Some recommend electrolysis to remove surface rust. You feed the rusted part electrons so the rusty iron can get its electrons from that rather than oxygen and turn the iron oxides back to plain iron.
“Is it safe? The solutions used are not hazardous; the voltages and currents are low, so there is no electrical hazard. No noxious fumes are produced. The method is self limiting: it is impossible to over clean an object. Small amounts of hydrogen are emitted in the electrolysis process. Good ventilation or an outdoor work site is all that is needed.” http://www.stovebolt.com/techtips/rust/
Lot’s of leeway and low risk of any damage make this something worth a bit of experimentation!
It’s for plain iron or steel, not for steel springs or hardened steel because the process might cause hydrogen embrittlement resulting in part failure. You should also avoid any metals that aren’t just iron because the alloys or other metals may produce harmful or dangerous byproducts in the process. Your waste electrode needs to also be ‘just iron’ or perhaps graphite for the same reason.
An old battery charger makes for a good current source: Positive lead to waste electrode, negative lead to rusty part.
For electrolyte, sodium carbonate (a.k.a. washing soda or pool pH increasing stuff) works. Sodium hydroxide (Lye) may add a bit of oomph. Baking soda or TSP might also work. About 1 tablespoon sodium carbonate per gallon of water should suffice to allow the electrons to move (that’s about 1 cup – a big handful – per 15 gallons).
For a sacrificial electrode, one suggestion is to look for iron pots, pans or cookie sheets at your local thrift store if you don’t have any scrap around.
You should also use gloves to protect your hands from the electrolyte. 3M non-metallic gray finishing pad part number 10144NA (usually found in paint departments) is suggested as a good cleanup after the rust is converted back to iron. A small toothbrush sized wire brush can also be useful. You’ll also need something to protect the iron after de-rusting. Table saw types like Johnson’s wax; WD-40 but that may not be nice to paint and japanning; Kit brand car wax and Tri-flo penetrating oil are recommended by some; check the web for options and preferences to see what best suits your style.
Resources:
http://www.oldengine.org/members/orrin/rustdemo.htm
http://www.frets.com/HomeShopTech/QuickTricks/
http://www.rickswoodshopcreations.com/
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