WBE联合EIS技术研究缺陷涂层下金属腐蚀

用电化学阻抗谱(EIS)结合丝束电极(WBE)技术研究了缺陷涂层浸泡在3.5%(质量分数)NaCl溶液中的劣化过程.从浸泡开始到完好涂层鼓泡失效,缺陷涂层丝束电极阻抗响应一直是缺陷区电极腐蚀反应过程特征,而完好涂层的劣化过程和涂层下的腐蚀反应过程特征被"平均掉".根据电极表面的电流分布,结合阻抗谱技术实现了对表面任意局部阴极和阳极区阻抗测试.研究发现,浸泡开始时,缺陷涂层阴极电流和阳极电流均出现在缺陷区,随着腐蚀过程的发展,阳极电流仍然保持在缺陷区,但阴极电流逐渐向完好涂层下扩展.根据实验结果,对缺陷处和涂层下金属腐蚀反应发生发展的机理进行了深入讨论.

Evaluation of Metal Corrosion under Defective Coatings by WBE and EIS Technique

We investigated the corrosion of steel under defective coatings in 3.5% (mass fraction) NaCl solution by the wire beamelectrode (WBE) and electrochemical impedance spectroscopy (EIS) technique. During the entire coating deterioration process, the EIS diagrams were dominated by the substrate corrosion process of the defect while the coatings and underlying electrochemical processes were“averaged”out. However, according to the current distribution maps plotted using the WBE, EIS responses of the anodic and cathodic regions of the defect and underlying coatings were detected. Initially, the high anodic and cathodic current densities were only monitored at the defect areas and then the cathodic sites spread out beneath the coatings around t2948he defect while the anodic sites remained on the defect. The substrate corrosion initiation and development mechanism of the defect and underlying coatings is discussed based on experimental results.