麦芽糖对氨羧配位体系无氰镀镉的影响

Effect of maltose on cyanide-free cadmium electroplating with amino carboxylic complexing agent

采用氨羧酸配位体系无氰镀液对45钢电镀镉。镀液组成和工艺条件为:CdCl_(2)·2.5H_(2)O 45 g/L,NH_(4)Cl 200 g/L,氨三乙酸70 g/L,乙二胺四乙酸25 g/L,麦芽糖0~2.5 g/L,pH 6.5~7.5,室温,电流密度1 A/dm^(2),时间20 min。通过电化学分析和霍尔槽试验研究了麦芽糖质量浓度对镉电沉积行为和镀液均镀能力的影响。利用光泽度计测定、扫描电镜分析、塔菲尔曲线测量等手段研究了麦芽糖质量浓度对镉镀层光泽、表面形貌和耐蚀性的影响。结果表明,镀液中添加麦芽糖对镉电沉积行为的影响不大,但能够细化镉镀层的晶粒,改善镀层外观和耐蚀性。麦芽糖质量浓度为1.0~1.5 g/L时镀液的均镀能力较高,所得镉镀层的综合性能较好。

Cadmium electroplating was conducted on 45 steel substrate in a cyanide-free bath with amino carboxylic compound as complexing agent.The bath composition and process parameters are:CdCl_(2)·2.5H_(2)O 45 g/L,NH_(4)Cl 200 g/Lnitrilotriacetic acid 70 g/L,ethylenediamine tetraacetic acid 25 g/L,maltose 0-2.5 g/L,pH 6.5-7.5,room temperature,current density 1 A/dm^(2),and time 20 min.The effect of mass concentration of maltose on the electrodeposition behavior of cadmium and throwing power of the bath was studied by electrochemical analysis and Hull cell test,respectively.The effect of mass concentration of maltose on the gloss,surface morphology,and corrosion resistance of cadmium coating was studied by using gloss meter,scanning electron microscopy,and Tafel plot measurement.The results showed that the addition of maltose to the bath had little effect on the electrodeposition behavior of cadmium.While the grains of cadmium coating were refined,and its appearance and corrosion resistance were improved.The bath containing 1.0-1.5 g/L of maltose featured high throwing power,and the cadmium coating electroplated therefrom had excellent comprehensive performance.