Electrolysis FAIL

[SteveHGraham]

I had my first disappointing experience with electrolysis recently, and I'm not referring to removing the hair from my back. I had a 3-lb. sledge that was a freebie, and I decided to try to get the thick coating of rust off of it. I ended up with a hammer which is partly grey and partly black.

I learned a few things during the process. Maybe they will help other people.

First of all, the anode (positive) apparently has to have a pretty decent amount of bare iron exposed. I had problems with the electrolysis slowing down, and it seemed to speed up considerably when I applied a knot wheel to the anode. It seemed like the process kept slowing down as the anode rusted. Maybe wet rust doesn't conduct? I do not know. Dry rust will kill a connection, but I would have thought rust soaking in an electrolyte solution would be okay.

Another problem: I ended up with two new coatings to replace the rust. One was new, porous iron. I don't know why this happened, but sometimes with electrolysis, the rust right up against the metal turns into pure iron. The other unwanted coating is Fe3O4, or magnetite. It's black, and it seems like it wants to stay on the hammer. I read that it dissolves slowly in HCl, but I haven't tried it yet.

Some people claim the black stuff is sodium carbonate, but it looks like that is not true. Maybe someone here is a chemist and could comment on it.

The biggest disappointment was getting most of the thick rust off and finding "CHINA" stamped into the hammer! But it was free, so I guess things could be worse.

I let this thing sit for two whole days, and now I have a nasty-looking black and grey Chinese hammer to show for my effort. All the other things I de-rusted came out great.

[ctwo]

I've seen various rust removing solutions on cast iron cause deep pores to be exposed. Well, that's just because the rust has been dissolved out of them. One of the older bottle of rust stripper I have has either HCL acid in it and that leaves a true bare metal finish. (and using that stuff in the shop leads to everything else getting rusty from the vapor)

[SteveM]

I have heard that there are carbon electrodes used in welding that can be used as the anode, and those reduce the blackening and flash rusting. Have not tried it yet.

Steve