Galvalume is a coating made of silicon, aluminum, and zinc coating that is applied to metals, typically steel, to prevent oxidation. Similar to galvanizing, it is a protective metal coating that shields the basic metal.
Iron-based alloys that are prone to rust are typically protected with Galvalume. Galvalume-coated steel resists oxidation better than plain carbon steel because zinc and aluminum shield the underlying steel from the environment. Additionally, the zinc will oxidize more quickly than the steel it comes into touch with.