温度对3Cr钢在CO2-O2环境中腐蚀的影响

摘要：为了研究注多元热流体吞吐热力采油过程中温度对油套管钢的影响，利用高温高压电化学釜模拟注多元热流体采油工况，分别在60、100和100～60℃循环的温度条件下，对3Cr钢进行失重腐蚀挂片试验和电化学腐蚀试验，利用高温高压电化学釜得到了3Cr钢在模拟工况下的腐蚀速率和极化曲线，并利用SEM、XRD、EDS分析了腐蚀产物膜形貌和成分。结果表明，温度由60升高至100℃时，腐蚀速率由0.552增长至1.920mm/a，在100-60℃高-低温循环时，腐蚀速率进一步升高至4.292mm/a；60和100℃时，腐蚀产物均为单层膜结构，且存在点蚀坑；在100-60℃高 低温循环时，腐蚀产物为双层膜结构，且存在直径约为4μm的腐蚀坑。温度主要影响3Cr钢腐蚀产物膜的结构和点蚀的形态，60和100℃时，点蚀坑内的聚集的Cl-离子使点蚀向纵深处发展，在100.60℃高 低温循环时，溶液中的O2促进了点蚀的横向发展，而腐蚀坑底部富集的Cr将阻碍点蚀的纵向发展。注多元热流体热力采油过程应充分考虑温度变化对3Cr钢腐蚀的影响，同时也要考虑温度变化引起3Cr钢点蚀的敏感性。

Effect of temperature on corrosion of 3Cr steel in CO2-O2 environment

To study the influence of temperature on oil casing steel in the thermal oil recovery by multiple thermal fluid injection, the weight loss and electrochemical tests of 3Cr steel were carried out under the stable temperature of 60 and 100℃ as well as the temperature cycle of 100 60℃. HTHP electrochemical autoclave was used to simulate the oil recovery process and then the corrosion rate and electrochemical polarization curves of 3Cr steel were obtained. The surface morphology and composition of corrosion products were investigated by scanning electron microscopy (SEM), energy dispersive X ray spectroscopy (EDS) and X ray diffraction (XRD). The results showed that the corrosion rate of 3Cr steel increased from 0.552 to 1.92mm/a when the temperature rose from 60 to 100℃. The corrosion rate further increased to 4.292mm/a with the temperature cycling between 100 and 60℃. The corrosion products were identified to be single layer and tiny pitting exists on the surface at 60 or 100℃. While the temperature cycled between 100 and 60℃, the corrosion products were double layer and a corrosion pit was found with a diameter of 4μm. The structure of corrosion scales and the morphology of corrosion pits were mainly affected by temperature. At stable temperature of 60 and 100℃, Cl- ions enriched in the pitting increase the corrosion depth. Under temperature cycle of 100-60℃, O2 in the solution increased the pitting size, while Cr enriched at the bottom of corrosion pits increased the corrosion depth. In the thermal oil recovery by multiple thermal fluid injection, the influence of temperature on the corrosion of 3Cr steel should be fully considered, as well as the pitting sensibility caused by temperature change.