Spot Painting to Extend Highway Bridge Coating Life: Volume 2: Research Overview (2018) / Chapter Skim
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NCHRP Project 14-30 B-1 APPENDIX B Laboratory Test Protocol for Repair Test Coatings
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NCHRP Project 14-30 B-2 Recommended Practice for Testing and Evaluating Spot Coatings over Substrates with both Previously Corroded Steel Prepared by SSPC-SP 3 Power Tool Cleaning and Existing Coatings Using Flat Panel Specimens 1.0 Scope 1.1 This practice covers specific procedures for using cyclic salt fog/UV exposure and salt fog testing to evaluate coatings applied on power tool cleaned corroded steel and existing coatings. The former test method is intended to determine the suitability of coatings for repair service in spot painting operations involving conditions of bold exposure (direct UV exposure and condensation/evaporation)
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NCHRP Project 14-30 B-3 G154 Standard Practice for Operating Fluorescent Light Apparatus for UV Exposure of Nonmetallic Materials 2.2 SSPC Standards SSPC PA-15 Material and Preparation Requirements for Steel Test Panels Used to Evaluate the Performance of Industrial Coatings SSPC-SP 3 Power Tool Cleaning SSPC-SP 5 White Metal Blast Cleaning SSPC Technology Guide 15 Field Methods for Retrieval and Analysis of Soluble Salts on Steel and Other Nonporous Substrates SSPC-VIS 3 Guide and Reference Photographs for Steel Surfaces Prepared by Power and Hand Tool Cleaning 2.3 Other Documents Coating manufacturer product and safety data sheets 3.0 Summary of Practice 3.1 Cyclic corrosion/UV exposure shall be performed per ASTM D5894. The test specimens are exposed to alternating periods of one week in a fluorescent UV/condensation chamber and one week in a cyclic salt fog/dry chamber.
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NCHRP Project 14-30 B-4 acceptable coating performance. 4.3 The practice includes the use of selected coating systems to replicate existing coating systems on bridges.
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NCHRP Project 14-30 B-5 The panels should be conditioned per ASTM G85 Annex 5 for 250 hours of exposure in accordance with ASTM D5894. The fog/dry chamber runs at a 1-hour cycle of fog spray at ambient temperature ~ 72o F (22.2o C )
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NCHRP Project 14-30 B-6 contamination range is achieved. If the chloride contamination is in the range of 20-30 µg/cm2 (~166 to 250 µS/cm)
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NCHRP Project 14-30 B-7 test surfaces. Application conditions should be monitored -- as with liquid-applied coatings -- with applications being performed when the surface temperature of the specimens is 5o F above the dew point to ensure that these coatings are not applied over moist substrates.
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NCHRP Project 14-30 B-8 coating in 1,008-hr intervals will be reported along with performance of the set of test panels up to failure. A repair test coating that is found to fail in the 3,024-hour evaluation is deemed to have performed for 2,016 hours without failure.
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