CHEMISTRY & CHEMICAL TECHNOLOGY Chem. Chem. Technol., 2018, Chemical Vol. 12, No. 3, pp. 405–409 Technology AQUEOUS EXTRACTS OF OPUNTIA FICUS-INDICA AS GREEN CORROSION INHIBITOR OF A283C CARBON STEEL IN 1N SULFURIC ACID SOLUTION Ferial Krid 1, * , Emna Zouaoui 1 , Mohamed Salah Medjram 1 https://doi.org/10.23939/chcht12.03.405 Abstract. 1 The effect of concentration and temperature were studied to measure the inhibiting capacity of extract Opuntia ficus-indica by using polarization and electrochemical impedance spectroscopy. The adsorption of the studied extract on carbon steel surface obeys the Langmuir adsorption isotherm. Keywords: corrosion inhibition, polarization, adsorption, Nyquist diagram, green inhibitor. 1. Introduction Carbon steel is one of the most important alloys, which is frequently used in a wide range of industrial applications. Corrosion problems arise due to the inter- ction of carbon steel with aqueous solutions, particularly during the pickling process, in which the alloy is brought into contact with highly concentrated acids [1, 2]. The use of inhibitors has been identified as a convenient and cheap means of combating steel corrosion. The inhibitors influence the kinetics of the electrochemical reactions which constitute the corrosion process, either by reducing the rate of metal dissolution in the corrosive medium and/or the cathodic reduction reaction. Corrosion inhibitors adsorb on the metal surface and thereby change the structure of electrical double layer [3]. Most of the efficient inhibitors used in industry are organic compounds that contain oxygen, sulfur, nitrogen atoms, π-bonds, and/or aromatic ring(s) in their molecules [4]. These electronegative atoms and functional groups have been reported to facilitate the adsorption of the inhibitors on metal surface [3, 5, 6]. This paper reports the effect of Opuntia ficus- indica extract as corrosion inhibitor for carbon steel in sulfuric acid solution. 1 Laboratoire de Recherche de Génie Chimique et Environnement, LGCE, Faculté de Technologie, Université du 20 Août 1955-Skikda, Algérie * kridoudferial@hotmail.fr Krid F., Zouaoui E., Medjram S. M., 2018 2. Experimental 2.1. Test Solutions Working electrode is prepared from the carbon steel A283C. The chemical composition of the steel A283C is (wt %): carbon 0.18, S 0.05, P 0.06, Cu 0.20, the rest is iron [7]. The exposed area was mechanically abraded with 400, 500, 600, 1200 grade emery paper, washed with double distilled water, degreased with acetone and finally dried before each experiment. A stock solution of 1N sulfuric acid with M = 98.8 g/mol and density of 1.83 g/cm 3 was prepared from the concentrated acid solution (96 %), that was purchased from Merck and was used as received. 2.2 Inhibitor Preparation The extract of Opuntia ficus-indica (OFI) is obtained from the fig cladodes using vacuum filtration. Then we left the extract at the temperature of 277 K in the absence of light until the preparation of working solution. 2.3. Electrochemical Measurements The electrochemical measurements were carried out using a Volta lab PGZ 301 potentiostate and controlled by Tacussel corrosion analysis software model (Voltamaster 4 and EC-labdemo). The corrosion cell was a conventional three-electrode electrolysis cylindrical Pyrex glass cell. The working electrode had the form of a disc which was cut from a steel sheet. The surface area exposed to the corrosive solution was 1 cm 2 . A saturated calomel electrode SCE and a platinum electrode were used as reference and auxiliary electrodes, respectively. Electrochemical impedance spectroscopy (EIS) measurements were carried out after obtaining steady-state condition at the frequency ranged from 50 kHz to 100 mHz with a sine wave voltage (10 mV) peak to peak. The EIS data were given in Nyquist representation.