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Phosphatizing standards -- MIL-DTL-16232

Q. Is there a QPL (document ID) for DOD-DTL-16232?

Mr. R. Andrew
- Phila. Pennsylvania

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,

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

Closely related historical posts, oldest first ...

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


Suchart Pancharoen
- Lincoln, Nebraska

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):

  Conversion/Phosphate Coatings- AMS2473 [affil. link]
  Conversion/Phosphate Coatings- AMS2474 [affil. link]
  Conversion/Phosphate Coatings- AMS2475 [affil. link]
  Conversion/Phosphate Coatings- AMS2480 [affil. link]
  Conversion/Phosphate Coatings- AMS2481 [affil. link]
  Conversion/Phosphate Coatings- AMS2485 [affil. link]
  Conversion/Phosphate Coatings- AMS2486 [affil. link]
  Conversion/Phosphate Coatings- DOD-P-16232 [ed. note: replaced by MIL-DTL-16232 [affil. link or from DLA] ]
  Conversion/Phosphate Coatings- MIL-C-13924 [affil. link]
  Conversion/Phosphate Coatings- MIL-C-5541 [affil. link or DLA]
  Conversion/Phosphate Coatings- MIL-F-495 [affil. link]
  Conversion/Phosphate Coatings- MIL-M-3171 [affil. link]
  Conversion/Phosphate Coatings-Other
  Conversion/Phosphate Coatings Fed TT-C-490 [affil. link or DLA]

Douglas A. Hahn
- Rocky Mount, North Carolina

MIL-DTL-16232 Class 4 Questions

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

Reading the documentation MIL-DTL-16232 [affil. link or 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

Ivan Santos
shop employee - Sao Jose dos Campos, SP, Brasil
October 23, 2018

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 [affil. link or from DLA] Type Z Class 3?

J Barge
Metals worker - Brighton, Michigan
October 15, 2021

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,

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

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