铜表面电化学制备黑陶质感转化膜的研究

对铜在无硒电化学发黑液中的行为进行了研究.首先通过试验选择NaOH-H3BO3作为缓冲溶液体系,研究了铜在含0.1 mol/L Na2S的缓冲溶液中的循环伏安行为.根据循环伏安曲线上氧化峰的位置,确定铜电化学发黑的适宜电势.然后在不同电势下通过恒电势氧化或循环氧化-还原等方法制备了发黑膜.采用目视和电化学阻抗谱测量等方法,对发黑膜的色度、均一性、致密性和腐蚀防护性能进行了比较.结果表明,循环氧化-还原不能形成性能优良的发黑膜.在-0.8 V和-0.6 V (vs SCE)下形成的发黑膜颜色不均匀,色泽不佳,而在-0.05 V(vs SCE)条件下进行恒电势氧化则可在铜金属表面形成均匀致密、具有黑陶质感的发黑膜.

Preparation of Conversion Coating with Black Pottery Finish on Copper Surface

Behaviors of copper in blackening bath without selenium were studied.First the NaOH-H_3BO_3 buffer solution was chosen to control the acidity of blackening bath by experiment.The potential appropriate for electrochemical blackening of copper was determined by examining cyclic voltammetric (CV) properties of copper in 0.1 mol/L Na_2S(pH=9.75)buffer solution.According to the oxidation peaks appearing in the CV curve,the copper electrodes were anodized at -0.80,-0\^60,,-0.05V,and +0.20 V(vs SCE),respectively.Black conversion films could be fabricated using both the potentiostatic anodization and cyclic oxidation-reduction method.The properties of black conversion film such as colority,uniformity,compactness and corrosion resistance were evaluated by observation and electrochemical impedance spectroscopy.It is found that potentiostatic anodization is much better than cyclic oxidation-reduction for fabrication of black conversion coating.The conversion films formed at -0.8 V and -0.6 V(vs SCE),is neither uniform nor adhesive.However,a compact conversion coating with black pottery finish and good adhesion can be obtained while anodizing the copper at -0.05 V(vs SCE).