Definition
A Mill Test Certificate (MTC), sometimes called a Mill Test Report (MTR), Material Test Certificate or Inspection Certificate, is the document issued by a steel mill that certifies the chemical composition, mechanical properties and dimensional conformity of a specific consignment of steel. The MTC is the legal and engineering link between the steel that left the mill and the structural code the project must satisfy. Every legitimate structural steel, stainless steel, aluminium, GI or brass shipment ships with an MTC. The classification of that MTC under EN 10204 determines whether the project's inspector accepts it.
EN 10204 classes
2.1, Declaration of compliance, no test results. Rarely acceptable on structural projects. 2.2, Test report based on non-specific (general production) inspection results. Acceptable for commodity carbon steel where no critical performance is required. 3.1, Inspection certificate issued by the manufacturer's QA function, with test results from the specific consignment, signed by mill QA independent from production. The GCC infrastructure default. 3.2, Inspection certificate validated by an independent third party (TUV, SGS, Bureau Veritas, Lloyd's) or by the purchaser's authorised inspector. Required for bridges, lifting structures, oil & gas critical service and pressure vessel work.
The class is printed on the certificate header and must match the purchase order.
What every MTC must contain
Mill identification: manufacturer name, address and works code. Product identification: standard reference (EN 10025-2, ASTM A572, etc.), grade, dimensions, mass, surface condition. Heat / cast number: the unique identifier traceable from MTC to mill stamp on every piece. Chemical composition: percent of C, Si, Mn, P, S, N, Cu, Cr, Ni, Mo, V, Nb, Ti, Al as applicable to the grade. Mechanical properties: yield strength, tensile strength, elongation, impact energy at the specified temperature. Delivery condition: +AR, +N, +NL, +M, +Q, +QT. NDT results: ultrasonic, magnetic particle or dye penetrant test results if required. Marking: how the heat number, grade and standard are stamped on the product. Signature and date: by mill QA (3.1) or by independent inspector (3.2).
How to verify an MTC
1. Match the heat number on the MTC to the heat number stamped on each piece. Mismatched stamps are the single most common forgery indicator.
2. Match the product description, dimensions and mass to the bill of lading and packing list. Quantities must reconcile.
3. Recompute carbon equivalent (CEV) from the listed chemistry: CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. Compare to the standard's CEV cap and to the WPS preheat tables.
4. Verify the mill stamp and signature. Most major mills publish QA signature samples; a quick email to the mill QA contact confirms validity.
5. For 3.2 certificates, verify the third-party inspector's stamp and the witnessing report reference number.
6. Cross-check the standard reference on the MTC against the structural drawings. A drawing calling S355 J2 with an MTC referencing S355 JR is a substitution flag, not a clerical error.
When 3.1 vs 3.2 is required
3.1 is acceptable for: general buildings, warehouses, industrial sheds, ancillary steelwork, residential and commercial frames.
3.2 is required for: bridges (per Eurocode 3 and most GCC roads departments), high-rise primary frames in seismic zones, oil & gas critical service per Aramco SAES-M-001 and ADNOC HSE, pressure vessel and process piping, lifting equipment, offshore structures, military and security applications.
When the consultant's masterspec is silent, default to 3.1 for buildings and 3.2 for infrastructure.
MTCs across other materials
Stainless steel ships with MTCs under EN 10204 to ASTM A240, EN 10088 or equivalent, including PMI (Positive Material Identification) reports for grade verification. Aluminium MTCs reference EN 485, EN 573 or ASTM B209 and include heat treatment (temper) data. GI coils ship with EN 10346, ASTM A653 or JIS G3302 MTCs including zinc coating mass per square metre. Brass and copper ship with EN 12166, EN 1652 or ASTM B36 MTCs including alloy composition and temper.
The EN 10204 class structure (2.2, 3.1, 3.2) is the same across all material families.
GCC procurement notes
TIC Dubai issues original MTCs to EN 10204 3.1 by default with every consignment, coordinating EN 10204 3.2 third-party inspection (TUV, SGS, Bureau Veritas) at the mill or load port for projects that require it. MTCs are delivered both as scanned PDFs (immediately on shipment) and as physical originals shipped with the bill of lading. For Aramco, ADNOC and other major EPC supply chains, MTC and inspection documentation is pre-cleared with the project QA function before container release.