I had a ARB bullbar blasted and powdercoated for $300.
The original condition was borderline sand blasted anyway as it was a car used to drive cops around remote SA, Coober pedy etc...
For $300 it was done with a zinc primer as well and ever since then all the major deep gauges in the bar show no rust.

If i was to paint it, i'd be simply doing the whole thing in the Whit Knight rust guard gloss.