Inhibitive and Synergistic Properties of Ethanolic Extract of Moringa oleifera Leaves on the Corrosion of Zinc in HCl Solution

The potentials of ethanolic extract of Moringa oleifera leaves as corrosion inhibitor was investigated by evaluating the corrosion behaviour of Zinc immersed in 0.5M, 1.0M, 1.5M and 2.0M HCl (corrodent) solutions each containing varied concentration of the extract (0.1 g/L, 0.3 g/L and 0.5 g/L) and halides (0.1M, 0.3M and 0.5M each of KCl and KI) for synergism using thermometric method. Maximum temperature attained, reaction time, synergism parameter and adsorption characterizations were utilized to evaluate the corrosion inhibition, synergism and adsorption properties of the extract. The results revealed that the corrosion of Zinc decreases with increase in concentration of ethanol extract and halides which are both inhibitors; also, it increases with increase in HCl (corrodent) concentration. The addition of KI and KCl to the extract, improve the values of inhibition efficiency of the extract in the order KI > KCl. In all cases, KI exhibits least effect on the corrosion of Zinc in comparison with KCl. Results obtained from adsorption studies indicated that, the ethanol extract, KCl and KI were adsorbed on the surface of the Zinc and that the adsorption fit excellently with the assumptions of the Langmuir adsorption isotherm model on the platform of Chemical Adsorption. All data acquired revealed that the ethanol extract is an efficient inhibitor of corrosion in acid medium due to its phytochemicals: saponins, tannins, flavonoids, glycosides, carbonhydrates, reducing sugars, terpenoids, steroids and alkaloids.