Dry and wet lab studies for some benzotriazole derivatives as possible corrosion inhibitors for copper in 1.0 M HNO 3 K.F. Khaled a, * , Mohammed A. Amin b a Electrochemistry Research Laboratory, Chemistry Department, Faculty of Education, Ain Shams University, Roxy, Cairo 11711, Egypt b Chemistry Department, Faculty of Science, Ain Shams University, Abbassia, Cairo 11566, Egypt article info Article history: Received 1 April 2009 Accepted 29 May 2009 Available online 7 June 2009 Keywords: A. Copper B. In silico B. Polarization B. EIS C. Acid inhibition abstract With contrast to the traditional techniques of identifying and synthesizing new corrosion inhibitors in wet lab, a prior dry-lab process, followed by a wet-lab process is suggested by using cheminformatics tools. Quantum chemical method is used to explore the relationship between the inhibitor molecular properties and its inhibition efficiency. The density function theory (DFT) is also used to study the struc- tural properties of three selected benzotriazole derivatives namely, benzotriazole-1-carboxamide (BCA), 1H-benzotriazole-1-acetonitrile (BAN) and benzotriazole-1-carbonyl chloride (BCC) in aqueous phase. It is found that when the benzotriazole derivatives adsorb on the copper surface, molecular structure influ- ences their interaction mechanism. The inhibition efficiencies of these compounds showed a certain rela- tionship to highest occupied molecular orbital (HOMO) energy, Mulliken atomic charges and Fukui indices. A wet lab study has been carried out using weight loss, Tafel polarization and impedance mea- surements to evaluate their inhibition performance in 1.0 M HNO 3 solutions at 25 °C. Adsorption takes place by a direct chemisorption on the exposed copper surface, while it most probably occurs via hydro- gen bonding on the oxidized surface. BCA was the most effective among the tested inhibitors, while BCC was less effective than BAN. Results obtained from dry-lab process are in good agreement with those recorded from wet-lab experiments. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Copper is a metal that has a wide range of applications due to its good properties. It is used in electronics, for production of wires, sheets, tubes, and also to form alloys. The use of copper corrosion inhibitors in acid solutions is usually to minimize the corrosion of copper during the acid cleaning and descaling. The possibility of the copper corrosion prevention has attracted many researchers so until now numerous possible inhibitors have been investigated [1–3]. The inhibiting action of these inhibitors is attributed to their adsorption to the metal/solution interface. It has been observed that adsorption depends mainly on certain physico-chemical prop- erties of the inhibitor group. Like functional groups, aromaticity, electron density at the donor atoms and p-orbital character of donating electrons and also the presence of hetero-atom such as N, O and S, as well as multiple bonds in their molecular structure, are assumed to be active centers of adsorption [4]. Traditionally, scientists identify new corrosion inhibitor mole- cules either by fiddling with existing inhibitors or by testing hun- dreds of compounds in laboratory, which is a laborious, expensive and time-consuming process. Thus, it became necessary to develop new inhibitors which behave like corrosion inhibitors in less time, by in silico approach [5]. As computing power has grown exponen- tially, this approach to research often referred to as in silico (as op- posed to in vitro), has amassed more attention especially in the area of cheminformatics. DFT (density functional theory) methods have become very popular in the last decade due to their accuracy that similar to other methods in less time and with a smaller investment from the computational point of view [6]. In agreement with the DFT, the energy of the fundamental state of polyelectronic systems can be expressed through the total electronic density, and in fact the use of the electronic density instead of the wave function for the calculation of the energy constitutes the fundamental base of DFT [6]. The local reactivity of the molecules was analyzed through an evaluation of the Fukui indices [7]. These are a measurement of the chemical reactivity, as well as an indicative of the reactive re- gions and the nucleophilic and electrophilic behaviour of the mol- ecule. The Fukui function, f ð ~ rÞ, is defined as the derivative of the electronic density, qð ~ rÞ, with respect to the number of electrons, N, at a constant external potential, tð ~ rÞ f ð ~ rÞ¼ @qð ~ rÞ @N   tð ~ rÞ ð1Þ 0010-938X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.corsci.2009.05.038 * Corresponding author. Tel.: +20 227650485; fax: +20 222581237. E-mail address: khaledrice2003@yahoo.com (K.F. Khaled). Corrosion Science 51 (2009) 2098–2106 Contents lists available at ScienceDirect Corrosion Science journal homepage: www.elsevier.com/locate/corsci