Letter 18068

Zirconium Nitride Plating on Steel  

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Our facility though not a metal finishing company utilizes many finishing processes to enhance metal surfaces for our end product. I am currently researching potential processes and formulas to add to our electroplating facility. Our one and only electroplating process is a non alkaline zinc on 1008 Steel. What processes are available which will enable our organization to add titanium or zirconium nitride plating? The ultimate goal is to add a gold finish to an existing product, but keep our zinc electroplating as well. What options are available to us to enhance our current plating line to add another finish? What are the waste treatment liabilities and options for adding a zirconium nitride process?

Michele La Vasseur
- East Bloomfield, New York

Titanium nitride and zirconium nitride are not applied by electroplating. They are applied by PVD processes (gaseous processes) in a vacuum chamber. However, it is often desirable or necessary to include an electroplated underplate--perhaps nickel plating--underneath the PVD coating.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Just to add to the previous response, it depends very much on what you are looking for in a finish. For decorative coating purposes, a thin ZrN is usually deposited over electroless nickel, sometimes with a hard chrome interface. For wear applications, a much thicker ZrN coating is applied directly on the substrate. As the ZrN is deposited by PVD, there is no waste stream.

Jim Treglio
- San Diego, California

Ted is correct that an electroplated layer is needed. TiN and ZrN like coatings are noble in nature and will cause severe corrosion in steels if applied directly. You need to seal the steel similar to that in decorative chrome. These need to be applied as the final finish. Also, severe difference in thermal expansion coefficient will result in cracking of nitrides if applied directly. Depending on size and shape, there may be a limitation where it can be applied.

Mandar Sunthankar
- Fort Collins, CO

Isn't zinc one of the elements that sublimes in vacuum when it gets hot? If so, depositing ZrN or TiN over the zinc plating might be very difficult. The plating will be coming off when the coating is going down.

John Davis
- Berthoud, CO, USA

It is generally a bad idea to heat zinc coated objects in a vacuum system. In fact, it's not a good idea to put them in there in the first place. Zinc has a very high vapor pressure, and will contaminate the chamber.

Jim Treglio
- San Diego, California

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