交流电对X80钢在近中性环境中腐蚀行为的影响

Effect of Alternating Current on Corrosion Behavior of X80 Pipeline Steel in Near-Neutral Environment

通过数据采集、电化学测试、浸泡实验和表面分析技术研究了交流电对X80钢在近中性环境中腐蚀行为的影响。结果表明,交流电干扰下,随着交流电密度的增大,交流腐蚀形态发生变化,由全面腐蚀转变为局部腐蚀,且试样表面产生较多的点蚀坑。全波交流电正负半波交替干扰下,X80钢发生阴阳极极化,导致Fe的局部溶解和H的析出;负半波交流干扰下会导致析氢而发生氢致阳极溶解,产生的点蚀坑均较尖锐;正半波干扰下,只发生阳极溶解,产生的点蚀坑呈现凹形,且比较平滑。不同波形交流干扰下,X80钢表面产生的腐蚀产物不一致:全波和正半波干扰下,腐蚀产物较疏松且发生龟裂,无a-FeOOH;负半波交流干扰下,X80钢表面腐蚀产物较致密,腐蚀产物存在a-FeOOH,对基体具有一定的保护作用。

The rapid development of energy, electricity, and transportation industries has created a market for steel pipes; however, buried steel pipelines near high-voltage transmission lines and electrified railways often experience alternating current （AC） corrosion at the damaged coating of pipelines; such phenomenon is mostly due to the resistance between the capacitance and inductance coupling, especially for long-distance pipelines in parallel operation. AC corrosion can cause pipeline corrosion perforation and stress corrosion cracking （SCC） in some cases, which has been a vital threat to the pipeline safety, In this work, the influence of AC on corrosion behavior of X80 pipeline steel was investigated in NS4 nearneutral solution by data acquisition technique, electrochemical test, immersion tests and surface analysis techniques. Results show that with the increasing of AC density, corrosion morphology changed from uniform corrosion to localized corrosion with many pits. Under the full AC interference, X80 steel occurred cathodic and anodic polarization which resulted in iron dissolution and hydrogen precipitation. The negative half wave AC would lead to hydrogen evolution and hydrogen induced anodic dissolution, the pits in X80 steel surface present sharp. However, under disturbance of positive half-wave AC, only anodic dissolution occurred and the pitting appeared spill shape and smoothly. Under various AC waveform interference, the corrosion products of X80 steel surface were different. Under full AC wave and positive half- wave interference, the corrosion products were loose, had have no α-FeOOH and occurred cracks; however, under negative half-wave AC interference, the corrosion products were denser and contained α- FeOOH which has protective effect on substrates.