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Why Dark Rhodium


#1

I’ve noticed several manufacturers are supplying white gold pieces,
rhodium plated, that have the whitish look of (unplated) sterling. My
own work that is rhodium plated is darker and steel-colored, like
platinum. It always has been this way and it’s no surprise to me�
except many customers are now asking for that whitish look. Why is
there a difference in color? Are they using an additive to the
solution? Are they underplating with something?

Brian Charles


#2

What kind of anode are you using. I know a lot of people use
stainless. I have even seen text that supports this. The carrier
solution, forgive the non chemist is sulfuric acid, and this slowly
contaminates the solution. I will get darker and darker until the
solution is no longer good. This method also depleates the solution,
while using a platinum or platinumised titanium anode actually helps
replenish the solution.

Gesswein, if I remember correctly sell a rhodium solution plus a
replinisher. When I was working in the trade, that was my rhodium of
choice.

don


#3

Brian, I do a lot of plating of pieces in Rhodium.What type of anode
do you use?I use a platinized titanium anode and make sure the piece
is buff to a high luster and steamed clean once the piece has been
cleaned I do not touch it again to keep from contaminating it.I plate
the piece and rinse it in cold water.If your plating solution is old
or contaminated your pieces could have a gray appearance also if you
are not leaving it in the solution long enough or with not enough
current or too much current for too long.Many variables.Once you get
the recipe down you should come out with bright
pieces. Best J Morley Coyote Ridge Studio


#4

Hello

Nice steel depletion, but it should be very white like pure silver,
Your problem is the contaminations of the rhodium solution by the
iron in the stainless steel. This will give your rhodium depletion a
steel like colour. Normally the rhodium is attaching like flat
microscopic mirrors. But the iron will make it a bit rough, and the
light will deflect in an darker colour. The only way is to use a
platinum coated titanium anode. This will not contaminate the
solution, and you will get a very white coating Also the solution from
the degreasing bath should be completely washed of in water. And never
get in contact with the rhodium bath.

Martin Niemeijer


#5

Thanks for your reply. The pieces are cleaned well, though the
spolution may be too old. But how to get a white, not paltinum tone out of it?


#6

Thanks. I am using a platinized titanium alloy and Gesswein solution,
actually. The result is not so much dark, but platinum-colored, which
is what I expect. The 18kt pieces I have from the manufacturer are
the color of sterling. The next step is to check with them.