Corrosion Performance of AISI 304 Stainless Steel in CO2-Saturated Brine Solution

Corrosion behavior of 304 stainless steel exposed to a NaCl (3.5 wt %) solution saturated with CO2 has been analyzed using electrochemical techniques including, potentiodynamic polarization, polarization resistance, and electrochemical impedance measurements. The stainless steel samples were evaluated having different surface and pre-oxidation treatments. The oxide scales formed on 304 stainless steel oxidized in different pO2 at 1100°C have also been studied and compared. Different morphologies and chemical composition of the oxide scales were observed after oxidation at low and high oxygen partial pressures. Oxide layers with high chromium content were formed on the ground sample pre-oxidized in Ar while iron-rich oxides were mainly formed under air atmosphere. The electrochemical corrosion results indicate that non-oxidized 304 SS exhibits the best corrosion performance followed by the ground sample heat-treated in argon. For the oxidized stainless steels, the differences in the electrochemical responses are associated to the morphological characteristics and composition of the oxide layer. Homogeneous and dense Cr-rich oxide scale provides protection to 304 SS during exposure to CO2-saturated solutions while the formation of Fe-oxides with porous morphology increases the corrosion rate of 304 stainless steel.