# Silver contact with mystery core



## etack (Jul 26, 2014)

I have some contacts that have a core with a different metal in them. I put them in nitric and the silver dissolved off however a core was left. This metal core will not dissolve in nitric, HCL, or AR. it is complacently malleable and melts with my propane torch. Afrter they come out of nitric the core is white like silver but no longer reacts with the nitric. There is no color change when placed in HCl and only a slight discoloration with AR.

The Ag nitric solution is a jade or jungle green after the Ag is removed.

color reference chart.
http://dmozleem.files.wordpress.com/2011/05/green.jpg


The contacts came from cell tower equipment

Eric


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## Claudie (Jul 27, 2014)

Is it magnetic?


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## etack (Jul 27, 2014)

No.

I think it was a patience problem it has now dissolved into nitric. 

Eric


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## patnor1011 (Jul 27, 2014)

Tungsten?


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## butcher (Jul 27, 2014)

Electrical Contacts and points

If the concentration of the nitric is high, it can take longer to dissolve silver, when 68% nitric is diluted 50/50 with water it will react faster.

Some metals can be difficult or passivate in nitric acid.

Note contacts and points can have some dangerous metals to work with; melting can make for some very dangerous gases.

Electrical contacts and points, can be made from many different silver/metal compositions, there are many metals that can be used.
Base metals as well as valuable metals, even Gold and the platinum group metals can be plated or in the alloys.

Dangerous metals can also be involved in the compositions of these alloys....

Relay contact point's, switch's, circuit breakers and the like, will usually contain other metals, some of higher value than just the silver.


Group1: Ag-Mo, Ag-Cu, Ag-Cd, Ag-Fe, Ag-Ni, Ag-Wc, Ag-C
Group2: Ag-Cu-Ni, Ag-Cd-Ni, Ag-Ni-Mg, Ag-Fe-Cu, Ag-CdO
Group3: Ag-Au, Ag-Pt, Ag-Pd
Group4: Cu-W, Cu-WC

Normally silver is the majority Contacts and points
of alloy compositions, some examples percents by weight:
Ag 72 - Cu 7.5
Ag 75 - Cu 24.5-Ni 0.5
Ag 97.5 - CdO 2.5
Ag 95 - CdO 5
Ag 90 - CdO 10
Ag 86.7 - CdO 13
Ag 85 - CdO 15
Ag 77 - Cd-O 22.6 - Ni 0.4
Ag 86.8 - Cd-O 5.5 - Ni 0.2 - Cu 7.5
Ag 95 - Ni 0.5
Ag 90 - Ni 10
Ag 85 - Ni 15
Ag 70 - Ni 30
Ag 60 - Ni 40
Ag 40 - Ni 60
Ag 99.75 - C 0.25
Ag 99.5 - C 0.5
Ag 99 - C 1.0
Ag 90 - C 10
Ag 88 - C 2.0 - Ni 10
Ag 90 - Fe 10
Fe 50 - Cu 25 - Ag 25
Ag 99.34 -MgO 0.41 - Ni 0.25 
Ag 99.55 - Mg-O 0.25 - Ni 0.20
Ag 97 - Pt 3.0
Ag 90 - Pd 10
Ag 97 - Pd 3
Ag 99 - Pd 1
Ag90 - Au 10
Ag-Cu-Cd-Au
Some of the tungsten compositions:
Ag 27.5 - W 72.5
Ag 35 - W 65
Ag 49 - W 51
Ag 50 - W 50
Ag 46 W 53 - C 1.0
Ag 48 - W 51.75 - C 0.25
Ag 90 - W 10
Ag 65 - WC 35
Ag 50 - WC 50
Ag 40 - WC 60
Ag 40 - Mo 60
Ag 50 - Mo 50

Just a few of the gold or PGM types:
Pt-Rh 10
Pt-Ir 10
Pd-Ag 40
Au 99.99
Au-Ni 8
Au-Ag 15 Ni 10

Springs can contain beryllium, bronze, Kovar...
Bus bars can be made from other metals like copper or brass, stainless steels or other iron compounds...
Brazing alloys can have barium, cadmium, phosphates, chromium, lithium, and well as others...

Gold flashed silver, gold overlay base metals, silver nickel, silver cadmium oxide, silver tin indium, silver copper nickel, gold silver nickel, gold silver nickel palladium tungsten.

Some of the metals to watch for, Au, Pt, Pd, Rh, Ir, In, Os, Ag, Ni, Cu, Fe, Co, Cd, Mo, Sn, Pb, Hg, Mg, W, C, Zn, and oxides of several of these metals.

Tungsten (W) usually used in high current type, high melting point 3380 deg C, this can make melting difficult, not easily dissolved, hot HCl with concentrated H2O2 will attack.

The metals or combinations of metals, used are usually dependent on the purpose and use of the contact points (relay, breaker, switch, etcetera), the voltage, current, environments, inductance or capacitance in circuit, Arcing, welding, oxidation, pitting, inrush current, contact bouncing, whether AC or DC application...

Well lets just say there are many factors that come into play when a contact point is used in electronics or electrical applications, and these little buttons of metals are in most all electronic and electrical devices.

Edited: correction, looks like a made a mistake in listing of Group 3, Ag-A, (Ag-A must have been Ag-Au) I will do more research of where I got this information, and the list of the groups (which I made the mistake in my notes) and update with corrections as needed.


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## Claudie (Jul 27, 2014)

Butcher, sometimes after reading one of your posts, I feel like I have just taken a class on the subject. Very informative.


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## kmann1969 (Sep 15, 2014)

the other metal inside the contacts is molybdenum (mo) it has a menting point of 4753 f . It will dissolve in nitric but takes awhile. I have been doing a lot of contact points. I have a xrf so I can assure it is molybdenum


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## Richard NL (Dec 7, 2014)

I just like to add this, if you don't mind.
https://www.scribd.com/doc/249434210/Kontaktteile-Silber-Basis

Best regards,
Richard.


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## Platdigger (Dec 7, 2014)

Thank you for that Richard. Good info.


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