INHIBITION OF ALUMINUM CORROSION IN CHLORIDE MEDIA - AN IMPEDANCE STUDY

Inhibition of the corrosion of pure aluminium by nitrite and chromate anions in near neutral aqueous chloride solution has been studied by e lectrochemical impedance spectroscopy, keeping the ionic strength cons tant by addition of potassium sulphate electrolyte. Negative of the ch loride pitting potential impedance spectra show that both anions are s uccessful in reducing corrosion through adsorption, nitrite more than chromate. Positive of this value, nitrite becomes ineffective, whereas chromate remains adsorbed and continues to prevent pitting corrosion, probably through its ability to repair defects in the oxide film. Imp edance techniques successfully show the qualitative and quantitative d ifferences between the two inhibitors.