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Rhodium issue


#1

Hi All.

I have been a jeweller now for about 25 years. The other week I went
to re-rhodium a ring in the same fashion I always do and the rhodium
wouldn’t take.

I spent some time playing with it and I noticed that the cleaning
solution kept beading on the surface.

The ring wasn’t my own creation but was 18ct.

Nothing I did would stop this, even cleaning in the ultrasonic with
acetone. The result was the rhodium was patchy and riddled with black
or dark blotches.

This is not the first time I have come across this same problem.

Does anyone have any idea what causes this?

Thanks.
Darren.


#2

Darren,

I’ve done lots of rhodium plating since the mid 70’s. I’d ask you
these questions re: your issue: I apologize if my questions are very
basic.

  1. Under magnification do you see porosity in the piece you are
    having problems with? If so the problem may be dirt of some kind in
    the pits.

  2. Could you have accidentally reversed polarities of the anode &
    cathode?

  3. Could the piece have been coated, or plated, with some type of
    clear polymer that is preventing electrical contact?

  4. Is your rhodium solution contaminated? Rhodium solution must be
    stored in a sealed container after using to keep it clean.

  5. Check the voltage! Maybe it’s too high?

  6. Is the rhodium fresh enough?

For people just starting to rhodium plate some suggestions: (Much
applies to all electroplating)

  1. Cleaning. If you have high mineral tap water steam cleaning may
    leave a residue that can adversely effect plated results. I use an
    ultrasonic with a special solution but most commercial solutions
    work O. K. Many U. cleaners are too low power, operate at the wrong
    (too high) frequency for jewelry, but correct for delicate parts, or
    people do not use clean, ‘heated’ solutions or they overload their
    cleaner (load is based on cleaner wattage & bath size) so their
    cleaning results are poor. Generally it’s best not to use an insert
    basket to hold items because baskets absorb too much transducer
    energy. Hang things from wires suspended from a couple stiff wires
    resting across the top of the tank.

  2. Tap water rinse is fine if your water is O. K. If not O. K. then
    a distilled water rinse is better.

  3. Sometimes I use a 10% sulfuric dip after the ultrasonic & wash
    swishing a piece around a few seconds then rinsing well again. An
    acid dip is not required most of the time though. Putting a washed
    piece down on a clean paper towel is O. K. for a minute after the
    last rinse before you plate. Do not pick the piece up with your
    fingers though.

  4. Only use a platinized titanium anode (for rhodium). Very
    Important.

  5. Rhodium solution is used at about 70F up to about 100F max.

  6. Pyrex container that is clean.

  7. 2 to 3 VDC (I plate rhodium at about 3 VDC, never higher). Other
    metals require different voltages.

  8. You do not need a current controlled rectifier. A couple D size
    1.5V batteries in series works great too and lasts quite awhile if
    you don’t have a rectifier or do occasional plating. Get a battery
    holder at Radio shack.

  9. Move the piece back and forth in the rhodium solution medium
    slowly. The moving (agitation) helps knock off the small bubbles
    that form on the piece being plated. Bubbles block the plating
    somewhat. Also, turn the piece around as you are plating so all
    sides are facing the anode. This gives you a more even plate. Keep
    the piece you are plating in the center area of the beaker, not
    right next to the anode.

  10. About 10-15 seconds plating time for rhodium. Too long a plating
    time can cause rhodium to flake off the plated piece. The whole
    piece you are plating goes completely into the plating solution, not
    part way in. After plating rinse the piece in water and dry. Drying
    is important to prevent water spotting. (facial tissue twisted up is
    good to suck up water between prongs & recessed areas).

Several other things to pay attention to like only having the
platinized grid (anode) in the solution, NOT the stainless part of
the anode grid. The surface area of the piece you are plating must
be smaller than the area of the anode that’s in the solution. That
is Important. I use a short, 20 gauge platinum wire to hang the
object I’m plating hooked up as follows: The +/- wires from the
power source are terminated with alligator clips. One alligator
clips onto the stainless part of the platinized anode. The other
alligator clips on a short length of platinum wire bent in a U-shape
on one end to hold the object being plated. Only the platinum wire
on the cathode wire and the grid of the anode go into the rhodium,
not the alligator clips. The grid part of the anode where the
stainless strip is bonded does not go in the solution. A mantra with
all plating, especially rhodium plating, is having the object being
plating very clean. You CAN NOT touch-up polish (buff) or repolish
after rhodium plating because the plated on rhodium is too hard.
Your final finish on an object must be done FIRST, before being
plated. The finish before the rhodium plate can be polished, satin,
sand blasted, hammered, engraved, etc. If you need to repolish after
rhodium plating the rhodium must be stripped off first. Many gems
can go in the rhodium solution bur some can not, e. g. pearls can
not. Rhodium is an acid bath. You also do not want anything to
dissolve during the few seconds in the rhodium and contaminate the
solution.

These are the basics. Use a high quality solution. In time the
solution will wear out because the rhodium has been depleted. If you
need to mask off an area not to be plated cheap finger nail polish
works great. I use red because it’s easy to see. Easy removal of the
fingernail polish with acetone. Any masking off is done after the
final cleaning. Be careful not to touch the piece with your fingers.
Use tweezers. With some metals it’s beneficial to under plate first
with another metal (various reasons for this) but with rhodium you
can plate directly on gold (yellow or white alloys) & silver.

When I see some of the ‘expensive’ plating setups offered by some
suppliers I cringe. Simple, inexpensive setups are so easy to put
together and can give top results. Very long post, hope it helps
some people.

Richard Paille
Paige Tools


#3

Hi,

As an experienced jeweler, professionally since 1968, I agree with
about 90% of the presented here. A couple of points need
to be discussed a little further and even a bit of mild disagreement
is in order.

  1. Regarding cleanliness, I always use an electro cleaner to get my
    jewelry absolutely chemically clean before plating, and after the
    ultrasonic, no touching. A very inexpensive cleaner can be made with
    a couple of tablespoons of Tri Sodium Phosphate (Used to clean garage
    floors etc., etc.) in a pint of water heated to around 150 degrees F.
    I use a stainless beaker for the solution, the beaker becomes the
    anode, the jewelry item is the cathode, same as plating. I immerse
    the item for about 10 seconds running about 10 volts or more. (By the
    way, 10 volts can actually draw 20 amps of current or more if you are
    doing a bracelet or something large. A decent rectifier is needed in
    this case.) Rinse well under running water. Observe that water just
    sheets over the object. Using just an Ultrasonic, as clean a job as
    it does, water will bead and not work as well for plating. Regarding
    using a steamer, the steam coming from it is distilled water, no
    minerals, so I’ll steam before actually plating.

  2. There are 4 metals I’ll plate with Rhodium, Gold, Platinum,
    Palladium, and Nickel. Never silver or copper unless nickel plated
    first. Silver and copper will dissolve in the sulphuric acid used in
    the rhodium solution. even as you are plating it. Also, Rhodium plate
    is porous and silver will actually tarnish under it.

  3. You can rescue a rhodium bath sometimes if it starts plating
    dark, and the process I’ll explain is something I do as maintenance
    every few weeks. Stuller has a kit containing a plastic sealable
    container, a large funnel, a glass stirring rod, activated carbon,
    and laboratory quality filter paper. You mix a couple of scoops of
    the activated carbon into the solution and stir with the glass rod.
    Repeat stirring every couple of hours, and let it go at least
    overnight, still stirring it when you are available. Continue for
    about 24 hours or more. Pour the solution through the filter paper
    into the container. The filter paper will stop the carbon with it’s
    absorbed impurities from passing through.

If the solution is still weak, warm it to evaporate some of the
water from it. This has always worked for me, and I’ve had a pint of
solution last over a year, using it almost every day. Still using it
as a matter of fact.

  1. As far as the holder for holding the jewelry, I’ve made a number
    of hooks and tweezers out of nickel brazing rod. It works just fine
    and will not contaminate the solution.

As far as the rest of Richards aside from the above, he
has done a very fine job of describing the plating process. You
really can’t go wrong following his detailed instruction. We have
slightly different experiences and approaches, so consider my
comments as appending to his comments.

Tom Tilney
pbase.com/tomdesgn


#4

Darren

Richard seems to covered the gambit of Rhodium Plating

Then, it worked before, I have a post code in AU of 2000. Like you
never a problem then there years of chop and change. Now even the
steamer runs on demineralised water, then two rinses of distilled
water before plating. The tap water has (been) changed.

Worth a read is Johnsom Matthey"s web site for plating times for
Rhodium, like only two people in a room get that one right at
"Question time".


#5

Hi Richard!

You wrote “Drying is important to prevent water spotting.” It seems
so strange that plain old water can damage rhodium…:-)… How
does that work…?

Janet in Jerusalem


#6

Hi all and thank you for all the responses.

@ Tom Tilney. “Observe that water just sheets over the object” This
is where the question starts. No matter what I did in this case the
water kept beading.

After electro-cleaning. As I said before, I then cleaned with
acetone to try to remove any stubborn oils and then electro cleaned
again, and still the water beaded. I don’t understand what would do
this.

The rest of the process is much as described. I electro-clean rinse
in a distilled bath, rinse in a second distilled bath. Plate with a
proper plating rectifier. I can’t/wouldn’t mix anode/cathode. Same
process I use for all the other plating I do.

The one thought I had that Richard touched on is whether someone
plated it with a clear inhibitor like tarnavoid, but this seems like
an odd thing to do to 18kwg.

Regards, Darren.


#7

Hi

the guys at JCR suggested to add methylated spirits to the water as
it breaks the surface tension.

And so the piece can be dried more easily.

all the best
Richard


#8

Hi Darren, After reading your procedures & follow through, our
immediate thought was–it’s the piece, not you. We are seeing more
strange coatings, plating etc. on jewelry and we have each been
around for 36-40+ years at the bench. My worst nightmare now is
working on sterling silver anything–it’s all got plating of some
sort, including clear stuff. (Including charms from a well known
vendor recently discussed here on the listserv.) Coating is just s.
o. p.–whatever it is…

So, I’m not sure what else you can do. Maybe take the item, repolish
off all large areas & then do your procedure. Or not rhodium at all
after polishing…

Ciao, Jo-Ann & John Donivan in SF CA


#9

Hello All,

I have found that to remove Rhodium Plating that is already coming
offI can put the piece is old silver test solution, watching and
checking every 10 to 15 minutes and the acid will etch under the
Rhodium without really harming the silver. The silver will need to be
repolished.

Veva


#10

I used to get the same problems when I used a so-called room
temperature plating solution and it was fine when the bath was
heated, so perhaps an upward adjustment of the bath temperature to
just under boiling point might help.

Nick Royall


#11

Nick- I have found the same thing. My rhod. plating solution says use
at room temp. I warm it ever so slightly and get better results.
Before I open the bottle I put it in a bath of hot tap water for
about 10 min. Then I pour it into a pyrex beaker that I have pre
heated the same way. Just enough to take the chill off the solution.

Have fun and make lots of jewelry.

Jo Haemer
timothywgreen.com


#12

I see the same thing Darren. I assume it’s some kind of coating that
is covering up something bad (people are rotten and can stamp it as
anything), so I’m reluctant to remove it all in an attempt to plate
it properly. Usually I will talk to the customer about it and they
typically say to leave it alone.

I also occasionally come across a white gold piece that rhodium
plates kinda brown, like it’s stained with tea. I know it’s
something with the alloy because I’m down to the metal and I know
it’s not the rhodium because I will have rhodium plated other pieces
and they are all perfect, but I have this one dud. I will repolish
and follow the same procedures as have been mentioned in this thread
and it’s dark again. I’ve seen this many times over the years but
don’t know what’s causing it?

The only comments I have about the recommendations is that I find
that palladium doesn’t rhodium plate well, not that you need to
plate it at all. But when I have a white gold piece with palladium
components the Pd seems a bit cloudy while the wg is perfect after
rhodium. The second comment is that if you are really stuck with a
rhodium issue, call the guys at Cohler. You can talk to one of the
chemists who make the stuff and they are great at picking apart
problems.

Mark


#13

12 Step Program for Successful Rhodium Plating

With modern alloys, how do jewelers achieve a really white color? In
two words Rhodium Plating. A quality rhodium plated finish should be
standard procedure on all white gold mountings and this leads to
another frequently asked question, How do I get a good rhodium
plated finish?

To answer that question lets begin with a few basic principles, then
to keep it simple take a bullet point approach to this process.

The three most important things to know about Rhodium Plating are:

  1. Clean 2. Clean 3. Clean!

If it isnt clean, it wont plate! Simple!

Other Critical Issues

  1. Temperature Control: Minor changes = inconsistent and poor
    results

  2. Current Control: Never more than 4.5 volts for Rhodium, 3.5 volts
    is better

  3. Proper Rinsing: Clean running water for 1 minute.

Safety glasses are a must.

  1. Skin contact with rhodium plating solution can result in skin
    irritations or acid burns

  2. When skin contact occurs, neutralize with a paste of baking soda.
    Rinse with plenty of running water.

  3. Protect skin and clothing with rubber gloves and neoprene apron.

  4. As Rhodium plating may produce some acidic fumes, it is
    recommended to work under good ventilation and to wear a NIOSH
    approves mask when plating.

Twelve Steps to Successful Rhodium Plating

  1. Polish to a brilliant high finish.

  2. Clean thoroughly in an ultrasonic cleaner.

  3. Rinse in distilled water.

  4. Steam clean.

  5. Electro clean: 150F, 6 volts for 30 seconds in a stainless
    beaker. Positive lead attached to beaker, negative attached to ring.
    OR: 150F, 6 volts for 30 seconds in a glass beaker with a stainless
    steel anode. Positive lead attached to anode, negative attached to
    ring.

  6. Rinse in clean running water.

  7. Activator: room temp, no voltage, 30 seconds

  8. Rinse in clean running water.

  9. Dip in fresh distilled water

  10. Rhodium plate: Room temperature, 4.5 volts, 20-30 seconds.
    Negative lead attached to mounting, positive to platinized titanium
    anode.

  11. Wash under clean running water.

  12. Steam dry, then (optional) heat dry using blow dryer. Allow
    articles to cool before handling.

Helpful Tips:

Use a gold hook to suspend object from alligator clip, never steel.
Suspend object in solution with current ON. Be sure voltage setting
is constant when actually plating article.

Plating Bath Maintenance:

Avoid contamination; keep covered when not in use. Replace evaporated
water by adding steam distilled water to original level.

Trouble Shooting:

Rhodium plates black:

Mounting is not clean, clean, clean.

Current too high. Try lower amperage (1.5 " 2 amps) and longer times
(1 " 2 min) for best results.

Rhodium solution is contaminated. Give a carbon treatment to plating
bath.

Dark spots on rhodium:

Clean, clean, clean

Air bubbles are sticking to mounting; gently agitate to dislodge air
bubbles.

Rhodium looks frosty:

Amperage is too high, reduce to 1.5 amps

Rhodium Plating Kit

Quantity Item # Description

1 29-0010 Safety Glasses
1 45-4030 10 Amp Plating Rectifier
1 45-6402 600 ml Stainless Beaker (electro-cleaning) OR:
1 45-0326 Stainless Steel Anode with)
(1 45-6401 Beaker Covers and)
(1 45-6400 600 ml Pyrex Beakers)

3 45-6401 Beaker Covers (activator, rhodium, rinsing)
3 45-6400 600 ml Pyrex Beakers (activator, rhodium, rinsing)
1 45-0320 Platinized Titanium Anode
1 45-2020 Electro Cleaner
1 45-2040 Activator
1 45-4142 Rhodium Plating Solution
1 45-6420 Thermometer
1 45-7120 Hot Plate
1 47-3068 Apron

For gold plating add:

1 45-6400 Pyrex Beaker
1 45-0334 24k Gold Anode
1 45-2120 14k yellow gold plating solution

For plating of two-tone, yellow & white gold jewelry:

1 45-7990 Masking Lacquer
1 45-7995 Lacquer Stripper

For rhodium plating over sterling silver:

1 45-6400 Pyrex Beaker
1 45-0330 Nickel Anode
1 45-2100 Nickel Mirror Plating Solution
Electric hot plate
Palladium Solution
Platinized Titanium Anode

If you do not have adequate ventilation please consider adding the
following safety equipment. Rhodium fumes are very acidic and should
not be inhaled.

1 47-4099 Solder Pure w/ Rhodium Filter or
1 47-4085 Ductless Fume Hood

Andy “The Tool Guy” Kroungold


#14

Hi all

With modern alloys, how do jewelers achieve a really white color?
Very simple, use Argentium. It is whiter than rhodium, platinum and
palladium and does not need the customer to pay for re-plating.

When heat hardened it is about the hardness of 14 kt for setting and
stronger than sterling.

Also using Argentium saves a lot of the technical problems of
rhodium plating.

All the best
Richard