Adsorption of 3-(4-amino-2-methyl- 5-pyrimidyl methyl)-4-methyl thiazolium chloride on mild steel Olusegun K. Abiola * Department of Pure and Industrial Chemistry, P. M. B. 5323, University of Port Harcourt, Port Harcourt, Nigeria Received 31 January 2005; accepted 1 December 2005 Available online 23 February 2006 Abstract The adsorption of 3-(4-amino-2-methyl-5-pyrimidyl methyl)-4-methyl thiazolium chloride (AMMPTC) or vitamin B 1 at the mild steel surface from hydrochloric acid (HCl) solution is studied using chemical techniques. The surface coverage with the adsorbed AMMPTC is used to calculate the free energy of adsorption, DG 0 ads , of AMMPTC using Bockris–Swinkels isotherm. The depen- dence of free energy of adsorption, DG 0 ads , with surface coverage, h, is ascribed to surface heteroge- neity of the adsorbent. The effect of AMMPTC is discussed from the viewpoint of adsorption model. The adsorption of AMMPTC molecules on the surface occurs without modifying the kinetic of corrosion process which is of first order with respect to mild steel. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: A. Mild steel; 3-(4-Amino-2-methyl-5-pyrimidyl methyl)-4-methyl thiazolium chloride; Hydrochloric acid; B. Hydrogen evolution; C. Bockris–Swinkels isotherm; Free energy of adsorption 1. Introduction It is indeed remarkable the extent to which adsorption effects are emphasized, in the development of electrochemistry concept in the literature [1–3]. Adsorption played a very 0010-938X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.corsci.2005.12.001 * Tel.: +234 8033 360 504. E-mail address: abiolaolusegun@yahoo.com Corrosion Science 48 (2006) 3078–3090 www.elsevier.com/locate/corsci