Portugaliae Electrochimica Acta 2017, 35(3), 143-158 DOI: 10.4152/pea.201703143 PORTUGALIAE ELECTROCHIMICA ACTA ISSN 1647-1571 Evaluation of Grewa Venusta (Wild Jute Tree) Extract as Corrosion Inhibitor for Mild Steel in Acidic Environment I.Y. Suleiman, a,* Sani A. Salihu, b O.S. Emokpaire, a O.C. Ogheneme c and Lasisi Shuaibu a a Department of Metallurgical Engineering, Waziri Umaru Federal Polytechnic, Birnin Kebbi, Kebbi State, Nigeria b Department of Mechanical Engineering, Faculty of Engineering, Kebbi State University of Science and Technology, Aliero, Kebbi State, Nigeria c Department of Mechanical Engineering, Waziri Umaru Federal Polytechnic, Birnin Kebbi, Kebbi State, Nigeria Received April 21, 2016; accepted December 21, 2016 Abstract The feasibility of using extract of Grewa Venusta (wild jute tree) root as corrosion inhibitor with mild steel was investigated using gravimetric and electrochemical techniques in 1.0 M hydrochloric acid. The inhibitor’s concentration, temperature and time were varied in the range of 0-10% v/v at 2% v/v interval, 30 - 75 o C at 15 o C interval and 1-6 hours at 1 hour interval. Characterizations of the extract were done by quantitative method (AAS) and Gas Chromatography-Mass Spectrometry (GC-MS). Scanning electron microscope (SEM) was used to analyze the surface morphology of the samples. The synergetic effect of the inhibitor was evaluated by addition of halide ions (KBr - , KCl - and KI - ). The results showed that corrosion rate increased with an increase in temperature, and decreased with an increase in inhibitor’s concentration and time; maximum inhibition efficiency was 97.60% and 99.88% in the presence of KI - addition, and was assumed to occur via adsorption of the inhibitor molecules on the metal surface. The extract contains metallic elements such as calcium, magnesium, mono acetate (C5H10O4) and 4H-Pyrazole (C9H10F6N2S) that suppressed the anodic dissolution. The adsorption of the extract molecules on the mild steel surface obeys Langmuir adsorption isotherm. The results showed that the inhibitor acted as a mixed- type inhibitor. Keywords: Adsorption isotherm; characterizations; GC-MS; SEM; halide ions. Introduction Engineering metals are unstable in natural and industrial environments. In the long term, they inevitably revert to stable chemical species akin to the chemically combined forms from which they were extracted. In that sense, metals are only * Corresponding author. E-mail address: onoruoizadanjumas@yahoo.co.uk