Rust prevention is the easiest way to keep sheet metal in top condition. Constant inspections and attention to detail are necessary for keeping metal in good condition. Areas where water can be trapped and bubbles are allowed form will likely reveal small rusty holes beneath the surface. Salt is an excellent rust accelerator and should be washed off sheet metal as frequently as possible. Coating sheet metal with a good rust-resistant primer and topcoat will help prevent corrosion from forming.
Light surface rust is the easiest to eliminate. Quick scuffing with light-grit sandpaper is a simple solution to getting rid of this type of rust. There are also a number of rust-removal products that can get the job done. After removing the rust, the area should be immediately coated with a primer to prevent the light rust from returning. On external body panels, use a two-part etching primer. Rust-conversion chemicals are a new alternative to removing rust, which converts the rust to a hard, paintable surface.
Heavy rust is nearly impossible to completely remove and is likely to reappear. The best option is to completely replace an entire panel of sheet metal. If repair is the only option available, a portable sand blaster should be used to clean the area, and a patch welded to cover the hole formed by the blaster.