Copper plating on stainless during cell use

[Smitty]

I've ran my cell semi successfully I guess, but the same thing comes up that I still can't solve.

When the pins I am deplating is finished the pins begin to plate on copper over the stainless. It seems as if the copper plating might be an oxide because the conductivity of the pins are greatly decreased and I end up with a lot of unplated gold pins. They are not fully unplated but stripes, wherever the gold plating has been stripped, the spot is replaced with the copper. It does help to shake the copper basket to move the pins around, but I still end up with a few pins that are not fully deplated.

Cell Setup information:
The first time I did the cell I had used a plumbing sulfuric so I had thought that was the problem, but I've decided to start this batch fresh with battery acid boiled down to condense the solution.

The power supply used is a 6V 6Amp power supply1 in parallel with a 6V 1.5Amp power supply2. The only way I can get any reaction from the cell and also helps reduce the load on the power supply1 making it last longer.

Basket used is made of 100% copper.

 

[Palladium]

Alright, don't everybody hate at one time.
I do have a question or sort of an Idea, maybe an experiment just to see.
Do you use Glycerine in your cell ?

 

[Palladium]

Then again i think voltage is related to the stripping time and current is related to the surface area to be stripped. Why not go with a 12 volt 15 amp battery charger. I bet it's the voltage and current issue. Not for sure but my guess.

 

[Smitty]

No Glycerin is used, the reason glycerin was used in Steve's set up was because the system that he was originally was taught had called for glycerin, another member on this forunm did not use glycerin and it worked for them in a larger scale operation. This topic was brought forth in one of my other threads before I started this cell. Stripping alone it works, is there a link between glycerin and copper plating I do not know about? Please enlighten me if you can.

Yes,12 volts and 15 amps will be faster due to the increase total power to the cell, but I'd rather be safe from any explosion from acids and the bubbling to a minimum. My cell is a replica of Steves very own and it's spec says 6V 10 Amps. It workes well for the way Steve's setup intended. If I was using a larger scale stripping cell then yes I would jack it up to 12V 15Amps, it'll kick up a lot of big bubbles though. Keep in mind that my setup is the size You see in Steves setup. As it is the bubbles I am producing right now is slightly shooting acid outside of the dish.

I've already decreased the amount of pins to strip at one time in order to test if it's voltage versus amp idea and it still does the same effect. My current solution is to pick up the unplated ones and dip them individually in the acid to deplate them, that's were I am wasting time.

 

[istari9]

I started my cell before I found this forum. That having been said I used the drain cleaner with gly. I found lower voltage worked slower and the higher voltage did splash the bubbbles out of my bowl(dish). that in turn made a mess, caused pin holes in my clothes. I do believe slower is better in this case. I did not find any copper plating though. I would suggest using fewer pins allowing for better agitation upon shaking, that may cure the problem. Have you redone the striped parts in new fresh acid bath?
You could also soak them in AP to see how they react.

Ray

 

[banjags]

When I ran my cell, i was deplating about 50-60 pounds of av connectors. Higher voltage lead to higher amps which lead to faster deplating. I ran it around 15-17v 15-20 amps depending on how much was in the cell to start.
I never had any issues with spitting or splashing. I never used glycerine.
I had some stuff appear to have had copper plated on to it... or it never deplated the copper un sure of which is correct... Either way it only happened when I ran a large batch in my basket. So I would suggest small batches. In the end the time will be the same.

 

[Smitty]

I actually have used a small batch of 20-30 pins. The pins were half an inch long and 1mm wide, clean connector pins without solder or such on it. I've read that if you wanted to remove the copper from the solution, you would have to run the cell with stainless anode and cathode. Could that be the effect I am seeing with the stainess pins. I did one individual pin and it deplated the entire pin. After holding it in the solution for a few minutes it started to plate copper onto it. The higher the voltage I run it on the faster the stainless pin plates the copper, but if I run it too low then the pins will not deplate.

Sorry though Banjags higher voltage does not get you higher amps. It gives you higher power that is if you increase the voltage and keep the current constant. Power(Watts) = current(Amps) * voltage(Voltage).

 

[Harold_V]

It's unlikely you're depositing copper. What may be happening is you're removing the nickel barrier, which in turn is allowing the brass pins to have their zinc content leached. That would give you the impression you are plating copper on the surface. Check your pins to see if that's what's happening.

Harold

 

[Smitty]

You mention brass pins. These pins are actually stainless connectors. I've actually deplated one clean and it is not brass. Although I don't have the spec sheets for these pins, I'm sure I can get my hands on it because they are mil spec connectors. The sulfuric liquid is blue green so I was assuming it was copper, never thought about it being nickel. But can Nickel plate back onto the stainless pins. I'll try and get some pics posted to help with reference, this may take some visual help. From the previous batch I was able to get a gold nugget made, but like i said it's causing me to slow down in order to salvage as much gold as possible.


I was thinking of soaking the copper? plated pins into Hcl and see if it would strip the plated material off, then I can run it once more to make sure all gold is taken. This run is actually going to help me determine yield for these pins before I purchase more so I'm being extra careful.

 

[Scott2357]

Smitty, A couple of questions/comments. When you say,

6V 6Amp power supply1 in parallel with a 6V 1.5Amp power supply2

do you mean those are the currents you measured from each or the current limit of each supply? If it's measured then the current difference is probably because one's output voltage is slightly higher than the other causing uneven loading. To parallel regulating supplies the output voltage needs to be within about .1v or less of each other.

I'm still working on it but I think voltage low/current high will work best. Say 3-6v and minimum 8-15 amps. Of coarse current is proportional to anode/cathode surface area exposed between the two in the electrolyte. I've always told my wife I'd find a use for those 5v 250A supplies I've been saving in the garage. 8)

Also, some helpful current/voltage formula links for those who would like to tweak their electrodes or optimize their electrolyte mixture. Adjust without any metals dissoved in it.

http://www.sengpielaudio.com/calculator-ohm.htm

http://www.mathconnect.com/ENGINEERING-Formula.htm

 

[banjags]

Sorry though Banjags higher voltage does not get you higher amps. It gives you higher power that is if you increase the voltage and keep the current constant. Power(Watts) = current(Amps) * voltage(Voltage).

hmm thats weird cuz when I turned the dial on my power supply the volts went up and so did the amps output.

 

[goldsilverpro]

With a totally variable power supply and a constant load, an increase in voltage always gives an increase in amperage.

In the H2SO4 stripper, here's the way I used the variable power supply, which is the only type power supply that I used or, would use.

1) I put the part(s) in with the voltage at zero. I then determined the amps I wanted and adjusted the volts to provide that number of amps - lets say 10 amps. At first, the required voltage was quite low - maybe 2-3 volts.

2) As the gold strips, the amps will fall and, simultaneously, the voltage will increase. I would frequently increase the voltage, even more, to maintain the 10 amps.

3) At some point, the voltage would be pegged (I like about 12-20 volts, max) and the amps would be less than 10. I would leave the voltage pegged until the amps read zero. Then, I would turn the volts to zero, in case of accidental shorting, and remove the part(s).

 

[Harold_V]

You mention brass pins. These pins are actually stainless connectors.

That would be unusual, to say the least. If the pins were made to be soldered, they most assuredly are not stainless. Most pins (not all) are made of brass, with a plated nickel barrier to prevent gold migration into the base metal, which is a well documented phenomenon.

As you likely know, stainless has a high percentage of nickel in it's composition, thus your pins appear to be stainless, which has a soft yellow appearance.

I'm of the opinion you've removed the nickel and have leached zinc from the brass, as I said previously. I'd be interested in hearing if I'm wrong.

Cut a pin in half with a side cutter, then apply a drop of nitric to the cut portion. Tell me what you see.

I've actually deplated one clean and it is not brass.

How did you determine it's not brass? Stripping it clean of gold won't do it if it has a nickel barrier. It will look like stainless.

The sulfuric liquid is blue green so I was assuming it was copper, never thought about it being nickel. But can Nickel plate back onto the stainless pins.

If they were stainless, I'd have a question about where you got the copper that was being "plated" back on the pins. I don't think it is. That's the point. It's already there, just being exposed.

Let me know the outcome of the simple test I proposed. It might save you a lot of unneeded work, considering if I'm right, the pins are already fully stripped unless you can see gold showing.

Harold

 

[Smitty]

That sounds pretty solid. I'll post pics this weekend since I'm pre-occupied on the weekdays, I'll definitely cut one and drop acid on it. Hope your right so I can stop the insanity. thnx

 

[Smitty]

Good info Harold the pins were brass with nickel covering. I was removing the gold plating and leaving the nickel thinking it's stainless. Now I have to dissolve the nickel before I dissolve the gold powder on the bottom. This information also helps me answer my questions about a previous thread I had regarding abnormal material in the solution of auric that i precipitated. Thnx for the help sir.

 

[Harold_V]

Good info Harold the pins were brass with nickel covering. I was removing the gold plating and leaving the nickel thinking it's stainless. Now I have to dissolve the nickel before I dissolve the gold powder on the bottom. This information also helps me answer my questions about a previous thread I had regarding abnormal material in the solution of auric that i precipitated. Thnx for the help sir.

Glad it worked out for you, Smitty.

Don't sweat the nickel. It comes out real easy with a touch of nitric and water. I'd recommend incineration, then a nitric digest----then it's ready for AR. Should yield gold of excellent quality.

Harold