ABSTRACT

Studies on corrosion inhibition potential of Indigo Carmine extract on mild steel in acidic medium was carried out using weight loss and electrochemical techniques. It was observed that the Indigo Carmine extract retarded the dissolution of mild steel in the acidic medium. The corrosion rate decrease with increase in concentration. The CR decrease from 37.59mm/yr to 27.50mm/yr in presence of the inhibitor. The CR also increase with increase in temperature up to 60^oC. The increase in CR with temperature suggests both physical and chemical adsorption of the Indigo Carmine (IC) on the mild steel. Potentiodynamic polarization measurements showed reduction in corrosion rate of mild steel surface. The potentiodynamicstudies shows a corrosion inhibition of 26.8% by the extract. Indigo Carmine was therefore found effective in inhibiting the corrosion of mild steel in acid medium.

TABLE OF CONTENTS

Contents

TITLE PAGE.. i

DECLARATION.. ii

CERTIFICATION.. iii

ACKNOWLEDGEMENT.. v

ABSTRACT.. vi

TABLE OF CONTENTS. vii

LIST OF FIGURES. ix

LIST OF TABLES. x

CHAPTER ONE.. 1

1.0 INTRODUCTION.. 1

1.1 Corrosion. 1

1.2 Causes and Economic effects of corrosion. 1

1.3 Mechanism of corrosion inhibition. 6

1.4 Corrosion Inhibition. 7

1.3 Mild steel 9

1.4 AIMS AND OBJECTIVES. 10

CHAPTER TWO.. 11

2.0 LITERATURE REVIEW... 11

CHAPTER THREE.. 16

3.0        MATERIALS AND METHODS. 16

3.1        Apparatus and Reagents. 16

3.2        Preparation of Extract 16

3.3 Preparation of Mild Steel 17

3.4 Weight Loss Experiment 17

3.5 Temperature Dependence Measurements. 18

3.6 Electrochemical Measurement 18

CHAPTER FOUR.. 19

4.0 RESULTS AND DISCUSSIONS. 19

4.1 Effect of Inhibitor Concentration on Corrosion Rate. 19

4.2 Effect of Temperature. 19

4.3 Adsorption Studies. 20

4.4 Electrochemical Measurement 22

CHAPHTER FIVE.. 25

5.0 CONCLUSIONS AND RECOMMENDATION.. 25

5.1 CONCLUSIONS. 25

5.2 RECOMMENDATION.. 25

REFERENCES. 26

APPEDIX A.. 29

APPEDIX B.. 29

APPEDIX C.. 30

LIST OF FIGURES

FIGURE        TITLE                                                                                                       PAGE

1.1                   Oil pipeline Corrosion             -           -           -           -           -           -           3

1.2                   Gas pipeline corrosion -           -           -           -           -           -           3

1.3                   Inner view of corroded pipeline         -           -           -           -           -           4

1.4                   Corrosion in heat exchanger   -           -           -           -           -           -           5

1.5                   Corrosion in heat exchanger   -           -           -           -           -           -           6

1.6                   Corrosion in boilers.    -           -           -           -           -           -           -           6

1.7                   Stainless steel sheet before and after pickling            -           -           -           9

4.1                   Variation of corrosion rate (gcm^-2h^-1) with concentration of inhibitor -         19

4.2                   Arrhenius plot for mild steel corrosion in Blank         -           -           -           21

4.3                   Arrhenius plot for mild steel corrosion in 10ppm Indigo Carmine     -           21

4.4                   Transition state plot for mild steel corrosion in Blank            -           -           23

4.5                   Transition state plot for mild steel corrosion in 10ppm of Indigo Carmine - 23

LIST OF TABLES

TABLE          TITLE                                                                                                       PAGE

4.1                   Arrhenius Parameters for the Inhibition of the Corrosion of Mild Steel        22

4.2                   Value for thermodynamic Parameters calculated from Transition state

adsorption plot            -           -           -           -           -           -           -           24

4.3                   Table of values obtained from linear polarization measurement         -           24