Attacking Kovar pins with combo H2SO4 and HNO3

[Anonymous]

Back on topic.

Phil could you confirm for me please what the type of pins were in the 7oz you used in the pictures above please? i.e. the source material.

Many thanks in advance Sir.

Jon

 

[philddreamer]

Phil could you confirm for me please what the type of pins were in the 7oz you used in the pictures above please? i.e. the source material.

Hi Jon!
I did some recovery and refining, (in two different batches), of very, very high grade pins. The owner of the pins told me:
"The source would be a 20 year old Supercomputer which was decommissioned." They were small, but with a very heavy gold plating.
The yield from each pound of pins was 1 T oz of gold.
The first batch was about 2.5 pounds; the second 1.7 pounds. The yield a bit over 4.25 T oz.
I dissolved the base metal in Poorman's nitric; then refined them twice more in AR.

Take care!
Phil

 

[bswartzwelder]

I have read where some people put their pins in HCl to get rid of the solder. I have also read where some people put their pins in HNO3 to get rid of the solder. Is one method better than the other? Once the solder is gone, placing the bare (well washed) pins in an electrolytic cell with H2SO4 seems to be the method of choice. Pros? Cons? Preferences? I'm just a little bit curious.

Removing foils from circuit boards and leaving the gold is best done by the AP method provided the components and solder have been removed (before using AP) as well.

Bert

 

[philddreamer]

I have read where some people put their pins in HCl to get rid of the solder.

Hi Bert!
I do too IF there's a big amount of solder, otherwise I won't. I like to inspect each type of material, and then decide the best process for the recovery of values. These particular pins had no solder, and time was of essence, that's why I decided to digest the base metal thru Poorman's nitric. In 4 days I had the final product.

I have also read where some people put their pins in HNO3 to get rid of the solder.

I don't! You'll end up having to deal with metastannic acid, not good at all! :evil:

Is one method better than the other?

HCl.

Once the solder is gone, placing the bare (well washed) pins in an electrolytic cell with H2SO4 seems to be the method of choice.

Not all the time, IMHO; it depends on the type of pins! For example, If I have gold plated brass pins, or long, (over 1/2 inch), or thick pins, I run them thru the sulphuric cell. These pins were about 1/16th of an inch wide x 3/32 of an inch long!

Removing foils from circuit boards and leaving the gold is best done by the AP method provided the components and solder have been removed (before using AP) as well

That's another subject... :mrgreen:

Take care!
Phil

 

[Anonymous]

Thanks Phil I appreciate that.

If it's of any use let me return the favour. From the pic those pins are from the plates that sit between the old pinless superprocessors and the motherboards- in the enterprise servers that didn't have "sockets."

I would imagine you probably knew that anyway but I thought I would take a wild stab in case you didn't. In addition to that, the processors themselves that came out of those were large lumps of ceramic that you could break apart and physically see the gold strands within, in large quantities. They were trading at over $700 per kilogramme last year if anyone could still find them.

Regards

Jon

 

[Alentia]

Can some one with better knowledge of chemistry help with all equations happening during the process.

Kovar = 54Fe + 29Ni + 17Co

At least one of my derivatives in small amount is CoS2 - insoluble in anything

Fe + H2SO4 = H2 + FeSO4
Fe + 4HNO3 = Fe(NO3)3 + NO + H2O.

Co + 2HNO3 = Co(NO3)2 + H2
Co + H2SO4 = CoSO4 + H2

Ni + 2HNO3 = Ni(NO3)2 + H2
Ni + H2SO4 + 6H2O = NiSO4(H2O)6 + H2 (will this even happen or will Nitrate form first and create chain reaction as below)

I saw the NiSO4(H2O)6 salts being crystallized in aq solution at around 20C somewhat interesting.

The 2 reactions below seems like they are in a chain feeding each other until there are both metals exist, are they?

H2SO4 + Ni(NO3)2 = 2 HNO3 + NiSO4
FeSO4 + HNO3 = FeO + H2SO4 + NO2
H2SO4 + FeO = FeSO4 + H2O

At some point HNO3 or NH3 or both being regenerated from NO2+NO+H2?
Co(NO3)2 + H2SO4 - no reaction I assume, once cobalt reacting with one of the acids, cobalt reaction should stop, does it?

Here are few more pictures of the reaction in progress.

 

[mrgoldman]

Hot Nitric Acid

 

[butcher]

Alentia,

With heating and evaporation eventually the sulfates "WIN" the battle over most of the cations.

 

[solar_plasma]

While reading this interesting thread, I wondered, if it would be of benefit, if we would classify processes in categories of risc like this:

cat1: fx. CuCl2 leaching
cat2: fx. dilluted HCl/Cl
cat3: fx. AR, HNO3/H2O2
cat4: everything which only can be done safely with special setup, that would exceed most small labs fx. CN^- leaching

That might make it easier for someone to decide, if he already has the abilities and the setup to try a new process, especially if someone already has some experience to compare with. The point is, we can discuss endlessly about safety, but fact is, a process, that may be self-mutilation to one person, may be absolutely safe to another, examples cyanide, extremely exotherm acid reactions and so on.

Such categories are also used in fire and emergency services and in facilities with special hazards.

What do you think? Could it make things easier or just more complicated?

 

[solar_plasma]

Am I right to assume, that this is as dangerous as the processes we have locked for any discussion. Or is it only dangerous, but can be handled safely in ammounts up to let us say 200g kovar by an experienced....,just as an example, chemistry teacher?

After all I am not satisfied with all cold methods. This kovar can be quite frustrating. Don't know, if this alloy I have is a special kind of kovar invented for the only reason to drive me insane.

 

[Geo]

GSP says this is a forbidden topic. It's in his signature line. This is piranha solution and can not be discussed on the open forum. It is that dangerous.

 

[solar_plasma]

I guessed so. Just wanted to be sure. Thanks, Geo!