carpet replacement source

Im sure you will get alot of varied advice on this subject... and I guess POR15 is the most recommended. BUT- it is expensive. I asked a few oldschool body guys when I was at the same point as you, and they said "go to Ace Hardware and get a bottle of OSPHO for $12... put in a sprayer and follow the directions". Ospho did a great job- I then used Rust-Oleum Clean Metal anti-corrosive primer/paint to finish the job. I have read all the literature on POR15 and it looks like great stuff- but for the surface rust I had... this stuff did the job. I did have a couple minor areas that had pins holes that I grinded, and used Duraglass to repair, but also very easy to use.
Good luck...

OSPHO link: http://www.ospho.com/ open/read the directions for use header