EN 10204 3.1 vs 3.2 Mill Certificates: What the Difference Means

When you ask a supplier for a mill test certificate, the type matters as much as the document itself. EN 10204 is the European standard that classifies inspection documents for metallic products, and its categories tell you who tested the steel, whether the results are specific to your batch, and how independent the verification is. Understanding them stops you accepting a weak document for a critical application.

The four EN 10204 document types

• 2.1 — Declaration of compliance: the manufacturer states the product meets the order, with no test results. Weakest form.
• 2.2 — Test report: the manufacturer states compliance and gives results of non-specific testing (not necessarily your batch).
• 3.1 — Inspection certificate: results of specific testing on your actual product, validated by the manufacturer's authorised, independent-of-production inspection representative.
• 3.2 — Inspection certificate: as 3.1, but countersigned by an independent third party or the purchaser's inspector as well as the manufacturer.

Which one should you demand?

For most commercial steel, a 3.1 is the practical standard: it certifies testing on the specific heat/batch you are buying and is validated by someone independent of the production department. For safety-critical or high-consequence applications — pressure equipment, structural steel in major projects, or anywhere a failure is catastrophic — a 3.2 adds independent third-party countersignature and is often specified by code or client.

A 2.1 is a promise. A 3.1 is specific test data validated in-house. A 3.2 adds an independent signature. Match the document to the consequence of failure.

A certificate is only as good as its verification

Whatever the type, the certificate must reconcile with the physical steel. Check that heat numbers on the certificate match the markings on the product, that the chemistry and mechanical results meet your specified grade, and — for high-value orders — confirm results with independent positive material identification (PMI) and testing. A perfect-looking 3.2 is worthless if the heat numbers do not match what is in the container.

Fold the certificate type into your purchase order and your inspection scope. For step-by-step verification, read the mill test certificate verification guide, and use third-party inspection to reconcile the paperwork against the actual metal.