Cathodic protection of offshore wind structures (ISO 24656:2022)

This European Standard will address the external and internal cathodic protection for offshore wind farm structures. It will be applicable for structures and appurtenances in contact with seawater or seabed environments.  This Standard addresses:
•   Design and implementation of cathodic protection systems for new structures,
•   Assessment of residual lifetime of existing cathodic protection systems,
•   Design and implementation of retrofit cathodic protection systems for improvement of the protection level or for life extension of the protection,
•   Inspection and performance monitoring of cathodic protection systems installed on existing structures,
•   Guidance on cathodic protection of reinforced concrete structures

Kathodischer Korrosionsschutz von Offshore-Windparkstrukturen (ISO 24656:2022)

Diese Europäische Norm behandelt den äußeren und inneren kathodischen Korrosionsschutz für Offshore-Windparkstrukturen. Sie ist für Strukturen und Zubehörteile anwendbar, die mit Meerwasser oder Umgebungen am Meeresboden in Berührung kommen. Diese Norm behandelt:
- die Konstruktion und Umsetzung von kathodischen Korrosionsschutzsystemen für neue Stahlkonstruktionen;
- die Bewertung der Restlebensdauer von bereits vorhandenen kathodischen Korrosionsschutzsystemen;
- die Konstruktion und Umsetzung von nachgerüsteten kathodischen Korrosionsschutzsystemen zur Verbesserung des Schutzgrades oder zur Verlängerung der Lebensdauer des Schutzes;
- die Überprüfung und Leistungsüberwachung von kathodischen Korrosionsschutzsystemen, die bei vorhandenen Strukturen eingebaut sind;
- einen Leitfaden bezüglich des kathodischen Korrosionsschutzes von Stahlbetonkonstruktionen.

Protection cathodique des structures éoliennes offshore (ISO 24656:2022)

Le présent document spécifie les exigences relatives à la protection cathodique extérieure et intérieure des structures des parcs éoliens en mer. Il est applicable aux structures et équipements en contact avec l'eau de mer ou les fonds marins. Le présent document couvre:
—    le dimensionnement et la mise en œuvre de systèmes de protection cathodique pour les structures en acier neuves;
—    l'évaluation de la durée de vie résiduelle de systèmes de protection cathodique existants;
—    le dimensionnement et la mise en œuvre de systèmes de protection cathodique pour remise à niveau, destinés à améliorer le niveau de protection ou à prolonger la durée de vie de la protection;
—    le contrôle et la surveillance des performances de systèmes de protection cathodique mis en place sur des structures existantes; et
—    les recommandations relatives à la protection cathodique de structures en béton armé.

Katodna zaščita vetrnih konstrukcij na morju (ISO 24656:2022)

General Information

Status
Published
Public Enquiry End Date
19-Dec-2020
Publication Date
30-Jun-2022
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
20-Jun-2022
Due Date
25-Aug-2022
Completion Date
01-Jul-2022

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SLOVENSKI STANDARD
SIST EN ISO 24656:2022
01-september-2022
Katodna zaščita vetrnih konstrukcij na morju (ISO 24656:2022)
Cathodic protection of offshore wind structures (ISO 24656:2022)
Kathodischer Korrosionsschutz von Offshore-Windparkstrukturen (ISO 24656:2022)
Protection cathodique des structures éoliennes offshore (ISO 24656:2022)
Ta slovenski standard je istoveten z: EN ISO 24656:2022
ICS:
47.020.99 Drugi standardi v zvezi z Other standards related to
ladjedelništvom in shipbuilding and marine
konstrukcijami na morju structures
77.060 Korozija kovin Corrosion of metals
SIST EN ISO 24656:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN ISO 24656:2022
---------------------- Page: 2 ----------------------
SIST EN ISO 24656:2022
EN ISO 24656
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2022
EUROPÄISCHE NORM
ICS 47.020.99; 77.060
English Version
Cathodic protection of offshore wind structures (ISO
24656:2022)

Protection cathodique des structures éoliennes Kathodischer Korrosionsschutz von Offshore-

offshore (ISO 24656:2022) Windparkstrukturen (ISO 24656:2022)
This European Standard was approved by CEN on 6 May 2022.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 24656:2022 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 24656:2022
EN ISO 24656:2022 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

---------------------- Page: 4 ----------------------
SIST EN ISO 24656:2022
EN ISO 24656:2022 (E)
European foreword

This document (EN ISO 24656:2022) has been prepared by Technical Committee ISO/TC 156

"Corrosion of metals and alloys" in collaboration with Technical Committee CEN/TC 219 “Cathodic

protection” the secretariat of which is held by BSI.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by December 2022, and conflicting national standards

shall be withdrawn at the latest by December 2022.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

Any feedback and questions on this document should be directed to the users’ national standards

body/national committee. A complete listing of these bodies can be found on the CEN website.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO 24656:2022 has been approved by CEN as EN ISO 24656:2022 without any modification.

---------------------- Page: 5 ----------------------
SIST EN ISO 24656:2022
---------------------- Page: 6 ----------------------
SIST EN ISO 24656:2022
INTERNATIONAL ISO
STANDARD 24656
First edition
2022-05
Cathodic protection of offshore wind
structures
Protection cathodique des structures éoliennes en mer
Reference number
ISO 24656:2022(E)
© ISO 2022
---------------------- Page: 7 ----------------------
SIST EN ISO 24656:2022
ISO 24656:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO 2022 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 24656:2022
ISO 24656:2022(E)
Contents Page

Foreword ....................................................................................................................................................................................................................................... vi

Introduction .............................................................................................................................................................................................................................vii

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Symbols and abbreviations ......................................................................................................................................................................5

4.1 Symbols ......................................................................................................................................................................................................... 5

4.2 Abbreviations .......................................................................................................................................................................................... 7

5 Competence of personnel ...........................................................................................................................................................................8

6 Structural considerations .......................................................................................................................................................................... 9

6.1 Structures to be protected ........................................................................................................................................................... 9

6.2 Materials ................................................................................................................................................................................................... 10

6.3 Corrosion protection strategy ............................................................................................................................................... 10

7 Cathodic protection criteria .................................................................................................................................................................15

7.1 Temporary protection ................................................................................................................................................................... 15

7.2 Steel structures ........................................................................................................................................... ........................................ 16

7.3 Reinforced concrete structures ........................................................................................................................................... 17

8 Cathodic protection design ....................................................................................................................................................................17

8.1 Objectives ................................................................................................................................................................................................. 17

8.2 Design considerations ................................................................................................................................................................... 18

8.2.1 General ..................................................................................................................................................................................... 18

8.2.2 External cathodic protection ............................................................................................................................... 19

8.2.3 Internal cathodic protection ................................................................................................................................. 19

8.3 CP Design life ........................................................................................................................................................................................ 20

8.4 Surface area considerations ....................................................................................................................................................20

8.4.1 General .....................................................................................................................................................................................20

8.4.2 Structure subdivision .................................................................................................................................................20

8.5 Environmental factors .................................................................................................................................................................. 21

8.5.1 General ..................................................................................................................................................................................... 21

8.5.2 Seawater flow velocity ............................................................................................................................................... 21

8.5.3 Electrolyte resistivity .................................................................................................................................................22

8.5.4 Seawater temperature ............................................................................................................................................... 22

8.5.5 Calcareous deposits ...................................................................................................................................................... 22

8.6 Protection current demand .....................................................................................................................................................23

8.6.1 General .....................................................................................................................................................................................23

8.6.2 Calculation of current demand, external surfaces ............................................................................23

8.6.3 Calculation of current demand, internal surfaces ............................................................................. 26

8.7 Electrical continuity and continuity bonds ............................................................................................................... 26

8.8 Current drains and interactions .......................................................................................................................................... 27

8.9 Installation considerations during design .................................................................................................................. 27

9 Galvanic anode systems ............................................................................................................................................................................28

9.1 General ........................................................................................................................................................................................................28

9.2 Anode current availability ........................................................................................................................................................28

9.3 Galvanic anode alloys ....................................................................................................................................................................28

9.4 Anode selection ................................................................................................................................................................................... 29

9.5 Anode requirements ....................................................................................................................................................................... 30

9.6 Anode distribution ........................................................................................................................................................................... 31

10 Impressed current systems ...................................................................................................................................................................32

10.1 General ........................................................................................................................................................................................................ 32

10.2 Design considerations ................................................................................................................................................................... 33

iii
© ISO 2022 – All rights reserved
---------------------- Page: 9 ----------------------
SIST EN ISO 24656:2022
ISO 24656:2022(E)

10.2.1 General ..................................................................................................................................................................................... 33

10.2.2 Resilience of impressed current CP system by design .................................................................. 33

10.2.3 Current requirement of impressed current CP system .................................................................34

10.2.4 Impressed current CP system components .............................................................................................34

10.2.5 DC power source ..............................................................................................................................................................34

10.2.6 Impressed current anodes ......................................................................................................................................36

10.2.7 Reference electrodes ................................................................................................................................................... 37

10.2.8 Dielectric shields ............................................................................................................................................................. 37

10.3 Installation of impressed current CP systems ........................................................................................................38

10.4 Hybrid systems and temporary power for impressed current systems ..........................................39

10.5 Continuity bonds ............................................................................................................................................................................... 39

11 Cable systems .......................................................................................................................................................................................................39

11.1 General ........................................................................................................................................................................................................39

11.2 Cathodic protection DC cables ...............................................................................................................................................40

11.3 Inter-array and export AC cables ........................................................................................................................................ 41

12 Commissioning and surveys .................................................................................................................................................................43

12.1 Objectives ................................................................................................................................................................................................. 43

12.2 Galvanic anode systems .............................................................................................................................................................. 43

12.2.1 General ..................................................................................................................................................................................... 43

12.2.2 Detailed external surveys .......................................................................................................................................44

12.2.3 Detailed internal surveys ........................................................................................................................................44

12.3 Permanent CP monitoring systems ................................................................................................................................... 45

12.4 Impressed current systems ..................................................................................................................................................... 45

13 CP surveying and monitoring ........................................................................................................................................... ...................46

13.1 Objectives .................................................................................................................................................................................................46

13.2 General considerations.................................................................................................................................................................46

13.3 Reference electrodes ......................................................................................................................................................................48

13.4 Frequency of survey and monitoring ..............................................................................................................................48

14 Retrofit cathodic protection systems .........................................................................................................................................49

14.1 General considerations.................................................................................................................................................................49

14.2 Survey before retrofit....................................................................................................................................................................49

14.3 Retrofit for inadequate protection ....................................................................................................................................50

14.4 Retrofit for structure life extension .................................................................................................................................50

14.5 All retrofits ............................................................................................................................................................................................. 51

14.6 Equipment considerations ........................................................................................................................................................ 52

15 Documentation ...................................................................................................................................................................................................53

15.1 General ........................................................................................................................................................................................................53

15.2 Design report ........................................................................................................................................................................................ 53

15.2.1 General .....................................................................................................................................................................................53

15.3 Material specification requirements ............................................................................................................................... 55

15.3.1 General ..................................................................................................................................................................................... 55

15.3.2 Galvanic anodes ................................................................................................................................................................ 55

15.3.3 Impressed current CP materials .......................................................................................................................56

15.4 Installation drawings and specifications .................................................................................................................... 59

15.5 As-built installation and commissioning report requirements ............................................................... 59

15.6 Operation and maintenance requirements ................................................................................................................60

16 Safety and cathodic protection ..........................................................................................................................................................60

16.1 Objectives .................................................................................................................................................................................................60

16.2 Physical obstructions .................................................................................................................................................................... 61

16.3 Protection against electric shock ....................................................................................................................................... 61

16.4 Gas evolution ......................................................................................................................................................................................... 61

16.4.1 Hydrogen evolution ........................................................................................................................................... ............ 61

16.4.2 Chlorine evolution .......................................................................................................................................................... 62

Annex A (informative) Environmental checklist .................................................................................................................................63

© ISO 2022 – All rights reserved
---------------------- Page: 10 ----------------------
SIST EN ISO 24656:2022
ISO 24656:2022(E)

Annex B (normative) Method of using metocean data to calculate marked-up seawater flow

velocity ........................................................................................................................................................................................................................65

Annex C (informative) Guidance on cathodic protection current density requirement for

cathodic protection of wind offshore structures ...........................................................................................................78

Annex D (informative) Coatings and coating breakdown for CP design ....................................................................86

Annex E (normative) Anode resistance and life calculation ...................................................................................................90

Annex F (normative) Calculation of voltage drop down connection cables ............................................................97

Annex G (normative) Typical electrochemical characteristics for commonly used

impressed current anodes ......................................................................................................................................................................99

Annex H (informative) Permanent monitoring system design process .................................................................. 101

Annex I (informative) Cathodic protection modelling .............................................................................................................. 105

Bibliography ......................................................................................................................................................................................................................... 108

© ISO 2022 – All rights reserved
---------------------- Page: 11 ----------------------
SIST EN ISO 24656:2022
ISO 24656:2022(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys, in

collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC

219, Cathodic protection, in accordance with the Agreement on technical cooperation between ISO and

CEN (Vienna Agreement).

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listin
...

SLOVENSKI STANDARD
oSIST prEN ISO 24656:2020
01-december-2020
Katodna zaščita vetrnih konstrukcij na morju (ISO/DIS 24656:2020)
Cathodic protection of offshore wind structures (ISO/DIS 24656:2020)

Kathodischer Korrosionsschutz von Offshore-Windparkstrukturen (ISO/DIS 24656:2020)

Protection cathodique des structures éoliennes offshore (ISO/DIS 24656:2020)
Ta slovenski standard je istoveten z: prEN ISO 24656
ICS:
47.020.99 Drugi standardi v zvezi z Other standards related to
ladjedelništvom in shipbuilding and marine
konstrukcijami na morju structures
77.060 Korozija kovin Corrosion of metals
oSIST prEN ISO 24656:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN ISO 24656:2020
---------------------- Page: 2 ----------------------
oSIST prEN ISO 24656:2020
DRAFT INTERNATIONAL STANDARD
ISO/DIS 24656
ISO/TC 156 Secretariat: SAC
Voting begins on: Voting terminates on:
2020-10-19 2021-01-11
Cathodic protection of offshore wind structures
ICS: 77.060; 47.020.99
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 24656:2020(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. ISO 2020
---------------------- Page: 3 ----------------------
oSIST prEN ISO 24656:2020
ISO/DIS 24656:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO 24656:2020
ISO/DIS 24656:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................vi

Introduction ..............................................................................................................................................................................................................................vii

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Symbols and abbreviations ....................................................................................................................................................................... 2

3.1 Symbols ......................................................................................................................................................................................................... 2

3.2 Abbreviations ........................................................................................................................................................................................... 3

4 Terms and definitions ..................................................................................................................................................................................... 4

5 Competence of personnel ............................................................................................................................................................................ 8

6 Structural considerations ........................................................................................................................................................................... 8

6.1 Structures to be protected ............................................................................................................................................................ 8

6.2 Materials ....................................................................................................................................................................................................10

6.3 Corrosion protection strategy .................................................................................................................................................10

7 Cathodic protection criteria ..................................................................................................................................................................15

7.1 Temporary protection ....................................................................................................................................................................15

7.2 Steel structures ....................................................................................................................................................................................15

7.3 Reinforced concrete structures .............................................................................................................................................16

8 Cathodic protection design .....................................................................................................................................................................16

8.1 Objectives..................................................................................................................................................................................................16

8.2 Design considerations....................................................................................................................................................................16

8.2.1 General...................................................................................................................................................................................16

8.2.2 External cathodic protection ..............................................................................................................................17

8.2.3 Internal cathodic protection ...............................................................................................................................17

8.3 Design Life................................................................................................................................................................................................18

8.4 Surface area considerations......................................................................................................................................................18

8.4.1 General...................................................................................................................................................................................18

8.4.2 Structure sub-division ........................................................................................................................................... ...19

8.5 Environmental factors ...................................................................................................................................................................19

8.5.1 General...................................................................................................................................................................................19

8.5.2 Seawater flow velocity .............................................................................................................................................20

8.5.3 Electrolyte resistivity ................................................................................................................................................20

8.5.4 Seawater temperature..............................................................................................................................................20

8.5.5 Calcareous deposits ....................................................................................................................................................21

8.6 Protection current demand .......................................................................................................................................................21

8.6.1 General...................................................................................................................................................................................21

8.6.2 Calculation of current demand, external surfaces ...........................................................................21

8.6.3 Calculation of current demand, internal surfaces ............................................................................23

8.7 Electrical continuity and Continuity Bonds ................................................................................................................24

8.8 Current drains and interactions ............................................................................................................................................24

8.9 Installation considerations during design ...................................................................................................................25

9 Galvanic anode systems ..............................................................................................................................................................................26

9.1 General ........................................................................................................................................................................................................26

9.2 Anode current availability ..........................................................................................................................................................26

9.3 Galvanic anode alloys .....................................................................................................................................................................26

9.4 Anode selection ...................................................................................................................................................................................27

9.5 Anode requirements .......................................................................................................................................................................28

9.6 Anode distribution ............................................................................................................................................................................29

10 Impressed current systems ....................................................................................................................................................................30

10.1 General ........................................................................................................................................................................................................30

10.2 Design considerations....................................................................................................................................................................31

© ISO 2020 – All rights reserved iii
---------------------- Page: 5 ----------------------
oSIST prEN ISO 24656:2020
ISO/DIS 24656:2020(E)

10.2.1 Resilience of impressed current CP system by design .................................................................31

10.2.2 Current Requirement of impressed current CP system ..............................................................32

10.2.3 Impressed current CP system components ...........................................................................................32

10.2.4 DC power source ...........................................................................................................................................................32

10.2.5 Impressed current anodes .................. ..................................................................................................................33

10.2.6 Reference electrodes .................................................................................................................................................34

10.2.7 Dielectric shields .................. .................................................... .....................................................................................35

10.3 Installation of impressed current CP systems ..........................................................................................................35

10.4 Hybrid systems and temporary power for impressed current systems .............................................36

10.5 Continuity Bonds ................................................................................................................................................................................36

11 Cable systems ........................................................................................................................................................................................................36

11.1 General ........................................................................................................................................................................................................36

11.2 Cathodic protection DC cables ................................................................................................................................................37

11.3 Inter-array and export AC cables .........................................................................................................................................38

12 Commissioning and surveys ..................................................................................................................................................................41

12.1 Objectives..................................................................................................................................................................................................41

12.2 Galvanic anode systems ................................................................................................................................................................41

12.2.1 Detailed External Surveys .....................................................................................................................................42

12.2.2 Detailed Internal Surveys ......................................................................................................................................42

12.3 Permanent CP monitoring Systems ....................................................................................................................................42

12.4 Impressed current systems .......................................................................................................................................................43

13 CP surveying and monitoring ...............................................................................................................................................................44

13.1 Objectives..................................................................................................................................................................................................44

13.2 General considerations .................................................................................................................................................................44

13.3 Reference electrodes .......................................................................................................................................................................46

13.4 Frequency of Survey and Monitoring ...............................................................................................................................46

14 Retrofit cathodic protection systems ...........................................................................................................................................47

14.1 General considerations .................................................................................................................................................................47

14.2 Survey before retrofit .....................................................................................................................................................................47

14.3 Retrofit for inadequate protection ......................................................................................................................................48

14.4 Retrofit for life extension ............................................................................................................................................................48

14.5 All retrofits...............................................................................................................................................................................................48

14.6 Equipment considerations .........................................................................................................................................................50

15 Documentation ....................................................................................................................................................................................................50

15.1 Design report .........................................................................................................................................................................................51

15.1.1 General...................................................................................................................................................................................51

15.2 Material Specification requirements .................................................................................................................................53

15.2.1 General...................................................................................................................................................................................53

15.2.2 Galvanic anodes .............................................................................................................................................................53

15.2.3 Impressed current CP materials ......................................................................................................................54

15.3 Installation Drawings and Specifications ......................................................................................................................57

15.4 As-built installation and commissioning report requirements .................................................................57

15.5 Operation and Maintenance requirements .................................................................................................................57

16 Safety and cathodic protection ...........................................................................................................................................................58

16.1 Objectives..................................................................................................................................................................................................58

16.2 Physical obstructions .....................................................................................................................................................................58

16.3 Electric shock ........................................................................................................................................................................................58

16.4 Gas evolution .........................................................................................................................................................................................59

16.4.1 Hydrogen evolution ....................................................................................................................................................59

16.4.2 Chlorine evolution .......................................................................................................................................................59

Annex A (informative) Environmental checklist ...................................................................................................................................60

Annex B (informative) Method of using metocean data to calculate marked-up seawater

flow velocity ............................................................................................................................................................................................................61

iv © ISO 2020 – All rights reserved
---------------------- Page: 6 ----------------------
oSIST prEN ISO 24656:2020
ISO/DIS 24656:2020(E)

Annex C (informative) Guidance on Cathodic Protection current density requirement for

cathodic protection of wind offshore structures .............................................................................................................73

Annex D (informative) Coatings and coating breakdown for CP design .......................................................................81

Annex E (informative) Anode resistance and Life calculation ................................................................................................85

Annex F (informative) Calculation of voltage drop down connection cables ..........................................................93

Annex G (informative) Typical electrochemical characteristics for commonly used

impressed current anodes ......................................................................................................................................................................95

Annex H (informative) Permanent monitoring system design process ........................................................................97

Annex I (informative) Cathodic Protection Modelling ................................................................................................................101

Bibliography .........................................................................................................................................................................................................................104

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oSIST prEN ISO 24656:2020
ISO/DIS 24656:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
vi © ISO 2020 – All rights reserved
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oSIST prEN ISO 24656:2020
ISO/DIS 24656:2020(E)
Introduction

Cathodic protection (CP), possibly together with protective coating, is applied to protect the immersed

external surfaces of offshore wind farm structures and appurtenances from corrosion due to seawater

or seabed environments.

CP, possibly together with protective coating, can be applied to protect the internal flooded and seabed

and sediment exposed surfaces from corrosion.

The general principles of CP in seawater are detailed in ISO 12473, see chapter 2.

CP involves the supply of sufficient direct current to the surfaces of the structure in order to reduce the

steel to electrolyte potential to values where corrosion is considered insignificant or acceptably low.

CP is designed to protect the submerged and buried areas of the structure from corrosion. The parts

that are not permanently immersed will not be permanently protected by the CP system.

This standard introduces guidance for the use of available metocean data to
• assess the CP demand of immersed and frequently wetted areas
• determine seawater flow velocities to assess the CP design parameters

This is in addition to the primary use of the metocean data in structural design.

© ISO 2020 – All rights reserved vii
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oSIST prEN ISO 24656:2020
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oSIST prEN ISO 24656:2020
DRAFT INTERNATIONAL STANDARD ISO/DIS 24656:2020(E)
Cathodic protection of offshore wind structures
1 Scope

This European Standard will address the external and internal cathodic protection for offshore wind

farm structures. It will be applicable for structures and appurtenances in contact with seawater or

seabed environments. This Standard address:

• Design and implementation of cathodic protection systems for new steel structures,

• Assessment of residual lifetime of existing cathodic protection systems,

• Design and implementation of retrofit cathodic protection systems for improvement of the protection

level or for life extension of the protection,

• Inspection and performance monitoring of cathodic protection systems installed on existing

structures,
• Guidance on cathodic protection of reinforced concrete structures
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

EN 206, Concrete — Specification, performance, production and conformity

EN 1992-1-1, Eurocode 2: Design of concrete structures — Part 1-1: General rules and rules for buildings

ISO 8044, Corrosion of metals and alloys — Vocabulary

ISO 8501-1, Preparation of steel substrates before application of paints and related products — Visual

assessment of surface cleanliness — Part 1: Rust grades and preparation grades of uncoated steel substrates

and of steel substrates after overall removal of previous coatings
ISO 12473, General principles of cathodic protection in seawater
ISO 12696, Cathodic protection of steel in concrete

ISO 12944-2, Paints and varnishes — Corrosion protection of steel structures by protective paint systems —

Part 2: Classification of environments

ISO 12944-9, Paints and varnishes — Corrosion protection of steel structures by protective paint

systems — Part 9: Protective paint systems and laboratory performance test methods for offshore and

related structures
EN 13670, Execution of concrete structures

EN 17243, Cathodic protection of internal surfaces of steel tanks, equipment, structures and pipi

...

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