Sulfuric acid pickle problem

[TheCynic6]

I had 3 rings and a chain soaking in sulfuric acid pickle. One of the rings "had" a white gold solitaire mounting, which looks like its been soaked in bleach now. The other two rings both 10k were covered with a dark brown coating. The chain, which was 14k, appeared fine. I threw all four pieces into the tumbler with steel shot. I was quite confused to find that when I removed the two rings which were brown they now appear to be plated white. The solder joint on the catch of the chain also appears plated white. The solitaire has a redish powdery substance where parts of the mounting were dissolved. The "white gold plating" that appeared buffs off and will also dissolve rapidly in nitric acid.

Has anyone had this problem? Any Ideas on what the cause might be? Could the mounting have been something other than white gold???

Thanks,
Matt

[Lee_Lyssimachou]

Hey Matt,

Don't know what the problem is but I have had some pieces whiten or
go red in the pickle especially if they were under high heat and
left over-night. Anyway, have you tried sanding the problem areas
with a fine grain sandpaper(800 would do fine)? That'll probably
help. It's only a surface reaction anyway.

Lee Lyssimachou
Lee Feenix Art Waorkshop
Greece

[Red_Rodder]

Can't imagine what the problem was. I used sulfuric acid for pickle
for six years when I first worked on the bench. My first reaction to
such situations is to clean the items thoroughly and then polish.
Usually works okay.

Why did you tumble the work?

bruce

[TheCynic6]

These were left for maybe thirty minutes at most. The coating isn't
a problem I removed it from the other rings. I just don't understand
why the mounting on the one ring deteriorated. If it was truly gold
the pickle shouldn't have done that. I was curious If anyone else
might have had a similar experience so that the cause might be
found.

Regards,
Matt

[TheCynic6]

Why did you tumble the work?

When I took the two 10k rings out of the pickle they were covered
with an almost rust like coating. That is why I tumbled them.

This is the first time I've ever seen anything like it. I would
assume it was something in the mounting on the 14k solitaire that
reacted in the acid, but i don't know why it would deposite on the
10k rings and the solder joint on the 14k chains catch. Appearantly
it was the higher copper, silver, or other alloy content that it was
reacting with.

The coating is not the problem. It is easily removed by buffing,
nitric acid wash, or heating. Im left wondering what the mounting
contained that would cause this problem and how to spot this
potential problem in the future.

I belive it could be either silver or nickle alloy in the mounting.
I have had both silver and gold jewelry pickleing in the same
solution at the same time and did not have such a reaction take
place. Thus I would eliminate silver content as the problem. That
leaves nickle as the culpret. Once again I am left with more
questions than answers. Does nickle form a brown sulfate salt? What
could the 10k rings and solder be alloyed with to precipitate the
nickel? Iron, magnesium, chromium, titanium, scandium,aluminum, and
manganese are the only metals more reactive then nickle. It seems
highly unlikely that any of these would be present as a gold alloy.
Does anyone see something I have overlooked?

Matt