外加电位对X80管线钢模拟海岸土壤腐蚀的影响

为探究双相X80管线钢在沿海土壤模拟溶液环境中的腐蚀机理，采用极化曲线、慢应变速率拉伸试验(SSRT)和交流阻抗(EIS)法对不同外加电位(-750,-900和-1 050 mV vs.饱和甘汞电极(SCE))下双相X80管线钢的应力腐蚀和电化学腐蚀行为进行研究。结果表明，双相X80管线钢在-1 050 mV电位下对应力腐蚀(SCC)最为敏感。慢应变拉伸呈现为脆性断裂，断口可见铁素体区域圆形或椭圆形的凹坑，这是由于过度阴极反应产生的氢原子扩散进入到钢中在铁素体晶界聚集，氢气析出产生的较高氢压超过材料的强度产生圆形孔洞，在拉伸应力作用下变为椭圆形。在此电位下EIS模拟电阻最小，耐腐蚀性最差。-750 mV的外加电位可起到一定的电化学保护作用，但不足以防止X80管线钢应力腐蚀的发生。-900 mV的外加电位可有效抑制X80管线钢的阳极溶解，SSRT的强度和延展性均高于0 mV电位试样，表现出韧性断裂特征，EIS模拟电阻最高，因此双相X80管线钢在模拟海岸土壤环境下最佳的阴极保护电位约为-900 mV vs. SCE。双相X80管线钢在沿海土壤模拟环境中的应力腐蚀行为的研究可对其在实际使用过...

Effect of applied potentials on the corrosion of X80 pipeline steel in simulated coastal soil solution

In order to explore the corrosion mechanism of dual-phase X80 pipeline steel in the coastal soil simulation solution environment, the stress corrosion and electrochemical corrosion behavior of dual-phase X80 pipeline steel under different applied potentials (-750,-900 and -1 050 mV vs. saturated calomel electrode (SCE)) were studied by using polarization curve, slow strain rate tensile test (SSRT) and electrochemical impedance spectroscopy (EIS). The results show that dual-phase X80 pipeline steel is the most sensitive to stress corrosion (SCC) under -1 050 mV potential. SSRT exhibits brittle fracture, with circular or elliptical pits visible on the fracture at the ferrite region. This is due to the diffusion of hydrogen atoms generated by excessive cathodic reaction into the steel and aggregation at the boundaries of ferrite grains. When the hydrogen pressure generated by hydrogen gas precipitation exceeds the material strength, circular pits are generated and become elliptical under tensile stress. Meanwhile, EIS of sample, under-1 050 mV has the smallest simulated resistance, indicatingits worst corrosion resistance. The external potential of-750 mV can provide some electrochemical protection, yet it is not enough to reduce the stress corrosion of dual-phase X80 pipeline steel. The external potential of-900 mV can effectively inhibit the anodic dissolution of X80 pipeline steel. The strength and ductility of X80 pipeline steel after SSRT under-900 mV are both higher than those without external potential, exhibiting ductile fracture characteristics . Its EIS simulationresistances are the highest.Therefore, the optimal cathodic protection potential of dual-phase X80 pipeline steel in simulated coastal soil environment is about -900 mV vs. SCE. The study on the stress corrosion behavior of the dual-phase X80 pipeline steel in the simulated coastal soil environment can provide a theoretical basis for its safe service and provide a reference for corrosion suppression and protection in practical application.