A neighbor of mine had an old bike he used for running around on the dirt roads where we lived. He took his tank down to bare metal and basically polished it the same as you would aluminum. It didnt shine up mirror like, but looked good. He then hit it with a bare metal sealer I think called Gibb(s?). It was like a gun oil or something. That bike sat outside for at least 2 years that I know of. The shine dulled a bit, but I never noticed any rust. Might be worth testing on some scrap metal?
