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topic 19274

Gold plating aluminum



A discussion started in 2000 & continuing through 2017

Need to Gold Plate Over Plugged Holes in Aluminum Plate

(2000)

Q. For optimum electrical conductivity, I need to hard gold plate an aluminum vacuum plate (.5" x 8" x 8") that has been lapped for a very flat and smooth surface on the top. The top of the plate has 300 pin holes (.025) thru the plate. I need to plug up 200 of the holes prior to hard gold plating. The plate is used in a clean room.

Can you advise what method of fill will be compatible with the nickel / gold plating process? I'm hoping not to have to use alum .025 dowels.

Thanks, Brent

Brent Cadroit
- San Diego, California


(2000)

A. That is one nasty job. So tiny and so many in a relatively small area.

I would check to see if any vendor makes a "pull plug" out of soft silicone. A 0.030 would probably be a proper size.

You can get taper plugs that small, but they are not easy to install.

You can take vinyl tubing, about .030 OD, cut the ends on a taper at appropriate lengths and pull these thru. They work, very well, but are more time consuming than a pull plug.

Do you absolutely have to plug them, Could 0.001 oversize and plated do the same thing? I assume that they cannot be plated and chased afterwards because of edge burrs.

James Watts
- Navarre, Florida


(2000)

Q. I don't have to plug the aluminum block before gold plating.

So, can you advise a gold type filler to fill the holes after the plate has been gold plated?

thanks, Brent

Brent Cadroit [returning]
- San Diego, California


Gold Plating Technology

(2000)

A. I don't understand what you are looking for. Please explain what you mean by "I need to plug up 200 of the holes prior to hard gold plating" but "I don't have to plug the aluminum block before gold plating". I guess you're saying that 200 of the holes have to be permanently "blocked" and after reconsideration it really doesn't matter that it be done before plating? Maybe a reader who has done something similar will have more insight :-)

I can't speak for James Watts, but I'm a little lost, Brent. Sorry :-(

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


(2000)

A. Me too.

James Watts
- Navarre, Florida



Gold plating aluminum with no nickel layer

(2003)

Q. I would like to gold plate an ultra high vacuum electron spectrometer made entirely out of aluminum. I have heard of gold plating aluminum using a nickel substrate but nickel is to be avoided as it is a magnetic material and thus inappropriate for electron spectroscopy. The reason I would like to gold plate the spectrometer is to get rid of possible charge up effects due to the non-conducting layer of aluminum oxide that can form.

Theo Zouros
Kansas State University - Manhattan, Kansas


(2003)

A. Hi Theo. This should not be a problem. The aluminum can be zincated, then copper plated, then gold plated. Although gold and copper will interdiffuse at high temperature over time, if the part is not hot the plating should meet your needs. Good luck.

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


(2003)

A. High phosphorus electroless nickel deposits are non-magnetic unless heated to over 250 °C.

don baudrand
Don Baudrand
Consultant - Poulsbo, Washington

(Don is co-author of the
book "Plating on Plastics")



Gold plating an aluminum sword

(2003)

Q. I am an artist, and I have been crafting a decorative sword for a while now. The sword is very important to me, because it symbolizes me. I have been reinventing the metal working process during the sword's construction. The blade is made of construction grade steel and has been chrome plated. I cast an aluminum handle around the base of the blade. When the blade was plated the electrode had to be attached to the aluminum handle. Unfortunately, the current which passed through the handle oxidized the piece of the handle below the electrode. I am in the process of trying to repair the oxidization right now. Next, I want specific regions of the handle to be gold plated, but I am concerned that the handle, or worse the blade, will be damaged when electricity passes through the sword. I would like to know a few things. I want to do as much of the work as possible. Is there a way I could plate the handle safely myself? How can I clean the residue from the handle if it needs to be plated professionally? I would also like to do this as cheaply as possible. Any suggestions y'all have would be greatly appreciated.

25895-1  25895-2

Thank you:)

Brandon Christeson
artist - Plano, Texas



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



Gold plating on electroless nickel plated aluminum

(2005)

Q. Some electroless nickel plated aluminum parts must be done gold plating. The parts have been drilled after EN, that is to say the base aluminum is exposed too.
Are there any methods to do gold plating on the parts? Any suggestion.

Dadong Fu
Plating Shop - Vancouver, BC, Canada


Electroless Plating
Mallory & Hajdu

(2005)

A. Exposed aluminum immediately forms an oxide layer that impedes further plating or coating. EN also forms an oxide layer that does the same thing. Both have to be activated to receive a gold plate but the sequence and chemicals are different. It is better to EN plate after drilling, then you'd have a single metal to plate onto.

Guillermo Marrufo
Monterrey, NL, Mexico



Cyanide gold plate directly on zincate?

(2006)

Q. Is is possible to directly plate cyanide gold directly onto zincated aluminium? I'm trying to avoid bringing up a CuCN bath we used to use on the zincate. We've done EN directly on the zincate with beautiful plating results but then I've had problems etching that nickel out of the finished hollow electroform.

I'm hoping that alum-zincate-pure gold-acid copper is possible, but I can't find an online reference saying yeah or neah.

Thanks,

Gerry Petencin
nrao - Charlottesville, Virginia


(2006)

? You need to clarify. Gold Acid Copper? Do you mean acid gold and/or acid copper solution?

Trent Kaufman
Trent Kaufman
   electroplater
Galva, Illinois



(2006)

A. Hello Gerry,
I understood part of the question, so I'll answer that. Plating gold directly on zincated aluminum is a bad idea. The zincate will migrate through the gold in no time and affect the appearance of the part. If gold is to be the final finish you will need a barrier plate such as Ni. Without Ni or a sufficient diffusion barrier even the copper will migrate through the gold layer. Acid copper is widely used in electroforming, but you may want to consider a copper strike before acid copper either Cn or alkaline to ensure good adhesion. Good Luck!

Mark Baker
process engineer - Malone, New York


(2006)

Q. My English was a little confusing there :-)

To clarify, I'd be starting with an Alum. mandrel which is eventually etched out of the finished piece.

We always zincate the Alum. before further plating. In the past we would zincate the mandrel, CuCN flash, plate a few hundred microinches of gold, CuCN flash over the gold, and then go into our acid Cu to build up copper for the bulk of the part.

After the finished piece is machined we etch out the alum-zn-cu, leaving the gold plate as the interior working surface of a microwave waveguide structure. (alum-zn come out with HCl or NaOH, little HNO3 to get the copper).

Recently we've experimented with: Alum mandrel - zincate - EN - gold - straight into acid copper. This seems to work generally OK, but I think I've had trouble etching out the nickel, EN. (it's an interior surface, hard to inspect)

My thought was that if I could gold plate directly on Zn then my etch out would just be aluminum-zinc. IF the Zinc-Gold dissolving happens fairly slowly I could live with it, since the Zn will be etched out within 3-4 weeks anyhow. I realize the Zn-gold may have "fingered" together some and when the Zn is etched away I'll have roughened the gold surface some, but how much? I don't need a mirror, just a decent gold surface to finish the waveguide interior.

Maybe I should bite the bullet and just set up a CuCN bath, but the acid copper seems to plate fine directly onto gold, so if I can just get a plateable but easily dissolved flash over the alum or zinc we'll be in business.

Thanks for the replies.

Gerry Petencin [returning]
- Charlottesville, Virginia


(2006)

thumbs up signDid a quick experiment re plating gold directly on zincate.

I took a thin alum. plate, few square inches, zincated it on one side (other side masked with plastic).

I went into my CN-gold with that and plated on .0005" of gold.

Good news is, it plated nicely from the first second, no signs of any strangeness at all. Went in hot, hope I'm not contaminating the bath with zinc at all. But the plated gold came out nice as anything.

I then etched the Alum-zinc away with HCl to get a rare look at the "inside" of some plating. That inside surface (was against the zinc layer) looked nice, but had a "brassy" look. So possibly after just 2-3 hours in contact with zinc, at bath and ambient temps, we've had enough zinc go into the gold to change it's appearance.

I might take this a little further, let the next test piece set at room temperature for 3-4 weeks and try elevated temp also.

Gerry Petencin [returning]
- Charlottesville, Virginia



February 5, 2010

Q. Hi,

I have a similar application to above where the gold plated aluminum cannot be magnetic. It is also in ultra high vacuum, so I would worry that the high vapor pressure of zinc and phosphates would contaminate our system. Can aluminum be gold plated without zincate and nickel preplate processes?

Tony Levand
- Lemont, Illinois


February 2010

A. Hi, Tony. Atotech offers (or used to offer) their Alstan system for metallizing aluminum in lieu of zincating. The trade name is a play on "all tin". But I can't guarantee that there is no zinc or phosphates or danger of sublimation; you'd need to contact them. Good luck.

Regards,

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



Black spots on gold and nickel plated aluminium

July 25, 2013

Q. Our company has recently changed back to a Schlotter medium phosphorous bright electroless Nickel from another medium phos bright EN due to problems with step plating in the nickel on Aluminium. We could not consistently dummy the tank to eradicate this issue.

The new EN gives a brilliant finish with no apparent marks until we put soft bondable gold over it. At this point the gold shows spots which look black but when examined with the XRF are in fact areas of no gold.The EN is not pitted in any way where the spots are. These spots are no more than 0.5 mm dia. generally and randomly distributed over the part. They also do not have a defined edge to the spots. We are putting 12 - 15 microns of Ni on the aluminium followed by 0.5 - 1.0 microns of gold.

We do not see this effect with our hi phosphorous EN nor indeed have I ever seen this effect before. If we decrease the amount of time in the electrolytic activator just before the gold, the situation gets worse. If we increase the time in the activator it gets better but we are now at 20 mins (6 mins is standard) and although improved, is still there. If we increase the time too much then there will be the worry of pitting the EN.
Any thoughts would be greatly appreciated.

Steve Britton
Engineering and plating shop employee - Honiton, Devon, England


July 29, 2013

A. Steve, there is some more information needed. First of all, I would recommend reading Mil-G-45204 [linked by editor to free spec at Defense Logistics Agency, dla.mil] and Mil-C-26074 [linked by editor to free spec at Defense Logistics Agency, dla.mil]. You may find all of your questions answered. Is there any chance the process is overloaded? The step plating should have triggered an investigation into overloading. Next, you'll need a process map to understand C&E and inputs. Is the current process electrolytic or electroless gold? Is there any embrittlement relief or intermediate steps before the gold but after the nickel? Your message almost made it sound as if there is nothing wrong with the new EN and all you are seeing is voids in the gold. If that is the case you can look into drag-out and rinsing. The 20 minute step you describe is not a step I am familiar with. All signs seem to point to overloading but when you are using such a thin gold layer it could be something else, take a look at Mil-G-45204 and you'll see what I mean. I would think a good process would be EN, drag-out, rinse (fast), gold strike, gold. That is the process I am familiar with. One big problem is when people plate the nickel and then let the nickel dry. If the nickel dries just a tiny bit, it can cause spots. This could be causing your problem. The nickel must not dry if you want to use the process I described. Another thing you need to do is verify the EN coating is good. You can do that by destructive testing. There's no sense in curing a gold problem if you really have a nickel or pre-treatment problem. One last thing is to blow dry the parts with dry N2 immediately after gold and rinsing. You can also use IPA rinses and hot rinses after the gold, it's highly recommended, but based on your message it sounds like the gold not being dried properly is not the problem here but it is certainly worth looking into because if you don't dry the parts quickly and properly after gold, you will see a similar spotting condition. Good luck.

blake kneedler
Blake Kneedler
Feather Hollow Eng.
Stockton, California




August 13, 2015

Q. I need a clarification regarding gold plating process,
Like one of our products is AL 6061 T6/t651, The requirement for the surface finish is in Gold plating. Our engineers specified gold plating 0.25 microns over copper & nickel plating. They have not specified whether the pre coating is electro or electroless and the coating thickness, standards to be referenced, etc.

I need to know is there any difficulty in this process, and how do I specify the finish details in clear manner to avoid such discrepancy like visual or functional?

Bharathi manoharan
- chennai, tamilnadu, india


August 2015

A. Hi Bharathi. Unfortunately, one must acquire a good understanding both of finishing processes & the needs of the specific product in order to do what you'd like. There isn't a "standard" type of plating; rather, the plating is designed and specified for the particular application.

0.25 microns of gold is rather little, so the underlying nickel plating will definitely be functional and critical. Some of the first things you need to determine include the function of the plating, and the environment to which it will be subjected. Is the gold for decorative purposes or for low contact resistance electronic application? Then, what type of gold plating do you need (hard gold, soft, solderable, etc.). Then what kind of nickel plating. Yes, there are certainly ASM, ASTM, ISO, and other plating specs which you'll want to reference -- but you can't choose them until you've clearly delineated the general requirements of the plating. Good luck.

Regards,

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



November 18, 2017

Q. I have a 1957 Chevy Bel air. The grille as well as the Vee on the hood and trunk is gold anodized aluminum, which is not like bright gold.

19274_Grille   19274_Trunk_Vee   19274_Hood_Vee   19274_Fender_Louvers  

Can these pieces be gold plated in bright shiny gold?

Glenn Marshall
- Tillatoba, Mississippi USA


November 2017

A. Hi Glenn. Yes, it can be done. The anodizing must be stripped, then the aluminum zincated, plated with something compatible with zincate (possibly cyanide copper), then nickel plated, then chrome plated.

If you're going to gold plate or chrome plate something though, it's better to not make it out of aluminum if practical. You would have been better off starting with steel or zinc diecast parts if available. Happy restoration!

If you've got the money for full restoration, Hammer & Dolly in Traverse City just finished a beautiful 1956 Nomad per their Facebook page. Adam Hammer is the son of Chris Hammer, president of Hill-Cross Company [a finishing.com supporting advertiser].

Regards,

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


November 25, 2017

A. Hi Glenn.
It can be done. But if you intend to use the car rather than stand it in a showroom you should know that roads have one of the most corrosive environments known to plating. Thin gold is porous and will rapidly fail. Sufficiently thick gold say 5+ microns is going to cost serious money.

wikipedia
Docker Daimlers

Back in the 1950s Daimler produced a gold plated model for Lady Docker =>
At that time gold was about $35/oz
It's not now!

Most anodizing shops can offer a very good looking gold finish and a clear lacquer can provide the shine.

geoff smith
Geoff Smith
Hampshire,
       England




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