We painted the chassis and bed of my pickup with protectakote and it hasnt chipped/come off after 12 months of chucking stuff in the back/carrying around branches/machinery etc. Expensive though and the finish isn't as good as "normal" paint - but very strong.
used protectakote myself Dan as a paint in floormat on my buggy showed you guys at one of the shows couple years back very good stuff has tiny rubber chips in it that gives a tough textured finish . It is sometimes used as a kind of paint in loadbed liner on pick up trucks so is pretty tough and easily repaired/painted if scuffed (hard) should do what you require no problems at all