National foreword

This British Standard is the UK implementation of ISO 25018:2026.

The UK participation in its preparation was entrusted to Technical Committee ISENFE/8.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 28 February 2026.

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.

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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.

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.

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

3 Terms and definitions

4 Principle

4.1

4.2

5 Apparatus

5.1 Loading apparatus

5.2 Construction materials

5.3 Specimen holders

6 Sampling

6.1

6.2

7 Specimens

7.1 Type and sizes

7.2 Surface preparation

7.3 Specimen identification

7.4 Precautions

8 Test environment

8.1

8.2

8.3

8.4

8.5

8.6

8.7

8.8

9 Procedure

9.1

9.2

9.3

9.4

10 Test report

Bibliography

BS ISO 25018:2026

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

Current

Published:

28 Feb 2026