低浓度镀铬工艺

PROCESS OF LOW Cr PLATING

本文对低浓度镀铬工艺从沿革、基本原理、配方、催化剂的作用、催化剂最佳含量的调整、稀土的选用到经济效益与社会效益,作了全面而具体的叙述,打破“稀土”神秘感。作者认为铬酐浓度以120～200 g/L最佳;只有在两种催化剂(硫酸根与氟离子)存在下,才能达到低的浓度、温度和阴极电流密度及高的电流效率;稀土的加入改善深镀能力和电流效率;调整催化剂含量须用直角阴极法;低浓度镀铬维护较高浓度严格;低浓度镀铬目前仅适于镀镍后装饰镀铬。

Process of low Cr plating is discussed completely and concretely from its history, basic pricinples, formulations, action of catalysts, adjusting of their optimum contents, selection of rare earth metals to economic and social benefits. It is concluded that optimum concentration range of chromic anhydride is 120-200g/L; low concentration, temperature and cathodic current density as well as high current efficiency can only be obtained at presence of two kinds of catalysts (SO_4^(2-) and F^-); addition of rare earth metals can improve throwing power and current density; optimum content of catalysts should be adjusted with right-angle cathode, maintenance for low Cr plating bath is stricter than that for high one and the process is now suitable to decorative Cr over Ni coating only.