Getting back to your main chassis metal, and as what to do with it. I just very lightly, and unevenly, dust a coat of rust-o-leum aluminum spray paint over the repaired areas. I mean dust, not cover. It gives the impression of cad plating, and stops further corrosion. Sometimes I tone it down with a cotton ball moistened in lacquer thinner, dabbing at the paint to age, dull, or blotch it, so it blends with the rest of the chassis. The idea is not to make it perfect. It works, and easy to undo and try again.
