Household Aluminum Foil

Household aluminum foil is a thin, flexible sheet made from aluminum, typically with a thickness between 0.016 mm and 0.024 mm. Its smooth, metallic silver surface has a reflective shiny side and a matte side. The foil's malleability is due to the densely packed aluminum atoms in its structure, allowing it to be easily bent or shaped without tearing. This structure also contributes to its high barrier properties, making it impermeable to light, air, and moisture, which helps preserve food freshness by preventing oxidation and contamination. Aluminum's natural ability to form a thin oxide layer gives it excellent corrosion resistance, adding to its durability. With a thermal conductivity of about 235 W/m·K, aluminum foil efficiently transfers heat, making it ideal for cooking. Its density is approximately 2.7 g/cm³, with a tensile strength of around 70 MPa, ensuring both lightness and strength in everyday applications.

High Malleability
With a thickness ranging from 0.016 mm to 0.024 mm, aluminum foil can be easily bent, folded, or wrapped. This malleability is due to the metallic bonding in aluminum atoms, which allows for easy movement between layers without tearing. This flexibility enables the foil to tightly cover or wrap food items, providing a snug seal to keep out contaminants.

Barrier Properties
The foil's barrier performance is attributed to its dense atomic structure and the naturally occurring oxide layer, typically around 2-4 nanometers thick, which further enhances its protective qualities. With a water vapor transmission rate (WVTR) of less than 0.01 g/m² per 24 hours, aluminum foil provides an almost impenetrable shield against moisture. It also has an oxygen transmission rate (OTR) of approximately 0.0001 cm³/m² per 24 hours, preventing air from penetrating and causing oxidation. These properties are especially vital in food packaging, where they help retain freshness, flavor, and nutrients for extended periods.

Corrosion Resistance
Aluminum foil forms a natural protective oxide layer, typically around 2-4 nanometers thick, when exposed to air, preventing corrosion. This oxide layer acts as a barrier, protecting the underlying aluminum from further oxidation. Even when in contact with acidic foods (pH less than 4) or salty environments (sodium chloride concentrations up to 3.5%), the foil maintains its integrity, unlike other metals such as iron or copper, which may corrode or leach harmful substances into the food. This corrosion resistance allows aluminum foil to safely wrap acidic items like citrus fruits or tomato sauce without affecting the food's taste or safety.