X80管线钢在近中性pH溶液中腐蚀行为研究

目的研究X80管线钢在近中性p H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p H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p H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p H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 m V,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 m V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 m V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 m V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p H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p H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。

Corrosion Behaviour of X80 Pipeline Steel in Near-neutral pH Solution

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 research corrosion behavior of X80 pipeline steel in near-neutral pH solution. Slow strain rate tensile tests were also conducted to research 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 just active and no passive region in polarization curve of X80 pipeline steel in near-neutral pH solution. The OCP was measured to be about -750 mVSCE. No oxidation film was formed in the surface of X80 pipeline steel after immersed 195 days, but pits were observed. At OCP, a lot of secondary stress corrosion cracks were found in the surface of X80 pipeline steel. At applied anodic potential of -500 mVSCE, hardly secondary stress corrosion cracks were found in the surface of X80 pipeline steel. At applied cathode potential of -850 mVSCE, a few secondary stress corrosion cracks were found in the surface of X80 pipeline steel, but the number of secondary stress corrosion cracks increased as applied cathode potential negative shifted to -1300 mVSCE. Conclusion Uniform corrosion occurs of X80 pipeline steel in near-neutral pH solution, but pits form in the surface because inclusions disbonded. At OCP, the sensitivity of stress corrosion crack initiation of X80 pipeline steel are strongest in near-neutral pH solution. Stress corrosion crack initiation is inhibited by applied cathode potential, but the sensitivity of stress corrosion crack initiation increases as applied cathode potential negative shifted. At applied anodic potential, the sensitivity of stress corrosion crack initiation is weak because of uniform corrosion.