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topic 28851p3

Process of Zinc-Nickel Plating

A discussion started in 2004 but continuing through 2020

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March 31, 2016

Q. Hi all. I have a question about zinc-nickel plating. We are making a part and have to send to our finisher for getting zinc-nickel plating. This part has two PEMs; if we use zinc plated PEMs, after plating the color of PEMs turn black. I do not know what is the reason? Material of PEMs, thickness of zinc on the PEMs, or washing time and composition before plating?


peyman basirian
quality engineer - vancouver, BC, Canada

April 12, 2016

Q. We are facing problem in Alkaline Zinc Nickel Plating Self Tap screws M5 x 18 . Carbonitriding process with 340 HV hardness. Even after 3 Hours of Plating coating thickness found 2 - 4 Microns in the parts. Load Qty : 40 Kgs Current : 500 Amps.

Any suggestion to overcome this problem.

Geetha Muthuramalingam
- Tamil Nadu India

June 14, 2016

Q. Hi,
We are doing zinc nickel plating on alloy steel components. Some of these components have tubular shapes and cavities about 40 mm in dia and 50 mm deep. We are getting zero thickness in the inner side of these cavities and the salt spray fails within 120 -150 hrs. On the outside, the thickness achieved is around 25 - 30 micron and the salt spray test is also okay from the outside area only. Can you please suggest any remedy to achieve thickness at the inside area of these parts. Voltage = 4 - 6 V. Time = 30 minutes.

Yasir Khan
- Karachi, Pakistan

July 14, 2016

Q. Dear sir .
Please help me regarding acid zinc-nickel. I am starting acid zinc-nickel plating in barrel plating; I don't know what are the standard parameters of this bath, and some problems face me every day. After 2 barrel plating the fastener threads are not bright and if I am doing Hull Cell test then Hull panel LCD area is full dull. What should I do I don't understand. Please help me with standard bath parameters and maintenance of acid zinc-nickel bath.
Thanks sir .

amit awasthi
- mumbai , maharastra , india

A. Hi, Amit. The supplier you are purchasing your zinc-nickel plating process from will have a "technical data sheet" instructing you how to operate it. It's a fairly complex process because you don't just need the right thickness and brightness, you need to maintain the correct percentage of nickel in the deposit or it will not offer the proper corrosion resistance. Good luck.


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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
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July 22, 2016

Q. We want to use Zn-Ni Electroplated coating for our clamps and thinking to get the 25 µm to 30 µm Zn-Ni electroplated coating thickness with 12 wt% of Nickel content. Does this thickness improve the corrosion resistance purposes or it's detrimental? Should we need to adhere to 8 µm to 14 µm coating thickness to achieve the optimal performance?

John Stacey
- Sydney, Australia

December 2016

A. Hi John. For standard zinc plating there is no doubt that 25 microns is better than 8 to 14. Standards like ASTM B633 [affil. link to spec at Techstreet] call for 5 microns for mild exposure, 8 for moderate, 13 for severe, and 25 for very severe. To my knowledge 25-30 microns of zinc-nickel is not deleterious, but you might check with your supplier because there might possibly be difficulty with chromating, roughness, or something else they caution you about for their process at that thickness.


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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
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December 9, 2016

Q. I am trying to deposit Zn-Ni on 4 inch x 2 inch CM steel sample using a chloride bath with pH 5.5-6.0. I am plating two samples simultaneously using a 15 L bath. I am seeing black and burnt coating at the bottom up to a height of nearly 1.5cm. Kindly suggest how to overcome. I am using a filtration system and the cathode movement is very slow.


Manju Srinivasan
- UP India

December 20, 2016

A. Hi Manju,

Please enlighten us with:

- Barrel or rack plating?
- Acid Zinc-Nickel: which nickel percentage (low or high)? Do you test in hull cell? What are your parameters (potassium chloride, metallic zinc, voltage, time, temperature)? Do you test for iron?

I think that we can help you if you can give us more information.

Best regards!


Daniel Montanes
N FERRARIS S.A. - Canuelas, Buenos Aires, Argentina

January 13, 2017



January 2017

A. Hi Gagadeep. Are you a highly experienced zinc plater venturing into zinc nickel? Sorry, but those 10 words don't comprise a realistic request. Please start with a few paragraphs summarizing your situation and what you know and don't know about the subject, and hopefully we can begin a back & forth and make some progress. Good luck.


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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
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January 13, 2018

Q. Respected sir, I'm running acid zinc nickel plating. All parameters are maintained, but after plating a white salt appears on plated parts both before and after passivation. Please tell me the solution.

Kamaldeep singh
- Delhi india

February 26, 2018

Q. I'm having difficulties of high insertion forces (8-12 kn) of a steel tube into an Aluminum housing. The tube with ZnNi plating per Ford standard WSS-M1P87-B4.
Ra =0.9 vs. a normal zinc plating of 0.2.

The tube diameter is 19.03 mm in a machined hole of 18.950 (0.080 mm interference)

A normal Zinc plated tube is inserted with 3kn.

The total thickness of the plating is 0.017 - 0.024 mm.

The inorganic sealant is FINIGARD 200A.

I get values of chemical composition of a 12.4 % nickel concentration in plating.
It looks like it has a Cr 0.06 layer after Zn-Ni..

jaime puente
Bocar - Mexico City

March 14, 2018

A. Hello Jaime!

Finigard 200A has an (approximate) friction coefficient of 0,22. This is a little high for this application. Talk to you vendor to use another sealer with a friction coefficient more like 0,12-0,10. I think that with this values you will have a better (and stable) performance in this application.

Best of luck!

Daniel Montanes
TEL - N FERRARIS - Canuelas, Buenos Aires, Argentina

March 3, 2018

Q. Sir, we [don't know?] required SST life of (MFZn Ni 1 - B) Zinc Nickel plating salt spray life, like for white rust and red rust, because we have not found HES D2003-03 [Honda Electroplating Standard (for corrosion prevention, rust prevention and decoration)].


March 14, 2018

A. Hi Ravinder. If you are a Honda supplier, ask for this spec. They should give it to you because they are the only source of up-to-date Honda specs. I don't recall the "B" in ZnNi Honda specs, so it may be a new type of topcoat or a typing error.

Best of luck!

Daniel Montanes
TEL - N FERRARIS - Canuelas, Buenos Aires, Argentina

Black spots on ZnNi plated parts from water soluble cutting oil

August 20, 2018

Q. Issue of black spots on ZnNi plated parts when comes in contact with water soluble cutting oil, please guide what is the element which which causes the same from either cutting oil or plating.

laxman Ramdasi
- india

August 20, 2018

A. Hello Mr. Ramdasi,
Some waterborne cutting fluids can be rather caustic. They may contain detergents, and also substances to prevent mould growing. To begin your troubleshooting, you should determine the pH of the fluid in question. That information will give you a clue as to what the reaction could be.

Rachel Mackintosh
Plating Solutions Control Specialist /
Industrial Waste Water Treatment - Brattleboro, Vermont

August 2018

thumbs up sign  That was a concise and practical answer, Rachel. Should have thought of it myself … maybe I will next time :-)


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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
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August 21, 2018

There's a first time for everything. Even brevity ;)

Rachel Mackintosh
Plating Solutions Control Specialist /
Industrial Waste Water Treatment - Brattleboro, Vermont

Black patches, pit marks on Zn-Ni plating

September 4, 2018 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Dear all,
we are suffering quality issue black patches, pit mark and rust on Zn-Ni plating.
Due to this issue, we get much more rejects.
Kindly anybody suggest a reworkable method to remove black patches.
So suggest how to remove black patches.

Mangesh taware
employee - pune, india

September 2018

A. Hi Mangesh. For some fast ideas, please read this thread which we appended your inquiry to.

To take it further, please give us some data: pictures of the defects, substrate material, barrel vs. rack plating, alkaline vs. acid plating, chromate and sealer details. Is this a problem that just came up or have you been suffering from it for years? One reject per hundred parts or 99?

I'm not sure if we have a language difficulty or if you are actually looking for a salvage method rather than corrective action, so please clarify that point. Thanks.


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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
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September 5, 2018

Q. Dear sir,
We are facing pit mark , black patches on zn- Ni plating from last couple of months.

28851-3c 28851-3b 28851-3d 28851-3a

Please share with me your experience how to remove black patches from plating permanently.

Until the problem is solved, could you tell me about any rework able method available to remove black patches temporarily because percentage of rejection is 50%

Mangesh taware [returning]
employee - pune, india

September 22, 2018

A. for black spots or pits on your alkaline ZnNi plated components, your ZnNi bath might be low in caustic -- this for me is the most common cause of blackness in the final product. So ensure you do a thorough bath analysis and check your level of Zn and caustic in your zinc nickel bath, then you can add a calculated amount of caustic or zincate concentrate. Also, ensure your pre-treatment process is effective,

I do hope this is helpful

Oladimeji Isaac
- Osogbo, Osun State, Nigeria

September 2018

thumbs up sign  Thanks Zik.


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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading

September 29, 2018

thumbs up sign Thanks ZIK sir.
After checking all parameters, definitely will come back with you.

Mangesh taware [returning]
- pune, Maharshtra, india

October 5, 2018

A. Kindly Check your Pre-treatment -- maybe acid pickle concentration is not in desired range.

Rahul Potphode
- Pune, MS India

November 7, 2018

Q. I am seeing a similar situation with AISI1008 machined products displaying black spotting quite significantly.

Can anybody comment on whether this would impact on the integrity of the base metal?

Randhir Singh
- United Kingdom

Black spots/patches on Zinc Nickel Plated parts

November 15, 2019 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I am MN from India. One of my suppliers is exporting parts to Europe. These are machined parts made out of 16MnCr5. Zinc Nickel Plating is done on this part. After receipt of parts from Plating, the Machining supplier cleans part with Ultrasonic cleaning process and then dispatches parts to Europe.
When the parts reach by Air or Sea the customer can see black patches and spots on part and if they do SST on these parts white rust is observed within 60 hours.

Mohan Nikam
- Satara, Maharashtra, India

November 2019

A. Hi Mohan. Although there is a lot of discussion about black spots and patches on this thread, it is not clear to me why the 'machining supplier' cleans these plated parts. Are they assembled into something and then the whole assembly cleaned?

It is not a sure thing, but certainly possible, that the ultrasonic cleaning is harming the parts. Zinc nickel plating is invariably chromate conversion coated; the chromate is necessary, and it is certainly possible that an undefined cleaning solution in the ultrasonic cleaner is stripping the chromate. For example, thread 9406 says that you can remove the chromate conversion coating by immersion into alkaline cleaner or by boiling for 15 minutes.


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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading

November 19, 2019

Q. There is Millipore requirement, and need to ensure no oil is present during dispatch. Also there is bore area where plating is not done and masking is done during plating other part of flange.
Also there is no 100% rejection. Black Spots are observed on 10% of lot.

Mohan Nikam [returning]
- Satara, maharashtra, India

November 2019

A. Hi Mohan. Although there is only 10% rejection, you said they get white rust in 60 hours whereas a good chromate conversion coating should deter white rust for 96 hours minimum, and a 192-hour or 256-hour requirement is often expected.

Other readers are welcome to offer their takes, but my first guess remains that the ultrasonic cleaning is harming the chromate conversion coating ... and it should be very easy to test by simply putting some plated parts and some ultrasonic cleaned parts in a salt spray cabinet together and tracking what happens. Good luck.


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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading

December 6, 2019

A. Hi Mr Mohan,

I don't think your plating guy is doing a very good job with the plating.

Please also check the water quality of the process line.

Khozem Vahaanwala
Khozem Vahaanwala
Saify Ind
supporting advertiser 
Bengaluru, India
Saify Ind

Passivation and polishing of Zinc Nickel plating

February 12, 2020

Q. I am renovating a MB 170S 1950 and zinc plating many parts like bolts and nuts. I dip the plated parts in nitric acid and finally in clear / blue passivation fluid and the result is satisfactory.
Then I have tried zinc-nickel plating for parts internal in the car that require higher surface finish, and here it is not going so well.
All steps are the same as zinc plating except the electrolyte and the anodes, all other fluids are the same.


1. The zinc-nickel plated part immediately turns black when I dip it in the nitric acid and the same happens if I just dip it in clear / blue passivation liquid. According to the instruction, a strong stream of bubbles should come when you dip it in the nitric acid but it does not happen.
2. It is excellent to polish the plated part and I get it very glossy, the layer of the plating seems to be of good thickness as I do not manage to polish it off and get down to the original material. But what happens to the different layers of surface treatment: am I polishing off the top protective layer and getting less protection?

Jonathan Hübinette
- Östhammar / Sweden

February 25, 2020

Q. Hello everyone.

As a part of new investment, we started a demo-line for our zinc-nickel alloy plating operations to test effects of parameters in a way that represents factual business circumstances.

However, by the end of day one we hit a huge road-bump.

In order to investigate the effect of zinc concentration on throwing speed, we diluted our trial bath to 7 g/L from our regular 8,5 g/L. I expected a significant rise in plating time. That being said our operation times increased more than three times. (1 hr for given thickness in normal operation, more than 3 hrs for demo-bath)

My question is, what am I missing? Did I underestimate Zn concentration's effect? Or Zn ratio started a "domino-effect" on other parameters that I can not observe easily? 7 g/L should still be acceptable but 3 hr for just one rack? It is by no means feasible!

Thanks in advance.

Serhat Ozturk
Platech Metal Plating Technology - Sakarya, Turkey

March 9, 2020

Hi Serhat!

Did you dilute all the bath or only zinc content? Did you use the same water you use in the process or distilled water? Is it alkaline or acid zinc-nickel?

Zinc content of 7 g/l for an alkaline bath isn't a problem, you get more plating time but not triple. You should see if anything is off parameters in this "dilution". High nickel content (in relation with zinc) decreases your throwing power, too, so as a complex bath as it is, you need to watch all the parameters at once and not one to one.

Help me with the other data and we can solve this mystery!


Daniel Montanes
N. Ferraris S.A. - CaƱuelas, Buenos Aires, Argentina

simultaneous March 16, 2020

A. Hi,


you are using wrong process so that your plated component has became blackish.
you should follow the given process

Zn Ni plating-drag out-water rinse - wr - hot water rinse - 0.2% sulphuric dip (not necessary)- water rinse dm water -passivation - two times water rinse - top coat/sealer.

You will get very good colour as well very good salt spray life also more than 1000 hours.

Awadhesh Avasthi
- NEW DELHI, India

March 16, 2020

A. Hi.

Just to share my experience in Zn Ni alloy plating (alkaline).

If you increase Zn concentration, it will reduce plating time, but you cannot increase too much, 9.5g/L, it will ruined your appearance.

If you increase Ni concentration (still within the range), it will increase plating time. But too much Ni will take longer time to complete plating (my exp. up until 3 hours plating time.

But, you need to be careful, make sure there is a balance between ZN an Ni content.

I will control Zn between 7.5- 8.3 g/L and Ni 1.3-1.7 g/L

Please bear in mind, current density will effect your throwing power and appearance.

Thank you,

Izzuddin Jaafar
Asahi Aero Malaysia Sdn Bhd - Selangor, Malaysia

March 17, 2020

Q. Hello team,
We are facing repetitive zinc nickel plating peel off issue from our customer during crimping process.
Requirement of Plating thickness is min 8 microns & nickel content is 12-16%.
Plating supplier claims plating thickness can't be maintained evenly on surface.
Base material is VS13111.


Raja Beri
Quality Assurance - Bangalore, Karnataka, India

April 2020

thumbsdown Hi Raja. I give up :-)
Google finds me no pages with that spec number or alloy. Please tell us whose spec it is or exactly what the substrate is. Thanks.


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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
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