Corrosion Inhibition of Mild Steel in Acidic Medium Using Ethanolic Extract of Christ Thorn Leaves

The study involves the corrossion inhibition of mild steel in acidic medium using ethanolic extract ofchrist thorn leaves. An experimental extract of Christ thorn leaves was carried out in 0.9 M HCl solutions using the weight loss technique. The result has proved that the extract is a good inhibitor of corrosion of mild steel in HCl. The inhibition efficiencies ranged from 47.15% to 60.04% and 44.31% to 54.09% at 303 and 323 K respectively. The corrosion rate CR decreases with an increase in the concentration of inhibitors. Moreover, surface coverage (θ) and percentage inhibitor efficiency (% IE) increase with increasing concentrations of inhibitor. The adsorption of the inhibitor on the surface of mild steel was found to be exothermic, spontaneous and consistent with the mechanism of physical adsorption as the value for heat of adsorption ranged from -22.04 to -17.73 kJmol-1. The adsorption data fitted well to the Langmuir adsorption isotherm. The surfaces morphology also revealed that severe corrosion on the metal surfaces in the uninhibited solution, indicating uniform damage characterized by cracks across the entire metal surface, but by the addition of the plant extracts the metal surfaces were effectively inhibited.