Corrosion Behavior of Mild Steel in Acetic Acid Solutions

The corrosion behavior of mild steel in acetic acid (CH₃COOH) solutions was studied by weight loss and potentiostatic polarization techniques. The variation in corrosion rate of mild steel with concentrations of CH₃COOH, evaluated by weight loss and electrochemical techniques, showed marked resemblance. From both techniques, the maximum corrosion rate was observed for 20% CH₃COOH solution at all three experimental temperatures (25, 35, and 45°C). Anodic polarization curves showed active-passive behavior at each concentration, except at 80% CH₃COOH. Critical current density (i_c), passive current density (i_n), primary passivation potential (E_pp), and potential for passivity (E_p) had their highest values in 20% CH₃COOH solution. With an increase in temperature, while the anodic polarization curves shifted toward higher current density region at each concentration, the passive region became progressively less distinguishable. With the addition of sodium acetate (NaCOOCH₃) as a supporting electrolyte, the passive range was enlarged substantially. However, the transpassive region commenced at more or less the same potential. Cathodic polarization curves were almost identical irrespective of the concentration of CH₃COOH or temperature.