X70管线钢在热带海水-海泥跃变区的腐蚀行为研究

Corrosion Behavior of X70 Pipeline Steel in the Tropical Juncture Area of Seawater-Sea Mud

利用阵列电极技术、线性极化和电化学阻抗等电化学分析技术及腐蚀形貌观察和腐蚀产物物相分析,研究了X70管线钢在海水-海泥跃变区中的腐蚀行为与规律。结果表明,X70管线钢在海水-海泥跃变区形成宏观氧浓差电池,海泥区域及近海水-海泥界面的海水区域为电偶腐蚀阳极区域,海水区域为电偶腐蚀阴极区域;腐蚀后期阶段,海泥下部的电极变为阴极,成为主要的阴极反应区域。海水中的电极腐蚀速率大于海泥中的,而在近海水-海泥界面的区域形成了腐蚀电流峰。海水中高含量的溶解氧促进了电极表面腐蚀产物层的致密化,电荷转移电阻增大;在腐蚀后期,海泥底部硫酸盐还原菌参与了腐蚀反应,生成了硫化物,导致阴极电流密度增大,加快了整个电极的腐蚀速率。

The corrosion behavior of X70 pipeline steel in the tropical juncture area of seawater-sea mud has been studied by means of wire beam electrode technique, linear polarization, electrochemical impedance spectroscopy and other electrochemical analysis technique, coupled with the methods of corrosion morphology observation and corrosion products analysis. The results show that X70 pipeline steel has formed an oxygen concentration cell in the juncture area of seawater-sea mud, the electrodes in the sea mud and in the vicinity of interface of seawater-sea mud act as anode, and the electrodes in the seawater act as cathode. In the last stage of corrosion, the electrodes in the bottom of sea mud become cathode region where the main cathode reaction is occurred. The corrosion rate of the electrodes in the seawater is greater than the electrodes in the sea mud, and there is a peak of corrosion current in the vicinity of interface of seawater-sea mud. Dissolved oxygen promotes corrosion products gradually firmly and densely, the charge transfer resistance increased with the time, sulfate reducting bacteria in the bottom of the sea mud participate in the reaction, produced iron sulfide, the corrosion rate of the whole electrodes speed up with the cathode current density increased.