CO2 Corrosion Behavior and Mechanism of Carbon Steel and Alloy Steel

Abstract The influence of environmental factors such as temperature, CO2 partial pressure, flow velocity and so on, on CO2 corrosion was investigated in the laboratory test. As the results, the characteristic features of CO2 corrosion are focussed to the following three factors. The first one is the catalytic acceleration effect of desolved CO2 on the corrosion rate. The second one is the effect of temperature on CO2 corrosion of carbon steel, which means both the occurrence of the ringworm corrosion and the climaxed corrosion rate observed in the vicinity of 100°C. The third is the temperature dependency of chromium (Cr) steel. To make clear the CO2 corrosion behavior of carbon steel, the pH- potential-temperature diagrams are newly produced and the analysis of corrosion product is done. As the results, it is clarified that the low corrosion rate in higher temperature region than 120°C attributes to the formation of adhesive ferrous carbonate (FeCO3) film, which is closely related with both the dissolution rate of iron through anodic corrosion reaction, i.e. the concentration of ferrous ion [Fe2+] on the surface of substrate and the solubility of FeCO3. The corrosion behavior of Cr steel is discussed in relation with the prevention of CO2 corrosion. Finally, the mechanism of catalytic action of CO2 in cathodic corrosion reaction is also discussed.