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E-Journal of Chemistry
Volume 5, Issue 2, Pages 355-364
http://dx.doi.org/10.1155/2008/138407

Corrosion Inhibition of Aluminium Using Exudate Gum from Pachylobus edulis in the Presence of Halide Ions in HCl

S. A. Umoren,1 I. B. Obot,1 and E. E. Ebenso2

1Department of Chemistry, Faculty of Science, University of Uyo, Uyo, Nigeria
2Department of Chemistry and Chemical Technology, National University of Lesotho, P.O. Roma 180, Lesotho

Received 27 August 2007; Revised 18 September 2007; Accepted 10 October 2007

Copyright © 2008 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The anti-corrosive effect of Pachylobus edulis exudate gum in combination with halides ions (Cl, Br and I) for aluminium corrosion in HCl was studied at temperature range of 30-60°C using weight loss method. Results obtained showed that the naturally occurring exudate gum acts as an inhibitor for aluminium corrosion in acidic environment. Inhibition efficiency (%I) increases with increase in concentration of the exudate gum and synergistically increased to a considerable extent on the addition of the halide ions. The increase in inhibition efficiency (%I) and surface coverage (θ) in the presence of the halides was found to be in the order I > Br > Cl which indicates that the radii as well as electronegativity of the halide ions play a significant role in the adsorption process. Pachylobus edulis exudate gum obeys Temkin adsorption isotherm. Phenomenon of physical adsorption is proposed from the values of kinetic and thermodynamic parameters obtained. The values of synergism parameter (S1) obtained for the halides are greater than unity suggesting that the enhanced inhibition efficiency of the P. edulis caused by the addition of the halide ions is only due to synergistic effect.