Thermodynamic Parameters and Adsorption Mechanism of Corrosion Inhibition in Mild Steel Using Jatropha Leaf Extract in Hydrochloric Acid

Corrosion inhibition performance, thermodynamic parameters and adsorption mechanism of jatropha leaf extract in 2 M HCl solution have been investigated. Inhibition efficiency and corrosion rate were evaluated using gravimetric method, based on ASTM G-31 standards. Activation energy, entropy and enthalpy changes were determined using relevant thermodynamic equations. The mechanism of adsorption was studied using six different adsorption isotherm models. Results obtained show that corrosion rate increased with increase in temperature and decreased with increase in concentration of jatropha leaf extract beyond a maximum dosage. The activation energy of the inhibited process was higher than that of the uninhibited process. The enthalpy and entropy changes obtained were positive and negative, respectively. While the constant of adsorption was positive, Gibb’s free energy change of adsorption was negative with values less than 20KJ/mol. Data obtained fit into Langmuir, Frumkim, El-Awady, Freundlich, Flory Huggins and Tempkin isotherm adsorption models. It was observed that Tempkin model had the best fit and as such was used to evaluate the adsorption constant and Gibb’s free energy change of adsorption. The study found that the adsorption of jatropha leaf extract, on the surface of mild steel, is feasible, spontaneous and follows physical adsorption mechanism.