Surface effects on the electrochemistry of iron and carbon steel electrodes in aqueous CO{sub 2} solutions

Abstract

The objective was to generate knowledge about the effects of the corrosion induced changes of the surface on the corrosion and electrochemical kinetics of carbon steels and pure iron exposed to aqueous CO{sub 2} solutions. Besides its fundamental interest, the knowledge is needed for the development of better steels and for working out better models for the prediction of CO{sub 2} corrosion of carbon steel exposed to the corrosive water phase from oil wells. The exposures were carried out at 25 to 100 C with CO{sub 2} partial pressure of 0.65 to 3.2 bar. The paper discusses the fundamentals of the anodic and cathodic reactions and the consequences of the formation of corrosion films of Fe{sub 3}C and FeCO{sub 3}. Effects of microstructure and chromium additions to the steel are taken up. The influence of very small concentrations of sulfide ions (e.g., 20 {micro}Mol/l) is also briefly treated.