ISO 23721:2022

Corrosion of metals and alloys — Rating method by appearance of rust and stains of atmospheric corrosion for stainless steels

This document specifies a method for evaluating the aesthetic appearance of stainless steels qualitatively by rating rust and stains formed by atmospheric corrosion. The rust and stains on stainless steels formed by atmospheric corrosion are rated by using 10 photographic standards. This method is especially suitable for evaluating the appearance of specimens and structures made of stainless steels under atmosphere exposure.

Corrosion des métaux et alliages — Méthode de cotation par l'apparence de la rouille et des taches de corrosion atmosphérique pour les aciers inoxydables

General Information

• Status: Published
• Publication Date: 13-Mar-2022
• ICS: 77.060 - Corrosion of metals
• Technical Committee: ISO/TC 156 - Corrosion of metals and alloys
• Drafting Committee: ISO/TC 156/WG 4 - Atmospheric corrosion testing and classification of corrosivity of atmosphere
• Current Stage: 6060 - International Standard published
• Start Date: 14-Mar-2022
• Due Date: 04-Feb-2022
• Completion Date: 14-Mar-2022

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 23721
First edition
2022-03
Corrosion of metals and alloys —
Rating method by appearance of rust
and stains of atmospheric corrosion
for stainless steels
Corrosion des métaux et alliages — Méthode de cotation par
l'apparence de la rouille et des taches de corrosion atmosphérique
pour les aciers inoxydables
Reference number
ISO 23721:2022(E)
© ISO 2022

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ISO 23721:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
  © ISO 2022 – All rights reserved

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ISO 23721:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 Photographic standard. 1
4.2 Rating method . . . 11
5 Expression of results .12
6 Test report .12
Annex A (informative) Relationship between rating number and total area of rust and
stains .13
Bibliography .14
iii
© ISO 2022 – All rights reserved

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ISO 23721:2022(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
  © ISO 2022 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 23721:2022(E)
Introduction
Stainless steels contain at least 10,5 % Cr and are widely used in domestic electric utilities, kitchen
utensils, transportation vehicles, and industrial plants. Corrosion-resistant stainless steels are also
used as architectural materials, e.g. exterior parts and roofs of buildings. Furthermore, stainless steels
are used as braid materials for automotive parts.
Corrosion loss and pitting depth are important factors for selecting, deciding the thickness and
estimating the lifetime of materials. Aesthetic appearance is also important for stainless steels used in
exterior parts. Therefore, a method for evaluating the appearance of stainless steels under atmospheric
exposure is required.
v
© ISO 2022 – All rights reserved

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INTERNATIONAL STANDARD ISO 23721:2022(E)
Corrosion of metals and alloys — Rating method by
appearance of rust and stains of atmospheric corrosion for
stainless steels
1 Scope
This document specifies a method for evaluating the aesthetic app
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 23721
ISO/TC 156
Corrosion of metals and alloys —
Secretariat: SAC
Rating method by appearance of rust
Voting begins on:
2021-12-13 and stains of atmospheric corrosion
for stainless steels
Voting terminates on:
2022-02-07
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 23721:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO 2021

---------------------- Page: 1 ----------------------
ISO/FDIS 23721:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
  © ISO 2021 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/FDIS 23721:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 Photographic standard. 1
4.2 Rating method . . . 11
5 Expression of results .12
6 Test report .12
Annex A (informative) Relationship between rating number and total area of rust and
stains .13
Bibliography .14
iii
© ISO 2021 – All rights reserved

---------------------- Page: 3 ----------------------
ISO/FDIS 23721:2021(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
  © ISO 2021 – All rights reserved

---------------------- Page: 4 ----------------------
ISO/FDIS 23721:2021(E)
Introduction
Stainless steels contain at least 10,5 % Cr and are widely used in domestic electric utilities, kitchen
utensils, transportation vehicles, and industrial plants. Corrosion-resistant stainless steels are also
used as architectural materials, e.g. exterior parts and roofs of buildings. Furthermore, stainless steels
are used as braid materials for automotive parts.
Corrosion loss and pitting depth are important factors for selecting, deciding the thickness and
estimating the lifetime of materials. Aesthetic appearance is also important for stainless steels used in
exterior parts. Therefore, a method for evaluating the appearance of stainless steels under atmospheric
exposure is required.
v
© ISO 2021 – All rights reserved

---------------------- Page: 5 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 23721:2021(E)
Corrosio
...