Attacking Kovar pins with combo H2SO4 and HNO3

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Alentia

Alentia

Well-known member
Joined
Oct 8, 2010
Messages
242
Location
Richmond Hill, ON
While it is pain trying to work on kovar pins with only HCL due to too many metals involved, specifically Nickel plate. I am to try and publish results attacking the pins with H2SO4 and HNO3 combo.

I wonder if anyone has already tried this method.

On another thought and I am thinking on experimenting using all 3 acids to obtain clean gold at the bottom during whole reaction, while everything else should be dissolved. The logic behind this theory:

Fe + 2HCl = FeCl2
Fe + H2SO4 = FeSO4 + H2
FeCl2 + H2SO4 = FeSO4 (will drop gold) + HCl (will be re-engaged into reaction)
Au + HCl + HNO3 = HAuCl4 + NO + H2O
2 HAuCl4(s) → Au2Cl6(s) + 2 HCl(g)
AuCl3 + 3 FeSO4 = Au + 3 FeCl + 3 SO2 + 3 O

Iron being represented in Kovar at 50% content should serve as catalyst for all of the reactions to occur. Wonder if anyone tried it already.
 
While it is pain trying to work on kovar pins with only HCL due to too many metals involved, specifically Nickel plate. I am to try and publish results attacking the pins with H2SO4 and HNO3 combo. I wonder if anyone has already tried this method.
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I've done it with sulphuric acid/sodium nitrate/distilled water. After digesting the base metals, I digested the "sediment" in HCl/sodium nitrate; Then refined digesting again in AR.
If the pins are too thick or brass, I use the sulphuric cell for de-plating the pins.

On another thought and I am thinking on experimenting using all 3 acids to obtain clean gold at the bottom during whole reaction, while everything else should be dissolved. The logic behind this theory:...
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I've done that, too, but find it counterproductive.

Take care!
Phil
 
Phil,

Would you expand on your findings, how did it work with NaNO3 and H2SO4, what were the results?

Did you try HCl + H2SO4 on kovar pins? If so, how did it work what were the results?

Why using 3 acids for Kovar pins is counterproductive?
 
As the most obvious reason, using all three acids at the same time will dissolve gold.

In fact, it will pretty much dissolve everything metallic, with only a few notable exceptions, and the sulfuric will even start to go to town on many plastics.
 
Would you expand on your findings, how did it work with NaNO3 and H2SO4, what were the results?]
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Al, I used a formula that Barren Realms shared with me for making some weak nitric, 100 ml water/170 g sodium nitrate/57 ml sulphuric.
I added enough solution until most of the base metals were dissolved. I ended up with gold foils and some dark sediment. After decanting and filtering the solution, I dissolved the foils and sediment in Poorman's AR. I precipitated with SMB; and proceeded to refine in AR.

Did you try HCl + H2SO4 on kovar pins? If so, how did it work what were the results?
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No, I haven't. Just HCl/Peroxide, but its too slow!

Why using 3 acids for Kovar pins is counterproductive?
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I tried that; the problem I find is, you end up dissolving everything and its a pain to recover the gold. I don't like to cement gold, I prefer to precipitate it with SMB; (some day, very soon), I'll be using oxilic acid.
 

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Just tried sample batch of Kovar laden CPUs with H2SO4 and HNO3 - it worked wonders.

CPUs were sitting in in HCL/CuCl2 for about 3 weeks with little or no effect.

<removed any possible traces of HCl prior to treatment>

H2SO4 and 1ml of HNO3 per CPU removed all pins within 3 hours with no heating as H2SO4 reaction is exothermic by itself.
 
Here is the video of the intensity of the reaction. Comparing this to 3-5 days boiling in HCl and than still dealing with messy AR. Reaction was on about 20 min after acids are added. It went even more active 10 min after I have shot the video.

http://www.youtube.com/embed/4loYtEf3rH0

Hope moderator can properly embed the video
 
Good video, but a little short - Perhaps you could show the setup, ingredients, and a time lapse to the finish?

If you don't speak English well, I have little doubt you could find someone here to help you narrate (heck, if you can't find anyone else, I'd gladly help with that).
 
chlaurite said:
Good video, but a little short - Perhaps you could show the setup, ingredients, and a time lapse to the finish?

If you don't speak English well, I have little doubt you could find someone here to help you narrate (heck, if you can't find anyone else, I'd gladly help with that).
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Sarry claurite, i is in kommunite pipl spik fue inlish kold Kanada. you nou it is veir yite bears liv, vi spik ugundu hir. bat wen you ken help mi this vil veri gut. I si you hav saim nambar post in les 1 yiar, i hav in 3. tis is hau i spik not tranlsator. it huvy for me tu explain tu sam 1 hu did not rid post from start.
 
Cool, so basically you take 20% sulfuric add 1 ml of nitric per cpu and let it digest away the kovar, then filter out the gold foils to refine?

What is the concentration of the nitric you used?
 
To fully dissolve kovar you will need about 2.5-3ml of HNO3 per CPU

WARNING!!!

The reaction when adding HNO3 is vigorous. Add HNO3 in small portions about 25-50ml to start the reaction in cold solution. Than not more than 5ml at a time or you will risk overboiling. Never perform in more than half full beaker, however I would strongly recommend enclosed reaction vessel with complete vacuumed scrabber. When last 5ml will not produce a reaction, you are done.

On the good note, I just witnesses pins done to foils floating a top from about 70 CPUs in just a 10min and I did have little overboiling into the condenser, as I had added too much HNO3 too fast (25ml). Next time I would rather wait for 50 min but I do not want to see what I saw again.
 
Patt,

You are absolutely correct. That is why I issued warning! In any case, doing it in safe environment and adding 5ml of HNO3 at a time while vessel is half full will not trigger rigorous reaction, it will be contained.

It is about as dangerous as putting 50ml of HNO3 into 250ml beaker with hot HCl filled to the top. Anything we discuss here is dangerous one way or another.

As a matter of fact, we have to discourage any posts mentioning reactions with HNO3 producing NOx "under fume hood" or "outside" as it does poison our environment.
 
Alentia,

sorry again , I was too tired when I posted, and to much of a newbie to give that comment, but my intentions where good :lol:
I know a lot of the things we do or talk about here are dangerous if not executed correctly or done with the right equipment,
but we know some newbies just try anything what they read here or see on youtube without thinking or reading much about it, and I thought
I needed to give a warning in this case, like I said I am to much of a newbie myself to give a warning about things that are beyond my own knowledge :roll: :lol:
so I deleted it, 1 minute after posting it :lol:

greetings

Pat
 
pattt,
If you thought I was going to fall off a cliff, I would be glad for the warning, even if you were mistaken.
Nitric acid, its deadly gases, and the violent reactions are dangerous.
 
I still think new members should be forced to download Hoke prior to becoming a member. Then there should be a time limit before they can post. I know that sounds harsh but how many people show up here every week asking "how do I get the gold" There are way to many people watching a half done youtube clip and jumping right in.
Sorry about the rant.
 
Alentia said:
Sarry claurite, i is in kommunite pipl spik fue inlish kold Kanada. you nou it is veir yite bears liv, vi spik ugundu hir. bat wen you ken help mi this vil veri gut. I si you hav saim nambar post in les 1 yiar, i hav in 3. tis is hau i spik not tranlsator. it huvy for me tu explain tu sam 1 hu did not rid post from start.
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Pssst - Plenty of people can write better English than native speakers but have crap for pronunciation. If you care, I based that comment on the fact that in at least three posts now, you have shown the most curious habit of omitting indefinite articles in your sentences. Perhaps you do that stylistically, but don't cop an attitude when I assume that you don't have aspirations to sound like Gertrude Stein.

I gave constructive feedback and even offered to help you out. No need to act like a jerk in response.
 

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