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Hard anodize for 2024 Al alloy

Q. Can 2024 aluminum alloy material be anodized in Hard anodizing bath (H2SO4 conc. :150 - 175 g/L& Temp:4 to -2 °C )? What is the suitable current density setting? Please advise.Thank you.

Neo Tiang Hua
- Singapore


A. Hi,

Of course, the 2024 alloy can be hard anodized. It is a tad more difficult but you can anodize it nonetheless!

You can control your tank:

T = -2 deg C to 0 deg C
Free H2SO4 : 200 to 230 g/l, at around 210 g/l, you obtain the hardest coating.
Current density = about 40 Amps/sqft

Best of luck,

Dr. Hocine Djellab
anodizing shop - Verdun, Quebec, CANADA

A. Hardcoating 2024 (or any other hi copper alloys) is a problem.

My shop does regular anodize & hardcoat anodize.

There are many proprietary systems used for hardcoating hi copper alloys. For the last 40 years we used a system called IMPERV-X which hardcoated 2024 & other hi copper alloys no problem. Other people use pulse rectifiers or other so called tricks.

We gave up our IMPERV-X system last year & now do not do much hi copper alloy hardcoating. We have a few jobs that are 2024 for hardcoat that require a very thin coating (.0002"-.0004" thick) & those jobs are no problem in our normal hardcoat process, but we can not do full spec thickness (.002"±.0004") jobs anymore.

David A. Kraft
- Long Island City, New York

A. We do 2024 and normally use 32 ASF.

Martin Trigg-Hogarth
Martin Trigg-Hogarth
surface treatment shop - Stroud, Glos, England

Q. Hard anodize of 2024. Is a coating thickness of 0.003" a bit too much for 2024 aluminum.
What is the effect of Type III anodize on a shot peened surface?

Russ Sherman
metallurgist - Santa Monica, California, USA

A. Yes, Russ, that is probably a bit too high to specify, especially on 2024 alloy, unless there is a particular reason. The most conventional thickness would probably be .002".

Why was the surface shotpeened? Sometimes that is done to counter fatigue stresses, so it is important for you to know that hard anodizing will destroy that compressive effect; parts should not be hard anodized if there will be fatigue loading. If you are able to express your question in terms of what you are trying to do in your own specific situation, rather than in the abstract, we may be able to offer better help. Thanks.

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

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