POR15, undercoat, or sprayon bedliner?

well the epoxy primer is what the industry has to useto maintain the manufacturer coating warranty on new vehicles. when they are repaired to pre collision status years ago we stripped a car to bare metal an epoxy primed it. a personal car. the shop got busy and had to put the car out side for paying jobs. it sat outside through the entire winter and the springs rainy season before we could get back to it. when we brought it in a dried it off the epoxy had accomplished what it was supposed to. there was no rust on the car at all