SIST EN 14868:2005

Protection of metallic materials against corrosion - Guidance on the assessment of corrosion likelihood in closed water circulation systems

This European Standard gives a review of influencing factors on the corrosion likelihood of metallic components (pipes, tanks, vessels, heat exchangers, pumps etc.) in water circulation systems in buildings.
The water circulation systems considered are:
   heating systems (up to 110 °C service water temperature);
   cooling and chilling systems;
which are filled with potable water or water of similar composition according to the Directive 98/83/EC.
NOTE 1   Sanitary hot water systems with a re-circulation loop are not considered in this European Standard as they are not really closed system, because the water is continually renewed. The corrosion likelihood of these systems is discussed in EN 12502 Parts 1 to 5 [1],  [2],  [3],  [4],  [5].
NOTE 2   Cooling systems with open atmospheric towers are not considered in this European Standard because fresh water is generally added to the system periodically to compensate for losses by evaporation or blow-down.
NOTE 3   Heating systems in buildings, connected to district heating systems without an intervening heat exchanger, are not considered in this European Standard. However, local heating systems, where several buildings are heated by one boiler plant, are included.

Korrosionsschutz metallischer Werkstoffe - Leitfaden für die Ermittlung der Korrosionswahrscheinlichkeit in geschlossenen Wasser-Zirkulationssystemen

Diese Europäische Norm gibt einen Überblick über die Einflussfaktoren der durch Innenkorrosion bedingten Korrosionswahrscheinlichkeit metallischer Bauteile (Rohre, Behälter, Kessel, Wärmeaustauscher, Pumpen usw.) in Wasser-Rezirkulationssystemen in Gebäuden.
Bei den betrachteten Wasser-Rezirkulationssystemen handelt es sich um:
-   Heizsysteme (bis zu 110 °C Betriebstemperatur des Wassers);
-   Kühl- und Kältesysteme,
die mit Trinkwasser entsprechend der EU Direktive 98/83/EG oder Wässern ähnlicher Zusammensetzung gefüllt sind.
ANMERKUNG 1   Warmwasser-Zirkulationssysteme der Sanitärhausinstallation werden in dieser Norm nicht betrachtet, da sie keine geschlossenen Systeme darstellen, weil das Wasser regelmäßig erneuert wird. Die Korrosionswahrscheinlichkeit in derartigen Systemen wird in EN 12502 Teil 1 bis 5 behandelt [1], [2], [3], [4], [5].
ANMERKUNG 2   Kühlsysteme mit zur Atmosphäre hin offenen Kühltürmen werden in dieser Norm nicht behandelt, weil hier dem System regelmäßig Frischwasser zugesetzt werden muss, um die Wasserverluste durch Verdunstung oder Absalzen auszugleichen.
ANMERKUNG 3   Heizsysteme in Gebäuden, die ohne einen zwischengeschalteten Wärmeaustauscher direkt mit Fernwärmesystemen verbunden sind, werden in dieser Norm nicht  betrachtet. Eingeschlossen sind jedoch örtliche Heizsysteme, in denen mehrere Gebäude durch ein Heizwerk versorgt werden.

Protection des matériaux métalliques contre la corrosion - Recommandations pour l'évaluation du risque de corrosion dans les systemes fermés a recirculation d'eau

Protikorozijska zaščita kovinskih materialov – Navodilo za ocenjevanje verjetnosti nastanka korozije v zaprtem sistemu vodnega kroženja

General Information

• Status: Published
• Publication Date: 31-Oct-2005
• ICS: 77.060 - Corrosion of metals
• Technical Committee: IPKZ - Protection of metals against corrosion
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Nov-2005
• Due Date: 01-Nov-2005
• Completion Date: 01-Nov-2005
• Ref Project: EN 14868:2005 - Protection of metallic materials against corrosion - Guidance on the assessment of corrosion likelihood in closed water circulation systems

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 14868:2005
01-november-2005
3URWLNRUR]LMVND]DãþLWDNRYLQVNLKPDWHULDORY±1DYRGLOR]DRFHQMHYDQMHYHUMHWQRVWL
QDVWDQNDNRUR]LMHY]DSUWHPVLVWHPXYRGQHJDNURåHQMD
Protection of metallic materials against corrosion - Guidance on the assessment of
corrosion likelihood in closed water circulation systems
Korrosionsschutz metallischer Werkstoffe - Leitfaden für die Ermittlung der
Korrosionswahrscheinlichkeit in geschlossenen Wasser-Zirkulationssystemen
Protection des matériaux métalliques contre la corrosion - Recommandations pour
l'évaluation du risque de corrosion dans les systemes fermés a recirculation d'eau
Ta slovenski standard je istoveten z: EN 14868:2005
ICS:
77.060 Korozija kovin Corrosion of metals
SIST EN 14868:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 14868:2005

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SIST EN 14868:2005
EUROPEAN STANDARD
EN 14868
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2005
ICS 77.060

English Version
Protection of metallic materials against corrosion - Guidance on
the assessment of corrosion likelihood in closed water
circulation systems
Protection des matériaux métalliques contre la corrosion - Korrosionsschutz metallischer Werkstoffe - Leitfaden für
Recommandations pour l'évaluation du risque de corrosion die Ermittlung der Korrosionswahrscheinlichkeit in
dans les systèmes fermés à recirculation d'eau geschlossenen Wasser-Zirkulationssystemen
This European Standard was approved by CEN on 8 July 2005.
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
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 14868:2005: E
worldwide for CEN national Members.

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SIST EN 14868:2005
EN 14868:2005 (E)
Contents page
Foreword .3
Introduction.4
1 Scope .5
2 Normative references .5
3 Terms and definitions.5
4 Symbols and abbreviations.6
5 Types of corrosion.6
6 Role of oxygen .7
7 Microbial corrosion.8
8 Corrosion damage in Case I conditions.8
9 Corrosion damages in Case II systems.11
10 Corrosion protection methods.15
Annex A (informative) Important corrosion reactions in the systems under consideration.19

Bibliography.22

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Foreword
This European Standard (EN 14868:2005) 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 February 2006, and conflicting national standards shall be withdrawn
at the latest by February 2006.
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.
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Introduction
This European Standard results mainly from investigations into and experience gained on the corrosion of
metallic materials normally present in water circulation systems in buildings (unalloyed and low alloyed steels,
cast iron, aluminium, copper and copper alloys, stainless steels).
Because of the complex interactions between the various influencing factors, which can alter during service
life due either to normal operation changes in service conditions or accidental events, the extent of corrosion
can only be expressed in terms of likelihood. This European Standard therefore is a guidance document and
does not set explicit rules for the use of metallic materials in water systems.
A correct evaluation of the corrosion likelihood therefore needs a corrosion expert (or at least a person with
technical training in the corrosion field) and knowledge of the technology and operating conditions of the
system considered.
Though incidences of severe damage because of corrosion (and/or scaling) are generally rare, certain basic
precautions should be taken in order to maintain a long-term, trouble-free service. This European Standard
should therefore be considered as a guidance document. On the basis of the information provided herein,
decisions can be made during design, installation and service life to minimize the likelihood of corrosion
damage occurring.
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1 Scope
This European Standard gives a review of influencing factors on the corrosion likelihood of metallic
components (pipes, tanks, vessels, heat exchangers, pumps etc.) in water circulation systems in buildings.
The water circulation systems considered are:
 heating systems (up to 110 °C service water temperature);
 cooling and chilling systems;
which are filled with potable water or water of similar composition according to the Directive 98/83/EC.
NOTE 1 Sanitary hot water systems with a re-circulation loop are not considered in this European Standard as they are
not really closed system, because the water is continually renewed. The corrosion likelihood of these systems is discussed
in EN 12502 Parts 1 to 5 [1], [2], [3], [4], [5].
NOTE 2 Cooling systems with open atmospheric towers are not considered in this European Standard because fresh
water is generally added to the system periodically to compensate for losses by evaporation or blow-down.
NOTE 3 Heating systems in buildings, connected to district heating systems without an intervening heat exchanger, are
not considered in this European Standard. However, local heating systems, where several buildings are heated by one
boiler plant, are included.
2 Normative references
The following referenced documents are indispensable for the application of this European Standard. 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 and definitions
For the purposes of this European Standard, the terms and definitions given in EN ISO 8044:1999, EN
12502-1:2004 and the following apply.
3.1
ferrous materials
cast iron, unalloyed and low alloyed steel (excluding stainless steel)
3.2
sludge formation
build-up of non-adherent particulate corrosion products which can be suspended and/or deposited in the
system
3.3
scaling
formation of relatively thick layers of calcium carbonate and/or corrosion products, especially on heat transfer
surfaces
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4 Symbols and abbreviations
- -1
c(Cl ) Concentration of chloride ions in mmol l
- -1
c(HCO ) Concentration of hydrogen carbonate ions in mmol l
3
2- -1
c(SO ) Concentration of sulphate ions in mmol l
4
- -1
c(NO ) Concentration of nitrate ions in mmol l
3
5 Types of corrosion
When evaluating the corrosion likelihood in water circulation systems almost all types of corrosion should be
taken into consideration.
The following types of corrosion can occur in the systems under consideration:
 uniform corrosion;
 localised corrosion:
 pitting corrosion;
 bimetallic corrosion;
 crevice corrosion;
deposit corrosion;

 water-line corrosion;
 selective corrosion (de-alloying);
 erosion corrosion;
 cavitation corrosion;
 stress corrosion cracking;
 microbial corrosion.
These types of corrosion can lead to different kinds of corrosion damage:
 leakage;
 constriction of flow;
 reduction of efficiency;
 boiler noise;
 seizure of movable components and other detrimental effects.
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6 Role of oxygen
6.1 General
In the systems under consideration, the corrosion processes are mainly determined by the extent of oxygen
ingress into the system. Generally, oxygen reduction is the driving force for anodic metal dissolution reactions.
If the ingress of oxygen can be prevented, the rate of corrosion will be minimised to the extent that corrosion
damages will normally not occur.
Oxygen can enter the system in different ways:
 as dissolved oxygen in the filling and any make-up water;
 from the atmosphere into the water within an open expansion vessel or some so-called de-aeration units
and with some kinds of pressurisation systems (e.g. compressor or pump pressurisation systems);
 from the atmosphere in the case of negative pressure (e.g. through gaskets, O-rings on valves or some
automatic air vents);
 from the atmosphere by diffusion through organic materials (e.g. plastic pipes without barrier, rubber
hoses or rubber membranes of air-filled expansion vessels and some so-called de-aeration systems);
 as dissolved oxygen in drinking water in the case of defective secondary heat exchangers for domestic
hot water, where the pressure in the domestic hot water is greater than in the primary heating water;
 from air pockets remaining in the system after refilling during maintenance or modification.
Corrosion becomes negligible after consumption of the oxygen initially present in the filling water provided that
the water is not renewed and no air entry is possible. The main concern with a closed system is therefore to
maintain water and air tightness. However, in some systems, especially large complex ones, maintaining
complete air tightness can be impractical.
6.2 Influence of design and operating conditions on oxygen ingress
With respect to oxygen ingress, two cases should be considered:
 Case I: systems with no significant oxygen ingress;
 Case II: systems with continuous or intermittent oxygen ingress.
Case I is defined by the fact that practically no oxygen ingress is possible during service. Oxygen dissolved in
the initial fill water is quickly used up in forming corrosion products, which in most cases does not lead to
impairment of the system.
Case II is characterised by the fact that oxygen ingress is possible during service either occasionally, regularly
or continuously.
Systems designed to represent Case I can become Case II during service depending on operating conditions.
Examples of Case I are as follows:
a. Systems with a closed expansion vessel, which are correctly designed, installed and maintained.
b. Open vented heating systems under conditions where only negligible amounts of oxygen are introduced
into the circulating water.
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Examples of Case II are as follows:
c. Open vented systems where during service the re-circulating water is regularly enriched with oxygen.
d. Systems with closed expansion vessels in situations where:
 volume of the expansion vessel is too small;
 gas pressure within the dry expansion vessel is not correctly adjusted to match the water pressure;
 gas pressure decreases during service;
 water volume decreases because of water loss (e.g. from valves and pumps).
Such circumstances can result in negative pressure in the system during cooling phases (e.g. overnight),
leading to oxygen ingress through O-rings or gaskets and automatic air vents.
e. Systems with continuous oxygen ingress by diffusion through the walls of organic materials, e.g. plastic
pipes, rubber hoses.
NOTE Refilling of a system does not normally lead to significant oxygen ingress. However, if the circulation water is
regularly renewed because of losses in the system and excessive amounts of fresh water are added (more than 2 times
initial fill volume) oxygen ingress will almost certainly lead to significant impairment of the system.
7 Microbial corrosion
Micro-organisms (algae, yeasts, fungi, bacteria etc.) can exist in debris left in the system after construction or
can enter the system with the initial filling water or via open header tank during operation. In Case II systems,
this can lead to bio-fouling problems and can also give rise to microbial corrosion irrespective of metallic
materials used in the system.
Although corrosion is favoured at moderate temperatures, not even the high temperatures in heat exchangers
are always sufficient to kill all micro-organisms and some bacteria are thermophiles. Favourable conditions
(nutrients, inorganic ions and organic contaminants, possibly also from some water treatment additives) favour
growth of microbiological organisms. Bacterial growth is also favoured by stagnant conditions, especially
under deposits, in dead legs or crevices formed during manufacturing operations. Their metabolism produces
organic acids, which promote initiation and acceleration of localised corrosion cells. The most well known case
is anaerobic bacteria, especially sulphate reducing bacteria, developing under deposits.
2+ 3+
In addition, in Case II systems, aerobic bacteria in the bulk water can oxidize ferrous (Fe ) to ferric (Fe ) ions
leading to an enhanced uniform corrosion.
8 Corrosion damage in Case I conditions
8.1 Ferrous materials
8.1.1 Leakage
Leakage caused by corrosion generally does not occur under Case I conditions.
8.1.2 Constriction of flow
In the normal course of events, corrosion of iron does not lead to sludge formation to the extent that it
constricts flow. However, in special cases, where the ratio of water volume to surface area of iron is very high
(i.e. with large buffering vessels or large surfaces of non-oxygen consuming materials such as plastic or
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stainless steel) the oxygen content of filling water can give rise to the build-up of non-adherent sludge
composed of corrosion products (see 9.1.2).
8.1.3 Reduction of efficiency
In systems containing waters of relatively low pH (< about 8) increased concentration of iron(II) ions can lead
to enhanced formation of magnetite (Fe O ) according to equation (A.5), Annex A.1, on the hot walls of heat
3 4
transfer surfaces. This scale, which can be associated with lime scale, reduces boiler efficiency irrespective of
the boiler material. However, in the majority of systems the pH of the re-circulating water rises quickly above
8,0 and this corrosion damage does not occur.
The deposition of iron corrosion products on the inside surfaces of plastic pipes, formed according to (A.4),
Annex A.1, can also lead to the reduction of heat transfer efficiency by decreasing water flow.
8.1.4 Boiler noise
On directly heated heat transfer surfaces, unevenly distributed scale (e.g. iron oxides and calcium carbonate)
can lead to boiler noise because of nucleate boiling, particularly in the case of small, high efficiency heat
exchangers.
8.2 Copper and copper alloys
8.2.1 Leakage
Generally no leakage caused by pitting corrosion happens with copper and copper alloys.
Leakage caused by stress corrosion cracking of brass can occur when a critical level of tensile stress together
with a sufficient concentration of nitrite and/or ammonia is present. Critical tensile stresses can be induced
during construction, for example by over-tightening threads or use of male tapered threads with female
parallel threads. Nitrites and/or ammonia are normally not present in potable water in concentrations sufficient
to induce stress corrosion. However, nitrates in water are reduced in oxygen-free conditions in re-circulating
systems and in critical areas, for example in crevices or under deposits.
8.2.2 Constriction of flow
There is generally no constriction of flow caused by corrosion of copper and copper alloys under Case I
conditions.
8.2.3 Reduction of efficiency
There is generally no reduction of efficiency caused by corrosion of copper and copper alloys under Case I
conditions.
Nevertheless, corrosion of other materials in the system can lead to a reduction of efficiency, see 8.1.3 and
8.3.3.
8.2.4 Boiler noise
There is generally no boiler noise caused by corrosion of copper and copper alloys under Case I conditions.
Nevertheless, corrosion of other materials in the system can lead to boiler noise, see 8.1.4 and 8.3.4.
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8.3 Aluminium
8.3.1 Leakage
Leakage caused by non-uniform corrosion will not occur if potable water without further treatment is used as
filling water.
Only in very soft waters with low buffer capacity, in cases of self alkalization or when alkaline products are
added, which raise the pH value above 8,5 (e.g. some alkaline inhibitors for protection of ferrous materials), is
corrosion likely because of the formation of aluminates and evolution of hydrogen. In such situations, leakage
is usually caused by erosion corrosion in areas of turbulent flow.
In special cases, where the ratio of water volume to surface area of aluminium is very high (i.e. with large
buffering vessels or large surfaces of non-oxygen consuming materials such as plastic or stainless steel) the
oxygen content of filling water in combination with a high chloride content can lead to pitting corrosion and
leakage.
8.3.2 Constriction of flow
Constriction of flow because of aluminium corrosion will not occur if potable water without further treatment is
used.
If the water is treated with alkaline products (see 8.3.1), corrosion can lead to the formation of aluminates,
which can be transformed to solid corrosion products on hot walls of heat exchangers. In extreme cases, this
effect can lead to total blockage of a heat exchanger. Furthermore, the evolution of hydrogen can induce the
formation of gas pockets, which can in turn constrict flow.
8.3.3 Reduction of efficiency
Reduction of efficiency solely caused by aluminium corrosion will not occur if potable water without further
treatment is used as filling water.
If the water is treated with alkaline products (see 8.3.1) corrosion can lead to the formation of aluminates,
which can be transformed to solid corrosion products on hot walls of heat exchangers. As with lime scale
formation, the build-up of aluminium oxide scale increases thermal resistance of the wall which, in turn,
decreases heat transfer and hence reduces boiler efficiency, irrespective of the boiler material. The poorly
soluble nature of aluminium corrosion products formed on AlSi-alloys in most acids effectively prevents
restoration of desired boiler efficiency by chemical cleaning.
8.3.4 Boiler noise
Boiler noise caused by the formation of corrosion products will not occur if potable water without further
treatment is used as filling water.
If the water is treated with alkaline products (see 8.3.1), unevenly distributed aluminium oxide scale formed on
directly heated heat transfer surfaces can lead to boiler noise particularly in the case of small, high efficiency
heat exchangers. The poorly soluble nature of aluminium corrosion products formed on AlSi-alloys in most
acids effectively prevents elimination of boiler noise by chemical cleaning.
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8.4 Stainless steel
8.4.1 Leakage
There is generally no leakage caused by corrosion of stainless steels under Case I conditions.
8.4.2 Constricton of flow
There is generally no constriction of flow caused by corrosion of stainless steels under Case I conditions.
8.4.3 Reduction of efficiency
There is generally no reduction of efficiency caused by corrosion of stainless steels under Case I conditions.
Nevertheless, corrosion of other materials in the system can lead to a reduction of efficiency, see 8.1.3 and
8.3.3.
8.4.4 Boiler Noise
There is generally no boiler noise caused by corrosion of stainless steels under Case I conditions.
Nevertheless, corrosion of other materials in the system can lead to boiler noise, see 8.1.4 and 8.3.4.
9 Corrosion damages in Case II systems
9.1 Ferrous materials
9.1.1 Leakage
Under exceptional circumstances, perforation of radiators, steel boilers and tubes can occur. Any such
perforations are usually associated with localised corrosion cells. The anodic parts of these corrosion cells are
located mainly under deposits, in crevices and at three-phase boundaries, i.e. metal-water-air (water-line
corrosion). In radiators, localised corrosion takes place preferentially at the bottom or at welded points.
Localised corrosion can also occur because of residual flux deposited in steel radiators.
The critical conditions with regard to initiation and stabilisation of corrosion cells are encountered in situations
where a heating system has been drained (e.g. after pressure testing or for frost damage prevention) owing to
the unavoidable effects of residual water.
NOTE When using water-antifreeze mixtures for a limited period of time, it is recommended the pH of the refilled
circulation water is controlled and adjusted, because organic reactions with antifreeze residues can lead to a decrease of
pH and an increase of corrosion likelihood.
In the case of cast iron heat exchangers, severe scaling can lead to thermal overload increasing the risk of
crack formation.
9.1.2 Constriction of flow
Constriction of flow can occur because of the accumulation of solid corrosion products or gases.
The solid corrosion products essentially comprise poorly soluble black sludge, which can be formed according
to equations (A.4) or (A.5), Annex A.1. This sludge will settle in areas of low flow. In radiators, this can lead to
the formation of cold spots if vertical water ways become blocked. Because of its magnetic properties,
magnetite can accumulate on ferrous components which, in areas of small cross section (e.g. metallic
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connections to rubber hoses), can lead to blockage. Sludge formation can be exacerbated because of
flocculation by aluminium species in the water.
In the case of plastic pipes or rubber hoses, oxygen permeation leads to the formation of poorly soluble,
orange/brown hydrated iron(III) oxide (FeOOH) species on the inside surfaces. This process can result in
relatively thick corrosion product layers, and large flakes can become detached and cause blockages
downstream. Any such flakes on plastic pipework surfaces are characterised by a smooth, bright appearance
and a matt appearance on the water side.
The presence of gas in radiators can prevent water circulation predominantly in radiators fixed in the higher
parts of an installation. This gas consists mainly of nitrogen but can contain significant amounts of hydrogen
from reactions (A.5) and (A.6), Annex A.1.
9.1.3 Reduction of efficiency
The mechanism of reduction of efficiency in Case II systems is similar to Case I systems (see 8.1.3), but can
be enhanced due the higher amount of corrosion products in circulation. In situations where untreated fresh
water is regularly introduced into a system, additional lime scale formation will further enhance the reduction
of efficiency.
9.1.4 Boiler noise
The conditions with respect to boiler noise are similar to those described in 8.1.4. As with reduction in
efficiency, in situations where fresh water is regularly introduced into a system, additional lime scale formation
will increase the likelihood of boiler noise.
9.1.5 Seizure of movable components and other detrimental effects
Seizure of movable components (e.g. pumps, valves, energy meters) can occur from deposition of suspended
magnetite. This effect can be enhanced by the magnetic properties of the ferrous substrate, as can be seen in
energy meters with rotating magnets.
In cast iron pumps used in systems incorporating non-barrier plastic pipes or rubber hoses, seizure can also
occur because of the direct formation of corrosion products on the iron surfaces.
Cast iron pump housing can occasionally suffer cavitation damages if the pump characteristics are not
appropriate for the system or if uninhibited acidic cleaners are used.
Wear of pump shafts, bearings and seals can also occur from circulation of solid corrosion products.
9.2 Copper and copper alloys
9.2.1 General
There are generally no significant corrosion damages with copper and its alloys under Case II conditions.
However, there are two main exceptions:
 in the presence of ammonia and critical tensile stresses;
 in the presence of deposits (e.g. iron corrosion products) on copper surfaces without protective layers.
9.2.2 Leakage
In general, copper and its alloys have good corrosion resistance in systems with continuous or intermittent
oxygen ingress. However, the deposition of other materials (i.e. water borne debris such as corrosion products
from other metallic components, silt, fluxes etc.) on fresh copper surfaces without protective layers can lead to
the development of localised corrosion cells similar to those described in 9.1.1 for ferrous materials.
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Under certain conditions which give rise to the presence of ammonia and/or nitrites, stress corrosion cracking
of brass components can occur along the lines described in 8.2.
In certain large systems where sodium sulphite is used as an oxygen scavenger, corrosion damage from the
formation of thick copper(I) sulphide layers can occur. This can manifest itself in the form of perforation of
pipework or failure of joints containing phosphorus-bearing brazing alloys.
Extreme cases of dezincification of brass components can lead to leakage.
9.2.3 Constriction of flow
Copper generally poses no problems in terms of constriction of flow in these systems.
Dezincification of alpha/beta duplex brasses can result in the formation of zinc hydroxy-carbonate deposits
which can become detached and accumulate in small orifice valves, etc., resulting in constricted flow or
blockage. However, the risk of any such occurrence can be obviated by the use of immune or dezincification
resistant copper alloys.
9.2.4 Reduction of efficiency
With the exception of copper(I) sulphide formation described in 9.2.2, there are generally no problems in terms
of reduction of efficiency from the formation of copper corrosion products.
9.2.5 Boiler noise
With the exception of copper(I) sulphide formation
...