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Rhodium doesn't plate evenly


#1

Im new to rhodium plating, though i’ve read so much about it,
including articles on ganoksin that relate to rhodium plating. I
decided to build my own rhodium plating set up. So i got a dc power
supply, i bought a rhodium plating solution and electro cleaner. Im
using a platinized titinium anode. I know about polishing the item
really well and cleaning it. I use only distilled water. I even clean
with sandpaper the copper wires that i hang pieces from. But somehow
can’t put rhodium plating professionally to practice. The only weak
sides are that im using a small branson ultrasonic machine(no heater)
with reguilar soap in it. And that my steamer is only up to 90 psi.

Somehow the rhodium doesn’t plate evenly, in some areas on the ring
it would be nice and shiny, in others completely dull and non
reflective. And the in side of the ring - forget about it.

Anyone, please help.
Cheers,
George.


#2

One big mistake is using copper wire. Rhodium solution is acid based
and the copper will dissolve destroying the Rhodium solution. Only
use gold, platinum or nickel for hang the object to be plated, NOT
copper, or silver for that matter. There are so many variables using
Rhodium, it is not very forgiving of mistakes. Be sure you know what
you are doing.

Tom
pbase.com/tomdesgn


#3

Hello George,

I would suggest you look at the following factors.

The operating temperature of the rhodium bath.

The voltage & the current density recommended by the technical
chart.

The rectifier should produce ripple free current.

The Standard operating procedure recommended by the rhodium
technical chart.

The method of preparation of the rhodium bath.

We use umicore rhoduna J1 rhodium.

We heat the solution.
Cheers,
Umesh


#4

George,

  1. This is not my site, but it might help you.
    http://www.ganoksin.com/gnkurl/ep7z33

  2. Another work around is not to just hang your piece while plating,
    make sure there is movement, rotating and agitating it slowly.

  3. Make sure your piece is clean and free from oil. (Don’t use your
    hand to pick it up when you haven’t finished plating it. Use a
    tweezer.)

Marvel


#5

Try using a gold or Plat. hook to hold the piece to plate.

Steve
arista designs llc


#6

Are you heating the rhodium solution in my experience it doesn’t
plate evenly when cold. Can’t remember the temp required but it is
quite critical. Regards Hamish


#7

A couple of things that make a big difference are plating bath
temperature and agitation. Copper wire is not so good for the contact
either, I use silver and even that is not ideal. you can try masking
off all of the wire that would otherwise be in the solution.
temperature-I have found that room temp solutions only work when
warmed up to about 60 deg C. agitation- you must keep the solution
in motion so stirring with a glass rod is simplest. Finally, what
voltage and current are you using? Best results will be had with a
low V and high current so 5v and 1 amp is much better than 10v and
0.5 amps.

Nick Royall


#8
Are you heating the rhodium solution in my experience it doesn't
plate evenly when cold. Can't remember the temp required but it is
quite critical. 

I get great results at room temperature.


#9
Are you heating the rhodium solution in my experience it doesn't
plate evenly when cold. Can't remember the temp required but it is
quite critical. Regards Hamish 

Hmm. I have a couple bottles of rhodium solution, from different
vendors. All state to plate at room temp. The electroclean, however,
works a lot better when hot…

Peter Rowe


#10

Here’s how we handled Rhodium.

Many folks buy it in a bottle, then pour it into a beaker, use it,
then pour it back into a bottle, maybe thru a funnel.

We found this procedure to trap and collect dirt and contaminate the
fluid.

What I’m going to explain, we started with a fresh bottle because of
it not plating well. But your decision. You can buy rhodium
replensisher that will refresh it.

  1. We bought a glass jar that you keep sugar or flour in, wide open
    mouth. The kind with a rubber seal and pull down metal strap. Maybe
    4" tall. Washed it first.

  2. When we bought the rhodium we emptied it into the glass jar. It
    was stored here and we dropped the rings into this jar to plate them.
    So we never poured back and forth.

  3. We had a rhodium anode and the hook on the other end was made
    from a piece of platinum wire.

  4. Although we didn’t do this a lot, other jewelers have told me
    they use an “Electro Cleaner” after the ring is polished and cleaned
    to clean the item before plating it. You reverse the + and - to
    reverse and the ring extracts away from itself any dirty surface
    particles.

  5. We put the bottle of rhodium into the ultrasonic to gently warm
    it up.

  6. After polishing/cleaning/steaming/electro cleaning the ring
    BEFORE you rhodium plate it, imperative to not touch it with your
    finger before immersing it into the rhodium.

  7. Think like a surgeon on handling the jewelry (cleanliness) and
    with new you should do great.

By the way there are strengths of rhodium. a 1 gram bottle has a
gram of rhodium in it and a 2 gram bottle has twice as much and of
course cost twice as much. Many jewelers use a 1 gram bottle on
plating repaired jewelry and a 2 gram bottle on items purchased from
their store.

Sincerely

David Geller
www.JewelerProfit.com


#11

Stainless steel wire is the best for hooking your work onto. Silver
or Copper wire can contaminate the solution which contains sulphuric
acid. So it is possible for them to dissolve into the solution

Regards
Hamish


#12
Copper wire is not so good for the contact either, I use silver and
even that is not ideal. 

I use a piece of gold wire. Works great.


#13
I use a piece of gold wire. Works great. 

Basically, you need a wire that is a good electrical conductor, that
is also not affected by suphuric acid, which is the basis of rhodium
plating solution. Gold (both white or yellow) or platinum or
palladium are the usual choices. Both copper and silver will react
with the solution, contaminating it and interfering with a good
deposit.

Peter


#14
Although we didn't do this a lot, other jewelers have told me they
use an "Electro Cleaner" after the ring is polished and cleaned to
clean the item before plating it. You reverse the + and - to
reverse and the ring extracts away from itself any dirty surface
particles. 

You’ll only have to do this once to learn that it’s not correct.
Don’t reverse your wires. Negative to the piece just like when you’re
plating. (I know it doesn’t seem to make logical sense, but results
don’t lie)


#15

Thanks so much everyone for your generous replies.

Interestingly, the person that taught me rhodium plating uses copper
wire all the time, and it doesn’t seem to contaminate his solution.

My voltage is 5 and current would be around 4.

Also, i used a beaker from the dollar store, it seems to be glass.
But who knows… Does it matter?


#16
You'll only have to do this once to learn that it's not correct.
Don't reverse your wires. Negative to the piece just like when
you're plating. (I know it doesn't seem to make logical sense, but
results don't lie) 

It may help to realize that electrocleaning is NOT electrostripping.
For the latter, you are actually reverse plating, and you do reverse
the wires so the ring, or whatever, becomes the anode to remove
metal. For electrocleaning, you’re not using the same action.
Rather, the current causes the water in the solution to break down
into bubbles of oxygen and hydrogen. That vigorous bubbling at the
rings surface, coupled with the caustic nature of the solution (often
a solution of sodium or potassium hydroxide is used…) is what lifts
the dirt away.

Peter


#17

Much has been said about the type of wire in answer to your
question. I prefer wire with plastic insulation I then expose only
enough metal wire to make contact with piece 1/4 inch or so on the
dipping end as i only wish to plate the jewelry. I didnt see the
original post and am wondering if the uneven plate you are describing
is spots or spottiness such as leopard print ? If it is this type of
unevenness I have found it to be that the solution is becoming
depleted of rhodium. If it is 1/2the ring plating and the other 1/2
not I have corrected this by using heavier gauge wire. I at one time
had trouble getting the rhodium to adhere to platinum,after some time
and trouble I attributed my less than satisfactory results to the
acidity of the plating solution being compromised. goo


#18

I’ve seen many responses that are excellent…and some that were not
so accurate.

To begin, the biggest problem regarding uneven plating is
cleanliness. I’m talking about having a chemically pure surface to
plate on, not just a visually clean surface. You can check this by
dipping a cleaned object into a glass of water, withdraw it and see
if the water beads up on the piece. If it does, you are NOT
chemically clean. A really clean piece will allow the water to wet
the entire surface of the piece with no beading. To achieve this,
you need to electro clean the piece with any of the several
commercial products available or you can make your own for a couple
of cents (US) a quart. (I’ll go into this later)

The second major problem regarding Rhodium plating is the
contamination of the solution. This can happen in several ways. Not
rinsing the piece thoroughly is one by introducing a cleaning agent
into the solution. Another is by introducing a foreign metal into
solution, anything dissolvable by sulfuric acid will contaminate it.
I only use nickel, gold, platinum or palladium when plating rhodium.
Using silver or copper will eventually destroy the solution.

Different rhodium providers have different requirements regarding
the temperature of the solution. Some are set at room temperature,
some are at 100 degree F, I’m sure there are other out there too. I
usually work at room temp. I plate at 4 to 5 volts, the amperage is
relative to the size of the piece and not settable by separate
setting. A couple of flashlight batteries in series can work as a
simple power supply.

Electro cleaning is a whole different matter. I make my own cleaner
with TSP (Tri Sodium Phosphate) available from any hardware store or
auto supply business as a degreasing agent for garage floors and mold
cleaners. I add a couple of table spoons of the powder to a pint
stainless flask, mix with tap water, and bring up to around 150
degrees F or higher. I attach my positive cable to the flask, and
negative to the work. Use heavy wire for this, and a heavy wire to
the piece. I run 10 to 12 volts through this for about 30 seconds.
(You can easily draw 20 to 30 amps through the solution, thus the
heavy wire) Rinse well under running water, do the bead test from
the beginning of the post, and you are ready to plate. Do not handle
the piece until after plating. Good luck.

Tom Tilney
http://www.pbase.com/tomdesgn/jewelry_designs


#19
It may help to realize that electrocleaning is NOT
electrostripping. For the latter, you are actually reverse plating,
and you do reverse the wires so the ring, or whatever, becomes the
anode to remove metal. For electrocleaning, you're not using the
same action. Rather, the current causes the water in the solution
to break down into bubbles of oxygen and hydrogen. That vigorous
bubbling at the rings surface, coupled with the caustic nature of
the solution (often a solution of sodium or potassium hydroxide is
used...) is what lifts the dirt away. 

In electro-cleaning you can in fact gain some advantage from
reversing the polarity. At the Anode oxidation of the ions or
neutral molecules is occurring and oxygen gas is liberated, at the
Cathode reduction of the ions and neutral molecules is occurring and
hydrogen gas is being liberated. As long as you do not have an anode
that will release metal ions into the electrolyte solution you will
not plate if you have the work as the cathode and in fact you can
reduce the surface oxides on the work. There are electro-cleaning
baths that operate on with a switched DC power source where the
potential is constantly being reversed so that the workpiece is going
from + to - at a rate set by the operator. The bath chemistry and the
material of the electrodes all play a part in this os it is possible
to really screw things up if you reverse the polarity with the wrong
set of materials but it is not a given that electro-cleaning must be
a fixed polarity operation.

James Binnion
James Binnion Metal Arts


#20

I’m posting this in the hope it will be useful. I’m well aware that
it isn’t the right and proper way to do things, but I’m waiting for
the day when my dad buys a proper plating system, or the day I build
one. Until that day comes, here’s how I do it…

2x glass beaker, 1x 12v battery, 1x platinum plated titanium
contact, 1x white gold contact, 1x small bottle of rhodium, 1x large
bottle of rhodium, 1x large “used” rhodium bottle, caustic soda, hot
water, 12000 grit microfinishing cloth.* Clean jewellery in the
ultrasonic, rinse, steam clean, then rinse again* Mix caustic soda
in one beaker, hang items in that and ultrasonic. Run the hot tap
over this afterwards, to thoroughly rinse ALL traces of caustic off
the items. This will degrease the item. Then fill this container
with water, so that the items to be plated don’t dry out and leave
any mineral traces.* Heat up your small bottle of rhodium (keeping
it in the bottle); I do this by putting it in a jug of boiled water
for a few minutes while I wait for the caustic to work.* Clean the
second beaker, pour the rhodium into it, then attach the contacts to
the battery. The items will be hung on the gold contact which is
connected to the “-” end of the battery. The platinum/titanium
contact is attached to the “+”.* Make sure your hands are clean and
dry. Sit down at a bench, and plate the items one at a time. Each
time, just transfer the item from one hanger to the other (the white
gold contact should be a hook to hold the item). Do not use your
fingers or any other implement! I plate for 30 seconds or so,
controlling the current by dipping more or less of the “+” contact
in the rhodium solution. Agitate the item if it looks like there are
too many bubbles stuck to the item. Then remove the item and rinse
under the tap to remove any traces of rhodium. Items with hollow
parts will want washing more throughly, to ensure no rhodium is
trapped inside.

I get really good results, the only problem I sometimes get is a
slight white stain where the contact was - I don’t know if this is
too much current at that point, of bubbles, but I generally solve it
by giving the inside of the ring a gentle rub with 12000 grit
micromesh. I am NOT suggesting that you do this, and I am NOT
suggesting this is a right and proper way to rhodium plate things,
but it might be worth you stripping things down to the absolute
basics, and see if that makes any difference. I’ve no experience
with electrocleaning, just methodical washing and degreasing.

Jamie Hall
http://primitive.ganoksin.com