铝合金防护涂层老化动力学研究

在紫外/盐雾加速综合环境条件下，研究了铝合金试样上聚酰胺清漆老化过程。采用环境扫描电子显微镜观察了防护涂层表面形貌的变化，采用电化学阻抗(EIS)分析了涂层的老化过程，同时还测量了光泽度、颜色、表面电阻和体积电阻在涂层老化过程中的变化。结果表明：在涂层老化过程中，涂层孔隙率增加，而体积电阻、表面电阻则降低， EIS给出了在涂层老化的不同阶段的特征。采用光泽度、颜色、表面电阻和体积电阻以及电化学阻抗数据作为性能参数，建立了涂层老化动力学方程，并给出了涂层失效判据，并对涂层老化动力学的参数进行了讨论，认为采用体积电阻或低频阻抗模值作为性能参数描述涂层老化动力学过程更为合理。

DEGRADATION KINETICS OF PROTECTIVE COATING FOR ALUMINUM ALLOY

The degradation process of polyamide epoxy varnish for aluminum alloy was studied in ultraviolet/ salt spray combined environmental test,the morphology of the coating was observed by environmental scanning electron microscopy(ESEM),other physical parameters such as volume resistance,surface resistance were also measured in the exposure test.Meanwhile,EIS(electrochemical impedance spectroscopy) was utilized to monitor degradation process of the coating.The results showed that the porosity of the coating increased and the volume resistance and surface resistance decreased in the degradation process.EIS illustrated different stages of the degradation process.First order type degradation kinetics or simplified KWW model are suggested and discussed based on the quantitative measurements;coating failure criterion determined from EIS was also suggested.It is considered that the electrical resistance and electrochemical impedance modulus at low frequency is suitable to construct degradation kinetics.