08/03/2026
Some important tips for using epoxy under body work. (This is for high end hot rods/restorations)
First, the sole purpose of epoxy in this situation is a moisture barrier to prevent corrosion on the metal, that’s it.
Epoxy is not a miracle product, nor is it a guarantee of any kind. ➡️ By a long shot the most important factor is quality prep work. Just because you used epoxy doesn’t mean anything. You need to be insane about the quality of the prep work.
♦️ The epoxy should be cured before putting body filler over it. The only way to guarantee the won’t be adhesion or delamination problems of the filler over the epoxy is by giving it plenty of time to cure, which is a minimum of one week. The epoxy will then need to be sanded before body filler is applied.
♦️ You must spray enough epoxy so you don’t sand through while prepping it for body filler. If you’re sanding through the epoxy, not only do you lose the effect of the moisture barrier, you are also then only relying on 120 grit scratches for the filler to stick to the metal. That’s not enough.
♦️ 3-4 coats of epoxy is usually enough to have enough build to be able to sand it with 120 by hand before applying filler.
♦️ When epoxy is under the body filler, it does not need to be over the filler as well, especially if you’re using Vinylester primer (and you should be). Vinylester is water proof as well. Nothing good is going to come of epoxy being in 120 grit scratches, and you already have the moisture barrier under the filler. There’s zero reason to have epoxy over the filler again. It’s very easily arguably worse off adding more epoxy.
♦️ Epoxy is not a magic product. Your prep work is what matters, by a lot. Just because you spray epoxy on bare metal absolutely does not mean it’s better. If everything isn’t executed completely correctly with epoxy, you’re probably worse off using it. (this statement is worth saying twice)
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