# Stripping pins with HCl alone



## P_CARROLL (May 26, 2008)

When processing pins you should use just HCl alone for the first step as it dissolves all the base metals while leaving the gold intact.never use the HCl H2O2 method to do the primary stripping of any gold plated item as you may put the gold into solution with the other metals.I always do the prelininary stripping with HOT HCl in a crockpot setup as shown in my posts in the past.This leave the gold plating left to be processed.Here are some pics of my latest batch. They were strippid with straight HC then will be processed with A/R


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## Noxx (May 26, 2008)

Nice pics


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## lazersteve (May 26, 2008)

P_Carroll,

Nice work. The foils look great. 

How long does the hot HCl take to work on the pins?

How much HCl do you use on a pound of pins?

Have you ever tried HCl-Cl to dissolve the foils? This step would remove nitric (or sodium nitrate) from your shopping list and you wouldn't have to get rid of any NOx. If you haven't tried it, you should. It works great and is very economical. Foils are very easy to dissolve with room temperature HCl-Cl and stirring.

Great post,

Steve


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## Rag and Bone (May 26, 2008)

Cool. I tried stripping pins and fingers with HCl. I let them soak for up to 3 weeks. Very little base metal went into solution. I guess some heat will do the trick. 

Lookin' good!


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## P_CARROLL (May 27, 2008)

It takes a couple of days to dissolve the base metals. I put 1Lb of pins in a 2 litre erlenmeyer flask then add 2 litres of HCl. Heat in a crockpot for 24-36hrs,drain then add more HCl for a second bath for another 24-36hrs. Drain off luid into a bucket and let cool. I usually dont strt stripping until I have 10lbs of pins so I stroe the chemicals in the bucket until it gets almost full then siphon and filter. Most of the gold is still in the bottom of the bucket. then when im done with the pins I collect all fo the gold then process with A/R. I have a source for nitric so I use that. Go here to see the flask/crockpot in action http://goldrefiningforum.com/phpBB3/viewtopic.php?t=645&highlight=


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## Oz (May 27, 2008)

I know I don’t really know what I’m talking about here with evaporation and boiling of Muriatic, but if I don’t ask I won’t learn.

Do you have a guess as to what temperature you are heating it to? I’m just thinking of the low boiling point and the vapor I see come off my muriatic opening it at room temperature. Do you think this would still work if you diluted the HCL to 20% so the boiling point was greater than water? Or am I just totally mixing up vaporization and boiling here?


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## P_CARROLL (May 28, 2008)

The crock pot heats the hcl up to approx 200 deg which id below its boiling point but csome does still evaporate during the process.


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## Oz (May 28, 2008)

Thanks,

I was using the chart at Wikipedia http://en.wikipedia.org/wiki/Hydrochloric_acid for boiling points.
With the heat you use I may try a small coffee pot batch. If I read your post correctly it requires 4 liters of muriatic per pound of pins between the 2 reactions. HCl is cheap but it does seem to be a lot for 1 pound of pins.
This would work nicely with Steve’s HCl-Cl, I just tried this way using finger foils and using SMB to bring it down. It’s a very nice reaction coming down finely divided.

OZ


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## goldsilverpro (May 28, 2008)

That's about a pound per gallon of HCl, if the 2nd acid application was also 2 liters. Nitric or aqua regia will both dissolve 2 pounds of copper per gallon. Therefore, the amount dissolved by HCl sounds about right - maybe a little low. Nothing wrong with a little overkill.


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## eagle2 (Jun 4, 2008)

One of the great ideas here is not being stressed. And that is the use of the Erlenmeyer flask!! 

The principle of this type of flask is to reduce the evaporation of the liquid that is being heated. The hot acid steams hit the slanting closing sides of the flask, cool, condense and fall back into the solution. Also note the small pyrex beaker over the top!

This is the main reason P_Carrol gets the leaching done so quickly. you can use a really hot leach this way. H2O2 would be useless anyway, it would decompose quickly at this heat. 

Once some Copper or Iron gets into solution, the whole process becomes a faster leach. Cupric and Ferric ions continuing the leach dissolutions much faster than HCl would by itself. 

You have to be really safety minded here. Acid that hot will do terrible damage on your body. 

An experiment comes to my mind, with the use of the flask. With using a solution composed of Water, a large amount of Salt and enough HCl to keep it acid. Add just a small amount of H2O2 to get the leach going. Then with a boiling hot liquid, I would test how long the dissolution would take.

This would be a safer solution than boiling HCl. The temp of a boiling azeotrope of 22% HCl is 108 C. With dissolved base metals in it, the boiling temp should be a little higher. 200 F. is about 95 C. 

Al


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## P_CARROLL (Jun 6, 2008)

Im glad someone finally recoginized the value of my erlenmeyer flask setup. Proper safety equipment is required when handling the hot flasks when changing out the fluids.rubber gloves with thick insulating golves over them to protect your hands. Face shield and apron as well. Plus a box fan to blow the vapors away from you while pouring out fluids or a fume hood if your lucky enough to be equipped with one.

edited once due to fat fingers and new laptop keyboard


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## eagle2 (Jun 9, 2008)

There`s been a lot of discussion on the forum about the best way to process pins. Their are a lot of different viewpoints and variations on viewpoints! :roll: You have settled it in my mind, although I would use a different leach composition. :lol: 

The main thing is acheiving the highest temperatures. Because the dissolution rate is increased two or three times near boiling like just between 95 C. and 100 C. 

So, I have earlenmyer flasks, just never thought about about using them for pins and small objects. 

Here`s a great patent number, that discusses, a leach composition using salt or other Chloride salts. Just Google `patent 4668289` 

Thank You! Al


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## viktor1984 (May 21, 2010)

If i put my cpu's ram sticks and pins that are still unpulled from the plastic slots in HCL in crockpot. till all base metals dissolve. would it be ok to drain the sollution after base metals are dissolved. then maybe rinse 1 time with HCL and drain the sollution agian. then drop everything into AR to dissolve the rest will it work ok? becuase i hate to pull the pins from the plastic slot


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## jimdoc (May 21, 2010)

viktor1984 said:


> If i put my cpu's ram sticks and pins that are still unpulled from the plastic slots in HCL in crockpot. till all base metals dissolve. would it be ok to drain the sollution after base metals are dissolved. then maybe rinse 1 time with HCL and drain the sollution agian. then drop everything into AR to dissolve the rest will it work ok? becuase i hate to pull the pins from the plastic slot




You should keep each group of scrap to process separate.Pins with pins fingers with fingers, and CPU's with CPU's.Mixing them will bring you problems. Try to keep the solder out of the processing also, by trimming the fingers on the ram.

Also I would try to get rid of the plastic before processing, or at least try small batches to see what happens.

Jim


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## eagle2 (May 21, 2010)

Thats not the way to handle parts that have plastic or fiber with them. Fingers with gold foils on them will loosen up very nicely in a few days with your leach solution at room temp. Those can be shaken or stirred (shades of 007!) to separate them from the fiber base.

But plastic connectors should not be handled that way. First a boiling leach will probably melt some of the plastic or deform them at least. A warm leach will take weeks to do. If you manage to get some of the base metals out (and you definately will not get all the base metals out), the gold foils will stick to the inside of the plastic slots where they are really hard to remove. 

Also AR, or Nitric alone, dissolves plastic. Imagine that mess! 

So you have to pull the pins or buy a grinding machine to get a powder that a leach will reach to dissolve all the base metals. Then you can use the HCl + Cl leach on the gold and plastic residue to remove the gold.

Al


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## Barren Realms 007 (May 21, 2010)

eagle2 said:


> Thats not the way to handle parts that have plastic or fiber with them. Fingers with gold foils on them will loosen up very nicely in a few days with your leach solution at room temp. Those can be shaken or stirred (shades of 007!) to separate them from the fiber base.
> 
> But plastic connectors should not be handled that way. First a boiling leach will probably melt some of the plastic or deform them at least. A warm leach will take weeks to do. If you manage to get some of the base metals out (and you definately will not get all the base metals out), the gold foils will stick to the inside of the plastic slots where they are really hard to remove.
> 
> ...



Actually you can do them while they are still in the plastic, I would use HCL/peroxide to get all the base metals in the pin disolved inside the plastic. You can then filter out the plastic or if you have gold flake still in the crevices you can run them in HCL/Clorox. It is just more of a pain and a lot more material to deal with if the plastic is still there. If you can remove the pins take the time to do it your reward of time use will be greater


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## Palladium (May 22, 2010)

When i do plugs i don't pull the pins either. I just toss the whole thing in ap and let it sit until it eats the copper center out. It takes longer that way but i have found that if i add more air and tumble them in a basket set up after i wash them real good i can get about 98-99 % of the gold out of the plugs.
Lot less labor !!!
Forget pulling pins. :twisted:


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## patnor1011 (May 24, 2010)

Heavier plated pins will leave you with nice foils. Flash plated low grade pins plating will disinegrate into fine gold powder no matter if you use HCl only or HCl+H2O2 (when using AP on pins i usually put only half of recomended amount of H2O2).


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