Influence of dissolved oxygen on the corrosion of mild steel in a simulated cement pore solution under supercritical carbon dioxide

To understand the influence of oxygen on initiation of the localized corrosion of mild steel in the underground casing/cement system for carbon capture and sequestration, the corrosion behavior of P110 steel was systematically investigated by means of electrochemical and analytical measurements in a simulated cement pore solution under supercritical carbon dioxide at 80 degrees C and 10 MPa. With the increasing concentration of dissolved oxygen from < 150 to 300 mu g/L, the protective corrosion product layer on the steel was locally destabilized, producing a reactivation current peak and a lower repassivation potential on the potentiodynamic polarization curve. The presence of more oxygen did not change the cathodic reaction mechanism and the formation of the corrosion product layer. The localized corrosion protrusion would expansively grow as the formation of iron hydroxides at the interfacial region with the penetration of dissolved oxygen and chloride through the preformed corrosion product layer on steel substrate.