Evaporative Coating using Black Chromium
A friend of mine wants to know how to do coating using a black Chromium. Can this be coated using a resistance boat or Electron beam gun, inside a vacuum chamber? Who are the players or company that sell this kind of evaporation materials? How can this be deposited on a glass substrate?
Thanks,Gener G [last name deleted for privacy by Editor]
filters - Newark, California, USA
For decorative, solar collection, or optical purposes it is possible to contaminate a chrome electroplating bath such that the chrome deposit ranges from a smoked glass appearance (for decoarative use) to lampblack appearance (for optical use), and we call the finish black chrome by general acceptance. But we recognize that there is really no such isotope as a black chromium, and we are just using the term 'black chrome' as slang to describe that color range of chrome plating.
So, in the case of vacuum deposited finishes, where I personally haven't heard of the term black chrome being used, I am left with a description that isn't familiar to me, and with no understanding of what your friend is trying to achieve. Could you please tell us what properties your friend is after? Thanks.
Ted Mooney, P.E.
Pine Beach, New Jersey
Black chrome has been a staple of the optical coating industry for many years. It was first developed for use in targeting reticles for gun sights in WWII. Since that time there have been many variants of the black chrome process developed. It has uses as an absorber and in the reduction of stray light in optical systems. Some of these variants can be deposited from a resistant boat but they can have problems with environmental durability. For a listing of these suppliers I suggest that you go to Photonics.com.
I hope this helps.
- Santa Rosa, California, USA
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