# removing gold plate off aluminium.



## shel8483 (Jun 14, 2012)

Tried to remove gold plate off aluminum connectors. Very nice pieces with heavy plate. But when soaked in hcl/peroxide hot or cold dose nothing. Anyone know of a common way to remove gold from aluminium.


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## Lou (Jun 14, 2012)

Seems to strip ok with cyanide from what I've been told.


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## NobleMetalWorks (Jun 14, 2012)

shel8483 said:


> Tried to remove gold plate off aluminum connectors. Very nice pieces with heavy plate. But when soaked in hcl/peroxide hot or cold dose nothing. Anyone know of a common way to remove gold from aluminium.



Have you tried NaOH (Lye)?

If you use HCl, you have to score below the gold plate, it's the gold plating that is protecting them Al underneath from reacting with the HCl. You can score the top of the Al, just like you might a hard drive platter, The HCl should then attack the Al. But be careful, the reaction is violent, allow room for foaming and some expansion.

Also, you are going to want to do both of these reactions in a container that can handle heat as both reactions cause heat as a by product. Also you are going to want to do this in a well ventilated area, maybe outside.

If I have missed something, will someone please correct me or post and confirm what I have stated. I don't want to steer anyone wrong.

Scott


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## goldsilverpro (Jun 14, 2012)

shel8483 said:


> Tried to remove gold plate off aluminum connectors. Very nice pieces with heavy plate. But when soaked in hcl/peroxide hot or cold dose nothing. Anyone know of a common way to remove gold from aluminium.



You say nothing. Are you saying that the HCl didn't attack the Al or that it did eat the Al and no gold foils were produced? You say it is heavy gold plate. How do you know that if you got nothing? Wishful thinking? Can you provide a photo? I've never seen gold plated Al connectors. Actually, I don't think I've ever see connectors made from Al - I have seen Al Cannon plugs with gold plated copper pins. I have also seen a lot of yellow dyed anodized Al that looks very much like gold. 

If it is gold plate on Al (doubtful, in my estimation), the electrolytic sulfuric stripper will remove it with minimal attack on the Al. Hot 50/50 nitric would probably dissolve the nickel underneath the gold without attacking the Al and produce gold foils. Anything alkaline will likely attack the Al.


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## Westerngs (Jun 14, 2012)

I suggest HCl over NaOH. Have done this many times with both and the NaOH solutions are more difficult to filter if you need to filter.

If you have tried HCl and it did not dissolve the Al it may be that the gold plating is too thick or else the substrate is not Al.

Scratch deep into the gold plating in several places in order to expose the aluminum underneath.

If the substrate turns out not to be aluminum, then nitric acid is the way to go.


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## samuel-a (Jun 14, 2012)

Usually, due to diffusion, a nickel barier is plated over the Al.
A 48 - 72 hours soak in dilute nitric acid will remove the nickel under plate and leave gold foils. The Al of course will be left unharmed.

Second best, would be a sulfuric stripping cell.


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## shel8483 (Jun 14, 2012)

I have tried smashing them and still they are not reactive to anything sodium hydroxide,hcl nothing they just sit there. They are very light. I have the other piece(the male connector that goes inside it has a 90 deg elbow. With a rubber insulator where the wire goes in , inside is a single mylar insulated gold plated pin. The connector is light like aluminum and it looks like gold plate. Maybe its not but when scratched it is a silver color like alum. These are IR boards with 85-90 % gold coverage on them. There are 5 points on the board that have these connectors soldered to it. Like someone said maybe its not gold but I should be able to eat the metal up. So far no luck. I think I'm going to melt it and see what happens. they may be anodized titanium as these boards when working are 2000 each. So PM coverage is not a issue with these. I was lucky to get a couple hundred of them. I would send someone a sample to play with if anyone is interested. Also found gold all under the solder mask. Also the board when broken into pieces Has gold wires all through it. But any how back to the connector. Cannot get it to react with acid


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## NobleMetalWorks (Jun 14, 2012)

shel8483 said:


> I have tried smashing them and still they are not reactive to anything sodium hydroxide,hcl nothing they just sit there. They are very light. I have the other piece(the male connector that goes inside it has a 90 deg elbow. With a rubber insulator where the wire goes in , inside is a single mylar insulated gold plated pin. The connector is light like aluminum and it looks like gold plate. Maybe its not but when scratched it is a silver color like alum. These are IR boards with 85-90 % gold coverage on them. There are 5 points on the board that have these connectors soldered to it. Like someone said maybe its not gold but I should be able to eat the metal up. So far no luck. I think I'm going to melt it and see what happens. they may be anodized titanium as these boards when working are 2000 each. So PM coverage is not a issue with these. I was lucky to get a couple hundred of them. I would send someone a sample to play with if anyone is interested. Also found gold all under the solder mask. Also the board when broken into pieces Has gold wires all through it. But any how back to the connector. Cannot get it to react with acid



Can you please provide pictures? Is there some type of protective coating over the gold plate? Are these pins or PCB boards? It's all very confusing, a picture would make it much easier to understand what it is you are attempting to describe.

Scott


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## goldsilverpro (Jun 14, 2012)

I would also use nitric. I'm not a big believer in dissolving the base metal when it's not necessary. I wouldn't melt them, especially if they are Al. If Ti, you can't melt them.


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## Geo (Jun 14, 2012)

im with GSP on this one. ive never seen connectors made of aluminum and coated with gold. i would have to see it to be sure.


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## nickvc (Jun 15, 2012)

If they are titanium try very hot hydrochloric that should get things moving.


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## Harold_V (Jun 15, 2012)

shel8483 said:


> I think I'm going to melt it and see what happens.


What happens is it will melt. 

Then what?

If you're not achieving success with the material as it is, what makes you think melting is going to help? Assuming you manage to melt the board(s), you may end up with something that is difficult to deal with, and you most likely will. Right now you can avoid it because the value (if as claimed) is on the surface, not alloyed with troublesome material.

Have you read Hoke's book? If not, why not? Do you understand testing procedures? If you do, you shouldn't have to guess at what you're doing---you could run a couple tests and know what you have to do for success in extracting the values (assuming they're there). 
Please stop what you're doing and start reading, so you better understand these things. It's a choice you can make that will pay huge dividends. 



> they may be anodized titanium as these boards when working are 2000 each.


You can make that determination readily by simply removing a single pin and applying it to an aluminum oxide grinding wheel. Should yield a huge shower of white sparks. However, while I'm not about to suggest that titanium wouldn't be found in pins, it lacks many of the desirable properties that would make me think that's what they may be. 

Titanium is a rather strange color---not easily confused with aluminum, aside from its weight. Aluminum is very white, while titanium is more subdued, rather dirty looking, somewhat yellowish gray in color. 



> But any how back to the connector. Cannot get it to react with acid


If all else fails, have you tried simply dissolving the gold with AR? Not a recommended practice, but if the pins happen to be titanium, that may work. Be certain that you have eliminated base metals before attempting AR, so it doesn't consume your acid and cement the values. 

Harold


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## goldsilverpro (Jun 15, 2012)

Without photos, everything said is guesswork.


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## sena (Jun 15, 2012)

goldsilverpro said:


> Without photos, everything said is guesswork.




well said !


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