tumadre
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diy continuous electrowinning copper sheet metal
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]
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Rainwater
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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.
"You can't do that" - challenge accepted
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semiconductive
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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. 
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j_sum1
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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.
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tumadre
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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.
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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]
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Johanson
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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]
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j_sum1
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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.
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Johanson
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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...
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clearly_not_atara
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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.
[Edited on 04-20-1969 by clearly_not_atara]
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Rainwater
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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,
"You can't do that" - challenge accepted
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semiconductive
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| 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.
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