This study aims to investigate the synergistic effects of Terminalia ivorensis leaf and stem bark extracts in the presence of chloride ions on the corrosion inhibition of mild steel in 1.0 M H2SO4 solution. The aim is to determine possible improvements in inhibition efficiency because of KCl additions to the extracts.
Corrosion behaviour was evaluated using gravimetric and gasometric techniques across varying extract concentrations and temperatures. Adsorption characteristics were examined by fitting the experimental data to Langmuir, Freundlich and Temkin adsorption isotherm models to elucidate the mechanism of inhibitor interaction with the metal surface.
Both leaf and stem bark extracts of Terminalia ivorensis effectively inhibited mild steel corrosion in acidic media, with inhibition efficiency enhanced significantly by synergistic interaction with chloride ions. Gravimetric measurements indicate that the stem showed higher inhibition efficiency compared to the leaf at ambient temperatures, but the reverse was observed at elevated temperatures, as indicated by the gasometric results, although across board the efficiency was enhanced by the presence of KCl. Inhibition efficiency increased consistently with extract concentration but decreased with rising temperature, indicating physisorption as the dominant adsorption mechanism. Adsorption data correlated well with the Langmuir adsorption isotherm compared to Freundlich and Temkin isotherms.
To the best of the authors’ knowledge, this study provides one of the few comparative evaluations of leaf and stem bark extracts of Terminalia ivorensis in the presence of chloride ions for mild steel corrosion protection. The combined gravimetric–gasometric approach offers robust validation of inhibitor performance, while the adsorption modelling delivers deeper insight into the underlying inhibition mechanism. These findings contribute to the development of cost-effective, plant-based and environmentally benign corrosion inhibitors for industrial acid-cleaning processes.
