# What is a typical yield from gold coated electrical relay contacts?



## Forgeweld (Mar 6, 2022)

I found a ton of electrical relays with gold coated contacts in abandoned equipment in a mill. Sadly someone had gone in already and plucked a ton of them and smashed a bunch up, but I was still able to collect about 4.5 oz of contacts including the little copper bits. 

So question for someone who has dealt with these, what is the yield like compared to board scrap and fingers and stuff? 

The gold coat is pretty thick, I was surprised to see that cutting into one with a fine too file leaves gold shavings for a few strokes before I reach base metal. 

The relays are all two models, made by MSD and Struthers Dunn. Also these list for around 150$

This will be my first attempt at gold refining so I'm thinking about doing a small batch with just these to see what I yield (I'm new to this but I'm not hoping for anything outlandish)


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## kurtak (Mar 6, 2022)

Forgeweld said:


> So question for someone who has dealt with these, what is the yield like compared to board scrap and fingers and stuff?



Hard to say - depends somewhat on age & manufacture --- generally speaking the plating will be heavier the say fingers


Forgeweld said:


> The gold coat is pretty thick, I was surprised to see that cutting into one with a fine too file leaves gold shavings for a few strokes before *I reach base metal.*



per the bold print - the *actual point* is likely not a base metal but silver 

In other words - you have the bus bar that has a point on the end of it --- the buss bar is a base metal (like copper or brass or ?) the point it self is likely silver & in this case that point has also been gold plated

Therefor the best way to process is to first use nitric which will dissolve the (bus bar) bass metal & the silver

That will leave you with your gold foils & you can then recover the silver from you nitric solution

Just guessing here - but because of how close to the points you have nipped the points from the bus bar you are likely looking at around 30% maybe 40% silver recovery ---plus the gold plating - again just guessing but maybe around 1 gram gold (plus/minus)

Kurt


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## Alondro (Mar 6, 2022)

Those are very high-recovery materials. Like Kurtak wrote, those contact 'buttons' are mostly silver with heavy gold plating. They're one of the easiest things to process, since they don't have solder to contaminate the reactions and make goo.

Some of those smaller buttons look different, though. The luster is more brilliant, and the places with heavy wear do not show any sign of another metal beneath. There is the possibility that they are solid gold.

I found some solid gold contact points in a few old relays from high-end equipment, but those were very tiny contact points, pin-head size round dots, or even tinier rectangles (some solid gold, some gold-plated nickel). The arms were also gold-plated in those relay switches, so that was nice too.


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## GoIdman (Mar 7, 2022)

Forgeweld said:


> So question for someone who has dealt with these, what is the yield like compared to board scrap and fingers and stuff?





Alondro said:


> I found some solid gold contact points in a few old relays from high-end equipment, but those were very tiny contact points, pin-head size round dots, or even tinier rectangles (some solid gold, some gold-plated nickel). The arms were also gold-plated in those relay switches, so that was nice too



Like @kurtak and @Alondro said, every relay is slightly different so there is no correct answer for you yield question. 

I have processed same manufacturer relays (i am collecting relays), same model but different years, and the yield diferred every time. Old precision relays before 1990 (medical equipment, military etc. ) i have found solid gold contacts, but those are smaller in size then regular relay contact points. I just collect the contacts without any parts of bus bars by using a knipex. (see attached photo)

I also have had the misfortune to find relays with gold coated brass! (yes brass, have no idea why would someone bother to do that or what purpose had it serve). Misfortune because i thought it was 18-22K gold (silly me), after recovery almost zero amount of gold (ha, ha).

The regular silver contact relays, actuators and high voltage main switches are the best reliable source of silver, regarding consistency.(at least for me)

Sorry if i deviated from yout topic.

Be safe.

Pete


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## orvi (Mar 7, 2022)

Forgeweld said:


> I found a ton of electrical relays with gold coated contacts in abandoned equipment in a mill. Sadly someone had gone in already and plucked a ton of them and smashed a bunch up, but I was still able to collect about 4.5 oz of contacts including the little copper bits.
> 
> So question for someone who has dealt with these, what is the yield like compared to board scrap and fingers and stuff?
> 
> ...


These could be tricky to process. There is one catch.
If the gold plating is uniform all over the contact, nitric acid cannot reach the silver underneath, leaving the contact dot as is.
If you have time, you could try to smack the contacts with hammer, trying to damage the uniformity of the coating and ease the access of the nitric to the silver base.
We also often smelted these contacts (assuring no cadmium is present with XRF) and electrorefined the silver, leaving gold anode mud. Or eventually we dissolved the formed alloy in nitric, and then used flocculant to scavenge the gold microdust formed.

If you are lucky, these could have quite thick layer of gold. Most of the time the smallest ones do. My friend once had like two 10 L buckets of the small mixed relays with gold plated contacts, and he managed to trimm like 300 g of contacts. Getting over 7g of gold 
My case scenario was different. I had mostly bigger ones, with larger contacts. These old USSR/NDR types had very thin plating, opposed to the small USSR/NDR relays which were insane in gold recovery. You can see it on the places of contact dot, where it touch the other one. If relay was used and there is no sign of colour change to dark violet/black, it will be thick gold. If there is "burnt" place on the contact of the relay, gold plating would probably be thin.
Mine cut contact points were more like 0,2% gold for weight. Such a sobering weighing 

In the beaker it looked like ton of foils (assuming they are heavy and thick), and it was really only 0,09g


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## kurtak (Mar 7, 2022)

orvi said:


> These could be tricky to process. There is one catch.
> If the gold plating is uniform all over the contact, nitric acid cannot reach the silver underneath, leaving the contact dot as is.


That should not be a problem as the gold plating (even if very heavy) will only be plated over the exposed part of the point

However the bottom side of the point will be ether riveted or brazed to the bus bar thereby giving it an exposed area for the nitric to do its job 

Kurt


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## orvi (Mar 7, 2022)

kurtak said:


> That should not be a problem as the gold plating (even if very heavy) will only be plated over the exposed part of the point
> 
> However the bottom side of the point will be ether riveted or brazed to the bus bar thereby giving it an exposed area for the nitric to do its job
> 
> Kurt


I was also thinking this won´t be an issue. Some of the points were spot welded and some were riveted as well. I dont know exactly how this could happen, but quite a bit of the rivetted points refused to react with nitric, even in hot acid for one day. I must have removed them, wash them and smack with hammer in order to get some tiny area exposed. 
Most of the times the place where contacts were touching each other was somewhat damaged from sparks, making it easy for nitric to access silver inside. 

As we were doing mixed batches only, we realised that it would be much quicker and straightforward to just melt the bulk into shot, and dissolve it in nitric. Took like 20 minutes for making the shot in induction furnance and like 1,5 hour to dissolve the shot in hot nitric. For these small plated contacts, we did not experienced cadmium in our batches, even if the material was very old.
After experimenting with some flocculants, we chose some resin-type flocculant, which performed quite well. Overnight, agglomerated particles settled to the bottom, enabling us to decant more than 90% of clear solution. Rest was filtered through quality filter paper, burned to ash and smelted using oxidizing flame and bit of borax/nitrate. With this operation, we get rid of the tin compounds, which were very stubborn to remove by other ways (mainly when processing anode slimes from electrorefining). Resulting gold was around 95% pure. 

As we were oriented more to the recovery, we did not bothered to refine the gold when I was doing this.

After these experiences, I also done multiple batches on my own, mainly with mix of every kind of contact, even Pd ones. Because bulk wasn´t Au plated, I did it classical way with nitric first, then scavenging the insoluble remains. It was easy to separate gold foils from untouched, unetched still intact points ("panning" like technique in large beaker).


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## Ohiogoldfever (Mar 7, 2022)

Reading this thread last night drove me to sort my bowl full of contacts. Wish there were more of these buggers. Man they are dense. Much heavier than silver contacts of the same general size. Fingers crossed!


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## orvi (Mar 7, 2022)

Ohiogoldfever said:


> Reading this thread last night drove me to sort my bowl full of contacts. Wish there were more of these buggers. Man they are dense. Much heavier than silver contacts of the same general size. Fingers crossed!


I cannot see any major "dents" in the places where contacts touch one another, so I will expect it to be more on the better side  Also they look more dull than shiny. That is usually also a good sign. From my observations.

Waiting for the result


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## Alondro (Mar 7, 2022)

GoIdman said:


> Like @kurtak and @Alondro said, every relay is slightly different so there is no correct answer for you yield question.
> 
> I have processed same manufacturer relays (i am collecting relays), same model but different years, and the yield diferred every time. Old precision relays before 1990 (medical equipment, military etc. ) i have found solid gold contacts, but those are smaller in size then regular relay contact points. I just collect the contacts without any parts of bus bars by using a knipex. (see attached photo)
> 
> ...


Yeah, I had some gold-plated brass ones. Fortunately, it was aluminum brass which dissolved away swiftly in HCl alone and left perfectly clean gold foils in my little test batch.

Doing a test batch of military-grade pins from 1976, which has some kind of tough corrosion-resistant brass. Very high copper content (based on the amount of copper I'm dropping from the HCl waste), but also some other metal that really interferes with dissolving it in HCl.

Produces a lot of CuCl as well (white crystals that would dissolve only in conc HCl, and which I could reduce to blue solution when they were put in 3% H2O2, then cement out pure copper crystals on some steel wire), so the other metal eats up the chloride quickly and shifts the equilibrium of the reaction, maybe prevents full oxidation of the copper in the brass.


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