Phenyltriazolobenzodiazepine derivatives: Synthesis, characterisation, and electrochemical assessment as effective mild steel corrosion inhibitors in acidic environments

Abstract

This study investigates the corrosion inhibition potential of two ethyl-substituted phenyltriazolobenzodiazepine derivatives, CH₃Ph_EH and NO₂Ph_EH, on mild steel in a 1 M HCl solution. Potentiodynamic polarization and electrochemical impedance spectroscopy were employed to evaluate inhibition efficiency. Results revealed that CH₃Ph_EH and NO₂Ph_EH achieved maximum inhibition efficiencies of 97.6 % and 98.0 %, respectively, at an optimal concentration of 10⁻⁴ M. Thermodynamic analysis indicated spontaneous and endothermic adsorption, following the Langmuir adsorption isotherm, with free energy values (ΔG°_ads) of −51.4 kJ/mol and −50.5 kJ/mol, respectively. Density functional theory and molecular dynamics simulations provided insights into charge distribution and metal interaction, demonstrating strong adsorption and protective layer formation on the steel surface. The study addresses a research gap in the exploration of benzodiazepine derivatives as corrosion inhibitors, particularly the impact of electron-donating and electron-withdrawing substituents on adsorption efficiency. The findings suggest that CH₃Ph_EH and NO₂Ph_EH are promising candidates for industrial corrosion protection applications.