Corrosion behavior of 35CrMo steel in a CO2/O2 coexistent simulating environment of fire-drive tail gas

Abstract

Fire-driven technology has triggered significant interest as an effective technology to improve oil recovery. However, corrosion can easily occur since fire-drive tail gas usually contains corrosive gases, such as CO2 and O2. In this work, the corrosion behavior of several 35CrMo steel samples in a fire-drive tail gas environment was studied using weightlessness measurements, surface characterization techniques, and high temperature-pressure electrochemical tests. The research results show that the average corrosion rate of 35CrMo steel in a CO2–O2 coexisting environment is much higher than the average corrosion rate in a CO2-containing environment or O2-containing environment. The localized corrosion rate of 35CrMo steel in an O2-containing environment is higher than the localized corrosion rate in both the case of a CO2-containing environment or a CO2–O2 one. The pitting factor shows that 35CrMo steel exhibits a localized corrosion in an O2-containing environment. The surface characterization results demonstrate that, in a typical fire-drive tail gas environment, the corrosion products are composed of Fe2O3, FeOOH, and Fe3O4. The high temperature-pressure electrochemistry test data shows that in a CO2–O2-oexisting environment, the membrane resistance decreases upon an increase in the O2 content.