X70钢在酸性土壤模拟溶液中的应力腐蚀行为

STRESS CORROSION BEHAVIOR OF X70 PIPELINE STEEL IN SIMULATED SOLUTION OF ACID SOIL

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.

Stress corrosion cracking （SCC） of the acid soil environment of Yingtan in China was observation of fracture surfaces and potentiodynamic X70 pipeline steel in the simulated solutions of studied by slow strain rate test （SSRT）, SEM polarization curves. Results show that SCC has a transgranular cracking mode at varying potentials. The applied polarization potential played an important role in facilitating SCC. Within anodic potential range X70 pipeline steel was controlled by anode process and unsensitive to SCC, but tended to be attacked by pitting and uniform corrosion. At cathodic potential range, X70 pipeline steel was controlled by a combined electrochemical process of anodic and cathodic processes at a higher potential range, but as the applied cathode potential lowered further, only controlled by the cathodic process. Under the two conditions X70 pipeline steel was sensitive to SCC, under the anodic/cathodic combined electrochemical condition, SCC originated closely together with pits, and under single cathodic condition, cracks originated sparsely and no pits appeared nearby.