ISSN 2070-2051, Protection of Metals and Physical Chemistry of Surfaces, 2015, Vol. 51, No. 4, pp. 667–679. © Pleiades Publishing, Ltd., 2015. 667 1 1. INTRODUCTION Steel is the most important engineering and con- struction material in the world. It is used in every aspect of our lives, from automotive manufacture to construction products, from steel toe caps for protec- tive footwear to refrigerator and washing machines and from cargo ships to the finest scalpel for hospital sur- gery. There are several thousand steel grades pub- lished, registered, or standardized worldwide, all of which have different chemical compositions, and spe- cial numbering systems have been developed in several countries to classify the huge number of alloys. Corrosion problems have received a considerable amount of attention because of their attack on materi- als. The use of inhibitors is one of the most practical methods for protection against corrosion. Several works have studied the influence of organic com- pounds containing nitrogen on the corrosion of steel in acidic media [2–10]. Most organic inhibitors act by adsorption on the metal surface [5]. Organic com- pounds containing polar groups including nitrogen, sulfur and oxygen [11–20], and heterocyclic com- pounds with polar functional groups and conjugated double bonds [21–25] have been reported to inhibit corrosion. Thermodynamic model is an important 1 The article is published in the original. tool to study the mechanism of inhibition on the cor- rosion of metal [26–27]. It has been known that effi- cient inhibitors should possess plentiful p-electrons and unshared electron pairs on either nitrogen atoms or sulfur atoms of the inhibitors and by means of trans- ference of electrons, chemical adsorption may occur on the steel surface. Thus, the steel corrosion may be suppressed by the protective film on the steel surface. The corrosion inhibition of mild steel by BMTDT in acidic solutions has been studied using weight loss measurements, electrochemical impedance spectros- copy and potentiodynamic polarization curves. The steel surface was also examined by scanning electron microscopy (SEM) and XRD. FT-IR and UV-Visible spectroscopy were used to identify if there occurs adsorption and to provide new bonding information about the adsorption process. 2. EXPERIMENTAL DETAILS 2.1. Preparation of BMTDT The method used to prepare BMTDT was adopted from the procedure described by [1]. The structure of BMTDT is as shown in Fig. 1. 1 Adsorption and Corrosion Inhibiting Behavior of a New S-Triazine Derivative 1 R. Karthik a , P. Muthukrishnan b , A. Elangovan c , M. M. Sri vidhya c , B. Jeyaprabha d , and P. Prakash c a Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, Taipei, Taiwan 106 (ROC) b Department of Chemistry, Karpagam University, Coimbatore-641021, India c Department of Chemistry, Thiagarajar College, Madurai-625009, India d Department of Civil Engineering, Fatima Michael College of Engineering &Technology, Madurai-625 020, India *e-mail: kmpprakash@gmail.com Received May 07, 2014 Abstarct—The inhibiting effect of 4, 6-bis (5-mercapto-1, 3, 4-thiadiazol-amine) 2-phenylamino-1,3,5-tri- azine BMTDT on the corrosion of mild steel in acidic media has been investigated by weight loss and elec- trochemical methods. Results obtained reveal that this organic compound is a very good inhibitor. BMTDT is able to reduce the corrosion of steel more effectively in 1M HCl than in 1M H 2 SO 4 . The effect of polariza- tion studies show that the adsorption of BMTDT follows physical adsorption in both acids without changing the mechanism of the hydrogen evolution reaction. Surface analyses were also carried out to establish the mechanism of corrosion inhibition of mild steel in acidic media. The adsorption of this inhibitor on the mild steel surface in obeys the Langmuir absorption isotherm in 1M HCl and Frumkin adsorption isotherm in 1M H 2 SO 4 . The corrosion behavior of mild steel with addition of different concentration of BMTDT was studied in the temperature range 308–333 K. The associated activation parameters and adsorption free energies have been determined and discussed. DOI: 10.1134/S2070205115040152 PHYSICOCHEMICAL PROBLEMS OF MATERIALS PROTECTION