electrolyte for reverse electroplating

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K

Klunch

New member
Joined
Aug 29, 2022
Messages
4
Location
Germany
Hi there,

I'va got a big pile of mixed different gold plated pins/connectors etc. and after studying different methods it seems to me that stripping in a sulfuric cell would be the best method to deplate the material in order to extract the gold. The only thing is, I personally don't like it to deal with sulfuric acid. Is there any electrolyte that may be used to deplate pins?

I tried to use a concentrated NaCl-Solution and ended up with low yield and lots of yellow/orange mud, probably iron-salts.

An other method is it to soak all the material in HCL solution, let it stay for some time (few days), rince and let it dry. All the material gets covered by a thick layer of copper salts. Then again soak in HCL (the same solution from before may be used several times). Repeat this process until almost all gold came off. It works, BUT it takes very long time and assilver is present in some of the pins, it forms silver chloride. Not the best method, but more efficient in regard of the yield in ratio to acid consumption. Very inefficient in regard of time.

Dissolving all the pins in AP solution takes huge amounts of acid and produces too much waste for little gold.

So I'am coming back to my original question, is there any other electrolyte than sulfuric acid to reverse electroplate the mixed pins?
 
Klunch said:
Hi there,

I'va got a big pile of mixed different gold plated pins/connectors etc. and after studying different methods it seems to me that stripping in a sulfuric cell would be the best method to deplate the material in order to extract the gold. The only thing is, I personally don't like it to deal with sulfuric acid. Is there any electrolyte that may be used to deplate pins?

I tried to use a concentrated NaCl-Solution and ended up with low yield and lots of yellow/orange mud, probably iron-salts.

An other method is it to soak all the material in HCL solution, let it stay for some time (few days), rince and let it dry. All the material gets covered by a thick layer of copper salts. Then again soak in HCL (the same solution from before may be used several times). Repeat this process until almost all gold came off. It works, BUT it takes very long time and assilver is present in some of the pins, it forms silver chloride. Not the best method, but more efficient in regard of the yield in ratio to acid consumption. Very inefficient in regard of time.

Dissolving all the pins in AP solution takes huge amounts of acid and produces too much waste for little gold.

So I'am coming back to my original question, is there any other electrolyte than sulfuric acid to reverse electroplate the mixed pins?
Click to expand...
Can you get or make potassium nitrate ?
 
Klunch said:
Hi there,

I'va got a big pile of mixed different gold plated pins/connectors etc. and after studying different methods it seems to me that stripping in a sulfuric cell would be the best method to deplate the material in order to extract the gold. The only thing is, I personally don't like it to deal with sulfuric acid. Is there any electrolyte that may be used to deplate pins?

I tried to use a concentrated NaCl-Solution and ended up with low yield and lots of yellow/orange mud, probably iron-salts.

An other method is it to soak all the material in HCL solution, let it stay for some time (few days), rince and let it dry. All the material gets covered by a thick layer of copper salts. Then again soak in HCL (the same solution from before may be used several times). Repeat this process until almost all gold came off. It works, BUT it takes very long time and assilver is present in some of the pins, it forms silver chloride. Not the best method, but more efficient in regard of the yield in ratio to acid consumption. Very inefficient in regard of time.

Dissolving all the pins in AP solution takes huge amounts of acid and produces too much waste for little gold.

So I'am coming back to my original question, is there any other electrolyte than sulfuric acid to reverse electroplate the mixed pins?
Click to expand...
I also love electrolysis, but i don't know of any other good option to strip gold from a copper, brass or stainless steel base.
If it's only copper and brass:
Melt it all together and run it in a copper sulfate cel. You will be left with pure copper and an anode bag full of goodies to refine.
gold on stainless: See what a nitric bath does.

The slow HCl option you mentioned is actually CuCl2, add air and lots of time, the copper will dissolve.
Those copper salts you see CuCl1 are the degrading product of the actual copper salts CuCl2 dissolving metal copper.
 
Martijn said:
I also love electrolysis, but i don't know of any other good option to strip gold from a copper, brass or stainless steel base.
If it's only copper and brass:
Melt it all together and run it in a copper sulfate cel. You will be left with pure copper and an anode bag full of goodies to refine.
gold on stainless: See what a nitric bath does.

The slow HCl option you mentioned is actually CuCl2, add air and lots of time, the copper will dissolve.
Those copper salts you see CuCl1 are the degrading product of the actual copper salts CuCl2 dissolving metal copper.
Click to expand...
Often the pins have underneath the gold plating a mix of different other thin metal layers and when there is some nickel on it, they react on a magnet. So it'snot that easy to determine, whether it's steel or copper/brass with some nickel. But the idea on melting a part of it may be a good one. The steel pins will not melt and can be removed with the slag on melting. After removing the non molten steel pins it should remain some brass alloy. It's worth a try in a copper sulfate cell. Thx!
 
Klunch said:
Often the pins have underneath the gold plating a mix of different other thin metal layers and when there is some nickel on it, they react on a magnet. So it'snot that easy to determine, whether it's steel or copper/brass with some nickel. But the idea on melting a part of it may be a good one. The steel pins will not melt and can be removed with the slag on melting. After removing the non molten steel pins it should remain some brass alloy. It's worth a try in a copper sulfate cell. Thx!
Click to expand...
If you melt it, it will become an alloy and you can not easily separate anything.
Melt it into an ingot and run it through an electrolytic cell as Martijn suggested.
 
Klunch said:
Unfortunately, I don't have access to nitric.
Click to expand...

Evaporate the automotive electrolyte to at least 75% sulfuric acid,
further KNO3 + H2SO4(conc.) = HNO3↑ + KHSO4, then distillation (in a round bottom flask only!) under vacuum through a Liebig refrigerator. You will receive WFNA 70-75% depending on conditions.

The reaction is relatively dangerous but simple.
The strength of the resulting WFNA acid depends on the concentration of sulfuric acid.

But if you don't have enough qualification in basic chemistry, it's better not to do it.
 
"Poor man's nitric acid" will contain impurities of sodium chloride, which will interfere with reduction.
As a last resort, of course applicable.
 
Shark, thanks for posting this video !!

Although I do have the chemicals on hand to make poor man's nitric I have only used tech grade acids and have always kept nitrate salts on hand just in case I run out of tech grade.

Just curious if it is possible to add hydrochloric acid once the base metals dissolve to make a dirty Aqua Regia to dissolve the gold and then drop with SMB ?
Or maybe filter out the gold and use the poor man's nitric along with hydrochloric acid the same way you would do it with tech grade by adding the homemade nitric into your hydrochloric acid a little at a time until the gold dissolves ?
 
Old member named catfish had a formula for gold filled and pins years ago, I can’t recall right off hand the quantities, but he ran them in Poormans AR. Something like a gallon of HCl, a pound of sodium nitrate and a bucket heater in a five gallon bucket for extra headspace. This would do about a pound of pins or gold filled if I remember right. His post may still be available on the forum and would be worth looking into even if just for historical references.
 
Last edited:
Ultrax said:
"Poor man's nitric acid" will contain impurities of sodium chloride, which will interfere with reduction.
As a last resort, of course applicable.
Click to expand...
Yes and the left over salts can be a pain at times to deal with. Geo mentions it in the video, but many viewers seem to miss that detail. For those who want to try it I suggest watching his video several times and pay attention to the smallest of details.


Personally, per the OP, I would bite the bullet and build a sulfuric cell.
 
Look on forum for ferrocyanide leach, iodine/iodide leach or thiourea cell. Dissolving bigger contacts make no sense. I did some experiments and while it was small scale I am sure it can be scaled up a bit.



 

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