Paints and coating are commonly used to provide both protection to substrate and aesthetically pleasing appearance, but these functions can be affected as a result of exposure to outdoor environment. Sunlight especially in the short wavelength/high energy ultraviolet (UV) region, moisture, oxygen, and heat are identified as four major factors involved in weathering. These elements contribute individually as well as in combination to cause coating failures, such as discoloration, change in gloss, chalking, peeling, blistering, and loss of adhesion, etc.
QUV accelerated weathering tester is one type of artificial weathering devices that designed to reproduces the damage caused by sunlight, rain and dew in controllable and reproducible test conditions. The QUV test chamber uses fluorescent lamps to provide a radiation spectrum centered in the ultraviolet wavelengths, and built-in heaters to control temperature and to provide moisture by forced condensation.
In this test, specimens are mounted in brackets, which are stationary and set at an angle so condensate can run off the test surface and be replaced by fresh condensate in a continuous manner. The specimens are cycled between exposure to UV light and condensation in a heated environment. Various cycles can be defined depending upon the intended end use application – for examples, a typical cycle for automotive exterior applications would be 8 hours UV exposure at 70°C followed by 4 hours of condensation at 50°C, and a typical cycle for marine coating applications would be 4 hours UV exposure at 60°C followed by 4 hours of condensation at 50°C. These cycles would be continued for extended periods of time – up to thousands of hours – simulating even longer periods of time in the real world.
Test methods for QUV are available in:
- ASTM G154
- ASTM D4329
- ASTM D4587
- ISO 4892-3
- ISO 16474-3
- SAE J2020
- Other standards that QUV is part of a cyclic corrosion, such as ASTM D5894, ISO 12944-9
3″×6″or 3″×12″ all-side coated steel panels