INTRODUCTION
1.1 Background of the Study
There has been growing efforts in the exploration of natural products origin as corrosion, inhibiting agents. This has gain prominence due principally to the low cost and eco-friendliness of these products; and this is fast replacing the synthetic and expensive harzadous organic inhibitors (Okafor, Ebenso, and Ekpe, (2010).
The exploration for alternative compounds for controlling corrosion behaviour of metals stems form the industrial, economic and social implication of the corrosion of metal. Remarkably, there have been intensive research works on the corrosion behaviour of mild steel as a result of its high usage in major construction works, and its extensive use in chemical and allied industries for the handling of acid, alkaline and salt solution (Noor and Al-Moubaroki, 2008).
Given the detrimental effect of corrosion, which is a major problem in both construction and other life sustaining ventures in both developing and developed nations of the world, the need to control losses due to corrosion has become paramount. From industrial economic and social points of view, corrosion has been identified to be of great significance. Apart from few corrosion reactions, which arc of practical importance, for example, the corrosion of metallic lead (Fontana, 1987; Sharma et al., 2010), the effects of corrosion are industrially economic and social debilitating. This led J. M. West to write that. “Corrosion kills people, wastes resources and costs money we can ill afford”. This prompted the need to carry out thorough studies to examine the behaviour of steel in various compounds, with a view to ascertaining procedures to reduce corrosion of steel.
The main factor that causes corrosion of metals is the consequence of their temporal existence in a stage of higher energy level due to the absorbed energy during extraction from the ones. This makes them unstable and certain environments enhance their combination and certain environments in their combination chemically with element in their environment to form compounds and return to their natural stable are state with accompanying reduction in the free energy of the system (Ekuma and Idenyi, 2006).
Interestingly, there has been a report from past investigations of the inhibiting potential of natural product origin on the corrosion of metals. The significance of such investigation and findings are not unrelated to the highly economic, industrial and social values of steel. Thus, given the remarkable chemical and biological properties of Azadirachta Indica (commonly known as Neem tree), which is one of the richest sources of secondary metabolities in nature (Ekaidem et al., 2010), the need to investigate its effects on the corrosion behaviour of mild steel in acidic, basic and sea water media become imperative. Importantly, the inclusion of tetraoxosulphate (vi) acid among the media is informed by the fact that teteraoxosulphate(vi) acid is the most difficulty of the common acides to handle from the stand points of corrosion and materials of custruction. It is very corossive to most of the common metals and alloys (Fontana, 1987).
The significance of Azadirachta Indica in chemical analysis has been reinforced by the fact that, to date, more than 300 natural products have been isolated form different parts of the tree with new compounds added to this list every year (Kumer et al., 1996; Okafor and Ebenson. 2000; Morgan and Wilson, 1999). A number of these compounds have been shown to have some health benefits to man, and the leaf extracts have been reported to effectively inhibit the acidic corrosion of metals (Okafor et al., 2008). However, the yield of these compounds as well as their corrosion inhibiting ability vary widely depending on the part of the plant, and its location (Kumar et al., 1996; Okafor et a!: 2008). Morevoer, the corrosion controlling behaviour of other parts of the plant, reported lo compose of numerous organic compound is yet to be reported. Thus, given the increasing interest in environmentally friendly corrosion inhibitors the present study aims at broadening the application of plant extracts in controlling metallic corrosion by investigation the effect of Azadirachta Indica extract on the corrosion behaviour of dead mild steel in acidic, basic and sea water media.
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