I know this is an old thread, but I'm resurrecting it. I've had pretty good success with powder coating a clear coat over water slide. I use an HP Laserjet printer and sunnyscopa water slides. It's taken some time and a handful of messed up enclosures. But, here's the process...
Depending on if I get an unpainted enclosure (which then I'll powder coat it whatever color I choose).
* If it's an unpainted enclosure, I'll bake the bare enclosure for 20 minutes at 400 F. This is to get any impurities out of the metal. After it's cooled, I'll rub it down with some pre-coat from Eastwood. Then paint it a color.
* I'll put the decal on and use a little squeegee to get all the water out. I'll let it dry completely.
* I then bake the graphic at about 210 F for 20 mins. It could stand a little hotter, but this is going by the graphic papers recommendation.
* When it's cooled, I'll rub the sides of the enclosure down with Eastwood pre-coat to get any impurities off of the sides.
* I'll put a nice coat of powder on it and bake it at 400 F for 10 mins. Let it cool then bake it again at 400 F for 10 mins. The recommended curing time for Prismatic powders is usually 20 mins at 400F. But, obviously that would burn the graphic. Depending on the color of the enclosure (let's say, white), there may be a hint of brown tint to it, but it's not bad enough to really notice. Colors like orange, yellow, purple you can't even tell.
* I then wet sand and buff the top of the enclosure with some Meguiar's Ultimate Compound until it has a nice and shiny finish. I don't bother with the sides. I have done the sides a few times, but you take too much of a risk of scuffing a corner.
I make a signature pedal for Chris Robertson of Black Stone Cherry, and this is my process I use. The powder coating offers more protection than screen printing and it is something that any pedal maker can do. It's just a process.
I know this is an old thread, but hope that my process can help some others out.