I have used POR15 on frames and other parts. It's great stuff. Powdercoating is best for bumpers or an epoxy based paint if you want to shoot it yourself is good. I touch up my bumpers and rock rails with POR15 after a day in the rocks. Try it out, if you don't like it, you can always sandblast and powdercoat later.
97 TJ 4.0, AX15, E-Fan, 5" Full Traction Long Arm - D44s /4:88s, 36" TSL/SX Swampers on Cragar Bead Locks, Atlas ll, Outback Extreme OnBoard Air, Hand Throttle, Homemade Sliders, Homemade Rear Roll Cage, M.O.R.E. High Clearance Bumpers, Currie Currectlync Steering, Currie Anti rock, Warn 9.5XP, OR Fab Sport Cage Up Front, I've lost control.