Metal finishing Q&As since 1989

Phosphatizing standards -- MIL-DTL-16232

Q. Is there a QPL (document ID) for DOD-DTL-16232 [ed. note: replaced by MIL-DTL-16232 [from DLA] ]?

A. Hi R.

It doesn't appear that a QPL-16232 exists, and Section 3.1 "Preproduction inspection" of DTL-16232 seems to me to imply that there is no such QPL.

Luck & Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
August 7, 2022

⇩ Related postings, oldest first ⇩

Q. Is Phosphatizing a standard process? Is there an industry or a Mil standard for this?

Thanks!

Surely! It all depends what type you want, and if you are the design source or a subcontractor. I'll cut-and-paste a typical list used in aerospace (MIL and AMS specifications):

MIL-DTL-16232 Class 4 Questions

Q. Hi, a client requested a class 4 zinc or manganese phosphate.

Reading the documentation MIL-DTL-16232 [from DLA] , I got confused with the statement:

Class 4
"Chemically converted (may be dyed to color as specified)
With no supplementary coating or coating as specified"

Looking for more information on what is class 4 I found that, according the paragraph 3.2.4d and 3.2.5, it shall not be treated in a chromic acid rinse. And that's clear for me.

In paragraph 3.7.3 and 3.7.5, for each type of phosphating class 4 systems, states that the phosphates that have been chemically converted by reaction with a reagent containing an inorganic salt, items shall be dyed to a specific color and should endure 72 hours of salt spray if supplementary treatment is applied, and 24 hours if no supplementary treatment is applied (Table II).

My issues:
  - What is the inorganic salt? Its something that is added to the phosphating solution? is post phosphating solution bath?

  - The dyeing process can be achieved by immersion in an aqueous aniline solution, just as an anodizing process?

My Zinc phosphate line use a commercial product (SurTec 610). And we been doing class 1, 2 and 3.

Thanks for the attention on this issue, I tried to look on the forums for this kind of topic before posting, but I could not find anything.

Best regards

Ivan Santos

Q. I can only find the channel I am using in galvanized condition, can I still zinc phosphate the end product per MIL-DTL-16232 [from DLA] Type Z Class 3?

A. Hi J. The phosphatization process should work. Galvanizing can be phosphatized essentially as described in MIL-DTL-16232. But it will be non-compliant with the spec, or at best questionably compliant, because the spec itself says its for ferrous metal, and it's probably a stretch to call a galvanized surface ferrous :-)

Luck & Regards,

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