Ginseng root: A new efficient and effective eco-friendly corrosion inhibitor for aluminium alloy of type AA 1060 in hydrochloric acid solution

We report for the first time the inhibitive action of the root of ginseng on aluminium corrosion in HCl solution using weight loss method at 30-60 °C. Results obtained showed that ginseng root functioned as an effective and excellent inhibitor in the acid medium. Corrosion rate increased both in the absence and presence of inhibitor with increase in temperature. Corrosion rate was also found to decrease in the presence of inhibitor compared to the free acid solution. Inhibition efficiency increases with increase in concentration of the inhibitor but decreases with increase in temperature reaching a maximum of 93.1% at 30 °C at 50 % v/v concentration of ginseng. Addition of iodide ions to the root extracts of ginseng enhances the inhibition efficiency considerably and the effect is more pronounced at higher temperatures. The adsorption of extract components onto the aluminium surface was found to be a spontaneous process and to follow the Freundlich adsorption isotherm. The free energies, enthalpy and entropy for the adsorption process as well as the energy of activation, enthalpy of activation and entropy of activation for the dissolution process were determined and discussed. A mechanism of physical adsorption of the root components on the surface of the metal is proposed for the inhibition behaviour.