rayc

Topic: How to keep Pink Gold Plating From Tarnishing ?

Dear all,

I run into a big problem now, the current object is a silver pendant comprising two parts - one big round outside border, and inside which is a small circle. All in 925 silver, but the small circle needs to be pink gold plated.

During soldering, there are cases that the pink gold tarnished and we need to repeat the pink gold plating again. And even the whole piece is finished, the pink gold plated area changed color when undergoing the anti-tarnish test ( 5% potassium sulphide )

We tried immersing the entire piece into anti-tarnishing solution for few minutes, the anti-tarnish test results are mixed, some ok, some not.

* May i know if top coat with " Tarniban " is a solution ?

* Should i topcoat it first onto the pink plated area before soldering or to the entire piece ?

Any comment is highly appreciated,

Thank you very much!

RAYC





DustinGebhardt

Re: How to keep Pink Gold Plating From Tarnishing ?

Gold, by itself does not tarnish.  So what you are seeing must be from some other source.  Perhaps the other metal in the pink gold-alloy is tarnishing.  When I think of pink metals, I immediately think of copper, which easily tarnishes to a green color.  Silver can also tarnish easily, but it tends to become black.

Try these ideas:

1) Plate more pink gold to prevent any underlying deposit from bleeding through. 

2) reduce the amount of "other" material in the gold to reduce the chance that it will tarnish

3) try soldering your joint in the presence of an inert gas, like carbon dioxide, nitrogen, or argon.  This should help prevent oxygen from tarnishing the heated surface.

-Dustin Gebhardt,
CEF
Plating Engineer
Danaher Tool Group
Gastonia, NC