EN 10346 Continuously Hot-Dip Coated Steel

1. Definition and Scope

EN 10346 is the current European standard specifying requirements for continuously hot-dip coated flat steel products. It supersedes the earlier EN 10142 (low-carbon zinc coated), EN 10147 (structural zinc coated), EN 10292 (zinc-aluminum coated), and EN 10326 and EN 10327 standards, consolidating all hot-dip metallic coating types and associated steel grades into a single document. EN 10346 covers strip and sheet in thicknesses typically from 0.35 mm to 6.0 mm, supplied in coils or cut lengths.

For roll forming manufacturers, EN 10346 is the primary material standard for specifying feedstock steel. The standard defines steel grade names (mechanical properties), coating type codes (Z, ZA, AZ, ZM, AS), coating mass designations (+Z275, +AZ150, +ZM200, etc.), surface quality classes, and surface treatment codes. Roll-formed profiles inherit the properties of the EN 10346 feedstock; the forming process does not alter the coating type or steel grade, though it affects dimensional tolerances governed separately by EN 10162.

EN 10346 products are manufactured on continuous hot-dip coating lines where cleaned cold-rolled or hot-rolled strip passes through a molten coating bath, emerges with a metallurgically bonded layer, and is cooled, passivated, oiled, and recoiled. The standard applies to products intended for further cold forming, including roll forming, press braking, and deep drawing.

2. Steel Grades

EN 10346 defines two families of steel grades: DX grades for cold forming applications and SxxGD grades for structural applications requiring defined minimum yield strength. Both families are available with any coating type specified in the standard.

2.1 DX Grades (Forming)

2.2 SxxGD Grades (Structural)

The "D" suffix on DX grades indicates cold forming quality; the "GD" suffix on structural grades indicates suitability for forming (the "G" historically denoted galvanized, now generalized to all coating types). Higher-numbered DX grades generally provide improved formability and higher elongation requirements, making them suitable for more demanding forming and drawing operations.

3. Coating Types and Designations

EN 10346 defines five coating type codes representing different hot-dip metallic coating compositions. Each code appears in the product designation after the steel grade name, prefixed with "+" and followed by the coating mass number.

Each coating type is available on all DX and SxxGD steel grades. The coating is metallurgically bonded to the steel substrate through an intermetallic layer formed in the coating bath. Coating adherence is verified by bend test per EN 10346: the coated strip is bent 180° over a mandrel and examined for flaking.

4. Coating Mass Designations

Coating mass is expressed as the total mass of coating on both surfaces in g/m². The designation number equals this total mass. Higher numbers indicate thicker coatings and longer corrosion protection life.

4.1 Z (Zinc) Coating Mass

4.2 AZ, ZM, ZA Coating Mass

Coating mass is measured gravimetrically per ISO 1460 (destructive) or instrumentally per ISO 2178 (magnetic induction). Mill test certificates report actual coating mass per EN 10204 3.1. Roll forming does not measurably reduce coating mass on flange surfaces; bend outer radii may show micro-cracking that is within normal acceptance criteria.

5. Mechanical Properties

Mechanical properties in EN 10346 apply to the base steel substrate before coating. The hot-dip coating process involves heating the strip to approximately 450–480°C (for Z bath) during coating, which may slightly alter mechanical properties of the substrate compared to the original cold-rolled condition. EN 10346 values are measured after coating.

5.1 Thickness Tolerance (EN 10143)

Dimensional tolerances for EN 10346 products are specified in EN 10143. Representative normal and special thickness tolerances are summarized below for roll forming planning.

5.2 Width Tolerance

6. Surface Quality and Treatment

EN 10346 specifies surface quality classes and post-coating treatment codes that define the acceptable appearance and handling characteristics of the coated strip.

6.1 Surface Quality Classes

6.2 Surface Treatment Codes

7. Designation System

EN 10346 product designation follows the structure: steel grade + coating type and mass + optional surface quality + optional surface treatment. The complete designation appears on mill test certificates, order documents, and coil labels.

7.1 Designation Components

7.2 Worked Designation Examples

8. Roll Forming Applications

EN 10346 coated strip is the dominant feedstock for roll forming production across building construction, storage systems, solar energy, and industrial equipment. The following table maps common roll-formed products to their typical EN 10346 specification.

When specifying EN 10346 feedstock for roll forming orders, the purchaser states steel grade, coating designation, dimensions (thickness and width), surface quality (if other than A), and surface treatment. The roll forming manufacturer adds profile cross-section dimensions and tolerance class per EN 10162 to complete the finished product specification. Mill test certificates per EN 10204 3.1 accompany each coil, providing certified mechanical properties, coating mass, and adherence test results traceable to the finished profile batch.