American Journal of Chemistry and Materials Science 2014; 1(1): 1-6 Published online March 20, 2014 (http://www.openscienceonline.com/journal/ajcms) Electrochemical and gravimetric studies of the corrosion inhibition of mild steel in HCl medium by cephalexin drug I. A. Akpan * , N. O. Offiong Department of Chemistry, University of Uyo, Uyo, Akwa Ibom State, Nigeria Email address iaakpanchem2007@yahoo.com (I. A. Akpan) To cite this article I. A. Akpan, N. O. Offiong. Electrochemical and Gravimetric Studies of the Corrosion Inhibition of Mild Steel in HCl Medium by Cephalexin Drug, American Journal of Chemistry and Materials Science. Vol. 1, No. 1, 2014, pp. 1-6 Abstract The inhibition effect of cephalexin drug on the corrosion of mild steel in hydrochloric acid medium was investigated by electrochemical and gravimetric techniques at room temperature. The results obtained show that the drug significantly increased the polarization resistance of mild steel by reducing corrosion current densities. The inhibition efficiency increased with corresponding increase in the concentrations of the test drug. The drug inhibitor followed Langmuir’s adsorption isotherm. The gravimetric measurements aided in the classical prediction of a first order kinetics for the corrosion inhibition process. Keywords Linear Polarization Resistance, Gravimetric Technique, Corrosion Inhibition, Cephalexin, Mild Steel, HCl 1. Introduction The deterioration of metallic materials has been at the forefront of various other factors that pose serious threats to the durability and, in consequence, the integrity of many metals. Due to a wide spectrum of application of metals across industries as well as homes, researchers have designed various techniques to fight against metallic corrosion [1-4]. The quest for efficient corrosion inhibitor is justified by the reasons that it causes colossal economic and industrial wastes. As a fundamental progressive step in this quest, it has been found that the use of corrosion inhibitors is one of the most practicable ways for providing protection for metals in aggressive media [4-8]. The ability of these compounds to inhibit corrosion has been attributed to their ability to adsorb, by any means, on the metal surfaces, thereby hindering attacks from aggressive species [9-13]. El Ouali et al. [14] have presented that the adsorption process on the metal surface is by the displacement of the water molecules carrying aggressive species from the corroding interface as shown below: Several organic as well as inorganic inhibitors have been used to provide protection for metals, but quite often these compounds are either potentially toxic, or very costly, or difficult to isolate and characterize from their natural sources [15, 16]. For these reasons, recent researches have been directed towards drugs [17-25], with known structures, and in which reactivity (a major factor for effective inhibition) can be predicted, and commercially available at low costs. As part of our contribution to the search for a substance which do not only posses good inhibitive effect but is eco- friendly and can be accessed with ease, the present work envisages the inhibitory effect of cephalexin drug for mild steel corrosion in 0.1M HCl solution. 2. Experimental Hitherto, various techniques have been employed to monitor corrosion of metals, viz: gravimetric (weight loss)