ASTM D7869-17

5.1 This test procedure is used to simulate the physical and environmental stresses that a coating for exterior transportation applications (for example, automotive) is exposed to in a subtropical climate, such as southern Florida. It has been found that such a subtropical climate causes particularly severe deterioration of such coatings. The long water exposures and wet/dry cycling found in southern Florida are particularly important for this deterioration, in addition to the high dosage of solar radiation (3). This practice was developed to address the deficiencies of historical tests used for transportation coatings, especially automotive coatings (4).

1.1 This practice specifies the operating procedures for a controlled irradiance xenon arc light and water apparatus. The procedure uses one or more lamp(s) and optical filter(s) to produce irradiance similar to sunlight in the UV and visible range. It also simulates the water absorption and stress cycles experienced by automotive exterior coatings under natural weathering conditions. This practice has also been found applicable to coatings on other transportation vehicles, such as aircraft, trucks and rail cars.

1.2 This practice uses a xenon arc light source with specified optical filter(s). The spectral power distribution (SPD) for the lamp and special daylight filter(s) is as specified in Annex A1. The irradiance level used in this practice varies between 0.40 and 0.80 W/(m²·nm) at 340 nm. Water is sprayed on the specimens during portions of several dark steps. The application of water is such that the coatings will absorb and desorb substantial amounts of water during testing. In addition, the cycling between wet/dry and warm/cool will induce mechanical stresses into the materials. These test conditions are designed to simulate the physical and chemical stresses from environments in a subtropical climate, such as southern Florida.

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.4 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 and health practices and determine the applicability of regulatory limitations prior to use.