ASTM D822/D822M Standard Practice for Filtered Open-Flame Carbon-Arc Exposures of Paint and Related Coatings

Scope:

Paints and coatings’ physical or optical properties can deteriorate due to light, heat, and water. To prevent these changes, paints and coatings must resist them. ASTM D822/D822M determines coatings’ resistance to exposure.

These test subjects paint or coatings to sunlight, moisture, and heat to simulate the property changes that occur in service. However, it does not intend to simulate the deterioration caused by localized weather phenomena such as atmospheric pollution, biological attack, and saltwater exposure.

ASTM D822/D822M outlines the basic principles and operating procedures for using Filtered Open-Flame Carbon-Arc Exposures to reproduce the weathering effects that materials experience during service.

Test Procedure:

In ASTM D822/D822M, specimens undergo repetitive cycles of light and moisture under controlled environmental conditions. Moisture is typically produced by spraying demineralized water onto the test specimen or by condensation of water vapor onto it.

The exposure condition can be varied by selecting lamp filters, the lamp’s irradiance level, the type of moisture exposure, the timing of light and moisture exposure, the temperature of light exposure, the temperature of moisture exposure, and the timing of a light/dark cycle.

Specimen Size:

Coatings are applied to flat panels with substrate, preparation method, application method, coating system, film thickness, and drying method consistent with anticipated use in service or as mutually agreed upon between the producer and user.

Panel specifications and preparation methods include Practices D609 or D1730, or Specification D358. Panel sizes should be suitable for exposure apparatus. Test panels are coated per Test Methods D823, and film thickness is measured in accordance with an appropriate procedure selected from Test Methods D1005, D1186, or D1400.

Coating panels are conditioned at 23 °C and 50 % relative humidity, depending on the type of coating: Baked coatings are conditioned for 24 hours, radiation-cured coatings for 24 hours, and all other coatings for 7 days. At least three replicate specimens of each test and control material are required.

Data:

The following information is reported:

• Type and model of the exposure device
• Type of light source
• Type and age of filters at the beginning of the exposure and whether any filters were replaced during the period of exposure
• Type of black panel used (uninsulated or insulated)
• Elapsed exposure time
• Light and dark-water-humidity cycles employed
• Type of spray water, if used
• Total solids and silica level of water used for specimen spray
• Results of property tests

Conclusion:

The ASTM D822/D822M standard practice is widely accepted by regulatory bodies, testing laboratories, and coatings manufacturers. Test results obtained using this standard can ensure that coatings provide sufficient protection against environmental factors such as sunlight and moisture, which can cause coatings to degrade over time.

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