ISO 4212:2023
(Main)Corrosion of metals and alloys — Method of oxalic acid etching test for intergranular corrosion of austenitic stainless steel
Corrosion of metals and alloys — Method of oxalic acid etching test for intergranular corrosion of austenitic stainless steel
This document specifies a method to test for intergranular corrosion (IGC) in austenitic stainless steels using an oxalic acid etch. This method can evaluate non-sensitization of austenitic stainless steels by observing the structure of the etched surface with a microscope after performing electrolytic etching (hereinafter called “etching”) on austenitic stainless steel in an oxalic acid solution.
Corrosion des métaux et alliages — Méthode d'essai de gravure à l'acide oxalique pour la corrosion intergranulaire de l'acier inoxydable austénitique
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 4212
First edition
2023-02
Corrosion of metals and alloys —
Method of oxalic acid etching test for
intergranular corrosion of austenitic
stainless steel
Corrosion des métaux et alliages — Méthode d'essai de gravure
à l'acide oxalique pour la corrosion intergranulaire de l'acier
inoxydable austénitique
Reference number
ISO 4212:2023(E)
© ISO 2023
---------------------- Page: 1 ----------------------
ISO 4212:2023(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023
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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
© ISO 2023 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 4212:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General principles . 2
5 Apparatus . 2
6 Sensitization heat treatment for test specimens. 2
7 Test specimens . 2
8 Test solution . 2
9 Test procedure .3
10 Evaluation of etching structure .4
11 Test report . 4
Bibliography . 6
iii
© ISO 2023 – All rights reserved
---------------------- Page: 3 ----------------------
ISO 4212:2023(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 2023 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 4212:2023(E)
Introduction
Intergranular corrosion (IGC) is a form of localized corrosion which occurs along grain boundaries. IGC
of stainless steel is attributable to grain boundary segregation and precipitates. When the formation
of chromium-rich grain boundary carbides occurs, it leads to continuous chromium depletion adjacent
to the grain boundary, and IGC occurs in certain corrosive media. This process is usually known
as sensitization. Sensitization of stainless steel can be evaluated by ISO IGC tests for austenitic
stainless steels: such as ISO 3651-1, ISO 3651-2, and ISO 12732. On the other hand, oxalic etching
tests (JIS G0571:2003 and ASTM A262-15 Practice A) cannot evaluate sensitization, however, they
can evaluate non-sensitized condition of austenitic stainless steels and suspicions of sensitization by
observing the etched surface of the stainless steels. This is because it does not etch chromium depletion
adjacent to the chromium-rich grain boundary precipitates but chromium-rich grain boundary carbides
themselves. If sensitization is suspected, IGC tests, ferric sulfate-sulfuric acid test (see ISO 3651-2),
65 % nitric acid test (see ISO 3651-1), copper sulfate-sulfuric acid test (see ISO 3651-2) or EPR test
(ISO 12732) should be conducted to evaluate sensitization of austenitic stainless steels.
The main benefits of these oxalic acid etching tests are that they are simple, easy and rapid. This
document is based on JIS G0571:2003.
v
© ISO 2023 – All rights reserved
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 4212:2023(E)
Corrosion of metals and alloys — Method of oxalic acid
etching test for intergranular corrosion of austenitic
stainless steel
1 Scope
This document specifies a method to test for intergranular corrosion (IGC) in austenitic stainless steels
using an oxalic acid etch. This method can evaluate non-sensitization of austenitic stainless steels by
observing the structure of the etched surface with a microscope after performing electrolytic etching
(hereinafter called “etching”) on austenitic stainless steel in an oxalic acid solution.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.