Mask of areas that you do not want touched with plastic sheets and tape.
Clean the corroded area of dirt and debris. Using a wet, soft sponge scrub the area to remove dirt, oil or exhaust stains so that you have a better look at the entire surface.
Strip the paint from the corroded area. Use a paint stripper and rub with a coarse sandpaper to remove the paint.
Mix a chromic acid solution. The solution should contain 24 oz. of chromium trioxide mixed with 1 gallon of water in a stainless steel, lead-lined steel or 1100 aluminum container.
Apply the chromic acid solution with a nonmetallic bristle brush. Allow the solution to set on the area for 15 minutes.
Rinse the solution off the treated area. Use clean water and rinse thoroughly.
Feel the thickness of the metal to be certain is will not collapse from hand pressure.
Remove the corrosion. Scrub the area with a bristle brush until all signs of corrosion have been removed.
Polish the area. Use a 400-grit aluminum oxide abrasive paper and scrub the area clean.
Apply a chromic acid brush-on treatment. The solution should contain 1.3 oz. of chromic acid mixed with 1 gallon of water and 1 oz. of calcium sulfate. Brush on the solution until the metal surface appears dull in color.
Apply the primer to the area and allow it to dry according to the product’s instructions.
Apply the paint to finish restoring the area.
Remove the plastic from the protected areas.
