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Ted Mooney, P.E. RET
Pine Beach, NJ
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MIL-DTL-5541 Chem film fails humidity test
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(to provide context, hopefully helping readers more quickly understand the Q&A's)
MIL-DTL-5541 [on DLA] specifies a chromate conversion coating for aluminum. In the USA, the slang "chem film" is often used as a synonym. Two proprietary trade names for the process, "Alodine" and "Iridite" are so common that people often use them generically to refer to the process.
Q. Have a finishing problem on a following material after 10 day 95% humidity test.
Material: .090 thk. AL ALLOY 5052 H32 PER AMSQQA250
Finish: Chem film per MIL-DTL-5541
[on DLA] TYPE II (Trivalent Chromium) CLASS 3 Color Clear.
My question is why the finishing is not holding up, or do I need to use harder finish like Anodize
Help !!
- Ronkonkoma New York
December 29, 2022
A. Hi Onder.
MIL-DTL-5541
[on DLA] requires 168 hours of ASTM B117 salt spray testing and specifies how to determine whether the sample passed or failed. You are doing a 10-day humidity test instead of the 7-day salt spray test, and my guess is that that they should pass, but what is your pass/fail criteria since MIL-DTL-5541
[on DLA] is silent on that?
There is a lot you haven't told us yet, like whether this is a new problem or a long-running one, whether it affects all parts or just a particular part, whether it affects all of that style part or just a small percentage, and whether you are doing the processing in house or buying the processing service. If you are buying the finishing service, have you considered the possibility that the parts were missed and not chem-filmed? What test or evidence do you have that they were processed per the spec?
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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