20/316L双金属管的腐蚀失效原因分析

随着20/316L双金属管在油气生产中的推广应用,关于内衬316L不锈钢的腐蚀失效问题日益突出,尤其是条件苛刻的酸性集输环境下,目前相关研究不多.利用扫描电镜(SEM)、能谱仪(EDS)等测试手段对20/316L双金属管在含H2S-Cl-的酸性集输环境中出现的腐蚀失效问题进行了系统分析,探讨了腐蚀失效的原因.结果表明:20/316L双金属管腐蚀类型为局部腐蚀,主要分布于内衬管316L的底部.腐蚀失效的主要原因是腐蚀介质中存在高浓度的H2S与Cl-,共同促进了钝化膜的破裂与点蚀的发展.当存在较高浓度的H2S与Cl-时,钝化膜薄弱处与电位较低的非金属夹杂物处易发生钝化膜的破裂与金属基体的快速溶解而成为点蚀源,形成点蚀.

Analysis on Corrosion Failure of 20/316L Bimetal-Lined Pipe

A system analysis on the corrosion failure of 20/316L bimetal-lined pipe was conducted by scanning electronic microscopy (SEM)and energy dispersive spectrometer (EDS).Furthermore,the main reasons of the failure were defined.Results showed that the corrosion occurred on the inside wall of 316L stainless steel,especially on the bottom of 316L stainless steel tubing.High concentrations of H2 S and Clpromoted the cracking of surface passive film and the improvement of pitting on the 316L stainless steel.When the high concentrations of H2S and Cl-existed,the passivation layers on the locations of poor passivation layer and nonmetallic inclusions were susceptible to the local structural damage and the local dissolution of metal substrate became the sources of pitting corrosion.Ultimately the pitting corrosion was developed.