You can protect the bare areas by treating them with a phosphoric acid solution. There are several preparations made for this purpose. In my area of California I cannot find it at Home Depot or Lowes but the automotive paint shops have some. I use Jasco. Do not rinse it off with water afterwards as some people recommend- it will rust. I used this method on all my parts and several pieces have been this way for over a year (stored inside) without any signs of rust.

When I first started I used a heavy coating and let it dry overnight. The next day I hit it again loosening the previous day's dried material and then wiped it fairly clean leaving just a thin film. I did this with all the major body parts and it was probably overkill. Since then I have just used 1 coating, left it on for about 30 minutes, then wiped it off. The results seem the same either way.

Chuck