铈盐对铝合金硼酸?硫酸阳极氧化膜的封闭效应

将铝合金硼酸-硫酸阳极氧化膜浸入铈盐转化液中进行封闭。采用交流阻抗谱技术研究各封闭参数对氧化膜耐蚀性的影响,比较了不同方法封闭的氧化膜的耐蚀性差异。结果表明:将硼酸-硫酸阳极氧化试样浸入30℃的铈盐转化液(5 g/L Ce(NO3)3+0.5%H2O2)中处理30 min后,多孔层电阻Rp大幅增加,且腐蚀电流密度降低1个数量级,耐蚀性明显优于沸水封闭氧化膜的,也稍优于稀铬酸封闭氧化膜的耐蚀性。结合EDS分析表明:铈盐转化封闭后硼酸-硫酸阳极氧化膜的外表面形成了一层完整致密的铈盐转化膜,多孔层内也充满了铈的封闭产物,二者的协同作用几乎完全封住了硼酸-硫酸阳极氧化膜的孔隙,从而有效地提高了氧化膜的耐蚀性。

Sealing effect of cerium salt on boric-sulfuric acid anodic film of aluminum alloy

The boric-sulfuric acid anodic(BSAA) film on aluminum alloy was sealed by cerium salt conversion solution.The effects of sealing parameters on the corrosion resistance of BSAA film were researched through electrochemical impedance spectroscopy(EIS),while the corrosion resistance of anodic films sealed by different methods was studied.It is found that the resistance of porous layer increases significantly,the corrosion resistance is improved greatly and the corrosion current density is reduced by about 1 order of magnitude when the BSAA film was immersed in the cerium conversion solution(5 g/L Ce(NO3)3+0.5% H2O2) at 30 ℃ for 30 min.Besides,the corrosion resistance of BSAA film sealed by this method is much better than that by boiling water sealing,and also slightly superior to that of the dilute CrO3 solution sealing.Combined with EDS analysis results,it is indicated that a intact,compact cerium conversion film forms on the outside surface of BSAA film,and the porous layer is also filled with sealing products when the BSAA film is sealed by cerium salt conversion solution.The synergism of the two actions almost completely sealed the pores of BSAA film,thereby effectively improving the corrosion resistance of anodic film.