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

This document gives a review of influencing factors of the corrosion likelihood of copper and copper alloys used as tubes, tanks and equipment in water distribution and storage systems as defined in EN 12502-1.

Korrosionsschutz metallischer Werkstoffe - Hinweise zur Abschätzung der Korrosionswahrscheinlichkeit in Wasserverteilungs- und speichersystemen - Teil 2: Einflussfaktoren für Kupfer und Kupferlegierungen

Dieses Dokument enthält eine Übersicht der Einflussfaktoren für die Korrosionswahrscheinlichkeit von Rohren, Behältern und Zubehörteilen, die aus Kupfer und Kupferlegierungen hergestellt sind, in Wasserleitungssystemen, wie sie in prEN 12502-1:2004 definiert sind.

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 a considérer pour le cuivre et les alliages de cuivre

Le présent document étudie les facteurs d'influence du risque de corrosion pour les tubes, les réservoirs et les équipements en cuivre ou en alliages de cuivre des installations de distribution et de stockage d'eau, tels que définis dans le prEN 12502-1.

Protikorozijska zaščita kovinskih materialov - Navodilo za ocenjevanje verjetnosti nastanka korozije v porazdeljeni vodi in skladiščnih sistemih - 2. del: Vplivni dejavniki za baker in bakrove zlitine

General Information

Status
Published
Publication Date
28-Feb-2005
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Mar-2005
Due Date
01-Mar-2005
Completion Date
01-Mar-2005

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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



SIST EN 12502-2:2005



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
Management Centre: rue de Stassart, 36
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



EN 12502-2:2004 (E) 2 Contents Page Foreword.3 Introduction.4 1 Scope.5 2 Normative references.5 3 Terms, definitions, and symbols.5 3.1 Terms and definitions.5 3.2 Symbols .5 4 Types of corrosion.5 4.1 General.5 4.2 Uniform corrosion.7 4.3 Pitting corrosion.9 4.4 Selective corrosion.12 4.5 Bimetallic corrosion.13 4.6 Erosion corrosion.14 4.7 Stress corrosion.15 4.8 Corrosion fatigue.16 5 Assessment of corrosion likelihood.16 Bibliography.17
SIST EN 12502-2:2005



EN 12502-2:2004 (E) 3 Foreword This document (EN 12502-2:2004) 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 latest 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 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.
SIST EN 12502-2:2005



EN 12502-2:2004 (E) 4 Introduction This document results mainly from investigations into and experience gained of the corrosion of copper materials in drinking water distribution systems in buildings. However, it can be applied analogously to other water systems. The corrosion likelihood of copper and copper alloys depends on the formation of a corrosion product layer that begins to form as soon as these materials come in contact with water. The more this layer prevents ionic and electronic exchanges between the metal and water, the more protective it is and the higher the durability of the metal. Copper and copper alloy drinking water systems are, in general, resistant to corrosion damage in normal use. However, there are certain conditions under which they will sustain corrosion damage. 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 copper and copper alloys 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. SIST EN 12502-2:2005



EN 12502-2:2004 (E) 5 1 Scope This document gives a review of influencing factors of the corrosion likelihood of copper and copper alloys used as tubes, tanks and equipment in water distribution and storage systems as defined in 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(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



EN 12502-2:2004 (E) 6 Table 1 — General characteristics of the different types of corrosion of copper and copper alloys Type of corrosion Uniform corrosion Pitting corrosion Erosion corrosion Selective corrosion Stress corrosion Corrosion fatigue Manifestation Thin adherent layer Adherent layer Non-protective layer of corrosion products Locally perforated protective layer Protective layer destroyed mechanically or removed
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.
SIST EN 12502-2:2005



EN 12502-2:2004 (E) 7 The types of corrosion considered for copper and copper alloys comprise the following:  uniform corrosion;  pitting corrosion;  selective corrosion;  bimetallic corrosion;  erosion corrosion;  stress corrosion;  corrosion fatigue. For each type of corrosion, the following influencing factors, described in EN 12502-1:2004, Table 1 and Clause 5, are considered:  characteristics of the metallic material;  characteristics of the water;  design and construction;  pressure testing and commissioning;  operating conditions. 4.2 Uniform corrosion
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



EN 12502-2:2004 (E) 8  the concentration of the carbonic acid species and total organic carbon ;  the duration of stagnation of water in pipes;  the age of the installation;  the dilution caused by mixing with fresh water;  the method of sampling. The quantity of loosely adherent copper corrosion products that can be removed from the tube walls will depend on:  the duration of low water velocity;  the extent of any sudden turbulent flow. 4.2.2 Influence of the characteristics of the metallic material Within a group of alloys with the same major alloying elements the material composition, heat treatment and differences of the surface condition resulting from the manufacturing process, are not known to influence the long-term behaviour of copper and copper alloys with respect to uniform corrosion. 4.2.3 Influence of the characteristics of the water Under flowing conditions in oxygen-containing waters, the rate of uniform corrosion of copper mainly depends on the pH value of water. Generally, it increases with decreasing pH value of the incoming water and is negligible above pH 7,5. In waters of low hydrogen carbonate content, i.e. when c(HCO3-) < 1,0 mmol/l, corrosion products other than copper hydroxycarbonate can become those of the lowest solubility, e.g. copper hydroxysulphate Cu2(OH)2SO4 which forms loosely adherent layers. Loosely adherent corrosion products are easily dislodged into the water stream. In these cases, the analytically observed copper concentration in the water can exceed the values expected from the dissolution of the corrosion products alone, since copper in particulate form will also be present. In waters with pH values less than 7,5, the detectable number of copper ions generally increases with increasing total organic carbon. The rate of uniform corrosion can be decreased by the addition of inhibitors, e.g. orthophosphates, or by alkalization of the water by addition of NaOH and/or Na2CO3, by addition of Ca(OH)2 or by use of filters e.g. marble, limestone, dolomite. 4.2.4 Influence of design and construction The formation of protective layers will be favoured by regular renewal of the water. This can be facilitated by avoiding areas of stagnation. 4.2.5 Influence of pressure testing and commissioning If pressure testing is not carried out in accordance with the recommendations given in EN 12502-1:2004, 5.5, so that residual water is left in the system after draining, the likelihood for the formation of loosely adherent corrosion products is increased. SIST EN 12502-2:2005



EN 12502-2:2004 (E) 9 4.2.6 Influence of operating conditions 4.2.6.1 Influence of temperature The effects of temperature and temperature variations on uniform corrosion are not known to influence the long-term behaviour of copper and copper alloys. 4.2.6.2 Influence of flow conditions Regular renewal of the water, especially in the initial stage, promotes the formation of protective layers.
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



EN 12502-2:2004 (E) 10 4.3.1.4 Microbially influenced pitting corrosion Another seldom observed form of pitting corrosion, which is characterized by well defined areas of attack, within which there can be numerous pits covered by voluminous corrosion products, is influenced by microbial processes. Those pits are similar in appearance to those of Type 1 pitting being hemispherical and having a copper (I) oxide layer at the level of the original copper surface. Under this layer macro-crystalline copper (I) oxide is present and, above this layer, voluminous corrosion products consisting of copper hydroxysulfate are present. Surrounding the pits the surface is covered by a black layer of copper (II) oxide. Common to all cases of this type of pitting is the presence of organic films, e.g. polysaccharides, because of microbial activity. The corrosion rate of this type of pitting is about the same as that of pitting
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