Synergistic experimental and theoretical investigation of 3-benzylsulfanyl-4H-(1,2,4)triazole as an efficient corrosion inhibitor for mild steel in hydrochloric acid

This study systematically evaluates the corrosion inhibition potential of 3-benzylsulfanyl-4H-(1,2,4) triazole (BST) on mild steel in a 1.0 M HCl environment. The investigation utilized a multi-faceted approach combining weight loss analysis, potentiodynamic polarization (PDP), scanning electron microscopy (SEM), and density functional theory (DFT). Gravimetric results indicated that inhibition efficiency is temperature-and concentration-dependent, peaking at 93.0% with a 0.5 mM concentration after 5 hours at 303 K. Adsorption analysis confirmed the data fits the Langmuir isotherm, suggesting a mechanism driven by both physisorption and chemisorption. PDP measurements corroborated these findings, showing a mixed-type inhibition behavior that suppresses both anodic and cathodic reactions, achieving a maximum efficiency of 96.3%. Surface analysis via SEM revealed that a protective layer was formed by the inhibitor, significantly reducing surface damage compared to the uninhibited acid solution. Furthermore, DFT calculations provided molecular-level evidence of strong interaction between the inhibitor and the steel surface, characterized by favorable HOMO-LUMO energy levels. These findings establish BST as a highly effective corrosion inhibitor that performs comparably to or better than existing triazole derivatives.