镀硬铬出现麻点的原因及对策

Cause and settlement measure of pitting during hard chromium plating

镀硬铬时出现麻点主要与基体表面局部产生点蚀有关。镀铬本身没有整平能力,点蚀处的电沉积层比平面部位少得多,故形成凹凸不平的镀层。其根源主要有工序间防锈不良、酸洗时间过长、阳极电流密度过大和阳极刻蚀时间过长,退铬方法不当等。针对上述情况给出了预防措施,包括加强待镀工件的质检和工序间的防锈,控制酸洗除锈时间、阳极刻蚀时间和电流密度,采用适当的退铬方法等。

The cause of pitting appeared during hard chronaium plating is pitting corrosion occurred on matrix local surface. The surface could not be striked up during chromium plating. The deposit on pitting corrosion areas is thinner than that on smooth areas, so the deposit is uneven. The reasons include bad rust prevention between working procedures, overlong pickling time, overhigh current density and overlong etching time of anode, poor chromium stripping and so on. The preventive measures were given aiming at settling the above problems including strengthening quality control of workpiece to be plated and the rust prevention during working procedures, controlling the pickling time, etching time and anode current density, and using proper methods of chromium stripping.