I would not suggest spay on bed liner or undercoating, as you will inevitably coat some things you don't mean to coat (like wiring, air lines, bolt threads, etc.) making your life miserable when you need to crawl under the truck and work on it. Stick to the rustoleum. Brush makes a nice heavy coat to keep the rust away, but the spray gun does a better job on the nooks and crannies. Toss a coin.
Way back in the day we used a primer call zinc chromate from 3M on our stake body beds and tank trucks when we would sandblast and recondition them to go onto a new chassis. Sprayed over the freshly blasted metal the stuff was virtually indestructible. I remember after years of service the paint topcoat would eventually chip off inside the wheel wells from rocks etc, but that primer coat would never chip off. It was a hideous ugly yellow-green (which you painted over anyway) but I am her to tell you it worked. I don't know if the stuff is still available, probably the epa got rid of it like everything else that actually worked good.
|