利用浸泡实验研究金属基材上不同表面污染条件下环氧富锌/环氧云铁/聚氨酯涂层体系的电化学阻抗特征,用Nyquist图、低频阻抗、相对介电常数、特征频率等评价表面污染对涂层防护性能的影响.结果表明:锈层存在会加强金属表面离子吸附,增大体系电容,降低腐蚀反应阻力;可溶盐污染主要作用为加速侵蚀组分渗透,促使涂层起泡;粉尘污染为微孔成形提供条件,且涂层会因应力集中及早形成破损点而丧失保护能力.4种涂层体系整体防护性能排序为:正常涂层＞锈层污染＞可溶盐污染＞粉尘污染.
The failure process of zinc-rich epoxy/micaceous iron oxide epoxy/ polyurethane coatings on steels with different surface pollution was investigated by electrochemical impedance spectroscopy (EIS).The Nyquist diagrams,low-frequency impedance (LFI),relative dielectric constant and break-point frequency were applied to evaluate the protection characteristics of four coating systems.The results showed that the rust layer can enhance the adsorption of ions on the metal surface,increase the system capacitance and reduce the corrosion resistance.The main effect of soluble salt contamination was to accelerate the infiltration of the erosive components which made the coating blistering.The existence of dust could result in the form of the micropore,and the stress concentration could accelerate the coating failure with the formation of damage point.The sequence of four coating systems in terms of protective performance was that the normal sample was superior to all specimens,the specimen with rust contamination was better than the specimen with soluble salt contamination,and the specimen with dust contamination sample had the worst protection capability.
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