剥离涂层下的X80钢在鹰潭土壤模拟溶液中的腐蚀行为

CORROSION BEHAVIOR OF X80 STEEL IN YING-TAN SOIL SIMULATED SOLUTION UNDER DISBONDED COATING

构建了埋地管线钢在鹰潭土壤模拟溶液中的矩形缝隙剥离涂层模型,采用原位电化学测量方法对剥离区的X80钢进行电化学交流阻抗谱(EIS)表征,并对其腐蚀行为进行了研究.结果表明.腐蚀初期剥离区各位置的电化学反应特征相同、EIS由高频容抗弧和低频感抗弧组成.随着腐蚀反应进行,高频容抗弧半径增大.低频感抗弧消失.距漏点不同距离的X80钢试样的腐蚀程度有所区别:漏点处和剥离区底部的腐蚀最严重.为吸氧腐蚀和阳极溶解所致;剥离区中部腐蚀较弱,去除腐蚀产物的X80钢表面出现明显的点蚀坑,点蚀倾向加重,腐蚀类型由全面腐蚀向局部腐蚀转变.根据EIS规律和实验结果.剥离区的腐蚀进程可分为氧耗尽、阴离子迁移和腐蚀扩展3个阶段.

In this work, a rectangular crevice disbanded coating model of buried steel pipeline in Yingtan soil simulated solution was made, and the in situ electrochemical measurement of electro- chemical impedance spectroscopy （EIS） was used for characterization of XS0 steel under the disbonded coating, at the same time, the corrosion behavior was also investigated. The results showed that the electrochemical characteristics in each position of disbonded area was almost same in the early corrosion time, and the EIS was composed of high-frequency capacitance and low-frequency inductance. After corrosion occurred, the high-frequency capacitance radius increased, and the low-frequency inductance disappeared. The extent of corrosion of XS0 steel specimen surface was rather distinct with distance from holiday. The corrosion at holiday and the bottom of disbonded area was most serious because of oxygen corrosion and anodic dissolution. However, in the central, it was weaker. After removing the corrosion product, pits appeared obviously on the specimen surface in the central of disbonded area, indicating that the tendency of pitting occurring increased, and the type of corrosion changed from general corrosion to localized corrosion. According to the EIS and experimental results, the corrosion process under disbanded area could be divided into three steps： oxygen depletion, anion migration and corrosion expansion.