In the present research, the corrosion resistance of Ni–P and Ni–P–Cr coatings on AA7075-T6 aluminum plates under simulated anodic and cathodic conditions of polymer electrolyte membrane fuel cells (PEMFC) has been studied by electrochemical impedance spectroscopy (EIS). Three Ni–P coatings 20 μm, 30 μm, and 40 μm thick applied by electroless deposition were tested. Besides, a two-layer Ni–P–Cr coating 30 μm thick was also analyzed. It was formed by an inner Ni–P layer, and an outer 10 μm thick chromium one added by electroplating. Corrosion tests were combined with interfacial contact resistance (ICR), roughness, contact angle, and SEM-EDX measurements. The best results were obtained for the 20 μm Ni–P and the two-layer Ni–P–Cr coatings, although the latter showed a high ICR value due to the high electrical resistivity of the chromium oxide surface formed. It was verified that coating degradation occurs when the electrolyte penetrates the micro-cracks and the nodular surface interfaces, reaching the base metal and causing the coating delamination. This behavior is associated with a sharp decrease in the polarization resistance (R_p) of the equivalent circuit model fitted to the EIS results.

在本研究中，已经通过电化学阻抗谱（EIS）研究了AA7075-T6铝板上的Ni-P和Ni-P-Cr涂层在模拟阳极和阴极条件下在聚合物电解质膜燃料电池（PEMFC）上的耐腐蚀性。 。测试了三种通过化学沉积方法涂覆的20μm，30μm和40μm厚的Ni-P涂层。此外，还分析了厚度为30μm的两层Ni–P–Cr涂层。它由一个内部Ni-P层和一个外部10μm厚的铬（通过电镀添加）形成。腐蚀测试与界面接触电阻（ICR），粗糙度，接触角和SEM-EDX测量相结合。对于20μm的Ni–P和两层Ni–P–Cr涂层，可获得最佳结果，尽管后者由于形成的氧化铬表面的高电阻率而显示出高ICR值。证实了当电解质穿透微裂纹和球状表面界面，到达母材并引起涂层分层时，涂层发生降解。此行为与极化电阻（R_p）拟合到EIS结果的等效电路模型。