Corrosion Resistance of Aluminum

Corrosion Resistance of Aluminum and Magnesium Alloys: Understanding, Performance, and Testing / E. Ghali (2010)

Brief Contents

Part One – Electrochemical Fundamentals and Active–Passive Corrosion Behaviors

1. Fundamentals of Electrochemical Corrosion

• Overview

     A. Thermodynamic Considerations of Corrosion

• Electrolytic Conductance
  • Faraday Laws
• Tendency to Corrosion
• The Electrochemical Interface
  • Electric Double Layer
  • Equivalent Circuit of the Electric Double Layer
• Nernst Equation
• Standard Potentials of Electrodes
  • Standard States in Solution
  • Hydrogen Electrode
  • Positive and Negative Signs of Potentials
  • Graphical Presentation

     B. Activity and Conductance of the Electrolyte

• Activity of the Electrolyte
  • Constant and Degree of Dissociation
  • Activity and Concentration
  • Theory of More Concentrated Solutions
  • Electrolytic Conduction
• Mobility of Ions
  • Law of Additivity of Kohlrausch
  • Ion Transport Number or Index
• Conductance
• Potential of Decomposition

     C. The Different Types of Electrodes

• Gas Electrodes
• Metal–Metal Ion Electrodes
• Alloyed Electrodes
• Metal–Insoluble Salt or Oxide Electrodes
  • Metal–Insoluble Salt Electrodes
  • Metal–Insoluble Oxide Electrodes
• Electrodes of Oxidation–Reduction
• Selective Ion Electrodes
• Glass Electrodes
• Copper Ion-Selective Electrodes

     D. Electrochemical and Corrosion Cells

• Chemical Cells
  • Chemical Cell with Transport
  • Chemical Cell Without Transport
• Concentration Cells
  • Concentration Cell with Difference of Activity at the Electrode and Electrolyte
  • Junction Potential
• Solvent Corrosion Cells
  • Cathodic Oxidoreduction Reaction
  • Displacement Cell
  • Complexing Agent Cells
  • Stray Current Corrosion Cell
• Temperature Differential Cells
• Overlapping of Different Corrosion Cells

     E. Chemical and Electrochemical Corrosion

• Definition and Description of Corrosion
• Electrochemical and Chemical Reactions
  • Electrochemical Corrosion
  • Film-Free Chemical Interactions
• References

2. Aqueous and High-Temperature Corrosion

• Overview
• Atmospheric Media
  • Description
  • Types of Corrosion
  • Atmospheric Contaminants
  • Corrosion Prevention and Protection
• Aqueous Environments
• Organic Solvent Properties
• Underground Media
• Water Media Properties
  • Water Composition
  • The Oxidizing Power of Solution
  • Scale Formation and Water Indexes
• Corrosion at High Temperatures
  • Description
  • The Pilling–Bedworth Ratio (PBR)
  • Kinetics of Formation
  • Corrosion Behaviors of Some Alloys at Elevated Temperatures
• References

3. Active and Passive Behaviors of Aluminum and Magnesium and Their Alloys

• Overview
• Potential–pH Diagrams of Aluminum and Magnesium
  • Construction of Pourbaix Diagrams
  • Predictions of E–pH Diagrams
  • Utility and Limits of Pourbaix Diagrams
• Active Behavior and Overpotentials
  • Active Behavior and Polarization
  • Overpotentials
• Passive Behavior
  • The Phenomenon of Passivation
  • Passive Layers and Their Formation
  • Breakdown of Passivity
  • Electrochemical and Physical Techniques for Passive Film Studies
• Active and Passive Behaviors of Aluminum and Its Alloys
  • The E–pH Diagram of Aluminum
  • Active and Passive Behaviors
  • Pitting Corrosion of Aluminum Alloy 5086
• Active and Passive Behaviors of Magnesium and Its Alloys
  • E–pH Diagram of Magnesium
  • Passive Mg Layers (Films)
  • Passive Properties and Stability
  • Temperature Influence in Aqueous Media
  • Atmospheric and HighTemperature Oxidation
• References

Part Two – Performance and Corrosion Forms of Aluminum and Its Alloys

4. Properties, Use, and Performance of Aluminum and Its Alloys

• Overview

     A. Properties of Aluminum

• Physical and General Properties of Aluminum
• Cast Aluminum Alloys
  • Designation of Cast Aluminum Alloys and Ingots
  • Alloying Elements
  • Cast Alloys Series
• Wrought Aluminum Alloys
  • Designation of Wrought Aluminum Alloys
  • Alloying Elements
  • Wrought Aluminum Alloys Series
  • Description of the Wrought Alloys Series
• Aluminum Powders and Aluminum Matrix Composites
  • Aluminum Powders
  • Rapid Solidification Processing
  • Aluminum Matrix Composites and P/M- MMCs
  • Al MMC Particles and Formation

     B. Use of Aluminum and Aluminum Alloys

• Use of Cast Aluminum Alloys
  • Standard General Purpose Aluminum Alloys
  • Some Specific Uses
• Use of Wrought Aluminum Alloys
  • Aerospace Applications
  • Automotive Sheet and Structural Alloys
  • Shipping
  • Building and Construction
  • Packaging
  • Electrical Conductor Alloys

     C. Aluminum Performance

• Resistance of Aluminum Alloys to Atmospheric Corrosion
• Factors Affecting Atmospheric Corrosion of Aluminum Alloys
• Water Corrosion
• Seawater
• Soil Corrosion
• Some Aggressive Media: Acid and Alkaline Solutions
• Acids
• Alkalis
• Dry and Aqueous Organic Compounds
• Gases
• Mercury
• Corrosion Performance of Alloys
  • Performance of the Cast Series
  • Performance of the Wrought Series
• Aluminum High-Temperature Corrosion
• References

5. General, Galvanic, and Localized Corrosion of Aluminum and Its Alloys

• Overview

     A. General Corrosion

• General Considerations
• Description
• Mechanisms
• Prevention
  • Design Considerations
  • Surface Pretreatment
  • Corrosion Control
  • Aluminum Alloys and Resistance to General Corrosion

     B. Galvanic Corrosion

• General Considerations
• Galvanic Series of Aluminum Alloys
• Mechanisms
  • Cu–Al Galvanic Cell
  • Mg–Al Galvanic Cell
  • Galvanic Effect of a Coating
• Deposition Corrosion
• Stray Current Corrosion
• Prevention
• Basic Study of Al–Cu Galvanic Corrosion Cell

     C. Localized Corrosion

• Pitting Corrosion
  • Occurrence and Morphology
  • Kinetics
  • The Pitting Potential
  • Mechanisms
  • Possible Stages of Pitting
  • Prevention of Pitting Corrosion
  • Corrosion Resistance of Aluminum Cathodes
• Crevice Corrosion
  • General Considerations and Description
  • Poultice Corrosion
  • Mechanisms
  • Water Stains on AA3xxx
• Filiform Corrosion
  • General Considerations
  • Aluminum Alloys and Filiform Corrosion
  • Kinetics, Mechanism, and Prevention
  • Filiform Occurrence
• References

6. Metallurgically and Microbiologically Influenced Corrosion of Aluminum and Its Alloys

• Overview

     A. Metallurgically Influenced Corrosion (METIC)

• Fundamentals of METIC
  • Influence of Metallurgical and Mechanical Treatments
• Types of Metallurgically Influenced Corrosion
  • Dealloying (Dealuminification)
  • Intergranular Corrosion
  • Exfoliation
• Joining and Welding
  • Corrosion Resistance of Brazed, Soldered, and Bonded Joints
  • Welding Fundamentals
  • Welding Influence on Behavior of Aluminum Alloys
  • Frequent Corrosion Types of Welded Aluminum Alloys
  • Corrosion Resistance of Wrought and Cast Al Alloys
• Metal Matrix Composites for Nuclear Dry Waste Storage

     B. Microbiologically Influenced Corrosion: The Basics

• Microorganisms
  • Bacteria (Prokaryotes)
  • Fungi and Yeast (Eukaryotes)
  • Algae (Eukaryotes)
  • Lichens
• Natural and Artificial Media
  • Air Media
  • Aqueous Media
  • Soils
• Anaerobic and Aerobic Bacteria in Action
  • Anaerobic Bacteria
  • Aerobic Bacteria
  • Co-action of Anaerobic and Aerobic Bacteria
• MIC of Aluminum and Aluminum Alloys
  • Fungi and Bacteria (Space)
  • Geotrichum (Tropical Atmosphere)
  • Cyanobacteria and Algae (Polluted Freshwater)
  • Rod-Shaped Bacteria and Algae (Polluted Seawater)
  • SRB (Industrial and Seawater)
  • Hormoconis resinae (Kerosene)
• Mechanisms of MIC and Inhibition
  • Corrosion Mechanisms
  • Influence of Biofilms on Passive Behavior of Aluminum
  • Corrosion Inhibition by Microorganisms
• MIC Prevention and Control
• References

7. Mechanically Assisted Corrosion of Aluminum and Its Alloys

• Overview

     A. Erosion Corrosion

• Impingement with Liquid-Containing Solid Particles
• Corrosion by Cavitation
• Water Drop Impingement Corrosion
• Fretting Corrosion
• Fretting Fatigue Corrosion
• Prevention of Erosion Corrosion

     B. Corrosion Fatigue

• General Considerations and Morphology
• Parameters
  • Environmental Considerations
  • Cyclic Stresses
  • Material Factors
• Mechanisms of Corrosion Fatigue
• Corrosion Fatigue of Aluminum Alloys
  • Corrosion Fatigue of AA7017- T651
  • Corrosion Fatigue of AA7075- T6
  • Corrosion Fatigue of Al–Mg–Si Compared to Al–Mg Alloys
  • Modeling of the Propagation of Fatigue Cracks in Aluminum Alloys
• Prevention of Corrosion Fatigue
• References

8. Environmentally Induced Cracking of Aluminum and Its Alloys

• Overview
• Introduction and Definition of SCC
• Key Parameters
  • Stress
  • Environment
• SCC Parameters of Aluminum Alloys
  • Influence of Stress
  • Role of Environment
• SCC Mechanisms
  • Overlapping of Cracking Phenomena
  • Significance of the Magnitude of Strain Rates
  • Cracking Initiation and Propagation
• SCC of Aluminum Alloys
  • SCC Resistance of Aluminum Alloys
  • Influence of Heat Treatments on Corrosion Forms
• SCC of Welded Aluminum Alloys
  • Galvanic Corrosion and SCC of Welded Assemblies
  • SCC Knife-Line Attack
  • Localized Corrosion and SCC of LBW AA6013
  • Mechanically Influenced Corrosion and SCC of Welds
  • Corrosion Fatigue of Friction Stir Welding White Zone
  • SCC of Friction Stir Welded 7075 and 6056 Alloys
  • SCC of FSW of 7075-T651 and 7050-T451 Alloys
• Prevention of SCC
  • Design and Stresses
  • Environmental Considerations
  • Metallurgical Considerations
  • Surface Modification
  • Prevention of Hydrogen Damage
• References

Part Three – Performance and Corrosion Forms of Magnesium and Its Alloys

9. Properties, Use, and Performance of Magnesium and Its Alloys

• Overview

     A. Properties of Magnesium Alloys

• Physical and General Properties of Magnesium
• Properties of Cast Magnesium Alloys
  • Designation of Cast Magnesium Alloys
  • Alloying Elements
  • Cast Magnesium Alloys Series
• Properties of Wrought Magnesium Alloys
• Magnesium Powder
• Magnesium Composites
• Particles Reinforcing Magnesium Alloy Matrix
  • SiC
  • Mg2Si
  • Nanosized Alumina Particulates

     B. Use of Magnesium and Magnesium Alloys

• Applications of Cast Magnesium Alloys
  • Automotive and Aerospace Applications
  • Application as Refractory Material
  • Other Uses
• Applications of Wrought Magnesium Alloys

     C. Magnesium Performance

• Resistance of Magnesium Alloys to Atmospheric Corrosion
• Factors Affecting Atmospheric Corrosion of Magnesium Alloys: Effect of Sulfites and Sulfates
• Water Corrosion
• Salt Solutions
• Acid and Alkaline Solutions
• Aqueous Organic Compounds
• Dry Organic Compounds
• Gases at Ambient Temperature Up to About 100 ⁰C
• Magnesium High-Temperature Corrosion
• References

10. General, Galvanic, and Localized Corrosion of Magnesium and Its Alloys

• Overview

     A. General Corrosion

• Corrosion Resistance of Passive Magnesium
  • E_corr and Corrosion Rates in Natural and Aqueous Media
  • Corrosion Rate Methods of Mg–Al Alloys
  • Critical Evaluation of the Passive Properties of Magnesium Alloys
• The Negative Difference Effect (NDE)
• Kinetic Studies of General and Pitting Corrosion of Magnesium Alloys
• Electrochemical Noise Studies
• Corrosion Prevention

     B. Galvanic Corrosion

• Hydrogen Overpotentials
• Galvanic Corrosion of Pure and Alloyed Magnesium
  • Cathodic Corrosion of Aluminum
  • Cathodic Damage to Coatings
• Composite Coat for Molten Magnesium
• Metal Matrix Composite Galvanic Corrosion
• Prevention of Galvanic Corrosion
  • Joining Magnesium to Dissimilar Metal Assemblies
  • Joining Magnesium to Nonmetallic Assemblies

     C. Localized Corrosion

• Pitting Corrosion
  • The Pitting Potential Determination
  • Polarization Curves and Pitting Potential of AXJ Alloy
• Crevice Corrosion
• Filiform Corrosion
  • Initiation and Kinetics Parameters
  • Mechanism of Proppagation
• References

11. Metallurgically and Microbiologically Influenced Corrosion
    of Magnesium and Its Alloys

• Overview

     A. Metallurgically Influenced Corrosion of Magnesium Alloys

• Casting Alloys and Alloying Elements
  • Casting Alloys
  • Magnesium–Rare Earth, Magnesium–Thorium, and Magnesium–Silver Alloys
  • Alloying Elements and Tolerance Limit
• Corrosion Influenced By Metallurgical Properties
  • Galvanic Corrosion and Secondary Phases
  • Intergranular Corrosion
  • Exfoliation Corrosion
  • High-Temperature Corrosion and Creep Deformation
  • Microstructure and Corrosion Creep of Magnesium Die-Cast Alloys
  • The OCP, icorr, and Corrosion Creep
  • Corrosion Creep and Aging
  • Corrosion Creep of HighStrength AE42 and MEZ 397
• Influence of the Microstructure, Different Phases, and Welding
  • Influence of Heat Treatments
  • Effect of Rapid Solidification
  • Influence of the Microstructure of Some Mg Alloys
  • Influence of Joining and Welding
  • Cold Chamber Processes
  • Hot Chamber Processes and Corrosion Resistance of Thin Plates

     B. MIC of Magnesium and Magnesium Alloys

• Rational Degradation
  • Behavior of Sacrificial Magnesium
  • Rational Biocorrosion of Mg and Its Alloys in the Human Body
• Stress Corrosion Cracking and Implants
• Approaches to Control Biodegradation
  • Alloying
  • Surface Treatment (Anodizing)
  • Magnesium Implants and Bone Surgery
• References

12. Mechanically Assisted Corrosion of Magnesium and Its Alloys

• Overview
• Erosion Corrosion and Fretting Fatigue Corrosion
  • Erosion Corrosion
  • Fretting Fatigue Corrosion
• Corrosion Fatigue of Magnesium Alloys
  • Corrosion Fatigue of Cast Magnesium Alloys
  • Corrosion Fatigue of High-Strength Magnesium Alloys
  • Crack Propagation of Wrought Extruded Alloys
  • Welding and Corrosion Fatigue of AZ31
  • Mechanisms of Corrosion Fatigue: Initiation and Propagation
  • Prevention of Corrosion Fatigue
• References

13. Environmentally Induced Corrosion of Magnesium and Its Alloys

• Overview
• Use of Magnesium Alloys and Stress-Corrosion Cracking Failures
• Key Parameters
  • Alloy Composition and Magnesium Impurities
  • Microstructure and Crack Morphology
  • Effect of Stress
  • Effect of the Environment
• Influence of Other Forms or Types of Corrosion on SCC
  • Effect of General Corrosion
  • Bimetallic or Galvanic Corrosion
  • Pitting and Localized Corrosion
  • Welded Material and SCC
  • Environment-Enhanced Creep and SCC of Mg Alloys
• Propagation Mechanisms of Corrosion
  • Electrochemical Dissolution Models
  • Hydrogen Embrittlement
• SCC–HE of Some Magnesium Alloys
• SCC Prevention
• References

Part Four – Coating and Testing

14. Aluminum Coatings: Description and Testing

• Overview
• Inhibitors
• Metallic Coatings
  • Conventional Plating and Electroless Plating of Aluminum
  • Surface Preparation for Thermal Spraying
  • Sacrificial Protection by Aluminum Alloys
  • Aluminum Powder as a Coating
  • Cathodic Protection of Aluminum Alloys
• Conversion Coating
  • Phosphates and/or Chromates
  • Chromate–Phosphate Treatments
  • Chromate Alternatives
• Anodization
• Organic Finishing
  • Thermoplastic Coatings or Liquors
  • Converted Coating During or After Application
  • Coatings Containing Metals More Active than Aluminum
  • Electrodeposited Coatings
• Corrosion Testing of Coated Metal
  • Electrochemical Testing of Coatings
  • Conventional Testing
  • Corrosion Fatigue of Thermal Spraying of Aluminum as a Coating
  • Environmentally Assisted Cracking of Metallic Sprayed Coatings
• References

15. Magnesium Coatings: Description and Testing

• Overview
• General Approach and Surface Preparation
• Metallic and Conversion Coatings
  • Metallic Coatings
  • Chemical Conversion Surface Treatments
• Anodic Treatments
  • Anodizing Description and Approaches
  • Formation of Anodized Coatings
  • Properties and Chemical Composition
  • Some Industrial and Developing Anodizing Processes
  • Forms of Surface Corrosion: Anodized or with Conversion Treatments
• Surface Modification
  • Chemical and Physical Vapor Deposition
  • The H-Coat and Magnesium Hydrides
• Electrochemical Characterization of the Metal–Film Interface
  • OCP and Polarization Studies of the Metal–Oxide Interface
  • Impedance Measurements
• Organic Finishing and Corrosion Testing of Coated Material
  • Organic Coatings
  • Conventional Corrosion Testing of Coated Metal
• References

Part Five – Evaluation and Testing

16. Conventional and Electrochemical Methods of Investigation

• Overview
• Corrosion Testing Approaches and Methods of Investigation
  • Testing Approach
  • Categories of Corrosion Testing
  • Testing Duration
  • Testing Modes
  • Removal of Corrosion Products
• Physical and Mechanical Testing of Corroded Materials
  • Visual and Microscopic Techniques of Testing
  • Nondestructive Evaluation Techniques
  • Mechanical Testing
  • Chemical Analysis
  • Surface Chemical Analysis
  • Published Data of Performance and Corrosion Resistance
• Electrochemical Polarization Studies
  • Measurements of the Corrosion Potential
  • Potentiodynamic Methods
  • Cyclovoltammetry Techniques and Pitting
  • Potentiostatic, Galvanostatic, and Galvanodynamic Methods
• The ac Electrochemical Impedance Spectroscopy Technique
  • Introduction
  • EIS Terms and Equivalent Circuits
  • Impedance Plots
• Electrochemical Noise Measurements
  • Historical and Electrochemical Noise Definition
  • EN Generation and Data Acquisition Systems
  • Analysis of ENM Data
  • Potentiodynamic, Potentiostatic, and Galvanostatic EN Studies
• Scanning Reference Electrode Technique
• Microsystems and Wire Beam Electrode
  • Microsystems and Atomic Force Microscopy
  • Wire Beam Electrode
• References

17. Evaluation of Corrosion Forms of Aluminum and Its Alloys

• Overview
• General Corrosion of Aluminum and Its Alloys
• Galvanic Corrosion
  • General Considerations
  • Influence of the Composition and Microstructure
  • Electrochemical Testing
• Localized Corrosion of Aluminum and Its Alloys
  • Pitting Corrosion
  • Crevice Corrosion
  • Filiform Corrosion Testing of Al Alloys
• Metallurgically Influenced Corrosion
  • Intergranular Corrosion Testing
  • Exfoliation Testing
  • Joining and Testing
• MIC and Biodegradation Evaluation
• Mechanically Influenced Corrosion of Aluminum and Its Alloys
  • Erosion Corrosion Testing
  • Corrosion Fatigue Testing
• Environmentally Influenced Corrosion
  • SCC Testing Procedures of Aluminum Alloys
  • Test Specimens
  • Stressors
  • Fracture Morphology and SCC of Aluminum Alloys
• References

18. Evaluation of Corrosion Forms of Magnesium and Its Alloys

• Overview
• Testing Solutions
  • Hydroxide Solutions
  • Chloride, Sulfate, and Hydroxide Solutions
  • ASTM D1384-96 Corrosive Water
  • Buffered Solutions
• General Corrosion Form
  • Immersion Testing and Corrosion Rate
  • Salt Spray Corrosion Test
  • Some Electrochemical Methods of Investigation
• Galvanic or Bimetallic Corrosion of Magnesium and Its Alloys
• Localized Corrosion of Magnesium and Its Alloys
  • Open Circuit Potential and Pitting Corrosion Studies
  • Electrochemical Noise Measurements
  • Magnesium SRET Studies
• Metallurgically Influenced Corrosion of Magnesium and Its Alloys
• MIC and Biodegradation of Magnesium and Its Alloys
• Corrosion Fatigue
• SCC Testing and Evaluation of Magnesium Alloys
  • Static Loading of Smooth Specimens and General Considerations
  • Stresses
  • Solutions and Operational Conditions
  • Constant Extension Rate and Linearly Increasing Stress Tests
  • SCC CERT Versus LIST Techniques
• References

Part Six – Bibliography, International Units, and Abbreviations

Appendix 1. Corrosion and Prevention Books, Data, and ASTM Standards

• 1. Some Recommended Books on Corrosion
• 2. Bibliography of Corrosion Data for Performance of Materials
• 3. ASTM Standards

Appendix 2. International Units and Some Equations

• 1. Constants, Conventions, and Key Equations
• 1.1. Constants
• 1.2. Conventions
• 1.3. Key Equations
• 2. Examples of Reference Electrodes and Metallic and Ionic Reduction Reactions
• 3. Electrochemical Cells and Their Potentials
• 4. Standard Electrode Potential of Cations (T¼25 C)
• 5. The Periodic Table

Appendix 3. Abbreviations and Symbols

Index

PREVIEW