Inhibitory Effect of African Pumpkin (<i>Momordica balsamina</i> Linn.) Leaf Extract on Copper Corrosion in Acidic Media

Abstract

Inhibition of copper corrosion in acidic medium by ethanolic extract of Momordica balsamina leaves was investigated. Findings reveal that the rate of copper corrosion increases with increasing temperature of the medium but decreases as the concentration of the Momordica balsamina extract added to the medium increases. Examination of the surface morphology of copper using Scanning Electron Microscopy (SEM) also reveals that while the surface of copper was seriously damaged in acidic solution in the absence of Momordica balsamina extract, addition of 0.8 mgL^-1 of the extract significantly protected the copper surface from corrosion. Results obtained from adsorption and thermodynamic studies reveal that the adsorption of the inhibitor on the surface of the copper metal fitted well to both Freundlich ( R²≥ 0.948) and Temkin ( R²≥ 0.940) adsorption models and the low values of activation energies obtained ( Ea≤ 34.02 kjmol^-1) indicate that the adsorption of the inhibitor on the copper surface favors the mechanism of physical adsorption. Negative signs of ΔG_ads obtained in the study suggest that the adsorption of Momordica balsamina on the copper metal is thermodynamically favorable. The data obtained in this study demonstrate that extract of Momordica balsamina leaves probably contains one or more chemical species that protect copper against corrosion through the mechanism of physical adsorption. 

Keywords: Adsorption, Copper, Corrosion, Inhibitor, Momordica balsamina