温度对X70钢在含CO2地层水中腐蚀行为影响

利用高温高压反应釜,采用失重、SEM、XRD、EDS和电化学方法研究了不同温度下X70管线钢在含CO2地层水中的腐蚀行为。讨论了X70钢CO2腐蚀机理的热力学和动力学机制。结果表明:温度通过影响FeCO3过饱和度、晶粒形核率和长大速率,进而影响X70钢腐蚀速率。在温度为30℃时,FeCO3的过饱和度较小,不能在X70钢表面连续析出,难以形成保护性产物膜,X70钢腐蚀速率较高。温度为60~90℃时,FeCO3的形核速率大于生长速率,X70钢表面形成致密的FeCO3膜,腐蚀速率开始下降。继续升温至120和150℃,FeCO3的形核速率小于生长速率,X70钢表面不能形成完整的具有保护性的FeCO3膜,或膜内应力增大导致膜破裂。FeCO3膜与基体金属形成电偶电池,发生局部腐蚀。

Effect of Temperature on Corrosion Behavior of X70 Steel in an Artificial CO-containing Formation Water

The corrosion behaviour of X70 pipeline steel in an artificial CO2-containing formation water at various temperatures was studied in a high-temperature,high-pressure reaction kettle via mass loss measurements,scanning electron microscopy,energy dispersive spectroscopy,X-ray diffractometer,and electrochemical methods.Thermodynamic and kinetic factors related to the CO2 corrosion mechanism of X70 steel were assessed.The results show that the temperature influenced the corrosion rate of X70 steel by affecting the supersaturation,nucleation rate,and grain growth rate of FeCO3.The corrosion product scale could not form on the surface of X70 steel at 30℃ because of the lower FeCO3 supersaturation.A dense FeCO3 scale formed at 60 and 90℃,resulting in a decrease in the corrosion rate.When the temperature was higher than 120℃,the nucleation rate of FeCO3 was less than its growth rate,consequently,a complete protective FeCO3 scale could not form on the X70 steel surface,while the stress accumulation inside the scale led to the rupture of the scale,which may be the cause leading to the formation of a galvanic cell consisting of the FeCO3 film and matrix metal,which resulted in local corrosion.