Anti-Corrosive Potentials of 1,2,4-Triazole-5-thiones For Mild Steel 1030 in Acidic Environment

Abstract

Corrosion is a phenomenon that directly related to the environment. The surface protection by potential inhibitors is one of the possible solutions to combat metal/or metallic alloy corrosion. Here, we are reporting two 1,2,4-triazole-5-thione derivatives – 4-amino-3-(N-phthallimidomethyl)-1,2,4-triazole-5-thione (Tz-1) and 3-(N-phthalimidomethyl)-4-(4-pyridine)amino-1,2,4-triazole-5-thione (Tz-2) for corrosion inhibition performance on mild steel (MS) surface in 1 M HCl. Electrochemical experiments were carried for potentiodynamic polarization (PDP) and impedance spectroscopic (EIS) measurements of corroded MS surface before and after the addition of compound’s concentrations. Variations in the PDP responses and in the relevant parameters after compound’s addition confirmed that both Tz-1 and Tz-2 are mixed-type inhibitors. An increase in the diameter of a capacitive loop with inhibitor’s concentration in EIS studies revealed the formation of an adsorbed layer on the MS surface; hence protecting corrosion reaction by controlling the charge transfer process. The data obtained from PDP and EIS were reasonably in good agreement. The IE% (inhibition efficiency) of both Tz compounds showed increasing trend as inhibitor’s concentration was increased and the values were evaluated up to 95% and 94%, respectively, at their optimal concentration of 2.5 × 10⁻⁴ M. Adsorption studies using the Langmuir model further confirmed the involvement of physisorption process on MS in the presence of both compounds. Theoretical DFT (density functional theory) analysis results were supportive to comparatively more inhibitory efficiency of Tz-1. SEM (scanning electron microscopic) studies indicated more resistive behavior of MS surface for corrosion in the presence of Tz-1.