Help with reverse electro plating

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skullsbox01 said:
I friend, i have one question on the process:

After having stripped the gold with the cell, can i recovery gold from sludge, filtering the soltuion and whashing the powder?

Thanks :)
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your gold will actually be the "sludge" precipitate in the cell. citing Hoke on this, the "sludge" should be referred to as "slimes" or "cell slimes". the gold can not stay in solution in the stripping cell environment. from what i understand (if im wrong, someone will correct me) persulfate is formed in the immediate vicinity of the anode dissolving the gold. the gold ions get carried with the current flowing to the cathode. as the gold ions leave the area where the persulfate is being formed, they precipitate out as metallic gold. this precipitate can be very fine and can float for days before settling.

i would like to edit this. im changing the "perchlorate" to "persulfate". sorry about that
 
Geo,
You got it right as far as I know.
Might also want to mention the gold that re-forms in the Sulfuric acid will be black and look like soot, but that is the gold.
Good catch on the missed name
 
I recently did some experimentation with reverse plating on a small gold plated baby spoon onto a stainless steel 5/8 round. I used a commercial gold stripper that is noncynanide. It seemed to strip the spoon quickly, I had my power 1.5- 2.5 volts but what showed up on my stainless was a black residue coating. I did not see a gold 24 K color which was on the spoon. Also my stainless is not a super high grade it that matters or not. Is that residue the gold?
Please set me straight! thanx!
 
The commercial stripper is proprietary and the ingredients are a mystery. It might help if you would post a copy of the operating instructions.
 
hiscomm said:
I recently did some experimentation with reverse plating on a small gold plated baby spoon onto a stainless steel 5/8 round. I used a commercial gold stripper that is noncynanide. It seemed to strip the spoon quickly, I had my power 1.5- 2.5 volts but what showed up on my stainless was a black residue coating. I did not see a gold 24 K color which was on the spoon. Also my stainless is not a super high grade if that matters or not. Is that residue the gold?
Please set me straight! thanx!
Click to expand...


Temperature 120-150ºF (49E - 65E C)
Current Density Reverse plate at 3-6 Volts (30-100 ASF)
PH 4-4 2
Beaker Pyrex
Anodes Stainless Steel
Bath Set Up:
1. Fill beaker with Strip-Free™ and heat to 140EF.
2. Check connections from rectifier to anode and work to be sure they are
reversed. Negative (-) and positive (+) wires are connected properly.
The work should be charged positive (+) , and the anode negative (-).
Turn rectifier on.
3. Reverse Plate for 30-90 seconds at 3-6 volts depending on size of part
and thickness of gold which is being stripped.
4. Larger parts require slightly higher voltage, while smaller parts
require lower voltage. If part shows any burning such as dark grey or
rough deposits around the edges, you are burning the part and must
lower the voltage. If part is not stripped after 3- 5 minutes of
stripping, voltage it too low, there increase voltage slightly.
5. After stripping rinse part thoroughly in water and either dry or
replate. If replating: Dip part in Activator-T for 2 minutes, rinse, plate
a mirror finish, rinse, then continue plating process with a Decorative
finish such as gold or silver.
Trouble Shooting:
Pieces not Plating
Plated layer under gold is black or
grey
or
Pieces turn hazy, cloudy, and too
dull
$ Check power supply, make sure
switch is on.
$ If switch is on, check fuse.
$ Check connections from power
supply to anode and part.
$ Voltage too low
$ Anode/ Cathode connections are
reversed to plate not strip.
$ Voltage is too high.
$ Excessive stripping time
 
Geo said:
brand new battery acid needs to be evaporated roughly two thirds of its volume to be concentrated. the battery acid i get is about 25%? maybe, ill have to check the box. battery acid is simply diluted sulfuric acid. if you were using the acid straight from the box, you were using diuted sulfuric.
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Geo is right, battery acid is diluted sulfuric acid. Also, you are going to pay a lot more for it and at least in the State of California, you have to give personal information when you purchase it.

I would try to look for a different source for your sulfuric acid, and make sure it's 95% or better, preferably 98%.

The reason your sulfuric stripping cell doesn't work when you have lower concentrations of sulfuric acid is because it cannot produce persulphuric acid when the electricity is applied. Sulfuric acid doesn't dissolve gold, it's the creation of persulphuric acid at the cathode that dissolves/deplates the gold from the material, and as it changes back to sulfuric acid, then drops the gold out of solution as black sand. But in order to create persulphuric acid, you need to start with a concentrated solution of sulfuric acid.

Scott
 
NobleMetalWorks said:
it's the creation of persulphuric acid at the cathode that dissolves/deplates the gold from the material
Click to expand...

this should be anode, otherwise, nice explanation.
 
As per my last post, I reverse plated a gold 24K spoon on to a 5/8 stainless steel round. The spoon was stripped and the stainless area that was in solution had a black soot looking appearance built up on it. I assume that is gold. If so what is the best way to get it off the round?
 
the black "soot" is the gold. it should not be adhered to the stainless too tightly to just rinse off. you might use a a soft brush and gently brush it under water to remove the powder. im accustomed to the sulfuric stripping cell and have never used what you describe but from your description, im sure it didnt redeposit on the stainless steel tightly.
 
Geo said:
the black "soot" is the gold. it should not be adhered to the stainless too tightly to just rinse off. you might use a a soft brush and gently brush it under water to remove the powder. im accustomed to the sulfuric stripping cell and have never used what you describe but from your description, im sure it didnt redeposit on the stainless steel tightly.
Click to expand...


Thanx Geo, my theory was to transfer on to stainless, which I thought would replate in the form of gold plate and since I wasn't interested in an actual plate finish, but to just scrape off and when I got enough, melt it into a transferable form. I'm wondering if I can build onto what I have started on the stainless and when builds up more scrape it off, I have other pieces that can be stripped?
 
I have question about reverse electroplating:

- how about popular stainless steel (grade 316, or other available in mesh form) as material for anode?

I have already 1dm3 of 98% Analytic grade H2SO4 on shelf, and a lot of 300 or 400 stainless mesh (and other sizes). I don't want to contaminate my acid with other metals. From pdf on links it's look like that any kind of stainless steel should be apropriate for this job. Its look like even it wold be superior than copper mesh.

Anyone try it? If i don't find answer I will try it, because I have too much plated items to fully dissolving in HNO3, some of them are partially stripped, some of them not. Cyanade leaching looks interesting, but without proper safety setup, I'm not looking this way.

Of course I will submit photos later

References:

http://www.parrinst.com/wp-content/...1/07/Parr_Stainless-Steels-Corrosion-Info.pdf

http://stainless-steel-world.net/pdf/sswsup1005_duplex_rolledalloys.pdf
 
I some time's use an Ammonium and sodium Chloride electrolyte in my stripping cell. U.S. Patent 4895626
It works very much like sulphuric acid but is much easier to handle have never used it with pins only to take off gold plating from flat ware and bangles.
 
Here's what the patent states: "This invention relates to the refining and purification of karat gold to 98% purity." Even though it may dissolve the impurities in karat gold leaving the mostly pure gold, I dont see this working for electronic scrap. For one thing, it dissolves the impurities while leaving the pure gold undissolved in the anode bag. Stripping is the opposite of that where the gold is dissolved and base metal stays intact. As for the second thing, it doesn't self precipitate the base metal as a true stripping cell self precipitates the gold. The base metals stay locked in the ammonia solution. Pins yielding as little as 0.01% or even as high as 0.1% would be impossible to process this way due to chemical cost. Header pins may yield 2g per pound. How much solution would you need to process 15-16 pounds of pins?
 
I have not used the Ammonium chloride for pins but if you hang a plated item like a large bangle in it it parts the plate very nicely.
I have tried it with 375 gold but I found the process messy and i could not be sure that I had not lost any fine gold.
Thick Plate comes off in nice flakes and I take the pice out as soon as it has been cleaned, so i though I would suggest it as the chloride's are pennies and are reasonably safe unlike sulphuric acid which is pounds and very hazardous
I like your method of letting pins rust which is what I will try my self next time.
 
Anyone that reads patents should bear in mind that there is no requirement that the process should work. This patent is from our well known Peter Shor.

There is at least one wrong statements in that patent and it just shows how much of an expert Peter is.
Peter Shor about the electrolytic gold cell used in mints said:
The gold deposited is "mint" grade, 98.5% purity.
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And as an example he talks about refining 14k gold...
The powdered gold was washed from the anode bag and assayed. It was found to be 98.7 to 99.3% gold. The impurities in this refined gold were 0.3 to 1.0% silver, 0.1 to 0.2% silicon and copper and less than 0.005% each of platinum, boron, palladium, manganese, tin, nickel, bismuth and chromium. Thus the recovered gold was considered purer than "mint grade" and suitable for re-use in the jewelry trade.
Click to expand...
I don't think anyone on this forum would consider 99% good enough to sell to manufacturers and if they did they would probably lose a customer.

The patent is only referenced in two other parents, both from Shor. If this was working good then we would have seen the patent referenced from later patents and the process implemented in working methods. At best this is a recovery method and not a refining method.

Göran
 
Is it possible to filter sulfuric acid after R.E.P., without rising, to reuse the acid? And rising remainder into same filter yet different container and at that point let the slime and gold dry completely eventually placing sediment into AR for further dissolution?
 
leeloo said:
Is it possible to filter sulfuric acid after R.E.P., without rising, to reuse the acid? And rising remainder into same filter yet different container and at that point let the slime and gold dry completely eventually placing sediment into AR for further dissolution?
Click to expand...
Welcome to the forum, leeloo. This is a good thread to read
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=17025

And you should take your time to read all the introduction threads and how to search the forum too. Everything is here for you to read. 8)

Göran
 
Since chlorine would evolve at the anode, why wouldn't it just dissolve the gold? I am sure it will. If this is working at all, all dissolved gold would cement at basemetals or get reduced by reducing chlorides. Though a strong oxidizer like Clnasc would leave all chlorides in there highest oxidation stage. Not that I expect any advantages from Shor's cell, I dislike the idea of adding ammonium to my recovery processes, but just for the curiosity.
 

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