Metal finishing Q&As since 1989
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Anodizing 2024: Bare vs. Clad
Q. I am newbie here so please be nice. I am also a newbie in the field so please forgive me if I got certain things wrong.
So, recently we have been anodizing Clad aluminum panels that are cladded like a sandwich (A5052 sheet on both sides and A1100 in the middle). The overall thickness is 3mm (0.5mm for A5052 and 1mm for A1100. Due to the recent problems we had to restart the testing and we found out that the Cladded sheets (a5052xa1100xa5052) are producing lower quality color compared to the uniform A5052 sheets. Although the film thickness remains relatively similar (±2µ). Is there any possibility that the Clad aluminum is having issues with conductivity due to the A1100 sheet in the middle? If you are too busy to type all the possible issues, could you at least suggest relevant research papers? I cannot find any articles on this issue. Thank you everyone!
- Ansan (South Korea)
April 18, 2024
A. Hi Foteh. I have a general understanding of what 1100 is (relatively pure aluminum sometimes used as the outside "purer" layer of Alclad) and 5052 (a strong corrosion resistant grade) ... but I don't know enough to understand the purpose of cladding 1100 with 5052 :-)
1100 is more suited to decorative anodizing than 5052, and more conductive, so I'm not understanding why you are having this problem. That cladding is very thick, so you're surely not penetrating it by pretreatment or anodizing.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
⇩ Related postings, oldest first ⇩
Q. Our company designs replacement, repair and modification parts for light aircraft, particularly seaplanes and their floats. Many of them are made from thin sheets of 2024 Alclad material per AMSQQA250 /5 because of its high strength and good formability. Most of these exterior parts are then anodized (AMSA8625) and then primed and painted for maximum corrosion protection because of their exposure to seawater. A finishing house once told me that bare 2024 material actually takes the anodizing process better than clad material. Is this true? Does the thin layer of "pure" aluminum disrupt the anodizing, or is it "lost" or somehow "reduced" in the process? Does the cladding give any additional benefit when the part is anodized? Given the above situation, would bare or clad material result in a more corrosion-resistant product? I have checked all the standard references, including Electroplating Engineering Handbook [on AbeBooks or eBay or Amazon] and the Anodizing Specification itself, but I can find no reference to this topic. Any information you can provide would be greatly appreciated.
Thank you,
Bruce Taylor- Kingston, Washington
2003
"The Surface
Treatment &
Finishing of
Aluminium and
Its Alloys"
by Wernick, Pinner
& Sheasby
on
AbeBooks
or
eBay
or
Amazon
(affil links)
A. You have been given bad advice. Alclad 2024 is more corrosion resistant than 2024 in both bare and anodized conditions. The anodic coating grown on the cladding is also more abrasion resistant than that on 2024 for both conventional and hard anodize.
The cladding also provides backup corrosion protection if the anodized layer is damaged, e.g., by flexure. The only precaution regarding anodizing Alclad is due to the thinness of the cladding: ALCLAD 2024 "Nominal cladding thickness is 5% on gauges under 0.062 in. (1.57 mm) or less; 2.5% on gauges over 0.062 in. (1.57 mm)." This amounts to only 0.0016 inch for 0.063 inch material. References: Alcoa Al-2024techsheet.pdf, MIL-A-8625F (paragraph 3.7.2.2), The Surface Treatment and Finishing of Aluminum and Its Alloys by S. Wernick, R. Pinner, P.G. Sheasby, 6th Edn., p. 429-426 or 5th Edn. p. 370-376. ⇨
- Goleta, California
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.
Q. Regarding ALCLAD 2024T3 per AMSQQA250/5
Our customer's spec calls for a conductivity of 31.5 % MAX IACS, we bought the right material but with a conductivity of 34-35.5 %
Question,Is it possible to find this material as per the same spec, with the required conductivity of MAX 31.5 % ?
I was wondering myself, how could we find the same material with a different conductivity if both of them have the same chemical composition and they are both as per the AMS spec?
Thank you in advance.
mechanical manufacturing - Montreal, QC, Canada.
2007
Q. Is there any difference in result in term of bonding when you process phosphoric anodizing on Al-Clad vs bare aluminum?
Liz Nguyen- Oklahoma-City, Oklahoma
June 5, 2013
Q. Can you please confirm the Alclad thickness for 2024 T3 Material? The 5% they talk about, is that 5% per side or for total material thickness? Thanks.
Andre van der merweairway - Gauteng south africa
July 25, 2016
July 2016
A. Hi Andre. It's per side. But cladding on one side is possible, although less common; and the 5% is a nominal number, not an exact guarantee.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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