Comparison on long-term corrosion performance of WC-CoCr and Al2O3-TiO2 ceramic coatings in sulphide-containing 3.5 wt% NaCl solution

Abstract

In this study, the WC-CoCr coating and Al2O3-TiO2 coating were deposited by high-velocity oxygen-fuel (HVOF) spraying and atmospheric plasma spraying (APS), respectively. Both coatings were immersed in 3.5 wt% NaCl solution with 20 ppm Na2S to investigate their long-term corrosion resistances in the simulated seawater environment. The corrosion behaviors of both coatings for different times were investigated by potentiodynamic polarization, EIS, XRD, EDS and SEM. The electrochemical measurement results showed that the corrosion resistance of both coatings decreased obviously after long-term immersion in sulphide-containing solution, while the Al2O3-TiO2 coating exhibits more stable corrosion performance during the whole immersion process compared with the WC-CoCr coating. The corrosion resistance of the WC-CoCr coating in sulphide-containing solution after long-term immersion was inferior to that of the Al2O3–40TiO2 coating.