EN 12502-5:2004

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Korrosionsschutz metallischer Werkstoffe - Hinweise zur Abschätzung der Korrosionswahrscheinlichkeit in Wasserverteilungs- und
speichersystemen - Teil 5: Einflussfaktoren für Gusseisen, unlegierte und niedriglegierte StähleProtection des matériaux métalliques contre la corrosion - Recommandations pour l'évaluation du risque de corrosion dans les installations de distribution et de stockage d'eau - Partie 5 : Facteurs a considérer pour la fonte, les aciers non alliés et faiblement alliésProtection of metallic materials against corrosion - Guidance on the assessment of corrosion likelihood in water distribution and storage systems - Part 5: Influencing factors for cast iron, unalloyed and low alloyed steels91.140.60Sistemi za oskrbo z vodoWater supply systems77.060Korozija kovinCorrosion of metals23.040.99Drugi sestavni deli za cevovodeOther pipeline componentsICS:Ta slovenski standard je istoveten z:EN 12502-5:2004SIST EN 12502-5:2005en01-marec-2005SIST EN 12502-5:2005SLOVENSKI
STANDARD
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 12502-5December 2004ICS 77.060; 23.040.99; 91.140.60English versionProtection of metallic materials against corrosion - Guidance onthe assessment of corrosion likelihood in water distribution andstorage systems - Part 5: Influencing factors for cast iron,unalloyed and low alloyed steelsProtection des matériaux métalliques contre la corrosion -Recommandations pour l'évaluation du risque de corrosiondans les installations de distribution et stockage d'eau -Partie 5 : Facteurs à considérer pour la fonte, les aciersnon alliés et faiblement alliésKorrosionsschutz metallischer Werkstoffe - Hinweise zurAbschätzung der Korrosionswahrscheinlichkeit inWasserverteilungs- und
speichersystemen - Teil 5:Einflussfaktoren für Gusseisen, unlegierte undniedriglegierte StähleThis European Standard was approved by CEN on 22 November 2004.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2004 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 12502-5:2004: ESIST EN 12502-5:2005

Part 4: Influencing factors for stainless steels Part 5: Influencing factors for cast iron, unalloyed and low alloyed steels Together these five parts constitute a package of interrelated European Standards with a common date of withdrawal (dow) of 2005-06. According to the CEN/CENELEC Internal Regulations, the national 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, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
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 is a guidance document and does not set explicit rules for the use of unalloyed and low alloy ferrous materials 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 in 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 an accurate assessment of corrosion likelihood or failure analysis.
NOTE See EN 12502-1. 2 Normative references The following referenced documents are indispensable for the application 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 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. EN ISO 8044:1999, Corrosion of metals and alloys — Basic terms and definitions (ISO 8044:1999). 3 Terms, definitions, and symbols 3.1 Terms and definitions For the purposes of this document, the terms and definitions given in EN ISO 8044:1999 and EN 12502-1:2004 apply. 3.2 Symbols c(O2)
concentration of oxygen in mmol/l c(HCO3-)
concentration of hydrogen carbonate ions in mmol/l c(Ca2+)
concentration of calcium ions in mmol/l 4 Types of corrosion 4.1 General The most common types of corrosion are described in EN 12502-1:2004, Clause 4.
The types of corrosion considered for steels and cast irons are the following:  uniform corrosion;  pitting corrosion;  selective corrosion;  bimetallic corrosion;  erosion corrosion. SIST EN 12502-5:2005

> 3 mg/l
and pH
> 7,0
and c(HCO3-)
> 2 mmol/l and c(Ca2+)
> 1 mmol/l
The type and concentration of natural components (e.g. phosphates, aluminosilicates) dissolved in the water can play an important part in the formation of protective layers. In the absence of protective layers, the corrosion rate is determined by the concentration of oxidizing agents and/or acidic agents, e.g. carbon dioxide. The uniform corrosion rate is very low if: c(O2)
< 0,1 mg/l and
pH
> 8,5 SIST EN 12502-5:2005
4.2.5 Influence of pressure testing and commissioning
Pressure testing and commissioning have no influence on uniform corrosion. 4.2.6 Influence of operating conditions Significant variations of operating conditions can modify uniform corrosion. If no protective scale is formed the rate of uniform corrosion increases with increasing flow rate and/or temperature. For the effect of stagnant conditions, see 4.2.4. 4.3 Pitting corrosion 4.3.1 General Pitting corrosion is the most frequent corrosion effect on steels and cast irons in water distribution and storage systems. It develops from galvanic cells depending on surface conditions of materials, water parameters and service conditions. Anodic areas always form in metallic regions, when the entry of oxygen is hindered by geometrical factors, e.g. in crevices. The bare metallic areas with non-restricted oxygen access form the cathodic area. The corrosion manifests itself in either shallow or steep-sided pits. Pitting corrosion can be enhanced by microbial activity, which can take place in anaerobic conditions, especially under debris. Generally, corrosion rates are high and can rapidly lead to wall perforation of the system. The outer manifestation of corrosion is the formation of tubercles under which anodic areas are to be found, cathodic areas being characterized by relatively thin surface layers. 4.3.2 Influence of the characteristics of the metallic material Pitting corrosion is influenced by the fact that steels and cast irons are iron-carbon alloys with additional elements, intentionally present or as impurities. For materials with compositions given in EN 545, the influence of alloying elements is usually less important than that of other heterogeneities. The surface quality influences the formation of galvanic cells. Anodic areas are favoured by deposits of all types, e.g. oxide scales, residues of oil and paint, corrosion products.
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