A coworker put together a beautiful palladium ring recently. The
metal is white but not truly as white as seen in rhodium plated white
gold or in the newer white golds, X1 from Stuller or Precise White
from Cobb.
The thought was had toapply a simple rhodium plate to the palladium.
The customer desired a less grey metal but liked the palladium ok if
it could not be plated. Seemed simple enough. Don’t do it unless you
are prepared to go back and refinish the item! The simple
electrocleanng and rhodium dip left an orange peel surface on the
palladium. This had to be sanded off to regain a smooth and fine
surface.
Why did this happen? We experimented with electrocleaner alone,
rhodium alone, distilled water with just enough salt to conduct a
current and even mild ultrasonic solution as the “plating bath”. In
each case, there was some orange peel on the palladium. A piece of
scrap was used for the experimenting.
Palladium alone immersed in the electrocleaner or rhodium solution
with no current is totally unaffected, as it should be. Palladium
immersed in any of the “experimental” baths is unaffected. Only when
there is a current flowing does the orange peel show. Is it the
electricity? Is palladium adverse to electroplating processes?
Can anyone tell me what is going on here? With all the hype on the
wonders of palladium as a “white metal of the future”, needing no
rhodium plate, why is there no mention that “if” plating is
attempted there may very well be frustrating and time consuming
refinishing needed. We were quite surprised at the orange peel
effect.
The item in question was a forged shank and cast top. The palladium
was 950 with either iridium or ruthenium as the alloy additive.
Thanks for any insight. Also, I hope this post saves you the same
problem if for some reason you want to rhodium plate a palladium
item.
Only when there is a current flowing does the orange peel show. Is
it the electricity?
I’d double check the polarity. If the current is flowing from the
piece it will tend to strip it as it is acting like an anode. My
oldest gold anodes look like this. Positive for the anode, negative
for the work. Don’t rely just on lead wire color. Check your physical
connections. You didn’t mention acid dip and distilled water rinse.
This step is critical. Also, if the electrocleaner was ever
overheated its useless.
as a test…keeping your setup just as it was use a copper wire on
your palladium and see what happens. if its correct the copper should
plate white.
Also beware of voltage. Too high a voltage will often frost the
surface being plated, or too long immersion. Also check that you are
using the correct anode.
Orange peel is generally the result of large grain size. If the Pd
parts were over annealed or not sufficiently worked to reduce the
grain size, the ‘plating’ might just be ‘bringing out’ the coarse
underlying structure. Sanding and repolishing won’t eliminate the
structure at this point. If you put a very heavy/expensive rhodium
plating you might cover the large grain structure.
Palladium will require some adjustments to your shop practice. Does
that make sense? All (precious) metals are not created equal.
Thankyou very much for the reply to my post on this subject. I thank
Neilthejeweler and Paul Finelt.
I have written Hoover and Strong to see if they can shed any light
on the problem. If and when I receive a reply I will certainly post
it here.
As for polarity, all is fine and correct. This is a good suggestion
and would seem an obvious problem but we have been in the business a
while now and the polarity is correct. Certainly, reverse polarity
could and would cause a problem but this time that is not the reason.
As for grain size, etc., affecting the plating and electroclening
process, there might be something to that. The shank was forged,
annealed, formed and soldered to the ring top with palladium
solders. The shank was quite flat on the sides and did show more of
the effect than the cast top. The cast top did show the orange peel
but perhaps to a lesser amount:; considering the detail in the top
section of the ring it was really difficult to determine if it was
less affected or the same as the shank.
Yes, different metals are different! No doubt about that regardless
if from the same “family” of metals. Also, who knows for certain what
other elements are in the PD alloy besides ruthenium. The makers
state trace amounts of other elements are added to improve ductility,
etc. Palladium seemed to fail some many years ago, in the market
place overall and in workability. Perhaps the new alloys will solve
such problems.
Regardless, if there are problems with rhodium plating the basic
alloy, the manufacturers it would seem should alert the jewelers to
this issue. Why plate in the first place? The customer wants the
color of the ring to match with their white gold rhodium plated items
and it would seem simple enough. Simple? No way.
I truly appreciate the replies and will let you know if I hear from
Hoover and Strong. Thanks again. Thomas.