SIST EN ISO 9224:2012

SLOVENSKI STANDARD
SIST EN ISO 9224:2012
01-maj-2012
1DGRPHãþD
SIST EN 12500:2000
Korozija kovin in zlitin - Korozivnost v atmosferskem okolju - Vodilne vrednosti za
kategorizacijo korozivnosti (ISO 9224:2012)
Corrosion of metals and alloys - Corrosivity of atmospheres - Guiding values for the
corrosivity categories (ISO 9224:2012)
Korrosion von Metallen und Legierungen - Korrosivität von Atmosphären - Anhaltswerte
für die Korrosivitätskategorien (ISO 9224:2012)
Corrosion des métaux et alliages - Corrosivité des atmosphères - Valeurs de référence
relatives aux classes de corrosivité (ISO 9224:2012)
Ta slovenski standard je istoveten z: EN ISO 9224:2012
ICS:
77.060 Korozija kovin Corrosion of metals
SIST EN ISO 9224:2012 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 9224:2012

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SIST EN ISO 9224:2012


EUROPEAN STANDARD
EN ISO 9224

NORME EUROPÉENNE

EUROPÄISCHE NORM
February 2012
ICS 77.060 Supersedes EN 12500:2000
English Version
Corrosion of metals and alloys - Corrosivity of atmospheres -
Guiding values for the corrosivity categories (ISO 9224:2012)
Corrosion des métaux et alliages - Corrosivité des Korrosion von Metallen und Legierungen - Korrosivität von
atmosphères - Valeurs de référence relatives aux classes Atmospären - Anhaltswerte für die Korrosivitätskategorien
de corrosivité (ISO 9224:2012) (ISO 9224:2012)
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 9224:2012: E
worldwide for CEN national Members.

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SIST EN ISO 9224:2012
EN ISO 9224:2012 (E)
Contents Page
Foreword .3

2

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SIST EN ISO 9224:2012
EN ISO 9224:2012 (E)
Foreword
This document (EN ISO 9224:2012) 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 9224:2012 has been approved by CEN as a EN ISO 9224:2012 without any modification.

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SIST EN ISO 9224:2012

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SIST EN ISO 9224:2012

INTERNATIONAL ISO
STANDARD 9224
Second edition
2012-02-01

Corrosion of metals and alloys —
Corrosivity of atmospheres — Guiding
values for the corrosivity categories
Corrosion des métaux et alliages — Corrosivité des atmosphères —
Valeurs de référence relatives aux classes de corrosivité




Reference number
ISO 9224:2012(E)
©
ISO 2012

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SIST EN ISO 9224:2012
ISO 9224:2012(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 9224:2012
ISO 9224:2012(E)
Contents Page
Foreword . iv
Introduction . v
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 1
4  Principle . 2
5  Prediction of corrosion attack after extended exposure . 2
6  Specific criteria for calculation of corrosion rates of structural metals . 3
6.1  Steels . 3
6.2  Zinc materials . 4
6.3  Copper alloys . 4
6.4  Aluminium alloys . 4
7  Long-term exposures . 4
Annex A (informative) Example of maximum corrosion attack after extended exposures for
corrosivity categories . 7
Annex B (informative) Average initial corrosion rates and average steady corrosion rates in
intervals relative to classified corrosivity categories . 9
Annex C (informative) Prediction of corrosion attack of steels with regard to steel composition . 10
Bibliography . 12

© ISO 2012 – All rights reserved iii

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SIST EN ISO 9224:2012
ISO 9224:2012(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 9224 was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys.
This second edition cancels and replaces the first edition (ISO 9224:1992), which has been technically revised.
iv © ISO 2012 – All rights reserved

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SIST EN ISO 9224:2012
ISO 9224:2012(E)
Introduction
The “corrosivity category” established in ISO 9223 is a general term suitable for engineering purposes, which
describes the corrosion properties of atmospheres based on current knowledge of atmospheric corrosion.
Guiding values of corrosion attack can be used to predict the extent of corrosion attack in long-term exposures
based on measurements of corrosion attack in the first-year exposure to the outdoor atmosphere in question.
These values can also be used to determine conservative estimates of corrosion attack based on
environmental information or corrosivity category estimates as shown in ISO 9223.
Corrosion attack estimates obtained by using the methods in this International Standard can be used to
predict the useful life of metallic components and, in some cases, of metallic coatings exposed to outdoor
atmospheres covered by ISO 9223. The corrosion attack results can also be used to determine whether or not
protective measures, such as coatings, are required to achieve desired product lives. Other uses include the
selection of construction materials for outdoor atmospheric service.
Guiding values of corrosion can be used as information for the selection of a protection method against
atmospheric corrosion according to ISO 11303.
The guiding values in this International Standard are based on a large number of exposures in many locations
throughout the world. However, the procedure used in this International Standard cannot possibly cover all the
situations in natural environments and service conditions which can occur. In particular, situations that result
in significant changes in the environment can cause major increases or decreases in corrosion rates. Users of
this International Standard are cautioned to consult with qualified experts in the field of outdoor atmospheric
corrosion in cases where localized corrosion can be more important than general attack. The specific issues
of galvanic (bi-metallic) corrosion, pitting corrosion, crevice corrosion, environmental cracking and corrosion
product wedging are not addressed in this International Standard.

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SIST EN ISO 9224:2012

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SIST EN ISO 9224:2012
INTERNATIONAL STANDARD ISO 9224:2012(E)

Corrosion of metals and alloys — Corrosivity of atmospheres —
Guiding values for the corrosivity categories
1 Scope
This International Standard specifies guiding values of corrosion attack for metals and alloys exposed to
natural outdoor atmospheres for exposures greater than one year. This International Standard is intended to
be used in conjunction with ISO 9223.
Guiding corrosion values for standard structural materials can be used for engineering calculations. The
guiding corrosion values specify the technical content of each of the individual corrosivity categories for these
standard metals.
Annex A provides examples of calculated maximum corrosion attack after extended exposure (up to 20 years)
for six standardized corrosivity categories.
Annex B provides presumed average initial and steady-state corrosion rates of standard metals in intervals
relative to six standardized corrosivity categories.
Annex C provides the calculation procedure for corrosion attack of steels in regard to their composition.
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 9223, Corrosion of metals and alloys — Corrosivity of atmospheres — Classification, determination and
estimation
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8044 and the following apply.
3.1
guiding corrosion value
corrosion rates, mass loss, penetration or other corrosion characteristics expressing the expected corrosive
action of the atmospheric environment of a given corrosivity category towards standard metals
3.2
corrosion rate after extended exposure
corrosion rate after exposures longer than one year
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SIST EN ISO 9224:2012
ISO 9224:2012(E)
3.3
average corrosion rate
r
av
yearly corrosion rate calculated as an average value for the first 10 years of atmospheric exposure of a metal
3.4
steady-state corrosion rate
r
lin
yearly corrosion rate derived from a long-term atmospheric exposure of a metal, not including the initial period
NOTE For the purposes of this International Standard, the corrosion rate after 10 years of exposure is considered
constant.
4 Principle
The corrosion rate of metals and alloys exposed to natural outdoor atmospheres is not constant with exposure
time. For most metals and alloys, it decreases with exposure time because of the accumulation of corrosion
products on the surface of the metal exposed. The progress of attack on engineering metals and alloys is
usually observed to be linear when the total damage is plotted against exposure time on logarithmic
coordinates. This relationship indicates that the total attack, D, expressed either as mass loss per unit area or
penetration depth, may be given as:
b
D = r t (1)
corr
where
t is the exposure time, expressed in years;
r is the corrosion rate experienced in the first year, expressed in grams per square metre per year
corr
2
[g/(ma)] or micrometres per year (μm/a), in accordance with ISO 9223;
b is the metal-environment-specific time exponent, usually less than 1.
5 Prediction of corrosion attack after extended exposure
This procedure should be used in cases where the extent of corrosion attack in the first year is available or
can be estimated by the procedures in ISO 9223, and the desire is to predict the extent of attack after an
extended exposure.
The attack prediction is calculated by substituting the values in Equation (1).
An appropriate b value is selected or calculated according to Clause 7. In cases where long-term metal loss
data are available, use the b value from this data. In cases where the detailed composition of the metal is not
known, select the B1 value from Table 2 for the metal or alloy in question. This is the b value to be used in
Equation (1).
The B1 values were taken as the average time exponents from regression analyses of the flat panel long-term
[1]
results of the ISO CORRAG atmospheric exposure programme .
NOTE It is necessary to distinguish between metal-environment-specific time exponent, b, in Equation (1), estimated
from exposure data, and B1 and B2 values assumed or calculated from the ISO CORRAG programme as generalized b
values.
b
Table 3 contains values of the function t for time values up to 100 years with the B1 exponents to simplify the
calculations. However, it is possible for Equation (1) not to apply to exposures beyond 20 years (see Clause 7
below for a discussion of long-term exposures).
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SIST EN ISO 9224:2012
ISO 9224:2012(E)
In cases where it is important to estimate a conservative upper limit of corrosion attack after an extended
exposure, the b value used in Equation (1) should be increased to account for uncertainties in the data. One
way to do this is to add two standard deviations to the average value to obtain a value at the upper 95 %
[1]
confidence level. For the four metals shown in Table 2, the standard deviations of the b values are:
 Carbon steel: 0,026 0
 Zinc: 0,030 0
 Copper: 0,029 5
 Aluminium: 0,039 5
NOTE Estimation of a conservative upper limit of corrosion attack after an extended exposure is based on
uncertainties in b. This estimation does not take into account uncertainties in r , which are defined in ISO 9223.
corr
The B2 values in Table 2 include the two standard deviation additions and may be used where an upper limit
of corrosion attack is desired when using the flat panel data from the ISO CORRAG programme. Table 3 also
b
provides calculated values for the function, t , up to 100 years using B2 values for b (see Clause 7 for
exposures beyond 20 years).
Annex A provides maximum corrosion attack for the standard metals covered in ISO 9223 for exposures up to
20 years for the six corrosion categories. These calculations are made using the time exponents given in
Table 2.
6 Specific criteria for calculation of corrosion rates of structural metals
6.1 Steels
The protectiveness of rust layers on steels in atmospheric exposures is very strongly affected by the alloying
elements in the steel. Weathering steels, in particular, have specific alloying additions to promote the
formation of a protective rust layer that develops during the exposure. Other carbon and low-alloy steels vary
significantly in their performance in atmospheric exposures depending on their specific alloy content. The
calculation procedure for corrosion
...