About Aluminized Steel

Overview of Aluminized Steel

Aluminized steel is steel that has been hot-dip coated on both sides with an aluminum-silicon alloy. This process creates a strong metallurgical bond between the steel and its aluminum coating, resulting in a material that combines the properties of both metals. Aluminized steel is highly resistant to corrosion and retains the strength of steel at temperatures below 800°C (1,470°F). It is commonly used in heat-related applications such as residential furnaces, HVAC units, automotive mufflers, ovens, and kitchen appliances due to its excellent heat transfer capabilities.

Types of Aluminized Steel

Type 1

Type 1 aluminized steel is hot-dip coated with a thin layer of aluminum-silicon alloy, containing 5% to 11% silicon for better adhesion. This type is designed for heat-resistant and corrosion-resistant applications, including mufflers, furnaces, ovens, heaters, and baking pans. It can withstand temperatures up to 550°C (1,022°F) with minimal changes to the base material. Type 1 is also gaining popularity in the food industry, replacing galvanized steel in bakery trays due to its lead-free composition.

Type 2

Type 2 aluminized steel is hot-dip coated with pure aluminum, primarily for applications requiring strong atmospheric corrosion resistance. It is commonly used in corrugated roofing, siding, grain bins, drying ovens, and air-conditioner housings.

Properties of Aluminized Steel

Aluminized steel has a layered structure consisting of an outer aluminum oxide layer, an intermetallic layer (a mix of aluminum, silicon, and steel), and a steel core. Both Type 1 and Type 2 offer high reflectivity, reflecting up to 80% of heat at temperatures up to 842°C (1,548°F). While stainless steel is stronger, aluminized steel’s electrostatic surface provides superior heat reflection. The aluminum and silicon layers offer strong corrosion resistance, especially against salt exposure, but damage to the aluminum coating can lead to steel oxidation and corrosion.

Uses and Consumption

Aluminized steel is widely used for its durability, strength, and cost-effectiveness, especially in corrosive environments. It is commonly found in automobile and motorcycle exhaust systems, water heaters, furnaces, and space heaters. In North America, nearly 700,000 tons of aluminized steel are consumed annually.

Processing Methods

Aluminized steel is typically produced using the hot-dip method, which involves cleaning the steel, dipping it into an Al-11%Si bath at 988K, and then allowing it to air dry. This process creates an intermetallic layer between the steel and aluminum, with the aluminum coating providing corrosion resistance. Hot dipping is the most cost-effective method of producing aluminized steel compared to other processes like cladding, galvanic coating, and metallizing.