it's the nature of the beast. Keeping he ashes cleaned out and wipe it down with Pam when it is still warm will help. To get rid of the rust you can sandblast it or aggressively attack it with with a Cup wheel on a grinder repaint with High temp header paint and wipe it own with pam while it i warm.
I never met a Cow that I didn't like with a little Salt & Pepper! Certified PORK-A-HOLIC