Zinc Plating / Electrogalvanizing Mild Steel Wire

A. Hi Sajjad,
I have seen silver plating on copper wire, and tin plating on copper wire, and in those cases drawing it down after plating was certainly better, economically, logistically, and probably quality-wise as well. I think the general answer is always plate before drawing down if it works :-)
Unfortunately, I have zero expertise in wire drawing, and no experience as to whether zinc plating on steel wire can be reliably drawn down -- we'll have to wait for someone who knows :-(

As for the weight of the zinc plating, that depends on the application, and I'm not quite sure what staple pins are; but specified zinc plating thicknesses in standards such as as ASTM B633 range from 5 microns to 25 microns. If you're talking office staples, even 5 microns may be more that you need.

Luck & Regards,


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

A. Does it work?
Do you get what you want?

If the answer to both is "yes", then you are doing it right. If not, you are doing it wrong.

Trevor is not being a "wise guy", cousin Mohit, but is emphasizing that "performance specifications" are more important than "process specifications". If the work is satisfactory, no need to worry about whether the process is satisfactory ... it is :-)

Regards,

A. There is no real minimum or maximum anode-to-cathode distance. Whatever suits your condition should work. But in general terms, the larger the distance, the more solution resistance, so the more wasted power and heat. But the cathode must never touch the anode, and for shapes that are more complicated than wire, you may want a bit of distance so that the ratio of distance from the closest point to furthest point is as close as practical to unity.

As electrolysis proceeds, some water will be converted to H2 and 2OH-. The H2^ evolves as a gas and the OH- tends to raise the pH of the solution. Boric acid is a buffer to help stabilize the pH.

A. No, buffers are to stabilize the pH rather than to raise or lower it.

Re. ammonium chloride: hopefully a supplier will offer a more authoritative response here, but pending that, ammonium chloride is itself a buffer, eliminating the need for boric acid; I believe that ammonium chloride baths operate at higher pH than potassium chloride baths.

A. Mohanraj, use muriatic acid (HCl) diluted 50% with water to adjust pH down. pH of this bath should be 5.0-6.0. Boric acid is a buffer. Should be in a range of 3.5-6.0 oz/gal. Boric acid helps prevent burning of the parts.

In an ammonia/potassium bath, the ammonia chloride replaces the boric acid. The mixed ammonia [on eBay or Amazon]/potassium bath does allow higher current densities to be applied to the part. There are benefits with both baths. Temperature is also important when zinc chloride plating. Should be kept between 70-100 °F (don't have metric conversion available).

A. NEVER add boric to adjust you pH! Keep boric within 22-25 gms / Lit for wire plating, otherwise higher boric will encrust upon your anodes which may be at the bottom of your tank!

Muriatic acid is called Hydrochloric acid in this part of the world. Please use it judiciously and do not lower the pH below 4.8 to 5.0 as you have to remember that you are doing wire plating and a pH lower than this will cause immense build up of iron!

A. Hi,

During the drawing process what kind of fluid or soap is been used, is it getting cleaned well before you go for zinc plating? I guess you check on the cleaning, activation part, and at last what kind of zinc sulphate additives you are using?

A. Hi, Ranjit. There are a dozen or more brands of bright zinc plating solution, so if you are dissatisfied with what you are using, there are numerous alternatives. Please tell us the general composition of your bath your bath (cyanide, sulphate, chloride, etc.) because many wire platers use zinc sulphate but zinc chloride solutions would usually be used when brightness is wanted.

The composition of chloride zinc brighteners has been largely trade secret for many decades (ASM Metals Handbook, Vol. 5 says ALL are proprietary) so I don't think you'll find much published literature on the subject.

Sometimes these brighteners aren't mixtures anyway, but organic compounds synthesized from precursors, which it is not possible to mix from generic materials, but good luck and hopefully someone will point us to literature. I personally think your time may be better spent searching for another supplier than in trying to make your own, but good luck either way!

Regards,

? Please provide more data:
- By the products you mention, you use a potassium-boric acid zinc bath. So, you have a vendor for brighteners for this bath, have you asked them? Or you make your own bath?

- Provide conditions: Time? Current? Conditions of the wire when you plate (straightened, in rolls...)? pH? Concentrations?

- Do you use chromate conversion coatings? Lacquers?

If you give us more information, we can assess you better. Hope you can solve your issue!

Regards,

? Dear sir
Please tell us the process you're running, and after that the problem you are facing.
Thanks.

Hi Mukesh. Umer has told us that his problem is that the wire he is plating is not shiny enough after one day, and it turns black in a few days.

I think he needs to change his dilute nitric acid to a chromate treatment. What do you think?

Regards,

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

A. Hi, A.M.
Faraday's Law says that the deposit thickness is directly proportional to the ampere-seconds applied. There might be some small variation based on the cathode efficiency of the solution, but essentially the only way to get 5X more thickness is to apply 5X more ampere-seconds. Unfortunately, you'll probably find that you can't increase the current much without causing burning, and the answer is going to be that you need to run the wire at 1/5 the current speed and produce only 1/5 as much wire.

Regards,

A. 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.

Regards,

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" [on Amazon, AbeBooks] by Geduld; it has a 13-page chapter on continuous plating of strip and wire, and was published in 1988.

Regards,

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).

P.S.: You asked a particular reader to contact you personally, but this forum doesn't work that way: it would cut adrift the interested readers who have been trying to follow along; it would rewards vendors for not supporting the site by letting them reap free commercial benefit from it anyway; and it would make me spend my time and our advertisers' money in match up potential customers with non-advertisers. Sorry, anything that is shared must be shared publicly.

Regards,

A. Hi. Regarding the black foam, please see "Black Tar on surface of Acid Zinc Chloride bath" on thread 40095.

Can you run a Hull Cell panel to get an idea what is going on?

Luck & Regards,

A. Hi Yahya. Wire plating can be done from cyanide baths, straight sulphate baths, sulphate acetate, ammonium sulphate, and potassium chloride and/or ammonium chloride baths as you have described, and several more. Your bath sounds okay, and yes, distilled or demineralized water is always a safer bet than city water with unknown quantities of minerals in it.

It is a tall order to design plating line chemistry with "no experience in these things". If a consultant or plating process supplier is available, you should try to get their help. If not, a trustable book such as Herb Geduld's "Zinc Plating" [on Amazon, AbeBooks] is probably second best ⇨

Luck & Regards,


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