Asian Journal of Engineering and Technology (ISSN: 2321 – 2462) Volume 02 – Issue 03, June 2014 Asian Online Journals (www.ajouronline.com ) 235 Corrosion Inhibition of Steel in Petroleum Medium by Ficus Carica Leaves Extract Rana Afif Anaee 1 , Mohammed H. Alzuhairi 2 , Hiba Anwer Abdullah 3 1 University of technology, Materials Engineering Department Baghdad, Iraq Email: Dr.Rana.A.Anaee {at} uotechnology.edu.iq 2 University of technology, Materials Engineering Department Baghdad, Iraq 3 University of technology, Materials Engineering Department Baghdad, Iraq _________________________________________________________________________________ ABSTRACT— This work involves study the corrosion inhibition of steel in petroleum medium using alcoholic extracted of Ficus carica leaves with four concentrations of extracted (1, 3, 5 and 7mL/L) at four temperatures over the range 50 – 80 o C. Inhibition efficiency IE% results show that 3 and 5 mL/L the best concentrations which they gave efficiencies in the range of 71 – 80%. Thermodynamic functions of adsorption processes were calculated from experimental polarization data and the interpretation of the results reveals that Ficus carica extract Ficus carica extract obey Langmuir adsorption isotherm. Polarization curves indicate that Ficus carica extract is a mixed type inhibitor. The small values of the equilibrium constant of the adsorption-desorption process K ads refer to physical adsorption process. The values of free energy of adsorption ΔG o ads , enthalpy ΔH o ads and entropy ΔS o ads were negative indicating the spontaneous and exothermic adsorption process as well as Ficus carica extract retained the metal ions and reducing the dissolution of steel and the activated complex in the rate determining step denotes an association rather than a dissociation step. Keywords— Ficus carica extract; inhibition of steel; Petroleum medium. _________________________________________________________________________________ 1. INTRODUCTION In refineries and petrochemical plants, the amount of water is usually small, but the corrosivity is high and is localized at regions where the aqueous phase contacts the metal. The water may contain dissolved hydrogen sulfide (H 2 S), carbon dioxide (CO 2 ), and chloride ions (Cl‾). Corrosion may occur even when the produced water content is as low as 0.1%, or corrosion activity may not begin until after several years of production. Refineries and petrochemical industries employ a variety of film-forming inhibitors to control wet corrosion. Most of the inhibitors are long-chain nitrogenous organic materials, including amines and amides. Water-soluble and water-soluble-oil-dispersible type inhibitors are continuously injected, or oil-soluble and oil-soluble-water-dispersible type inhibitors (batch inhibitors) are intermittently applied to control corrosion. Film-forming inhibitors anchor to the metal through their polar group. The nonpolar tail protrudes out vertically. The physical adsorption of hydrocarbons (oils) on these nonpolar tails increases film thickness and the effectiveness of the hydrophobic barrier for corrosion inhibition. Because inhibitors are interfacial in nature, they are active at liquid-liquid and/or liquid-gas interfaces and can lead to emulsification. As a result, foaming is sometimes experienced in the presence of inhibitors [1]. A number of organic and synthetic compounds showed a good anticorrosive activity, most of them are highly toxic to both human and environment. These toxic affection have led to the use of natural products as anticorrosion agents which are eco-friendly and harmless. In 1930, plant extracts dried stems, leaves, seeds and other plants were used in H 2 SO 4 acid pickling baths. Animal proteins found in products of meat and milk industries were also used for retarding acid corrosion. Recently, many authors investigated the inhibition by green inhibitors using electrochemical method and FTIR spectra as well as adsorption isotherm calculations. Ambrish et al. studied the inhibition by the fruits extract of Shahjan (Moringaoleifera), Pipali (Piper longum) and Orange (Citrus aurantium) using weight loss, electrochemical impedance spectroscopy, potentiodynamic polarization and linear polarization techniques [2]. Extracts of kola plant and