Computational, Monte Carlo simulation and experimental studies of some arylazotriazoles (AATR) and their copper complexes in corrosion inhibition process

The inhibition properties of three synthesized 3-(-arylazo)-l, 2, 4-triazole (AATR) derivatives were investigated for copper corrosion in aerated 0.5 M HNO₃ acid using potentiodynamic polarization, cyclic voltammetry, and spectrophotometric measurements. DFT calculations and Monte Carlo simulation are applied to further explain the anti-corrosion mechanism. Quantum chemical indexes, are performed using DFT/B3LYP methods with SDD, 6-31++G (d,p) and 6-31 G basis sets in gas and aqueous phase. The inhibitors can be adsorbed onto surfaces by both physical and chemical means obeys Langmuir and that of El-Awady adsorption isotherm. Potentiodynamic polarization curves revealed that AATRs behave as mixed-type inhibitors. Both thermodynamic and kinetic: (K_ads, ∆G°_ads, A, 1/y, Ea, ∆H°_a and ∆S°_a) parameters were determined and discussed. The adsorption behaviour of the AATR derivatives on Cu (111) surface was investigated by Monte Carlo simulation in the presence of water to verify their corrosion inhibition efficacies. The results showed that AATRs were good inhibitors and the inhibition efficiency increased with increasing of their concentration but decreased with rising temperature. The high IE (%) is due primarily to the adsorption behaviour of both free ligand inhibitor, together with overlapping chelate [Cu (I) and Cu (II)-AATR] complex molecules in the ratio (1:1) and/or (1:2) depending on concentration. DFT calculations and Monte Carlo simulation indicate that the order of IE (%) is: AATR_3 ≅ AATR_2 > AATR_1. The theoretical results were found to be consistent with the experimental data reported.