三价铬镀液中配体的作用

三价铬镀铬液中的配体对镀液的稳定性和沉积速度影响极大,从三价铬镀液的化学和电化学特性分析入手,介绍了镀液中所加配体(如羧酸、羟基羧酸、氨基羧酸及其盐)的作用:(1)与三价铬离子形成活性配位离子加快电沉积速度;(2)抑制Cr3 的羟桥化反应;(3)可以掩蔽杂质金属离子,减少杂质金属离子对镀层质量的干扰,使电镀能持续进行;(4)可以稳定镀液.特别指出,只有选用能形成活性配位离子的配体,使电镀能持续进行,才能获得性能良好的厚铬镀层.

Role of Complexant in Trivalent Chromium Plating Baths

With a view to the significant effect of the complexant in trivalent chromium plating bath on the stability of the bath and plating rate,the roles of the complexants(e.g.,carboxylic acid,hydroxyl substituted carboxylic acid,amino substituted carboxylic acid and their salts) in the trivalent chromium bath were summarized.It was pointed out the roles of the complexing agents could be briefed as the follows.First,they were capable of increasing the electrodepositing rate by way of forming active complexing ions.Secondly,they were able to retard the hydroxo-bridge polymerization reaction.Thirdly,they were able to shelter metallic impurities and hence decrease the effects of the metallic impurities on the quality of the electroplating and maintain smooth ongoing of the electroplating process.Finally,they were capable of increasing the stabilities of the electroplating solution.Specifically,it was imperative to select proper complexing agent capable of forming active complexed ions so as to ensure smooth chromium electroplating and obtain quality and thick chromium electroplating.