Do you mean like THIS ?

I did this cab corner in September and it looks exactly like that today. I keep the truck inside my garage & like you said, it doesn't get wet, but there is the Florida humidity and it has not formed any rust at all.
I did replace my roof with a used roof from another truck, and that did flash rust. I just used a wire wheel on my drill to remove it and sprayed Eastwood rust encapsulator on it.

1957 Chevrolet 1/2-ton Stepside LB in the Gallery
My Photobucket shots

The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself." - John Stuart Mill (1806 - 1873)