S.A. Umoren1,*, I.B. Obot1, E.E. Ebenso2,3, P.C. Okafor2
1Department of Chemistry, Faculty of Science, University of Uyo, Uyo, Nigeria
2Physical Chemistry Unit, Department of Pure and Applied Chemistry, University of Calabar, Nigeria
3Department of Chemistry and Chemical Technology, National University of Lesotho, P.O. Roma 180, Lesotho, Southern Africa
Received 29 August 2007; accepted 5 December 2007
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Abstract
Exudates gums from Pachylobus edulis (PE) and Raphia hookeri (RH) were evaluated as corrosion inhibitors for aluminium in HCl using weight loss and thermometric measurements at 30 – 60 oC. The exudates were found to retard corrosion rate of aluminium. The inhibition efficiency (%1) increased with increase in concentration of the exudates. Increase in temperature increased the corrosion rate in the absence and presence of inhibitors but decreased the inhibition efficiency. Both PE and RH exudate gums were found to obey Temkin adsorption isotherm and Kinetic-Thermodynamic Model of El-Awady et al. at all the concentrations and temperatures studied. Phenomenon of physical adsorption is proposed from the activation parameters obtained. Thermodynamic parameters reveal that the adsorption process is spontaneous. Exudate gum from RH was found to be a better inhibitor than PE.
Keywords: corrosion inhibition, Pachylobus edulis, Raphia hookeri, adsorption isotherm, aluminium.
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* Corresponding author. E-mail address: saviourumoren@yahoo.com
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