Factors affecting the corrosion behaviour of aluminium in acid solutions. II. Inorganic additives as corrosion inhibitors for Al in HCl solutions

CrO42-, WO42- and HPO42- ions affect on the corrosion behaviour of Al in 2 M HCl. The inhibition efficiencies of the additives depend on their type and increase with increasing concentration. Oxide filth destruction and/or repair follow a direct logarithmic law. The inhibitive action of these anions is discussed in terms of competitive adsorption with Cl- ions on the electrode surface followed by a reduction mechanism to form metal oxides. The calculated values of Delta G degrees(ads) of the inhibition process reveal a physical adsorption of the inhibitors. The inhibition efficiency is found to decrease in the order: CrO42- > WO42- > HPO42-. (C) 2012 Elsevier Ltd. All rights reserved.