Aloha, fun & authoritative answers -- no cost, no registration, no passwords, no popups
(as an eBay Partner & Amazon Affiliate we earn from qualifying purchases)

Home /
Site 🔍
pub  Where the
world gathers for metal finishing
Q&As since 1989


Ruthenium Plating Process

Q. I've been doing some electroforming of gold onto copper mandrels and etching out the gold with nitric acid. Now the customer wants to have a "medium Z" material (Ruthenium to Antimony) electroformed. In one of the ancient "Ask plater B" queries I had read a response to a similar question which suggested Ruthenium as being resistant to attack from nitric acid. Is this true? Can I plate Ru directly onto copper? (The customer doesn't want stress cracks so I've shied away from Rhodium). I need to plate ~25 microns (1 mil) onto the substrate. Does Ru sound possible?

Fred E [last name deleted for privacy by Editor]

Need low temperature Ruthenium Plating

Q. Usually Ruthenium is electroplated at temperature of 60-70 °C. In my application, I need to plate Ruthenium at a temperature of 50 °C or lower. Is there such chemical and process available?


Larry Zhang
- Milpitas, California, USA

Want Jet Black Color with Ruthenium Plating

June 21, 2008

"Jewelry Concepts and Technology"
by Oppi Untracht

on AbeBooks

or Amazon

(affil links)

Q. Hello

My Name is Sudhir, I'm basically a watchmaker, recently my client in Belgium wanted me to plate his watch movements in black colored, I have been using white rhodium plating on mechanical watch movements, using intermediate coating of Palladium. Ever since my buyer wanted to get black finish, I have been researching all around internet, I just saw that Umicore came up with "Blacker" Ruthenium product number 479, also I read some articles on net stating that Pen plating Black Rhodium [adv: black rhodium plating solution on eBay or Amazon] gets a better blacker finish than bath Rhodium, at the same time some articles saying that pen plating don't ever get you even finish.

Now I'm really not in a position to settle down to any solution, please help me about this problem, I'm willing to hire any professional help in this regard,

Thanking you

Sudhir Ostwal
- Chennai, TN, India

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)

A. Sudhir,
If you are unsure on what solution to use, have a local precious metal supplier plate some samples for you. Watch movements are very small and it would seem pen plating would be difficult. Bath plating would have lower thickness variations than pen plate because human error is minimized, and bath plating can plate better in recessed areas. It is hard for anyone just to give you a product name to suit your needs. What if the color of the deposit does not match your needs?

Mark Baker
process engineer - Malone, New York
June 25, 2008

A. Hi, Sudhir Ostwal,
Ruthenium plating, and bath not pen plating, as Mark said rightly is the answer.
There are supply houses making and marketing Ruthenium process. But I want to tell you that this will not be jet black in colour but an attractive dark grey.
Kindly look around in your city itself as I understand there are suppliers of this process.

t k mohan
T.K. Mohan
plating process supplier - Mumbai, India
June 29, 2008

sidebar notes

Q. Hello, I am a goldsmith. I'd like to have a new design on our gold and silver collection of chains and pendants. I want to use Ruthenium bath to give a black color to our gold and silver collection to get a fixed and heat resistant color (I have to solder next components on it after coloration). I want to use a Nickel Strike bath. I heard about Wood's Nickel Strike bath and Sulfamate Nickel Strike solution. Please, can you give me more information how to make it. What solution is better for me. Or if you have other idea how to do it. Thank you very much. J.T.

Jana Tietz
goldsmith - Czech
March 10, 2010

Ed. note: Please search the site for "Wood's Nickel" and/or "Nickel Strike", Jana. We have a dozen threads about nickel strike formulations, and non-allergenic alternatives.

Earliest known use of ruthenium plating on 18k white gold?


"Workbench Guide to Jewelry Techniques"
by Anastasia Young

on AbeBooks

or eBay or


(affil links)

Q. Hi - I'm a hobbyist jeweler and collector and I'm trying to date an 18 carat white gold pendant found recently at an antique fair.

It has clear UK hallmarks for 18k gold and the London assay office, but unfortunately the shape of the shield round the date letter is obscured, putting the piece somewhere between 1840 and 1960!

The pendant is in a late 19th century / early 20th century style - white gold in a loose fleur de lys shape, pave set with diamonds with pendant aquamarine & peridot briolette drops on white gold chain. However, the gold behind the pave set diamonds is blackened with what I think is ruthenium electroplating, so I assume it must be a much later piece than c. 1900.

Is there anyone out there who knows when ruthenium plating was first used on 18k gold or is aware of any earlier techniques that might have been used to blacken white gold?


Sarah Larvor
collector - London, England

Need Ruthenium plating on hard nickel parts

RFQ: My company has a technical application requiring Ruthenium plating on thin hard nickel panels.

If you can do it consistently and reliably this would be an on-going requirement for our business.

An NDA will be required.

Ned Kottmeyer
Electronics - Minneapolis, MN, USA
May 26, 2009

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)

Q. Hi everyone. I have a question about ruthenium plating onto jewellery!
The obtained layers have a very dark colour. What's the problem?
10 v, 1 min, 65 degrees.

Mazaher [last name deleted for privacy by Editor]
June 12, 2012

A. Hi, You can use a complex (alloy) solution of ruthenium and rhodium.

Gurudatta Thakur
- Mumbai, India
September 14, 2012

Ruthenium plating onto titanium

Q. Is a gold strike necessary when plating ruthenium onto titanium or can the Ru be plated directly to the Ti.

RFQ: I need to plate some titanium round bar .250 - .500 " dia. with ruthenium oxide. I could use some tech support with this to see if it is practical to do it myself. I would also consider jobbing it out if someone is already doing this.

Rusty Shuping
Safe Drinking Water Tech for third world poor - Rockwell, North Carolina, USA

A. Hi Rusty. Rather than definitively answering that, because I can't, I will at least suggest that the hard part is not the electrodeposition of ruthenium, but getting anything to properly plate onto and adhere to titanium. If you are able to get the gold to adhere, count your blessings rather than trying to skip the gold :-)

Please see letter 40558, "Poor adhesion of plating onto titanium", where Hamilton Solidum relates his successful procedure for plating gold onto titanium, or search the site for "plating on titanium". Good luck.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey
November 2013

How to get harder Ruthenium deposit?

Q. How to achieve a harder deposit of 0.1 µm of black ruthenium?
Because this deposit is not OK at the wear test (Turbula 30 minutes).
Thank you for your reply.

- Italy
November 16, 2013

A. Hi Gregorio. Sorry, I'm not familiar with the Turbula wear test. But 0.1µm seems awfully thin to me, no matter how hard the surface :-)


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey
November 22, 2013

Looking to create a durable black on nickel based white golds

Q. I am looking to create a durable black oxidation on all white golds. Also, palladium and platinum would be a bonus. I have tried pen-plated black rhodium, finding it is not all that black. But it also seems to wear off quickly as well. I have tried tellurium solutions as well and with the same results. Most of these will last only a few days to a few weeks. Has anyone had success with a blackening agent on gold that is very dark, and long lasting? Thank you

Peter Jon
goldsmith - Bend Oregon
March 30, 2014

"a User's Guide to Vacuum Technology"
by John F. O'Hanlon

on AbeBooks

or Amazon

(affil links)

A. We had a customer come to us with a similar problem -- trying to get black on white gold. We didn't see how it could be done with plating, so we applied a black coating by PVD. Worked fine, customer is happy and likely to go into production.

jim treglio portrait
Jim Treglio -
PVD Consultant & Wine Lover - San Diego,

April 2, 2014

Q. Dear All,

We have a 30 liter tank made of PP sheets; we use it for dark ruthenium electroplating. But our ruthenium electrolyte makes everything including our pp sheets black. How can we fix this problem? I hear there is a stabilizer salt but I don't know it. Hope to hear from you soon.

Many Thanks.

Jalal Jafari
- Isfahan, Iran
November 13, 2015

Q. I'm looking to purchase a couple items made of Rhuthenium ^ Ruthenium. Should I be concerned of the toxicity of the element?

Allen Schertz
- El Campo, Texas, USA
January 6, 2017

The editor's fave "coffee table book" for years now...

The Elements by Theodore Gray

on AbeBooks

or eBay or


(affil links)

A. Hi Allen. There is no material anywhere which nobody considers harmful, toxic, or allergenic :-)

But ruthenium (we corrected your spelling for better Googling) is a fairly widely used precious metal plating considered by most to not be toxic in any way.


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey
January 2017

Black Rhodium vs Black Ruthenium wear resistance

Q. Hi,

My fiancé bought me a black ruthenium plated ring, and the plating started to wear off in less than a day. After a week it was almost entirely gone. The shop said they had sold lots of them and it had never happened before, so it must be my skin. Do you think there is any validity to the argument that my skin can break down a metal as hard at this? They are getting it re-plated; I asked if I could have a thicker plate, or if they could try black Rhodium but they say there is only one thickness option with Ruthenium and that it's better than Rhodium.

I am also a student jeweler so I want to know for the future, what will last longer, black ruthenium or black rhodium? I see lots of posts about the colour, but none about durability.



Laura Gillings
- London, UK
October 12, 2017

A. Hi Laura,

Rhodium and ruthenium hardness are similar at ~800-1000 HV with excellent wear and corrosion resistance but rhodium price is almost 9 times of ruthenium.

The problem happened on you could due to too thin ruthenium deposit thickness, low ruthenium deposit purity, poor adhesion between ruthenium and underlying metal, too frequent wearing, etc.


David Shiu
David Shiu
- Singapore
January 18, 2018

Black color plating for jewelry

Q. I would like to know how to make it very deep black color for jewelry plating and not effect with skin and not have any allergic reaction.

Sittikorn Rakjai
Jewelry plating manufacture - Bangkok , Thailand
April 2, 2018

A. Hi Sittikorn. We added your inquiry to a related thread. Black ruthenium and black rhodium are your two plating choices, with the rhodium costing a lot more as David Shiu has advised. We are left with the question of whether the colors are up to your desire for a "very deep black color", and durable enough for the quality of jewelry you wish to offer.

Jim Treglio has advised that you may be able to get the desired color with a PVD process -- but these are usually only available and applicable for very high production requirements. What type of jewelry do you wish to color, and what is the production volume? Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey
April 2018

Q. Is David correct in that the wear resistance of black ruthenium plating is similar to black rhodium?

Can anyone recommend a black ruthenium pen plating solution available in the USA that yields a very black glossy finish?


Thomas Keith
- Chicago, Illinois US
May 15, 2019

A. Hi Thomas. Yes, Ruthenium is very wear resistant; it's a good choice. Readers are encouraged to offer any helpful technical thoughts, but sorry, we don't post suggestions of brands or sources (why?).


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey
May 2019

May 20, 2019

Q. How can I get the darkest black on sterling silver, as in making a bracelet. Not liver of sulfur, but a dark black ... and then I want to add 24 kt gold like keum-boo to the black. Years ago I remember gun metal plating.

Alexa Smarsh
jeweler - Paradise, Florida

A. Hi Alexa. Black ruthenium plating should give you the hard black look you seek. However, I don't know how well keum-boo will adhere because they might be addition agents which interfere. Give it is try :-)


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey
May 2019


Q. This is my situation. I have over 100 custom pieces to finish by the end of September. I have done fine jewelry plating before but I am having trouble with Umicore's RUTHUNA 479 black ruthenium plating solution. Was wondering if anyone here has tried this solution before. I am open for any help to get a great finish.

The main issue have is understanding the pH balance and getting the pre-gilding right.

Miguel Ponce Cervantes
Jeweler employee - Houston, Texas, United States
August 28, 2019

Ed. note: Readers may also be interested in thread 0023, "Ruthenium plating Q&A's".

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
Consult'g, Train'g
& Software

About/Contact  -  Privacy Policy  -  ©1995-2024, Pine Beach, New Jersey, USA  -  about "affil links"