EN 12502-2:2004

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 2: Einflussfaktoren für Kupfer und KupferlegierungenProtection 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 2 : Facteurs a considérer pour le cuivre et les alliages de cuivreProtection of metallic materials against corrosion - Guidance on the assessment of corrosion likelihood in water distribution and storage systems - Part 2: Influencing factors for copper and copper alloys91.140.60Sistemi 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 12502-2:2004SIST EN 12502-2:2005en01-marec-2005SIST EN 12502-2:2005SLOVENSKI
STANDARD
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 12502-2
December 2004 ICS 77.060; 23.040.99; 91.140.60 English version
Protection of metallic materials against corrosion - Guidance on the assessment of corrosion likelihood in water distribution and storage systems - Part 2: Influencing factors for copper and copper alloys
Protection 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 2 : Facteurs à considérer pour le cuivre et les alliages de cuivre
Korrosionsschutz metallischer Werkstoffe - Hinweise zur Abschätzung der Korrosionswahrscheinlichkeit in Wasserverteilungs- und
speichersystemen - Teil 2: Einflussfaktoren für Kupfer und Kupferlegierungen This 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 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 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 translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions.
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 STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
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B-1050 Brussels © 2004 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12502-2:2004: ESIST EN 12502-2:2005

c(HCO3-) concentration of hydrogen carbonate ions in mmol/l c(SO42-) concentration of sulphate ions in mmol/l c(O2) concentration of oxygen in mmol/l 4 Types of corrosion 4.1 General The most common types of corrosion are listed in EN 12502-1. Internal corrosion of copper and copper alloys in water distribution and storage systems generally leads to the build-up of layers formed by corrosion products, which can or cannot be protective. In some cases corrosion can lead to the impairment of the function of the system or failure because of corrosion damage (see Table 1). SIST EN 12502-2:2005

Dezincification Cracks perpendicular to the principal tensile stress Cracks perpendicular to tensile stress and parallel to bending stress Visible corrosion products Brown/ black Cu2O/ CuO Green Cu2(OH)2CO3a Blue Cu2(OH)2SO4 green Cu2(OH)2CO3a Pits covered with nodules Cu2(OH)2CO3 (Type 1)a Pits covered with nodules Cu2(OH)2SO4 (Type 2 and microbially induced)a No products covering the pits (Type 2)a None White products of Zn(OH)2
and/or Zn5(OH)6(CO3)2 None None Corrosion effect Negligible uniform corrosion attack Negligible uniform corrosion attack Significant uniform corrosion attack with release of corrosion products Pitting corrosion attack Profiled attack Change in colour and structure of the alloy Cracks visible to the naked eye or under microscope Visible cracks Possible corrosion damage None None Staining of sanitary equipment
Leakage Leakage Leakage, disfunction of valves Leakage Leakage a Within a layer of Cu2O.
4.2.1 General
Experience shows that corrosion damage to copper and copper alloys as a result of uniform corrosion is rare. The occurrence of uniform corrosion of these materials strongly depends on the properties of the surface layers that are formed. Blue-green staining of sanitary equipment and blue-green coloured water arising from dripping taps is an indicator of copper ions in the water and hence of uniform corrosion, but it cannot be taken as an indicator of corrosion damage of the copper or copper alloy component itself. Copper ions in water can promote pitting corrosion of less noble metals (e.g. zinc, iron) in the same circuit by depositing as metallic copper, which enhances the local activity of the cathodic oxygen reduction. Protective layers consisting of copper corrosion products normally form on copper and copper alloys. In a few cases the layer is very thin, brown and homogeneous and consists of copper (I) oxide and copper (II) oxide. In most cases, however, there is sufficient hydrogen carbonate in the water to allow the formation of a layer of copper hydroxycarbonate Cu2(OH)2CO3 above the copper (I) oxide and copper (II) oxide. This occurs during the initial operating period, progressively forming a green scale. The actual copper concentration is influenced by the water composition and the time and conditions of operation such as high flow rates and water hammer. Although copper corrosion products are only sparingly soluble, copper ions are released into water. The formation of copper ions caused by uniform corrosion and dissolution of corrosion products under stagnant conditions leads to an increase of the concentration of copper ions in the water. The detectable number of copper ions will depend on: SIST EN 12502-2:2005

4.3 Pitting corrosion 4.3.1 General 4.3.1.1 Manifestations of pitting corrosion There are different types of pitting corrosion of copper in water distribution and storage systems. Copper alloys are not endangered by pitting corrosion. The type of pitting corrosion depends on the water temperature, the water composition and the operating conditions.
Corrosion cells can develop under critical circumstances in the initial stage after the first filling of the system. Whether a corrosion cell stabilizes and results in macroscopic pitting, or as in most cases becomes repassivated, depends on the water composition and the service conditions.
4.3.1.2 Type 1: Pitting corrosion in cold water Pitting corrosion of copper observed in cold water (Type 1) is characterized by hemispherical pits and an increased formation of green nodules consisting of copper hydroxycarbonate above the attacked area. Under these nodules, the pit is almost always covered by a continuous copper (I) oxide layer at the level of the former surface. Under this copper (I) oxide layer ruby-red macro-crystalline copper (I) oxide and sometimes finely crystalline white copper (I) chloride are present. The corrosion rate of Type 1 pitting in cold water is relatively high which means that within a period of months to a few years complete perforation of the wall can occur. If failures do not occur within this time, the risk of failure decreases from that time on. However, a change of water composition can induce this type of corrosion in relatively old tubes because of reactivation of previously passivated cells. If parts of heated water systems remain cold for long periods, they can demonstrate the characteristics of pitting observed in cold water. 4.3.1.3 Type 2: Pitting corrosion in heated water
Pitting corrosion of copper observed in heated water (Type 2) is characterized by pits with a narrow mouth and an irregular interior geometry. These pits are not normally covered with corrosion products. They are completely filled with copper (I) oxide and sometimes the mouths are covered by crusts containing blue copper hydroxysulfate. The corrosion rate of Type 2 pitting is usually lower than that of Type 1 pitting. Unlike Type 1 pitting as observed in cold water, there is a greater variety of manifestations of Type 2 pitting. SIST EN 12502-2:2005
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