阴极电位对X80管线钢在碱性土壤模拟溶液中应力腐蚀行为的影响

Effect of cathode potentials on stress corrosion behavior of X80 pipeline steel in simulated alkaline soil solution

采用慢应变速率拉伸试验(SSRT)、动电位极化技术及交流阻抗技术研究不同阴极电位下X80管线钢在库尔勒土壤模拟溶液中的应力腐蚀开裂(SCC)行为,并结合扫描电子显微镜(SEM)对试样断口形貌进行表征。实验结果表明:随着阴极电位的降低,X80管线钢的SCC敏感性呈现先下降后上升的趋势;Ecorr下,金属表面裂纹萌生于点蚀坑,试样的开裂机制为阳极溶解机制;外加电位在-0.80 V至-0.95 V间试样处于阴极保护电位区,此区域内金属的应力腐蚀敏感性较低,SCC机制为阳极溶解和氢致开裂混合机制;当阴极电位为-0.90 V时,试样处于受保护状态;电位为-1.0 V和-1.2 V时,金属的SCC敏感性不断增大,金属应力腐蚀开裂表现为氢致开裂机制。

Slow strain rate testing（SSRT）, potentiodynamic polarization and electrochemical impedance technology were employed to study the stress corrosion cracking（SCC） behavior of X80 pipeline steel at different cathode potentials in Ku＇erle soil simulated solution. Fracture surfaces were observed by SEM under applied cathode potential conditions. The results show that the SCC sensitivity of the metal first decreases but then increases with the reduction of cathodic potential. The cracks are generally initiated at corrosion pits with open circuit potential. The crack generation mechanism of X80 steel is attributed to anodic dissolution. When the applied potential is from-0.80 V to-0.95 V, the metal exhibited lower SCC sensitivity under the potential area and their cracking generation mechanism is anodic dissolution and hydrogen embrittlement. When the cathode potential is-0.90 V, the metal is protected. When the applied potentials are-1.0 V and-1.2 V, the process of hydrogen evolution plays the dominant role in SCC occurrence, meaning that the SCC mechanism is hydrogen embrittlement. Moreover, SCC susceptibility increases with the decrease of the applied cathodic potential.