Aluminized
Most people are familiar with galvanized steel, which is steel that has been coated with a thin layer of zinc. However, what most people don't know is that you also get a type of metal product called aluminized steel.
Like galvanized steel, aluminized steel is coated with a thin layer of aluminum, usually mixed with a small amount of silicon.
This aluminum alloy coating protects the steel below, which slows down the natural process of oxidization or rusting of the metal.
Aluminized metal is much less common in the fence world than galvanized metal.