What Nadcap Chemical Processing Accreditation Covers in Anodizing and Conversion Coating
A finishing shop can hold ISO 9001, run a clean-looking line, and still fail a Nadcap audit, because the two things measure different layers. ISO 9001 asks whether you follow your own documented process. Nadcap asks whether that process actually produces a coating that meets the specification, on a production job, with the bath chemistry and test data to prove it. If you source anodizing or conversion coating for aerospace and defence work, the difference shows up in your receiving inspection. Here is what the accreditation covers, how the audit criteria are structured, and what to check before you accept a certificate at face value.
What Nadcap Is and Who Runs It
Nadcap is a cooperative accreditation programme for special processes in aerospace and defence, administered by the Performance Review Institute. Prime contractors and suppliers agree on the audit criteria, and accredited suppliers are audited against them by specialist auditors rather than by a general QMS auditor. The point is consistency: one supplier is audited the same way as another, so a buyer does not have to re-audit every shop on their own.
It is process-specific, not company-wide. A shop accredited for anodizing is not thereby accredited for painting, passivation, or heat treat. Each process is a separate scope line with its own criteria, its own audit and its own findings.
How the Audit Criteria Are Structured
Chemical processing sits under AC7108, with general requirements in AC7000. The slash sheets under AC7108 are where the real scope lives — each one is a distinct process family, and a certificate lists exactly which ones were audited.
| Criteria | Covers | Typical scope lines |
|---|---|---|
| AC7000 | General Nadcap accreditation requirements | Quality system, documentation, corrective action |
| AC7108 | Chemical processing, base criteria | Facility-wide requirements for the shop |
| AC7108/8 | Anodizing (not for metal bond) | Sulphuric acid, hard anodize, chromic acid, dye, seal, PTFE impregnation |
| AC7108/11 | Conversion coating | Aluminium, non-hexavalent chrome alternatives, steel, titanium |
| AC7108/4 | Solution analysis and testing in support | Salt spray, coating weight, coating thickness, conductivity, adhesion, Taber wear |
| AC7108/12 | Cleaning, descaling, passivation, electropolishing | Steels, nickel and cobalt alloys, titanium |
Reading that list tells you what to expect from a supplier. A shop holding AC7108/8 with a “seal” and “hard anodize” line can quote hardcoat work against MIL-A-8625 with the process validated. A shop holding only AC7108/11 is set up for conversion coating and aluminium chem film, which is a different line, different bath control and a different set of tests.
What the Auditor Actually Checks
Process Control and Bath Chemistry
Anodizing and conversion coating are chemistry-driven processes, so the audit starts with bath control: concentration limits, temperature limits, analysis frequency, and what happens to parts when a bath drifts out of range. Records have to show the bath was in control while your parts were in it, not just that it was analysed at some point that month. Load configuration, racking and contact points come next, because a part that shadows another one in the rack gets a thinner film.
In-House Test Capability Under AC7108/4
If a shop performs its acceptance testing internally, that testing gets audited too. Coating thickness measurement, coating weight, salt spray exposure, conductivity and adhesion tests each have their own requirements around equipment calibration, procedure and technician competency. This is the part that catches suppliers out: the coating is fine, but the thickness gauge used to accept it was last calibrated three years ago.
Audit on Real Production Work
Nadcap audits are performed against live jobs, with real parts and real travellers. The auditor follows a part through the line — pre-clean, etch, anodize or conversion coat, seal, inspect — and checks that what the procedure says is what the operator does, and that the recorded values match what the instruments read. Any finding requires root cause and corrective action, not just a correction.
Reading a Certificate Scope
The certificate itself is a summary. The authoritative scope — which slash sheets, which alloys, which specifications, and the expiry date — lives on the Qualified Manufacturer’s List at eAuditNet, and procurement teams should check it there rather than filing the PDF. Accreditation length is typically granted in 12-month cycles and can be extended on merit to 18 or 24 months depending on audit history, so a certificate near its expiry date is a normal and expected state, not a red flag — but an expired one is.
Two things to verify specifically: that the accredited scope covers your specification (a supplier accredited for MIL-A-8625 Type II is not automatically covered for Type III, and MIL-DTL-5541 Class 1A and Class 3 are separate lines), and that the accredited facility is the facility that will run your parts, not a sister plant. Our own scope and inspection equipment are listed on the certifications page.
Nadcap Versus ISO 9001 and AS9100
| Framework | What it certifies | What it does not tell you |
|---|---|---|
| ISO 9001 | The quality management system is documented and followed | Whether the anodic film meets MIL-A-8625 |
| AS9100 | QMS with aerospace additions: risk, configuration, counterfeit parts | Whether the bath chemistry was in control on your job |
| Nadcap | A specific special process is technically capable and controlled | Whether the shop runs a good QMS overall |
They stack. A shop with ISO 9001 plus Nadcap chemical processing has both the system and the technical validation; a shop with only one of them has a gap that shows up as either inconsistent paperwork or inconsistent coatings.
What It Means for Your RFQ
- Send the specification, not just the process name. MIL-A-8625 Type II Class 1 versus Type III Class 2 changes the process window and the audit scope.
- State whether the parts are flight or non-flight. Documentation, traceability and inspection depth follow from that, not from the part drawing alone.
- Ask which facility will run the work and check its scope on eAuditNet before award.
- Confirm whether the required acceptance testing is done in-house under AC7108/4 or subcontracted — subcontracted testing moves lead time and responsibility.
- Expect first-article inspection data with the first shipment, and keep it as the baseline for repeat orders.
Where the requirement is conductivity rather than paint adhesion, the relevant line is Class 3 under MIL-DTL-5541 — covered in the Class 3 conductive chem film notes — and where the driver is the hexavalent chrome restriction instead, the RoHS-compliant conversion coating route and the non-hexavalent chrome alternatives under AC7108/11 are what the scope should list. Conversion coating to MIL-DTL-5541 is quoted against the class, and general anodizing service work against type and class, so both belong on the RFQ line rather than the process name alone. For thin film work outside chemical processing, see the separate PVD coatings for aerospace route, which is not covered by AC7108.
Frequently Asked Questions
Does Nadcap accreditation guarantee good parts?
No. It means the process was audited and found controlled at the time of the audit. Parts still need inspection, and process drift between audits is exactly why buyers keep trending first-article data across repeat orders.
Is a supplier without Nadcap automatically disqualified?
For prime-contractor flowdown requirements, usually yes for the specific process. For commercial and industrial work, no — what matters is whether the supplier can produce data that meets the specification. Ask for coating thickness records, salt spray results and calibration certificates instead.
Do we need Nadcap for medical or robotics parts?
Not usually. Those programmes are normally driven by ISO 13485 or customer-specific validation instead, and the finishing requirements are quoted against the coating specification rather than a Nadcap scope. Material and process references from ASM International are the common technical baseline there.
How often is the audit repeated?
Typically on a 12-month cycle, with merit-based extensions to 18 or 24 months for suppliers with clean audit histories. Re-audit drives the expiry date on the QML listing, which is why procurement should check the live listing rather than a stored PDF.
Sending One In
Send the drawing, the coating specification with type and class, the applicable flowdown and the expected annual quantity. If the work is for aerospace or defence programmes, note the prime contractor and any special process requirements on the RFQ so the accredited scope is confirmed before scheduling rather than after. The facility page shows the lines and inspection equipment behind those scope lines.
