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topic 10612

PVD coating on hinges


 

Dear Sir/s:

We produce continuous hinges 1.5" width x 126" length x 0.6 mm thick from cold rolled steel. They are currently zinc plating followed by yellow chromating. Since we have clients who want their hinges to look like brass to match their Baldwin hardware, we are considering PVD coating for our product:

1. Is it possible for our hinge to be PVD coated to produce gold or brass like finish(zirconium nitride)? Will it peel off due to the flexibility of the product?

2. Do we still have to zinc plate it?

3. Cost comparison, if our current process cost US$1.00 per, how much more would be PVD coating cost us %?

Thank you in advance!

Andrew Kaw
- Valenzuela City, Philippines


 

If properly deposited, the PVD coating will not peel off. It is, however, very thin. The industry generally coats first with electroless nickel to provide corrosion resistance, then electrolytic (hexavalent) chrome, then the PVD coating is applied. Zinc plating is an absolute no-no.

Because of all the steps involved, the PVD coating will be more expensive.

jim treglio portrait
Jim Treglio
- Vista, California


 

Dear Jim:

Thank you for your time. Is it possible for you to explain why zinc plating is an absolute no-no? Or do you have any article or book to recommend for my reference?

Thanks,

Andrew Kaw (returning)
- Valenzuela City, Philippines


 

In general, zinc plating is bad for vacuum systems because zinc has a high vapor pressure. If heated even a small amount the zinc gets everywhere, contaminating the system. In addition, ZrN and other decorative PVD coatings are very hard, with very high elastic moduli. Zinc is too soft and flexible as a base coating.

jim treglio portrait
Jim Treglio
- Vista, California

 

I suggest that you look up the Society of Vacuum Coaters (SVC) who has a number of papers on the subject at their annual meeting and publishes Conference Proceedings. A book of interest is "Handbook of Physical Vapor Deposition (PVD) Processing" [link is to info about the book at Amazon].

Donald M. Mattox
Society of Vacuum Coaters
Albuquerque, New Mexico

Ed. note:
            Mr. Mattox is
            the author of -->




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