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Is it possible to anodize zinc?




Q. I would like to know if it is possible to anodize zinc.

If so ...
Is it a radically different process from anodizing aluminum?
What kind of finish is possible?(i.e. colors)
Where can I find some literature on it?
Who does it?

Erin W. Hood
- Naples, Florida
2002


A. Yes it's possible, yes it's radically different -- done at 90 to 200 volts. It is not a decorative finish and colors range from green through grey to brown, but dyeing is not to my knowledge possible. Fred Perlstein had an article in Plating & Surface Finishing March 1979 later reprinted in some AESF Shop Guides entitled "Anodic Coatings for Other Metals". I don't know of any shop doing it although I understand that internal parts of washing machines have had this process done to them in the past.

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


A. Hello Erin,

Yes it is possible to anodize zinc. But I have yet to actually see a process, or any specifications associated with anodize on zinc. But I have read in numerous differing sources that it is possible, but there was never much more than just that statement.

I'd assume that its functions and possibilities would fall in line with something along the lines of titanium, whereby you can attain color by the use of inorganic coloring functions.

The only issue I'd see with anodizing zinc would be its porosity, and its likeliness to provide a porous and low strength coating.

Matthew Stiltner
plating company - Toledo, Ohio


A. Yes it is possible and was done commercially in the late 1970's, but the problem is the process uses "AC" power, and is quite dangerous without the proper guarding. To my knowledge only one company did provide it commercially, and they stopped offering it many years ago. The biggest benefit was not cosmetic, but corrosion resistant properties; The darker the olive green color, the better the corrosion properties; It gave a dramatic CASS test result; One of the markets was commercial grade marine hardware replacing the steel galvanized castings. But cost was a factor, and it never caught on because alternate materials provided better results at a reduced cost.

Joseph DeAmicis
Academy - Edison, N.J.


A. The main points to aluminium anodising are either/both produce a hardwearing surface / retain dye. For zinc you should examine chloride/carbonate conversion coatings. They are cheap and performed at low temp.

John Tuohy
- Ireland
2002




Multiple threads were merged: please forgive repetition, chronology errors, or disrespect towards other postings [they weren't on the same page] :-)



Anodizing ZA27 die cast material

Q. I have a customer that is looking for an anodized finish of a material that is call ZA27. He is telling me this is a zinc die-cast with 27% aluminum. I would not think that that could be done with conventional sulfuric acid process. Is it possible with one of the other types?

Michael Pecjak
- Mentor, Ohio, USA
2002


A. You are correct, zinc anodizing requires an altogether different chemistry, which can include phosphates, silicates, aluminates, chromates, vanadates and/or tungstates. The process and product also differ considerably from aluminum anodizing.

ANODIC COATING FOR ZINC AND ZINC ALLOYS per MIL-A-81801A [affil link or DLA]: 6.1.2

...During the anodizing of zinc, a complex fritted compound (of fused particles) is formed by anodic spark discharge beginning at about 65 to 70 volts. The coating is hard, porous, absorbent, and has excellent masking properties. It is thicker, harder, and more corrosion resistant than zinc chromate (MIL-C-17711 [affil link or DLA]) or phosphate conversion coatings MIL-DTL-16232 [affil link or from DLA] ...

Eastern Alloys, Inc.: "Zinc anodizing is...recommended for marine atmospheres or for aggressive environments. The green ceramic-like coating is nonconductive and is particularly resistant to salt water." 'The Zinc Alloys Property Guide' shows ZA27 to have very good anodizing properties (www.eazall.com/techlit/Zinc%20Alloy%20Guide.pdf).

However, zinc anodizers are few and far between. A response to thread 13606 stated that the process "never gained commercial acceptance because the equipment set up was prohibitively expensive." - Robert H. Probert

One supplier is CHN Anodizing, Pawtucket, RI.

Ken Vlach [deceased]
- Goleta, California

contributor of the year Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.


Ed. note: The struck-through link no longer exists and was not captured by archive.org



Q. MIL-A-81801A [affil link or DLA] is inactive for design. What other specs cover anodizing of Zinc?

Jerry Mandel
Aerospace - Richardson, Texas
2006




Multiple threads were merged: please forgive repetition, chronology errors, or disrespect towards other postings [they weren't on the same page] :-)



Q. I'm master student taking master in design technology in University of Technology MARA, Shah Alam, Selangor, Malaysia.My research is on the uses of zinc in Malaysian craft. I would like to use anodizing technique on pure zinc. My question; is it possible to anodize pure zinc?

Thanks,

Noor Adila Mohd Rajili
Student - Shah Alam, Selangor, Malaysia
2005


A. Yes it is possible, and it can produce a very corrosion resistant coating. It is not often done in production, perhaps because the required anodizing voltages (100 to 200 volts) are too dangerous to employ with the usual methodology of exposed bus bars and contacts.

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


A. Anodic oxidation of zinc and its alloys:
20 gm potassium hydroxide
1 lit water
45 °C temp.,15-30 A/dm2

or

60 gm potassium dichromate
1 lit water
0,5 A/dm2 , 15-20 °C temp
According to Fedotjew, Grilikhes: Electropolishing, Anodizing and Electrolytic Pickling of Metals, Teddington 1960 [adv: this book on AbeBooks]

Goran Budija
- Cerovski vrh Croatia


Q. Thanks for the info (last letter). I would like to know what type of equipment should I use for anodising pure zinc, and the price and picture as well. As I know zinc cannot be soldered, I will cast pure zinc to make a product that I want to propose. Is it suitable to anodise the cast zinc product?

Thank you.

Noor Adila Mohd Rajili [returning]
Master Student - Batu Caves, Selangor, Malaysia





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