1Ezeugo, J. N. O., 2Onukwuli, O. D., 1Nwanekezie, M. N, and 3Umeonyiagu, I. E.
1Chemical Engineering Department, Chukwuemea Odumegwu Ojukwu University, Uli, Anambra State
2Chemical Engineering Department, Nnamdi Azikwe University Awka, Anambra State
3Civil Engineering Department, Chukwuemea Odumegwu Ojukwu University, Uli, Anambra State
The inhibitive action of the ethanol extract of oil from Picralima nitida seeds, towards acid corrosion of zinc, is tested using weight loss, and thermometry methods. It was found that the extract acts as a good corrosion inhibitor for zinc corrosion in 0.1M HCl solution. The inhibitory action of the extract was discussed in view of Langmuir adsorption isotherm. It was revealed that the adsorption of the extract on zinc surface is governed by spontaneous process. The inhibition efficiency (IE) increases in line with corresponding increase in extract concentration. The temperature effect of the corrosion inhibition on the IE was studied. Revelation from the studies indicated that the presence of extract increases the activation energy of the corrosion reaction. Furthermore, from the calculated thermodynamic parameters, it was observed that Picralima nitida extract provides good protection to zinc against pitting corrosion in chloride ion containing solutions.
Keywords: Zinc, Corrosion, Picralima Nitida Seed, Inhibitor.
Corrosion is an electrochemical process that gradually returns metals such as zinc to its natural state in the environment. In other words, corrosion can be said to be destruction of material resulting from exposure and interaction with the environment. It is a major problem that requires immediate confrontation for safety, environment, and economic reasons. This ugly menace was also identified by Thompson et al, 2007. Zinc consists of wide variety of alloys used since ancient times. Building industry frequently uses zinc alloys in roofing of house and other construction work because of its ductility and malleability. Therefore, zinc alloys are widely used in the production of many components and die-casting fittings in automobile and manufacturing and the mechanical industry, thanks to its super or super plasticity.
Zinc in spite of the so called super plasticity is not spared by corrosion, especially after prolonged period of exposure in corrosive environment, such as HCl. For this reasons a lot of efforts have been made using corrosion preventive practices and the use of green corrosion inhibitors is one of them (Anuradha et al, 2007). The use of green inhibitors for the control of corrosion of zinc and alloys which are in contact with aggressive environment is an accepted and growing practice as confirmed by (Valdez et al, 2003; Taylor 2007; Khaled et al, 2008; Bothi et al, 2008). Large numbers of organic compounds are being studied to investigate their corrosion inhibition potential. Relation of these studies shows that organic compounds are not only expensive, but also toxic to living beings.
Plant extracts and organic species have therefore become important as an environmentally acceptable, readily available, and renewable source for a wide range of inhibitors (Rajendran et al 2004; Mesbah et al, 2007; Okafor et al, 2007). They are the rich sources of ingredients which have very high inhibition efficiency and hence termed “Green Inhibitors”( Lebrini et al, 2008; Radijcic et al, 2008; Refeay et al, 2008). Oguzie et al 2006, experimentally suggested that green corrosion inhibitors are biodegradable and do not contain heavy metals or other toxic compounds. The successful use of naturally occurring substances to inhibit the corrosion of the metals in acidic and alkaline environment have been reported by some research groups (Sharma et al 2009; Mabrouk et al, 2011; Eddy et al, 2012). Research efforts to find naturally organic substances or biodegradable organic materials to be used as effective corrosion inhibitors of a wide number of metals has been one of the key areas in this research work.
The aim of this study is to investigate the inhibitive properties of Picralima nitida seed extract onto zinc in hydrochloric acid media. Several studies have already been carried out and have remained focused on the PNS extract for their various pharmacological activities. Firstly, Picralima nitida plant is a tree that can reach a height of 35 meters, but is usually less. It is a commonly used herbal remedy in West Africa. All parts of the plant are bitter throughout its distribution area. The seeds, barks, roots and leaves have a reputation as a febrifuge and remedy for malaria as well as also being extensively used for pain relief and treatment of chest and stomach problems, pneumonia and intestinal worms (Nagam et al, 2012). A decoction of the seed is taken as a treatment for measles.The Picralima nitida seed contains many organic compounds, such as phenolics, terpenoids, and tannins as their major phytocompounds and also saponins, flavonoids and alkaloids in moderate amount to scavenge free radicals induce detoxification.
Presently, to the best of our knowledge no reported work in area of corrosion control has been carried out on the corrosion inhibitive properties of the Picralima nitida seeds extract. The study was carried out using weight loss (Gravimetric) method and FTIR analysis. The effect of temperature and concentration on the rate of corrosion were also studied, while isotherm parameters were calculated and listed on table.