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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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What Does "Chromated" Mean?
Q. What is "Chromated"? is there any difference between chromated and chromium plated? if so what is the difference? I want to include it my Project.
Sheshagiri.KStudent - Bangalore, Karnataka, India
2000
A. Hello Sheshagiri.
Chromium plated means electroplated with chrome, such that the chrome is in metallic form. Chromated means treated with a solution of chromate, usually hexavalent (valence +6), as a corrosion-fighting passivation layer--usually applied to zinc and cadmium plated parts, or to aluminum. Chromium plating is usually bright and metallic, hard, low friction. Chromate coatings are a thin gel.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 23, 2008
Tip: Readers want to learn from your situation,
often just skipping abstract questions.
Q. Chromate conversion coating to aluminium furniture.
What is the advantage to applying before powder coat
What protection does it give.
- Hialeah Florida
A. Hi, Robert. Chromate (or a trivalent or chromate-free) conversion coating is essential. It is actually a several step process (cleaning, etching, desmutting, chromating) that leaves the surface of the aluminum properly prepared to accept paint; and the chromate is also important to keep corrosion from blooming and spreading in the event of a pinhole or scratch in the powder coating. Aluminum is a very active metal that oxidizes instantly; this oxidation layer is inconsistent in thickness & composition, and without a conversion coating the powder coating will be trying to adhere to this rather than to aluminum.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 25, 2008
March 11, 2013
Tip: Readers want to learn from your situation,
often just skipping abstract questions.
Q. Hi,
Does chromating help with corrosion resistance before electroplating on high pressure die cast aluminium? Is this possible?
Many thanks,
Mike
- Manly, NSW, Australia
A. Hi Mike. The answer to your question is no. Aluminum is never chromated before electroplating. Rather, aluminum is almost always zincated before electroplating. But I have to wonder if maybe the nomenclature is a bit off, and that's why you are confused on this?
Electroplating involves the electrodeposition of metals. There is a somewhat analogous process called electrocoating which involves the electrodeposition of organics (paints) ... and chromating the aluminum before electrocoating is a conventional and very good practice.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 11, 2013
Hi Ted, Thanks for clearing that up. Mike
- Sydney, Australia
March 14, 2013
June 16, 2020
Tip: Readers want to learn from your situation,
often just skipping abstract questions.
Q. Hi there,
I want to know is there any impact on resistance (spot) welding by Chromated surface on both sides of sheet?
- Haridwar, Uttrakhand, India
A. Hi Vipin. Sorry but it is not clear if you are thinking of spot welding aluminum (in which case thread 20304 and thread 12517 address that subject pretty exhaustively), or if you were under the impression that steel is chromated, which it is not. Please gives us the details of your own situation rather than casting the proposition in the abstract. Thanks!
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 2020
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