Experimental and Computational Investigation of Spearmint (Mentha spicata L.) Extract as a Green Corrosion Inhibitor for Copper in a Sulfuric Acid Environment

The need for sustainable corrosion inhibitors has driven research into eco-friendly alternatives to harmful chemical inhibitors. Copper is highly susceptible to corrosion, necessitating effective protection strategies. This study evaluates the efficacy of spearmint extract as a green corrosion inhibitor for copper using experimental and computational approaches. Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP) tests reveal that spearmint extract significantly reduces corrosion current, achieving 91% inhibition efficiency at 500 ppm. Nyquist plot analysis shows an increase in charge transfer resistance (Rct), indicating the formation of a stable protective layer. Adsorption studies confirm that spearmint extract follows the Langmuir isotherm model, suggesting monolayer adsorption. GC-MS analysis identifies carvone (31.87%), Limonene (18.58%), and Menthol (3.05%) as key active compounds. Quantum chemical analysis demonstrates that carvone has the lowest energy gap and highest adsorption energy, making it the dominant protective agent. Monte Carlo simulations further confirm carvone's strong interaction with the Cu(111) surface, facilitated by its planar molecular orientation. These results confirm that spearmint extract, particularly carvone, is a highly effective, sustainable corrosion inhibitor for copper, with promising applications in industrial corrosion control.