THE ELECTROCHEMICAL-BEHAVIOR AND CORROSION OF ALUMINUM IN CHLORIDE MEDIA - THE EFFECT OF INHIBITOR ANIONS

The effect of nitrite and chromate inhibitor ions in varying concentrations on the corrosion of aluminium in near-neutral chloride solution has been studied using measurements of the open circuit potential and its variation with time, cyclic voltammetry, potential step chronoamperometry and electrochemical impedance measurements. A concentration dependence is shown, more marked in the case of chromate, as is the effect on oxide film growth through the variation of corrosion potential with the logarithm of time. Differences between the mode of action of the two inhibitors are demonstrated, particularly by impedance measurements. At potentials close to the corrosion potential, nitrite is the more effective inhibitor, acting through strong adsorption. Above the pitting potential, nitrite becomes ineffective and chromate acts through repairing the oxide film and aiding oxide growth, as shown through corrosion potential, chronoamperometry and impedance data.