Bridges, Tunnels and other Transportation Structures
Durability and structural integrity of steel bridges can be compromised when it is unprotected or inadequately protected from the exposure environment due to corrosion. In US, approximately 15% of all bridges are structurally deficient due to corrosion. Application of protective coatings has been widely used for corrosion mitigation of structural steel. Zinc-rich-primer three-coat (ZRP) systems have been used for highway steel bridges since the 1980’s. However, coating failure of ZRP has been identified within 15 years of application, well short of typical 75 year bridge design service life. Maintenance of bridge coating is costly and as estimated, annually half a billion dollar is spent only for coating maintenance of steel bridges. For these reasons durable novel coating systems are of interest. Nanoparticles are being considered in the development of a coating system due to their beneficial chemical, electrical and mechanical properties. The present study aims to investigate the corrosion durability of a nanoparticle enriched zinc rich primer (NPE-ZRP) coating for steel infrastructure application in aggressive marine environment. Test parameters included introduction of local coating defects along with as-received condition, exposed to harsh outdoor marine exposure as well as immersion in 3.5% (w/w) NaCl aqueous solution. A conventional ZRP coating was evaluated as a reference to assess the influence of nano-particles. NPE-ZRP showed good barrier protection, higher bond strength and also rust development was minimal. Comparative testing with regular ZRP showed similar positive results to date but improved performance in coating adhesive strength. Results so far showed there was no detrimental effect of replacement of nanoparticles with conventional zinc content.