Desalination 229 (2008) 279–293 *Corresponding author. Some thiazole derivatives as corrosion inhibitors for carbon steel in acidic medium A.A. Al-Sarawy a , A.S. Fouda b , W.A. Shehab El-Dein a* a Department of Mathematics and Physical Science, Faculty of Engineering, Mansoura University, Mansoura, Egypt Tel. +20 123252770; Fax +20 502224469; email: waleedazmy1967@yahoo.com b Department of Chemistry, Faculty of Science, Mansoura University, Mansoura, Egypt Received 7 February 2006; accepted revised 20 September 2007 Abstract The effect of some prepared compounds, namely thiazole derivatives on the corrosion of C-steel in 2 M HCl solutions has been studied using the weight loss and electrochemical polarization methods. The results showed that the inhibition efficiency of the investigated compounds was found to depend on the concentration and the nature of the inhibitor. The presence of the substituted donating group (–OCH 3 ) plays an important role in the inhibition percentage of these investigated compounds. The effect of temperature on the corrosion behavior of C-steel in 2 M HCl without and with the inhibitors was studied in the temperature range from 30 to 50°C. The activation and thermodynamic parameters E * a, ΔH * and ΔS * were calculated. The inhibitors were adsorbed on the C-steel surface according to Frumkin’s adsorption isotherm. The synergistic effect of some cations (Cu 2+ , Ni 2+ , Co 2+ and Ca 2+ ) on the corrosion inhibition of C-steel in 2 M HCl in the presence and absence of the investigated compounds was also studied by the weight loss method. Keywords: Corrosion inhibitor; Thiazole derivatives; C-steel; Weight loss method; Galvanostatic polarization method; Frumkin’s isotherm 1. Introduction The industrial consumption and development of new corrosion inhibitors have continuously in- creased because this corrosion control technique is one of the most effective and economical meth- ods to protect metal corrosion in acidic medium [1,2]. The development of corrosion inhibitors is based on organic compounds containing nitrogen, oxygen, sulfur atoms, and multiple bonds in the molecules that facilitate adsorption on the metal surface [3]. The corrosion inhibition efficiency of organic compounds is related to their adsorption properties. Adsorption depends on the nature and the state of the metal surface, on the type of cor- rosive medium and on the chemical structure of doi:10.1016/j.desal.2007.09.013 0011-9164/08/$– See front matter © 2008 Published by Elsevier B.V.