Journal of Global Ecology and Environment

The mild steel corrosion in strongly acidic solutions remains a significant concern in industrial processes, including acid pickling, petrochemical processing, and oil-well acidizing. The performance of corrosion inhibition of the leaf extract of L. cupanioides as a sustainable, eco-friendly inhibitor for mild steel in 2 M HCl solution was investigated. Gravimetric measurements, Potentiodynamic polarization, Fourier transform infrared spectroscopy (FTIR), adsorption isotherm analysis, thermodynamic evaluation, and scanning electron microscopy (SEM) were integrated to elucidate the inhibition mechanism. Loss of weight data showed a substantial decline in the rate of corrosion from 1.305 × 10^-3 to 3.12 × 10^-4 g/h/cm² as inhibitor concentration elevated from 0 to 1 g/100 mL, corresponding to a maximum inhibition efficiency of 78.17 %. Electrochemical analysis further validated the improved coating, producing an increased performance of 88.82% at a similar concentration, accompanied by a significant decrease in the current density of corrosion from 626.27 to 70.00 µAcm^-2. Thermodynamic parameters indicated elevated energy of activation in inhibited systems (up to 25.59 kJ/mol) when compared to the blank (15.28 kJ/mol), while negative Gibbs free energy change with values −13.83 KJ/mol to −13.17 kJ/mol showed spontaneous adsorption driven by physisorption. Langmuir adsorption isotherm adequately described the adsorption behavior (R² ≈ 0.99). Results from SEM validated the development of a protective adsorbed film on the steel surface. Collectively, LCE exhibits promising potential as a green corrosion inhibitor for mild steel in highly acidic solutions.