Metal finishing Q&As since 1989

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PrePlate Processes

 

Using Zinc plating, on steel, with a clear chromate finish does not protect the plating from finger prints. This is being used on computer chassis'. I am looking for a plating process that will do that. I have seen some preplate materials with a very nice semigloss finish on steel that does not show any finger prints. Does anyone know the preplate processes that various manufacturers use?

Any help is much appreciated.

Richard Robinson
- Fremont, California, USA

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It is possible to scratch-brush, or otherwise unsmooth the surface so that fingerprints are somewhat less obvious--but the chromate surface is highly subject to fingerprinting, and if there is no reason to prevent it, you can lacquer the panels to minimize fingerprints.

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

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Many millions of zinc plated parts are handled every day, and fingerprinting is not a problem for most of them. I would institute the use of cotton gloves for packagers and assemblers for two reasons:

1.) peanut butter and jelly sandwiches (personal experience on this one)
2.) chromated surfaces contain hexavalent chromium, and the better and deeper-pocket corporations are concerned about exposure to worker's skin from handling.

  
Tom Pullizzi
Falls Township, Pennsylvania
 

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Zinc coatings are sacrificial by design, so they protect the base material by self-decomposition. The longer the fingerprint remains on the surface, the more permanent the spot will become as the deposit combats the corrosive properties of the fingerprint(the organic acids.) If you really want to allow fingerprints but want no adverse effects from them, then you must switch the exposed surface from Zinc to a non-corrodable deposit. These will all be way more expensive than zinc. Paints, enamels, powdercoats, etc. will also do the job. A new alloy, "Tin-Cobalt" has appeared recently as a Chrome replacement that you may want to test. It goes down with a satin finish and it is now appearing on many popular hand tools, which are the most fingerprinted item made. The satin or matte finish, as opposed to a glaring brite finish may aid in hiding the fingerprint as well.

Dave Kinghorn
Chemical Engineer
SUNNYvale, California