Determine the grade of an aluminum alloy by using the four-digit identification system developed by the Aluminum Association and published in the association's book, "International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys." The first digit of this classification system refers to the principal alloying element, while extra digits identify the additional treatment or modification used to create the alloy.
Aluminum alloys in the 1000-series contain a minimum concentration of 99 percent aluminum. For this reason, metallurgists often refer to this series as the pure aluminum series. They are not heat-treatable, but have superior corrosion resistance.
The 2000-series aluminum alloys are treated with copper, making them ideal for aircraft and aerospace applications. Aluminum alloys in the 3000-series are non-heat treatable alloys with manganese additions ranging between 0.05 and 1.8 percent. The 4000-series aluminum alloys contain between 0.6 and 21.5 percent silicon. This series is the only aluminum alloy series that contains both heat treatable and non-heat treatable alloys.
The 5000-series aluminum alloys contain between 0.2 and 6.2 percent magnesium, making them ideal for use in shipbuilding, bridge construction and transportation applications. Aluminum alloys in the 6000-series are typically applied as extrusions in the welding fabrication industry due to their combination of magnesium and silicon. The 7000-series aluminum alloys contain zinc, making them some of the strongest aluminum alloys available.