Electrochemical Behavior of Magnetite on a Carbon Steel Electrode in Hydrochloric Acid-Disodium Citrate Buffer Solutions

The behavior of magnetite on a carbon steel electrode in HCl-disodium citrate buffer-complexing solutions, at 35°C, on open circuit and under polarization has been studied. The experimental results are attributed to a nonprotective, incoherent oxide layer, which, with time, exhibited faults, cracks, preferential reduction, and undermining detachment, increasing the metal area on which the two main potential-determining reactions take place, i.e., iron dissolution and hydrogen evolution. The effect of the other cathodic reactions, such as the electrochemical reduction of magnetite and hydrogen evolution (or oxygen reduction), on magnetite is to slow down the last part of the open circuit Ecorr-t curve.