Authoritative Answers, Fun, & Aloha -- no cost, no passwords, no popups
(as an eBay Partner & Amazon Affiliate we earn from qualifying purchases)

Home /
Site 🔍
pub     mobile?
Metal finishing Q&As since 1989


Flaking anodize on Alloy 2024 aluminum

none is made possible by ...
this text gets replaced with bannerText
spacer gets replaced with bannerImages

Q. We are having issues with our dyed parts on 2024 aluminum. The Dye keeps flaking off along with some of the anodize we believe. We've tested the Voltage and its consistent during the runs. We use 50% sodium hydroxide in all tanks requiring pH balancing including the dye tanks. Could this be the issue?

Joey roth
Chem La Tech/ Anodizer - New port Richey, Florida
January 30, 2024

A. Hi Joey,
The dye is IN the anodizing rather than on it; so if the dye is flaking off, yes, the anodizing is flaking off.
Luck & Regards,

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

⇩ Related postings, oldest first ⇩

Q. We have some black anodized 2024-T851 piece parts which exhibit flaking of the anodize, exposing the base metal. The parts see a thermal cycle of -50C to 160C with a ramp rate of 3C/min. We have used this cycle previously and have never experienced flaking. Could this be attributable to poor surface preparation prior to anodize and/or improper anodizing conditions?

Bill Park

Multiple threads merged: please forgive chronology errors :-)

Q. We had a problem with anodizing and dying some parts in gold. There appears to be "corrosion" marks on the finished surface.

corrosion on gold anodized parts

Material: 2024T3 ALCLAD
Sulfuric Acid Type II anodizing

I wonder what variables may have caused this problem and how I should investigate / validate each of the variables.

Jason Chow
- Calgary, Alberta
April 23, 2021

A. Hi Jason. Unfortunately that photo is poorly focused so it's hard to say whether you have flaking, areas of pitting, or whatever. Based on the location of the discoloration it doesn't look like burning. From what I can see I'd probably call it "splotchy"; it's possible the part just wasn't clean enough. Maybe you can measure the anodizing thickness in the splotchy spots vs. the other areas?

One way to answer your question of what to investigate / validate would be to say "Why do you want to reject this part?". I am not saying the part is satisfactory by any means, I'm saying that very clearly and specifically annunciating exactly what you feel is wrong with it can be an essential step in fixing it.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey
April 2021

Q. Thank you Ted. This part was rejected first time by the customer when we first ran it. Then we reworked it and still got the same defect. Here is a better picture.:

corrosion in anodized 2024 aluminum

Jason Chow [returning]
- Calgary AB
April 26, 2021

A. Jason.
2024 is a problem alloy to anodize, I'm not saying it cannot be done but problems with burning and accepting dye are always a factor. My general rule for 2024 is stay away from etching as much as possible, if possible don't etch. Use a good deox and stay longer in it. One last thing, a slow ramp to the correct current 8-12 min is always a help.

drew nosti
Drew Nosti, CEF
Anodize USA
supporting advertiser
Ladson, South Carolina

A. Are you sure it is 2024. Did it turn black in the alkaline etch? Do you know if has been heat treated, hence disrupting the copper coming out of alloy? Do we have floating soil in the anodizing post rinsing that can enter the pores and limit dye adsorption?

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina

Q. Thank you Robert. According to our customer, the material is 2024-T3 ALCLAD. It did look blackish after etching. We don't know if it was heat treated or not before the customer sent the part to us. The post anodizing rinse appears to be clean without floating soil if you are referring to floating soil to naked eyes. We anodized and dyed another part (of same material according to the customer) on the same load from the same customer and had no such a problem.

Jason Chow
- Calgary, AB

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
& Software

About/Contact  -  Privacy Policy  -  ©1995-2024, Pine Beach, New Jersey, USA  -  about "affil links"