ISO INTERNATIONAL STANDARD 6957 First edition 1988-10-01 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION tso ORGANISATIONINTERNATIONALEDENORMALISATION MEKAYHAPOAHAAOPTAHW3ALWANOCTAHAAPTM3ALMM Copper alloys - Ammonia test for stress corrosion resistance Alliages de cuivre - Essai a I'ammoniaque pour la résistance a la corrosion sous contrainte Referencenumber ISO 6957: 1988 (E) ISO 6957 : 1988 (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 technicai committee has been established has the right to be represented on that committee. International organizations, govern- mental 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. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the Iso Council. They are approved in accordance with ISO procedures requiring at least 75 % approval by the member bodies voting. International Standard ISO 6957 was prepared by Technical Committee ISO/TC 26, Copperandcopperalloys. Annexes A and B of this International Standard are for information only. @ International Organization for Standardization, 1988 Printed in Switzerland INTERNATIONAL STANDARD ISO 6957 : 1988 (E) Copper alloys --- Ammonia test for stress corrosion resistance 1 Scope 3.5 Hydrogen peroxide, 30 % (m/m) solution, for addition to the pickling solution. This International Standard specifies a test, using an am- moniacal atmosphere, for the detection of applied or residual stresses in copper alloy products which can cause failure of the Apparatus material in service or storage through stress corrosion cracking. The method can also be used for testing assemblies and partial Ordinary laboratory apparatus and assemblies (of limited size). 4.1 pH-meter. be regulated by changing the pH value of the solution produc- ing the ammoniacal atmosphere. 4.2 Closed vessel (such as a desiccator). The appropriate pH-value for the test shall be specified in the 4.3 Equipment for examining test pieces at × 10 to × 15 product specification or agreed upon with respect to the alloy magnification. and its application. In annex A, recommendations are given for the choice of pH- 5 Definitions values to be used for some frequently occurring applications. For the purpose of this International Standard, the following definitions apply. 2 Principle 5.1 stress corrosion: A process involving conjoint cor- Exposure of test pieces to an ammoniacal atmosphere for 24 h rosion and straining of the metal due to residual or applied followed by examination for cracks at a magnification of × 10 stresses. to × 15. 5.2 applied stress: Stress in a body due to application of an external load. Reagents and materials 5.3 residual stress: Stress remaining within a body as the Use only reagents of recognized analytical grade and onily result of plastic deformation. distiled water or water of equivalent purity. 6 Test media 3.1 Ammonium chloride, 4 mol/l solution, for the prep- aration of the test solution. 6.1 Slowly add sodium hydroxide solution (3.2) to am- monium chloride solution (3.1) to give a test solution with the Dissoive 107 g ± 0,1 g of ammonium chioride (NHgCi) in specified pH-value ± 0,05 (see annex A). Maintain the solution water,makeupthevolumeto500 mlandkeepthesolution ina closed vessel. at ambient temperature and dilute with water up to a volume of 1 000 ml. Check the pH-value with the pH-meter (4.1) after dilution. Prepare the solution preferably in a fume cupboard in a 3.2 Sodium hydroxide, 30 to 50 % (m/m) solution, for laboratory and store it in