双向脉冲电镀纳米镍层的耐腐蚀性能

Corrosion Resistance of Nanoscale Nickel Coating Prepared by Reverse Current Pulse Electroplating

镍镀层作为防护装饰性镀层应用广泛,过去多采用单向脉冲电镀制备纳米镍镀层,且对其耐蚀性及机理研究较少。为此,分别用直流电镀和双向脉冲电镀制备了2种镍镀层,利用X射线衍射仪(XRD)、扫描电镜(SEM)研究了2种镀层的相结构、晶粒尺寸和表面形貌,通过孔隙率测定、静态浸泡腐蚀试验、中性盐雾腐蚀试验和电化学方法研究了2种镀层的耐腐蚀性能。结果表明:双脉冲电镀镍层均匀、致密,粒径达到纳米级;与直流电镀镍层相比,双脉冲电镀镍层的孔隙率大为减少,在5.0%HCl溶液中静态浸泡的失重和腐蚀速率更小,耐中性盐雾腐蚀性明显提高,在3.5%NaCl溶液中的自腐蚀电位正移、腐蚀反应电阻增大,耐蚀性更强。

Two kinds of Ni coatings were prepared using direct current and reverse current pulse electroplating respectively.The phase structure,grain size and surface morphology of both kinds of Ni coatings were analyzed by means of X-ray diffraction and scanning electron microscopy.The porosity of the coatings was also measured,and their corrosion resistance was evaluated by conducting static immersion corrosion test,salt-spray test and electrochemical test.It was found that Ni coating prepared by reverse current pulse electroplating was uniform and compact,with grain size being nanoscale.Besides,it had much smaller porosity than the Ni coating prepared by direct current electroplating,corresponding to its smaller weight loss and corrosion rate in 5.0%HCl solution as well as better corrosion resistance against salt spray.Moreover,the Ni coating prepared by reverse current pulse electroplating had positively shifted corrosion potential,increased resistance of corrosion reaction and better corrosion resistance in 3.5%NaCl solution.