Two-Coat Inorganic Coating System for Steel Bridges

Design considerations for steel bridge coatings include exposure environment, aesthetics, application, and cost. Steel bridge coatings must offer protection against corrosion. Current techniques include the traditional three-coat zinc, epoxy, urethane systems, galvanizing, and thermal spray metallization. Another pathway for steel protection includes the use of decades-old inorganic zinc spray-applied coatings. This approach offers the performance of a metallized coating while using a conventional spray application. What is new is the use of an inorganic topcoat that maintains performance and fab shop throughput while adding color and aesthetics. This study compared a two-coat inorganic coating system alongside a galvanized, thermal spray metallizing, and a sealed thermal spray metallizing system in corrosion resistance lab testing. A discussion of applied costs and throughput is presented along with a review of the chemistry of this approach and the sustainability benefits it offers.