AZ31镁合金表面聚吡咯-钼酸盐膜的腐蚀性能

Corrosion Properties of the Polypyrrole-molybdate Film Electro-polymerized on the AZ31 Mg Alloy

摘要:

在水杨酸钠溶液中采用循环伏安法在AZ31镁合金表面分别电聚合聚吡咯(PPy)膜和聚吡咯-钼酸根膜(PPy-MoO42-)。利用扫描电子显微镜（SEM）观测PPy膜和PPy-MoO42-膜层腐蚀前后的表面形貌，衰减全反射红外光谱（ATR-IR）反映了PPy膜和PPy-MoO42-膜的特征吸收峰，研究了MoO42-的存在对PPy特征吸收峰的影响。使用四探针法测量薄膜的表面电阻；采用开路电位（OCP），电化学交流阻抗谱（EIS）和动电位极化曲线测试PPy膜和PPy-MoO42-膜在3.5%NaCl溶液中浸泡12h后的耐腐蚀性能。结果显示，PPy-MoO42-膜层更紧凑，PPy-MoO42-膜层的腐蚀电流密度比PPy膜的低三个数量级。钼酸根的存在使得PPy-MoO42-膜的表面电阻比PPy膜小，且PPy-MoO42-膜的耐腐蚀性能较好。

Abstract:

The polypyrrole (PPy) coating and polypyrrole-molybdate (PPy-MoO42-) coating were electro-polymerized in sodium salicylate solution by using cyclic voltammetry (CV) on the AZ31 Mg alloy surface. Surface morphology of PPy coating and PPy-MoO42- coating on Mg alloy surface before and after being corrupted was observed by scanning electron microscopy (SEM). Attenuated total reflection-infrared (ATR-IR) spectra showed the characteristic ring stretching peaks of the PPy coating and PPy-MoO42- coating, and also revealed the influence of MoO42- on the characteristic ring stretching peaks for PPy. The surface resistance was measured by four-point probe method. The open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization analyzed the corrosion resistance performance of PPy coating and PPy-MoO42- coating on the Mg alloy surface in 3.5 % NaCl solution for 12 h. The results showed that the surface morphology of PPy-MoO42- coating is compact. And the corrosion current density of PPy-MoO42- coating is three orders lower than the PPy coating, the PPy-MoO42- coating on the Mg alloy surface had better corrosion resistance and smaller surface resistance than the PPy coating because of the existence of the molybdate ion.