ASTM B858-06 pdf download.Standard Test Method for Ammonia Vapor Test for Determining Susceptibility to Stress Corrosion Cracking in Copper Alloys.
7. Reagents and Materials
7.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such specifications are available. 3 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.
7.2 Purity ofWater—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by Type IV or better, of Specification D1193.
7.3 Ammonium Chloride Solution (4N)—Dissolve 107 g of ammonium chloride (NH 4 Cl) in water and dilute to 500 mL. Store the solution in a closed vessel. 7.4 Hydrogen Peroxide (H 2 O 2 ), 30 to 35 % technical grade. (Warning—Hydrogen peroxide in high concentrations can cause severe skin burns. Use of proper safety equipment is advised.) 7.5 Sodium Hydroxide Solution (300 to 500 g/L)—Dissolve 300 to 500 g of sodium hydroxide (NaOH) into water and dilute to 1 L. (Warning—Sodium hydroxide can cause chemi- cal burns to the skin and eyes. Use of proper safety equipment is advised.) 7.6 A clean organic solvent or hot alkaline solution that contains no ammoniacal-type groups or substituents.
7.7 Sulfuric Acid Solution (50 mL/L)—Slowly add 50 mL of concentrated sulfuric acid (H 2 SO 4 ) into water and dilute to 1 L. 8. Test Media 8.1 Slowly add the sodium hydroxide solution to the am- monium chloride solution to give a test solution with a pH value appropriate for the intended application (see Annex A1). Maintain the solution at ambient temperature and dilute with DI water up to a volume of 1 L. Check the pH value with the pH meter after dilution. Prepare the solution preferably in a fume hood in a laboratory using appropriate safe laboratory procedures and store it in a closed vessel. Before use, check the pH value again, and adjust if necessary. 8.1.1 In the closed test vessel, the ratio of surface area of test solution to air volume ofthe vessel above the solution shall be a minimum of 20 cm 2 /L.
8.2 The pickling solution for cleaning test pieces before and after testing shall be 5 % sulfuric acid. If necessary, for cleaning test pieces after testing, a small amount of hydrogen peroxide solution may be added to the pickling solution (for example, 20 to 30 mL of hydrogen peroxide solution per litre of pickling solution). 9. Test Specimen Preparation 9.1 The test specimen size shall be prescribed in the specification of the product or part being tested. In the event that a test specimen size is not prescribed in a given rod, wire, or tube specification, a full cross section having a minimum length of 152 mm shall be tested.
9.2 The presence of burrs on the test specimen may con- tribute to acceleration of stress corrosion cracking if not removed before the ammonia vapor test. The burrs shall be removed by fine file or abrasive paper to facilitate this test.
9.3 Degrease the test specimen using the clean organic solvent or alkaline solution.
9.4 After degreasing, clean the test piece in the pickling solution and immediately thereafter thoroughly rinse it, first in cold running water, then in hot water, and finally, completely dry it in a stream of warm air. 10. Test Procedure
10.1 Allow the dry test piece to reach the exposure tem- perature specified below, and transfer it immediately to the closed vessel (see 6.2) at the same temperature, and containing the freshly prepared test solution at the specified pH value (see 8.1). 10.1.1 Suspend (or place) the test piece such that the ammonia vapor has free access to all surfaces, not less than 50 mm above the test solution surface. 10.1.1.1 When placed on a porcelain support within the test vessel, the region of the test piece within 5 mm of the support shall be disregarded when inspecting for cracks. 10.1.1.2 The test piece shall be placed no less than 10 mm from the inside walls of the test vessel. 10.1.1.3 When more than one test piece is placed in the vessel, the test pieces shall be no less than 10 mm apart.
10.2 The volume ofthe test solution shall be at least 200 mL per square decimeter of test piece surface. The exposure temperature shall be between 20 and 30 °C and shall be kept constant to within 61 °C during the test. In case ofdispute, the exposure temperature shall be 25 6 1 °C. 10.3 The exposure time shall be 24 h. 10.4 After exposure, remove the test piece from the closed vessel and immediately clean it in pickling solution for a few minutes at ambient temperature (below 40 °C), or until the surfaces of the test piece are sufficiently clean from corrosion products to allow observation of possible cracks. After rinsing in water and drying in warm air, examine the surface ofthe test piece for cracks at a magnification of 10 to 15×. 10.5 Before inspection, deform the test piece slightly by bending or flattening to open up fine cracks to make them more easily observable.ASTM B858 pdf download.