the best stuff i know of other than stainless is a nickel copper line which is really easy to bend and never rusts, its aroun 3 dollars a foot for 3/16
The only problem with copper/nickel line would be that I can't weld it. I want to use it as a bead around the hood opening on my fenders.
The more I think about it though, the worse the idea seems. I'm afraid the metal underneath the tube will start rusting and bleed out.
This pic shows a piece I mocked up with regular brake line. Maybe with a good coat of epoxy primer it would be OK but I'm sure I will scrape off the epoxy in some places as I slide it on.
I may need to stick with my original plan and weld a solid s/s or cold rolled steel rod on top of the rim.