Corrosion of metals and alloys - Determination of AC corrosion - Protection criteria (ISO 18086:2015)

ISO 18086:2015 is applicable to buried cathodically-protected pipeline that is 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.
ISO 18086:2015 provides limits, measurement procedures, mitigation measures, and information to deal with long term AC interference for AC voltages at frequencies between 16,7 and 60 Hz and the evaluation of AC corrosion likelihood.
It deals with the possibility of AC corrosion of metallic pipelines due to AC interferences caused by inductive, conductive 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.
It does not cover the safety issues associated with AC voltages on pipelines. These are covered in national standards and regulations.

Korrosion von Metallen und Legierungen - Bestimmung der Wechselstromkorrosion - Schutzkriterien (ISO 18086:2015)

Corrosion des métaux et alliages - Détermination de la corrosion occasionnée par les courants alternatifs - Critères de protection (ISO 18086:2015)

L'ISO 18086:2015 est applicable 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.
L'ISO 18086:2015 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 engendré par ces courants.
Elle traite de la possible corrosion des canalisations métalliques due à l'influence des courants alternatifs provoquée par le couplage inductif, conductif ou capacitif avec des systèmes à courant alternatif, ainsi que des limites maximales admissibles des effets de cette influence. Elle 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.
Elle 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.

Korozija kovin in zlitin - Ugotavljanje nastanka AC korozije - Merila zaščite (ISO 18086:2015)

Standard ISO 18086:2015 se uporablja za vkopane katodno zaščitene cevovode pod vplivom izmeničnih vlečnih sistemov in/ali izmeničnih napajalnih vodov.
Če je prisotna izmenična motnja, merila zaščite, podana v standardu ISO 15589 1, ne zadostujejo kot dokaz, da je jeklo zaščiteno pred korozijo.
Standard ISO 18086:2015 določa omejitve, merilne postopke, ukrepe za ublažitev in informacije za obravnavo dolgoročne izmenične motnje za izmenične napetosti s frekvenco 16,7–60 Hz ter oceno verjetnosti nastanka korozije.
Obravnava verjetnost nastanka AC korozije kovinskih cevovodov zaradi izmeničnih motenj, ki jih povzroča induktivni, konduktivni ali kapacitivni sklop s sistemom za izmenično napajanje, in največje sprejemljive omejitve vplivov teh motenj. Upošteva, da gre za dolgoročni vpliv, do katerega pride med običajnimi delovnimi pogoji sistema za izmenično napajanje.
Standard ne zajema varnostnih vprašanj v zvezi z izmenično napetostjo v cevovodih. Varnostna vprašanja obravnavajo nacionalni standardi in predpisi.

General Information

Status
Withdrawn
Public Enquiry End Date
14-Jun-2017
Publication Date
15-Oct-2017
Withdrawal Date
12-Jan-2021
Current Stage
9900 - Withdrawal (Adopted Project)
Start Date
13-Jan-2021
Due Date
05-Feb-2021
Completion Date
13-Jan-2021

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SLOVENSKI STANDARD
SIST EN ISO 18086:2017
01-november-2017
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Corrosion of metals and alloys - Determination of AC corrosion - Protection criteria (ISO

18086:2015)
Korrosion von Metallen und Legierungen - Bestimmung der Wechselstromkorrosion -
Schutzkriterien (ISO 18086:2015)

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

courants alternatifs - Critères de protection (ISO 18086:2015)
Ta slovenski standard je istoveten z: EN ISO 18086:2017
ICS:
77.060 Korozija kovin Corrosion of metals
SIST EN ISO 18086:2017 en

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

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SIST EN ISO 18086:2017
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SIST EN ISO 18086:2017
EN ISO 18086
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2017
EUROPÄISCHE NORM
ICS 77.060
English Version
Corrosion of metals and alloys - Determination of AC
corrosion - Protection criteria (ISO 18086:2015)

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 18086:2015) Schutzkriterien (ISO 18086:2015)
This European Standard was approved by CEN on 23 August 2017.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, 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: Avenue Marnix 17, B-1000 Brussels

© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 18086:2017 E

worldwide for CEN national Members.
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SIST EN ISO 18086:2017
EN ISO 18086:2017 (E)
Contents Page

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

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SIST EN ISO 18086:2017
EN ISO 18086:2017 (E)
European foreword

The text of ISO 18086:2015 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 18086:2017 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 March 2018, and conflicting national standards shall

be withdrawn at the latest by March 2018.

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.

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, Former Yugoslav Republic of Macedonia,

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

Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 18086:2015 has been approved by CEN as EN ISO 18086:2017 without any modification.

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SIST EN ISO 18086:2017
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SIST EN ISO 18086:2017
INTERNATIONAL ISO
STANDARD 18086
First edition
2015-06-01
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 18086:2015(E)
ISO 2015
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SIST EN ISO 18086:2017
ISO 18086:2015(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2015, Published in Switzerland

All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2015 – All rights reserved
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SIST EN ISO 18086:2017
ISO 18086:2015(E)
Contents Page

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

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

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

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

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

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

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

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

5.2 Assessment of the level of interference ............................................................................................................................. 5

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 .................................................................................................................................... 6

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 ...................................................................................................................... 7

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 ......................................................................................................................................................... 8

7 Acceptable interference levels ............................................................................................................................................................... 8

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 ..........................................................................................................................................................10

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

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

8.4.2 Current measurements............................................................................................................................................11

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 ........................................................................................................................13

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 2015 – All rights reserved iii
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SIST EN ISO 18086:2017
ISO 18086:2015(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 ...............................................................................................................................................................17

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 2015 – All rights reserved
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SIST EN ISO 18086:2017
ISO 18086:2015(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 on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers

to Trade (TBT), see the following URL: Foreword — Supplementary information.

The committee responsible for this document is ISO/TC 156, Corrosion of metal and alloys.

© ISO 2015 – All rights reserved v
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SIST EN ISO 18086:2017
ISO 18086:2015(E)
Introduction

This International Standard 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

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

— in 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 International Standard 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 commissioning of any AC corrosion mitigation system. Note that Annex E proposes other

parameters and thresholds that require further validation based on practical experiences.

vi © ISO 2015 – All rights reserved
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SIST EN ISO 18086:2017
INTERNATIONAL STANDARD ISO 18086:2015(E)
Corrosion of metals and alloys — Determination of AC
corrosion — Protection criteria
1 Scope

This International Standard is applicable to buried cathodically-protected pipeline that is 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 International Standard provides limits, measurement procedures, mitigation measures, and

information to deal with long term AC interference for AC voltages at frequencies between 16,7 and

60 Hz and the evaluation of AC corrosion likelihood.

This International Standard deals with the possibility of AC corrosion of metallic pipelines due to

AC interferences caused by inductive, conductive 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 International Standard 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 referenced documents are indispensable for the application 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 15589-1, Petroleum, petrochemical and natural gas industries — Cathodic protection of pipeline

systems — Part 1: On-land pipelines
ISO 8044, Corrosion of metals and alloys — Basic terms and definitions

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

Part 1: General requirements
EN 13509, Cathodic protection measurement techniques

EN 15257, Cathodic protection — Competence levels and certification of cathodic protection personnel

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.

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;
© ISO 2015 – All rights reserved 1
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SIST EN ISO 18086:2017
ISO 18086:2015(E)
— 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 and includes overhead lines, cables,

substations and all apparatus associated with them
3.3
AC power system
AC electric traction system or AC power supply system

Note 1 to entry: Where it is necessary to differentiate, each interfering system 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 between a metallic structure and a reference electrode
3.6
interfering system

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

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

Note 1 to entry: In this International Standard, 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, whose electric potential at any point is conventionally taken as equal to

zero
[SOURCE: IEC 60050 826]
3.10
operating condition
fault-free operation of any system
Note 1 to entry: Transients are not to be considered as an operating condition.
2 © ISO 2015 – All rights reserved
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SIST EN ISO 18086:2017
ISO 18086:2015(E)
3.11
fault condition

non-intended condition caused by short-circuit to earth, the fault duration being the normal clearing

time of the protection devices and switches

Note 1 to entry: The 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 which occurs when a proportion of the current belonging to the interfering system returns to

the system earth via the interfered system 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: The coupling being quantified by the mutual impedance of the two circuits, and 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: The coupling being quantified by the capacitance between the conductors and the capacitances

between each conductor and earth, and the results of which are interference 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, capacitive, inductive coupling between systems and which can

cause malfunction, dangerous voltages, damage, etc.
3.16
disturbance

malfunction of an equipment losing its capability to work properly for the duration of the interference

Note 1 to entry: When the interference disappears, the interfered system starts working properly again without

any external intervention.
3.17
damage

permanent reduction in the quality of service which can be suffered by the interfered system

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, etc.
3.18
danger
state of the influenced system which is able to produce a threat to human life
© ISO 2015 – All rights reserved 3
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SIST EN ISO 18086:2017
ISO 18086:2015(E)
3.19
interference situation

maximum distance between the pipeline system and AC power system for which an interference is to

be considered
3.20
interference voltage

voltage caused on the interfered system by the conductive, inductive, and capacitive coupling with the

nearby interfering system between a given point and the earth 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 x R)
3.22
IR-free potential
IR-free

pipe to electrolyte potential measured without the voltage error caused by the IR drop 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
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 or from the exposed
...

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