The inhibitive effect of some tetrazole derivatives towards Al corrosion in acid solution: Chemical, electrochemical and theoretical studies

Corrosion inhibition of aluminum in 1.0 M HCl was investigated in the absence and presence of different concentrations of tetrazole derivatives namely, 1-phenyl-1H-tetrazole-5-thiol (A), 1-phenyl-1H-tetrazole (B), 1H-tetrazol-5-amine (C), 1H-tetrazole (D). Weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements were employed. Impedance measurements showed that the charge transfer resistance increased and double layer capacitance decreased with increase in the inhibitor's concentration. Potentiodynamic polarization study showed that the inhibitors acted as cathodic-type inhibitors. Also, results obtained reveal that compound A is the best inhibitor and the inhibition efficiency (IE%) follows the sequence: A > B > C > D. Obvious correlations were found between corrosion inhibition efficiency and some quantum chemical parameters such as energy of highest occupied molecular orbital (HOMO), energy of lowest unoccupied molecular orbital (LUMO), HOMO-LUMO energy gap and electronic density etc. Calculated results indicated that the difference in inhibition efficiencies between these compounds can be clearly explained in terms of frontier molecular orbital theory. The inhibitor performance depends mainly on the type of function groups substituted on tetrazole ring. The adsorption of these compounds on the aluminum surface obeys a Langmuir adsorption isotherm and has a mixed physisorption and chernisorption mechanism. (C) 2008 Elsevier B.V. All rights reserved.