Weathering techniques, accelerated

L S Crump, Evaluating the durability of gel coats using outdoor and accelerated weathering techniques a correlation study . Proceedings 51st Annual Conference, Composites Inst, SPI, Feb 1996, 22-B. 

There are numerous factors which will affect the performance of light stabilizers in each polymer and application. Therefore, although careful definition of specific application requirements can help to develop some initial stabilizer options, testing of these systems via accelerated weathering techniques is often required. Numerous useful references are available describing accelerated test... 

MIL-STD-304 is a commonly used accelerated-exposure technique to determine the effect of weathering and high humidity on adhesive specimens.66 In this procedure, bonded panels are exposed to alternating cold (-54°C) and heat and humidity (71°C, 95 percent RH) for 30 days. The effect of MIL-STD-304 conditioning on the joint strength of common structural adhesives is presented in Table 15.20. However, only relative comparisons can be made with this type of test it is not possible to extrapolate the results to actual service life. 

Feist (20) and Williams ( ) have used xenon arc accelerated weathering to determine the efficacy of surface treatments of wood. The degradation of the surface is manifest as erosion and can be measured microscopically (2). In recent work at the Forest Products Laboratory (22), these techniques were used to determine the effect of acid treatment on the erosion rate of western redcedar (Thuja plicata Bonn ex D. Don). 

Anderson et al. (30) have been developing a technique for weathering neat samples of suspect oils (i.e., with total absence of water) in a thin film under long-wavelength ultraviolet radiation with air passed over the surface. This technique permits convenient accelerated weathering of small samples—from approximately 1 mL in a small petri dish to 30 mg on an infrared salt plate. Under these conditions, the ultraviolet becomes an important factor in weathering, particularly in the generation of carbonyl. 

Present research work has been carried out in two parts field exposme tests and accelerated laboratory tests on unexposed panels. Under field exposme test three representative sites PI very close to sea shore and free firom SO2, P2 away from sea with presence of SO2 and P3 industrial environment with presence SO2 were chosen. Analytical techniques (EDX, XRD and Raman spectroscopy) were used for rust characterisation and SEM was employed for understanding the morphological state. Corrosion rates were estimated after different periods of exposure at sites. It is found that though accelerated laboratory test can predict the general trend of corrosion, actual field test data cannot be created in laboratory. So an attempt was made to simulate protective rust coating in the laboratory that is typical of field exposure protective rust formation on weathering steel. 

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