Epoxy and powercoating - coating inside of rails

[HO455]

When you box your frame the welds will burn off whatever coating you use and you will have unprotected metal inside and out. The outside is an easy fix if you haven't powder coated it. If the inside rust is a problem you can recoat the inside with an undercoating sprayer that has a flexible wand like My48Chevy said. There are several products you can use to prevent rust. From organic products like Fluid Film to rust convertors to coatings like POR-15. I went the POR-15 route on my Burban to protect the voids in the body. Organic products like Fluid Film are much easier to clean up and may the best bet on something already restored. I have used it extensively at work on ocean going tugboats. It works well but must be reapplied from time to time. (At least on the boats it does, but that is a much harsher environment). They are less toxic too. If your interested I posted some more info on my process that I used in my WMB thread below.