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Nickel plating problem (and a disposal question)

April 26, 2011

Hello,

I am a research scientist electroplating copper cloth using Nickel sulphate 6-Hydrate, Boric Acid and Saccharin. I am usually running a 2 mA/cm^2 current through either a platinum or nickel anode. The solutions usually run great but every once in a while, the plating doesn't take and all that is deposited on the copper cloth is a thin light black soot-like substance that is not magnetic. The solution refuses to plate after that and it seems it is impossible to plate the metal out of the solution.

The main problem here is that for waste purposes (200 ml to 1L batches), I need to plate all the metal out of the solution so I can then convert the remaining liquid solution into a disposal friendly liquid. But since the solution then refuses to plate, I am left with only creating Ni salt (which would be stored and disposed in a facility at a high price) which is time consuming and inefficient.

I try to plate all the metals out of solution using a carbon rod anode and a solid wire. This didn't work so I tried increasing the plating surface using Ni gauze and still didn't plate.

Is it possible that the solution is plating a thin layer of nonconductive material?

The "non-plating" symptom of the solution can be induced by adding Ammonium Molybdate 4-hydrate. Yet all the other normal Ni base solution never came in contact with Mo.

Are there other ways of efficiently disposing of 200 ml and 1L batches of Ni Solution?

Thank you for your time!

Dan Yerukhimov

Dan Yerukhimov

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Firstly, all plating solutions have certain criteria that need to be met for them to deposit good metal. These criteria include having enough metal in solution, be at the correct pH, temperature and current density. It looks like your cd is OK, but there is nothing about the others. I suspect you are depleting the nickel solution as you mention the occasional use of an inert anode. I suggest you read up on how to successfully deposit nickel from solution and follow the instructions, then you won't need to dispose of the nickel solution because it will go on for many happy years if it is treated properly

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
April 28, 2011

The criteria for depositing is kept constant through all the procedures. The solutions have proven to plate NUMEROUS times. Are you saying that the concentration of Ni ions within the solution is depleted to a certain concentration that does not allow deposition? If that is the case then plating out all the metal within a solution is impossible and dehydrating all solutions into salts will be my only option of storage.

Dan Yerukhimov
- Newbury Park California USA
May 2, 2011

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May 2011

Hi, Dan.

What happens in electroplating is that some portion of the applied electricity goes to reducing metal ions in solution into metal on the cathode, and some portion goes to electrolizing water into hydrogen and hydroxide (or oxygen). The percentage of electricity wasted to liberating hydrogen is probably about 10% at the normal nickel concentrations used in electroplating, but asymptotically increases towards 100% as the metal concentration decreases. It's not that you can't plate any of the nickel out but that you can't plate it all out, and as the concentration gets lower, very close anode to cathode spacing, extreme solution agitation, careful pH control, and a very large cathode become increasingly important.

The soot-like substance is probably an extreme example of what we call "burning"; it's very finely divided particles of nickel and or nickel oxide/hydroxide caused by the lack of available nickel and the alkaline state of the solution within the boundary layer.

Regards,

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