Outdoors Rust Wedge display at the Exploratorium shows the enormous expansive force of rusting iron. Rust is another name for iron oxide, which occurs when iron or an alloy that contains iron, like steel, is exposed to oxygen and moisture for a long period of time.Over time, the oxygen combines with the metal at an atomic level, forming a new compound called an oxide and weakening the bonds of the metal itself.utdoors Rust Wedge display at the Exploratorium shows the enormous expansive force of rusting iron. Rust is another name for iron oxide, which occurs when iron or an alloy that contains iron, like steel, is exposed to oxygen and moisture for a long period of time.