SIST EN 12496:2013
(Main)Galvanic anodes for cathodic protection in seawater and saline mud
Galvanic anodes for cathodic protection in seawater and saline mud
This European Standard specifies the minimum requirements and gives recommendations for the chemical composition, the electrochemical properties, the physical tolerances, and the test and inspection procedures for cast galvanic anodes of aluminium, magnesium and zinc based alloys for cathodic protection in sea water and saline mud. This European Standard is applicable to the majority of galvanic anodes used for seawater and saline mud applications, i.e. cast anodes of trapezoidal, "D", or circular cross section and bracelet type anodes. The general requirements and recommendations of this European Standard may also be applied to other anode shapes, e.g. half spherical, button, etc., which are sometimes used for seawater applications.
Galvanische Anoden für den kathodischen Schutz in Seewasser und salzhaltigem Schlamm
Diese Europäische Norm legt die Mindestanforderungen fest und die chemische Zusammensetzung, die elektrochemischen Merkmale, die physischen Toleranzwerte, die Prüfverfahren und Prüfrichtlinien für galvanische Gussanoden aus auf Aluminium, Magnesium oder Zink basierende Legierungen für kathodischen Schutz in Seewasser und salzhaltigem Schlamm an.
Diese Europäische Norm gilt für die meisten galvanischen Anoden, die für Anwendungen in Meerwasser und salzhaltigem Schlick verwendet werden, d. h. Gussanoden mit trapez-, "D"-, oder kreisförmigem Querschnitt und Manschettenanoden.
Die allgemeinen Aspekte dieser Europäischen Norm dürfen auch für andere Anodenformen, beispielsweise halbrund, knopfförmig usw., angewendet werden, die manchmal für Meerwasseranwendungen benutzt werden.
Anodes galvaniques pour la protection cathodique dans l'eau de mer et les boues salines
La présente Norme européenne décrit des anodes galvaniques destinées à des applications dans l’eau de mer et les boues marines. Elle donne les exigences et recommandations minimales concernant les tolérances physiques, les caractéristiques ou propriétés électrochimiques, les modes opératoires d’essai et les normes d’inspection relatives aux anodes galvaniques coulées en alliages d’aluminium, de magnésium et de zinc destinées à la protection cathodique ; elle ne traite pas les aspects liés à l’assurance qualité.
La présente Norme européenne s’applique à la majorité des anodes galvaniques utilisées pour les applications dans l’eau de mer et les boues marines, c'est-à-dire des anodes coulées de section transversale trapézoïdale, « en D » ou circulaire et des anodes de type bracelet.
NOTE Les aspects génériques de la présente Norme européenne sont également applicables à d’autres formes d’anodes, par exemple demi-sphère, bouton, etc., parfois utilisées pour les applications dans l’eau de mer.
Galvanske anode za katodno zaščito v slani vodi in slanem blatu
Ta evropski standard določa minimalne zahteve in podaja priporočila za kemično sestavo, elektrokemične lastnosti, fizične tolerance ter preskusne postopke in postopke pregledovanja za lite galvanske anode iz zlitin aluminija, magnezija in cinka za katodno zaščito v slani vodi in slanem blatu. Ta evropski standard velja za večino galvanskih anod za katodno zaščito v slani vodi in slanem blatu, tj. za lite anode s trapeznim, »D« ali krožnim prerezom in anode v obliki zapestnice. Splošne zahteve in priporočila tega evropskega standarda lahko veljajo tudi za druge oblike anod, npr. anoda polkrožne oblike, v obliki gumba itd., ki se včasih uporabljajo v slani vodi.
General Information
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Galvanische Anoden für den kathodischen Schutz in Seewasser und salzhaltigem SchlammAnodes galvaniques pour la protection cathodique dans l'eau de mer et les boues salinesGalvanic anodes for cathodic protection in seawater and saline mud77.060Korozija kovinCorrosion of metalsICS:Ta slovenski standard je istoveten z:EN 12496:2013SIST EN 12496:2013en,de01-september-2013SIST EN 12496:2013SLOVENSKI
STANDARD
SIST EN 12496:2013
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 12496
June 2013 ICS 77.060 English Version
Galvanic anodes for cathodic protection in seawater and saline mud
Anodes galvaniques pour la protection cathodique dans l'eau de mer et les boues salines
Galvanische Anoden für den kathodischen Schutz in Seewasser und salzhaltigem Schlamm This European Standard was approved by CEN on 25 April 2013.
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
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Avenue Marnix 17,
B-1000 Brussels © 2013 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12496:2013: ESIST EN 12496:2013
bk k2n9p:2Mkm bbc 2 Contents Page coreword .m fntroduction .n k pcope .o 2 kormative references .o m Terms and definitions .o n dalvanic anode materials and their properties .8 n.k deneral .8 n.2 Anode alloy composition .8 n.m
blectrochemical properties .9 n.m.k deneral .9 n.m.2 motential .9 n.m.m Current capacity.9 n.m.n Anode consumption rate . kM o Anode design and acceptance criteria . kM o.k deneral . kM o.2 Chemical composition . kk o.m mhysical properties . kk o.n blectrochemical testing . kk o.o Anode core materials . k2 o.p Cable connections . km Annex A bnormativec
mhysical tolerances for galvanic anodes . kn A.k Anode mass . kn A.2 Anode dimensions and straightness . kn A.m pteel core . ko A.n Anode surface irregularities . ko A.o Cracks in cast anodic material . ko A.o.k deneral . ko A.o.2 ptand-off and flush mounting anodes . kp A.o.m Bracelet anodes . kp A.p fnternal defects and destructive testing . kp Annex B binformativec
Composition and performance properties for galvanic anodes . k8 B.k Aluminium alloys . k8 B.k.k Anode material . k8 B.k.2 blectrochemical properties . k9 B.2 Magnesium alloy . 2M B.2.k Anode material . 2M B.2.2 blectrochemical properties . 2k B.m winc alloy . 22 B.m.k Anode material . 22 B.m.2 blectrochemical properties . 2m Annex C binformativec
aescription of various electrochemical tests . 2n C.k cree running test. 2n C.2 dalvanostatic test . 2n C.m motentiostatic test . 2n C.n nuality control testing . 2o Bibliography . 2p
SIST EN 12496:2013
bk k2n9p:2Mkm bbc m coreword This document (EN 12496:2013) 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 December 2013, and conflicting national standards shall be withdrawn at the latest by December 2013. 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 organisations 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. SIST EN 12496:2013
bk k2n9p:2Mkm bbc n fntroduction The anticipated performance, including design life, of the cast galvanic anodes for use in sea water and saline mud is determined by their composition and the quality of their manufacture.
This European Standard specifies the minimum requirements for the galvanic anodes quality levels and verification procedures.
SIST EN 12496:2013
bk k2n9p:2Mkm bbc o k pcope This European Standard specifies the minimum requirements and gives recommendations for the chemical composition, the electrochemical properties, the physical tolerances, and the test and inspection procedures for cast galvanic anodes of aluminium, magnesium and zinc based alloys for cathodic protection in sea water and saline mud. This European Standard is applicable to the majority of galvanic anodes used for seawater and saline mud applications, i.e. cast anodes of trapezoidal, "D", or circular cross section and bracelet type anodes. The general requirements and recommendations of this European Standard may also be applied to other anode shapes, e.g. half-spherical, button, etc., which are sometimes used for seawater applications. 2 kormative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 287-1, Qualification test of welders Fusion welding Part 1: Steels EN 12473, General principles of cathodic protection in sea water EN ISO 8044,
EN 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 8501-1) 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) ISO 10474:1991, Steel and steel products Inspection documents m Terms and definitions For the purposes of this document, the terms and definitions given in EN ISO 8044 and EN 12473 and the following apply. m.k acidity presence of an excess of hydrogen ions over hydroxyl ions (pH <7) m.2 active surface surface condition where corrosion occurs m.m anode consumption rate
mass consumption rate amount of anode material consumed for a current output of one ampere during one year Note 1 to entry: The anode consumption rate is expressed in kilograms per amp year (kg/A.y). SIST EN 12496:2013
bk k2n9p:2Mkm bbc p m.n batch charge cast
unit that defines molten metal and identifies the anodes cast from it m.o bracelet anode anode shaped as half- or part-rings to be positioned on tubular items Note 1 to entry: Two or more part-ring anodes will have to fit together to become a bracelet anode. m.p calcareous deposit layer consisting of a mixture of calcium carbonate and magnesium hydroxide deposited on surfaces being cathodically protected in seawater due to the increased pH adjacent to the protected surface m.T cast see "batch" m.8 charge see "batch" m.9 closed circuit potential potential measured at the anode when a current is flowing in between the anode and the surface being protected m.kM cold shut horizontal surface discontinuity caused by solidification of a portion of a meniscus during the progressive filling of a mould, which is later covered with more solidifying metals as the molten metal level rises Note 1 to entry: Cold shuts generally occur at corners remote from the point of pour. m.kk core see "insert" m.k2 crack fracture of metal along a path producing a discontinuity similar to a ragged edge Note 1 to entry: It can occur during the solidification of the anode (hot cracking), during the contraction of the anode after solidification, or under externally applied loads. Hot cracking can be associated with the shrinkage depression that can occur in open-topped moulds. m.km current capacity total amount of electricity that is produced when one kilogram of anode material is consumed Note 1 to entry: The current capacity is expressed in amp-hours per kilogram (A.h/kg). m.kn driving voltage voltage established between the operating potential of a galvanic anode and the protection potential of the structure SIST EN 12496:2013
bk k2n9p:2Mkm bbc T Note 1 to entry: This figure is used in the calculation of anode current output from the anode/electrolyte resistance. m.ko electrochemical properties properties of potential and current capacity that characterise a galvanic anode and can be assessed by quantitative tests m.kp flush mounted anode anode fitted to a structure with one face in contact with or very close to the structure m.kT free running test electrochemical test where potential and current are not controlled m.k8
gas hole blow hole, channel or porosity produced by gas evolution during solidification Note 1 to entry: Gas holes can indicate contamination of the mould or core prior to casting. m.k9
heat product that is cast to a planned procedure in one melting operation in one furnace, without significant interruption Note 1 to entry: If the casting sequence is interrupted, the anodes produced before, between, and after the interruptions constitute "batches". m.2M insert core form over which the anode is cast and which is used to connect the anode to the structure requiring protection m.2k ladle sample specimen taken from a molten metal stream m.22 mass consumption rate see “anode consumption rate” m.2m non-metallic inclusions particles of oxides and other refractory materials entrapped in liquid metal during the melting or casting sequences m.2n passive surface condition of low surface activity or resistance to corrosion of a metal, as a result of protective film formation m.2o pit localised corrosion resulting in pits, i.e. cavities extending from the surface into the metal m.2p polarisation change in the potential of an electrode as the result of current flow to or from that electrode SIST EN 12496:2013
bk k2n9p:2Mkm bbc 8 m.2T shrinkage depressions natural concave surfaces produced when liquid metal is allowed to solidify in a container without the provision of extra liquid metal to compensate for the reduction in volume that occurs during the liquid-solid transformation Note 1 to entry: The term also applies to the concave surfaces produced when liquid metal is solidified in a closed mould in such a manner that the area is not "fed" by the liquid metal provided by the mould design. m.28 stand-off anode anode which is offset a certain distance from the object on which it is positioned
m.29 surface lap discontinuity caused by solidification of the meniscus of a partially cast anode as a result of interrupted flow of the casting stream Note 1 to entry: The solidified meniscus is covered with metal when the flow resumes. Cold laps can occur along the length of an anode. m.mM surface morphology description of the features or structure of the anode surface m.mk undercutting cutting away metal from below, e.g. caused by pitting corrosion or inter-granular corrosion n dalvanic anode materials and their properties n.k deneral Alloys used for galvanic anodes in seawater or saline mud shall be based on aluminium (Al), magnesium (Mg) and zinc (Zn). The performance, and therefore the suitability of a particular alloy for a specific application, will depend on the composition and characteristics of both the alloy and the electrolyte, temperature of operation and the anode current density. The properties of an anode alloy may be obtained from the performance data in the given environmental conditions. The performance data shall include the current capacity in amp-hours per kilogram (A.h/kg), and the closed circuit potential of a working anode measured against a standard reference electrode.
Alloys shall be ordered either in compliance with a generic alloy composition, where required performance properties have been previously established or to meet a specific performance characteristic. In the latter case, the supplier should be required to provide confirmation of performance as demonstrated against defined test procedures (see 5.4). n.2 Anode alloy composition The chemical composition of any alloy used for galvanic anodes shall be specified by the supplier and the corresponding electrochemical properties shall be determined and documented. The supplier shall provide supporting evidence for ensuring chemical composition according to 5.2. The performance of an alloy is dependent on the specific alloy composition, resulting in variations in activation, resistance to passivation, current capacity and consumption morphology. In particular, some elements are known to have a detrimental effect on the anode performance and their content is normally subject to strict control. SIST EN 12496:2013
bk k2n9p:2Mkm bbc 9 The most common galvanic anode compositions for aluminium, magnesium and zinc based anode alloys are given in Annex B. The required range of alloying elements will vary significantly, the tolerance on the composition changes with the range. For example, zinc content in aluminium based alloys can range from 2 % to 6 % (tolerance ± 0,5 %), while indium content will typically be 0,01 % to 0,05 % (tolerance ± 0,005 %). n.m
blectrochemical properties n.m.k deneral The performance of a galvanic anode material (alloy) is dependent on its actual chemical composition and homogeneity, current density and the environmental conditions in which it is exposed. Since the method of cathodic protection is electrochemical in nature, the anode material's electrochemical properties shall be determined under the expected environmental operating conditions. These may include: potential; current capacity; anode consumption rate. In addition, anode surface morphology affects the efficiency and shall also be determined. These properties of the anode material shall be determined by appropriate tests (see 5.4). Annex C describes the test methods that are most often used. n.m.2 motential The selected anode alloy shall have a closed circuit potential more negative than the protection potential required for cathodic protection. The anode alloy operating potential shall be stable with time to ensure long-term performance and shall be documented by long-term testing for the particular operating environment. Where long-term performance data relating to anode operating potential are not available for a specific alloy/environmental combination, additional tests should be carried out to determine the effect of current density, temperature and time on the operating potential in the particular environment and the various operating conditions of the anode. Anode alloys will polarise, i.e. change potential, when current is passed. It is the potential of a working anode, i.e. the closed circuit potential, that is important. The potential of an anode material will also vary with the surrounding environment. The potential may change with time even when exposed to constant conditions due to corrosion products being formed on the anode surface and due to variations in the current demand.
The anode operating potential is generally more negative than -1,00 V measured with a Ag/AgCl/seawater reference electrode. However, where a low driving voltage is required either special anode compositions (with operating potential of -0,85 V vs. Ag/AgCl/seawater reference electrode) or anodes with a voltage controller (such as diode or resistive bond) between the anode and the structure can be used.
n.m.m Current capacity The current capacity for a galvanic anode alloy is expressed in ampere.hours per kilogram (A.h/kg) and is the total amount of electricity (A.h) that is produced in practice when one kilogram of the anode material is consumed for a given operating condition. The practical current capacity is different for anode materials exposed to different environmental conditions such as hot and cold seawater, seabed mud, etc. SIST EN 12496:2013
bk k2n9p:2Mkm bbc kM The anode alloy practical current capacity shall be documented by long-term testing for the particular operating environment. Where long-term performance data relating to anode capacity are not available for a specific alloy/environmental combination, then additional tests should be carried out to determine the effect of current density, temperature and time on the current capacity of the alloy in the particular environment and the various operating conditions of the anode. NOTE Due to self-corrosion, all anode materials have a practical current capacity lower than that calculated by consideration of the theoretical electrical equivalence determined by Faraday’s Law (i.e. some of the current produced by consumption of the anode is used for self-corrosion of the anode material and is not available for cathodic protection). It is the practical current capacity that is used in cathodic protection design. For example, the theoretical capacity of alloy M1 is approximately 2 220 A.h/kg whereas the practical capacity is only 1 200 A.h/kg. The electrochemical properties of galvanic anodes are temperature dependent and should be known for the design of cathodic protection systems for risers and submarine pipelines transporting commodity at elevated temperature. The practical current capacity decreases with increasing temperature both in seawater and in marine sediments.
The practical current capacity increases with increasing anode current density. At extremely low current densities, self-corrosion may be more pronounced and can give a significant reduction in the practical current capacity.
n.m.n Anode consumption rate The anode consumption rate for a galvanic alloy anode is expressed in kilograms per ampere.year (kg/A.y) and is the total amount of anode material consumed in practice for a current output of one ampere during one year. Like current capacity (see 5.3), all anode materials have a practical consumption rate different from their theoretical consumption rate. In this case, the consumption rate is higher than that calculated by Faraday’s Law.
The anode consumption rate and the current capacity are related by:
where E is anode consumption rate (kg/A.y); Q is current capacity (A.h/kg); 8 760 is number of hours in one year. o Anode design and acceptance criteria o.k deneral The anodes, including cores and supports, shall be designed in such a way as to give the specified performance during fabrication, transport, installation and operation. The dimensions and shape of the anodes, steel core and attachments shall be designed to withstand the mechanical forces that may act on the anodes, for example waves, currents, pile driving or vibration. For all anodes, the anode and anode core dimensions shall be designed for the proposed fitting requirements. Any special provisions needed to make the core compatible with the attachment to the protected structure shall take preference over other requirements. In subsea areas where divers or remote operated vehicles are likely to operate, stand-off type anodes should be provided so that the support cores protrude through the end-faces of the anode, in order to reduce the danger of entangling wires, ropes, umbilical cables, etc.
8 760 = ⋅ Q E SIST EN 12496:2013
bk k2n9p:2Mkm bbc kk Over-pouring to fill shrinkage depressions shall be kept to a minimum. All pouring of molten anode alloy shall be finished before the surface of the cast anode solidifies. The surface of the anode may be kept in a liquid state for a while by applying heat, i.e. from gas burners, but once solidified, no re-melting shall be allowed, not even to fill shrinkage depressions.
The exposed (external) surfaces of the anode shall not be subject to any coating, except for flush mounted and bracelet anodes where the anode surface facing, immediately adjacent, to the structure surface to be protected may be coated. Physical tolerances of anodes shall be confirmed in accordance with the requirements of Annex A.
NOTE
Further information for inspection of anodes is given in NACE SP0492-2006 and NACE SP0387-2006.
o.2 Chemical composition Galvanic anode material performance is related to the chemical composition. Therefore, strict control of the alloy chemical composition, both alloying elements and impurities, is essential.
All samples shall be identified with the cast number. All anodes should be similarly identified with the cast number. The samples shall be analysed to prove compliance with the agreed chemical composition limits of the alloy being produced. Additional sample(s) may be taken and stored for future determination of chemical composition.
Two samples from each heat shall be taken for chemical analysis. The samples shall be taken in the beginning and at the end of casting from the pouring stream. For smaller alloying furnaces (max. 500 kg), one sample per heat may be sufficient. The sample shall be taken at the beginning of the first heat and at the end of the second heat, then in the beginning of the third heat and so on. The samples shall be analysed to verify the required chemical composition.
Anodes from heats whose chemical composition do not meet the required chemical composition shall be rejected. For alloys where heat treatment forms part of the specification, details of the heat treatment history for each furnace charge shall be recorded. The chemical analysis and the temperature sensing and recording equipment shall be suitably calibrated. o.m mhysical properties The physical and dimensional tolerances determined by the anode design shall be complied with. No anode or its steel core shall have any defect either on its surface or within its body that will affect the transportation, installation and future performance of the anode. Tolerances defined in Annex A shall be respected. o.n blectrochemical testing Where there are no reliable historical or laboratory data relating to the performance of a specific anode alloy in a particular environment, electrochemical testing shall be carried out to confirm the relevant anode operating potential and anode capacity. The same kind of testing shall also be performed on any field proven alloy composition when manufactured by a supplier that has not been qualified for this composition. The laboratory test procedure shall be selected to provide best representation of the expected operating conditions (including electrolyte, temperature and anode current density).
The three main electrochemical techniques used for anode testing are: free running, galvanostatic (constant current) and potentiostatic (constant potential) methods. Each of these test methods emphasises different SIST EN 12496:2013
bk k2n9p:2Mkm bbc k2 aspects of the anode performance. It is therefore important when choosing a test method that the relevant factors of the anode performance will be revealed by that technique.
Galvanostatic tests (as described in C.2) should only be used as a quality assurance test to confirm the performance of known alloy type in a known environment. Where a new alloy is to be used or where an alloy is to be used in a different environment (e.g. salinity, temperature) where there are no documented historical field perf
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