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Plating zinc die casting without copper cyanide strike.


A discussion started in 2008 and continuing through 2017 . . .

March 25, 2008

Q. Hi, I'm trying to assist a customer who wishes to plate polished die cast parts without the use of a cyanide copper strike. My company is a supplier of plating chemicals with emphasis on Anodizing and electroless nickel. We all know die cast zinc is hard to plate without a cyanide copper strike, but my customer cannot get a permit from the South Coast Air Quality Management District, to install a new cyanide copper strike. So we are looking at alternatives. The volume of work is several hundred 2-5 square foot pieces monthly.

We have tried mechanical cleaning with poor results, blisters, poor adhesion and grainy appearance.

We have tried chemical processes such as soak clean, rinse, electroclean (anodic), rinse, with and without activator/neutralizer, and alkaline electroless nickel as a strike, followed by acid copper for thickness, before bright nickel and chrome.

All processes so far have blistered both on the polished side and the raw zinc die cast side. We know we need to improve the cleaning step, especially following the cleaners, but we don't know what chemistry to use to "bright dip" the polished zinc die cast part, sufficiently to a "white state", without etching it beyond use. Acid, of course, attacks zinc quickly. So, we are searching for an alkaline chemistry, to make the die cast surface clean of impurities and active enough to accept alkaline electroless nickel. Has anyone tried using an alkaline zinc plate, used as a strike, followed by electroless nickel followed by acid copper etc. etc.? Any help would be greatly appreciated.

Bob W [last name deleted for privacy by Editor]
supplier of chemicals and equipment - Placentia, California, USA


March 2008

A. Hi, Bob. Cyanide is a dangerous and nasty chemical, and indeed we should constantly be looking for alternatives and trying to make progress away from it. One promising possibility may be a proprietary copper strike. EPI (Electrochemical Products Inc.) [a finishing.com supporting advertiser], offers one specifically for die castings that may work well for you. See if they can offer case histories, sample parts, and a distributorship arrangement with you. I know there is also a proprietary nickel strike for diecastings too although I don't currently know the suppliers of it.

Safranek & Brooman
Finishing and Electroplating Die Cast and Wrought Zinc

politics  But we can't put the cart before the horse! It's good to work towards progress in chemistry, including reduction of hazardous substances ... but shall we ask people to board airliners with components built in an area where an air quality bureaucrat forbade the shops from using the correct treatments? I can imagine the lawsuit :-)

"Yes, we knew the correct & proven process sequence presented in texts, symposiums, & tested in peer-reviewed papers for decades ... but a regulator wouldn't let us do it in his area. So we played around and produced blistered defective parts and made some that looked like, well, let's give it a go, and we used them on that airliner" :-)

The jury's response would be: "You have no business making parts incorrectly. How could you talk yourself into mixing up priorities like that? Your business should have moved!"

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


March 26, 2008

A. Ted points to a proprietary non-CN copper which may work. A pyrophosphate strike may work too, however nothing is as reliable as cyanide copper.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg,
      South Carolina



March 26, 2008

A. Hi Bob,

I once saw on web, one of the electroless nickel supplier claiming to have Electroless nickel which plates directly on Zinc Die Casts.

-Sridhar

Sridhar Bushigampala
- Toronto, Canada



Electroplating Engineering Handbook

March 27, 2008

Q. Our metal finishing company specializes in refinishing antique parts and frequently we find that the customer's zinc die cast parts are often deteriorated and very difficult (and costly) to plate. I understand that zinc die cast parts are difficult in general to plate due to the aluminum and various impurities that it inherently contains; my hypothesis is that if the zinc die cast is first zinc plated, it will then be easier (due to the layer of pure zinc) to copper plate a zinc die cast part.

My question is: When a piece of zinc die cast is deteriorated, is it any easier to zinc plate it than copper plate? I know that the type of bath is certainly important to consider so I am also interested in suggestions for different plating baths, either zinc or copper.

My copper strike bath is a non cyanide, non pyrophosphate, alkaline solution specially designed for zinc die cast.

Jared Juntunen
Electroplater - Muskegon, Michigan, USA


February 10, 2012

Q. Hi
I'm a zamak parts producer by hot chamber die casting machines. How can I surface finish my products by "Alkaline Zinc Plating"? What is the "Alkaline Zinc Plating" process?

Amir Edjtehadi
- Tehran, IRAN

Zinc Plating
by Geduld

February 10, 2012

A. Hi, Amir. An alkaline zinc plating process is simply a process for electroplating zinc onto a component where the plating bath uses an alkaline solution rather than an acid solution or a cyanide solution. Electroplating is at best a rather complex industrial science even on "easy" substrates, let alone on zamak diecastings. So, unfortunately, I don't think anyone can offer you forum length instructions on this; but start with a study of plating on diecastings, and with a study of alkaline zinc plating, and you'll surely make progress. Best of luck!

Regards,

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



February 24, 2017

Q. Is there any process on zamak where we can do nickel and chrome without using any of the copper (acid, cyanide, pyro)?

Rumit Shah
- Jamnagar, Gujarat, India


February 2017

A. Hi Rumit. I know there was a plating supplier in Brooklyn New York who offered a nickel strike for zinc diecastings, and I saw it in operation at two locations, but I don't know if they are still in business. Shridhar says there is also an electroless nickel process for diecastings.

I am not aware of the specific technical literature on the subject, but surfacequery.com does show a number of articles on it if you are willing to pay for access to the database. Hopefully another reader will be able to point you to more details.

Please do not keep it abstract, but tell us what you're plating, how many, and why you need it copper-free -- so people know which proposals might be useful to you or not. Good luck.

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

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