Corrosion Inhibition Properties Of Acetone Extract Of Cassia Fistula Pods On Mild Steel And Aluminium In HCL Medium

OBETA | 133 pages (28553 words) | Theses
Chemistry | Co Authors: UCHECHUKWU RUTH

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

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APA

OBETA, O (2023). Corrosion Inhibition Properties Of Acetone Extract Of Cassia Fistula Pods On Mild Steel And Aluminium In HCL Medium . Repository.mouau.edu.ng: Retrieved Jul 19, 2024, from https://repository.mouau.edu.ng/work/view/corrosion-inhibition-properties-of-acetone-extract-of-cassia-fistula-pods-on-mild-steel-and-aluminium-in-hcl-medium-7-2

MLA 8th

OBETA, OBETA. "Corrosion Inhibition Properties Of Acetone Extract Of Cassia Fistula Pods On Mild Steel And Aluminium In HCL Medium " Repository.mouau.edu.ng. Repository.mouau.edu.ng, 31 Aug. 2023, https://repository.mouau.edu.ng/work/view/corrosion-inhibition-properties-of-acetone-extract-of-cassia-fistula-pods-on-mild-steel-and-aluminium-in-hcl-medium-7-2. Accessed 19 Jul. 2024.

MLA7

OBETA, OBETA. "Corrosion Inhibition Properties Of Acetone Extract Of Cassia Fistula Pods On Mild Steel And Aluminium In HCL Medium ". Repository.mouau.edu.ng, Repository.mouau.edu.ng, 31 Aug. 2023. Web. 19 Jul. 2024. < https://repository.mouau.edu.ng/work/view/corrosion-inhibition-properties-of-acetone-extract-of-cassia-fistula-pods-on-mild-steel-and-aluminium-in-hcl-medium-7-2 >.

Chicago

OBETA, OBETA. "Corrosion Inhibition Properties Of Acetone Extract Of Cassia Fistula Pods On Mild Steel And Aluminium In HCL Medium " Repository.mouau.edu.ng (2023). Accessed 19 Jul. 2024. https://repository.mouau.edu.ng/work/view/corrosion-inhibition-properties-of-acetone-extract-of-cassia-fistula-pods-on-mild-steel-and-aluminium-in-hcl-medium-7-2

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