ABSTRACT
The deterioration of metal surface especially iron due to oxidation or other chemical reactions results in the formation of rust. Rust consists of hydrated iron (III) oxide (Fe2.O3. nH2O), which is generated when iron, is in contact with both moisture and oxygen. The formation of rust causes enormous loss to the economy of the country and compromises the integrity of the structures. Therefore, there is a need to develop solutions which can remove rust from metallic surfaces. The objective of this study was to prepare some rust removal formulations using selected reagents and to evaluate their rust removal properties. The formulations were prepared using compositions of different low molecular weight organic acids (LMWOs) at room temperature. Formulation one contained citric acid, sulphamic acid, and iron sulphate whereas, formulation two was composed of acetic acid, sulphamic acid, and iron sulphate. Formulation three contained hydroxyacetic acid, sulphamic acid, and iron sulphate. Formulation four was composed of oxalic acid, sulphamic acid, and iron sulphate, whereas formulation five was composed of extracted citric acid, sulphamic acid, and iron sulphate. The study established that the % rust removal for formulation one was in the range of 35- 63%, 71-85%, and 77-92%, after 30 minutes, 60 minutes, and 90 minutes respectively. The percentage of the rust removed by formulation two ranged from 38-60%, 60-87% and 73- 79%, after 30 minutes, 60 minutes and 90 minutes, respectively. The percentage rust removal by formulation three was 62-77%, 78-81% and 55-88% while for formulation four the range was 14-29%, 32-63% and 11-21% and for formulation five the range was 0.3-66%, 0-1.6 % and 0.7-1.9 % after 30, 60, and 90 minutes respectively. The study showed that at room temperature after 30 minutes the percentage rust removal was in the following order: Formulation 3 with a mean of 81%, followed by formulation 1 at 47.6%, then formulation 2 at 42.4%. This was followed by formulation 5 and 4 at 22.7% and 22.5% respectively.FTIR analysis was conducted on the composition of all formulations before and after the reaction with the rusted metal surface to establish the functional groups involved in the process of rusting. The FTIR study showed that the peaks produced by formulations had some peaks disappear, others shifting from original positions. Based on the study, the prepared formulations indicated the ability to remove rust from the rusted nails of this project. The amount of removed rust depended on the nature of the formulation. Formulation one gave the optimum rust removal property at room temperature.
TABLES OF CONTENTS
ABSTRACT iii
ACKNOWLEDGEMENT iv
LIST OF TABLES ix
LIST OF FIGURES xi
LIST OF ABBREVIATIONS AND ACRONYMS xiii
CHAPTER ONE
INTRODUCTION
1.1 Background Information 1
1.1.1 Rust remover 2
1.2 Statement of the problem 3
1.3 Objectives 3
1.3.1 General objective 3
1.3.2 Specific objectives 3
1.4 Justification and significance of the study 4
CHAPTER TWO
LITERATURE REVIEW
2.1 Chemistry of iron 5
2.1.1 Forms of Iron 5
2.2 Isolation of Iron 6
2.3 Classification of steel 9
2.3.1 Mild steel 9
2.3.2 Medium carbon steel 9
2.3.3 High carbon steel 9
2.4 Corrosion versus rusting of metals 11
2.4.1 Rusting and corrosion of metals in water 11
2.4.2 Rusting and corrosion electrochemistry 12
2.4.3 Anodic process 12
2.5 Types of rust 13
2.5.1 Red rust 13
2.5.2 Black rust 14
2.5.3 Yellow rust 14
2.5.4 Brown rust 15
2.5.5 White rust 16
2.5.6 Blue rust 16
2.6 Stages of rusting 17
2.6.1 Stage 1(surface rust stage) 17
2.6.2 Stage 2 (etched stage) 17
2.6.3 Stage 3 (penetration stage) 17
2.7 Prevention of rust 17
2.7.1 Organic coating 17
2.7.2 Inorganic coatings 19
3.7.3 Metallic coatings 20
2.8 Rust removal formulations 22
2.8.1 Use of mineral acidsto descale 22
2.8.2 Complexing agents for rust removal 23
2.8.3 Oxidizing agents for rust removal 23
2.8.4 Use of organic acids for rust removal 23
2.9 Additives used in enhancing the efficiency of organic acid for rust removers 31
2.9.1 Use of magnesium aluminium silicate 32
2.9.2 Xanthium gum 32
2.9.3 Ammonium chloride 32
2.9.4 Aluminium Chloride 33
2.9.5 Grapthol Green 33
2.10 Activating Agents 33
2.10.1 Ferrous sulphate 34
CHAPTER THREE
MATERIALS AND METHODS
3.1 Preparation of rust removal solutions 35
3.1.1 Preparation of rust remover solutions 35
3.2 Formation of rust in different solutions 39
3.3 The efficiency of rust removal by the prepared solutions 39
3.3.1 Rust removal by the solutions 39
3.4 Qualitative analysis 40
CHAPTER FOUR
RESULTS AND DISCUSSIONS
4.1 Rust removal by formulation 1 41
4.2 Rust removal by formulation 2 43
4.3 Rust removal by formulation 3 44
4.4 Rust removal by formulation 4 46
4.5 Rust removal by formulation 5 48
4.6 Qualitative analysis 53
CHAPTER FIVE
CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions 66
5.2 Recommendations 67
REFERENCES 68
LIST OF TABLES
Table 2.1: Type of coatings, compositions and their applications 22
Table 2.2: Properties of oxalic acid 24
Table 2.3: Properties of sulphamic acid 25
Table 2.4: Properties of hydroxyacetic acid 26
Table 2.5: Properties of citric acid 28
Table 2.6: Properties of acetic acid 30
Table 3.1: Amounts of the reagents used the in the preparation rust remover solutions 38
Table 4.1: Percentage of rust removed by formulation 1 at room temperature 41
Table 4.2: Percentage of rust removed by formulation 1 at 40 0C 42
Table 4.3: Percentage of rust removed by formulation 2 at room temperature 43
Table 4.4: Percentage of rust removed by formulation 2 at 40 OC 44
Table 4.5: Percentage of rust removed by formulation 3 at room temperature 45
Table 4.6: Percentage of rust removed by formulation 3 at 40 0C 46
Table 4.7: Percentage of rust removed by formulation 4 at room temperature 47
Table 4.8: Percentage of rust removed by formulation 4 at 40 0C 43
Table 4.9: Percentage of rust removed by formulation 5 at room temperature 49
Table 4.10: Percentage of rust removed by formulation 5 at 40 OC 50
Table 4.11: Percentage of rust removed by market standard (Holt) formulation at room temperature 51
Table 4.12: Percentage of rust removed by market standard (Holts) formulation at 40 oC 52
Table 4.13: Percentage of rust removed by South Africa anti-rust formulation at room temperature 53
LIST OF FIGURES
Figure 1.1: Rusted material 1
Figure 2.1: Blast furnace operation 6
Figure 2.2: Open Hearth Furnace 7
Figure 2.3: Bessemer Process 8
Figure 2.4: Red Rust 13
Figure 2.5: Black Rust 14
Figure 2.6: Yellow Rust 15
Figure 2.7: Brown Rust 16
Figure 2.8: White Rust 16
Figure 2.9: Blue Rust 16
Figure 2.10: Structure of polymethacrylate repeating unit 18
Figure 2.11: polydimethylsiloxane (PDMS) 19
Figure 2.12: Silane monomer 19
Figure 2.13: polysilane polymer 20
Figure 2.14: Structure of oxalic acid 24
Figure 2.15: Structure of sulphamic acid 25
Figure 2.16: Structure of hydroxyacetic acid 26
Figure 2.17: Structure of citric acid 28
Figure 2.18: Structure of acetic acid 29
Figure 2.19: Structure of aluminium chloride 33
Figure 2.20: Structure of aqua complex 34
Figure 3.1: Laboratory preparation of citric acid 37
Figure 4.1: FTIR data for formulation 1 before reaction 54
Figure 4.2: FTIR data for formulation 1 after the reaction 55
Figure 4.3: FTIR data for formulation 2 before the reaction 56
Figure 4.4: FTIR data for formulation 2 after the reaction 57
Figure 4.5: FTIR data for formulation 3 before the reaction 58
Figure 4.6: FTIR data for formulation 3 after the reaction 59
Figure 4.7: FTIR data for formulation 4 before the reaction 60
Figure 4.8: FTIR data for formulation 4 after the reaction 61
Figure 4.9: FTIR data for formulation 5 before the reaction 62
Figure 4.10: FTIR data for formulation 5 after the reaction 63
Figure 4.11: Holt anti rust (Unipro Limited) 64
Figure 4.12: Holt anti-Rust FTIR after reaction 64
Figure 4.13: South Africa anti-Rust FTIR after reaction 65
LIST OF ABBREVIATIONS AND ACRONYMS
EDTA Ethylenediamine tetraacetic acid
FTIR Fourier transform infrared spectrometer
MAS Magnesium aluminium silicate
PDMS Polydimethylsiloxane
ppm Parts per million
Rev/min Revolutions per minute
Sa Anodic surface
Sc Cathodic surface
V Volt
v/v Volume per volume
W1 Intial sample weight
W2 Stained weight
W3 Weight after rust removal
CHAPTER ONE
INTRODUCTION
1.1 Background Information
The coating that occurs on iron surfaces is usually referred to as rust. The presence of rust (hydrated iron (III) oxide (Fe2O3.H2O)) on the steel or iron surface can cause damage to the surface and when this happens, more of the metal surface will be exposed to oxygen, moisture and oxidation continues to occur. Rust is a corrosion product (reddish-brown) of iron consisting of several components (Evans and Taylor, 1972). Iron has certainly been the most applied and must have been among the first where serious corrosion problems were encountered though it was not the first metal utilized by man (Morgan, 1988). Rust exists in different combinations, as a chemical compound mainly of iron and oxygen to form reddish- orange color. Rust formation speed can be increased if an alloy (iron) is exposed in corrosive environments (Yari et al., 2017). Figure 1.1 shows a corroded industrial pipe.
Figure 1.1: Rusted material (Evans and Taylor, 1972)
Rust has devastating impacts on alloys (iron-based), which eventually can thin them until they are unsuitable for their original intended use. Excessive rusting leads to the bursting of pipelines and collapsing of structures. Rust also compromises the iron components' aesthetic appeal (Beacon, 2002). With the exception of Gold, other elements have oxidizing potential that is less positive that of oxygen gas. The half reduction potential for iron is as shown by the following half equations.
Fe2+(aq) + 2e-→Fe (s) E0=-0.44V(1.1)
Fe3+(aq) + 3e-→ Fe (s) E0=0.036V (1.2)
O2 (g) + 2H2O (l) + 4e-→ 4OH-(aq) E0=+0.40V (1.3)
Rust generates an oxide due to oxidation due to a difference in electrical potential in the electrolyte between the two materials. This difference creates an anode-cathode system, with the anode readily giving up electrons, whereas cathode electrode accepts electrons (antiqueengines.com, 2018). The oxygen atoms, either from an electrolyte or from the atmosphere, are transferred through the electrolyte during the rusting process. The atoms (oxygen) then react with the iron to form iron oxide, indicating that rusting can be reduced if the electrolyte is removed from the reaction, as shown by reactions 1.4 and 1.5.
2Fe (s) + O2 (g) +H2O (l) +4e-→ 2Fe2+ (aq) +4e- + 4OH- (1.4)
(𝐎𝟐, 𝐇𝟐𝐎)
2Fe (OH) 2(aq)→−−−−−−→ Fe2O3.nH2O (s) (1.5)
Corrosion is a natural process thus there is a tendency of iron and steel to combine at the lowest energy level with oxygen and water vapor, which leads to formation of hydrated iron oxide which produces an insoluble reddish brown solution of Fe(OH)3.
1.1.1 Rust remover
Rust remover is a liquid solution consisting of a blend of synergetic anti-oxidants and passivators. The remover is used to remove rust from any metallic iron and steel surfaces. Additionally, it contributes to the rust proofing of metals before any painting or coating application. On many occasions, there is always a need to remove rust from various objects like nails, bolts, engine parts, etc (Beacon, 2002).
Rust is a corrosion product of iron composed of different constituents (Evans and Taylor, 1972). The redox reaction prevails when iron interacts with oxygen in the presence of water and air moisture to form a red oxide product. Rust is a term used to describe iron corrosion and its alloys like steel, whereas corrosion is an operation of the slow destruction of metals when exposed to the environment. It is a term that covers the deterioration of metal by oxidation or other chemical reactions (Astrene, 2011).
The presence of rust (iron oxide) on the steel or iron surface can flake off and when this happens, more of the metal surface will be exposed to oxygen and oxidation continues to occur. On most metals rust can eat through the material leading to its destruction. When the metal is eaten away by rust, it is unable to withstand or support much weight. Items like bolts that are expected to hold chairs, desks, structures, bridges and buildings together weakens after rusting hence causing structural failure. The formation of rust leads to loss mainly in the damages to properties and economic losses.
1.2 Statement of the problem
Rust prevails in various environments of machines and facilities (iron and steel surfaces) when in contact with air and moisture, it results to the economic losses and deterioration of performance of machines and facilities. Hence there’s a need to develop a solution for removing rust from metallic surfaces. Most materials in use today are made of iron, which is prone to rust, which has made it necessary to develop ways of removing rust from these materials. Most if not all of these rust removers are imported. There is, therefore, a need to formulate rust removers locally to assist in saving our foreign exchange reserves.
1.3 Objectives
1.3.1 General objective
The general objective of this study was to prepare and evaluate the efficiency of various rust removal formulations.
1.3.2 Specific objectives
The specific objectives of the study were to:
(i). Evaluate rust removing efficiency of the various rust remover formulations.
(ii). To assess the functional group changes in the complexes formed from iron and sulphamic acid, acetic acid, citric acid, and hydroxyacetic acid.
(iii). To determine the optimum rust remover formulation in removing rust.
1.4 Justification and significance of the study
Kenya’s corrosion cost is indeed significant (Pierre, 2006). The successive reviews on corrosion concluded that it constitutes an enomous cost to the gross national product (GNP) of a country. The yearly corrosion cost (2019 GNP) of the United States per Uhlig’s report was found to be $276 billion, equivalent to 2.1 percent. (Virmani, 2002; Zeferani, 2015).
The cost of managing corrosion using rust removal formulations is therefore correspondingly high which necessitates its importation at great cost. According to the Nace.org report 2015, Kenya exchanges about $45.31 billion in anti-rust and corrosion products, with 29.3% used in the agricultural sector, 17.4% in the manufacturing industry, and 67.8% used in the service industry. Coming up with a viable rust remover in Kenya will therefore save the country from importation costs. By producing the formulations locally, Kenya will be saving importation costs worth USD 0.6 million annually (Exportgenius, 2021).
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