Letter 26009

Does my vendor's COLD passivation process for 300 series stainless steel meet the specs? [Tennessee]  

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Is there a cold process for satisfying the requirements of QQ-P-35C [link is to spec at TechStreet] Type VII or does the process have to be accomplished with a warm to medium nitric acid bath. Currently a subcontractor that is finishing parts for my company is maintaining that a cold bath, with extended soak time, satisfies the requirements of QQ-P-35C. (I am aware that the spec is now ASTM A-967 [link is to spec at TechStreet] )

I would appreciate a reply at the earliest....

JAMES SARLES
Ordnance Engineering - BRENTWOOD, TN, USA

James, if you take a Type VII bath (Nitric 3 in ASTM nomenclature) and use it at room temperature (70-90 F), you have a Type VI bath (Nitric 2). Unless your print calls out the bath, I'd guess you're OK to do that: they're used on similar alloys. The time is 30 minutes minimum rather than 20.

You know, if you take the opinion that QQ-P-35 was replaced by ASTM A 967, then in paragraph 6.1.1.5 of the ASTM it allows "Other combinations of temperature, time, and concentration of nitric acid, with or without other chemicals, including accelerants, inhibitors, or proprietary solutions, capable of producing parts that pass the specified test requirement." The specsmanship hassles come should you have to go the "QQ-P-35 becoming AMS-QQ-P-35 which will eventually be superseded by AMS-2700 [link is to spec at TechStreet]B" route.

Lee Gearhart
- East Aurora, NY

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