Computational study of some triazole derivatives (un- and protonated forms) and their copper complexes in corrosion inhibition process

• Electrostatic potential analysis was a powerful descriptor to predict the reactive sites on inhibitor.
• The protonation process has an important effect on the reactivity of inhibitors.
• The calculated quantum parameters for neutral molecules describe more the IE(%).

Three triazoles compounds used as corrosion inhibitors for copper in acidic medium, namely: 1,2,4 triazole (TR), 3-amino 1,2,4 triazole (3 ATR) and 3,5-diamino 1,2,4 triazole (3,5 DATR) have been studied theoretically in aim to investigate the correlation between its molecular reactivity indicators and the corresponding inhibition efficiency. All quantum chemical calculations at the B3LYP/6-31+G(d,p) method were performed with and without solvent effect. In the present paper, not only the neutral inhibitors has been studied, but also the first and the second protonation forms. A good correlation between theoretical and experimental data has been obtained both in gas and aqueous phases, notably for unprotonated inhibitors. Also, the interaction energy between inhibitors and copper has been calculated.

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