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Faraday's law on concentration of copper sulphate

WHAT ARE FARADAY'S RULES CONCERNING THE CONCENTRATION OF COPPER SULPHATE?

Rebecca Ogden
- Sutto, Surrey, ENGLAND
2002

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Hi, Rebecca. I don't think Saint Mike wrote any special rules specific to copper sulphate. I think his Law of Electrolysis applies to all metallic salts, and other things besides: one Faraday (96,485 coulombs or ampere-seconds) deposits one gram-equivalent-weight.

It makes pretty simple sense, actually: To reduce copper from +2 ions to metallic state requires 2 electrons per atom. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002

Why is the concentration of copper sulphate ⇦this on eBay or Amazon [affil links] solution needed in the experiment?

Mee Vo
- Adelaide,SA, Australia
May 17, 2010

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Hi, Mee. Your question is a bit brief and abstract for me to be confident that I understand it, but actually the concentration of the copper sulphate is irrelevant for the particular experiment that I was talking about.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May , 2010

Q. Sir,

We do acid copper plating on MS rods.
Can you suggest to me the plating time for 250 microns for 13.7 dia x 1500 mm length.

Abhiraj Naik
Engineer - Mumbai, Maharashtra, India
February 28, 2012

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Hi, Abhiraj. That is quite thick electroplating and will probably take a few hours. The easy way is to pull out your Metal Finishing Guidebook and look at the appendix in the back, which will give you the ampere-hours required to plate .001" of copper from an acid copper solution; then you multiply by 10 since you want to plate .01" thickness. Then you divide by your current density, which will probably be somewhere between 20 and 40 amps per square foot. The appendix in the guidebook simply incorporates the density of copper metal and a string of other conversion factors so that you can apply Faraday's Law to correlate amp-hours to thickness without a lot of calculation. I believe that appendix also offers the answers in metric.

Now I'll explain in more detail: Although electroplating is governed by some very simple theoretical rules like Faraday's Law, it is also limited by some very complex phenomena like efficiency and diffusion rates through the boundary layer, that we aren't yet able to calculate on first principles (although it may be possible to make some progress in that direction via Fick's Second Law which governs diffusion). Instead we rely on empirical knowledge for some of the factors. For example, you will probably find that you cannot satisfactorily electroplate, in a conventional tank system, at more than 40 amps per square foot (4.3 amps per square decimeter). Depending on the amount of agitation and other factors, you may find yourself limited to 75% or even 50% of this (hence my guess of 20 to 40 ASF).

Acid copper plating solutions contain copper ions in the +2 oxidation state, so 2 electrons must be supplied to reduce one atom of copper. Therefore, 96,485 amp-seconds of electricity will reduce 1 gram equivalent weight, or 1/2 gram molecular weight. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 28, 2012