Xylopia aethiopica EXTRACT AS GREEN AND ECO-FRIENDLY CORROSION INHIBITOR AND ITS QUANTUM CHEMICAL ANALYSIS.

Abstract

This work examines the corrosion inhibitory behavior of Xylopia aethiopica stem bark and root bark extracts respectively on corrosion of mild steel in 2M HCl solution and their quantum chemical analysis using gravimetric technique and quantum computational modeling. The corrosion rates of the mild steel coupons in blank HCl solutions were found to increase with increase in concentration of the corrodent, period of immersion and rise in temperature. On the other hand, the corrosion rate decreased in the acid solution containing the test extracts and the decrease became more pronounced on increase in the concentrations of Xylopia aethiopica stem bark and root bark extracts respectively. The decrease in corrosion rate indicates that the extracts inhibited corrosion of mild steel in the acid solution and inhibition efficiency increased with increase in extract concentrations. The inhibition is attributed to adsorption of the test extract constituent molecules on the mild steel surface, forming a film layer that protects the metal surface from the corrodent. Results of quantum chemical computational analysis proved that, 3-dimethyl- 1-vinylcyclohexene among the constituent compounds of Xylopia aethiopica bark extract would be the most likely organic compound to share electrons with the metal surface for possible adsorption bond. The adsorption of the extract molecules on the mild steel surface fitted into Langmuir adsorption isotherm with slope values of 0.86 and 0.98 for Xylopia aethiopica root bark and stem bark extracts respectively, and regression correlation (R2) values of 1.0 and 0.99 for root and stem extracts respectively.