Sciencemadness Discussion Board

diy continuous electrowinning copper sheet metal

tumadre - 30-3-2024 at 09:25

I'm wondering if anyone has any insight into why copper sheet metal, continuously pulled off of a stainless steel drum, spinning very slowly in an electrolyte bath... is not used directly for copper roofs and other non critical copper hardware where it is merely needed for corrosion resistance and not structural strength and ductility

No additional drawing, annealing, or rolling.

seems to me this has to be practical at a cost far less than the 25$ per pound that copper sheet metal has been sitting at for the last decade.

I know some folks here have deposited copper for making shaped charges. how ductile was the copper?

[Edited on 30-3-2024 by tumadre]

Rainwater - 30-3-2024 at 11:04

Not sure what your exactly asking.
Copper sheet stored on reels is often referred to as soft copper. Easy to scratch, mold, imprent, bend bow and stretch. The cold rolling/stretching acts upon the metal harding it so it better maintains its shape.
Often a thin layer of nickel is applied to decorative copper sheets, to slow oxidation into the beauty green carbonate and make the metal easier to polish.

For better electrical properties silver is applied, in a thicker, visible layer.

semiconductive - 1-4-2024 at 16:18

What's the purpose of the eletroplating? If the roll contains copper, isn't it already copper?

Or: Do you mean thickening an extremely thin copper foil, or do you mean steel metal being electroplated with copper as a corrosion resistance layer?

My brother has some stainless ... and well, Stainless steel is quite expensive. Copper's only just getting very expensive, recently.

Even the 304 type of stainless (with low chromium and can rust), is difficult to work with. It's not something contractors are going to like to work with.

For a roof, or non-structural, the issues are going to be weight of the material and life-span for corrosion resistance.
Tile roofs, or heavier metal roofs, require re-enforced trusses to bear the weight. The metal roofs I've seen are usually a corrugated steel with a zinc coating. After 25 years, it starts to rust.

It's one of the reasons I've been experimenting with plating iron pyrite; to make ultra thin ceramic tiles (lightweight.)
Adding zinc or copper for corrosion resistance and green beauty are desirable; but I don't have a way to make it ductile/flexible yet. Copper's getting too expensive to use except perhaps as a purposeful way to get the desired green color.

Besides:
Water tends to make a rattling sound against flat sheet metals. A lot of people don't like the sound of a 'tin' roof. ;)

j_sum1 - 2-4-2024 at 03:28

I think the idea is a mechanism to produce copper electrolytically in a continuous sheet. As opposed to a batch process making sheets of a specific size.
The idea has merit. I can see that once optimised it will be a lot easier to maintain constant production conditions.

I would not pretend that the copper needs no further processing. Cold-rolling will harden it and make it more useful for most applications.

tumadre - 2-4-2024 at 09:01

Quote: Originally posted by j_sum1  
I think the idea is a mechanism to produce copper electrolytically in a continuous sheet. As opposed to a batch process making sheets of a specific size.
The idea has merit. I can see that once optimised it will be a lot easier to maintain constant production conditions.

I would not pretend that the copper needs no further processing. Cold-rolling will harden it and make it more useful for most applications.

Yes that's exactly what i am talking about, this is how all the circuit board sheet copper is produced.

Commercially it is produced with a lead anode closely fitted to the stainless drum and the acid bath is replenished with more copper ions through some most likely proprietary processes.

I figure I can take copper scrap metal and compress it into a brick, closely fitted to the drum, and use that as an anode.

It seems to me even a 1000 amp operation, 3 foot wide drum, at 20 cents an hour electrical usage.. should be able to produce copper sheet metal for less than 25$ a pound.

If it is theoretically only 383 amp hours per pound of copper, at twice that (for amp hour efficiency) and twice again for the power supply inefficiency.. that's about 15 cents a pound for the electricity and you should get 1.5 pounds an hour.

[Edited on 2-4-2024 by tumadre]

Johanson - 2-4-2024 at 19:35

Okay I finally understand; so you're going to make relatively thick copper sheeting (for roofing, etc) the same way PCB copper is made in 5-10 micron sheets, by continuously plating/electrowinning scrap copper out of a bath using a rotating drum as cathode. Got it.

Let me try to knock it down in an effort to improve:
E-winning too slow. This needs to be thick Cu sheet.
Copper roofing is not flat; it has standing seams. So your continuous sheet would need downstream processing anyway.
Copper-clad metal roofing is already being made. I assume the substrate must be steel(?) but I'm not positive. Certainly that must be cheaper than solid copper if cheap is your goal.

Ideas:
Develop a copper coating. Install a standing seam steel roof, make it into an cathode temporarily and apply your Cu-containing coating with a brush-applicator which is also a anode.
Do the same for gutters. Coat before installing.


[Edited on 3-4-2024 by Johanson]

[Edited on 3-4-2024 by Johanson]

j_sum1 - 3-4-2024 at 00:47

Copper on a steel substrate is not a good idea.
IIRC, it does not stick well. I believe that you need explosion welding - the same as aluminium to steel that is used for connecting Fe to Al in electrodes in the aluminium smelting industry. You are connecting a FCC crystal structure to a BCC structure and the resulting phase diagram aint pretty.

I may have misremembered that. But even if you do get adhesion, there is another issue. Copper in contact with iron in a roofing environment is a bad idea. It means that the structural metal is being electrolytically attacked in use. Kind of the reverse of galvanised iron.

Johanson - 3-4-2024 at 15:26

Good point, so we're back to solid copper or galvanized. From a practical standpoint, solid Cu standing seam roofs and gutter systems are custom made for each job, and fabricator needs to cut and bend big sheets quickly. Electrowinning scrap Cu from plating bath not really a good match IMHO. But that said, interesting idea...

clearly_not_atara - 4-4-2024 at 12:26

Suppose that instead of iron, you plate copper onto a carbon fiber mat which is hopefully conductive enough to work. This should give a metal-matrix composite, and carbon is not susceptible to galvanic effects IIRC.

Rainwater - 4-4-2024 at 12:43

Maintaining the physical parameters (thickness) would be one of many challenges. Any manufacturer consumer would demand a uniform product. Their process would be dependent on these tolerances,

semiconductive - 7-4-2024 at 21:36

Quote: Originally posted by clearly_not_atara  
Suppose that instead of iron, you plate copper onto a carbon fiber mat which is hopefully conductive enough to work. This should give a metal-matrix composite, and carbon is not susceptible to galvanic effects IIRC.


Yup!
This works, I've tried it.
It's also very light compared to solid copper.
The only issue is that pores tend not to close unless you use pulse plating.
eg: It's best to allow the copper ions to penetrate into cavities with potential 'off', in order to encourage cracks to grow closed.

But, all the copper experiments I have done are extremely soft afterward. So, I'm not sure a carbon mat would still be work harden-able. I recall plating copper onto aluminum, at 1mm per minute rate once, and afterward bent it back and forth dozens of times. The aluminum fractured but my copper never did. Electroplated copper, in a good bath (low to no oxygen content) is extremely soft.

I just electroplated a tiny bit of aluminum onto graphite, yesterday. I wonder if I can electroplate an aluminum/copper bronze efficiently.... that should be stiffer and cheaper than pure copper. ;)

tumadre - 19-5-2024 at 20:13

Quote: Originally posted by semiconductive  
Quote: Originally posted by clearly_not_atara  
Suppose that instead of iron, you plate copper onto a carbon fiber mat which is hopefully conductive enough to work. This should give a metal-matrix composite, and carbon is not susceptible to galvanic effects IIRC.


Yup!
This works, I've tried it.
It's also very light compared to solid copper.
The only issue is that pores tend not to close unless you use pulse plating.
eg: It's best to allow the copper ions to penetrate into cavities with potential 'off', in order to encourage cracks to grow closed.

But, all the copper experiments I have done are extremely soft afterward. So, I'm not sure a carbon mat would still be work harden-able. I recall plating copper onto aluminum, at 1mm per minute rate once, and afterward bent it back and forth dozens of times. The aluminum fractured but my copper never did. Electroplated copper, in a good bath (low to no oxygen content) is extremely soft.

I just electroplated a tiny bit of aluminum onto graphite, yesterday. I wonder if I can electroplate an aluminum/copper bronze efficiently.... that should be stiffer and cheaper than pure copper. ;)


thank you, that was helpful.