Aluminum

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goldscraphobby
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Aluminum

Post by goldscraphobby » May 17th, 2020, 10:37 am

Hi,
I have done some aluminum housings in a weak nitric in the past and the gold would come off nicely, see post
http://goldrefiningforum.com/phpBB3/vie ... 49&t=20355

I did 2 housing and the aluminum on these being attacked and appears when I scrape it there is still gold underneath it. There are also flakes of gold mixed in the stuff on the bottom of the container that came off.

The only difference between these and the others I did are that these housings had been exposed to HCl vapors. What do I do with these now? How should I recover the gold off these and the gold mixed with the sediment in the bottom of the container?
Thanks
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goldscraphobby
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Re: Aluminum

Post by goldscraphobby » May 19th, 2020, 1:04 pm

Any suggestions?

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FrugalRefiner
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Re: Aluminum

Post by FrugalRefiner » May 19th, 2020, 1:53 pm

Are you sure they are aluminum? Nitric shouldn't attack aluminum that way.

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goldscraphobby
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Re: Aluminum

Post by goldscraphobby » May 19th, 2020, 10:26 pm

Pretty sure. Its still in the dilute nitric There has been no further action on it.
Not sure what to do. Rinse them off and try a dip in HCl. See if i can expose the gold

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Re: Aluminum

Post by Lino1406 » May 19th, 2020, 10:31 pm

Try a (small) segment with few drops reverse AR, may be it'l dissolve mainly the gold

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goldenchild
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Re: Aluminum

Post by goldenchild » May 20th, 2020, 12:27 pm

Truthfully, it would have been better to use HCL from the start. Just enough to get the gold leaf off of the objects. Being that it's all aluminum it would work fast and super clean. Processing the waste solution would be a breeze as well. It's always nice when the underlying metal is uniform.
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goldscraphobby
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Re: Aluminum

Post by goldscraphobby » May 20th, 2020, 1:00 pm

Thanks. I just did a search on reverse AR and seems possible. I'm limited on nitric but will try a sample.
Kind of afrid to do all HCl, I've seen how it reacts when a small piece got in. Pretty agressive.
With the way the aluminum is pitted I don't think the gold will lift off evenly.
How much HCl would it take to dissolve all the aluminum?

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goldenchild
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Re: Aluminum

Post by goldenchild » May 23rd, 2020, 5:37 pm

You don't need to use full strength HCL. I personally would just because I like things to work fast but you can simply dilute it until the reaction is tame. You also don't need to dissolve ALL of the aluminum. Just enough to get the gold off. That's why I was confused about you using nitric for this. HCL would work the same way you got the nitric to work. Curious though. When you say you don't think it will come off evenly do you mean it won't come off as a foil or it won't come off completely? If you meant it won't come off completely it certainly will. If you meant it won't come off as a foil, the gold won't care.
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goldscraphobby
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Re: Aluminum

Post by goldscraphobby » May 24th, 2020, 8:10 pm

When I did nitric on the others the gold came off like a skin, Because the aluminum is already pitted from HCl vapors it seems the HCl went the easy way to attach the aluminum that pitted instead of uniformly like the nitric did before. I had to digest all the aluminum - wow that was a pain. It was not fun filtering.
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Re: Aluminum

Post by goldenchild » May 25th, 2020, 8:53 am

Can you describe what happened during the reaction? Did the gold not come off the pieces causing you to have to digest all the metal?
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Re: Aluminum

Post by goldscraphobby » May 25th, 2020, 7:30 pm

Hi,
The gold did not come off evenly and there were patches around. I guess I could have cut out the areas but that would have taken too much time. I think because the aluminum is pitted in some spot the acid is attaching those areas first because its easier and making it like swiss cheese
I did use a dilute solution. For the next piece I will try stronger.

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