An 18-Year Exposure Test of Thermal-Sprayed Zn, Al, and Zn-Al Coatings in Marine Environment

Abstract The thermal spray committee of the Japan Association of Corrosion Control (JACC) has been conducting a marine corrosion test of thermal-sprayed Zn, Al, and Zn-Al coatings since 1986. The coating was applied to twelve steel pipes by arc- and flame-spraying to varied thicknesses and subjected to various post-spray treatments. The samples were set vertically into seawater at a port located approximately 80 km south of Tokyo. The corrosion performance of these coatings has been inspected annually by recording their appearance and thickness at the sea-air, splash, and tidal zones. No significant changes were observed for the first several years of exposure. After 7 years, however, Zn coatings with and without sealing started to suffer degradation in the immersed portion. Contrary to this, most of the Al and Zn-Al coatings still exhibit superb corrosion performance. In order to place the test in a proper perspective, a special team of about 20 members was formed to conduct a survey on corrosion prevent...