Galvanized Steel Sheets (DX Grades – EN 10346)

Galvanized steel sheets are carbon steel sheets coated with a layer of zinc to protect the steel from corrosion. The zinc coating acts as a protective barrier between the steel surface and the environment and also provides sacrificial protection. This means that zinc corrodes before the steel and protects it from rust.

Galvanized steel is widely used in industries where corrosion resistance, durability, and long service life are required. Typical applications include construction materials, HVAC systems, appliance housings, automotive parts, and electrical enclosures.

In Europe, galvanized forming steels are classified according to EN 10346, which defines the DX series of steel grades used for forming operations.

1. Hot-Dip Galvanizing Process

The most common method used to produce galvanized steel sheets is the hot-dip galvanizing process.

During this process:

1. Steel sheets are cleaned and degreased.

2. The sheets are immersed in molten zinc at approximately 450°C.

3. A metallurgical reaction occurs between steel and zinc.

4. Several zinc–iron alloy layers form on the surface.

After cooling, the steel sheet is covered with a protective zinc coating.

This coating protects the steel by two mechanisms:

• Barrier protection – preventing moisture and oxygen from reaching the steel surface

• Sacrificial protection – zinc corrodes first and protects the steel

2. Structure of the Zinc Coating

A galvanized steel sheet consists of several layers that provide corrosion protection.

Base Steel : Low carbon steel sheet

Zinc–Iron Alloy Layer : Bonding layer between steel and zinc

Pure Zinc Layer : Outer corrosion protection layer

The zinc coating strongly adheres to the steel surface, providing long-term protection against corrosion.

3. DX Steel Grades (Forming Grades)

Galvanized steels designed for forming operations are classified using DX grades under the European standard EN 10346.

The designation means:

• D → Flat steel product for cold forming

• X → No specified rolling direction property

• D → Hot-dip coated product

Common DX grades include:

DX51D Basic forming steel Standard forming

DX52D Drawing quality steel Moderate drawing

DX53D Deep drawing steel High formability

DX54D Extra deep drawing steel Very high formability

These steels allow forming operations such as bending, stamping, and drawing while maintaining corrosion resistance.

4. Zinc Coating Classification

Galvanized steel sheets are classified according to zinc coating weight, expressed in grams per square meter.

• Z100 100 g/m²

• Z140 140 g/m²

• Z200 200 g/m²

• Z275 275 g/m²

Higher coating weight provides better corrosion protection and longer service life.

Example designation: DX51D + Z275

Meaning:

• DX51D → Steel grade

• Z → Zinc coating

• 275 → Zinc coating weight (275 g/m²)

5. Surface Appearance

The appearance of galvanized steel depends on the cooling conditions of the zinc layer.

Typical surface finishes include:

• Regular Spangle Visible zinc crystal pattern

• Minimized Spangle Smaller crystal pattern

• Zero Spangle Smooth surface finish

Spangle refers to the crystalline pattern formed during the solidification of zinc.

6. Mechanical Properties

The mechanical properties of galvanized steel mainly depend on the base steel grade.

Typical values include:

Yield Strength : 140 – 300 MPa

Tensile Strength : 270 – 420 MPa

Elongation : 20 – 36 %

These properties make galvanized steel suitable for forming processes such as bending, stamping, and roll forming.

7. Typical Thickness Range

Galvanized steel sheets are commonly supplied in thicknesses between: 0.4 mm – 4 mm

They are typically delivered as:

• Steel coils

• Cut sheets

• Steel strips

8. Typical Applications

Galvanized steel sheets are widely used in industries requiring corrosion protection.

Common applications include:

• HVAC ducts

• Roofing and wall panels

• Electrical cabinets

• Automotive components

• Appliance housings

• Outdoor structures

For example, galvanized steel is frequently used for electric water heater outer shells and appliance enclosures.

10. Standards

Galvanized steel sheets are defined by several international standards.

• EN 10346 Continuously hot-dip coated steel flat products

• ASTM A653 Zinc-coated galvanized steel sheet

• ISO 3575 Continuous hot-dip zinc coated steel

These standards specify coating weight, mechanical properties, and dimensional tolerances.

11. Summary

Galvanized steel sheets provide effective corrosion protection through a zinc coating applied by the hot-dip galvanizing process. The coating protects steel both as a physical barrier and through sacrificial corrosion.

DX grades defined in EN 10346 provide different levels of formability, allowing galvanized steel sheets to be used in a wide range of forming operations. Because of its durability, corrosion resistance, and cost effectiveness, galvanized steel is widely used in construction, appliances, automotive manufacturing, and HVAC systems.