Unalloyed aluminum is highly corrosion resistant, low strength, workable, conductive.
2xxx Copper Gives strength, hardness, machinability. 3xxx Manganese Adds moderate strength, good workability. 4xxx Silicon 5xxx Magnesium Moderate to high strength. 7xxx Zinc For greatest strength. Other alloying elements such as copper, magnesium, chromium and zirconium may be specified.