Highly Corrosion Resistant Epoxy Zinc-rich Paint with Calcium Sulfate

This paper presents the effect of adding calcium sulfate on the anticorrosion performance of an epoxy zinc-rich paint （ZRP）. We focused on gordaite （NaZn4（SO4）（OH）6Cl･6H2O）, a protective corrosion product, and increased its amount by providing sulfate ions.First, pure zinc plates were corroded in a cyclic corrosion test （CCT） with a calcium sulfate saturated test solution to investigate the effect of sulfate on zinc corrosion behavior. The results showed that the portion of gordaite increased in the zinc corrosion products and the corrosion rate of the zinc plates decreased.Next, epoxy ZRP containing calcium sulfate was prepared, and the ZRP-coated steel specimens were subjected to a CCT and out-door exposure test on Miyako Island. In both tests, the ZRP with calcium sulfate showed a remarkably high corrosion resistance compared with ZRP without calcium sulfate.