Ce改性AZ91的微弧氧化膜制备及其耐蚀性能

利用交流恒压微弧氧化技术, 通过Ce改性镁合金基体制备高耐蚀微弧氧化膜. 在100、120和 140 V的外加电压下, 对3种试样: AZ91, 质量分数w(Ce) 分别为0.92%和1.80%改性的AZ91微弧氧化过程、微观结构和组成及氧化膜的耐蚀性能进行研究. 应用电子扫描显微镜(SEM), 电子能谱（EDS）和X射线衍射（XRD）等表征氧化膜的微观结构和化学组成. 利用稳态极化曲线和电化学阻抗谱（EIS）测试了氧化膜在质量分数w(NaCl)为3.5%的溶液中的腐蚀过程. 实验结果表明氧化膜成膜过程可以分为3个阶段; 氧化膜主要由MgO组成, 镁合金中的稀土元素Ce促进成膜过程, 增加膜层的致密性; 稀土改性后镁合金氧化膜的耐蚀性比镁合金基体提高4个数量级, 腐蚀电流密度低至10^-8 A/cm2．

The study of microarc oxidation coating on AZ91 modified by cerium and its corrosion resistance

Anodic coating with higher corrosion resistance was fabricated on AZ91 magnesium alloy modified by cerium element using constant AC voltage microarc oxidation (MAO) power source. The MAO process, microstructure and composition, corrosion resistance of anodic coatings formed on AZ91, AZ91 modified by 0.92 and 1.80% cerium were investigated. The microstructure and composition of the MAO coating were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The corrosion protection performance of MAO coatings was investigated by polarization curves and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. The results show that coating formation process is divided into three stages, and the coating is mainly composed of MgO. The more compact and dense coating is obtained and the rate of coating formation is accelerated by additional cerium element. Corrosion tests indicate that the corrosion resistance of the coating formed on magnesium alloy AZ91 modified by cerium is significantly enhanced about four orders of magnitude comparing with the magnesium alloy, while corrosion current density is even low to 10^-8 A/cm2．