Gold stripping cell ideas

[MvK]

Hi guys,

I got my hands on some material that i would like to de-plate using the sulfuric acid cell method.

I already got my bowl, power supply, copper mesh etc. I did some research, watched some videos but alot if them are messy and with alot exposed sulfuric acid.

I want to make a semi closed cell with a cooling system and a vibrating basket.

Im hoping to use only one cell, without having multiple open bowls or cooldown time. I would like to cool down by running glass pipes trough the cell.

I could suspend the basket in the fume hood, with a vibrator motor somewhere attached with an interval to shake the basket, not having to stir it.

What do you guys think, any tips or ideas i can steal from excisting machines?

Thx,
Mia van Kesselen

 

[Shark]

Hope this works. All it needs is a cover. If not large enough look for cell posts by phildreamer.

Www.Nulltime.com/zincplating/shop_setup/plating_barrel/index.html

 

[FrugalRefiner]

Instead of a vibrator, you might consider a tumbler. The drum holding the parts turns, constantly rolling the parts around inside, exposing fresh surfaces to the cathode. They're used in the plating industry and a few folks have made them for stripping.

Dave

 

[MvK]

Hope this works. All it needs is a cover. If not large enough look for cell posts by phildreamer.

Www.Nulltime.com/zincplating/shop_setup/plating_barrel/index.html

The Philddreamer one was very useful, thanks!

 

[MvK]

Instead of a vibrator, you might consider a tumbler. The drum holding the parts turns, constantly rolling the parts around inside, exposing fresh surfaces to the cathode. They're used in the plating industry and a few folks have made them for stripping.

Dave

Thanks Dave

I have some bigger parts to de-plate, i think a tumbler would indeed be better in this situation. Change of plan

 

[richoc]

Ok , might get a real up roar of back lash for this posting.
I can even do clean PBC boards in my deplating cells, working on designs to sell to companies to be able to take the gold off bad ones right in QC.

The biggest issue you will have is keeping moisture gain from your sulfuric acid, the purer the acid the slower it will heat up.
I like glass units that have well-fitting plastic lids.

The gold will move away from the parts with the flow of current.
No need for vibration or tumbling, your over think a very simple process.

I have used coolers from computer processers to try and cool the cells, issues if the fans toss acid.

Best thing I have found to do is set up 3 cells and first one gets hot move the work to the 2nd cell and so on.
In rotation getting a lot done with out over heating any single cell.
This can be done with a single power supply moving from cell to cell.
I make copper baskets that stand in the center of the cell , will all four sides of the glass bowls having lead wrapping.
Now this basket design and bowl size depends on the size of the parts you working with.

I would be glad to help you with this process to help make it safe and successful.

 

[MvK]

Ok , might get a real up roar of back lash for this posting.
I can even do clean PBC boards in my deplating cells, working on designs to sell to companies to be able to take the gold off bad ones right in QC.

The biggest issue you will have is keeping moisture gain from your sulfuric acid, the purer the acid the slower it will heat up.
I like glass units that have well-fitting plastic lids.

The gold will move away from the parts with the flow of current.
No need for vibration or tumbling, your over think a very simple process.

I have used coolers from computer processers to try and cool the cells, issues if the fans toss acid.

Best thing I have found to do is set up 3 cells and first one gets hot move the work to the 2nd cell and so on.
In rotation getting a lot done with out over heating any single cell.
This can be done with a single power supply moving from cell to cell.
I make copper baskets that stand in the center of the cell , will all four sides of the glass bowls having lead wrapping.
Now this basket design and bowl size depends on the size of the parts you working with.

I would be glad to help you with this process to help make it safe and successful.

You are right, i might overthink this but i really like building stuff so i wont toss the whole watercooling idea in the bin yet.

I think in the cooling down period of the cells the exposed acid will attract water. Maybe if the cell is covered and cooled this will be less of a problem.

At this point i might even make 3 cells just to compare the outcome


Thanks for the help!

 

[MvK]

I have found a brand of coolant wich offers waterless coolant, they claim its pure glycol. Im going to try and see if there will be a reaction to glycol and the sulfuric acid.

If i can make a closed system, and cool the glycol with pipes running trough a ice bath or something would be nice. Maybe overkill but i like the idea.

Also need to try sulfuric vs HDPE plastic, i did actually weld this type of plastic before. This would make a nice cell because i can weld piping straight trough the walls of the cell

The glycol would be my failsafe.

 

[Darkthirty]

I have found a brand of coolant wich offers waterless coolant, they claim its pure glycol. Im going to try and see if there will be a reaction to glycol and the sulfuric acid.

If i can make a closed system, and cool the glycol with pipes running trough a ice bath or something would be nice. Maybe overkill but i like the idea.

Also need to try sulfuric vs HDPE plastic, i did actually weld this type of plastic before. This would make a nice cell because i can weld piping straight trough the walls of the cell

The glycol would be my failsafe.

Pipe the coolant through the walls of a freezer with a thermostatically controlled bypass. Copper tube should hold the H2SO4

 

[MvK]

Pipe the coolant through the walls of a freezer with a thermostatically controlled bypass. Copper tube should hold the H2SO4

Thats a pretty good idea, mayeb even to use parts of a freezer to cool the coolant down.. Now i have to find out if a freezer will have enough capacity to cool down the cell.

Thanks!

 

[richoc]

The heat issue is really not that much to deal with, your power supply only puts out so much, keeping the water out of the acid also keeps the heat down. The more pure your acid is the less heat is produced while the power is on.

My theory here is the better contact in acid the less heat produced by resistance in the cell.

Lots of PPE, face shield , gloves that ar sulfuric safe, (check them)white lab aprons, plastic garbage bags over the metal chair, cardboard for drips covering the plastic sheet on the table. Flat cake pan as a catch basin around the sulfuric cell.

I have run plated Jewlery in a single cell powered with a old 12v battery charger using a stainless strainer as the basket and the non magnetic top from a Hard drive for 6 hours at a time.

Watching draw on the power meter , digital or a analog needle will let you know when the stripping process is complete, continuing to run past that point is generating extra heat in the cell.

Moving the parts with plastic tongs from the basket to a drip station, (glass jar for the acid to drain off in) then to multiple rinse stations.(glass jars with distilled water in them) But do not using the tongs that contacted water to get back to the acid in the cell. You will filter all this washing later for gold to process.

Moisture absorbed from the humidity in the air was an issue as the acid became thinner, it became more active and produced more heat faster.

I now use cells that seal well, for storage I can just stop and start up another day using the same acid until it is saturated with gold alloy to shorting out, now this is a heat issue also.
The black broken down alloy will build to a level in the cell that contacts the parts, this is no good, instant shorting can flash the gas coming off in the bubbles and this causes heat quickly in the cell,
resetting the cell with fresh acid is the answer to this problem.

I have used a sulfuric cell to strip 14k plated car rims, that I cut in to 4 arches with a Sawzall.
The cell can be built to the part of the parts.

Now a bonus is the later processes use a lot less acids to work with because the alloy is broken down so well in recovery and the reaction to use up the acid steps.

I ask that every one trying to design a cooled system , please start small and get some working experience with this before trying to reinvent the wheel.

 

[MvK]

The heat issue is really not that much to deal with, your power supply only puts out so much, keeping the water out of the acid also keeps the heat down. The more pure your acid is the less heat is produced while the power is on.

My theory here is the better contact in acid the less heat produced by resistance in the cell.

Lots of PPE, face shield , gloves that ar sulfuric safe, (check them)white lab aprons, plastic garbage bags over the metal chair, cardboard for drips covering the plastic sheet on the table. Flat cake pan as a catch basin around the sulfuric cell.

I have run plated Jewlery in a single cell powered with a old 12v battery charger using a stainless strainer as the basket and the non magnetic top from a Hard drive for 6 hours at a time.

Watching draw on the power meter , digital or a analog needle will let you know when the stripping process is complete, continuing to run past that point is generating extra heat in the cell.

Moving the parts with plastic tongs from the basket to a drip station, (glass jar for the acid to drain off in) then to multiple rinse stations.(glass jars with distilled water in them) But do not using the tongs that contacted water to get back to the acid in the cell. You will filter all this washing later for gold to process.

Moisture absorbed from the humidity in the air was an issue as the acid became thinner, it became more active and produced more heat faster.

I now use cells that seal well, for storage I can just stop and start up another day using the same acid until it is saturated with gold alloy to shorting out, now this is a heat issue also.
The black broken down alloy will build to a level in the cell that contacts the parts, this is no good, instant shorting can flash the gas coming off in the bubbles and this causes heat quickly in the cell,
resetting the cell with fresh acid is the answer to this problem.

I have used a sulfuric cell to strip 14k plated car rims, that I cut in to 4 arches with a Sawzall.
The cell can be built to the part of the parts.

Now a bonus is the later processes use a lot less acids to work with because the alloy is broken down so well in recovery and the reaction to use up the acid steps.

I ask that every one trying to design a cooled system , please start small and get some working experience with this before trying to reinvent the wheel.

Well that last part is exactly what im doing. Maybe im ahead of myself, but i got a nice design on paper. I did some experiments in a beaker but the little acid in there heated up quite fast. Maybe a larger cell with more acid will run cooler to begin with.

So do you have to agitate your material or does a fixed basket work fine for you?

Thanks for the input!

 

[richoc]

No need to agitate the current flow seams to pull the gold alloy away from the parts, and gravity will assist in the black alloy falling to the bottom of the cell.

I make the baskets, so they suspend well off the bottom of the cell, this leaves room for the gold to fall away to the bottom also keeping the basket from contacting the black alloy sludge.
This stops any shorts from happening in the cell, you can have sparks at the surface bad news, but you also do not want shorts in the acid crossing the cell through the black nano gold alloy trail.

This case would be an over loaded cell where the basket is in contact with a layer of the black alloy sludge that is in full contact across the cell. A straight short of the cell happens like this, excess heat and hope your ground fault circuit protection kicks off on this, shutting off the power.

Shorts and "hot acid" with high water content heat things up fast.
I call it "hot acid" the more moisture in the sulfuric acid the hotter it will run.
It at first seems to strip much faster, but in turn it gets hot fast like this, it will run away, cooler is better.

Running too long on the parts will heat it up faster than needed, I have seen a lot of times when teaching this in person that students want to run the part well past the copper plate stage. There can still be solid contact and higher current draw as this is being done, resulting in excess heating of the cell.

Say you need to stir your batch of small parts to get them all good contact, well then there are too many in the basket, but to keep the heat controlled turn off the power, then stir them, then turn the cell back on.

There will be black alloy left (nano dust) on the parts but this will come off in the rinses and can/will be recovered for further process, even the rinse water (distilled water) can/will be used in the process.

If lots of Gold Alloy coating is left on your parts you are overloading your basket, and each part is not getting good contact with the open flow of the cell, running this longer will cause excess heat, because you are still running the finished parts for no reason.
You are much better off, running these parts as small batches to clear them quick and efficient.

Some parts are do not run well in baskets, these will take other steps to prepare.
But this is a little advanced for the first timer, that is getting a good handle on how the cell process works.

 

[richoc]

I have found a brand of coolant wich offers waterless coolant, they claim its pure glycol. Im going to try and see if there will be a reaction to glycol and the sulfuric acid.

If i can make a closed system, and cool the glycol with pipes running trough a ice bath or something would be nice. Maybe overkill but i like the idea.

Also need to try sulfuric vs HDPE plastic, i did actually weld this type of plastic before. This would make a nice cell because i can weld piping straight trough the walls of the cell

The glycol would be my failsafe.

Easy check on HDPE is to check the bottles it is sold in as drain cleaner. (not saying any more or if safe).

One can get almost everything to build a cell and run it from a good well stocked Walmart, including the acid.
When I teach, we go out to start and find everything needed in their hometown, so they know how to start from scratch with nothing.

Power supply that will work is now the hardest component to find now a days because of the circuit sensing battery chargers.

I get My sulfuric acid at the acid supply house here in town, Lab grade 98% pure, and it comes in a clear plastic gallon bottle or even 5 gallon if you call ahead.

But when the acid gets hot gloves that were resistant to the acid cool, get eaten away when it is "hot acid" and active.
So not sure about a plastic cell with welded openings standing up to the hot acid.
If you try this, "PPE" make sure you work with a catch basin that will be resistant to the acid and hold way over the volume that could leak.

Pyrex with lids below, make good starter cells, the deeper the glass rectangle is the better.

 

[MvK]

Easy check on HDPE is to check the bottles it is sold in as drain cleaner. (not saying any more or if safe).

One can get almost everything to build a cell and run it from a good well stocked Walmart, including the acid.
When I teach, we go out to start and find everything needed in their hometown, so they know how to start from scratch with nothing.

Power supply that will work is now the hardest component to find now a days because of the circuit sensing battery chargers.

I get My sulfuric acid at the acid supply house here in town, Lab grade 98% pure, and it comes in a clear plastic gallon bottle or even 5 gallon if you call ahead.

But when the acid gets hot gloves that were resistant to the acid cool, get eaten away when it is "hot acid" and active.
So not sure about a plastic cell with welded openings standing up to the hot acid.
If you try this, "PPE" make sure you work with a catch basin that will be resistant to the acid and hold way over the volume that could leak.

Pyrex with lids below, make good starter cells, the deeper the glass rectangle is the better.

Very nice, your posts help out alot!
I already have the pyrex with a lid, a lab power supply, nice copper mesh and practicly everything for a starter cell.

The main reason id like to make a cooled cell is because of my material i want to process. One example is jewelry with a thick coating of gold, between 5 and 20 micron. I want to see if i can tackle this with the least amount of acid waste produced. I have a few kilos of this stuff.

Right now i am leaning towards sacrificing a stainless Bain-Marie. They are used those to keep food warm by having hot water under the stainless insert but this should be easily be converted to keep the cell cool. Maybe i can try to fit a pyrex dish in here. Picture below, what do u think?

 

[richoc]

You will be able to run many kilos of jewelry in less than one gallon of sulfuric acid, a dripping station will collect your excess acid from the parts, before you start the rinsing stations. You will be able to add this acid back to the cell for further use. You get great life on the acid, just keep the water out, you decant off the top acid and pour out the sludge to settle in a taller beaker. The acid will come to the top as the alloy sludge settles to the bottom, you can pour the clear acid back in the cell to use, over and over.

Remember even any color in your rinsing stations is the alloy and needs to be recovered for processing.
You can let this gravity settle and filter it out to refine.

The rings in my avatar photo were 24K gold plated, it took about 3 hours to run these through a freshly built cell run on a battery charger to teach the meathod. I recovered just under 3 grams Au. from these rings and used maybe 1 oz. of sulfuric acid in the exothermic reaction stage of adding 5x the volume of water to acid sludge mixture, this gets hot fast and expands fast and too a large volume of foam, so be prepared for this and do this in a very large vessel (larger than you think please).

You will only use up the sulfuric acid in the sludge reaction, the rest can be settled out and used again and again.

The alloy sludge at this point, (after water reaction) will be so fine that you will have issues getting it all collected in filtration.

I use 3/6 layered coffee filters over a thick cotton plug in a funnel, cheap and effective.

Once your alloy is all collected in to one beaker you will be able to be so light on your acid use and will not need to heat anything for reactions. I try and collect all of the sludge in to one final filter set before moving on to refinement. This way takes a lot of time, washing and rinsing but I am not using excess acids to deal with the filtering material, but that is up to you.

I mean working in drops of nitric acid will be the amount you will need to make the first AR solution dissolve the entire amount of alloy sludge to start your series of drops to do the recovery of the metals to remove in correct order of metals from the alloy during the refine.

 

[richoc]

Oh I forgot, no need for the stainless serving unit, no need to sacrifice it.

I just use dollar store plastic square cake containers for catch basins around the cells, drip station and rinse jars.
Ideally nothing will end up in them and if it happens, not in them for long.

I keep a large supply of baking soda on hand just in case.

Once you get the hang of doing this, it will run fast, unless there is a huge supply of this jewelry coming in fast and free you can handle running it without reinventing the wheel.

 

[MvK]

You will be able to run many kilos of jewelry in less than one gallon of sulfuric acid, a dripping station will collect your excess acid from the parts, before you start the rinsing stations. You will be able to add this acid back to the cell for further use. You get great life on the acid, just keep the water out, you decant off the top acid and pour out the sludge to settle in a taller beaker. The acid will come to the top as the alloy sludge settles to the bottom, you can pour the clear acid back in the cell to use, over and over.

Remember even any color in your rinsing stations is the alloy and needs to be recovered for processing.
You can let this gravity settle and filter it out to refine.

The rings in my avatar photo were 24K gold plated, it took about 3 hours to run these through a freshly built cell run on a battery charger to teach the meathod. I recovered just under 3 grams Au. from these rings and used maybe 1 oz. of sulfuric acid in the exothermic reaction stage of adding 5x the volume of water to acid sludge mixture, this gets hot fast and expands fast and too a large volume of foam, so be prepared for this and do this in a very large vessel (larger than you think please).

You will only use up the sulfuric acid in the sludge reaction, the rest can be settled out and used again and again.

The alloy sludge at this point, (after water reaction) will be so fine that you will have issues getting it all collected in filtration.

I use 3/6 layered coffee filters over a thick cotton plug in a funnel, cheap and effective.

Once your alloy is all collected in to one beaker you will be able to be so light on your acid use and will not need to heat anything for reactions. I try and collect all of the sludge in to one final filter set before moving on to refinement. This way takes a lot of time, washing and rinsing but I am not using excess acids to deal with the filtering material, but that is up to you.

I mean working in drops of nitric acid will be the amount you will need to make the first AR solution dissolve the entire amount of alloy sludge to start your series of drops to do the recovery of the metals to remove in correct order of metals from the alloy during the refine.

Very nice and clear, thanks! One question, what do you mean with a dripping station? Letting the materials drip out in a seperate basket before rinse?

 

[Martijn]

Yes. to save and reuse your concentrated acid.
Beware it collects moist from the air in time.

The hardest part imo is making good contact and stripping items completely.

Make sure you clean the jewelry properly to avoid any grease and dirt in the sulfuric.
It complicates refining.

Martijn.

 

[richoc]

Thanks, Martijn for answering and I will elaborate further with my answer.

The sulfuric acid is more or of a syrupy consistency in the "cool" state your working with it in and will coat and stick to the parts needing time for gravity to drip the parts mostly free of it.
You need to place the parts whether done with a clamp or in a basket in a dripping station to allow for the acid and sludge alloy to get off the parts before it gets wasted, in the rinse water washes.
You will still reuse the collected acid back in the cell, over and over again.

You will waste a lot of acid if you go right to a rinse bath with the parts.

Heat and water will thin the acid as you work, it will seem to work faster and this is when you start getting messed up, leading to hot acid issues, you will get the eye for it as you work with the cell.

You do need to clean all surfaces on the parts for good contact within the stripping cell.

What I do is a watertight plastic Miracle Whip jar and put in parts, like watch bands to half full, then Dawn dishwashing soap and hot water.
I then shake it until clean, doing this until I have all the parts I want in the stripping batch are cleaned.
I have put 2 jars at once on a rock tumbler to do the agitation for me.
I then rinse a few times to get off all the soap, then I do a final rinse with distilled water and let air dry.

I have never tried one yet but an ultra-sonic jewelry cleaner with a lite solution should do the job.

I have also thought about putting the parts in a "colander" and running them in a dish washing machine.

Please do not in any case try and burn them clean, your making carbon that end up in the cell, and that will gum up the works down the line.