This study explores the efficacy of an acetonic extract derived from Origanum majorana (OM) leaves as an environmentally benign corrosion inhibitor for carbon steel (CS) in acidic medium (1 M HCl). With the increasing demand for environmentally sustainable corrosion mitigation strategies, natural extracts have attracted significant attention. OM leaves were selected as a potential source of bioactive compounds capable of inhibiting CS corrosion. Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques were employed to evaluate the inhibition efficiency (IE%) of the OM acetonic extract over concentrations ranging from 0.125 to 1 g·L⁻¹ . The maximum inhibition efficiency reached 94 % at 1 g·L −1 . Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of the functional groups in charge of adsorption, while scanning electron microscopy (SEM) combined with energy-dispersive X-ray analysis (EDX) evidenced the formation of a homogeneous organic protective layer on the CS surface and the complete suppression of chloride adsorption. The inhibitor molecules exhibited Langmuir-type adsorption behavior. Thermodynamic parameters indicated a naturally favorable process predominantly governed by physisorption. Density functional theory (DFT) calculations further supported these findings, showing robust adsorption affinity of the inhibitor molecules toward the CS surface through a reduced frontier orbital energy gap (ΔE), consistent with the observed inhibition performance. • Origanum majorana extract was used as a corrosion inhibitor for carbon steel in 1 M HCl . • Maximum inhibition of 94 % at 1 g·L⁻¹ confirmed by PDP and EIS. • Adsorption obeyed Langmuir isotherm behavior. • SEM–EDX showed a compact protective organic film. • DFT identified sakuranetin as the most active compound.
Elharami et al. (Wed,) studied this question.