I've seen some steel wool filters used as exhaust filters. It goes beyond rust, the steel just sort of dissolves after a while... Exhaust gas is nasty.
Even though we use soot filters in our TIP Kits, they aren't necessary after the 304SS condensate coil has been through a few dozen thermal cycles.
We back flush the soot filters in the shop trucks a couple times a year, but don't bother using one on the drag truck - it clogs up within half a dozen passes, and the condensate coils do a better job of protecting the drive pressure gauge anyway.
I found the easiest solution for this problem is running an inline filter/water absorber for air tools. They are cheap and made of plastic. They last for a month or two then you replace it. Only like 5 bucks. I use push lock ends so they are a breeze to change.