2-Amino-5-ethyl-1,3,4-thiadiazole as a corrosion inhibitor for copper in 3.0% NaCl solutions E.M. Sherif 1 , Su-Moon Park * Department of Chemistry and Center for Integrated Molecular System, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea Received 1 June 2005; accepted 21 March 2006 Available online 22 June 2006 Abstract 2-Amino-5-ethyl-1,3,4-thiadiazole (AETDA) has been evaluated as a corrosion inhibitor for cop- per in 3.0% NaCl solutions using weight loss, pH, potentiodynamic polarization, potentiostatic cur- rent–time, and electrochemical impedance spectroscopic (EIS) measurements. The study was also complemented by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) investi- gations. Weight loss measurements gave an inhibition efficiency of about 60% with 1.0 · 10 3 M AETDA present, increasing to about 97% at the AETDA concentration of 5.0 · 10 3 M. Potentio- dynamic polarization measurements showed that the presence of AETDA in de-aerated, aerated and oxygenated 3.0% NaCl solutions decreases cathodic, anodic, and corrosion currents to a great extent and shifts the corrosion potential slightly towards more negative values. Potentiostatic current–time measurements, SEM and EDX investigations also confirmed that the protection of the copper sur- face is achieved by strong adsorption of AETDA molecules. EIS measurements revealed that the sur- face and the charge transfer resistances increase upon increasing the AETDA concentration. Results together showed clearly that AETDA is a good mixed-type inhibitor for copper corrosion and its inhibition efficiency increases in the order of oxygenated > aerated > de-aerated 3.0% NaCl solutions. Ó 2006 Elsevier Ltd. All rights reserved. 0010-938X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.corsci.2006.03.011 * Corresponding author. Fax: +82 54 279 5877. E-mail address: smpark@postech.edu (S.-M. Park). 1 Permanent address: Electrochemistry and Corrosion Laboratory, Department of Physical Chemistry, National Research Centre, Dokki, 12622 Cairo, Egypt. Corrosion Science 48 (2006) 4065–4079 www.elsevier.com/locate/corsci