Decided to do some electrorefining. I have some assorted copper on my shelf, ranging from pure pipe and wire, to pipe joints (tin and silver soldered), copper alloys, brasses and bronzes. I decided I want to clean up some of this, and decided to do it electrochemically. So I melted an ingot, about five pounds worth, broke it into sections and got to work. For the bath, I gathered all the copper sulfate I have, dumped it into solution, added a few hundred ml sulfuric acid and some Tarn-X (which contains thiourea, a levelling agent, for which without, the deposit ends up in dendritic crystals and useless sponge). I used a pure copper plate for the cathode, connected to the supply (about 6VDC) with a 1 ohm power resistor, limiting current to about 5A.
The deposit has been growing in an ugly pattern (or is it beautiful?), probably because of the uneven surface. As the anodes corrode away, they leave a precipitate of what I'm guessing is copper and some silver. More reactive metals, like tin and zinc, dissolve in solution. Incidentially, because I started with an impure solution, there was a high concentration of chloride. I've read you should have a little chloride in the bath, but any at all is quickly removed as a white deposit of CuCl on the anodes. After about a week, all the chloride had dropped out as sludge, which I collected and reacted with base, precipitating the rusty-colored Cu2O, amidst the other sludge that comes with. The other problem is, the sludge is of course conductive, and it settles on the bottom, and the cathode rests on the bottom. So even cleaning out the bath periodically, I get "tracks" of copper and sludge melted into the plastic tub, where the current was shorted out. Bah.