PRODUCTION OF GREEN INHIBITOR FOR MILD STEEL IN ACIDIC MEDIA USING BIOWASTE

Background of the study The corrosion of engineering materials is known to lower performance efficiency and lead to reduced service life, in severe cases it could serve as a precursor to catastrophic failures which result in grave losses (Alaneme, 2011). A lot of technological efforts have been put into developing strategies for mitigating corrosion through materials selection, changes in design philosophies, and the adoption of varied prevention techniques. Synthetic inorganic compounds used as inhibitors for corrosion prevention and control have been reported to have excellent performance. However, their toxic effects do not only affect living organisms but also poison the environment, hence the need for green/eco-friendly corrosion inhibitors (Al-Sehaibani, 2000). Therefore, effort towards identifying potential eco-friendly and less expensive inhibitors remains the subject of focus in current research efforts in corrosion science and engineering. Corrosion inhibitors are chemical substances that, when added to a corrosive system in optimum concentration, decrease the corrosion rate. The chemical substance modifies electrochemical reactions by their action from the solution side of the metal/solution interface; and the increase in corrosion resistance can be measured by various parameters (Eddy, 2009). To be effective, an inhibitor must be able to interact with anodic and cathodic reaction sites to respectively retard the oxidation and reduction corrosion reactions, and prevent transportation of water and active corrosion species on the metal surface (Maqsood et al., 2011). The use of inhibitors has been well-documented as an effective method of protecting metallic materials from corrosion (Tosun, 2006). Many industrial processes have put to use inorganic inhibitors for corrosion protection but as a result of cost and toxicity, attention is currently shifted towards the use of eco-friendlier inhibitors (Orubite., 2004). Organic substances (plant based) containing functional groups with oxygen, nitrogen, and /or sulphur atoms in a conjugate system have been reported to exhibit good inhibiting properties (El-Etre, 2006). This has made plant extracts an important choice for environmentally friendly, readily available, and renewable sources for a wide range of inhibitors referred to as green inhibitors (Raja 2010). Some of the advantages of green inhibitors are low cost of processing, biodegradability, and absence of heavy metals or other toxic compounds which pose great hazards to the environment (Ebenso et al., 2008). Natural products of plant origin containing different organic compounds (e.g alkaloids, tannins, saponins, steroids, terpenoids, flavonoids, phenols, oxalates, glycosides, pigments, organic, and amino acids) are known to have inhibitive action (Ebenso and Ekpe, 1994). They are generally eco-friendly, cheap, and easily available and have heteroatoms in their aromatic or long carbon chain (Abiola et al.,2007). Research by Obot et al. (2009) reported successful uses of extruded gum extract from natural plants as corrosion inhibitors of aluminum in alkaline media. Avwiri and Igho, (2003) reported that organic compounds having heteroatom O, N, and S are found to have basicity and electron density thus assisting in corrosion inhibitors. O, N, and S are the active centers for the adsorption on the metal surface. When an H atom attached to the C in the hydrocarbon ring is replaced by a substituent group (-NH2, -NO2, -CHO, or COOH) it improves inhibition. The electron density in the metal at the point of attachment changes thereby resulting in the retardation of the anodic and cathodic reactions. Electrons are consumed at the cathode and furnished at the anode, thus, corrosion is retarded (Amitha and Bharathi, 2011). Several authors have used different extracts of leaves, stems, roots, fruits, flowers, and seeds as inhibitors for aluminium and its alloys in different media (Babatunde et al.,2012; Wan et al., 2012); (Ihebrodike et al., 2011; Ajanaku et al.,2012; Rajkiran et al.,2010; Rajendran et al.,2009; Benali et al., 2012). Due to the economic importance of aluminium and its alloys, its protection against corrosion has attracted much attention (Yingchao et al., 2011; Zhenhua et al., 2011). Corrosion in metals is a chemical or electrochemical process that involves the reaction of a metal with its environment, resulting in the destruction of the metal and its mechanical properties (Callister, 2010; Baboian, 2005). This process ordinarily begins at the surface. Corrosion in steel is known as rusting due to iron being its major constituent. In industrialized nations, corrosion is known to cause significant economic problems with approximately 5% of the country’s budget going into maintenance, repairs, or replacement of infrastructure or products affected by corrosion reactions (Callister, 2010). The presence of four key elements is essential for the corrosion reaction to occur. The elements include a cathode, an anode, a conductive material and an electrolyte. In the case of steel corroding as a result of an acid attack, the anode and cathode are found in the steel, the steel itself serves as the conductive material and the acid serves as the electrolyte. The corrosion process involves two main reactions: 1. An anodic (oxidation) reaction which occurs at the anode. 2. A cathodic (reduction) reaction which occurs at the cathode. Metals in general are used in most constructional applications due to their relatively high strength compared to other material classes. They are usually alloyed to improve certain qualities such as toughness, ductility and corrosion resistance. There are two main classes of metal alloys: Ferrous Alloys and Non-ferrous Alloys (Callister, 2010). 1.2 Statement of the Problem Corrosion has adverse environmental consequences, the majority of the compounds used as corrosion inhibitors are toxic to man and the environment. Thus, Inorganic inhibitors such as chromates are highly toxic; some of them have been reported to be carcinogenic. In view of these observations, there exists a need for the development of eco-friendly, cheap, and readily available renewable corrosion inhibitors. 1.3 Aim and Objectives of the Study 1.3.1 Aim The aim of this research is to investigate the possibility of using bitter kola pod (Garcinia Kola) extract as corrosion inhibitors for Mild steel in the select aggressive environment. To achieve this aim, the following specific objectives were pursued. 1.3.2 Specific Objectives The specific objectives of this study are i) To determine the physicochemical and phytochemical properties of plant extract ii) Preparation of the biological inhibitor using biowaste (Garcinia kola) iii) To carry out corrosion test on the mild steel using weight loss technique by varying The concentration of the inhibitor. iv) To determine the corrosion efficiency of the green inhibitor v) To Investigate the mechanism of corrosion inhibition using Garcinia kola pod extract. This involves the characterization of active compounds adsorbed onto metal surfaces via FTIR. 1.4 Scope of the Study This study will be limited to the investigation of the inhibition effectiveness of extract from Garcinia kola pod in 1M of HCl solution on mild steel using the weight loss method in the presence of each inhibitor at various concentrations. Hence, the scope of this study includes the following: i) Laboratory-designed experimentation for weight loss study of mild steel specimens in hydrochloric acid media in the presence of varying concentrations. ii) Fourier transform infrared spectroscopy (FTIR) analysis of the extracts. iii) Corrosion analyses using the gravimetric technique. 1.5 Justification of the Study This study will be based on the premise that corrosion inhibition and protection of metals/alloys play a very important role in the chemical, manufacturing, construction, food, beverages, and oil and gas industry in Nigeria. The study will provide the basis for the utilization of Garcinia kola pod extract as an alternative to highly expensive and non-environmentally friendly corrosion inhibitors of mild steel, such as chromium oxide, polyethylene chloride, etc. Most corrosion inhibitors are not just only synthetic and hazardous in nature but also very expensive. Therefore, it is desirable to source cheaper and environmentally safe inhibitors. The development of alternative corrosion inhibitors that are effective and environmentally friendly substances is necessary in today’s world of climate change. As a result of the increasing ecological awareness and the strict environmental regulations limiting the use of toxic substances as corrosion inhibitors, the importance of this study which involves the development of ‘green’ alternatives to mitigating corrosion cannot be overemphasized.