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Easy hon.. don't have a stroke!
WEST SYSTEM - Projects - Testing house paint primers
Paint options over epoxy 603-435-7199
CASE STUDY: Real Life examples and fixes.
During the spring of 2011 I painted the bottom of an epoxy and varnish coated boat with rustoleum brand enamel. The enamel dried fine over the spar varnish but not over the epoxy were it stayed tacky for days and days, until I dragged the boat out into the hot summer sun for several days. After a series of experiments I discovered the 'enamel problem' happened when applied to epoxies containing nonyl phenol (most epoxies do - our Premium No Blush epoxy does not).The epoxy surfaces were cured from several days to several weeks prior to the application of the enamel and still the problem existed. I suspect that given a month or so of epoxy 'cure time' the problem would not occur (or we would hear about this problem all the time).The use of additional drying agent additives into the enamel helped a little bit. Location of the tests was New Hampshire. Temperatures in the 60s, 70s, 80s with dew points always over 60 degrees.
In there fall of 2011 I repeated my testing. Temperatures where now in the 40s and 50s and the dew points also now well below 50 degrees. Surprisingly the problem with the nonyl phenol containing epoxies had vanished. It would appear that the issue is caused by moisture (high dew point) in the air. The enamel dried quickly on the hard non porous epoxiy sufaces and not so fast on high solvent based coatings/primers (including Kilz primer (tm) and spray can enamel - especially when applied thickly over masking tape). I think the slow drying in the fall tests is temperature (solvent evaporation) related.
Summary of Alkyd Enamel potential problems
Warm and Humid Conditions (dew point over 50 F?) - Stay away from epoxies containing Nonyl Phenol under the enamel which will impede full drying. Prime Nonyl Phenol surfaces with either spar varnish, aluthane, Premium No Blush epoxy (which has no nonyl phenol), or Water Bond - water based epoxy primer prior to an enamel topcoat.
Cool Fall Conditions - Stay away from High Solvent spray paints and Primers under the enamel which will impede full drying. Epoxies with or without Nonyl Phenol, spar varnish or aluthane prior to an enamel topcoat.
Rcommendations for Surfaces to be painted with Alkyd (oil based) Enamels (under entire range of conditions)
1) do project with an non - Nonyl Phenol epoxy (like Premium No Blush) - or topcoat the epoxy with our Water Prime (pigmented water based epoxy paint)
2) prime the nonyl phenol epoxy with Spar Varnish prior to enamel topcoat. Varnish is easy to work with and smells nice. Has UV protection for epoxies. Downside: probably modest (but more than suitable) adhesion and durability. Amber color.
3) prime the nonyl phenol epoxy with our aluthane aluminum filled moisture cured coating. Advantages: can be applied in vry warm or cold conditions, amazing adhesion/bonding, aluminum color shows flaws in underlying surfaces and when sanded high spots turn darker in color.