Application of green Lemna gibba phytochemical extract as a corrosion inhibitor for mild steel in H₂SO₄

The effectiveness of Lemna gibba ‘s ethanolic extract as a natural corrosion inhibitor for carbon steel in a sulfuric acid environment is demonstrated for the first time in this study. Traditionally used in phytoremediation, this aquatic plant reveals new potential as a long-lasting anticorrosive agent. Electrochemical tests, including weight loss, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS), revealed inhibitory efficiencies of 82.85 %, 84.74 % and 79.99 % respectively at an ideal concentration of 800 ppm. The extract functions as an inhibitor of mixed types, and adsorption of the bioactive compounds present in the extract follows the Langmuir isotherm, making a protective monolayer on the steel surface, confirmed by SEM/EDX analysis. The inhibition mechanism is endothermic, involving both physisorption and chemisorption. Spectroscopic analyses (UV-Visible, FTIR, and GC-MS) revealed the presence of oxygen-rich functional groups - hydroxyls, carbonyls, and esters – able to form coordination bonds with ferrous ions (Fe²⁺). The adsorption of active molecules to the metal surface is facilitated by this chemical interaction, which enhances the development of the anti-corrosion layer. Lemna gibba could therefore be considered a promising, environmentally friendly, effective, and economically viable alternative to conventional corrosion inhibitors, without the need for external chemical additives. • First-time use of Lemna gibba extract as a green corrosion inhibitor for carbon steel in H₂SO₄. • Maximum inhibition efficiency of 84.74% achieved at 800 ppm via PDP. • Adsorption follows Langmuir isotherm with mixed-type inhibition mechanism. • SEM/EDX and spectroscopy confirm protective film formation via oxygen-rich groups.