压应力对P110套管钢CO2腐蚀产物膜的影响

Effect of Compressive Stress on Corrosion Product Films on P110 Casing Steel in CO2 Environment

目前,鲜见压力作用下P110钢在CO2环境中腐蚀行为的综合研究,采用高温高压釜制备了压应力作用下P110钢在CO2环境中的腐蚀产物膜,并用扫描电子显微镜(SEM)、X射线衍射仪(XRD)观察和分析了P110钢腐蚀产物膜的表面形貌和物相。利用电化学工作站得到了P110钢腐蚀产物膜在溶有饱和CO2的质量分数为3.5%的NaCl溶液中的电化学阻抗谱(EIS)、动电位极化曲线和Mott-Schottky(M-S)曲线等电化学性能。结果表明:P110钢在压应力作用下能形成一层完整的腐蚀产物膜,并且压应力不会改变腐蚀产物膜的物相组成;施加引起弹性形变的压应力(30%σs,90%σs)会使腐蚀产物膜的晶粒变大,晶界减少,腐蚀产物膜中的离子微观通道减少,电荷转移电阻增大,载流子浓度减小,腐蚀电流密度减小;在引起塑性形变的压应力(103%σs)的作用下,腐蚀产物膜的晶粒略微变小,晶界略微增多,载流子浓度和缺陷数量有所增加;对P110钢施加引起弹性形变的压应力能促进腐蚀产物膜的形成,增强膜对基体的保护作用,而施加引起塑性形变的压应力会略微破坏腐蚀产物膜的完整性,但膜仍对基体具有较好的保护作用。

The corrosion product films on P110 casting steel were gained by the high temperature and high pressure autoclave in CO2 environment.Scanning electron microscope(SEM)and X-ray diffractometer(XRD)were used to investigate the surface morphology and phase composition of the corrosion product films formed on P110 casing steels,and electrochemical workstation was used to obtain the electrochemical impedance spectroscopy(EIS),potential dynamic polarization curves and Mott-Schottky(M-S)curves of the corrosion product films in 3.5%Na Cl solution of saturated CO2 environment.Results showed that the integrated corrosion product films formed on P110 casing steels under different compressive stress and the phases of these films were not changed.Under the applied elastic compressive stress(30%σs,90%σs),the grain size of corrosion product films became bigger,and the grain boundaries and the micro-channels decreased,as well as the charge transfer resistance increased,which led to the decrease of electrochemical reaction rate and the concentration of carriers.Moreover,under the plastic deformed compressive stress(103%σs),the grain size of corrosion product films became smaller,and grain boundaries increased slightly as well as the carrier concentration and defects.It was revealed that applying elastic compressive stress on P110 steels could promote the formation of corrosion product films partly and enhance the protective capability of films.The applied plastic compressive stress could destroy the integrity of the corrosion product films partly and slightly,but the films still had the protective capability in a certain degree.