What is Aluminized Steel?

Aluminized steel is steel coated on both sides with an aluminum-silicon alloy through a hot-dip process. This creates a strong metallurgical bond between the steel and its aluminum coating, resulting in a material that combines the strengths of both. It resists corrosion effectively while retaining the properties of steel at temperatures below 800°C (1,470°F).

It is widely used in:

• Residential and commercial heating equipment (e.g., furnaces, HVAC units, and water heaters).
• Automotive and kitchen appliances (e.g., mufflers, ovens, ranges, and baking pans).
• Fireplaces and barbecue burners.

Key Features

• Excellent heat resistance and conductivity.
• Durable performance in high temperatures.
• Superior corrosion resistance.

Types of Aluminized Steel

Type 1

• Coated with an aluminum-silicon alloy containing 5-11% silicon for better adherence.
• Designed for heat-resistant and corrosion-resistant applications.
• Common uses: Mufflers, ovens, heaters, fireplaces, and baking pans.
• Can withstand temperatures up to 550°C (1,022°F).
• Advantages: Free from lead (non-toxic), increasingly replacing galvanized steel in bakery trays.

Type 2

• Coated with commercially pure aluminum.
• Best suited for environments needing atmospheric corrosion resistance.
• Common uses: Roofing, siding, grain bins, drying ovens, and air-conditioner housings.

Properties of Aluminized Steel

• Structure: Composed of a thin outer aluminum oxide layer, an intermetallic aluminum-silicon-steel layer, and a steel core.
• Reflectivity: Reflects up to 80% of heat at temperatures up to 842°C (1,548°F).
• Strength: Retains its strength at temperatures up to 677°C (1,251°F).
• Corrosion Resistance: Aluminum and silicon layers protect against oxidation and pit corrosion, especially in salty environments.

Note: If the aluminum coating is damaged, the exposed steel may corrode.

Manufacturing Process

The hot-dip process is the most efficient method for producing aluminized steel.

1. Steel is cleaned and dipped into an Al-11%Si alloy bath at 988K.
2. The aluminum diffuses into the steel, forming an intermetallic layer.
3. The outer aluminum coating oxidizes to prevent corrosion.
4. Silicon in the bath helps create a thinner aluminum layer for better adherence.

This process is cost-effective and reliable compared to other methods like cladding or galvanic coating.

Applications of Aluminized Steel

• Automotive and motorcycle exhaust systems.
• Heating equipment like water heaters and furnaces.
• Industrial uses such as roofing, grain bins, and air-conditioner housings.

Consumption in North America

Approximately 700,000 tons of aluminized steel are used annually for manufacturing various products, including heaters, grills, and ranges.