新型碱性无氰镀镉工艺及其镀液与镀层性能

A novel alkaline cyanide-free cadmium plating process and properties of its bath and coatings

开发了碱性无氰镀镉新工艺。镀液中含氯化镉25～35 g/L、配位剂90～140 g/L、氯化钾140～180 g/L、光亮剂1.5～2.5 mL/L和辅助剂25～35 mL/L,pH为7.5～8.5,温度20～35°C。对于挂镀,阴极电流密度为0.5～1.5 A/dm^2;对于滚镀,槽电压为5～10 V,滚筒转速为4～8 r/min。在1.0 A/dm^2下电镀,镉的沉积速率约为0.35μm/min。该工艺的电流效率为70%左右,均镀能力为43%～59%,深镀能力为8.3,热震结合力合格。镉镀层经过低铬彩色钝化后进行中性盐雾试验1 000 h,无白锈生成。弯曲测试结果表明,厚度为36μm左右的镉镀层也具有良好的柔软性。

A novel alkaline cyanide-free cadmium plating process was developed.The bath is composed of cadmium chloride 25-35 g/L,complexing agent 90-140 g/L,KCl 140-180 g/L,brightening agent 1.5-2.5 mL/L,and auxiliary agent 25-35 mL/L with a pH of 7.5-8.5 and operated at 20-35 °C.For rack plating,the cathodic current density is 0.5-1.5 A/dm^2;for barrel plating,the bath voltage is 5-10 V and the barrel rotation rate is 4-8 r/min.The deposition rate of cadmium is ca.0.35 μm/min at 1.0 A/dm^2.The bath features a current efficiency of ca.70.3%,a throwing power of 43%-59%,a covering power of 8.3,and a satisfactory adhesion strength(thermal shock resistance).The cadmium coatings treated by lowchromium iridescent passivation is able to endure a neutral salt spray test for 1000 h without the formation of white rust.The blending test result showed that even a 36.3 μm-thick cadmium coating had good flexibility.