Longer term answer for Rust in fridge burner

Electric fridge = no more rust..

I do not know of any way to stop the chimney on propane fridges from rusting. The heat burns off the paint exposing the steel tubing to moisture in the air which creates iron oxide (IE rust).

I do not know if it is advisable to paint with a high temp paint as the paint can possibly interfere with heat transfer that is required making your fridge less efficient.

If one was to attempt to paint with a high temp paint, one needs to treat the rust, typically one would use a rust converter like Ospho which turns the rust into a black paintable surface.. However, I have never tried this on any high temperature surface like what is found on your fridge coils.