gold plated palladium

[anarxi]

These are contact groups from a Soviet relay.
contact base alloy palladium silver 20/80.
gold is applied on top.
I correctly assume that if I throw the contacts into aqua regia, the gold will dissolve, but the contact itself, thanks to the silver in the alloy, will remain intact?

 

[4metals]

I correctly assume that if I throw the contacts into aqua regia, the gold will dissolve, but the contact itself, thanks to the silver in the alloy, will remain intact?

In theory that is correct, the 80% Silver may coat the Palladium sufficiently to keep it in the alloy. And the AR will dissolve the gold.

But you may also make a Silver Chloride mess. I would try a nitric etch to generate gold foils and a silver nitrate palladium nitrate solution. That could avoid the dreaded Silver Chloride crust.

I would be putting a few of these in a solution of half distilled water and half 68% nitric acid as a test.

 

[anarxi]

In theory that is correct, the 80% Silver may coat the Palladium sufficiently to keep it in the alloy. And the AR will dissolve the gold.

But you may also make a Silver Chloride mess. I would try a nitric etch to generate gold foils and a silver nitrate palladium nitrate solution. That could avoid the dreaded Silver Chloride crust.

I would be putting a few of these in a solution of half distilled water and half 68% nitric acid as a test.

Thanks for the answer.

The contacts are too small (1.3mm diameter) to be cut in half.

and too well gold plated (gold plated before being pressed into the holder).
they can be stored and boiled in nitric acid for several days and they will remain intact.

besides, I don’t have a burner or stove (yet) to melt palladium...

and another question for the future:
Will there be a normal inquartization (we call quartovanie) of a gold-silver alloy if there is only 3-4 percent gold?

 

[anarxi]

...

 

[nickvc]

If you melt them and cornflake that melt I would suggest a nitric acid dissolve which will remove the silver and palladium leaving the gold untouched for an AR treatment, to separate the silver simply add some HCl which will leave the palladium which can be recovered via cementation.

 

[anachronism]

Take a blade over the top of them and expose the base alloy before putting in dilute Nitric.

 

[anarxi]

everything turned out great.
having removed AR gold, washed it and even managed to fuse them together, it is still 20% palladium.
This is half of the contacts, those that were on brass holders weigh 0.4 grams.
motionless while I dissolve the holders.
nitrogen + sulfur does not take them.
but lemon + hydrogen peroxide works slowly but surely.

I was counting on a different weight, twice as much...
and then I realized that the reference book indicated the weight of solid gold contacts..
and the density of palladium with silver is almost two times less...

 

[orvi]

These are contact groups from a Soviet relay.
contact base alloy palladium silver 20/80.
gold is applied on top.
I correctly assume that if I throw the contacts into aqua regia, the gold will dissolve, but the contact itself, thanks to the silver in the alloy, will remain intact?

I processed similar material quite often, however in my case the alloy was AgPd30. AR will dissolve some Pd into the solution, but as rough separation, it can be used.
Nitric treatment is not that straightforward. In my case, gold plating was very thick, and contacts needed to be somewhat mangled or deformed to expose underlying AgPd. And even then it was painfully slow and in the end resulting gold foils were just 90% Au, as quite a bit of AgPd alloy was left inside. But this was manageable.

I will opt for AR or HCl/peroxide, as it is better to left AgPd alloy intact. Due to obviously more difficult refining, and also, it is nicely sold as is (commonly used alloy, refiners just check the purity and content and that´s basically it).

 

[anarxi]

gold from these contacts and a dozen more Siemens relays with gold-plated silver contacts..

In general, my first gold made through complete dissolution...