Concentration, Temperature and Kinetic Studies of Kola nitida Leave Extracts in Corrosion Prevention Lawrence Adebayo Oluwafemi 1* , Grace Ajayi Morenike 1 and Ayorinde Daodu Kayode 2 1 Department of Chemistry, College of Education, Ikere. Ekiti State, Nigeria. 2 Department of Biology, College of Education, Ikere. Ekiti State, Nigeria. *E-mail address: femtay41@yahoo.co.uk Keywords: Inhibition; Kola nitida; corrosion; isotherm; kinetics; Adsorption. Abstract. The inhibition efficiency and adsorption mechanism of kola nitida leaves extracts on mild steel protection in 2M HCl at various concentration, exposure time and working temperature was studied using Weight loss measurement. The results showed that ethanol extract of Kola nitida leaves is a good inhibitor for the corrosion of mild steel in acidic medium. The corrosion rate of mild steel decreases with increase in the concentration of the extract. The inhibition efficiency increases progressively as the concentration of the extract increases but decreases with rise in temperature and exposure time. The highest inhibition efficiency observed in the presence of the extract was 88.51%. The kinetics of the reaction in the presence of the extracts revealed that it follows a first-order reaction and the half-life increases as the concentration of the extract increases. Adsorption studies revealed that Langmuir adsorption isotherm is the best adsorption model applicable to the adsorption of the extract on mild steel surface. 1. Introduction Corrosion can be explained as the influence of the surrounding environments on metals causing a change in its physical and chemical properties. This phenomenon causes a serious economic loss due to the replacement of equipment, structure and plant repairing shutdown [1]. The usefulness of Mild steel in industries cannot be overemphasized; this has made researchers to search for various types of inhibitors to protect the mild steel from corrosion when exposed to various environmental conditions. In acidic condition, the use of inhibitors is the best way of preventing mild steel from corrosion [2–4]. The inhibitive reactivity of an inhibitor is fundamentally affected by the molecular structure of the inhibiting molecules [5]. Majority of the well-known corrosion inhibitors are organic compounds that have nitrogen, sulphur, oxygen, and phosphorus in their functional groups [6–9]. The system of these compounds has been suggested by some researcher to be by adsorption of a lone pairs of electron, of the organic functional groups on the metal surfaces [10]. Moreover, most of these functional groups are present in most of the inhibitors which has prompted researchers to identify cheap drugs, which are environmentally safe as corrosion inhibitors [11, 12]. Kola nitida plant is native to Sierra Leone, Liberia, Ivory Coast, Ghana and Nigeria. It is an evergreen tree growing to a height of 12 to 20 meters. The leaves have stalks and are alternate, oblong, glabrous, leathery and tough, with untoothed wavy margins and up to 33 cm (13 in). The leaves, twigs, bark, flowers and nuts serve many important purposes. The nuts are used industries for the production of drugs, soft drinks, wines, candies, and beverages such as Coca-Cola and Pepsi-Cola [13]. It has many pharmacological properties and contains some active principles: it prevents sleep, thirst, and hunger and acts as an antidepressant [14]. The cola nuts are source of antioxidants and contain a wide array of complex secondary plant metabolites such as theobromine, d-catechin, L- epicatechin, and kolatin [15]. The leaves, twigs, bark and flowers are also used in traditional medicine for maintenance of health as well as in the prevention, diagnosis, improvement or treatment of physical and mental illness [16]. International Journal of Engineering and Technologies Submitted: 2019-01-13 ISSN: 2297-623X, Vol. 17, pp 33-42 Revised: 2019-04-05 doi:10.18052/www.scipress.com/IJET.17.33 Accepted: 2019-04-05 2019 SciPress Ltd., Switzerland Online: 2019-05-16 SciPress applies the CC-BY 4.0 license to works we publish: https://creativecommons.org/licenses/by/4.0/