CORRELATION OF ACCELERATED EXPOSURE TESTING AND EXTERIOR EXPOSURE SITES

The Cleveland Society Technical Committee has undertaken a long-term s tudy which will provide some guidance and basic information for resear chers working in the areas of accelerated testing and exterior exposur e analysis. The ultimate goal will be the correlation of accelerated t est methods to several geographically different exposure sites. The Te chnical Committee began the study by choosing nine different coatings systems which offer a wide variety of performance characteristics. The se systems included a high-solids epoxy, a high-solids urethane, sever al types of waterborne systems (waterborne epoxy, epoxy ester, acrylic , direct-to-metal (DTM) acrylic, water reducible alkyd, and styrenated acrylic), and a Type TT-E-266 specification alkyd. All systems were c ommercially available and, except for the specification alkyd, are con sidered ''compliant coatings.'' These systems were placed on exterior exposure at nine different sites across the United States. Four are co mmonly referred to as heavy marine exposure sites and include Ocean Ci ty, NJ; Kure Beach, NC; Daytona Beach, FL; and San Francisco, CA (the Golden Gate Bridge). Three more can be considered moderate to heavy in dustrial exposure sites and include Cleveland, OH; North Kansas City, MO; and Miami, FL. Another site, the Los Angeles Basin area, is known for heavy smog, and the last site, Portland, OR, was chosen for high h umidity and rainfall. The first six month's exposure results and early correlations within these sites will be discussed, but longer exposur e times will be required before many conclusions can be drawn. These s ame nine systems were also tested by use of six accelerated methods ac cording to the protocol established by an ASTM Committee (D01.27.31) o n accelerated corrosion testing. The methods include salt fog, cyclic salt fog, Prohesion(R) Cabinet, Cyclic Prohesion(R)/QUV(R), and cyclic immersion/weathering (KTA-Envirotest(R)). These methods are either in use today or have been proposed as more realistic replacements to tho se in current use. Results of these accelerated tests will be discusse d and an attempt made to correlate the results among these accelerated methods. In addition, positron annihilation lifetime spectroscopy (PA LS) will be run at the end of the exposure period on the Daytona Beach panels. Future work will focus on direct correlation of the long-term exposure results to the different accelerated methods.