Investigation of Acetic Acid Effect on Carbon Steel Corrosion in CO2-H2S Medium: Mechanistic Reaction Pathway and Kinetics

Potentiodynamic polarization and electrochemical impedance measurements were employed to investigate the effect of acetic acid on the anodic dissolution of carbon steel in a CO2-H2S solution. Both polarization and impedance results unveil that the dissolution rate of carbon steel first increases and then decreases with an increase in acetic acid concentration. At lower concentrations of acetic acid, the corrosion rate increases due to the increase in cathodic current density. While the decrease in corrosion rate at higher acetic acid concentrations is attributed to the decrease in the anodic current density. The reaction mechanism of carbon steel dissolution in the CO2-H2S-acetic acid medium is elucidated along with the retrieval of kinetic parameters using the impedance data acquired at different overpotentials for various concentrations of acetic acid (1, 50, and 500 ppm). Further field emission scanning electron microscopy (FESEM) images confirm that the pitting corrosion occurs on carbon steel surface at higher acetic acid concentrations.