20钢在集输系统中不同CO_2分压下的腐蚀行为

Effect of CO_2 Partial Pressure on Corrosion of 20 Steel in Oil-Gas Gathering and Transporting

采用包括挂片失重、动电位极化扫描与交流阻抗(EIS)以及常规材料表征手段研究了20#钢在模拟现场含CO_2集输系统腐蚀环境中的腐蚀行为。结果表明:20#钢腐蚀速率随CO_2分压增加呈先增大后减小的趋势;腐蚀产物主要是FeCO_3晶体;腐蚀产物膜的状态和基体的腐蚀类型随环境中CO_2分压的不同而发生变化:当CO_2分压为0时,不能形成腐蚀产物膜,腐蚀为均匀腐蚀;CO_2分压为0.15MPa时,产物膜较为完整,腐蚀为均匀腐蚀;CO_2分压为0.30MPa时,20#钢基体表面没有产物膜覆盖且表现为典型的点蚀特征。FeCO_3所组成的腐蚀产物膜阴离子的选择透过性使产物膜对机体没有保护作用,反而会加速腐蚀。极化曲线显示,20#钢在含CO_2集输系统中的腐蚀主要以阳极溶解为主;交流阻抗数据表明20#钢的CO_2腐蚀有三个时间常数,中频感抗弧与中间产物的溶解吸收有关,低频容抗弧与腐蚀产物膜覆盖区的活化溶解有关。

Corrosion behavior of 20 steel in the stimulating environment of oil-gas gathering and transporting system containing CO2 was investigated systematically by weight loss, potentiodynamic polarization and EIS and some other conventional measurements.The results showed the corrosion rate of the 20# steel increases first then decreases with increasing CO2 partial pressure.A typical FeCO3 crystalline is observed in the scales of the 20# steel.The morphology and microstructure of the CO2 corrosion scales and types of corrosion vary with different CO2 partial pressures.Uniform corrosion and incomplete scale occur when CO2 partial pressure is 0 MPa.Uniform corrosion and complete scale occur at the partial pressure of 0.15 MPa.When the pressure rises to 0.3 MPa,the scale of corrosion becomes incomplete and pitting corrosion occurs.The FeCO3 scale has a property of the anion-passing-selectivity,which has little protection on the steel,but accelerates corrosion.The experiment of potentiodynamic polarization showed the major performance of corrosion is the anodic dissolution;it was found that the EIS characters have three time-loops.The middle frequency inductive is related to the dissolution and absorption of intermediate.The capacitive arc at low frequency is connected with the active dissolution of corrosion film.