The Passivation Behavior of Mild Steel in CO₂Saturated Solution Containing Nitrite Anions

Abstract

The passivation behavior of mild steel in CO2 saturated solution was studied with electrochemical methods and XPS. In CO2 saturated solution at the open circuit potential, NO2− may accelerate corrosion of mild steel to some extent. By addition of NO2− in CO2 saturated solution, the polarization behavior of mild steel changes from active dissolution to passivation. With the increase of NO2− concentration, during anodic polarization the current density increases faster and the active-passive transition potential moves to the negative direction. The passivation of mild steel is attributed to the formation of a protective Fe2O3 passive film on the mild steel substrate under the FeCO3 layer.