通过对某油田使用的N80钢油管的化学成分、显微组织、腐蚀形貌和腐蚀产物进行分析, 探讨了该油管腐蚀失效的原因。结果表明: 该油管的主要腐蚀形式为局部腐蚀, 外壁主要表现为大面积的点蚀, 内壁主要表现为涂层破坏引起的严重局部腐蚀; 腐蚀介质中的O2、Cl-和S2-导致油管发生吸氧腐蚀、氯盐腐蚀和硫化物腐蚀, 其中Cl-为主要的腐蚀介质;S2-和Cl-的协同作用会加速腐蚀产物膜的破坏, 从而导致腐蚀加剧。

Corrosion reasons for N80 steel tubing used in a oilfield were discussed by analyzing chemical composition, microstructure, corrosion morphology and corrosion products. The results show that the main corrosion forms of the tubing was local corrosion; outer wall showed a large area of pitting while inner wall manifested as severe local corrosion due to failure of corrosion coating. O2, Cl- and S2- in corrosion media caused oxygen-absorption corrosion, Cl- corrosion and sulfide corrosion, Cl- was the main corrosive media. Synergistic effect of S2- and Cl- accelerated the destruction of corrosion product film, and thus leading to corrosion accelerating.