The cathodic reduction of passive films on mild steel was investigated by using the potentiodynamic and galvanostatic techniques in carbonate-bicarbonate buffer solns. at various pH values. The reduction strongly depends on the pH of the solns. At 8.31 ?pH ?9.80, ferric oxide was simultaneously reduced to Fe and FeOH+; while at 9.80 ?pH ?11.37, ferric oxide was reduced to magnetite and Fe(CO3)22-. Both these reactions consisted of a no. of steps, and the rate-detg. step was the charge transfer reaction from FeOH2+ to (FeOH)ads.

Key words: CARBONATE, SODIUM CARBONATE, IRON COMPOUNDS, REDUCTION REACTION, LOW CARBON STEEL, POTENTIOSTAT, SODIUM BICARBONATE, PASSIVATION FILMS, CATHODE EFFECT