Adsorption and Thermodynamics Study of the Inhibition of Corrosion of Mild Steel In H<sub>2</sub>SO<sub>4</sub> Medium Using <i>Vernonia Amygdalina</i>

Abstract

In this work, adsorption and thermodynamics study of the inhibition of corrosion of mild steel in H 2 SO 4 medium using Vernonia amygdalina was carried out. The inhibitive and adsorptive properties of ethanol extract of Vernonia amygdalina for the corrosion of mild steel in 0.2 M H 2 SO 4 solutions was investigated using weight loss technique. The result has proved that that the extract is a good inhibitor of corrosion of mild steel in H 2 SO 4 . The inhibition efficiencies ranged from 23.37% to 38.59% and from 22.45% to 35.78% at 303 and 323 K respectively. The inhibition efficiency of the extract decreased as temperature and time of immersion increased but increased with increase in concentration of extract. The adsorption of the inhibitor on 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 -2.12 to -4.87 KJmol -1 . The adsorption data fitted well to Langmuir, Temkin, Frumkin and Flory-Huggins adsorption isotherms.