"It's easier on a Grubb" (tandem)

You need a bucket of water with washing soda in it, and a car battery charger. You set up the rusty parts as the cathode (-) and an old steel can or similar as the anode (+). Then something magic with the rust electrons(?) being attracted to the positive side happens. I’m no chemist (sorry dad!)

At the end of it there is some blackness on the formerly rusty part but this comes off with a bit of a scrub. The main advantage of using this method is that no real abrasion takes place.