Could you use electrolysis to remove it. I use it and it works very well.
what I suggest is getting some sodium carbonate, washing powder and mixing it in a five gallon bucket of water. I then use a iron rod to hook up the positive lead of a battery charger and then hook up the negative lead to the part. I use a 2amp trickle charge and let it sit over night most of the time. If you're interested, I can post a couple of links for you to look at. It really is very simple to do and removes all of the rust.