Inhibition effect of 2-mercaptobenzothiazole on the corrosion of copper in 2M HNO3.

D. Ehouman, J. S. Akpa, P. M.

Abstract

2-Mercaptobenzothiazole (MBT) was examined as a corrosion inhibitor for copper corrosion in 2M nitric acid solution, using mass loss technique and quantum chemical studies, based on density functional theory(DFT) at B3LYP level with different basis sets including 6-31G (d), 6-31G (d, p), and LanL2DZ. The percentage inhibition efficiency IE (%) was found to increase with increasing inhibitor concentration and increasing temperature. Adsorption of the molecule on copper surface follows the modified Langmuir adsorption isotherm. The thermodynamic functions related to the adsorption and the activation processes were calculated and discussed. The calculated quantum chemical parameters correlated to the inhibition efficiency are the highest occupied molecular orbital energy (EHOMO), the lowest unoccupied molecular orbital energy (ELUMO), the HOMO-LUMO energy gap, hardness (η), softness (S), the dipole moment (μ), the electron affinity (A), the ionization energy (I), the absolute electronegativity (χ), the fraction (ΔN) of electrons transferred from (MBT) to copper and the electrophilicity index (ω). The local reactivity has been analysed through the condensed Fukui function and the condensed softness indices in order to determine the sites for nucleophilic and electrophilic attacks. Theoretical results and experimental ones are in well accordance.