Doderman makes a good case for having real applied knowledge for corrosion removal.
Most "rusts" are simply metal oxides of the metal being electrically drawn from the base metal.
Both "electrolysis and chemical methods" are similar in NATURE.
Really? Would you like to explain to me how the hell you arrive at that statement?
The only similarity I see is the rust is gone.
Mechanical methods like grinding and steel wool are superficial at best. removal of a rust is best done where you get into the metal pore (grain).
The best method for me is the one I can use as needed safely and with quality real results with reasonable economics and minimal environmental impact. I can use a brush, dip or spray Cortec system as required. It can be used in a PVC pipe dip method over again.
As he said stay away from phosphoric acids, they can burn and do more harm than good with precision assemblies like chains, pins and cutting edges.
WHOA just a damn minute, don't put words in my mouth!
If you want to use an acid system Phosphoric is to only acid that stops acting when it reaches clean steel. Just about every other acid will continue to eat into good steel, including Acetic, Muriatic, Tannic, and Citric. Phosphoric at 5% concentration in water will convert rust to Iron Phosphate, and done properly become a bonded layer you can paint over. Phosphoric at 40% concentration will remove rust and leave clean steel.
BE DAMN CAREFUL WITH PHOSPHORIC AROUND ALUMINUM. Even at 2% concentration Phosphoric will dissolve aluminum.
As to being "green" phosphoric is used in agriculture to fertilize rowcrops and disinfect and clean milk lines.
The new liquid "green" cleaners can be very cost effective as well- and yes a molasses based system I would consider green.