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Gas pitting problem in Nickel plating

Current question:

January 5, 2022

Q. I am plating basically a rectangular open bottom nickel silver box. Am hanging it longways down. The bottom of the box always accumulates gas bubbles and leave a rough pitted texture. If I put my air hose directly under that surface, will the air bubbles displace the gas bubbles, knock them off to get a smooth plating there? Or will the air bubbles prevent plating too much?

Dave Stephens
- Battle Ground, Washington

January 2022

A. Hi Dave. It's possible to have too much air agitation, and we have several threads in the forum that discuss that situation. But you are probably using an aquarium bubbler with little likelihood of being too aggressive, and the immediate answer is that you can't let those accumulating hydrogen bubbles grow anyway. Agitation is one of the few weapons you have against them.

You probably need both a wetting agent and air agitation to dislodge those bubbles. However, I would not hang the part with a surface horizontal. I would tilt the parts in one or more planes so the bubbles have an angularly upward escape route they can follow. You should probably look at the pits with a jeweler's loupe and verify that the pits are shiny and hemispherical, as evidence that hydrogen gas is their cause.

Luck & Regards,

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

Closely related Q&A's, oldest first:

December 18, 2010

Q. Hi,
We are doing nickel plating on different automotive parts. But we are facing problem of gas pitting in particular part that is muffler. Pitting comes in low current area which is in the direction of manual agitation. Motion of cathode is 16 rpm perpendicular to anode area. Current is 2.17 A/dm2. Volume of tank is 5000 liter. Wetting agent is in excess, nickel content is 63 g/liter, nickel chloride is 27 g/liter, pH we are using is 4.4, temperature is 55° C but still facing gas pitting.Can anyone help me in solving this problem?

Muhammad Umair Khan

simultaneous December 23, 2010

A. I am not familiar with your nickel bath, but the nickel chloride seems to be a bit high. My guess is that your analysis is total nickel and chloride testing, and then assuming that all of the chloride is from nickel chloride. I would guess that you have a bit of HCl in it to control pH.

As far as gas pitting, if that is really the case, then your part needs to be reoriented or the stroke increased or the RPM increased to sweep the gas bubbles off.

James Watts
- Navarre, Florida

December 24, 2010

A. If nickel composition is ok maybe you can check for oil contamination, probably it will be the reason.

I can not know from here and with the data you provide if the cause is oil, but is probably the reason, the oil is dissolved with the wetting agent, some of the wetting agents make oil soluble in water.

And adding the fact that some exhaust systems have inner chambers difficult to be rinsed they can get oils trapped inside.

So if that is the reason maybe you can follow this advice

Do carbon treatment as it must be done and add fresh brightener, improve rinsing and check the result.

If contamination is severe you can add peroxide or permanganate treatment but just as the last resort.

why ? Because peroxide and permanganate "burn" the brighteners and leave residues that can affect plating bath performance and appearance.

I hope this helps


Daniel Hernandez
- Bucaramanga Santander Colombia

December 29, 2010

A. I assume that your bath is a watts standard bath in such case the pitting can be due to

Wrong wetting agent/lack of wetting agent
Low nickel content
Oil contamination
lack of cleaning in some cases

Daniel Hernandez
- Bucaramanga Santander Colombia

December 30, 2010

A. Dear Muhammad,

Pitting could be due to, but not limited, to the following reasons:
i) Gas (usually Hydrogen) bubbles
ii) Oil droplets
iii) Particles

Please send us some photographs as the shapes and appearance of the pits will give an indication as to what is causing the pitting.



Maurice Mason
- Danbury, Connecticut

December 31, 2010

A. Facing pitting problems should not only be considered as a "chemical" process issue. Most likely it could be caused either by air agitation (this information is missing from your side) as well as the whole electrolyte pumping circuit, check for possibilities of air in your electrolyte pump system. Also check your temperature and increase it in order reducing the surface tension to provide a better process related gas bubble escape.
I do expect that Anode-Cathode area, type of anodes in use as well as all other additives/chemicals are within range.

Happy New Year!


Dominik Michalek
- Melbourne,Australia

January 6, 2011

A. I'm sorry I forgot to comment that lack of boric acid causes pitting and organic and inorganic contaminants too...

Daniel Hernandez
- Bucaramanga Santander Colombia

June 25, 2012

Q. I am in the business of making wire mesh to filter light and sound and for the past few months the parts have been looking bad. They show signs of pitting on the first pull, and holes hydrogen bubbles, pimples (nickel balls) on the rest. We normally go through this in the spring months but this year it has been bad. Please give some ways to figure this out. Thank you

Corey R [last name deleted for privacy by Editor]
- mcgraw New York

"Trouble in Your Tank: Handbook for Solving Plating Problems"
by Larry Durney
from Abe Books

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June 26, 2012

A. Hi Corey.

Unfortunately, it's not usually as easy as that. Larry Durney wrote a whole book.
just on how to correctly approach the troubleshooting of electroplating operations :-)

But if you have pitting, and holes, and hydrogen bubbles, probably the first thing to look at is your surfactant and surface tension. Please provide additional details when you can.


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

June 27, 2012

A. First check your anti pit (wetting agent)
Second, add or increase your air agitation and insure that the bubbles sweep across the part.
Third, consider changing the angle of the parts in the tank so that the air will partially flow through the screen.

James Watts
- Navarre, Florida

July 2, 2012

A. Sounds to me like you need to thoroughly check the solution analysis, specification and operating conditions. Gas pitting is normally caused by low surfactant levels and/or poor agitation. Nickel nodules are often caused by poor agitation, solutions contaminated with dust particles, too higher cathodic current density, etc. Both effects can be caused by incorrect pH.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

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