# Small silver relay points



## ovidiuanghel (Apr 6, 2013)

Hello everyone,

I saw on the forum many topics about the silver contact points, but my problem is that i have about 500g of small silver points about 1-2 mm whit cooper or brass.
What is the best process for this? Can i use HNO3 directly ?

I work whit silver mylars and larger contact points but here i have also cooper and brass, i don't want to create a mess and lose my silver


Thank you,
Ovidiu


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## butcher (Apr 6, 2013)

If it is copper and brass (copper and zinc), you should not have trouble using nitric acid.

bronze (copper and tin) would become a problem.

You can try a small test tube experiment...


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## ovidiuanghel (Apr 6, 2013)

Thank you, i'll make a test and post the result


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## butcher (Apr 6, 2013)

Good job pictures would be nice, as you learn more we can learn more.


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## ovidiuanghel (Jun 27, 2013)

Ok my experiment fail, i put some small silver relay points whit cooper and bras in nitric. After all metals was dissolve i notice that something is going to the bottom of the jar, i assume that is silver, next i filter the solution and add some hno3 and distilled water on the grey precipitate and all was dissolve, again i filter the solution and the i cement whit cooper the two jars.

Here are the photos of cemented silver and the most ugly silver button in the world. I know is not only silver because of the color but i try another refining on the button and for the next test i want to put the silver points in AP to dissolve as much base metal that i can, then incinerate and then the silver points in nitric.

I am disappointed that i waste about 300 ml of nitric for this ugly 22g of silver...but i am happy that i have learn and still learning from this great forum.

Ovidiu

http://imageshack.us/photo/my-images/827/pc5g.jpg/

http://imageshack.us/photo/my-images/515/8ihi.jpg/


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## MysticColby (Jun 27, 2013)

With silver contacts, I like to decant the silver nitrate solution into a jar, then let that jar sit there for a day, then filter that into a beaker where the cementing happens. There seems to be a grey powder that precipitates out, possibly tungsten (from tungsten-alloyed silver contacts). I guessed that under heat it will go into solution in nitric, then when it cools it will slowly fall out of solution. I have no idea if this is right, only that this powder should be given the chance to get out of my silver before I try to collect the silver.
300 ml was probably excessive. unless there was a lot of copper. are these silver contacts ever attached to anything besides pure copper? It seems to me these contacts are used in electricity, and any copper material besides pure copper would be inferior to pure copper, especially when a silver contact is required. So I wouldn't expect brass or bronze. Either way, copper takes a lot of nitric to dissolve and as much as possible should be removed before dissolving.
dissolving the copper away first sounds like a good idea, as nitric is likely more expensive than HCl.


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## pimpneightez (Jun 28, 2013)

Are you sure the brass that you see is brass and not gold plating. I have seen a small percentage of contact points with gold plating.


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## butcher (Jun 28, 2013)

Silver contact can be made from a wide variety of metals silver is normally predominant but not the only metal, gold and other PGM's are also used.

Here is a list of the metals I know of so far.
http://goldrefiningforum.com/phpBB3/search.php?keywords=group1%3A+Ag-Mo%2C+Ag-Cu%2CAg-Cd&terms=all&author=Butcher&sv=0&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search


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## ovidiuanghel (Jun 28, 2013)

pimpneightez said:


> Are you sure the brass that you see is brass and not gold plating. I have seen a small percentage of contact points with gold plating.



i don't think that the point is soldered on little golden bar, i have separate the gold-silver points

I need to brake a small relay and i post some pictures


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## ovidiuanghel (Jun 28, 2013)

butcher said:


> Silver contact can be made from a wide variety of metals silver is normally predominant but not the only metal, gold and other PGM's are also used.
> 
> Here is a list of the metals I know of so far.
> http://goldrefiningforum.com/phpBB3/search.php?keywords=group1%3A+Ag-Mo%2C+Ag-Cu%2CAg-Cd&terms=all&author=Butcher&sv=0&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search




Thank you Sir, 

The points can be gold plated silver or a gold silver alloy? I know about silver alloy but i never heard about gold silver alloy in relay points.

I have separate the gold plated points,that i have to ask if is also gold silver alloys


Ovidiu


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## butcher (Jun 29, 2013)

I started a reply but it was getting about three pages long. :lol: 

To make the post a bit shorter and to the point, or points in this case,

Low current contacts like those used in electronics gold gives a good clean contact across points so the gold plated contacts will normally be found on the small points like those used in electronics where low current can pass across the point, silver oxidizes but gold does not, the high current contacts will normally be silver which can also be alloyed with other metals to make them harder or improve properties so they do not burn as bad from the high current arcing, or contact wear of friction as contact wipe each other to remove silver oxides, the high current can burn through an oxidized layer of silver.


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## bswartzwelder (Jun 29, 2013)

As stated in an earlier post, high current contacts need to be of a harder material. One problem high current contacts must overcome is the propensity to weld themselves together at higher current densities when they are opening. This is done in several ways. One, the chemical makeup is one that doesn't weld to itself when arcs occur. Tungsten is good for this. Two, the contacts are made large enough so that the current (upon breaking) is spread out over a larger surface area. And three, the relay design causes the contacts to have a wiping action which helps them break and also aids in wiping them clean (there is usually some carbon deposits). If you take a relay and slowly close the contacts until they just barely touch, then pull the armature down into the fully seated position, you might be able to observe this wiping motion. When I worked for Westinghouse building circuit breakers for power plants, we used an MG-6 model relay for the breaker control circuits. Not only could all 6 sets of contacts be configured individuall as Normally Open (N.O.), but, any or all of them could be configured as Normally Closed (N.C.). They even had one other interesting feature. By changing the geometry of the stationary contacts (bending them) and the springs on the moving contact arm, as the relay would energize and pull in, you could make any set of open contacts complete their respective circuit BEFORE the closed contacts would open (Make Before Break or M.B.B.). You could do this for when the relay de-energizes as well. The moving arms were set up so they had a fair amount of free play in both the opening and closing position which gave lots of wipe. Additionally there were two springs on each moving arm assembly. One was slightly stronger than the other so if you reversed them it wold place more tension on the contacts when closed, or help give the contact a little boost when opening. And THAT, my dear friends, is about all I know about relays.

The circuit breakers we made were all three phase with the largest current interrupting capacity up to 6,000 amps. The largest current breakers usually had a several sets of main contacts and one set of arcing contacts for each phase. When the breaker closed, the arcing contacts would make up first, followed by the main contacts. This would help limit inrush current. Main contacts had a very heavy silver plating and the individual fingers had to be adjusted to make solid contact. Arcing contacts were much smaller and had a tungsten based tip which would take the brunt of the arc as they were opening. The breakers were typically filled with oil which would make a small explosion when opening to help extinguish the arc. The extinguishing medium would then rush back in to insulate everything electrically. In later years, many of the higher voltage breakers (up to 765,000 volts) used Sulfur Hexafluoride gas as the extinguishing medium. Upon opening, the arc would alter the molecular structure of the gas and then it would return back to its original state after a short time. It was also an excellent insulator. Some of the circuit breakers were so large, they required 3 or 4 railroad flat cars to ship out to the customer where they had to be reassembled on site. Sorry for the rant, I hope it is not too boring.


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## g_axelsson (Jun 29, 2013)

bswartzwelder said:


> ... Sorry for the rant, I hope it is not too boring.


Not at all, just one of these small golden nuggets you find on GRF. :mrgreen: 

But then I just love all technological stuff, from learning about casting grey iron to electron beam melting, and now some interesting facts about relays. I'm going to look for those finer details when I run into any larger relays to scrap.

Göran


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## Geo (Jun 29, 2013)

a large percent of the very small relays on circuit boards DO have gold plated silver contact points. i have processed these types in AP solution that was almost un-usable. i made a post with pictures about them but its been awhile back. one thing i learned in dealing with them is that they need to be incinerated and rinsed before the nitric bath.


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## etack (Jun 29, 2013)

Geo said:


> a large percent of the very small relays on circuit boards DO have gold plated silver contact points. i have processed these types in AP solution that was almost un-usable. i made a post with pictures about them but its been awhile back. one thing i learned in dealing with them is that they need to be incinerated and rinsed before the nitric bath.



I had some product catalogs that listed the telecom and networking relays as gold overlay not plated. if you had a lot of them the $Au:$Ag price ratio would probably be close if not better for the gold.

Gold / Silver Ratio 62.83 today

Eric


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## Geo (Jun 29, 2013)

thanks Eric. i guess theres a big difference between plated and overlay.


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## ovidiuanghel (Jun 30, 2013)

Thank you for your help, here are some photos whit the relays and the silver points, the bigger ones have 2 mm.

http://imageshack.us/photo/my-images/507/79xo.jpg/

http://imageshack.us/photo/my-images/23/y67g.jpg/

http://imageshack.us/photo/my-images/849/9jgq.jpg/

Ovidiu


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## pimpneightez (Jul 1, 2013)

You have a lot of extra base metal there. I usually like to cut the contacts out of the copper with a pair of nippers. Just makes it a lot cleaner and less acid needs to be used.


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