Investigation of the Working Mechanism of CO2–H2O Flow Corrosion of Mild Carbon Steel

In this work, the working mechanism of the CO2–H2O flow corrosion of mild carbon steel is investigated by a two-dimensional simulation. Three models including a mass transfer model, an electrochemical model, and a convection–diffusion model are integrated to study the comprehensive working mechanisms. Several factors including temperature, pH, CO2 partial pressure, and flow velocity are considered. The results show that the flow corrosion increases with increasing temperature, decreasing pH or increasing CO2 partial pressure. As the temperature reaches above 60 °C, H2O reduction of the cathode becomes significant in the CO2–H2O flow corrosion. The cathode reaction of the corrosion at low pH is dominated by H+ reduction and sensitive to flow velocity, while with the increase of pH, H2CO3 plays an obvious buffer role to supplement H+. The effect of the flow velocity on CO2–H2O flow corrosion increases with the temperature, where the flow turbulence is found to play an important role in promoting corrosion enhancement.