Dirt on pins

[razzel8]

Hello all,
i found old boards from the 60's that had been laying outside rotting. After scraping some dirt off the contact pins I noticed they had gold plating. I've been saving these up as I thought I would clean them and than run them thru a cell. However I ran into problems getting them clean enough for the cell. I've tried every type of cleaner on small batches with no luck. Which brought to mind maybe incineration. I tried a very small batch with a propane torch, had kind of a greenish flame to them until i barely had it glowing and removed them to cool. After letting them cool in water I noticed I no longer have a gold plate and pins are still not clean enough. Can anybody offer any advice on very dirty pins? Maybe the plate is to thin even thou they are very dated. I have tried a few in hcl but it appeared the copper or plated metal was getting attacked before the dirt.
I can not tell which pic is which now that I've uploaded them but 1 is in the casing with a couple pounds scratched and the other is 2 after incineration.
Thank you,
Raz

 

[Geo]

Gold plated material is only as good as the environment around them. All gold plating has weak points. Different metals have different expansion rates when heating and cooling. Over a period of time, the plating develops cracks that moisture can get into. The unprotected metal under the plating starts to oxidize from the crack outwards. As the metal substrate degrades, the plating just flakes off. The reaction and green color proves that the copper alloy in the pins has oxidized to some degree. If you want to recover the gold, you should act quickly. Rinse off whatever dirt you can with just water and harvest the pins as is. Any heating could cause the loss of much of the plating. As the trapped moisture under the plating next to the substrate heats and expands, it will pop the plating off in much larger pieces than just pulling them off.

 

[razzel8]

Geo, no amount of rinsing budges this stuff. It is caked on each pin pretty thick. It does scrape off easy to the gold plate but that would be to time consuming and still leave residue. I fear no matter how they are processed it would contaminate my solutions with unknown materials. I may just submerge them in olive oil and leave them to slowly loosen it and come back later, much later. That leaves me in the dark if it is worth it to pursue the rest of the scrap pile thou.

 

[eastky]

That leaves me in the dark if it is worth it to pursue the rest of the scrap pile thou.

razzel if you are talking a few boards that amounts to a few ounces of pins. It wouldn't be worth it to me.

What I would do is scrape the crud off a couple connectors. Don't worry about the gold coming off. After scraping the pins clean of crud I would break the pins out of the connector to get a weight of pins per connector. That away you can get a estimate of how much the clean pins weigh. Count the number of connectors you have and times that by the weight of the
pins you removed from the connector.

I have connectors that the whole pin is plated. Your pins maybe be fully plated or just plated on the outside.

Being that they are old boards the gold plating is probably thick and you can get a good yield. Just because they are covered in crud doesn't mean they have lost the gold plating.

If you don't have hundreds of those connectors to process you have to decide if it worth your time and money spent on chemicals.

 

[g_axelsson]

I can not tell which pic is which now that I've uploaded them but 1 is in the casing with a couple pounds scratched and the other is 2 after incineration.
Thank you,
Raz

Just use the preview button, you know, the one to the left of submit button.

If I could wish for one new function on the forum it would be that you had to use preview first before submit was even possible. People seem to be afraid to use preview. :twisted:

Göran

 

[sri steve]

Hi, incineration is not the way to deal with this, as said if any of the Au plating lifts from the base metal pin; propane will be hot enough to evaporate it with it being very thin, my advice is to collect all your pins etc. and wash them hot water and remove any solid or organic material.

Then process them as normal with 50/50 HNO3, you will recover all the Au shells and then process them as normal, if you process them properly you will remove any contaminates with filtering and washing.

Some will say there is no need to AR this kind of Au but if you do you can safely say that the recovered Au will be clean.
Sri.

PS I don't know if but I will say so, that you know that the pins and any other type of this scrap must be clean of all other metals, otherwise you will end up with a mess.

 

[g_axelsson]

Hi, incineration is not the way to deal with this, as said if any of the Au plating lifts from the base metal pin; propane will be hot enough to evaporate it with it being very thin, my advice is to collect all your pins etc. and wash them hot water and remove any solid or organic material.

The boiling point of gold is 2,970 °C, there is no risk of evaporation of gold from the surface of the scrap when incinerating.
Loose flakes may be blown away and gold plate will diffuse into the surface of the base metal and alloy with it so it looks like it's disappeared but it will still be there.

Göran

 

[goldsilverpro]

When you heat gold plated material quite hot, the gold can fully migrate into the base metals (or is it the other way around?). The gold is still there, in my opinion, but it is now intermingled with the base metals.

 

[razzel8]

Hmmm.... would it not intermingle with the ions of dirt also and possibly be lost as smoke? These are quite old so it's very possible there is lots of breakdown of the metals underneath maybe allowing it to be carried off? I did not heat it enough to think it would alloy with the nickel or copper underneath and it doesn't look like it's there. Unfortunately I'm not going to spend time trying to discover where it went as it must be super thin and I'll have better luck with other methods. One interesting thing on my mind thou is if it was carried off, catching that in a fume filter would be possible, saving a large quantity of chemicals.

Raz

 

[eastky]

Unfortunately I'm not going to spend time trying to discover where it went as
it must be super thin. Raz

If the plating is 30 microinches plating. If you took just the gold off the pins. Your pin has 4 sides you would need quite a few pins to make a stack 1 inch tall. There isn't much gold there that's why you need pounds on e-scrap to have good recovery.

Edit: to correct micron to microinches. There is 1 000 000 microinches in 1 inch.

 

[razzel8]

That leaves me in the dark if it is worth it to pursue the rest of the scrap pile thou.

razzel if you are talking a few boards that amounts to a few ounces of pins. It wouldn't be worth it to me.

What I would do is scrape the crud off a couple connectors. Don't worry about the gold coming off. After scraping the pins clean of crud I would break the pins out of the connector to get a weight of pins per connector. That away you can get a estimate of how much the clean pins weigh. Count the number of connectors you have and times that by the weight of the
pins you removed from the connector.

I have connectors that the whole pin is plated. Your pins maybe be fully plated or just plated on the outside.

Being that they are old boards the gold plating is probably thick and you can get a good yield. Just because they are covered in crud doesn't mean they have lost the gold plating.

If you don't have hundreds of those connectors to process you have to decide if it worth your time and money spent on chemicals.

Eastky I have a little over a pound of fully plated pulled pins. I can have another estimated 2 to 4 pounds more if I choose to go after them. Kind of time consuming harvesting them from the rotten boards and than even more so pulling them from connectors. I'm not convinced any escrap is really worth my time lost but I keep wasting it and than wasting even more time trying to find the easiest, cheapest way to process it

 

[eastky]

Eastky I have a little over a pound of fully plated pulled pins. I can have another estimated 2 to 4 pounds more if I choose to go after them. Kind of time consuming harvesting them from the rotten boards and than even more so pulling them from connectors. I'm not convinced any escrap is really worth my time lost but I keep wasting it and than wasting even more time trying to find the easiest, cheapest way to process it

Being that I do construction work outside. Its winter time and short days so I concentrate on e-scrap this time of year.
Beats being bored at home. I hear you about is it worth processing. Good thing I am easily entertained. So I just turn on some music and get lost in what I am doing.

 

[eastky]

Raz This is what I would do after you get the pins pulled.

Take a old pan that you have one that has a lid with it. Put pins about a half inch deep put lid on and heat with a hot plate or a grill. Don't waste time with trying to use a propane torch. Heat from the bottom with the lid on. Per Geo if there is moisture that has migrated to the metal of the pins the lid will keep everything in the pot. Let it heat for a bit how long is up to you. You will need to move the pins around so all of them get heated up good. Doing this is burning off oils and organic matter.

After the pins are well heated and you cant see any smoke or fumes being released. Put them in AP and dissolve the base metals. Do a small batch maybe a ounce of pins. When pins are dissolved let settle and decant the AP. Collect the foils and the crud. Wash in boiling water. Let settle decant wash foils and crud with HCL heat a little not a boil. Let settle decant wash again with HCL with heat don't boil. Wash with water bring water to a boil and let settle and decant.

Washing with HCL will help remove more base metals and contaminants. You should continue the HCL washes until the HCL stays clear. You have to decide how much acids you are going to use on this recovery thing. If after a couple washes with HCL if it keeps turning a dark green color I would just put it back in to AP and try to remove more traces of base metals. At this time I wouldn't worry about the HCL having a little green color to it. Point being this is just recovery and you will want to refine whatever you recover 2 times. This is when the washes are very important.

My understanding on the water washes are to remove salts. If I am wrong someone will correct me or they should.

After the water wash let settle decant dry the foils and crud. If you use heat watch for steam explosions blowing things all over the place.
Now this is where you want the incineration to come into the equation. My understanding is when you have chloride salts involved and you incinerate you have a good chance of losing gold. You need to read upon this to see what you need to do. I really haven't read upon this so I wont advise you on this part.

Stainless steel or pyro cream for incineration. Read upon the basics of incineration. Heat from the bottom first and don't blow your foils and crud out of the dish.

After incineration crush the mess into a fine powder. Take some water and bring it to a boil. Add a little of the powder at a time. You need to make sure all the powder gets wet. Try and not to put so much in at once that it clumps up.

You need this powder to absorb water. Being that the crud most likely contains dirt and dust. Dry dirt and dust will absorb water and acids. Using hot water to mix the powder with will wet the powder easier. Hot water breaks surface tension better than cold water. After you have the powder in the water let it set for a couple days. Stir it a couple times a day.
Let the powder settle decant the water and collect the powder sludge.

Use HCL/Cl to dissolve the gold. Put some sludge in and stir. Keep doing this until you have added all your powder from the sample you did. How much acids and such you will need is what you need to get the job done is what you need to read on and find out.

Make sure you read upon using to much bleach and not being able to drop your gold from solution. Let the solution settle decant and drop your gold. Wash the powders with water to get the last bit of gold solution out of the powders.

The HCL/Cl solution will most likely not stay yellow it might have a different color due to base metal contamination. You will be refining that powder a second time so I wouldn't worry about that. Read upon removing chlorine from solution if your gold wont drop.

Good Luck

 

[goldsilverpro]

Razzel,

I didn't say "alloy". I said "migration". Big difference. Given enough time or temperature, metals will migrate into other metals. Thin nickel plating (usually from 1.25 to 2.5 microns thick) is commonly used as a barrier to prevent the gold from migrating into the copper. All plating is porous, including nickel and, at high temperature, the passivation in the nickel pores can be destroyed and this can allow copper to migrate through the pores. That's what I think has happened.

I've seen this happen many times. When heated quite hot and then cooled, it looks like the gold has disappeared or, at least, it's color has lightened considerably. Several times, I have taken heated pins that appear to have no gold on them and have recovered the gold from them by first dissolving the copper and nickel in nitric. I would bet the gold is still there. It's not going to fall off and it's not going to vaporize.

eastky,

You've been on here long enough to know that no gold plating on pins is 30 microns thick. 30 microinches or 30 millionths of an inch, yes. 30 microns, no. A micron is 40 microinches. 30 microinches is .75 microns.

 

[eastky]

eastky,

You've been on here long enough to know that no gold plating on pins is 30 microns thick. 30 microinches or 30 millionths of an inch, yes. 30 microns, no. A micron is 40 microinches. 30 microinches is .75 microns.

Thanks GSP I was thinking microinches and put micron instead. I edited my post stating the right thickness.

 

[razzel8]

GSP,
I apologize for calling it an "alloy" in my ignorance.

eastky,
Thank you for the detailed response. I think the only thing I will do different is boil them in plan tap water before anything. It does not help to liberate much crude, however anything flushed out is less I have to deal with later.

Thanks to all,

Raz

 

[necromancer]

maybe just process some of them & see what the end result is :?:
i can't see dirt, dust, bird poop, scrap yard goo. making it through a acid bath and the filtering process.

try 100 grams & see how it goes.

 

[goldsilverpro]

You might just try dissolving everything you can with the AP process, just like ordinary pins. Then, put everything that's left in aqua regia.

 

[kurtak]

Razzel,

I didn't say "alloy". I said "migration". Big difference. Given enough time or temperature, metals will migrate into other metals. Thin nickel plating (usually from 1.25 to 2.5 microns thick) is commonly used as a barrier to prevent the gold from migrating into the copper. All plating is porous, including nickel and, at high temperature, the passivation in the nickel pores can be destroyed and this can allow copper to migrate through the pores. That's what I think has happened.

I've seen this happen many times. When heated quite hot and then cooled, it looks like the gold has disappeared or, at least, it's color has lightened considerably. Several times, I have taken heated pins that appear to have no gold on them and have recovered the gold from them by first dissolving the copper and nickel in nitric. I would bet the gold is still there. It's not going to fall off and it's not going to vaporize.

GSP - thanks for posting this - I was going to post something very similar but have just been to busy lately to do any posting

Incineration is the way to go here with these pins --- I have incinerated "many" pounds of dirty pins & have not seen any noticeable loss in gold (per pound) when compared to the per pound recovery from clean pins that did not need incineration

In fact you are more likely to suffer loss by not incinerating --- 4 years ago when I first joined the forum some of the best advice I was given was from Harold on the importance of incineration for "dirty" starting material & for that matter at different points (steps) along the way of recovery &/or refining

I have been following Harold's advice to incinerate ever since & have never been disappointed by the results of doing so --- in fact it was when I thought I could get away with skipping the incineration step (back I my early days) that I ended up being disappointed & kicking my self in the butt wishing I had not skipped that step

Edit to say --- I would incinerate these pins without even giving it a second thought - it would be the first & last thought :!:

Kurt