EN 12502-1-2004 en Protection of metallic materials against corrosion - Guidance on the assessment of corrosion likelihood in water distribution and storage systems - Part 1 Genera.pdf

1、BRITISH STANDARD BS EN 12502-1:2004 Protection of metallic materials against corrosion Guidance on the assessment of corrosion likelihood in water distribution and storage systems Part 1: General The European Standard EN 12502-1:2004 has the status of a British Standard ICS 77.060; 23.040.99; 91.140

2、.60 BS EN 12502-1:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 19 January 2005 BSI 19 January 2005 ISBN 0 580 45298 0 National foreword This British Standard is the official English language version of EN 12502-1:2004. The UK particip

3、ation in its preparation was entrusted to Technical Committee ISE/NFE/8, Corrosion of metals and alloys, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement internat

4、ional or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport

5、 to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee a

6、ny enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 11 and

7、a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM EN125021 December2004 ICS77.060;23.040.99;91.140.60 Englishversion Protectionofmetal

8、licmaterialsagainstcorrosionGuidanceon theassessmentofcorrosionlikelihoodinwaterdistributionand storagesystemsPart1:General Protectiondesmatriauxmtalliquescontrelacorrosion Recommandationspourlvaluationdurisquedecorrosion danslesinstallationsdedistributionetdestockagedeau Partie1:Gnralits Korrosions

9、schutzmetallischerWerkstoffeHinweisezur AbschtzungderKorrosionswahrscheinlichkeitin WasserverteilungsundspeichersystemenTeil1: Allgemeines ThisEuropeanStandardwasapprovedbyCENon22November2004. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatetheconditionsforgivingthisEuro

10、pe an Standardthestatusofanationalstandardwithoutanyalteration.Uptodatelistsandbibliographicalreferencesconcernings uchnational standardsmaybeobtainedonapplicationtotheCentralSecretariatortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,French,German).Aversioninanyotherlangu

11、agemadebytra nslation undertheresponsibilityofaCENmemberintoitsownlanguageandnotifiedtotheCentralSecretariathasthesamestatusast heofficial versions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,Cyprus,CzechRepublic,Denmark,Estonia,Finland,France, Germany,Greece,Hungary,Iceland,Ireland,It

12、aly,Latvia,Lithuania,Luxembourg,Malta,Netherlands,Norway,Poland,Portugal, Slovakia, Slovenia,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2004CEN Allrightsofexploit

13、ationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No.EN125021:2004:EEN 12502-1:2004 (E) 2 Contents Page Foreword3 Introduction .4 1 Scope 5 2 Normative references 5 3 Terms and definitions .5 3.1 Terms and definitions .5 4 Types of corrosion.6 5 Factors influencing corrosion li

14、kelihood 6 5.1 General6 5.2 Characteristics of the metallic material.7 5.3 Characteristics of the water7 5.4 Design and construction.8 5.5 Pressure testing and commissioning9 5.6 Operating conditions.10 6 Assessment of corrosion likelihood10 Bibliography 11 EN 12502-1:2004 (E) 3 Foreword This docume

15、nt (EN 12502-1:2004) has been prepared by Technical Committee CEN/TC 262 “Metallic and other inorganic coatings”, 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 lat

16、est by June 2005, and conflicting national standards shall be withdrawn at the latest by June 2005. This standard is in five parts: Part 1: General; Part 2: Influencing factors for copper and copper alloys; Part 3: Influencing factors for hot dip galvanized ferrous materials; Part 4: Influencing fac

17、tors for stainless steels; Part 5: Influencing factors for cast iron, unalloyed and low alloyed steels. Together these five parts constitute a package of inter-related European Standards with a common date of withdrawal (dow) of 2005-06. According to the CEN/CENELEC Internal Regulations, the nationa

18、l standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portu

19、gal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EN 12502-1:2004 (E) 4 Introduction The water distribution and storage systems under consideration consist of a variety of metals and alloys in pipework and in other components, i.e. pumps, valves and heat exchangers. Corrosion o

20、n the water-side of these systems generally leads to a build-up of surface corrosion product layers, which, depending on the circumstances, can or cannot be protective. In some cases, corrosion leads to the impairment of the function of the system, i.e. corrosion damage. This impairment can manifest

21、 itself in: perforation (leakage); blockage of system components; detrimental changes of water composition. The type and rate of corrosion for any particular alloy system can depend on: characteristics of the metallic material; characteristics of the water; design and construction; pressure testing

22、and commissioning; operating conditions. As a result of the complex interactions between the various influencing factors, the extent of corrosion can only be expressed in terms of likelihood. This document therefore is a guidance document and does not set explicit rules for the use of metallic mater

23、ials in water systems. It can be used to minimize the likelihood of corrosion damages occurring by: assisting in designing, installing and operating systems from an anti-corrosion point of view; evaluating the need for additional corrosion protection methods for a new or existing system; assisting i

24、n failure analysis, when failures occur in order to prevent repeat failures occurring. However, a corrosion expert, or at least a person with technical training and experience in the corrosion field is required to give a correct assessment of corrosion likelihood or failure analysis. EN 12502-1:2004

25、 (E) 5 1 Scope This document gives guidance for the assessment of the corrosion likelihood of metallic materials in water distribution and storage systems, as a result of corrosion on the water-side. NOTE This document lists the different types of corrosion and describes in general terms the factors

26、 influencing corrosion likelihood. Water distribution and storage systems considered in this document are used for waters intended for human consumption according to EC directive 98/83/EEC and for waters of similar chemical composition. This document does not cover systems that convey the following

27、types of water. sea water; brackish water; geothermal water; sewage water; swimming pool water; open cooling tower water; recirculating heating and cooling water; demineralized water. Parts 2 to 5 of this document cover the factors influencing the corrosion likelihood for copper and copper alloys, h

28、ot-dip galvanized ferrous materials, stainless steels and cast iron, unalloyed and low alloyed steels in detail. This document does not cover lead. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition

29、 cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN ISO 8044:1999, Corrosion of metals and alloys Basic terms and definitions (ISO 8044:1999). 3 Terms and definitions 3.1 Terms and definitions For the purposes of this document,

30、 the following terms and definitions and those given in EN ISO 8044 apply. 3.1.1 water system system, including every metallic and non-metallic component (e.g. pipes, valves, fittings), constituting the water distribution and storage system, which can be in contact with the water EN 12502-1:2004 (E)

31、 6 3.1.2 uniform corrosion attack corrosion effect caused by uniform corrosion 3.1.3 pitting attack corrosion effect caused by pitting corrosion 4 Types of corrosion When assessing the corrosion likelihood for a given system, all types of corrosion are to be taken into consideration. The following t

32、ypes of corrosion can occur in water distribution and storage systems, depending on the corrosion system: uniform corrosion; localized corrosion: pitting corrosion; crevice corrosion; selective corrosion; knife-line corrosion; bimetallic corrosion; erosion corrosion; stress corrosion; corrosion fati

33、gue. These types of corrosion can lead to different types of corrosion damage: wall perforation; blockage of system components; detrimental changes of water composition. 5 Factors influencing corrosion likelihood 5.1 General Table 1 lists the factors that can influence the corrosion likelihood of a

34、particular metallic material in a water distribution and storage system, not in order of importance. In order to minimize corrosion damage, special care should be taken during design, construction, pressure testing, commissioning and operation of a water distribution and storage system. EN 12502-1:2

35、004 (E) 7 The behaviour of some metallic materials depends on the initial stage of formation of protective layers. When protective layers are formed under suitable conditions, subsequent adverse variations of the quality of water and/or service conditions have, in general, a reduced influence. Table

36、 1 Factors influencing the corrosion likelihood Characteristics of the metallic material Characteristics of the water Design and construction Pressure testing and commissioning Operating conditions Chemical composition/ Microstructure Surface condition Physico- chemical composition (see Table 2) Sol

37、id particles Geometry Multi-metal systems Joints Tensile stress Flushing Draining Disinfection/ Rinsing Temperature/ Temperature variations Flow conditions Disinfection 5.2 Characteristics of the metallic material 5.2.1 Chemical composition/Microstructure The effect of chemical composition and micro

38、structure on the corrosion likelihood for various metals is more or less dependent on the type of alloy. For some metals, a small change in the alloy composition has no significant effect, whereas for others a small change markedly alters the corrosion likelihood. NOTE Detailed information is given

39、in Parts 2 to 5 of this document. 5.2.2 Surface conditions Surface conditions (e.g. roughness, cleanliness, contamination with deposits) can influence the corrosion likelihood, especially with respect to the initial formation of corrosion cells. 5.3 Characteristics of the water Table 2 lists some of

40、 the principal physical and chemical parameters of water that can influence corrosion in a water distribution and storage system. EN 12502-1:2004 (E) 8 Table 2 Physical and chemical characteristics of the water Characteristics Unit Temperature C pH Conductivity at 20 C S/cm Total hardness (concentra

41、tion of soluble Ca + Mg components) mmol/l Calcium hardness (concentration of soluble Ca components) mmol/l Alkalinity (by titration down to pH 4,2) mmol/l Acidity (by titration up to pH 8,2) mmol/l Dissolved oxygen mmol/l Chloride ions mmol/l Nitrate ions mmol/l Sulphate ions mmol/l Phosphorous com

42、pounds mmol/l Silicon compounds mmol/l Total organic carbon mg/l The concentration of dissolved oxygen in the water is considered in these once-through systems to be at, or close to, saturation level. Therefore, anodic metal dissolution reactions can always be driven by the cathodic reduction of oxy

43、gen. Although drinking water conforming to EC Directive 98/83/EEC has strict limits placed on the maximum concentrations of dissolved species and pH range, the chemical composition of the water within this range can still significantly influence corrosion likelihood. The concentration and, more sign

44、ificantly the ratio of the concentration of different anions in the water are of vital importance for the corrosivity of water. Certain inorganic and organic species naturally occurring in water, e.g. phosphates and silicates, can inhibit corrosion reactions by assisting in the formation of protecti

45、ve layers. Assessment of corrosion likelihood will be more difficult if the composition of the water varies with time. Therefore, not only the composition, but also the range of variation should be known. If different waters are present, the most unfavourable scenario should be assumed. 5.4 Design a

46、nd construction 5.4.1 Geometry The geometry of a water system determines to a large degree the flow characteristics of the water it conveys. The presence of crevices in a system can create a special risk for the occurrence of crevice corrosion. The presence of dead legs creates stagnant conditions g

47、iving rise to the possibility of pitting corrosion beneath deposits that can be increased by microbial activity. The risk of locally high fluid velocities is increased at sharp bends, T-pieces, sharp reductions or enlargements of cross-sections. This can give rise to erosion corrosion. EN 12502-1:20

48、04 (E) 9 5.4.2 Multi-metal systems Direct electrical contact between dissimilar metals gives rise to the possibility of bimetallic corrosion, in which the corrosion rate of the less noble metal is increased. In general, the corrosion likelihood for bimetallic corrosion decreases with: decreasing difference in the corrosion potential of the metals; increasing anodic and/or cathodic polarization resistance; decreasing conductivity of t