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Zinc vs. nickel plating

Q. Sir,

I am a student of mechanical engineering, and you know better the criticality of the aspect 'surface finish' these days. Regarding this I want to know the difference between WHITE ZINC PLATING and NICKEL PLATING with respect to 1) finish 2) durability 3) cost 4) dimensional variation.

Would you kindly let me know? I will be very grateful to you. Thank you. I have 8 years of experience in mechanical field, if you find me eligible to answer any query please don't hesitate to forward it to me.

Bye,

Vishnu Vinayak Shirodkar
- Bombay (mumbai), INDIA
2001

A. Hi Vishnu. I never say that one finish is better than another, but zinc is usually the better answer for plating steel when you don't know which to specify and have no particular reason to prefer nickel. Here's why:

Zinc is anodic to steel and nickel is cathodic to steel. Just as a zinc anode can galvanically protect the steel hull of a ship, a zinc coating galvanically protects the steel. A nickel coating must be free of pinholes and porosity to function because the steel tries to galvanically protect it, so you will get rust blooms at any pinholes in the nickel. This also means that zinc coating can safely be thinner. Zinc is a substantially less expensive metal as well. So nickel wins for finish, but zinc wins for your other issues. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 18, 2013

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