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Abstract
Paint companies usually recommend that topcoats be applied to primer paint within two weeks. Unfortunately, this is not always possible. For example, onset of winter weather shortly after applying primer may delay topcoat application until spring. Scuff sanding or repriming are often recommended remedial methods for preparing a weathered primer for topcoats, but there is little research using modern paint formulations to support these practices. Western redcedar boards having a single coat of oil-alkyd or acrylic latex primer were placed outdoors for six months (November 1995 to May 1996) at our exposure sites near Madison, Wisconsin, and Gulfport, Mississippi. After exposure for six months, the weathered primers were prepared for topcoat application by light hand-sanding and washing without repriming (treatment 1), repriming (treatment 2), or topcoating "as is" (treatment 3). They were finished with a single topcoat of acrylic latex or oil-alkyd paint and evaluated for cracking, flaking, and mildew growth annually over 12 years. We found that light sanding and washing without repriming (treatment 1) had a deleterious effect. Topcoat performance was about the same for repriming (treatment 2) and topcoating “as is” (treatment 3). Water repellent preservative pretreatment of western redcedar prior to priming did not improve service life of the finishes.
Keywords
Weathering,
paint,
testing,
deterioration,
primers,
coatings,
finishes,
finishing,
western redcedar,
mildew,
wood-decaying fungi,
molds,
service life,
water repellents,
wood preservatives,
adhesion,
ultraviolet radiation,
testing,
Wisconsin,
Mississippi,
durability,
resistance to decay,
exposure tests,
sanding,
performance testing,
water repellent preservatives,
surface properties
Citation
Williams, R. Sam; Knaebe, Mark; Sotos, Peter. 2008. Effect of surface preparation on service life of top-coats applied to weathered primer paint. In: PRA’s 6th International Woodcoatings Congress : "preserve, protect, prolong", Amsterdam, the Netherlands, 14-15 October 2008, conference papers. Hampton : PRA Coatings Technology Centre, 2008: 16 p. ISBN: 9780955131752: 0955131758.
