Electrochemical corrosion kinetics of cold spray copper composite coatings in a high potential region

Abstract

In this paper, copper composite anticorrosion and antifouling coatings were prepared by a cold spray technique. Polarization experiments of the coatings were performed by rotating ring‐disk electrode technology at high potential. The electrochemical reaction mechanisms were proposed, and corresponding polarization kinetics models were built. Experimental results show that the copper and cuprous oxide formed corrosion microcells in the coatings, and the cuprous oxide did not alter the electrochemical reaction process of copper. In the high potential region (about 0.2–0.8 V), a CuCl film formed on the surface of the coatings was not damaged or broken down. The film played a role in corrosion protection. The currents in the high potential region increased relative to the limiting current 1. Because in the high potential region,0.33em CuCl 2− was produced by the dissolution of the CuCl film and was oxidized to Cu2+. In addition to being oxidized to Cu2+, CuCl 2− has the other two destinations, which were deposition as a CuCl film and diffusion to the solution bulk. The three processes were in parallel competition relations. In the limiting current 2 region, oxidation of CuCl 2− was dominant. A rate‐controlling step of electrochemical dissolution of the coatings in the high potential region was the diffusion processes of CuCl 2− and Cu2+. The electrochemical polarization kinetic models based on the reaction mechanisms established in this research accorded well to the experimental results. It demonstrated the rationality of polarization kinetics models and reaction mechanisms.