I am considering using Epoxy Coating Resin to coat some exterior woodwork (marine ply fascias) in the expectation that it will have a very long life (20+ years) especially when compared to traditional paint finishes.

1. I want it black.  Can I use gel-coat pigment (which I have) or do I need to use epoxy-specific pigment?
2. I understand that epoxy is not UV stable.  Does that mean that the epoxy can fail under natural light or simply that it does not retain its clear colour (which is of no consequence to me as I want to pigment it in black)?

Many thanks.

You must use the epoxy pigments and not polyester gel coat pigments.

Pretty much all epoxies are rubbish for UV and will go a flat reasonably quick with sun exposure.

Thanks for the reply.

I can accept the epoxy going flat so long as it doesn't degrade.  Can you advise whether UV affects its performance/resilience over and above just going from shiny to dull?  Can I reasonably expect 20+ years out of it before a re-coat?

If you use an UV stabilized Epoxy then you can probably expect up to 10 -15 years without it cracking up , peeling and letting moisture through to the wood..

This depends very much on the quality of the Epoxy .. adding a black pigment makes it less strong, since it will absorb more energy/heat /UV -- And also VERY much on how you prepare the surfaces, and the quality of your work!!!

I repaired an outside window-sill with West Systems close to 15 years ago. this was using the West Systems Coating hardener with UV stabilizer and "high density filler" but without any pigment-
This is still in very good condition, even though it is on the south facing facade of my garage, in direct sunlight almost all day (when the sun shines that is... )

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Is there a good epoxy for UV protection? I thought that was why most people use it for auto based resin infusion on CF?

All epoxies are UV sensitive. Some have additives to help but even they still degrade.