Marine Corrosion and Cathodic Protection

Cover
Half Title
Title Page
Copyright Page
Dedication
Table of Contents
Preface
Acknowledgements
Author
Units, abbreviations and symbols
Cathodic protection codes
1 The marine corrosion of steel
	1.1 The corrosion of steel in seawater
		1.1.1 How much do we know?
		1.1.2 Why does steel corrode?
		1.1.3 How does corrosion happen?
			1.1.3.1 A definition
			1.1.3.2 A school corrosion experiment
			1.1.3.3 Some electrochemistry
			1.1.3.4 Aerated seawater
			1.1.3.5 Deaerated seawater
		1.1.4 What doesn’t the basic science tell us?
	1.2 Corrosion rates
		1.2.1 Laboratory tests
			1.2.1.1 Weight loss tests
			1.2.1.2 The importance of the “Blank” weight loss measurements
			1.2.1.3 Limitations of laboratory testing
		1.2.2 Seawater immersion tests
			1.2.2.1 Effect of temperature
			1.2.2.2 Effect of water depth
		1.2.3 Information from existing structures
			1.2.3.1 Shipwrecks
			1.2.3.2 Harbour piling
			1.2.3.3 Seabed burial
			1.2.3.4 Intertidal and splash zones
		1.2.4 How do we use corrosion rate information?
	1.3 The microbiological dimension
		1.3.1 Clean seawater
		1.3.2 Slightly polluted seawater
		1.3.3 Heavily polluted seawater and sediments
			1.3.3.1 Sulfate reducing micro-organisms
			1.3.3.2 MIC mechanisms
			1.3.3.3 MIC morphology and rates
	1.4 The forms of corrosion
		1.4.1 General corrosion
		1.4.2 Galvanic corrosion
			1.4.2.1 Classic example
			1.4.2.2 Why does it happen?
			1.4.2.3 What are the risk factors?
		1.4.3 Pitting
		1.4.4 Crevice corrosion
		1.4.5 Fatigue and corrosion fatigue
		1.4.6 Other forms of corrosion
	References
2 Cathodic protection basics
	2.1 A theoretical experiment
		2.1.1 Removing electrons
		2.1.2 Adding electrons
	2.2 A simple model
		2.2.1 How does cathodic protection work?
		2.2.2 Implementation
	2.3 The two views of current flow
	2.4 Potential
		2.4.1 What do we mean by “Potential”?
		2.4.2 How do we measure the potential?
			2.4.2.1 The problem
			2.4.2.2 The solution
		2.4.3 Potential measurement
		2.4.4 What is the potential needed for protection?
	2.5 Current
		2.5.1 Bare steel
		2.5.2 Coated steel
	2.6 Power sources for CP
		2.6.1 Davy’s work
		2.6.2 Sacrificial anodes
		2.6.3 Impressed current
		2.6.4 Sacrificial anodes versus impressed current
			2.6.4.1 Sacrificial anodes: advantages
			2.6.4.2 Sacrificial anodes: disadvantages
			2.6.4.3 Impressed current: advantages
			2.6.4.4 Impressed current: disadvantages
			2.6.4.5 Selecting between sacrificial anodes and ICCP
		2.6.5 Hybrid systems
	2.7 What does CP achieve?
	2.8 Where do we go from here?
	References
3 Designing according to the codes
	3.1 Do we need CP?
	3.2 Who does the CP design?
		3.2.1 In the land of the blind
		3.2.2 Who is the “Expert”?
		3.2.3 Certification of competence
			3.2.3.1 Is it needed?
			3.2.3.2 NACE
			3.2.3.3 ISO 15257
	3.3 The basis of design
		3.3.1 System life
		3.3.2 Environmental parameters
		3.3.3 Coating
		3.3.4 Sacrificial versus impressed current?
		3.3.5 Which codes?
		3.3.6 Cathode parameters
			3.3.6.1 Protection potential
			3.3.6.2 The protection current density
		3.3.7 Anode parameters
			3.3.7.1 General
			3.3.7.2 Operating potential
			3.3.7.3 Charge availability
			3.3.7.4 Utilisation factor
	3.4 The design process
		3.4.1 Overview
		3.4.2 Calculating the cathodic current demand
			3.4.2.1 Interfaces
			3.4.2.2 Uncoated zones
			3.4.2.3 Coated zones
			3.4.2.4 Additional current demands
		3.4.3 Minimum anode mass
		3.4.4 Anode output
			3.4.4.1 General
			3.4.4.2 Estimating anode resistance
		3.4.5 Anode optimisation
	3.5 Example calculations
		3.5.1 Case 1 – uncoated structure
			3.5.1.1 Life
			3.5.1.2 Structure and area
			3.5.1.3 Current densities
			3.5.1.4 Current demand
			3.5.1.5 Minimum anode weight
			3.5.1.6 Anode selection
		3.5.2 Case 2 – coated structure
			3.5.2.1 Scope of CP design
			3.5.2.2 Design parameters
			3.5.2.3 Calculations
	3.6 Anode locations
	3.7 Anode manufacture and installation
	3.8 Limitations of the codes
		3.8.1 Can we use other codes?
		3.8.2 What if the codes gets it wrong?
		3.8.3 Where the codes are silent
4 Thermodynamics
	4.1 Introduction
		4.1.1 In the chemistry laboratory
		4.1.2 In the real world
	4.2 The science of thermodynamics
		4.2.1 Background
		4.2.2 Heat and mechanical energy
			4.2.2.1 Parameters
			4.2.2.2 The laws
		4.2.3 Chemical thermodynamics
		4.2.4 Application to corrosion
	4.3 Electrode potential
		4.3.1 The reversible electrode
		4.3.2 The Nernst equation
	4.4 E – pH diagrams
		4.4.1 The hydrogen electrode
		4.4.2 The oxygen electrode
		4.4.3 The metal and its corrosion products
		4.4.4 The metal-water system
			4.4.4.1 Zinc
			4.4.4.2 Copper
			4.4.4.3 Gold
			4.4.4.4 Iron
		4.4.5 Limitations of E–pH diagrams
			4.4.5.1 Pure metals
			4.4.5.2 Pure water
			4.4.5.3 Thermodynamic basis
	4.5 CP and thermodynamics
		4.5.1 Immunity
		4.5.2 Passivity
	References
5 Electrode kinetics
	5.1 Reversible electrodes
	5.2 Electrochemical experiments
		5.2.1 Some terminology
			5.2.1.1 Electrodes, electrolytes, anodes, cathodes and half-cells
			5.2.1.2 Potential
			5.2.1.3 Polarisation
			5.2.1.4 Overpotential and overvoltage
		5.2.2 Galvanostatic polarisation
		5.2.3 Potentiostatic polarisation
			5.2.3.1 The potentiostat
			5.2.3.2 Plotting polarisation curves
	5.3 Obtaining polarisation curves
		5.3.1 The experiments
		5.3.2 Tafel behaviour
	5.4 Analysing polarisation curves
		5.4.1 Fitting theory to data
		5.4.2 The concept of activation control
			5.4.2.1 Activation energy
		5.4.3 The Butler-Volmer equation
		5.4.4 Tafel extrapolation
			5.4.4.1 Exchange current density
		5.4.5 Polarisation curves and polarisation diagrams
		5.4.6 Departures from Tafel behaviour
	5.5 Non-reversible electrodes
		5.5.1 The mixed potential electrode
	5.6 Corrosion in seawater
		5.6.1 Oxygen-free seawater
		5.6.2 Aerated seawater
	5.7 Electrode kinetics and CP
		5.7.1 General
		5.7.2 The theory
		5.7.3 Implications for CP
	References
6 Protection potential – carbon steel
	6.1 Introduction
	6.2 What does CP need to achieve?
	6.3 What do the codes say?
		6.3.1 Aerated seawater
		6.3.2 Anaerobic environments
		6.3.3 Elevated temperature
	6.4 Aerobic environments: The –800 mV criterion
		6.4.1 Theoretical considerations
			6.4.1.1 Thermodynamics: immunity
			6.4.1.2 Thermodynamics: passivity
			6.4.1.3 Electrode kinetics
		6.4.2 Laboratory testing
			6.4.2.1 The predictions
			6.4.2.2 The results
			6.4.2.3 Evaluation of the evidence
		6.4.3 Practical experience
		6.4.4 Implications
	6.5 Anaerobic environments: The –900 mV criterion
		6.5.1 The codes
			6.5.1.1 British standards institution
			6.5.1.2 European and ISO standards
			6.5.1.3 NACE
			6.5.1.4 DNV
		6.5.2 Theoretical considerations
			6.5.2.1 Thermodynamics
			6.5.2.2 Electrode kinetics
		6.5.3 Laboratory investigations
		6.5.4 Field test data
			6.5.4.1 Onshore pipelines
			6.5.4.2 Offshore pipelines
	6.6 The effect of temperature
		6.6.1 What the codes say
		6.6.2 The theory
		6.6.3 Laboratory testing
		6.6.4 Field experience
	6.7 Excessively negative potentials
	6.8 Optimum potentials
	6.9 Potential distribution
	References
7 Current and polarisation
	7.1 What we need to know
	7.2 What the codes advise
		7.2.1 Current densities for seawater (offshore)
		7.2.2 Current densities for seawater (near-shore)
		7.2.3 Current densities for seabed burial
	7.3 The problem with the codes
	7.4 Laboratory testing: clean steel
	7.5 Calcareous deposits
		7.5.1 The chemistry
		7.5.2 Importance
			7.5.2.1 Benefits
			7.5.2.2 Possible drawbacks
		7.5.3 Laboratory investigations
			7.5.3.1 Deposit growth
			7.5.3.2 Deposit thickness
			7.5.3.3 Factors affecting deposit growth
	7.6 Site testing
		7.6.1 The limitations of the laboratory
			7.6.1.1 The microbiological dimension
			7.6.1.2 Modes of polarisation
		7.6.2 In-situ measurements
			7.6.2.1 Monitoring of existing structures
	7.7 Site experience
		7.7.1 South China Sea
		7.7.2 Middle East – operator 1
			7.7.2.1 The requirement
			7.7.2.2 Approach adopted
			7.7.2.3 Example of analysis – structure A
			7.7.2.4 Results of analyses – structures B - D
			7.7.2.5 Application to other structures
		7.7.3 Middle East – operator 2
	7.8 Deeper waters
		7.8.1 Codes
		7.8.2 The theory
		7.8.3 Laboratory testing
		7.8.4 Site testing
		7.8.5 The future
	7.9 S-curves
	7.10 The slope parameter
		7.10.1 What is it?
		7.10.2 Slope parameter versus “cookbook”
			7.10.2.1 Two perspectives
			7.10.2.2 SP0176
	7.11 The rate of polarisation
	References
8 Corrosion resistant alloys
	8.1 Why consider CRAs?
	8.2 Passivity
		8.2.1 What do we mean by passivity?
		8.2.2 Thermodynamics
		8.2.3 Electrode kinetics
		8.2.4 Passivity breakdown
			8.2.4.1 Nature of the passive film
			8.2.4.2 Pitting
			8.2.4.3 Crevice corrosion
			8.2.4.4 Stress corrosion cracking
	8.3 Stainless steels
		8.3.1 Corrosion resistance
			8.3.1.1 Passivity
			8.3.1.2 Passivity breakdown
		8.3.2 Designations
		8.3.3 Grades used offshore
			8.3.3.1 Allotropes
			8.3.3.2 Ferritic stainless steels
			8.3.3.3 Austenitic stainless steels
			8.3.3.4 Duplex stainless steels
			8.3.3.5 Superduplex
			8.3.3.6 Martensitic and supermartensitic
			8.3.3.7 Some stainless steels used subsea
	8.4 High nickel alloys
	8.5 Copper alloys
	8.6 Aluminium alloys
		8.6.1 Alloy types
		8.6.2 Corrosion threats and mitigation
	8.7 CP of corrosion resistant alloys
		8.7.1 Protection potential
			8.7.1.1 Theory and practice
			8.7.1.2 The codes
		8.7.2 Protection current densities
	8.8 Summary
	References
9 Underwater coatings
	9.1 Introduction
	9.2 Some polymer basics
		9.2.1 Polymerisation
		9.2.2 Linear polymers
			9.2.2.1 Polymers and copolymers
			9.2.2.2 Flexibility
		9.2.3 3-Dimensonal polymers
			9.2.3.1 Cross-linking
			9.2.3.2 Epoxies
		9.2.4 Elastomers
	9.3 Coatings and CP
		9.3.1 Do coatings benefit CP?
		9.3.2 Does CP benefit coatings?
		9.3.3 Coating systems
	9.4 Surface preparation
	9.5 Coating system selection
		9.5.1 Fixed steel structures
			9.5.1.1 Early paints
			9.5.1.2 Current systems
		9.5.2 Ships and floating installations
			9.5.2.1 External hulls
			9.5.2.2 Ballast spaces
		9.5.3 Submarine pipelines
			9.5.3.1 Factory applied coating systems
			9.5.3.2 Field joint coatings
	9.6 Cathodic disbondment
		9.6.1 Characteristics
		9.6.2 Corrosion threats under disbonded coatings
			9.6.2.1 Onshore pipelines
			9.6.2.2 Submarine pipelines
		9.6.3 Cathodic disbondment testing
	9.7 Coating breakdown predictions
		9.7.1 Coatings for fixed structures
		9.7.2 Ships’ coatings
		9.7.3 Pipeline coatings
	References
10 Sacrificial anodes
	10.1 What properties do we need?
		10.1.1 Potential
		10.1.2 Current
			10.1.2.1 Instantaneous output
			10.1.2.2 Capacity, consumption rate and efficiency
	10.2 Zinc alloys
		10.2.1 Background
		10.2.2 Present day alloys
		10.2.3 Limitations
			10.2.3.1 Elevated temperature
	10.3 Magnesium alloys
	10.4 Aluminium alloys
		10.4.1 The benefits
		10.4.2 Alloy research
		10.4.3 Alloy development
		10.4.4 Al-Zn-Sn and Al-Zn-Hg alloys
		10.4.5 Indium-containing anodes
			10.4.5.1 Al-Zn-In
			10.4.5.2 Al-Zn-Mg-In
		10.4.6 Al-Zn-Ga and Al-Ga
		10.4.7 The future
			10.4.7.1 The toxicity of indium?
			10.4.7.2 Al-Zn and Al-Zn-Mg
	10.5 Non-standard anodes
		10.5.1 Limiting the polarisation of the cathode
			10.5.1.1 The need
			10.5.1.2 Alloy composition
			10.5.1.3 Passive electronic components: resistors
			10.5.1.4 Passive electronic components: diodes
		10.5.2 Anodes for rapid polarisation
			10.5.2.1 Motivation
			10.5.2.2 Hybrid systems
			10.5.2.3 Dual anodes
			10.5.2.4 Shaped anodes
	10.6 Future developments
	10.7 Electrochemical testing
		10.7.1 Parameters measured
			10.7.1.1 Potential
			10.7.1.2 Capacity
		10.7.2 Testing modes and objectives
			10.7.2.1 Screening tests
			10.7.2.2 Performance tests
			10.7.2.3 Deep water
			10.7.2.4 Elevated temperature
			10.7.2.5 Biofouling
			10.7.2.6 Polluted environments
			10.7.2.7 Seabed sediments
			10.7.2.8 Estuarine waters
			10.7.2.9 Pre-qualification and production testing
		10.7.3 Testing configurations
			10.7.3.1 Constant current tests
			10.7.3.2 Constant potential tests
			10.7.3.3 Free-running tests
	10.8 Anode resistance
		10.8.1 Relevance to design
		10.8.2 How is R[sub(a)] calculated?
		10.8.3 What the codes advise
			10.8.3.1 Slender stand-off anodes
			10.8.3.2 Shorter stand-off anodes
			10.8.3.3 Long flush-mounted anodes
			10.8.3.4 Short flush-mounted anodes and bracelets
		10.8.4 Validation of resistance formulae
			10.8.4.1 In-service testing
		10.8.5 Anode clustering
			10.8.5.1 The problem
			10.8.5.2 The consequences
			10.8.5.3 The solution
	10.9 Anode design and manufacture
		10.9.1 Who does the design?
		10.9.2 The anode specification
		10.9.3 Anode inserts
			10.9.3.1 Insert configuration
			10.9.3.2 Insert surface preparation
		10.9.4 The casting process
	10.10 Quality control
		10.10.1 Sampling
		10.10.2 Dimensional and weight tolerance
		10.10.3 Casting quality
			10.10.3.1 Non-destructive examination
			10.10.3.2 Destructive examination
	10.11 Anode installation
	References
11 Impressed current systems
	11.1 The electrode reactions
		11.1.1 Cathodic reactions
		11.1.2 Anodic reactions
			11.1.2.1 Consumable anodes
			11.1.2.2 “Non-consumable” anodes
	11.2 ICCP anodes
		11.2.1 Requirements
		11.2.2 Onshore origins
		11.2.3 Anode development
			11.2.3.1 Early ICCP anode alloys
			11.2.3.2 Mixed metal oxide (“MMO”) anodes
		11.2.4 Anode configuration and resistance
		11.2.5 Anode shields
			11.2.5.1 Why do we need anode shields?
			11.2.5.2 Anode shield size
	11.3 Basic design
		11.3.1 Cathodic current demand
		11.3.2 System output calculations
			11.3.2.1 Current
			11.3.2.2 Voltage
		11.3.3 Design calculation process
		11.3.4 Anode locations
	11.4 Power supplies
		11.4.1 What we need to know
		11.4.2 The basics
		11.4.3 Manual control
		11.4.4 Automatic control
	11.5 Control inputs
		11.5.1 Ag|AgCl|seawater
		11.5.2 Zinc reference electrodes
		11.5.3 Dual references
	11.6 Cables
		11.6.1 Conductors
		11.6.2 Insulation
			11.6.2.1 What is required?
			11.6.2.2 What do the codes say?
			11.6.2.3 Candidate materials
			11.6.2.4 Current practice
			11.6.2.5 Mechanical protection of cables
			11.6.2.6 Cables connections
	11.7 Stray current interference
	11.8 ICCP system safety
		11.8.1 Transformer-rectifiers
		11.8.2 Diver safety
	References
12 The effect of CP on mechanical properties
	12.1 Introduction
		12.1.1 Outline
		12.1.2 Some basics
	12.2 Materials of interest
		12.2.1 Structures
			12.2.1.1 Medium-strength steels (SMSY < 550 MPa)
			12.2.1.2 Higher strength steels (>550 MPa)
		12.2.2 Pipelines
		12.2.3 Equipment
	12.3 Fatigue
		12.3.1 What is it?
		12.3.2 S-N testing
			12.3.2.1 Plain specimens
			12.3.2.2 Notched specimens
		12.3.3 Fracture mechanics
			12.3.3.1 Basics
			12.3.3.2 The Paris law
		12.3.4 Reliability of testing
	12.4 Corrosion fatigue
		12.4.1 Discovery
		12.4.2 Characterisation
		12.4.3 Theories
		12.4.4 Stress ratio (R-value)
	12.5 The effect of CP
		12.5.1 Information from S-N testing
		12.5.2 The interaction with CP
		12.5.3 The fracture mechanics perspective
		12.5.4 S-N testing versus crack growth rate data
	12.6 The codes
		12.6.1 Code development
			12.6.1.1 Laboratory testing
			12.6.1.2 The Cognac fatigue “experiment”
			12.6.1.3 Further testing
		12.6.2 Using the codes
			12.6.2.1 Overview
			12.6.2.2 Elements and fatigue loadings
			12.6.2.3 Select the S-N curve
			12.6.2.4 Assessment
		12.6.3 The role of the CP engineer
	12.7 Hydrogen embrittlement
		12.7.1 The problem
		12.7.2 What is the source of atomic hydrogen?
		12.7.3 What does the atomic hydrogen do?
			12.7.3.1 A simplistic view
			12.7.3.2 A less simplistic view
	12.8 Low- and medium-strength carbon steels
	12.9 High-strength low-alloy steels
		12.9.1 General
		12.9.2 Fasteners
	12.10 Corrosion-resistant alloys
		12.10.1 Stainless steels
			12.10.1.1 Classes
			12.10.1.2 Austenitic stainless steels
			12.10.1.3 Ferritic stainless steels
			12.10.1.4 Duplex stainless steels
			12.10.1.5 Martensitic stainless steels
		12.10.2 Nickel alloys
			12.10.2.1 Solid solution alloys
			12.10.2.2 Precipitation-hardened alloys
		12.10.3 Copper alloys
		12.10.4 Titanium
	References
13 Fixed steel structures
	13.1 Structures for hydrocarbon production
		13.1.1 Early sacrificial anode systems
		13.1.2 Early ICCP systems
		13.1.3 Deeper waters
		13.1.4 To coat or not?
		13.1.5 Weight saving
			13.1.5.1 Same problem – different solutions
		13.1.6 Into the sunset?
	13.2 Offshore wind farms
		13.2.1 Development
		13.2.2 Foundation options
		13.2.3 Monopiles
			13.2.3.1 Is external CP needed?
			13.2.3.2 CP design – codes
			13.2.3.3 CP design – challenges
	13.3 Harbour structures
		13.3.1 Historical background
		13.3.2 Current densities
		13.3.3 Sacrificial anodes
		13.3.4 ICCP systems
			13.3.4.1 Seabed anodes
			13.3.4.2 Pile-mounted anodes
			13.3.4.3 Conventional “onshore” anodes
			13.3.4.4 Harbour structures versus platforms
			13.3.4.5 How not to do it
	13.4 Allowances for current drainage
		13.4.1 Simple rules
		13.4.2 Well casings
		13.4.3 Other buried steelwork
		13.4.4 Concrete reinforcement
	13.5 CP retrofits
		13.5.1 What is a “retrofit”?
		13.5.2 Information on retrofits
		13.5.3 Do we need to retrofit?
			13.5.3.1 Design mishaps
			13.5.3.2 Life extension
			13.5.3.3 Unnecessary retrofits
		13.5.4 Retrofit requirements
		13.5.5 Current demand
		13.5.6 Retrofit strategies
			13.5.6.1 ICCP vs sacrificial anodes
		13.5.7 Retrofit implementation
			13.5.7.1 Sacrificial anodes
			13.5.7.2 Impressed current
			13.5.7.3 Connections
	13.6 The future
	References
14 Submarine pipelines
	14.1 Early submarine pipelines
	14.2 Pipeline types
		14.2.1 Flowlines
			14.2.1.1 General
			14.2.1.2 Production flowlines
			14.2.1.3 Injection and gas lift flowlines
		14.2.2 Trunk and service lines
			14.2.2.1 Export lines
			14.2.2.2 Sea lines
			14.2.2.3 Service pipelines
		14.2.3 Risers
	14.3 Code-based CP design
		14.3.1 Methodology
		14.3.2 Example calculation
			14.3.2.1 Pipeline condition
			14.3.2.2 Design factor
			14.3.2.3 Current demand
			14.3.2.4 Anode design – mean current
			14.3.2.5 Anode design – final current
	14.4 Anode spacing
		14.4.1 Early practice
		14.4.2 Extending the spacing
			14.4.2.1 The crucial resistance
			14.4.2.2 A worst-case approach
			14.4.2.3 Norsok method
			14.4.2.4 Potential attenuation
			14.4.2.5 Recommendation
	14.5 Electrical isolation: offshore
		14.5.1 Early offshore practice
		14.5.2 Recent codes
		14.5.3 Current drain
		14.5.4 Stray current interference
	14.6 Pipeline landfalls
		14.6.1 Some problems
		14.6.2 Isolation
	14.7 Hot pipelines and risers
		14.7.1 Ekofisk alpha
		14.7.2 CP criteria
			14.7.2.1 Protection potential
			14.7.2.2 Protection current density
			14.7.2.3 Coating breakdown
			14.7.2.4 Bracelet anode performance
		14.7.3 Flow assurance
			14.7.3.1 Keeping the product flowing
			14.7.3.2 Insulation
			14.7.3.3 Direct electrical heating
		14.7.4 Seawater cooling
			14.7.4.1 Pipelines
			14.7.4.2 Subsea coolers
	14.8 Pipeline retrofits
		14.8.1 Why retrofit?
			14.8.1.1 Something went wrong
			14.8.1.2 Life extension
		14.8.2 When to retrofit?
			14.8.2.1 What you cannot see…
			14.8.2.2 Lost in the Iron Mountain®
		14.8.3 Retrofit strategies
			14.8.3.1 Basic cases
			14.8.3.2 Connecting anode sleds to pipelines
	14.9 CRA and flexible pipelines
	References
15 Ships and floating structures
	15.1 Ships’ hulls
		15.1.1 Early days
		15.1.2 CP design
			15.1.2.1 Differences between fixed structures and ships
			15.1.2.2 Current demand
		15.1.3 Propellers and shafts
			15.1.3.1 Materials
			15.1.3.2 Bonding
			15.1.3.3 Current demand
		15.1.4 Rudders
			15.1.4.1 Bonding
			15.1.4.2 A cautionary tale
		15.1.5 Sacrificial anode systems
			15.1.5.1 Development
			15.1.5.2 Design
		15.1.6 Impressed current
			15.1.6.1 Early days
			15.1.6.2 Present day systems
			15.1.6.3 Fitting-out
			15.1.6.4 Laying-up
			15.1.6.5 Alongside berths
		15.1.7 Non-ferrous hulls
			15.1.7.1 Aluminium
			15.1.7.2 Copper and Cu-Ni hulls
			15.1.7.3 Pleasure craft
	15.2 Floating installations
		15.2.1 Drill ships and semi-submersibles
			15.2.1.1 Some history
			15.2.1.2 A recent example
		15.2.2 FPSOs
			15.2.2.1 Hulls
		15.2.3 Tension leg platforms
		15.2.4 Moorings
			15.2.4.1 Tethers and tendons
			15.2.4.2 Chains
	15.3 Jack-up rigs
	References
16 Internal CP
	16.1 “Fully sealed” systems
		16.1.1 Corrosion threats
			16.1.1.1 Corrosion by dissolved oxygen
			16.1.1.2 What really happens to the oxygen?
			16.1.1.3 What happens then?
			16.1.1.4 What about MIC?
		16.1.2 Is CP needed?
	16.2 Leaking systems
		16.2.1 Monopile foundations
		16.2.2 Corrosion implications
		16.2.3 Internal CP of wind turbine foundations
			16.2.3.1 A touch of schadenfreude?
			16.2.3.2 Code guidance
			16.2.3.3 Lessons learned
			16.2.3.4 But is CP needed?
		16.2.4 Water ballast tanks
			16.2.4.1 Ballast water and its management
			16.2.4.2 Corrosion management
	16.3 Steel structures containing aerated seawater
		16.3.1 Sea chests
		16.3.2 Seawater intakes
			16.3.2.1 Multi-metal systems
			16.3.2.2 Shore-side seawater intakes
			16.3.2.3 Seawater lift caissons
	16.4 Seawater piping systems
		16.4.1 Unlined carbon steel
		16.4.2 Lined carbon steel
		16.4.3 Corrosion resistant alloys
			16.4.3.1 Materials for handling seawater
			16.4.3.2 CRAs: selection and vulnerabilities
			16.4.3.3 Internal CP of stainless steel pipework
			16.4.3.4 Resistor-controlled cathodic protection
	16.5 Heat exchangers
		16.5.1 A corrosion machine
		16.5.2 Early CP systems
		16.5.3 Seawater exchangers
	References
17 Modelling
	17.1 What is a model?
	17.2 Physical modelling
		17.2.1 Full scale
		17.2.2 Reduced scale – reduced conductivity
		17.2.3 Reduced scale – full conductivity
	17.3 Early computer applications
	17.4 Computer modelling – the basics
		17.4.1 The convenience of the computer
		17.4.2 Potential and current distribution
		17.4.3 The Laplace equation
		17.4.4 Solving Laplace
			17.4.4.1 The need for a number-cruncher
			17.4.4.2 Defining the space
			17.4.4.3 Defining the boundaries
			17.4.4.4 The finite element method (FEM)
			17.4.4.5 The boundary element method (BEM)
			17.4.4.6 FEM versus BEM
			17.4.4.7 Other software approaches
	17.5 Computer modelling – applications
		17.5.1 Early days
		17.5.2 Moore’s law
		17.5.3 When modelling gets it wrong
		17.5.4 The boundary conditions
			17.5.4.1 The anodes
			17.5.4.2 The cathode
		17.5.5 What can computer modelling tell us?
			17.5.5.1 Reasons to be careful
			17.5.5.2 Uncoated steel structures
			17.5.5.3 Coated structures
			17.5.5.4 Sacrificial anodes
			17.5.5.5 Internal spaces and complex geometries
	17.6 Going forward
	References
18 CP system management
	18.1 Surveying, inspection and monitoring
		18.1.1 The need for measurement
	18.2 Measuring the potential
		18.2.1 The story so far
		18.2.2 Alternative references
			18.2.2.1 Standard hydrogen electrode
			18.2.2.2 Saturated calomel half-cell
			18.2.2.3 Silver chloride electrode
			18.2.2.4 Silver chloride (0.5 M KCl) electrode
			18.2.2.5 Copper sulfate electrode (CSE)
			18.2.2.6 Zinc
		18.2.3 Errors in potential measurement
			18.2.3.1 Operatives
			18.2.3.2 Equipment and operatives
			18.2.3.3 Temperature
			18.2.3.4 Liquid-junction or diffusion potential
			18.2.3.5 The IR problem
			18.2.3.6 IR-error mitigation
			18.2.3.7 The effect of seawater flow
		18.2.4 Potential surveys – structures
			18.2.4.1 Dip-cell surveys
			18.2.4.2 Diver and ROV surveys
			18.2.4.3 Survey frequency – sacrificial systems
		18.2.5 Potential surveys - pipelines
			18.2.5.1 Background
			18.2.5.2 Trailing wire surveys
			18.2.5.3 ROV surveys
			18.2.5.4 Beach crossings and shore approaches
			18.2.5.5 Telluric currents
			18.2.5.6 Survey frequency
		18.2.6 Fixed potential monitoring
			18.2.6.1 Structures
			18.2.6.2 Pipelines
	18.3 Current measurement
		18.3.1 ICCP systems
		18.3.2 Sacrificial systems
			18.3.2.1 Current clamp meters
			18.3.2.2 Monitored anodes
	18.4 Current density measurement
		18.4.1 Fixed monitoring
			18.4.1.1 Current density plates and probes
			18.4.1.2 Field gradients
		18.4.2 Surveys
			18.4.2.1 Pipelines
			18.4.2.2 Structures
	18.5 Interaction
		18.5.1 Sacrificial systems
		18.5.2 ICCP systems
			18.5.2.1 General
			18.5.2.2 Harbours
			18.5.2.3 Ships and boats
	References
Index