I was sold on the results of the vinegar method:
http://www.stovebolt.com/techtips/rust/vinegar/index.htmIt was especially good with odd shaped parts that were difficult to brush since the rust could be just blown off with water. A quick coating of phosphoric acid gives it that grey new steel look.
I did get it on my garage floor and it took the outermost smooth layer of the conrete off. I definitly recommend washing the area with baking soda right away.
It was that effect on my garage that led me to experiment with the electrolisys. I put some parts in a rubber tub with 20 mule team borax. I wrapped 110 volt copper electrical wire around the part and connected that to the negative clamp of a battery charger (to keep the clamp out of the solution). I clamped the other end to some re-bar and leaned it half in and half out of the solution. It took about two weeks, day and night, to turn black and I wasn't sure when it was done because of the black coating.
Maybe I should have clamped the battery charger directly to the parts and scrap submerged in the solution. Would that eat up the copper clamps on the charger? After that week I went back to vinegar and tried to be more careful about how I spilled it.
