Corrosion resistance of WC-10Co-4Cr coatings in NaCl and acid solution at different temperatures

Abstract

In order to improve the wear resistance of 1Cr18Ni9Ti stainless steel in NaCl and acid solution environment, the WC-10Co-4Cr coatings with two grain sizes were prepared by plasma spraying, and the corrosion resistance in 3.5%(mass fraction, the same below)NaCl and acid solution(pH=5.0) were investigated. The results show that the WC, W2C, W and η (CoxWxC) exist in these coatings. The corrosion potential of these coatings is higher than that of 1Cr18Ni9Ti substrate in 3.5% NaCl solution. In the acid solution (pH=5.0) at different temperatures, the potential difference for the nanometer WC-10Co-4Cr coatings has little change with the temperature. The corrosion mechanism of the coatings in NaCl and acid solution is shown as follows:the oxygen atoms adsorbed on the surface of WC-10Co-4Cr coating, can impel the Co and WC to form the galvanic couple in 3.5% NaCl solution. In the acid solution (pH=5.0), Co phase in the WC-10Co-4Cr coatings is dissolved to Co2+, and formed the galvanic corrosion with WC phase, so the isolated WC particles are formed on the coating surface.

Keywords

• electrochemical corrosion
• WC-10Co-4Cr
• plasma spraying
• salt solution
• acid solution