碱性环境下氯离子对埋地管道腐蚀特性研究

ON THE CORROSION CHARACTERISTICS OF BURIED PIPELINES BY CHLORIDE IONS IN ALKALINE ENVIRONMENT

氯离子是影响现场管道腐蚀过程的关键阴离子之一。通过电化学测试方法和图像分析方法对高温、碱性、含Cl^(-)环境中X60钢的腐蚀行为进行了研究。结果表明:在高温碱性环境下,Cl^(-)对金属表面钝化膜的破坏过程主要分为3个阶段:1)开路电位负移——形成致密腐蚀产物膜;2)开路电位正向偏移——Cl^(-)诱发点蚀;3)开路电位基本保持不变——系统达到动态平衡状态,电化学阻抗测试结果与开路电位测试结果相吻合。同时,随着时间的推移,金属表面状态由钝态转向点蚀状态。

Chloride ion is one of the key anions affecting the corrosion process of pipelines.In this paper,the corrosion behavior of X60 steel in high temperature,alkaline and Cl^(-) containing environment was studied by electrochemical measurement and image analysis.The results showed that in high temperature and alkaline environment,the destruction process of Cl^(-) on the metal surface passivation film can be divided into three stages:1)The negative shift of open circuit potential indicated the formation of dense corrosion product film;2)The positive shift of open circuit potential presented the occurrence of pitting corrosion induced by Cl^(-);3)The open circuit potential remained unchanged,meaning that the system reached a dynamic equilibrium state.Under this circumstance,the electrochemical impedance test results were consistent with the open circuit potential test results.Meanwhile,with the passage of time,the state of the metal surface changed from blunt state to pitting state.