Schiff bases of increasing complexity as mild steel corrosion inhibitors in 2 M HCl Canan Ku ¨stu ¨, Kaan C. Emregu ¨l * , Orhan Atakol Ankara University, Science Faculty, Department of Chemistry, 06100 Tandog ˘ an, Ankara, Turkey Received 6 June 2005; accepted 7 February 2007 Available online 2 March 2007 Abstract The effect of three Schiff base compounds with increasing number of coordination sites, namely, 2-{(E)-[(2-hydroxyethyl)imino]methyl} phenol (I), 2-[(E)-({2-[(2-hydroxyethyl)amino]ethyl}imino) methyl]phenol (II) and 2,2 0 -{iminobis[ethane-2,1-diylnitrilo(E)methylylidene]}diphenol (III) have been investigated at 298 K by weight loss measurements, potentiodynamic polarization and electro- chemical impedance spectroscopy (EIS) methods. The inhibition efficiencies obtained from all meth- ods employed are in good agreement. Results show compound III to be the best inhibitor with a mean efficiency of 93% at 10 2 M additive concentration. Studies showed all three compounds to act as mixed type inhibitors. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: A. Mild steel; B. EIS; B. Polarization; C. Acid inhibition 1. Introduction The widespread use of mild steel in many petroleum applications is quite well known. Hydrochloric acid is widely used in petroleum fields for cleaning and descaling of steel alloys. However, generally the corrosion current density is high so in order to reduce the corrosion current density of the metallic material, various types of inhibitors are injected into the system. 0010-938X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.corsci.2007.02.002 * Corresponding author. Tel.: +90 312 22 6720x1406; fax: +90 32 223 2395. E-mail address: kcemregul@yahoo.com (K.C. Emregu ¨l). Corrosion Science 49 (2007) 2800–2814 www.elsevier.com/locate/corsci