6.5%Cr钢在高温高压CO_2环境下的腐蚀行为研究

CORROSION BEHAVIOR OF 6.5%Cr STEEL IN HIGH TEMPERATURE AND HIGH PRESSURE CO_2 ENVIRONMENT

利用高压釜,研究了6.5%Cr钢在80℃和0.8 MPa CO_2条件下的腐蚀行为.利用SEM和EDS研究了腐蚀产物膜表面和截面微观形貌以及Cr在腐蚀产物膜中的富集状况.利用高温高压电化学测试研究了线性极化电阻和电化学阻抗谱(EIS)随腐蚀时间的变化.结合溶液离子浓度测试,探讨了腐蚀产物膜生长机制.结果表明,6.5%Cr钢腐蚀速率为0.72 mm/a,腐蚀产物膜中存在Cr的富集,Cr/Fe之比超过了5∶1.不同腐蚀时间下,溶液中Cr3+含量都很低,说明Cr很少进入溶液.

In the oil and gas industry,CO_2 in reservoirs generally causes severe corrosion of C steel in pipelines.Adding Cr to C steel can enhance CO_2 corrosion performance by a factor of at least 3,and even up to 10 times and more,whilst maintain a cost penalty less than 1.5 times that of C steels.Corrosion behavior of 6.5%Cr steel in high temperature and high pressure CO_2 environment is investigated in this work.The corrosion rate of6.5%Cr steel at 80 ℃ and 0.8 MPa is measured by autoclave.The surface and cross-sectional morphology is studied by SEM,and the enrichment of Cr in the corrosion scale is investigated by EDS.The change of LPR and EIS results with corrosion time is studied by high temperature and high pressure electrochemical tests.According to the test results of ion concentration in the solution,the mechanism of corrosion scale growth is discussed.The results show that the corrosion rate of 6.5%Cr steel is 0.72 mm/a.The Cr enriches in the corrosion scale,and the Cr/Fe ratio is higher than 5∶1.Under different corrosion time,the concentration of Cr3＋in the solution is always low,which demonstrates that Cr seldom enters into solution.