# Hey!, CPU golden pins turned silver coloured!



## zan13898 (Sep 7, 2018)

Its my first batch and i added my CPU pins in 10% HCL, thinking ill install the bubbler system in the morning, but when i saw it this morning, all golden pins are now silver coloured, no reaction is happening, niether did any happened yesterday, or very slow reaction is happening!, is everything going alright?..


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## Lino1406 (Sep 7, 2018)

The gold is below the silvery coating, continue as planned


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## zan13898 (Sep 7, 2018)

Yea, but the pins were golden coloured, now they seem silver coloured....you sure?..


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## nickvc (Sep 7, 2018)

Lino is usually spot on and can I add if you can’t see any foils or golden dust floating around then I’d say Lino was spot on again.


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## g_axelsson (Sep 8, 2018)

What type of CPU?

CPU-pins are almost always made up of kovar, an iron nickel alloy. If there is tin present it might dissolve in one place and cement out on top of the gold.

I don't know if a bubbler will help with CPU pins as they probably doesn't contain any copper.

Göran


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## zan13898 (Sep 10, 2018)

Thnks for the input guys, really appreciate it!...im still waiting for it all to disaolve, and since its less than 10% HCL, i think its gonna take a while!..


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## patnor1011 (Sep 11, 2018)

zan13898 said:


> Thnks for the input guys, really appreciate it!...im still waiting for it all to disaolve, and since its less than 10% HCL, i think its gonna take a while!..



Be prepared to wait a couple months. 
If you want to speed it up a little you can use crockpot or hotplate to use warm solution. It will take a long time even if heat is applied. Perhaps you should leave them in a covered bucket outside and stir them up once a day or so. You will need to pour off and add fresh acid from time to time depending on how many pins are there and how much acid you used.


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## Muratthechemist (Sep 27, 2018)

hello everyone, i think your problem is silver coated gold particles, if the percentage %8 and higer silver ions on solution, it can covered by silver and most dangerious part is silverchloride, if happens in chloride you need to add nh4oh( different process), bu its wouldnt chloride you need to add nitric acid(after seperated of hcl and wash) to dissolve silver ions and after filteration you can take back your gold and silver. (maybe out of the topic but i just want to say these infomations, this is my first post by the way ) have a good leaching


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## anachronism (Sep 28, 2018)

Muratthechemist said:


> hello everyone, i think your problem is silver coated gold particles, if the percentage %8 and higer silver ions on solution, it can covered by silver and most dangerious part is silverchloride, if happens in chloride you need to add nh4oh( different process), bu its wouldnt chloride you need to add nitric acid(after seperated of hcl and wash) to dissolve silver ions and after filteration you can take back your gold and silver. (maybe out of the topic but i just want to say these infomations, this is my first post by the way ) have a good leaching



How was the silver dissolved in HCl in order to precipitate out onto the pins?


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## g_axelsson (Sep 28, 2018)

Jon (anachronism) is totally correct.

Nice to see you back again, Jon.  

Göran


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## Yggdrasil (Sep 29, 2018)

I second that, good to have you back Jon.

But back to the topic at hand, I ran in to a similar situation a couple of years or so back.
Materials was desoldered low/medium grade mixed pins, appr 2.5 kg, divided in two batches.
My plan was to dissolve the tin and then use AP and time to dissolve most of the pins.

Actually I tried to save on acid, so after I had used HCl on one batch and cleaned it to my satisfaction, 
I poured it over the next batch which turned silver immideatly.
At the time I thought that the Tin had cemented out on the pins, it may or may not have been Indium too, since I had a few cpu lids as well in the batch. 
Actually the pins became a solid block that broke apart with difficulty, so strirring was not an option.

I proceeded with adding a bit more HCl and went straight to AP, It fixed the issue eventually but it took at least 6 months. (Time is my friend in most of my endeavours  ) 

Anyway I didn't bring this to the forum because I thought it to be a trivial issue that most had encountered already. 
In light of this post, I might have been wrong, again 

Per-Ove


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## g_axelsson (Sep 29, 2018)

I've seen it several times. I think it might be the source that some people think the gold dissolved in HCl. The gold is still there but covered with another metal.

... and the other metal is never silver, just saying it.

Göran


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## patnor1011 (Oct 1, 2018)

There is a faster process utilizing HCl for pins. It is called here crockpot method and it is just hot HCl bath. It still takes quite some time but it is faster than AP.


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## andersen113 (Oct 4, 2018)

I'm new here and have never written any thing, I do have a question..

I personally just recieved my first batch of CPU pins and all are very magnetic, so based on that I would you sulfuric acid stripping cell and not disolve the base metals? but first hot HCL bath for detinning?


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## Alondro (Jan 26, 2022)

Yggdrasil said:


> I second that, good to have you back Jon.
> 
> But back to the topic at hand, I ran in to a similar situation a couple of years or so back.
> Materials was desoldered low/medium grade mixed pins, appr 2.5 kg, divided in two batches.
> ...


The CPU lids have indium plating over the copper cores? Ah, that's good to know. I have 30 pounds of CPUs with the thick metal lids, I should think about recovering the indium. If it plates out from solution, there should be a simple way to get it.


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## Yggdrasil (Jan 26, 2022)

Alondro said:


> The CPU lids have indium plating over the copper cores? Ah, that's good to know. I have 30 pounds of CPUs with the thick metal lids, I should think about recovering the indium. If it plates out from solution, there should be a simple way to get it.


No they don't, but they have an Indium blob as a thermal compound between the lid and cpu core.
Most can be removed by gentle heating and scraping it off. 
But of course some will aleays remain.


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## Alondro (Jan 30, 2022)

Oh! So that's what that metal is in there! I removed a couple and wondered what on earth it was. Also found something that must have vanadium in it, as dissolving a bead of it in HCl gave a pale violet-pink solution.


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## Yggdrasil (Jan 30, 2022)

As to other things. It is hard for us to tell, when you found "something" and dissolved it.
If you want assistance it help to tell us the source, what you have done to it and what you plan to achieve.

Violet can be from alloyed gold in solder for instance. 

Anything from blueish to pinkish can come from this.


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