Galvalume sheet is a cold-rolled sheet steel to which a coating of aluminum-zinc alloy has been applied. The precise combination of aluminum, zinc and silicon for this remarkable coating was discovered nearly 30 years ago by engineers at Bethlehem's research laboratories. This technological breakthrough resulted in a highly corrosion-resistant sheet steel that delivers the optimum combination of characteristics of aluminum and zinc: the barrier protection and long-term durability of aluminum and the sacrificial or galvanic protection of sheared edges that is characteristic of zinc.