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Rhodium plating white gold and Titanium ring

Q. Hello,

I design and manufacture jewelry made from gold. Recently I started to manufacture some rings from titanium and some eyeglass frames from beta-titanium. I was told that titanium will change color within time if not protected with some type of plating or coating. What type of plating or coating can I use to prevent discoloration within time. We use rhodium on gold, can rhodium be also used on titanium?

Thank you
Gary

Gary Ferre
designer - Los Angeles, Virginia
February 14, 2008

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Try this process:
a)Use mechanical abrasion with compressive deposit. Mechanical abrasion can be achieved with grit blasting, vapour blasting, glass bead blasting. Use a nickel strike solution to assist adhesion.
b) Electrochemical processing;
Acid etch in:
NH4HF 10-40g/l
H2SO4 5%v/v
Temp 20C
Leave for 30 seconds or more AFTER gassing starts.

Activate in:
HF(40%) 50-70ml/l
HNO3 50-100ml/l
H2O2 100-200ml/l
Temp: RT
Time 5-10 secs

Strike plate with a suitable metal, such as nickel.

NOTE: DO NOT RINSE BETWEEN ACTIVATE AND STRIKE PLATE.

I have never used this process, but have it on good authority it should work!

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

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Hi Gary,
Read the letters 278, 13456, and in this letter you have a lots of plating tips for titanium materials.

Best regards
Anders Sundman
Surface Engineering

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden

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Gary,
You can have a micro-thin urethane coating e-coated on your pieces (any metal that is conductive).
E-Coating is well-known in the world of eye-glass frames offering clear and translucent "designer" colors with excellent corrosion resistance. We can do it for you if you wish.

Mike Dywan
- Phoenix, Arizona

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When coating on titanium you always have 2 problems:

1) Titanium is covered with titanium oxide film of TiO2, which restore itself in a fraction of seconds in aquatic environments, or in the air, if mechanically or chemically removed. TiO2 oxide film hinders the achievement of a good coating adhesion to titanium.

2) When trying to remove such oxide film in acids (HCl, HBr, HF, etc.), active etching of titanium takes place, in which atomic hydrogen, according to the reaction

Ti + 3H+ = Ti3+ + 4H

is absorbed by titanium surface, penetrates into micro holes of metal, and creates a layer of titanium hydride.

After plating on titanium hydrogen diffuses into the gaps under the plating and turns into gaseous hydrogen, creating bubbles, tearing plating off. Examples of such technologies: letter 3503, etching in HCl in letter 24365.

The only way to solve these problems is to develop method of oxide film removal, but without hard etching on above reaction. It's difficult but possible. Experiments and research allowed us to create method of removing titanium oxide, eliminating hydrogen absorption, and preventing recurrence of titanium oxide formation in the interim between oxide removal and plating on titanium.

It seems to us that the best way to protect titanium color change is not plating. Instead try to create thin oxide film, which prevents further oxidation of titanium. It is possible to select the thickness of such film so that it creates no noticeable interference or staining, on the other hand, gives the desired shade of color products.

You can try themselves to oxidize samples of your product at a voltage of 5, 10, 35 V to 5 - 10% solution NH4H2PO4 within 5 - 10 min. at room temperature and check on color changes. If you like this idea, we can help you achieve it.

Anna Berkovich
Russamer Lab

Pittsburgh, Pennsylvania

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Multiple threads merged: please forgive chronology errors :-)

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Q. I need to rhodium plate some white gold and Titanium rings that I have in stock.
Do you need to mask off the Titanium sections of the ring? I thought that I recalled someone telling me that you don't need to mask off titanium when rhodium plating.

William Button
jeweller - Brisbane, Australia
January 23, 2009

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Q. Dear Sir,

How to apply rhodium on titanium alloy surface?

Ruyter Silva
- Rio Calro SP Brasil
May 16, 2013

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Q. Thank you so much for your answer. How can I buy this book. We will try to plate titanium alloys: nickel titanium, titanium molybdenum, copper titanium.

Ruyter Silva
- Rio Claro SP Brazil
May 21, 2013

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Q. Thanks Ted. Do you think that I can plate nickel onto titanium and then plate rhodium onto nickel? Is it possible?How can I do that?

Ruyter S Silva
- Rio Claro SP Brasil
May 26, 2013

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