1.1 Introduction
Corrosion inhibition, Mild steel, Moringa oleifera, Sulphuric acid Mild steel which is a very important metal in the manufacturing industry is highly vulnerable to corrosion which has resulted in huge economic losses. Corrosion is defined as a destructive phenomenon, chemical or electrochemical, which can attack any metal or alloy through reaction by the surrounding environment and in extreme cases may cause structural failure. Corrosion inhibitors will reduce the rate of either anodic oxidation or cathodic reduction or both. This will give us anodic, cathodic or a mixed type of inhibition. In an attempt to find corrosion inhibitors that are environmentally safe and readily available, there has been a growing trend in the use of biological substrate such as leaves or plant extracts as corrosion inhibitors for metals in acid cleaning processes.
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Research questions, Limitations of the Study and Definition of technical terms.
1.2 Background of Study
Corrosion of materials has continued to receive interest in the technological world as its effects on the structural integrity of materials has been a question for some time. Metallic materials are still the most widely used group of materials particularly in mechanical engineering and the transportation industry. In addition, metals are commonly used in electronics and increasingly also in the construction industry (Buchweishaija, 2009a).
However, the usefulness of metals and alloys is constrained by one common problem known as corrosion. Hence, it has been studied comprehensively since the industrial revolution in the late eighteenth century (Sato, 2012). Corrosion is a naturally occurring phenomenon defined as deterioration of metal surfaces caused by the reaction with the surrounding environmental conditions (Buchweishaija, 2009a).
Corrosion can cause disastrous damage to metal and alloy structures causing economic consequences in terms of repair, replacement, product losses, safety and environmental pollution. Due to these harmful effects, corrosion is an undesirable phenomenon that ought to be prevented. Scientists are persistent in seeking better and more efficient ways of combating the corrosion of metals. There are several ways of preventing corrosion and the rates at which it can propagate with a view of improving the lifetime of metallic and alloy materials (Buchweishaija, 2009a).
Hunag and Chen (2012) highlighted the measures in preventing and control of corrosion as follows: use of resistant metal alloys, cathodic and anodic protection, use of protective coatings (Stack, 2002) and addition of corrosion inhibitors to the corrosion environment (Papavinasam, 2000).
Among the methods of corrosion control, the use of inhibitors is very popular. It is one of the acceptable practices used to reduce and/or prevent corrosion due to the ease of application. Mostly heterocyclic compounds containing oxygen, sulphur and nitrogen as heteroatoms serve as good inhibitors for corrosion (Kumar et al, 2009). To be effective, an inhibitor must also transfer water from the metal surface, interact with anodic and cathodic reaction sites to retard the oxidation and reduction corrosion reaction, and prevent transportation of water and corrosion-active species on the metal surface (Maqsood, 2011). Despite these promising findings about possible corrosion inhibitors, most of these substances are not only expensive but also toxic and non–biodegradable thus causing corrosion problems (Raja and Sethuraman, 2008).
The known hazardous effects of synthetic organic inhibitors, which have been in use (Popova et al., 2007; Li, et. al., 2009) and the need to develop cheap, non-toxic and ecofriendly processes have now made researchers to focus on the use of natural product (Umoren et al., 2008; Umoren & Ebenso, 2008; El-Etre, 2008). Plants have been recognized as naturally occurring compounds, some with rather complex molecular structures and having varying physical, chemical and biological properties (Buchweishaija, 2009a).
The present work therefore, has been designed to evaluate the effect of the leaf extracts of Moringa oleifera on the corrosion inhibition of mild steel in 5M and 1M hydrochloric acid solution with a view to contributing to the search for further beneficial uses of plant extract. Gravimetric and gasometric methods were used for the investigation.
Therefore, in Nigeria where the research was carried out, the activities that was conducted is to know the Inhibitory Effect of Ethanolic Extract of Moringa Oleifera Leaf on the Corrosion of Mild Steel.
1.3 Statement of Problems
Investigation revealed that corrosion is a serious problem in this modern age of technological advancement. This accounts for a lot of economic losses and irreversible structural damage. The cost of corrosion failures annually for any nation is difficult to estimate per annum, but it has been stated that the wastage of material resources by corrosion ranks third after war and disease (Olugbenga et al., 2011).
There are numerous failures and eventual losses in the oil and gas industry have been traced to corrosion processes. Failures resulting from the inability of metals to support designed load requirement because of losses imposed by corrosion effects and this can be combated economically through the use of chemical inhibitors despite the fact that synthetic inhibitors are effective; nonetheless they are associated with problems of toxicity disposal litigation and enormous cost.
1.4 Aim and Objectives of Study
The aim of the study is to examine the Inhibitory Effect of Ethanolic Extract of Moringa Oleifera Leaf on the Corrosion of Mild Steel. In achieving this aim, the following specific objectives were laid out as follows:
- To ascertain the Moringa Oleifera leaf extract inhibitory effect on the corrosion of mild steel and its mechanism of inhibition by gasometric and gravimetric methods; and
- To determine the use of the extract of Moringa oleifera seeds on the corrosion of mild steel in acidic media, using weight loss method of monitoring corrosion.
1.5 Research Questions
The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:
- What is the Moringa Oleifera leaf extract inhibitory effect on the corrosion of mild steel and its mechanism of inhibition by gasometric and gravimetric methods?
- What is the use of the extract of Moringa oleifera seeds on the corrosion of mild steel in acidic media, using weight loss method of monitoring corrosion?
1.6 Significance of Study
This study will be of immense benefit to other researchers who intend to know more on this study and can also be used by non-researchers to build more on their research work. This study contributes to knowledge and could serve as a guide for other study.
1.7 Scope of Study
The scope of the research is focused on the Inhibitory Effect of Ethanolic Extract of Moringa Oleifera Leaf on the Corrosion of Mild Steel.
1.8 Limitations of the Study
During the course of this study, many things militated against its completion, some of which are:
- Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
- Research material: availability of research material is a major setback to the scope of the study.
- Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
- Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet).
1.10 Definition of Terms
Corrosion: It is a destructive phenomenon, chemical or electrochemical, which can attack any metal or alloy through reaction by the surrounding environment and in extreme cases may cause structural failure.
