Contents lists available at ScienceDirect Corrosion Science journal homepage: www.elsevier.com/locate/corsci Synthesis, electrochemical and quantum chemical studies of some prepared surfactants based on azodye and Schiff base as corrosion inhibitors for steel in acid medium M.A. Bedair a, ⁎ , M.M.B. El-Sabbah a , A.S. Fouda b , H.M. Elaryian a a Department of Chemistry, Faculty of Science (Men’s Campus), Al-Azhar University, Nasr City 11884, Cairo, Egypt b Department of Chemistry, Faculty of Science, El-Mansoura University, El-Mansoura 35516, Egypt ARTICLE INFO Keywords: Polarization Electrochemical impedance spectroscopy Density function theory Molecular dynamics ABSTRACT Three nonionic surfactants based on azodye and Schiff base condensed with poly ethylene glycol were prepared. Their inhibition effect towards corrosion of steel in hydrochloric acid was investigated using electrochemical frequency modulation, electrochemical impedance spectroscopy, potentiodynamic polarization, quantum che- mical calculations and molecular dynamic simulation. The data revealed that the prepared surfactants had the ability to inhibit corrosion reaction with good agreement between experimental and computational results. The adsorption of surfactants on the carbon steel surface in 1 M HCl was found to obey Langmuir isotherm. Polarization results showed that these inhibitors act as mixed-type inhibitors. 1. Introduction Corrosion can be defined as the destructive attack of a material (mostly metal) by reaction with its environment [1] and it is a common potential hazard accompanied with oil and gas production and trans- portation facilities [2]. Almost the presence of metals in any aqueous environment can promote corrosion, which can be found under a lot of complex conditions in oil and gas production, processing, and pipeline systems [3]. Since the corrosion reaction cannot be stopped, controlling the corrosion rate (slowing down the rate) may be the most economical solution. Recently, the application of organic compounds as corrosion inhibitors has been widely used to protect the metals from corrosion [4,5]. Generally the most efficient organic inhibitors are heterocyclic compounds containing π-electrons, heteroatoms like N, O, or S and aromatic rings. Interest has increased for the using of Schiff bases as metal corrosion inhibitors in acidic medium due to their greater in- hibition efficiency than that of corresponding amine and aldehydes [6]. Several authors reported Schiff base compounds as effective inhibitors for the corrosion of steel in acid media [7–9]. Also azo dyes have mo- lecular structures that qualified them to be studied as possible corrosion inhibitors in comparison with other organic inhibitors. Some of re- search papers [10–12] proved that the inhibition of the corrosion by organic dyes is mainly a result of the formation of complex compounds between the metal and the nitrogen of the azo group binding at the electrode surface. It is also well known that surfactants molecules have a great ability for association with each other at interfaces and in so- lution forming aggregates. The employment of surfactants, as corrosion inhibitors is most interesting due to a lot of advantages as its low cost, practical use and safe effect [13–15]. Adsorption of surfactant mole- cules on metal surface can have a great effect on electrochemistry in fluids. The use of quantum chemical calculations is very important in es- tablishing the correlation between molecular structure and chemical reactivity and selectivity of corrosion inhibition process. The effec- tiveness of a compound in a chemical reaction is related to its spatial and electronic molecular structures [16]. Moreover, a theoretical study permits the pre-selection of organic compounds with the necessary structural characteristics to undergo chemical reaction. The present work is aimed to prepare three nonionic surfactants based on azodye and Schiff base and study their inhibition efficiency as corrosion inhibitors of steel in 1.0 M HCl on the basis of electrochemical frequency modulation, potentiodynamic polarization and electro- chemical impedance spectroscopy measurements. It also aimed to study the effect of the structural parameters of inhibitors on inhibition effi- ciency and study their adsorption mechanism on metal surface and so correlate the experimental results with the quantum chemical para- meters of the prepared surfactants. http://dx.doi.org/10.1016/j.corsci.2017.09.016 Received 21 April 2017; Received in revised form 1 September 2017; Accepted 13 September 2017 ⁎ Corresponding author. Tel.: +20 1014134321. E-mail addresses: m_bedier@yahoo.com, m_bedier@hotmail.com (M.A. Bedair). Corrosion Science xxx (xxxx) xxx–xxx 0010-938X/ © 2017 Elsevier Ltd. All rights reserved. Please cite this article as: Bedair, M.A., Corrosion Science (2017), http://dx.doi.org/10.1016/j.corsci.2017.09.016