交流干扰下近中性环境中涂层失效机制研究

Effect of AC Interference on Failure Mechanism of Coatings in Near-Neutral Solution

为明确交流环境中富锌环氧涂层失效演化的电化学机制,通过电化学实验分析了环氧富锌涂层在近中性环境中的电化学阻抗特征,考虑交流电的影响,研究了涂层的失效演化机理。结果表明:在近中性溶液中,当无交流干扰时,富锌涂层的防护效果依次体现在:涂层本身的物理屏蔽作用、涂层中分布的锌粉的电化学过程和腐蚀产物的堵塞、界面上锌粉的电化学保护作用。而交流电能够抑制涂层中锌颗粒的活化过程,导致溶液能够更快地到达涂层/金属界面上,形成Zn-Fe原电池,提供阴极保护作用;当涂层内部的锌粉被大量活化,交流电能够加速活化锌颗粒的反应过程,减弱阴极保护作用,但腐蚀产物阻塞扩散通道,增强了涂层的物理屏蔽作用。

To investigate the electrcochemical feature of zinc-rich coating under AC interference,the failure evolution mechanism of zinc-rich coatings in near-neutral environments with/without AC interference voltage were studied by electrochemical experiments,in which the electrochemical impedance characteristics of the coatings were analyzed. The results showed that in near-neutral environments with no AC interference,the protection of zinc-rich coatings behaved as follows :the physical shielding effect of the coatings,the electrochemical process of zinc distributed in the coatings and the plugging of corrosion products,and electrochemical protection of zinc at the coating/metal interface. However,under the influence of AC voltage,the activation process of zinc was inhibited,so the corrosion medium can reach the coating/metal interface more quickly to form Zn-Fe cathodic protection. When the zinc inside the coatings was activated in large quantities,AC voltage can promote the reaction process of activated zinc,weaking the cathodic protection. However,the corrosion products blocked the diffusion channel to enhance the physical shielding effect of the coating at this time.