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 Kads and ΔGads° are calculated and discussed. The values of ΔGads° reveal strong physisorption of the inhibitors on the metal surface.

► Phenylhydrazine, urea, thiourea, N-allylthiourea, and thiosemicarbazide are good inhibitors for corrosion Al in HCl.
► The additives decrease the rate of corrosion by the adsorption process.
► ΔGads of all used inhibitors reveal strong physisorption process.