Aluminized steel is created by coating carbon or mild steel with a metallic layer of aluminum or an aluminum-silicon alloy. This process combines the structural strength of the steel core with the surface protection provided by the aluminum. The coating shields the underlying steel from degradation, particularly in environments involving high heat or atmospheric moisture. This material retains the strength and formability of steel while gaining superior resistance properties, making it an alternative to bare steel for demanding applications.
How Aluminized Steel is Made
Aluminized steel is manufactured using a continuous hot-dip method, similar to galvanization, where the steel substrate is immersed in a bath of molten metal. The steel sheet is cleaned before entering the bath to ensure a proper metallurgical bond forms between the materials. The temperature and composition of the molten bath are controlled to create the desired coating.
The coating composition determines the steel’s classification into two main types. Type 1 aluminized steel uses a molten bath containing an aluminum-silicon alloy (5% to 11% silicon). The silicon promotes excellent adhesion and minimizes the formation of a brittle iron-aluminum layer, maintaining the material’s formability. Type 2 aluminized steel is coated in commercially pure aluminum and features a thicker coating for enhanced barrier protection against the atmosphere.
The Distinctive Properties of Aluminized Steel
The dual nature of aluminized steel provides exceptional resistance to high temperatures. When exposed to heat, the aluminum coating reacts with oxygen to form a stable, ceramic-like aluminum oxide layer (alumina). This thin, dense layer prevents further oxidation and scaling, allowing the material to maintain its structural integrity up to approximately 1250°F (677°C) for Type 1.
The material also exhibits superior corrosion resistance, especially in atmospheric conditions. The aluminum layer acts as a physical barrier, preventing moisture and corrosive elements from reaching the steel surface. Aluminum provides sacrificial protection, meaning it corrodes before the underlying steel if the coating is damaged. The thicker Type 2 coating is engineered to maximize atmospheric corrosion resistance.
Another property is its high heat reflectivity. The aluminum coating can reflect up to 80% of incident radiant heat. This characteristic makes aluminized steel effective for thermal shielding applications.
Where Aluminized Steel is Used
Aluminized steel is suitable for numerous applications across several industries. Its ability to withstand extreme heat and cyclical temperature changes makes it a primary choice for automotive exhaust systems, including mufflers and tailpipes. The material is also used to manufacture heat shields in engine compartments to protect sensitive components from radiant heat.
The combination of heat and corrosion resistance is useful in industrial heating equipment. This includes components like heat exchangers in residential furnaces, heating elements in industrial ovens, and water heater tanks. In the construction sector, Type 2 aluminized steel is often formed into corrugated roofing and siding materials. Its resistance to atmospheric corrosion and thicker coating ensures durability in severe outdoor environments.