Corrosion modeling for carbon steel under oxygen depleted underground environment

摘要

In the oxygen depleted underground neutral aqueous solution environment, carbon steel reacts with H2O, producing H2 gas and forming corrosion film on the steel surface. Corrosion rate is controlled by diffusion of reaction species through corrosion film. Diffusion constants of some species working in the corrosion process were obtained from literatures. However, no data were found on the diffusion constant of H2O in iron oxides, which were estimated based on an appropriate assumption. Mass transfer model for the corrosion rate was used to simulate the corrosion rate of carbon steel. Liquid phase diffusion model of Fe2+ or H2O through pores in the corrosion film and solid phase diffusion model of H20 through corrosion film itself were examined by simulation using the spread sheet of Excel. Change in corrosion current density and corrosion loss with time and pH and temperature dependence of corrosion current density were examined. By comparing simulated results with the experimental data, it was suggested that the solid phase diffusion of H2O in the corrosion film controls the corrosion rate of carbon steel in oxygen depleted environment.