EN 10204 3.1 vs 3.2: Which Certificate to Order

EN 10204 3.1 vs 3.2: the one line that decides your paperwork

You are releasing a purchase order for 5,000 hex head bolts, class 8.8, hot-dip galvanized, for a structural or pressure-piping scope. Somewhere in that order is a sentence about the certificate, and it decides what arrives:

• Say nothing, and the supplier may issue a declaration of compliance — no test data at all.
• Write “mill certificate”, and you still have not named a type: the phrase is not one of the documents EN 10204 defines.
• Write “EN 10204 3.1”, and the certificate must carry measured values traceable to the heat that became your bolts.
• Write “third-party inspection required”, and you need EN 10204 3.2, at a different cost and lead time.

Getting it wrong is not administrative: a certificate that does not cover the delivered lot fails acceptance at site, re-testing is billed to you, and a witness added late slips a packed order by weeks.

Routing in one line: commercial parts 2.2; structural, mechanical or pressure-piping fasteners with a rated property class 3.1, heat-traceable; sour service, offshore, nuclear and the higher PED categories 3.2.

What EN 10204 covers — and what it leaves to your order

EN 10204:2004, Metallic products — Types of inspection documents, replaced DIN 50049 in 2004. It does not say what to test. It defines four document types and, for each, two things: who may sign, and whether the testing applies to the material actually delivered to you.

Everything else is set by your order: type 2.1 carries no test data and is routinely offered where 2.2 was expected. An inspection document is not a product approval either — a 3.1 certificate does not make a gasket safe for drinking water.

EN 10204 and ISO 10474: two names for one subject

EN 10204 is the European designation. For steel products, the ISO document on the same subject is ISO 10474:2013, Steel and steel products — Inspection documents. Both are about inspection documents, and neither prescribes what to test.

Which name your order uses is a question for your specification: European and internationally tendered work normally names EN 10204, and that is the term used here. If a supplier offers an ISO 10474 document instead, put the question back to the specifier rather than assuming the two documents are interchangeable on your job.

The four types in one table

Type	Document name	Issued by	Testing basis	Heat / lot traceability	Independent witness
2.1	Declaration of compliance	Manufacturer	No test specific to the order	No	No
2.2	Test report	Manufacturer	Non-specific — production data for the same product, not your lot	Not guaranteed	No
3.1	Inspection certificate 3.1	Manufacturer’s authorized inspection representative, independent of the production department	Specific to the delivered lot	Yes	No
3.2	Inspection certificate 3.2	Manufacturer’s authorized representative plus the buyer’s representative or an appointed third party	Specific to the delivered lot, witnessed	Yes	Yes

Three columns carry the decision: who signs, whether the testing covers your lot, and whether anyone independent of the maker is involved.

2.2 vs 3.1 vs 3.2, type by type

Type 2.2: a report about production, not about your lot

A 2.2 test report is issued against production data — results from the same grade and process, not from the heat that became your bolts. It carries values, which is where the confusion starts; what it lacks is a traceable link between the material tested and the material in your crate. That is enough for commercial-grade parts with no specified property class and no pressure boundary.

Type 3.1: your lot, tested, signed inside the works

A 3.1 inspection certificate is issued against the lot delivered, and the signature must come from an authorized inspection representative independent of the department that produced the material. That independence is the point: whoever ran the heat-treatment furnace does not sign off their own work. For fasteners it is the default procurement gate — general mechanical and structural work, OEM parts outside safety-critical use, pressure-piping bolts, and any order where the customer’s quality system needs batch evidence. Count on roughly one to two extra weeks, because the tests run against the heat actually being shipped.

Type 3.2: the same certificate, witnessed from outside

Type 3.2 adds a second signature: the buyer’s representative, or an independent body acting for the buyer, witnesses the testing and countersigns; the content is otherwise the 3.1 content. That is what “third-party inspection required” means in a tender — it is not a synonym for 3.1, and a mill cannot produce it from its own quality department. Sour service, subsea and offshore work, nuclear and the higher PED categories are the classic triggers. And because the 3.1 signatory is independent only inside the works, an order that says “third-party inspection” has to ask for 3.2 by name.

When 3.1 is enough, and when 3.2 earns its cost

Application	Typical document	Why
Commercial hardware, no property class, no load path, no pressure boundary	2.1 or 2.2	Cost and lead time decide
General mechanical and structural work, OEM parts outside safety-critical use	3.1	The default procurement gate; a quality system that needs batch evidence
Pressure-piping bolts, or any line where the customer’s QMS asks for batch proof	3.1	Heat traceability plus measured mechanicals
Sour service, subsea, offshore, nuclear, higher PED categories	3.2	The buyer or an appointed body witnesses the testing

Cost and cycle time follow the same order: 2.1 and 2.2 cost nothing extra, a 3.1 adds roughly one to two weeks, a 3.2 roughly two to four more because an independent body has to be scheduled. Match the type to the consequence of a failure.

What a 3.1 inspection certificate must show for fasteners

A certificate saying a batch “conforms to ISO 898-1” has told you nothing you can check. A 3.1 inspection certificate is defined by carrying measured values for the delivered lot. The figures below come from ISO 898-1 and its Chinese counterpart GB/T 3098.1-2010.

Property	6.8	8.8 (d ≤ 16 mm)	10.9	12.9
Tensile strength Rm, nominal (MPa)	600	800	1,000	1,200
Tensile strength Rm, minimum (MPa)	600	800	1,040	1,220
Yield property measured	RPf (0.0048d)	RP0.2	RP0.2	RP0.2
Yield, nominal (MPa)	480	640	900	1,080
Yield, minimum (MPa)	480	640	940	1,100
Elongation after fracture, min	not specified — Af ≥ 0.20 on the fastener	12%	9%	8%
Hardness (HV)	190–250	250–320	320–380	385–435

Read the first two rows together, because that is where certificate arguments start. The class number is a labelling convention: the digit before the point, times 100, gives the nominal tensile strength, and the digit after the point gives the yield-to-tensile ratio — not the minimum. For 8.8 the two coincide at 800 MPa; for 10.9 and 12.9 the minimum sits above the nominal, so 1,020 MPa on a report for 10.9 is a genuine test value that still fails the grade. And 8.8 splits into two diameter bands, d ≤ 16 mm at 800 and 640 MPa and d > 16 mm at 830 and 660 MPa. The same designations run from 4.8 to 12.9 in our bolt property classes reference.

Heat number, and a match to the physical marking. One certificate may cover several heats, but it must list every heat, and the marking on the parts or packaging must let you match the crate to the certificate line. A certificate whose heat number appears nowhere on the goods is unverifiable however good the numbers look.

Coating values, measured — not a coating process name. “Hot-dip galvanized” describes a process; the acceptance criterion is a thickness in micrometres, and ASTM F2329 sets it for threaded fasteners in three tiers rather than one:

Thread size	Production-lot average	Lot-inspection average	Single-specimen average
Over 3/8 in [M10]	50 μm	43 μm	43 μm
3/8 in [M10] and under	43 μm	38 μm	38 μm

F2329 measures with ASTM E376 (magnetic or eddy-current) and ASTM B487 (metallographic cross-section, as the referee method). One conflict is worth a written question: class 12.9 sits at 385–435 HV, roughly the 39–44 HRC band, while F2329 prohibits hot-dip galvanizing threaded fasteners that reach 40 HRC or are made of carburized steel.

Comparing the 3.1 and 3.2 specimen: five places to look

The specimen above is synthetic: invented issuer, invented heat number, illustrative values. The same bolt sits under both document types — class 8.8, M12, one heat, one set of values. Five positions carry the comparison.

① Document type and file name, top of each sheet. Inspection certificate 3.1 on the left, inspection certificate 3.2 on the right — the only place the document commits itself, so read it first.

② Issuer block. Both sheets come from the works that produced the heat, and both carry the line “authorized representative independent of production”. That independence is internal, so a trader’s letterhead here is the common sign the document did not come from the mill.

③ Testing-basis statement. The sentence saying whether the results apply to the delivered lot or to production generally. Both sheets say the delivered lot; the right-hand sheet adds that the testing was witnessed.

④ Heat number and traceability line. One heat covering the whole lot, with the size and quantity it applies to. Match it against the marking on the parts before reading any test value: one set of results cannot describe several heats, so a mixed-heat lot needs a certificate per heat.

⑤ Third-party signature block — absent on the left, present on the right. This field separates the two documents, and on the specimen it fills the largest single area of the right-hand sheet: a named inspecting body, a verification statement, a second signature. The values are identical on purpose — 3.2 is not a different set of numbers, it is the same numbers with an outside witness behind them.

Writing the certificate requirement into your PO

The certificate becomes enforceable the moment it stops being an assumption and becomes an order line. Four things make it a delivery condition.

1. Name the type and the traceability. Keep it to one line, so the seller cannot interpret it:

Material to be supplied with EN 10204 Type 3.1 inspection certificate, heat-traceable to the delivered lot.

For risk-critical orders:

Independent third-party inspection (TPI) witnessing required; EN 10204 Type 3.2 inspection certificate.

2. State the minimum content, not just the type. Add the values you will check: measured tensile and yield, elongation and hardness for the ordered property class, the heat number matching the marking, and the coating thickness with its measurement method.

3. Make it a deliverable with a date. List the certificate among the delivery documents, not under quality notes, and give it a submission deadline — with the goods, or at least before release for shipment. A certificate requested after the containers are loaded is a negotiating position, not a requirement. This is practice from fastener sourcing, not from a standard.

4. Do not over-specify by reflex. Match the type to the consequence of failure.

One pattern is worth knowing before you draft that line. Public tender documents for municipal and water-works packages often state the requirement in local vocabulary — “manufacturer’s work test certificate”, “mill certificate”, “testing laboratory certificate” — without naming an EN 10204 type, and leave a reviewer discretion over what to accept. A supplier answering that wording literally can be compliant and still hand over a document the reviewer refuses. (Our reading of how such requirements are phrased, not a quotation from any standard.)

Before you release the PO

One type settled — now the receiving check

Choosing the type is half the job; accepting the arriving document is the other half, and the fastener receiving inspection checklist takes it line by line. The document-reading side, field by field, is in how to read a mill test certificate.

Where the project is water or wastewater treatment, the same pack carries two extra items: a PMI re-check on arrival, and a drinking-water listing where the specification asks for one. Both are set out in the document pack for water treatment fasteners.

Send us the certificate with the class and coating on your order and we will point at the line that does not hold. Whether we can supply a particular certificate type and form is agreed per order and confirmed before the contract.

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Frequently asked questions

What is the risk of using a 2.2 test report where a 3.1 certificate was ordered?

A 2.2 report is signed off against non-specific testing: the results may come from comparable production, not your batch, and heat traceability is not guaranteed. If your order names EN 10204 3.1, it does not close it.

Who is qualified to sign an inspection certificate 3.1?

An authorized representative of the issuing works who is independent of the production department — someone outside the function that ran the heat treatment. A trader’s signature does not qualify, and a third-party body is not the issuer either: SGS, Bureau Veritas or Intertek witness and countersign, which produces a 3.2 document.

When does 3.2 justify its cost?

When the consequence of a failure is high enough to pay for external eyes: sour service, subsea and offshore work, nuclear scope, the higher PED categories. It also applies whenever the buyer’s specification says “third-party inspection required”, because that phrase describes 3.2 and not 3.1.

The heat number on the certificate does not match the marking on the parts. What now?

Treat the certificate as invalid for that lot: its values describe a different heat of steel. Quarantine the shipment and request the certificate matching the marked heat.

Can a certificate of conformance be used instead of an inspection certificate 3.1?

Only if the order allows it. It declares that the product complies without carrying measured values or heat traceability, which is exactly what a 3.1 certificate is bought for — so the answer lies in your own specification and purchase order.

References

1. EN 10204:2004, Metallic products — Types of inspection documents: types 2.1, 2.2, 3.1 and 3.2; replaced DIN 50049 in 2004.
2. ISO 10474:2013, Steel and steel products — Inspection documents (positioning only).
3. GB/T 3098.1-2010: clause 5 (designation), Table 2 (minimum tempering temperature 425 °C for the 8.8 class), Table 3 (Rm, RP0.2, elongation, reduction of area, hardness, impact energy, diameter bands). Free public standard.
4. ISO 898-1:2013, Mechanical properties of fasteners made of carbon steel and alloy steel — Part 1: Bolts, screws and studs: the property system above; GB/T 3098.1-2010 is the Chinese counterpart.
5. ASTM F2329: coating thickness tiers by sampling level, per ASTM E376, arbitrated per ASTM B487; the 40 HRC / carburized-steel exclusion (year not verified in this pack).
6. Public pages behind the type definitions and authenticity checks: projectmaterials (2025); sinbo-machining (2026); huaxia-steel (2026); promisteel (2026).