碳钢在油水混相介质中的CO_(2)/H_(2)S腐蚀行为

CO_(2)/H_(2)S Corrosion Behavior of Carbon Steel in Oil-Water Heterogeneous Media

采用极化曲线和电化学阻抗测试,研究了N80钢在50℃的3%NaCl盐水与凝析油混相溶液中,不同CO_(2)、H_(2)S分压比(θ=PCO_(2)/PH_(2)S)条件下的腐蚀规律;采用SEM、XPS等分析了N80钢表面腐蚀产物的形貌和组成。结果表明:在饱和CO_(2)溶液中,随着H_(2)S含量的增加,碳钢电极的腐蚀减弱;当θ<20时,随着θ增大,腐蚀电流密度逐渐减小,腐蚀主要由H_(2)S控制,在N80钢表面生成了均匀致密的针状晶型腐蚀产物,主要是FeS和FeS_(1-x)膜;当20<θ<500时,随着θ的增大,腐蚀电流密度先增大后减小,腐蚀由CO_(2)和H_(2)S共同控制,钢片表面生成了多种晶型腐蚀产物,主要是FeCO_(3)和FeS_(1-x)膜;当θ>500时,随着θ的增大,腐蚀电流密度增大,腐蚀反应由CO_(2)控制,钢片表面生成了多边形不规则晶型腐蚀产物,主要是含有少量Fe_(3)O_(4)的FeCO_(3)膜。

Polarization curves and electrochemical impedance tests were used to study the corrosion behavior of N80 steel under different CO_(2)and H_(2)S partial pressure ratios in a mixed solution of 3%NaCl saline and condensate oil at 50℃.The morphology and composition of corrosion products on the surface of N80 steel were analyzed using SEM,XPS,etc.The results showed that in a saturated CO_(2)solution,the corrosion of carbon steel electrodes weakened with the increase of H_(2)S content.Whenθ<20,with the increase ofθ,the corrosion current density gradually decreased,and corrosion was mainly controlled by H_(2)S.Uniform and dense needle like crystal corrosion products were generated on the surface of N80 steel,mainly FeS and FeS_(1-x)films.When 20<θ<500.with the increase ofθ,the corrosion current density increased,the corrosion current density first increased and then decreased.The corrosion was jointly controlled by CO_(2)and H_(2)S,and various crystal corrosion products were generated on the surface of the steel sheet,mainly FeCO_(2)and FeS_(1-x)films.Whenθ>500,with the increase ofθ,the corrosion current density increased,the corrosion reaction was controlled by CO_(2),and polygonal irregular crystal corrosion products were generated on the surface of the steel sheet,mainly FeCO_(2)film containing a small amount of Fe_(3)O_(4).