Factors affecting the corrosion behaviour of aluminium in acid solutions. I. Nitrogen and/or sulphur-containing organic compounds as corrosion inhibitors for Al in HCl solutions

The corrosion behaviour of Al in 2 M HCl solution in the absence and presence of phenylhydrazine, urea, thiourea, N-allylthiourea, and thiosemicarbazide is investigated using different chemical and electrochemical techniques. The inhibition efficiencies of these compounds increase with increasing their concentration and molecular weights. The inhibitive action of these compounds is discussed in terms of blocking the electrode surface by adsorption of the inhibitor molecules according to Langmuir isotherm. The thermodynamic parameters K-ads and Delta G degrees(ads) are calculated and discussed. The values of Delta G degrees(ads) reveal strong physisorption of the inhibitors on the metal surface. (C) 2012 Elsevier Ltd. All rights reserved.