Impact of tautomerism on copper corrosion inhibition by 3-amino-1,2,4-triazole-5-thiol: A DFT and Monte Carlo study

corrosion is a significant issue that leads to costly damage in various industries. In the present study, the inhibitory effect of 3-amino-1,2,4-triazole-5-thiol (ATAT) and its tautomers as green corrosion inhibitors on Cu(100), Cu(110), and Cu(111) was investigated using computational methods. The inhibitors adsorbed most effectively in a parallel orientation to the copper surface through all available heteroatoms, indicating strong interaction with the metal. Density functional theory (DFT) calculations and Monte Carlo simulations were performed to analyze the electronic interactions, and key quantum chemical parameters, including adsorption energy, molecular orbitals (HOMO and LUMO), energy gap, Fukui indices, Mulliken charges, and partial density of states (PDOS), were systematically analyzed. DFT calculations were also performed in aqueous media using an implicit solvent model to evaluate solvent effects. This study highlights the role of tautomerism in modulating adsorption strength and inhibition efficiency, showing that ATAT can act as an excellent corrosion inhibitor by adjusting its molecular structure to enhance interaction with the copper surface. Among all inhibitors, 5-amino-2,5-dihydro-1H-1,2,4-triazole-3-thiol exhibited the strongest adsorption on three copper surfaces, making it the most effective inhibitor in this series. When comparing copper surfaces, the Cu(111) had the highest adsorption energies, making it the most stable surface among those studied.