# Advice needed for removing gold from copper



## Kieran93 (Mar 30, 2017)

I am looking for expert advice on how to remove the gold layer from the copper base. 

As a complete novice I will require any advice on extracting the gold layer. The top layer peels off which reveals a bottom film which I believe will need extracted via a chemical process.


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## Kieran93 (Mar 30, 2017)

I should add I have a large quantity of these that I need to separate, so I am very interested in this forum's advice


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## anachronism (Mar 30, 2017)

Hey Kieran

What's a large quantity please? That will make a difference to the advice mate.

Jon

Edit for spelling.


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## Kieran93 (Mar 30, 2017)

I have 200+ of the pieces illustrated in the photo

Thanks


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## Kieran93 (Mar 30, 2017)

Also I have had a sample tested locally and its confirmed to be either 22 or 24 karat


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## anachronism (Mar 30, 2017)

The plating usually is that high Kieran it's more a case of how much plating is on there. It certainly doesn't look thin from your pics. 

It's pretty straightforward to do it but I'd recommend a cyanide based leach in one form or another over messing around with huge quantities of acid.

On the one hand you've got a leach removing the gold and leaving the base metals- on the other hand you're dissolving all the base metals out and leaving the foils which then need processing separately. 

Jon

Edit final question - how wide are these things?


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## Kieran93 (Mar 30, 2017)

Thanks for the advice, it is very much appreciated. OK that is interesting, I will do some research into cyanide based leach and techniques to use it. 

They are each 25mm diameter and each one weighs 0.4 grams.


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## g_axelsson (Mar 30, 2017)

0.4g... is it hollow or was that the weight of the gold? If it is the weight of the base metal then I would suggest using nitric acid and just dissolve the base metal. (200x0.4g = 80g, 80 g copper can be dissolved in circa 200-250 ml nitric acid)

If they are high in base metals then a sulfuric reverse plating cell could be an alternative. That would dissolve the gold without touching the base metal. A simple rack to hold several disks during the deplating could easily be designed from some thicker copper wires.
Concentrated sulfuric isn't the nicest thing to use but cyanide have it's dangers too and you need to know how to handle it to keep safe. Treatment of waste is another thing that is easier with the sulfuric cell.

I'm curious, what was the application it came from? Thick gold film that sits loosely attached to a base metal puck reminds me of sputtering targets, but I can't see any erosion of the surface.

Göran


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## Kieran93 (Mar 30, 2017)

0.4g is the weight of just one gold plate once removed but there is another thin film underneath that I can't peel away from the copper. The gold plating is thick. 

They are from a type of transformer that I think is called a rectiformer of copper construction. I have over a tonne of rectiformers so I need to find the most efficient way of removing the gold


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## anachronism (Mar 30, 2017)

Goran

If these are solid copper then dissolving is just madness old friend.


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## snoman701 (Mar 30, 2017)

Use a lathe. Single facing operation. Send chips to a toll refiner.


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## Kieran93 (Mar 30, 2017)

I would rather not use a lathe there is too many and I would like to keep it all in-house without having to use any third parties

Thanks


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## g_axelsson (Mar 30, 2017)

anachronism said:


> Goran
> 
> If these are solid copper then dissolving is just madness old friend.


I agree, nitric isn't an alternative if it was solid, but his description was :


Kieran93 said:


> They are each 25mm diameter and each one weighs 0.4 grams.


And that is a bit ambiguous in my book. I wrote that if the 0.4g was the base metal then nitric was a viable alternative.

What I meant was that if they were massive then a sulfuric cell would be a good alternative to cyanide, nitric is not an alternative.

Kieran, thanks for sharing where the disks came from.  

Göran


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## snoman701 (Mar 30, 2017)

Hah...I just assume everyone has a lathe. 


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## anachronism (Mar 30, 2017)

Yeah it's ambiguous on multiple levels Goran especially when I read it as 4g each!! :roll: :roll:


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## snoman701 (Mar 30, 2017)

So sulfuric cell is a viable option correct? I have similar product that I need to do this weekend. If cell won't work I will have to use mechanical means.

Mine has a good thickness nickel plate, which I know can cause problems with sulfuric cell, but also know is regularly found as a base layer anyway.


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## snoman701 (Mar 30, 2017)

You know, I think it's better for me to mill the surface clean and save the chips. I really really don't want to set up a sulfuric cell yet. 


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## donald7755 (Mar 31, 2017)

2 questions ( just because i'm curious ) .

what's a rectiformer ? 

i know he said some type of transformer , but what exactly is the name of this part called ?

thanks


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## g_axelsson (Apr 1, 2017)

I had to look it up, a rectiformer is a transformer with a built in rectifier. By making it in a single package you avoid a lot of external cabling with losses and stray magnetic fields. It seems they are more or less custom built on demand depending on the application. Typical applications can be copper refinery for the electrolytic tanks, aluminium smelters... and so on. These things can be huge.

I'm still curious to what particular purpose a thick gold foil was used, maybe somewhere in the rectifier circuits. I don't think they would use it in modern equipment but if I ever see a large transformer at the scrap yard I will take a closer look at it.  

Göran


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## anachronism (Apr 1, 2017)

I'd get the base metal xrfed - if you can't do it there drop me a pm and I'll send you my address and you can send one piece down. 

Jon


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