Why does Kovar foam AP?

[jason_recliner]

What is it about kovar that seems to make CuCl2 / AP foam up like crazy?

This started a few weeks ago. I went down the local aquarium and picked up a $2 air stone, rather than just have the tube going to the bottom of the jar.
I expected a bit of a speed difference, but wow. A second identical AP batch went from over a month (it's winter), down to about a week. Yay.

So after 8 hours running on a batch using old AP with about 1/4 inch layer of bubbles on top, within a 20 minute period it had foamed like all hell and I had a massive overflow. Lucky I had it all in a plastic tray but it took a fair bit of cleaning up. I figured it had run out of HCl. No big deal, just add some more. But plenty enough for my fingers, that only fixed it for a while. Or maybe has it foamed because it needs more water to help dissolve salts? Because HCl is 68% water too.

The base material is springy tabs from EEPROM programmer ZIF sockets, and is likely to be kovar. I now see MGH mentions kovar causes foaming annoyingly. http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=61&t=21897&p=227623&hilit=kovar+foam#p227623
Does anyone know why it does this?

I've acquired a growing container of AP I have been reusing for over a year, just adding HCl to individual jobs occasionally, then once it's it done it goes back in the AP container. I already know it's full of all sorts of rubbish; heaps of tin, lead & iron... probably also zinc, beryllium, cobalt, insects, and a bit of frog. But because the first lot of AP that treated the kovar went back into the bulk container before I bought the air stone, I've possibly at least partly contaminated the lot. Though I do still have the last one separated.

I can't tell you how many times I've reread Butcher's post about rejuvenating copper(ii) chloride. http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=46&t=20006&p=204406&hilit=butcher+white+powder+ferrous+cuprous+cupric+cool+decant#p204406.
From this I have already managed to separate a nice lot of CuCl and CuCl2 powders (wet) if I want to start my AP over. Removing metals other than lead chloride is not so clear.

But I want to be as efficient with HCl as possible, reuse it as long as I can. I'm also lazy and want to treat as little waste as possible. The AP still seems to work, but this foaming is getting to me. Even on a small batch of RAM fingers, it's now foaming up. :evil: This is no good.

Have I wrecked my AP and just need to treat it for waste and start over?

Side note: I saw Nurdrage's video recently on lossless recovery of HCl and copper using sulfuric. I'd love a bit of distillation kit like that. 8)

 

[g_axelsson]

This started a few weeks ago. I went down the local aquarium and picked up a $2 air stone, rather than just have the tube going to the bottom of the jar.
I expected a bit of a speed difference, but wow. A second identical AP batch went from over a month (it's winter), down to about a week. Yay.

In most chemical processes the speed is proportional to surface are. In copper chloride process the limiting process seems to be the oxidation of copper chloride so more oxygen into the solution means a faster process. In this case smaller bubbles means larger surface area that oxygen can be absorbed into the liquid phase.

Can't help you with an explanation on the foaming though.

The base material is springy tabs from EEPROM programmer ZIF sockets, and is likely to be kovar. I now see MGH mentions kovar causes foaming annoyingly. http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=61&t=21897&p=227623&hilit=kovar+foam#p227623
Does anyone know why it does this?

Is it magnetic? Kovar is magnetic but I don't see a reason to use kovar in this application. I never thought of kovar as especially springy.

Göran

 

[butcher]

Kovar iron alloy, consisting of 29% nickel, 17% cobalt, (0.2% silicon, 0.3% manganese, 0.01% carbon), and a balance of iron (approximately 54% Fe).

Note the reactivity series of metals:
http://www.cod.edu/people/faculty/jarman/richenda/1551_hons_materials/Activity%20series.htm

Note the position of Hydrogen in the series, and the position of the other metals.

Copper is below hydrogen (it will not displace hydrogen from acids, like HCl in our copper chloride solution (which you are calling Acid peroxide or AP), this also indicates copper will not dissolve in HCl acid, but copper oxide will, or if we add an oxidizer to the HCl acid like hydrogen peroxide or air to provide free oxygen...

Note also the position of the metals in the series that make up the composition of the Kovar alloy, Iron, cobalt and nickel, all of which are above Hydrogen in the reactivity series of metals, theis shows us they all will dissolve in HCl (even without an oxidizer), and all will displace Hydrogen from our acid, this hydrogen will leave as a gas (which can cause foaming as it does), the more reactive the metal the more reaction the acid has on the metal, this is why aluminum is so reactive in HCl and displaces hydrogen in an more vilent reactions than say iron will...

Note Kovar has no copper involved (although many times you will have copper in other pins or material your working with) we see here that kovar or its metals of iron, nickel, cobalt, will all cement copper from a copper chloride solution, basically changing our copper II chloride leach to an iron chloride contaminated with other base metals nickel and cobalt, or a solution or soup of metals depending if our solution is acid enough to hold them all...

Note iron is above the cobalt, nickel, lead and copper in series, adding iron to the solution will cement the metals below iron, which can lead us to and iron chloride solution, that can be reused as a leach (ferric chloride) or treated for waste...

To understand better how to use you leach you need to understand more of what these leaches are, and how they work...
First by calling the copper II Chloride leach, acid peroxide or AP in my opinion is wrong and misleading.
Copper II chloride only uses the acid and peroxide to make the copper II chloride, which then the CuCl2 is what actually dissolves more copper, not the acid or oxidizer...
Understanding how other metal react with this solution you can also get a better grasp of what is going on with your solutions, if you want to keep your copper II chloride leach healthy and in good shape you will not want to put other metals more reactive than copper in the solution (like kovar), or limit how much other metals you leach sees.

If you do dissolve much kovar in your copper II chloride, you also need to understand you are changing the leach from being a copper II chloride leach, into an iron chloride leach, and after much of this you will no longer have a copper II chloride solution or leach (which you call AP)...

 

[jason_recliner]

Thank you kindly to both of you for your thoughtful responses.

This started a few weeks ago. I went down the local aquarium and picked up a $2 air stone, rather than just have the tube going to the bottom of the jar.
I expected a bit of a speed difference, but wow. A second identical AP batch went from over a month (it's winter), down to about a week. Yay.

In most chemical processes the speed is proportional to surface are. In copper chloride process the limiting process seems to be the oxidation of copper chloride so more oxygen into the solution means a faster process. In this case smaller bubbles means larger surface area that oxygen can be absorbed into the liquid phase.

And it's not just that there are more of them. One more thing helping is that large bubbles also rise very quickly, whereas thousands of tiny ones rise more slowly and spend more time in contact with the liquid.

Is it magnetic? Kovar is magnetic but I don't see a reason to use kovar in this application. I never thought of kovar as especially springy.

Hmm, good point. I have two types of socket. Both have pins or tabs which are magnetic. I am aware copper will be plated in nickel before the gold layer. But it seems a stronger attraction than I witness with plated pins. I am only guessing and assuming they're both kovar.

I found some internet pictures of similar items. One is a bit like this:

The other is this sort of thing. The tabs are quite hard. I suspected that it may have been copper plus beryllium, but it has a solid grip (stronger than the first) with a neodymium hard disk magnet.

Butcher, I agree that the name AP is misleading. I expect it probably annoys all the chemists. I'm ok just going with the flow of the forum. There hasn't been any "P" added for over a year anyway, just "A".
After a year of various materials, there's no telling whether it's cupric, cuprous, stannous and ferrous chloride. Or all sorts of other muck. It still works though.

I am wondering if the serious foaming is caused by the viscosity of the leach, and that either HCl or water would do the same thing.
The disconcerting thing is that it was stable for hours, at about 1/3 full, then suddenly went off like a stabbed rat to maybe 10-15 times volume when something hit a critical level.

if you want to keep your copper II chloride leach healthy and in good shape you will not want to put other metals more reactive than copper in the solution (like kovar), or limit how much other metals you leach sees

Well nickel is always going to happen, for one. A while back I started prewashing in HCl to remove tin, lead, etc. Though I have seen that it will even start to work on copper too, and after not very long.
I think you have answered my question. Time to ditch it (figuratively speaking) and try harder to keep a clean CuCl₂.

The forum seems used to the term AP, blatantly wrong as it is. Acid/Peroxide may be used to help create the leach. The problem is, when one has such a mixed up soup of randomness like this, what else to call it? Just CuCl_x leach? I'll go with whatever

 

[g_axelsson]

Well, I have used copper chloride leach as the name for a very long time. I don't remember if I used AP in the beginning, probably did that before I got an understanding for the chemistry of the process. In the circuit board industry it's called ammoniacal copper chloride leach as they use ammonia to dissolve the copper chloride and not hydrochloric acid.

The more people that use copper chloride over acid peroxide as a name, the less confusion it brings. It's a long way to go before we can get rid of AP as a name, but I'm optimistic that some time it will only be a part of the history of the forum.

Göran