A mill test certificate 3.1 vs 2.2 is not a ranking of quality — it is a question of who ran the test and who signed the paper. Get it wrong and the buyer's quality team holds the shipment; agree to a heavier certificate than the order needs and you pay for tests and lead-time nobody asked for. This is one of the most common documentation arguments between an export supplier and an industrial buyer, and it is settled by one sentence in a European standard.
Mill test certificate 3.1 vs 2.2: the one-word difference
A mill test certificate (MTC) — also called a mill test report (MTR), material test certificate, or inspection certificate — is the document that certifies a metal's chemical composition and mechanical properties and ties those results to the specific heat, or cast, of material that was delivered. The number in "3.1" or "2.2" is the document type defined by EN 10204, the European standard for inspection documents on metallic products.
The difference between a 2.2 and a 3.1 is one word: specific. A 2.2 is based on non-specific inspection — the manufacturer's routine test results, which may come from other material in the same production run, not necessarily the heat you shipped. A 3.1 is based on specific inspection — tests run on the products actually being supplied, and signed by an inspection representative who is independent of the production department.
| Document | Name | Inspection basis | Who confirms it |
|---|---|---|---|
| 2.1 | Declaration of compliance | None — no test values | The manufacturer |
| 2.2 | Test report | Non-specific inspection | The manufacturer |
| 3.1 | Inspection certificate 3.1 | Specific inspection | The manufacturer's inspector, independent of production |
| 3.2 | Inspection certificate 3.2 | Specific inspection | The manufacturer's inspector plus the purchaser's nominated inspector or an official inspector |
That table answers most of "what is the difference between a 2.2 and a 3.1 certificate." Everything past it is consequence.
What EN 10204 actually defines
EN 10204:2004 is the standard titled "Metallic products — Types of inspection documents," published on 25 October 2004. It replaced the 1991 edition and is adopted nationally as DIN EN 10204:2005-01 and equivalent designations. British Standards still list BS EN 10204:2004 as the current version, and it remains the document European and most international buyers name when they ask for a material certificate.
The 2004 revision simplified the old system. The 2.3 works certificate was dropped, and the old inspection-certificate variants 3.1A and 3.1C were folded into the new 3.2. The old 3.1B became today's 3.1. So a buyer whose old purchase order says "3.1B," or a distributor who still offers "3.1A," is speaking the 1991 dialect — map it to 3.1 or 3.2 before you confirm anything.
The standard splits its four document types by whether the inspection was non-specific (2.1 and 2.2) or specific (3.1 and 3.2). That split is the real dividing line, not the "how serious does it look" impression the numbers give.
EN 10204 2.2 vs 3.1: specific vs non-specific inspection
Think of the two this way. A 2.2 is a restaurant showing you the kitchen's hygiene inspection report. A 3.1 is the restaurant testing the exact dish on your plate and handing you the result.
- A 2.2 test report declares the goods comply with the order and provides results from the manufacturer's non-specific inspection. Those results prove the process is capable, but they are not guaranteed to come from your delivered heat. For a commodity fitting, a decorative steel, or a buyer who only needs grade traceability, a 2.2 is often exactly enough.
- A 3.1 inspection certificate declares compliance and reports results from specific inspection of the goods supplied. The chemistry and mechanicals are tied to the heat you shipped, and the certificate is signed by the manufacturer's inspection representative — an inspector who, by the standard, must not sit in the production department. This is the certificate that satisfies a structural, pressure, or machinery buyer's quality plan.
Here is where suppliers lose the argument: a 3.1 is not third-party inspection. Many buyers, and more than a few sales reps, assume "3.1" means an external body witnessed the test. It does not. The 3.1 signature is still the manufacturer's own inspector. Third-party, purchaser-nominated inspection is 3.2.
Inspection certificate 3.1 vs 3.2: when you need a third party
A 3.2 inspection certificate is a 3.1 with a second signature: the manufacturer's independent inspector and either the purchaser's nominated inspection representative or the inspector named in the applicable official regulations.
Where 3.2 shows up in practice:
- Pressure equipment and piping built to a regulated design code, where an authorised inspector must sign the material documents.
- Project orders — oil, gas, power, water — where the buyer or its engineering contractor nominates a third-party inspection (TPI) agency and requires its stamp on the MTC.
- Public and regulated procurement where the official regulations themselves prescribe an inspector.
If your order does not name a third party to witness the test, you almost never need a 3.2 — and paying for one "to be safe" adds cost and scheduling you cannot bill the buyer for.
Which certificate does your order need?
Your order's wording decides this, not the product's price. Run it through four scenarios.
Scenario A — the spec says "certificate of compliance" or "grade confirmation only." The buyer wants to know the grade is what was ordered. Quote a 2.1 or a 2.2, name the type in your quotation, and move on. Flag yourself if the drawing hints at a pressure or structural application, because that is where a 2.2 stops being enough.
Scenario B — the spec names a grade plus tested properties. Structural steel, fasteners, fittings, flanges, pressure parts, or anything the buyer will re-test. Quote a 3.1. This is the answer for the large majority of industrial export orders.
Scenario C — the spec names an inspector, a design code, or "TPI." Quote a 3.2, and confirm who the third party is before you promise a shipping date; the inspector's availability sets the date, not your production line.
Scenario D — the spec says only "certificate" or "MTC." Do not guess. Ask which EN 10204 type the quality plan requires and write the answer into the quotation. A one-line clarification before you quote beats a held container after you ship.
| Buyer's wording | Certificate type | Who signs | Friction to plan for |
|---|---|---|---|
| Grade confirmation | 2.1 | Manufacturer | Low — no test values at all |
| "MTC" with no detail | 2.2 (confirm) | Manufacturer | Low — clarify the type in writing |
| Grade + tested properties | 3.1 | Manufacturer's independent inspector | Medium — tests on the delivered heat |
| Code, TPI, or named inspector | 3.2 | Manufacturer + third party | High — inspector scheduling |
The 5 mistakes that get a shipment held
- Shipping a 2.1 where the order said 3.1. A 2.1 carries no test values; a buyer expecting chemistry and mechanicals reads it as a missing document, not a cheaper one.
- Calling a 3.1 "third-party." It is the manufacturer's own inspector. If the order truly needs an outside witness, you owe a 3.2 — and promising a 3.1 will not close it.
- A certificate heat number that does not match the packing list. The whole value of a 3.1 is traceability. If the heat on the certificate, the tag on the bundle, and the packing list disagree, the document is worthless even if every test passed.
- Reusing one certificate across several heats. A 3.1 covers the heat it names. Shipping two heats under one certificate is the fastest way to turn a clean order into a claim.
- Leaving the certificate type out of the quotation. "MTC included" means whatever the buyer later decides it means. Name the type — "3.1 to EN 10204:2004" — in the quote, the PI, and the packing list.
Before you ship a document-controlled order, run this list:
- The quotation names the EN 10204 type, not just "MTC"
- The certificate's heat or cast number matches the bundle tag and packing list
- The grade and dimensions on the certificate match the order line
- The signing inspector is independent of production (for 3.1)
- Any third party named in the order appears on the certificate (for 3.2)
How to read a 3.1 certificate line by line
A 3.1 is short, but buyers reject them over fields that are easy to overlook. Check each one against the order before you send it.
| Field | What to check |
|---|---|
| Standard and type | Reads "3.1 to EN 10204:2004" — not a vague "material certificate" |
| Manufacturer and works | The producing mill, not only the trading company |
| Purchaser and order no. | Matches the buyer's PO, so their system can file it |
| Product, grade, dimensions | Matches the order line, including any dimensional tolerances |
| Heat / cast number | Matches the physical tag on the goods |
| Chemical composition | Values against the grade spec, with the test method |
| Mechanical properties | Yield, tensile, elongation, and impact where the grade requires it |
| Heat treatment | Condition the material was delivered in |
| Signature and date | Signed by the inspection representative, independent of production |
The test values are the part buyers compare against their own re-test. If the certificate's chemistry or mechanicals sit close to the limit of the grade, say so in the quotation — a buyer who re-tests and finds a marginal pass will remember the surprise at the next order.
The certificate proves the material, not the fit
Whichever mill test certificate 3.1 vs 2.2 your order resolves to, it proves the material, not the fit. A certificate tells the buyer their steel's chemistry and mechanicals, but it says nothing about whether the delivered bracket matches the drawing — and that gap is where size disputes still start. The fix belongs on the image, where the buyer's eye already is: lock the measured dimensions onto the product photo, drawn from the actual part and the actual heat, so the certificate, the spec table, and the picture all carry the same measured figures. An industrial spec diagram built this way exports at the size each marketplace requires, so the buyer can confirm the number before ordering instead of measuring after delivery.
The contrast that matters: a restyled photo or an AI-generated image can show a plausible-looking number nobody can trace to a measurement. A measured annotation pins the real value to the real edge. That is the difference between a picture and a proof, and it is why the spec sheet vs technical drawing distinction keeps coming back to which document carries a verifiable number.
FAQ
What is the difference between a 2.2 and a 3.1 certificate?
A 2.2 relies on non-specific inspection — routine test results that may not come from your delivered heat — while a 3.1 relies on specific inspection of the goods actually supplied and is signed by the manufacturer's inspector, independent of production. Same standard, different inspection basis.
Is a 3.1 certificate the same as third-party inspection?
No. A 3.1 is signed by the manufacturer's own inspection representative. Third-party, purchaser-nominated inspection is a 3.2, which adds the purchaser's nominated inspector or the inspector named in the applicable official regulations.
Does a mill test certificate expire?
An MTC has no printed expiry date, because it is a traceability record tied to a specific heat, not a licence. What "expires" is its relevance: if a project or code later requires a certificate type the original did not meet — or names a third-party inspector — you need a new document, not a new date stamp.
What is the difference between a mill test certificate and a mill test report?
Nothing substantive. "Mill test report" (MTR), "mill test certificate" (MTC), and "inspection certificate" are names for the same class of document. What decides whether it is accepted is the EN 10204 type it is issued to, not the title on the page.
Can I ship metal products without a mill test certificate?
For many commodity products, yes — unless the buyer's order, the destination's regulations, or the product's application requires one. Structural, pressure, and regulated goods almost always do. If you need to send measured dimensions and test data together, pre-shipment inspection dimension checks is where the two meet, and the discipline of labelling metal product specifications applies to the certificate pack as much as to the listing.
Sources & References
- BSI — BS EN 10204:2004, Metallic products. Types of inspection documents (current standard; replaces the 1991 edition)
- Wikipedia (DE) — EN 10204: the four document types 2.1 / 2.2 / 3.1 / 3.2, their inspection basis, and who confirms each one
- Wikipedia — Mill test report: chemical and physical certification of metal products, and the 3.1 / 3.2 definitions
- Beuth Verlag — DIN EN 10204:2005-01, Metallische Erzeugnisse — Arten von Prüfbescheinigungen
- UK Health and Safety Executive — Pressure systems: why certified material and inspection records are required
- GOV.UK — Designated standards (the framework that keeps EN standards such as EN 10204 in force)