Ni-Cr合金在三价铬水溶液中的电沉积  

Electrodeposition of Ni-Cr Alloy Coating from Aqueous Trivalent Chromium Salts and Microstructure and Corrosion Resistance of the Coating

作　　者：杨余芳[1] 龚竹青[1] 罗娟[2] 马玉天[1] 阳征会[1] 

机构地区：[1]中南大学冶金科学与工程学院,湖南长沙410083 [2]湖南科技大学化学化工学院,湖南湘潭411201

出　　处：《材料保护》2006年第6期21-25,共5页Materials Protection

基　　金：国家自然科学基金资助项目(59674025)

摘　　要：Al基体上电镀Ni-Cr合金可以大幅度改善其防护性能，为此以铝为基体，以柠檬酸为配位体，在三价铬的硫酸盐-氯化物镀液中电沉积了光亮平滑、质量优良、与基体结合良好、Cr含量为1．4％～26．0％、厚度为10～30 μm、最大电流效率可达58．0％的Ni-Cr合金镀层。研究了电流密度、温度、pH值、CrCl3浓度等参数对电流效率和镀层厚度的影响。电位滴定显示，镀液的缓冲能力良好；阴极极化曲线表明，Ni-Cr合金的电沉积符合Tafel方程。SEM形貌观察发现，Ni-Cr合金表面布满了均匀密集的球形小颗粒；通过XRD检测确定，Ni-Cr合金为晶体结构，Cr含量升高使晶粒变小；Ni-Cr镀层的耐蚀性较好，Cr含量的升高有利于耐蚀性的提高。Ni-Cr alloy coating was electroplated on aluminium substrate using aqueous trivalent chromium salts of sulphate and chloride as the electrolyte and citric acid as the complexing agent.The effects of electrodeposition parameters such as current density,temperature,pH value and CrCl_(3)concentration on the current efficiency and thickness of the Ni-Cr alloy coating were investigated.The electrodeposition process of the Ni-Cr alloy coating was examined by measuring the cathodic polarization curve.The microstructure and phase composition of the Ni-Cr alloy coating were analysed by means of scanning electron microscopy and X-ray diffraction.Moreover,the corrosion resistance of the Ni-Cr alloy coating was primarily evaluated.It was found that the plating bath composed of trivalent chromium salts of sulfate and chloride had good buffering capacity and cathodic current efficiency as much as 58.0%.The resulting Ni-Cr alloy coating was smooth and had good adherence to the Al substrate,with the content of chromium to be 1.4%～26.0% and thickness to be 10～30 μm.As indicated by the cathodic polarization curve,the electrodeposition process of the Ni-Cr alloy coating was in accordance with Tafel equation.Moreover,the Ni-Cr alloy coating had crystal structure and contained evenly distributed spherical fine grains on the surface,and the grain size decreased with increasing chromium content.In addition,the Ni-Cr alloy deposit had good corrosion resistance,and its corrosion resistance increased with increasing chromium content therein.

关 键 词：电沉积 NI-CR合金 Al基体 三价铬 

分 类 号：TQ153.2[化学工程—电化学工业]