The main passivation standards are ASTM A967 (the current specification for chemical passivation of stainless steel), ASTM A380 (cleaning and descaling), and AMS 2700 (aerospace passivation, which superseded the old QQ-P-35). They define the passivation chemistry, process, and the tests used to prove the passive layer was restored.
The key passivation standards
| Standard | What it covers |
|---|---|
| ASTM A967 | Chemical passivation of stainless steel parts – nitric and citric methods, plus test methods |
| ASTM A380 | Cleaning, descaling, and passivation of stainless steel surfaces and systems |
| AMS 2700 | Aerospace passivation (Method 1 nitric, Method 2 citric) – superseded QQ-P-35 |
| QQ-P-35 | Legacy federal passivation spec, now largely replaced by ASTM A967 / AMS 2700 |
ASTM A380 is covered in depth on its own page: ASTM A380 — cleaning, descaling and passivation explained — including how A380 differs from A967, pickling versus passivation, the acceptance tests A380 defines, and the documentation an A380 scope should produce.
How passivation is verified
After passivation, the passive layer is confirmed with tests such as water-break, copper sulfate, ferroxyl (potassium ferricyanide), or high-humidity exposure – and documented. On regulated systems, that documentation is part of the turnover package.
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Frequently asked questions
What is ASTM A967?
ASTM A967 is the standard specification for chemical passivation treatments of stainless steel parts. It defines nitric and citric passivation processes, cleaning requirements, and acceptance tests for verifying that free iron has been removed and the passive film restored. Paul Industries passivates to A967.
What does ASTM A967 require for passivation?
It requires a clean surface free of oils and scale, a specified passivation treatment (nitric or citric with defined concentration, temperature, and time), thorough rinsing, and passing one or more acceptance tests confirming freedom from free iron and surface contaminants.
What acceptance tests are in ASTM A967?
ASTM A967 lists tests including water immersion, high-humidity, salt spray, copper sulfate, potassium ferricyanide-nitric acid (ferroxyl), and free-iron detection. The chosen test must show no rust staining or blue indication of free iron for the part to pass.
What is the difference between ASTM A967 and A380?
ASTM A967 covers passivation treatments and acceptance tests for parts; ASTM A380 covers cleaning, descaling, and passivation of equipment and systems, including in-situ procedures. They are complementary, and Paul Industries works to both depending on whether the work is parts or installed systems.
Does ASTM A967 specify citric or nitric?
Both. ASTM A967 defines nitric passivation treatment codes and citric passivation treatment codes, allowing either chemistry. The user or engineer selects the method and treatment code appropriate to the alloy and application; both are compliant when performed and tested correctly.
What are ASTM A967 treatment codes?
Treatment codes designate specific passivation processes, such as nitric types (Nitric 1, 2, 3, etc.) and citric types, each defining acid concentration, temperature range, and immersion time. Selecting the correct code for the alloy ensures effective, standard-compliant passivation.
Do I need ASTM A967 passivation for cGMP equipment?
cGMP process equipment is routinely passivated to ASTM A967 and A380 because regulators expect corrosion-resistant, contaminant-free product-contact surfaces. Meeting A967 with documented acceptance testing supports the corrosion-control and cleanliness evidence auditors look for.
How do you document ASTM A967 compliance?
Paul Industries records the treatment code, chemistry and concentration, temperature, dwell time, rinse-water quality, and the acceptance-test method and result. This package demonstrates the part or system met ASTM A967 and supports cGMP and IQ/OQ documentation.
Does ASTM A967 cover cleaning before passivation?
A967 requires the surface be clean and free of contaminants before passivation but points to ASTM A380 for detailed cleaning and descaling procedures. Grease, oil, and heavy scale must be removed first, since passivation acids do not remove organic soils.
Which acceptance test should I choose under ASTM A967?
It depends on the part and sensitivity. Copper sulfate and ferroxyl tests are fast free-iron indicators; high-humidity and water immersion are less aggressive; salt spray is more severe. Paul Industries selects a test appropriate to the alloy and application and documents the result.
Does ASTM A967 apply to welded assemblies?
Yes. Welded stainless assemblies are passivated and tested to A967 after welds are cleaned of heat tint. Because welds create chromium-depleted zones, passivation and acceptance testing across weld areas are important for verifying restored corrosion resistance.
Is ASTM A967 the same as AMS 2700?
No, but they overlap. AMS 2700 is an aerospace passivation specification with its own methods and tests; ASTM A967 is broader and widely used across process industries. Some specs reference both. Paul Industries works to A967/A380 for cGMP process equipment.
Can ASTM A967 passivation be verified in the field?
Yes. Portable tests such as copper sulfate and ferroxyl can verify free-iron freedom on installed equipment. Paul Industries performs in-situ passivation to A380 and applies A967 acceptance tests on site, documenting results for the customer’s records.
What happens if a part fails ASTM A967 testing?
A failure indicates residual free iron or incomplete passivation. The part is re-cleaned and re-passivated, then retested. Common causes are inadequate pre-cleaning, exhausted or contaminated solution, or wrong concentration, temperature, or dwell time for the alloy.
Does ASTM A967 guarantee corrosion resistance forever?
No. It verifies the passive film was properly restored at treatment. Service conditions like chlorides, abrasion, and deposits degrade the film over time, so periodic re-passivation may be needed. A967 confirms the starting condition, not lifetime performance.
Does Paul Industries passivate to ASTM A967 nationwide?
Yes. Paul Industries passivates parts and systems to ASTM A967 and A380, in its Kilmarnock, Virginia shop and via field crews in all 50 states, with acceptance testing and documentation. Call 201-450-8280 to scope an A967 project.
What is ASTM A967 passivation?
ASTM A967 is the current ASTM specification for chemical passivation of stainless steel, covering nitric and citric passivation methods and the test methods used to verify the passive layer.
What is the difference between ASTM A967 and ASTM A380?
ASTM A967 specifies passivation methods and tests; ASTM A380 covers the broader cleaning, descaling, and passivation of stainless steel surfaces and systems. They are often referenced together.
What is AMS 2700?
AMS 2700 is the aerospace passivation standard (Method 1 nitric, Method 2 citric) that superseded the legacy QQ-P-35 federal specification.
Do you provide a passivation certificate?
Yes. Paul Industries documents passivation with the applicable test results and a certificate/turnover package for your quality records.
Passivate to spec
Paul Industries is a single-source supplier, installer, and validator – one accountable partner from design through documented startup. Tell us about your project and we will scope it.