Click for next page ( 150


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 149
89 11 GENERIC SEALER SPECIFICATION 1. SCOPE This specification provides a general specification for sealers to be used on thermally sprayed metal coatings. A sealer is defined as a material applied to infiltrate and close the pores of a thermal spraying deposit for the purpose of improving the life expectancy of the thermally sprayed metal coating. A sealer is not intended to provide a dielectric barrier coating over the surface and is not intended to provide an aesthetic finish coat. Further intermediate or topcoats applied over the seal coat must be used for barrier coating protection and aesthetic purposes. This specification does not cover intermediate and finish coatings. Intermediate and finish coats must be compatible with the thermally sprayed metal coating and sealer. 2. APPLICABLE DOCUMENTS 2.1 AASHTO, "Thermally Sprayed Metal Coating Guide." 2.2 U.S. Army Corps of Engineers (USACE) Guide Specification for Construction CEGS-09965, Section 09965, Painting: Hydraulic Structures. 2.3 MIL-STD-2138A (SH), "Metal Sprayed Coatings for Corrosion Protection Aboard Naval Ships." 2.4 ASTM D1210, "Test Method for Fineness of Dispersion of Pigment-Vehicle Systems." 2.5 ASTM D2794 (Modified), "Test Method for Resistance of Organic Coatings to the Effects of Rapid Deformation (Impact)." 2.6 ISO 8502-3, "Clear Cellophane Tape Test." 2.7 The sealer manufacturer's product technical data sheets. 3. SAFETY AND ENVIRONMENTAL 3.1 Safety 3.1.1 Solvents used for cleaning or to apply sealers or topcoats (e.g., acetone, xylene, or alcohol) emit vapors that are harmful and can be fatal. 3.1.1.1 Use solvents only with adequate ventilation or proper respiratory protection and other protective clothing as needed. Avoid breathing solvent vapors and skin contact with solvents.

OCR for page 149
90 3.1.1.2 Most solvents are also flammable liquids. All solvent tanks must have lids and be covered when not in use. Take proper safety precautions. 3.1.1.3 Keep all solvents and flammable materials at least 50 ft (15.2 m) away from welding, oxyfuel cutting and heating, and thermal spraying operations. 3.1.2 Sealers and paint coats are typically applied by spray application. Spray application is a high-production rate process that may rapidly introduce very large quantities of toxic solvents and vapors into the air. 3.1.2.1 Airless spray systems operate at very high pressures. Very high fluid pressures can result in penetration of the skin on contact with exposed flesh. 3.1.2.2 Tip guards and trigger locks should be used on all airless spray guns. The operator should never point the spray gun at any part of the body. 3.1.2.3 Pressure remains in the system even after the pump is turned off and can only be relieved by discharging or "blow-down" through the gun. 3.1.3 The contractor should maintain current MSDSs for all materials used on the job. These materials include cleaning solvents, compressed gases, thermal spray wires or powders, sealers, thinners, and paints or any other materials required to have an MSDS (as specified in CFR 29 Part 1910, Section 1200). The MSDSs should be readily available to all personnel on the job site in a clearly labeled folder. 3.2 Environmental 3.2.1 Ensure compliance with the purchaser's and all pertinent government agency requirements and regulations for air-quality and hazardous-materials control. 3.2.2 The applicator and the purchaser should coordinate the specific requirements, responsibilities, and actions for the containment, storage, collection, removal, and disposal of the debris produced by the thermal spray coating operations. 3.2.3 All sealers must comply with federal, state, and local volatile organic compound (VOC) requirements for the area in which they are to be applied. 4. MATERIAL 4.1 The sealer must have the characteristics listed below. 4.1.1 The sealer must be capable of penetrating the pores of the thermally sprayed metal coating. Pigmented sealers must have a particle size nominally 5-fineness of grind (ASTM D1210).

OCR for page 149
91 4.1.2 The sealer must be capable of being applied to a low film thickness of 0.003 in. (76 m) or less. 4.1.3 The sealer must be compatible with the thermally sprayed metal coating. For example, on zinc thermally sprayed coating, do not use a sealer that saponifies the zinc. 4.1.4 The sealer must be compatible with intermediate coats and topcoats. 4.1.5 The sealer must be suitable for the intended service. 4.1.6 The sealer must meet local regulations on VOC content. 4.1.7 The sealer must meet all color and other aesthetic requirements for the application. 4.2 Acceptable materials for steel pilings include those listed below. 4.2.1 Vinyl butyral wash primer (SSPC Paint 27). This is suitable for use over zinc, aluminum, and 8515 weight percent (wt%) zinc/aluminum. Thin wash primer per manufacturer's instructions and apply to a dry film thickness of 0.0005 in. (12.7 m). 4.2.2 U.S. Army Corps of Engineers paint specification V-766E vinyl acetatevinyl chloride copolymer (CEGS-09965). 4.2.3 MIL-P-24441 Formula 150 polyamide epoxy thinned after the required period of induction with an equal volume amount of super hi-flash Naptha (boiling range 315F to 353F [157C to 179C]). The thinned coating shall not exceed local VOC limits (see MIL-STD-2138A [SH]). 4.2.4 Polyamide epoxy thinned 50 percent with approved solvent (or as directed by manufacturer) and applied to 1.5-mil (38.1-m) dry film thickness. 4.2.5 High-solids low-penetrating epoxy. 4.2.6 Penetrating polyurethane. 4.2.7 Coal tar epoxy. This is suitable for use over zinc, aluminum, and 8515 wt% zinc/aluminum. Thin approximately 20 percent and apply to 0.004 to 0.006 in. (101 to 152 m). 4.2.8 Aluminum epoxy mastic. This is suitable for use over zinc, aluminum, and 8515 wt% zinc/aluminum. Thin to the maximum extent per manufacturer's recommended extent and apply to 0.003 to 0.004 in. (76 to 101 m).

OCR for page 149
92 4.2.9 Tung-oil phenolic aluminum (TT-P-38). Suitable for use over zinc, aluminum, and 8515 wt% zinc/aluminum. Thin about 15 percent by volume and apply to a dry film thickness of 0.0015 in. (38 m). 5. APPLICATION 5.1 Apply all paint sealer and topcoating according to SSPC-PA-1, "Shop, Field and Maintenance Painting," and the paint manufacturer's recommendations for use of the product with a thermally sprayed metal coating system. The thermally sprayed metal coating before sealing shall have a uniform appearance. The coating shall not contain any of the following: blisters, cracks, chips or loosely adhering particles; oils or other internal contaminants; pits exposing the substrate; or nodules. 5.2 Surfaces that have had the thermally sprayed metal coating applied shall be inspected and approved by the inspector. The sealer shall be applied within 8 hours of the thermally sprayed metal coating application. If this is not possible, verify that the surface has not been contaminated and is dust free (cellophane tape test [ISO 8502- 3]). Visible oxidation of the thermal spray coating requires that the surface be further prepared to remove the oxidation by brush blasting. Subsequent paint coats are applied in accordance with the requirements of the painting schedule. 5.3 Blow down surfaces to be sealed using clean, dry compressed air to remove dust. 5.4 Where moisture is present or suspected in the thermal spray coating pores, heat the surface to 120F (49C) to remove the moisture prior to the seal coat application. When possible, the steel on the reverse side of the thermally sprayed metal coating should be heated to minimize oxidation and contamination of the thermally sprayed metal coating prior to sealing. 5.5 Apply sealers by conventional or airless spraying. Vinyl-type sealers must be applied using conventional spray techniques. 5.6 Thin sealers as recommended by the sealer manufacturer to effectively penetrate the TSMC. 5.7 Unless otherwise specified by the manufacturer or the project specifications, apply the sealer at a spreading rate resulting in a theoretical 1.5-mil (38-m) dry film thickness. 5.8 Apply intermediate coats and topcoats as soon as the sealer is dry and preferably within 24 hours, in accordance with the coating manufacturer. 6. QUALITY CONTROL 6.1 Visually confirm complete coverage during application. Look for uniform coverage using tint and wetness of the surface as guides.

OCR for page 149
93 6.2 Measure the thickness of the topcoat per SSPC-PA-2 using a Type 2 fixed-probe gauge. The measurement may be made on either a companion coupon or the sealed thermal spray coating if the thermal spray coating thickness has been previously measured. Alternately, the thickness can be measured destructively using ASTM D4138, Test Method A. This method has the advantage of being able to observe all the layers; however, this type of measurement should be minimized because the areas tested must be repaired in order to maintain the coating integrity. 6.2.1 As an alternative, measure the thickness of the sealer as applied to a flat panel that was attached to the surface being sealed. Refer to SSPC-PA-2. 6.3 Note and correct areas with deficient sealer coverage. Correct by adding sealer. Additional testing is necessary to determine the extent of the area with deficient sealer or paint thickness. The sealer thickness must be checked prior to the application of subsequent paint coats, and the measurement procedure repeated for the sealer and paint. 6.4 As applied to thermally sprayed metal coatings on a steel substrate, sealer must meet a minimum drop weight impact requirement of 188 ft-lbs (254 N-m) when tested in accordance with ASTM D2794 (Modified).