ISO 12473:2017

INTERNATIONAL ISO
STANDARD 12473
Second edition
2017-10
General principles of cathodic
protection in seawater
Principes généraux de la protection cathodique en eau de mer
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved

Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, abbreviations and symbols . 1
4 Application of cathodic protection in seawater . 5
4.1 General . 5
4.2 Galvanic anode method . 5
4.3 Impressed current method . 6
4.4 Hybrid systems . 6
5 Determination of level of cathodic protection . 9
5.1 Measurement of protection level . 9
5.2 Reference electrodes . 9
5.3 Potentials of reference electrodes . 9
5.4 Verification of reference electrodes . 9
5.5 Potential measurement .10
6 Cathodic protection potential criteria .10
6.1 General .10
6.2 Carbon-manganese and low alloy steels .10
6.3 Other metallic materials .13
6.3.1 General.13
6.3.2 Stainless steels .13
6.3.3 Nickel alloys .14
6.3.4 Aluminium alloys .14
6.3.5 Copper alloys .14
7 Design considerations .14
7.1 Introduction .14
7.2 Technical and operating data .15
7.2.1 Design life .15
7.2.2 Materials of construction.15
7.3 Surfaces to be protected .15
7.4 Protective coatings .15
7.5 Availability of electrical power .16
7.6 Weight limitations .16
7.7 Adjacent structures .16
7.8 Installation considerations .16
7.9 Current demand .16
8 Effect of environmental factors on current demand .16
8.1 Introduction .16
8.2 Dissolved oxygen .17
8.3 Sea currents .17
8.4 Calcareous deposits .17
8.5 Temperature .18
8.6 Salinity.18
8.7 pH .18
8.8 Marine fouling.18
8.9 Effect of depth .19
8.10 Seasonal variations and storms .19
9 Secondary effects of cathodic protection .19
9.1 General .19
9.2 Alkalinity .19
9.3 Environmentally-assisted cracking .19
9.3.1 General.19
9.3.2 Hydrogen embrittlement .20
9.3.3 Corrosion fatigue .20
9.4 Chlorine .21
9.5 Stray currents and interference effects.21
10 Use of cathodic protection in association with coatings .21
10.1 Introduction .21
10.2 Coating selection .22
10.3 Coating breakdown .22
Annex A (informative) Corrosion of carbon-manganese and low-alloy steels .24
Annex B (informative) Principles of cathodic protection .28
Annex C (informative) Reference electrodes .31
Annex D (informative) Corrosion of metallic materials other than carbon-manganese and
low-alloy steels typically subject to cathodic protection in seawater .35
Bibliography .37
iv © ISO 2017 – All rights reserved

Foreword
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