The authoritative public forum
  for Metal Finishing since 1989
-----

citric acid Passivation with Spec. QQ-P35?

 

ASTM A967 allows for citric acid passivation, but what about QQ-P-35C [from DLA] ? I don't see any mention of Citric. Could we use it and be in compliance?

Enrique Segovia
- Monterrey, Mexico

Sorry, No! Although the spec. has been discontinued, it is still being used by many, and unless the spec. can be substituted with the ASTM standard you MUST use the specific chemicals and concentrations noted in the mil-spec. ASTM standard is much more lax in the methods to achieve passivation- concerning itself with the end results as opposed to the means.

Bill Grayson
- Santa Cruz, California, USA

---

Hello Enrique!

Unfortunately QQ-P-35 mandates that you use one of the solutions that are listed, so you can't use citric acid solutions and certify to QQ-P-35, UNLESS you take exception to that portion of the specification. We have a number of vendors who take exception to various portions of our drawings or specifications before they process our parts, and these requests often find their way to my desk for engineering analysis. Sometimes we allow the exceptions, sometimes not, but you should ask.

Good luck!

Lee Gearhart
metallurgist - E. Aurora, New York
 

---

 

Enrique:

Nobody should be citing QQ-P-35C [from DLA] as a specification for passivation, since it has been long since cancelled. However, many companies take a long time to change prints, etc. The U.S. DOD has cancelled it in favor of ASTM A967, which allows the use of citric acid formulations on all applications except aerospace.

If you are doing aerospace parts you need to use AMS2700 or AMSQQP35 [canceled]. AMS2700 allows the use of citric, AMSQQP35 [canceled] does not, at this time.

So, unless you are doing aerospace parts specified to AMSQQP35 [canceled], you can use citric formulations. See our Web Page for more details on this. Call us if you do not understand.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois