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Plating aluminum with copper

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A discussion started in 1996 but continuing through 2018

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 sulfate [linked by editor to product info at Amazon] solution and a battery charger [linked by editor to product info at Amazon] 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.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
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,

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



1998

Q. I have a brush plating system and do gold and chrome plating of car emblems. My 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 an acid appropriate for the particular alloy, zincate, strip the zincate in nitric acid, re-zincate, cyanide copper plate, acid copper plate, nickel plate (often 2 or more layers), 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.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
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 monitor
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.

Khozem Vahaanwala
Khozem Vahaanwala
Saify Ind supporting advertiser
Bangalore, Karnataka, India

saify logo


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
Anders Sundman
3rd Generation in Plating
Consultant - Arvika, Sweden




To minimize your searching efforts and to offer multiple viewpoints, we've combined some threads into the dialog you're viewing. Please forgive any resultant repetition or failures of chronological order.



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


Modern Masters Green Patina

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.

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



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,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
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


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,

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



Copper plating of anodized aluminum

September 14, 2015

Q. I am trying to copper plate anodized aluminum. Any ideas?

John Allegro
- Dallas texas


September 2015

Hi John. You haven't yet introduced yourself (high school student, post-doctorate research, experienced plating shop owner, hobbyist with no plating experience) or what you are actually trying to build (must the anodizing stay in place or may it be stripped, one piece or thousands, etc.) ... which leaves me in the position of having to start with the very basics, at the risk of talking down to someone who may know 10X as much about it as I do -- so I apologize if that's the case but ... you do know that anodized aluminum is non-conductive, non-metallic, and that it's generally considered a non-platable material? Get back to us with your situation please.

Regards,

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



How to do cyanide-free plating of copper onto aluminum

November 15, 2015

Q. Hi,
I'm Research student and I have a problem with coating of copper on the aluminum substrate. The adhesion is weak and copper cyanide is not suggested on my research because of the toxicity. Do you have any suggestions in order to produce good copper coating on aluminum substrate?

mohammad hafizudden
MARA Technology University - shah alam, selangor, Malaysia


November 2015

Hi Mohammad. After zincating the aluminum you can try pyrophosphate copper or proprietary solutions from companies like EPI (Electrochemical Products Inc.) [a finishing.com supporting advertiser]. Good luck.

Regards,

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


June 2, 2016

A. To avoid oxidation on my metals I do the cleaning and plating all in an argon gas bath, I'm sure there are lots of explanations on this if you google it.

Nick scott
- Bangor, Maine, United states



April 18, 2017 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I want to electroplate aluminium.
I have al zincate from Growel,
I also have copper cyanide bath.

Kindly suggest the process

amish gala
electroplaters - mumbai,india


April 2017

A. Hi Amish. We appended your inquiry to a thread which already answers it. But get back to us if anything is unclear to you.

Regards,

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



March 10, 2018

Q. Dear Respected Sir,
I hope you are fine.
I would like to copper plating on aluminum so I have tried an experiment to achieve coating but failed. My electrolyte composition is CuSO4 200 g/L + 120 g/L Sulfuric acid;
I have put the aluminum M24 section piece about (6" * 2") and get 18v AC Current. After anodizing as a result brownish particles appear on aluminum surface roughly. Please tell me if any think there are other techniques which can improve it. So please tell me now, I shall be waiting on your answers.

Kamran khan
Pfizer Aluminum - lahore, Pakistan


March 2018

Plating/Anodizing Power Supply
0-15V 0-5A


A. Hi Kamran. I am trying to understand what you have said, but I am a bit confused.
First, you have used the word "anodizing", but I think you meant "electroplating", not the separate & different process of aluminum anodizing? Second, DC voltage is required for electroplating, not AC. Third, 18V is way too much; more like 3V would be right. Fourth, the aluminum must be prepared by cleaning, etching, desmutting, and zincating before plating. Fifth, you cannot use a copper sulfate plating bath on aluminum (actually on zincate).

My apologies if you really did mean "anodizing" and if you are meaningfully using 18V AC (we are having a little bit of language difficulties). In any case, we added your question to a topic about plating copper onto aluminum. Good luck.

Regards,

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


March 12, 2018

Q. Dear Ted Mooney,
What is desmutting, zincating -- please tell me more about this terms. And I explain my plating process step by step for you --
Degreasing
Rinsing
Etching
Rinsing
Neutralizing
Rinsing
Anodizing (H2SO4)
Rinsing
Plating (CuSO4+Acid)
But I am not gaining sufficient coating. I require 10µm copper thickness.

Kamran khan
Pfizer Aluminum - lahore, Pakistan


March 2018

A. Hi Kamran. Desmutting is a step which is often used in between etching and anodizing (dependent upon the particular aluminum alloy you are treating) to remove alloying materials from the surface because the etch dissolves aluminum but leaves any silicon, copper, and other alloying materials behind on the surface. Apparently you are trying to electroplate copper onto an A.C. anodized surface. Zincating doesn't seem to have anything to do with your experiment, so there's no sense confusing it.

I've never heard of attempting to electroplate onto a sulphuric acid anodized surface, so the ball is in your court. Where did you get the idea for this process, what papers did you read about it (when experimental plating methods remain only experimental methods, it's usually because they didn't work well). Why are you trying to electroplate copper onto aluminum in this odd way instead of using production proven methods? What is the end use of this copper plated aluminum?

Regards,

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


March 12, 2018

Hi Kamran
Anodising produces an oxide layer on aluminium. Aluminium oxide is non conductive to electricity. I am very surprised that you get any copper deposited. It is presumably down to the fact that you plate copper immediately after anodising and before the pores in the oxide layer are sealed. Whatever the reason, the adhesion must be very poor.
Can you explain the reason for anodising?
If you are simply aiming to plate copper on aluminium, the zincate process is standard practice and has been for many years.

geoff smith
Geoff Smith
Hampshire, England



March 13, 2018
555-1

Q. Sir Geoff Smith & Sir Ted Mooney, thank you so much for your replies. I am very glad for your kind replies. Firstly I will explain that I am achieving tornado color on our aluminum

1. "Where did you get the idea for this process?". Actually I have seem another company's aluminum section plated by copper so I am trying it.
2. "Why are you trying to electroplate copper onto aluminum in this odd way instead of using production proven methods?" Because I have successfully plated tin on aluminum by this process; then I would try to do copper plating on aluminum.
3. "What is the end use of this copper plated aluminum?" In the making of door/window profiles.
4. "Whatever the reason, the adhesion must be very poor." Sprinkling (shining Bubbles) appears in the electrolytes when passing electricity by which adhesion must be poor from my requirement.
5. "Can you explain the reason for anodising?" Actually in my company firstly aluminum section is anodized then plated by tin (acid bath) thus I was anodizing it.
My neutralizing tank composition is 80 g/L H2SO4+ 50g/L HNO3, is it desmutting or not?

Kamran khan
Pfizer Aluminum - lahore, Pakistan


July 18, 2018

A. Dear all,

This is very interesting reading, I had by chance to ponder upon plating copper onto aluminium as well, recently. I would go the way of using any of the new alkaline baths with organic binders/complexers, that is completely cyanide-free.

I will not go into detail as there are many competing designs (I mean compositions and usage parameters), some more exotic than others, starting with baths very similar to classical acid or alkaline baths, ending with baths of ionic liquids.

As someone above said: removing all traces of aluminium oxide is the most untrivial task imaginable, someone above went as far as aerating baths with Argon gas to get rid of all traces of oxygen imaginable!! That is expensive.

Also expensive is what was mentioned above and involved two or three nitric acid baths (yuck!). But then, that process works.

To learn to plate a mixed substrate such as aluminium alloys (unetched) and get SOME adhesion, it would be necessary to learn some or all of the chemistry that is used in semiconductor industry to plate copper onto silicon and similar materials. It requires non-trivial understanding of the competing additives and a lot of reading (not that much, really after reading 100 useful pages out of 1200 found you will have a pretty good understanding of the processes involved), after which you will get the idea how to get to designing your own process (because the bath, substrate, impurities, current density and a myriad of additives interact differently on various alloys).

555-2ext

The keyword here is Damascene process. It can plate and level a 10-nanometer wide pinhole, up to 0.15 mm blind holes (!!) But the additives there are competitive; a mismatch and you're done without understanding what to do.

Alternatively, a similar process of electroless copper deposition can be used, but that also, is very expensive and not to mention instability, heating and limited lifetime of a bath. If you end up activating the surface with SnCl2 and palladium ions, it gets even more expensive.

I do not think that half of the companies offering copper plating on windows use plating in the right sense of the word, you can get copper color onto material in various other, much simpler means. Many special synthetic varnishes would latch onto anodized aluminium, and these could have copper flakes/powder/platelets, etc, together with another additives to keep the copper shiny. (not telling, bwahaha) (...and there are faithful plastic copper imitations as well...)

But honestly, I would try to avoid dangerous stuff, like nitric acid, etc, and as my interest is in simpler shapes (cylinders), I would use mechanical copper blasting to prepare the aluminium surface, or even incorporate copper into it. If you had the money, HVAF would be able to blast as much copper onto aluminium as you'd like. Just clean, shine and protect it afterwards.


And, to add: ANYONE TRYING PLATING ALUMINIUM MUST UNDERSTAND THAT ALUMINIUM WILL QUICKLY FALL APART WITHOUT THE OXIDE LAYER.

Thus, trying to plate aluminium is like trying to paint a burning house. BUT, If the house isn't on fire, it is covered with teflon and your paint won't stick.

I hope the analogy is reasonable.


P.S. When I think about this: anodizing before copper plating does sound like an invitation to a damascene process, as anodizing would create a honeycomb structure into which the copper could be deposited into the deep holes. But then you are in the area of semiconductor specialists, and your level of understanding chemistry of quaternium nitrogen compounds and organosulphur compounds and aromatic rings... would need to catch up, if you want to provide a reliable process.
The dosing of the additives starts at ppm (parts per million) levels, and best if calculated at molar concentrations relative to other key constituents of the plating bath. I have seen pictures (taken by electron microscope), where 0.35ppm of an additive would do one thing and 1.0 ppm would do something else. And if you added 1 ppm of some other additive, it completely counteracted the first additive.


Did I mention that current density vastly changed what was going on in the bath as well? That too needs to be controlled, unlike at anodizing, which doesn't care.

Again: the current density per square decimeter needs to be well controlled, the adequate anode area must be provided, the bath agitation must be provided.

Jane D. Stanton
- Vienna, (The Coffee City), Austria


July 20, 2018

A. Even more: using process similar to classical photography:

1) soak copper salt or complex into the fresh anodized pores -- it must be compatible with the anodizing bath

2) drip off, soak in developer bath (reducer to change copper salt into copper and a soluble salt or complex)

(( alternatively 2a) change copper salt into insoluble precipitate like CuO by a redox reaction, 2b) convert CuO to Cu))

3) leach or wash soluble products sufficiently away

4) neutralize, passivate, seal, varnish, etc. in a usual manner.

555-3b

555-3c

555-3a

I tried a variant of this in a sample of the alkaline complexed bath. First adding alcoholic solution of methylene blue seemed to precipitate nanometric black CuO, after some time the dispersed crystals grew, the optical density of solution decreased. Then, dripping in a type of mouthwash, the floating microcrystals seem to grow even more into a metallic glitter instead, which on paper show as red color copper with a very pleasing metallic shine and glitter. The crystals can only move over surface of the paper, while the (blue) liquid soaks into the paper.

Jane D. Stanton
- Vienna, (The Coffee City), Austria


July 20, 2018

A. 3 more notes:
>90% of the published new (=innovative) research on copper and nickel plating, and various compositions of alloys plated (Such as Ni-P-Cu, Ni-P-Sn, etc.) is from 2016, 2017 and newer.

Copper imitation over eloxed aluminium would be best done utilizing the fresh unsealed pores in the oxide, filling them with copper particles. As the pores are small, special size particles have to be used. Solvent: ultra-low viscosity such as dimethylketone (=UN1090, =acetone) or methanol or such should be used. Copper passivator must be present in the bath. For me, it is easier to manage a highly flammable solvent in one bath than working with a set of 13 dangerous baths. Pressure spraying/mixing might be tried to increase impregnation, or electrophoretic deposition.

I have tried one complexed bath and oh my, you do need to think before mixing ingredients, order is important. Second, the complexed bath is of exactly methylene blue color, very, very deep. You won't see the sun through 1 inch of liquid.

Jane D. Stanton
- Vienna, (The Coffee City), Austria



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