Arab J Sci Eng (2012) 37:1293–1303 DOI 10.1007/s13369-012-0257-7 RESEARCH ARTICLE - CHEMISTRY B. Labriti · N. Dkhireche · R. Touir · M. Ebn Touhami · M. Sfaira · A. El Hallaoui · B. Hammouti · A. Alami Synergism in Mild Steel Corrosion and Scale Inhibition by a New Oxazoline in Synthetic Cooling Water Received: 8 March 2011 / Accepted: 10 October 2011 / Published online: 24 April 2012 © King Fahd University of Petroleum and Minerals 2012 Abstract The synergistic effect caused by molybdate ions and biocide on the inhibition of mild steel corrosion and scale in simulated-cooling water system in the presence of a newly synthesized oxazoline derivative, namely, 2-phenyl-4-methyl-4((tetrazol-5-yl)methyl)oxazoline (OXA) has been studied using potentiodynam- ic polarization and electrochemical impedance spectroscopic method. The obtained results show that OXA inhibits the corrosion in the considered medium. The corresponding inhibition efficiency increases with inhib- itor concentration and also by addition of molybdate ions. The increase of inhibiting efficiency in the presence of MoO 2- 4 indicates enhancement of OXA adsorption onto the metallic surface. Moreover, the effect of biocide, namely, cetyl trimethyl ammonium bromide on biofilm formation has been studied. Keywords OXA · Corrosion and scale inhibition · Potentiodynamic polarization · EIS · Biocide · Simulated-cooling water B. Labriti · A. El Hallaoui · A. Alami Laboratoire de Chimie Organique, Faculté des Sciences Dhar El Mahraz, Université Sidi Mohammed Ben Abdellah, BP 1796, 30000 Atlas, Fès, Morocco N. Dkhireche · R. Touir (B ) · M. Ebn Touhami Laboratoire d’Electrochimie, Corrosion et Environnement, Faculté des Sciences, Université Ibn Tofail, BP 133, 14000 Kénitra, Morocco E-mail: touir8@yahoo.fr M. Sfaira Laboratoire d’Ingénierie des Matériaux, de Modélisation et d’Environnement, LIMME, Faculté des Sciences Dhar El Mahraz, BP 1796, 30000 Atlas, Fès, Morocco B. Hammouti LCAE-URAC18, Faculté des Sciences, Université Mohammed Premier, BP 717, 60000 Oujda, Morocco 123