International Journal of Scientific and Research Publications, Volume 3, Issue 12, December 2013 1 ISSN 2250-3153 www.ijsrp.org Congo Red Dye As A Novel Corrosion Inhibitor for Zinc in Hydrochloric Acid Solution A.Pasupathy 1 *, S.Nirmala 1 , M.Raja 1 , P.Sakthivel 2 1 Department of Chemistry, Urumu Dhanalakshmi College, Tiruchirappalli 620019, Tamil Nadu, India 2 Department of Physics, Urumu Dhanalakshmi College, Tiruchirappalli 620019, Tamil Nadu, India *Corresponding author: Tel.: +919003427375 E-mail address: pasupathyudc@gmail.com (A.Pasupathy) Abstract: The inhibitive effect of congo red was examined as corrosion inhibitor for the corrosion of zinc in 1N HCl by conventional weight loss and gasometric methods. Results obtained show that congo red exhibited high inhibition efficiencies. The inhibition efficiency was found to increase with increase in the inhibitor concentration. The adsorption of the inhibitor molecules on the zinc metal surface obeyed Temkin adsorption isotherm. Index Terms: Congo red, acidic solutions, zinc corrosion, weight loss I. INTRODUCTION ecause of its immense use in various industries, the protection of zinc metal against corrosion has gained much importance. In order to remove the undesirable scale and rust from the surface of the metals several acids are used 1-4 in many industrial processes which may involve metal dissolution and excess acid consumption. Among the various methods available for the protection of metals against corrosion, use of inhibitors is an important one. Inhibitors are compounds when added in small amounts to a corrosive medium, control the reaction between the metal and the medium. A survey of the literature reveals the fact that organic compounds containing oxygen, nitrogen and sulphur atoms are widely used as corrosion inhibitors for zinc metal corrosion in various acidic environments 5-14 . The effectiveness of these compounds in bringing down the corrosion of metals largely depends on their ability to get adsorbed on the metal surface through the polar groups present in their molecular structure acting as active adsorption centres. Nowadays much attention is focused on organic dyes because of the existence some desirable characteristics such as possessing hetero atoms like oxygen, nitrogen and sulphur, triple bonds, conjugated double bonds and aromatic rings in their molecular structures which are rich sources of electrons essential for the adsorption process. Because of these characteristics organic dyes are expected to perform as efficient corrosion inhibitors for a wide variety of metals. In the present work, we have evaluated Congo red as a corrosion inhibitor for zinc in 1N HCl medium employing the conventional weight loss and gasometry methods. II. EXPERIMENTAL 2.1 Material The zinc metal specimens used in this work has the following composition: lead 1.03%, cadmium 0.04%, iron 0.001% and the remainder being zinc. Zinc metal specimens were pretreated before the experiments by B