与直流电镀相比,脉冲电镀具有许多优点;而目前有关脉冲参数对Nd Fe B表面镀镍层耐蚀性影响的研究少有报道。以Nd Fe B为基体材料,以不同的电流密度和占空比脉冲电镀镍,利用扫描电镜(SEM)观察镀层表面形貌,在3.5%Na Cl溶液中进行极化曲线和交流阻抗谱测试考察镀层的耐蚀性能,并测量镀层硬度以及结合强度,以获得最佳脉冲电镀工艺。结果表明:Nd Fe B表面脉冲电镀镍层较直流电镀层晶粒更细,表面更光滑平整;电流密度为2 A/dm2,占空比为0.4时,镀层表面晶粒均匀致密,表现出良好的耐腐蚀性能;脉冲电镀层的硬度大于直流电镀层,且在电流密度2 A/dm2,占空比0.4时硬度最大,达497.5 HV0.98 N,热震20次表现出良好的结合性能。
The localized and uniform corrosion resistances of bulk nanocrystalline 304 stainless steel（NC-304 SS）produced by severe rolling technique, and its conventional polycrystalline 304 stainless steel（CC-304 SS）counterpart, were investigated in high-concentration hydrochloric acid solutions at room temperature.NC-304 SS can scarcely suffer from localized corrosion in 4 mol/L and 5 mol/L HCl solutions during 5-day immersion tests, and in 1-3 mol/L HCl solutions during thirty-five-day immersion tests. The corrosion rate of NC-304 SS was also less than that of CC-304 SS during these immersion tests. The improved localized and uniform corrosion resistances of NC-304 SS were explained in terms of the adsorption and chemical activity of Cl;on NC-304 SS and CC-304 SS characterized by X-ray photoelectron spectroscopy,and the valence electron configurations of NC-304 SS and CC-304 SS were characterized by ultra-violet photoelectron spectroscopy rather than conventional electrochemical results.
