Enamel Quality` Steel (Porcelain Enamel Steel)

Enamel quality steel is a special type of low-carbon steel designed for porcelain enamel coating. In this process, a glass-like enamel layer is fused to the steel surface at high temperature to provide excellent corrosion protection, durability, and chemical resistance.

This material is widely used in applications where steel must be protected from water, chemicals, and high temperatures. One of the most common applications is electric water heater tanks, where enamel coating protects the steel tank from corrosion caused by hot water and dissolved minerals.

The enamel coating forms a strong chemical bond with the steel surface during firing, creating a durable protective layer.

1. What is Porcelain Enamel

Porcelain enamel is a glass coating fused onto steel at high temperature.

During the enameling process, powdered glass materials are applied to the steel surface and then fired in a furnace at approximately:  800 – 860 °C At this temperature:

• The glass melts

• The enamel chemically bonds with the steel

• A hard protective glass layer is formed

The result is a smooth and chemically stable surface that protects the steel from corrosion.

2. Characteristics of Enamel Quality Steel

Steel used for enameling must meet strict requirements to ensure strong adhesion between the enamel and the steel surface.

Key characteristics include:

• Very low carbon content

• Controlled chemical composition

• Clean steel surface

• Good enamel adhesion

• Good forming capability

These properties prevent gas formation during the firing process and ensure high coating quality.

3. Enamel Steel Grades (EN 10209)

In European standards, steels designed for porcelain enameling are defined in:

EN 10209 — Cold Rolled Steel for Vitreous Enameling

One of the most commonly used grades is DCEK.

Meaning of DCEK

• DC → Cold rolled flat steel

• E → Steel suitable for enameling

• K → Special killed steel with controlled composition

These steels are specifically designed to provide strong adhesion between steel and enamel .

4. DCEK Variants

Some enamel steel specifications reference several variants such as:

DCEK 1, DCEK 2, DCEK 3, DCEK 4, DCEK 5, and DCEK 6

These variants generally indicate differences in:

• steel purity

• gas control

• surface quality

• enameling process compatibility

However, not all variants are commonly used in industrial production.

Commonly Used Variants

DCEK 1  ,  Standard enamel steel used for general enameling applications.

DCEK 2   ,   Improved enamel steel with better gas control and coating adhesion.

DCEK 3 , 4   .   Steel designed for more demanding enameling processes and improved surface quality.

These grades are commonly used in:

• household appliances

• enamel cookware

• industrial enamel components

Less Common Variants

Variants such as DCEK 5, and DCEK 6 are more specialized and may be produced only by certain steel manufacturers.

They are typically designed for:

• multi-layer enamel systems

• thicker enamel coatings

• specialized industrial applications

5. Typical Chemical Composition

Enamel quality steels are usually based on very low carbon steel.

Typical composition:

Carbon (C) ≤ 0.08 %
Manganese (Mn) ≤ 0.40 %
Phosphorus (P) ≤ 0.03 %
Sulfur (S) ≤ 0.03 %

Low carbon content is important to prevent gas formation during firing, which could cause enamel defects.

6. Effect of Nitrogen (N), Hydrogen (H), and Titanium (Ti) in Enameling Steel

During the porcelain enameling process, several elements inside the steel influence the quality of the enamel coating. Among the most important are nitrogen (N), hydrogen (H), and titanium (Ti). These elements affect steel formability, surface quality, and enamel adhesion.

Effect of Nitrogen (N)

Nitrogen is an interstitial element that dissolves in the iron lattice. While it increases the strength of the steel, excessive nitrogen can reduce ductility and lead to strain aging.

Strain aging may cause surface defects such as:

• Lüders lines

• Stretcher strain marks

These surface defects can appear during forming operations and may reduce the surface quality required for good enamel coating adhesion.

To control this effect, nitrogen content in enameling steels is usually kept low or stabilized using alloying elements such as titanium or aluminum.

Effect of Hydrogen (H)

Hydrogen plays a critical role in enamel coating performance. During the firing process, hydrogen can diffuse into the steel from moisture or chemical reactions.

After cooling, hydrogen may migrate back toward the steel surface and accumulate beneath the enamel coating. This creates internal pressure that can cause the well-known fish-scale defect, where the enamel coating cracks or flakes off in small scales.

To reduce this problem, steel producers often apply treatments such as:

• vacuum degassing

• hydrogen control during steelmaking

• proper surface preparation before enameling

Effect of Titanium (Ti)

Titanium is commonly added to enameling steels as a stabilizing element. Titanium reacts with carbon and nitrogen to form stable compounds such as:

• TiC (titanium carbide)

• TiN (titanium nitride)

Lüders lines are surface deformation bands caused by strain aging in low-carbon steels, mainly due to carbon and nitrogen interacting with dislocations during plastic deformation. 

These compounds prevent carbon and nitrogen from causing defects during the enameling process.

Benefits of titanium addition include:

• improved enamel adhesion

• reduced strain aging

• improved steel stability

• better deep drawing performance

For these reasons, titanium-stabilized steels are often used in high-quality enamel applications, including electric water heater tanks.

Summary

Nitrogen may cause strain aging and surface defects, hydrogen can lead to fish-scale defects in enamel coatings, while titanium acts as a stabilizing element that improves enamel adhesion and steel stability.

7. Mechanical Properties of DCEK Steel

Property Typical Range

Yield Strength 180 – 260 MPa

Tensile Strength 300 – 380 MPa

Elongation ≥ 34 %

These properties allow the steel to undergo forming and deep drawing operations before the enameling process.

8. Enameling Process

The enameling process generally includes several stages.

Surface Preparation

The steel surface is cleaned and chemically treated to remove oils, scale, and contaminants.

Enamel Application

A slurry containing finely ground glass materials is applied to the steel surface.

Firing

The coated steel is fired in a furnace at high temperature.

During firing:

• the enamel melts

• the glass bonds with the steel

• a durable enamel layer is formed

9. Properties of Enamel Coated Steel

Enamel coated steel provides several important advantages.

Key properties include:

• excellent corrosion resistance

• high temperature resistance

• smooth hygienic surface

• high hardness and scratch resistance

• long service life

These properties make enamel steel ideal for water storage and heating equipment.

10. Applications

Enamel coated steel is widely used in:

• electric water heater tanks

• cooking appliances

• chemical containers

• industrial storage tanks

• household appliances

In electric water heaters, the enamel coating protects the steel tank from corrosion and works together with a magnesium anode to extend the service life of the tank.

11. Why DC04 Steel is Often Used Before Enamel Coating

Although specialized enamel steels such as DCEK exist, many electric water heater manufacturers use DC04 deep drawing steel as the base material for tank production.

Reasons for Using DC04

• Excellent Deep Drawing Capability

Water heater tanks require deep forming operations. DC04 provides excellent ductility and high elongation, making it ideal for deep drawing.

• Availability and Cost

DC04  is widely available and generally less expensive than specialized enamel steels.

• Compatibility with Enamel Coating

When properly prepared, DC04 steel provides good adhesion with porcelain enamel coatings.

Because of these advantages, DC04 is commonly used as the base steel for enamel-coated water heater tanks.

12. Standards

Enamel quality steels and coatings are defined by several international standards.

Standard Description

EN 10209 Cold rolled steel for vitreous enameling

ASTM A424 Steel sheet for porcelain enamel

ISO 28722 Vitreous enamel coatings for steel

13. Summary

Enamel quality steel is a specially designed low-carbon steel used for porcelain enamel coatings. The enamel layer forms a durable glass-like coating that provides excellent corrosion resistance and long service life.

Steels such as DCEK are developed specifically for enameling applications, while deep drawing steels such as DC04 are often used as base materials for water heater tanks due to their superior forming properties.

Because of its ability to withstand hot water, corrosion, and chemical exposure, enamel coated steel is widely used in electric water heaters and household appliances.