Corrosion Inhibition Properties Of Acetone Extract Of Cassia Fistula Pods On Mild Steel And Aluminium In HCL Medium
Subscribe to read and download this work.
ABSTRACT
Corrosion inhibition efficiency of Cassia fistula pod extract on mild in 0.5 M HCl solution was studied by gravimetric (weight loss) and quantum mechanical methods. Thermodynamic parameters such as activation energy, enthalpy, enthropy and Gibbs free energy of adsorption were determined. Results showed that the inhibition efficiency increased significantly by up to 82.9 % and 57.36 % for mild steel and aluminum respectively with increase in concentration of the inhibitor. However, the inhibition efficiency decreased slightly with increasing temperature in the range 303-343 K. This is supported by higher values of Kads (5.59-3.76) for mild steel and (1.10-0.73) for aluminium. It is observed that at lower temperature, there is higher value of Kads indicating that the inhibitor is more efficient at lower temperatures. The kinetic study shows that the inhibitory action follows a pseudo first order kinetics with the concentration of the extract. This was further supported by the thermodynamic parameters which reveal that the adsorption of both the individual seed extracts and their blends onto the metal surface was spontaneous, endothermic and followed physical adsorption mechanism. Cassia fistula was identified to have phytochemicals of phenol, saponins, tannins, alkaloids, terpenoids. These compounds are adsorbed by the surface of the metal, leading to corrosion inhibition. The experimental data fitted best into the Langmuir and Freundlich adsorption model for both mild steel and aluminium respectively at various temperatures studied with linearity coefficient (R2) of . The Gibbs free energy for Langmuir isotherm ranges from -15.230 to -14.453kJ/mol for mild steel and -10.558 to -10.238 kJ/mol for aluminium showing spontaneity and physisorption process. Thermodynamic adsorption consideration revealed that the positive values (31.890 - 35.63 kJ/mol) for mild steel and (19.44-21.018 kJ/mol) aluminium of enthalpy of activation with the inhibitor concentration (0.2 – 1.0 g/L) shows that the process of adsorption of the inhibitor on the mild steel surface is endothermic and spontaneous (negative values of ΔG°ads) and supported by the mechanism of physisorption (ΔG°adsless negative than -20kJ/mol). The compounds were optimized using density functional theory (DFT) with Becke three Yang Parr (B3LYP) and 6-31G(d) basis set; Quantum chemical studies indicated that inhibition was due to adsorption of active molecules leading to formation of a protective layer on surface of mild steel. Quantum chemical parameters such as highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) energy levels, HOMO–LUMO energy gap and electronic density were virtually identified. The calculated electronic properties and global reactivity description agree with experimental findings. The high dipole moment values (>4) and the electronic donating abilities (fraction of transferred electrons 0.8-1.08) of Cassia fistulafurther demonstrate good inhibition efficiency.
TABLE OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of Contents vi
List of Tables x
List of Figures xii
Abstract xv
CHAPTER 1: INTRODUCTION 1
1.1 Background of Study 1
1.2 Statement of the Problem 5
1.3 Justification of the Study 6
1.4 Aim of the Study 6
1.5 Scope of the Study 7
CHAPTER 2: LITERATURE REVIEW 8
2.2 Corrosion Cells and Reactions 8
2.3 Factors Responsible for Corrosion 9
2.4 Types of Corrosion 12
2.3.1. Localized Corrosion 12
2.3.2 Uniform surface corrosion 16
2.4 Corrosion in different media 18
2.4.1 Corrosion in alkaline solution 18
2.4.2 Corrosion in acid medium 19
2.4.3 Corrosion in free organic liquid and gases 19
2.4.4 Corrosion induced by bacteria 19
2.4.5 Corrosion in moist environment 19
2.5 Consequences of Corrosion 20
2.5.1 Economic effects 20
2.5.2 Health effects 22
2.5.3 Safety effects 22
2.5.4 Technological effects 23
2.5.5 Cultural effects 23
2.6 Prevention and Control of Corrosion 23
2.6.1 Applied coatings 23
2.6.2 Anodization 23
2.6.3 Galvanization 24
2.6.4 Biofilm coatings 25
2.7 Corrosion Inhibition and Inhibitors 26
2.8 Types of Inhibitors 26
2.8.1 Anodic (Passivating) inhibitors 29
2.8.2 Cathodic inhibitors 29
2.8.3 Organic inhibitors 32
2.8.4 Precipitating inhibitors 34
2.8.5 Green corrosion inhibitors 35
2.9 Limitations and Advantages of Plant Extract as Corrosion Inhibitors 39
2.10 Brief History of Cassia fistula (a.k.a Golden shower tree ) 40
2.10.1 Medicinal uses 42
2.10.2 Other uses 43
2.10.3 Places where cassia fistula can be found 44
2.10.4 Cassia fistula as a corrosion inhibitor 45
CHAPTER 3: MATERIALS AND METHODS 47
3.1 Materials 47
3.2 Methods 48
3.2.1 Determination of composition of metal coupons 48
3.2.2 Preparation of Cassia fistula seed extracts 49
3.2.3 Preparation of 0.5 M HCl 49
3.2.4 Phyto-chemical analysis 50
3.2.5 Gravimetric techniques 53
3.2.6 Corrosion data 54
3.2.7 Adsorption isotherm study 55
3.2.8 Thermodynamic studies 57
3.2.9 Corrosion adsorption kinetics 58
3.2.10 Computational method 59
CHAPTER 4: RESULTS AND DISCUSSION 62
4.1 Phytochemical Analyses 62
4.2 Determination of Composition of Metal Coupons 63
4.3 Analyses of FTIR Spectra 64
4.4 Effect of Concentration of Acetone Extract of Cassia Fistula Pod on the
Corrosion Rate of Metals (Mild Steel and Aluminium) and Inhibition
Efficiency in 0.5 M HCl. 65
4.5 Effect of Temperature 70
4.6 Kinetic Consideration 75
4.7 Thermodynamics 78
4.7.1 Arrhenius plots 78
4.7.2 Transition state plots 80
4.8 Adsorption Considerations 83
4.8.1 Langmuir adsorption isotherm 83
4.8.2 Freundlich adsorption isotherm 86
4.9 Quantum Studies 89
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS 102
5.1 Conclusion 102
5.2 Recommendations 103
References
LIST OF TABLES
3.1 List of materials used for the experiments 47
3.2 List of equipment for the experiments 48
4.1: Phytochemical test of extract of Cassia fistula pods 62
4.2 Chemical composition of studied metal samples 63
4.3: Surface coverage and inhibition efficiency of Cassia fistula pods
extracts on mild steel metal at varying time 66
4.4: Surface coverage and inhibition efficiency of Cassia fistula pods
extracts on aluminium metal at varying time 67
4.5: Surface coverage and inhibition efficiency of Cassia fistula pods extracts
on mild steel metal at varying temperature 72
4.6: Surface coverage and inhibition efficiency of Cassia fistula pods
extracts on aluminium at varying temperature 73
4.7: Pseudo first order parameters for corrosion inhibition of mild steel by
extract of Cassia fistula pods 77
4.8: Pseudo first order parameters for corrosion inhibition of aluminium by
extract of Cassia fistula pods 77
4.9: Arrhenius parameters for the corrosion of mild steel and aluminium
in acid containing various concentrations of the studied inhibitor 79
4.10: Eyring-Transition state parameters for the corrosion of mild steel
in acid containing various concentrations of the studied inhibitor 82
4.11: Langmuir isotherm parameters for the corrosion of mild steel and
aluminium in HCl medium containing various concentrations of the
studied inhibitor 85
4.12: Freundlich isotherm parameters for the corrosion of mild steel and
aluminium in HCl medium containing various concentrations of the
studied inhibitor 88
4.13 Electronic properties and global reactivity descriptors of Fistulic acid,
Catechin and Epicatechin 90
4.14: Selected calculated Fukui functions and Mulliken atomic charges of
Fistulic acid 97
4.15 Selected calculated Fukui functions and Mulliken atomic charges of
Catechin 98
4.16 Selected calculated Fukui functions and Mulliken atomic charges of
Epicatechin 99
LIST OF FIGURES
2.1: Schematic diagram of pitting corrosion 13
2.2: A schematic diagram of crevice corrosion 14
2.3: A schematic diagram of intergranular corrosion 14
2.4: A schematic diagram of filiform corrosion 15
2.5: A schematic diagram of uniform corrosion 16
2.6: A schematic diagram of dtress corrosion 17
2.7: A potentiostatic polarization diagram of a solution with
electrochemical behaviour of a metal in an anodic inhibitor 28
2.8: The mechanism of the anodic inhibitory effect 29
2.9: Potentiostatic polarization diagram 30
2.10: Theoretical potentiostatic polarization diagram 33
2.11: Illustration of the mechanism of actuation of the organic inhibitor:
acting through adsorption of the inhibitor on the metal surface. Where
the “Inh” represent the inhibitor molecules. 33
2.12: Pictures of the Cassia fistula tree, pod and pulp 41
3.1: Pictures of separated pulp and pod 54
3.2: Pictures of metal immersed in a solution of HCl acid and inhibitior 54
4.1: FTIR Spectrum of the extract of Cassia fistula pods 64
4.2: Effect of concentration of Acetone Extract of Cassia fistula pods
on the corrosion rate of mild steel in 0.5 M HCl 65
4.3: Effect of concentration of acetone extract of Cassia fistula pods on the
corrosion rate of aluminium in 0.5 M HCl 66
4.4: Effect of concentration of acetone extract of Cassia fistula pods on
inhibition efficiency on Mild Steel in 0.5M HCl at different contact times 69
4.5: Effect of concentration of acetone extract of Cassia fistula pods on
inhibition efficiency on Aluminium in 0.5M HCl at different contact times 69
4.6: Effect of concentration of acetone extract of Cassia fistula pods on
inhibition efficiency on Mild Steel in 0.5M HCl at different temperatures 71
4.7: Effect of concentration of acetone extract of Cassia fistula pods on
inhibition efficiency on aluminium in 0.5M HCl at different temperatures 71
4.8: Pseudo first order plot for the corrosion of mild steel in 0.5M HCl in the
absence and presence of acetone extract of Cassia fistula pods 75
4.9: Pseudo first order plot for the corrosion of aluminium in 0.5M HCl
in the absence and presence of acetone extract of Cassia fistula pods 76
4.10: Arrhenius plots for the corrosion of mild steel in 0.5M HCl containing
various concentrations of Cassia fistula pods extract 78
4.11: Arrhenius plots for the corrosion of aluminium in 0.5M HCl containing
various concentrations of Cassia fistula pods extract 79
4.12: Eyring Transition state plots for the corrosion of mild steel in 0.5
M HCl containing various concentrations of Cassia fistula pods extract 81
4.13: Eyring Transition state plots for the corrosion of aluminium in 0.5
M HCl containing various concentrations of Cassia fistula pods extract 81
4.14: Langmuir isotherm for the adsorption of the inhibitor on mild steel
surface in 0.5M HCl solution at various temperatures 84
4.15: Langmuir isotherm for the adsorption of the inhibitor on aluminuim surface
in 0.5 M HCl solution at various temperatures 84
4.16: Freundlich isotherm plots for the adsorption of the inhibitor on
mild steel surface in 0.5 M HCl solution at various temperatures 87
4.17: Freundlich isotherm plots for the adsorption of the inhibitor on
aluminuim surface in 0.5 M HCl solution at various temperatures 87
4.18a: Optimized structure of fistulic acid 92
4.18b: HOMO map of fistulic acid 92
4.18c: LUMO map of fistulic acid 92
4.18d: Electrostatic potential map of fistulic acid 93
4.19a: Optimized structure of catechin 93
4.19b: HOMO map of catechin 94
4.19c: LUMO map of catechin 94
4.19d: Electrostatic potential map of catechin 95
4.20a: Optimized structure of epicatechin 95
4.20c: 4.20b: HOMO map of epicatechin 96
4.20c: LUMO map of epicatechin 96
Reviews
No reviews yet.
APA
OBETA, & RUTH, U. (2023). Corrosion Inhibition Properties Of Acetone Extract Of Cassia Fistula Pods On Mild Steel And Aluminium In HCL Medium . Michael Okpara University of Agriculture. Retrieved June 8, 2026, from http://repository.mouau.edu.ng/works/corrosion-inhibition-properties-of-acetone-extract-of-cassia-fistula-pods-on-mild-steel-and-aluminium-in-hcl-medium-7-2
MLA
OBETA, and UCHECHUKWU RUTH. "Corrosion Inhibition Properties Of Acetone Extract Of Cassia Fistula Pods On Mild Steel And Aluminium In HCL Medium ." Michael Okpara University of Agriculture, 31 Aug. 2023, http://repository.mouau.edu.ng/works/corrosion-inhibition-properties-of-acetone-extract-of-cassia-fistula-pods-on-mild-steel-and-aluminium-in-hcl-medium-7-2. Accessed June 8, 2026.
Chicago
OBETA, and UCHECHUKWU RUTH. "Corrosion Inhibition Properties Of Acetone Extract Of Cassia Fistula Pods On Mild Steel And Aluminium In HCL Medium ." Michael Okpara University of Agriculture (2023). Accessed June 8, 2026. http://repository.mouau.edu.ng/works/corrosion-inhibition-properties-of-acetone-extract-of-cassia-fistula-pods-on-mild-steel-and-aluminium-in-hcl-medium-7-2