典型离子对碳钢CO_2腐蚀的影响

为了考察油气田生产液中典型离子对CO_2环境下管道腐蚀行为的影响,采用腐蚀模拟实验,结合极化测试、交流阻抗谱测试等电化学方法及p H值分析方法,研究了Cl~-、SO_4~(2-)、Ca~(2+)、HCO_3~-和CO_2共存环境下碳钢(N80钢)的腐蚀行为。研究结果表明:(1) Cl~-、SO_4~(2-)对N80钢的腐蚀作用基本相同,Ca~(2+)、HCO_3~-均能在一定程度上抑制N80钢的腐蚀,HCO_3~-对腐蚀的抑制作用明显优于Ca~(2+);(2)加入Cl~-和Ca~(2+)后溶液p H值的变化可以忽略,加入SO_4~(2-)和HCO_3~-后溶液p H值升高;(3) Ca~(2+)参与到腐蚀产物膜的生成,导致腐蚀产物膜孔隙率降低,因而在该介质环境下材料腐蚀速率低,感抗弧缩小;(4) HCO_3~-的存在升高了溶液p H值,降低了溶液的腐蚀性,同时也增大了CO_3~(2-)的离子浓度,促进了Fe CO_3的沉积,使腐蚀产物膜更加致密和完整,导致HCO_3~-溶液中测得的感抗弧消失,材料的腐蚀速率显著降低。结论认为,该研究成果可以为石油化工行业的防腐工作提供理论及技术支持。

Effect of typical ions on the corrosion behavior of carbon steel in CO2 environment

In order to investigate the effect of typical ions in produced liquids in oil and gas fields on the pipeline corrosion behavior in CO2 environment, the corrosion behavior of carbon steel (N80 steel) in the environment with Cl-, SO42-, Ca2+, HCO3- and CO2 was studied by means of corrosion simulation experiments, combined with the electrochemical method (e.g. polarization test and AC impedance spectroscopy test) and pH analysis method. And the following research results were obtained. First, Cl- and SO42- have a similar effect on the corrosion behavior of N80 steel, while Ca2+ and HCO3- can inhibit the corrosion to some extent. Moreover, the inhibition effect of HCO3- is better than that of Ca2+. Second, the variation of pH value after the addition of Cl- and Ca2+ is negligible. However, the addition of SO42- or HCO3- results in the increase of pH value. Third, Ca2+ participates in the generation of corrosion product film, leading to the decrease of its porosity. Therefore, the corrosion rate and the inductive reactance arc decrease in the environment of this medium. Fourth, the existence of HCO3- increases the pH value of the solution and decreases the corrosion of the solution. And it also leads to the increase of CO32- concentration and promotes the deposition of FeCO3 to make the corrosion product film more compact and complete, so that the inductive reactance arc measured in HCO3--containing solution disappears and the corrosion rate of the material declines greatly. In conclusion, the research results provide a technical and theoretical support for the corrosion control in the petrochemical industry.