In electroplating, they put the source metal in titanium baskets. Electrical current dissolves that metal (but not the titanium, I expect) into the solution and plates it onto the target. My question is - how does the titanium transfer current to the source metal without dissolving itself? I’m guessing the exposed titanium passivates itself though an oxide coating (much like aluminium), but if the oxide coating is insulating enough to prevent corrosion, won’t it also prevent conduction to the source metal? Or do they scrape the titanium after each batch, or move the source metal around so it scratches off the oxide?
I mean, if titanium is able to conduct electricity without corroding, why don’t we use it as counter-electrodes?
I’m not sure why you think the metal has to dissolve to conduct electricity; such is not the case.
In any event, titanium is actually pretty easy to oxidize, more so than your plating metals generally, which you would think would rule it out as an inert material. But, yes, the metal forms a tightly-adhering passivating oxide coat which makes any macroscopic object made of Ti very resistant to oxidation. Certainly the oxide coat adds a little bit to the electrical resistance of the basket, but not enough to matter, because it’s very, very thin. One way to rationalize the distinction is to realize that electrons can burrow through a very thin oxide layer a lot easier than Ti+2 or Ti+4 cations could.
So basically when electroplating (nickel, copper, maybe silver and gold) you are making the dissolved metal (e.g. nickel) deposit on your product. To replenish this dissolved metal you have to make an equal amount of nickel dissolve. This is easily done with an electrical current. So they put lumps of nickel in titanium baskets; the baskets both physically support the nickel and conduct electricity.
I think this might be it. But then why can’t we use titanium as counter electrodes? What happens if I leave the anode basket empty? I’d think people would much prefer to use titanium over gold or platinum.
Due to applied or inherent potential difference, electrons come off of metal A and travel through the wire to metal B. As metal A loses electrons, A cations are released into solution. They migrate through solution to metal B, where they receive electrons and plate onto the surface.
AaronX, IIRC the titanium baskets aren’t really electrodes. The metal lump is the electrode. The Ti basket just is a conductive holder that exposes as much surface of the metal to the electrolyte.
Well its not too complex - the entry point is to consider thus:
Fire engines are red because they have four wheels and eight ladders, four and eight makes twelve, there’s twelve inches in a ruler, Queen Elizabeth was a ruler, Queen Elizabeth was a ship, ships sail the seas, fish live in the sea, fish have fins, the Finns fought the Russians in the war, and that’s why fire engines are red ‘cause they’re rushin’ all over the place.
Yeah, I think that would work, since there are soluble silver salts. May not work for gold, though, I think it only dissolves in aqua regia. The urn has to have an electrically conductive surface, though.