[jspatz1]

No real way to prevent this on aluminum parts without some sort of coating. This is why most aluminum parts in commercial products are anodized. The simplest, cheapest, fastest drying clear coat is just the clear spray paint you will find in most spray paint collections at the hardware store. Krylon and most other brands have a clear paint. Comes in gloss,satin, or flat like other paints. Polyurethane or other clear wood finish can be used, but can leave a slight yellow tint. Clear laquer can give a very nice shiny finish, but takes a long time to dry. The best choice for a hectic build season is probably clear spray paint.