环境pH值对天然气管线腐蚀行为的影响

Influence of pH Value of Environment on Corrosion Behavior of Natural Gas Pipeline

环境pH值是影响埋地管线腐蚀的关键因素之一。以天然气管线钢X80钢为研究对象,以质量分数为3%的NaCl溶液为腐蚀性介质,通过电化学阻抗测试和腐蚀形貌观察,研究了环境pH值对X80钢腐蚀行为的影响。结果表明:在不同环境pH值下,X80钢的电化学阻抗特征均为双容抗弧。随着环境pH值的增大,扩散电阻减小,扩散电容增大,物质转移加速。同时,X80钢表面腐蚀形貌由全面腐蚀逐渐向点蚀转变。这是由于在碱性条件下容易生成致密腐蚀产物膜并存在Cl-导致的。

pH value of environment was one of the key factors influencing the corrosion of buried pipelines.X80 steel used for natural gas pipeline was taken as the research object,and NaCl solution with a mass fraction of 3%was used as the corrosive medium.The influence of pH value of environment on the corrosion resistance of X80 steel was studied through electrochemical impedance and corrosion morphology observation.The results show that the electrochemical impedance characteristics of X80 steel were both double reactance arcs under different pH value of environment.With the increase of pH value of environment,the diffusion resistance decreased,the diffusion capacitance increased,and the material transfer accelerated.At the same time,the surface corrosion morphology of X80 steel gradually changed from overall corrosion to pitting corrosion,which was caused by the easy formation of dense corrosion product film under alkaline conditions and the presence of Cl-.