The Faber and Worthingtons are both painted. No external rust on any of the 85's - my 125's rust a little, especially around the boot area, so every six months or so I just wirebrush it off and zap it with Rustoleum. Hot dip galvanizing would be nice, but a little external rust I can live with.
What has stopped the rust is that after diving, besides the normal rinse-off, I immerse the tanks in my high-tech gear washer - a big blue junk tub I got from Costco. I also use this to carry my gear instead of using a gear bag.