外加电位对X80钢在满洲里土壤应力腐蚀的影响

Influence of Applied Potential on Stress Corrosion Cracking of X80 Steel in Manchurian Soil

针对埋地管道应力腐蚀开裂(SCC)问题,开展了X80管线钢(X80钢)在满洲里土壤模拟溶液中的SCC研究,以期对X80钢的SCC防护提供数据支撑。采用交流阻抗技术、动电位极化技术和慢应变速率拉伸实验研究了X80钢在不同外加电位下满洲里土壤模拟溶液中的SCC行为,并用扫描电镜观察了断口表面微观形貌。结果表明:自腐蚀电位下,X80钢裂纹萌生于点蚀坑处,SCC机制为阳极溶解(AD);在外加电位为-850 mV和-930 mV时,X80钢的应力腐蚀受到抑制作用,SCC敏感性较低,-850 mV为最佳阴极保护电位。这两个电位下X80钢SCC机制为AD和氢致开裂(HIC)混合机制,其中-930 mV下SCC机制由HIC占主导地位;在外加电位为-1 000 mV和-1 200 mV时,X80钢表现出较高的SCC敏感性,SCC机制为氢和应力协同作用下的HIC。

Stress corrosion cracking (SCC) of X80 pipeline steel (X80 steel) in a simulated Manchurian soil solution was studied, with the aim of providing data to support the design of methods to prevent SCC in X80 steel used for manufacturing buried pipelines. By means of an AC impedance technique, a potentiodynamic polarization technique, and slow strain rate tensile tests, the SCC behavior of X80 steel in simulated Manchurian soil solution was investigated under different applied potentials, and the microscopic morphologies of the fracture surfaces were observed using a scanning electron microscope. The results indicated that the self-corrosion potential led to the initiation of cracks at corrosion pits in X80 steel, with anodic dissolution (AD) being the mechanism underlying SCC. Applied potentials of -850 mV and -930 mV provided inhibitory effects against SCC in X80 steel, and reduced sensitivity to SCC;in particular,-850 mV was determined to be the optimal cathodic protection potential. Under these two potentials, SCC in X80 steel occurred via a combination of AD and hydrogen-induced cracking (HIC), with HIC being the dominant mechanism of SCC under the applied potential of -930 mV. Under applied potentials of -1 000 mV and -1 200 mV, X80 steel exhibited higher sensitivity to SCC, with SCC occurring via HIC through the synergistic effects of hydrogen and stress.