corrosion inhibition of mild steel in 1 m hcl using 5-(3-methylphenyl)-4-((4-nitrobenzylidene)amino)-4h-1,2,4-triazole-3-thiol: experimental and theoretical insights

This study investigates the corrosion inhibition performance of 5-(3-methylphenyl)-4-((4-nitrobenzylidene)amino)-4h-1,2,4-triazole-3-thiol (mnatt) for mild steel in 1 m hcl, using both experimental weight loss techniques and density functional theory (dft) calculations. weight loss experiments were conducted at mnatt concentrations ranging from 0.1 to 1.0 mm and immersion times between 1 and 48 hours. the highest inhibition efficiency of 88.6 % was observed at 0.5 mm after 5 hours of immersion. a temperature-dependent study conducted at 303-333 °k revealed a mild improvement in inhibition performance with rising temperature, indicating thermal stability of the adsorbed layer. adsorption behavior followed the langmuir isotherm, and the calculated standard free energy of adsorption (                    = –14.33 kj·mol⁻¹) confirmed that the adsorption mechanism is physisorption. complementary dft analysis showed a homo-lumo energy gap (δe = 3.532 ev) and identified electron-rich active sites, supporting the molecule’s ability to interact with the metal surface. these findings demonstrate that mnatt is a promising, low-concentration, surface-friendly corrosion inhibitor for mild steel in acidic environments.