The formation mechanism of corrosion scale and electrochemical characteristic of low alloy steel in carbon dioxide-saturated solution

The formation mechanism of corrosion scale and electrochemical characteristic of low alloy steel in CO2-saturated solution were investigated by electrochemical measurements and surface characterization. The results show that the electrochemical behavior is associated with the formation of corrosion scale and the microstructure of steel. At the initial polarization stage, ferrite dissolves preferentially and leaves Fe3C behind, which results in high Fe2+ ions concentration between lamellar Fe3C. This situation facilitates the formation of FeCO3 scale between the lamellar Fe3C. With further increase of polarization times, the whole electrode surface is covered by FeCO3 scale.

► The electrochemical behavior corresponds to the formation of corrosion scale.
► The formation of corrosion scale is related to the microstructure of steel.
► Ferrite dissolves preferentially and leaves Fe3C behind.
► The remained lamellar Fe3C helps to anchor the FeCO3 scale.
► The accumulation of Fe3C cathodic phase increases the corrosion rate.