Effect of Copper Content on the Corrosion of Carbon Steel in a Sweet Brine

The effect of copper content, on the nature and roughness of the corrosion products formed on carbon steel in a synthetic brine saturated with CO₂ at room temperature, was studied using a jet impact chamber tuned at different impact angles. Corrosion rate was determined by linear polarization resistance, and steels behavior was described by electrochemical impedance spectroscopy. The corrosion products formed on steel were characterized by scanning electron microscopy, electron-dispersive analysis, optical profilometry and grazing incidence X-ray diffraction. The chemical composition and morphology of corrosion products affected corrosion rate. For the different steels, Fe₃C and iron oxides provided a low degree of protection. Steels with higher copper contents showed a decrease in corrosion rate due to the formation of copper oxides (CuO and Cu₂O), which apparently offered a stronger physical barrier between the aggressive environment and the substrate. Small roughness of corrosion products was correlated with more compact and uniform layers of corrosion products and also to lower corrosion rates.