Corrosion of metals and alloys - Corrosivity of atmospheres - Classification, determination and estimation (ISO 9223:2012)

ISO 9223:2012 establishes a classification system for the corrosivity of atmospheric environments. It
defines corrosivity categories for the atmospheric environments by the first-year corrosion rate of standard specimens,
gives dose-response functions for normative estimation of the corrosivity category based on the calculated first-year corrosion loss of standard metals, and
makes possible an informative estimation of the corrosivity category based on knowledge of the local environmental situation.
ISO 9223:2012 specifies the key factors in the atmospheric corrosion of metals and alloys. These are the temperature-humidity complex, pollution by sulfur dioxide and airborne salinity.
The temperature-humidity complex can be evaluated in terms of time of wetness. Corrosion effects of other pollutants (ozone, nitrogen oxides, particulates) are not considered decisive in the assessment of corrosivity according to ISO 9223:2012.
ISO 9223:2012 does not characterize the corrosivity of specific service atmospheres, e.g. atmospheres in chemical or metallurgical industries.

Korrosion von Metallen und Legierungen - Korrosivität von Atmosphären - Klassifizierung, Bestimmung und Abschätzung (ISO 9223:2012)

Diese Internationale Norm legt ein Einteilungssystem für die Korrosivität von atmosphärischen Umgebungen
fest. Sie
 definiert Korrosivitätskategorien von atmosphärischen Umgebungen auf der Grundlage der Korrosionsgeschwindigkeit
von Standardproben nach dem ersten Jahr in einer Umgebung,
 gibt Dosis-Wirkung-Funktionen für die normative Abschätzung der Korrosivitätskategorie auf der
Grundlage von berechneten Massenverluste durch Korrosion von metallischen Standardproben nach
dem ersten Jahr in einer Umgebung an, und
 ermöglicht eine informative Abschätzung der Korrosivitätskategorie auf der Grundlage der Kenntnis der
örtlichen Umgebungssituation.
Diese Internationale Norm legt die entscheidenden Faktoren bei der atmosphärischen Korrosion von Metallen
und Legierungen fest. Das sind der Temperatur-Feuchte-Komplex, Verunreinigung durch Schwefeldioxid und
Salzhaltigkeit der Luft.
Die Temperatur ist auch für die Korrosion in Gebieten außerhalb der gemäßigten makroklimatischen Zone als
ein wichtiger Faktor anzusehen. Der Temperatur-Feuchte-Komplex kann in Bezug auf die Befeuchtungsdauer
bewertet werden. Korrosionserscheinungen anderer Verunreinigungen (Ozon, Stickoxide, Staub) können die
Korrosivität und den ermittelten Korrosionsverlust nach einem Jahr beeinflussen, diese Faktoren werden
jedoch nicht als maßgeblich bei der Beurteilung der Korrosivität nach der vorliegenden Internationalen Norm
angesehen.
Diese Internationale Norm charakterisiert nicht die Korrosivität von speziellen Betriebsatmosphären, z. B.
Atmosphären in der chemischen oder metallurgischen Industrie.
Die klassifizierten Korrosivitätskategorien und eingeführten Verunreinigungsgrade können direkt zur
technischen und ökonomischen Analyse von Korrosionsschaden und zu einer rationalen Wahl von
Korrosionsschutzmaßnahmen genutzt werden.

Corrosion des métaux et alliages - Corrosivité des atmosphères - Classification, détermination et estimation (ISO 9223:2012)

L'ISO 9223:2012 établit un système de classification de la corrosivité des environnements atmosphériques. Elle
définit des classes de corrosivité des environnements atmosphériques en fonction de la vitesse de corrosion d'éprouvettes de référence sur la première année,
donne des fonctions dose-réponse pour l'estimation normative de la classe de corrosivité sur la base de la perte par corrosion sur la première année calculée sur des métaux de référence, et
rend possible une estimation informative de la classe de corrosivité fondée sur la connaissance de la situation environnementale locale.
L'ISO 9223:2012 spécifie les facteurs clés de la corrosion atmosphérique des métaux et alliages. Ces facteurs sont la relation température-humidité, la pollution par le dioxyde de soufre et les sels contenus dans l'air.
La relation température-humidité peut être évaluée en fonction de la durée de persistance de l'humidité. Les effets de la corrosion par d'autres polluants (ozone, oxydes d'azote, particules) ne sont pas considérés comme déterminants pour l'estimation de la corrosivité conformément à l'ISO 9223:2012.
L'ISO 9223:2012 ne caractérise pas la corrosivité d'atmosphères de service spécifiques, telles que les atmosphères des industries chimiques ou métallurgiques.

Korozija kovin in zlitin - Korozivnost v atmosferskem okolju - Razvrstitev, ugotavljanje in ocena korozivnosti (ISO 9223:2012)

Ta mednarodni standard vzpostavlja sistem razvrščanja za korozivnost v atmosferskih okoljih. Standard: – določa kategorizacijo korozivnosti za atmosferska okolja glede na hitrost korozije s standardnimi vzorci v prvem letu; – določa funkcijske povezave med odmerkom in odzivom za normativno oceno kategorije korozivnosti na podlagi izračunane korozijske izgube za standardne kovine v prvem letu; ter – omogoča informativno oceno kategorije korozivnosti na podlagi poznavanja lokalnih okoljskih razmer. Ta mednarodni standard določa glavne dejavnike pri atmosferski koroziji kovin in zlitin. Ti dejavniki so kombinacija temperature in vlažnosti, onesnaženost z žveplovim dioksidom ter slanost v zraku. Tudi temperatura je pomemben dejavnik pri koroziji na območjih, ki nimajo zmernih makroklimatskih razmer. Kombinacijo temperature in vlažnosti je mogoče oceniti z vidika časa mokrote. Korozijski učinki drugih onesnaževal (ozon, dušikovi oksidi, delci) lahko vplivajo na korozivnost in ocenjeno korozijsko izgubo v enem letu, vendar ti dejavniki ne veljajo za odločilne pri oceni korozivnosti v skladu s tem mednarodnim standardom. Ta mednarodni standard ne označuje korozivnosti v posebnih atmosferah; npr. atmosferah v kemični ali metalurški industriji. Razvrščene kategorije korozivnosti in uvedene ravni onesnaženosti je mogoče neposredno uporabiti za tehnične in ekonomske analize škode zaradi korozije in za racionalno izbiro protikorozijskih ukrepov.

General Information

Status
Published
Publication Date
11-Apr-2012
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
26-Mar-2012
Due Date
31-May-2012
Completion Date
12-Apr-2012

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SLOVENSKI STANDARD
SIST EN ISO 9223:2012
01-maj-2012
1DGRPHãþD
SIST EN 12500:2000
Korozija kovin in zlitin - Korozivnost v atmosferskem okolju - Razvrstitev,
ugotavljanje in ocena korozivnosti (ISO 9223:2012)
Corrosion of metals and alloys - Corrosivity of atmospheres - Classification,
determination and estimation (ISO 9223:2012)
Korrosion von Metallen und Legierungen - Korrosivität von Atmosphären -
Klassifizierung, Bestimmung und Abschätzung (ISO 9223:2012)
Corrosion des métaux et alliages - Corrosivité des atmosphères - Classification,
détermination et estimation (ISO 9223:2012)
Ta slovenski standard je istoveten z: EN ISO 9223:2012
ICS:
77.060 Korozija kovin Corrosion of metals
SIST EN ISO 9223:2012 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 9223:2012

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SIST EN ISO 9223:2012


EUROPEAN STANDARD
EN ISO 9223

NORME EUROPÉENNE

EUROPÄISCHE NORM
February 2012
ICS 77.060 Supersedes EN 12500:2000
English Version
Corrosion of metals and alloys - Corrosivity of atmospheres -
Classification, determination and estimation (ISO 9223:2012)
Corrosion des métaux et alliages - Corrosivité des Korrosion von Metallen und Legierungen - Korrosivität von
atmosphères - Classification, détermination et estimation Atmosphären - Klassifizierung, Bestimmung und
(ISO 9223:2012) Abschätzung (ISO 9223:2012)
This European Standard was approved by CEN on 22 January 2012.

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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9223:2012: E
worldwide for CEN national Members.

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SIST EN ISO 9223:2012
EN ISO 9223:2012 (E)
Contents Page
Foreword .3

2

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SIST EN ISO 9223:2012
EN ISO 9223:2012 (E)
Foreword
This document (EN ISO 9223:2012) has been prepared by Technical Committee ISO/TC 156 "Corrosion of
metals and alloys" in collaboration with 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 August 2012, and conflicting national standards shall be withdrawn at
the latest by August 2012.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 12500:2000.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 9223:2012 has been approved by CEN as a EN ISO 9223:2012 without any modification.

3

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SIST EN ISO 9223:2012

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SIST EN ISO 9223:2012

INTERNATIONAL ISO
STANDARD 9223
Second edition
2012-02-01

Corrosion of metals and alloys —
Corrosivity of atmospheres —
Classification, determination and
estimation
Corrosion des métaux et alliages — Corrosivité des atmosphères —
Classification, détermination et estimation




Reference number
ISO 9223:2012(E)
©
ISO 2012

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SIST EN ISO 9223:2012
ISO 9223:2012(E)

COPYRIGHT PROTECTED DOCUMENT


©  ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56  CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland

ii © ISO 2012 – All rights reserved

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SIST EN ISO 9223:2012
ISO 9223:2012(E)
Contents Page
Foreword . iv
Introduction . v
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 2
4  Symbols and abbreviated terms . 2
4.1  Symbols . 2
4.2  Abbreviated terms . 3
5  Category of corrosivity of the atmosphere . 3
6  Classification of corrosivity of the atmosphere . 3
7  Corrosivity determination based on corrosion rate measurement of standard specimens . 4
8  Corrosivity estimation based on environmental information . 4
8.1  Corrosivity estimation — General . 4
8.2  Normative corrosivity estimation based on calculated first-year corrosion losses . 5
8.3  Informative corrosivity estimation based on description of exposure conditions . 6
Annex A (informative) Sources of uncertainty associated with the determination and estimation of
atmospheric corrosivity . 7
Annex B (informative) Characterization of the atmosphere in relation to its corrosivity . 9
Annex C (informative) Description of typical atmospheric environments related to the estimation
of corrosivity categories . 13
Bibliography . 15

© ISO 2012 – All rights reserved iii

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SIST EN ISO 9223:2012
ISO 9223:2012(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 9223 was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys.
This second edition cancels and replaces the first edition (ISO 9223:1992), which has been technically revised.
iv © ISO 2012 – All rights reserved

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SIST EN ISO 9223:2012
ISO 9223:2012(E)
Introduction
Metals, alloys and metallic coatings can suffer atmospheric corrosion when their surfaces are wetted. The
nature and rate of the attack depends upon the properties of surface-formed electrolytes, particularly with
regard to the level and type of gaseous and particulate pollutants in the atmosphere and to the duration of
their action on the metallic surface.
The character of the corrosion attack and the corrosion rate are consequences of the corrosion system, which
comprises the metallic materials, the atmospheric environment, technical parameters and operation conditions.
The corrosivity category is a technical characteristic which provides a basis for the selection of materials and
protective measures in atmospheric environments subject to the demands of the specific application,
particularly with regard to service life.
Data on the corrosivity of the atmosphere are essential for the development and specification of optimized
corrosion protection for manufactured products.
The corrosivity categories are defined by the first-year corrosion effects on standard specimens as specified in
ISO 9226. The corrosivity categories can be assessed in terms of the most significant atmospheric factors
influencing the corrosion of metals and alloys.
The measurement of relevant environmental parameters is specified in ISO 9225.
The ways of determining and estimating the corrosivity category of a given location according to this
International Standard and the relationships among them are presented in Figure 1. It is necessary to
distinguish between corrosivity determination and corrosivity estimation. It is also necessary to distinguish
between corrosivity estimation based on application of a dose-response function and that based on
comparison with the description of typical atmospheric environments.
This International Standard does not take into consideration the design and mode of operation of the product,
which can influence its corrosion resistance, since these effects are highly specific and cannot be generalized.
Steps in the choice of optimized corrosion protection measures in atmospheric environments are defined in
ISO 11303.
© ISO 2012 – All rights reserved v

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SIST EN ISO 9223:2012
ISO 9223:2012(E)

Figure 1 — Classification of atmospheric corrosivity

vi © ISO 2012 – All rights reserved

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SIST EN ISO 9223:2012
INTERNATIONAL STANDARD ISO 9223:2012(E)

Corrosion of metals and alloys — Corrosivity of atmospheres —
Classification, determination and estimation
1 Scope
This International Standard establishes a classification system for the corrosivity of atmospheric environments.
It
 defines corrosivity categories for the atmospheric environments by the first-year corrosion rate of
standard specimens,
 gives dose-response functions for normative estimation of the corrosivity category based on the
calculated first-year corrosion loss of standard metals, and
 makes possible an informative estimation of the corrosivity category based on knowledge of the local
environmental situation.
This International Standard specifies the key factors in the atmospheric corrosion of metals and alloys. These
are the temperature-humidity complex, pollution by sulfur dioxide and airborne salinity.
Temperature is also considered an important factor for corrosion in areas outside the temperate macroclimatic
zone. The temperature-humidity complex can be evaluated in terms of time of wetness. Corrosion effects of
other pollutants (ozone, nitrogen oxides, particulates) can influence the corrosivity and the evaluated one-year
corrosion loss, but these factors are not considered decisive in the assessment of corrosivity according to this
International Standard.
This International Standard does not characterize the corrosivity of specific service atmospheres,
e.g. atmospheres in chemical or metallurgical industries.
The classified corrosivity categories and introduced pollution levels can be directly used for technical and
economical analyses of corrosion damage and for a rational choice of corrosion protection measures.
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.
ISO 8044, Corrosion of metals and alloys — Basic terms and definitions
ISO 9224, Corrosion of metals and alloys — Corrosivity of atmospheres — Guiding values for the corrosivity
categories
ISO 11844-1, Corrosion of metals and alloys — Classification of low corrosivity of indoor atmospheres —
Part 1: Determination and estimation of indoor corrosivity
ISO 11844-2, Corrosion of metals and alloys — Classification of low corrosivity of indoor atmospheres —
Part 2: Determination of corrosion attack in indoor atmospheres
© ISO 2012 – All rights reserved 1

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SIST EN ISO 9223:2012
ISO 9223:2012(E)
ISO 11844-3, Corrosion of metals and alloys — Classification of low corrosivity of indoor atmospheres —
Part 3: Measurement of environmental parameters affecting indoor corrosivity
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8044 and the following apply.
3.1
corrosivity of atmosphere
ability of the atmosphere to cause corrosion in a given corrosion system
3.2
category of corrosivity of atmosphere
standardized rating of corrosivity of atmosphere in relation to the one-year corrosion effect
3.3
type of atmosphere
characterization of the atmosphere on the basis of appropriate classification criteria other than corrosivity or of
complementary operation factors
EXAMPLE Rural, urban, industrial, marine, chemical, etc.
3.4
temperature-humidity complex
combined effect of temperature and relative humidity on the corrosivity of the atmosphere
3.5
time of wetness
period when a metallic surface is covered by adsorptive and/or liquid films of electrolyte to be capable of
causing atmospheric corrosion
3.6
pollution level
numbered rank based on quantitative measurements of specific chemically active substances, corrosive
gases or suspended particles in the air (both natural and the result of human activity) that are different from
the normal components of the air
3.7
category of location
conventionally defined typical exposure conditions of a component or structure
EXAMPLE Exposure in the open air, under shelter, in a closed space, etc.
3.8
dose-response function
relationship derived from results of field tests for calculation of corrosion loss from average values of
environmental parameters
4 Symbols and abbreviated terms
4.1 Symbols
r Corrosion rate for the first year of atmospheric exposure
corr
T Air temperature
2 © ISO 2012 – All rights reserved

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SIST EN ISO 9223:2012
ISO 9223:2012(E)
P SO deposition rate
d 2
P SO concentration
c 2

S Cl deposition rate
d
 Time of wetness
4.2 Abbreviated terms
C Atmospheric corrosivity category
RH Relative humidity
5 Category of corrosivity of the atmosphere
The corrosivity of the atmosphere is divided into six categories (see Table 1).
Table 1 — Categories of corrosivity of the atmosphere
Category Corrosivity
C1 Very low
C2 Low
C3 Medium
C4 High
C5 Very high
CX Extreme

6 Classification of corrosivity of the atmosphere
The corrosivity of atmospheric environments shall be classified either by determination of the corrosivity in
accordance with Clause 7 or, where this is not possible, by estimation of the corrosivity in accordance with
Clause 8. Both methods of the corrosivity evaluation represent a generalized approach and are characterized
by some uncertainties and limitations.
A corrosivity category determined from the first-year corrosion loss reflects the specific environmental situation
of the year of exposure.
A corrosivity category estimated from the dose-response function reflects the statistical uncertainty of the
given function.
A corrosivity category estimated using the informative procedure based on the comparison of the local
environmental conditions with the description of typical atmospheric environments can lead to
misinterpretations. This approach is to be used if experimental data are not available.
Annex A defines uncertainties related to the determination and normative estimation of atmospheric corrosivity
categories.
Detailed classification of low corrosivity of indoor atmospheres covering the corrosivity categories C1 and C2
in terms of this International Standard is specified in ISO 11844-1, ISO 11844-2 and ISO 11844-3.
© ISO 2012 – All rights reserved 3

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SIST EN ISO 9223:2012
ISO 9223:2012(E)
7 Corrosivity determination based on corrosion rate measurement of standard
specimens
Numerical values of the first-year corrosion rates for standard metals (carbon steel, zinc, copper, aluminium)
are given in Table 2 for each corrosivity category. One-year exposure tests should start in the spring or
autumn. In climates with marked seasonal differences, a starting time in the most aggressive period is
recommended. The first-year corrosion rates cannot be simply extrapolated for the prediction of long-term
corrosion behaviour. Specific calculation models, guiding corrosion values and additional information on
long-term corrosion behaviour, are given in ISO 9224.
Table 2 — Corrosion rates, r , for the first year of exposure
corr
for the different corrosivity categories
Corrosion rates of metals
Corrosivity
r
corr
category
Unit Carbon steel Zinc Copper Aluminium
2
C1 g/(ma) r  10 r  0,7 r  0,9 negligible
corr corr corr
μm/a r  1,3 r  0,1 r  0,1 —
corr corr corr
2
C2 g/(ma) 10  r  200 0,7  r  5 0,9  r  5 r  0,6
corr corr corr corr
μm/a 1,3  r  25 0,1  r  0,7 0,1  r  0,6 —
corr corr corr
2
C3 g/(ma) 200  r  400 5  r  15 5  r  12 0,6  r  2
corr corr corr corr
μm/a 25  r  50 0,7  r  2,1 0,6  r  1,3 —
corr corr corr
2
C4 g(ma) 400  r  650 15  r  30 12  r  25 2  r  5
corr corr corr corr
μm/a 50  r  80 2,1  r  4,2 1,3  r  2,8 —
corr corr corr
2
C5 g/(ma) 650  r  1 500 30  r  60 25  r  50 5  r  10
corr corr corr corr
μm/a 80  r  200 4,2  r  8,4 2,8  r  5,6 —
corr corr corr
2
CX g/(ma) 1 500  r  5 500 60  r  180 50  r  90 r  10
corr corr corr corr
μm/a 200  r  700 8,4  r  25 5,6  r  10 —
corr corr corr
NOTE 1 The classification criterion is based on the methods of determination of corrosion rates of standard specimens for the
evaluation of corrosivity (see ISO 9226).
2
NOTE 2 The corrosion rates, expressed in grams per square metre per year [g/(m ·a)], are recalculated in micrometres per year
(μm/a) and rounded.
NOTE 3 The standard metallic materials are characterized in ISO 9226.
NOTE 4 Aluminium experiences uniform and localized corrosion. The corrosion rates shown in this table are calculated as uniform
corrosion. Maximum pit depth or number of pits can be a better indicator of potential damage. It depends on the final application.
Uniform corrosion and localized corrosion cannot be evaluated after the first year of exposure due to passivation effects and decreasing
corrosion rates.
NOTE 5 Corrosion rates exceeding the upper limits in category C5 are considered extreme. Corrosivity category CX refers to specific
marine and marine/industrial environments (see Annex C).

8 Corrosivity estimation based on environmental information
8.1 Corrosivity estimation — General
If it is not possible to determine the corrosivity categories by the exposure of standard specimens, an
estimation of corrosivity may be based on corrosion loss calculated from environmental data or on information
on environmental conditions and exposure situation.
4 © ISO 2012 – All rights reserved

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SIST EN ISO 9223:2012
ISO 9223:2012(E)
8.2 Normative corrosivity estimation based on calculated first-year corrosion losses
Dose-response functions for four standard metals are given, describing the corrosion attack after the first year
of exposure in open air as a function of SO dry deposition, chloride dry deposition, temperature and relative
2
humidity. Functions are based on results of worldwide corrosion field exposures and cover climatic earth
conditions and pollution situation within the scope of this International Standard. Some limitations and
uncertainties are characterized in Annex A.
Dose-response functions for calculation of the first-year corrosion loss of structural metals:
Use Equation (1) for carbon steel:
0,52 0,62
rP= 1,77··exp(0,020·RH+f ) + 0,102··S exp(0,033·RH+ 0,040·T ) (1)
corr St
dd
f = 0,150·(T – 10) when T  10 °C; otherwise 0,054·(T – 10)
St
2
N = 128, R = 0,85
Use Equation (2) for zinc:
0,44 0,57
rP= 0,012 9··exp(0,046·RH +f ) + 0,017 5··S exp(0,008·RH+ 0,085·T ) (2)
corr Zn
dd
f = 0,038·(T – 10) when T  10 °C; otherwise, 0,071·(T – 10)
Zn
2
N = 114, R = 0,78
Use Equation (3) for copper:
0,26 0,27
rP= 0,005 3··exp(0,059·RH+f ) + 0,010 25··S exp(0,036·RH+ 0,049·T ) (3)
corr Cu
dd
f = 0,126·(T – 10) when T  10 °C; otherwise, 0,080·(T – 10)
Cu
2
N = 121, R = 0,88
Use Equation (4) for aluminium:
0,73 0,60
rP= 0,004 2··exp(0,025·RH+f ) + 0,0018··S exp(0,020·RH+ 0,094·T ) (4)
corr Al
dd
f = 0,009·(T – 10) when T  10 °C; otherwise 0,043·(T – 10)
Al
2
N = 113, R = 0,65
where
r is first-year corrosion rate of metal, expressed in micrometres per year (µm/a);
corr
T is the annual average temperature, expressed in degrees Celsius (°C);
RH is the annual average relative humidity, expressed as a percentage (%);
P is the annual average SO deposition, expressed in milligrams per square metre per day
d 2
2
[mg/(md)];

S is the annual average Cl deposition, expressed in milligrams per square metre per day
d
2
[mg/(md)].
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SIST EN ISO 9223:2012
ISO 9223:2012(E)
For details of the environmental parameters, see Table 3, which also gives the measured intervals of the
parameters. If P is replaced with 0,8P in the dose-response functions, as explained in the table footnote to
d c
Table 3, P shall also be an annual average.
c
Table 3 — Parameters used in the derivation of dose-response functions,
including symbol, description, interval and unit
Symbol Description Interval Unit
T Temperature 17,1 to 28,7 °C
RH Relative humidity 34 to 93 %

2
P SO deposition 0,7 to 150,4 mg/(md)
d 2
 2
S Cl deposition 0,4 to 760,5 mg/(md)
d
The sulfur dioxide (SO ) values determined by the deposition method, P , and volumetric
2 d
method, P , are equivalent for the purposes of this International Standard. The relationship
c
between measurements using both methods may be approximately expressed as
2 3
P = 0,8 P [P in mg/(md), P in µg/m ].
d c d c
NOTE All parameters are expressed as annual averages.

Care shall be taken when extrapolating the equations outside the intervals of environmental parameters for
their calculations (e.g. in coastal environments).
8.3 Informative corrosivity estimation based on description of exposure conditions
The corrosivity of an atmospheric environment increases with the effect of the temperature-humidity complex
(covering also time of wetness) and the levels of other corrosive agents.
Typical atmospheric types of pollution and levels are introduced in Annex B.
Exposure conditions (category of location) of material, component or structure influence the impact of
environment.
A qualitative description of typical environments related to the atmospheric corrosivity categories for the
purposes of informative corrosivity estimation is given in Annex C.
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SIST EN ISO 9223:2012
ISO 9223:2012(E)
Annex A
(informative)

Sources of uncertainty associated with the determination
and estimation of atmospheric corrosivity
A.1 General
The corrosivity of atmospheric environments shall be classified either through determination of the corrosivity
category based on the exposure of specimens or by estimation based on environmental parameters and the
use of a dose-response function. The use of these two different denominations for the assessment of a
corrosivity category implies that two different levels of uncertainty can be expected for the determination (low
uncertainty) and estimation (high uncertainty) procedures. This annex serves to establish those two levels of
uncertainty.
The basis for the details given in this annex is a separate statistical analysis performed in connection with the
derivation of the dose-response functions for the estimation procedure.
A.2 Distribution of errors
Log-normal distributions, i.e. normal distributions of logarithmic values, are observed for the corrosion rates. If
the uncertainty is expressed by a standard deviation of logarithmic values, s, then
ln(r ) = s (A.1)
corr
s
This means that the uncertainty interval in general is asymmetric and can be expressed as r ·e . However,
corr
if s is small, the interval becomes approximately symmetric. This can be illustrated by the following two
s s
examples. If s = 0,7, then e = 2 and e = 1/2, which corresponds to an interval from 50 % to +100 %. On the
s s
other hand, if s = 0,01, then e = 1,01 and e = 0,99, which corresponds to an interval from 1 % to +1 % or
1 %.
A.3 Levels of uncertainty
Table A.1 gives the estimated levels of uncertainty. The large difference between the two procedures is clear
from the table and this is what motivates the two different denominations of the assessment. A.4 gives a
description of possible sources of error and an explanation of those errors is included in the values given in
Table A.1.
Table A.1 — Estimated levels of uncertainty for assessment of the corrosivity category
based on determination (exposure of specimens) and estimation (dose-response function)
Level of uncertainty
Metal
Determination Estimation
Carbon steel 2 % 33 % to +50 %
Zinc 5 % 33 % to +50 %
Copper 2 % 33 % to +50 %
Aluminium 5 % 50 % to +100 %
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SIST EN ISO 9223:2012
ISO 9223:2012(E)
A.4 Sources of uncertainty
Regarding the determination of corrosivity categories based on exposure of specimens, it should first be
clarified that the levels given in Table A.1 are expressed for an average value calculated from three individual
values and not for an individual corrosion value.
The uncertainty levels given in Table A.1, both for determination and estimation, are based on the exposure of
materials at many different test sites, but only for one exposure period. Thus, the values should have a
general validity, but the variation in corrosion attac
...

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