【摘要】 油气输运管线工作于苛刻的腐蚀环境中,容易造成严重的破坏。利用SEM,EDS,XPS,XRD,EIS等现代分析技术,在油气输运条件下(温度30～80℃、PCO2为0.5～2.0MPa、流速1.4m/s),对油气输运管常用材料X56钢进行了测试分析。失重试验证明:X56钢的腐蚀速率随温度的升高而升高,表现为指数关系;随CO2分压增大而加大,表现为线性关系。SEM,EDS,XPS,XRD分析表明:腐蚀产物晶体主要是由反铁磁性物质FeCO3及(Fe,Ca……)CO3复相物组成,表现为台地浸蚀及孔穴腐蚀,腐蚀产物膜由3层构成。极化曲线表明:在PCO2=0.5MPa、30～90℃条件下,随温度升高,X56钢的自腐蚀电位Ecorr变负,Icorr升高;温度80℃、PCO2=0.5～2.0MPa时,自腐蚀电位Ecorr随PCO2的增加而变正,自腐蚀电流Icorr明显增大,且阴极极化及阳极极化有明显的弱极化Tafel区。电化学交流阻抗试验表明,由于腐蚀产物膜的存在,低频区出现了半无限扩散的的Warburg阻抗特征,高频端出现了容抗弧,反应受扩散控制。更多还原

【Abstract】 With a view to the serious corrosion damage of oil and gas transportation pipelines working in severe corrosion environment, the corrosion behavior of X56 steel——the steel commonly used for the oil and gas transportation pipelines in a simulated oil well production fluid （CO₂ partial pressure 0.5².0 MPa, temperature 30⁸0 ℃, flow rate 1.4 m/s） was studied. Thus the morphology and composition of the corroded steel surface and the corrosion process were analyzed by means of scanning electron microscopy, X-ray diffraction, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. It was found that the corrosion rate of the X56 steel exponentially increased with increasing temperature and linearly increased with increasing partial pressure of CO₂. The corroded steel surface was characterized by intense localized corrosion, mesa corrosion, and pitting corrosion. The corrosion product film could be divided into three layers mainly composed of antimagnetic FeCO₃ and compounded （Fe, Ca…）CO₃. The corrosion potential of the X56 steel shifted to be negative and the corrosion current density increased with increasing temperature, while the corrosion potential shifted to be positive and the corrosion current density obviously increased with increasing partial pressure of CO₂. There existed a weak Tafel zone during the cathodic and anodic polarization processes. Moreover, it was characterized by Warburg inductive arc with semi-infinite diffusion in the low frequency zone and by capacitive arc in the high frequency zone, and the electrode reaction was dominated by pervasion procedure, which was attributed to the formation of a corrosion product film.更多还原