Methanol extract of Canarium Sweinfurthii as a green inhibitor for the corrosion of mild steel in HCl: adsorption, kinetic, thermodynamic and synergistic studies

Weight loss and electrochemical linear polarization measurements were employed in the investigation of corrosion inhibitive properties of methanolic stem extract of Canarium sweinfarthii (CS) on mild steel in 1.0 M HCl. The stem extract inhibited the corrosion of the mild steel in the acid medium. The inhibition efficiency (%IE) of the plant extract increased with increasing concentration but decreased with increase in temperature. Inhibition efficiency of the stem extract was also enhanced in the presence of iodide ions. Linear polarization analysis shows that the plant extract function as a mixed inhibitor. The adsorption of the stem extract on the mild steel surface obeyed both Langmiur and Freundlich adsorption isotherm models. The values of Ea obtained suggests that the adsorption mechanism was physisorption. The values of enthalpy (ΔH◦) and entropy of activation, (ΔS◦) obtained signified that the plant extract adsorbed endothermically on the metal surface and the adsorption follows a dissociation mechanism.