Asian Journal of Applied Chemistry Research

The study reports the corrosion inhibition activity of methanol extract of Aframomum chrysanthum on mild steel in 0.1 M HCl, using gravimetry analysis. The weight loss of the mild steels was observed to increase with increasing immersion time. The inhibition efficiency (%IE) was also observed to have increased with increasing concentrations of the inhibitor but decreases with increasing immersion time. The effect of temperature change on the inhibition efficiency was also studied and it was observed that for every increase in temperature there was a corresponding increase in weight loss and decreased in the %IE. The highest values of %IE; 46.66, 56.66, 60.0, 80.0 & 93.33 was observed at temperature 303 K for 0.2, 0.4, 0.6, 0.8 & 1.0 g/L respectively. Activation energy (E_a) values and the enthalpy values reviews that the adsorption process followed a physisorption’s mechanism. Change in enthalpy (ΔH) and entropy change (ΔS) of the reaction was positive indicating the endothermic nature and the spontaneity of the reaction. Three adsorption isotherms were tried on the inhibition process and only the Temkin isotherm gave the best fit with R² value of 0.903, describing the best adsorption mechanism. The adsorption equilibrium constants K_­ads were positive, indicating the feasibility of the adsorption of the inhibitor to the metal surface. Gibb’s Free Energy change of adsorption, ΔG_ads are negative indicating that the adsorption of the extract of Aframomum chrysanthum on mild steel surface is spontaneous. The values of ΔG_ads shows physisorption mechanism. All confirming that Aframomumm chrysanthum extract is a good corrosion inhibitor on mild steel in 0.1 M HCl.