Cathodic protection of internal surfaces of metallic tanks, structures, equipment, and piping containing seawater

This document specifies the requirements and recommendations for cathodic protection systems applied to the internal surfaces of metallic tanks, structures, equipment, and piping containing raw or treated seawater or brackish waters, to provide an efficient protection from corrosion.
Cathodic protection inside fresh water systems is excluded from this document. This is covered by EN 12499.
NOTE   EN 12499 covers internal cathodic protection for any kind of waters, including general aspects for seawater; but excluding industrial cooling water systems. This document specifically details applications in seawater and brackish waters.

Kathodischer Schutz der inneren Oberflächen von metallischen Tanks, Strukturen, Ausrüstung und Rohrleitungen die Meerwasser enthalten

Dieses Dokument legt die Anforderungen und Empfehlungen für kathodische Korrosionsschutzsysteme fest, die auf Innenflächen von metallischen Tanks, Anlagen, Anlagenteilen und Rohrleitungen, die unbehandeltes oder behandeltes Meerwasser oder Brackwasser enthalten, angewendet werden, um dort einen wirksamen Korrosionsschutz zu bieten.
Der kathodische Korrosionsschutz von Frischwassersystemen fällt nicht in den Anwendungsbereich dieses Dokuments. Dies wird von EN 12499 abgedeckt.
ANMERKUNG   EN 12499 enthält Informationen zum kathodischen Korrosionsschutz von Innenflächen in allen Arten von Wasser, einschließlich allgemeiner Aspekte für Meerwasser, jedoch ausschließlich industrieller Kühlwassersysteme. Dieses Dokument beschreibt gezielt Anwendungen in Meerwasser und Brackwasser.

Protection cathodique des surfaces internes des réservoirs, ouvrages, équipements et tuyauteries métalliques contenant de l’eau de mer

Le présent document spécifie les exigences et les recommandations relatives aux systèmes de protection cathodique appliqués aux surfaces internes des réservoirs, ouvrages, équipements et tuyauteries métalliques contenant de l’eau de mer naturelle ou traitée ou des eaux saumâtres afin d’assurer une protection efficace contre la corrosion.
La protection cathodique interne des systèmes d’eau douce est exclue de la présente norme. Elle est couverte par l’EN 12499.
NOTE   L’EN 12499 couvre la protection cathodique interne pour tous les types d’eaux, y compris les aspects généraux pour l’eau de mer, à l’exclusion des systèmes industriels de refroidissement par eau. Le présent document détaille spécifiquement les applications en eau de mer et en eaux saumâtres.

Katodna zaščita notranjih površin kovinskih rezervoarjev, konstrukcij, opreme in cevovodov, ki vsebujejo morsko vodo

General Information

Status
Published
Public Enquiry End Date
24-Oct-2018
Publication Date
06-Apr-2020
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
31-Mar-2020
Due Date
05-Jun-2020
Completion Date
07-Apr-2020

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SLOVENSKI STANDARD
SIST EN 17243:2020
01-maj-2020
Katodna zaščita notranjih površin kovinskih rezervoarjev, konstrukcij, opreme in
cevovodov, ki vsebujejo morsko vodo

Cathodic protection of internal surfaces of metallic tanks, structures, equipment, and

piping containing seawater
Kathodischer Schutz der inneren Oberflächen von metallischen Tanks, Strukturen,
Ausrüstung und Rohrleitungen die Meerwasser enthalten

Protection cathodique des surfaces internes des réservoirs, ouvrages, équipements et

tuyauteries métalliques contenant de l’eau de mer
Ta slovenski standard je istoveten z: EN 17243:2020
ICS:
47.020.30 Sistemi cevi Piping systems
77.060 Korozija kovin Corrosion of metals
SIST EN 17243:2020 en,fr,de

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

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SIST EN 17243:2020
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SIST EN 17243:2020
EN 17243
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2020
EUROPÄISCHE NORM
ICS 47.020.30; 77.060
English Version
Cathodic protection of internal surfaces of metallic tanks,
structures, equipment, and piping containing seawater

Protection cathodique des surfaces internes des Kathodischer Schutz der inneren Oberflächen von

réservoirs, ouvrages, équipements et tuyauteries metallischen Tanks, Strukturen, Ausrüstung und

métalliques contenant de l'eau de mer Rohrleitungen die Meerwasser enthalten
This European Standard was approved by CEN on 11 November 2019.

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 17243:2020 E

worldwide for CEN national Members.
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SIST EN 17243:2020
EN 17243:2020 (E)
Contents Page

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

Introduction .................................................................................................................................................................. 4

1 Scope .................................................................................................................................................................. 5

2 Normative references .................................................................................................................................. 5

3 Terms and definitions ................................................................................................................................. 5

4 Competence of personnel .......................................................................................................................... 7

5 General considerations ............................................................................................................................... 7

6 Cathodic protection criteria ...................................................................................................................... 9

7 Design ............................................................................................................................................................. 11

8 Galvanic anodes system ........................................................................................................................... 18

9 Impressed current systems .................................................................................................................... 26

10 Commissioning, operation and maintenance .................................................................................. 30

Annex A (informative) Environmental checklist ......................................................................................... 36

Annex B (informative) Guidance on design values for internal cathodic protection for seawater

containing equipment .............................................................................................................................. 38

B.1 Typical design cathodic current densities ........................................................................................ 38

B.2 Coating breakdown factor of protective paint systems ............................................................... 39

Annex C (informative) Calculation of potential distribution inside a pipe or tube ........................ 40

C.1 Potential distribution inside a pipe (ignoring anode resistance) ............................................ 40

C.2 Potential distribution inside a pipe (with anode resistance) .................................................... 40

C.3 Potential distribution inside a tube .................................................................................................... 41

Annex D (informative) Design of galvanic anode systems ....................................................................... 42

D.1 Anode resistance formulae .................................................................................................................... 42

D.2 Calculation of the anode resistance at the end of life ................................................................... 43

D.3 Electrolyte resistivity ............................................................................................................................... 44

D.4 Galvanic anode current output ............................................................................................................. 46

D.5 Anode life ...................................................................................................................................................... 47

D.6 Minimum net weight requirement ...................................................................................................... 47

Annex E (informative) Typical electrochemical characteristics of impressed current anodes . 48

Annex F (informative) Design of impressed current systems ................................................................ 49

F.1 Internal cathodic protection of tanks ................................................................................................. 49

F.2 Evaluation of the maximum length of a rod anode projecting into the water flow for

mechanical integrity ................................................................................................................................. 50

Bibliography .............................................................................................................................................................. 52

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SIST EN 17243:2020
EN 17243:2020 (E)
European foreword

This document (EN 17243:2020) has been prepared 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 2020, and conflicting national standards shall

be withdrawn at the latest by September 2020.

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 organisations 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.
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SIST EN 17243:2020
EN 17243:2020 (E)
Introduction

Metallic structures containing seawater or brackish waters are exposed to the risk of corrosion. Even

when a coating is applied to reduce this risk, cathodic protection (CP) is usually used to ensure corrosion

control during the structure design life. This is especially important in the presence of galvanic couples

between various metals and alloys because corrosion is then concentrated to the less noble material.

Cathodic protection works by supplying sufficient direct current to the internal surface of the structures

in contact with water in order to change the structure to electrolyte potential to values where the

corrosion rate is insignificant.

The general principles and theoretical aspects of cathodic protection in seawater are detailed in

EN 12473.
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SIST EN 17243:2020
EN 17243:2020 (E)
1 Scope

This document specifies the requirements and recommendations for cathodic protection systems applied

to the internal surfaces of metallic tanks, structures, equipment and piping containing natural or treated

seawater or brackish waters to provide an efficient protection from corrosion.

Cathodic protection inside fresh water systems is excluded from this document. This is covered by

EN 12499.

NOTE EN 12499 covers internal cathodic protection for any kind of waters, including general aspects for

seawater but excluding industrial cooling water systems. This document specifically details applications in seawater

and brackish waters.
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.

EN 12473, General principles of cathodic protection in seawater
EN 12496, Galvanic anodes for cathodic protection in seawater and saline mud
EN 12499, Internal cathodic protection of metallic structures
EN 13509, Cathodic protection measurement techniques

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

EN ISO 9606-1, Qualification testing of welders — Fusion welding — Part 1: Steels (ISO 9606-1)

EN ISO 15257, Cathodic protection — Competence levels of cathodic protection persons — Basis for

certification scheme (ISO 15257)

EN ISO 15607, Specification and qualification of welding procedures for metallic materials —General rules

(ISO 15607)

EN ISO 15609-1, Specification and qualification of welding procedures for metallic materials — Welding

procedure specification — Part 1: Arc welding (ISO 15609-1)
3 Terms and definitions

For the purposes of this document the terms and definitions given in EN 12473 and EN ISO 8044 and the

following apply.

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

— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp/ui
3.1
anode redundancy factor

multiplier applied to the theoretical number of anodes to allow for anode damage and failures for

ensuring that protection will continue to be achieved when one or more anodes are lost, without

modifying the unit weight of anodes
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SIST EN 17243:2020
EN 17243:2020 (E)
3.2
back electro motive force
e.m.f

overvoltages generated at anode and cathode interfaces at the operating conditions

3.3
cathodic protection zone
CP zone

part of the structure that can be considered independently with respect to cathodic protection design

3.4
coating breakdown factor

ratio of cathodic current density for a coated metallic material to the cathodic current density of the bare

material
3.5
critical crevice potential

potential more positive than the potential which there is a risk of initiation of crevice corrosion for a given

environment and crevice geometry
3.6
driving voltage

difference between the structure to electrolyte potential and the anode to electrolyte potential when the

cathodic protection is operating
3.7
over-polarization

occurrence in which the structure to electrolyte potentials are more negative than those required for

satisfactory cathodic protection

Note 1 to entry: Over-polarization provides no useful function and can even cause damage to the structure such as

cracking due to hydrogen embrittlement of sensitive materials or coating disbondment.

Note 2 to entry: Often incorrectly referred to as over-protection.
3.8
ullage factor

ratio of the surface area of a ballast tank which may be in contact with water to the total surface area

Note 1 to entry: When the entire surface area may be wetted, u = 1.
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SIST EN 17243:2020
EN 17243:2020 (E)
3.9
wetting factor

fraction of structure design life when the internal surface of a tank or a structure is in contact with water

Note 1 to entry: When the tank is permanently filled with water, k = 1.
Note 2 to entry: For changing conditions an average value can be considered.

Note 3 to entry: Also known as loading factor, see Reference [1] in the Bibliography.

3.10
hydrogen embrittlement

process resulting in a decrease of the toughness or ductility of a metal due to absorption of hydrogen

3.11
hydrogen stress cracking
HSC

cracking that results from the presence of hydrogen in a metal and tensile stress (residual and/or

applied)

Note 1 to entry: HSC describes cracking in metals which may be embrittled by hydrogen produced by cathodic

polarization without any detrimental effect caused by specific chemicals such as sulphides.

4 Competence of personnel

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. This competence should be

independently assessed and documented.

EN ISO 15257 constitutes a suitable method of assessing and certifying competence of cathodic

protection personnel.

Competence of cathodic protection personnel to the appropriate level for tasks undertaken should be

demonstrated by certification in accordance with EN ISO 15257 or by another equivalent prequalification

procedure.
5 General considerations
5.1 Structures and equipment to be protected

This document applies to the internals of any metallic tanks, structures, equipment, and piping. Examples

include ballast tanks, aboveground or buried storage tanks including firewater tanks, filters such as sand

filters, heat-exchangers and condensers, flooded sections of harbour and lock gates, sea defence barriers,

dolphins, and offshore wind turbine foundations.

This document applies to the external submerged areas of appurtenances and other independent

equipment fitted within tanks, such as pumps and piping, when they are not electrically isolated from the

structure. Where this document is applied to tanks, internal items that are integral to the tank, such as

stiffeners, shall also be included

This document applies also to the internal cathodic protection of piping transporting seawater or

brackish waters, including valves, pumps and fittings. In such applications, additional considerations are

required for the design and installation of cathodic protection.
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SIST EN 17243:2020
EN 17243:2020 (E)

This document is also applicable for temporary cathodic protection systems used to prevent corrosion

by seawater or brackish waters when structures are being hydrotested (see 7.3.4) and when filled tanks

or other equipment is in storage before commissioning and operation.
5.2 Materials

This document covers the cathodic protection of structures fabricated from or containing low carbon

steel, carbon manganese steel or cast iron. This document is applicable to coated and to bare structures.

This document also covers the cathodic protection of structures fabricated from or containing stainless

steels, nickel alloys, copper alloys or titanium alloys. This document is applicable to coated and to bare

structures.

The requirements and the recommendations for the cathodic protection systems described in this

document are intended to ensure control over any galvanic coupling, which could be caused by the use

of various metallic materials, and minimize risks due to hydrogen embrittlement or hydrogen stress

cracking (see EN 12473).
5.3 Environment

This document is applicable only to structures containing seawater or brackish waters. Seawater may be

either natural or treated (e.g. using chlorination systems) for preventing fouling of piping systems or for

preserving biodiversity when ship ballast tanks are filled and emptied in various locations of the world,

see Reference [2]. Special requirements can be necessary for structures containing polluted seawater or

other fluids, e.g. slop tanks.

For surfaces which are alternately immersed and exposed to the atmosphere, cathodic protection is only

effective when the structure is submerged and the immersion time is sufficiently long for the metal to

remain polarized.
5.4 Safety and environmental protection
5.4.1 General

This document does not cover routine safety and environmental protection aspects which are not

especially associated with cathodic protection. Safety requirements specific to the application of cathodic

protection within the scope of this document are covered.
An environmental checklist is supplied in Annex A.

For impressed current cathodic protection systems (ICCP), automatic control of applied potential shall

be used (see subclause 9.1). Provision shall be made to prevent sparking if the anode is energized outside

liquid level. Procedures to be adopted may include positioning of the anode so that it is always submerged

and/or incorporation of emergency shutdown procedures so that if the anode is temporarily exposed all

DC current is disabled.

The use of impressed current systems and of some galvanic anodes can be prohibited for some

applications, for instance when in the vicinity of tanks containing hydrocarbons (see subclause 8.5).

5.4.2 Evolution of dangerous gases

Cathodic protection will generate gaseous hydrogen and can generate oxygen and chlorine. Some

mixtures of oxygen and hydrogen are explosive; chlorine can be toxic and corrosive.

The design and operation of the cathodic protection systems shall take these risks into account to ensure

that harmful and dangerous levels of gas accumulation are not allowed to occur. This may include the

control of potential and/or the use of ventilation systems.

With galvanic anodes, the selection of alloy material should be carried out to minimize the risk.

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SIST EN 17243:2020
EN 17243:2020 (E)
5.4.3 Release of hydrogen gas

For impressed current systems, and with galvanic anodes (particularly magnesium anodes), the

polarization causes evolution of hydrogen gas on the protected structure. Thus, in situations such as

closed tanks where hydrogen can collect, an explosion hazard can arise. To mitigate this hazard, it is

necessary for all designs to include venting to prevent the build-up of a significant gaseous volume of

hydrogen. Gas levels should be monitored.

The rate of hydrogen evolution is related to the structure to electrolyte potential. Where hydrogen

evolution can produce an explosion hazard the structure to electrolyte potential shall be limited by design

or control.
5.4.4 Chlorine evolution

For impressed current cathodic protection systems working in seawater and brackish waters, one of the

anodic reactions results in the electrolytic formation of chlorine. Such a formation can cause physical

discomfort or downstream corrosion effects.

NOTE References [3] and [4] of the Bibliography provide information on toxic levels.

Chlorine production is related to the operating potential and material of the Impressed Current Cathodic

Protection (ICCP). In order to reduce chlorine production, the anode current density can be reduced at

design stage.
5.4.5 Access and emptying

Before opening an enclosed structure the impressed current cathodic protection system shall be turned

off. For galvanic and ICCP systems, the enclosure gas levels shall be declared safe.

6 Cathodic protection criteria
6.1 General

The criteria for cathodic protection shall be in accordance with EN 12473. The criteria are based on the

structure to electrolyte potential and the measurement techniques used shall ensure that this is

measured accurately (see subclause 10.2).

When different metals and alloys are in electrical continuity, the protection potential shall be the most

negative one in order to prevent any galvanic corrosion of the less noble of them

A negative limit to the potential may be required depending upon the metallic material in order to avoid

coating disbondment (see ISO 15711) [5] and/or adverse effects due to hydrogen evolution or high pH.

The potential criteria and limit values are expressed without IR errors. IR errors, due to cathodic

protection current flowing through resistive electrolyte and surface films on the protected surface, are

generally considered insignificant in marine applications. However, potential measurements using

“Instant OFF” techniques or “coupon Instant OFF” techniques can be necessary in applications described

in this document in order to adequately demonstrate the achievement of the protection criteria

(see EN 13509). Particular attention should be given to this in brackish waters and sedimentary deposits

or close to impressed current anodes.

The errors due to variations in salinity when using Ag/AgCl/sea water reference electrode in brackish

waters shall be addressed (see EN 12473).
6.2 Carbon and low alloy steels

To ensure the protection of carbon and low alloy steels in aerated seawater a protection potential more

negative than – 0,80 V with respect to (wrt) Ag/AgCl/sea water shall be achieved. This corresponds

approximately to + 0,23 V when measured with respect to a pure zinc electrode (e.g. alloy type Z2 as

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SIST EN 17243:2020
EN 17243:2020 (E)

defined in EN 12496) or + 0,25 V when measured with respect to a zinc electrode made with galvanic

anode alloy types Z1, Z3 or Z4 as defined in EN 12496.

When the water temperature or surface temperature of steel is higher than 60 °C, the criterion shall be –

0,90 V wrt Ag/AgCl/sea water. Between 40 °C and 60 °C the protection potential shall be interpolated

between −0,80 and −0,90 V wrt Ag/AgCl/sea water.

For tanks and structures containing seawater or brackish where the electrolyte is not frequently renewed

(e.g. less than once a month) the criterion for anaerobic conditions, i.e. – 0,90 Vwrt Ag/AgCl/sea water,

shall be adopted regardless of temperature.
6.3 Stainless steels and nickel alloys

In chloride-containing aerated environments such as natural seawater and brackish waters, stainless

steels are known to resist uniform corrosion and the possibility for crevice corrosion and pitting remains

the principal concern. To ensure the protection of such alloys in these environments, the protection

potentials given in EN 12473 apply, i.e. −0,30 V wrt Ag/AgCl/sea water for stainless steels with PREN ≥ 40

and −0,50 V wrt Ag/AgCl/sea water for stainless steels with PREN < 40.

However, less conservative criteria can be used provided that these are justified and documented. In this

case, the selected protection criteria shall be more negative than the critical crevice potential determined

for a combination of a particular alloy (PREN, microstructure, etc.), crevice parameters (geometry,

surface finish, type of gaskets, sealing pressure of flanges, etc.), and operating environmental conditions

(composition, temperature, velocity, etc.).

The determination of the critical crevice potential shall be carried out on the basis of demonstrated

service feedback and/or on laboratory tests relevant to the service conditions. In the absence of a more

relevant method for a given practical situation, the methods given in the References [6][7][8] should be

used.

In the case of galvanic couples between parts in stainless steel or nickel alloy and parts in carbon and low

alloy steel, the protection potential criterion of the carbon and low alloy steel shall be more negative

than – 0,80 V wrt Ag/AgCl/sea water.

In chlorinated seawater, the recommended protection potentials criteria for stainless steels and nickel

alloys are the same as those in natural seawater, but the protection current densities can be less (see

subclause 7.2.7).
6.4 Cracking risks induced by over polarization

Where there is a risk of hydrogen embrittlement or HSC of high strength steels or other metals which

may be adversely affected by cathodic protection to excessively negative values, a less negative potential

limit shall be defined and applied. If there is insufficient information for a given material, this specific

negative potential limit shall be determined relative to the metallurgical and mechanical conditions by

testing. Refer to EN 12473 for more details.

For carbon and low alloy steels, a potential negative limit of – 1,10 V wrt Ag/AgCl/sea water is

recommended in order to minimize cathodic disbondment. Other potential negative limits shall be

applied to prevent HSC of vulnerable metal compositions (refer to EN 12473).

For stainless steels and nickel alloys, ferritic and martensitic microstructures can suffer from hydrogen

embrittlement when the potentials are too negative. Potentials more negative than the particular limit

values should be avoided. EN 12473 gives information on this risk and also provides recommendations

for qualification of the materials.

Titanium and its alloys are prone to titanium hydride formation in cathodic protection applications. This

hydride can lead to cracking when stresses reach a critical level.

Heat exchanger tube inlets are areas of high mechanical stress due to construction methods. When heat

exchanger tubes are swaged into the tube sheets the tubes may be subject to high residual stress.

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EN 17243:2020 (E)

Titanium grade 2 tubes should not be subject to a potential more negative than – 0,75 V wrt Ag/AgCl/sea

water [9], some more conservative figures being found in the literature, see References [10][11], e.g. –

0,70 V [12] and even −0,65 V [13].

This conservative approach can be replaced by other criteria provided that these are justified and

documented by an assessment to ensure that the risk is acceptable. Such an assessment shall consider all

load contributions causing stress and strain. In any case, potential of the titanium shall not be more

negative than – 1,00 V wrt Ag/AgCl/seawater as specified in EN 12499 and documented in the literature,

see Reference [9].

For other applications where stresses and strains are lower, e.g. tubular plates, a negative limit of – 1,05 V

wrt Ag/AgCl/seawater is sufficiently conservative, see Reference [14].
7 Design
7.1 General considerations

The objective of a cathodic protection system is to deliver sufficient current to each part of the internal

surfaces of metallic tanks and structures, including bonded equipment, to achieve the protection criteria

defined in Clause 6. This current should be distributed so that the structure to electrolyte potential of

each part is within the limits given by the protection criteria during its normal service conditions (see

Clause 6). Permanent reference electrodes should be installed to allow measurement of the potentials at

selected locations.

Uniform levels of cathodic protection may be difficult to achieve in some areas or parts of structures. In

this case the use of reference electrodes installed in shielded areas is recommended, especially for

assisting the commissioning. The cathodic protection system for tanks and structures is generally

combined with a protective coating system, even though some equipment such as pumps and small pipes

may not be coated. A good coating is especially recommended when temperature and/or velocity of the

water is high, such as in pipeline systems or heat-exchange
...

SLOVENSKI STANDARD
oSIST prEN 17243:2018
01-oktober-2018
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Cathodic protection of internal surfaces of metallic tanks, structures, equipment, and

piping containing seawater
Kathodischer Schutz der inneren Oberflächen von metallischen Tanks, Strukturen,
Ausrüstung und Rohrleitungen die Meerwasser enthalten

Protection cathodique des surfaces internes des réservoirs, ouvrages, équipements et

tuyauteries métalliques contenant de l’eau de mer
Ta slovenski standard je istoveten z: prEN 17243
ICS:
47.020.30 Sistemi cevi Piping systems
77.060 Korozija kovin Corrosion of metals
oSIST prEN 17243:2018 en,fr,de

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

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oSIST prEN 17243:2018
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oSIST prEN 17243:2018
DRAFT
EUROPEAN STANDARD
prEN 17243
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2018
ICS 47.020.30; 77.060
English Version
Cathodic protection of internal surfaces of metallic tanks,
structures, equipment, and piping containing seawater

Protection cathodique des surfaces internes des Kathodischer Schutz der inneren Oberflächen von

réservoirs, ouvrages, équipements et tuyauteries metallischen Tanks, Strukturen, Ausrüstung und

métalliques contenant de l'eau de mer Rohrleitungen die Meerwasser enthalten

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

CEN/TC 219.

If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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,

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Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17243:2018 E

worldwide for CEN national Members.
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Contents Page

European foreword ...................................................................................................................................................... 4

Introduction .................................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 6

3 Terms and definitions ................................................................................................................................... 6

4 Competence of personnel ............................................................................................................................ 8

5 General considerations ................................................................................................................................. 8

5.1 Structures and equipment to be protected ........................................................................................... 8

5.2 Materials ............................................................................................................................................................ 8

5.3 Environment ..................................................................................................................................................... 9

5.4 Safety and environmental protection ...................................................................................................... 9

5.4.1 General................................................................................................................................................................ 9

5.4.2 Evolution of dangerous gases ..................................................................................................................... 9

5.4.3 Release of hydrogen gas ............................................................................................................................... 9

5.4.4 Chlorine evolution ........................................................................................................................................ 10

5.4.5 Emptying and opening ................................................................................................................................ 10

6 Cathodic protection criteria ...................................................................................................................... 10

6.1 General.............................................................................................................................................................. 10

6.2 Carbon manganese steels ........................................................................................................................... 10

6.3 Stainless steels and nickel alloys ............................................................................................................ 11

6.4 Cracking risks induced by over polarization ...................................................................................... 11

7 Design ................................................................................................................................................................ 12

7.1 Objectives ........................................................................................................................................................ 12

7.2 Design parameters ....................................................................................................................................... 12

7.2.1 General.............................................................................................................................................................. 12

7.2.2 Subdivision of the surfaces to be protected ........................................................................................ 13

7.2.3 Effective surface areas to be considered for calculations .............................................................. 14

7.2.4 Calculation of current demand for coated surface areas .............................................................. 14

7.2.5 Calculation of current demand for bare surface areas .................................................................... 15

7.2.6 Protection current density for bare carbon manganese steels .................................................... 15

7.2.7 Protection current density for stainless steels and nickel alloys................................................ 15

7.3 Applications for specific equipment ...................................................................................................... 16

7.3.1 Piping systems ............................................................................................................................................... 16

7.3.2 Tube and shell condensers and heat exchangers .............................................................................. 17

7.3.3 Filters ................................................................................................................................................................ 17

7.3.4 Temporary systems for hydrotesting of tanks using seawater .................................................... 17

7.3.5 Offshore wind turbine monopile ............................................................................................................. 18

8 Galvanic anodes system .............................................................................................................................. 18

8.1 Type, size, shape and number of anodes .............................................................................................. 18

8.2 Selection of anode material ....................................................................................................................... 18

8.3 Reduction of driving voltage using a resistor or a diode ................................................................ 19

8.4 Number and dimensions of anodes ........................................................................................................ 20

8.5 Anode location and installation ............................................................................................................... 21

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

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8.5.2 Tanks and structures with flat surfaces ............................................................................................... 21

8.5.3 Piping ................................................................................................................................................................ 24

8.6 Anode selection, location and installation in ballast tanks adjacent to other tanks

likely to involve the presence of explosive gas mixtures ............................................................... 26

9 Impressed current systems....................................................................................................................... 26

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

9.2 Anode location and installation .............................................................................................................. 27

9.2.1 General ............................................................................................................................................................. 27

9.2.2 Tanks and structures with flat surfaces ............................................................................................... 28

9.2.3 Piping ................................................................................................................................................................ 28

10 Commissioning, operation and maintenance ..................................................................................... 31

10.1 General ............................................................................................................................................................. 31

10.2 Measurement methods and monitoring ............................................................................................... 31

10.3 Commissioning and performance assessment ................................................................................... 32

10.4 Operation and maintenance ..................................................................................................................... 33

10.5 Objectives ........................................................................................................................................................ 33

10.6 Impressed current system......................................................................................................................... 33

10.7 Galvanic anode systems ............................................................................................................................. 34

Annex A (informative) Environmental checklist ............................................................................................ 35

Annex B (informative) Guidance on design values for internal cathodic protection for

seawater containing equipment ............................................................................................................. 37

B.1 Typical design cathodic current densities ........................................................................................... 37

B.2 Coating breakdown factor of protective paint systems .................................................................. 38

Annex C (informative) Calculation of potential distribution inside a pipe or tube ........................... 39

C.1 Potential distribution inside a pipe (ignoring anode resistance) ............................................... 39

C.2 Potential distribution inside a pipe (with anode resistance) ....................................................... 39

C.3 Potential distribution inside a tube ....................................................................................................... 40

Annex D (informative) Design of galvanic anode systems .......................................................................... 41

D.1 Anode resistance formulae ....................................................................................................................... 41

D.2 Calculation of the anode resistance at the end of life ...................................................................... 42

D.3 Electrolyte resistivity .................................................................................................................................. 43

D.4 Galvanic anode current output ................................................................................................................ 45

D.5 Anode life ......................................................................................................................................................... 46

D.6 Minimum net weight requirement ......................................................................................................... 46

Annex E (informative) Typical electrochemical characteristics of impressed current anodes .... 47

Annex F (informative) Design of impressed current systems .................................................................. 48

F.1 Internal cathodic protection of tanks .................................................................................................... 48

F.2 Evaluation of the extension of a rod anode for cathodic protection inside flowing

water ................................................................................................................................................................. 49

Bibliography ................................................................................................................................................................. 51

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European foreword

This document (prEN 17243:2018) has been prepared by Technical Committee CEN/TC 219 “Cathodic

protection”, the secretariat of which is held by BSI.
This document is currently submitted to the CEN Enquiry.
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Introduction

Metallic structures containing seawater or brackish waters are exposed to the risk of corrosion. Even

when a coating is applied to reduce this risk, cathodic protection is usually used to ensure corrosion

control during the design lifetime of the structure. This is especially important in the presence of

galvanic couples between various metals and alloys, because corrosion is then concentrated to the less

noble material.

Cathodic protection works by supplying sufficient direct current to the internal surface of the structures

in contact with water in order to change the steel to electrolyte potential to values where the corrosion

rate is insignificant.

The general principles and theoretical aspects of cathodic protection in seawater are detailed in

EN 12473.
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1 Scope

This document specifies the requirements and recommendations for cathodic protection systems

applied to the internal surfaces of metallic tanks, structures, equipment, and piping containing raw or

treated seawater or brackish waters, to provide an efficient protection from corrosion.

Cathodic protection inside fresh water systems is excluded from this document. This is covered by

EN 12499.

NOTE EN 12499 covers internal cathodic protection for any kind of waters, including general aspects for

seawater; but excluding industrial cooling water systems. This document specifically details applications in

seawater and brackish waters.
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.

EN 12473, General principles of cathodic protection in seawater
EN 12496, Galvanic anodes for cathodic protection in seawater and saline mud
EN 12499, Internal cathodic protection of metallic structures
EN 13509, Cathodic protection measurement techniques

EN ISO 8044, Corrosion of metals and alloys - Basic terms and definitions (ISO 8044)

EN ISO 9606-1, Qualification testing of welders - Fusion welding - Part 1: Steels (ISO 9606-1)

EN ISO 15607, Specification and qualification of welding procedures for metallic materials - General rules

(ISO 15607)

EN ISO 15609-1, Specification and qualification of welding procedures for metallic materials - Welding

procedure specification - Part 1: Arc welding (ISO 15609-1)
3 Terms and definitions

For the purpose of this document, the terms and definitions given in EN ISO 8044 and EN 12473 and the

following apply.

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

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
anode redundancy factor

multiplier applied to the theoretical number of anodes to allow for anode damage and failures for

ensuring that protection will continue to be achieved when one or more anodes are lost, without

modifying the unit weight of anodes
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3.2
cathodic protection zone

that part of the structure which can be considered independently with respect to cathodic protection

design
3.3
coating breakdown factor

ratio of cathodic current density for a coated metallic material to the cathodic current density of the

bare material
3.4
critical crevice potential

potential under which there is no risk of initiation of crevice corrosion for a given environment and

crevice geometry
3.5
driving voltage

difference between the structure to electrolyte potential and the anode to electrolyte potential when

the cathodic protection is operating
3.6
over-polarization

occurrence in which the structure to electrolyte potentials are more negative than those required for

satisfactory cathodic protection

Note 1 to entry: Over-polarization provides no useful function and might even cause damage to the structure such

as cracking due to hydrogen embrittlement and coating disbondment.
Note 2 to entry: Often incorrectly referred to as over-protection.
3.7
ullage factor

ratio of the surface area of a ballast tank which may be in contact with water to the total surface area

Note 1 to entry: When the entire surface area may be wetted, u = 1.
3.8
wetting factor

fraction of design life when the internal surface of a tank or a structure is in contact with water.

Note 1 to entry: When the tank is permanently filled with water, k = 1.
Note 2 to entry: For changing conditions an average value can be considered.
Note 3 to entry : Also known as loading factor [1].
3.9
hydrogen embrittlement

process resulting in a decrease of the toughness or ductility of a metal due to absorption of hydrogen

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3.10
hydrogen stress cracking
HSC

cracking that results from the presence of hydrogen in a metal and tensile stress (residual and/or

applied)

Note 1 to entry: HSC describes cracking in metals which may be embrittled by hydrogen produced by cathodic

polarization without any detrimental effect caused by specific chemicals such as sulphides

4 Competence of personnel

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. This competence should be

independently assessed and documented.

EN ISO 15257 constitutes a suitable method of assessing and certifying competence of cathodic

protection personnel which may be utilised.

Competence of cathodic protection personnel to the appropriate level for tasks undertaken should be

demonstrated by certification in accordance with EN ISO 15257 or by another equivalent

prequalification procedure.
5 General considerations
5.1 Structures and equipment to be protected

This European Standard applies to internal surfaces of ballast tanks, aboveground or buried storage

tanks including firewater tanks, filters such as sand filters, heat-exchangers and condensers, flooded

sections of harbour and lock gates, sea defence barriers, dolphins, and offshore wind turbine

foundations.

This European Standard applies to the external submerged areas of appurtenances and other

independent equipment fitted within tanks, such as pumps and piping, when they are not electrically

isolated from the structure. It also covers items that are integrated to the structure such as stiffeners.

This European Standard applies also to the internal cathodic protection of piping transporting seawater

or brackish waters, including valves, pumps and fittings. In such applications, additional considerations

are required for the design and installation of cathodic protection.

This European Standard is also applicable for temporary cathodic protection systems used to prevent

corrosion by seawater or brackish waters when they are used for hydrotesting and when they are

stored before commissioning and operation of tanks or other equipment.
5.2 Materials

This European Standard covers the cathodic protection of structures fabricated principally from bare or

coated carbon manganese steels.

This European Standard also covers the cathodic protection of structures fabricated from stainless

steels, nickel alloys, copper alloys or titanium alloys.

The requirements and the recommendations for the cathodic protection systems described in the

present standard ensure control over any galvanic coupling, which could be caused by the use of

various metallic materials, and minimise risks due to hydrogen embrittlement or hydrogen stress

cracking (see EN 12473).
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5.3 Environment

This European Standard is applicable only to structures containing seawater or brackish waters.

Seawater may be either raw or treated (e.g. using chlorination systems) for preventing fouling of piping

systems or for preserving biodiversity when ship ballast tanks are filled and emptied in various

locations of the world [2]. Special requirements can be necessary for structures containing polluted

seawater or other fluids, e.g. slop tanks.

For surfaces which are alternately immersed and exposed to the atmosphere, cathodic protection is

only effective when the structure is submerged and the immersion time is sufficiently long for the steel

to become polarised.
5.4 Safety and environmental protection
5.4.1 General

This European Standard does not cover routine safety and environmental protection aspects which are

not especially associated with cathodic protection. The relevant national or international regulations

shall apply.

Safety requirements specific to the application of cathodic protection within the scope of the present

European standard are covered.
An environmental checklist is supplied in Annex A.

For impressed current systems, automatic control of applied potential should be considered and/or

provision shall be made to prevent sparking if the anode is energized outside liquid level. Procedures to

be adopted may include positioning of the anode so that it is always submerged and/or incorporation of

emergency shutdown procedures so that if the anode is temporarily exposed all d.c. current is disabled.

The use of impressed current systems and of some galvanic anodes can be prohibited for some

applications, for instance when in the vicinity of tanks containing hydrocarbons [41] (see 8.6.).

5.4.2 Evolution of dangerous gases

Cathodic protection can generate gaseous hydrogen, oxygen and chlorine. Some mixtures of oxygen and

hydrogen are explosive; chlorine can be toxic and corrosive.

The design and operation of the cathodic protection systems shall take these risks into account to

ensure that harmful and dangerous levels of gas accumulation are not allowed to occur. This may

include the control of potential and/or the use of ventilation systems.

With galvanic anodes, the selection of alloy material should be carried out to minimise the risk.

5.4.3 Release of hydrogen gas

For impressed current systems, and with galvanic anodes (particularly magnesium anodes), the

polarisation causes evolution of hydrogen gas on the protected structure. Thus, in situations such as

closed tanks where hydrogen can collect, an explosion hazard can arise. To avoid this hazard, it is

necessary for all designs to include venting to prevent the build-up of a significant gaseous volume of

hydrogen. Gas levels should be monitored.

The rate of hydrogen evolution is related to the structure to electrolyte potential. Where hydrogen

evolution can produce an explosion hazard. The structure to electrolyte potential shall be controlled

and monitored.
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5.4.4 Chlorine evolution

For impressed current cathodic protection systems working in seawater and brackish waters, one of the

anodic reactions results in the electrolytic formation of chlorine. Such a formation can cause physical

discomfort or downstream corrosion effects.

NOTE Information on toxic levels can be found in the European Union Risk Assessment Report or the US

Department of Health and Human Services report [3].

In order to reduce chlorine production, the anodic current density should be minimised by a reduction

in the cathodic protection current demand and by an increase in the surface area of the anodes.

5.4.5 Emptying and opening

Before opening an enclosed structure the impressed cathodic protection system shall be turned off and

the enclosure gas levels declared safe.
6 Cathodic protection criteria
6.1 General

The criteria for cathodic protection generally used are given in the European Standard EN 12473

"General principles of cathodic protection in seawater". The criteria are based on the potential at the

surface of the metal to be protected and the measurement techniques used should ensure that this is

measured accurately (see 10.2).

When different metals and alloys are in electrical continuity, the protection potential achieved shall be

the most negative one in order to prevent any galvanic corrosion of the less noble of them.

A negative limit to the potential may be required depending upon the metallic material in order to avoid

coating disbondment (see ISO 15711) and/or adverse effects due to hydrogen evolution or high pH.

The potential criteria and limit values are expressed without IR errors. IR errors, due to cathodic

protection current flowing through resistive electrolyte and surface films on the protected surface, are

generally considered insignificant in marine applications. However, potential measurements using

“Instant OFF” techniques or “coupon Instant OFF” techniques can be necessary in applications

described in this European Standard in order to adequately demonstrate the achievement of the

protection criteria (see E
...

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