采用电化学方法研究了2A12铝合金基体、硬质阳极氧化膜层、不同厚度2A12铝合金微弧氧化陶瓷层的腐蚀性能。结果表明, 微弧氧化处理的铝合金样品耐蚀性能强烈地依赖于陶瓷层的厚度, 陶瓷层越厚其耐腐蚀能力越强。随着微弧氧化时间的延长, 陶瓷层回扫曲线的腐蚀电位逐渐高于正扫的腐蚀电位, 说明没有局部腐蚀倾向, 陶瓷层表面发生了再钝化, 抗点蚀能力增强。采用局部电化学阻抗技术获得的微弧氧化陶瓷层表面阻抗的分布图结果表明, 铝合金微弧氧化陶瓷层表面的阻抗分布很不均匀, 与其表面形貌一致; 微弧氧化60 min的陶瓷层表面的阻抗值在1.0×104~8.0×104 Ω之间, 而微弧氧化90 min的陶瓷层表面的阻抗值在1.8×105~1.4×106 Ω之间。随着微弧氧化时间的延长, 阻抗逐渐增大。

The electrochemical corrosion behaviors of the micro-arc oxidation (MAO) coatings with different thicknesses were evaluated by electrochemical methods. The results show that corrosion resistance of MAO ceramic coatings is significantly dependent on coating thickness, and with the thickness increase, corrosion resistance increases. The corrosive potential of the reverse-scanning curve is gradually higher than that of positive scanning with the increase of MAO treatment time, which illustrates that there is no corrosion tendency, MAO coating surface is re-passivated and anti-pitting corrosion resistance is enhanced. The surface impedance distribution maps of MAO ceramic coatings were obtained by LEIS ( Local Electrochemical Impedance Spectroscopy) technology. It is shown that the impedance is not uniform and is as same as surface morphology, and the impedance range was from 1.0×104 Ω to 8.0×104 Ω for the MAO ceramic coating after 60 min treatment, from1.8×105 to 1.4×106 Ω for the MAO ceramic coating after 90min treatment, indicating that the impedance increases with MAO treatment time.