ASTM D7869: Standard Practice for Xenon Arc Exposure Test with Enhanced Light and Water Exposure for Transportation Coatings

Test Parameters

ASTM D7869 uses a variety of cyclic test conditions to create a realistic exposure environment that simulates and accelerates the benchmark South Florida climate. While developed specifically for transportation coatings, the fundamental principles make the test suitable for any durable outdoor product.

• Overall cycle summary
  • ASTM D7869 is meant to simulate the complete range of conditions that coatings experience in South Florida. The rationale for each step is explained clearly in the document, something that is rarely if ever found in accelerated weathering tests.
  • The cycle begins with a long, 4-hour period of dark and water spray to ensure full uptake of water by coatings, simulating overnight condensation
  • A short, 30-minute "morning" phase simulates drying when the sun rises
  • A 4:30 "daytime" step simulates the hot, sunny conditions of a Florida day
  • A short, 30-minute "evening" phase transitions to the evening, as when the sun sets
  • A moderate-length 2:30 dark plus spray step reproduces shorter periods of outdoor moisture
  • A series of four three-hour cycles (30 min dark+spray, 20 min low-intensity light, 120 min high irradiance, 10 min dark) reproduces cyclic stresses that outdoor materials experience.
• Irradiance
  • ASTM D7869 calls for the use of a very carefully-defined optical filter to deliver the most realistic spectrum. The spectral definition is much more narrow than most other standards.
    • This specialized spectrum allows for higher irradiance levels, helping to produce realistic results faster.
    • Q-Lab's Daylight-F optical filter meets the spectral requirements of ASTM D7869
  • Light intensity is controlled at 340 nm, using SOLAR EYE onboard irradiance sensors. Some steps simulate morning and evening sun and have a low irradiance of 0.40 W/m²/nm. Other steps have a high irradiance of 0.80 W/m²/nm to simulate peak daytime sunlight.
• Temperature
  • Temperature is measured and controlled by an uninsulated black panel temperature sensor during the dry steps (2, 3, 4, 7, and 8).
    • The morning / evening phases at lower irradiance (steps 2,4,7) also feature a lower BPT of 50°C ,
    • The peak daylight phases (steps 3, 8) are at elevated temperature of 70°C.
  • ASTM D7869 specifies chamber air temperature (CAT) in every step.
    • The morning / evening phases specify CAT of 42°C
    • The peak daylight phases have a CAT of 50°C.
    • All Dark steps - with or without water spray (1, 5, 6, 9) - specify CAT of 40°C.
• Moisture
  • Water delivery in ASTM D7869 is primarily accomplished through water spray (steps 1, 5, and 6). This cycle features longer spray steps than most xenon arc weathering tests.
  • Relative humidity (RH) control is also included in ASTM D7869 to influence materials' time of wetness. All light steps specify 50% RH, while dark steps specify 95% RH.

You can find in-depth information on how to program the ASTM D7869 test cycle into your Q-SUN xenon-arc weathering chamber by logging into your Q-Portal account.