Comparison of traditional methods for testing paint service life with new methods for service life prediction

Abstract

Western redcedar siding was "preweathered" by placing it outdoors for 1, 2, 4, 8, or 16 weeks prior to being painted. Panels were painted following the preweathering and tested for paint adhesion. The amount of time these panels were exposed (preweathered) directly affected paint adhesion. As much as 50% paint adhesion loss was shown for specimens preweathered for 16 weeks. For matching panels that were painted and exposed outdoors, the longer the panels were preweathered, the shorter the service life of the paint: The paint on panels preweathered for 16 weeks began to flake and peel after 4 to 5 years; for 8 weeks, after 7 to 8 years; for 4 weeks, after 9 to 10 years; for 2 weeks, after 10 to 11 years; and for 1 week, after 13 years. Unexposed controls were still in almost perfect condition after 17 years of exposure, This work spanned 17 years—there must be a more timely means of getting this kind of information. In recent outdoor exposure studies, the response of materials was measured directly every few minutes during exposure and this response was matched to the weather causing the response. Changes in specimens could be observed as they occurred. This work involved measuring the load and deflection of sealants, but the methods that were developed may be useful for many materials. By measuring materials response and weather during outdoor exposure, early failures could be linked directly to their causes.

Citation

Williams, R. Sam; Lacher, Steve; Winandy, Jerrold E.; Halpin, Corey; Feist, William C.; White, Christopher. 2004. Comparison of traditional methods for testing paint service life with new methods for service life prediction. IUFRO Working Party 5.04.12 3rd International Symposium on Surfacing and Finishing of Wood : 2004 November 24-26, Kyoto, Japan. Kyoto, Japan : IUFRO, 2004: pages 166-190.