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Topic #2681 "How to remove Zinc contamination from Nickel plating bath"

Topic #3778 "Problems in Nickel (& nickel-chrome) plating on Zinc Diecastings"

Topic #41906 "Dummying" an electroplating bath?"

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Allowable ppm of metallic contamination in nickel plating bath

Q. We plate bright nickel on ferrous parts everyday. Once in a while we plate on zinc die cast parts, only a couple of Barrels. Lately we have problems one or two days after processing the zinc die cast, we have white spots on the ferrous parts after nickel plating.

Can this be zinc contamination from the die cast? Our cycle is; Clean, activate in acid salt, Copper Strike for 30 minutes, Copper plate for one hour, activate, Nickel plate for one hour. I have doubts that we are dissolving zinc from the die cast, since we apply a heavy copper underplate.

Also we are working 2 shifts everyday in a 6 barrel line, and this problem occurs two days after processing Zinc die cast, maybe 2 to 4 barrels, even do we process approximately 42 barrels everyday of ferrous parts. I would think that all this work will be plating out the small amounts of zinc that can be dissolved during plating.

I'd like opinions on this so that we can come up with an idea to prevent this from happening. Thanks in advance for any help provided.

Sergio Hernandez
plating job shop - Guadalajara, Jalisco, Mexico

A. Hello...

That's interesting. Because you think zinc contamination, but then in your part's low current density area would be dark not white. So I couldn't say zinc contamination. So we must think different reasons. I think it must be white Wash or rinse contaminant (stains). And your transfer time from copper to nickel must be short. And also I offer to you very important advice: You must use separate nickel baths for zinc die casting and ferrous bath. And you must use hot water for final rinse.

Good luck.

Emre Tuna
- Turkey

A. Sergio,

I plate a lot of zinc in my nickel tanks so I am very familiar with the contamination problem. I would recommend grabbing a bath sample when it is good and one when the spots show up and have it analyzed for trace metals. It is a ten minute test on an AA. Your chemical supplier ought to do this for you for free.

From my experience zinc doesn't cause white spots. I see darkness in the very low current density areas of my parts. I also see something we call "zebra stripes" on the mid current density areas at [Zn}>= about 80 ppm.

I'd probably look elsewhere to solve this one.

Good Luck

Trent Kaufman
Trent Kaufman
electroplater - Galva, Illinois

Q. Thanks to Emre and Trent,

Trent, what do you think of our cycle:
Clean, activate in acid salt, Copper Strike for 30 minutes, Copper plate for one hour, activate, Nickel plate for one hour?

I'll do what you recommend regarding the tests. The white spots went away when we dummied the tanks. I'll do the test as soon as these spots show up again, and right now, when everything is o.k.

Could it be copper dissolving in the tank?

Thanks again,

Sergio Hernandez
Job Shop - Guadalajara, Jalisco, Mexico

A. Sir:

What you are seeing is the start of zinc contamination. It starts out as a white haze in the LCD but goes to black or even zebra stripes with the increased contamination of zinc.

Switch your primary brightener (saccharin) to dibenzene sulfanomide. It will allow you to plate with much greater concentrations of zinc in your nickel bath. Some say up to 100 PPM.

Barrel plating parts burnish against each other creating greater zinc contamination. There are also many LCD areas that are not getting covered well. Perhaps a Low metal copper strike would cover better.

It may be necessary to drag your nickel tank or even pump it out on a regular basis to remove parts that getting out of the barrels. Dummy your bath @ 5 asf with the pH @ 3.5 with steel grate. Ramp rectifier to 40 ASF every hour to seal zinc on dummy. Use as much surface area of grate as possible.

Hope that helps.

Pat Mchugh
- Winchester, Tennessee

A. Sergio. I believe you have iron contamination in your nickel solution. Talk to your supplier to clean your nickel solution by pH cleaning or with a filter with ion exchange cleaning type NP-A supplies by Atotech.


Anders Sundman
Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,

A. Sergio,

Copper usually shows up as cloudy gray to black in LCD areas with roughness at higher levels. Anders has a good point about iron contamination. I have used Atotech's NP-A and it did a fine job of keeping the effects of iron contamination away. Iron (as well as silicates, phosphates, ammonia [on eBay or Amazon] and very high levels of potassium or sodium) will cause white to gray looking stains. Can't tell you much about your cycle. Sounds OK but don't know amps/ft2. When iron was a problem in my tanks I usually experienced roughness. The point about saccharine brighteners is a very good one. They have practically no zinc tolerance as I learned the hard way.

I think your trace metals analysis will show you the correct solution.

Trent Kaufman
Trent Kaufman
electroplater - Galva, Illinois

Multiple threads were merged: please forgive repetition, chronology errors, or disrespect towards other postings [they weren't on the same page] :-)

Q. Hello ...

What are the numerical values (ppm) of the iron, zinc, aluminium and another metallic contaminations in nickel bath?
What are the threshold values optimum and maximum? I searched this question's answer but I couldn't find it.

Could you answer this question?



Emre Tuna
engineer - Istanbul, Besiktas, turkey


1. Al 60
2. Cu 40
3. Lead 02
4. Zn 50
5. Iron 150
6. Hexavalent Cr 10

ajay raina
Ajay Raina
Ludhiana, Punjab, India

A. The Metal Finishing Guidebook has a chart that agrees with Ajay's posting except for suggesting 50 rather than 150 ppm Iron. Optimum would be zero, Emre. Unfortunately, the chemical world doesn't have go/no-go gauges where 49 ppm is okay and 50 ppm results in failure. The Canning Handbook [on eBay, Amazon, AbeBooks] has more detailed information, but also reveals that the sensitivity to particular contaminants depends to an extent upon the particular brightener systems used. If you use proprietary solutions, the technical data sheet should contain these numbers.

To expand upon your question just a little bit, probably the preferable thing to do, as the Canning Handbook suggests, is to frequently run Hull Cell test panels -- watching for the usual effects of this contamination in the lab before it becomes it becomes an actual problem on production parts; your technical data sheet will then give you hints at what is causing the Hull Cell problems, you will remove the contaminant on a sample per the instructions, and verify what levels of contaminant cause problems at different current densities. Good luck!

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

A. It depends on your customer. If you are plating 24K gold, it is probable that the contaminant level could be sub part per million. If it'ss a commercial plate job of some metal, the contaminant level could easily be where it affected the cosmetics of the plate. Another limitation is the point where it poisons the bath to the point of slowing down the plate rate too much.

In short, it will be very specific to your plating application and your customer.

James Watts
- Navarre, Florida

A. Mr. Tuna,

Mr. Mooney is (as usual) right. I've had several different brightener systems for my nickel tanks. Some were somewhat tolerant of contamination (zinc is my biggest problem), and some would show the effects at very low concentration (zebra stripes and dark plate in LCD @ [Zn]>5 ppm). My current brightener can plate acceptably at < 80 ppm [Zn}. If you are plating zinc die castings and you anticipate parts falling into your nickel tanks, I would purchase a small electrolytic purification cell for continuous low current dummy loading. It has helped my operation. In any case, contact your vendor. Good Luck.

Trent Kaufman
Trent Kaufman
electroplater - Galva, Illinois


Q. Hello Mr. Mooney et al,

Thanks your answer. I absolutely agree with you. But I have some hesitations. We plate door locks whose base metal is iron, zinc die castings and brass. When we chemically maintain every weekend the nickel baths, I find lots of parts fall over the bath. And our tanks are made from PP. When you look at tank/bath edges you can see redness. And plated parts have little pits. So,I assume iron contamination is high in nickel baths. But, when I run Hull-Cell test panel,I don't see any sign from iron contamination like pits or hazy deposit. And more interesting, when I measure iron and zinc contamination with spectrophotometer (Odyssey DR/2500), I find amazing results;

Total iron (in Rack)........4 ppm
Total iron (in Barrel)......22 ppm
Total Zinc (in Rack).......Under range
Total Zinc (in Barrel).....0,33 ppm

What do you think about these results? Are these results and situations normal?

Could you help me?


Emre Tuna [returning]
- Turkey

Q. Hello Ted Mooney... How are you? If you remember,I had asked this question a few days ago and you had answered. In your answer, you had wanted some trying from me. I struggled for this trying a few days. And I send results about tryings. But you didn't turn me again to re-answer. I think you forgot it or you haven't any time. If you possible, could you look at results and give me some explanations?

Thanks Sincerely,

Emre Tuna
- Turkey

A. Hello again, Mr. Tuna. Yes, sorry I was away; but I think your question was well answered by Mr. Raina and the other respondents.

[affil link to this on eBay, AbeBooks, Amazon ] gives generic values for iron contamination of 5 ppm as normal and 50 ppm maximum, and zinc contamination as 1 ppm normal and 10 ppm maximum. The Metal Finishing Guidebook says 50 ppm maximum for each. But as related by Mr. Kaufman, these values really depend on the particular nickel plating solution.

So your contamination values sound quite normal. I don't think metallic contamination is a major cause of pitting anyway. Besides insufficient agitation or wetting agent, other causes are porosity of the substrate, organic contamination, too much acid or too little nickel, particles in solution, or parts not being clean.

Because the Hull Cell panels look good, and you have trouble with both brass and steel parts, I'd suspect part cleanliness. Are you sure you see a waterbreak-free surface on the way into the nickel plating tank?

opinion! Parts should not be allowed to fall off the racks, and should certainly not be allowed to dissolve into the solution. This is a 1960's situation, not acceptable in this new millennium. If you make it a policy to stop the line and "magnet it" immediately every single time a part falls, you are on your way towards corrective action of no more parts falling. If you talk yourself into some particular number of parts being allowed to fall off the racks before it is a problem, you've already lost the QA war :-)

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

A. Mr. Tuna,

This message is long so grab a snack from the kitchen before you start!

The nickel sulfamate solution I use has the following contaminants:
Calcium <5 mg/L Cobalt <1 mg/L Copper <0.5 mg/L Iron <4 mg/L Lead <1 mg/L Manganese <0.5 mg/L Zinc <2 mg/L ammonia 180 mg/L sulphates 0.1 percent

This is directly from the manufacturer. Once I get the solution I dummy plate onto a corrugated plate at 5 A/sf and 0.5 A/sf to preferentially remove metallics such as copper, iron, etc. I also run continuous carbon filtration to reduce the organic contamination. The only catch is that you have to monitor the surface tension of the bath since wetting agent is removed by the carbon filters. After some time the filters become partially saturated with the wetting agent and consume less but, from experience, are still effective at removing organics.

As for your problem, pitting and hazy products I can offer you my experience. I believe I read another post of yours where you stated you electroform rather than plate. If this is incorrect I apologize.

I electroform optical reflectors for the projection market. For our first generation reflector module I used rotation and masks to achieve uniform reflector thickness. When we were in high production the motors were running nearly continuously. This caused the motors to become warm which caused the grease and lubricant to become less viscous. Over time a small trail of oil made its way down the rotating shaft and into the bath causing an oil slick on the surface. When a mandrel was lowered into the bath the surface received a thin coating of oil/grease. The result was a hazy optical surface. If I remember correctly, pitting was also observed.

My suggestion to you is to dummy plate to remove metallics run carbon filtration while washing the surface of the bath with your wetting agent. The wetting agent will trap the organics so they can be filtered by the carbon. Also check your agitation.

Best regards,

Christopher Jensen
- Bohemia, New York, USA

Q. Dear Sir,

How much metallic impurities (PPM) are allowable in Nickel Plating solution. And is it applicable for continuous nickel plating process on CRCA steel strip.
Please suggest .


Sastry VSA
- Hyderabad, Andhra Pradesh, India.
January 4, 2014

A. Hi Sastry,

Below metallic impurities tolerance for your ref:

1. Iron < 150 ppm - Speckling surface.
2. Aluminium < 60 ppm - Reduce limiting CD and create rough deposit.
3. Zinc < 50 ppm - Whitish or dark deposit at low CD area and shiny black streaks on deposit.
4. Copper < 50 ppm - Dark deposit at low CD area.
5. Hexavalent chromium < 10 ppm - Skip plating at low CD area.
6. Lead < 10 ppm - Dark, brittle and poorly adherent deposit.
7.Stannous tin < 10 ppm - Dark deposit at low CD area.


David Shiu
David Shiu
- Singapore

Accidentally put pickle aid into bright nickel plating tank

Q. Dear Sir

I have accidentally added 5 ltr of pickle aid to my bright nickel vat which is 1300 ltr. I have started the carbon treatment; it has been 4 hours and I plan on treating it with carbon for the next 24 hours.

Is there any way that my solution can be saved, or does this mean I have to dump and start fresh?

Hama ali
- United kingdom
April 21, 2016

A. Good day Hama.

That all depends on the make-up of the pickle solution. What are you pickling, steel? Check for iron. What is the composition of the pickle and is there a wetter involved (organics)? Have you run hull cell panels on your bright nickel and analyzed for chlorides, pH etc.? More info would be helpful. I would try peroxide/permanganate with the carbon. What concentration carbon, temperature etc

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

A. Hi Hama,
Peroxide/permanganate and carbon treatments are for removal of organic contaminants. They will not help with your problem.
If you give us a clue what your pickle bath is and what was treated in it we might be able to help. But the only safe option is to replace the bath.

geoff smith
Geoff Smith
Hampshire, England

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