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How to Silver Plate Aluminum

Current question:

May 11, 2021

Q. Good morning everyone,
We are currently doing the Silver plating process on Electrical part,
Our current process is-
1 Caustic dip
2 Nitric-Sulphuric-Gictane 70 dip
3 Nitric Acid dip
4 Zincate 1
5 Nitric acid 2
6 Zincate 2
7 Copper strike
8 Copper plate
9 Silver strike
10 Silver plate
After silver plating part is visually okay, but after oven for 30 mins we get minor bubbles in line inside the ID step.
Please recommend the solution regarding this issue.

Prasad Patwardhan
- Pune, Maharashtra

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Closely related Q&A's, oldest first:

1997

Q. I WOULD LIKE TO PLATE ALUMINIUM WITH SILVER. I HAVE USED THE GLASS SILVERING PROCESS BUT THE RESULTS ARE NOT VERY ENCOURAGING. CAN SOMEONE SUGGEST AN ALTERNATIVE DIRECT PLATING PROCESS.

M. Khawar
Islamabad, Pakistan


affil. link
"The Surface Treatment & Finishing of Aluminum"
from Abe Books

or

1997

A. Hi M. Two-part silvering isn't the best way to plate onto aluminum. There are two possible methods: phosphoric acid anodizing followed by plating, or, more conventionally, zincating (or proprietary mixed-metal zincate alternatives like Atotech's Alstan or Gumm's Bondal) followed by plating.

Very briefly--and you'll need to consult a handbook for more detail--you clean, etch, and desmut the aluminum, zincate it, strip in nitric acid, re-zincate, and alkaline copper plate. Then you may need a barrier layer of nickel, then silver plate. Obviously, there are alternatives here and there, but it is more complex than simply dipping the aluminum into a silvering solution.

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



Silver plating over aluminum for PIM (Passive Intermodulation) avoidance

2004

Q. I'm looking for a silver plating over aluminum process to be used in radio frequency applications, does anyone knows about which is the correct process to avoid Passive Intermodulation (PIM)? any hints?

Regards,

Matias d [last name deleted for privacy by Editor]
electronic mfgr - Miami, Florida, USA


2004

A. Hi,

First of all, do you want to inhibit PIM in junctions (connections, etc.) or just in the device itself? The silver plating for the reduction of PIM in metallic walls of RF devices is DC standard electroplating. For the case of connectors, etc., the process used can be the same or maybe it is even better to use a softer metal. Anyway, silver always shows very good PIM response.

Regards,

Carlos Vicente
- Darmstadt, Germany



Problems silver plating aluminum castings

2004

Q. We use silver plated castings in electrical circuits where silver plating is necessary for making good contact.

We perform silver plating on Aluminum castings. We find that a large percentage of castings have problems of micro-porosity opening up after first cleaning (pickling) using mixture of HF and HNO3 acid. Can someone advise me how to avoid such porosity.

Plating on such microporosity causes the plating to get damaged (maybe due to entrapped acid/ chemicals) which in turn increases contact resistance.

Gunvantray Patel
- Vadodara, India



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



Silver plating on 2024 aluminum

2005

Q. Dear sir,
I want to silver plate the components on aluminum 2024 alloy material; the components are for aerospace application, and thickness of base material is about 2~3mm. Actually I want to plate silver and whatever the starting process it will not matter. It may be copper or any other suitable process. So please tell me the procedure how I can start this process. We have more then 10 years experience plating, with personnel involved in cadmium and zinc plating on ferrous alloys and anodizing, Alodining also on aluminium parts. So please tell me any suitable process to plate silver on these parts.

Mahboob Alam
AERO - Islamabad, Pakistan


2005

A. The most direct process would seem to me to be to zincate the aluminum after giving it a pretreatment similar to what you use when Alodining, strike it with a copper cyanide, cyanide copper plate it, cyanide silver strike, and cyanide silver plate. This sequence uses cyanide in all five processes, but at least there's no going back and forth between acid and cyanide processes, and I don't think there's anything "iffy" in it. It may be possible to skip the copper plate and/or the silver strike, but that would require some testing to verify.

You may need approvals and mil specs for aerospace applications though.

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


2005

A. Mahboob,

Ted is right, cyanide plating lines are very easy to maintain, consistent and work relatively well when used in conjunction with a zincate or double zincate prior to your copper strike. But there are also Nickel strike and electroless Nickel baths that can be used successfully,if a good process is put in place. Start with your chemical suppliers. They should be more than happy to provide you with all the technical support you will need to find the process that best suits your needs.
Good Luck,

Michael Null
Plater - Methuen, Massachusetts, U.S.A.



Silver plating an aluminum heatsink?

2006

Q. Hi, I'm a university student and I study electronics to become an engineer. In my spare time, I mod computers. I also study electronics and electronic parts cooling issues for pleasure.

I need help to electroplate a thick layer of silver on a big heatsink made of mostly aluminum and copper. It has some tight bends and a complex shape and I'm not sure how to go with the "silvering".
I wanna do this for 2 purposes: 1. better contact between fins and unsoldered parts 2. a nicer look, but not necessarily mirror-finish. Just a nice silver coat.

I have studied electroplating and found out I need some chemicals like AgNO3 for my solution, which I can easily obtain. I would be grateful to know what concentration I need, what voltage I should use, how much time I should allow the reaction to take place, in what configuration should I place the silver elements that will be consumed and what additives/acids should the solution contain. Or any helpful advice.

41989

Thanks in advance,

Nemes Calin
student - Baia Mare, MM, Romania


2006

A. Try to find good plating shop--most of silver plating solutions are cyanide based.If you want you can use do it yourself cyanide free solutions.
Ferrocyanide based plating solution:
40 gm silver chloride
200 gm potassium ferrocyanide [affil. link to info/product on Amazon]
20 gm potassium carbonate
1 lit water,stainless steel anodes
Dissolve ferrocyanide in boiling water,add carbonate and then add chloride(fresh,you can make it by mixing AgNO3 solution with kitchen salt solution),boil 30-180 minutes,then filter it when cold,then you may use it!
Never try to mix it with strong acids!
Phosphate based solution:
25 gm silver nitrate(or better pyrophosphate)
100 gm potassium pyrophosphate
25 gm ammonium carbonate
1 lit water
Stainless steel anodes
Aluminium must be zincated!Hope it helps and good luck!

Goran Budija
- Zagreb, Croatia



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



How to do antimicrobial silver plating on aluminum?

June 23, 2008

Q. Is there a way to apply an anti-microbial silver plating over 6061AL? Can this be applied over Type II (Anodize) or Type III (Hardcoat) already in place?

Kevin Klocek
product designer - Norristown, Pennsylvania


June , 2008

A. Anodizing is a very good electrical insulator which makes it impossible to directly electroplate Type II anodized aluminum, Kevin. Is it possible to electroless nickel plate the aluminum instead of anodizing it? This is a more typical route towards eventual silver plating.

Regards,

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


June 25, 2008

A. Ted,
The anodizing process vendor out near Reno, NV has a process where they silver treat anodizing to make it conductive. My guess is that it is a bit like the two step anodizing process which electroplates cobalt or another metal into the anodize for color.
If I remember correctly, one of the anodizing greats, possibly Charlie Grubbs, mentioned a similar process a couple of years ago.
Now, if that is enough to make it anti microbial is a good question.

James Watts
- Navarre, Florida



August 9, 2013

Q. We produce a medical device whose components are either Type II or Type III Anodized. These are devices that are being constantly touched. Is there a method for doing a Copper Anodized surface, or would plating be a better, or more cost effective option? The main purpose is for Copper's antimicrobial properties to help prevent infections.

Thanks!

Steve Moulden
- Phoenixville, Pennsylvania, USA


August 12, 2013

A. Hi Steve. Thanks for bringing this one up. Antimicrobial finishes seem to be the next big thing. We received a press release from Macdermid on the subject this week, and I'm sure they'd be happy to try to answer your question as it relates to their potential solutions. Other major vendors are no doubt also intensely involved with the subject.

I doubt that anodizing and dyeing with a copper-colored dye would do much, and that you would need to p[late the aluminum to achieve anti-microbial properties.

Regards,

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

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