TABLE OF CONTENT
TITLE - - - .. - - - - - ..i
ABSTRACT - - - . - - - ii
DEDICATION - - - - - .iii
ACKNOWLEDGEMENTS - - . - - - .iv
CERTIFICATION - - - . - - - v
ABBREVIATION - - - . - - - vi
TABLE OF CONTENT - - - -
LIST OF TABLES - - - - - ..
LIST OF PLATES - - - - .
CHAPTER ONE1.0 Introduction 1
1.1.1 Corrosion XX
1.1.2 Corrosion Environment 2
1.1.3 Principle of Corrosion 2
1.2 Forms Corrosion 4
1.2.1 Uniform Corrosion 5
1.2.2 Galvanic or Bimetallic Corrosion 8
1.2.3 Pitting corrosion / Crevice corrosion 8
1.2.4 Erosion Corrosion 9
1.2.5 Filliform Corrosion 10
1.2.6 Graphitic Corrosion 11
1.2.7 Fretting Corrosion 11
1.2.8 Corrosion Inhibitors 12
1.2.9 Classification of Inhibitors 13
1.2.10 Natural Corrosion Inhibitors for Metals 17
1.2.11 Carica papaya as a Green Inhibitor 17
1.2.12 Azadirachta indica as a Green Inhibitor 18
1.2.13 Aluminium 18
1.2.14 Applications of Aluminium 18
1.2.15 Alloy Designation 19
1.2.16 Corrosion behavior of Aluminium and its Alloys 19
1.2.17 Aims and Objective 20
CHAPTER TWO2.0 Literature Review 21-29
CHAPTER THREE3.0 Materials and Method 30
3.1 Materials 30
3.2 Reagent 30
3.3 Material Preparation 31
3.3.1 Preparation of Extract 31
3.4 Corrosion Inhibition Test 32-34
CHAPTER FOUR4.0 Results and Discussion 35-38
4.1 Hydrogen Evolution and Corrosion Rate 38-40
4.2 Inhibition efficiency of Azadirachta indica and Carica papaya 41
4.3 Corrosion Rate of Azadirachta indica and Carica papaya Extract on Aluminium 44
4.4 Adsorption Studies 44-51
CHAPTER FIVE5.0 Conclusion 52
5.1 Recommendation 52
LIST OF TABLESTable 1.0: Green inhibitors for some metals 15
Table 4.1: Line equation and regression values for graph of volume of
hydrogen gas evolved (Azadirachta indica) 34
Table 4.2: Line equation and regression values for graph of volume of
hydrogen gas evolved (Carica papaya) 34
Table 4.3: Correlation coefficient for different adsorption isotherms
(Azadirachta indica) 47
Table 4.4: Correlation coefficient for different adsorption isotherms
(Carica papaya) 49
LIST OF FIGURESFig. 1.1: Uniform Corrosion 5
Fig. 1.2: Galvanic Corrosion 7
Fig. 1.3: Pitting Corrosion 9
Fig. 1.4: Crevice Corrosion 9
Fig. 1.5: Erosion Corrosion 10
Fig. 1.6: Filliform Corrosion 11
Fig.1.7: Graphitic Corrosion 11
Fig. 1.8: Fretting corrosion 12
Fig. 3.1 Experimental set up for gasometric method 30
Fig.4.1: Variation of volume of hydrogen (cm3) evolved with time (min) of Al coupons (Azadirachta indica) extract 34
Fig.4.2: Variation of volume of hydrogen (cm3) evolved with time (min) of Al coupons (Carica papaya) extract 36
Fig.4.3: Percentage inhibition efficiency of varying concentrations of Carica papaya extracts 40
Fig.4.4: Percentage inhibition efficiency of varying concentrations of Azadirachta indica extracts 41
Fig.4.5: Corrosion rate of varying concentrations of Azadirachta indica extract 42
Fig.4.6: Corrosion rate of varying concentrations of Carica papaya extract 42
Fig.4.7: Temkin isotherm plot for aluminium corrosion in Azadirachta indica extract 44
Fig.4.8 Freundlich isotherm plot for aluminium corrosion in Azadirachta indica extract 45
Fig.4.9: Frumkin adsorption isotherm plot for aluminium in Azadirachta indica extract 45
Fig.4.10: Langmuir isotherm plot for aluminium in Azadirachta indica extract 46
Fig.4.11 Freundlich isotherm plot for aluminium corrosion in Carica papaya extract 47
Fig.4.12: Frumkin adsorption isotherm plot for aluminium in Carica papaya extract 48
Fig.4.13: Temkin isotherm plot for aluminium corrosion in Carica papaya extract 48
Fig.4.14: Langmuir isotherm plot for aluminium in Carica papaya extract 49.