含Cr钢的CO2腐蚀行为及成膜动力学研究

Investigation of CO2 Corrosion Behavior and Film Formation Kinetics of Cr-Containing Steel

目前对含Cr钢CO2腐蚀中的产物膜生长动力学过程研究不多。为此,采用高温高压反应釜、动电位极化、电化学阻抗谱、光电子能谱、高分辨拉曼光谱等方法研究了不同Cr含量钢在模拟油井下环境中的CO2腐蚀行为及成膜动力学。结果表明:Cr含量的升高会明显降低含Cr钢在模拟CO2腐蚀环境中的腐蚀速率,其中3Cr钢和5Cr钢的腐蚀速率相近,腐蚀速率高于3 mm/a;6Cr钢和7Cr钢的腐蚀速率明显低于3Cr和5Cr钢,腐蚀速率低于1mm/a;腐蚀产物膜成膜过程可以分为2个阶段,阶段1为Cr(OH)3的生长过程,成膜电流I和时间t取对数后满足线性关系;阶段2中随着腐蚀时间的增加,腐蚀电流逐渐增大;产物膜在成膜初期以直接成膜的Cr(OH)3为主,随着腐蚀时间的延长,Cr(OH)3发生溶解,留下的位置被FeCO3沉淀填充。

The CO2 corrosion behaviors and film formation kinetics of Cr-containing steel with different Cr contents in simulated oil well environments were studied by high-temperature and high-pressure reactor,dynamic electrode polarization,electrochemical impedance spectroscopy,photoelectron spectroscopy and high-resolution Raman spectroscopy. Results showed that the increase of Cr content could significantly reduce the corrosion rate of Cr-containing steel in simulated CO2 corrosion environment. Among them,the corrosion rates of 3 Cr steel and 5 Cr steel were similar,higher than 3 mm/a;the corrosion rates of 6 Cr steel and 7 Cr steel were lower than 1 mm/a,which were significantly lower than those of 3 Cr and 5 Cr steel. The filming process of corrosion product film could be divided into two stages. Stage 1 was the growth process of Cr( OH)3;the current I and the time t of film formation took the logarithm and satisfied the linear relationship. In the Phase 2,the corrosion current increased with the increase of the etching time. Furthermore,at the initial stage of the film formation,the direct film-forming Cr( OH)3 played a dominate role. As the corrosion time was prolonged,Cr( OH)3 was dissolved,and the remaining position was filled by Fe CO3 precipitation.