镁合金涂装体系盐雾条件下失效过程的电化学阻抗谱特征

对比碳钢涂层试样,对镁合金涂装体系进行了盐雾实验,跟踪检测了涂层失效过程的电化学阻抗谱特征.结果表明:镁合金涂装试样均比碳钢涂层试样易受扩散控制,扩散特征直线斜率均小于1,并分析了可能的原因;证明了铬酸盐体系中感抗因素的存在;同时利用数学解析的方法获得了涂层电容与电阻的信息,表明介质渗透至界面后,镁合金涂漆试样吸水量急剧增加,且腐蚀程度也远比碳钢涂漆试样严重;涂层电容与电阻的计算值并不恒定,为弥散区间,并且腐蚀越严重,区间变化幅度越大.

Degradation of Paint Finishing on Magnesium Alloys in Salt Spray Characterized by Electrochemical Impedance Spectroscopy

Compared with painted carbon steel, the degradation of the paint finishing system of magnesium alloys in salt spray was studied by Electrochemical Impedance Spectroscopy (EIS). The result showed that whether based on chromate conversion coating or not, the electrode process of the paint system on magnesium alloys was more inclined to be controlled by diffusion than that on carbon steel, and the slop of the diffusion line was less than 1. The possible reason was given. It was proved that inductance unit existed in the finishing system with chromate conversion coating. The coating resistance and capacitance were calculated with all EIS data. The finishing system with chromate conversion coating absorbed much more water and corroded more severely than that without chromate conversion coating. The calculated values were not fixed but varied, and the more severely the coating degraded, the more widely the value ranged.