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Studies of the anti‐corrosive effect of Raphia hookeri exudate gum‐halide mixtures for aluminium corrosion in acidic medium

Studies of the anti‐corrosive effect of Raphia hookeri exudate gum‐halide mixtures for aluminium... Purpose – The purpose of this paper is to investigate the effect of Raphia hookeri exudate gum and halide ions on the corrosion inhibition of aluminium in HCl solutions at 30‐60°C and to study the mechanism of action. Design/methodology/approach – The corrosion rates were determined using the gravimetric (weight loss), gasometric (hydrogen evolution) and thermometric techniques. The results obtained in the absence and presence of Raphia hookeri , halides and Raphia hookeri – halides combination were used to calculate the inhibition efficiency (% I ), degree of surface coverage and to propose the mechanism of inhibition and type of adsorption. Findings – Results obtained showed that the Raphia hookeri exudates gum acted as an inhibitor for aluminium corrosion in acidic environment. Inhibition efficiency (% I ) increased with increase in concentration of the Raphia hookeri exudates gum and synergistically increased to a considerable extent on the addition of halide ions. The increase in inhibition efficiency (% I ) and surface coverage ( &thetas; ) 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. Raphia hookeri exudates gum obeys Freundlich, Langmuir and Temkin adsorption isotherms. Phenomenon of physical adsorption is proposed from the values of kinetic/thermodynamic parameters obtained. The values of synergism parameter ( S I ) obtained for the halides are greater than unity suggesting that the enhanced inhibition efficiency of the Raphia hookeri caused by the addition of the halide ions is only due to synergistic effect. Research limitations/implications – Electrochemical studies such as polarization and AC impedance spectra will throw more light on the mechanistic aspects of the corrosion inhibition and more exudate gums need to be evaluated as corrosion inhibitors. Practical implications – Raphia hookeri exudate gum can be used as corrosion inhibitor and the addition of halides to it improves the inhibition efficiency considerably. Originality/value – This paper provides new information on the use of exudate gums as corrosion inhibitors and addition of halides in acidic medium. This environmentally friendly inhibitor could find possible applications in metal surface anodizing and surface coatings. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Pigment & Resin Technology Emerald Publishing

Studies of the anti‐corrosive effect of Raphia hookeri exudate gum‐halide mixtures for aluminium corrosion in acidic medium

S.A. Umoren; E.E. Ebenso
Pigment & Resin Technology , Volume 37 (3): 10 – May 23, 2008
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References (43)

Publisher
Emerald Publishing
Copyright
Copyright © 2008 Emerald Group Publishing Limited. All rights reserved.
ISSN
0369-9420
DOI
10.1108/03699420810871020
Publisher site
See Article on Publisher Site

Abstract

Purpose – The purpose of this paper is to investigate the effect of Raphia hookeri exudate gum and halide ions on the corrosion inhibition of aluminium in HCl solutions at 30‐60°C and to study the mechanism of action. Design/methodology/approach – The corrosion rates were determined using the gravimetric (weight loss), gasometric (hydrogen evolution) and thermometric techniques. The results obtained in the absence and presence of Raphia hookeri , halides and Raphia hookeri – halides combination were used to calculate the inhibition efficiency (% I ), degree of surface coverage and to propose the mechanism of inhibition and type of adsorption. Findings – Results obtained showed that the Raphia hookeri exudates gum acted as an inhibitor for aluminium corrosion in acidic environment. Inhibition efficiency (% I ) increased with increase in concentration of the Raphia hookeri exudates gum and synergistically increased to a considerable extent on the addition of halide ions. The increase in inhibition efficiency (% I ) and surface coverage ( &thetas; ) 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. Raphia hookeri exudates gum obeys Freundlich, Langmuir and Temkin adsorption isotherms. Phenomenon of physical adsorption is proposed from the values of kinetic/thermodynamic parameters obtained. The values of synergism parameter ( S I ) obtained for the halides are greater than unity suggesting that the enhanced inhibition efficiency of the Raphia hookeri caused by the addition of the halide ions is only due to synergistic effect. Research limitations/implications – Electrochemical studies such as polarization and AC impedance spectra will throw more light on the mechanistic aspects of the corrosion inhibition and more exudate gums need to be evaluated as corrosion inhibitors. Practical implications – Raphia hookeri exudate gum can be used as corrosion inhibitor and the addition of halides to it improves the inhibition efficiency considerably. Originality/value – This paper provides new information on the use of exudate gums as corrosion inhibitors and addition of halides in acidic medium. This environmentally friendly inhibitor could find possible applications in metal surface anodizing and surface coatings.

Journal

Pigment & Resin Technology – Emerald Publishing

Published: May 23, 2008

Keywords: Corrosion inhibitors; Metals; Acids; Halides

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