Harnessing Bio-Based Compounds for Corrosion Control: An Efficient Green Inhibitor for Mild Steel in Acidic Media

The growing demand for sustainable corrosion protection strategies has stimulated significant interest in the development of environmentally friendly inhibitors derived from natural resources. In this context, the present study investigates the corrosion inhibition performance of a bio-based product, denoted as EEO, for mild steel in a hydrochloric acid medium. A series of electrochemical techniques, including potentiodynamic polarization and electrochemical impedance spectroscopy, were employed to evaluate the corrosion behavior, with particular emphasis on the effect of inhibitor concentration. The obtained results reveal a marked improvement in inhibition efficiency with increasing EEO concentration, indicating a strong affinity of the active phytochemical constituents toward the metal surface. This behavior suggests the progressive formation of an adsorbed protective layer, which effectively isolates the metal from the aggressive acidic environment. The EEO acts as a mixed-type inhibitor, simultaneously suppressing anodic metal dissolution and cathodic hydrogen evolution reactions, thereby reducing the overall corrosion rate. The formation of a stable and adherent film at the metal–solution interface plays a crucial role in hindering charge transfer processes, as confirmed by electrochemical data. Furthermore, surface morphological analyses provide additional evidence of the protective barrier formed in the presence of the inhibitor, showing a significantly smoother and less damaged surface compared to the uninhibited system. The adsorption mechanism is predominantly governed by physicochemical interactions, involving both electrostatic attraction and possible chemical bonding between the bioactive molecules and the steel substrate. Overall, these findings highlight the high efficiency of EEO as a green corrosion inhibitor and emphasize its potential as a sustainable and eco-friendly alternative to conventional corrosion control agents in aggressive acidic environments.