Aluminum is a common alloy used in steam casting for a number of reasons, primarily because it is readily available and relatively inexpensive. Once cast, aluminum accepts a high polish and forms a thin, transparent, corrosion-resistant oxide layer.
In a pure form, iron is grey, and a relatively soft metal. It is both tough and malleable which makes it good for casting. Cast iron is hard, brittle and nonmalleable.
Once cast, copper can accept a high polish and turns shiny pink. It is a highly ductile and durable metal, and withstands corrosion to a significant degree, even in very polluted environments. Copper oxidizes over time, turning green.
An alloy of copper and tin, sometimes containing small amounts of zinc, lead, silver, aluminum, or phosphorus, bronze is usually yellowish gold in color. If the percentage of copper is high, then it can be red. High levels of tin can make the bronze hard, brittle and grayish in color. Once cast, bronze can accept a high polish.