Removing rust spots and blisters
Rust repairs generally cover two areas; surface rust and rust holes (perforation ) Surface rust can usually be removed and held at bay successfully, perforated metalwork will need much more extensive work to provide a lasting repair.
Where surface rust and pitting is evident, additional stages to the normal sanding/feathering process are required. Use a wire brush attachment or "flap-wheel" type flexible abrasive to completely remove any trace of corrosion from the pitted surface, paying careful attention to seams and out-of-sight folded edges, to prevent rust creeping around door edges, etc. When perfectly clean, treat with a proprietary rust remover surface Rust spotstreatment. Apart from the range available in motor accessory shops, paint suppliers also supply metal conditioning/surface treatment fluids which are usually phosphoric acid based. Whichever type is used, follow the manufacturers' instructions, rinse thoroughly and dry the metal immediately. Follow this with etch primer before any further filling of minor surface defects is attempted. Note: etch primer should not be used as a base for polyester bodyfillers. Use a primer-filler followed by a stopper intended for use on primers.
Repairing rusted holes in bodywork
More serious rusting can lead to obvious holes in the metalwork, or as often happens in double skinned areas such as rear wheelarches or door bottoms, rust or blisters which appear because the panel has rusted quietly away from the inside. By the time the first signs show, the metal in that area is already beyond help. The only long term repair will involve a panel\section replacement, or if the area is very small and the rest of the panel is absolutely sound, body solder can be used effectively.
-