A passivation certificate is the written evidence that a stainless steel surface was chemically passivated to a named specification and that the result was tested. It is not a certificate that the steel is stainless, and it is not a material test report. Engineers who ask what is a passivation certificate are usually holding one of three different documents: a one-line certificate of conformance, a passivation test report with data on it, or a vendor letter that says “passivated” and nothing else. Only the first two have standing in an audit, and only the second tells you anything about the surface.
What the certificate proves, and what it cannot
Passivation removes free iron from the surface and lets the chromium-rich oxide reform. The result is invisible. A passivated part looks the same as an unpassivated one, so the record is the only way a purchaser, an inspector or a validation engineer can tell that the process happened and worked. The certificate of passivation carries that burden. It cannot prove the passive layer will survive service, and it cannot substitute for the degreasing step that comes before the acid. It proves that on a given date a defined lot of material went through a defined process and passed a defined test. Anything beyond that is inference.
What ASTM A967 and ASTM A380 require the record to contain
ASTM A967 is the specification. Its certification clause applies when the purchase order asks for it, and it requires the supplier to state that the material was passivated in accordance with A967 and to identify the acceptance test used to verify it. A test report is furnished when the order calls for one. ASTM A380 is a practice rather than a specification. It describes cleaning, descaling and passivation methods and the tests that check them, and leaves the record to the purchaser’s quality system. In pharmaceutical and medical device work, 21 CFR 211 and 21 CFR 820 do the rest: they require that a process whose result cannot be fully verified by later inspection is controlled and documented.
A complete passivation record, whichever standard governs, carries these items:
- Specification and treatment: ASTM A967 with the nitric or citric treatment designation, or the A380 method, plus any owner specification number.
- Solution: acid type and concentration, bath or circulation temperature, and immersion or contact time as they were run, not as the specification allows.
- Pre-clean: how the surface was degreased and the water-break check, because acid does not passivate through oil.
- Rinse: final rinse water quality and, for circulated systems, the endpoint conductivity or pH that closed the rinse.
- Verification: the acceptance test used, the practice letter under A967, the result, and who witnessed it.
- Lot identification: part numbers, quantity, heat numbers or the system tag and the drawing revision.
- Date, location, and the name and signature of the person who performed the work and the person who released it.
The ASTM A967 acceptance tests at a glance
A967 lists six practices. The purchaser chooses the one written on the order, and the certificate must name it. Each detects something slightly different and each suits a different kind of part.
| Practice | Test | What it detects | Typical use |
|---|---|---|---|
| A | Water immersion, alternating one hour wet and one hour dry for 24 hours | Free iron that rusts when wetted | Machined parts and fittings in a job shop |
| B | High humidity, 24 hours at 97 percent relative humidity and about 38 °C | Free iron on parts that cannot be immersed | Assemblies and batches of small parts in a humidity cabinet |
| C | Salt spray per ASTM B117 for 2 hours | Free iron and marginal passivation | Parts with a corrosion requirement in service |
| D | Copper sulfate, 6 minutes wet | Free iron, shown by copper plating onto it | General parts; A967 excludes it for food-processing surfaces |
| E | Potassium ferricyanide-nitric acid, the ferroxyl test | Free iron at very low levels, shown as blue spots | Welds, tanks and installed piping where sensitivity matters |
| F | Damp cloth held on the surface for 24 hours | Free iron on large surfaces | Tanks and vessel walls too large to immerse |
The practice letter on the certificate tells the reader how closely the surface was checked. A part that passed Practice E has been examined more sensitively than one that passed Practice F. Neither is wrong; they answer different questions, and the purchaser’s order should have picked one for a reason. How each test is run in practice is covered on our passivation testing page.
Certificate of conformance vs passivation test report
A certificate of conformance is a signed statement that the work met a named specification. It is short, often one page, and its value lies in the signature and the traceability to a lot. A passivation test report records what was actually measured: the test practice, the specimen or location, the observation and the pass or fail call, with the process parameters alongside. The two are not interchangeable. A conformance certificate without a report behind it is a promise; a report without a conformance statement is data with nobody taking responsibility for it. Regulated purchasers normally want both on the same document or cross-referenced by lot number. For a job-shop batch of parts, a one-page certificate that cites the practice and the result is usually enough. For an in-place system in a pharmaceutical plant, the report becomes part of installation qualification and needs the full parameter set.
What an auditor reads first
An FDA investigator, a notified body auditor or a customer quality engineer reads a passivation certificate in a fixed order. First, does the specification on the certificate match the specification on the drawing or the purchase order? A certificate to A380 when the drawing says A967 Citric 3 is a finding. Second, is the lot identification tight enough that this certificate cannot be attached to a different batch? Third, was a test done, which one, and is there a result rather than a checkbox? Fourth, are the process parameters inside the range the specification allows, and do the temperature and time make sense together? Fifth, who signed it, and is that person on the supplier’s approved list? Only after those five does an auditor look at anything else on the page.
How to verify a passivation certificate you did not witness
Most certificates arrive with the parts and were never witnessed. Verification is still possible. Compare the heat numbers on the certificate with the material test reports for the same parts. Ask the supplier for the bath log or solution analysis for the date shown; a citric or nitric bath that is titrated on a schedule leaves a record. Confirm the test practice suits the part; a damp cloth result on a 10 millimeter fitting is a mismatch. Where the risk justifies it, run an independent check: a ferroxyl test on a sample from the lot, or a chromium to iron ratio measurement on a coupon by surface analysis. For installed systems, verification is easier, because the passivation contractor should have left a circulation log with temperature, time and rinse endpoint against the clock.
Red flags on a passivation certificate
- No test practice named, or “tested” with no method and no result.
- Process parameters listed as a range copied from the specification rather than the values used that day.
- A temperature and time that do not match the treatment designation on the same page.
- Lot identification that covers “all parts shipped” with no quantity and no heat number.
- A copper sulfate result on parts destined for food contact, where the standard excludes the method.
- A certificate dated before the parts were machined or welded, which means the surface tested is not the surface delivered.
- A signature block with a company name and no person.
Any one of these is a reason to hold the parts and ask questions. Two or more usually mean the passivation was never tested at all.
What to require from a passivation provider before the work starts
The certificate is only as good as the order that asked for it. Write these into the purchase order or the scope of work: the governing specification and edition; the treatment designation or method; the acceptance test practice and, for in-place work, the locations to be tested; the rinse endpoint; the lot or system identification that must appear; a sample certificate from a previous job so the format is seen before commitment; and the name of the person who will sign. Ask whether the provider keeps bath titration records and how long they are retained. For pharmaceutical work, ask that the certificate be issued in a form that files directly into the IQ package. A provider who cannot answer these questions before the job will not produce a usable certificate after it.
What Paul Industries does
After in-place passivation of a piping system, tank or water loop, Paul Industries issues a passivation report that records the specification and treatment, the acid, concentration, temperature and contact time as circulated, the pre-clean and water-break check, the rinse endpoint, the verification test with its locations and results, the system tag and drawing references, the date and the technicians who performed and released the work. After batch passivation of OEM stainless parts we issue a certificate of passivation per lot that names the A967 treatment, the test practice and the result, tied to the customer part number, quantity and heat numbers. Both are signed by a named person and formatted to file into an installation qualification or a device history record. Our passivation services page describes the in-place and batch work the certificate stands behind.
Standards referenced: ASTM A967 · ASTM A380 · 21 CFR 211 · 21 CFR 820 · ASME BPE · ASTM F86
Frequently asked questions
What is a passivation certificate?
A passivation certificate is a signed document stating that a defined lot of stainless steel parts or an identified system was passivated to a named specification, usually ASTM A967, and that a named acceptance test was performed with a stated result. It identifies the lot, the date, the treatment and the person responsible. It is distinct from a material test report, which certifies the alloy, not the surface treatment.
Does ASTM A967 require a certificate on every order?
No. The A967 certification clause applies when the purchase order or contract specifies it, and a test report is furnished when the order asks for one. If the order is silent, the supplier may passivate correctly and issue nothing. Purchasers in regulated industries therefore write the certificate and report requirement into the order rather than assuming it.
What is the difference between a certificate of conformance and a passivation test report?
A certificate of conformance states that the work met the specification and is signed by the supplier. A passivation test report records the actual test practice, location or specimen, observation and result, alongside the process parameters. The certificate assigns responsibility; the report supplies the evidence. Regulated purchasers usually require both, on one document or cross-referenced by lot number.
Which A967 practice letter should appear on the certificate?
The one the purchase order specified. A967 lets the purchaser choose among water immersion, high humidity, salt spray, copper sulfate, potassium ferricyanide-nitric acid and damp cloth. The certificate must name the practice used, because each has a different sensitivity and different restrictions. A certificate that says only that the parts were tested, with no practice letter, is incomplete.
Can a passivation certificate be issued without running a test?
A certificate of conformance can be signed on the basis of process control alone, and some suppliers do that for low-risk parts. Under A967, though, the certification is expected to identify the acceptance test performed. For cGMP equipment, medical devices and anything entering a validation package, a certificate with no test result is a weak record and most quality units will reject it.
How long should a passivation certificate be kept?
As long as the record it supports. For pharmaceutical equipment that means the life of the system plus the retention period the quality system applies to installation qualification records. For medical devices it follows the device history record and the device master record retention rules under 21 CFR 820. The supplier should retain the bath and test logs for at least the same period.
Does a certificate of passivation still apply after the parts are welded?
No. Welding creates a new heat-affected surface with oxide and depleted chromium, and machining or grinding embeds fresh iron. A certificate covers the surface as it existed on the test date. Parts that are welded, ground or machined afterwards need a new passivation and a new certificate that references the finished condition, which is why in-place systems are passivated after the last weld.
Who is allowed to sign a passivation certificate?
A named individual with authority under the supplier's quality system, typically a quality or production supervisor who witnessed or reviewed the process record and the test. A company name without a person, or a signature that cannot be traced to an approved signatory list, is one of the first things an auditor questions. The signer accepts responsibility for the statement.
Is a passivation certificate issued for citric passivation as well as nitric?
Yes. ASTM A967 covers both nitric and citric treatments with numbered designations, and the certificate simply states which one was used along with the concentration, temperature and time. The acceptance tests are the same for either chemistry. A certificate that names citric passivation is not a lesser document; the test result is what matters.
What does a passivation test report for an installed WFI loop include?
The system tag and isometric or P&ID references, the pre-clean method and water-break check, the acid, concentration, circulation temperature and contact time logged against the clock, the rinse endpoint conductivity, the test practice and each test location with its result, deviations and their resolution, and the names of the technicians who performed and released the work. Photographs of test locations are common.
Is a material test report the same thing as a passivation certificate?
No. A material test report, sometimes called a mill cert, certifies the chemistry and mechanical properties of the alloy heat as it left the mill. A passivation certificate certifies a surface treatment applied later, usually by a different party. Both belong in the record, and the heat numbers on the material test report should match those on the passivation certificate.
How can a passivation certificate from a new supplier be checked?
Match the heat numbers to the material test reports, ask for the bath titration log for the date on the certificate, confirm the test practice suits the part geometry, and run an independent ferroxyl or copper sulfate check on a sample from the lot before accepting the shipment. A supplier with a real process will produce the bath log without difficulty.
Does ASTM A380 have a certification clause like A967?
Not in the same form. A380 is a standard practice that describes cleaning, descaling and passivation methods and the tests used to check them; it leaves documentation to the purchaser's requirements. When a drawing calls out A380, the purchase order should say what record is wanted, or the supplier will decide. Many purchasers cite A967 for the certificate and A380 for the method.
What if the certificate names a different specification than the drawing?
Treat it as a nonconformance until resolved. A certificate to A380 against a drawing that calls for A967 Citric 3, or the reverse, means either the wrong process was run or the wrong form was filled in. Ask the supplier for the process record, determine which happened, and either re-passivate to the drawing or document a justified deviation with quality approval.
Can one passivation certificate cover several lots or heat numbers?
It can, provided every lot and heat number is listed and each was processed under the same parameters on the same date. A certificate that lists multiple heats but one set of parameters and one test result should state which lot the test sample came from. If lots were run on different days or in different baths, they need separate certificates or separate entries.
Related: Passivation Standards Explained: ASTM A967 and AMS 2700 · Passivation Testing & Verification Services · Passivation Services · What Is Passivation? · Passivation in the Pharmaceutical Industry: Why & When · ASTM A380: Cleaning, Descaling and Passivation of Stainless Steel · Request a quote