Hydroxy- and methoxy-aromatics as corrosion inhibitors for automotive steel in 1.0 M HCl: Experimental and theoretical study

Corrosion protection of automotive steels is essential for extending service life and reducing maintenance costs. This study introduces three oxygen-rich aromatic compounds, 2-hydroxy-5-methoxyacetophenone (B1), 2,3,4-trimethoxybenzoic acid (B2), and 3,4,5-trimethoxybenzoic acid (B3), as novel, sustainable inhibitors for S420MC automotive steel in 1.0 M HCl. Electrochemical measurements revealed mixed-type inhibition with efficiencies exceeding 91 %. Scanning Electron microscope- Energy Dispersive X-ray Spectroscopy confirmed the formation of compact protective films. Adsorption followed the Langmuir model (Kads > 9 x 10(5) L mol(-)(1); Delta G degrees ads approximate to -45 kJ mol(-)(1)), indicating spontaneous chemisorption. Temperature-dependent studies showed endothermic adsorption and reduced interfacial disorder. Complementary DFT, DFTB, and Monte Carlo simulations demonstrated parallel adsorption on Fe (110) via Fe-O and Fe-C coordination, consistent with experimental findings. This integrated experimental-theoretical approach identifies oxygen-bearing aromatics as a new class of efficient, environmentally compatible inhibitors.