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topic 40095 p.3

Problems in Acid Chloride Zinc Plating

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A discussion started in 2001 but continuing through 2020

affil. link
Zinc Plating
by Herb Geduld
from Abe Books

June 17, 2017


asghar norouzi
CROUSE CO - tehran,iran

A. Hi Asghar. The largest source of iron is usually a part which has fallen off the plating rack and is sitting at the bottom of the tank, dissolving in the acidic plating solution. I could be wrong but I don't think people tweak their pH up and down to try to control the iron content in an acid zinc plating bath.

You perhaps need to fish parts off the tank bottom, make sure no burrs of cast iron are being knocked off your parts in the plating tank, clean your filters to make sure no iron particles are dissolving in them, and do a peroxide treatment? Good luck.


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

July 4, 2017

Q. Sir

We do electrogalvanizing of wire for staple making. During rainy season the wire turns yellow from white. This is not acceptable in our product. How to avoid this problem?

Manish Kunar
- India

affil. link
Trouble in Your Tank: Handbook for Solving Plating Problems
by Larry Durney
from Abe Books
info on Amazon

Hi Manish, "turns yellow from white" is a bit vague. Are you talking about the incoming wire? Is it possible that the wire is slightly rusty? Are you talking about immediately after chromating, that the chromate color goes yellow in higher humidity? Are you saying that over the course of a month or so it turns yellow in storage.

Please see if you can locate a copy of Durney's "Trouble in Your Tank?". It's basic premise is that it can take us all from flailing to an orderly way of troubleshooting. Good luck.


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

February 4, 2018

Q. Hello Sir,
Can we achieve 10 micron filtration with acid zinc chloride filters using horizontal discs instead of cartridge filters?

Best Regards,

Aditya V. Gupta
wire & allied industries - Punjab, India

April 22, 2018

Q. What is oilout phenomena in acid ammonium chloride mix zinc bath? I am plating castings in this bath. Bath capacity is 1300 ltrs.
How to treat this and avoid recurrence?
Will this have any effect on Salt Spray Test?

Ramnath Dikshit
- Pune, Maharashtra, India

April 2018

A. Hi Ramnath. Please see our on-line library article "Improving Your Chloride Zinc Plating Operation" where Stephen Schneider tells us the causes and preventions for oilout, including excessive temperature and putting your additions all in one spot, resulting in over-concentration.

As for salt spray testing, its purpose is to alert you that the process got out of control; since you already know that it has, conducting a salt spray test doesn't seem helpful. If you are asking whether parts which were processed wrong will still pass, sorry, I don't know if salt spray testing is sensitive enough to catch this problem :-)


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

April 27, 2018

Q. 1. How much coating can we get from cold dip process on wire without making the deposit brittle?
2. Please suggest best book to refer electrogalvanising process?
I deal with wire.
Thank you.

Mandar Mhatre
- mumbai, maharashtra, India

April 2018

A. Hi Mandar. I am not terribly familiar with acid zinc plating of wire; but for zinc plating of discrete objects, up to 25 microns is a standard spec and 12 microns is very common for automotive requirements. And bending parts around a mandrel for adhesion testing is common, so this would probably not be considered a "brittle" plating.

But the diameter of the test mandrel would be proportional to the diameter of the wire, so it's easy to picture a wire so thin that 12 microns of plating would be problematical. Please try your best to present your actual needs.

The only book which I am familiar with about zinc plating is the previously illustrated "Zinc Plating" [affil. link to book on Amazon] by Geduld; it has a 13-page chapter on continuous plating of strip and wire, and was published in 1988.


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

Hull Cell/Barrel Line Disconnect

July 2, 2018

Q. My situation: We have a chloride zinc barrel line (potassium) that shows normal quality brightness of stampings, yet the hull cell shows a uniform dullness that presents as severely low brightener.

Since the hull cell calls for brightener, operators add it, and the parts quickly become flaky and blistering, which is a sure sign of high-brightener.

What situations could explain this disconnect?

Are there normal contaminants that could act as a brightening agent?

Keith Bowers
Consultant - Versailles, Kentucky, USA

July 2018

A. Hi. I think the most likely thing is something wrong in the Hull Cell plating procedure like a defective rectifier for the cell, a miscalculation of required amperage, etc. This is a standard 267 ml cell?


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

July 2, 2018

Q. No issue with the Hull cell operation. The panels respond correctly as additives are adjusted. As-is solution reflects no brightener at all.

Keith Bowers [returning]
- Versailles, Kentucky, USA

Q. My situation:
We are running a Continuous M. S. Wire Electroplating Plant using Zinc Chloride Bath along with Boric Acid as pH Maintaining agent. I am facing a lot of problems in the same and want to upgrade my processes to ensure quality. Kindly let me know what all information you would like me to provide to help you understand my process better.

Rishabh Agarwal
Business Owner - Kanpur, Uttar Pradesh, India

July 2018

A. Hi Rishabh! Are you describing an entire old processing line that your plan to scrap and replace, or do you wish to just put more efficient process chemistry in the existing tanks? If you want better chemistry for existing tanks can you please briefly give us your process/tank sequence (like: soak clean, electroclean, rinse, rinse, acid dip, rinse, plating, rinse, nitric acid dip, chromate, rinse, rinse, warm rinse).

(You wanted a particular reader to contact you personally, but this forum doesn't work that way because it cuts adrift the readers who are trying to follow along, rewards vendors for not supporting the site while reaping free commercial benefit, and makes me spend my time and our advertisers' money in matchmaking potential customers with non-advertisers. Sorry!)


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

Ammonium chloride + zinc chloride coating problems

July 29, 2018

Q. Hello,
There are 5 tanks, except passivation and oil rust removal tanks.
Ammonium Chloride: 165 gr / lt.
Zinc Chloride: 65 gr / lt.
Carrier: 4%
Brightener: 2%

Due to the misting and adequate coverage of the products, I made a new tank in accordance with the prescription in a university thesis. (I found a similar recipe on the forum). New recipe:
Ammonium Chloride: 135 gr / lt.
Zinc Chloride: 22,5 gr / lt.
Carrier: 4%
Brightener: 0.2%

But now the problem of fogging has increased much more. Completeness problems began to emerge. I saw black burns in the areas where there was a low level of entrainment when the product exited the passive.
I increased the amount of carrier slightly (0.7%). But I could not solve the problem of assertiveness again. I now increase the amount of zinc chloride by 0.8%.

(click on thumbnails for higher rez pics)
40095-2aThm   40095-2bThm   40095-2cThm   40095-2dThm  

Now these black burns appear before passivation.

I need your referrals on the subject.

Axmet Babacak
- Oryol / Russia

July 2018

A. Hi Axmet (apologies but your name came through with Russian language characters that our English e-mail and browser system made a mess of).

Thanks for the photos. It looks to me like you are zinc plating assembled step ladders, or something similar, and that the problems are in the paint tray area. Am I understanding it properly? Is there a possibility that the current flow to this area comes only through the rivets or hinge pins and they are not reliably conducting?

Unless it's just the lighting, it looks like half of the plating in two of the pictures is charcoal grey instead of bright, which is definitely a problem occurring in the plating tank, whether it be formulation or inadequate current to those areas. I can't easily identify other defects, with the exception of the large 'black spot' which could be a burn from the component touching the anode; but there also looks to be small black spots, which per my guess, would indicate that inadequate cleaning or pickling is also a problem (perhaps again due to poor contact during electrocleaning).

Please research the subject: "Hull Cell" on this site or other sites. It's usually not a good idea to make up or adjust the concentrations in large tanks from theoretical or book knowledge. Rather, you probably should use a Hull Cell to make up a tiny 267 mL volume, then electroplate small sample plates, and see how they look across the whole current density spectrum, make necessary adjustments, and then scale up those results. I think Hull Cell testing is your fastest way out of this problem short of possibly trying an electrical jumper to the paint tray area. Good luck.


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

Remove titanium contamination from acid zinc plating bath

September 19, 2018

Q. I service an ammonium chloride zinc barrel line that has been severely over-rectified recently, creating organic burned (oiled)-out and dissolved titanium anode baskets.

We've recovered from the oil, but still find high levels of titanium (33 ppm). My question is twofold:

1. Will this amount of titanium create any plating issues, defects, or efficiency changes?

2. How can I remove it efficiently?

Keith Bowers
Technical Service - Versailles, Kentucky USA

January 9, 2019

Q. What happens if my zinc chloride is at 60 g/l and it rises to 80 g/l?

luis baca
student - tijuana mexico

January 2019

A. Hi Luis. We might be having some language or translation difficulties but -- although you may add zinc chloride to the bath -- you wouldn't normally titrate or analyze for "zinc chloride", you analyze for zinc and you analyse for chloride. I'm not sure quite what 60-80 g/l of zinc chloride in the analysis would mean ... surely you have at least several times as much chloride in the bath as those numbers translate to?

Maybe you are expressing the zinc content in terms of what it would be if all the zinc were zinc chloride, in other words, 48% x 60 to 80 = 28.8 to 38.4 g/l of zinc = 3.84 to 5.12 oz/gal of zinc? Please try your best to explain your actual situation, what actually happened, rather than posting a hypothetical. Usually acid zinc has the rather opposite problem of growing in volume rather than concentration. Thanks!


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

How to analyze/titrate a mixed ammonium chloride & potassium chloride acid zinc bath

February 15, 2019

Q. Hi,
I want to ask how to calculate by volumetric/titration method the mixed ammonium chloride and potassium chloride in acid zinc bath. Because our customer has an acid zinc bath consisting of zinc chloride, ammonium chloride mixed with potassium chloride. We want to know a procedure to calculate each of the components in their bath solution by titration method. Thanks

Anis anis
Chemical analyst, SCA PT., - jakarta, Indonesia

White layer forms during acid zinc plating but not on Hull Cell panels

January 9, 2020

Hi, I write from Italy.
In my company we have an acid zinc bath 12000 lt.
For a month now our problem has been that during the electrodeposition a white layer forms on the piece that we are unable to remove.
Our problem is that in the laboratory the Hull Cell does not show any problems.
Has anyone happened?
Thank you for taking the time, for those who will read and reply.


January 10, 2020

A. Hello Anna, have you tried cleaning your zinc anodes in the plating bath? How is the thickness of the deposit when this problem occurs? Has your pre - clean process changed and are all chemicals within spec? Unfortunately many times the cause of a plating problem cannot be zeroed in on one particular defect in the process. You can also send out some parts to a reputable lab that has XRF capabilities. It's also possible that your zinc supplier can get it done for you. Good Luck and hope you get your problem solved.

Mark Baker
Retired - Winston Salem, North Carolina USA

January 16, 2020

A. First try entering the plating tank "hot". Then, in case where other racks are already in the tank, look for galvanic voltage on the new rack just before it makes contact. Then with an ohmmeter, check each anode connection.
Finally, if more than one rack is in the tank, watch the ammeter and note if one rack is not continually making contact and thus causing a "bi-polar" effect on the rack with the white film.

robert probert

Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina

January 17, 2020

Q. Thank you gentlemen for replying.
We tried them all. We started with 25 kg of potassium permanganate to drain the tank from any impurities.
We cleaned the zinc baskets and replaced the bags around them.
Replaced current rectifiers. Having never had the problem we went for exclusion.
Ironically, my brother tried to put 5 liters of ethanol into the tank.
The coating has improved but we have not understood if ethanol helped to bind some crazy molecule or improved the wettability of the pieces or it was a coincidence.
We have replaced the passivation at the end of the line.
At the moment we have not yet resumed our work rhythms but we are getting closer.
I am attaching some photos of our works.

40095-3a   40095-3b   40095-3c   40095-3d  

Thank you all and sorry for my english.

Anna Mascolo [returning]

September 25, 2020

Q. Hello

I am a manufacturer of fasteners. The problem I am facing is related to acid zinc plating. After parts come out of barrel are bright and shiny but Post trivalent dip and drying, they appear dull and lose their brightness. And also develop film of white powdery type which can be wiped with a slight touch. These parts when sent to customer and when opened are found to be heavily rusted.

Powdery film on zinc plated parts a   Powdery film on zinc plated parts b   Powdery film on zinc plated parts c  

Please guide where am I going wrong and help me with the solution.

Thank you

Kapil Dhanraj
- Hyderabad Telangana, India

September 2020

A. Hi Kapil. The parts being rusted when received indicates that either they were not packaged fully dry, or the packaging material is improper, or the plating is not thick enough. It looks like you are packaging the fasteners in large plastic (visqueen?) bags, which will hold in any moisture if they aren't bone dry.

There could be a number of causes for an appearance problem after chromating but not before: from excessive brightener to badly made up trivalent, to bad post-chromate sealer, to possibly a need for a nitric acid dip before chromating, etc. But I think the first issues are how thick is the zinc plating (nominal, minimum measured)? And have you done, or can you do, a Hull Cell panel to see if it gives a clue about brightener levels/residues?

Luck & Regards,

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

September 28, 2020

Q. I think that the most likely cause is that the rivets - which have a blind hole - weren't fully dry. A 'quick and dirty' test is to put some of the finished parts in a Ziplock (r) bag, seal it and let it sit for a few hours. Or in an oven for a few minutes. Condensation on the inside of the bag is a very, very bad sign.

Tom Rochester
Plating Systems & Technologies, Inc.  
supporting advertiser
Jackson, Michigan, USA
plating systems & technologies banner ad

October 9, 2020

Q. I am plating some small parts with acid zinc plating, I am controlling all the parameters and trying to go with vendor's instructions. Until today everything was working fine, but today I was barrel plating a Disc shape part, the deposit looked shiny, the thickness was correct as predicted, but I had some problem with the edges of the part which was not coated.
The part is like a quarter coin. Any suggestion or idea?
Thanks for your help

Hamid Asgari
- Austin, Texas

October 2020

A. Hi Hamid. In general, edges should plate as much as the faces, maybe more. Please tell us what the substrate is -- low carbon steel or what? Is there a possibility that these disks were laser cut, or that there is some other explanation for the character of the edge to be different than the character of the faces? It sounds to me like the edges may not be in plateable condition.

Luck & Regards,

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

October 9, 2020

Q. Hi,
Thank you for your kind response.
The part is a magnet composed of Rare earth elements mostly Fe.
I had some good deposit on rectangular and cube shape parts and had no problem on the edges.
I am thinking to reduce the rotation speed of the barrel.
I run the Hull Cell test and all were good.
Thanks and best regards

Hamid Asgari
- Austin, Texas


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