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topic 0338

Zinc plating & chromating of Carburetors

A discussion started in 1996 and continuing through 2013.
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Q. I am looking for info on Zinc plating carburetors and was wondering if this could be done by immersion plating?

Also black chromate on older carburetors with an aluminum alloy in them?

Robert Grabell
- Canada

A. You can immersion deposit zinc on aluminum, Robert; the process is called zincating. However, this finish is neither durable nor attractive -- rather it is used as a base for subsequent electroplating. If the carburetor is zinc, you could for example copper-nickel-chrome plate it, or you could zinc electroplate it and chromate conversion coat it. A possible reason for zinc electroplating and then chromating rather than simple chromating is so that you can chromate it more consistently.

Both aluminum and zinc can be chromate conversion coated (which is an immersion process), and the chromate can be black, or gold, red, or blue. But chromating an old raw die casting, whether zinc or aluminum, will probably give you a mottled, inconsistent finish that you won't be happy with. Chromating the electroplated zinc may be more aesthetically pleasing.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

June 21, 2013

Q. I am curious if anyone here has vast experience with zinc plating carburetors, or doing the original zinc dichromate finish on them when they were brand new.

I've heard it may be necessary to zinc electroplate a stripped carb body before immersion dipping them in dichromate, to prevent blotchy results. I have also heard that if you zinc plate a carb, and then dichromate it, you will end up with that cheap China tool look, instead of the nice original zinc dichromate finish.

If anybody worked for Holley or other manufacturers and did this process when they were new, I would love to know if the carbs were electroplated first.

On a related note, does anybody have experience with any other colors than yellow? It seems like some carburetors were more of an olive-drab color than yellow. And I would be interested to hear about results using black, or a more tan than yellow.

Could it be possible to mix say the yellow with a little black, to get a more tan color?

Steve Hulett
- Ocala, Florida USA

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