I take it you're talking about a VTR FireStorm here and not an SP, if so you need to get the old paint off, use fine emery cloth/wet and dry/scotchbright to get rid of the corroded area, scotbright the whole area to form a key for the new paint and re-spray, better still shot blast them if you can, if not use a paint srtipper, rub them down and re-spray, other than that you'll just be papering over the cracks and it'll all come back
