Coatings are widely used to mitigate corrosion of structural steel in aggressive humid environments. Zinc-rich primer three-coat paint systems are widely used to mitigate corrosion of steel bridges. However, the associated costs of its required maintenance are high. As part of a research program, chemically bonded phosphate ceramics (CBPC), thermal diffusion galvanizing (TDG) and metallizing coatings along with the current 3-coat systems were exposed in outdoor conditions for up to 2 years and in salt-fog exposure for up to 14,600 hours. Testing included visual photo-documentation, coating thickness, coating pull-off strengths, and optical microscopy. Generally, the coatings provided corrosion mitigation of the steel but some limitations including possible surface staining, iron consumption, and coating degradation should be further addressed. Moisture presence was observed to be important in the degradation of all of the coating systems.

Subject
Test methods, Zinc rich coatings, Steel surfaces, Coatings, Materials, Galvanized coatings, Coating degradation, Phosphates, Salt spray corrosion testing, Steel, Zinc, Durability, Thermal spray coatings
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2018
Association for Materials Protection and Performance (AMPP)
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