BS EN 12473-2014 General principles of cathodic protection in seawater《海水中阴极保护的一般原则》.pdf

1、BSI Standards PublicationBS EN 12473:2014General principles of cathodicprotection in seawaterBS EN 12473:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN 12473:2014. Itsupersedes BS EN 12473:2000 which is withdrawn.The UK participation in its preparation was

2、 entrusted to TechnicalCommittee GEL/603, Cathodic protection.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The

3、 British Standards Institution 2014. Published by BSI StandardsLimited 2014ISBN 978 0 580 77497 3ICS 47.020.01; 77.060Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee

4、on 28 February 2014.Amendments issued since publicationDate Text affectedBS EN 12473:2014EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 12473 February 2014 ICS 47.020.01; 77.060 Supersedes EN 12473:2000English Version General principles of cathodic protection in seawater Principes gnraux de la

5、 protection cathodique en eau de mer Allgemeine Grundstze des kathodischen Korrosionsschutzes in Meerwasser This European Standard was approved by CEN on 16 November 2013. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this Europea

6、n 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 (

7、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, Belgi

8、um, 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, Switzer

9、land, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2014 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national

10、Members. Ref. No. EN 12473:2014 EBS EN 12473:2014EN 12473:2014 (E) 2 Contents Page Foreword 4 1 Scope 5 2 Normative references 5 3 Terms, definitions, abbreviations and symbols .5 4 Application of cathodic protection in seawater 9 4.1 General 9 4.2 Galvanic anode method 9 4.3 Impressed current metho

11、d 10 4.4 Hybrid systems . 10 5 Determination of level of cathodic protection . 12 5.1 Measurement of protection level . 12 5.2 Reference electrodes . 12 5.3 Potentials of reference electrodes 12 5.4 Verification of reference electrodes 12 5.5 Potential measurement 12 6 Cathodic protection potential

12、criteria . 13 6.1 General . 13 6.2 Carbon-manganese and low alloy steels . 13 6.3 Other metallic materials . 15 6.3.1 General . 15 6.3.2 Stainless steels . 15 6.3.3 Nickel alloys 16 6.3.4 Aluminium alloys 16 6.3.5 Copper alloys 17 7 Design considerations . 17 7.1 Introduction . 17 7.2 Technical and

13、operating data 17 7.2.1 Design life 17 7.2.2 Materials of construction . 17 7.3 Surfaces to be protected 18 7.4 Protective coatings . 18 7.5 Availability of electrical power 18 7.6 Weight limitations . 18 7.7 Adjacent structures 18 7.8 Installation considerations 18 7.9 Current demand 19 8 Effect of

14、 environmental factors on current demand . 19 8.1 Introduction . 19 8.2 Dissolved oxygen . 19 8.3 Sea currents 19 8.4 Calcareous deposits . 19 8.5 Temperature 20 8.6 Salinity . 20 8.7 pH . 21 8.8 Marine fouling . 21 8.9 Effect of depth . 21 8.10 Seasonal variations and storms 21 BS EN 12473:2014EN 1

15、2473:2014 (E) 3 9 Secondary effects of cathodic protection . 21 9.1 General . 21 9.2 Alkalinity . 22 9.3 Environmentally-assisted cracking . 22 9.3.1 General . 22 9.3.2 Hydrogen embrittlement . 22 9.3.3 Corrosion fatigue . 22 9.4 Chlorine 23 9.5 Stray currents and interference effects 23 10 Use of c

16、athodic protection in association with coatings 24 10.1 Introduction 24 10.2 Coating selection . 24 10.3 Coating breakdown . 25 Annex A (informative) 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

17、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

18、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 BS EN 12473:2014EN 12473:2014 (E) 4 Foreword This document (EN 12473:2014) has been prepared by Technical Commi

19、ttee 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 August 2014, and conflicting national standards shall be withdrawn a

20、t the latest by August 2014. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 12473:2000. According to the

21、CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hun

22、gary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. BS EN 12473:2014EN 12473:2014 (E) 5 1 Scope This European Standard covers the general principles of cath

23、odic protection when applied in seawater, brackish waters and marine mud. It is intended to be an introduction, to provide a link between the theoretical aspects and the practical applications, and to constitute a support to the other European Standards devoted to cathodic protection of steel struct

24、ures in seawater. This European Standard specifies the criteria required for cathodic protection. It provides recommendations and information on reference electrodes, design considerations and prevention of the secondary effects of cathodic protection. The practical applications of cathodic protecti

25、on in seawater are covered by the following standards: EN 12495, Cathodic protection for fixed steel offshore structures; EN ISO 13174, Cathodic protection of harbour installations (ISO 13174); EN 12496, Galvanic anodes for cathodic protection in seawater and saline mud; EN 13173, Cathodic protectio

26、n 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 cathodi

27、c 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

28、 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 T

29、erms, 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

30、 7) BS EN 12473:2014EN 12473:2014 (E) 6 3.3 anaerobic condition absence of free oxygen dissolved in the electrolyte 3.4 calcareous deposits minerals precipitated on the metallic cathode because of the increased alkalinity caused by cathodic protection 3.5 cathodic disbondment failure of adhesion bet

31、ween a coating and a metallic surface that is directly attributable to the application of cathodic protection 3.6 cathodic protection system entire installation that provides cathodic protection Note 1 to entry: It may include anodes, power source, cables, test facilities, isolation joints, electric

32、al bonds. 3.7 coating breakdown factor fc ratio of cathodic current density for a coated metallic material to the cathodic current density of the bare material 3.8 copper/copper sulphate reference electrode reference electrode consisting of copper in a saturated solution of copper sulphate 3.9 diele

33、ctric shield alkali resistant organic coating applied to the structure being protected in the immediate vicinity of an impressed current anode to enhance the spread of cathodic protection and minimize the risk of hydrogen damage to the protected structure in the vicinity of the anode 3.10 driving vo

34、ltage difference between the structure/electrolyte potential and the anode/electrolyte potential when the cathodic protection is operating 3.11 electro-osmosis passage of a liquid through a porous medium under the influence of a potential difference 3.12 environmentally assisted cracking cracking of

35、 a susceptible metal or alloy due to the conjoint action of an environment and stress 3.13 groundbed system of immersed electrodes connected to the positive terminal of an independent source of direct current and used to direct the cathodic protection current onto the structure being protected 3.14

36、hydrogen embrittlement process resulting in a decrease of the toughness or ductility of a metal due to absorption of hydrogen BS EN 12473:2014EN 12473:2014 (E) 7 3.15 hydrogen stress cracking HSC cracking that results from the presence of hydrogen in a metal and tensile stress (residual and/or appli

37、ed) 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. 3.16 isolating joint (or coupling) electrically discontinuous joint or coupling between two lengt

38、hs of pipe, inserted in order to provide electrical discontinuity between them 3.17 master reference electrode reference electrode, calibrated with the primary calibration reference electrode, used for verification of reference electrodes used for field or laboratory measurements 3.18 over-polarizat

39、ion 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. 3.19 pitting resistance equivalent PREN indication o

40、f the resistance of a corrosion resistant alloy to pitting in the presence of water, chlorides and oxygen or oxidation environment, accounting for the beneficial effects of nitrogen Note 1 to entry: For the purposes of this standard, PREN is calculated as follows: PREN = % Cr + 3,3(% Mo) + 0,5 (% W)

41、 + 16 (% N). 3.20 potential gradient difference in potential between two separate points in the same electric field 3.21 primary calibration reference electrode reference electrode used for calibration of master reference electrodes is the normal hydrogen electrode (N.H.E.) Note 1 to entry: The offi

42、cial reference electrode, standard hydrogen electrode (S.H.E.), which considers the fugacity coefficient for hydrogen gas and the activity coefficient for H+ions, is practically impossible to manufacture. 3.22 protection current current made to flow into a metallic structure from its electrolytic en

43、vironment in order to achieve cathodic protection of the structure 3.23 reference electrode electrode having a stable and reproducible potential that is used as a reference in the measurement of electrode potentials BS EN 12473:2014EN 12473:2014 (E) 8 Note 1 to entry: Some reference electrodes use t

44、he electrolyte in which the measurement is carried out. Their potential varies according to the composition of this electrolyte. 3.24 resistivity (of an electrolyte) resistivity is the resistance of an electrolyte of unit cross section and unit length Note 1 to entry: It is expressed in ohm.metres (

45、.m). The resistivity depends, amongst other things, upon the amount of dissolved salts in the electrolyte. 3.25 saturated calomel reference electrode reference electrode consisting of mercury and mercurous chloride in a saturated solution of potassium chloride 3.26 silver/silver chloride reference e

46、lectrode reference electrode consisting of silver, coated with silver chloride, in an electrolyte containing a known concentration of chloride ions Note 1 to entry: Silver/silver chloride/ saturated KCl electrodes are electrodes currently used in the laboratory and for master reference electrode. No

47、te 2 to entry: Silver/silver chloride/seawater (Ag/AgCl/seawater) electrodes are electrodes currently used for field measurements in seawater. 3.27 slow strain rate test test for evaluating susceptibility of a metal to environmentally assisted cracking (3.12 in this document) that most commonly invo

48、lves pulling a tensile specimen to failure in a representative environment at a constant displacement rate chosen to generate nominal strain rates usually in the range 105s1to 108s1Note 1 to entry: Slow strain rate testing may also be applied to other specimen geometries, e.g. bend specimens. 3.28 s

49、pecified 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 refer