# Anodized Aluminum or Gold Plated



## nivrnb (Oct 6, 2013)

Hello everyone,

Just wanted to post a few pics of some scrap telecom boards, to see if anyone is familiar with these heat sinks. Just wanted to know if these are worth keeping or should I send them to the scrap yard. They are very light so it leads me to believe that they are aluminum and not copper. Sorry for the photos taken on my phone, the color is very much gold. 

Rob


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## Woodworker1997 (Oct 6, 2013)

Scrap yard. Those are definatly anodized.

Derek


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## nivrnb (Oct 6, 2013)

Derek,

You just ruined my day. I was hoping these would be worth keeping. But seriously thank you for you reply, now I will just add it to the aluminum stack.

Rob


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## Geo (Oct 6, 2013)

i would test a couple of different samples just to be sure. they do look like anodized heat sinks but it also look like some old stuff i have found that was good. its always better to test and not assume.


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## Woodworker1997 (Oct 6, 2013)

nivrnb said:


> Derek,
> 
> You just ruined my day. I was hoping these would be worth keeping. But seriously thank you for you reply, now I will just add it to the aluminum stack.
> 
> Rob


Im sorry Rob,

I have had many of those as well. But, as Geo said test before taking my word on a picture.

Derek.


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## nivrnb (Oct 6, 2013)

Derek and Geo,

My hopes have been renewed, I have taken off two pretty good size pieces and will place them in some AP, and take some photos. Wanted to post some better photos of these heat sinks. Here are some of the boards that they came off of. Thanks again.

Rob


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## g_axelsson (Oct 6, 2013)

I don't know if AP would be such a good test. If you use old AP (copper chloride) then the copper would plate out on the surface as aluminum goes into solution. It would be hard to spot any gold in the resulting mess.
If you use hydrochloric and hydrogen peroxide I would advice to drop the peroxide as it doesn't add anything to the reaction, it can actually slow it down. A scratch and a drop of HCl will dissolve the Al and let the gold loose. It goes fast on the deep so only a small amount of gold is released as foils.

I would first test them by making a scratch and placing a drop of nitric on it. If it is plated there is a base metal between the aluminum and gold and nitric would dissolve only the thin barrier metal. The Al is left intact and the gold is released as foils.

If gold is evaporated onto aluminum you need to use HCl as above to spot the gold as foils.

Good luck and let us know the result.

Göran


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## Geo (Oct 6, 2013)

i would test in the other direction. Göran's test is assuming it is gold. i would test assuming it is anodized. use a warm solution of sodium hydroxide and water and dip a piece in the liquid. i would submerge i/2 of one piece in the solution for a minute or so and if it is indeed anodized, the submerged half will come out bright and shiny aluminum.


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## g_axelsson (Oct 6, 2013)

That is really good Geo!

If I might revise my advice I would start with Geo's test but I would use only a drop of lye on the suspected gold, no need to make up a lot of chemicals for dipping the pieces. Keeps the amount of waste down.
My test is more suited for discerning between evaporated gold and plated gold.

Göran


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## Smack (Oct 6, 2013)

I see a lot of extruded aluminum there Rob, so if there is no gold, be sure you get extruded aluminum price from scrap yard, it will be a little more than sheet and cast aluminum. And it doesn't matter that it's anodized, if they say it does matter tell them they better check ISRI code again.


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## nivrnb (Oct 7, 2013)

Wow, is all I can say about all this incredible information, thanks everyone. I am going to try Geo's testing method. Nitric is out of the question for me in Hawaii. I all most did not want to post this question due to the fact that I do not have the resources to the acids I would need. I only have hcl to work with at the moment. I am glad I did not rush into a big mess with the AP. 

Smack, thanks for the information about extruded aluminum, I have never heard of this before and will research. This stuff looks so good I am hoping it has gold content. Thanks everyone again, now I am on a quest for lye, this field is a never ending wealth of information. Not only is it cool in the refining forum, but it is a very good learning experience.

Rob


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## a_bab (Oct 8, 2013)

Before hoping too much get realistic and ask yourself: why in the word would someone plate massive pieces of Al used as heat spreaders? Al does not oxidize, and if it does the rest of the board is a wreak already.

Look at the side connectors: lots of pins, but only the tips are plated, and and it's a lousy plating btw.
This is a good indication of the board quality.

Gold is only used where absolutely needed, and in the amount needed to do the job for a few years at best.
We should really pin this.

You clearly got bit by the YAA syndrome (as in Yellow Anodized Aluminum).

(Too) many hopes = lots of disappointment.
Less hopes= nice surprises.

Sorry for the slapping but you needed it


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## glondor (Oct 8, 2013)

There are lots of gold plated aluminum parts, but they do not look like that.
http://www.pcrtechnologies.com/cnc-milling-aluminum-rf-microwave-housing-telecommunication-industry.html


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## Geo (Oct 8, 2013)

i may have a biased location because of all the aerospace companies located nearby but i have had quite a few gold plated parts that defied rational thinking as to why and functionality. thats why i say test to be sure.


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## Woodworker1997 (Oct 8, 2013)

Hi. If you cannot get nitric, can you buy a gold test kit online and have it shipped to you?

Derek


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## nivrnb (Oct 9, 2013)

a_bab,

Yes, my YAA is acting up. : ) But I don't put it past the government (people) to do such a thing, meaning putting gold on frivolous things.





"Gold is only used where absolutely needed, and in the amount needed to do the job for a few years at best."
I agree with you.

Derek,

"can you buy a gold test kit online and have it shipped to you?"
I might have to go this route, but like you and a_bab are saying this is proudly Anodized.

Rob


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## g_axelsson (Oct 9, 2013)

I'm often skeptical, but I think there could be gold flash on those aluminum boxes. It looks like radio equipment and one reason to flash plate it is to ensure a good connection between lid and box. In that case anodizing would create a thicker aluminum oxide layer and insulate the surface. Skin effects and high frequency radio signals could create RF (radio frequency) leaks and affect sensitive components unless you have a good RF seal.
The inside in high precision RF equipment needs a good conductive surface, any changes in surface oxidation can affect the electrical properties and the tuning of the components.
It is also very expensive equipment so the cost of flash plating isn't a large part of the cost.

Göran


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## etack (Oct 9, 2013)

some of them look gold to me.

If you can't get nitric take a utility knife and cut a sliver off and put it into HCl this will eat up the Al.

whats left you treat like gold foil.

Eric


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## nivrnb (Oct 9, 2013)

Took some small samples to test with hcl. I'll post results when finished.


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## nivrnb (Oct 9, 2013)

Update,

What do you think? It looks like it survived the hcl.


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## Geo (Oct 10, 2013)

hmm, smells like gold, taste like gold. :lol: looks good to me. place that small amount of foil in something small like a test tube and dissolve it in hcl/Cl and test the solution with stannous.


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## niteliteone (Oct 10, 2013)

Kind of looks like gold foils to me :twisted: 
Goes to show how it is always best to "test" any material you suspect might contain PM's, as even skilled eyes here said their was no PM's, just by looking at the pictures.


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## g_axelsson (Oct 10, 2013)

I don't want to write "I told you so!" and brag a bit... oops, I just did! :mrgreen: 

Congratulations, now to the fun part, how are you going to get the gold off the aluminum?
At least it looks to be quite thick, it didn't fall apart in small flakes.

Göran


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## Harold_V (Oct 10, 2013)

a_bab said:


> Al does not oxidize,


Sorry, but you're very wrong. Not only does aluminum oxidize, it does so rapidly, at ambient temperatures. That's one of the problems that must be overcome when welding aluminum. It is addressed by using AC and high frequency. The aluminum is also prepared by applying a stainless brush, to remove the oxide coating that is quite common. 

Are you familiar with grinding wheels? The vast majority you'll find in life are made of aluminum oxide.

Harold


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## Harold_V (Oct 10, 2013)

Geo said:


> i may have a biased location because of all the aerospace companies located nearby but i have had quite a few gold plated parts that defied rational thinking as to why and functionality. thats why i say test to be sure.


Your advice was spot on. Readers need to learn that testing is critical to success in refining. 
Don't judge things using what you might consider to be good logic. Let me explain. 

It is generally assumed that gold plating is never applied heavily. That is true even when gold was selling for $35/ounce. However, it's not true. Many years ago I was asked to process a large amount of scrap plated military items, all from what was reputed to be microwave. I intended to strip with cyanide, but I was not aware at that time of the addition of an oxidizer, so I had issues with the gold perforating, then the cyanide attacking the base metal. At that point gold recovery slowed to a halt, although the vast majority of the gold had been stripped. 

I do not recall the exact yield for these plated parts, but they rivaled gold filled material. The guy had at least a couple hundred pounds of the stuff. I was not satisfied with the process I had chosen, so I put the project on the back burner, in preparation for running the material in a sulfuric stripping cell. He grew short of patience and requested the material be returned, so I never processed the rest. 

Sure, it's not common to find gold in volume, and not common to find aluminum gold plated, but that doesn't mean it's impossible. Keep an open mind, setting your expectations low. If you happen to discover a find that goes against the rules, you'll be pleasantly surprised instead of being constantly disappointed when you think everything you see is gold. 

Had a real funny experience about ten years after I had started refining. I was to meet a couple in a public place, because they had a large ingot of gold that they wanted to liquidate. Needless to say, I was skeptical. 

We met in a restaurant, where they promptly pulled out a large bar that had a corner removed. To my trained eye, it was obvious that there was no gold present, that what I was seeing was a bar of common yellow brass. A test with nitric proved my hunch to be correct. (For the record, I carried a test kit with me at all times when conducting business away from my lab). 

What these people had was a bar that had been stolen from a display, although they never made it clear from where it was taken. I was in the company of crooks, who didn't trust anyone (why should they? They couldn't be trusted, otherwise they wouldn't have had possession of a stolen "ingot"). 

Harold


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## bswartzwelder (Oct 10, 2013)

Glad to hear you found some gold. I do not trust pictures to convey something as critical as to whether an item has gold plating on it or not.

I have several digital cameras and two of them are supposed to be of good quality. I, cannot get a good clear sharp picture of anything at close range with them. Pictures taken from a distance are usually always very clear and sharp, but close ups are just not possible. It's because of the focal length of the camera. Most cameras have a focal length of about 3 feet to infinity and that works just fine for most photography. Lately, I have found that if I step back, and then use the "zoom" feature I can get a fair picture. Then I "photo shop" it and crop the edges down to a manageable size. However, by doing this, I lose some of the clarity.

Just curious what everyone else is using for the nice close photos they post?


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## nivrnb (Oct 10, 2013)

bswartzwelder said:


> Just curious what everyone else is using for the nice close photos they post?



I was just using me phone camera for the shots on this post. But I found something interesting on the internet posted below.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=19361


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## a_bab (Oct 22, 2013)

Well, I have to excuse myself for not believing that Al can be gold plated. It's the first time I see it. Seing is believing...
I never seen anything then computer related Al heat spreaders, and in this area they are always anodized.

Harold, I'm perfectly aware Al does oxidize in the atmosphere. What I wanted to say is that it does not do it like iron for instance: that is, in a humid enviroment Al would resist better then copper for instance. I've seen heavily coroded pieces of Al, but this only occures in harsh enviroments, or in contact with iron/copper under water/high humidity (anodic protection).


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## Woodworker1997 (Oct 22, 2013)

Harold_V said:


> a_bab said:
> 
> 
> > Al does not oxidize,
> ...


All of the cast Al under the hood of my Tacoma agrees with you Harold. It all has white oxide all over it.

Derek


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## nivrnb (Oct 22, 2013)

Just some photo updates.

Didn't do a good job rinsing the pieces.


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## bigjohn (Oct 22, 2013)

Just my 2 cents but those foils look to thick to be gold plating. If that is gold, Thats one nice find :lol:


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## a_bab (Oct 24, 2013)

It's not just gold; probably gold plated Cu/Ni. 

I've seen copper plated Al used in electrical wires.


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## butcher (Oct 25, 2013)

It looks like a fish to me. :lol:


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## g_axelsson (Oct 25, 2013)

It looks like there are some copper left on the gold foil, then there probably is nickel with the gold.

Do you have any nitric acid? This would be perfect material for dissolving the thin copper+nickel layer under the gold without dissolving the aluminum.

Göran


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## Anonymous (Oct 25, 2013)

Is it just my eyes or does it look like an extremely thin layer of plating?


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## Geo (Oct 25, 2013)

not necessarily. if the parts were made when gold was relatively cheap, and especially if it was originally aerospace or military, it could be much thicker than, say RF shielding.


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## nivrnb (Oct 28, 2013)

All,

Just wanted to post some great threads on this subject, so I could go back and read.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=19177&p=194083&hilit=thick+gold+plating#p194083

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=12129&p=119372&hilit=thick+gold+plating#p119372

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

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=42&t=8578&p=80245&hilit=thick+gold+plating#p80245


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## kyle95 (Apr 10, 2014)

However If you have access to a furnace and crucible you could melt it down with borax and silica and it will separate


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