Aluminized Steel Coil Explained: Heat Resistance, Coating Types & Industrial Applications

Aluminized steel is carbon steel coated with aluminum using a hot-dip process.

Aluminized Coil (For Heat Applications)

Aluminized steel is carbon steel coated with aluminum using a hot-dip process. It is engineered primarily for high-temperature performance, oxidation resistance, and heat reflectivity.

Unlike Galvalume (Al-Zn), aluminized steel is designed specifically for thermal environments, such as:

Exhaust systems
Furnaces
Ovens
Heat shields
Chimneys
Industrial ducting
Automotive components

In roll forming and coil processing, aluminized coil is selected when heat resistance is more critical than long-term atmospheric corrosion performance.

1️⃣ What Is Aluminized Steel?

Aluminized steel is steel coated with nearly pure aluminum.

There are two primary types:

Type 1 Aluminized Steel

Aluminum-silicon coating (approx. 90% Al, 10% Si)
Designed for heat resistance
Most common for exhaust systems and furnace components

Type 2 Aluminized Steel

Pure aluminum coating
Designed more for corrosion resistance than extreme heat

For heat applications, Type 1 is dominant.

2️⃣ How Aluminized Coating Protects Steel

Aluminized steel protects through:

2.1 Barrier Protection

Aluminum forms a stable oxide layer that slows oxidation at elevated temperatures.

2.2 High Temperature Stability

Unlike zinc coatings (which begin to degrade around 200°C), aluminum remains stable at significantly higher temperatures.

Typical performance:

Continuous use: 450–650°C (depending on grade)
Intermittent exposure: Higher short-term tolerance

Zinc-based coatings are not suitable for sustained high-temperature environments.

3️⃣ Aluminized vs Galvalume vs Galvanized (Engineering Comparison)

Property	Galvanized (Z)	Galvalume (AZ)	Aluminized
High heat resistance	Poor	Moderate	Excellent
Atmospheric corrosion	Good	Excellent	Moderate
Cut-edge protection	Strong	Moderate	Weak
Reflectivity	Moderate	High	Very High
Automotive exhaust use	No	No	Yes

Key takeaway:

Galvalume is for roofing.
Galvanized is for general corrosion protection.
Aluminized is for heat-dominant applications.

4️⃣ Forming Behavior in Roll Forming

Aluminized steel behaves differently from AZ or Z coatings.

4.1 Surface Characteristics

Smoother, dull grey surface
Less spangle
Slightly harder feel than galvanized

4.2 Coating Adhesion

Silicon in Type 1 coating improves adhesion to substrate.

However:

Tight bends may cause coating cracking
Excessive forming pressure can damage surface

4.3 Tooling Recommendations

Polished roll surfaces
Avoid aggressive early-stage forming
Use gradual radius transitions
Maintain clean rolls to avoid aluminum pickup

5️⃣ Temperature Performance

Aluminized Type 1 steel typically withstands:

Continuous 450–650°C service
Short-term exposure up to 700°C+

Galvanized coatings begin vaporizing and degrading at far lower temperatures.

This is why aluminized is used for:

Exhaust manifolds
Heat exchanger components
Furnace housings
Fire-resistant duct systems

6️⃣ Corrosion Performance

Aluminized steel is excellent in:

Dry heat environments
High-temperature oxidation zones

It is weaker in:

Constant wet exposure
Coastal marine environments
Acidic agricultural buildings

It does not provide strong sacrificial protection at cut edges like zinc.

7️⃣ Thickness & Substrate Grades

Common base metal thicknesses:

0.40 mm
0.50 mm
0.60 mm
0.80 mm
1.00 mm
1.20 mm

Substrate grades typically:

Mild steel
Formable structural grades

High tensile grades are less common compared to roofing materials.

8️⃣ Welding & Fabrication Considerations

Aluminized steel can be welded, but:

Aluminum coating affects weld pool behavior
Surface preparation may be required
Fumes must be properly extracted

Compared to galvanized:

Less zinc vapor hazard
Still requires proper ventilation

9️⃣ Storage & Handling

To avoid cosmetic corrosion:

Keep dry
Avoid condensation
Store elevated
Avoid water trapping between coils

Unlike zinc coatings, aluminized surfaces may darken when exposed to moisture but retain heat resistance.

🔟 Common Buyer Mistakes

Using aluminized for roofing expecting AZ-level corrosion life
Confusing aluminized with Galvalume
Choosing Type 2 when high heat resistance is required
Ignoring bend radius during profile design
Using in highly acidic environments

1️⃣1️⃣ International Standards

Common governing standards:

ASTM A463 (Aluminized Steel Type 1 and Type 2)
EN equivalents for coated heat-resistant steel
Automotive OEM specifications

Always verify:

Coating type (Type 1 vs Type 2)
Base metal thickness
Mechanical properties
Heat performance rating

1️⃣2️⃣ When to Choose Aluminized Coil

Choose aluminized when:

Temperature exposure exceeds 200–300°C regularly
Heat reflectivity is required
Oxidation resistance is priority
Component is part of exhaust or furnace system

Do not choose aluminized when:

Marine corrosion is dominant
Cut-edge corrosion protection is critical
Long-term wet exposure exists

Summary

Aluminized steel is engineered for heat resistance and oxidation control, not primarily for atmospheric corrosion.

It outperforms galvanized and Galvalume in:

High-temperature environments
Exhaust systems
Furnace and heating equipment
Fire-rated duct systems

However, it does not provide the same cut-edge corrosion protection as zinc-based coatings.

Correct material selection depends entirely on environmental exposure and temperature conditions.

Frequently Asked Questions (6)

1. What is the difference between aluminized and Galvalume?

Aluminized is coated with nearly pure aluminum for heat resistance. Galvalume is aluminum-zinc for corrosion resistance in roofing.

2. What temperature can aluminized steel withstand?

Typically 450–650°C continuous exposure, depending on grade and coating type.

3. Is aluminized steel good for outdoor roofing?

No. Galvalume or galvanized steel is better for long-term atmospheric corrosion resistance.

4. What is the difference between Type 1 and Type 2 aluminized?

Type 1 contains aluminum-silicon for heat resistance. Type 2 is nearly pure aluminum for corrosion resistance.

5. Can aluminized steel be roll formed?

Yes, but bend radius must be controlled to prevent coating cracking.

6. Does aluminized steel rust?

The aluminum coating resists oxidation, but exposed steel at damaged areas can corrode over time.