I've done a lot of electrolysis. It's relatively foolproof... even if you don't optimize everything it'll still work, just a little more slowly. About the only thing that can go horribly wrong is if you reverse the polarity.
Here's what works for me:
- Degrease your item thoroughly. It's a good idea to get rid of whatever loose rust is on there. A stiff scrub brush works well.
- Get a large rubbermaid container that'll hold whatever you're de-rusting.
- Get some Arm and Hammer Super Washing Soda.
- Add about 1/2 cup per gallon. Too much is OK since it'll just precipitate out. Too little will cause your reaction to proceed more slowly.
- Find some electrodes. There are lots of choices here.
The best thing to use is carbon graphite rods (available at welding supply places or eBay). They last a really long time and don't cause the solution to sludge up. They also don't collect rust, so if you're doing a large or very rusty part, you can leave them going for days.
Steel plates work well but you need to stop every 4-5 hours and scrape the rust off of them. Rebar works in a pinch but it crusts up fast.
DO NOT USE STAINLESS STEEL. While it's tempting because it lasts a long time and stays clean, it precipitates
hexavalent chromium which is a very nasty carcinogen.
Expanded steel mesh is a good choice since you can mold it to the shape and keeping the electrodes close to (but never touching) the item does speed things along.
Submerge your item (I don't like it to sit on the bottom since rust and gunk will accumulate... I have a couple of fire bricks I put in the bottom of the tank)
Now just run some wires and hook the positive lead to your sacrificial electrode(s) and the negative to your piece. If you mix this up, you'll end up with a pile of rust instead of an Anvil Vise.
For power, older battery chargers work great. 6 or 12 volts. Newer ones tend to have circuitry that'll shut them down when they decide that your 'battery' isn't charging. Old PC Power supplies work well too. Good instructions are found
here.
Higher voltage power supplies can be used, but I'd avoid anything higher than 24v for safety reasons. You'll also end up wasting energy heating your electrolyte and you might actually boil it if you use too much juice.
For something large and rusty, I usually go 4-5 hours, then pull it out, clean it up with a scrub brush and some water, then dunk it back in for another 3-4 hours before checking it. Electrolysis is somewhat line of sight, so you might want to turn it over a few times.
It can get a little messy, but it's by far the safest and least labor intensive way to remove rust... there's a good reason that it's the method of choice for restoring historical metal artifacts.
I just fired up the barbie to help pass the time.
