Non-Chemical stripping base metals and depopulating boards

[Topher_osAUrus]

I figured it was just a small typo, we all have them (i have them alot)

The long thin needles that have came out of solution while cooling are most likely lead chloride (long thin needles, actually quite pretty to look at)
If it were me, i would remove the boards/solids from the solution, let it cool, dropping the PbCl needles and any other slightly solubles, then filter the acid off from them, and return the acid to the pot with the boards to keep working.

 

[rewalston]

I figured it was just a small typo, we all have them (i have them alot)

The long thin needles that have came out of solution while cooling are most likely lead chloride (long thin needles, actually quite pretty to look at)
If it were me, i would remove the boards/solids from the solution, let it cool, dropping the PbCl needles and any other slightly solubles, then filter the acid off from them, and return the acid to the pot with the boards to keep working.

Tophur, the needles are long and thin, they are more like metallic whiskers. PbCl needs are generally (from what I've seen) long and almost white in appearance.

Rusty

 

[Topher_osAUrus]

Now you have me curious what yours look like, when you said long and thin, i thought you meant the "whisker needles". Do you have a picture you could upload?

 

[rewalston]

Now you have me curious what yours look like, when you said long and thin, i thought you meant the "whisker needles". Do you have a picture you could upload?

This first picture is the first bucket I used with HCl/H2O no heat.

This picture shows the bucket with just water for rinsing the parts in after I scraped off the parts. The parts and the boards are in the bucket for now.

This is one of the boards that are still working in the crockpot, no heat added this time. You can make out the little metallic whiskers. Notice also that it appears that the gold has been removed from the fingers.

The whole thing is rather confusing. I know that I should have used straight HCl, but I ran out and thought that adding water to it wouldn't complicate things. I won't have any more acid until end of the month.

Rusty

 

[g_axelsson]

Easy!

The water is actually an electrolyte, a lot of metal salts and acid traces. So the board, containing a lot of different metals in electrical contact with each other creates small "batteries" where a current runs through the circuit and more noble metals are plated out and less noble goes into solution. With tin in solution your needle like metallic crystals is probably tin, it often creates a fluffy mass of thin crystals.

This is an example of electrolysis of tin chloride.
https://www.youtube.com/watch?v=G1sq4hnrBgM

Your gold hasn't been removed, it is just covered in a thin layer of metallic tin, try wash it with HCl.

Göran

 

[rewalston]

Easy!

The water is actually an electrolyte, a lot of metal salts and acid traces. So the board, containing a lot of different metals in electrical contact with each other creates small "batteries" where a current runs through the circuit and more noble metals are plated out and less noble goes into solution. With tin in solution your needle like metallic crystals is probably tin, it often creates a fluffy mass of thin crystals.

This is an example of electrolysis of tin chloride.
https://www.youtube.com/watch?v=G1sq4hnrBgM

Your gold hasn't been removed, it is just covered in a thin layer of metallic tin, try wash it with HCl.

Göran

Thank you Göran, I had a feeling it was tin. I'll finish depopulating what I have. And put all the boards, etc in my bucket of water and at the end of the month, I'll get some more HCl and do a wash of everything before I do anything else.
Rusty

 

[kernels]

Certainly looks like Tin crystals

 

[Grelko]

Since you should take out the plastic (already spent the last few days pulling pins from holders), what about the older dipped capacitors, ceramic or glass resistors/diodes, or other Items like fuses that are encased in a rectangle ceramic shell, glass screens from old VCRs, stereos and other bits of trash? I'm trying to sort my pile of components a bit before processing.

So far I've removed alot of the copper windings, aluminum caps, iron and plastic.

I'm thinking for certain pieces, I'll need to incinerate or pyrolize, then crush and reprocess.

I won't be using nitric for this.

 

[rewalston]

Ok, I finally got my goofed up solutions filtered. And the parts are ready to go into pure HCl to correctly remove the tin. The filters I have I'm assuming that I can, after the boards, etc have desoldered, put into the HCl to remove the tin that was caught in the filters along with everything else. Just for safety sake I checked my solution with SnCl to make sure there was no gold dissolved. I'm safe . That HCl/H2O solution is now been placed into my waste bucket to neutralize. I also was wonder the water that I rinse everything off into, after everything is filtered out of it, that goes to waste as well correct? Because there would be some HCl in it from rinsing off parts.

Rusty

edit: The filters that I have currently from my screw-up has a lot of black sediment.

 

[g_axelsson]

That black sludge from depopulating components could contain metallic gold. Easily tested by dissolving a small sample in AR and tested with stannous.

The main source of metallic gold in the black sludge would be from gold dissolved in the solder. Boards using ENIG on solder pads or gold plated component legs will have the gold dissolved by the molten tin. This is released when the solder is dissolved.

Even on boards without ENIG or gold plated legs there could be a bit of gold in the solder, transferred from other boards in the wave solder machine. For pure surface mounted boards there is no cross contamination between boards, but for boards with through hole mounted components there is a distinct possibility.
Gold in solder baths is a problem for some manufacturers, whenever the gold content reaches close to 0.5% the solder bath has to be replaced. Too much gold creates fragile solder connections that easily crack over time.

Göran

 

[rewalston]

That black sludge from depopulating components could contain metallic gold. Easily tested by dissolving a small sample in AR and tested with stannous.


Göran

That is what I suspect. I'm going to be using A/P on everything once the remainder of the tin/solder is removed. Once the A/P recovery is done, the refining will be with HCl/bleach.

Rusty

 

[Grelko]

I had a bit of trouble with processing "because of my old A/P solution", after manually stripping off components.

I'm just double checking that everything is working properly now.

I had left over AP (possibly just CuCl2 since it was a nice emerald green) from when I first started processing material. I had previously "partially" neutralized it, so the PH was around 2-2.5.

I put a few pounds of components into the bucket with the old AP and turned the bubbler on. When I checked it later, I noticed that it had foamed up a bit, so I took a spray bottle and knocked the foam down. The next day, I had to knock the foam down again (the foam looked dark orange).

Today, I put in 1/2 gallon of HCl and mixed it up, so the PH should be around 1-1.5, but I haven't checked it yet. The green is completely gone and now the color is grey (so far, there's no more foam). It seems to be working fine now. The grey color "getting more clear", should be any tin or zinc from plated wire/legs or solder.

I was going to let it run for another week or two, then collect any left over pieces and powder.

I'll be checking the solution with stannous periodically, and possibly post a few pictures, if I have any problem figuring out certain "mixed" stannous colors. There may be some Pt or Pd in solution at some point because of the MLCCs.

Everything that is collected "any plastic, powder, chips etc" along with a good bit of un-dissolved copper, will be rinsed with clean water into a bucket, to remove any powder that may be trapped within some pieces.

Afterwards, any plastic will be removed to be incinerated later on, just incase there's any trapped powder left, while the rest of the undissolved material/powder is put into fresh AP to continue processing.

Once the rest has been dissolved, I'll be saturating the solution with copper to make sure any PMs are dropped, then collect all of the black and grey powder for further processing.

Edit - Seeing that at the end of processing this, my old AP should be mainly "if not completely" zinc chloride, from brass etc. Would I still need to use iron in the disposal? I'll probably put in a chunk anyways to be on the safe side.

Edit - spelling

 

[rewalston]

When I placed the boards that I have into NaOH solution to remove the mask, I noticed that some gold came off with the mask. I plan on filtering the solution, but before dissolving the gold should I incinerate first as this is an alkaline solution I'm dealing with. Or would just rinsing well with water be ok.

Rusty

 

[anachronism]

Rinsing with water and washing it well will be perfectly fine. Some advocate incineration for everything however opinions do differ.

 

[rewalston]

Rinsing with water and washing it well will be perfectly fine. Some advocate incineration for everything however opinions do differ.

Thank you, I was looking over some other posts that I have bookmarked and it appears that just a good washing should do it.

Rusty

 

[rewalston]

Well, starting to clean up my waste buckets before dissolving PMs. I started with the easiest one, my 2 gallons of rinse water that I washed all of the stripped boards in. Tested it with a PH strip and it's definitely acidic. I took the NaOH solution (approx. 1/2 gal) that I used to strip the boards with (after filtering solids out of it) and poured it into my rinse bucket. Definitely some metals dissolved in the rinse water, the solution immediately started to cause metals to come out of solution. I stirred it up really well so that everything was mixed well. The solution took on a bright navy blue color, thought it was pretty cool. I'll let it sit for a few days so that the precipitant settles out and then I'll filter it. Now my next question, the PH right now is above 9. My test strips were to test pools with so my range of PH is only 6.2 - 9. To bring the PH back down to 7ish, how should I go about that, add HCl or H2SO4 until it's in the 7 range?

Rusty

 

[anachronism]

If you're happy that the metal is out, then sure use HCl to bring it back down to pH7.

 

[Barren Realms 007]

Well, starting to clean up my waste buckets before dissolving PMs. I started with the easiest one, my 2 gallons of rinse water that I washed all of the stripped boards in. Tested it with a PH strip and it's definitely acidic. I took the NaOH solution (approx. 1/2 gal) that I used to strip the boards with (after filtering solids out of it) and poured it into my rinse bucket. Definitely some metals dissolved in the rinse water, the solution immediately started to cause metals to come out of solution. I stirred it up really well so that everything was mixed well. The solution took on a bright navy blue color, thought it was pretty cool. I'll let it sit for a few days so that the precipitant settles out and then I'll filter it. Now my next question, the PH right now is above 9. My test strips were to test pools with so my range of PH is only 6.2 - 9. To bring the PH back down to 7ish, how should I go about that, add HCl or H2SO4 until it's in the 7 range?

Rusty

I know you are trying to do what you can with what you have at hand but you need to stop using the test strips for pools they are not even useful when working with the chemicals we work with. You can find some really inexpensive PH meters on Ebay that would do you a better job.

 

[rewalston]

Thanks Barrens, those are on my buy list. But it still didn't answer my question.

 

[anachronism]

Thanks Barrens, those are on my buy list. But it still didn't answer my question.

That's ok Rusty. I already answered it two posts up.