This paper discusses a comparative evaluation of the performance of various types of protective coatings available for the corrosion protection of structural steel components located in marine environments. The study is based on accelerated testing conducted at the Corrosion Research Laboratory of the Florida Department of Transportation (FDOT) in the United States and at the Centro de Estudios de Corrosión (CEC) of the Universidad del Zulia in Venezuela. An inorganic zinc primer, thermally applied zinc (99%), aluminum (99.5%), 85/15 zinc aluminum alloy, and a new dual coat system comprised of one coat of thermally applied zinc with a top coat of thermally applied aluminum were evaluated at the FDOT. All the systems were also evaluated with an epoxy or wash primer top coat sealer. Thermally applied zinc (99%), aluminum (99.5%), and the new dual coating system comprised of one coat of zinc and a top coat of aluminum were evaluated at the CEC. Some of the thermally applied systems were evaluated with and without a sealcoat. Also evaluated were hot dipped galvanized specimens with and without the top coat sealer, and specimens treated with a thermal diffusion galvanizing process.
Discussion of the results from salt fog chamber (ASTM B 117) and salt water immersion testing at FDOT, and Prohesion chamber (ASTM G 85 A5) and natural exposure to an aggressive coastal-marine atmosphere (outdoor evaluation) testing at CEC are presented. Both evaluations showed excellent behavior of the dual thermally applied system.
Keywords: cathodic protection, corrosion, metalizing, partial immersion, prohesion chamber, sacrificial anode, salt fog, thermally applied coating