In industrial markets, epoxy coatings (liquid, powder and electrocoat) often are used outside because of their corrosion resistance. If the coated parts will be inside or covered, the epoxy will not break down. But if you leave an epoxy-coated part in the sun for a long period of time, the sun's ultraviolet (UV) rays will begin to break down the epoxy finish whether it is liquid, powder or electrocoat. The ability of the coating to break down is not due to the coating technology but to the intrinsic chemistry of corrosion-resistant epoxies.
There are a few solutions to keep the part from degrading. First, a UV-durable topcoat (liquid, powder or electrocoat) can be applied to the epoxy primer. This topcoat keeps the sun from penetrating the epoxy finish, leaving the coating intact. Second, an epoxy electrocoat primer with added UV durability has been developed, but is somewhat higher in cost. This product may be a good fit for epoxy-coated products that are left outside for short periods of time. Finally, acrylic electrocoat is available for parts that are exposed to sunlight for long periods of time. It will provide a high quality finish with good UV durability and some corrosion resistance.