How does surface chemistry explain aluminum’s resistance to corrosion?

Although aluminum is a chemically active metal, it is highly resistant to corrosion due to the formation of a protective surface layer. When exposed to air, aluminum reacts with oxygen to form a hard, tough, and stable oxide film on its surface.12

This oxide film acts as an impermeable barrier that isolates the underlying metal from the environment, preventing the corrosion process from proceeding. While this natural layer provides significant protection, the thickness and durability of this film can be further enhanced through a process known as anodizing, where the aluminum part is made to function as the anode in an electrolytic cell.2

Because this passive oxide layer is so effective, aluminum remains stable in many environments, though it can be compromised by exposure to certain substances, such as alkalies or concentrated hydrochloric acid, which can attack the metal.1