5,5-二甲基乙内酰脲含量对碱性无氰镀镉的影响

Effect of 5,5-dimethylhydantoin content on cadmium electroplating in alkaline cyanide-free bath

选用5,5-二甲基乙内酰脲(DMH)作为配位剂、CdO作为主盐在45钢基体上进行碱性无氰镀镉。通过阴极极化曲线测试、循环伏安分析、扫描电镜(SEM)、X射线衍射(XRD)等手段研究了DMH质量浓度对镉电沉积行为及镀层性能的影响。结果表明,随着DMH质量浓度从120 g/L增大至180 g/L,镉离子的初始沉积电位显著负移,阴极极化增强,Cd镀层结晶更加细致,耐蚀性有所改善。继续增大DMH质量浓度至210 g/L时,Cd镀层的形貌和耐蚀性变化不大,但镀液稳定性变差。当DMH的质量浓度为180 g/L时,在1.0 A/dm~2下电镀40 min时可以获得结晶细致、耐蚀性良好的Cd镀层。

Cadmium electroplating was conducted in an alkaline cyanide-free bath comprising 5,5-dimethylhydantoin(DMH)as complexing agent and CdO as main salt.The effect of mass concentration of DMH on the cadmium electro-deposition behavior and properties of the electrodeposited coating was studied by cathodic polarization curve measurement,cyclic voltammetry,scanning electron microscopy(SEM),and X-ray diffraction(XRD).The results showed that the initial deposition potential shifted to negative direction greatly,the cathodic polarization was enhanced,the grains of Cd coating were refined,and the corrosion resistance of Cd coating was improved when the mass concentration of DMH was increased from 120 to 180 g/L.The morphology and corrosion resistance of Cd coating changed little when the mass concentration of DMH was increased from 180 to 210 g/L,but the bath stability became worse.The Cd coating electrodeposited with 180 g/L of DMH at current density 1.0 A/dm2 for 40 min featured fine-grained and compact structure and good corrosion resistance.