EN ISO 15589-2:2014

SLOVENSKI STANDARD
01-julij-2014
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Petroleum, petrochemical and natural gas industries - Cathodic protection of pipeline
transportation systems - Part 2: Offshore pipelines (ISO 15589-2:2012)
Erdöl- und Erdgasindustrie - Kathodischer Schutz für Transportleitungssysteme - Teil 2:
Offshore-Pipelines (ISO 15589-2:2012)
Industries du pétrole, de la pétrochimie et du gaz naturel - Protection cathodique des
systèmes de transport par conduites - Partie 2: Conduites en mer (ISO 15589-2:2012)
Ta slovenski standard je istoveten z: EN ISO 15589-2:2014
ICS:
75.200 2SUHPD]DVNODGLãþHQMH Petroleum products and
QDIWHQDIWQLKSURL]YRGRYLQ natural gas handling
]HPHOMVNHJDSOLQD equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 15589-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2014
ICS 75.200
English Version
Petroleum, petrochemical and natural gas industries - Cathodic
protection of pipeline transportation systems - Part 2: Offshore
pipelines (ISO 15589-2:2012)
Industries du pétrole, de la pétrochimie et du gaz naturel - Erdöl- und Erdgasindustrie - Kathodischer Schutz für
Protection cathodique des systèmes de transport par Transportleitungssysteme - Teil 2: Offshore-Pipelines (ISO
conduites - Partie 2: Conduites en mer (ISO 15589-2:2012) 15589-2:2012)
This European Standard was approved by CEN on 6 March 2014.

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, 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
© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 15589-2:2014 E
worldwide for CEN national Members.

Contents Page
Foreword .3
Foreword
The text of ISO 15589-2:2012 has been prepared by Technical Committee ISO/TC 67 “Materials, equipment
and offshore structures for petroleum, petrochemical and natural gas industries” of the International
Organization for Standardization (ISO) and has been taken over as EN ISO 15589-2:2014 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 September 2014, and conflicting national standards shall be
withdrawn at the latest by September 2014.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] 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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 15589-2:2012 has been approved by CEN as EN ISO 15589-2:2014 without any modification.

INTERNATIONAL ISO
STANDARD 15589-2
Second edition
2012-12-01
Petroleum, petrochemical and natural
gas industries — Cathodic protection
of pipeline transportation systems —
Part 2:
Offshore pipelines
Industries du pétrole, de la pétrochimie et du gaz naturel —
Protection cathodique des systèmes de transport par conduites —
Partie 2: Conduites en mer
Reference number
ISO 15589-2:2012(E)
©
ISO 2012
ISO 15589-2:2012(E)
© ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any
means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the
address below or ISO’s member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – All rights reserved

ISO 15589-2:2012(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and abbreviated terms . 4
4.1 Symbols . 4
4.2 Abbreviated terms . 4
5 General . 5
5.1 Competence assurance . 5
5.2 Compliance . 5
6 Cathodic protection system requirements . 5
6.1 General . 5
6.2 Selection of CP systems . 6
6.3 Isolating joints . 6
7 Design parameters . 7
7.1 General . 7
7.2 Protection potentials . 8
7.3 Design life .10
7.4 Design current densities for bare steel .10
7.5 Coating breakdown factors .12
8 Galvanic anodes .15
8.1 Design of system .15
8.2 Selection of anode material .16
8.3 Electrochemical properties .17
8.4 Anode shape and utilization factor .17
8.5 Mechanical and electrical considerations .18
9 Galvanic anode manufacturing .18
9.1 Pre-production test .18
9.2 Coating .18
9.3 Anode core materials .19
9.4 Aluminium anode materials .19
9.5 Zinc anode materials .20
10 Galvanic anode quality control .20
10.1 General .20
10.2 Steel anode cores .20
10.3 Chemical analysis of anode alloy .21
10.4 Anode mass .21
10.5 Anode dimensions and straightness .21
10.6 Anode core dimensions and position .22
10.7 Anode surface irregularities .22
10.8 Cracks .22
10.9 Internal defects, destructive testing .23
10.10 Electrochemical quality control testing .24
11 Galvanic anode installation .25
12 Impressed-current CP systems .26
12.1 Current sources and control .26
12.2 Impressed-current anode materials .26
12.3 System design.26
ISO 15589-2:2012(E)
12.4 Manufacturing and installation considerations.27
12.5 Mechanical and electrical considerations .27
13 Documentation .28
13.1 Design, manufacturing and installation documentation .28
13.2 Commissioning procedures .29
13.3 Operating and maintenance manual .29
14 Operation, monitoring and maintenance of CP systems .30
14.1 General .30
14.2 Monitoring plans .30
14.3 Repair .30
Annex A (normative) Galvanic anode CP design procedures .31
Annex B (normative) Attenuation of protection.37
Annex C (normative) Performance testing of galvanic anode materials .40
Annex D (normative) CP monitoring and surveys .42
Annex E (normative) Laboratory testing of galvanic anodes for quality control .49
Annex F (informative) Interference .51
Annex G (informative) Pipeline design for CP.53
Bibliography .59
iv © ISO 2012 – All rights reserved

ISO 15589-2:2012(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International
Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
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.
ISO 15589-2 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offhore structures
for petroleum, petrochemical and natural gas industries, Subcommittee SC 2, Pipeline transportation systems.
This second edition cancels and replaces the first edition (ISO 15589-2:2004), which has been technically
revised as follows:
— In Clause 6 recommendations for isolating joints are included.
— In Clause 7 a subclause on hydrogen-induced stress cracking evaluation is included.
— In Clause 7 coating breakdown factors have been reorganized by splitting into “with” and “without”
concrete coating. More conservative values for some coating systems have been selected based on
feedback from daily practice in industry.
— In Clause 8 recommendations on anode electrochemical properties for seawater with low salinity
are included.
— Design values for electrochemical capacity in Clause 8 have been reduced. Higher values are
permitted if properly documented.
— Quality control of anodes has been adjusted regarding tolerances, straightness, mass, surface
irregularities and cracking (Clause 10).
— The guidance on attenuation calculation has been significantly extended. A new Annex B has been
introduced and includes several examples and alternative methods.
— Regarding anode testing, only free-running testing is accepted (see Annex C).
ISO 15589 consists of the following parts, under the general title Petroleum, petrochemical and natural
gas industries — Cathodic protection of pipeline transportation systems:
— Part 1: On-land pipelines
— Part 2: Offshore pipelines
ISO 15589-2:2012(E)
Introduction
The technical revision of this part of ISO 15589 has been carried out in order to accommodate the needs
of industry and to move this International Standard to a higher level of service within the petroleum,
petrochemical and natural gas industry.
Pipeline cathodic protection is achieved by the supply of sufficient direct current to the external pipe
surface, so that the steel-to-electrolyte potential is lowered on all the surface to values at which external
corrosion is reduced to an insignificant rate.
Cathodic protection is normally used in combination with a suitable protective coating system to protect
the external surfaces of steel pipelines from corrosion.
Users of this part of ISO 15589 should be aware that further or differing requirements may be needed
for individual applications. This part of ISO 15589 is not intended to prevent alternative equipment or
engineering solutions from being used for individual applications. This may be particularly applicable
where there is innovative or developing technology. Where an alternative is offered, it is intended that
any variations from this part of ISO 15589 be identified and documented.
This part of ISO 15589 can also be used for offshore pipelines outside the petroleum, petrochemical and
natural gas industries.
vi © ISO 2012 – All rights reserved

INTERNATIONAL STANDARD ISO 15589-2:2012(E)
Petroleum, petrochemical and natural gas industries —
Cathodic protection of pipeline transportation systems —
Part 2:
Offshore pipelines
1 Scope
This part of ISO 15589 specifies requirements and gives recommendations for the pre-installation
surveys, design, materials, equipment, fabrication, installation, commissioning, operation, inspection
and maintenance of cathodic protection (CP) systems for offshore pipelines for the petroleum,
petrochemical and natural gas industries as defined in ISO 13623.
This part of ISO 15589 is applicable to carbon steel, stainless steel and flexible pipelines in offshore service.
This part of ISO 15589 is applicable to retrofits, modifications and repairs made to existing pipeline systems.
This part of ISO 15589 is applicable to all types of seawater and seabed environments encountered in
submerged conditions and on risers up to mean water level.
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 1461, Hot dip galvanized coatings on fabricated iron and steel articles — Specifications and test methods
ISO 8044, Corrosion of metals and alloys — Basic terms and definitions
ISO 8501-1, Preparation of steel substrates before application of paints and related products — Visual
assessment of surface cleanliness — Part 1: Rust grades and preparation grades of uncoated steel substrates
and of steel substrates after overall removal of previous coatings
ISO 9606-1, Qualification testing of welders — Fusion welding — Part 1: Steels
ISO 13623, Petroleum and natural gas industries — Pipeline transportation systems
ISO 15589-1, Petroleum, petrochemical and natural gas industries — Cathodic protection of pipeline
transportation systems — Part 1: On-land pipelines
ISO 15607, Specification and qualification of welding procedures for metallic materials — General rules
1)
ASTM D1141 , Standard Practice for the Preparation of Substitute Ocean Water
2)
AWS D1.1/D1.1M , Structural Welding Code — Steel
3)
EN 10025 (all parts) , Hot rolled products of structural steels
EN 10204:2004, Metallic products — Types of inspection documents
1) American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, USA.
2) American Welding Society, 550 NW Le Jeune Road, Miami, FL 33126, USA.
3) European Committee for Standardization, Management Centre, Avenue Marnix 17, B-1000, Brussels, Belgium.
ISO 15589-2:2012(E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8044 and the following apply.
3.1
anode potential
anode-to-electrolyte potential
3.2
anode sled
anodes installed on a structure and connected to the pipeline by a cable
3.3
closed-circuit anode potential
anode potential while electrically linked to the pipeline to be protected
3.4
coating breakdown factor
f
c
ratio of current density required to polarize a coated steel surface as compared to a bare steel surface
3.5
cold shut
horizontal surface discontinuity caused by solidification of the meniscus of the partially cast anodes as
a result of interrupted flow of the casting stream
3.6
driving voltage
difference between the pipeline/electrolyte potential and the anode/electrolyte potential when the
cathodic protection is operating
3.7
electric field gradient
change in electrical potential per unit distance through a conductive medium, arising from the flow of
electric current
3.8
electrochemical capacity
ε
total amount of electric charge that is produced when a fixed mass (usually 1 kg) of anode material is
consumed electrochemically
NOTE Electrochemical capacity is expressed in ampere hours.
3.9
final current density
estimated current density at the end of the lifetime of the pipeline
NOTE Final current density is expressed in amperes per square metre.
3.10
hydrogen-induced stress cracking
HISC
cracking due to a combination of load and hydrogen embrittlement caused by the ingress of hydrogen
formed at the steel surface due to the cathodic polarization
2 © ISO 2012 – All rights reserved

ISO 15589-2:2012(E)
3.11
IR drop
voltage due to any current, measured between two points of the metal of the pipe or two points of the
electrolyte, such as seawater or seabed, in accordance with Ohm’s law
NOTE IR drop and electric field gradient are related terms.
3.12
master reference electrode
reference electrode, calibrated with the primary calibration reference electrode, used for verification of
reference electrodes that are used for field or laboratory measurements
3.13
mean current density
estimated average cathodic current density for the entire lifetime of the pipeline
NOTE Mean current density is expressed in amperes per square metre.
3.14
protection potential
structure-to-electrolyte potential for which the metal corrosion rate is considered as insignificant
3.15
pitting resistance equivalent number
PREN
number, developed to reflect and predict the pitting resistance of a stainless steel, based on the
proportions of Cr, Mo, W and N in the chemical composition of the alloy
3.16
primary calibration reference electrode
reference electrode used for calibration of master reference electrodes
3.17
remotely operated vehicle
ROV
underwater vehicle operated remotely from a surface vessel or installation
[ISO 14723]
3.18
riser
part of an offshore pipeline, including any subsea spool pieces, which extends from the seabed to the
pipeline termination point on an offshore installation
[ISO 13623]
3.19
utilization factor
µ
fraction of the anodic material weight of a galvanic anode that can be consumed before the anode ceases
to provide the minimum required current output
ISO 15589-2:2012(E)
4 Symbols and abbreviated terms
4.1 Symbols
ε electrochemical capacity
f coating breakdown factor
c
µ utilization factor
4.2 Abbreviated terms
CAT cold-applied tape
CE carbon equivalent
CP cathodic protection
CRA corrosion-resistant alloy
EPDM ethylene propylene diene monomer
FBE fusion-bonded epoxy
HISC hydrogen-induced stress cracking
HSS heat-shrinkable sleeve
PE polyethylene
PP polypropylene
PREN pitting resistance equivalent number
PU polyurethane
ROV remotely operated vehicle
SCE saturated calomel electrode
SMYS specified minimum yield strength
SRB sulphate reducing bacteria
3LPE three-layer polyethylene
3LPP three-layer polypropylene
4 © ISO 2012 – All rights reserved

ISO 15589-2:2012(E)
5 General
5.1 Competence assurance
Personnel who undertake the design, supervision of installation, commissioning, supervision of
operation, measurements, monitoring and supervision of maintenance of cathodic protection systems
shall have the appropriate level of competence for the tasks undertaken.
NOTE 1 EN 15257 or the NACE Cathodic Protection Training and Certification Programme constitute suitable
methods that can be used to assess competence of cathodic protection personnel.
NOTE 2 Competence of cathodic protection personnel to the appropriate level for tasks undertaken can 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.
5.2 Compliance
A quality system and an environmental management system should be applied to assist compliance
with the requirements of this part of ISO 15589.
NOTE ISO/TS 29001 gives sector-specific guidance on quality management systems and ISO 14001 gives
guidance on the selection and use of an environmental management system.
6 Cathodic protection system requirements
6.1 General
The CP system shall be designed to prevent external corrosion over the design life of the pipeline and to:
— provide sufficient current to the pipeline to be protected and distribute this current so that the
selected criteria for CP are effectively attained on the entire surface;
— provide a design life of the anode system commensurate with the required life of the protected
pipeline, or to provide for periodic rehabilitation of the anode system;
— provide adequate allowance for anticipated changes in current requirements with time;
— ensure that anodes are installed where the possibility of disturbance or damage is minimal;
— provide adequate monitoring facilities to test and evaluate the system’s performance.
The CP system shall be designed with due regard to environmental conditions and neighbouring structures.
Offshore pipelines that are protected by galvanic anode systems should be electrically isolated from
other pipelines and structures that are protected by impressed-current systems. Offshore pipelines
shall be isolated from other unprotected or less protected structures, which could drain current from
the pipeline’s CP system. If isolation is not practical or stray current problems are suspected, electrical
continuity should be ensured.
Care shall be taken to ensure that different CP systems of adjacent pipelines or structures are compatible
and that no excessive current drains from one system into an adjacent system.
The pipeline CP design shall take into account the pipeline installation method, the types of pipeline and
riser, and the burial and stabilization methods proposed. Further guidance is given in Annex G.
The CP system based on galvanic anodes shall be designed for the lifetime of the pipeline system using
the calculation procedure given in Annex A.
For areas with high water velocities and areas with erosion effects (e.g. from entrained sand, silt, ice particles),
the design of the CP system needs special attention and additional design criteria shall be considered.
ISO 15589-2:2012(E)
Installation of permanent test facilities should be considered, taking into account specific parameters
such as pipeline length, water depth and underwater access related to the burial conditions.
ISO 15589-1 should be used for the cathodic protection of short lengths of offshore pipelines and their
branches that are directly connected to cathodically protected onshore pipelines.
6.2 Selection of CP systems
6.2.1 General
CP shall be achieved using either galvanic anodes or an impressed-current system. Galvanic anodes
shall be connected to the pipe, either individually or in groups
NOTE 1 Galvanic anodes are limited in current output by the anode-to-pipe driving voltage and the electrolyte
resistivity. Generally, anodes are attached directly to the pipe as bracelets. Sleds of anodes can also be placed at
regular intervals along the pipeline.
NOTE 2 Some pipelines can be protected by anodes located at each end. Typically, this type of installation
is used on inter-platform pipelines. Anodes for the pipeline can be attached to the platform if the pipeline is
electrically connected to the platform.
Items that shall be considered in selecting the system to be used are covered in 6.2.2.
6.2.2 System selection considerations
Selection of the CP system shall be based on the following considerations:
— magnitude of the protective current required;
— resistivity of the seawater;
— availability and location of suitable power sources for impressed-current systems;
— existence of any stray currents causing significant potential fluctuations between pipeline and
earth that can preclude the use of galvanic anodes;
— effects of any CP interference currents on adjacent structures that might limit the use of impressed-
current CP systems;
— limitations on the space available, due to the proximity of foreign structures, and related construction
and maintenance concerns;
— future development of the area and any anticipated future extensions to the pipeline system;
— cost of installation, operation and maintenance;
— reliability of the overall system;
— integrity of other pipelines and/or structures existing in the same area that could be affected by
impressed-current systems unless proper measures are taken to prevent these effects.
NOTE Impressed-current systems can be preferred on short pipelines which terminate at platforms that
have impressed-current systems installed or where an impressed-current system is operated from the shore.
Impressed-current systems can also be preferred as a retrofit system on pipelines with galvanic anode failures,
excessive anode consumption, operation beyond original design life or excessive coating deterioration. Impressed
current can also be the preferred method for high-resistivity water.
6.3 Isolating joints
Isolating joints should be considered at the following locations:
— at connections to onshore pipelines or onshore receiving facilities;
6 © ISO 2012 – All rights reserved

ISO 15589-2:2012(E)
— at connections to pipelines that require different protection criteria;
— between cathodically protected pipelines and non-protected facilities or less protected facilities;
— between pipeline systems (or structures) protected by impressed current and galvanic anodes.
If isolating joints are used they shall be designed and installed to ensure long-term integrity and shall
be positioned to allow easy access for inspection and maintenance. Detailed design requirements are
given in ISO 15589-1.
7 Design parameters
7.1 General
The design of a pipeline CP system shall be based on:
— detailed information on the pipeline to be protected, including material, length, wall thickness,
outside diameter, pipe-laying procedures, route, laying conditions on the sea bottom, temperature
profile (operating and shut in) along its whole length, type and thickness of corrosion-protective
coating(s) for pipes and fittings, presence, type and thickness of thermal insulation, mechanical
protection and/or weight coating;
— environmental conditions, including diurnal and seasonal variations, such as seawater salinity,
temperature and resistivity, tides and seabed resistivity along the whole length of the pipeline;
— burial status (extent of backfilling after trenching or natural burial) and soil resistivity;
— design life of the system;
— information on existing pipelines in close proximity to or crossing the new pipeline, including
location, ownership and corrosion-control practices;
— information on existing CP systems (platforms, landfalls, subsea structures, etc.) and electrical
pipeline isolation;
— availability of electrical power, electrical isolating devices, electrical bonds;
— applicable local legislation;
— construction dates, start-up date (required for hot lines);
— presence of fittings, J-tubes, risers, clamps, wyes, tees and other appurtenances; and
— performance data on CP systems in the same environment.
If CP performance data for similar environments is not available (for example when moving into deeper
water), data on the seawater characteristics (dissolved oxygen, salinity, pH, sea currents, and fouling)
shall be obtained as these can affect cathodic polarization and calcareous deposit formation. For these
situations, the required information shall be obtained from field surveys and/or corrosion test data
including the following:
— protective current requirements to meet applicable criteria;
— electrical resistivity of the electrolyte, including seasonal changes if relevant;
— pipe burial depth (if buried) and identification of exposed span lengths and locations;
— water temperature at the seabed;
— oxygen concentration at the seabed;
— water flow rate at the seabed, including seasonal changes if relevant;
ISO 15589-2:2012(E)
— seabed topography.
When reviewing operating experience, the following additional data should be considered:
— electrical continuity;
— electrical isolation;
— external coating integrity;
— deviation from specifications;
— maintenance and operating data.
Design procedures for the CP based on galvanic anode systems shall be in accordance with Annex A.
7.2 Protection potentials
7.2.1 Potential criteria
To ensure that adequate CP of a pipeline is being achieved, the measured potential shall be in accordance
with Table 1.
NOTE 1 The effectiveness of CP or other external corrosion-control measures can be confirmed by direct
measurement of the pipeline potential. However, visual observations of progressive coating deterioration and/or
corrosion, for example, are indicators of possible inadequate protection. Physical measurements of a loss of pipe
wall thickness, using divers, or using internal inspection devices such as intelligent pigs, can also indicate
deficiencies in the level of corrosion protection.
Table 1 — Potential criteria
a
Materials Minimum negative potential Maximum negative potential
V V
Carbon steels
b
Immersed in seawater − 0,80 − 1,10
f b
Buried in sediments − 0,90 − 1,10
g
Austenitic stainless steels
c d
PREN ≥ 40 − 0,30 − 1,10
c d
PREN < 40 − 0,50 − 1,10
d e
Duplex stainless steels − 0,50
d
Martensitic stainless (13 % Cr) − 0,50
e
steels
The potentials are referenced to an SCE reference electrode, which are equivalent to a silver/silver chloride
reference electrode (Ag/AgCl/seawater) in 30 Ω⋅cm seawater.
a
These negative limits also ensure negligible impact of CP on pipeline coatings.
b
Where pipeline systems are fabricated from high-strength steel (SMYS > 550 MPa), the most negative potential that
can be tolerated without causing hydrogen embrittlement shall be ascertained.
c
PREN = %Cr + 3,3 %(Mo+0,5W) + 16 %N.
d
For stainless steels, the minimum negative potentials apply for aerobic and anaerobic conditions.
e
Depending on the strength, specific metallurgical condition and stress level encountered in service, these alloys can
be susceptible to hydrogen embrittlement and cracking. If a risk of hydrogen embrittlement exists, then potentials more
negative than −0,8 V should be avoided. See also 7.2.3.
f
This covers the possibility of SRB activity and/or high pipeline temperature (T > 60°C).
g
If a metallurgical structure is not fully austenitic, these stainless steels can be susceptible to hydrogen-induced stress
cracking (HISC) and high negative potentials should be avoided.
8 © ISO 2012 – All rights reserved

ISO 15589-2:2012(E)
The potential of the Ag/AgCl/seawater reference electrode is dependent upon the concentration of
chloride ions in the electrolyte, and hence the seawater resistivity. If the chloride concentration and
hence the resistivity is known to differ significantly from that of ordinary seawater (typically 3,5 % and
30 Ω⋅cm respectively), the protection potential criteria shall be adjusted in accordance with Figure 1.
NOTE 2 The term “Ag/AgCl/seawater (undersaturated) reference electrode” can be used for this electrode.
Key
1 potential, in volts
2 resistivity, in Ω⋅cm
Figure 1 — Nomogram for the correction of potential readings made with the Ag/AgCl/seawater
[17]
electrode in waters of varying resistivity against the SCE and Cu/CuSO reference electrodes
EXAMPLE If brackish water of 100 Ω⋅cm resistivity exists at the pipeline potential measurement site, the
least negative potential for the effective corrosion-protection electrode will be −0,84 V and not −0,80 V as given
in Table 1, with reference to the Ag/AgCl/seawater reference electrode.
Alternative reference electrodes for specific conditions are given in D.3.2.
7.2.2 HISC evaluation for martensitic and duplex stainless steel materials
HISC is a non-ductile mode of failure caused by an interaction between stresses, the cathodic protection
system and a susceptible material. A special assessment shall be carried out to ensure that the risk of
HISC is minimized. All load contributions causing stress and strain shall be included.
[8]
For duplex stainless steels, DNV-RP-F112 may be used to assess acceptable stresses and strains.
ISO 15589-2:2012(E)
Fillet wel
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