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目的：研究X80管线钢在近中性pH溶液中的腐蚀与应力腐蚀裂纹萌生行为。方法采用电化学实验和浸泡实验研究X80管线钢在近中性pH溶液中的腐蚀行为,采用慢应变速率拉伸实验研究X80管线钢在近中性pH溶液中,在自腐蚀电位和外加电位下的应力腐蚀裂纹萌生行为。结果 X80管线钢在近中性pH溶液中的极化曲线只有活化区,没有钝化区,其自腐蚀电位约为-750 mV,浸泡195天后,试样表面没有氧化膜出现,但是观察到点蚀坑。在自腐蚀电位下,X80管线钢试验表面有大量的应力腐蚀裂纹；在-500 mV阳极外加电位下,X80管线钢试验表面几乎没有观察到应力腐蚀裂纹；在-850 mV阴极外加电位下,X80管线钢试验表面的应力腐蚀裂纹很少,但是随着外加阴极电位负移到-1300 mV时,X80管线钢试验表面的应力腐蚀裂纹增多。结论 X80管线钢在近中性pH溶液中发生均匀腐蚀,但是夹杂物剥落能在X80管线钢表面形成点蚀坑。在近中性pH溶液中,在自腐蚀电位下,X80管线钢应力腐蚀裂纹萌生敏感性最强；外加阴极电位抑制应力腐蚀裂纹萌生,但是随着外加阴极电位的负移,应力腐蚀裂纹萌生敏感性增强；外加阳极电位下,由于均匀腐蚀的作用,应力腐蚀裂纹萌生敏感性较弱。

ABSTRACT:Objective To study corrosion and stress corrosion crack initiation behaviour of X80 pipeline steel in near-neutral pH solution. Methods In this paper, electrochemical measurement and immersion test were conducted to study the corrosion behavior of X80 pipeline steel in near-neutral pH solution. Slow strain rate tensile tests were also conducted to study the stress corrosion crack initiation behavior of X80 pipeline steel in near-neutral pH solution at open circuit potential ( OCP) and applied potential. Results There was only active region and no passive region in the polarization curve of X80 pipeline steel in near-neutral pH solu-tion. The OCP was measured to be about-750 mV. No oxidation film was formed on the surface of X80 pipeline steel after 195-day immersion, but pits were observed. At OCP, a lot of secondary stress corrosion cracks were found on the surface of X80 pipeline steel. When the applied anodic potential was -500 mV, hardly any secondary stress corrosion cracks were found on the surface of X80 pipeline steel. At an applied cathode potential of-850 mV, few secondary stress corrosion cracks were found on the surface of X80 pipeline steel, but the number of secondary stress corrosion cracks increased when the applied cathode potential negative shif-ted to-1300 mV. Conclusion Uniform corrosion occurred on X80 pipeline steel in near-neutral pH solution, but pits formed on the surface because inclusions disbonded. At OCP, the sensitivity of stress corrosion crack initiation of X80 pipeline steel was the high-est in near-neutral pH solution. Stress corrosion crack initiation was inhibited by applied cathode potential, but the sensitivity of stress corrosion crack initiation increased as the applied cathode potential negative shifted. At applied anodic potential, the sensi-tivity of stress corrosion crack initiation was low because of uniform corrosion.