Review certificate records, scope and current status. Confirm order-specific documentation and inspection requirements with the export team.
What Is a Mill Test Certificate MTC for Galvanized Coil?
A mill test certificate MTC for galvanized coil is an official quality document issued by the steel mill that certifies the chemical analysis, mechanical properties, and zinc coating weight of a specific production lot. For GI coil, the MTC must include the heat number, steel grade (such as DX51D, DX52D, or SGC440), tensile strength, yield strength, elongation, and the actual zinc coating mass in grams per square meter (g/m²). The certificate also shows the spangle type (regular, minimized, or zero spangle), surface treatment (chromated, oiled, or passivated), and the coil dimensions (thickness, width, and inner diameter).
Certificate records — Review the certificate holder, scope and current verification status. Confirm the documents applicable to your order.
Key Data Included in a Galvanized Coil MTC
Every mill test certificate for hot dip galvanized coil contains these mandatory fields:
- Heat number and production date
- Steel grade (e.g., DX51D+Z, DX53D+Z, SGH340)
- Chemical composition: carbon (C), manganese (Mn), silicon (Si), phosphorus (P), sulfur (S), aluminum (Al)
- Mechanical properties: yield strength (MPa), tensile strength (MPa), elongation (%)
- Zinc coating weight: single-side or triple-spot test results (g/m²)
- Spangle type and surface finish
- Coil dimensions: thickness (mm), width (mm), weight (kg)
- Inspection standards: EN 10142, ASTM A653, JIS G3302, or GB/T 2518
How to Verify a Mill Test Certificate for Galvanized Coil
Fake or altered MTCs are a growing problem in the global steel trade. In 2026, we have seen cases where unscrupulous traders copy certificates from reputable mills and attach them to low-quality GI coil from unknown sources. To protect yourself, follow this verification checklist:
- Check the heat number – Every coil has a unique heat number stamped on the outer wrapper. The MTC heat number must match exactly.
- Verify the mill name and address – The certificate should show the actual production mill, not a trading company address. Our factory in Boxing, Binzhou details appear on every ChinaCNU Steel MTC.
- Confirm zinc coating tolerance – For Z275 grade, the triple-spot average must be ≥275 g/m². Some fake certificates show a single-spot value that is higher than the actual average.
- Certificate records — Review the certificate holder, scope and current verification status. Confirm the documents applicable to your order.
- Cross-check mechanical properties – If the yield strength is unusually high or low for the declared grade, suspect a false certificate.
Common MTC Mistakes That Cost Buyers Money
Even genuine mill test certificates can contain errors. The most frequent issues we see in the galvanized coil market include: incorrect conversion of coating weight (e.g., reporting g/m² when the standard requires oz/ft²), missing spangle type, or using an outdated standard revision. ChinaCNU Steel employs a dedicated quality assurance team that triple-checks every MTC before shipment. Our 15+ years of export experience means we know exactly what documentation customs authorities in the USA, Europe, Southeast Asia, and Africa require. When you order from us with MOQ 25 tons, you receive a complete MTC package that includes the original certificate, a translation if needed, and a certificate of origin.
Mill Test Certificate Comparison: Z60 vs Z120 vs Z275 Galvanized Coil
Choosing the right zinc coating weight depends on your application. Below is a data comparison table showing typical MTC values for three common GI coil grades supplied by ChinaCNU Steel:
| Parameter | Z60 (DX51D+Z) | Z120 (DX51D+Z) | Z275 (DX51D+Z) |
|---|---|---|---|
| Zinc coating (g/m²) triple-spot | 60-90 | 120-150 | 275-310 |
| Yield strength (MPa) | 140-300 | 140-300 | 140-300 |
| Tensile strength (MPa) | 270-500 | 270-500 | 270-500 |
| Elongation (%) | ≥22 | ≥22 | ≥22 |
| Carbon content max (%) | 0.12 | 0.12 | 0.12 |
| Typical application | Indoor ducting, light profiles | Roofing sheets, wall cladding | Outdoor structures, agricultural silos |
| Corrosion resistance (hours to 5% red rust) | ~72 | ~150 | ~400 |
| FOB price per ton (USD, 2026 estimate) | $680-$720 | $750-$800 | $850-$920 |
As the table shows, the mill test certificate will report actual values within these ranges. For example, a Z120 coil might test at 138 g/m², which is acceptable. If the MTC shows exactly 120 g/m², it could indicate a certificate was copied from a different batch. ChinaCNU Steel always provides actual test results, not nominal values. Our FOB pricing includes the cost of full MTC documentation, so you never pay extra for compliance paperwork.
Why ChinaCNU Steel Is Your Trusted Galvanized Steel Supplier
Our minimum order quantity is 25 tons per size and grade. This MOQ is designed for serious buyers who need consistent quality for ongoing production. We offer Z60, Z80, Z120, Z180, Z225, Z275, and Z350 coatings in thicknesses from 0.12mm to 4.0mm and widths from 600mm to 1500mm. Every coil is edge-trimmed, oiled, and packaged for sea freight. The mill test certificate is emailed within 24 hours of coil production and the original is shipped with the goods. We also provide third-party inspection reports from SGS or Bureau Veritas upon request.
Frequently Asked Questions About Mill Test Certificates for Galvanized Coil
1. Can I use the same MTC for multiple coils?
No. Each coil has its own heat number and production parameters. A mill test certificate MTC for galvanized coil is valid only for the specific coil listed on the document. Using one MTC for multiple coils is a common fraud indicator. At ChinaCNU Steel, we issue individual MTCs for every coil in your order.
2. What if my MTC shows a lower zinc coating than ordered?
You have the right to reject the coil. The MTC must match the ordered grade within standard tolerances (typically -0% to +15% for zinc coating). If the actual coating is below the minimum, we replace the coil at our cost. Our quality control ensures every Z275 coil tests above 275 g/m² before shipment.
3. How do I verify a digital MTC from ChinaCNU Steel?
Each digital MTC contains a unique QR code and serial number. Scan the code with your smartphone to access our secure verification portal. The portal displays the original certificate image and production data. You can also email the serial number to our quality team for manual verification within 4 hours.
4. Is a mill test certificate required for all galvanized coil shipments?
Yes, for international trade. Customs authorities, insurance companies, and end users all require a valid MTC. Without it, you risk delays at port, rejected cargo, and liability claims. ChinaCNU Steel includes the MTC as a standard document with every order over MOQ 25 tons.
5. What is the difference between an MTC and a certificate of analysis (COA)?
An MTC is a comprehensive document that includes chemical composition, mechanical properties, and coating data. A COA typically only shows chemical analysis. For galvanized coil, always request a full mill test certificate. Our documents meet both EN 10204 Type 3.1 and ASTM A653 standards.
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