EN 12473:2014

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Allgemeine Grundsätze des kathodischen Korrosionsschutzes in MeerwasserPrincipes généraux de la protection cathodique en eau de merGeneral principles of cathodic protection in seawater47.020.01Splošni standardi v zvezi z ladjedelništvom in konstrukcijami na morjuGeneral standards related to shipbuilding and marine structures25.220.40Kovinske prevlekeMetallic coatingsICS:Ta slovenski standard je istoveten z:EN 12473:2014SIST EN 12473:2014en,fr,de01-julij-2014SIST EN 12473:2014SLOVENSKI
STANDARDSIST EN 12473:20001DGRPHãþD

EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 12473
February 2014 ICS 47.020.01; 77.060 Supersedes EN 12473:2000English Version
General principles of cathodic protection in seawater
Principes généraux de la protection cathodique en eau de mer
Allgemeine Grundsätze des kathodischen Korrosionsschutzes in Meerwasser This European Standard was approved by CEN on 16 November 2013.
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Corrosion of carbon-manganese and low-alloy steels . 26 A.1 Nature of metallic corrosion . 26 A.2 Polarization . 27 Annex B (informative)
Principles of cathodic protection . 30 Annex C (informative)
Reference electrodes . 33 C.1 General . 33 C.2 Silver/silver chloride/seawater electrode . 33 C.3 The zinc/seawater electrode . 35 C.4 Verification of reference electrodes . 35 Annex D (informative)
Corrosion of metallic materials other than carbon-manganese and low-alloy steels typically subject to cathodic protection in seawater . 37 D.1 Stainless steels . 37 D.2 Nickel alloys . 37 D.3 Aluminium alloys . 37 D.4 Copper alloys . 38 Bibliography . 39
(ISO 13174); — EN 12496, Galvanic anodes for cathodic protection in seawater and saline mud; — EN 13173, Cathodic protection for steel offshore floating structures; — EN 16222, Cathodic protection of ship hulls; — EN 12474, Cathodic protection of submarine pipelines; — ISO 15589-2, Petroleum, petrochemical and natural gas industries — Cathodic protection of pipeline transportation systems — Part 2: Offshore pipelines. For cathodic protection of steel reinforced concrete whether exposed to seawater or to the atmosphere, EN ISO 12696 applies. 2 Normative 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 50162, Protection against corrosion by stray current from direct current systems EN ISO 8044, Corrosion of metals and alloys — Basic terms and definitions (ISO 8044) 3 Terms, definitions, abbreviations and symbols For the purposes of this document, the terms and definitions given in EN ISO 8044 and the following apply. NOTE The definitions given below prevail on their versions in EN ISO 8044. 3.1 acidity presence of an excess of hydrogen ions over hydroxyl ions (pH < 7) 3.2 alkalinity presence of an excess of hydroxyl ions over hydrogen ions (pH > 7) SIST EN 12473:2014

Slow strain rate testing may also be applied to other specimen geometries, e.g. bend specimens. 3.28 specified minimum yield strength SMYS minimum yield strength prescribed by the specification under which steel components are manufactured, obtained through standard analysis and representing a probabilistic value Note 1 to entry: It is an indication of the minimum stress steel components may experience that will cause plastic (permanent) deformation (typically 0,2 %). 3.29 stray currents current flowing through paths other than the intended circuits 3.30 structure to electrolyte potential difference in potential between a structure and a specified reference electrode in contact with the electrolyte at a point sufficiently close to, but without actually touching the structure, to avoid error due to the voltage drop associated with any current flowing in the electrolyte 3.31 sulphate reducing bacteria SRB group of bacteria that are found in most soils and natural waters, but active only in conditions of near neutrality and absence of oxygen and that reduce sulphates in their environment, with the production of sulphides and accelerate the corrosion of structural materials SIST EN 12473:2014

Key 1 seawater 2 galvanic anode 3 anode attachment 4 protected structure in seawater Figure 1 — Representation of cathodic protection using a galvanic anode on a structure in the seawater SIST EN 12473:2014

Key 1 insulated cathode cable 2 power supply (dc) 3 insulated anode cable 4 seawater 5 impressed current anode 6 protected structure in seawater Figure 2 — Representation of impressed current cathodic protection using inert anode in seawater Table 1 — Comparison of galvanic and impressed current systems
Galvanic systems Impressed current systems Environment Use can be impracticable in soils or waters of high resistivity. Use is not restricted by resistivity of soils or waters Installation Simple to install. Needs careful design otherwise can be complicated. Power source Independent of any source of electric power. Cannot be wrongly connected electrically. External supply necessary. Care needs to be taken to avoid electrical connection in wrong direction. Anodes Bulk of anode material can restrict water flow and introduce turbulence and drag penalties. Usually lighter and few in number. Anodes can be designed to have minimum effect on water flow. Control Tendency for their current to be self adjusting. Controllable. Control usually automatic and can be continuous. Interaction They are less likely to affect any neighbouring structures. Effects on other structures situated near the anodes need to be assessed. Maintenance Generally not required. May be renewed in some circumstances. Equipment designed for long life but regular checks required on electrical equipment in service. Continual power required. Damage Anodes are robust and not very susceptible to mechanical damage. Where a system comprises a large number of anodes, the loss of a few anodes has little overall effect on the system. Connections have to be able to withstand any forces applied to the structure. Electrical insulation of cables is not necessary. Anodes lighter in construction and therefore less resistant to mechanical damage. Loss of anodes can be more critical to the effectiveness of a system. Complete electrical insulation of positive cables exposed to electrolyte is mandatory. SIST EN 12473:2014

In aerobic environment −0,80 −1,10 In anaerobic environment and/or steel temperature > 60°C −0,90 −1,10 High strength steels (SMYS higher than 550 N/mm2) −0,80 −0f83 to −0fs5 (see cootnote a) Aluminium alloys
(Al Mg and Al Mg Si) −0,80 (negative potential swing 0,10 V) −1,10 Austenitic steels or nickel base alloys containing chromium and/or molybdenum
- (PREN ≥ 40) −0,30 no limit if fully austenitic, if not see Footnote c - (PREN < 40) −0,50 (see Footnote b) no limit if fully austenitic,
if not see Footnote c Duplex or martensitic stainless steels −0,50 (see Footnote b) see Footnote c Copper alloys without aluminium with aluminium
−0f45 to −0f60 −0f45 to −0f60
no limit −1,10 Nickel - copper alloys −0,50 see Footnote d a The negative potential limit should be determined by testing of the high strength steel for specific metallurgical and mechanical conditions (see 9.3.2). b For most applications these potentials are adequate for the protection of crevices although more positive potentials may be considered if documented. c Depending on metallurgical structure, these alloys can be susceptible to Hydrogen Stress Cracking (HSC) and potentials that are too negative should be avoided (see 6.3.2 and 9.3.2). d High strength nickel copper alloys can be subject to HSC and potentials that result in significant hydrogen evolution should be avoided (see 9.3.2). SIST EN 12473:2014

Figure 3 — Corrosion, cathodic protection and over-polarization regimes of steel expressed as a function of electrode potential 6.3 Other metallic materials 6.3.1 General General information on corrosion of metallic materials other than carbon-manganese or low alloy steels typically subject to cathodic protection in seawater is given in Annex D. 6.3.2 Stainless steels 6.3.2.1 Role of microstructure Austenitic microstructure is compatible with the range of potentials experienced in cathodic protection. Ferritic and martensitic microstructures can suffer from hydrogen embrittlement at too negative potentials in the form of HSC (Hydrogen Stress Cracking) which is a non-ductile mode of failure caused by an interaction between stresses, cathodic protection and a susceptible material (see 9.3.2). 6.3.2.2 Austenitic stainless steels Austenitic stainless steels can be generally protected using a potential of −0,50 V (Ag/AgCl/seawater reference electrode) but for the more corrosion resistant stainless steels (PREN ≥ 40c a potential of −0f30 V (Ag/AgCl/seawater reference electrode) is accepted for most applications. However, in view of the wide range of austenitic stainless steels available, other potentials should only be used if they are substantiated by documented service performance or appropriate laboratory tests. Austenitic stainless steels are not vulnerable to HSC if over-polarized when their metallurgical structure is fully austenitic. However, limitations identical to duplex stainless steels (see 6.3.2.3) shall be observed when ferritic and/or martensitic phases are present, e.g. due to cold deformation or welding (see DNV RP B401 [17]). SIST EN 12473:2014
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