论文部分内容阅读
Hard chromium deposits were prepared from a trivalent chromium plating bath as an alternative to conventional hexavalent chromium deposits.The influences of bath composition on the trivalent chromium electrodeposition process and deposited coating properties were studied.The effects of plating parameters such as current density,bath pH and plating time on structure and morphology of deposited coatings were investigated.The chemical transformation behaviors of Cr(Ⅲ) complex ions during chromium electrodeposition from trivalent chromium electrolytes have been analyzed.Results show that the hard chromium deposits exhibited crack-free surface and amorphous structure with thickness of 50-100μm and acceptable quality for functional coatings.The hard chromium deposits exhibited better wear resistance as well as corrosion resistance than that of hexavalent chromium deposits.The hardness of as-deposited chromium coatings is about 600-700 HV.Heat treatment could improve the wear resistance and hardness of the hard chromium deposits.The formation of polynuclear coordination compounds from hydroxyl complex ions at high pH is the main disadvantageous factor for the sustained trivalent chromium plating process.Results show that a better understanding of the chemistry involved during chromium deposition is very useful to the development of trivalent chromium plating.