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"Dummying" a Nickel Plating Bath -- Problems & Solutions



FAQs & TUTORIAL:
(to provide context, hopefully helping readers more quickly understand the Q&A's)

Facilities which do a lot of electroplating must contend with a buildup of impurities in their tanks. One common situation is for nickel plating tanks to start having too much copper dissolved in them from dropped parts, plating rack hooks, drag in from an earlier copper plating step, etc.

A common way of dealing with this is by 'dummy plating' either periodically or continuously. The 'scrap' plate which is used as the dummy cathode has only a very low voltage imposed on it. Because of this, copper (being more noble) tends to plate out preferentially to the nickel, helping to purify the bath.

Current questions & answers:

October 19, 2021

Q. Scraping Copper off Dummy Plate? We have a dummy plate in our Phosphoric bath and it is not very user friendly. The plates are heavy and there is not much room underneath our plating line. Right now every so often they have to pick up the plates out of the tank and put them in another tank to scrape the plates. When they pick up the plates a lot of the copper falls right off. I was just wondering if anyone had any other user friendly set ups? Thank you!

Kristin Trevisani
- Niagara Falls, New York
^


October 2021

A. Hi Kristin. It seems to me that you could put an anode bag around the dummy plates without interfering with their function. When it comes time to remove the dummy, the anode bag should catch most everything that gets jostled off.

Luck & Regards,

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



November 1, 2021

Q. Dear all, Could you offer me a solution that enables me to easily remove the impurities on dummy plates and make them clean again to reuse?

Afshin Ja
- Tehran, Iran
^




Closely related Q&A's, oldest first:

2007

Q. We run a dummy plate in our Ni bath once a week over night and have never had problems.. In the last two weeks our plate has become very dark black, what could cause this?... Our boric acid, pH, Ni level, and baumé are all in spec... Thanks...

Jason Combs
plating specialist - Chattanooga, TN
^


simultaneous

2007

That is the purpose of the dummy plate. You are removing tramp metal ions, probably copper and iron. Check the bottom of your tanks for "lost" parts that are dissolving. Dummy more frequently until the black is only at the inside corners of your wiggle plate.

James Watts
- Navarre, Florida
^


2007

Jason,
Typically if the dummy panel or grid turns dark during lcdlysis, you are removing metallic impurities generally copper and/or zinc as well as some organic materials. Eventually they will be removed and the dummy plate will be "white" again. If this does not happen you either have too high a level of these impurities to remove in the time you are operating the dummy or have impurities which show up in the low current are but need to be removed in another manner. Typically these are organic contaminants and can be removed by oxidation with hydrogen peroxide or potassium permanganate coupled with carbon treatment.
Rather than guessing, why don't you ask your supplier to check out your bath?

Gene Packman
process supplier - Great Neck, New York
^


October 2021

thumbs up sign Hi Gene, I love your word lcdlysis -- it's very descriptive -- but I'm having a bit of trouble pronouncing it :-)

Luck & Regards,

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


2007

It seems a little odd that you would have to dummy plate a nickel tank that often. Typically, black dummy plating is produced by trace (less than 10 ppm) of copper or zinc. If you're a plater of a lot of zinc die casting, then perhaps you should consider a continuous dummy plate. More importantly, you should make sure you don't have a bunch of half dissolved zinc die cast parts in the bottom of your tank. I have seen one extreme example of a nickel tank being poisoned by nitric acid that someone had used for pH adjustment instead of sulfuric acid. The bath had to be dumped.

Daryl Spindler
Daryl Spindler, CEF
decorative nickel-chrome plating - Greenbrier, Tennessee
^


2007

The dummy plate is supposed to be dark gray to black if it is pulling out metallic impurities.

If earlier your plates were silvery gray, then you did not have noticeable metallic contamination. So recently you have increased the level of metallic contamination by (1) drag-in of impurities (2) dropped parts in the bottom of the tank (3) or by mere increase of production you chew up more nickel anodes and copper is a natural impurity in the anodes and it plates out black in the low current density area of the dummy plate.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina
probertbanner
^


2007

Just a reminder, be sure to clean that black smut before using your dummy plates again. The idea is to extract as much smut as you can, not to put it back in the bath.

Guillermo Marrufo
Monterrey, NL, Mexico
^


2007

DEAR ROBERT,

THE BLACK COLOR OF THE DEPOSITS CAN EITHER BE INORGANIC (MAINLY METALS) OR ORGANIC.

AS THE TREATMENT DEPENDS ON WHETHER THE CONTAMINANTS ARE INORGANIC OR ORGANIC, HOW CAN YOU TELL WITHOUT A CHEMICAL ANALYSIS WHETHER THE DEPOSITS ARE INORGANIC OR ORGANIC ?

THANKS,

MAURICE MASON
- DANBURY, Connecticut, USA
^


2007

Dear Maurice,
Let me politely disagree with you. A dummy plate will only remove some metal ions. It will not remove all metal ions and certainly will only lower the amount that it does remove. It will not touch the non metallic cations like sodium and potassium. It will not touch any pure organics. There are very few organometallics in a nickel bath, so we can forget about any of those ions.
So, his black is only tramp metal and nickel that is commingled with the tramp ions. Consider it an alloy for lack of a better comparison.
Organics are typically removed with carbon treatment of some kind.

James Watts
- Navarre, Florida
^


2007

A. Dear James,
Maybe you didn't mean it, but I must disagree with you in that Sodium and Potassium are non-metallic cations. They are 100% metallic but too electronegative to plate out from an aqueous solution.

Best regards,

Guillermo Marrufo
Monterrey, NL, Mexico
^


thumbs up sign Hi all. It seems that plating has left the building and we've moved on to a semantics discussion :-)

Guillermo is surely right that sodium and potassium are metals, but so is James in saying, in a plating forum, that they are not. We've all seen chunks of aluminum, brass, copper, gold, magnesium, silver, steel, titanium, and zinc -- but how many readers have, in their whole life, seen even a chunk of sodium or potassium? :-)

Luck & Regards,

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


2007

? Dear James,

Thanks for your response. I am already learning a lot.

However, I am not sure what you disagree with. This was what I wrote:

"DEAR ROBERT,

THE BLACK COLOR OF THE DEPOSITS CAN EITHER BE INORGANIC (MAINLY METALS) OR ORGANIC.

AS THE TREATMENT DEPENDS ON WHETHER THE CONTAMINANTS ARE INORGANIC OR ORGANIC, HOW CAN YOU TELL WITHOUT A CHEMICAL ANALYSIS WHETHER THE DEPOSITS ARE INORGANIC OR ORGANIC ?"

I did not say that all metal ions would be removed. I really wanted to know if there was a method to distinguish between organic and inorganic contaminants so that I could determine the method to remove the contaminants.

Also, in your response you refered to Sodium and Potassium as non metallic cations. I always thought that Sodium and Potassium were metals and that Cations were derived from metals.

Thanks again,

Maurice Mason
- Danbury, Connecticut, USA
^


2007

If this were chemistry class, James' answer would be wrong, but in this context I found the phrase "non metallic cations" very clear -- they don't function like metallic materials as far as dummy plating is concerned -- and I liked it. Continuing in the semantic vein, black deposits certainly "can be" organic in a theoretical sense, but James is telling you that the black deposits in dummy plating are not organics.

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


2007

Ok, my bad. When I called them non metal cations, I was trying to imply metals in common everyay use such as iron, copper, nickel and etc. I fully agree that solid sodium and solid potassium are metallic by definition, but you can not lay them on an anvil and form them with a hammer, or draw it into an electrical wire or ... etc.
Anyway, as Ted said, you can not plate them out of a "normal" solution.

James Watts
- Navarre, Florida
^


2007

My Dear James, Ted,

With due respect, I must say I strongly and politely (if possible) disagree with you both. Chemistry class or not, Sodium and Potassium will always be metals.

I have seen the chemical symbols for Iron (Fe) and Chlorine (Cl) written as Ir and CH respectively for the same reason, "This is not a Chemistry class"

However, I must commend you both for your tremendous knowledge about plating, and that I have learnt a lot from you. Keep up the good work !

Maurice.

Maurice Mason
- Danbury, Connecticut, USA
^


August 17, 2010

Well all the answers are based on dummy plating done in the appropriate way.
But if one of the dummy plates are not doing a good contact to the bus bar this will act as a bipolar anode and the current drawing from the one that is isolated will turn the "cathode" dark gray

It is just a possibility

Daniel Hernandez
- Bucaramanga Santander
^

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