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Plating aluminum with copper

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An ongoing discussion from 1996 through 2014 . . .

(1996)

Q. I am fabricating 6 inch dia. aluminum mirrors and would like to plate them with copper. I have never electroplated anything in my life before but have brushed up on my university electrochemistry. I tried a sample piece of polished aluminum with copper sulfateamazoninfo solution and a battery charger amazoninfo but the build up was very pulpy and did not adhere to the aluminum surface, flaking off when I tried to polish it to a smooth finish.
What can I do to produce a mirror like quality smooth layer of copper over my aluminum blank?

Any and all suggestions greatly appreciated.

Thank you.

Note: These mirrors will be used to reflect IR (heat) from an oven to focus the energy and may be operating at a very high temperature.

Dr. A. Dovigi
- Canada


(1996)

A. Dr. Dovigi:

The surface of aluminum items almost instantly oxidizes, so that the surface is not active and not amenable to plating. A solution is to zincate the item first, replacing the aluminum surface with a zinc surface, which is plateable. Even then, copper is far more noble than zinc and will immersion deposit pulpy and non-adherently from a copper sulphate solution. You would need to cyanide copper plate or copper pyrophosphate plate before you do the acid copper. There is a lot to the process, and you'll need to read a few chapters on this from the plating texts before starting.

Even then I question whether you are approaching things the best way. My belief is that infrared reflectors are usually bright dipped, anodized, and gold dyed, rather than copper plated. It's simpler, less expensive, and more reliable.

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


(1996)

Q. Dear Ted,

Thank you for your reply and information. I know a gold surface is a much better reflector at infrared wavelengths. The only reason for using copper was to try and keep the costs down. Being a dentist I have worked with gold foil and considered this an option to plate the finished surface of the mirror blank, but again I ran into the problem with the gold foil not adhering to the aluminum surface. Now that you have explained why (aluminum oxide coating forming) I understand why this failed as well. Can you offer any suggestions on the most cost effective way to go about plating my mirrors?

Thank you Al

Dr. A. Dovigi [returning]
- Canada


(1996)

A. Sir,

As an anodizer I agree with Ted ... hardly any of the platers I know plate on Aluminum. We process many reflectors here with bright dip and clear and colored anodize.

David A. Kraft
- Long Island City, New York


(1996)

Q. Thank you for your reply and information on trying to electroplate aluminum with copper and why I failed. I have also tried to coat the aluminum surface with gold foil but it failed to adhere to the surface. I understand now the oxide coating is the source of the problem.

Any suggestions on how to over come this problem and to coat the reflecting surface of my aluminum mirror with gold foil?

Thank you

Note this mirror will be operating at high temperatures. Will thermal cycling pose a problem with adhesion?

Dr. A. Dovigi [returning]
- Canada


A. Hi again. Please research whether I am right that bright dipping, anodizing and gold dyeing will deliver the infrared reflectivity you desire. It doesn't make sense to keep struggling to invent a process for adhering gold foil or gold plating onto the aluminum unless the well developed and much cheaper, simpler, and more robust method I described fails to offer something you need. Good luck.

Regards,

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



(1998)

Q. I have a brush plating system and do gold and chrome plating of car emblems. M question is how can I gold, chrome or nickel plate aluminum emblems or motorcycle parts using a brush system?

Also where may I get info on designing brush plating equipment and tank plating systems

ted izzo


(1998)

A. Plating on aluminum usually requires a zincating step. Your supplier, or the brush plating suppliers listed at www.finishing.com/chemicals, can provide the zincate. The actual process is to clean the aluminum, etch it with caustic, desmut with acid, zincate, cyanide copper plate, nickel plate, then gold or chrome.

I don't know of any articles that tell you how to design brush plating systems, but
- The Electroplating Engineering Handbook, edited by Larry Durney is all about designing tank plating systems, and
- Rubinstein's Electrochemical Metallizing is an encyclopedia of info about brush plating.

Best of luck.

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


(1998)

A. All of the major brush plating vendors have methods for plating on aluminum.

At least one vendor has a procedure for plating on aluminum (simple shapes) without the zincate and claims good adhesion. You have to be quick and good to do it however.

James Watts
- Navarre, Florida


(1999)

Q. I am with a company active in HF PCB as electromagnetic field radiators. These boards have very few soldering points and therefore I laminated plastic substrates with aluminum foil instead of expensive copper. My idea was to plate copper 1-2 microns thick after etching off the extra aluminum on the sides of the board leads.

The etching shop that supports our R&D initially was positive about prospects to have another massive project in a little while, but after three weeks of experimenting is not giving me anything.

Meanwhile I learned of a "Aluminum Bonder" - material that allows copper built up on the brushed with it aluminum.

Will appreciate any kind of advice, offer to cooperate.

(Mr) Valery Ostrovsky
- Rosh Ha'Ayin, Israel


(1999)

A. Dear Mr. Ostrovsky,

Thank you for your letter.

It sounds to me that you want to make the circuit paths of a wiring board using aluminum, and you just want to plate "tabs" at the soldering points using some kind of copper plating. Using a robust activation system using a metal cleaner, then a zincate as you describe as the aluminum bonder, followed by an aluminum tolerant electroless nickel, then a electroplated copper, then electroplated tin should provide a solderable surface for your connections.

Regards,

Tom Pullizzi
Falls Township, Pennsylvania 



Cyanide Copper Strike Bath

(2001)

Q. Hi! I have a couple of questions about a cyanide copper strike bath: When comparing a "standard" strike bath with a low efficiency Rochelle bath; which one of them is "kindest" to the zincate layer. That is, which one is the least aggressive to zinc? If so, I have the following questions: What possible interference/contaminants can have a negative effect on the previously applied zincate immersion layer? In other words, what can destroy or dissolve the zinc layer when I immerse the work in the copper strike bath?

If possible, I'm also interested in the chemical explanation involved.

Tips about books and articles about this subject would be great.

Stefan Johansson
- Sweden


(2001)

A. Dear Stefan,

It's the other way around. In my experience the Rochelle baths don't work well once you use zincate covered parts in them . A Standard bath works better, has better LCD coverage when using zincate or zinc diecast parts.

khozema Khozema Vahanwala
Saify Ind
 
Bangalore, Karnataka, India


(2001)

A. Hi Stefan,

The best copper solution to use for plating on zincate is follow copper solutions:

Alternative No. 1. Copper cyanide 41 g/l Sodium cyanide 56 g/l Rochelle salt 60 g/l Sodium carbonate 30 g /l pH-range 10-10,5 Free Cyanide 8,0-10,0 g/l Temperature 45-60 °C. Current 2-3 A/dm2

Alternative No. 2. Copper cyanide 26 g/l Sodium cyanide 32 g/l Rochelle salt 30 g/l Sodium carbonate 30g /l Free cyanide 1,5-3,0 g/l Temperature 45-60 °C. Current 2-3 A/dm2.

You should also use pre-contact when you plate on zincate in electrolytic solution. The zincate dissolves in copper solution. Zincate is only one protection for eliminate at the aluminum shall oxidize and thereby create bad adhesion between copper and aluminum. It is only a very thin zincate films on the aluminum substrate under copper deposit.

Regards,

Anders Sundman
    surface finishing engineer
- Malmo, Sweden



thrashing

(2003)

Q. I am trying to coat copper on Aluminum foam using copper cyanide, potassium cyanide solution, KOH, rochelle salt and potassium carbonate and platinum counter electrode.

I do standard pretreatment to aluminum substrate before coating and my problem is after plating (one day) foam start to getting black/blue color. Looks like copper is slowly reacting.

Is it a usual thing?
Is there anything I could do to avoid this happening?.

I would appreciate if someone can answer my question.

Manjula B.
student - Lansing, Michigan , USA


(2003)

A. I can tell you general plating method of copper on aluminium:

1. etching(NaOH)
2. desmut(HNO3)
3. zincate
4. strip(HNO3)
5. zincate
6. copper cyanide strike
7. copper cyanide(high concentration)
8. acid copper
9. nickel
10. chrome

Why use Pt anode? Copper ion source are solution and anode.

Thank you!

SE DO JANG
- KOREA



Copper plating an aluminum bike

(2007)

Q. Hi,

I would like to ask, which method should I use for creating a copper plating on aluminum.
I've decided to turn my racing bicycle to little bit of an 'art-project'. The goal is to cover AN6 aluminum frame with a layer a copper and let it get some natural patina over time. The method should be non-destructive to the thin-walled frame tubes.

Thank you for your opinions.

All the best,

Michal Kalnicky
hobbyist / designer - Bratislava, Slovakia


(2007)

A. Electroplating is more of an industrial science than a hobbyist art, Michal, and it's not clear what facilities, training, and experience you have. But plating copper onto aluminum would require zincating, followed by cyanide copper plating, followed by bright acid copper plating. Our "must-have booklist" will cover each of these subjects in depth.

But I think you should be able to more simply "paint" your bike with a system of primer, copper-based paint, and patinating solution instead. Good luck with it.
pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

Modern Masters Green Patina



Coating aluminum with copper for conductivity

February 6, 2013

Q. Hi,
I am trying to coat copper on aluminium. I want to know if the resultant conductivity is more than the parent metals?

Thanks

Venkata Amaresh
- Vizag, Andhra Pradesh, India


February 17, 2013

A. Hi Venkata. Aluminum bus bar is commonly copper plated because the copper has better surface conductivity (because aluminum quickly oxidizes in air to form an insulative aluminum oxide coating on its surface). But the copper plating is usually not thick enough to significantly alter the DC capacity of the bus bar. For example, if an aluminum bus bar has 50-60% of the conductivity of a copper bus bar of equivalent size, then it will still have 50-60% of the conductivity of a copper bus bar after plating it with copper.

But we have to be careful with general terms like "conductivity" because there is thermal conductivity vs. electrical conductivity, surface conductivity vs. solid conductivity, the fact that high frequency currents are carried by the skin rather than the core of a conductor, etc.

Regards,

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


Best formulation for cyanide copper strike over double zincated aluminium

November 25, 2014 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I operate a small electroplating shop and frequently process mainly decorative aluminium pieces, which are ultimately finished in gold or platinum. I use a very basic cyanide copper strike (50 g/l copper cyanide, 90 g/l Pot cyanide) after double zincating and sometimes experience blistering of the copper (and subsequent deposits). Could anyone please suggest the most suitable and reliable cyanide copper formulation for this application?

Many thanks,

Jonathan Stromberg
- Plymouth, Devon, UK
  ^- Privately contact this inquirer -^


November 2014

A. Hi Jonathan. We appended your letter to a thread where Khozema Vahanwala and Anders Sundman have offered their opinions on optimum formulation. We'll see whether a third opinion is forthcoming. Good luck.

Regards,

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



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