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Is Cathode-only plating possible for metal recovery

Is it possible to plate using only a cathode with a direct currect power source if the amperage/voltage is high enough?

I have a Nitric/Hydrofluoric acid etch bath with dissolved metal ions and was just wondering if it is possible to "pull" these Ions out of solution without a complete current since having an anode would only dissolve more metal ions. Thanks.

Randall McDaniel
chemical process tech - Naples, Florida, USA
April 16, 2008

Hi, Randall. No, that's not possible -- but you may find that a platinized titanium anode does not dissolve. In general it is difficult to plate out of nitric acid because plating is a reduction process and nitric acid is a powerful oxidizing agent.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 18, 2008

April 18, 2008

I once attempted to plate nickel out of a nitric acid based nickel stripper. I succeeded in plating out the traces of copper that were in it, but no Ni plated out though the concentration was in excess of 50 g/l.

This is because of what Ted pointed out - the nitric is a powerful oxidizer. The preferred cathode reaction winds up being the reduction of nitrate to nitrite, rather than the reduction of Ni2+ to Ni 0.

If the metals you are trying to plate out are far down enough in the electromotive series, you may have luck. Compare the standard potential of the reduction of the metal ion to the undesired NO3- ---> NO2- potential. This will tell you whether thermodynamics is on your side, or not. Water may flow in many ways on a hillside, but it will not flow uphill. :)

You may also use graphite as an inert anode.

Dave Wichern
Consultant - The Bronx, New York

Hi, Dave. Very informative post, thanks. As you see, I had some understanding of the issue, but not to the depth you gave us.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 18, 2008

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