氯化钠溶液浓度和阴极保护对环氧粉末涂层性能的影响

Effects of Concentration of Sodium Chloride Solution and Cathodic Protection on Performance of Epoxy Powder Coating

为进一步研究Q235钢表面环氧粉末涂层在海洋环境中的失效机制,利用称重法研究了60℃下不同浓度的Na Cl溶液中水在不同阴极保护条件下的环氧粉末涂层中的扩散行为,利用电化学阻抗谱技术(EIS)研究了不同Na Cl溶液浓度和阴极保护水平对涂层性能的影响。结果表明:随Na Cl溶液浓度增加,涂层的饱和吸水量减少,水在涂层中的扩散系数变大,其扩散机制符合Fick扩散模型;Na Cl溶液浓度增加加速了环氧粉末涂层的劣化,阴极保护一定程度上也降低了环氧粉末涂层的性能,过保护则会明显影响涂层性能,涂层起泡过程中涂层电容经历明显的3个阶段,在第3阶段中涂层结构可能发生变化,直至涂层起泡失效。

In order to study the failure mechanism of the epoxy powder coating on the Q235 steel under marine environments,the diffusion behavior of water in the coating was investigated in different concentrations of NaC l solution under cathodic protection at 60 ℃ by gravimetric method,and the effects of the concentration of NaC l solution and the cathodic protection level on the coating properties were investigated by electrochemical impedance spectroscopy( EIS). The results showed that with the increase of the concentration of NaC l solution,the amount of saturated absorbed water decreased and the diffusion coefficient of water in the coating rose. The diffusion mechanism complied with the Fick diffusion model. The higher concentration of NaC l solution accelerated the degradation of epoxy powder coating. The cathodic protection also reduced the performance of epoxy powder coating in a certain degree and the overprotection significantly affected the coating performance. The change of coating capacitance underwent three stages during the cathodic blistering process of coating,and at the third stage the coating structure might change until the coating failed and blistered.