ASTM A967 vs. AMS 2700? Which is the right passivation spec?

A. First question: The current ASTM versions are ASTM A380 "Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems" and ASTM A967 "Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts".

It is relatively easy to modify a passivation process to satisfy ASTM A380 , and ASTM A967, and QQ-P-35C (canceled) [link is to free spec at Defense Logistics Agency, dla.mil] and AMS2700 (primarily, a little paperwork). Have the plater do so, and then certify to multiple standards. (Lee Kremer has pointed out that A380 is not a Specification, only a Practice).

Second question: A guessing game? "Standard passivation" is meaningless unless the standard is specified.

A. As Ken says, ASTM A380 should not be used as a passivation specification, and QQ-P-35 has been canceled. The 3 consensus specifications used at this time, and that should be used for all specifications of passivation are:

ASTM F86 for Orthopedic implants,
AMS2700for Aerospace,
ASTM A967 for all other applications.
There are other in-house specifications for some companies.

A-380 has a lot of excellent recommendations on general cleaning etc. of stainless steel, but should never be used as a passivation spec.

AMSQQP35 [canceled] is being canceled in favor of AMS2700 (at the moment it is version B)

You should never ask for "standard passivation" on imports. Always specify exactly what you want-- e.g., ASTM A967 01e, Citric 4 or AMS2700 B Nitric 1. If you do not specify, they can use whatever they want, even ways that are not in any of the specifications! What is standard to you may not be standard to them.

A. The "right" spec is the one that your customer requires. ASTM A967 is certainly more lax regarding passivation verification testing, which can be a good thing or a bad thing. AMS2700 requires both solution and per-lot corrosion resistance testing. Since you're considering an AMS spec, I assume you have aerospace customers. If not, I would stick with ASTM. Terry Lycans Aerospace - Dayton, Ohio, USA A. One of the differences is in the definition of 'a lot' for testing purposes. ASTM A967 uses the same definition as did the old Federal Specification, QQ-P-35.html, which allowed one to consider all production of similar material done in 24 hours to be a single lot. AMS2700 considers different parts, or the same part made at different times, to be different lots (with the exception for parts with the legacy QQ-P-35 called out, when you can use the older definition.) You can guess the increase in the amount of testing involved. There are other differences- ASTM A967 allows the use of any mix of nitric and water, so long as you show it works (Nitric 5 solution). The ASTM doesn't default to the nitric acid formulations, as AMS2700 does. AMS2700 has an iron concentration maximum, absent from ASTM A967. AMS2700 exempts 440C from testing. And there are other differences. We design our own parts, and do our own passivation in house, and hence prefer the testing requirements of ASTM A967. If you're having it done for you, the testing is someone else's problem, so you might consider AMS2700. Lee Gearhart metallurgist - E. Aurora, New York

Terry/Lee, Thanks for your responses. They were helpful.

A. The two standards are essentially equivalent. Both contain a carryover of QQ-P-35C with the addition of the more recently developed citric acid based process. The AMS standard is used by the aerospace industry while the ASTM standard is used by generally everyone else.

QQ-P-35B contained six nitric acid bath Types. The C revision removed four of those and added two, leaving as options, Types II, VI, VII, and VIII. A967 renumbers those to 1 through 4 (there is no such thing as A967 Type 6 or 7) while 2700 restores the missing four for a total of eight Types.

A. Hi Dan. There is no AMSQQP35 [canceled] anymore. It was cancelled in early 2003 in favor of AMS2700.

Regards,

A. Hi Bill. As you see, we added your question to a thread which hopefully answers it. Good luck.

Regards,

A. Hi Justin. It seems to me that ASTM F86 is only for orthopedic implants.

Regards,

A. ASTM A967 is a standard covering treatments to passivate stainless steel (regardless of what it will be used for) and then test methods to show that it was passivated.

F86 refers to surgical implants of any metallic alloy, and basically just says "do whatever treatment is applicable and appropriate to ensure corrosion resistance".

And then there's ASTM F1089, which is test methods to show stainless steel surgical instruments have been passivated.

As far as the stainless steel passivation process itself, you're pretty much always going to work your way back to A967. But if it's a medical instrument or implant, then you're also going to have to show the appropriate tribute to an F standard.

A. Tom,
Correct. Method 1 is subdivided into 8 Types (corresponding to the types in old QQ-P-35) while Method 2 is not subdivided.

So the question is, did they mean "Method 1 Type 2" or "Method 2 OR Method 1 Type 2"

A. Juan,
If you process parts within the parameter ranges given by ASTM A967, and one part per lot passes one of the listed test methods, then all you can say is you ran the parts in accordance with A967.

Determining the suitability of A967 for your specific parts is up to you, or requirements set by your customer. I.e., in some cases the best minimum time for your process may be longer than A967's stated minimum time. Some customers ask for the parts to pass salt spray testing longer than A967's required 2 hours, etc.

"Validation" as a term is not defined or used in A967 and means several different things depending on who you talk to. The best thing do to is ask the customer what they expect.

This auditor you are dealing with, what organization is he with? Your customer? What requirement or standard is he auditing you against, since clearly it is not A967?

A. Jan,
Both standards are based heavily on the old QQ-P-35.

Revision C of QQ-P-35 had some of the formulas taken out, so it had only types II, VI, VII, and VIII. ASTM A967 renumbered those to nitric 1 through 4, while AMS2700 brought back the ones that had been removed and has types 1 through 8.

Both standards express the formulas as volume percent of nitric acid, though only 2700 actually mentions the nitric stock solution is 42 °Baumé/67 wt%. This is actually an oversight of A967 that will be corrected in the next revision.

 Ray,

Thank you for answering.
Indeed also my conclusion is that it is an omission.
In the ASTM A967 and the nitric acid concentrations mentioned must be percentage by volume of a reagent of 67 wt.% nitric acid.

A. Hi Shrinivas. We appended your question to a thread which should clearly answer it for you: ASTM F86 is "Standard Practice for Surface Preparation and Marking of Metallic Surgical Implants" -- but get back to us if you are still confused.

But please describe your situation. Is your business surgical implants, or are you with a passivation shop, or what? Thanks.

Regards,

A. Prajan,
You have that correct, so I'm not sure why you are confused. The text for that in both standards was copied almost directly from the old MIL-STD-753. A967 later added duplex and precipitation hardening grades, which were not mentioned as either "recommended" nor "not recommended" in the original MIL 753.

A. Andrea,
AMS2700 is intended for use in the aerospace industry, while everybody else pretty much goes with ASTM A967.

In general with the new standards you should be able to switch over to citric acid , but that does still depend on what's stated on the part drawing/purchase order/etc. and what your customer agrees to accept.

  Thank You for your response.