Thermally Sprayed Metal Coatings to Protect Steel Pilings: Final Report and Guide (2004) / Chapter Skim
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From page 61... ...
THERMALLY SPRAYED METAL COATING GUIDE CONTENTS 2 SECTION 1 Introduction 3 SECTION 2 Safety and Environmental 12 SECTION 3 Coating Materials and Selection 23 SECTION 4 Surface Preparation 31 SECTION 5 TSMC Application 45 SECTION 6 Sealer Selection and Application 51 SECTION 7 Repair and Maintenance 56 SECTION 8 Quality Control and Inspection 68 SECTION 9 Qualifications 74 SECTION 10 Referenced Documents 89 SECTION 11 Generic Sealer Specification 94 GLOSSARY
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From page 62... ...
They are Thermal Spraying: New Construction and Maintenance (U.S. Army Corps of Engineers, Washington, D.C., January 29, 1999)
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Provide mechanical ventilation in blasting operations that are not performed in the open or in a properly designed and ventilated room.
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• Wear approved earmuffs and properly fitted approved earplugs when thermal spray operators and personnel are in the immediate vicinity of thermal spray operations to reduce the high-intensity noise levels to acceptable conditions. • All personnel in the vicinity of blasting operations shall be provided with hearing protection if the noise exposure exceeds the limitations established by OSHA in paragraph 1910.95, "Occupational Noise Exposure".
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From page 65... ...
Electrically conductive safety shoes should be worn in any work area where an explosion is a concern. During thermal spray operations, including the preparation and finishing processes, employees should wear approved protective coveralls or aprons, hand protection, eye protection, ear protection, and respiratory protection.
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• Thermal spray operators and other workers in the vicinity of the thermal spray operation should wear approved hearing protection at all times. • Protection against the effects of noise exposure should be provided in accordance with the requirements of EM 385-1-1, Section 5, "Personal Protective and Safety Equipment," Subsection 05.C, "Hearing Protection and Noise Control," and CFR 29 Part 1910, Section 95.
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7 Thermal Spray Process Noise Level, dB(A) Minimum Recommended Protection Wire-flame spraying 114 Earplugs Wire-arc 111–116 Earplugs and earmuffs TABLE 1 Typical noise levels and hearing protection requirements
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• Compressed air for thermal spraying or blasting operations should only be used at pressures recommended by the equipment manufacturers. The air-line should be free from oil and moisture.
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away from the spraying area to preclude ignition from the flame or heat of the thermal spray process. • Thermally sprayed aluminum and zinc powders, nominally 40 to 110 µm (0.0016 to 0.0044 in.)
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This may include partial or complete containment of the work site for surface preparation and thermal spraying and the collection and safe disposal of used blasting media and thermal spray overspray. Ensure compliance 10
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with the purchaser's requirements and all pertinent government agency requirements and regulations for air-quality and hazardous-materials control. 2.7.2 Handling Debris 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 TSMC operations.
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From page 72... ...
Zinc, aluminum, and zinc/aluminum alloy coatings provide sacrificial corrosion protection to a steel substrate, even when areas of the substrate are exposed to the corrosive environment. The relatively low corrosion rates of these coatings, in combination with the sacrificial corrosion protection that they offer, make them suitable for use in such harsh environments.
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Wire-arc sprayed aluminum is the recommended thermal spray system for this application. 13 Environment Coating Thickness mils [µm]
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These surface preparation methods do not impart the surface profile that is needed for some types of coatings to perform well. In the case of thermally sprayed 14
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Thermal spraying should never be selected for applications in which it is not possible to provide the highest quality surface preparation. 3.2.2 Ease of Application Coating selection may also be limited by the ability of the applicator to access the surfaces to be coated.
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High winds will tend to carry surface preparation debris and paint overspray over longer distances. This problem can be avoided by using methods other than open abrasive blasting and spray application of paints.
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To calculate life-cycle costs, the installed cost of the coating system and its expected service life must be known. Life-cycle costs for coating systems are readily compared by calculating the average equivalent annual cost (AEAC)
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The basic installed cost of a TSMC system is calculated by adding the costs of surface preparation, materials, consumables, and thermal spray application. The cost of surface preparation is well known.
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For the less severe mildly corrosive atmospheric exposure, thermal spray was no more or less cost-effective than other coating options. Report FHWA-RD-96-058 provides the details of the study.
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compared with $18.38/ft2 ($1.71/m2) for the zinc/aluminum TSMC.
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The coating must be applied to a lesser thickness within the joint. The coating thickness should be no more than 3 to 5 mils (76 to127 µm)
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All visible holidays on new structures should be repaired using appropriate materials prior to the pile being placed in service. 3.8 Thermally Sprayed Metal Wire Storage Temperature, humidity, and dew point cause problems if thermal spray feedstock is not properly stored.
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is a procedure for removing surface contaminants, including oil, grease, dirt, drawing and cutting compounds, and soluble salts, from steel surfaces by means of solvents, water, detergents, emulsifying agents, and steam. Solvent cleaning is not designed to remove mill scale, rust, or old coatings and precedes the use of abrasive blast cleaning.
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From page 84... ...
4.3 Abrasive Blast Cleaning Abrasive blasting is performed in preparation for thermal spray after the removal of surface contaminants by solvent cleaning. Abrasive blasting is conducted to remove mill scale, rust, and old coatings, as well as to provide the surface roughness profile necessary to ensure good adhesion of the thermally sprayed coating to the substrate.
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SSPC-SP-5 and NACE #1 describe the condition of the blast-cleaned surface when viewed without magnification as free of all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products, and other foreign matter. SSPC-SP-VIS 1-89 supplements the written blast standards with a series of photographs depicting the appearance of four grades of blast cleaning over four initial grades of mill scale and rust.
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Standoff, or nozzle-to-surface distance, will also affect the quality and speed of blast cleaning. The lower the standoff distance, the smaller the blast pattern will be, and the longer it will take to cover a given area.
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. 27 Thermal Spray Material Spray Process Blasting Media Aluminum, zinc, 85:15 zinc-aluminum Wire flame spray Aluminum oxide Angular steel grit Aluminum, zinc, 85:15 zinc-aluminum Arc spray Aluminum oxide Angular steel grit Angular iron oxide TABLE 3 Recommended blast media for thermal spray surface preparation
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Blasting and thermal spraying should not occur simultaneously unless the two operations can be adequately isolated to prevent contamination of the thermal spray surfaces. 28 Abrasive Size Profile, mils (µm)
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A maximum holding period of 6 hours should be allowed to elapse between the completion of blast cleaning and thermal spraying. Shorter holding periods should be used under humid or damp conditions or when it is clear that the quality of the blast or coating is degraded.
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More information is available in the joint NACE International/SSPC Standard, NACE #5/SSPC-SP-12, "Surface Preparation and Cleaning of Steel and Other Hard Materials by High- and Ultrahigh-Pressure Water Jetting Prior to Recoating." 4.5 Surface Contamination Surface contamination from chlorides (deicing salts and sea salts) prior to applying the TSMC can lead to loss of coating adhesion, particularly with aluminum TSMC.
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From page 91... ...
With wire-flame spraying, the wire-flame spray gun or torch consists of a drive unit with motor and drive rollers for feeding the wire and a gas head with valves, gas nozzle, and an air cap that controls the flame and atomization air. Compared with wire-arc spraying, wireflame spraying is generally slower and more costly because of the relatively high cost of the oxygen-fuel gas mixture compared with the cost of electricity.
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5.1.2 Thermal Spray Guns (Wire-Arc and Flame) Figure 3 illustrates a typical wire-arc spray gun or torch and Figure 4 illustrates a typical flame spray gun.
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Under continuous use conditions, the actual oxygen and fuel gas flow rates and pressures should remain nearly constant and, ordinarily, should not deviate from the set values by more than 5 percent. Flame spraying equipment shall permit spraying with the combustible gases, atomizing gas (if any)
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Under continuous use conditions, the actual arc voltage should remain nearly constant and, ordinarily, should not deviate from the set value by more than 5 percent. 5.1.9 Wire Feed Control (Wire-Arc and Flame Spray)
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Processing of the feedstock materials shall be possible without any degrading deposit buildup on the gun, air nozzle, or both. 5.2 Thermal Spray Equipment Setup and Validation • The thermal spray equipment should be set up, calibrated, and operated as per the manufacturer's instructions and technical manuals.
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. Flame spray equipment shall be deemed to comply with the requirements if the values of supply gas pressure and gas flow volume meet the class deviations of the following from the set values over a 10-minute period of spraying.
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Under continuous use conditions, the actual wire feed rate should remain virtually constant and, ordinarily, should not deviate from the set value by more than 5 percent. 5.4.2 Holding Period 5.4.2.1 Correct surface cleanliness and profile.
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This procedure should be validated using a tensile adhesion test or bend test, or both, by spraying a flash coat and waiting through the delay period before applying the final coating thickness. 5.4.2.5 Small and moveable parts.
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5.6.3 Low Ambient Temperature Thermal spraying in low-temperature environments, below 40oF (5oC) , must (1)
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It is very important that the applicator's arm move parallel to the substrate in order to maintain a consistent standoff distance. Holding the thermal spray gun too close to the surface may result in poor coverage and variations in coating thickness because of the reduced size of the spray pattern.
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[mm] Air Cap Thermal Spray Method Perpendicular Standoff in.
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Each day, or every time the thermal spray equipment is used, the inspector should record and confirm that the operating parameters are the same as those used to prepare the job reference standard (Section 8.3.3)
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5.9 Handling, Storage, and Transportation of Thermally Sprayed Metal Coated Piles 5.9.1 Aluminum, Zinc, and Zinc-Aluminum Coatings Thermally sprayed metal surfaces are tough and are ready to be handled immediately after the application of the coating. However, aluminum, zinc, and zinc-aluminum coatings are softer than the steel substrate and are subject to scratching, gouging, and impact damage.
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Dragging or skidding the pile should not be permitted. 5.9.7 Repairing Damaged Coating Damaged coating should be repaired in accordance with Section 7 of this guide.
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In particular, the sealer may prevent the accumulation of corrosive salts, rain-borne corrosives, and bird droppings. Thermally sprayed coatings on a steel substrate should be sealed or sealed and topcoated under any of the following conditions: • When the environment is very acidic or very alkaline (the normal useful pH range for pure zinc is 6 to 12 and for pure aluminum is 4 to 11)
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• The U.S. Army Corps of Engineers Engineering and Design Manual, Thermal Spraying: New Construction and Maintenance, EM 1110-2-3401, Washington, D.C., January 29, 1999.
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Coal tar epoxy may be applied as a relatively thick film single-coat sealer for use over zinc, aluminum, and 8515 wt% zinc/aluminum thermal spray coatings. The coal tar epoxy sealer should be thinned approximately 20 percent by volume and applied in a single coat to a dry film thickness of 0.004 to 0.006 in.
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From page 108... ...
6.4 Application 6.4.1 Application Work Period In general, surface preparation, thermal spray application, and sealing of a given area should be accomplished in one continuous work period of not longer than 16 hours, and preferably within 8 hours of the thermal spray coating step. Subsequent paint coats should be applied in accordance with the requirements of the painting schedule.
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From page 109... ...
6.4.6 Thinning Sealers may need to be suitably thinned to effectively penetrate the TSMC. 6.4.7 Dry Film Thickness Typically the sealer coating is applied at a spreading rate resulting in a theoretical 1.5-mil (38-µm)
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From page 110... ...
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 since the areas tested must be repaired in order to maintain the coating integrity.
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From page 111... ...
Steps in assessing the need to repair a thermal spray coating system are listed below. 7.2.1 Identification of the Type of Thermal Spray and Sealer Material Originally Applied Historic records should be reviewed for information on the type of TSMC and sealer used as well as any previous repairs.
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From page 112... ...
; the presence of rust and bare steel; and cracked, blistered, and delaminated areas. 7.3 Determination of Repair and Recoat Intervals 7.3.1 TSMC The need to repair or replace the metal coating depends on how much corrosion the structure can tolerate, the type of corrosion that can be tolerated, and the corrosion rate of the structure in the environment.
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From page 113... ...
The thermal spray repair procedure includes solvent cleaning, scraping with a hard blade tool, abrasive blast cleaning to near white metal, edge feathering, TSMC application, sealing, and topcoating. 7.4.3 Description of Repair Procedure 7.4.3.1 Solvent cleaning.
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The thermal spray repair metal should be the same as that originally applied. Flame sprayed coatings should be repaired only by the flame spray technique.
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• Surface cleanliness, • Surface profile, • Adhesion, • TSMC thickness, • Sealer thickness, and • Topcoat thickness.
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From page 116... ...
8.2 Quality Assurance Functions for Owners 8.2.1 Informed Selection An informed selection should be made of TSMCs taking into account planned use of the coatings and the environment in which they are to be used. 8.2.2 Provide Definitive Specifications Specifications should include, as a minimum and as an addition to contractual provisions, the following: • Scope of work, to include the structure to be coated and portions not to be coated; • All applicable references; • Provisions for payment; • Definitions; • A list of required submittals; • Safety provisions; • Requirements for delivery, storage, and handling of materials and supplies; • Chemical composition, finish, coil weight, and preparation of metallizing wire; • Requirements for sampling and testing thermally sprayed materials and the applied sealer; • A job reference standard with a description of appearance and adhesion requirements; • Requirements for surface preparation; • Metallizing application; • Workmanship; • Atmospheric and surface conditions; 56
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From page 117... ...
The inspector should record the production and quality control information required by the purchaser or the purchasing contract. Among the items that should be recorded are • Information about the contractor and purchaser; • Surface preparation and abrasive blasting media requirements; • Flame or wire-arc spray equipment used; • Spraying procedure and parameters used; • TSMC requirements; • Safety precautions followed; • Environmental precautions; • Test data taken, including – Nature of the test, – When conducted, – Where conducted, 57
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From page 118... ...
Thermal spray can be quite sensitive to the quality of surface preparation, thermal spray equipment setup, and application technique. Therefore, it is important to specify an appropriate level of inspection.
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The JRS and the measured values may be used as a visual reference or job standard for surface preparation, thermal spray coating, sealing, and painting, in case of dispute. 8.3.3.3 Preparing the JRS.
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Prior to abrasive blasting, inspect the substrate for the presence of contaminants including grease and oil, weld flux and spatter, heat-affected zones, flame-cut edges, pitting, sharp edges, and soluble salts. • Grease and oil.
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Most abrasives used to prepare steel substrates for thermal spraying are unlikely to contain appreciable amounts of soluble salts. However, 61
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From page 122... ...
• The compressed air used for abrasive blasting, thermal spraying, sealing, and painting should be clean and dry. Oil or water in the blasting air supply may contaminate or corrode the surface being cleaned.
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From page 123... ...
SSPC-VIS-1 may be used to interpret the cleanliness of various blast-cleaned substrates based on the initial condition of the steel and the type of abrasive used. Initial conditions depicted include the following: – Rust Grade A -- a steel surface completely covered with adherent mill scale with little or no rust visible; – Rust Grade B -- a steel surface covered with both mill scale and rust; – Rust Grade C -- a steel surface completely covered with rust with little or no pitting; and – Rust Grade D -- a steel surface completely covered with rust with visible pitting.
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From page 124... ...
) should be specified in the contract documents.
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The mandrel diameter for the threshold of cracking depends on substrate thickness and coating thickness. Table 9 summarizes a very limited bend-test cracking threshold for arc-sprayed zinc TSMC thickness versus mandrel diameter for steel coupons 0.050 in.
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The bond should be considered unsatisfactory if any part of the TSMC along the cut lifts 66 Thermal Spray Material Tensile Adhesion psi [MPa]
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. The tested area and coated surfaces that have been rejected for poor adhesion shall be blast cleaned and recoated.
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It shall be possible to adjust the spraying material feed rate. Under conditions of continuous use, the actual wire feed rate should remain nearly constant and should not deviate from the set value by more than 5 percent during a 15-minute period.
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From page 129... ...
The wire feed mechanism should be designed for automatic alignment. Under conditions of continuous use, the actual wire feed rate should remain nearly constant and should not deviate from the set value by more than 5 percent during a 15-minute period.
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for abrasive blasting and thermal spray feedstock materials. • EN 657, Thermal spraying -- Terminology, classification, April 1994.
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, and 750 psi (5,171 kPa) for 8515 wt% zinc/aluminum alloy, aluminum, and zinc coatings, respectively.
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9.3.1.6 Job reference standard. The inspector should be skilled in setting up a job reference standard as described in Section 8.
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• Knowledgeable about the ASTM test methods available to quantify coating defects. 9.3.1.8 Communications and conflict-resolution skills.
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ANSI/AWS C2.18-93 Guide for the Protection of Steel with Thermal Sprayed Coatings of Aluminum and Zinc & Their Alloys and Composites American National Standards Institute 1819 L Street, NW Washington, DC 20036 www.ansi.org Provides guidelines for the selection, surface preparation, application, and inspection of thermal spray metal coatings. TO BE SUPERCEDED BY ANSI/AWS C2.18A-XX ANSI/AWS C2.18A-XX SSPC CS 23.00A-XX NACE TPC #XA Guide for the Application of Thermal Spray Coatings (Metallizing)
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75 Reference Title Address Comments ANSI Z49.1 Safety in Welding and Cutting American National Standards Institute 1819 L Street NW Washington, D.C. 20036 www.ansi.org ANSI Z87.1 Standard Practices for Occupational and Educational Eye and Face Protection ANSI Z89.1 Safety Requirements for Industrial Head Protection ANSI Z88.2 Standard Practices for Respiratory Protection ANSI/NFPA 51B Standard for Fire Prevention in Use of Cutting and Welding Processes ANSI/NFPA 70 National Electrical Code ASTM B833 Standard Specification for Zinc and Zinc Alloy Wire for Thermal Spraying (Metallizing)
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From page 136... ...
ASTM D610 Test Method for Evaluating Degree of Rusting on painted Steel Surfaces – provides standard charts for quantifying the amount of rusting on a steel surface ASTM D660 Test Method for Evaluating Degree of Checking of Exterior Paints ASTM D661 Test Method for Evaluating Degree of Cracking of Exterior Paints ASTM D662 Test Method for Evaluating Degree of Erosion of Exterior Paints ASTM D714 Test Method for Evaluating Degree of Blistering of Paints
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From page 137... ...
77 Reference Title Address Comments ASTM D1186 Standard Test Methods for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to a Ferrous Base ASTM D3359 Test Method for Measuring Adhesion by Tape Test ASTM D4214 Test Method for Evaluating Degree of Chalking of Exterior Paint Films ASTM D4285 Standard Test Method for Indicating Oil or Water in Compressed Air ASTM D4417 Standard Test Methods for Field Measurement of Surface Profile of Blast Cleaned Steel ASTM D4541 Standard Test Method for PullOff Strength of Coatings Using Portable Adhesion Testers Tensile adhesion testing of coatings using a dolly attached to the coating with an adhesive. The dolly is pulled off the surface using a handheld device and the tensile force is indicated.
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From page 138... ...
ASTM F1130 Standard Practice for Inspecting the Coating of a Ship – useful for standardizing the method of reporting the extent of corrosion and coating deterioration AWS C2.1 Recommended Safe Practices for Thermal Spraying American Welding Society 550 NW LeJeune Rd. Miami, FL 33126 www.aws.org AWS TS1 Recommended Safe Practices for Thermal Spraying AWS TSM Thermal Spray Manual AWS TSS Thermal Spraying: Practice, Theory and Application
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From page 139... ...
Current but partially replaced with EN standards. Compressed Gas Association CGA G7.1 Commodity Specification for Air Compressed Gas Association 4221 Walney Rd., 6th Floor Chantilly, VA 20151-2423 www.cganet.com EN 473 Non-destructive Testing – Qualification and Certification of Personnel European Committee for Standardization Rue de Stassart 36 B-1050 Brussels, Belgium www.cenorm.be EN 582 Thermal Spraying – Determination of the Adhesive Tensile Strength EN 657 Thermal Spraying – Terminology – Classification EN 1395 Thermal Spraying – Acceptance Testing of Thermal Spraying Equipment
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From page 140... ...
80 Reference Title Address Comments EN 13214 Thermal Spraying – Thermal Spray Coordination – Tasks and Responsibilities European Committee for Standardization Rue de Stassart 36 B-1050 Brussels, Belgium www.cenorm.be prEN 13214 Thermal Spraying – Thermal Spray Coordination – Tasks and Responsibilities EN ISO 14918 Thermal Spraying – Approval Testing for Thermal Sprayers prEN ISO 14919 Thermal Spraying – Wires, Rods and Cords for Flame and Arc Spraying – Classification – Technical Supply Conditions EN 22063 Metallic and Other Inorganic Coatings – Thermal Spraying – Zinc, Aluminum and Their Alloys FHWA-RD-96-058 Environmentally Acceptable Materials for the Corrosion Protection of Steel Bridges Federal Highway Administration Turner Fairbank Highway Research Center 6300 Georgetown Pike McLean, VA 22101-2439 www.tfhrc.gov Research report on the use of environmentally friendly coatings, including thermally sprayed metal coatings.
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From page 141... ...
ISO 14922-1 Thermal Spraying – Quality Requirements of Thermally Sprayed Structures – Part 1 Guidance for Selection and Use Specifies guidelines to describe thermal spraying quality requirements suitable for application by manufacturers for coating new parts, repair and maintenance. Reference to European (EN)
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From page 142... ...
ISO 2063 Metallic Coatings – Protection of Iron and Steel against Corrosion – Metal Spraying of Zinc, Aluminum and Alloys of these Materials ISO 8502 Preparation of Steel Structures Before Application of Paint and Related Products – Tests for the Assessment of Surface Cleanliness JIS H 8300 Zinc, Aluminum and their Alloys Sprayed Coatings – Quality of Sprayed Coatings Japan Standards Association 4-1-24 Akasaka Minato-ku Tokyo 107-8440 Japan www.jsa.or.ip Contains QA provisions for thermally sprayed aluminum and zinc.
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From page 143... ...
Contains requirements for qualification of procedures and operators, use of thermal spray equipment and material, quality assurance requirements and qualification tests.
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From page 144... ...
84 Reference Title Address Comments NACE Publication 1G194 Splash Zone Maintenance Systems for Marine Steel Structures NACE International 1440 South Creek Dr. Houston, TX 77084-4906 www.nace.org NACE Publication 6G186 Surface Preparation of Contaminated Steel Surfaces NACE Standard RP0287 Standard Recommended Practice, Field Measurement of Surface Profile of Abrasive Blast Cleaned Steel Surfaces Using a Replica Tape NACE TM0170 Visual Comparator for Surfaces of New Steel Airblast Cleaned with Sand Abrasive NACE TM0175 Visual Standard for Surfaces of New Steel Centrifugally Blast Cleaned with Steel Grit and Shot NACE Technical Report T-60-5 A Manual for Painter Safety
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From page 145... ...
85 Reference Title Address Comments NIOSH Respiratory Protection – An Employer's Manual National Institute for Occupational Safety & Health Robert A Taft Laboratories 4676 Columbia Parkway Cincinnati, OH 45226 www.cdc.gov/niosh NIOSH Respiratory Protection – A Guide for the Employee OSHA CFR 29 Part 1910 Occupational Safety and Health Standards Occupational Safety & Health Administration 200 Constitution Ave.
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From page 146... ...
1 White-Metal Blast Cleaning SSPC VIS-1-89 Visual Standard for Abrasive Blast Cleaned Steel SSPC AB-1 Mineral and Slag Abrasives SSPC AB-2 Specification for the Cleanliness of Recycled Ferrous Metallic Abrasives SSPC AB-3 Newly Manufactured or ReManufactured Steel Abrasives
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From page 147... ...
SEE ALSO ASTM AND NACE DOCUMENTS. SSPC PA-1 Shop, Field and Maintenance Painting SSPC PA-2 Measurement of Dry Paint Thickness with Magnetic Gages SSPC PA Guide 3 A Guide to Safety in Paint Application SSPC QP- Standard Procedure for Evaluating Qualifications of Painting Contractors SSPC SP-1 Solvent Cleaning Provides details for removing grease and oil contamination prior to final surface preparation.
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From page 148... ...
Engineering Manual EM 1110-2-3401 Engineering and Design, Thermal Spraying: New Construction and Maintenance U.S. Army Corps of Engineers Champaign, IL http://www.usace.army.mil/inet/ usace-docs/ Provides information on thermal spray metal coatings for coating selection, surface preparation, application, testing and quality assurance.
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From page 149... ...
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.
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From page 150... ...
away from welding, oxyfuel cutting and heating, and thermal spraying operations. 3.1.2 Sealers and paint coats are typically applied by spray application.
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From page 151... ...
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.
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From page 152... ...
. Visible oxidation of the thermal spray coating requires that the surface be further prepared to remove the oxidation by brush blasting.
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From page 153... ...
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.
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From page 154... ...
GLOSSARY Abrasive A material used for wearing away a surface by rubbing; a fine, granulated material used for blast cleaning. Abrasive particles of controlled mesh sizes are propelled by compressed air, water, or centrifugal force to clean and roughen a surface.
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From page 155... ...
Cathodic Protection A technique to reduce the corrosion rate of a metal surface by making it a cathode of an electrochemical cell. Centrifugal Blast Cleaning Use of motor-driven bladed wheels to hurl abrasive at a surface by centrifugal force.
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From page 156... ...
Epoxy Resin Cross-linking resins based on the reactivity of the epoxide group. Flame Spray Any process whereby a material is brought to its melting point and sprayed onto a surface to produce a coating.
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Metallizing Spraying a coating of metal onto a surface. See also Thermal Spraying.
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Rural Environment An atmospheric exposure that is virtually unpolluted by smoke and sulfur gases and that is sufficiently inland to be unaffected by salt contamination or the high humidity of coastal areas. Corrosion depends on temperature, humidity, and moisture retention.
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From page 159... ...
Surface preparation methods include washing with water, detergent solution, or solvent; cleaning using hand or power tools; water washing or jetting without abrasive; or abrasive blast cleaning. Thermally Sprayed The technician or specialist who applies the thermally sprayed Coating Applicator coating.
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From page 160... ...
White Metal Blast Blast cleaning to white metal. This standard is defined in SSPC-SP-5 as a cleaned surface that, when viewed without magnification, shall be free of all visible oil, grease, dirt, dust, mill scale, rust, paint, oxides, corrosion products, and other foreign matter.
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