www.derpharmachemica.com t Available online a Scholars Research Library Der Pharma Chemica, 2014, 6(4):181-186 (http://derpharmachemica.com/archive.html) ISSN 0975-413X CODEN (USA): PCHHAX 181 www.scholarsresearchlibrary.com Corrosion inhibition of cold rolled steel in 0.5M H 2 SO 4 by potassium iodide Tarik Attar 1,2* , Lahcène Larabi 1 and Yahia Harek 1 1 Laboratory of Analytical Chemistry and Electrochemistry, Department of Chemistry, Faculty of Sciences, University Abou-BekrBelkaïd, Tlemcen, Algeria 2 University Center of Naama, Algeria _____________________________________________________________________________________________ ABSTRACT The inhibition of the corrosion of cold rolled steel in 0.5 M H 2 SO 4 solution by potassium iodide has been investigated by using weight loss. The results show that KI as a good inhibitor, and its maximum inhibition efficiency is higher than 90% even at low concentration.The temperature effect on the corrosion behaviour of the cold rolled steel with and without the inhibitor was studied in the temperature range (293-323K). Some thermodynamic functions of dissolution and adsorption processes were also determined. The adsorption of the inhibitor on the cold rolled steel surface is in agreement with Langmuir adsorption isotherm. Keywords: Adsorption isotherm, corrosion inhibition, potassium iodide, cold rolled steel, weight loss. _____________________________________________________________________________________________ INTRODUCTION Corrosion can cause disastrous damage to metal and alloy structures causing economic consequences in terms of repair, replacement, product losses, safety, and environmental pollution [1]. The environmental consequence of corrosion is enormous, and its inhibition has been deeply investigated [2]. It has been found that one of the best methods of protecting metals against corrosion involves the use of inhibitors which are substances that slow down the rate of corrosion [3,4]. The corrosion inhibitor is widely used and acts as one of the most economical and effective ways [5-7]. The use of inorganic inhibitors as an alternative to organic compounds is based on the possibility of degradation of organic compounds with time and temperature [8,9]. The inhibition efficiency depends on the parameters of the corrosive system [pH, temperature, duration, metal composition, etc.] and on the nature of the inhibitor [10]. Sulfuric acid is one of the most aggressive acids for iron and its alloys and is often used during cleaning, pickling, descaling, acidizing, and so forth [11, 12]. The adsorption of the inhibitors can be described by two main types of interaction: physical adsorption and chemisorptions [13, 14]. The adsorption is also influenced by the structure and the charge of the metal surface, and the type of testing electrolyte [15-17]. The present work was designed to study the corrosion inhibition of cold rolled steel in 0.5 M H 2 SO 4 solution using potassium iodide as corrosion inhibitors. Weight loss measurements were used to know the effect of time, temperature and concentration of KI on the inhibition properties. Adsorption and activation parameters were calculated to establish the kinetic behaviour of the inhibition process. MATERIALS AND METHODS 2.1. Materials Tests were performed on a cold rolled steel of the following composition (wt.%): 0.10% C, 0.5% Mn, 0.025% P, 0.025% S, and bal. Fe. The test pieces were polished with emery paper(grade 320–500–800-1200). The specimens were weighed by electronic digital analytical balancewith five decimal accuracy before and after exposure.