Anodized Aluminum or Gold Plated

[nivrnb]

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

 

[Woodworker1997]

Scrap yard. Those are definatly anodized.

Derek

 

[nivrnb]

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

 

[Geo]

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.

 

[Woodworker1997]

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.

 

[nivrnb]

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

 

[g_axelsson]

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

 

[Geo]

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.

 

[g_axelsson]

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

 

[Smack]

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.

 

[nivrnb]

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

 

[a_bab]

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

 

[glondor]

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

 

[Geo]

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.

 

[Woodworker1997]

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

Derek

 

[nivrnb]

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

 

[g_axelsson]

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

 

[etack]

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

 

[nivrnb]

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

 

[nivrnb]

Update,

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