I was thinking of making a video to demonstrate the near-magical process of electrolytic de-rusting that I mention in this column, but I don't need to, because someone already has:
Everything you need to know is in the video.
Note that it's fine to immerse an alligator clip holding onto the part to be de-rusted, but the clip attached to the sacrificial positive-terminal steel must not be immersed, or you'll sacrifice the clip too.
Note also that even a strong sodium bicarbonate solution won't hurt your skin - well, not quickly, anyway.
Commercial electrolytic derusting is often done in a sodium hydroxide bath, which will (a) turn you into soap if it gets a chance and (b) produce some really choice fumes.
9 December 2006 at 4:19 am
Presumably, though, one should be a bit careful with electrolyte-soaked hands and 12 volts - at the least you could get a nasty burn.
9 December 2006 at 5:25 am
No, not really. If you held both clips in one wet hand it might be a bit uncomfortable, but if the electricity can pass through the electrolyte on top of the skin rather than through the flesh underneath it, then much of it will.
If you really, really try (like, with probes stabbed into either side of your chest) then you can kill yourself with 12V, but getting enough current flow through your flesh to get a burn is pretty much impossible (maybe if the probes are stabbed in right next to each other on one hand...), and realistically there's no chance of any kind of electrical injury.
I'm sure some specially talented individual somewhere has managed it, but I'd be much more worried about the electrolyte splashing all over the mains-connected $8.99 Chinese battery charger :-).
(You could burn yourself if you shorted out the charger through something that then got hot; plenty of people have scars from car electrical adventures of this sort, and a heavy duty car battery charger can deliver enough current to smoke some wire too. That's not what most people mean when they say "electrical burn", though.)
9 December 2006 at 9:48 am
I work in a phone company central office and the main power plant is 48VDC. It's hard to get a tingle out of that. A sweaty arm across a buss bar and a good ground might do it. This is mind-boggling to anyone that isn't familiar with Ohm's law when they see an apartment-sized room filled with a hundred or more storage cells (batteries) weighing about 600 lbs apiece. They freak out when I reach up and grab onto a 6-inch square copper buss bar that's flowing many thousands of amps.
Interesting thing about that video... Why go through all the trouble of de-rusting it when he goes over it with a wire brush anyway? He could have saved the trouble and mess by just using a grinder with a wire brush to take off the rust in one go. Granted, it'll never get into the corners in the way reverse-plating can but on a fairly flat piece of bracketry you don't have to worry about it.
9 December 2006 at 11:02 am
I think a brush would leave a lot of rust in the pits, unless you brushed away a lot of `good' metal. Rust goes into the metal, remember?
9 December 2006 at 7:42 pm
So what would be a good choice for the sacrificial rod? Something common and cheap, one would hope. I'm seeing possiblities here. Help me out.
dio
9 December 2006 at 8:29 pm
Any old piece of scrap non-stainless steel or iron will do for the sacrificial piece. Old "tin" cans are fine.
And yes, you can clean rust off a flat surface faster with a wire wheel than electrolytically. But electrolytic de-rusting does indeed work in crevices and crannies; surprisingly often, it can turn a rusted lump back into a working tool. If the rust bugs have eaten something important then this obviously isn't going to happen, but it's surprising how often they haven't.