Corrosion behavior of carbon steel covered with a coating film containing metallic compounds under a sulfuric acid mist environment containing chloride

The corrosion behavior of carbon steel covered with coating films containing Al2(SO4)3, CaO, and BaO was examined under a sulfuric acid mist environment containing chloride. CaSO4 ?2H2O and BaSO4 were formed as the corrosion products in the coating film and prevented the penetration of corrosives, in particular BaSO4 was highly effective. Furthermore, the rust layer containing CaCO3 adhered to the carbon steel substrate suppressed the penetration of chloride. The formation of these corrosion products suppressed the anodic reaction, resulting in higher corrosion resistance of the carbon steel in the chloride-containing acid environment. Polarization curves of carbon steel (CS-specimen) and that coated with resin containing powders of Al2(SO4)3, CaO, and BaO, where specimen with high addition of CaO is Ca-specimen, and that with the same molar concentrations of CaO and BaO is Ba-specimen, after corrosion test. The anodic current of Ba-specimen is the lowest.image