Warren, After I posted the question about painting with polyurethanes, I began to wonder=\did I dream that ??? Drove me crazy as I searched all my airplane magazines...
Now, I found the article ---I'm not crazy--- It is in the September 1999 FAA Aviation News - page 6. Article is "Corrosion, The Insidious Foe"...and is taken from a slide presentation on corrosion by Pacific Corrosion Control Corporation. Under Para. 8. Filiform Corrosion " Filiform corrosion is a special form of oxygen concentration cell corrosion that occurs on metal surfaces that have been coated with polyurethanes. The problem is that the paint is so thick with pigments and resins that the surface of the metal cannot breathe. This means that if there was any moisture there to begin with, it will stay there and grow as filiform corrosion. Filliform corrosion may also start at breaks in the coating system." Now, I ask, just how is one to eliminate all moisture unless the airplane is painted after being heated, dried, and kept in a dessicated area? Not practical, I think. At what relative humidity is it safe to paint with polyurethanes ? Is this a real concern? Is this a significant concern ? I suspect it may be over stated. Appreciate comments from the experts.....as I WAS planing to again paint my coupe with polyurethanes..... Harry Francis 93530 Blacksburg, VA
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