高压干法X65管线钢GMAW焊接接头在模拟海水中的腐蚀行为

高压干法熔化极气体保护焊(简称GMAW)在海底油气管道等水下构件的组装和维修中有着非常广泛的应用,焊接接头在海水中的腐蚀行为对于海底输油管道的安全运行至关重要.通过模拟浸泡试验和极化曲线法研究不同环境压力下(常压,0.3?MPa,0.5?MPa)?X65管线钢干法GMAW焊接接头在人工海水中的腐蚀行为及机理.?结果表明...

Corrosion behavior of X65 pipeline steel welded joints by hyperbaric GMAW in simulated seawater

Hyperbaric dry GMAW is widely employed commercially in the fabrication and maintenance of submarine oil and gas pipelines. The corrosion behaviors of welded joint in seawater are therefore of utmost importance in security operation of the pipelines. The corrosion performance and mechanism of X65 pipeline steel welded joints by hyperbaric GMAW under different ambient pressures (0.1, 0.3, 0.5 MPa) were studied by polarization curves and immersion simulation experiments in artificial seawater. It was found that compared with the welding base metal and welded zone, the corrosion resistance of heat affected zone is the worst, and the ambient pressure has little effect on the corrosion resistance of the welded joint. Corrosion morphology and corrosion product shows that pitting corrosion is the main corrosion form for the welded joints, and serious local pitting corrosion occurs at the late immersion stage. The corrosion product is composed of FeOOH, Fe₂O₃ and Fe₃O₄. The corrosion product on the surface of the welded joints can mitigate the corrosion at the initial immersion stage. With prolonged immersion durations, the compactness of the corrosion products layer reduces, the metal under the layer is vulnerable to the corrosion by Cl?, and thus the local pitting corrosion process is promoted.