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Daedronus

Thu Oct 11 2012, 12:38PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
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What determines what can be electroplating on what?

For example, can I electroplate copper on silver or gold (I know usually it's the other way around) ?

Cheers.

Steve Conner

Thu Oct 11 2012, 07:59PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I think you can electroplate any metal on any other. Or even on another piece of the same metal. Metals all form positive ions, and there's no chemical reaction between the plating metal and the substrate.

ConKbot of Doom

Fri Oct 12 2012, 04:45PM

Registered Member #509 Joined: Sat Feb 10 2007, 07:02AM
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In theory what Steve says makes sense, but caswell plating sells various kits and lists what you can and cant plate on. It appears that stuff such as surface oxides (especially on aluminum) really interferes. Not sure about the caveats, just was looking into copper plating some aluminum at one point.

Daedronus

Fri Oct 12 2012, 04:54PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
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Yep, I'm aware surface oxide films are a problem.

Should not be a problem with copper on silver/gold.

I guess I should get off my a** and actually go get some CuSo4/sulfuric acid and try it.

Edit:

Hmm, looking at caswell plating for copper kits:
"Plates bright copper over non-ferrous metals like Nickel, Brass, Bronze etc."

So you can't plate some metals, regardless of the oxides...

Conundrum

Sat Oct 13 2012, 08:25PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

You can apparently make CuSO4 from MgSO4 and copper electroplated onto a graphite cathode.

Its an ion replacement reaction where the more reactive magnesium ends up as an oxide and precipitates out.

Daedronus

Wed Oct 31 2012, 08:31PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
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I got a bag of CuSo4 today, and yes, it does plates on silver.

Normally you also need sulfuric acid for copper plating (or so I have read) but plain CuSo4 does plate on silver.

hboy007

Fri Nov 02 2012, 08:35PM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
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As far as I know, you'd only run into problems with ion concentration, current density and overpotential phenomena

to mitigate problems with ion concentrations, pH and complex ligands can be chosen adequately. Please stay away from mercury cyanide.

Daedronus

Fri Nov 02 2012, 10:27PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
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I will definitely stay away from cyanides !

I will try propylene glycol as a leveling agent first.

And maybe add the sulfuric acid, at the needed concentration it seems dilute enough not to be too scary.

Daedronus

Tue Nov 27 2012, 12:10AM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
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Ok, an update on my copper plating.

All the tests are on nikel, because I have a lot of coins out of that metal :)

First of all, just CuSO4 plates, but it's rough, not very uniform, has big grains, the solution has high resistivity/you need high voltage, 2.6v in my tests.

Adding sulfuric acid improves a lot the conductivity of the solution, and the deposition rates, but, everything else turns to crap, the adhesion is almost non-existent, and it's not uniform.
The voltage needed drops to about 0.5V.

Adding Polyethylene glycol (PEG for short) (molecular weight 6000) makes a HUGE difference. The adhesion is excellent, extremely uniform, a single anode will plate both sides of the cathode, very smooth.

Instead of pure PEG I also tried a laxative (forlax 10g if you want to know) made of PEG + some other junk flavoring, unknown molecular weight. The results where similar.
If you look for a laxative containg PEG ask for something with Macrogol. This is what they call PEG in medicine. This one is Macrogol 4000....so maybe it's molecular weight 4000.

In principle you can go for as high molecular weight as you can, higher is supposed to give finer grains, but I don't think you will see much of a improvement after about 4000.

Adding PEG also lowered the deposition a bit, I had to raise the voltage a little.

On top of that we can also add HCl, this will further inhibit (in combination with the PEG) the deposition, but it doesn't make a lot of difference in my case, a rather flat coin. Maybe if you plate vias.

I will add a picture of the tests later.

Daedronus

Tue Nov 27 2012, 03:13PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
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CuSO4 + H2SO4 + Forlax (PEG) + HCl (this was exposed to air for several days, fresh after plating was a little bit brighter):
1354028866 2329 FT1630 01 Forlax

CuSO4:

CuSO4 + H2SO4:
1354028866 2329 FT1630 03 Cuso4 H2so4

CuSO4 + H2SO4 + PEG 6000:
1354028866 2329 FT1630 04 Cuso4 H2so4 Peg6000

CuSO4 + H2SO4 + PEG 6000 + HCl:
1354028866 2329 FT1630 05 Cuso4 H2so4 Peg6000 Hcl

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