ISO 25018:2026

International
Standard
ISO 25018
First edition
Corrosion of metals and alloys —
2026-02
Determination of 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
Reference number
© ISO 2026
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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
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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
International Standard ISO 25018:2026(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
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 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
...