sentences:  Described in NACA-TN-259, of August 1927, as "a new corrosion resistant aluminum product which is markedly superior to the present strong alloys.Its use should result in greatly increased life of a structural part.Alclad is a heat-treated aluminum, copper, manganese, magnesium alloy that has the corrosion resistance of pure metal at the surface and the strength of the strong alloy underneath.