ASTM G155-21 PDF

SIGNIFICANCE AND USE 5.1 The apparatus exposes specimens to light, heat, and optionally moisture, often to attempt to replicate specimen property changes observed in outdoor and indoor end-use environments. Exposures are not intended to simulate the deterioration caused by localized weather phenomena, such as atmospheric pollution, biological attack, and saltwater exposure. 5.2 This practice allows a wide range of exposure conditions that may produce significantly different results. Therefore, no reference shall be made to results from its use unless accompanied by a report in conformance with Section 10 detailing the specific operating conditions. 5.2.1 A control (a similar material of known performance) should be exposed simultaneously with the test specimen to provide a reference for comparative purposes. It is best practice to use two different control materials: one known to have relatively poor durability and one known to have relatively good durability. At least three replicates of each test specimen and control material should be exposed concurrently to permit statistical evaluation of results. 5.3 Comparison of results obtained from specimens exposed in different apparatus (even if the apparatus is the same model) using the identical setpoints and operational controls should not be made unless reproducibility has been established between apparatus for the material to be tested. 5.4 Refer to Practice G151 for cautionary guidance applicable to all laboratory weathering apparatus. 5.5 It is recommended that users follow good laboratory practices in order to reduce variability in exposures (1).8 SCOPE 1.1 This practice is limited to the basic principles and procedures for operating a xenon arc lamp and water apparatus; on its own, it does not deliver a specific result. 1.2 It is intended to be used in conjunction with a practice or method that defines specific exposure conditions for an application along with a means to evaluate changes in material properties. This practice is intended to reproduce the weathering effects that occur when materials are exposed to sunlight (either direct or through window glass) and moisture as humidity, rain, or dew in actual use. This practice is limited to the procedures for obtaining, measuring, and controlling conditions of exposure. Note 1: A number of exposure procedures are listed in an appendix; however, this practice does not specify the exposure conditions best suited for the material to be tested. Note 2: Practice G151 describes general procedures and performance requirements to be used when exposing materials in an apparatus that uses laboratory light sources. 1.3 Test specimens are exposed to light from an optically-filtered xenon arc lamp under controlled environmental conditions. Different types of optical filters in combination with xenon arc light sources are described. 1.4 Specimen preparation and evaluation of the results are covered in ASTM methods or specifications for specific materials. General guidance is given in Practice G151. Note 3: General information about methods for determining the change in properties after exposure and reporting these results is described in Practice D5870. 1.5 This practice is not intended for corrosion testing of bare metals. 1.6 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.7 This practice is technically similar to the following ISO documents: ISO 4892-2, ISO 16474-2, ISO 105-B02, ISO 105-B04, ISO 105-B05, ISO 105-B06, and ISO 105-B10. 1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.8.1 Should any ozone be generated from the operation of the la...