Casting is a process in which molten metal is poured or injected and allowed to solidify in a suitably shaped mold cavity. During or after cooling, the cast part is removed from the mold and then processed for delivery. Aluminum's unique combination of properties make it a versitile engineering and construction material. It is light in weight, yet some of its alloys have strengths greater than that of structural steel. It has high resistance to corrosion, does not discolor products that it comes into contact with, has no toxic reaction, and can easily be worked into many forms and readily accepts a wide variety of surface finishes.