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What is MIL-STD-171 finish 5.3.11 or 5.3.2.1 with MIL-C-16173, GR 3 ?

Quoting new part for DOD customer. Protective Finish call out is: Finish 5.3.1.1 or 5.3.2.1 of MIL-STD-171 with MIL-PRF-16173 [on DLA, GR 3 supplementary oil treatment. Matte Surface
I've read the MIL standard and besides knowing that the finish should be "Heavy" phosphate type can anyone shed some light on what the finish should be. Is it Black Oxide with oil dip?
Thank you,
Greg

Gregory Kaplan
precision job shop - Wood Dale, Illinois
February 6, 2008

Very simply, it's either heavy manganese or zinc phosphate with an oil preservative. Black oxide it's not - in fact, while black oxide provides little corrosion protection, each lot of mil spec phosphate must pass a 90 minute dry salt spray and a 24 or 48 hour wet (i.e. oiled) salt spray test depending on the type of oil preservative specified. Mil spec phosphate also requires the processing house to submit their phosphating procedure to the government thru the machine shop contracted to manufacture the parts. Once approved, there can be no deviation from that procedure (and you're locked into that phosphating house). There are lots of phosphate houses out there; I would advise you to check out their previous performance on government contracts. Otherwise you could end up with completed parts that the government won't buy!

Milt Stevenson, Jr.
Syracuse, New York
February 15, 2008

what is AMSQQP416, paragraph 4.5, 4.5.1,4.5.2 , I have a client who require his part to comply with such requirement.

Ada Sun
metal parts - Dongguan, Guangdong, China
April 25, 2009

Hi, Ada. We have linked your mention of this cadmium plating spec to a specifications clearing house from which you can download it immediately. There are other clearinghouses, or you can go to SAE to download the spec -- but, sorry, whichever way you go, this is a copyrighted spec which is not available for free. Happy trails.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 27, 2009

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