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topic 7022

How to Strip Plated Silver Off Copper

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A discussion started in 2001 & continuing through 2017

(2001)

Q. I am looking for a system that doesn't involve cyanide, nitric acid or machining to strip plated silver off of copper, so that the copper can be reused and replated as needed. Thank you, Peter.

Peter Slade
electrical controls mfgr. - Horseheads, New York


(2001)

A. Dissolve 4 oz/gal sodium nitrate in concentrated sulfuric acid. Electrostrip with a lead cathode at 3V, 70-120 °F.

James Totter
James Totter, CEF
- Tallahassee, Florida


(2002)

Q. I am looking for a solution to strip plated silver from copper powder (30~40 micrometer), so that the copper can be reused and replated as needed. Thank you, very much.

Gyu-Sik KIM
- Asan, ChungNam, KOREA


(2002)

A. James Totter's reply should be essentially applicable, Kim; however, remember to develop this process in extremely small batches and with all precautions until you are familiar with it because conventional plating and stripping chemistry proceeds so rapidly on powder (because of it's very tiny mass and huge surface area) that reactions which would be fairly slow on large parts can be virtually explosive on powder.

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



(2007)

Q. Hi,

I would like to remove silver plating from copper and brass items and collect, I have seen these systems and cannot find the manufacturer, do you know who produces this type of equipment.

Thanks,
Mike

michael coletta
- Rockville Centre, New York, USA


July 31, 2008

Q. Would like to remove silver plating from copper and brass items and collect, I have seen these systems and cannot find the manufacturer, do you know who produces this type of equipment, or how to do it without harsh chemicals.

Kathryn Mueller
artist - Edwardsville, Illinois


August 2012

A. Hi Michael; hi Kathryn.

Silver plating wouldn't be very functional and useful if it easily dissolved away in dishwater or milk & honey. You can probably find a plating shop who will strip the silver for you; if you do it yourself, you will be using chemicals and you will be creating waste products. James has mentioned probably the best electrochemistry. To my knowledge, machines of this type are not available as catalog items, but you could contact the manufacturers of "Brush plating" systems shown at the top of the page and see what they can offer you. Good luck.

Regards,

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


February 26, 2013

Q. Is using an electrical current required? thanks.

Bill Peters
- Farmington, New Mexico, USA


February 27, 2013

A. Hi Bill. Yes, it is an electrostrip, with the article you are stripping being the anode.

Regards,

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



December 15, 2017

Q. James Totter presented a solution to strip silver but forgot to mention how to recover the silver.
Could somebody fill this void?

Alfred Fischer
- Canberra Australia


December 2017

thumbs up sign Hi Alfred. I doubt that James forgot to discuss recovery of the silver; rather, he probably chose not to because the question he was answering was how to strip the silver in such a fashion as to not harm the underlying copper, so that it can be readily electroplated again. I'm guessing his thoughts, but he probably would not recommend that a plating shop try to recover the silver from such an operation in-house because of potential dangers, and the cost of recovery probably exceeding the value of the silver.

If you are from a small plating shop, that would probably be my answer to you, although electrolytic recovery or ion exchange in the rinse water is a possibility if the stripping is part of the process rather than a response to a rejected item. We'll move this to the "Hot Topics"^"Current Topics" section to see if other readers have thoughts.

Please introduce yourself and your situation if it is different than the original question. Thanks.

Regards,

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


simultaneous December 16, 2017

Q. Thank you for your reply
First I like to let the forum know that navigating this web side is not easy for a new comer.
I was unable to find "Hot Topics" for example or the place where I could introduce myself deeper.
I still would like to know in which form the silver is after James Totter's recipe and how to recover it.

Thanks for your help

Alfred Fischer [returning]
- Canberra Australia


December 16, 2017

A. For small amounts, zinc dust may work by immersion plating the silver onto the zinc. The recovered metal can be sent to a refiner, but unless there are several thousand dollars worth of metal, the fees may be more than the value.

Lyle Kirman
Consultant - Cleveland Heights


sidebar2
December 2017

thumbs up sign Thanks for the site suggestions, Alfred; it's hard to see through another's eyes, so it's always great to hear about what they see.

We have a page at https://www.finishing.com/letters, which lists the current topics from the last several weeks; when a new question is added to an old thread, we index that thread there so our regular readers will see the new addition. Based on your suggestion, I'll start using 'current topics' universally instead of 'hot topics' -- a little less ring to it, but probably more understandable :-)

The forum doesn't have a meet-&-greet room. When we ask you to introduce yourself and your situation, we simply mean that your inquiry should tell us what you do -- elementary school student, post-doc researcher, regulator, plating shop manager, scrapper, refinery operator, etc. -- so the readers have a better insight into what your question is about. And why you are interested: Do you want to know a practical recovery method for a test-tube of solution, a 500-gallon vat, or 2 gallons per minute? Do you want to write a regulation, do you want to go into the business, do a science project on the subject, etc.? The "hard to see through another's eyes" cuts both ways. Thanks again.

Regards,

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


December 16, 2017

Q. Thank you for the directions on the website.
The instructions how to recover the silver does not make sense.
How to electroplate to Zinc Dust?

Alfred Fischer [returning]
- Canberra Australia


December 18, 2017

A. Alfred,

Electroplating, as in a process requiring a power supply, is not involved. The process is essentially the same as immersion plating. Zinc metal powder can be used to precipitate silver, as a metallic powder, from many different solutions. It is basically an exchange process. Silver and zinc switch places. The metallic zinc dissolves and the dissolved silver precipitates as a metal. Theoretically, I'm thinking that 1 g of Zinc will drop about 3.4 g of silver. However, if the solution contains chemicals that will dissolve zinc on their own, additional zinc will dissolve until this chemical is consumed and only then will the silver start dropping. An example of these chemicals, in this case, would be free nitric acid in an acid solution or a lot of hydroxide or free oxidizer in a cyanide solution containing free cyanide.

If you search for "electromotive series" (EM series) on the internet, you will find a chart which has the more active metals, such as magnesium, aluminum and zinc, at the top (usually - sometimes, but not often, the chart is reversed), and the less active metals, such as gold, silver, and copper, at the bottom. The general rule is that a metal in metallic form will drop out in metallic form, any and all dissolved metals that are below it on the chart. This assumes that the more active metal is soluble in that particular solution. There are also other peculiarities that can hinder certain combinations from occurring.

When silver in in a nitrate acid solution, you are much better off using copper than zinc to drop the silver. The main reason is that copper is right next to and above silver on the EM series. Therefore, it is very unlikely that there would be any other metals between copper and silver that would drop along with the silver. With zinc, which is far above copper, there are many other possible metals that might drop along with the silver - lead, cobalt, nickel, iron, e.g. Instead of copper powder, I would use a pure copper bar, the best being clean, scrap bus bar with no solder or plating on it. With copper powder, you are very likely to contaminate the silver with copper, unless you know exactly how much silver is in solution and use exactly the amount of copper needed to drop that exact quantity of silver. Almost impossible to do. With bus bar cut into lengths long enough to stick up out of the solution, so you can easily remove them, you can achieve a purity of 99+% silver, with very thorough rinsing.

Chris Owen
- Benton, Arkansas, USA



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