通过电化学阻抗谱(EIS)技术研究了LY12铝合金/钝化膜/环氧涂层复合电极在NaCl水溶液中的腐蚀行为.结果表明, 随浸泡时间的延长, 复合电极体系的阻抗不断增大；在浸泡初期, 复合电极体系的阻抗谱中即出现了低频扩散阻抗, 认为该阻抗由金属表面钝化膜的溶解产物的传质引起. 扫描电镜(SEM)观察表明铬酸盐钝化膜呈现明显的裂纹形貌; 利于溶解的铬盐通过裂纹到达合金基体使其钝化,是复合电极阻抗不断增大的原因所在.
The corrosion performance of LY12 aluminum alloys/passivation film/epoxy coatings was characterized by electrochemical impedance spectroscopy (EIS) in NaCl solution. The results showed that with the increasing of immersion time, the impedances of composite electrodes continuously increased. In the beginning of immersion, the diffusion impedance emerged in the impedance spectroscopy of composite electrode, which was considered to result from the mass transport behavior of solving products of passivation film prepared on metal substrates. The observation of scanning electron microscope (SEM) suggested that the chromate conversion film presented the obvious crack morphology on metal substrates, which was favour for solving chromate to penetrate through the film and passivate the metal substrate surface. This may be the possible reason of the continuous increasing of impedance of composite electrodes.
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