Electrochemistry Reverse electroplating

[Adam Dilem]

Hi everyone,
I am a new member here and for some reason I can't find the option to be able to start a new thread. This thread seams to be the closest to my specific case of interrest. So if anyone can help me out, here is my question:

I have about 80lbs of copper pins heavily plated with silver (4% silver content according to an assay done to them). I have attached pics of the pins.

Since the pins are much thinner than kitchenware (1.5 mm thick, 3mm wide 30mm long) I am tempted to try this methode of reverse electroplating using 95% sulphuric + 5% Nitric. However Since they are thin I am worried I end up saturating the electrolyte (sollution) with copper and that will defeat the purpose. But I am speaking from no experience, so this is more of a question than anything else.

If this process will work what are the optimum acid concentrations?, Amps and volts? Set up, material Ect?

If there is a link to a video or a detailed similar process that would be much appreciated too.

Many thanks in advance for any help.

 

[4metals]

Welcome to the forum Adam.

To start a new thread select new topic in the section you want to post in. Once you are in an existing thread the option does not appear for anything other than a reply to the thread you are in.

I don't hold out a lot of hope you will selectively strip the silver off copper with acids which will both dissolve silver and copper. I would be thinking dilute cyanide. This will also take off both silver and copper but a timed immersion can limit the effect on the copper. It will take some perfecting to get it right. Do you have a lot of these things?

 

[UncleBenBen]

I think if it were my scrap, I would look into a deal with scrapman1077.

His thread can be seen here...
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=58&t=14782

 

[nickvc]

Welcome to the forum.
The truth is that if your assay is correct you have around 1.5 kilos of silver but the problem is that it's plated over copper which reacts to all the chemicals that silver does, if you have more higher grade silver to process then melting the pins and using the bars to cement that silver out is your best and cheapest way to recover the silver from the pins.
Failing that you could set up a copper cell again using the melted pins as feed stock, if the only other metal there is copper it should work fairly well and would be a relatively cheap method if you have a decent rectifier.
The only other option I can think of is list them on eBay in kilo lots and see if you can get a decent price.

 

[goldsilverpro]

The 95/5, H2SO4/HNO3 method is not a reverse electroplating process. It is an immersion process that is usually run hot at 180F. This makes it extremely dangerous. It was developed as a method to strip faulty silver plating on copper so it could be re-plated. It will not dissolve copper unless it is diluted. Dilution can occur simply by it sitting around and absorbing water from the air. Of course, running it hot will tend to evaporate any of the water that has been absorbed. Reclaiming the silver from this solution is not that simple. It can, in itself, be dangerous and requires some experience.

Probably, silver plated copper scrap is one of the most difficult and least profitable types of scrap there is. I know of no refinery that will accept it. Essentially, it is copper contaminated with silver.

What assay method was used? If fire assay was used, the results are reliable. If XRF (x-ray) was used, the results are meaningless and worthless.

 

[4metals]

Probably, silver plated copper scrap is one of the most difficult and least profitable types of scrap there is. I know of no refinery that will accept it. Essentially, it is copper contaminated with silver.

Interesting way to describe silver plated scrap.

The hot sulfuric should scare off any rational back yard hobbyist refiner, let alone the exacting analysis and additions to extract out the silver.

There are a few proprietary silver strips on the market and I do remember an iodine based strip method which all operate at more reasonable temperatures. But they still require you to jump through hoops to get your silver back out of the strip.

 

[goldsilverpro]

I think that Technic sells an electrolytic silver over copper stripper but, here again, it's designed to remove faulty plating. Silver recovery may be difficult.

I once developed an anodic electrolytic stripper for silver on copper. It contained 30-45g/l of sodium cyanide and 150g/l of sodium hydroxide. It ran about 4V at room temp. using a stainless sheet cathode(s). The silver dissolved and plated out simultaneously on the stainless cathode(s). The solution could be analyzed, chemically brought up to snuff, and re-used. The high NaOH somehow prevented the copper from dissolving. For small things like pins, a tumbler is required (a barrel plater is best). For large items like flatware, plating racks are the best way to go. If I had a large ongoing supply of silver plated objects, this is the way I would go.

 

[4metals]

I used a cyanide peroxide bombing solution to strip gold and silver off plated parts. The values were simply recovered using zinc. This technique requires good ventilation and caution because it can boil over violently if you are not careful. But once you are used to it and know what to look for it can be used effectively. Again the solution was to remove the plating and preserve the base material so it could be re-plated, so these pins would produce a silver cyanide solution with very little effect on the underplate or base metal.