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Problem with rhodium on white gold


#1

Help Ganoksin geniuses!!!

Here is my problem. I frequently have white gold wedding rings plated
with Rhodium when I have a customer that is looking for that
conventional store bought look. I made a wedding set for friends of
mine in September.

Both rings are 10K white gold from an ingot I made myself. His ring
is a simple chunky band and hers is a delicate floral motif. The
rings were hand finished with 600 grit sandpaper. I took meticulous
care to finish them thoroughly and carefully, and cleaned the
tarnation out of them before sending them to the plater.

I had them plated by my usual plating company. While in Italy on
their honeymoon, the couple noticed the plating starting to flake
and delaminate.

By the time they returned both rings were completely bare, all
plating had flaked off. They had worn the rings for a grand total of
9 days. I returned the rings to my plater who is refusing to replate
them - says there is a “problem” with the surface.

What could be causing this problem with adhesion? Can anyone help me
to understand the factors at play here. (other than a surly and
unhelpful plating company)

Troy


#2

Adhesion of the rhodium is dependent on a good electro-cleaning
process along with proper rinse, good rhody solution and proper
amount of time in solution.


#3
What could be causing this problem with adhesion? 

Be certain that your plating company actually knows how to put
rhodium onto sterling silver. While rhodium can go directly over gold
and some other metals, on silver, it requires an under plate to
adhere properly, as well as to avoid issues with the silver
contaminating the rhodium bath. Usually, a copper flash and then a
nickel under plate are used, though there are other combinations
that also work.

For any good adhesion with plating, proper cleaning is essential.
The metal must be oxide free, as well as free of any dirt or oils.
I’d assume most electroplating firms use a proper electro cleaning
stage for this, but some jewelers do not, using simply an ultrasonic
and steam clean. These are not always adequate. In the case of
silver, the need for it to be oxide free is also significant. If your
work has fire stain on it (not black fire scale, but rather the
somewhat subtle creamy colored or reddish tinted cast on otherwise
silver looking metal, caused by penetrating copper oxide), then this
can interfere with the adhesion of the plated layer.

Also, if a nickel under plate was used, there is the possibility of
the nickel layer being exposed to air for too long before the rhodium
is applied. Nickel also oxidizes, and if the nickel under plate is
allowed to dry and sit before the rhodium goes on, then it can form a
transparent thin oxide film. The fix to this is a mild acid bath dip
to remove this oxide layer. Called an activating acid dip, phosphoric
acid is a common agent used, but even ordinary pickle will do it in a
pinch. If the nickel doesn’t get this activating dip, and has been
allowed to sit too long between plating steps, then the rhodium will
not adhere well, and can do just what you’ve described.

Finally, it’s also possible to mess up a rhodium electroplate, or
the under plate layers, by simply trying to put too much metal on too
fast. Too high a current density can give a thick but poor deposit
that won’t adhere well.

Peter Rowe


#4

buy the stuff and do it on your own it is not all that difficult the
people who make the soloution are always happy to help answer
questions. better in my opinion to work through a problem than deal
with snarky service providers

goo


#5

If its flaking, its not prepped properly.

The 10K itself could have something in it. The electrocleaner could
have been overheated or not processed long enough or at the wrong
voltage or even polarity. Maybe the guy used steam instead of
electrocleaner. I’ve seen people use steam, myself included, and
’most’ of the time its OK. But unless the steamostats are brand new
they’ve accumulated some gunk on the tips, kinda defeats the purpose
of cleaning, no? Could be the rinse water or acid dip need changing.

Since it didn’t flake right away contaminated metal becomes a more su
spicious source of the problem. Maybe porosity that slowly leached
electrocleaner, loosening the plate. Zinc die cast is notorious for
this and acts in the same way, looks good new, like trash later.