电镀Al-Mn合金及后续阳极氧化对镁合金防护性能的影响

为提高镁合金的耐腐蚀性能,采用无机熔盐电镀技术在镁合金表面电镀铝锰合金,其后在草酸溶液中对铝锰合金镀层进行阳极氧化处理,以制备耐蚀性优良的阳极氧化膜。采用扫描电镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)等对阳极氧化膜的微结构进行表征,采用电化学测试方法对阳极氧化膜的耐腐蚀性能进行评价。结果表明,Al-Mn合金镀层在草酸溶液中形成的阳极氧化膜主要由稳态的α-Al2O3和亚稳态的γ-Al2O3所组成,并含有少量的MnO2及Al(MnO4)3,该阳极氧化膜具有很强的绝缘特性,其腐蚀电流密度较Al-Mn合金镀层下降了约3个数量级,较基体镁合金下降了约6个数量级,极大地提高了镁合金的耐腐蚀性。

Influence of AlMn Alloy Plating and Post Anodizing on Corrosion Resistance of Mg Alloy

To improve the corrosion resistance properties of Mg alloys,Al-Mn alloy coating was pre-plated on magnesium alloy through molten salt electroplating,the Al-Mn alloy plating was then anodized in oxalic acid solution to prepare an anode film on magnesium with much more corrosion resistance.The microstructure,composition and phase constituents of the oxidation film was investigated by scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),and X-ray diffraction(XRD),while the corrosion behaviors of the anode film was tested by electrochemical measurements.Results show that the oxidation film formed on Al-Mn alloy plating in oxalic acid solution is mainly composed of α-Al2O3 and γ-Al2O3,with a small amount of MnO2 and Al(MnO4)3.This kind of oxidation film considerably shows good insulativity and enhanced the corrosion resistance of magnesium alloy,reducing the corrosion current density of Al-Mn alloy plating and Mg alloy substrate by 3 and 6 orders of magnitude,respectively.