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Inhibition of steel corrosion in HCl media by phosphite compound

L. Herrag (Laboratoire de Chimie Appliquée et Environnement, Faculté des Sciences, Oujda, Morocco)
B. Hammouti (Laboratoire de Chimie Appliquée et Environnement, Faculté des Sciences, Oujda, Morocco)
S. Elkadiri (Laboratoire de Chimie Appliquée et Environnement, Faculté des Sciences, Oujda, Morocco)
B. El Bali (Laboratory of Mineral Solid and Analytical Chemistry, Department of Chemistry, Faculty of Sciences, Oujda, Morocco Laboratoire d'Ingénierie des Matériaux Organométalliques et Moléculaires, Faculté des Sciences, Fès, Morocco)
M. Lachkar (Laboratoire d'Ingénierie des Matériaux Organométalliques et Moléculaires, Faculté des Sciences, Fès, Morocco)
R. Ouarsal (Laboratoire d'Ingénierie des Matériaux Organométalliques et Moléculaires, Faculté des Sciences, Fès, Morocco)

Pigment & Resin Technology

ISSN: 0369-9420

Article publication date: 23 May 2008

Abstract

Purpose

The purpose of this paper is to investigate the inhibitive effect of the phosphite NaCo(H2PO3)3•H2O (PhCo) for the corrosion of mild steel in HCl solutions. The study is another trial to find a mineral inhibitor for mild steel corrosion.

Design/methodology/approach

The inhibitory effect has been evaluated by gravimetric and polarisation techniques at various temperatures. The type of adsorption inhibition and adsorption and kinetic data are determined.

Findings

Results show that PhCo inhibits the corrosion of steel in acidic solution. The inhibition efficiency at 308 K increases with the inhibitor concentration to reach 96 per cent for 10−4 M, and then decreases at higher temperatures. Kinetic parameters such as Ea, ΔHa ∘ and ΔSa ∘ were calculated. The adsorption of inhibitor obeys the Langmuir isotherm model. Thermodynamic parameters of adsorption including ΔGad, ΔHad, ΔSad, and Keq(ad) were calculated in the presence of inhibitor.

Research limitations/implications

Electrochemical studies (polarization method) show the partial action of inhibitor on anodic and cathodic reactions of the corrosion inhibition.

Practical implications

The efficiency of the tested phosphite increases with its concentration to reach 96 per cent. It can be used in chemical cleaning and pickling processes at moderate temperature.

Originality/value

This paper reveals the possible application of phosphites as environmentally valid inhibitors for corrosion under the specified conditions.

Keywords

Citation

Herrag, L., Hammouti, B., Elkadiri, S., El Bali, B., Lachkar, M. and Ouarsal, R. (2008), "Inhibition of steel corrosion in HCl media by phosphite compound", Pigment & Resin Technology, Vol. 37 No. 3, pp. 167-172. https://doi.org/10.1108/03699420810871011

Publisher

:

Emerald Group Publishing Limited

Copyright © 2008, Emerald Group Publishing Limited