Electrochemical, surface, DFT, and ADMET insights into (E)-2-(2-hydroxybenzylidene)hydrazine-1-carboxamide as a corrosion inhibitor.

In this work, (E)-2-((2-hydroxybenzylidene))hydrazine-1-carboxamide (HBHC) was investigated as a new organic and eco-friendly corrosion inhibitor for mild steel in acidic medium through electrochemical measurements including potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), long-term immersion tests, surface characterization, theoretical calculations, and ADMET studies. HBHC demonstrated excellent inhibition performance, achieving 94.50% efficiency by PP and 93.33% by EIS at 200 ppm, and retained remarkable stability over 30 days of immersion with 97.64% efficiency. Adsorption behavior was consistent with the Langmuir isotherm, with negative values indicating a mixed physisorption-chemisorption mechanism. SEM micrographs, EDX analysis, and elemental mapping analysis confirmed the formation of a uniform protective film enriched with heteroatoms on the steel surface. DFT calculations, including analysis of HOMO-LUMO frontier orbitals, revealed a low HOMO-LUMO energy gap (ΔE), supporting the high reactivity of HBHC and its strong donor-acceptor interactions with the Fe(110) surface, while MD simulations further confirmed its adsorption stability. Furthermore, ADMET predictions indicated low toxicity and good bioavailability, supporting the environmentally benign character of HBHC.