X70钢在酸性土壤模拟溶液中的应力腐蚀行为

在不同的阴极保护电位下,采用慢应变速率拉伸实验、动电位极化方法以及SEM研究了X70钢在酸性土壤模拟溶液中的应力腐蚀行为.结果表明: X70钢发生穿晶应力腐蚀裂纹;应力腐蚀开裂(SCC)萌生与外加保护电位有关,完全受阳极过程控制时X70钢的SCC敏感性较低,但会发生点蚀和严重的均匀腐蚀;受混合电极过程控制和全受阴极过程控制时均能发生SCC;受混合电极过程控制时,SCC二次裂纹与点蚀伴生,裂纹形核密度大;而完全受阴极过程控制时,SCC裂纹附近未见点蚀坑,裂纹形核密度低;混合电极过程控制时比完全阴极电极过程控制下更容易发生SCC裂纹.

SCC OF X70 PIPELINE STEEL IN SIMULATED ACID SOIL ENVIRONMENT

In order to study the SCC susceptibility of X70 pipeline steel in solutions which simulated the acid soil environment of Yingtan, China, slow strain rate testing (SSRT), microstructural observation of fracture areas by SEM and potentiodynamic polarization curves were used here. SCC did occur in the as-received material, with a transgranular cracking mode charged with different cathodic potential.The applied cathodic polarization potential played a important role in facilitating the occurrence of SCC.X70 pipeline steel was little sensitive to SCC in a athodic potential condition, but tended to be attacked by pits and uniform corrosion. However, as the applied cathodic potential droped, a combined electrochemical reaction of athode and cathode controlled the SCC behaviour of X70 steel, and as the applied cathodic potential droped further, cathodic reaction controlled SCC origination of X70 only. At the combined electrochemical condition, cracks occurred with pits together, which were more crowded than those at single cathodic condition at which cracks originated by themselves.