Summary for mil-dtl-13924 class 2 vs class 4 Discussion
Mil-13924 class 2 vs class 4 is the core question here, but the excerpt only shows the opening request: the poster says they have a requirement for black oxide per MIL-DTL-13924 and asks about the difference between class 2 and class 4. Because the answer text is not included in the source provided, no specific technical conclusion can be confirmed from this thread excerpt alone. The page is therefore best understood as a black oxide specification question under MIL-DTL-13924, with the missing reply presumably addressing the class distinction and any finish or performance implications. If you need the exact guidance from the thread, the full answer text would be necessary.
Q. I have a requirement for Black Oxide per MIL-DTL-13924
[⇦ this spec on DLA] Class 2 on a 304, 316, welded assembly subjected to intermittent high heat approaching 900 °F. My suppliers don’t do class 2 and suggest class 4. I know the EPA difference, but I cannot discern the functional difference from the spec. Can someone help? Thanks
Bob West
QA rep – Phoenix, Arizona
February 21, 2017
A. Hi Bob. It seems from a quick read that the biggest difference is that Class 4 requires the parts to pass a 96-hour salt spray test without any supplemental treatment — which your shops apparently aren’t worried about passing.
I think you’ll find paragraph 6.3.2 helpful to your understanding. Although it’s problematical for anyone to interpret a spec as it pertains to your parts, when they really don’t know much about your parts, Class 4 sounds quite reasonable to me for your type 304 & 316 parts. Good luck.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
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February 2017
Thanks Ted. I’ve read it several times and just couldn’t grasp a functional difference. I appreciate the help!
Bob West [returning]
– Phoenix, Arizona USA
February 21, 2017