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topic 2191

Alumilite Finish Needed


My customer has specified the following finish on a 2024-T6 aluminum U-bolt:"U" BOLTS SHALL BE FINISHED IN ACCORDANCE WITH Mil-A-8625 [link is to free spec at Defense Logistics Agency,]A BY A TYPE II NON-DYED OR CLEAR ANODIC OXIDATION TREATMENT. THE ANODIC COATING SHALL BE SEALED WITH A #204 ALUMILITE FINISH.

No problem with the first part, a standard sulfuric acid anodize with a clear finish. But what is and who can supply ALUMILITE? I assume this is some type of lubricant as they are looking for a non-galling film that meets specific torque/tension requirements.

David B [last name deleted for privacy by Editor]


See the responses to Letter #2131- your question is quite similar. The old ALCOA Alumilite 204 finish was actually an anodizing specification which called for 30 minutes anodize followed by a hot water seal. The MIL-A 8625A type II is essentially the same, except the seal in the MIL spec is normally a dichromate seal, "unless otherwise specified". Your customer is probably trying to say he wants a true clear anodize, and not a yellow-green finish that the dichromate seal would give. If your customer actually needs to meet the requirements of the MIL spec., there could be another problem, because with 2024 alloy it is very difficult to pass the 336-hour salt spray requirements of the MIL spec without a dichromate seal.

phil johnson
Phil Johnson
- Madison Heights, Michigan



Phil has provided you with very detailed information on Alumilite 204 finish. If an alternative finish with the appearance similar to Alumilite 204 is acceptable to your customer, I would like to suggest a Type-II anodic coating followed by nickel acetate sealing. With the latest development in anodizing technology, 0.7 mil coatings produced on 2024-T3 by MLT-II process with Ni acetate sealing are able to pass more than 3,000 hours on neutral salt spray test with respect to ASTM ASTM B117 [link by ed. to spec at TechStreet] or Mil-A-8625 [link is to free spec at Defense Logistics Agency,]F spec.


Ling Hao
- Grand Rapids, Michigan



We can help you out if you need clear anodize and a nickel acetate seal or deionized Hot water seal. The answers above are correct about hot water seal and salt spray testing. Feel free to contact myself or Tony at the plant or by E-Mail.


Bob Bramson
B&M Finishers / Prismatic Stainless Steel
supporting advertiser
Kenilworth, New Jersey

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Need to know what process "Alumilite 724" is. What is a current equivalent.

Dennis K [last name deleted for privacy by Editor]
industrial products - Erie, Pennsylvania

March 17, 2008

I know nothing about metal finishing but have a question about Alumilite.

Are kitchen utensils (vintage pie plates in particular) safe for food use? I'm wary of buying vintage utensils because what science deemed safe 50 years ago might not be considered safe now.

Any feedback is appreciated.

Ginger Strand
- Dallas, Texas

March , 2008

Hi, Ginger. Anodized aluminum is still widely sold today and I see no reason to fear it.


Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

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