Studies on the Inhibitive Effect of Exudate Gum from Dacroydes edulis on the Acid Corrosion of Aluminium

 

S.A. Umoren^a, I.B. Obot^a,*,E.E. Ebenso^b, N. Obi-Egbedi^c

 

^aDepartment of Chemistry, Faculty of Science, University of Uyo, Uyo, Nigeria

^bPhysical Chemistry Unit, Department of Pure and Applied Chemistry, University of Calabar, Calabar, Nigeria

Department of Chemistry and Chemical Technology, National University of Lesotho, P.O.Roma 180, Lesotho, Southern Africa

^cPhysical Chemistry unit, Department of Chemistry, University of Ibadan, Ibadan, Nigeria

 

Received 24 April 2007; accepted 13 June 2007

 

Abstract

The inhibitive effect of exudate gum from Dacroydes edulis in the corrosion of aluminium in HCl solutions was studied using weight loss and thermometric methods at 30-60 ^oC. The results reveal that the exudate gum acts as an inhibitor for corrosion of aluminium in HCl solution. The inhibition efficiency increases with an increase in the concentration of the exudate gum but decreases with increase in temperature. The Temkim adsorption isotherm was tested for its fit to the experimental data. The result confirms that the corrosion inhibition of the exudate gum from DE is attributed to the adsorption of molecules of phytochemicals present in the exudate gum on the surface of the metal. The free energies and equilibrium constant for the adsorption process were determined. A mechanism of physical adsorption is proposed.

Keywords: corrosion inhibition, aluminium, Dacroydes edulis, adsorption, Temkin isotherm.

 

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* Corresponding author. E-mail address: proffoime@yahoo.com