Wrought Alloy Designation System -   The 4-digit wrought aluminum alloy identification system is common. The first digit (Xxxx) indicates the principal alloying element, which has been added to the aluminum alloy and is often used to describe the aluminum alloy series, i.e., 1000 series, 2000 series, 3000 series, up to 8000 series.

The second single digit (xXxx), if different from 0, indicates a modification of the specific alloy, and the third and fourth digits (xxXX) are arbitrary numbers given to identify a specific alloy in the series. Example: In alloy 5183, the number 5 indicates that it is of the magnesium alloy series, the 1 indicates that it is the 1^st modification to the original alloy 5083, and the 83 identifies it in the 5xxx series.

 But for 1xxx series aluminum alloys (pure aluminums) in which case, the last 2 digits provide the minimum aluminum percentage above 99%, i.e., Alloy 13(50) (99.50% minimum aluminum),Alloy 10(50 )(99.95% minimum aluminum).

          WROUGHT ALUMINUM ALLOY DESIGNATION SYSTEM