20G钢输气管线腐蚀失效研究

Investigation on the Corrosion Failure of 20G Gas Pipeline

针对某20G钢输气管线腐蚀穿孔失效,对管线失效特征和腐蚀环境特征进行了分析,试验研究了20G钢的组织结构、腐蚀速率及腐蚀产物,探讨了20G钢与环境介质的相互作用。结果表明:腐蚀失效发生在沟壑积液处;20G钢是铁素体和渗碳体的复相组织,晶粒粗大,在液相中具有较高的腐蚀破坏风险,CO2和Cl-是影响腐蚀的主要因素,腐蚀速率随它们的含量增加而增大;腐蚀产物沿晶面条状堆垛易引发局部腐蚀,使腐蚀产物膜鼓包并破裂,Cl-对其具有促进作用,导致管线局部穿孔失效。由此对该油田所属气井输气管线进行了腐蚀失效风险预判,提出了防腐措施。

For the corrosion failure of 20G gas pipeline,the failure characters of pipeline and environmental factors were analyzed.The metallurgical structure,corrosion rate and corrosion scale were studied in experiments.Thus,the interaction of 20G steel and aggressive medium was discussed.It indicates the failure locates in the liquid accumulation when the pipeline traverses the gully.20G steel is composed of ferrite and pearlite.It has high corrosion risk in the corrosive solution due to the coarse crystalline grains.CO2 and Cl-play most important role on the corrosion.The corrosion rate increases with the increasing concentrations of them.Wattle corrosion scale grows along the crystal plane.Pitting initiates under the scale,and it makes the scale bulge and then crack.Cl-accelerates the localized corrosion.As a result,the pipeline is damaged.Based on these cases,the corrosion risk predication and anti-corrosion measures are suggested to the pipelines in this gas field.