Not sure if you guys have ever heard of Ospho, but I have been using it to convert rust before painting and it works great! I spray it on the rust and overnight the rust (iron oxide) is converted to iron phosphate . Not only that, but is also etches the metal to allow for better paint adhesion. It is easy to use (spray or brush on), but it contains phosphoric acid, therefore you need to adhere to proper safety procedures (masks, gloves, goggles, no skin exposed, etc...) when handling it.
I have had great results using this product. Just thought i would share my experience with using this awesome product. I believe Ace Hardware carries it.
If your doing rust repair/neutralizing and can't just cut it out and replace metal, I believe this will help. It helped me while repairing the Benz, since replacement parts were just too expensive. I blasted everything i could and then ospho to paint. Saved me hundreds of dollars.
http://www.ospho.com