扫描电化学显微镜原位观察碳钢涂层缺陷处的交流腐蚀行为

将原位微区电化学与传统宏观电化学技术相结合，应用电化学扫描显微镜(SECM)技术和电化学阻抗谱技术并结合微观形貌分析，研究了碳钢涂层缺陷处在不同交流电流强度下的腐蚀行为。结果表明：SECM拓扑形貌直观反映了碳钢涂层缺陷处局部腐蚀过程中电化学活性点的变化。交流电流使涂层缺陷处腐蚀活性点的数量明显增多，且使表面腐蚀产物积累对腐蚀产生的抑制作用明显减弱；浸泡初期涂层缺陷处的腐蚀为电子转移控制过程，浸泡10 h后转为扩散控制过程；随着交流电流强度的增大和浸泡时间的延长涂层的剥离程度提高，点蚀坑的深度和宽度随之增大。

In Situ SECM Observation of Corrosion Behavior of Carbon Steel at Defects of Epoxy Coating under AC Current Conditions

The carbon steel corrosion behavior at defects of epoxy coating in the effect of different AC current densities was investigated by means of in situ micro-area electrochemistry and traditional macro-electrochemical techniques, namely electrochemical scanning microscopy (SECM) and electrochemical impedance spectroscopy techniques. SECM observation can directly reveal the change of electrochemical active points during the local corrosion process of carbon steel at coating defects. The results show that when AC current is present, the number of corrosion active points at the coating defects is significantly more than that in the absence of AC current, correspondingly, the inhibitory effect of the corrosion products is significantly weaker than that in the case without AC current. The corrosion at the coating defect at the initial stage of immersion is an electron transfer control process, and it is converted to a diffusion control process after soaking for 10 hours. With the increase of AC current intensity and immersion time the degree of coating peeling increases, and the depth and width of the pits increase.