# Gold plated aluminum



## hpjim (Nov 25, 2011)

Hi.
Nuby question . What is the best process for this combination? TIA


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## jimmydolittle (Nov 25, 2011)

What's TIA?


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## qst42know (Nov 25, 2011)

I haven't encountered gold plated aluminum.

Have you tested this to be sure it's gold and not just anodized?


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## hpjim (Nov 25, 2011)

TIA = Thanks in advance


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## Geo (Nov 25, 2011)

yellow colored aluminum isnt normally gold but anodized aluminum.it really can be misleading and it is pretty but im afraid its not gold.


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## jimmydolittle (Nov 26, 2011)

hpjim, consider this to be an admonition not to use punctuations, or text language on this forum. Geo, I once pulled a gold plated aluminum shaft like thing out of a Xerox copy machine (not sure of the brand name). It was about 2” diameter, and 14” long, best I recall. It’s been 10 years or more. That was back before I started refining. I just sold it to one. Being a machinist, I know anodized aluminum.


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## goldenchild (Nov 26, 2011)

99 out of 100 times an H2SO4 cell is going to be your best bet for plated scrap.


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## qst42know (Nov 26, 2011)

If this is gold on aluminum I expect this to be the 1 of 100 times where H2SO4 cell is a bad choice.

Is aluminum even compatable with any type of gold plating?


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## goldsilverpro (Nov 26, 2011)

qst42know said:


> If this is gold on aluminum I expect this to be the 1 of 100 times where H2SO4 cell is a bad choice.
> 
> Is aluminum even compatable with any type of gold plating?



Actually, the H2SO4 stripper works quite well for gold on aluminum. I have only seen a few parts of gold on aluminum but it can be plated on aluminum just like any other metal - with difficulty.


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## qst42know (Nov 26, 2011)

Would this be a case where concentrated acid is far less reactive to the metal?


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## goldsilverpro (Nov 26, 2011)

qst42know said:


> Would this be a case where concentrated acid is far less reactive to the metal?


I guess you could say that. Once, one of the big Silicon Valley companies brought me about a dozen heavily gold plated thick Al cans, about 2"x2"x3". The cans were machined and quite expensive to make and these were the only ones in existence. The gold plating was faulty and they wanted me to strip them so they could re-plate them. I stripped them with conc. sulfuric with no damage to the Al. They took awhile since the gold was so thick.


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## darshevo (Nov 26, 2011)

I have a few pieces of gold plated Al floating around the shop still. Pics can be seen in this thread:

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=10106

I noticed I never responded with my results but when a piece was clipped off and put into HCl it did indeed dissolve the base metal leaving me with just a thin gold husk.


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## Geo (Nov 26, 2011)

i didn't say it wasn't gold plated.i said normally you don't find gold plated aluminum,it is possible but unlikely.i have found some gold plated aluminum before in some old military test equipment but it was all unique custom made parts.


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## butcher (Nov 26, 2011)

I have seen anodized aluminum that is gold color.
I have seen gold plated aluminum junk jewelry, and also other pot type metals plated.
Even some that looked like pewter or lead (also silver plated).seems like some of these countries can plate most anything, and will. 
I always wondered if some of this was not made from our trash scrap electronics we sent to them and some guy learned how to sell it back to us at a profit, some of these poor people are very smart and can make most anything from almost nothing.

I have a 24K gold plated flower from Hawaii, and have seen gold plated plastic.


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## hpjim (Nov 26, 2011)

Thanks for the input. The items came from the mixing chambers of HP signal gens so I know they are plated in gold


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## butcher (Nov 26, 2011)

For me its a guess it is gold, until my test shows positive.

I can polish and oil brass to look like gold.


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## Geo (Nov 26, 2011)

if its aluminum an easy way to remove a sample for testing is take a piece cut a few grooves through the plating and boil in hcl acid to dissolve the aluminum and then dissolve any solids with hcl/cl and test with stannous chloride.


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## steyr223 (Dec 10, 2011)

Hello every one
I have some aluminum that's gold plated
It came. From a cell site manufacturer
Also I noticed in my stupid days nitric acid
did nothing to the bottom of an aluminum
can
steyr223


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## butcher (Dec 10, 2011)

you must have had concentrated nitic acid.

It passivated the aluminum; the nitric acid oxidized the outside layer (this aluminum oxide salt layer) then protected the rest of the aluminum metal from attack.

But this also depends on the concentration of the acid, a dilute acid will attack the metal much easier, than the concentrated acid that forms a passivation layer.

Also the alloy involved in the metal can also play a big part in how it will react to the acids.

Much aluminum is not always pure but can be a mixture of metals an alloy.
Many metals are alloys.

Stainless steel will passivate in very concentrated nitric acid, the nickel and chromium oxidizes making the passivation oxide layer to protect the steel (iron), so the non magnetic stainless steel with higher nickel and chromium content are more resistant to concentrated nitric acid.

Many junk gold plated jewelry (costume jewelry).can be aluminum or alloys, they make this stuff out of about any metals you can melt and pour into a mold, (i would not doubt the car battery and pewter cups and other stuff shipped to china was meted poured into jewelry plated and sold to your wife).


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## Geo (Dec 12, 2011)

muriatic acid attacks aluminum and aluminum alloys vigorously. it is the acid of choice when dissolution of aluminum is required. as a side note a trick taught to me while working in a scrapyard to differentiate between aluminum and diecast is to file a notch and spray a little white vinegar on the piece,diecast will react while aluminum will not.


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## Dr. Poe (Dec 14, 2011)

You fellas are all correct. It's the formation of aluminum oxide (Al2O3) also called 'Sapphire that protects or 'anodizes aluminum in a stripping cell with an oxidizing acid. Dr. Poe :|


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## Photobacterium (Dec 17, 2011)

qst42know said:


> If this is gold on aluminum I expect this to be the 1 of 100 times where H2SO4 cell is a bad choice.
> 
> Is aluminum even compatable with any type of gold plating?



i have used gold plated aluminum often in the microwave instrumentation industry.

but the aluminum wasn't gold-plated directly. our drawing call-outs were typically 50 micro-inches of gold OVER copper - over aluminum.


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## nōnāgintā trēs (Dec 10, 2012)

If it's really gold platted Al, and not just yellow Al, then throw it in some NaOH and dissolve the Al. The gold will be untouched!!


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## goldsilverpro (Dec 10, 2012)

Use the sulfuric stripper


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