高含H2S/CO2介质中X60钢腐蚀产物膜分析

Analysis of corrosion scales on X60 steel under high H_2S/CO_2 content environments

利用高温高压H2S反应釜进行腐蚀模拟实验,研究X60钢在高压H2S/CO2共存条件下的腐蚀规律,并利用扫描电子显微镜和X射线衍射等方法观察用分析了腐蚀产物膜的形貌和组成.在H2S/CO2分压比为1.74、H2S分压0.15～2.0 MPa条件下,腐蚀产物以硫铁化合物为主,未见碳酸亚铁,X60钢腐蚀过程由H2S控制.H2S分压较低时腐蚀产物以四方FeS1-x为主,H2S分压2.0 MPa时则出现六方FeS、六方Fe1-xS和立方FeS2.疏松的富S腐蚀产物及腐蚀产物膜局部剥落促使高H2S分压时X60钢出现明显局部腐蚀,并使全面腐蚀速率随H2S分压升高先升后降.

Corrosion of X60 steel under high-pressure H2S/CO2 coexist environment was investigated using a high-temperature and high-pressure H2S autoclave. The structure and constitution of corrosion scales were studied through scanning electron microscopy （SEM） and X-ray diffraction （XRD）. Corrosion experiments were carried out under situations with the same H2S/CO2 partial pressure ratio （1.74） and different H2S partial pressures from 0.15 MPa to 2.0 MPa. The results show that the corrosion scales mainly consist of ferrous sulfide. The absence of ferrous carbonate in the corrosion scales suggests that the corrosion process was controlled by H2S. Under low H2S partial pressure conditions, tetragonal FeS1-x is the predominant corrosion product. When the H2S partial pressure was increased to 2.0 MPa, hexagonal FeS, hexagonal Fe1- xS and cubic FeS2 could also be observed in the corrosion scales. Localized corrosion observed on X60 steel under a higher HaS partial pressure condition can be attributed to the loose scale with S-rich corrosion products and the local breaking of corrosion scales, which also induced the decreasing of general corrosion rate at a higher H2S partial pressure level.