What's the final word on Kovar...?

[AuggieDog]

I have successfully processed, recovered, and refined gold, platinum, and copper from E-waste thanks to this forum and Sreetips' Youtube videos. During the process I decided to segregate and keep aside any suspected Kovar based pins, tophat transistors and other magnetic material from my batches. There are a few discussions on Kovar within the forum, and plenty of refiners talking about it being troublesome; BUT- I have yet to read anything about a definitive, effective method for dissolving Kovar. The best I can come up with is a combo of heated Nitric and Sulphuric by one user in the forum, but I haven't found any validation for that anywhere else. I have also been diligent about searching this forum, and elsewhere for answers. I have a LOT of this material and frankly would love to get started on it. Things have been pretty cut and dry for me so far with my recovery work. I spent many months researching before getting started and up until now have had decent success and very few problems, any of which I solved on "my own" with the help of GRF. Thus, this is my first post as a long-time lurker. Below was my first button (before re-refining) which was 26 grams with less impurities than seen here.
Thank you for your advice for dealing with Kovar.

 

[Alondro]

I've found a slow method using the HCl-copper chloride reaction. It will eventually eat the Kovar away, but it's not for people looking to process quickly.

The advantage is that it's dirt-cheap, using just HCl and copper chloride waste solution.

 

[Lou]

The final word is it sucks. I hate Kovar.

I think you are better off not dissolving it.

 

[Lou]

By the way, excellent job solving your own problems and using the forum like the resource it is. This is exactly the type of membership we want.

To expand, kovar is terrible for commercial refiners too. My usual solution, when greeted with lots and lots of it, is to melt it with lots and lots of copper.

 

[AuggieDog]

I should probably add that I am talking roughly 30-40 pounds of Kovar material, possibly more. The tophats and pins I have are very old (60s-70s) and I suspect very rich in Au.
I need an answer not the usual "Kovar Sucks" replies

 

[AuggieDog]

I've found a slow method using the HCl-copper chloride reaction. It will eventually eat the Kovar away, but it's not for people looking to process quickly.

The advantage is that it's dirt-cheap, using just HCl and copper chloride waste solution.

I haven't even gotten to finger boards and other PCB materials I have, so I haven't used the AP method yet. Can I produce the solution in 5 gallon buckets using copper rods? Then maybe I can process multiple buckets simultaneously. Finally, how long are we talking? I DO like the sound of cheap though! This would also be a MUCH cleaner and safer method than using H2SO4 & HNO3....Maybe patience is the way to go.

 

[Yggdrasil]

I haven't even gotten to finger boards and other PCB materials I have, so I haven't used the AP method yet. Can I produce the solution in 5 gallon buckets using copper rods? Then maybe I can process multiple buckets simultaneously. Finally, how long are we talking? I DO like the sound of cheap though! This would also be a MUCH cleaner and safer method than using H2SO4 & HNO3....Maybe patience is the way to go.

When you have AP you do not need much more Copper.
If there are some Copper available in the leach and plenty of air, you basically just need to give it some more HCl from time to time.
Timeline is days to months depending on temperature and amount of material.

 

[Alondro]

I haven't even gotten to finger boards and other PCB materials I have, so I haven't used the AP method yet. Can I produce the solution in 5 gallon buckets using copper rods? Then maybe I can process multiple buckets simultaneously. Finally, how long are we talking? I DO like the sound of cheap though! This would also be a MUCH cleaner and safer method than using H2SO4 & HNO3....Maybe patience is the way to go.

It takes weeks, and several changes of acid-CuCl2 solution (or less if you use very large volumes per pound of pins). Heating and cooling alternately every day seems to make it go significantly faster. But I've never done a full comparison, since I just process small batches in between my various other works and hobbies.

Making the copper-HCl solution is fairly easy, and with AP to start with, it forms fairly fast. Using slightly corroded copper and thin wires works faster, because some of the oxides will almost immediately go into solution and the thin wires have vastly larger surface area to work on.

 

[Ohiogoldfever]

I have been breaking down two kilos of top hats in AP. It’s been months but they are breaking down. I’m in no hurry. It’ll be done when it’s done.

 

[NobleMetalsRecovery]

Here's something to consider regarding Kovar. I used to use AR to dissolve it. Then by accident I found that soaking gold plated Kovar in dilute nitric acid would cause the gold to lift off of it in a single sheet of gold foil. I can;t tell you what the dilution was, but I would guess about 25% or less nitric. Only took about a day as I recall. This was over 20 years ago.

Just to be clear, I did this with only one type of computer scrap. It was the metal caps off of CPU's. 486's etc. Did it several times, always worked great. There was no need to dissolve the metal (Kovar I think?).

 

[vgecas]

Hi,
I have dealt with kovar using HNO3+ H2SO4+heat quite effectively. I would suggest you trying it on a small batch to get assumption on time/acid consumption. In my opinion it is reasonably fast and inexpensive method on small batches. If you have a lot of material - maybe consider sulfuric stripping cell or some leaching process.

 

[nickvc]

I would go with the dilute nitric as when dilute the nickel strike will dissolve, try 10% nitric to water in two samples , one you could heat and the other just leave, then determine if heating which should increase the speed is worth the effort.
I have used dilute nitric on several types of plated material and it works but it can be slow but if time isn’t your problem then just let it sit until the foils release.

 

[Martijn]

How does kovar react with the sulfuric stripping cell? You could save a lot on waste treatment compared to dussolving it all.

 

[AuggieDog]

Hi,
I have dealt with kovar using HNO3+ H2SO4+heat quite effectively. I would suggest you trying it on a small batch to get assumption on time/acid consumption. In my opinion it is reasonably fast and inexpensive method on small batches. If you have a lot of material - maybe consider sulfuric stripping cell or some leaching process.

I actually tried this yesterday using 50/50 H2O with 70% HNO3 (heated) & adding H2SO4 incrementally. I did this with about 30 "tophat" transistors that have Au plated legs and bases. The tophat portion of the transistors dissolved rapidly. The soup was a little too concentrated and seemingly saturated, and went dormant unless more & more H2SO4 was added. I decanted and what was left were the legs and the "tablet" shaped bases which are completely Au plated but these were still fully intact after the first treatment. The second treatment dissolved the tablet bases leaving just the foils, but 95% of the legs were unscathed by the brew! The legs seem to be so well plated that this treatment has a hard time getting to the Kovar base of the legs. I got impatient after that and the rest of the story is that I threw it all into AR and the legs still put up a hell of a battle. It was a mess, my fault, but I was able to (finally) refine a BB sized pure button out of the filthy recovery. It taught me a lesson (again); gold fever doesn't pay. Patience would have yielded better results. But this process may work OK if I cut the legs off before the treatment allowing the solution to penetrate the base metal.

 

[AuggieDog]

I would go with the dilute nitric as when dilute the nickel strike will dissolve, try 10% nitric to water in two samples , one you could heat and the other just leave, then determine if heating which should increase the speed is worth the effort.
I have used dilute nitric on several types of plated material and it works but it can be slow but if time isn’t your problem then just let it sit until the foils release.

This will be the next experiment I'll try. Thank you for the suggestion. I truly hope it works as that would be somewhat economical. Pardon me, but when people say 10% Nitric to H2O, is it assumed that the Nitric being used is already a 67-70% solution? Or am I looking for 10% overall?

 

[AuggieDog]

How does kovar react with the sulfuric stripping cell? You could save a lot on waste treatment compared to dussolving it all.

This would not be effective at getting 50% of the gold which is basically encapsulated beneath the transistor cover. If you look at the base where the legs are attached you can see it is Au plated. This base is basically a 3D tablet shape and is plated inside the cap as well. HOWEVER, it may work with a single treatment as I did above and after the caps are dissolved the material can then be moved to a stripping cell. Hmmmmm...????

 

[nickvc]

This will be the next experiment I'll try. Thank you for the suggestion. I truly hope it works as that would be somewhat economical. Pardon me, but when people say 10% Nitric to H2O, is it assumed that the Nitric being used is already a 67-70% solution? Or am I looking for 10% overall?

The substrate of nickel dissolves better in dilute nitric so I’d measure out 10% by volume of acid and 90% water.

 

[goldshark]

Just thinking out loud here. Since the melting temperature of Nickel is 2651 F, could one suspend the Kovar in a high temp mesh, draped inside a crucible, maybe with fluxes, if necessary, and fire at say 2100 F? This would leave the Kovar caught in the mesh, allowing Au to sink, fluxes top layer, remove screen with aforementioned worthless Kovar, pour into mold, let cool, hit with slag hammer. I don't know the properties of Kovar, somebody please enlighten me as to the composition, melting point, etc..

 

[Lou]

I wish it worked like that. That gold'll stick to it like flies on poo!

 

[orvi]

This would not be effective at getting 50% of the gold which is basically encapsulated beneath the transistor cover. If you look at the base where the legs are attached you can see it is Au plated. This base is basically a 3D tablet shape and is plated inside the cap as well. HOWEVER, it may work with a single treatment as I did above and after the caps are dissolved the material can then be moved to a stripping cell. Hmmmmm...????

From my experience, most of the gold is on the inside plating of the transistor, not on the legs and outside. I learned there are no easy shortcuts with this type of material.

I do them in in straight AR, as it is most convenient option. I do kg batches on monthly basis. Be aware that nickel reacts much more violently in AR than copper. All in all, I go with AR just to save the dissolution time. The ones I do are relatively pure nickel, so I also tried straight HCL dissolution. Using classic 31% tech HCL, optimal temperature for the dissolution is in the 40-70°C window from the start. When you get to the concentration of 18% or below HCL, you can ramp it higher.

Nitrosulfuric can also be used, and with careful additions of nitric, you can then take the waste liquid and electrorefine it, if you feel like it. Compacted waste, just electricity cost