Efficacy Of The Blend Of Extracts From Afzelia Africana, Brachystegia Eurycoma And Momordica Charantia Seeds For Corrosion Inhibition Of Mild Steel In 1m Hcl Solution
ABSTRACT
The efficacy of blend of Afzelia africana (AA), Brachystegia eurycoma (BE) and Momordica charantia (MC) seed extracts was investigated as a cheap and ecologically friendly alternative mild steel corrosion inhibitor. The experimental aspect of the corrosion inhibition process was carried out in 1.0 M hydrochloric acid at temperatures ranging from 303K to 343K and concentration range of 0.1 to 0.5 g/L using Phytochemical Screening, gravimetric/weight loss, thermometric and hydrogen evolution techniques. The surface characterization was done using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopic (FTIR) techniques. The theoretical aspect was studied using the density functional theory calculations and modeling of the electronic structures of some of the most effective extract constituents, including physisorptive interactions with the mild steel surface. The inhibition efficiency was determined by comparison of the corrosion rates in the absence and presence of the seed extracts. The inhibition efficiency increases gradually in the order: blend > AA > BE > MC with the blend reaching a maximum value of 95.4% within the first 60 minutes of exposure at a concentration of 0.5 g/L and temperature of 303K. The inhibition efficiencies by both the hydrogen evolution and thermometric methods when compared with that obtained by weight loss method, followed the same trend. The adsorption parameters showed that the Freundlich isotherm was the best model for the individual seed extracts and the modified Langmuir adsorption isotherm for the blend. The kinetic study shows that the inhibitory action follows a first order kinetics with the concentration of both the individual seed extracts and their blends. 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. The low values of adsorption equilibrium constant, Kads indicate low interaction between the adsorbed molecules and the metal surfaces which further confirmed that the extracts were physically adsorbed onto the metal surface. FTIR study of the blended seed extracts and the corrosion product of mild steel showed an interaction between the inhibitor and the metal surface. SEM analyses of the corrosion product also confirmed the formation of a protective layer on the surface of the metal. 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. Therefore, the inhibition of mild steel corrosion is proposed to occur through synergistic combination of the constituents of the inhibitor, which leads to the formation of inhibitor-metal complex and subsequent protection of the metal from further corrosion attack.
TABLE OF
CONTENTS
Cover
page i
Title
Page ii
Declaration iii
Certification iv
Dedication v
Acknowledgement vi
Table
of Contents vii
List
of Tables xiii
List
of Figures xvi
List
of Plates xxiv
Abstract xxv
1.0 Chapter 1: Introduction 1
1.1 Background of Study 1
1.2 Statement
of the problem 4
1.3 Aim of the Study 5
1.4 Objectives of the Study 5
1.5 Significance
of the Study 6
1.6 Scope
of the Study 6
1.7 Justification of the Study 7
2.0 Chapter 2: Literature
Review 8
2.1 Corrosion 8
2.2 Corrosion Chemistry 9
2.3 Classification of
Corrosion 11
2.3.1 Dry Corrosion 11
2.3.2 Wet Corrosion 11
2.4 Forms of Corrosion 11
2.4.1 Uniform Corrosion 12
2.4.2 Galvanic or Two Metal
Corrosion 12
2.4.3 Carbon dioxide Corrosion 13
2.4.3.1 Pitting Corrosion 13
2.4.3.2 Mesa-Type Attack 14
2.4.3.3 Flow-Induced Localized Corrosion 14
2.4.4 Crevice Corrosion 14
2.4.5 Intergranular Corrosion 14
2.4.6 Selective Leaching 15
2.4.7 Erosion Corrosion 15
2.4.8 Stress Corrosion 16
2.5 Factors Affecting
Corrosion 16
2.6 The Problem of Corrosion 17
2.7 Corrosion Control 18
2.7.1 Materials selection and design 19
2.7.2 Surface Coatings 19
2.7.3 Modification of the Electrolyte 20
2.7.3.1 Removal
of the Aggressive Species 20
2.7.3.2 The
Addition of Corrosion Inhibitors 20
2.8 Types
of Corrosion Inhibitors 21
2.8.1 Organic
Inhibitors 21
2.8.1.1 Synthetic Organic
Inhibitors 22
2.8.1.2 Natural Organic Inhibitors 23
2.8.2 Inorganic
Inhibitors 24
2.8.2.1 Anodic Inhibitors 24
2.8.2.2 Cathodic Inhibitors 26
2.9 Corrosion Monitoring
Techniques 27
2.9.1 Weight loss
method 27
2.9.2 Gasometric/Hydrogen Evolution Method 28
2.9.3 Thermometric Method 30
2.10 Plant Description 31
2.10.1 Afzelia Africana (AA) 31
2.10.2 Brachystegia Eurycoma (BE) 32
2.10.3 Momordica Charantia (MC) 33
2.11 Methods Used For Extraction
Of Plant Materials 35
2.12 Phyto-Chemical Analysis as a Tool in
Corrosion Inhibition 36
2.13 Adsorption Isotherm 38
2.13.1 Langmuir Adsorption Isotherm 40
2.13.2 Temkin Adsorption Isotherm 42
2.13.3 Freundlich Adsorption Isotherm 43
2.13.4 Choice of Appropriate
Adsorption Isotherm Model 44
2.14 Determination of Associated
Thermodynamic and Kinetic Parameters 44
2.14.1 Thermodynamic Considerations 44
2.14.2 Kinetic Considerations 46
2.14.2.1Effect
of Concentration on Reaction Rate 46
2.14.2.2Effect
of Temperature on Reaction Rate 48
2.15 Theoretical
and Quantum Chemical Studies as a Corrosion
Monitoring Techniques 49
2.16 Scanning Electron Microscopy (SEM) 54
2.17 Empirical Review 56
2.17.1 Effects of Concentration on
Corrosion Inhibition 56
2.17.2 Effect of Immersion Time on
Corrosion Inhibition 61
2.17.3 Effect of Temperature on
Corrosion Inhibition 64
2.18 Adsorption Isotherm Studies 68
2.19 Thermodynamics and Kinetic
Treatment 71
2.20 Quantum Chemical Studies 76
3.0 Chapter 3: Methodology 79
3.1 Materials and Methods 79
3.1.1 Materials 79
3.2 Experimental Procedure 80
3.2.1 Preparation of Specimen 80
3.2.2 Surface Area and density of specimen 80
3.2.3 Preparation
of Blends of Afzelia Africana,
Brachystegia Eurycoma and
Momordica Charantia seed
extracts 81
3.2.4 Preparation of 1.0M HCl 82
3.3 Phyto-Chemical
Analysis 83
3.3.1 Test for Alkaloids 84
3.3.2 Test for Saponins 84
3.3.3 Test for Tannins 84
3.3.4 Test for Phenol 84
3.3.5 Test for Flavonoids 84
3.3.6 Test for Glycosides 84
3.3.7 Test for Steroids 85
3.3.8 Test for carbohydrates 85
3.3.9 Test for Reducing Sugar 85
3.3.10 Test
for Proteins 85
3.3.11 Test
for Amino acids 86
3.4 Gravimetric
Technique 86
3.5 Hydrogen Evolution
(Gasometric) Method 88
3.6 Thermometric Method 88
3.7 Adsorption Isotherm Study 89
3.
7.1 Langmuir
Adsorption Isotherms 89
3.8 Thermodynamic
and Kinetic Studies 90
3.8.1 Standard Gibbs free energy
change of Adsorption, ΔG°ads 90
3.8.2 Activation Energy, Ea 90
3.8.3 Rate Constant for the
Corrosion Rate, k 91
3.8.4 Half-life, t1/2 91
3.9
Scanning Electron Microscopy (SEM) 91
3.10 Fourier
Transform Infrared Spectroscopy (FTIR) 91
3.11 Theoretical and Quantum Chemical
Calculations 92
4.0 Chapter 4: Results and Discussion 93
4.1 Elemental
Composition of Mild Steel 93
4.2 Phytochemical Screening 94
4.3 Weight
Loss Results 97
4.3.1 Effect of Concentration of extracts on Corrosion
Rate and Inhibition Efficiency 99
4.3.2 Effect
of Immersion Time on Corrosion Inhibition 104
4.3.3 Effect of Temperature on Corrosion
Rate and Inhibition Efficiency 106
4.4 Gasometric Results 111
4.5 Thermometric Results 116
4.6 Adsorption Mechanism 118
4.7 Thermodynamic
and Kinetic parameters for the corrosion inhibition of both the
individual seed extracts and their
Blends 128
4.7.1 Standard
Gibbs free energy of adsorption, ΔG°ads 129
4.7.2 Activation
Energy (Ea) for
the Corrosion Process 130
4.7.3 Activation
Parameters for the Corrosion Process 132
4.7.4 Rate of Reaction and Rate
Constant of the Reaction 134
4.7.5 Half Life 147
4.8 Surface
Studies by Scanning Electron Microscopy 149
4.9 Fourier transform infrared spectroscopy
(FTIR) analysis
151
4.10 Theoretical
and Quantum Chemical Studies 155
4.10.1
Mulliken
charge distribution of Glucose, Arginine, Flavonol and Leucine 163
5.0
Chapter 5: Conclusion and
Recommendations 166
5.1 Conclusion 166 5.2 Recommendations 168
References
169
Appendixes 183
LIST OF TABLES
3.1 List of
Materials Used for the Experiments 79
3.2 List of Equipment for the Experiments 80
4.1 Elemental composition of mild steel
employed in the study 93
4.2 Phytochemical
Constituent of blends
of AA, BE and MC extract 94
4.3 Hydrogen evolution data
for mild steel corrosion in 1 M HCl solution in the absence
and presence of the blended seed extract 111
4.4 Thermometric
data for mild steel in 1.0 M HCl solution in the absence and presence of blended seed extract (AA, BE and MC) 116
4.5 Isotherm parameters for the adsorption of
ethanolic extract of Afzelia africana seed
on the surface of mild steel in HCl 118
4.6 Isotherm parameters for the adsorption of
ethanolic extract of Brachystegia
eurycoma
seed on the
surface of mild steel in HCl 120
4.7 Isotherm parameters for the adsorption of
ethanolic extract of Momordica charantia
seed on the
surface of mild steel in HCl 122
4.8 Isotherm parameters for the adsorption of
ethanolic extracts of the blends of Afzelia africana, Brachystegia eurycoma and
Momordica charantia seeds on the surface
of
mild steel in HCl 124
4.9 Calculated values of
thermodynamic and kinetic parameters for mild steel corrosion in
1 M HCl in the absence
and presence of Afzelia africana seed
extract as inhibitor 128
4.10 Calculated values of
thermodynamic and kinetic parameters for mild steel corrosion in
1 M HCl in the absence
and presence of Brachystegia
eurycoma seed extract
as
inhibitor 128
4.11 Calculated values of thermodynamic and kinetic parameters for mild steel
corrosion in
1 M HCl in
the absence and presence of Momordica
charantia seed extract as
inhibitor 128
4.12 Calculated values of thermodynamic and kinetic parameters for mild steel
corrosion in
1 M HCl in
the absence and presence of blended seed extracts
as inhibitor 129
4.13 Calculated values of the rate
constant for mild steel corrosion in 1 M HCl in the absence
and presence
of Afzelia africana seed extract 141
4.14 Calculated values of the rate
constant for mild steel corrosion in 1 M HCl in the absence
and presence of Brachystegia
eurycoma seed extract 141
4.15 Calculated values of the rate
constant for mild steel corrosion in 1 M HCl in the absence
and presence
of Momordica charantia seed extract 142
4.16 Calculated values of the rate constant for mild steel corrosion in
1 M HCl
in the absence and
presence of blended seed extracts 143
4.16 Calculated values of the half life
for mild steel corrosion in 1 M HCl in the absence
and presence
of Afzelia africana seed extract 147
4.17 Calculated values of the half life
for mild steel corrosion in 1 M HCl in the absence
and presence
of Brachystegia eurycoma seed
extract 147
4.18 Calculated values of the half life
for mild steel corrosion in 1 M HCl in the absence
and presence
of Momordica charantia seed extract
148
4.19 Calculated values of the half life
for mild steel corrosion in 1 M HCl in the absence
and presence
of blended seed extracts
148
4.21 IR Absorption of Afzelia africana seed extract 151
4.22 IR Absorption of Brachystegia eurycoma seed extract 151
4.23 IR Absorption of Momordica charantia seed extract 151
4.24 Quantum chemical parameters for most
important components of the ethanol extract
of Blend of AA, BE and MC
155
4.25 Mulliken Charge
Distribution on Flavonol, Leucine, Arginine and Glucose 165
LIST OF FIGURES
2.1 Anodic
Inorganic Inhibitors Effect and their Mechanism of Action 25
2.2 Mechanism of Actuation of
the Cathodic Inhibitors 26
2.3 Gasometric
assembly for measurement of hydrogen gas evolved 29
2.4 Extraction method used for preparation
of plant extracts 36
2.5 Schematic representation
of an adsorption isotherm 39
4.1 Structures of the
Phytochemicals Present in the blended seed extracts 95
4.2 Variation of weight loss with time for
mild steel coupons in 1 M HCl solutions
containing Afzelia africana at 303K 97
4.3 Variation of weight loss with immersion
time for mild steel coupons in 1 M HCl
solutions containing Brachystegia eurycoma at 303K 97
4.4 Variation of weight loss with immersion
time for mild steel coupons in 1 M HCl
solutions containing Momordica charantia at 303K. 97
4.5 Variation of weight loss with immersion
time for mild steel coupons in 1 M HCl
solution containing the Blend at
303K 98
4.6 Variation of corrosion rate with
concentration of Afzelia africana extract
for mild steel
coupons in 1 M HCl solution at different time intervals at 303 K 99
4.7 Variation of corrosion rate with
concentration of Brachystegia eurycoma
extract for
mild steel coupons in 1 M HCl
solution at different time intervals at 303 K 99
4.8 Variation of corrosion rate with
concentration of Momordica charantia
extract for mild
steel coupons in 1 M HCl solution at
different time intervals at 303 K 100
4.9 Variation of corrosion rate with the
concentration of Blend extract for mild steel coupons in 1 M HCl solution at different
time intervals at 303 K 100
4.10 Comparisons of corrosion rate of the
individual extract with the blend at 60 min
at 303 K 101
4.11 Variation of inhibition efficiency with
concentration of Afzelia africana
extract
for mild steel coupons in 1 M HCl
solution at different time intervals at 303 K 101
4.12 Variation of inhibition efficiency with
concentration of Brachystegia eurycoma
extract for mild steel in 1 M HCl solution at different
time intervals at 303 K 102
4.13 Variation of inhibition efficiency with
concentration of Momordica charantia
extract for mild steel in 1 M HCl
solution at different time intervals at 303 K 102
4.14 Variation of inhibition efficiency with
extract concentration of the blend for mild steel
coupons in 1 M HCl solution at
different time intervals at 303 K 103
4.15 Comparisons of inhibition efficiencies of
the individual extracts with the blend
at 60 min at 303 K 103
4.16 Variation of corrosion rate with
different concentrations of Afzelia
africana extract
showing the effect of temperature on
the corrosion inhibition process 106
4.17 Variation of corrosion rate with
different concentrations of Brachystegia
eurycoma
extract showing the effect of
temperature on the corrosion inhibition process 106
4.18 Variation of corrosion rate with
different concentrations of Momordica
charantia
extract showing the effect of
temperature on the corrosion inhibition process 107
4.19 Variation of corrosion rate with different
concentrations of the blend showing the effect
of temperature on the corrosion inhibition
process 107
4.20
Variation of inhibition efficiency with
different concentrations of Afzelia
africana
extract showing the effect of temperature on
the corrosion inhibition process 108
4.21
Variation of inhibition efficiency with
different concentrations of Brachystegia
eurycoma
extract
showing the effect of temperature on the corrosion inhibition process 108
4.22 Variation of inhibition efficiency with
different concentrations of Brachystegia eurycoma
extract showing the effect of temperature on the corrosion inhibition
process 108
4.23 Variation of inhibition efficiency with
different concentrations of the blend
showing the effect of
temperature on the corrosion inhibition process 109
4.24 Variation of volume of H2 gas
evolved with time for mild steel corrosion in
1.0 M HCl in the absence and presence of the blended seed extract at 303 K 111
4.25 Variation of volume of H2 gas
evolved with time for mild steel corrosion in
1.0 M HCl in the absence and
presence of the blended seed
extract at 313 K 112
4.26 Variation of volume of H2 gas
evolved with time for mild steel corrosion in 1.0 M HCl
in the absence and presence of the blended seed extract at
323 K 112
4.27 Variation of volume of H2 gas
evolved with time for mild steel corrosion in 1.0 M HCl
in the absence and presence of the blended seed extract at
333 K 113
4.28 Variation of volume of H2 gas
evolved with time for mild steel corrosion in1.0 M HCl
in the absence and presence of the blended seed extract at
343 K
113
4.29 Variation of
inhibition efficiency with the concentration of the blended seed extracts
for mild steel corrosion
in 1.0 M HCl solution at different temperatures 114
4.30 Variation of temperature with time in 1.0 M
HCl for mild steel corrosion in the absence
and presence of the blended seed extracts 116
4.31 Plot of RN against Log of inhibitor
concentration 117
4.32 The Langmuir isotherm for
the adsorption of Afzelia africana extract on mild steel
surface in 1.0 M HCl 118
4.33 The Freundlich isotherm for
the adsorption of Afzelia africana extract on mild steel
surface in 1.0 M HCl 119
4.34 The Temkin isotherm for the
adsorption of Afzelia africana extract on mild steel surface in 1.0 M HCl 119
4.35 The Langmuir isotherm for
the adsorption of Brachystegia
eurycoma extract on mild
steel surface in 1.0 M HCl 120
4.36 The Freundlich isotherm for
the adsorption of Brachystegia
eurycoma extracts on mild
steel surface in 1.0 M
HCl 121
4.37 The Temkin isotherm for the
adsorption of Brachystegia
eurycoma extracts on mild
steel surface in 1.0 M
HCl 121
4.38 The Langmuir isotherm for
the adsorption of Momordica
charantia extract on
mild steel surface in
1.0 M HCl 122
4.39 The Freundlich isotherm for
the adsorption of Momordica
charantia extract on
mild steel surface in
1.0 M HCl 123
4.40 The Temkin isotherm for the adsorption of Momordica charantia extract on
mild steel surface in
1.0 M HCl 123
4.41 The Langmuir isotherm for
the adsorption of the blended
seed extracts on mild steel
surface in 1.0 M HCl 124
4.42 The Freundlich isotherm for
the adsorption of the blended
seed extracts on mild steel
surface in 1.0 M HCl 125
4.43 The Temkin isotherm for the
adsorption of the blended
seed extracts on mild steel
surface in 1.0 M HCl 125
4.44 Plot of log CR against 1/T
for mild steel in 1 M HCl solution in the absence and presence
of various concentrations of Afzelia
africana extract 130
4.45 Plot of log CR against 1/T
for mild steel in 1 M HCl solution in the absence and presence
of various concentrations of Brachystegia
eurycoma extract 130
4.46 Plot of log CR against 1/T
for mild steel in 1 M HCl solution in the absence and presence
of various concentrations of Momordica
charantia extract 131
4.47 Plot of log CR against 1/T
for mild steel in 1 M HCl solution in the absence and presence
of various concentrations of blended seed extracts 131
4.48 Plot of log CR/T against 1/T for mild steel in 1 M HCl solution in the absence and
presence of various
concentrations of Afzelia africana extract
132
4.49 Plot of log CR/T against 1/T for mild steel in 1 M HCl solution in the absence and
presence of various
concentrations of Brachystegia
eurycoma extract 132
4.50 Plot of log CR/T against 1/T for mild steel in 1 M HCl solution in the absence and
presence of various
concentrations of Momordica
charantia extract 133
4.51 Plot of log CR/T against 1/T for mild steel in 1 M HCl solution in the absence and
presence of various
concentrations of blended seed extracts 133
4.52 Plot of Log Wf
vs Time for mild steel in 1 M HCl
solution in the absence and
presence of various
concentrations of Afzelia africana extracts
at 303 K 134
4.53 Plot of Log Wf
vs Time for mild steel in 1 M HCl
solution in the absence and
presence of various
concentrations of Afzelia africana extracts
at 313 K 134
4.54 Plot of Log Wf
vs Time for mild steel in 1 M HCl
solution in the absence and
presence of various
concentrations of Afzelia africana extracts
at 323 K 135
4.55 Plot of Log Wf
vs Time for mild steel in 1 M HCl
solution in the absence and presence
of various
concentrations of Afzelia africana extracts
at 333 K 135
4.56 Plot of Log Wf
vs Time for mild steel in 1 M HCl
solution in the absence and presence
of various
concentrations of Afzelia africana extracts
at 343 K 135
4.57 Plot of Log Wf
vs Time for mild steel in 1 M HCl solution
in the absence and presence
of
various concentrations of Brachystegia
eurycoma extracts at 303 K 136
4.58 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various
concentrations of Brachystegia
eurycoma extracts at 313 K 136
4.59 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various
concentrations of Brachystegia
eurycoma extracts at 323 K 136
4.60 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various
concentrations of Brachystegia
eurycoma extracts at 333 K 137
4.61 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various
concentrations of Brachystegia
eurycoma extracts at 303 K 137
4.62 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various
concentrations of Momordica
charantia extracts at 303 K
137
4.63 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various
concentrations of Momordica
charantia extracts at 313 K
138
4.64 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various
concentrations of Momordica
charantia extracts at 323 K
138
4.65 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various
concentrations of Momordica charantia extracts at 333 K 138
4.66 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various
concentrations of Momordica
charantia extracts at 343 K
139
4.67 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various
concentrations of blended seed extracts at 303 K 139
4.68 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various concentrations of blended seed extracts
at 313 K 139
4.69 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of
various concentrations of blended seed extracts at 323 K 140
4.70 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various
concentrations of blended seed extracts at 333 K 140
4.71 Plot of Log Wf vs Time for mild steel in 1 M HCl solution in the absence and presence
of various
concentrations of blended seed extracts at 343 K 140
4.72 Plot
of Wf
vs Time for mild steel in 1M HCl
solution in the absence and presence of
various
concentrations of Afzelia africana extracts at 303K 144
4.73 Plot
of 1/Wf
vs Time for mild steel in 1M HCl
solution in the absence and presence
of
various concentrations of Afzelia
africana
extracts at 303K 144
4.74 Plot
of Wf
vs Time for mild steel in 1M HCl
solution in the absence and presence of
various
concentrations of Brachystegia
eurycoma extracts at 303K
144
4.75 Plot
of Wf
vs Time for mild steel in 1M HCl
solution in the absence and presence of
various
concentrations of Brachystegia
eurycoma extracts at 303K
145
4.76 Plot
of Wf
vs Time for mild steel in 1M HCl
solution in the absence andpresence of
various
concentrations of Momordica
charantia extracts at 303K 145
4.77 Plot
of Wf
vs Time for mild steel in 1M HCl
solution in the absence and presence of
various
concentrations of Momordica
charantia extracts at 303K 145
4.78 Plot
of Wf
vs Time for mild steel in 1M HCl
solution in the absence and presence of
various
concentrations of blended seed extracts at 303K
146
4.79 Plot
of 1/Wf vs Time for mild steel in 1M HCl solution in the absence and presence
of
various concentrations of blended seed extracts at 303K 146
4.80 SEM
micrograph of mild steel immersed in hydrochloric acid without inhibitor at
200μm magnification 149
4.81 SEM
micrograph of mild steel immersed in hydrochloric acid in the presence of
ethanol extract of Blend of AA, BE
and MC at 200μm magnification 149
4.82 FTIR spectra of the ethanol extract of
Blend of AA, BE and MC 152
4.83 FTIR spectra of the corrosion product of
mild steel in the presence of the blended extracts
in
1 M HCl acid 152
4.84 Optimized Structure of Glucose Leucine,
Arginine and Flavonol 156
4.85 HOMO and
LUMO orbitals of Leucine 157
4.86 HOMO and
LUMO orbitals of Flavonol 157
4.87 HOMO and
LUMO orbitals of Glucose 157
4.88 HOMO and
LUMO orbitals of Arginine 158
4.89 ESP Optimized mapped density of (a) Leucine, (b)
Flavonol and (c) Glucose
(d) Arginine 162
LIST OF PLATES
2.1 Afzelia
africana (Akparata) seeds 32
2.2 Brachystegia eurycoma (Achi) seeds 33
2.3 Brachystegia eurycoma (Achi) processed
seeds and fruits 33
2.4 Unripe Momordica charantia fruits and leaves 34
2.5 Ripe Momordica
charantia fruits and Seeds 35
0.0
CHIMEZIE, P (2023). Efficacy Of The Blend Of Extracts From Afzelia Africana, Brachystegia Eurycoma And Momordica Charantia Seeds For Corrosion Inhibition Of Mild Steel In 1m Hcl Solution . Mouau.afribary.org: Retrieved Nov 17, 2024, from https://repository.mouau.edu.ng/work/view/efficacy-of-the-blend-of-extracts-from-afzelia-africana-brachystegia-eurycoma-and-momordica-charantia-seeds-for-corrosion-inhibition-of-mild-steel-in-1m-hcl-solution-7-2
PETER, CHIMEZIE. "Efficacy Of The Blend Of Extracts From Afzelia Africana, Brachystegia Eurycoma And Momordica Charantia Seeds For Corrosion Inhibition Of Mild Steel In 1m Hcl Solution " Mouau.afribary.org. Mouau.afribary.org, 15 Aug. 2023, https://repository.mouau.edu.ng/work/view/efficacy-of-the-blend-of-extracts-from-afzelia-africana-brachystegia-eurycoma-and-momordica-charantia-seeds-for-corrosion-inhibition-of-mild-steel-in-1m-hcl-solution-7-2. Accessed 17 Nov. 2024.
PETER, CHIMEZIE. "Efficacy Of The Blend Of Extracts From Afzelia Africana, Brachystegia Eurycoma And Momordica Charantia Seeds For Corrosion Inhibition Of Mild Steel In 1m Hcl Solution ". Mouau.afribary.org, Mouau.afribary.org, 15 Aug. 2023. Web. 17 Nov. 2024. < https://repository.mouau.edu.ng/work/view/efficacy-of-the-blend-of-extracts-from-afzelia-africana-brachystegia-eurycoma-and-momordica-charantia-seeds-for-corrosion-inhibition-of-mild-steel-in-1m-hcl-solution-7-2 >.
PETER, CHIMEZIE. "Efficacy Of The Blend Of Extracts From Afzelia Africana, Brachystegia Eurycoma And Momordica Charantia Seeds For Corrosion Inhibition Of Mild Steel In 1m Hcl Solution " Mouau.afribary.org (2023). Accessed 17 Nov. 2024. https://repository.mouau.edu.ng/work/view/efficacy-of-the-blend-of-extracts-from-afzelia-africana-brachystegia-eurycoma-and-momordica-charantia-seeds-for-corrosion-inhibition-of-mild-steel-in-1m-hcl-solution-7-2