Corrosion Inhibitive Properties and Adsorption Behaviour of Acetone Extract of Anacardium occidentale on Mild Steel and Aluminium in HCl

Abstract

The corrosion inhibition of aluminium and mild steel in hydrochloric acid by acetone extract of Anarcardium occidentale was studied using the weight loss technique at 28 ºC. The result of the study reveals that the different concentrations of the extract of Anarcardium occidentale inhibit aluminium and mild steel corrosion. The inhibition efficiency and surface coverage increases with an increase in the concentration of the extract. Thermodynamic consideration reveals that the adsorption on mild steel and aluminium surface is spontaneous and occurs according to Temkin and Freundlich adsorption isotherms. The phenomenon of physical adsorption is proposed from the free energies DGº_ads i.e. the DGº_ads is > 40 KJ/mol and negative; suggestive of adsorption on the metal. The DGº for mild steel is -7.695 KJ/mol and -9.23 KJ/mol for aluminium. A first order type of mechanism has been deduced from the kinetic treatment of the results and values of some thermodynamic parameters were evaluated and compared with reference to mild steel and aluminium.