硼砂-对苯二甲酸电解液中AZ91D镁合金的阳极氧化处理

摘要

研究了硼砂-对苯二甲酸环保型电解液中AZ91D镁合金的阳极氧化.考察了对苯二甲酸对镁合金阳极氧化过程及其氧化膜性能的影响,并利用扫描电镜(SEM)、X射线衍射(XRD)、能量散射谱(EDS)、动电位极化和电化学交流阻抗谱(EIS)等进行了分析表征.结果表明,对苯二甲酸的浓度对阳极氧化成膜过程、氧化膜的表面形貌、厚度、相结构和耐腐蚀性能都有重要影响.在硼酸盐电解液中加入适量的对苯二甲酸后,氧化电流密度降低,过度放电现象受到了明显的抑制,所制得的阳极氧化膜的质量也有了显著改善.氧化膜表面变得光滑、致密,膜厚度略有降低.氧化膜与镁合金基底的结合更紧密,而且其耐腐蚀性能也得到了明显增强.该研究对于镁合金阳极氧化处理工艺的环保化及阳极氧化膜质量的提高都具有积极意义.%Anodizing a AZ91D magnesium alloy in environmentally friendly borate-terephthalic acid (TPA)electrolyte was studied.The effect of TPA on the anodizing process and the properties of the resultant anodized film were investigated by scanning electron microscopy (SEM),X-ray diffraction (XRD),energy dispersive spectrometry (EDS),potentiodynamic polarization,and electrochemical impedance spectroscopy (EIS).The results showed that the anodizing process,the surface morphology,thickness,phase structure,and corrosion resistance of the anodized film were strongly dependent on the concentration of TPA.In the presence of adequate TPA,a moderate anodizing process was obtained.The currant density of the anodizing process was reduced and excessive sparking in the anodizing process was obviously inhibited.In the presence of TPA,the quality of the anodized film improved.The film became more compact and smooth in structure.The thickness of the film decreased slightly.The interface between the anodized film and the magnesium substrate became indistinct indicating a better adhesion between them.The corrosion resistance of the anodized film was obviously enhanced.From these highly positive results,TPA can be used as an effective additive for the anodizing treatment of magnesium alloy.The proposed anodizing process is of importance to make the existing anodizing process ｀greener＇ and to improve the quality of the anodized film.