Inhibition of the Corrosion of Mild Steel and Aluminium in Acidic Media by Some Purines

Filed in Chemistry Project Topics, Current Projects by on September 18, 2022

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ABSTRACT

Studies on the corrosion inhibition potentials of adenine (AD), guanine (GU), hypoxanthine (HYP) and xanthine (XN) on mild steel and aluminium in 0.1 M solutions of HCl, H2SO4 and H3PO4 were carried out using electrochemical impedance spectroscopy (EIS), potentiodynamic polarisation and gravimetric techniques.

The study was carried out at 303 and 333 K respectively.

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The results obtained revealed that AD, GU, HYP and XN had moderate inhibitive effects on corrosion of mild steel in the three acid media in the decreasing order: AD> HYP> GU> XN in HCl; HYP> AD> GU> XN in H2SO4 and GU> AD> HYP> XN in H3PO4 at 303 K.

The results obtained also showed that AD, GU, HYP and XN inhibited the corrosion of aluminium in HCl in the order: GU> HYP> AD> XN.

It was observed that only HYP inhibited the corrosion of aluminium in H2SO4 solution while none of the purines inhibited the corrosion of aluminium in H3PO4 solution. Potentiodynamic polarisation studies showed that the purines surpressed both the anodic and cathodic half reactions of the corrosion processes. Thereby acting as mixed inhibitors, while impedance data indicated that inhibition was achieved via adsorption of the inhibitor species on the mild steel and aluminium surfaces.

TABLE OF CONTENTS

Title page         ii

Declaration         iii

Certification    iv

Dedication     v

Acknowledgments         vi

Abstract        vii

Table of content           viii

List of figures               xi

List of tables              xii

Abbreviations and Symbols    xiii

CHAPTER ONE INTRODUCTION

  • Background to the Study – –     –           1
  • Forms of Corrosion – –             3
    • Uniform corrosion – –              –           3
    • Galvanic corrosion – –             3
    • Pitting corrosion – –           –           3
    • Crevice corrosion – –                 4
    • Intergranular corrosion – –                   4
    • Erosion corrosion – –                4
    • Cavitation corrosion –          5
    • Interfilm corrosion – –           –  –           5
    • Fretting corrosion – –                  5
  • Corrosion Monitoring Techniques – – –            6
    • Gravimetric technique- – –                6
    • Gasometric technique – – –              7
    • Thermometric technique – –                  8
    • Potentiodynamic polarisation techniques – –             8
    • Linear polarisation resistance (LPR) – – –     9
    • Electochemical noise – – –           –           –       9
    • Electrochemical impedance spectroscopy (EIS) – –           –           9
    • Galvanic/potential monitoring – –           –           –           –           10
  • Common Methods of Corrosion Prevention – –           –           11
    • Selection of materials and design against corrosion – –           –           11
    • Cathodic protection – –           –           –           –           –           –           12
    • Protective coatings – –           –           –           –           –           –           12
    • Environment modification and addition of inhibitors- – –           12

1.5       Inhibitors       –           –          –           –           13

1.5.1    Classification of inhibitors      –           –           13

  • Adsorption Isotherms – –           –           –           –           –           18
    • Langmuir adsorption isotherm – –           –           –           –           19
    • Freundlich isotherm – –           –           –           –           –           –           19
    • Temkin adsorption isotherm – –           –           –           –           –           19
    • Flory-Huggins adsorption isotherm – –           –           –           –           20
    • El-Awady et al. kinetic-thermodynamic adsorption isotherm – 20
    • Frumkin adsorption isotherm – – –           –           –           –           21

1.7       Purines                   22

1.7.1    Adenine                    22

1.7.2    Guanine           –        23

1.7.3    Hypoxanthine –           –    –           23

1.7.4    Xanthine         –              23

  • Statement of the Problem – –           –           23
  • Justification for the Choice of Purines as Corrosion Inhibitors – 24
  • Aims of the Research – –                26
  • Objectives of the Research – –     –           26

CHAPTER TWO LITERATURE REVIEW

  • Corrosion Inhibitors – – –           28
    • Triazoles and benzotriazoles derivativesas corrosion inhibitors – 28
    • Dyes as corrosion inhibitors – —           30
    • Amino acids as corrosion inhibitors – –             32
    • Schiff bases as corrosion inhibitors – –           33
    • Imidazoles as corrosion inhibitors – –      –           33
    • Purines as Corrosion Inhibitors – –          34

CHAPTER THREE MATERIALS AND METHODS

  • Material Preparation – –           –           –           –           –           37
  • Gravimetric Method – – –           –           –           –           –           37
  • Electrochemical Impedance Spectroscopy (EIS) – –           –           38
  • Potentiodynamic Polarisation – –           –           –           –           39
  • Synergistic Effects – –           –           –           –           –           –           39
  • Fourier Transform Infrared Spectrophotometery(FTIR) – 39
  • Scanning Electron Microscopy (SEM) – –           –           –           40
  • Computational and Theoretical Considerations – –           –           40
    • Quantum chemical calculations – –           –           –           –           40
    • Molecular dynamics simulation – –           –           –           –           41

CHAPTER FOUR RESULTS

CHAPTER FIVE DISCUSSION

Gravimetric Measurements –          –           –           102

Half Lives (t1/2) of Mild Steel and Aluminium in the Test Solutions         106

Effect of Temperature /Thermodynamics Study  –         –           123

Adsorption Study       –               130

Electrochemical Tests at 303 K        –        170

  • Electrochemical impedance measurements – – –           170

5.5.2    Potentiodynamic polarization measurements –           172

Synergistic Considerations  –        –           173

Infrared Spectroscopic Analysis      –          175

Scanning Electron Microscopy        –           178

Quantum Chemical Calculations     –         179

Molecular Dynamics Simulations    –             180

Mechanism of Inhibition      –            –           182

CHAPTER SIX SUMMARY, CONCLUSIONS AND RECOMMENDATIONS

Summary and Conclusions –          186

Recommendations     –                 188

REFERENCES        –           189

APPENDICES  –              202

INTRODUCTION

Corrosion of metals is an electrochemical process that occurs whenever a metal is in contact with an aggressive medium such as acids, bases and salts. The susceptibility of a metal to corrosion depends on the nature of the metal and the environment.

Despite the invention and over-usage of plastics in most industrial applications, metals still rule manufacturing industries. Metals like steel (iron), aluminium, copper, zinc and tin are commonly used in most industries.

Mild steel is one of the best preferred materials for industries due to its easy availability and excellent structural properties. Aluminium on the other hand, is the most abundant metal in the earth’s crust (8.1%), although it is not found free in nature.

The versatility of aluminium makes it the most widely used metal after steel. Most often, during industrial processes such as pickling and etching, these metals come in contact with aggressive media such as acids, bases and salts thereby exposing them to corrosion attack.

REFERENCES

Abdallah, M. (2004). Guar gum as corrosion inhibitor for carbon steel in sulphuric acid solutions. Portugaliae Electrochimica Acta, 22:161-175.

Abdeli, M., Ahmadi, N. P. and Khosroshahi, R. A. (2009). Nile blue and indigo  carmine organic dyes as corrosion inhibitor of mild steel in hydrochloric acid. Journal of Solid State Electrochemistry, 14(7): 1317-1324.

Achebe, C.H., Nneke, U.C. and Anisiji, O. E. (2012). Analysis of oil pipeline failures in the oil and gas industries in the Niger Delta area of Nigeria. Proceedings of the International MultiConference of Engineers and Computer Scientists, IMECS (Vol II, pp. 14 – 16). Hong Kong.

Adejo, S.O., Ekwenchi, M.M., Momoh, F. and Odiniya, E. (2012). Adsorption characterization of ethanol extract of leaves of Portulaca oleracea as green corrosion inhibitor for corrosion of mild steel in sulphuric acid medium. International Journal of Modern Chemistry, 1(3): 125-134.

Ahamad, I., Prasad, R. and Quraishi, M.A. (2010). Experimental and quantum chemical characterization of the adsorption of some Schiff base compounds of phthaloyl thiocarbohydrazide on the mild steel in acid solutions. Materials Chemistry Physics, 124: 1155-1165.

CSN Team.

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