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Passivate finish vs. Cadmium Plating?

Q. What is meant by "passivate" finish on CRES nutplates? How is passivate finish different than Cad Plating?
Alex J Kimaerospace - Federal Way, Washington, USA
2006
A. Unfortunately, Alex, 'passivate' only means to render a surface less active. It's a very inexact term. But it can mean:
- the application of a chromate conversion coating to a cadmium plated surface (cadmium plating will quickly get white rust without it, and cadmium plated parts are virtually always chromium conversion coated, i.e., 'passivated' ...
- or it can mean to dip stainless steel (CRES) in nitric acid, or nitric acid plus chromic acid, or citric acid ⇦ on eBay or Amazon [affil link] to make it less prone to rusting.
Since you are talking about CRES, the latter seems more applicable, but it's only a guess until the exact context is understood. There should be a spec number you are expected to comply with, and that spec number should supply the necessary context. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
(Ted can offer longterm or instant help)
finishing.com - Pine Beach, New Jersey
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