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Zinc plating & chromating of Carburetors



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Current Q&As:

"How to Rebuild & Modify Rochester Quadrajet"
by Cliff Ruggles
from Abe Books
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October 30, 2021

Q. I too am trying to electroplate my Rochester quadrajet carb for a restoration project. I have the plating rectifier and am try to determine if I can make the kit myself? I believe I need to zinc-nickel plate, with brightener and then dip in a chromate of some color. Has anyone had success in this as I would be very appreciative for some expert advice. I know hobby plating suppliers have a kit but I was hoping to build the kit on my own or find another supplier. Thanks in advance.

Todd Anderson
hobbyist - Winston [Georgia]
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Ed. note: As always, gentle readers, technical replies in public and commercial replies in private please ( huh? why?)



"Holley Carburetor
Haynes TECHBOOK"

by John Haynes
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December 11, 2021

A. I have re-chromated Holleys and other die cast carburetor bodies for 30+ years. The original process was more than likely right out of the mold and into the chromate and rinse. Problem is with used metal that has been exposed to the elements it is difficult to properly prepare the metal to take the chromate evenly and not burn the metal which gives an ugly grey color if the chromate is too strong or the part is dipped too long.

I glass bead the bodies then go into a very mild nitric bath to "open the pores" so to speak, rinse, then into the chromate. The chromate I use has been off the market for 20 years so no help there. Darker tan or lighter green/red/gold is not in my control. The alloy controls that and these parts were not strictly controlled.

Donald C Dorfman
Retired Machinist / Engineer/ Business Owner - Edgewood, Washington
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Closely related Q&A's, oldest first:

1996

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



2000

Q. I need to find a fool-proof way to correctly 're-color' old carburetor bodies to their original "iridescent yellow / gold rainbow" coloring. These bodies are made of a zinc die-cast alloy ('ZAMAK 3 & 5'). Does anyone know the correct procedure for doing this re-coloring ? I appreciate your help! Thank you!

LARRY FULTON
- Great Falls, Montana
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2002

A. Hi Larry. I am told that the best way is by zinc plating the carburetor bodies first. To me "fool-proof" probably dictates "best way" not "a possible way". Good luck.

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


2003

A. Regarding recolouring carburetor bodies, particularly zinc die-cast types such as Holleys, Zinctone from Turco is a professional product used in Australia. Available from Avanti in 20L drums. In USA check with Turco division of Henkel Technologies.

Gavin Campbell
- ORMEAU, QUEENSLAND, AUSTRALIA
^



Carb electroplating problems

"How to Super Tune and Modify Holley Carburetors"
by David Vizard
from Abe Books
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2004

Q. Dear Finishing,

I work for a carb restoration shop and am trying to replate carburetors. We have purchased a small copy cad electroplating system. It does not work well for plating the complex shapes and irregular surfaces of the carburetors. After much research it seems that electroplating is not really the correct application for carbs, rather electroless. Here are my questions .

1) Can electroplating work and provide a professional uniformly plated carburetor ?

2) How would you do this ?

3) How do the big carb manufacturers plate their carbs, electro or non electroless tank plating ? How do most large restoration shops replate ?

4) Are there electroless kits for carb replating on the market ? We would like to set up a facility to plate @ two carbs a week.

Thank you very much.

Fred Haring
carb restoration shop - Fargo, North Dakota, USA
^


2004

A. I believe the answer to your third question is that big carb manufacturers don't plate their carbs. The carburetors are diecast zinc, so they prep them, then chromate conversion coat them. Chromate is a product that works on aluminum, zinc, zinc plating, and cadmium plating; it is not really either a plating process nor an electroless plating process. However, once the casting is old and pitted, it's a different matter since the chromate will not properly treat pits, bloomed areas, and differentially corroded areas.

At that point the carburetors can be zinc plated before re-chromating, but that's no assurance of good appearance or corrosion resistance since it will not restore pitted areas.

Probably the ideal way to go would be to cyanide copper strike the units, acid copper plate them, mush buff them to fill pits, then nickel plate or electroless nickel plate them. This is not easy, and for this low volume it might be better to make an arrangement with a plating shop than to try to get into the business yourself.

Another writer suggested that you powder coat the carbs instead of plating them, put paint really isn't the same thing as metal plating and may not satisfy your needs.

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



2005 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I need information on the process for recoloring classic car carburetors to the original yellow dichromate color. I believe it is a hot dipping process.

Lynn Palmer
Car restorer/hobbyist - Houston,Texas, USA
^

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Ed. note: We appended your inquiry to a thread which may answer it for you, Lynn. It's an aqueous process and may be warm (say 100 °F), but not hot. But feel free to follow up if this is insufficient.



"Holley Carburetors: How to Rebuild"
by Mike Mavrigian
from Abe Books
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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
^

Carburetor cleaning and refinishing has been a perennial subject. Please see also --

Topic 11847 "Restoring gold Iridite color to diecast parts"

Topic 16200 "Zinc plate carburetors & diecastings vs. chromating"

Topic 33779 "Clean and brighten carburetor bodies"

Topic 35697 "Carburetor re-plating / re-coloring"

Topic 37255 "Restoring the yellow dichromate finish on automobile carburetors"


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