Black marks on palladium

Hello

I made a palladium ring with a 9ct white gold band soldered around
the middle, the customer has had it about two weeks and it now has
black marks showing!! Picture below! Any idea how it happened or
what it is and best way to get rid of, I assume filing it off but is
it just a surfacereactione Thank you in advance!!

Hello

I made a palladium ring with a 9ct white gold band soldered around
the middle, the customer has had it about two weeks and it now has
black marks showing!! Picture below! Any idea how it happened or what
it is and best way to get rid of, I assume filing it off but is it
just a surfacereactione Thank you in advance!!

http://www.ganokin.com/ftp/photo1.jpg
http://www.ganokin.com/ftp/photo2.jpg

As mentioned in my previous post, the photos are too small to see
the actual problem, but it occurred to me later that you might have
fallen into the Pd solder trap. The composition of the only two Pd
solders available from Cookson’s here in UK are:

Easy - 800-850C, 12% Au, 47% Ag and 17% Pd
Med - 870-940C, 89.8% Ag, 4.6% Pd.

If you use Medium, then its nearly all silver, and silver is turned
black by some people.

Could it be that?

The photos, apart from having the wrong link (ganokin instead of
ganoksin), were too small to see the problem. Have you got better
photos?

Here is a better picture, the solder may be the problem as it is
where the two metals meet, this is the worst mark of the three, so
filing would remove the excess then?

If you used Pd solder then yes, filing away the surplus and
re-polishing would probably do it.

Because of this problem I’ve given up using Pd solder - I use white
gold or Pt instead.