inhibition effect of some dyes on the corrosion of mild steel in h2so4 acid solutions

164 Pages·2013·6.21 MB·English

University of Benghazi
Faculty of Science
Chemistry Department

INHIBITION EFFECT OF SOME DYES ON THE
CORROSION OF MILD STEEL IN H SO ACID
2 4
SOLUTIONS

M. Sc. – Dissertation By
Ehab Lutfi Mohammad ElGahani
B. Sc. Chem., Benghazi University

For the partial fulfillment of M. Sc. degree requirements in Chemistry
(Physical Chemistry)

Based on research carried out in the
Laboratory of Corrosion Science (LCSc.)
E-mail: moh_n_r@yahoo mail.co.uk

Supervisor: Dr. Mohammed Nuri Rahuma 
Co- Supervisor: Prof. Dr. Mohammed Mohsen Badr El-Sabbah

University of Benghazi
Benghazi-Libya
2013
DEDICATION TO

MY FAMILY, MY PARENTS,
Dr. MOHAMED RAHUMA
AND
Prof. Dr. MOHAMED EL-SABBAH

I
ACKNOWLEDGEMENT
First and foremost I wish to give all the praise to almighty ALLAH for giving me
strength and time to complete this thesis.
I thank my lovely family, my father, mother, brothers and sisters for great
support and encouragement.
I wish to express my respectful thanks to Dr. Mohamed Nuri Rahuma for his
careful guidance and patient assistant. Also I should offer my esteem and gratitude
to Prof. Dr. Mohamed Mohsen Badr El-Sabbah, who has always supported me
during stages of my studies also for his help me in many things.
I would also like to acknowledge my committee members: Prof. Dr. Fathi El-
Ashhab Who is my internal examiner and Dr. Mohamed Saleh Suliman who is my
external examimer. It is great honor to have you in my thesis committee.
I would like to thank the head of Chemistry Department Dr. Younis O. Ben Amer
and the coordinator of the post graduate studies Dr. Ali Farag Bukhzam to cross
the opportunity to provide Master’s thesis. My thanks go to the faculty members,
Department of Chemistry and especially who taught me.
I am thankful also for my all partners and thanks also to all teachers and doctors
of chemistry department and thanks also to all technicians of chemistry lab.
II
Also I would like to thank: Dr. A. El-houd, Dr. Abdallah El-hansheri, Osama H.
Burshan and Faozia R. Lahmer for their help in using SEM in petroleum research
center in Tripoli.
And send my thanks to Dr. Mahmoud Hashem Mahross and Chemistry
Department-Faculty of science-Al-Azher University-Assiut Branch in cairo for his
help in electrochemical measurements.
Finally I would like to express my gratitude for all who had helped me in any
way they could to complete this work.
III
CONTENTS
Subject Page

DEDICATION I
ACKNOWLEDGEMENT II
CONTENTS IV
LIST OF FIGURES VIII
LIST OF TABLES XI
SUMMARY XIII
CHAPTER ONE
1. INTRODUCTION 2
1.1 Importance of Corrosion and Prevention Efforts 4
1.2 Forms of Electrochemical Corrosion 5
1.2.1 Uniform (General) Corrosion 5
1.2.2 Galvanic or bimetallic Corrosion 6
1.2.3 Pitting Corrosion 6
1.2.4 Crevice Corrosion 6
1.2.5 Intergranular Corrosion 7
1.2.6 Selective Leaching 7
1.2.7 Erosion Corrosion 7
1.2.8 Stress Corrosion Cracking 8
IV
1.3 Mechanism of Electrochemical Corrosion 8
1.4 Acid Corrosion 10
1.5 Corrosion Prevention 11
1.5.1 Materials Selection 11
1.5.2 Proper Design 11
1.5.3 Corrosion Protection by Coatings 12
1.5.4 Cathodic Protection 12
1.5.5 Anodic Protection 12
1.5.6 Change of Environment 1 3
1.6. Corrosion Inhibitors 13
1.6.1 Passivating (anodic) 14
1.6.2 Cathodic Inhibitors 15
1.6.3 Precipitation Inhibitors (or mixed inhibitors) 15
1.6.4 Volatile Corrosion Inhibitors 16
1.6.5 Organic inhibitors 16
1.6.5.1 Effect of Organic Inhibitors on the Behaviors of Steel in Acidic Media 17
1.6.5.2 Effect of Dyes on the Behavior of Metals in Aqueous Solutions 24
CHAPTER TWO
2. EXPERIMENTAL 35

2.1 Instrumentation 35
2.2 Electrodes 36
V
2.3 Chemicals 36
2.4. Inhibitors 36
2.5. Adopted Techniques 38

2.5.1 Weight loss Measurements 38
2.5.2 Open Circuit Potential Measurements 39
3.4.3 Potentiodynamic polarization Measurements 40
3.4.4 Scanning Electron Microscopy (SEM) 41
CHAPTER THREE
3. RESULTS AND DISCUSSION 44
3.1. Weight-loss Measurements 45
3.1.1 Effect of sulfuric acid concentrations 46
3.1.2 The inhibition behavior of some dyes on the corrosion 49
of mild steel in 1.0M H SO at 30 0C
2 4
3.1.3 Adsorption consideration 59
3.1.4 Kinetic parameters 63
3.1.5 Thermodynamic considerations 65
3.2. Electrochemical Techniques 77
3.2.1 Open Circuit Potential Measurements 77
3.2.2 Rate of Oxide Film Thickening 88
3.2.3 Potentiodynamic Polarization Measurements (Linear and 94
Tafel Polarizations)
3.3. Mechanism of Inhibition 104

VI
3.4. Surface Morphology of Mild Steel Electrode 105
3.4.1. Scanning Electron Microscope (SEM) 106
CONCLUSIONS 112
REFERENCES 115
APPENDIX 127
ARABIC SUMMARY )يبرعلا صخلملا(

VII
LIST OF FIGURES
Figure No.  Figure Title  Page 
Fig.(1)  The corrosion cell (model K47, EG and G-PARC)  39 
Fig.(2)  Potentiostat (Model 273 SoftCroo)  40 
Fig.(3)  Scanning Electron Microscopy (SEM, Model LEO 1430 VP)  42 
Fig.(4)  Effect of the time and the concentrations of H SO on 46 
2 4
mild steel electrode at 30 0C
Fig.(5)  Weight-loss/ time curves for mild steel electrode in 1.0M 50 
H SO acid in absence and presence of different
2 4
concentrations of D at 30 0C
1
Fig.(6)  Weight-loss/ time curves for mild steel electrode in 1.0M 51 
H SO acid in absence and presence of different
2 4
concentrations of D at 30 0C 
2
Fig.(7)  Weight-loss/ time curves for mild steel electrode in 1.0M 52
H SO acid in absence and presence of different
2 4
concentrations of D at 30 0C
3
Fig.(8)  Weight-loss/ time curves for mild steel electrode in 1.0M 53
H SO acid in absence and presence of different
2 4
concentrations of D at 30 0C
4
Fig.(9)  Weight-loss/ time curves for mild steel electrode in 1.0M 54
H SO acid in absence and presence of different
2 4
concentrations of D at 30 0C
5
Fig.(10)  Corrosion rate of mild steel in 1.0 M H SO at different 57
2 4
concentrations of dyes
Fig.(11)  Inhibition efficiency (I.E%) of mild steel in 1.0M H SO 58
2 4
at different concentrations of dyes
Fig.(12)  Langmuir adsorption isotherm model of dyes on mild 61
steel surface in 1.0M H SO
2 4
Fig.(13)  Variation of log C.R. with log C For mild steel 64
inh.
corrosion in 1.0M H SO with dyes at 30 0C
2 4
Fig.(14)  Weight-loss/ time curves of mild steel electrode in 1.0M 66
H SO in the absence and presence of 1.25x 10-3M
2 4
of dyes at 300C
VIII
Fig.(15)  Weight-loss/ time curves of mild steel electrode in 1.0M 67
H SO in the absence and presence of 1.25x 10-3M
2 4
of dyes at 350C
Fig.(16)  Weight-loss/ time curves of mild steel electrode in 1.0M 68
H SO in the absence and presence of 1.25x 10-3M
2 4
of dyes at 400C
Fig.(17)  Weight-loss/ time curves of mild steel electrode in 1.0M 69
H SO in the absence and presence of 1.25x 10-3M
2 4
of dyes at 450C
Fig.(18)  Weight-loss/ time curves of mild steel electrode in 1.0M 70
H SO in the absence and presence of 1.25x 10-3M
2 4
of dyes at 500C
Fig.(19)  Effect of temperature on the corrosion rate (C.R.) X103 of 71
mild steel electrode in 1.0M H SO and in presence
2 4
of 1.25x 10-3M Dyes
Fig.(20)  Effect of temperature on the inhibition efficiency (I.E%) 72
of mild steel electrode in 1.0M H SO and in presence
2 4
of 1.25x 10-3M of Dyes
Fig.(21)  Relation between log C.R. and 1/T (K-1) for mild steel 74
electrode in 1.0M H SO in the absence and presence
2 4
of 1.25x 10-3M of different dyes
Fig.(22)  Relation between log C.R/T and 1/T (K-1) for mild steel 75
electrode in 1.0M H SO in the absence and presence
2 4
of 1.25x 10-3M of different dyes
Fig.(23)  Potential-time curves for mild steel in different 79
concentrations of H SO (1, 0.1, 0.01and 0.001M)
2 4
Fig.(24)  Potential-time curves for mild steel in 1.0M H SO 82
2 4
and two concentrations of Dye 1
Fig.(25)  Potential-time curves for mild steel in 1.0M H SO 83
2 4
and two concentrations of Dye 2
Fig.(26)  Potential-time curves for mild steel in 1.0M H SO 84
2 4
and two concentrations of Dye 3
Fig.(27)  Potential-time curves for mild steel in 1.0M H SO 85
2 4
and two concentrations of Dye 4
Fig.(28)  Potential-time curves for mild steel in 1.0M H SO 86
2 4
and two concentrations of Dye 5
Fig.(29)  Potential-time curves for mild steel in 1.0M H SO 87
2 4
and (0.002) of all dyes
Fig.(30)  Potential-Log t curves for mild steel in 1.0M H SO 91
2 4
and different concentrations of a) D and b) D
1 2
IX