Curated with aloha by
Ted Mooney, P.E. RET
The authoritative public forum
for Metal Finishing 1989-2025
-----
Chemical ratios for nitric acid passivation of stainless steel
Q. When AMS2700, QQ-P-35, and A967 call out a nitric acid concentration (ie 25%) Do they mean 25% 42 Baume Nitric Acid (1 part 42 Baume nitric acid to 3 parts water), or 25% total nitric acid, meaning your 42 Baume nitric acid is roughly 67% and you have to factor for the 33% that is water? If my math is correct, it would be 2.68 parts water for every part 42 Baume nitric acid if I do need to account for the fact that it is 67% nitric acid and not 100%.
Will- Connecticut
January 21, 2025
A. We appended your inquiry to a thread where Ken Vlach (R.I.P.) had answered it.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. Ted,
Just FYI for everyone: The (now cancelled) QQ-P-35 references a second document (O-N-350) which defined the nitric acid used in the passivation bath recipes as the 67%/42 Baume commercially available stuff.
If your copy of ASTM A967 or AMS 2700 (both derived from QQ-P-35) is missing this information, it is an OLD COPY. Both documents have since rectified the oversight.
Ray Kremer
Stellar Solutions, Inc.
McHenry, Illinois
January 24, 2025
Ed. note: Thanks for bringing this up to date, Ray!
⇩ Related postings, oldest first ⇩
Q. We want to develop a small in-house passivation process to be used for limited qty parts (clinicals).
I have ASTM A967 but would like a free copy of qq-p-35 so we can get the chemical concentration numbers. We already have a lab being used for electro polish development so the equipment is in place to use for small quick batch process of passivation.
Are the volume % based upon 100% Nitric Acid or are they in ratio to the commercial available 70% solution you purchase from the distributor?
Eric Harmonymedical instruments - Woburn, Massachusetts
2003
A. QQ-P-35C can still be freely downloaded at the Defense Department's ASSIST site (http://assist2.daps.dla.mil/quicksearch/ ⇩). When last checked, it was identical to SAE's QQ-P-35C (canceled) [link is to free spec at Defense Logistics Agency, dla.mil].
The volumetric concentrations are based upon the use of 67 wt% HNO3, Technical Grade Nitric Acid (not 70 % reagent grade). Same forASTM A380
& A967.
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
Ed. update: That site for MIL specs is now https://quicksearch.dla.mil/qsSearch.aspx.
Please see Ray Kremer's important update of Jan 24, 2025 regarding volumetric concentrations.
A. Both the DOD QQ-P-35C [from DLA] and the AMSQQP35 [canceled] have been canceled and are no longer specifications to be used for passivation.
QQ-P-35c is replaced by ASTM A967 except for aerospace, which should use AMS2700B (replacement for AMSQQP35 [canceled]).
Commercial citric acid formulations are an alternative to the nitric formulations.
Lee Kremer
Stellar Solutions, Inc.
McHenry, Illinois
Q. I just checked for the latest revision for AMSQQP35 [canceled] And the SAE website is still showing Revision: MAY 1998, I cannot find where this has been (Canceled and replaced with AMS2700 B) can you please let us know where we may find this information?
Thank you,
Jim DentonAnodizer - Elkhart, Indiana
2003
A. AMSQQP35 [canceled] was canceled in April of 2003 by SAE/AMS Committee B, reconfirmed in the September meeting. It was canceled in favor of AMS2700.
Lee Kremer
Stellar Solutions, Inc.
McHenry, Illinois
Most of my suppliers have their own standard of passivation process and they are not certain whether they conform to the AMS2700 B standards. What must I ensure that exist in the passivation process of my suppliers before I declare that it is within the AMS2700 B standards.
Masrurah Marzuki- Singapore
2006
A. As others have mentioned in this thread, when QQ-P-35 was cancelled it was replaced by ASTM A967, and by AMSQQP35
[canceled] for aerospace jobs; AMSQQP35 was then replaced by AMS2700.
My follow-up question to this is, when specs on a print for non-aerospace jobs call out QQ-P-35 Type II (or any other Type), is there any requirement to process by any particular way within ASTM A967, or can ANY process in ASTM A967 be used?
- Madison Heights, Michigan, USA
April 15, 2010
Q, A, or Comment on THIS thread -or- Start a NEW Thread