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Front Cover
Corrosion of Aluminium
Corrosion of Aluminium
Copyright
Dedication
Contents
Foreword
Foreword to the original edition
Preface
Introductory remarks
Reference
A
A.1 - Historical reviews
1.1 Chemically produced aluminium
1.2 Electrochemically produced aluminium
References
A.2 - Physical properties of aluminium
A.3 - The advantages of aluminium
3.1 The hymn of the cannonball
3.2 Lightness
3.3 Thermal conductivity
3.4 Electrical conductivity
3.5 Resistance to corrosion
3.6 Suitability for surface treatments
3.7 The diversity of aluminium alloys
3.8 The diversity of semi-products
3.9 The functionality of castings and extrusions functionality
3.10 Ease of use
3.11 Recycling
References
A.4 - Aluminium alloy series
4.1 Alloy series
4.2 Alloying elements
4.3 Additives
4.4 Impurities
4.5 Designation of aluminium alloys
A.5 - Cast aluminium alloys
5.1 Principal casting alloys
5.1.1 Unalloyed aluminium, 1xx.x series
5.1.2 Aluminium-copper, 2xx.x series
5.1.3 Aluminium-silicon, 4xx.x series
5.1.4 Aluminium-magnesium, 5xx.x series
5.2 Methods of elaboration
5.3 Heat treatments
A.6 - Wrought aluminium alloys
6.1 Strain-hardenable alloys
6.1.1 Strain-hardenable alloys
6.1.2 Softening by thermal annealing
6.1.3 Concept of metallurgical tempers
6.2 Age-hardenable alloys
6.2.1 The principle of age hardening
6.2.1.1 Solution heat treatment
6.2.1.2 Quenching
6.2.1.3 Natural ageing
6.2.1.4 Artificial ageing
6.2.2 Intermediate (soft) annealing
6.2.3 Designation of metallurgical tempers
Reference
A.7 - Selection criteria
7.1 General remarks
7.2 Selecting an alloy
7.2.1 Selecting an alloy series
7.2.2 Selecting a metallurgical temper
7.2.2.1 Strain-hardenable alloys.
7.2.2.2 Age-hardenable alloys
7.3 Principal applications of aluminium and its alloys
B
B.1 - The corrosion of aluminium
1.1 Short historical introduction
1.2 Corrosion: an irreversible phenomenon
1.3 Electrochemical basis for metal corrosion
1.4 Electrical double layer
1.5 Electrochemical basis of metal corrosion
1.6 Electrochemical reactions of aluminium corrosion
1.7 Role of oxygen
1.8 Aluminium as a passive metal
1.9 Aluminium passivity and pH
1.9.1 Oxide film stability
1.9.2 Dissolution rate
1.9.3 Aluminium polarization curves
1.10 Electrochemical equilibrium - Pourbaix diagrams
1.10.1 Significance of E-pH diagrams
1.10.2 Impossible immunity of aluminium
1.10.3 Experimental E-pH diagram of alloy AA5086
References
B.2 - The notion of potential
2.1 The standard potential of a metal
2.1.1 Measurement of standard potentials
2.1.2 Galvanic series of standard potentials
2.1.3 Meaning of standard potential
2.1.4 The aluminium standard potential
2.2 Corrosion potentials
2.3 Pitting potential
2.3.1 The measurement of Epit
2.3.2 Influence of chloride ion concentration
2.3.3 Influence of pH
2.3.4 Influence of temperature
2.3.5 The significance of the aluminium pitting potential
2.4 The protection potential of aluminium
2.5 The corrosion potential or open circuit potential
2.5.1 Definition of the open circuit potential
2.5.2 Properties of the open circuit potential
2.6 Mesurement of open circuit potentials
2.6.1 Selection of a standard solution
2.6.2 Reference electrodes
2.7 Parameters for measuring corrosion potentials
2.7.1 Influence of immersion time
2.7.2 Influence of temperature
2.7.3 Influence of aeration
2.7.4 Influence of stirring
2.7.5 Influence of the measured area.
2.8 Galvanic series of open circuit potentials
2.9 Meaning of open circuit potentials
2.10 The open circuit potential of aluminium
2.10.1 Open circuit potential of aluminium alloys
2.10.2 Influence of temper on the open circuit potential
2.11 The Volta potential
References
B.3 - The oxide film and passivity of aluminium
3.1 The protective role of oxide films
3.2 The mechanism of formation of oxide films on aluminium
3.3 Parameters affecting the formation of oxide films on aluminium
3.3.1 Influence of oxygen pressure
3.3.2 Influence of temperature
3.3.3 Influence of the surface state
3.3.4 Influence of alloying element additions
3.3.4.1 Magnesium
3.3.4.2 Copper
3.3.4.3 Zinc
3.4 Rate of reconstitution of the oxide film
3.5 Structure of the oxide film
3.6 Low-temperature oxide film growth
3.6.1 Growth of the oxide film in air
3.6.2 Growth of the oxide film in water
3.7 Oxide film properties
3.8 Influence of pH on aluminium passivation
3.9 Note
References
B.4 - Disturbed surface layers on wrought sheet
4.1 Formation of the disturbed surface layer on wrought sheet
4.2 Consequences on the properties of the sheet
4.3 Structure of the disturbed surface layer
4.4 Activation and susceptibility to corrosion of the disturbed surface layer
4.4.1 Influence of heat treatments
4.4.2 Influence of alloy composition
4.5 Effect of grinding and machining
4.6 Elimination of the disturbed surface layer
References
B.5 - Influence of alloy composition
5.1 The influence of intermetallics on the corrosion resistance of aluminium alloys
5.1.1 Formation of intermetallic compounds
5.1.2 Types of intermetallic compounds
5.1.3 The main intermetallic compounds occurring in aluminium alloys
5.1.4 The role of intermetallic compounds.
5.1.5 Electrochemical properties of intermetallics
5.1.6 The mode of action of intermetallics
5.2 The influence of the chemical composition on the corrosion resistance
5.3 Influence of iron
5.4 Influence of silicon
5.5 Influence of copper
5.5.1 The role of AlCu intermetallics
5.5.2 The S-phase
5.5.3 Dealloying of the S-phase
5.6 Influence of manganese
5.7 Influence of magnesium
5.7.1 The Al3Mg2 intermetallic (β-phase)
5.7.2 The Mg2Si intermetallic
5.7.3 The MgZn2 intermetallic
5.8 Influence of cadmium
5.9 Influence of chromium
5.10 Influence of lithium
5.11 Influence of mercury
5.12 Influence of lead
5.13 Influence of rare earth elements
5.14 Influence of scandium
5.15 Influence of strontium
5.16 Influence of tantalum
5.17 Influence of tin
5.18 Influence of titanium
5.19 Influence of zinc
5.20 Influence of zirconium
References
C
C.1 - Uniform corrosion
1.1 Mechanism of uniform corrosion
1.2 Parameters of uniform corrosion
1.3 Measurement of the rate of corrosion
1.4 Mass loss conversions
References
C.2 - Pitting corrosion
2.1 Mechanism of pitting corrosion
2.1.1 Pitting initiation
2.1.2 Passivity breakdown
2.1.3 Propagation of pitting
2.1.4 Reduction of pitting propagation
2.1.5 Stages in the development of pitting
2.2 Role of intermetallics
2.3 Rate of development of pitting
2.4 Characterization of pitting corrosion
2.4.1 Pitting density
2.4.2 Pitting depth
2.4.3 Probability of pitting
2.5 Sensitivity of aluminium alloys to pitting corrosion
References
C.3 - Intergranular corrosion
3.1 Role of grain boundaries
3.1.1 Grain boundaries
3.1.2 Properties of grain boundaries
3.1.3 The angle of disorientation between grains
3.2 The mechanism of intergranular corrosion.
3.2.1 Intergranular corrosion propagation modes
3.2.2 Development of an anodic depleted zone (precipitate-free zone
PFZ)
3.2.3 Precipitation of an anodic phase
3.3 Anisotropy of intergranular corrosion
3.4 Influence of load constraints
3.5 Influence of heat treatment conditions
3.6 Evaluation of intergranular corrosion
References
C.4 - Exfoliation corrosion
4.1 Mechanism of exfoliation corrosion
4.1.1 Intergranular corrosion
4.1.2 Hydrogen embrittlement
4.1.3 Mechanical effect
4.1.4 Mechanisms of intergranular dissolution-induced damage and intergranular fracture-induced damage
4.2 Conditions giving rise to exfoliation corrosion
4.2.1 Influence of the microstructure
4.2.2 Thickness of semi-finished products
4.2.3 Cutting
4.2.4 Influence of humidity
4.2.5 Influence of heat treatments
4.3 Assessment of exfoliation corrosion
References
C.5 - Stress corrosion cracking
5.1 Historical notes
5.2 Definition of stress corrosion cracking
5.3 Mechanism of stress corrosion
5.4 Electrochemical theory of propagation
5.4.1 Mode of propagation
5.4.2 Reactions occurring at the base of cracks
5.4.3 Intergranular corrosion and stress corrosion
5.4.4 Limitations of electrochemical theory
5.5 Hydrogen embrittlement
5.5.1 Proof of hydrogen embrittlement in aluminium
5.5.2 Gruhl's demonstration
5.5.3 Cathodic charging
5.5.4 Penetration of hydrogen in aluminium
5.5.5 Moisture as a source of hydrogen
5.5.6 Hydrogen diffusion
5.5.7 Hydrogen interactions
5.5.8 Mode of crack propagation
5.5.9 Sensitivity of Al-Zn-Mg(Cu) 7XXX series alloys
5.6 Possible synergy between anodic dissolution and hydrogen embrittlement
5.7 Rate of crack propagation under stress corrosion
5.8 Stress corrosion parameters
5.9 Prevention of stress corrosion.
5.10 Measurement of stress corrosion sensitivity.
Corrosion of Aluminium
Corrosion of Aluminium
Copyright
Dedication
Contents
Foreword
Foreword to the original edition
Preface
Introductory remarks
Reference
A
A.1 - Historical reviews
1.1 Chemically produced aluminium
1.2 Electrochemically produced aluminium
References
A.2 - Physical properties of aluminium
A.3 - The advantages of aluminium
3.1 The hymn of the cannonball
3.2 Lightness
3.3 Thermal conductivity
3.4 Electrical conductivity
3.5 Resistance to corrosion
3.6 Suitability for surface treatments
3.7 The diversity of aluminium alloys
3.8 The diversity of semi-products
3.9 The functionality of castings and extrusions functionality
3.10 Ease of use
3.11 Recycling
References
A.4 - Aluminium alloy series
4.1 Alloy series
4.2 Alloying elements
4.3 Additives
4.4 Impurities
4.5 Designation of aluminium alloys
A.5 - Cast aluminium alloys
5.1 Principal casting alloys
5.1.1 Unalloyed aluminium, 1xx.x series
5.1.2 Aluminium-copper, 2xx.x series
5.1.3 Aluminium-silicon, 4xx.x series
5.1.4 Aluminium-magnesium, 5xx.x series
5.2 Methods of elaboration
5.3 Heat treatments
A.6 - Wrought aluminium alloys
6.1 Strain-hardenable alloys
6.1.1 Strain-hardenable alloys
6.1.2 Softening by thermal annealing
6.1.3 Concept of metallurgical tempers
6.2 Age-hardenable alloys
6.2.1 The principle of age hardening
6.2.1.1 Solution heat treatment
6.2.1.2 Quenching
6.2.1.3 Natural ageing
6.2.1.4 Artificial ageing
6.2.2 Intermediate (soft) annealing
6.2.3 Designation of metallurgical tempers
Reference
A.7 - Selection criteria
7.1 General remarks
7.2 Selecting an alloy
7.2.1 Selecting an alloy series
7.2.2 Selecting a metallurgical temper
7.2.2.1 Strain-hardenable alloys.
7.2.2.2 Age-hardenable alloys
7.3 Principal applications of aluminium and its alloys
B
B.1 - The corrosion of aluminium
1.1 Short historical introduction
1.2 Corrosion: an irreversible phenomenon
1.3 Electrochemical basis for metal corrosion
1.4 Electrical double layer
1.5 Electrochemical basis of metal corrosion
1.6 Electrochemical reactions of aluminium corrosion
1.7 Role of oxygen
1.8 Aluminium as a passive metal
1.9 Aluminium passivity and pH
1.9.1 Oxide film stability
1.9.2 Dissolution rate
1.9.3 Aluminium polarization curves
1.10 Electrochemical equilibrium - Pourbaix diagrams
1.10.1 Significance of E-pH diagrams
1.10.2 Impossible immunity of aluminium
1.10.3 Experimental E-pH diagram of alloy AA5086
References
B.2 - The notion of potential
2.1 The standard potential of a metal
2.1.1 Measurement of standard potentials
2.1.2 Galvanic series of standard potentials
2.1.3 Meaning of standard potential
2.1.4 The aluminium standard potential
2.2 Corrosion potentials
2.3 Pitting potential
2.3.1 The measurement of Epit
2.3.2 Influence of chloride ion concentration
2.3.3 Influence of pH
2.3.4 Influence of temperature
2.3.5 The significance of the aluminium pitting potential
2.4 The protection potential of aluminium
2.5 The corrosion potential or open circuit potential
2.5.1 Definition of the open circuit potential
2.5.2 Properties of the open circuit potential
2.6 Mesurement of open circuit potentials
2.6.1 Selection of a standard solution
2.6.2 Reference electrodes
2.7 Parameters for measuring corrosion potentials
2.7.1 Influence of immersion time
2.7.2 Influence of temperature
2.7.3 Influence of aeration
2.7.4 Influence of stirring
2.7.5 Influence of the measured area.
2.8 Galvanic series of open circuit potentials
2.9 Meaning of open circuit potentials
2.10 The open circuit potential of aluminium
2.10.1 Open circuit potential of aluminium alloys
2.10.2 Influence of temper on the open circuit potential
2.11 The Volta potential
References
B.3 - The oxide film and passivity of aluminium
3.1 The protective role of oxide films
3.2 The mechanism of formation of oxide films on aluminium
3.3 Parameters affecting the formation of oxide films on aluminium
3.3.1 Influence of oxygen pressure
3.3.2 Influence of temperature
3.3.3 Influence of the surface state
3.3.4 Influence of alloying element additions
3.3.4.1 Magnesium
3.3.4.2 Copper
3.3.4.3 Zinc
3.4 Rate of reconstitution of the oxide film
3.5 Structure of the oxide film
3.6 Low-temperature oxide film growth
3.6.1 Growth of the oxide film in air
3.6.2 Growth of the oxide film in water
3.7 Oxide film properties
3.8 Influence of pH on aluminium passivation
3.9 Note
References
B.4 - Disturbed surface layers on wrought sheet
4.1 Formation of the disturbed surface layer on wrought sheet
4.2 Consequences on the properties of the sheet
4.3 Structure of the disturbed surface layer
4.4 Activation and susceptibility to corrosion of the disturbed surface layer
4.4.1 Influence of heat treatments
4.4.2 Influence of alloy composition
4.5 Effect of grinding and machining
4.6 Elimination of the disturbed surface layer
References
B.5 - Influence of alloy composition
5.1 The influence of intermetallics on the corrosion resistance of aluminium alloys
5.1.1 Formation of intermetallic compounds
5.1.2 Types of intermetallic compounds
5.1.3 The main intermetallic compounds occurring in aluminium alloys
5.1.4 The role of intermetallic compounds.
5.1.5 Electrochemical properties of intermetallics
5.1.6 The mode of action of intermetallics
5.2 The influence of the chemical composition on the corrosion resistance
5.3 Influence of iron
5.4 Influence of silicon
5.5 Influence of copper
5.5.1 The role of AlCu intermetallics
5.5.2 The S-phase
5.5.3 Dealloying of the S-phase
5.6 Influence of manganese
5.7 Influence of magnesium
5.7.1 The Al3Mg2 intermetallic (β-phase)
5.7.2 The Mg2Si intermetallic
5.7.3 The MgZn2 intermetallic
5.8 Influence of cadmium
5.9 Influence of chromium
5.10 Influence of lithium
5.11 Influence of mercury
5.12 Influence of lead
5.13 Influence of rare earth elements
5.14 Influence of scandium
5.15 Influence of strontium
5.16 Influence of tantalum
5.17 Influence of tin
5.18 Influence of titanium
5.19 Influence of zinc
5.20 Influence of zirconium
References
C
C.1 - Uniform corrosion
1.1 Mechanism of uniform corrosion
1.2 Parameters of uniform corrosion
1.3 Measurement of the rate of corrosion
1.4 Mass loss conversions
References
C.2 - Pitting corrosion
2.1 Mechanism of pitting corrosion
2.1.1 Pitting initiation
2.1.2 Passivity breakdown
2.1.3 Propagation of pitting
2.1.4 Reduction of pitting propagation
2.1.5 Stages in the development of pitting
2.2 Role of intermetallics
2.3 Rate of development of pitting
2.4 Characterization of pitting corrosion
2.4.1 Pitting density
2.4.2 Pitting depth
2.4.3 Probability of pitting
2.5 Sensitivity of aluminium alloys to pitting corrosion
References
C.3 - Intergranular corrosion
3.1 Role of grain boundaries
3.1.1 Grain boundaries
3.1.2 Properties of grain boundaries
3.1.3 The angle of disorientation between grains
3.2 The mechanism of intergranular corrosion.
3.2.1 Intergranular corrosion propagation modes
3.2.2 Development of an anodic depleted zone (precipitate-free zone
PFZ)
3.2.3 Precipitation of an anodic phase
3.3 Anisotropy of intergranular corrosion
3.4 Influence of load constraints
3.5 Influence of heat treatment conditions
3.6 Evaluation of intergranular corrosion
References
C.4 - Exfoliation corrosion
4.1 Mechanism of exfoliation corrosion
4.1.1 Intergranular corrosion
4.1.2 Hydrogen embrittlement
4.1.3 Mechanical effect
4.1.4 Mechanisms of intergranular dissolution-induced damage and intergranular fracture-induced damage
4.2 Conditions giving rise to exfoliation corrosion
4.2.1 Influence of the microstructure
4.2.2 Thickness of semi-finished products
4.2.3 Cutting
4.2.4 Influence of humidity
4.2.5 Influence of heat treatments
4.3 Assessment of exfoliation corrosion
References
C.5 - Stress corrosion cracking
5.1 Historical notes
5.2 Definition of stress corrosion cracking
5.3 Mechanism of stress corrosion
5.4 Electrochemical theory of propagation
5.4.1 Mode of propagation
5.4.2 Reactions occurring at the base of cracks
5.4.3 Intergranular corrosion and stress corrosion
5.4.4 Limitations of electrochemical theory
5.5 Hydrogen embrittlement
5.5.1 Proof of hydrogen embrittlement in aluminium
5.5.2 Gruhl's demonstration
5.5.3 Cathodic charging
5.5.4 Penetration of hydrogen in aluminium
5.5.5 Moisture as a source of hydrogen
5.5.6 Hydrogen diffusion
5.5.7 Hydrogen interactions
5.5.8 Mode of crack propagation
5.5.9 Sensitivity of Al-Zn-Mg(Cu) 7XXX series alloys
5.6 Possible synergy between anodic dissolution and hydrogen embrittlement
5.7 Rate of crack propagation under stress corrosion
5.8 Stress corrosion parameters
5.9 Prevention of stress corrosion.
5.10 Measurement of stress corrosion sensitivity.