendly measurement technique for angularity was found in this study. Measurements using a surface profile gauge that measures RPC and RQ showed that high values of RPC and low values of RQ provided higher tensile adhesion than low RPC and high RQ values. Further work is recommended to determine the optimum values of RPC and RQ. 3.2. Until the critical values of RPC and RQ can be defined, angularity should be defined by a surface compara- tor chart such as the chart showing abrasive grit shapes that was published in the Journal of Protec- tive Coatings and Linings in 1994 (38). Acceptable grit shapes, as determined under 25-power magnifi- cation and the standard chart, should be “very angu- lar,” “angular,” and “subangular.” 4. Application Parameters 4.1. Increased gun-to-surface distance decreases the adhe- sion of aluminum, but does not affect the adhesion of the zinc or zinc/aluminum coatings. The angle of the gun to the work surface did not affect the adhe- sion of any of the TSMCs tested at the angles used in this study. 4.2. The corrosion tests indicate that aluminum TSMC is insensitive to the application parameters tested in this study. 4.3. The corrosion tests indicate that the zinc TSMC is sensitive to the gun-to-workpiece angle, showing lower performance at an angle of 45 degrees. 5. Steel Hardness 5.1. Similar surface profiles (as measured by depth) and adhesion values for aluminum and zinc TSMCs were observed on the A36 and Grade 50 steel panels. 5.2. Both zinc and aluminum thermally sprayed coatings applied to the A36 and Grade 50 steels are perform- ing similarly to date. 6. Carbon Steel and HSLA Steel Aluminum, zinc, and zinc/aluminum thermally sprayed coat- ings applied over carbon steel and HSLA steel showed no differences in performance in previously conducted studies and in galvanic studies conducted in this research.

7. Edge Geometry 7.1. A smoother edge promotes more uniform coating coverage at the edge. 7.2. No differences in corrosion performance caused by edge geometry have been observed to date. 8. Defects Small narrow defects in the TSMC where the substrate has been exposed are protected by the galvanic behavior of the TSMC. However, the TSMC cannot provide complete cathodic protection to larger holidays. 9. Chloride Contamination 9.1. Aluminum TSMC is sensitive to chloride contami- nation on the metal surface, showing loss of adhe- sion at even the lowest level of contamination used (5 µg/cm2). On the basis of the adhesion results, zinc TSMC was insensitive to chloride contamination up to the 10 µg/cm2 used in this study. 42 9.2. Aluminum is more tolerant to chloride contamina- tion than zinc TSMC in corrosion tests, showing bet- ter overall corrosion performance, but it has more tendency to blister. 9.3. The presence of defects has not affected the perfor- mance of the coatings on contaminated panels to date. SUGGESTED RESEARCH 1. Initiate a study to examine the effects of grit angularity on RPC, RQ, adhesion, and performance of TSMCs; to define acceptable limits of angularity; and to establish a standard for angularity. 2. Continue to monitor the test panels currently in immer- sion and cyclic immersion testing at Corrpro’s Ocean City facility. The testing should be continued until a clear difference is observed between the panels pre- pared by different processes, or for at least 5 years. A report should be prepared at the end of that period, and changes should be made to the guide to TSMCs as appropriate.

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Bardal, E. “The Effect of Surface Preparation on the Adhesion of Arc and Flame-Sprayed Aluminum and Zinc Coatings to Mild Steel.” Norwegian Institute of Technology, University of Trondheim, Trondheim, Norway. 28. Call, T., and R. A. Sulit. “Protecting the Nation’s Infrastructure with Thermal-Sprayed Coatings.” Presented at AWS Interna- tional Welding Exposition, Houston, n.d. 29. Chandler, K. A. Marine and Offshore Corrosion. Butterworth, London, 1985. 30. Perkins, R. A. Metallized Coatings for Corrosion Control of Naval Ship Structures and Components (Report NMAB-409). Committee on Thermal Spray Coatings for Corrosion Control, National Materials Advisory Board, National Research Council, National Academy Press, Washington, D.C., February 1983. 31. Escalante, E., W. P. Iverson, W. F. Gerhold, B. T. Sanderson and R. L. Alumbaugh. “Corrosion and Protection of Steel Piles in a Natural Seawater Environment.” Institution for Materials Research, National Bureau of Standards, June, 1977. 32. 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44 35. Padavich, J. F. “How to Access Proper Surface Preparation.” Journal of Protective Coatings and Linings, Vol. 2, No. 1, Jan- uary 1985, pp. 22–28. 36. Personal communication with Hugh Roper, Pan Abrasive, Inc. 37. Beitelman, A. D. Recycled Steel Abrasive Grit. ERDC/CERL TR-01-37. U.S. Army Corps of Engineers, August 2001. 38. Hansink, J. D. “Maintenance Tips.” Journal of Protective Coat- ings and Linings, Vol. 11, No. 3, March 1994, p. 66, Figure 1. 39. Beitelman, A. D., and W. Corbett. “Evaluation of Surface Preparation and Application Parameters for Arc-Sprayed Metal Coatings.” U.S. Army Corps of Engineers, CERL, ERDC/ CERL TR-01-53, July 2001. NTIS ADA401295. 40. Lewis, C. F. “Processing Makes the Difference in Thermal Spray Coatings.” Materials Engineering, August 1988. 41. LaQue, F. L. Marine Corrosion, Causes and Prevention. John Wiley and Sons, New York, 1975. 42. Appleman, B. R. “Advances in Technology and Standards for Mitigating the Effects of Soluble Salts.” Journal of Protective Coatings and Linings, May 2002, pp. 42–47. 43. Bland, J. “Corrosion Testing of Flame-Sprayed Coated Steel— 19 Year Report.” American Welding Society, Miami, 1974. 44. Kain, R. M., and W. T. Young. Corrosion Testing in Natural Waters (2nd Volume). ASTM Report No. STP 1300, West Conshohocken, Pennsylvania, 1997. 45. Kuroda, S., and M. Takemoto. “Ten Year Interim Report of Thermal Sprayed Zn, Al and Zn-Al Coatings Exposed to Marine Corrosion by Japan Association of Corrosion Control.” Presented at the International Thermal Spray Conference, Montreal, 2000. 46. Tsourous, A. “The Restoration of the Historic Trenton Non- Toll Bridge Using Field Applied Thermal Spray Coatings.” Presented at SSPC International Conference, 1998. 47. Kogler, R. A., J. P. Ault, and C. L. Farschon. “Environmentally Acceptable Materials for the Corrosion Protection of Steel Bridges.” FHWA-RD-96-058. FHWA, January, 1997. 48. “Thermal Spraying with Zinc and Zinc/Aluminum Alloy Wire.” Metallize (quarterly newsletter). The Platt Brothers and Com- pany, 1996.

A-1 APPENDIX A LIST AND DESCRIPTION OF EXISTING TSMC SPECIFICATIONS Testing Specifications for Metallizing Steel Structures STANDARD TITLE SCOPE DATE COMMENTS ASTM C 633 Standard Test Method for Adhesive or Cohesive Strength of Flame- Sprayed Coatings Consists of coating one face of a substrate fixture and bonding this coating to the face of a loading fixture. This assembly of coating coating. Reapproved in 1993 ASTM D 4417 Standard Test Methods for Field Measurement of Surface Profile of Blast Cleaned Steel Discusses techniques to measure the profile of abrasive blast cleaned surfaces in the laboratory, field, or fabricating shop. Three methods are discussed: visual comparison, fine pointed probe, and reverse image Last revised in 1993 ASTM D 4541 Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers Evaluates adhesion by application of a concentric load and counter load to a single surface. Last revised in 1995 ASTM D 4285 Standard Test Method for Indicating Oil or Water in Compressed Air Used to determine the presence of oil or water in compressed air used for abrasive blast cleaning and coating application. Reapproved in 1993 Other types of contamination may require additional analytical techniques for detection. ASTM E 1920 Standard Guide for Metallographic Preparation of Thermal Sprayed Coatings This guide provides general recommendations for sectioning, cleaning, mounting, grinding, and polishing to reveal the microstructural features of thermal sprayed coatings and the substrate when examined microscopically. Last revised in 1997 This standard also references ASTM E 3 Practice of Preparation of Metallographic Specimens. ASTM F 1978- 99 Standard Test Method for Measuring Abrasion Resistance of Metallic Thermal Spray Coatings by Using the Taber Abraser This test method quantifies the abrasion resistance of thermal spray metallic coatings on flat metallic surfaces. This test uses the Taber abraser which causes wear to the coating surface by rolling and rubbing. Wear is quantified as cumulative mass loss. 1999 Developed by ASTM Subcommittee F04.15. ISO 14918 Thermal Spraying – Approval Testing of Thermal Sprayers This standard provides procedural instructions for approval testing of thermal sprayers. It defines essential requirements, test conditions and acceptance and certification requirements. October 1, 1998 ISO 14922-1 Thermal Spraying – Quality Requirements of Thermally Sprayed Structures Four parts discuss the quality requirements for thermal spraying for application by the manufacturers using the thermal spraying process for coating new parts, for repair and for maintenance. June 15, 1999 NACE Standard RP0287-95 Standard Recommended Practice, Field Measurement of Surface Profile of Abrasive Blast Cleaned Steel Surfaces Using a Replica Tape Provides a procedure to measure the surface profile of abrasive blast cleaned steel. A tape is utilized to replicate the surface profile. Originally prepared in 1987 and reaffirmed in 1991 and 1995 Limited to the surface profile defined in the standard (1.5 to 4.5 mils). SSPC-PA 2 Measurement of Dry Paint Thickness with Magnetic Gages This standard describes the procedures to measure the thickness of a dry film using commercially available magnetic gages. The procedures for calibration and measurements are described for pull-off gages and constant pressure probe gages. November 1, 1982; editorial changes August 1, 1991 and fixtures is subjected to a tensile load normal to the plane of the Materials/Equipment Specifications for Metallizing Steel Structures STANDARD TITLE SCOPE DATE COMMENTS ASTM A 690 Standard Specification for High-Strength Low-Alloy Steel H-Piles and Sheet Piling for Use in Marine Environments This specification covers high-strength low-alloy steel H- piles and sheet piling of structural quality for use in the construction of dock walls, sea walls, bulkheads, excavations and like applications in marine environments. Last revised in 1994 ASTM B 833 Specification for Zinc Wire for Thermal Spraying (Metallizing) This specification covers zinc wire used in depositing zinc coatings by oxy-fuel and electric arc thermal spray. 1997 Developed by ASTM Sub- committee B02.04. MIL-W-6712C Military Specification: Wire; Metallizing Specifies wire for use in deposition of metallic coatings by flame-spray. Last amended May 21, 1987 MIL-M-80141C Metallizing Outfits, Powder-Guns and Accessories April 30, 1987 Canceled without replacement, November 20, 1998. MIL-P-83348/1 Powders, Plasma Spray, Nickel Aluminum Powder Type I, Composition G, Class 2 October 25, 1984 Canceled without replacement December 27, 1990. AWS A3.0 Welding Terms and Definitions Including Terms for Brazing, Soldering, Thermal Spraying and Thermal Cutting Provides a glossary of terms used in the welding industry. May 23, 1994 ANSI approved.

A-2 Application and Surface Preparation Specifications for Metallizing Steel Structures STANDARD TITLE SCOPE DATE COMMENTS ANSI/AWS C2.23-XX Guide for Corrosion Protection of Steel with Metallic Thermal Spray Coatings of Aluminum, Zinc, Their Alloys and Composites Specifies required equipment, application procedures and in- process quality control checkpoints. This paper discusses procedures and equipment for abrasive blasting, coating application and sealer application. Working Draft #2, February 25, 1999 SSPC/NACE/AWS Tri-Society Thermal Spray Committee for the Corrosion Protection of Steel. Last known C2B Tri-Society meeting was in April, 1999. BPS 677 Metallic Coatings — Protection of Iron and Steel Against Corrosion — Metal Spraying of Zinc and Aluminum Approved in 1990 This standard is not approved by ANSI or DoD. ISO 2063 Metallic Coatings – Protection of Iron and Steel Against Corrosion – Metal Spraying of Zinc, Aluminum and Alloys of these Materials This international standard defines the characteristic properties and specifies methods of test of coatings obtained by the spraying of zinc and aluminum and alloys based on these metals for the general purposes of corrosion protection. ISO 14920 Thermal Spraying – Spraying and Fusing of Self-Fluxing Alloys This standard covers thermal spraying of self fluxing alloys that are simultaneously or subsequently fused to create a homogeneous diffusion bonded coating. February 1, 1999 MIL-STD-2138A(SH) Metal Sprayed Coatings for Corrosion Protection Aboard Naval Ships (Metric) Specifies requirements for the use of metal sprayed aluminum coatings on naval ships. Last notice of change August 29, 1994 Due to excessive weight and hazards, zinc was eliminated as a metal sprayed coating material. SSPC CS 23.00 Specification for the Application of Thermal Spray Coatings (Metallizing) of Aluminum, Zinc and their Alloys and Composites for the Corrosion Protection of Steel Covers the requirements for thermal spray metallic coatings on steel substrates. June 1, 1991 Serves as a guide for preparing specifications for thermal spray applications. SSPC SP-1 Solvent Cleaning This specification covers the requirements for the solvent cleaning of steel surfaces. November 1, 1982 SSPC SP-5/NACE No. 1 White-Metal Blast Cleaning A white metal blast cleaned surface shall be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products and other foreign matter. September 15, 1994 SSPC SP-10/NACE No. 2 Near-White Blast Cleaning A near-white blast cleaned surface shall be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products and other foreign matter, except for staining. Staining shall be limited to no more than 5% of each unit area of surface. September 15, 1994 SSPC Vis 1-89 Visual Standard for Abrasive Blast Cleaned Steel Provides standard reference photographs illustrating four unpainted steel surfaces cleaned to white metal, near-white metal, commercial blast and brush-off blast finishes. Conforms with ASTM D 2200.

A-3 Foreign Standards for Metallizing Steel Structures STANDARD TITLE SCOPE DATE COMMENTS JIS H 8300 Zinc Spray Coating on Iron or Steel This Japanese Industrial Standard specifies zinc spray coating on iron or steel products with the object of prevention of corrosion. The standard discusses quality, testing and inspection. Japanese Industrial Standard JIS H 8301 1971 Aluminum Spray Coating on Iron or Steel This Japanese Industrial Standard specifies aluminum spray coating on iron or steel products with the objects of prevention of corrosion and high temperature oxidation. The standard discusses quality, testing and inspection. Japanese Industrial Standard EN 22063 Metallic and Other Inorganic Coatings – Thermal Spraying – Zinc, Aluminum and Their Alloys 12 pages provide information on thermal spraying of aluminum, zinc and their alloys. The standard discusses surface preparation, coating metal, thermal spraying and sealers. Adhesion test methods are located in an appendix. 1994 Has the status of a British Standard; supersedes BS 2569. BS 5493 Protective Coating of Iron and Steel Structures against Corrosion. Handling, Transport, Storage and Erection 114 pages provide a guide on how to specify a chosen protective system, how to ensure its correct application and how to maintain it. Does not include specific recommendations for ships, vehicles, offshore platforms, specialized chemical equipment, cladding materials, plastic coatings, cement mortar linings or weathering steels. British Standard SS-EN 1395 Thermal Spraying – Acceptance Inspection of Thermal Spraying Equipment This European standard specifies requirements for the acceptance inspection of thermal spraying equipment including plasma, arc and flame spraying plants used to produce high-quality sprayed coatings. The purpose of acceptance inspection as part of a quality assurance system for spraying equipment serves to provide proof that the equipment is suitable for producing sprayed coatings of uniform quality in particular to satisfy the requirements of this standard. March 1996 Swedish Standard SS-EN 1274 Thermal Spraying – Powders – Composition – Technical Supply Conditions This standard covers powders, which are currently applicable in thermal spraying on the basis of the physical and chemical properties. Properties and property determination of powders for thermal spraying include: • Sampling and sample splitting, • Chemical composition, • Particle size range, • Particle size distribution, • Manufacturing process and particle shape, June 1996 Swedish Standard • Apparent density, • Flow properties, • Microstructure, and • Determination of phases. Safety Standards for Metallizing Steel Structures STANDARD TITLE SCOPE DATE COMMENTS SSPC PA-3 A Guide to Safety in Coating Application This guide defines methods and practices which are most practical in maintaining safety during application of protective coatings on steel structures. Complete coverage of all aspects is not presented. The objective of this guide is to itemize basic actions. Section titles include coatings, solvents, airless sprayers, ladders, scaffolding, rigging, personnel protection, respirators, ventilation, and barricades. November 1, 1982; editorial changes July 1, 1995 AWS TS1 Recommended Safe Practices for Thermal Spraying AWS Thermal Spraying: Practice, Theory and Application. Chapter 11 of this book discusses the potential hazards associated with thermal spraying. May, 1993 OSHA 29 CFR 1910 Occupational Safety and Health Standards Part 1910 contains several subparts that discuss safety issues regarding hazardous materials, welding, cutting and brazing, electrical and toxic and hazardous substances, to name a few.

B-1 APPENDIX B LIST AND DESCRIPTION OF EXISTING TSMC GUIDES Surface Preparation STANDARD BLAST PROFILE BLAST FINISH BLAST ABRASIVE ANSI/AWS C2.23-XX SSPC SP-5/NACE No.1 (marine and immersion); SSPC SP-10/NACE No. 2 (other) 2.5-mil angular IAW ASTM 4417 (Method B - profile depth gauge or Method C - replica tape or both) Clean, dry and sharp angular abrasive Draft #2 ANSI/AWS C2.18-XX SSPC CS 23.00A-XX NACE TPC #XA SSPC SP-10 2.0- to 4.0-mil anchor tooth profile for TSMC thickness of 12 mils or less; measured with replica tape Clean, sharp, angular abrasive of suitable mesh size; steel grit, mineral slag or aluminum oxide EN 22063 Surface is to have a white metallic appearance and uniform texture According to specifications agreed upon by relevant parties Hematitic chilled iron grit, aluminum oxide grit or other (grit size of 0.5 to 1.5 mm) ISO 2063 Surface is to have a white metallic appearance and uniform texture Surface shall be verified with a reference surface Hematitic chilled cast iron grit, aluminum oxide grit or other (grit size of 0.5 to 1.5 mm) JIS H 8300 JIS H 8301 None specified None specified None specified MIL-STD-2138A(SH) SSPC SP-5 2.0- to 3.0-mil profile IAW ASTM 4417 (Method B or C) Aluminum oxide (16 to 30 mesh) or angular chilled iron (25 to 40 mesh) U.S. Army COE Manual EM 1110-2-3401 SSPC SP-5 2.0- to 3.0-mil profile, depending on TSMC material and thickness Hard, dense, angular blast media such as aluminum oxide, iron oxide and angular steel grit

B-2 TSMC Application STANDARD HOLDING PERIOD ENVIRONMENTAL CONDITIONS COATING THICKNESS SPRAY PARAMETERS ANSI/AWS C2.23-XX Typically within 6 hours of blasting, depending on environmental conditions 5°F above dew point Ref. AWS C2.18 below To be validated at each crew change with a bend test Draft #2 ANSI/AWS C2.18-XX SSPC CS 23.00A-XX NACE TPC #XA Typically within 6 hours of blasting, depending on environmental conditions 9°F above dew point For 10- to 20-year life in salt water immersion: Zinc – 14 to 16 mils Aluminum – 10 to 12 mils Zinc/Aluminum – 14 to 16 mils Several perpendicular overlapping passes EN 22063 Typically within 4 hours of blasting, depending on environmental conditions 5°F above dew point Varies Zinc – 2 to 10 mils Aluminum – 4 to 12 mils Zinc/Aluminum – 2 to 8 mils None specified ISO 2063 Shall not exceed 2 to 12 hours, depending on environmental conditions 5°F above dew point Varies Zinc – 6 to 14 mils Aluminum – 4 to 10 mils Zinc/Aluminum – at least 6 mils 2-ft square block pattern JIS H 8300 JIS H 8301 None specified None specified Varies Zinc – up to 12 mils Aluminum – up to 16 mils None specified MIL-STD-2138A(SH) Spraying must be started and completed within 4 and 6 hours, respectively 10°F dew point spread 10 to 15 mils Angle of spray stream shall be close to 90° and never less than 45° U.S. Army COE Manual EM 1110-2-3401 Within 4 hours of blasting At least 5°F above the dew point Aluminum – 10 mils for seawater Zinc/Aluminum – 6 to 16 mils for fresh water Block pattern measuring 24 in. on a side

B-3 TSMC QA Procedures STANDARD FINISH POROSITY BEND TEST BOND TEST ANSI/AWS C2.23-XX Uniform without blisters, cracks, loose particles, or exposed steel when viewed at 10X Measurements may be used to qualify process and parameters Mentioned, but not defined ASTM D4541 – 1 test per 500 ft2 Zinc - >500 psi Aluminum - >1,000 psi 85/15 Zn/Al - >700 psi Al/Al2O3 - >1,000 psi Draft #2 ANSI/AWS C2.18-XX SSPC CS 23.00A-XX NACE TPC #XA No degraded TSC Used for qualifying spraying parameters; not normally used for process control Bend coupons and a mandrel with a suitable diameter (0.5 in. for TSC thickness of 7 to 12 mils) ASTM C 633 EN 22063 Uniform without blisters or bare patches and free from non-adhering metal and defects Not specified None specified Grid test and tensile test ISO 2063 Uniform without blisters, bare patches, non-adhering metal and defects Not specified None specified Grid test, adhesive tape and/or tensile test JIS H 8300 JIS H 8301 Free from blisters, cracks and other harmful defects Zinc – not specified Aluminum – IAW JIS H 8663 None specified Zinc – IAW JIS H 8661 Aluminum – IAW JIS H 8663 MIL-STD-2138A(SH) Uniform appearance with surface defects limited to small nodules not greater than 0.025 in. in height. The coating shall not contain blisters, cracks, chips, loosely adhering particles, oil, internal contaminants or pits exposing the undercoat or substrate Not specified No disbonding, delamination, or gross cracking shall occur due to bending Minimum bond strength of 1,500 psi and an average bond strength of 2,000 psi U.S. Army COE Manual EM 1110-2-3401 Smooth with no blisters, cracks, chips, loosely adhering particles, oil, pits exposing the substrate and nodules Not specified No cracks or minor cracking with no lifting of the coating Not specified

B-4 Sealers and Topcoats STANDARD WHEN TO SEAL RECOMMENDED MATERIALS ANSI/AWS C2.23-XX Acidic or alkaline environments, direct chemical attack, decorative finish is required, abrasion resistance is required, splash or immersion service is intended None specified Draft #2 ANSI/AWS C2.18-XX SSPC CS 23.00A-XX NACE TPC #XA Recommended Wash primers (0.3 to 0.5 mils) or sealers (1.5 mils) EN 22063 Not specified Natural sealing (by oxidation), chemical conversion (phosphating, reactive painting, etc.) or application of a paint system ISO 2063 Aggressive environments, such as industrial or marine PVB primers or paints with a single vinyl component; paints based on chlorinated rubber or epoxy systems JIS H 8300 JIS H 8301 Not specified None specified MIL-STD-2138A(SH) Not specified High temperature: heat resistant aluminum paint IAW TT-P-28 or equivalent seal coat Low temperature: MIL-P-24441 Polyester powder U.S. Army COE Manual EM 1110-2-3401 Recommended to fill porosity Coal tar epoxy, vinyl

Maintenance and Repair STANDARD SURFACE PREP TSC/SEALER APPLICATION TOUCH-UP ANSI/AWS C2.23-XX Not specified Inspect and maintain on a periodic basis, before maintenance repair and recoating is required Not specified Draft #2 ANSI/AWS C2.18-XX SSPC CS 23.00A-XX NACE TPC #XA Solvent clean; scrape off loosely adherent paint; hand brush, abrasive brush blast, power tool and abrasive blast; feather and lightly abrade As specified Spray can degreasing and spray can painting may be used for temporary repairs EN 22063 Not specified Not specified Not specified ISO 2063 Not specified Not specified Not specified JIS H 8300 JIS H 8301 Not specified Not specified Not specified MIL-STD-2138A(SH) Solvent clean; scrape, brush, blast, abrade – depending on level of damage As specified Paint coating may be replaced when TSC facilities are unavailable U.S. Army COE Manual EM 1110-2-3401 SSPC SP-10 Same as original application Repair with TSC, sealer, and paint as required B-5

C-1 APPENDIX C LITERATURE REVIEW REFERENCES AND SUMMARIES* No. References Comments 1 R. Avery, “Application of Thermal Sprayed Coatings in a Shop Environment – Some Practical Considerations,” SSPC International Conference, 1995. This paper discusses the advantages of thermal spray coatings in comparison with conventional air dry coatings systems. Some of these advantages include resistance to mechanical damage, provisions for barrier and sacrificial protection, low VOC emissions, and rapid turnaround. However, the author cautions that quality control, surface preparation, and operator training are necessary to provide superior long-term performance. Compared with air dry coatings, application of TSMCs is more cost competitive with respect to labor, material and schedule costs. 2 J. C. Bailey, “Corrosion Protection of Welded Steel Structures by Metal Spraying,” Metal Construction , 1983. This paper provides a general overview of the use of thermal spray coatings (zinc and aluminum) and sealers on steel. In waters where carbonate hardness is high, zinc is generally recommended. In waters where chloride content is high, aluminum is the recommended coating. In comparing combustion spraying versus electric arc spraying, the author states that the latter provides application at higher deposition rates, hotter particles and higher coating adhesion strengths. The author notes that since the corrosion product of zinc coatings is often readily removed, they benefit greatly from the use of a sealer. The corrosion products of aluminum coatings, on the other hand, are generally more corrosion resistant and adherent and, thus, benefit less so than zinc coatings from the application of a sealer. Recommended sealers include vinyl chloride/acetate copolymers, phenolic resins, silicone modified alkyds, silicone resins or polymers, and, for higher temperatures, aluminum pigmented silicone resins. 3 J. C. Bailey, F. C. Porter, and M. Round, “Metal Spraying of Zinc and Aluminum in the United Kingdom.” This paper discusses metal spraying of zinc and aluminum on bridges in the U.K. The authors conclude that zinc is preferable in alkaline conditions while aluminum is preferable in slightly acidic conditions and at high temperatures. 4 E. Bardal, “The Effect of Surface Preparation on the Adhesion of Arc and Flame-Sprayed Aluminum and Zinc Coatings to Mild Steel,” Norwegian Institute of Technology, University of Trondheim, Trondheim, Norway. This paper provides significant experimental data on the relationship between adhesion and surface profile: • Arc spraying of aluminum provides about 3x the bond strength to a steel substrate vs. flame spraying of zinc or aluminum, or arc spraying of zinc. Grit type also makes a large difference, with angular iron grit preferred over copper slag or silica sand. • This work was for low thickness coatings, 0.15 to 0.25 mm (9 mils). • Adhesion was found to increase with measured reflectivity, as compared to a standard light gray tile. This also correlated to a degree with improving from a Sa 2 to 2 to a Sa 3 standard of cleanliness. • The paper also shows that cleanliness is not the only factor. Adhesion values also increase with Ra x n where Ra is the center-line average of roughness times the number of peaks, and also with an electrochemically determined value of total surface area. Ra is defined by (1/L)* integral (o to L) of y dx. N is the number of peaks in the profile length. The electrochemical principal is based on the assumption that Rp is a material constant in a passivating solution, thus differences in Rp will be related to different surface areas in contact with the electrolyte. Rp values are compared on blasted steel substrates vs. polished surfaces of the same material. 5 V. Begon, J. Baudoin, and O. Dugne, “Optimization of the Characterization of Thermal Spray Coatings,” International Thermal Spray Conference, 2000. This paper discusses the metallographic process, describing it as the primary way to evaluate thermally sprayed coatings. The management and organization of a metallographic process is of prime importance to keep the process both repeatable and expedient. The paper defines a complete method for metallographic preparation based on a pragmatic approach. 6 Alfred D. Beitelman, “Evaluation of Surface Preparation and Application Parameters for Arc-Sprayed Metal Coatings,” USACERL Technical Report 99/40, April 1999. The U.S. Army Corps of Engineers uses 85-15 zinc aluminum alloy arc-sprayed coatings on hydraulic structures exposed to corrosive environments. Premature failure of these coatings has been attributed to poor surface preparation and application procedures. This study evaluated various materials used for metallizing, specifically the effects of surface preparation and application parameters on adhesion, cavitation, erosion, porosity, and oxide content. 7 Thomas Bernecki, “Final Report to U.S. Army-CERL: Evaluation of Two-Wire Electric Arc Systems,” February 26, 1996. This program evaluated the suitability of seven two-wire arc-spray systems to apply coatings of zinc, aluminum, 85-15 Zn-Al and 90-10 Al-Al2O3. The authors found that only three of the seven units tested were capable of continuously applying 85-15 Zn-Al. The average adhesion values, performed in accordance with ASTM D4541-93, for the combustion wire coatings of zinc, 85-15 Zn-Al, aluminum, and 90-10 Al-Al203 were 200, 435, 200, and 400 psi, respectively. The authors discuss some potential factors that may affect adhesion: • Unlike combustion, wire arc has no open flame to remove moisture and preheat the surface of the substrate. This may be factor in applications involving structures in water. • ASTM C633 is based on the measurement of normal forces. The presence and magnitude of a surface profile may affect the accuracy of the measurement. Also the porosity at the surface could also affect measured adhesion values. • Power settings define initial particle size and velocity. Stand-off distance can affect final impact velocities. Low velocities and/or large particles can result in lower temperature on impact, thereby affecting the splatting characteristics of the coating. 8 M. Bhursari and R. Mitchener, “Ski- Lift Maintenance: Wire Arc Spray vs. Galvanizing,” SSPC International Conference, 1998. This paper reviews the use of wire arc spray zinc vs. galvanizing on ski lifts. The authors discuss a case study in which painted lifts required repainting every 3 years, hot dipped lifts showed signs of corrosion in fewer than 5 years and thermal sprayed ski lifts exhibited no corrosion after 5 years. It was estimated that the wire arc-spray zinc coating, depending upon the thickness, would have a life expectancy of 20 years with minimal maintenance. The authors concluded that thermal spray coatings were more resistant to abrasion and wear than thin galvanized coatings. 9 M. M. Bhusari and R. A. Sulit, “Standards for the Thermal Spray Industry,” International Thermal Spray Conference, 2000. This paper provides a brief compilation of information on thermal spray standards set by various professional societies, including American Society for Testing and Measurement (ASTM), American Welding Society, American Water Works Association (AWWA), International Association of Corrosion Engineers (NACE), and Society of Protective Coatings (SSPC). These efforts have the ultimate objective of making the coating system performance more reliable and predictive. * References and Summaries not verified by TRB.

C-2 No. References Comments 10 J. Bland, “Corrosion Testing of Flame- Sprayed Coated Steel – 19 Year Report,” American Welding Society, Miami 1974. This report presents the results of a 19-year study of the corrosion protection afforded by wire-flame-sprayed aluminum and zinc coatings applied to low carbon steel. The program was initiated in July, 1950 by the Committee on Metallizing (now the Committee on Thermal Spraying) of the American Welding Society. The first panels were exposed in January, 1953. This report presents the results of an inspection of the flame-sprayed coated steel panels made after all panels had been exposed for 19 years. Aluminum-sprayed coatings 0.003 in. to 0.006 in. (0.08 mm to 0.15 mm) thick, both sealed and unsealed, gave complete base metal protection from corrosion in sea water and also in severe marine and industrial atmospheres. Where aluminum coatings showed damage such as chips or scrapes, corrosion did not progress, suggesting the occurrence of galvanic protection. The use of flame-sprayed aluminum and zinc coatings is recommended as a means to extend the life of such iron and steel structures as bridges, highway or street light poles, marine piers or pilings, ship hulls, storage tanks, industrial structures, etc. Corrosion is thereby combated, and the natural resources needed in the manufacture of iron and steel are conserved. 11 P. E. Bonner, “The Corrosion of Zinc, Zinc Alloy and Aluminum Coatings in the Atmosphere.” This paper discusses an exposure test of mild steel panels coated with wire-sprayed aluminum, powder-sprayed aluminum, wire-sprayed zinc, powder-sprayed zinc, hot-dipped aluminum, hot-dipped zinc, powder-sprayed 65 w/o Zn-35 w/o Al and electrodeposited 60 w/o Zn-40 w/o Fe. The five exposure sites used were located in rural, marine, and industrial environments. Metallographic examination revealed that the powder-sprayed coatings of aluminum and zinc were significantly more porous and less uniform than the wire-sprayed coatings. The powder-sprayed 65 w/o Zin-35 w/o Al coating was the least uniform of the sprayed-metal coatings, being of variable quality and somewhat discontinuous. After 6 months of exposure, the zinc-aluminum alloy coatings at all sites were in excellent condition and showed little corrosion product. Even after 2 years, only a few white areas of corrosion product were visible on some of the Zn-Al specimens. The paper goes on to discuss metallographic examinations of the coatings following these exposure tests. Pores were observed in the sprayed aluminum coatings where corrosion product was visible. A few pores were also observed in the sprayed zinc coatings, but with little or no corrosion product. Very few corrosion product filled pores were observed in the zinc-aluminum alloy coatings; however, some corrosion product was visible in some of the surface valleys when exposed to the more aggressive environments. 12 J. M. Brodar, “Blundering Towards Success with Metal Spray,” SSPC International Conference, 1995. This paper discusses case histories involving zinc thermal spray coatings. The author discusses advantages of TSMCs over paint type coatings, including no cure time; durability; no VOC; and a single coating method for immersion, atmospheric, and alternating wet and dry exposures. The author emphasizes the need for a high zinc-to-steel surface area ratio – in excess of 100,000:1 for freshwater immersion. 13 T. Call and R. A. Sulit, “Protecting the Nation’s Infrastructure with Thermal- Sprayed Coatings,” AWS International Welding Exposition. This paper summarizes some metallizing applications for the maintenance and repair of the infrastructure and provides a general overview of metallizing technology. The authors provide data on aluminum and zinc spray rates and coverage of arc-spray machines, a comparison of vinyl and zinc metallized coating life cycle cost (LCC) to include maintenance interval, current cost and so forth, and applications. Thermal sprayed aluminum and zinc provide the long-term corrosion control coatings. However, its initial application is usually more expensive than painting or galvanizing if thermal spraying (metallizing) is not integrated into the design and fabrication phases of new construction and repair projects. Aluminum and zinc metallized coatings are tough enough to withstand fabrication, transportation, and assembly operations. The improved capabilities and productivity of metallizing equipment for aluminum and zinc spraying are a major factor in their current cost competitiveness. The net result is that the costs of metallizing, paint, and galvanizing are getting closer every day. Even though the initial application cost of metallizing may be higher, the life cycle cost (LCC) and average equivalent annual costs are lower than paint coating systems. Metallizing LCCs, when properly engineered into the construction schedule, are equal to or less than paint coating LCCs. 14 K. A. Chandler, Marine and Offshore Corrosion, 1985. This book discusses corrosion and its control in marine environments. Topics discussed include forms of corrosion, material selection, coatings (paint and metallic), and steel pilings (although no discussion of metallic coatings on steel pilings). 15 W. Cochran, “Thermally Sprayed Aluminum Coatings on Steel,” Metal Progress, December 1982. This is a brief technical paper outlining the performance features of thermal spray applied aluminum coatings. Pertinent issues from this paper include the following: ∞ Coatings are applied to white metal substrates at 3–7 mils. Sealers are useful for cosmetic concerns, primarily to reduce dirt build-up. ∞ TSA coatings have been used in freshwater supply systems by a Texas utility for over 25 years. 16 Committee on Thermal Spray Coatings for Corrosion Control, “Metallized Coatings for Corrosion Control of Naval Ship Structures and Components, National Materials Advisory Board,” National Academy of Sciences, Washington, D.C., Report NMAB-409, February 1983. This is a comprehensive document which attempts primarily to review the U.S. Navy’s approach to the use of metallizing for corrosion control on Navy ships. The report does provide several major conclusions that seem meaningful with respect to the subject contract. • TSA coatings are known to be excellent corrosion control coatings for below-deck applications. However these coatings perform inconsistently on the weather deck. This is attributed to the lack of consistent application and quality control, which is especially evident in the more harsh environments. • Long-term performance data for TSA materials are based on coatings applied using best practices with extensive QA. It is not clear that the same level of QA is achieved in production applications. The report notes that there are not good NDT techniques available for finding critical defects such as excessive porosity, bond-separation, local coating penetrations, and excessive oxide inclusions. This is where future research should focus. • Risk factors can be mitigated by the use of a good seal coat. These are especially good at mitigating porosity. • The report suggests that TS pure aluminum is the best material for marine use. • The report suggests that humidity and surface cleanliness during application are key and need to be carefully specified and controlled during material application. • While it is clearly understood that low bond strength of TSM reduces performance, high bond strength does not guarantee good performance. There is no demonstrated minimum acceptable bond strength to guarantee performance. 17 T. Cunningham, “Quality Control of Thermal Spray Coatings for Effective Long-Term Performance,” SSPC International Conference, 1995. This paper discusses the benefits of thermal spray coatings, as well as quality control parameters, surface preparation, and application technique. The author concluded that while TSMCs have relatively high initial applied costs, they can provide economical long-term protection because of their long service life. Ideal coating characteristics include low porosity, a smooth surface, closely controlled DFT, and good adhesion. Quality control measurements should examine surface profile, film thickness, coating adhesion, and porosity.

C-3 No. References Comments 18 T. Cunningham and R. Avery, “Thermal Spray Aluminum for Corrosion Protection: Some Practical Experience in the Offshore Industry,” SSPC International Conference, 1998. This paper describes specific experiences with TSA on offshore components: • Wellhead support structures – SP-5, 12 mils TSA; little mechanical damage and a few blisters after 5 years of exposure. • Riser pipe – 8 to 10 mils TSA plus 0.6 mil conventional sealer (aluminum pigmented silicone or thinned epoxy; concern for overspray contamination in the weld bead). • Flotation chambers – Large structures (63 ft long) were coated with TSA applied by an automated process. • Sealers – traditionally either vinyl or aluminum pigmented silicone. Silicone exhibits superior performance, but is intended to be heat cured and is difficult to see. 19 T. Cunningham and R. Avery, “Sealer Coatings for Thermal Sprayed Aluminum in the Offshore Industry,” Materials Performance, January 2000. This paper summarizes findings on the performance of sealers on thermal spray coatings in offshore environments. Two thermal spray coating sealers are commonly used: aluminum-pigmented silicone (for high temperature applications) and vinyl etch primer. While the performance of the silicone sealer is reportedly better than that of vinyl, the aluminum silicone sealer is virtually invisible and requires heat cure. The lack of visibility causes difficulties for sprayers and inspectors. Epoxy sealers are available in any color, but there is occasionally an adverse reaction to the visual appearance of a thin sealer. The authors recommend that the two-pack epoxy be thinned, suggesting that more than half of the applied materials should be thinner. 20 K. DuPlissie, “Lessons Learned of the I-95 Thermal Spray Project in Connecticut,” Fifth World Congress on Coating Systems for Bridges and Steel Structures, 1997. The Research Division of the Connecticut Department of Transportation, sponsored by the FHWA, completed an 8- year project to evaluate the performance of zinc-based coatings for abrasive blast-cleaned structural steel. This study concluded that • In order for the coating to adhere to a steel surface, an anchor tooth (jagged) surface profile is necessary. • Performance of a bend test is important because 1. It enables adjustment of equipment to proper settings and proper techniques. 2. It allows the inspectors to test the blast and the coating prior to the actual application. 21 E. Escalante, W. P. Iverson, W. F. Gerhold, B. T. Sanderson, and R. L. Alumbaugh, “Corrosion and Protection of Steel Piles in a Natural Seawater Environment,” Institution for Materials Research, National Bureau of Standards, June, 1977. This paper discusses the results for the first 8 years of a long-term evaluation of various coating and cathodic protection systems. These systems include nonmetallic coatings, metallic pigmented coatings, nonmetallic coatings on metal-filled coatings, nonmetallic coatings on metallic coatings, metallic coatings and cathodic protection on bare and coated piles. With 25 systems tested, the following conclusions were made: • Above the high-water line was the most corrosive zone on bare steel samples, on the order of 8 to 12 mils per year; some pitting was visible above and below the mudline. • Coal tar epoxy coatings exhibited severe damage below the water line due to sand impingement; general attack and some undercutting were visible in the atmospheric zone; undercutting resistance was improved in the tidal zone, but general attack was still visible; coatings were susceptible to mechanical damage during installation. • Electrochemical measurements indicated that phenolic mastic and polyester glass flake exhibited good resistance to deterioration; the phenolic mastic was good over the entire surface of the pile after 6 years of exposure – little pitting in the erosion zone, maximum corrosion rate of 0.15 mpy just below the mean high-water line, moderate undercutting in the atmospheric zone with a maximum penetration of 1 in., some coating failure at the flange edge; the polyester glass flake, with an average coating thickness of 32 mils, exhibited minor pitting, little coating breakdown, difficult to remove coating by sandblasting, minor deterioration at the flange edges in the erosion zone, little damage in the atmospheric or splash zones, and undercutting of up to 1 in. in the atmospheric zone. • Polyvinylidene chloride, when compared with phenolic mastic and polyester glass flake, exhibited a significantly higher degree of deterioration – corrosion rate of 5 mpy in the erosion zone, average corrosion rate of 2.4 mpy over entire pile, considerable deterioration in the atmospheric zone, undercutting of up to 0.3 in. in the tidal zone and 2 in. below the mudline. • Aluminum pigmented coal tar epoxy exhibited high electrical resistivity, very little deterioration, some coating damage in the erosion zone with a corrosion rate of less than 0.1 mpy, minor pitting over most of the pile, less than 1.2 in. of undercutting and some rust staining in the atmospheric zone, 0.1 in. of undercutting in the tidal zone, no undercutting or coating deterioration below the mudline; the aluminum pigmented coal tar epoxy system with a 30% thinner coating thickness exhibited more damage overall, little deterioration at the flange but some deterioration and pitting 2 to 3 in. from the edge, average corrosion rate of 0.2 mpy over the entire pile, undercutting of 1.5 in. in the atmospheric zone and as much as 2 in. below the mudline, and minor coating damage in the tidal zone. • Nonmetallic coatings on metal-filled coatings were also tested; coal tar epoxy over zinc rich organic primer performed well, exhibited an average corrosion rate of 0.2 mpy, severe coating damage with undercutting of almost 2 in. in the atmospheric zone, minor undercutting in the tidal zone, negligible damage below the mudline; epoxy polyamide over zinc rich inorganic primer exhibited good resistance with an average corrosion rate of less than 0.1 mpy, some deterioration in the erosion zone, negligible damage below the mudline, good undercutting resistance in all zones with less than 0.5 in. in the atmospheric zone, some blistering below the mudline; coal tar epoxy over zinc rich inorganic primer exhibited good resistance to deterioration, no metal loss near the flange, minor pitting, undercutting of 0.6 in. in the atmospheric zone, minor undercutting in the tidal zone, no measurable undercutting below the mudline; vinyl over zinc rich inorganic primer exhibited general attack over the pile length with more attack in the erosion zone, an average corrosion rate of 0.2 mpy, undercutting of less than 0.5 in. with some edge deterioration in the atmospheric zone, undercutting of less than 0.1 in. but extensive general deterioration in the tidal zone, undercutting of less than 0.1 in. below the mudline; vinyl mastic over zinc rich inorganic primer exhibited an average corrosion rate of less than 0.25 mpy, little attack and undercutting of less than 0.1 in. in the atmospheric zone, general deterioration with undercutting of less than 0.1 in. in the tidal zone, and undercutting of 0.2 in. with some blistering below the mudline. • Nonmetallic coatings on metallic coatings: vinyl sealer over flame-sprayed aluminum exhibited an average corrosion rate of less than 0.05 mpy, a small amount of metal loss in the erosion zone, practically insignificant pitting, excellent corrosion resistance in the atmospheric zone, visible general coating failure and immeasurable undercutting in the tidal zone, some coating deterioration below the mudline; polyvinylidene chloride over flame- sprayed zinc developed a nonconducting film over time which gradually improved the coating performance, exhibited an average corrosion rate of less than 0.1 mpy, little and uniform metal loss, minor scattered pitting, minor damage in a few areas in the atmospheric zone, significant blistering of the topcoat (but the zinc coating still provided protection) in the tidal zone; vinyl-red lead over flame-sprayed zinc exhibited the most deterioration of the three systems with the topcoat beginning to fail during the first year of exposure followed by the gradual deterioration of the zinc (the total coating thickness of this system was only 50% of that of the polyvinylidene chloride over zinc flame spray).

C-4 similar piles without cathodic protection; in general, the anodes located below the mudline provided more protection than similar anodes above the mudline. 22 Karl P. Fischer, William H. Thomason, Trevor Rosbrook, and Jay Murali, “Performance of Thermal Sprayed Aluminum Coatings in the Splash Zone and for Riser Service,” NACE 1994. This paper discusses the performance of thermal sprayed aluminum after 8 years of service on offshore TLP risers and tethers. The authors believe that a 30-year service life is achievable with a 200 micron TSA coating with the use of specific sealer systems. The authors concluded that a silicone sealer adequately fills the pores of the TSA coating and prevents the formation of blistering. After 8 years of service, the TSA coating on the Hutton TLP production risers and tethers was in good condition. The splash zone area was indistinguishable from the remainder of the inspected components. 23 K. P. Fischer, W. H. Thomason, J. E. Finnegan, “Electrochemical Performance of Flame-Sprayed Aluminum Coatings on Steel in Seawater,” Materials Performance, September 1987. This paper studies the electrochemical behavior of flame-sprayed aluminum (FSA) coating in natural seawater. The authors concluded that FSA generally performs well in both the submerged and splash zone exposure, primarily as a very strong barrier-type coating. The free corrosion potential of the FSA coating in strongly flowing seawater was – 930 to –950 mV vs. Ag-AgCl at ambient temperature. The authors claim that the use of a silicone sealer paint on the FSA coating will increase the service life of the system. An FSA coating with silicon sealer paint will have some reduced anodic capabilities, yielding a current density output of 30 to 200 mA/m2 in a potential range of –950 to –850 mV. For FSA coating without sealer, the current output can be up to 500 mA/m2 in an initial exposure period. However, at a high constant current density, the aluminum coating will be consumed during a few months of exposure. 24 Brendan Fitzsimons, “Thermal Spray Metal Coatings for Corrosion Protection,” Corrosion Management, December 1995/January 1996. This article provides an introduction to the uses of thermal sprayed metal coatings as corrosion protection for steel, as an alternative to paint coatings. Arc spray, when compared with flame spray, has been shown to give faster output and superior adhesion. Flame spray may be favorable in areas that are difficult to access. Aluminum and aluminum alloys are used and an alloy with 5% magnesium is currently widely specified, although Fitzsimons is not convinced it provides the best protection offshore. Aluminum-5% magnesium is highly efficient for offshore platforms and ship topsides, where the anodic advantages of the metal are shown. Although experience has shown that sealers are of benefit on exposed aluminum coatings, areas not exposed to driving rain (e.g., undersides of platforms and bridges) may be better left unsealed to reduce the effect of “sweating” or condensation. Sprayed aluminum has been shown to be effective against corrosion under insulation, which might have become wet due to leakage of rainwater through the weather cover. Thermally sprayed aluminum works well on plant operating at elevated temperatures, coated with epoxy sealers for use up to 120°C and with a silicone aluminum sealer above that temperature. Fitzsimons also discusses the advantages and disadvantages (cathodic vs. anodic, cost, adhesion, etc.) of different coatings (aluminum, zinc, tin, lead, etc.). 25 M. Funahashi and W. T. Young, “Development of a New Sacrificial Cathodic Protection System for Steel Embedded in Concrete,” Report FHWA-RD-96-171, FHWA, Washington, DC, May 1997. This interim report studies aluminum and zinc alloys as anodes to cathodically protected steel embedded in concrete. Laboratory studies indicated that a series of aluminum-zinc-indium alloys outperformed both pure zinc and pure aluminum as anodes. zone, no undercutting or coating deterioration below the mudline; the aluminum pigmented coal tar epoxy system with a 30% thinner coating thickness exhibited more damage overall, little deterioration at the flange but some deterioration and pitting 2 to 3 in. from the edge, average corrosion rate of 0.2 mpy over the entire pile, undercutting of 1.5 in. in the atmospheric zone and as much as 2 in. below the mudline, and minor coating damage in the tidal zone. • Nonmetallic coatings on metal-filled coatings were also tested; coal tar epoxy over zinc rich organic primer performed well, exhibited an average corrosion rate of 0.2 mpy, severe coating damage with undercutting of almost 2 in. in the atmospheric zone, minor undercutting in the tidal zone, negligible damage below the mudline; epoxy polyamide over zinc rich inorganic primer exhibited good resistance with an average corrosion rate of less than 0.1 mpy, some deterioration in the erosion zone, negligible damage below the mudline, good undercutting resistance in all zones with less than 0.5 in. in the atmospheric zone, some blistering below the mudline; coal tar epoxy over zinc rich inorganic primer exhibited good resistance to deterioration, no metal loss near the flange, minor pitting, undercutting of 0.6 in. in the atmospheric zone, minor undercutting in the tidal zone, no measurable undercutting below the mudline; vinyl over zinc rich inorganic primer exhibited general attack over the pile length with more attack in the erosion zone, an average corrosion rate of 0.2 mpy, undercutting of less than 0.5 in. with some edge deterioration in the atmospheric zone, undercutting of less than 0.1 in. but extensive general deterioration in the tidal zone, undercutting of less than 0.1 in. below the mudline; vinyl mastic over zinc rich inorganic primer exhibited an average corrosion rate of less than 0.25 mpy, little attack and undercutting of less than 0.1 in. in the atmospheric zone, general deterioration with undercutting of less than 0.1 in. in the tidal zone, and undercutting of 0.2 in. with some blistering below the mudline. • Nonmetallic coatings on metallic coatings: vinyl sealer over flame-sprayed aluminum exhibited an average corrosion rate of less than 0.05 mpy, a small amount of metal loss in the erosion zone, practically insignificant pitting, excellent corrosion resistance in the atmospheric zone, visible general coating failure and immeasurable undercutting in the tidal zone, some coating deterioration below the mudline; polyvinylidene chloride over flame- sprayed zinc developed a nonconducting film over time which gradually improved the coating performance, exhibited an average corrosion rate of less than 0.1 mpy, little and uniform metal loss, minor scattered pitting, minor damage in a few areas in the atmospheric zone, significant blistering of the topcoat (but the zinc coating still provided protection) in the tidal zone; vinyl-red lead over flame-sprayed zinc exhibited the most deterioration of the three systems with the topcoat beginning to fail during the first year of exposure followed by the gradual deterioration of the zinc (the total coating thickness of this system was only 50% of that of the polyvinylidene chloride over zinc flame spray). • Metallic coatings: hot-dipped galvanized steel pile exhibited a decreasing corrosion current for the first 3 years of exposure followed by a steadily increasing corrosion current (approaching that of bare steel) for the next 5 years, exhibited an average corrosion rate of 0.15 mpy, significant corrosion in the erosion zone, some corrosion in the atmospheric zone, coating failure in the form of pits above the high-water line, pitting and undercutting in the tidal zone, thin and no coating below the mudline; flame-sprayed aluminum exhibited a steadily increasing corrosion current (approaching that of bare steel as the aluminun deteriorated), exhibited some metal loss in the erosion zone, virtually no pitting, minor corrosion damage in the atmospheric and tidal zones, and extensive coating damage below the mudline. • Cathodically protected steel piles: electrochemical measurements indicated corrosion rates much lower than No. References Comments

No. References Comments 26 P. O. Gartland and T. G. Eggen, “Cathodic and Anodic Properties of Thermal Sprayed Al- and Zn- Based Coatings in Seawater,” Corrosion 1990, Paper Number 367. This paper studies the performance of thermal spray (arc and flame spray) coatings of Al, AlMg, and ZnAl for 18 months in seawater. The arc-sprayed specimens exhibited better adhesion than the flame-sprayed specimens. The authors concluded the following: • Al and AlMg were acceptable barrier coatings in combination with a sacrificial anode system. ZnAl exhibited blistering at low potentials and high corrosion rates at higher potentials. • The use of a silicone sealer significantly improves the barrier properties of the thermal spray coatings. The corrosion rate at the free corrosion potential was reduced by a factor of two to three. At higher potentials, the corrosion rate is not affected. • Coating thickness and surface preparation had only a minor influence on coating properties. 27 N. D. Greene, R. P. Long, J. Badinter and P. R. Kambala, “Corrosion of Steel Piles,” Innovative Ideas for Controlling the Decaying Infrastructure, NACE Paper No. 95017, 1995. This paper discusses case histories of pile corrosion, as well as theoretical and experimental analyses. The authors concluded that pile corrosion is the result of macrocell activity along the pile surface. Different oxygen concentrations can lead to rapid localized corrosion. 28 Robert M. Kain and Walter T. Young, Corrosion Testing in Natural Waters (Second Volume), ASTM Rep. No. STP 1300, 1997. This publication contains papers presented at the Second Symposium on Corrosion Testing in Natural Waters in 1995 in Norfolk, Virginia. Some of the papers include: • Ashok Kumar, Vicki L. Van Blaricum, Alfred Beitelman, and Jeffrey H. Boy, “Twenty Year Field Study of the Performance of Coatings in Seawater.” Steel H piles were coated with various coatings including coal tar epoxy, polyurethane and flame-sprayed zinc and aluminum. Electrochemical techniques (polarization resistance and Tafel plots) were periodically utilized. Long-term coating evaluation showed that flame-sprayed aluminum with a topcoat sealer performed best at the cooler temperatures in Massachusetts waters (Buzzards Bay, Cape Cod) and polyester glass flake performed best in Florida waters (La Costa Island) • R. E. Melchers, “Modeling of Marine Corrosion of Steel Specimens.” This paper proposes a conceptual model for immersion corrosion, tidal corrosion, and atmospheric corrosion for steel under marine conditions. Diffusion and kinetic theory are utilized in the development of phenomenological modeling. 29 W. R. Kratochvil and E. Sampson, “High Output Arc Spraying – Wire and Equipment Selection,” SSPC International Conference, 1998. This paper discusses the deposition of two wire diameters (1/8” and 3/16”), three wire materials (Al, Zn/Al, and Zn) and two spray rates (rated at 300A and 450A). The authors concluded that 3/16” wire, when compared with 1/8”, exhibits higher deposition rates and deposits over 60% more material for Al, 32% more for Zn/Al, and 34% more for Zn. The stiffness of the thicker wire affects operator comfort, range of motion, and fatigue levels. 30 S. Kuroda and M. Takemoto, “Ten Year Interim Report of Thermal Sprayed Zn, Al and Zn-Al Coatings Exposed to Marine Corrosion by Japan Association of Corrosion Control,” International Thermal Spray Conference, 2000. The thermal spray committee of the Japan Association of Corrosion Control (JACC) has been conducting a corrosion test of thermal sprayed zinc, aluminum, and zinc-aluminum at a coastal area since 1985. Arc-spray and flame-spray coatings were applied to steel piping at varied thicknesses and subjected to various post-spray treatments. No significant changes were observed in the coating systems after 5 years of exposure. After 7 years, zinc coatings with and without sealing exhibited degradation in the immersion zone. However, the aluminum and zinc-aluminum coatings still exhibited excellent corrosion resistance. The test is scheduled to continue until 2001. 31 F. L. LaQue, Marine Corrosion Causes and Prevention, 1975. This book discusses the various mechanisms involved in marine corrosion. The author describes an experiment involving continuous and isolated specimens in seawater to demonstrate the effects of macrocell corrosion. 32 Eric S. Lieberman, Clive R. Clayton, and Herbert Herman, “Thermally- Sprayed Active Metal Coatings for Corrosion Protection in Marine Environments,” Final Report to Naval Sea Systems Command, January 1984. This paper evaluated flame and electric arc-sprayed coatings of zinc, aluminum, zinc-15 wt% aluminum and duplex layered coatings onto mild steel substrates. These systems were exposed to a variety of corrosive conditions in a 3.0 wt% sodium chloride solution and in natural sea water. The sprayed coatings were sealed with an epoxy polyamide to reduce surface porosity. Electrochemical, salt spray, immersion, and adhesion tests were utilized to evaluate the coating systems. The authors concluded that because of zinc’s strong electrochemical activity, zinc does not afford as long-lasting protection as does aluminum. Zinc-15 wt% aluminum, although electrochemically similar to zinc, provides barrier protection similar to aluminum, while still maintaining zinc’s degree of protection. The zinc-aluminum coatings exhibit strong corrosion protection, high adhesive strength, and a high coating density. A duplex-layered coating of aluminum sprayed onto zinc-coated steel proves to be effective in reducing crevice attack of the aluminum coating. Electric arc-sprayed deposits, when compared with flame-sprayed deposits, were less porous, exhibited higher adhesive strength and superior corrosion resistance. Studies on the microstructure of electric arc-sprayed coatings of different wire diameters revealed that as the wire diameter is decreased, a more dense coating will arise due to better atomization. 33 R. T. R. McGrann, J. Kim, J. R. Shandley, E. F. Rybicki, and N. G. Ingesten, “Characterization of Thermal Spray Coatings Used for Dimensional Restoration,” International Thermal Spray Conference, 2000. Thermal spray coatings are used for dimensional restoration of worn parts during aircraft overhaul. Residual stress, tensile bond strength, porosity, oxides, impurities, and hardness affect the performance of thermal sprayed parts. An understanding of the relation of these coating characteristics to process variables (material selection, spray process, spray angle, and coating thickness) is needed. The authors studied four nickel alloys applied by plasma spray and high velocity oxy-fuel (HVOF) using different spray angles and coating thickness ranges. The authors investigated how the thermal spray process variables affect the thermal spray characteristics. 34 C. G. Munger, Corrosion Prevention by Protective Coatings, NACE, 1984. This book discusses the use of protective coatings for corrosion control. One specific case that the book references is the use of galvanizing and inorganic zinc in tidal seawater conditions. The galvanized test panels exhibited significant pinpoint rust, while the inorganic zinc-coated panels exhibited no visible corrosion after 2 years of exposure. 35 P. Ostojic and C. Berndt, “The Variability in Strength of Thermally Sprayed Coatings,” National Thermal Spray Conference Proceedings, ASM International, September 1987, p. 175. This paper shows the variation in tensile adhesion test data for TS coatings. The authors conclude that adhesion values based on the average of several tests are meaningless. The data seem to fit a standard Weibull distribution, and thus such an analysis needs to be conducted to adequately characterize this critical QA parameter. 36 Timothy D. Race, “Evaluation of Seven Sealer Systems for Metallized Zinc and Aluminum Coatings in Fresh and Salt Waters,” Final Report for HQUSACE, September 1992. This study evaluated seven sealer systems for zinc and aluminum metallized coatings in fresh and salt waters. Conclusions: • For zinc in fresh and salt waters, recommend epoxy and epoxy with wash primer. • For aluminum in fresh water, recommend pigmented urethane or white pigmented vinyl. • For aluminum in salt water, none of the tested sealers performed adequately. C-5

C-6 No. References Comments 37 Tim Race, Vince Hock, and Al Beitelman, Performance of Selected Metallized Coatings and Sealers on Lock and Dam Facilities, August 1989. This paper evaluates metallized coating and sealer systems for highly abrasive environments. Four thermal spray materials were evaluated, including aluminum-bronze (89Cu, 10Al, 1Fe), stainless steel (18Cr, 8Ni), zinc-aluminum (85Zn, 15Al), and pure zinc. The authors concluded that coatings anodic to mild steel, such as 85-15 zinc-aluminum and pure zinc, are possible alternatives to conventional paint coatings for use in highly abrasive environments. However, a performance evaluation is required to establish the service lives of these materials. They also concluded that coatings cathodic to mild steel, such as aluminum-bronze and stainless steel, are not recommended for such environments. 38 F. S. Rogers, “Benefits and Technology Developed to Arc Spray 3/16 Inch (4.8 mm) Diameter Wires Used for Corrosion Protection of Steel,” International Thermal Spray Conference, 2000. This paper provides an overview of the variables that determine spray rate with the twin wire arc-spray process. A U.S. patent for spraying wire larger than 3.2 mm (1/8 inch) has resulted in surprising improvements in deposit efficiency and spray rates. The authors also discuss some other design improvements, such as • a new innovative nozzle system that atomizes and distributes the spray into a desirable spray pattern, • a new patented electrical design mastered arc starting by automatically gapping the wire at the end of each spray cycle, and • wire straighteners that prevent kinks and bends. 39 F. S. Rogers and W. Gajcak, “Cost and Effectiveness of TSC Zinc, Zinc/Aluminum and Aluminum Using High Deposition Low Energy Arc Spray Machines,” SSPC International Conference, 1997. This paper discusses the advantages of 3/16” wire feedstock over 1/8”. These advantages include higher spray rate at lower amperages, better deposit efficiency, higher quality, lower labor costs, lower material cost, lower equipment maintenance cost. 40 T. Rosbrook, W. H. Thomason, J. D. Byrd, “Flame Sprayed Aluminum Coatings Used on Subsea Components,” Materials Performance, September 1989. This article reviews the in-service performance of FSA on subsea components of the Hutton Tension Leg Platform in the North Sea. While some blistering was observed after 2 years in service, the rate of consumption was not excessive, and it was concluded that the coating would exceed the 20-year design life. The blisters were believed to be the result of inadequate sealing of the aluminum by the vinyl sealer. Although the silicone type sealer may not crosslink without a high temperature cure, it penetrates the porosity of the FSA and provides a good barrier to water penetration. The authors recommend the use of chilled iron grit (grade C17/24) to overcome the possibility of contamination from the use of aluminum oxide abrasives. 41 M. M. Salama and W. H. Thomason, “Evaluation of Aluminum Sprayed Coatings for Corrosion Protection of Offshore Structures,” Society of Petroleum Engineers, 1984. This paper discusses corrosion protection methods for offshore structural high-strength steel to avoid problems with fatigue and hydrogen embrittlement. 42 E. R. Sampson and P. Sahoo, “New Arc Wire Approvals for Aircraft Power Plant Overhaul,” International Thermal Spray Conference, 2000. The increasing use of arc-spray systems in the overhaul of aircraft engine components has created a demand for new wire approvals. This paper discusses some historical background of the arc-spray process, materials that are presently approved and those that have been submitted for approval. The paper discusses advances in arc-spray systems that make them suitable replacements for plasma spray and HVOF coatings. 43 Brian S. Schorr, Kevin J. Stein, and Arnold R. Marder, “Characterization of Thermal Spray Coatings,” Materials Characterization, 1999. This paper attempts to correlate analytical techniques to characterize the microstructures of thermal spray coatings to understand in-service properties. The authors focus on cermet thermal spray coatings and show the breakdown of carbides during spraying. This breakdown produces a mixture of oxides and various carbides. The authors also reference other papers that discuss metallographic preparation and routine analysis of thermal spray coatings to avoid erroneous porosity readings. 44 B. A. Shaw and P. J. Moran, “Characterization of the Corrosion Behavior of Zinc-Aluminum Thermal Spray Coatings,” DTNSRDC/SME- 84/107. This testing was designed to illustrate the marine performance of various thermal spray alloys. Pure zinc and aluminum were control materials. The Zinc-Aluminum alloys of interest were intended to be of nominal 85/15 (weight %) zinc-aluminum. These alloys were sprayed from either a pre-alloyed 85/15 mixture or via feeding controlled amounts of each material (a pseudo-alloy) during the thermal application. Key points include: • The 85/15 wt.% ratio provides for 32 vol.% of aluminum in the alloy. • The porosity levels in the pure aluminum coatings range from 5 to 15% vs. 5% for the zinc. The lower melting point for the zinc allowed for more material “flow” before freezing on the steel substrates. This higher liquid-time tends to reduce the material porosity. • There is a drastic difference in the material microstructure between the pseudo-alloy and the pre-alloyed materials. The average material grain size is drastically smaller with the pre-alloyed material. It consists of a fine dispersion of zinc-rich and aluminum-rich areas as opposed to the larger, distinct areas of zinc and aluminum in the pseudo- alloy. • For the pseudo-alloy, there were wide variations in local material content and little true alloying in the matrix. Wight percentage variations ranged from 85% zinc/15% aluminum to 40% zinc/60% aluminum. • All of the coatings stilled showed areas of imbedded grit and voids extending to the substrate—details that must be minimized in any thermal spray application. • In seawater immersion, after 6 months, the panels with pure zinc had significantly less fouling than those coated with pure aluminum. • At 6 months of seawater immersion, the pseudo-alloy showed areas of inter-coat blistering, not at the coating- substrate interface. This appeared to be attributed to attack of the zinc material and protection of the aluminum material. This would be in accordance with the expected material passivation behavior. Chloride was found to have permeated to these sites. • For the pre-alloyed materials, the coatings started as whitish-silver materials and turned a charcoal gray. These coatings also exhibited flaking and blistering. Blisters as large as 5 mm were noted. Again, the blisters were within the coating, not at the substrate. Corrosion product was noted within the blisters. In atmospheric exposure, 2 of 15 panels showed some flaking of the thermal coating. With both exposure conditions, the attack does seem to occur along oxide layers. • For the electrochemical testing, materials were applied to both PTFE and 1018 steel substrates. There was little difference in material performance as a result of the substrate. For the aluminum, the Ecorr values stabilized at – 800 mV ±50mV. For the zinc and the alloy materials, the potential was nominally in the range of –1.0 to –1.05 volts. All potentials are vs. SCE. Reported exposure periods are only 30 days. Anodic polarization data were obtained after 1-hour and 14-day immersion. After 14 days, the aluminum was found to be in a passive state. The zinc and zinc alloy materials were more active. Thus, at this time in the test, the aluminum would not be expected to provide much cathodic current vs. the zinc and zinc alloy materials.

C-7 No. References Comments • The report conclusions of note include the following: (1) the pseudo-alloy provided the best overall protection— on the basis of being able to provide current to bare steel areas at scribes, (2) the pre-alloyed 85:15 wire is not suitable for immersion service due to accelerated attack along the material oxide boundaries. 45 B. A. Shaw and P. J. Moran, “Characterization of the Corrosion Behavior of Zinc-Aluminum Thermal Spray Coatings,” Corrosion 85, Paper No. 212. This paper provides an evaluation of the corrosion behavior of zinc-15% aluminum pre-alloyed wire coating and zinc- aluminum pseudo alloy coating of approximately the same composition. This evaluation consisted of corrosion field exposures, electrochemical testing, and coating characterization (optical microscopy, scanning electron microscopy, electron probe microanalysis and X-ray diffraction). After 6 months of atmospheric and splash and spray exposure, the pseudo alloy coatings provided the better overall corrosion performance. Zinc-aluminum (and aluminum-zinc) coatings appear to be capable of combining the long-term protection provided by aluminum and the sacrificial protection provided by zinc. However, in order to obtain long-term protection, an alloy with a more coherent aluminum rich phase than the zinc-15% aluminum pre-alloyed wire and a more even distribution of phases than the pseudo alloy coating is needed. 46 H. D. Steffens and Dr. Ing, “Electrochemical Studies of Cathodic Protection Against Corrosion by Means of Sprayed Coatings.” This paper evaluates the electrochemical behavior of zinc and aluminum thermal spray coatings in seawater and sulfuric acid. Adhesion tests indicated that the adhesion of aluminum was twice that of zinc. The authors concluded that electric arc spraying, compared with flame spraying, of aluminum was more economically sound and led to better adhesion. 47 Robert A. Sulit, Ted Call, and Dave Hubert, Arc-Sprayed Aluminum Composite Nonskid Coatings for AM-2 Landing Mats, June 1993. This paper discusses the use of Duralcan 90/10 aluminum composite nonskid coating for AM-2 Mats which are interlocking aluminum extrusions. The aluminum composite is composed of 90 vol% Al + 10 vol% Al2O3 (8 to 10 microns in diameter). The authors concluded that the Duralcan 90/10 nonskid coating, when compared with existing epoxy nonskid coating systems, exhibited superior wear resistance and a 30% less 20-year life cycle cost. 48 R. A. Sulit, F. West, and S. L. Kullerd, “Wire Sprayed Aluminum Coating Services in a SIMA Corrosion-Control Shop,” National Thermal Spray Conference, September 1987. This paper discusses the installation and operation of Corrosion-Control (CC) Shops in Navy Shore Intermediate Maintenance Activities (SIMAs) to deliver wire sprayed aluminum (WSA) coating services. The Navy-specified ambient temperature WSA coating system consists of an anchor tooth profile of 2 to 3 mils coated with 7 to 10 mils WSA, sealed with one thinned epoxy polyamide, two coats of epoxy polyamide barrier, and two coats of silicone alkyd topcoats for a total thickness of 16 to 20 mils. 49 Herbert E. Townsend, “Twenty Five Year Corrosion Tests of 55% Al-Zn Alloy Coated Steel Sheet,” Materials Performance, April 1993. This paper discusses the results from a long-term atmospheric corrosion test of steel sheets hot-dipped and coated with various aluminum-zinc alloy compositions. The author concluded that coatings composed of at least 44.6% aluminum exhibited a longer service life than conventional galvanizing. 50 Mark Trifel, “The Use of Metallic Protective Coatings in the Soviet Union,” News from the Field. This paper discusses the use of zinc and aluminum coatings on offshore (both fresh and salt water) pilings. Trifel concluded that thermal diffusion zinc coatings outperform thermal spray zinc coatings with respect to adhesion and service life. Thermal diffusion zinc coatings are applied by covering the tubes with zinc powder and increasing temperature to 680°F (360°C) for twelve hours. An average coating thickness of 4.7 mils (0.12 mm) is deposited on to the tubes. In splash zones, this coating has a service life greater than 17 years w/o sealer (25 to 30 years w/sealer). The author also concluded that aluminum coatings provide more corrosion resistance than zinc and are well suited for river water immersion. Electric arc metallizing produces more heat than flame spray and improves the adhesion of the lining. 51 A. Tsourous, “The Restoration of the Historic Trenton Non-Toll Bridge Using Field Applied Thermal Spray Coatings,” SSPC International Conference, 1998. This paper discusses the use of thermal spray zinc coating on an existing bridge superstructure. The project specified an SP-10 surface preparation and a minimum DFT of 8 mils. Deposition efficiency was approximately 75%. The material cost was $0.80 per ft2 and direct labor cost was approximately $4.32 per ft2. The author concluded that while application costs typically exceed those of traditional high-performance coating systems, metallizing’s life cycle cost far outperforms most of these systems. 52 D. J. Varacalle and D. P. Zeek, “Corrosion Resistance of Zinc and Zinc/Aluminum Alloy Coatings,” SSPC International Conference, 1998. This paper studies twin wire electric arc spraying of 1/8” diameter Zn and 85:15 wt% Zn-Al wire and the suitability of such systems for anticorrosion applications. In general, the 85:15 wt% Zn-Al coating, when compared with Zn, exhibited higher bond strength, higher hardness, and higher deposition efficiency. The Zn coating exhibited higher corrosion resistance (salt spray) and higher density. 53 J. Wigren, “Grit-Blasting as Surface Preparation Before Plasma Spraying,” National Thermal Spray Conference Proceedings, ASM International, September 1987, p. 99. This is a general paper with several interesting conclusions: • The paper focuses on TSA adhesion as a function of surface roughness parameters. • The research shows that excessive blasting and particle embedment are concerns. • The paper concludes that the as-coated adhesion does not correlate with adhesion in service—as is the case with most coatings. American Welding Society References 54 Thermal Spray Manual, 1996. 180-page training manual discusses the results of a National Shipbuilding Research Program performed by Puget Sound Naval Shipyard. Covers the fundamentals of thermal spraying: sequencing the job, processes, safety, and so forth. 55 Guide for the Protection of Steel with Thermal Sprayed Coatings of Aluminum and Zinc and their Alloys and Composites, 1993. 30 pages provide a guide to select, plan, and control thermal sprayed coatings over steel. Discusses quality control checkpoints, maintenance and repair, job control records, and operator certification. 56 Guide for Thermal Spray Operator Qualification, 1992. 9 pages discuss recommended thermal spray operator qualification procedures. 57 Thermal Spraying: Practice, Theory and Application, 1985. 181 pages discuss thermal spraying and selection of suitable processes. Emphasis on practical shop and field procedures. Other References 58 Metals Handbook - Desk Edition, ASM International, Materials Park, Ohio. 59 NACE International Publication 1G194, “Splash Zone Maintenance Systems for Marine Steel Structures,” NACE International, Houston, TX, 1994. 60 SSPC Volume I Good Painting Practice, Fourth Edition, Chapter 4.4 Thermal-Spray (Metallized) Coatings for Steel, SSPS: The Protective Coatings Society, Pittsburgh, PA.

D-1 APPENDIX D BIBLIOGRAPHY* REFERENCES COMMENTS 1 John R. Birchfield, “Stainless Steel Metallized Superheater Tubes,” Welding Design and Fabrication, October 1985. This paper is a case study of the use of D-gun (JETKOTE) spraying of 316 stainless steel to increase the corrosion resistance of tube assemblies. 2 M. S. J. Hashmi, C. Pappalettere, and F. Ventola, “Residual Stresses in Structures Coated by a High Velocity Oxy-Fuel Technique,” Journal of Materials Processing Technology, 1998. This paper discusses the use of the hole-drilling strain-gauge method to measure residual stresses that can develop in the coating. The authors concluded that the HVOF thermal spray process yields residual tensile stresses that can decrease the fatigue life of the component. 3 Robert R. Irving, “JET KOTE: A Supersonic Coating Method Ready to Take on ‘D-Gun’,” June 1984. This paper discusses Thermal Dynamics’ JET KOTE system and Union Carbide’s D(detonation)-gun system. The JET KOTE system is a supersonic coating device capable of reaching temperatures of 5,500°F and exhaust velocities of 4,500 fps. The author discusses the advantages and disadvantages of JET KOTE, D-gun, and plasma. The JET KOTE system reportedly gives harder coatings than those produced by D-gun and plasma spray. 4 Robert A. Kogler, J. Peter Ault, and Christopher L. Farschon, “Environmentally Acceptable Materials for the Corrosion Protection of Steel Bridges,” Federal Highway Administration Report FHWA-RD-96-058, January, 1997. Abstract: The recently promulgated environmental regulations concerning volatile organic compounds (VOC) and certain hazardous heavy metals have had a great impact on the bridge painting industry. As a response to these regulations, many of the major coating manufacturers now offer "environmentally acceptable" alternative coating systems to replace those traditionally used on bridge structures. The Federal Highway Administration sponsored a 7-year study to determine the relative corrosion control performance of these newly available coating systems. A battery of accelerated laboratory tests was performed on candidate coating materials with a maximum VOC content of 340 g/L (2.8 lbs./gal). Accelerated tests included cyclic salt fog/natural marine exposure, cyclic brine immersion/natural marine exposure, and natural marine exposure testing. Natural exposure test panels were exposed and evaluated for a total of 6.5 years. The most promising coating systems were selected for long-term field evaluation based on accelerated test performance. The long-term exposure testing was conducted for 5 years in three marine locations. Panels were exposed on two bridges, one in New Jersey and one in southern Louisiana. The third long-term exposure location was in Sea Isle City, New Jersey. Thirteen coating systems were included for long-term exposure testing. These included 2 high-VOC controls and 11 test systems having a VOC level of 340 g/L (2.8 lbs./gal) or less. Five of the test systems contained high-solids primers, two of the test systems contained waterborne primers, one system was based on a powder, and three systems were metallizing. The best performing systems were the three metallized coatings. These were initially less aesthetic than coating systems with high-gloss topcoats, but they displayed near-perfect corrosion performance after 5 to 6.5 year exposure periods. Of the traditional liquid applied coating systems, those incorporating inorganic zinc primers performed the best over near- white blasted and power-tool cleaned surfaces. High-solids epoxy coatings had a tendency to undercut at intentional scribes and rust worse than coatings with zinc-rich primers over less than ideal surface preparations. Current bridge painting methodologies and corrosiveness of various bridge substructures were investigated. Various bridge maintenance painting options were evaluated on a life- cycle cost basis using data developed in the program. The analysis points to the potential advantages of long-term durable coatings such as metallizing and alternative painting practices such as zone painting. 5 P. A. Kulu and T. A. Khalling, “Flame Spray Coatings on Powder Metallurgy Materials,” 1987. This paper discusses the method of application and properties of fused coatings on powder metallurgy materials. 6 S. Lathabai, M. Ottmüller, and I. Fernandez, “Solid Particle Erosion Behavior of Thermal Sprayed Ceramic, Metallic and Polymer Coatings,” Wear, 1998. This paper studies the role of particle properties, such as hardness and shape in slurry and airborne erosion, on thermal sprayed coatings. The authors concluded that hard, angular particles cause more severe damage than softer, more rounded particles. Coating properties, such as hardness, do not exhibit a correlation with erosion rates. However, coating microstructure and defect population influence erosion mechanisms. 7 Clifford F. Lewis, “Processing Makes the Difference in Thermal Spray Coatings,” Materials Engineering, August 1988. This paper discusses various methods to apply thermal spray coatings. Methods discussed include Union Carbide’s D-gun and Stoody Deloro Stellite, Inc.’s JET KOTE II hypervelocity oxy-fuel (HVOF) system and plasma spray. One of the benefits of JET KOTE II is the ability to control oxide content with the choice of fuel. 8 “Thermal Spraying with Zinc and Zinc/Aluminum Alloy Wire,” Metallize, The Platt Brothers and Company. The Platt Brothers & Company is a manufacturer of zinc and zinc alloyed wire used in the thermal spray process. Platt publishes Metallize, a quarterly newsletter to promote the advantages of zinc thermal spraying. This particular issue discussed comparative studies of various thermally sprayed materials at dams and canals. The newsletter, in these applications, obviously concluded that thermal spray zinc and zinc alloys exhibited superior performance when compared with conventional paint coatings, coal tar enamel, emulsion and epoxy, aluminum-bronze coatings, and stainless steel coatings. In one case, a service life between 100 and 200 years was estimated for the zinc thermal spray coating. 9 K. V. Rao, “Characteristics of Coatings Produced Using a New High Velocity Thermal Spray Technique,” October, 1985. This paper discusses the JET KOTE thermal spray technique when it was new. JET KOTE relies on continuous internal combustion of oxygen and a fuel to produce a high velocity exhaust jet stream. The author focuses on four JET KOTE coatings: WC-12%Co, WC- 17%Co, TRIBALOY alloy T-800, and HASTELLOY alloy C. 10 Ronald W. Smith and Richard Knight, “Thermal Spraying I: Powder Consolidation – from Coating to Forming,” JOM, August 1995. This article discusses thermal spray processes and characteristics. The authors present a range of thermal spray processes and the materials systems that are able to be produced.

D-2 11 Ronald W. Smith and Richard Knight, “Thermal Spraying II: Recent Advances in Thermal Spray Forming,” JOM, April 1996. This article discusses the economics and reliability concerns over material structure, uniformity, and materials properties associated with thermal spray formings. REFERENCES COMMENTS 12 Yu N. Tyurin, A. D. Pogrebnjak, “Advances in the Development of Detonation Technologies and Equipment for Coating Deposition,” Surface and Coating Technologies, 1999. This paper discusses new devices and methods for plasma detonation deposition of coatings which give a permanent delivery of gases and powders into the combustion chamber. The authors focus on α -Fe2O3 and WC(88%)-Co(12%) coatings. It was concluded that while plasma detonation technology may be used in various applications, an increased concentration of the γ-phase and other metastable phases in the Al2O3 coating reduce its micro-hardness, wear resistance, and corrosion resistance while, at the same time, improving its density and adhesion to the substrate. Thus, care must be taken to control the parameters to produce the desired coating characteristics. 13 D. J. Varacalle, Jr., D. P. Zeek, G. S. Cox, D. Benson, K. W. Couch, E. Sampson, and V. Zanchuck, “Twin Wire Arc for Infrastructure,” J. Therm. Spray Technol., Vol 7 (No.4), December 1998. Accelerated corrosion testing was performed to evaluate arc sprayed 85:15 wt% Zn-Al and 70:30 wt% Zn-Al coatings. Experiments were performed to evaluate coating performance as a function of process conditions (nozzle diameter, spray distance, current, etc.). 14 D. J. Varacalle, Jr., D. P. Zeek, V. Zanchuck, E. Sampson, K. W. Couch, D. M. Benson, and G. S. Cox, “Zinc and Aluminum Coatings Fabricated with the Twin-Wire Electric Arc Spray Process,” SSPC International Conference, 1997. This paper discusses the suitability of zinc and aluminum coatings, applied by a twin-wire arc process, for corrosion protection. The authors performed a sequential regression analysis to establish a relationship between process parameters (orifice diameter, gun pressure, current, and spray distance), coating microstructural attributes, and corrosion performance. This analysis generally indicated that corrosion resistance increased with increasing porosity and lower oxide content. However, the authors concluded that, based on confirmation testing, the combination of lower porosity and lower oxide content mitigates corrosion. 15 “Preparing Flame-cut Edges for Thermal Spray,” Journal of Protective Coatings and Linings, Problem Solving Forum, May 2002, pp. 17–18 Question and answer article. Responses are uniform in recommending that flame cut edges be ground to remove the hardened layer formed from flame cutting. Unless this is done, the hardened layer (having a hardness of Rc 50 or more) will prevent adequate profile from being formed. 16 H. X. Zhao, H. Goto, M. Matsumura, T. Takahashi, M. Yamamoto, “Slurry Erosion of Plasma-Sprayed Ceramic Coatings,” Surface and Coatings Technology, 1999. This paper investigates the effects of slurry erosion on ceramic coatings under different plasma spray conditions. The authors concluded that ceramic coatings, such as Al2O3 and Cr2O3, generally exhibit improved wear resistance, but become significantly weakened under normal impact conditions. Also, slurry resistance varied with different plasma spray methods. Methods (using a “jet-in-slit type apparatus) were used to assess the slurry erosion properties quantitatively and qualitatively. National Association of Corrosion Engineers (NACE) International References 17 Classic Papers and Reviews on Anode Resistance Fundamentals and Applications, 1986. This book provides a compilation of technical papers on anode resistance. These papers discuss fundamentals of anode resistance and specific applications including ships and offshore platforms. 18 Innovative Ideas for Controlling the Decaying Infrastructure, 1995. This book provides a compilation of papers presented at the NACE symposium held in Orlando, Florida in March 1995. These papers discuss case histories and innovative and cost-effective ideas for resolving corrosion problems in marine environments. * Bibliography not verified by TRB.

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Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide Get This Book
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TRB’s National Cooperative Highway Research Program (NCHRP) Report 528: Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide investigtes thermally sprayed metal coatings (TSMCs) and offers a guide for the application of TSMCs to protect steel pilings from corrosion.

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