Inhibitory Action of Methanol Leaf Extract of <i>Irvingia Gabonensis</i> on the Corrosion of Mild Steel in H<sub>2</sub>SO<sub>4</sub>

Abstract

The corrosion inhibition efficiency of methanol leaf extracts of Irvingia gabonensis for mild steel in 0.4, 0.5, 0.6 and 2.5M H 2 SO 4 was investigated using weight loss and gasometric techniques in other to determine the phytochemical components of the crude leaf extract, the corrosion inhibition potential of the leaf extract, the thermodynamic parameters that aided the corrosion inhibition, the adsorption isotherm of the corrosion inhibition of the extracts using the Langmuir and Freundlich models and investigate the kinetics of the corrosion inhibition process. Preliminary phytochemical screening revealed the presence of tannins, saponnins, flavonoids, terpenes and alkaloids. From the results, the corrosion rates decreased with increase in inhibitor concentration. The maximum inhibition efficiency of 58.71% was obtained at extract concentration of 0.6g/L in 0.4M H 2 SO 4 at 303K, 41.83% at extract concentration of 0.6g/L at 303K in 0.5M H 2 SO 4 and 57.33% at extract concentration of 0.6g/L in 0.6M H 2 SO 4 at 303K, for the gravimetric technique. In 2.5M H 2 SO 4 , maximum inhibition efficiency for the gasometric technique was 53.53% in 0.6g/L inhibitor concentration at 303K and for the gravimetric technique, the maximum inhibition efficiency was 29.42% in 0.6g/L inhibitor concentration at 303K. The kinetic and thermodynamic studies showed that activation energy (E a) in the presence of inhibitor is greater than in the absence of inhibitor. From the E a and ∆G o ads values obtained, a physical adsorption mechanism was proposed. The Langmuir isotherm was found to show better correlation (R 2) at lower temperature while the Freundlich isotherm had better correlation at higher temperature.