Gold plated copper blocks: best approach?

Trying to find the best approach to refine a bunch of gold plated copper blocks. Here’s what I’ve done so far:

Mechanically scraped the plating that was loose. I’m guessing that accounted for 1% of the gold in the whole batch. Melted with borax and that yielded a 0.89g button (flattened in photo). This gave me reason to think it’s worth perusing further.

Put a sample of blocks in 30% HCl solution with some 3% H2O2 and heated up. The acid attacked the copper however did not make the gold peel. Unlike “fingers”, these have a lot more copper and the acid is more interested in going down into the copper than sideways and peeling the gold off.

Thinking about next logical step.... electrolysis? Hydrochloric with Chlorine? Sell on a Ebay? Send to a refiner?

Much appreciate the help and advice here!
Alex

I’d try a very weak, 5% nitric soak with a few days to allow it to work which should loosen the plated gold so it flakes off.

That was already answered. Make it anodic vs. Lead or stainless steel cathode in a concentrated sulfuric acid bath, voltage above 7v

Ahh a stripping cell:

https://youtu.be/WgprlL-wmCk

That sounds like a good way to go.... might have to give this a try.

Yes, that is the way to go, it works like magic the first time you try it.

Just take care, don't run it so hard the acid heats up, it will stop working then. Also keep it capped whenever not in use, concentrated sulfuric acid sucks moisture from the air and when the acid is diluted down to 90% the cell starts to eat base metal instead of gold.

Most important is to think ahead about personal safety a well as the fine mist of acid coming off of the bath when you use it. Plan ahead for an accident to happen. What happens when you drop a piece of metal into the bath. If you use a glass container, what will catch the acid when it breaks... and so on. Keep it well away from any kids or animals.

Good luck and may your scrap contain lots of gold.

Göran

Make sure they are all Cu parts. If they are Al they will react to the acid.



Eric

I have seen both stainless and aluminum base metal in the parts similar to what you are showing.