基于高频电化学阻抗谱测试的涂层防护性能评价方法

Evaluation of Protectiveness of Organic Coatings by means of High-Frequency EIS Measurement

研究了施加掺杂铁红粉的环氧涂层的Al在3.5 mass%NaCl溶液(模拟海洋环境)中的电化学阻抗谱(EIS)随浸泡时间的变化,提出了两种基于高频EIS测试数据的快速评价涂层防护性能方法:局部拟合涂层电阻法和修正的特征频率法。结果表明,虽然局部拟合所得的涂层电阻值与全谱拟合所得值有一定偏差,但它们的变化趋势吻合,且很好反映了涂层的失效过程,说明局部拟合涂层电阻的方法有望被用于涂层防护性能的监检测。此外,针对传统涂层快速评价所用的特征频率法未考虑涂层电容弥散效应的不足,提出了考虑涂层电容弥散效应时特征频率的修正方法。实验观察到,在涂层浸泡过程中涂层电容对应的n值逐渐下降,而修正值与传统特征频率值差别也越来越大,说明在涂层防护性能监检测中对传统特征频率法进行修正十分必要。

In this paper,the evolution of Electrochemical Impedance Spectroscopy（EIS） behavior for the red iron oxide pigmented epoxy coatings on aluminum alloys in 3.5 mass% NaCl solution was investigated,and two methods for rapidly evaluating the protectiveness of organic coatings based on high-frequency EIS data were proposed,i.e.the partial fitting coating resistance method and the corrected break-point frequency method.The partially fitted coating resistance from high-frequency EIS data and the coating resistance fitted from all-frequency EIS data showed similar evolution trends as a function of immersion time,although they had different values.The partially fitted coating resistance also well reflected the degradation of the coatings,indicating it could be used for monitoring the performance of coatings.In addition,we corrected the traditional break-point frequency method which was generally used for rapidly evaluating the protectiveness of coatings by considering the non-ideal coating capacitance.It was observed that as the immersion went on,the CPE power n of the coating decreased,and the difference between corrected break-point frequency and the traditional break-point frequency became more remarkable,indicating the necessity of correction for the traditional break-point frequency method.