Phosphate of Aluminum as Corrosion Inhibitor for Steel in H₃PO₄

L. Malki Alaoui ¹, S. Kertit² , A. Bellaouchou¹, A. Guenbour ¹, A. Benbachir ¹, B. Hammouti ^3,*

¹ Laboratoire d’Electrochimie et Corrosion,  Faculté de Sciences, Rabat, Morocco

² Ecole Supérieure d’Optique Appliquée (ESOA), Rabat, Morocco

³ Laboratoire de Chimie Appliquée et Environnement, Faculté des Sciences, B.P. 717, Oujda, Morocco

 

Received 28^th December 2007; accepted 1^st February 2008

 

 

Abstract

The influence of phosphate of aluminum (PA) on the corrosion inhibition of mild steel in phosphoric acid solution was studied using the weight-loss method. The electrochemical performance of the inhibitors was also investigated through potentiodynamic polarisation and EIS measurements. The inhibition efficiency of inhibitor increases with concentration to attain 84 % at 10^-2M of PA in 0.33 M H₃PO₄. Polarization studies show that PA is a mixed-type inhibitor and acts both on the cathodic and anodic reactions without changing the mechanism of the hydrogen evolution reaction. The inhibition efficiency of PA is temperature-dependent in the range 298 - 363 K, the associated activation energy has been determined. PA adsorbs on the steel surface according to a Langmuir isotherm adsorption model.

 

Keywords: mild steel, phosphate of aluminum, phosphoric acid, corrosion.

 

 

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* Corresponding author. E-mail address: hammoutib@yahoo.fr