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Picking a Coating for a Ni Surface

I would like to apply a coating (no matter organic or inorganic) on the Ni surface to achieve the following objectives:

- To prevent the Ni plated products from sticking together when the Ni surface touches the backside of the product (Cu surface)
- minimize the tarnishing of the Ni surface.

Would anyone have a suggestion of the coating? Thanks.

Kelvin YU
- Hong Kong

I don't know what other constraints you may have, but these two constraints have chrome plating written all over them.

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


Dear Mr.Mooney,

If I prefer the coating is transparent and organic in nature, any suggestion for the coating?

Thanks a lot for your kindly help.

Kelvin YU

Kelvin YU
- Hong Kong

You could certainly apply a clear organic coating by lacquering, clear-coat powder coating, or electrophoretic coating. All will protect the nickel from tarnishing, but probably none will work as well or as practically as chromium plating. Chromium is virtually transparent when plated on nickel; it will just give it a slight bluish tint in place of the slight yellowish tint on nickel.

I don't know exactly what you mean by the parts sticking together (wet? dry? cold welding? acting as suction cups?), and I don't really know of organic coatings designed to discourage it. But if you could explain in more detail what you mean by 'sticking together', then maybe someone else can help you.

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

Ted, a correction may be in order. It is hard to believe that chromium being a metal could be transparent at the thickness applied even for decorative purpose. All metals typically start becoming opaque above 100 angstrom (0.01 micron) thickness. Any transparency is due to pinholes and discontinuities in the coating.

Mandar Sunthankar
- Fort Collins, Colorado


Thanks for the important note, Mandar.

I'm sure you are absolutely right that chromium plating is not 'virtually transparent'. What I meant to say was it is virtually invisible.

Oops, that got me into even more trouble!

What I am really trying to say is that someone has to work hard to see the difference between a nickel plated surface and a surface that is nickel plated followed by a flash of chrome. The only difference you see by eye is the movement from the yellow cast to the blue cast.

But if Mr. Yu actually requires a transparent coating for some optics-related need, chromium is absolutely not transparent, not a good choice at all, and your clarification is appreciated and imperative.

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

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