How can I keep sanded bare metal from rusting?

If wanting the bare metal look just clear coat it

 

Cody Walls did a test a few years back, using Gibbs Oil and a few others. His test showed that Bulldog Adhesion Promoter surp***ed the others in rust prevention plus it actually helps paint stick to the metal. You can't ask for more than that.

http://kleanstripauto.com/products/bulldog-adhesion-promoter

 

Don't see what the problem is. I'm just across the border from you in Alberta. The climate is so dry here that I just leave the metal alone and it does not rust.