[Jacques Reed]

I note phosphoric acid and mollasses has been mentioned in the post a couple of times. I have used those means to de-rust most of my parts smaller than the chassis and cab floor.
For those that may want to try the phosphoric acid method, it is available as various metal prep solutions at most auto parts stores but it is a very expensive way to obtain it.
I obtain 5 litre to 20 litre drums of the stuff from ship's chemical suppliers. Commonly called "rust stain remover" it is used to tidy up paint on ships to save frequent repainting. Thats how cruise ships stay white and U-boats became rusty brown in the winter North Atlantic.
Some brands are Unitor, Allied Chemicals, Gamlen to name a few. I use in Australia "Scale Off" made by True Blue Chemicals.
Although it is an acid, about a 5% solution, and gloves are required if you get some on your fingers they won't dissove or even burn. the fact I am typing this reply proves it.

Brgds,