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topic 41906

What is the meaning of "dummying" a plating bath?

A discussion started in 2006 & continuing through 2017


Q. I have read that, in order to treat a acid zinc plating bath contaminated with copper it is recommended "dummying" the bath. What does it mean by dummying?
Thanks Gracias y Saludos,

Guillermo Castorena G.
Jobshop - San Luis Potosí, Mexico


A. The term "dummying" probably comes from "plating a dummy load". And it means to plate onto scrap (preferably a corrugated steel sheet) at a very low current density to try to get the copper contamination to plate out preferentially to the zinc. Copper, being more noble than zinc, should plate out well at a current density that is too low for much of the zinc to plate out.

Ted Mooney, amadeya42.com Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


A. Dummying, Dummy Plating = Limpieza selectiva

Saludos cordiales,

Dominik Michalek
- Mexico City, Mexico


thumbs up signThanks a lot for the answers.
Mil Gracias!

Guillermo Castorena G. [returning]
- San Luis Potosí, Mexico

sidebar (2006)

A. Not only electroplating baths, electroless plating such as electroless copper, electroless nickel also need dummying during re start-up after bath idle for certain time to consume excess stabilizer and activate the metal ions reduction reaction to prevent skip plating in following production.

David Shiu
David Shiu
- Singapore

November 8, 2016

Q. How do you dummy an electroless nickel bath after a new make up?
I am plating nickel on ceramic capacitors and the first loads usually fail and I get black parts. After a few runs, then I get good results.


Reynaldo Arroyo
- Sylmar, California, USA


A. By the term dummying it generally indicate LCD (Low Current Density) plating for Nickel as Zn and Cu are the most common impurities and can be deposited at Low current. While for Chrome it is done at high voltage and still call as dummying. So we can say that 'plating out' impurities from the main bath can be termed as dummying.

t k mohan
T.K. Mohan
plating process supplier
Mumbai, India

October 30, 2009 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hello, I am Vu.
I am not sure about the meaning of dummy plating.
- they usually apply the dummy plating after make up a new electroplating bath. What for?
- they apply the dummy when has some of the impurity of another metal in bath.

Could you please explain more details of the dummy plating? Working condition? How is the cathode? etc.

Thank you very much for your help.

Vu Ha
- HCM city, Vietnam

October 30, 2009

A. Hello, Cousin Vu. Dummy plating is one of several ways to deal with contaminants in a plating bath. It is usually used against metallic impurities, especially if the contaminant is more noble than the main metal of the plating bath. For example, copper contamination in a nickel plating bath.

In theory, you simply plate at a low voltage onto scrap cathodes, in hopes that the contaminant metal will plate out preferentially, so you will plate out the contaminant onto the scrap, without plating out too much of contents of the plating bath.

In practice, the dummy cathode is often a sheet of corrugated metal. In the old days, nickel plating tanks often had dummy plating compartments, so that you were continuously plating out copper and other contaminants. These days dummy plating is usually a periodic batch type operation instead. Good luck.


Ted Mooney, amadeya42.com
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

October 30, 2009

Q. Dear Ted,

Thank you for your explanation.
I've just come to customer and service them to make up the copper pyrophosphate plating. After the make up, they plate the dummy with grille cylinder as cathode.

So could you please let me know what did they plate the dummy after make up for?
Beside that, I worry about the grille cathode for dummy plating. This is the Japanese style and is not the same with my experience.

best regards,
Ha Uy Vu

Vu Ha [returning]
- HCM city, Vietnam

October 31, 2009

A. Hi, Vu. I don't know what a grille cylinder is, but what is used as the dummy cathode may not matter. I do not know why it is suggested to dummy a brand new copper pyrophosphate bath. If this is a proprietary bath there should be a technical data sheet for it that describes whether or not it requires dummying. If it is a "home brew" bath, perhaps the copper pyrophosphate is not pure enough.

I would suggest plating hull cell panels and seeing if they look good without dummying.


Ted Mooney, amadeya42.com
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

January 17, 2011

Q. Hello,
Is it advisable to do dummy plating in barrel plating operation. I heard that for dummy plating operation air agitation is must. In barrel plating operation during that dummy plating there won't be any air agitation in the bath. Will this be effective. Will it contaminate the bath instead of purifying.

Does this dummy plating operation remove iron impurities from the bath.

Please clarify?

Neelakandan M
Electroplating - India

February 2012

A. Hi Neelakandan.

You did not mention what kind of plating you are doing, so it is hard to answer your question. But in acid zinc plating it is usual to add peroxide to precipitate the iron, and filter it out. Good luck.


Ted Mooney, amadeya42.com
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

February 24, 2012 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread


george faizan
- pakistan

December 21, 2013

Q. Sir,
What type of Dummying is preferred for continuous nickel plating process? Stainless steel or Mild steel with corrugated sheet?
Please suggest with this regard.

Sastry Vsa
power systems - Hyderabad, Andhra Pradesh, India

December 23, 2013

A. Hi Sastry. Plain steel corrugated roofing sheets ought to be fine. Good luck.


Ted Mooney, amadeya42.com
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

December 24, 2013

Q. Sir,
Dummy current is 5 amps/SFT of the dummy size.
Is it correct or not ? How much current is applied for the one SFT?
Awaiting for your reply.


Sastry VSA
- Hyderabad, Andhrapradesh, India

December 2013

A. Hi Sastry. Yes, 5 ASF (amps per square foot) ought to be fine. Please see brief excerpt from the nickel plating chapter of "Electroplating Course Manual - Basic Practical Electroplating" published by the Garden State Branch of American Electroplaters' and Finishers' Society Inc., edited by F.J. LaManna



Ted Mooney, amadeya42.com
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

Nickel platers - do you dummy your tanks?

October 31, 2015

Q. This seems to be hotly contested. I'm a believer in dummying. Here's why:

Faraday's law applies to the anode as well as the cathode. There are going to be HCD areas on the crowns, or whatever, where the primary reaction becomes oxide formation rather than Ni dissolution. These oxide coated areas are apt to serve as sites for brightener oxidation. This introduces undesirable contaminants that aren't readily removed by carbon filtration because they are charged anions. I think they're removed so some extent by LCD electrolysis.

Another thing that might work is treatment with an anionic ion exchange resin. I once had some luck with this in the lab but never tried it on an actual bath.

dave wichern
Dave Wichern
Consultant - The Bronx, New York

November 4, 2015

A. Some dummy regularly and some run forever without ever dummying.

IMO dummying is necessary only if contaminants (primarily lead, zinc and copper) are present, or if anode and cathode densities are unreasonable.

However there was at one time a well known supplier who sold a self-contaminating nickel brightener.

jeffrey holmes
Jeffrey Holmes, CEF
South Carolina

November 5, 2015

A. Good day Dave.

I think dummying requirements are directly proportional to good housekeeping and proper process control.

That is a very interesting explanation regarding the oxide formation on HCD areas of the anode producing brightener oxidation. I would think the anode/cathode ratio is at play here regarding HCD oxidation. I would also think the anode ratio is too small, as it is producing HCD oxides.

I must agree with Jeffrey regarding metallics. Dependent on the substrate, one will get contamination depending on load size and ASF. Parts do fall in the solution, and as you well know, they are not always discovered/removed.
They will dissolve in solution and cause shelf roughness issues = dummying.
Proprietary brighteners/additives can address copper contamination in LCD areas as darkness.
A brightener overload will cause LCD problems/darkness/poor throw/coverage = dummying.
Just thought I might throw in my two cents.


Eric Bogner, Lab Tech.
Aerotek Mfg. Ltd. - Whitby, Ont., Canada

November 9, 2015

A. High current density dummying removes sulfur from the bath. So if your Ni deposits are compressively stressed, high CD dummying will make them less compressive and eventually tensile.

Only drawback is that high CD dummying is expensive.

Pat Mentone
Pat Mentone
St Paul, Minnesota

May 13, 2016

Q. I would like to know if anyone thinks you can dummy plate Zinc contamination out of a hex chrome plating solution. I would like to try it on Nickel plated corrugated steel. Maybe? High or low current density and any suggestions most appreciated.

Rich Mancinelli
- Newnan, Georgia USA

October 6, 2016

A. Rich,

I never heard dummy chrome to take out zinc contamination, but you can decant chrome solution to cut contamination out.
make sure LCD dummy not create trivalent chrome problem, once you create trivalent chrome you can not chrome plate on part.

popat patel
Popat Patel
Howard amadeya42
Roseville, Michigan

October 16, 2016

Doubt you'll have much luck dummying out Zn.

Try a porous pot purifier.

dave wichern
Dave Wichern
Consultant - The Bronx, New York

October 15, 2016

Q. Why dummy should be in zig zag shape? At what current density do we have to run it. Low current or high current density?

Ragul Rajendran
plating shop employee - coimbatore,tamilnadu, India

October 2016

A. Hi Ragul. The zig zag shape is preferred both because it offers a bit of range in current density, and because it offers more surface area than a flat sheet. Why it might be done at high current density was explained by Pat Mentone. But as others have said, it's usually low current density, about 5 ASF. But you haven't yet told us what kind of plating you are doing nor what kind of contaminants you are trying to remove, so it's hard to expand upon the good information already offered. Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

October 15, 2016

A. In many cases a current density of only 3 ASF is used and the current density is calculated on the projected area of the zig-zag plate (as if it was a flat sheet) not the actual area.

Lyle Kirman
consultant - Cleveland, Ohio

October 21, 2016

A. You dummy a chromium bath to activate the anodes and reduce trivalent chromium.
If you are using dummying to remove impurities at low CD often best to do a Hull Cell first and see if there is a dark band and then estimate the CD that that band is and then "dummy' at that average CD. Don't use too sharply corrugated sheets as you will waste too much metal on the high CD areas, and not get at enough at the targeted CD.
In the case of nickel always plate at normal CD first to get a coherent coat before lowering to the dummy CD so you get a coherent coat first as often the contaminated coating is porous and non adherent.
Don't dummy continuously unless you know you have a need, as you will just waste metal and power.
There are many other positions to "DUMMYING'

Geoffrey Whitelaw
Geoffrey Whitelaw
- Port Melbourne, Australia

December 3, 2017

Q. How can I remove the impurities such as copper & iron from an acidic zinc electroplating?

mark smith
- warsaw, poland

December 2017

A. Hi cousin Mark. There is no "such as" in this case, there are only specific suggestions for specific impurities in specific baths :-)

This thread started with a discussion about using dummying to remove copper from acid zinc, and my response of February 2012 suggested adding hydrogen peroxide to acid zinc to precipitate the iron and make it filterable. There may be other approaches if you have a detailed problem with these suggestions. Good luck!


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

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