Quantum study of the inhibition of corrosion

of steel in H2SO4 0.5 M by thiophene and its derivatives

 

K. Laarej1, H. Harek2, M. Bouklah1, B. Hammouti1*, Y. Harek2

1 LCAE-URAC18, Faculté des Sciences, Université Mohammed Premier, B. P. 717, 60 000 Oujda, Morocco.

2 Département de Chimie, Faculté des Sciences, Université Abou Bakr Belkaïd, Tlemcen 13000, Algeria

* Corresponding author: E-mail: hammoutib@gmail.com

Received: 01 June 2010; revised version accepted: 08 October 2010

 

Abstract

     The inhibitory effect of thiophene and its derivatives Thiophene (T), 2 - thienylmethanol (TM), Méthyl 2 - thiophene carboxylate (MTC), Ethyl 2 - thiophene carboxylate (ETC)  against the corrosion of steel surface in 0,5 M H2SO4 is studied by the means of density functional approach B3LYP/6-31G calculations. It has been found that thiophene molecules have the highest inhibition efficiency among the Thiophene derivatives TM, MTC and ETC. In addition, MTC and ETC have a catalytic effect; the values of their inhibition efficiency are negative respectively -11% and -27%. Chemical quantum parameters calculated and correlated to the inhibition efficiency are; the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), the separation energy (?E), the dipole moment (µ), the softness (s), the fraction of electrons transferred from the inhibitor to the metal surface (?N), the total negative charge (TNC) and the total energy (TE). The inhibitors adsorption on steel surface was also studied in 0.5 M H2SO4 media. It was shown that adsorption is not favoured with MTC and ETC molecules because of presence of acidic functional groups. The experimental results correlate with those obtained by theoretical calculations.

 

Keywords: Steel ; Thiophene ; Inhibition ; Corrosion ; DFT calculations.

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