ISO/FDIS 25018

Corrosion of metals and alloys — Determination of resistance to stress corrosion cracking of copper and copper-zinc alloys in ammonia vapour

This international standard specifies a test method to evaluate the resistance to stress corrosion cracking of copper and copper-zinc alloys in ammonia vapour.

Corrosion des métaux et alliages — Détermination de la résistance à la fissuration par corrosion sous contrainte du cuivre et des alliages de cuivre et de zinc dans la vapeur d'ammoniac

General Information

• Status: Not Published
• ICS: 77.060 - Corrosion of metals
• Technical Committee: ISO/TC 156 - Corrosion of metals and alloys
• Drafting Committee: ISO/TC 156/WG 2 - Environmentally assisted cracking
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 24-Oct-2025
• Completion Date: 24-Oct-2025

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/TC 156
Corrosion of metals and alloys —
Secretariat: SAC
Determination of resistance to
Voting begins on:
stress corrosion cracking of copper
2025-10-24
and copper-zinc alloys in ammonia
Voting terminates on:
vapour
2025-12-19
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
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
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.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 156
Corrosion of metals and alloys —
Secretariat: SAC
Determination of resistance
Voting begins on:
to stress corrosion cracking of
copper and copper-zinc alloys in
Voting terminates on:
ammonia vapour
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.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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 Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 2
5 Apparatus . 2
5.1 Loading apparatus .2
5.2 Construction materials .2
5.3 Specimen holders .2
6 Sampling . 3
7 Specimens. 4
7.1 Type and sizes .4
7.2 Surface preparation .4
7.3 Specimen identification .4
7.4 Precautions .4
8 Test environment . 4
9 Procedure . 5
10 Test report . 5
Annex A (informative) An example of the SCC test by uniaxially loaded tension . 7
Bibliography . 9

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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
Introduction
Copper and copper alloys are excellent in thermal conductivity, electrical conductivity, workability and
corrosion resistance. They are among the most commonly used materials in industry and society. However,
some copper and copper alloys are known to suffer stress corrosion cracking (SCC) when tensile stress is
applied in an environment that contains ammonia. This SCC occurs in various industrial processes, sanitary
equipment environments, polluted atmospheres and the like, even in environments that contain a small
amount of ammonia, and can pose a serious problem.
Therefore, evaluation of SCC resistance of copper alloys in an ammonia-containing environment is an
indispensable technology. This can be achieved by standardizing the test methods which can reproduce the
specific mode of corrosion in those materials.

v
FINAL DRAFT International Standard ISO/FDIS 25018:2025(en)
Corrosion of metals and alloys — Determination of resistance
to stress corrosion cracking of copper and copper-zinc alloys
in ammonia vapour
1 Scope
This document specifies a method for the determination of resistance to stress corrosion cracking (SCC) of
copper and copper-zinc alloys in ammonia vapour.
This document covers the method of sampling, the types of specimens, the loading procedure, the type of
environment and the interpretation of results.
This document is aimed at determining resistance to SCC as a function of the chemical composition, the
method of manufacture of copper and copper-zinc alloys.
This document applies to wrought copper and copper-zinc alloys in the form of products and parts.
This document can be used to rank materials performance and select candidate materials under atmospheres
containing ammonia. However, the results of this test should not be considered as an absolute criterion for
the quality of alloys.
This document specifies a method for exposing test specimens in ammonia vapour coexisting with an
aqueous ammonia solution and specifies the environmental conditions and test procedures.
This document specifies two methods of loading:
— under constant total strain;
— under constant load.
It does not cover slow strain rate test methods and determination of maximum admissible stress by the
method of permanent deformation for copper and copper-zinc alloys, although an effort is now being made
to apply such methods to these alloys (see ISO 7539-7).
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 (including any amendments) applies.
ISO 7539-1, Corrosion of metals and alloys — Stress corrosion testing — Part 1: General guidance on testing
proc
...

ISO/TC 156 N7836
ISO/TC 156
Secretariat: SAC
Date: 2025-08-1310-10
Corrosion of metals and alloys – — Determination of resistance to
stress corrosion cracking of copper and copper-zinc alloys in
ammonia vapour
FDIS stage
ISO/DISFDIS 25018:2025(en)
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
EmailE-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
© ISO #### 2025 – All rights reserved
ii
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 2
5 Apparatus . 2
5.1 Loading apparatus . 2
5.2 Construction materials . 2
5.3 Specimen holders . 3
6 Sampling . 3
7 Specimens . 5
7.1 Type and sizes . 5
7.2 Surface preparation . 5
7.3 Specimen identification . 5
7.4 Precautions . 5
8 Test environment . 5
9 Procedure . 6
10 Test report . 7
Annex A (informative) An example of the SCC test by uniaxially loaded tension . 8
Bibliography . 12

iii
ISO/DISFDIS 25018:2025(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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.
© ISO #### 2025 – All rights reserved
iv
Introduction
Copper and copper alloys are excellent in thermal conductivity, electrical conductivity, workability and
corrosion resistance. They are among the most commonly used materials in industry and society. However,
some copper and copper alloys are known to suffer stress corrosion cracking (SCC) when tensile stress is
applied in an environment that contains ammonia. This SCC occurs in various industrial processes, sanitary
equipment environments, polluted atmospheres and the like, even in environments that contain a small
amount of ammonia, and can pose a serious problem.
Therefore, evaluation of SCC resistance of copper alloys in an ammonia-containing environment is an
indispensable technology. This can be achieved by standardizing the test methods which can reproduce the
specific mode of corrosion in those materials.
v
DRAFT International Standard ISO/FDIS 25018

Corrosion of metals and alloys – — Determination of resistance to
stress corrosion cracking of copper and copper-zinc alloys in
ammonia vapour
1 Scope
This document specifies a method for the determination of resistance to stress corrosion cracking (SCC) of
copper and copper-zinc alloys in ammonia vapour.
This document covers the method of sampling, the types of specimens, the loading procedure, the type of
environment and the interpretation of results.
This document is aimed at determining resistance to SCC as a function of the chemical composition, the
method of manufacture of copper and copper-zinc alloys.
This document applies to wrought copper and copper-zinc alloys in the form of products and parts.
This document can be used to rank materials performance and select candidate materials under atmospheres
containing ammonia. However, the results of this test should not be considered as an absolute criterion for
the quality of alloys.
This document specifies a method for exposing test specimens in ammonia vapour coexisting with an aqueous
ammonia solution and specifies the environmental conditions and test procedures.
This document specifies two methods of loading:
— — under constant total strain;
— — under constant load.
It does not cover slow strain rate test methods and determination of maximum admissible stress by the
method of permanent deformation for copper and copper-zinc alloys, although an effort is now being made to
apply such methods to these alloys (see ISO 7539-7).
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 (including any amendments) applies.
ISO 7539--1, Corrosion of metals and alloys — Stress corrosion testing — Part 1: General guidance on testing
procedures
ISO 7539--2, Corrosion of metals and alloys — Stress corrosion testing — Part 2: Preparation and use of bent-
beam specimens
ISO 7539--3, Corrosion of metals and alloys — Stress corrosion testing — Part 3: Preparation and use of U-bend
specimens
ISO/DISFDIS 25018:2025(en)
ISO 7539--4, Corrosion of metals and alloys — Stress corrosion testing — Part 4: Preparation and use of
uniaxially loaded tension specimens
ISO 7539--5, Corrosion of metals and alloys — Stress corrosion testing — Part 5: Preparation and use of C-ring
specimens
ISO 7539--6, Corrosion of metals and alloys — Stress corrosion testing — Part 6: Preparation and use of pre-
crackedprecracked specimens for tests under constant load or constant displacement
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7539-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
4 Principle
4.1 4.1 The evaluation criteria for corrosion cracking of alloys are:
— — σSCC: the threshold stress, which is the maximum stress under which no failure of the samples occurs
during the fixed period of the test;
— — τSCC: the time of failure, which is the moment of the appearance of the first visible crack (or under
magnification up to x 30) for specimens under constant strain.
4.2 4.2 The selection of the method of loading, the value of stresses, corrosive environment and
criteria of evaluation can be subjected to between the interested parties and should be defined by the test
programme.
5 Apparatus
5.1 Loading apparatus
Tensile stresses in the specimens are produced with yokes, stressing screws, springs, lever devices and special
testing machines.
5.2 Construction materials
If in contact with the ammonia vapour and the aqueous ammonia solution, the materials shall not be affected
by the corrodent to su
...