某成品油外输管道腐蚀失效案例的原因分析

Cause Analysis of Corrosion Failure of Product Oil Export Pipeline

某成品油外输管道在建成后并未立即投产使用,而是在严密性试压后封存高压空气放置约1年时间。正式投产前,在上水作业测试严密性时出现管道漏水现象,泄漏点位置处发生腐蚀失效。为明确管道腐蚀失效原因,本次研究利用扫描电子显微镜(SEM)、X射线能谱分析(EDS)、X射线衍射(XRD)分析等方法,对管道原材料性能、腐蚀产物组成以及腐蚀坑形貌、组织及成分进行了全面分析。结果表明,管道内壁发生氧腐蚀,且在圆周方向具有较为一致的腐蚀环境;腐蚀坑SEM形貌特征显示腐蚀存在明显的闭塞电池效应,通过对腐蚀坑产物能谱分析进一步发现,其中管材中的硫化物夹杂物为点蚀提供诱发源;而氯元素向腐蚀坑底的迁移聚集将会加速管道腐蚀过程,直至发生穿孔。上述研究成果可为类似管道腐蚀问题的原因判断和防护提供参考。

A newly built product oil pipeline was not put into use immediately,but was sealed with high-pressure air for about one year.Before being put into production,leakage occurred in the pipeline during watertight operation,and corrosion failure occurred at the leakage point.In order to clarify the causes of pipeline corrosion failure,the properties of pipeline raw materials,the composition of corrosion products and the morphology,structure and composition of corrosion pits are comprehensively analyzed in this study.The results show that oxygen corrosion occurs on the inner wall of the pipeline,and the corrosion environment in the circumference direction is relatively consistent.SEM morphology characteristics of the corrosion pits show that the corrosion had an obvious blocking cell effect,and energy spectrum analysis of the corrosion pits products further finds that the sulfide inclusions in the pipe provide the induction source for pitting.The migration and accumulation of chloride ions towards the bottom of corroded pits will accelerate the corrosion process until perforation occurs.The above research results can provide a reference for the cause judgment and protection of similar pipeline corrosion problems.