CORROSION INHIBITION PERFOMANCE OF FOUR NATURAL THIAZOLE DERIVATIVES: QUANTUM CHEMICAL AND MONTE CARLO SIMULATION STUDIE

Abstract

Some thiazole derivatives: 2-acetyl-thiazole, 2-isobutyl-thiazole, 4-methyl-5-(2-hydroxyethyl)-thiazole, 2,4,5-trimethyl-thiazole used as corrosion inhibitors for iron were calculated at DFT-PBEPBE/6-31+G(d,p) level of theory and by Monte Carlo simulations. Quantum chemical parameters such as EHOMO, ELUMO, and HOMO and LUMO energy gap, chemical potential (m), electronegativity (c), global hardness (h), softness (S), dipole moment and electrophilicity index (w) have been calculated and discussed in detail to evaluate their inhibiting effectiveness. Mulliken-charges distribution and Fukui function were also calculated in order to visualize the reactive sites of the inhibitor molecules. Calculated results show that 2-acetyl-thiazole represents as the most efficient corrosion inhibitor. The –C4=C5– atomic center of thiazole ring demonstrates as the adsorption site in reaction with metallic surface. Corrosion inhibition effectiveness can be classified in decreasing order: ATZ > TMTZ » SFR > ISTZ.  Adsorption energies and interaction configurations of the four thiazole derivatives on Fe (110) were obtained using the Monte Carlo simulations. The results indicate that sulphur and nitrogen atoms as well as π-electronic systems within the thiazole ring aided the interaction between the inhibitor molecules and the Fe surface. All the four thiazole molecules adsorbed in parallel orientations on Fe (110) surface which ensures strong interactions with Fe. The adsorption energies were in accord with the results obtained using quantum chemical calculations.