油套管用钢P110的CO_2腐蚀动力学研究

利用高温高压腐蚀试验及电化学原位测量技术,并辅以SEM、EDS和XRD等微观分析手段研究了油套管用钢P110在CO2分压为2 MPa、温度为100℃的3.5%NaCl水溶液中的腐蚀失重、界面反应电化学特性、腐蚀产物膜的微观形貌、成分和结构特征,探讨了油套管用钢CO2腐蚀动力学.研究结果表明:油套管用钢P110的CO2腐蚀产物为FeCO3;随腐蚀时间的延长及腐蚀产物膜的形成,平均腐蚀速率逐渐降低、趋势变缓,产物膜生长满足抛物线生长规律;腐蚀产物晶粒逐渐长大并堆垛紧密,逐渐成膜覆盖于金属表面,膜厚先增加后逐渐趋于稳定,对基体保护能力增强;不同腐蚀时间交流阻抗图谱(EIS)的拟合结果表明,极化电阻随着腐蚀时间增加逐渐增大,电极反应由最初的活化控制变为扩散控制.

Research of CO_2 corrosion kinetics of tubing and casing steel P110

Under simulation corrosion environment of 3.5%NaCl solution,2MPa CO2 partial pressure and 100 ℃,the corrosion weight loss,the electrochemical characteristics of interface reaction,the morphology,composition and structural features of the corrosion product films of tubing and casing steel P110 were studied by means of high-temperature high-pressure test and electrochemical in-situ measurement technique,as well as scanning electron microscope(SEM),energy disperse spectroscopy(EDS) and X-Ray diffraction(XRD) analysis methods.CO2 corrosion kinetics of tubing and casing steel P110 was also discussed.The results show that,CO2 corrosion product of tubing and casing steel P110 is FeCO3,and the average corrosion rate becomes lower and lower with the increase of corrosion time.The growth of the corrosion product film presents parabolic law: the particles of FeCO3 are growing up and stack together at beginning,and gradually cover the metal surface to form a film.The thickness of the corrosion product film increases firstly and then trends stable,and its protection effect to metal surface enhances with its thickness increasing.EIS shows that with the reaction time increasing,polarization resistance increases gradually and the electrode reaction controlled by activation at first becomes gradually controlled by diffusion.