2016 年 3 巻 2 号 p. 15-00623
Hard chromium coating is mainly used to improve the surface performance of pistons, brake disks and gears. In the future, better abrasion resistance and better corrosion resistance of hard Cr coating are demanded. Co-deposition of ceramic particles in Cr coating improved these characteristics. The Cr-ZrO2 composite coating is one of the prospective candidates for improvements of mechanical properties. In the present work, the measurement of polarization behavior of low carbon steel in CrO3-H2SO4 electrolyte with ZrO2 addition was conducted to investigate corrosion resistance. Microstructure of coating surface was observed with Electron Prove Micro Analyzer (EPMA) and Transmission Electron Microscope (TEM). Vickers hardness of coating surface was measured. The addition of ZrO2 had no effect on pH. Electrolyte was still strong acid. The shape of polarization curve was changed by the addition of ZrO2 particles. Polarization point was shifted higher by the addition of ZrO2 particles. The corrosion resistance was improved by the addition of ZrO2 particles. ZrO2 particles made the reduction reaction slowly. Coating surface consisted of Cr nano-crystal whose average size was 32.7 nm. Aggregation of ZrO2 particles was not observed in the resolution of EPMA. Addition of ZrO2 particles improved Vickers hardness of coating surface.
