Corrosion of metals and alloys - Determination of AC corrosion - Protection criteria (ISO 18086:2019)

This document specifies protection criteria for determining the AC corrosion risk of cathodically protected pipelines.
It is applicable to buried cathodically protected pipelines that are influenced by AC traction systems and/or AC power lines.
In the presence of AC interference, the protection criteria given in ISO 15589-1 are not sufficient to demonstrate that the steel is being protected against corrosion.
This document provides limits, measurement procedures, mitigation measures, and information to deal with long-term AC interference for AC voltages at frequencies between 16,7 Hz and 60 Hz and the evaluation of AC corrosion likelihood.
This document deals with the possibility of AC corrosion of metallic pipelines due to AC interferences caused by conductive, inductive or capacitive coupling with AC power systems and the maximum tolerable limits of these interference effects. It takes into account the fact that this is a long-term effect, which occurs during normal operating conditions of the AC power system.
This document does not cover the safety issues associated with AC voltages on pipelines. These are covered in national standards and regulations (see, e.g., EN 50443).

Korrosion von Metallen und Legierungen - Bestimmung der Wechselstromkorrosion - Schutzkriterien (ISO 18086:2019)

Dieses Dokument legt Schutzkriterien für die Bestimmung des Wechselstromkorrosionsrisikos von kathodisch geschützten Rohrleitungen fest.
Es ist anzuwenden für erdverlegte kathodisch-geschützte Rohrleitungen, die durch Wechsel-strom Fahrleitungssysteme und/oder Wechselstromleitungen beeinflusst werden.
Bei Vorhandensein einer Beeinflussung durch Wechselstrom sind die in ISO 15589 1 angegebenen Schutzkriterien nicht ausreichend, um nachzuweisen, dass der Stahl vor Korrosion geschützt ist.
Dieses Dokument liefert Grenzwerte, Messverfahren, Schutzmaßnahmen und Informationen zum Umgang mit Langzeitbeeinflussung durch Wechselstrom für Wechselspannungen bei Frequenzen zwischen 16,7 Hz und 60 Hz und zur Beurteilung der Korrosionswahrscheinlichkeit durch Wechselstrom.
Dieses Dokument behandelt die mögliche Wechselstromkorrosion von metallischen Rohrleitungen aufgrund der Beeinflussung durch Wechselstrom der durch Wechselstromsysteme verursachten Streuströme durch ohmsche, induktive oder kapazitive Kopplung mit Wechselstromnetzen und die maximal zulässigen Grenz¬werte dieser beeinflussenden Effekte. Es wird die Tatsache berücksichtigt, dass das ein Langzeiteffekt ist, der bei normalen Betriebsbedingungen des Wechselstromsystems auftritt.
Dieses Dokument behandelt nicht die mit Wechselspannungen an Rohrleitungen verbundenen Sicherheitsaspekte. Diese werden in nationalen Normen und Rechtsvorschriften behandelt (siehe z. B. EN 50443).

Corrosion des métaux et alliages - Détermination de la corrosion occasionnée par les courants alternatifs - Critères de protection (ISO 18086:2019)

Le présent document spécifie des critères de protection pour la détermination du risque de corrosion due aux courants alternatifs pour les canalisations protégées cathodiquement.
Il s'applique aux canalisations enterrées qui sont protégées cathodiquement et influencées par des systèmes de traction à courant alternatif et/ou des lignes électriques haute tension en courant alternatif.
En présence d'une influence due aux courants alternatifs, les critères de protection spécifiés dans l'ISO 15589‑1 sont insuffisants pour démontrer que l'acier est protégé contre la corrosion.
Le présent document spécifie les limites, les modes opératoires de mesurage, les mesures d'atténuation et les informations relatives à l'influence en régime de fonctionnement permanent des courants alternatifs pour les tensions de courant alternatif à des fréquences comprises entre 16,7 Hz et 60 Hz, et à l'évaluation du risque de corrosion due aux courants alternatifs.
Le présent document traite de la possible corrosion des canalisations métalliques due à l'influence des courants alternatifs provoquée par le couplage conductif, inductif ou capacitif avec des systèmes électriques à courant alternatif, ainsi que des limites maximales admissibles des effets de cette influence. Il prend en compte le fait qu'il s'agit d'un effet à long terme qui se produit uniquement lors de conditions normales d'exploitation du système électrique à courant alternatif.
Le présent document ne traite pas des problèmes de sécurité liés aux tensions de courant alternatif sur les canalisations. Ceux-ci sont traités dans les normes et réglementations nationales (voir par exemple l'EN 50443).

Korozija kovin in zlitin - Ugotavljanje nastanka AC korozije - Merila zaščite (ISO 18086:2019)

General Information

Status
Published
Public Enquiry End Date
19-Oct-2020
Publication Date
20-Jan-2021
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
11-Jan-2021
Due Date
18-Mar-2021
Completion Date
21-Jan-2021

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SLOVENSKI STANDARD
SIST EN ISO 18086:2021
01-februar-2021
Nadomešča:
SIST EN ISO 18086:2017

Korozija kovin in zlitin - Ugotavljanje nastanka AC korozije - Merila zaščite (ISO

18086:2019)

Corrosion of metals and alloys - Determination of AC corrosion - Protection criteria (ISO

18086:2019)
Korrosion von Metallen und Legierungen - Bestimmung der Wechselstromkorrosion -
Schutzkriterien (ISO 18086:2019)

Corrosion des métaux et alliages - Détermination de la corrosion occasionnée par les

courants alternatifs - Critères de protection (ISO 18086:2019)
Ta slovenski standard je istoveten z: EN ISO 18086:2020
ICS:
77.060 Korozija kovin Corrosion of metals
SIST EN ISO 18086:2021 en,fr,de

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

---------------------- Page: 1 ----------------------
SIST EN ISO 18086:2021
---------------------- Page: 2 ----------------------
SIST EN ISO 18086:2021
EN ISO 18086
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2020
EUROPÄISCHE NORM
ICS 77.060 Supersedes EN ISO 18086:2017
English Version
Corrosion of metals and alloys - Determination of AC
corrosion - Protection criteria (ISO 18086:2019)

Corrosion des métaux et alliages - Détermination de la Korrosion von Metallen und Legierungen -

corrosion occasionnée par les courants alternatifs - Bestimmung der Wechselstromkorrosion -

Critères de protection (ISO 18086:2019) Schutzkriterien (ISO 18086:2019)
This European Standard was approved by CEN on 13 December 2020.

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

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 18086:2020 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 18086:2021
EN ISO 18086:2020 (E)
Contents Page

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

---------------------- Page: 4 ----------------------
SIST EN ISO 18086:2021
EN ISO 18086:2020 (E)
European foreword

The text of ISO 18086:2019 has been prepared by Technical Committee ISO/TC 156 "Corrosion of

metals and alloys” of the International Organization for Standardization (ISO) and has been taken over

as EN ISO 18086:2020 by 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 June 2021, and conflicting national standards shall be

withdrawn at the latest by June 2021.

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.

This document supersedes EN ISO 18086:2017.

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 18086:2019 has been approved by CEN as EN ISO 18086:2020 without any

modification.
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SIST EN ISO 18086:2021
---------------------- Page: 6 ----------------------
SIST EN ISO 18086:2021
INTERNATIONAL ISO
STANDARD 18086
Second edition
2019-12
Corrosion of metals and alloys —
Determination of AC corrosion —
Protection criteria
Corrosion des métaux et alliages — Détermination de la corrosion
occasionnée par les courants alternatifs — Critères de protection
Reference number
ISO 18086:2019(E)
ISO 2019
---------------------- Page: 7 ----------------------
SIST EN ISO 18086:2021
ISO 18086:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 18086:2021
ISO 18086:2019(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

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

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

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

4 Cathodic protection persons competence .................................................................................................................................. 5

5 Assessment of the AC influence ............................................................................................................................................................. 5

5.1 General ........................................................................................................................................................................................................... 5

5.2 Assessment of the level of interference ............................................................................................................................. 6

6 Evaluation of the AC corrosion likelihood.................................................................................................................................. 6

6.1 Prerequisite ............................................................................................................................................................................................... 6

6.1.1 General...................................................................................................................................................................................... 6

6.1.2 AC voltage on the structure .................................................................................................................................... 7

6.2 AC and DC current density ............................................................................................................................................................ 7

6.2.1 General...................................................................................................................................................................................... 7

6.2.2 AC current density .......................................................................................................................................................... 7

6.2.3 High cathodic DC current density ..................................................................................................................... 7

6.2.4 Low cathodic DC current density ...................................................................................................................... 8

6.2.5 Current ratio “I /I ” ............................................................................................................................................... 8

a.c. d.c.

6.2.6 Soil resistivity ..................................................................................................................................................................... 8

6.3 Corrosion rate .......................................................................................................................................................................................... 8

6.4 Pipeline coatings ................................................................................................................................................................................... 8

6.5 Evaluation of the metal loss ......................................................................................................................................................... 9

7 Acceptable interference levels ............................................................................................................................................................... 9

8 Measurement techniques ............................................................................................................................................................................ 9

8.1 Measurements ......................................................................................................................................................................................... 9

8.1.1 General...................................................................................................................................................................................... 9

8.1.2 Selection of test sites .................................................................................................................................................... 9

8.1.3 Selection of measurement parameter ........................................................................................................10

8.1.4 Sampling rate for the recording of interference levels ................................................................10

8.1.5 Accuracy of measuring equipment................................................................................................................10

8.1.6 Installation of coupons or probes to calculate current densities........................................10

8.2 DC potential measurements .....................................................................................................................................................10

8.3 AC voltage measurements ..........................................................................................................................................................11

8.4 Measurements on coupons and probes ..........................................................................................................................11

8.4.1 Installation of coupons or probes ..................................................................................................................11

8.4.2 Current measurements............................................................................................................................................12

8.4.3 Corrosion rate measurements...........................................................................................................................12

8.5 Pipeline metal loss techniques ...............................................................................................................................................13

9 Mitigation measures ......................................................................................................................................................................................13

9.1 General ........................................................................................................................................................................................................13

9.2 Construction measures .................................................................................................................................................................13

9.2.1 Modification of bedding material ...................................................................................................................13

9.2.2 Installation of isolating joints ............................................................................................................................13

9.2.3 Installation of mitigation wires ........................................................................................................................14

9.2.4 Optimization of pipeline and/or powerline route ...........................................................................14

9.2.5 Power line or pipeline construction.............................................................................................................14

9.3 Operation measures ........................................................................................................................................................................14

9.3.1 Earthing ................................................................................................................................................................................14

9.3.2 Adjustment of cathodic protection level ..................................................................................................15

9.3.3 Repair of coating defects ........................................................................................................................................15

© ISO 2019 – All rights reserved iii
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SIST EN ISO 18086:2021
ISO 18086:2019(E)

10 Commissioning ....................................................................................................................................................................................................16

10.1 Commissioning ....................................................................................................................................................................................16

10.2 Preliminary checking ......................................................................................................................................................................16

10.2.1 General...................................................................................................................................................................................16

10.2.2 Coupon AC voltage and current startup ...................................................................................................17

10.2.3 Verification of effectiveness.................................................................................................................................17

10.2.4 Installation and commissioning documents .........................................................................................17

11 Monitoring and maintenance ...............................................................................................................................................................18

Annex A (informative) Simplified description of the AC corrosion phenomenon ..............................................19

Annex B (informative) Coupons and probes ..............................................................................................................................................21

Annex C (informative) Coulometric oxidation .........................................................................................................................................26

Annex D (informative) Influence of soil characteristics on the AC corrosion process ...................................27

Annex E (informative) Other criteria that have been used in the presence of AC influence ....................28

Annex F (informative) Parameters to take into account to choose a DC decoupling device ....................32

Annex G (informative) Method to determine the reference electrode location to remote earth .......34

Annex H (informative) Simultaneous measurement on coupon current densities with high rate ...36

Bibliography .............................................................................................................................................................................................................................38

iv © ISO 2019 – All rights reserved
---------------------- Page: 10 ----------------------
SIST EN ISO 18086:2021
ISO 18086:2019(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 metal and alloys.

This second edition cancels and replaces the first edition (ISO 18086:2015), of which it constitutes a

minor revision. The changes compared to the previous edition are as follows:

— references cited informatively (EN 13509 and EN 15257) have been moved from Clause 2 to the

Bibliography;

— in Clause 7, the two instances of the phrase “AC current density” have been changed to “AC average

current density”.

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.
© ISO 2019 – All rights reserved v
---------------------- Page: 11 ----------------------
SIST EN ISO 18086:2021
ISO 18086:2019(E)
Introduction

This document has incorporated criteria and thresholds together with experience gained from the

most recent data. Various countries have a very different approach to the prevention of AC corrosion

depending primarily on the DC interference situation. These different approaches are taken into

account in two different ways:

— in the presence of “low” on-potentials, which allows a certain level of AC voltage (up to 15 V);

— in the presence of “high” on-potentials (with DC stray current interference on the pipeline for

instance), which requires the reduction of the AC voltage towards the lowest possible levels.

This document also gives some parameters to consider when evaluating the AC corrosion likelihood,

as well as detailed measurement techniques, mitigation measures, and measurements to carry out for

the commissioning of any AC corrosion mitigation system. Annex E proposes other parameters and

thresholds that require further validation based on practical experiences.
vi © ISO 2019 – All rights reserved
---------------------- Page: 12 ----------------------
SIST EN ISO 18086:2021
INTERNATIONAL STANDARD ISO 18086:2019(E)
Corrosion of metals and alloys — Determination of AC
corrosion — Protection criteria
1 Scope

This document specifies protection criteria for determining the AC corrosion risk of cathodically

protected pipelines.

It is applicable to buried cathodically protected pipelines that are influenced by AC traction systems

and/or AC power lines.

In the presence of AC interference, the protection criteria given in ISO 15589-1 are not sufficient to

demonstrate that the steel is being protected against corrosion.

This document provides limits, measurement procedures, mitigation measures, and information to

deal with long-term AC interference for AC voltages at frequencies between 16,7 Hz and 60 Hz and the

evaluation of AC corrosion likelihood.

This document deals with the possibility of AC corrosion of metallic pipelines due to AC interferences

caused by conductive, inductive or capacitive coupling with AC power systems and the maximum

tolerable limits of these interference effects. It takes into account the fact that this is a long-term effect,

which occurs during normal operating conditions of the AC power system.

This document does not cover the safety issues associated with AC voltages on pipelines. These are

covered in national standards and regulations (see, e.g., EN 50443).
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

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

ISO 8044, Corrosion of metals and alloys — Basic terms and definitions

ISO 15589-1, Petroleum, petrochemical and natural gas industries — Cathodic protection of pipeline

systems — Part 1: On-land pipelines

IEC 61010-1, Safety requirements for electrical equipment for measurement, control, and laboratory use —

Part 1: General requirements

EN 50443, Effects of electromagnetic interference on pipelines caused by high voltage AC electric traction

systems and/or high voltage AC power supply systems
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 8044 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
© ISO 2019 – All rights reserved 1
---------------------- Page: 13 ----------------------
SIST EN ISO 18086:2021
ISO 18086:2019(E)
3.1
AC electric traction system

AC railway electrical distribution network used to provide energy for rolling stock

Note 1 to entry: The system can comprise the following:
— contact line systems;
— return circuit of electric railway systems;

— running rails of non-electric railway systems, which are in the vicinity of and conductively connected to the

running rails of an electric railway system.
3.2
AC power supply system

AC electrical system devoted to electrical energy transmission, which includes overhead lines, cables,

substations and all apparatus associated with them
3.3
AC power system
AC electric traction system (3.1) or AC power supply system (3.2)

Note 1 to entry: Where it is necessary to differentiate, each interfering system (3.6) is clearly indicated with its

proper term.
3.4
copper/copper sulfate reference electrode
CSE

reference electrode consisting of copper in a saturated solution of copper sulfate

3.5
AC voltage

voltage measured to earth (3.9) between a metallic structure and a reference electrode

3.6
interfering system

general expression encompassing an interfering high voltage AC electric traction system (3.1) and/or

high voltage AC power supply system (3.2)
3.7
interfered system
system on which the interference (3.15) effects appear
Note 1 to entry: In this document, it is the pipeline system (3.8).
3.8
pipeline system
system of pipe network with all associated equipment and stations

Note 1 to entry: In this document, pipeline system refers only to metallic pipeline system.

Note 2 to entry: The associated equipment is the equipment electrically connected to the pipeline.

3.9
earth

conductive mass of the earth, of which the electric potential at any point is conventionally taken as

equal to zero
[SOURCE: IEC 60050-826]
2 © ISO 2019 – All rights reserved
---------------------- Page: 14 ----------------------
SIST EN ISO 18086:2021
ISO 18086:2019(E)
3.10
operating condition
fault-free operation of any system
Note 1 to entry: Transients are not to be considered as an operating condition.
3.11
fault condition

non-intended condition caused by a short-circuit to earth (3.9), the fault duration being the normal

clearing time of the protection devices and switches

Note 1 to entry: A short circuit is an unintentional connection of an energized conductor to earth or to any

metallic part in contact with earth.
3.12
conductive coupling

coupling that occurs when a proportion of the current belonging to the interfering system (3.6) returns

to the system earth (3.9) via the interfered system (3.7) or when the voltage to the reference earth of the

ground in the vicinity of the influenced object rises because of a fault in the interfering system and the

results of which are conductive voltages and currents
3.13
inductive coupling

phenomenon whereby the magnetic field produced by a current carrying circuit influences another circuit

Note 1 to entry: Coupling is quantified by the mutual impedance of the two circuits. The results of which are

induced voltages and, hence, currents that depend on, for example, the distances, length, inducing current, circuit

arrangement and frequency.
3.14
capacitive coupling

phenomenon whereby the electric field produced by an energized conductor influences another

conductor

Note 1 to entry: Coupling is quantified by the capacitance between the conductors and the capacitances between

each conductor and the earth (3.9). The results of which are interference (3.15) voltages into conductive parts or

conductors insulated from earth. These voltages depend, for example, on the voltage of the influencing system,

distances and circuit arrangement.
3.15
interference

phenomenon resulting from conductive, inductive or capacitive coupling (3.12, 3.13, 3.14) between

systems, which can cause malfunction, dangerous voltages, damage (3.17), etc.
3.16
disturbance

malfunction of a piece of equipment that loses its capability to work properly for the duration of the

interference (3.15)

Note 1 to entry: When the interference disappears, the interfered system (3.7) starts working properly again

without any external intervention.
3.17
damage

permanent reduction in the quality of service that can be suffered by the interfered system (3.7)

Note 1 to entry: A reduction in the quality of service could also be the complete cancellation of service.

EXAMPLE Coating perforation, pipe pitting, pipe perforation, permanent malfunction of the equipment

connected to the pipes.
© ISO 2019 – All rights reserved 3
---------------------- Page: 15 ----------------------
SIST EN ISO 18086:2021
ISO 18086:2019(E)
3.18
danger
state of the influenced system that is able to produce a threat to human life
3.19
interference situation

maximum distance between the pipeline system (3.8) and AC power system for which an interference

(3.15) is to be considered
3.20
interference voltage
voltage caused on the interfered sy
...

SLOVENSKI STANDARD
oSIST prEN ISO 18086:2020
01-oktober-2020

Korozija kovin in zlitin - Ugotavljanje nastanka AC korozije - Merila zaščite (ISO

18086:2019)

Corrosion of metals and alloys - Determination of AC corrosion - Protection criteria (ISO

18086:2019)
Korrosion von Metallen und Legierungen - Bestimmung der Wechselstromkorrosion -
Schutzkriterien (ISO 18086:2019)

Corrosion des métaux et alliages - Détermination de la corrosion occasionnée par les

courants alternatifs - Critères de protection (ISO 18086:2019)
Ta slovenski standard je istoveten z: prEN ISO 18086
ICS:
77.060 Korozija kovin Corrosion of metals
oSIST prEN ISO 18086:2020 en,fr,de

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

---------------------- Page: 1 ----------------------
oSIST prEN ISO 18086:2020
---------------------- Page: 2 ----------------------
oSIST prEN ISO 18086:2020
INTERNATIONAL ISO
STANDARD 18086
Second edition
2019-12
Corrosion of metals and alloys —
Determination of AC corrosion —
Protection criteria
Corrosion des métaux et alliages — Détermination de la corrosion
occasionnée par les courants alternatifs — Critères de protection
Reference number
ISO 18086:2019(E)
ISO 2019
---------------------- Page: 3 ----------------------
oSIST prEN ISO 18086:2020
ISO 18086:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO 18086:2020
ISO 18086:2019(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

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

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

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

4 Cathodic protection persons competence .................................................................................................................................. 5

5 Assessment of the AC influence ............................................................................................................................................................. 5

5.1 General ........................................................................................................................................................................................................... 5

5.2 Assessment of the level of interference ............................................................................................................................. 6

6 Evaluation of the AC corrosion likelihood.................................................................................................................................. 6

6.1 Prerequisite ............................................................................................................................................................................................... 6

6.1.1 General...................................................................................................................................................................................... 6

6.1.2 AC voltage on the structure .................................................................................................................................... 7

6.2 AC and DC current density ............................................................................................................................................................ 7

6.2.1 General...................................................................................................................................................................................... 7

6.2.2 AC current density .......................................................................................................................................................... 7

6.2.3 High cathodic DC current density ..................................................................................................................... 7

6.2.4 Low cathodic DC current density ...................................................................................................................... 8

6.2.5 Current ratio “I /I ” ............................................................................................................................................... 8

a.c. d.c.

6.2.6 Soil resistivity ..................................................................................................................................................................... 8

6.3 Corrosion rate .......................................................................................................................................................................................... 8

6.4 Pipeline coatings ................................................................................................................................................................................... 8

6.5 Evaluation of the metal loss ......................................................................................................................................................... 9

7 Acceptable interference levels ............................................................................................................................................................... 9

8 Measurement techniques ............................................................................................................................................................................ 9

8.1 Measurements ......................................................................................................................................................................................... 9

8.1.1 General...................................................................................................................................................................................... 9

8.1.2 Selection of test sites .................................................................................................................................................... 9

8.1.3 Selection of measurement parameter ........................................................................................................10

8.1.4 Sampling rate for the recording of interference levels ................................................................10

8.1.5 Accuracy of measuring equipment................................................................................................................10

8.1.6 Installation of coupons or probes to calculate current densities........................................10

8.2 DC potential measurements .....................................................................................................................................................10

8.3 AC voltage measurements ..........................................................................................................................................................11

8.4 Measurements on coupons and probes ..........................................................................................................................11

8.4.1 Installation of coupons or probes ..................................................................................................................11

8.4.2 Current measurements............................................................................................................................................12

8.4.3 Corrosion rate measurements...........................................................................................................................12

8.5 Pipeline metal loss techniques ...............................................................................................................................................13

9 Mitigation measures ......................................................................................................................................................................................13

9.1 General ........................................................................................................................................................................................................13

9.2 Construction measures .................................................................................................................................................................13

9.2.1 Modification of bedding material ...................................................................................................................13

9.2.2 Installation of isolating joints ............................................................................................................................13

9.2.3 Installation of mitigation wires ........................................................................................................................14

9.2.4 Optimization of pipeline and/or powerline route ...........................................................................14

9.2.5 Power line or pipeline construction.............................................................................................................14

9.3 Operation measures ........................................................................................................................................................................14

9.3.1 Earthing ................................................................................................................................................................................14

9.3.2 Adjustment of cathodic protection level ..................................................................................................15

9.3.3 Repair of coating defects ........................................................................................................................................15

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10 Commissioning ....................................................................................................................................................................................................16

10.1 Commissioning ....................................................................................................................................................................................16

10.2 Preliminary checking ......................................................................................................................................................................16

10.2.1 General...................................................................................................................................................................................16

10.2.2 Coupon AC voltage and current startup ...................................................................................................17

10.2.3 Verification of effectiveness.................................................................................................................................17

10.2.4 Installation and commissioning documents .........................................................................................17

11 Monitoring and maintenance ...............................................................................................................................................................18

Annex A (informative) Simplified description of the AC corrosion phenomenon ..............................................19

Annex B (informative) Coupons and probes ..............................................................................................................................................21

Annex C (informative) Coulometric oxidation .........................................................................................................................................26

Annex D (informative) Influence of soil characteristics on the AC corrosion process ...................................27

Annex E (informative) Other criteria that have been used in the presence of AC influence ....................28

Annex F (informative) Parameters to take into account to choose a DC decoupling device ....................32

Annex G (informative) Method to determine the reference electrode location to remote earth .......34

Annex H (informative) Simultaneous measurement on coupon current densities with high rate ...36

Bibliography .............................................................................................................................................................................................................................38

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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 metal and alloys.

This second edition cancels and replaces the first edition (ISO 18086:2015), of which it constitutes a

minor revision. The changes compared to the previous edition are as follows:

— references cited informatively (EN 13509 and EN 15257) have been moved from Clause 2 to the

Bibliography;

— in Clause 7, the two instances of the phrase “AC current density” have been changed to “AC average

current density”.

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.
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Introduction

This document has incorporated criteria and thresholds together with experience gained from the

most recent data. Various countries have a very different approach to the prevention of AC corrosion

depending primarily on the DC interference situation. These different approaches are taken into

account in two different ways:

— in the presence of “low” on-potentials, which allows a certain level of AC voltage (up to 15 V);

— in the presence of “high” on-potentials (with DC stray current interference on the pipeline for

instance), which requires the reduction of the AC voltage towards the lowest possible levels.

This document also gives some parameters to consider when evaluating the AC corrosion likelihood,

as well as detailed measurement techniques, mitigation measures, and measurements to carry out for

the commissioning of any AC corrosion mitigation system. Annex E proposes other parameters and

thresholds that require further validation based on practical experiences.
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INTERNATIONAL STANDARD ISO 18086:2019(E)
Corrosion of metals and alloys — Determination of AC
corrosion — Protection criteria
1 Scope

This document specifies protection criteria for determining the AC corrosion risk of cathodically

protected pipelines.

It is applicable to buried cathodically protected pipelines that are influenced by AC traction systems

and/or AC power lines.

In the presence of AC interference, the protection criteria given in ISO 15589-1 are not sufficient to

demonstrate that the steel is being protected against corrosion.

This document provides limits, measurement procedures, mitigation measures, and information to

deal with long-term AC interference for AC voltages at frequencies between 16,7 Hz and 60 Hz and the

evaluation of AC corrosion likelihood.

This document deals with the possibility of AC corrosion of metallic pipelines due to AC interferences

caused by conductive, inductive or capacitive coupling with AC power systems and the maximum

tolerable limits of these interference effects. It takes into account the fact that this is a long-term effect,

which occurs during normal operating conditions of the AC power system.

This document does not cover the safety issues associated with AC voltages on pipelines. These are

covered in national standards and regulations (see, e.g., EN 50443).
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

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

ISO 8044, Corrosion of metals and alloys — Basic terms and definitions

ISO 15589-1, Petroleum, petrochemical and natural gas industries — Cathodic protection of pipeline

systems — Part 1: On-land pipelines

IEC 61010-1, Safety requirements for electrical equipment for measurement, control, and laboratory use —

Part 1: General requirements

EN 50443, Effects of electromagnetic interference on pipelines caused by high voltage AC electric traction

systems and/or high voltage AC power supply systems
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 8044 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
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3.1
AC electric traction system

AC railway electrical distribution network used to provide energy for rolling stock

Note 1 to entry: The system can comprise the following:
— contact line systems;
— return circuit of electric railway systems;

— running rails of non-electric railway systems, which are in the vicinity of and conductively connected to the

running rails of an electric railway system.
3.2
AC power supply system

AC electrical system devoted to electrical energy transmission, which includes overhead lines, cables,

substations and all apparatus associated with them
3.3
AC power system
AC electric traction system (3.1) or AC power supply system (3.2)

Note 1 to entry: Where it is necessary to differentiate, each interfering system (3.6) is clearly indicated with its

proper term.
3.4
copper/copper sulfate reference electrode
CSE

reference electrode consisting of copper in a saturated solution of copper sulfate

3.5
AC voltage

voltage measured to earth (3.9) between a metallic structure and a reference electrode

3.6
interfering system

general expression encompassing an interfering high voltage AC electric traction system (3.1) and/or

high voltage AC power supply system (3.2)
3.7
interfered system
system on which the interference (3.15) effects appear
Note 1 to entry: In this document, it is the pipeline system (3.8).
3.8
pipeline system
system of pipe network with all associated equipment and stations

Note 1 to entry: In this document, pipeline system refers only to metallic pipeline system.

Note 2 to entry: The associated equipment is the equipment electrically connected to the pipeline.

3.9
earth

conductive mass of the earth, of which the electric potential at any point is conventionally taken as

equal to zero
[SOURCE: IEC 60050-826]
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3.10
operating condition
fault-free operation of any system
Note 1 to entry: Transients are not to be considered as an operating condition.
3.11
fault condition

non-intended condition caused by a short-circuit to earth (3.9), the fault duration being the normal

clearing time of the protection devices and switches

Note 1 to entry: A short circuit is an unintentional connection of an energized conductor to earth or to any

metallic part in contact with earth.
3.12
conductive coupling

coupling that occurs when a proportion of the current belonging to the interfering system (3.6) returns

to the system earth (3.9) via the interfered system (3.7) or when the voltage to the reference earth of the

ground in the vicinity of the influenced object rises because of a fault in the interfering system and the

results of which are conductive voltages and currents
3.13
inductive coupling

phenomenon whereby the magnetic field produced by a current carrying circuit influences another circuit

Note 1 to entry: Coupling is quantified by the mutual impedance of the two circuits. The results of which are

induced voltages and, hence, currents that depend on, for example, the distances, length, inducing current, circuit

arrangement and frequency.
3.14
capacitive coupling

phenomenon whereby the electric field produced by an energized conductor influences another

conductor

Note 1 to entry: Coupling is quantified by the capacitance between the conductors and the capacitances between

each conductor and the earth (3.9). The results of which are interference (3.15) voltages into conductive parts or

conductors insulated from earth. These voltages depend, for example, on the voltage of the influencing system,

distances and circuit arrangement.
3.15
interference

phenomenon resulting from conductive, inductive or capacitive coupling (3.12, 3.13, 3.14) between

systems, which can cause malfunction, dangerous voltages, damage (3.17), etc.
3.16
disturbance

malfunction of a piece of equipment that loses its capability to work properly for the duration of the

interference (3.15)

Note 1 to entry: When the interference disappears, the interfered system (3.7) starts working properly again

without any external intervention.
3.17
damage

permanent reduction in the quality of service that can be suffered by the interfered system (3.7)

Note 1 to entry: A reduction in the quality of service could also be the complete cancellation of service.

EXAMPLE Coating perforation, pipe pitting, pipe perforation, permanent malfunction of the equipment

connected to the pipes.
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3.18
danger
state of the influenced system that is able to produce a threat to human life
3.19
interference situation

maximum distance between the pipeline system (3.8) and AC power system for which an interference

(3.15) is to be considered
3.20
interference voltage

voltage caused on the interfered system (3.7) by the conductive, inductive or capacitive coupling (3.12,

3.13, 3.14) with the nearby interfering system (3.6) between a given point and the earth (3.9) or across

an insulating joint
3.21
IR drop

voltage due to any current, developed in an electrolyte such as the soil, between the reference electrode

and the metal of the structure, in accordance with Ohm’s Law (U = I × R)
3.22
IR-free potential
IR-free

pipe to electrolyte potential measured without the voltage error caused by the IR drop (3.21) due to the

protection current or any other current
3.23
off-potential
off

pipe to electrolyte potential measured after interruption of all sources of applied cathodic protection

current with the aim of approaching an IR-free potential (3.22)
Note 1 to entry: The delay before measurement varies according to circumstances.
3.24
on-potential

pipe to electrolyte potential measured while the cathodic protection system is continuously operating

3.25
spread resistance

ohmic resistance through a coating defect to earth (3.9) or from the exposed metallic surface of a

coupon (3.26) towards earth

Note 1 to entry: This is the resistance which controls the AC or DC current through a coating defect or an exposed

metallic surface of a coupon for a given AC or DC voltage.
3.26
coupon

metal sample of defined dimensions made of a metal equivalent to the metal of the pipeline

3.27
probe

device incorporating a coupon (3.26) that provides measurements of parameters to assess the

effectiveness of cathodic protection and/or corrosion risk
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4 Cathodic protection persons competence

Persons who undertake the design, supervision of installation, commissioning, supervision of operation,

measurements, monitoring and supervision of the maintenance of cathodic protection systems shall

have the appropriate level of competence for the tasks undertaken.

EN 15257 or the NACE Cathodic Protection Training and Certification Programme constitute suitable

methods of assessing and certifying the competence of cathodic protection personnel.

The competence of cathodic protection persons to the appropriate level for tasks undertaken should be

demonstrated by certification in accordance with prequalification procedures such as EN 15257, the

NACE Cathodic Protection Training and Certification Programme, or any other equivalent scheme.

5 Assessment of the AC influence
5.1 General

This document is applicable to all metallic pipelines and all high voltage AC traction systems and high

voltage AC power supply systems and all major modifications that can significantly change the AC

interference effect.
The effects are the following:

— danger to people who come in direct contact or contact through conductive parts with the metallic

pipeline or the connected equipment;
— damage of the pipeline or to the connected equipment;
— disturbance of electrical/electronic equipment connected to the pipeline.

Electrical/electronic systems installed on a pipeline network shall be chosen such that they will neither

become dangerous nor interfere with normal operating conditions because of short-term voltages and

currents, which appear during short circuits on the AC power system.

Long-term AC interference on a buried pipeline can cause corrosion due to an exchange of AC current

between the exposed metal of the pipeline and the surrounding electrolyte.

This exchange of current depends on an AC voltage of which the amplitude is related to various

parameters such as the following:
— configuration of AC power line phase conductors;
— presence and configuration of the earthing conductor;
— distance between the AC power line/traction system and the pipeline;
— current flowing in the AC power line/traction system phase conductors;
— average coating resistance of the pipeline;
— thickness of the coating;
— soil resistivity;
— presence of earthing systems;
— voltage of th
...

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