Why Is The Copper Basket Dissolving In The Sulfuric Cell?

Hello members,

I've processed gold plated material before with my sulfuric cell, but for some reason when I used a new piece of copper mesh to make my basket and placed it in the cell, within 30 minutes it dissolved the front of the basket and much of my plated material was on the bottom of the cell. So, I replaced it with another piece of new copper mesh, and when I only placed a few pieces of plated jewelry in the basket and put it in the cell, within 3 minutes of the cell running, I noticed the basket starting to lean towards the edge of the cell and when I turned off the power and took out the basket, the same thing happened.

I have been using a car battery charger and I have it set to 10 amps.
I am using fresh Sulfuric Acid
I am using brand new 60 mesh copper
I am still using a the same lead cathode

Any ideas as to why this is happening?

Thanks

You have done it before so asking if the sulfuric is 93%+ won't be of any help. Sulfuric does absorb water from air humidity but you have also used fresh acid so this is also to exclude. Many times I've read the power supply could cause similar issues, could you try to swap it with another one?

I don't have an answer, but I have a few questions to try to help diagnose the problem.

You started by telling us you used a new piece of copper mesh to make your basket. By "new", do you mean it's not an old, used piece of mesh, or is it a piece of mesh that's new to you, meaning you've made baskets before out of different mesh, but this is a different piece of mesh?

When you started this run, what else might have changed in your system. You say you're using fresh sulfuric acid. Is it new acid that might be a different brand, or is it fresh acid from the same acid you've used in the past?

Are you using concentrated acid? Can you tell us the concentration and where it came from?

My first thought is your mesh could just be copper plated. If it's copper, my next thought would be the acid concentration.

Others may have better ideas.

Dave

100% positive its pure copper mesh?

Whoops, Dave and I must have replied about the same time. sorry

Nothing to be sorry about. :lol: Marco mentioned the acid concentration while I was writing my post. It's good to get multiple ideas and opinions.

Dave

MarcoP said:

You have done it before so asking if the sulfuric is 93%+ won't be of any help. Sulfuric does absorb water from air humidity but you have also used fresh acid so this is also to exclude. Many times I've read the power supply could cause similar issues, could you try to swap it with another one?

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The sulfuric is 98%. I just cracked the seal on it today. I doubt that it's the charger. As for the water/moisture, it's not that either, not unless the sulfuric isn't 98%. It's not humid here at all. I've done this same exact setup a few times and never had a problem. I took all the time yesterday to portion all my plated material and setup shop this morning, and then this crap happens.

However, it was stripping the material, but at the rate it's dissolving the basket, I'll have more copper than gold.

acpeacemaker said:

100% positive its pure copper mesh?

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LaserSteve would know that answer, even though I should know it too. I will need to put some in Nitric to see for sure.

To FrugalRefiner, I'm using 98% from Dudadiesel. I believe I bought from them before. I'll have to check to be certain. Also, the copper mesh is new, and never used at all. I just cut it today.

My thoughts also have to be with you Frugalrefiner that either the copper basket isn't copper and (or) the sulfuric isn't 98%. I still have 3 more sealed bottles. But I'm leaning to the copper as the culprit.

Did you build the basket any differently such as make a raised lip on the front of the basket so it would support more?

On another note, when would it be needed to replace the lead cathode? That's the only thing I'm using that's not new, but it's cleaned very well. I cleaned it with a dry green scrub pad, and wiped it with a damp cloth and then a dry paper towel.

Barren Realms 007 said:

Did you build the basket any differently such as make a raised lip on the front of the basket so it would support more?

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Now that you mention it, I didn't this time. I usually fold the copper at the end so that the positive(anode) could conduct better. That might be the problem, but I don't understand why the submerged portion of the basket is dissolving.

I have an idea that I'm going to try to see if the copper is the culprit.

I'm going to take one of my copper alligator clips and clip a piece of that copper mesh and a piece of gold plated material to it and run the cell. If it strips the gold plated material AND dissolves the mesh, then the mesh is the problem. But, if it doesn't dissolve the mesh and still strips the gold plated material, then I'll have to do some more thinking on that one.

I'll be back in about 10 minutes.

I would suspect the acid concentration. Measure the density to see if it's full strength. It might be a faulty batch, an error with the labels or some other thing that's happened.

The concentration can be looked up from the density and the density can be calculated with the help of a scale and a beaker.

Sulfuric acid density data : http://goldrefiningforum.com/phpBB3/viewtopic.php?f=33&t=1068&p=8891#p8891

Göran

I was going to say take a piece of stripped copper wire from another source and clip it on and see what would happen. Time frame wise.

I'm leaning toward the acid too. If yoou got the mesh from lazersteve, it's probably not the problem.

You say "The sulfuric is 98%. I just cracked the seal on it today.", so that's also a change.

Check the specific gravity of the acid and let us know.

Dave

Problem Solved!
Of all the steps I usually take to prepare my baskets, I failed today.... two times at that.

FrugalRefiner, your question about the mesh made me do my last piece I had and fold it at the top, which I always did, except today, and then I remembered what I didn't do was the problem.

If you don't want your copper mesh to dissolve in the sulfuric acid/cell, then you need to fold the lip/top end of the copper at least two(2) times, about 1/4" each turn. Somehow, by doing that step this time, the copper mesh is holding up and my solution isn't getting almost boiling hot like it was doing before. Without folding the copper on the top end, chances are the basket is going to simply fall apart within 1 -3 minutes once the power is applied to it.

Now I have to try to salvage some of that copper I wasted.

I also learned that one simple, but actually crucial step can make the difference in how the refining turns out.

Thanks again for all the help!

I'm glad you solved your problem. When something goes wrong, always consider anything that's changed since the last time. Like I said, I didn't have the answer, just questions.

Dave

MrMylar said:

If you don't want your copper mesh to dissolve in the sulfuric acid/cell, then you need to fold the lip/top end of the copper at least two(2) times, about 1/4" each turn. Somehow, by doing that step this time, the copper mesh is holding up and my solution isn't getting almost boiling hot like it was doing before. Without folding the copper on the top end, chances are the basket is going to simply fall apart within 1 -3 minutes once the power is applied to it.

Click to expand...

That is a detail you never told us before. If we had known the solution became hot then we would have told you that it's a sure way to start dissolving copper.

By folding the copper mesh you probably increased the area that carries current and lowered the power dissipation in the mesh. If you run the cell so hard it becomes boiling hot then you have passed the working temperature with a good margin. I don't remember the correct maximum temperature but you can find it on the forum with a search.

Göran

Is it possible that an exposed mesh edge, which points out at the cathode, creates a lot more ionisation? I noticed that the flat-cut end of my copper wire became extremely sharp. So it's certainly dissolving more just at that location, even at 27°C. Mesh, that is not folded over, has heaps of pointy ends and could do that on a much greater scale.

I've ran a few small cells for quite some time. Your charger could be malfunctioning. It sounds like you are drawing too many amps and the charger must be a champ not to automatically shut off due to heat building in the current limiting resistor. By the time the acid gets that hot and eats copper like that, the charger should shut down on it's own to cool off. You can try everything as you had it but limit the amps going to the cell until the reaction is barely noticeable. Of coarse this is after you are sure of the concentration of the acid first.