QQ-P-35: the evolution of stainless steel passivation specifications and the selection of applicable standards

What was QQ-P-35?

QQ-P-35, Passivation Treatments for Corrosion-Resistant Steel, was a US federal specification covering passivation requirements for corrosion-resistant steel parts.

It appeared widely in engineering drawings, purchasing documents and processing specifications for stainless steel components, particularly in manufacturing sectors with stringent material, surface condition and process requirements.

Stainless steel passivation uses appropriate chemical treatment to remove free iron and certain surface contaminants. This can support the formation or maintenance of a protective, chromium-rich passive film and improve corrosion resistance.

The outcome nevertheless depends on the material, previous processing, treatment procedure and service environment. Citing a specification alone does not guarantee corrosion performance.

When was QQ-P-35 cancelled?

The DLA ASSIST record identifies 11 September 1998 as the date of the final cancellation notice for QQ-P-35C, Notice 3.[1]

That notice directed attention to ASTM A967 or SAE AMS-QQ-P-35 and included separate guidance for aerospace applications. These documents already existed at the time; their development did not begin only after QQ-P-35C was cancelled.[1][2]

The notice also explicitly limited its replacement guidance to US Department of Defense activities. It should not be applied automatically to other uses. Even within that scope, suitability for the particular application must be evaluated before citing a replacement document.[1]

Cancellation therefore does not mean that existing parts must immediately be processed differently, or that other standards are fully equivalent. Where drawings still cite QQ-P-35, first establish the original revision, treatment type and customer requirements.

Which standards should be assessed as a replacement for QQ-P-35?

Related specifications should be assessed against the application and applicable revision.

ASTM A967/A967M: chemical passivation of stainless steel parts

ASTM A967/A967M addresses chemical passivation treatments for stainless steel parts, including different treatment methods and verification requirements. Engineering, manufacturing and purchasing teams can refer to it when specifying processing requirements.[3]

The material grade, specified treatment, inspection requirements and applicable revision must still be established. The designation alone is insufficient.

SAE AMS2700 and AMS-QQ-P-35: aerospace and specific requirements

SAE records show that AMS-QQ-P-35 was issued in May 1998, and that AMS-QQ-P-35A was cancelled in February 2005. SAE AMS2700 is another specification relevant to stainless steel passivation.[2][4][5]

Where documentation still cites AMS-QQ-P-35, consult the formal cancellation document and the relevant AMS2700 revision. The responsible authority should determine the appropriate approach after reviewing treatment types, applicability and acceptance requirements.

Differences between standards mean that processing procedures and acceptance outcomes cannot be assumed to be identical solely from their names.

What if an older engineering drawing still specifies QQ-P-35?

Legacy references can remain on drawings for industrial components manufactured over many years. Engineering, purchasing and quality teams should establish:

For aerospace, defence and other components subject to stringent quality controls, drawing requirements should not be changed without the necessary formal approval.

1. Specification revision: Which QQ-P-35 revision is cited, and is a treatment type specified?
2. Material information: Are the stainless steel grade, heat treatment and previous processing conditions defined?
3. Applicable standards: Does the customer specify ASTM A967/A967M, SAE AMS2700 or another standard?
4. Acceptance requirements: Are particular tests, surface conditions or quality documents required?
5. Engineering approval: Has any proposed substitution been approved by the responsible design or customer authority?

How specification changes affect precision surface treatment

A revised specification can affect processing, inspection methods, quality documentation and technical communication between suppliers; the change may extend beyond the document designation.

For precision stainless steel parts, surface treatment quality is closely related to material composition, prior processing, contamination and subsequent service conditions. A passivation enquiry should therefore clarify the processing objective, material condition and acceptance requirements, as well as the specification designation.

The KUN-QI perspective

A clear understanding of engineering drawings and technical specifications is fundamental to assessing processing requirements. For parts citing historical documents such as QQ-P-35, material information, surface requirements, specified standards and acceptance criteria should be established before selecting a suitable approach.

KUN-QI follows developments in international materials and surface treatment specifications, with an emphasis on matching processing requirements to actual application conditions.

For precision stainless steel surface treatment, individual prototypes, small batches or development trials, please provide material details, engineering drawings and technical requirements so that KUN-QI can discuss a suitable processing assessment.

References

1. DLA ASSIST: QQ-P-35 record and Revision C Notice 3 cancellation notice.

2. SAE International: AMSQQP35 official record.

3. ASTM International: ASTM A967/A967M.

4. SAE International: AMSQQP35A official record.

5. SAE International: AMS2700G official record.

Technical note: This is a historical review and discussion of industrial applications, rather than a report of a recent cancellation. Actual processing, testing and acceptance remain governed by the applicable formal specification revisions, engineering drawings and customer-approved documents. The linked records were available at the time of checking; the linked revision is not necessarily appropriate for every project.