United States Department of Transportation
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TRIS Online Accession Number:00798941
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OCLC Number:44946333
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Abstract:The study on which this report is based sought to compile data on both accelerated and natural exposure of coating and corrosion test panels and then to relate their deterioration to environmental conditions. The report presents data gathered over a 5-year period, incorporating seven different test sites across the United States. Specifically, the report looks at how the local environment affects the performance of eight coating systems and two weathering steels. For coated steel, the report concludes that an absolute humidity of 0.015 moles H2O/mole of dry air is the critical level for increasing the likelihood of corrosion. In such environments, a bridge engineer should utilize a zinc-rich coating system to prevent premature failures. Blistering failure is predominant in panels with high initial salt contamination on the substrate. To minimize failure due to blistering, the substrate should be as clean as possible. Cutback is chiefly affected by the high amount of rainfall and salt-fall (marine environments). A zinc-rich coating system is the best method for preventing cutback and should be incorporated unless the environment exhibits low annual rainfall and little salt contamination. Loss of gloss was mainly related to southern latitudes, while color change was most closely related to high relative humidity. For weathering steels, it was concluded that most high-chloride marine sites are unsuitable environments. It is expected that the information found and presented will be a useful resource to bridge maintenance engineers for coating selection decisions.
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