Jatropha gossypifolia Ethanol Extract as Corrosion Inhibitor for Galvanized Steel in 0.5M of Hydrochloric Acid

Abstract

The study investigated the corrosion inhibition properties of Jatropha gossypifolia extract in 0.5 M HCl solution on galvanised steel with a view to understanding the reaction mechanisms as well as kinetics and thermodynamics of adsorption step in the corrosion reaction. The experimental investigation was conducted using weight-loss, gasometric techniques and Polarization curves. The surface morphology of the exposed steel was studied using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The results of this study revealed that the acidic medium increased the corrosion rate of galvanised steel. It was deduced that the adsorption of Jatropha gossypifolia extract on galvanised steel surface obeyed the Langmuir adsorption isotherm. The negative value of Standard Change in Gibbs Free Energy of adsorption () showed that the reaction was thermodynamically feasible and spontaneous. Data obtained from weight loss and polarisation measurements show that Jatropha gossypifolia extract has fairly good inhibiting properties for galvanized steel corrosion in acidic medium, with inhibition efficiency of 89% at optimum concentration of 0.4 g/L.  Addition of the extract to corrosive medium reduces current densities at both cathode and anode of the electrochemical cell thereby act as a mixed inhibitor. The SEM images confirmed that galvanised steel corroded in acidic environment and Jatropha gossypifolia extract inhibited the rate of corrosion in galvanised steel in 0.5 M HCl solution. All the studied techniques revealed that galvanised steel could corrode in 0.5 M HCl and that corrosion progress could be in hindered by adding Jatropha gossypifolia extract as an inhibitor.