|
ASTM B858M is a test method for determining the susceptibility of copper alloys to stress corrosion cracks by ammonia vapor test. The following is an overview of the test methods according to the ASTM B858M standard: 1. Overview of the standard Standard number: ASTM B858M Scope of application: Only applicable to copper alloy products that are known to be sensitive to stress corrosion cracks in an ammonia vapor environment. 2. Test requirements Test principle A critical step in the crack mechanism is the formation of a condensate film rich in a copper-ion complex on the upper surface of the sample, which is simulated by accelerated corrosion testing to identify the stress corrosion crack susceptibility of the copper alloy. Sample Preparation: The size of the specimen should be agreed according to the specifications of the product or part, and if it is not specified, the specimen with a maximum cross-section length of 152 mm should be taken. Remove burrs and oil from the sample to avoid accelerating the development of stress corrosion cracks. Reagents & Solutions: To prepare the solution required for an ammonia vapor environment, ammonium chloride (NH4Cl) is usually dissolved in water, and sodium hydroxide (NaOH) may be added to adjust the pH of the solution. The pH of the solution needs to be determined according to the product specification or by agreement between the supplier and the buyer to simulate different corrosive environments. 3. Test steps Solution Preparation: Dissolve a certain amount of ammonium chloride in water, and add sodium hydroxide as needed to adjust the pH value of the solution to the specified range. Store the prepared solution in an airtight container for later use. Sample exposure: The prepared test specimen is placed in an airtight container filled with ammonia vapor at a specified pH and ambient temperature. Samples should be placed in such a way that ammonia vapor can come into contact with all surfaces with complete freedom, and that the sample should be kept at a distance from the solvent surface, container walls, and other samples. Exposure time: The exposure time is 24 hours to ensure that the corrosion process in an ammonia vapor environment is fully simulated. Follow-up Treatment: After exposure, the sample is removed from an airtight container and immediately washed in a pickling solution to remove surface corrosion. The washed sample is rinsed in warm water and dried in warm air, followed by a magnifying glass or metallographic microscope to observe the surface of the sample for cracks. Fourth, the test report The test report should contain the identification information of the sample, the reference test method, the pH value of the ammonia vapor environment solution, the number of specimens, the test results (with or without cracks), and the test time. 5. Precautions This test method is an accelerated corrosion test, and its results can be affected by a variety of factors, such as the quality of the specimen preparation, the pH of the solution, and the exposure conditions. When conducting tests, the relevant safety operating procedures should be strictly adhered to to ensure the safety of personnel and the environment. In summary, the ASTM B858 standard provides a systematic ammonia vapor test method to evaluate the susceptibility of copper alloys to stress corrosion cracks. By tightly controlling the test conditions and procedures, the corrosion resistance of copper alloy products in specific environments can be accurately evaluated.Huanickel related products strictly implement this standard. For more information about the standard and the corresponding product information, please contact Sinonickel [email protected] |