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Zinc Chromate vs. Ethanol

I would like to know if anyone has information regarding Clear Zinc Chromated steel parts and exposure of said parts to petroleum or ethanol? Also, what is the comparison of Zinc Chromating vs. Galvanizing, any differences in performance or similarities?

Galen Burns
- Bement, Illinois, U.S.A.

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Galen:

Chromate refers to an additional protective coating applied over a galvanized part to prolong its durability. So, it improves durability of galvanized surface (zinc plate) and it retains for longer time the color or aspect of said plate. Very little information is available about zinc (either bare or chromated) for the purpose of contact with liquids other than condensed humidity. I would tend to believe that a thick chromate will be somewhat good. How long will it last? Only trial and error to my knowledge. Can other plates be considered? If so, nickel is far better. Good luck.

Guillermo Marrufo
Monterrey, NL, Mexico

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The question of comparing zinc plating to galvanizing has been asked here many times before, so I apologize to any readers who are tired of hearing the answer :-)

... which is, to a large extent, "zinc is zinc" whether applied electrolytically or by hot dipping. When applied by hot dipping it is several times thicker, so it is far more corrosion resistant.

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

Hi ,

Suffice to say that all the Automobile manufacturers I am aware of that supply parts or cars / trucks to markets that add Ethanol to their gasoline use electroless nickel to coat parts that come in contact with this mixed fuel , one I know of even requires Zinc plating and black chromate on top of the outside of an EN plated hollow part .

Regards,

John Tenison - Woods
- Victoria Australia