There are several systems of aluminum standards available for aluminum alloys identification and designation, and for specifying their properties.
As with other metals, the most prominent standards for aluminum are European EN (Euronorm), US SAE and ASTM, Japanese JIS, international ISO, and standards of BRIC countries: Chinese GB and YB, Indian IS, Brazilian NBR, and Russian GOST.
Euronorm aluminum standards use four digits to identify the wrought alloys and five digits to identify the cast alloys and are broadly the same as the ISO aluminum standards and US numerical methods of identification where a four digit number identifies the unique alloy designation. This is in agreement with the International Designation System issued by The Aluminum Association in the USA. This Aluminum Association system (AA) is specific for aluminum and it is a basis for aluminum standards and designations worldwide. For example, the chemical composition limits specified in the Euronorm aluminum standards are identical with those registered with Aluminum Association for the equivalents alloys.
A prefix is used to designate the standard AA of the Aluminum Association or EN AW for the European aluminum standards. In the European system, the prefix “AB” denotes ingots for remelting, “AC” denotes a cast product, “AM” a cast master alloys, the prefix “AW” a wrought product e.g. EN AW-1050. A suffix "A" indicates a national variation of the alloy, e.g. EN AW-6005A.
In the AA aluminum alloy designations, there are four numeric digits. The meanings of the four digits are: First digit: Principal alloying constituent(s); second and third digits: Specific alloy designation (number has no significance but is unique); fourth digit: Casting (0) or ingot (1, 2) designation.
Another widely known alloy classification system is the Unified Numbering System (UNS). The UNS system has the advantage of covering all metallic alloy systems. For aluminum alloys, this system is essentially an adaptation of the Aluminum Association alloy designation system to fit the UNS format. UNS numbers are obtained by taking the three digits to the left of the decimal point in the Aluminum Association system and adding A9 (meaning aluminum alloys) and a digit reflecting the letter prefix to the alloy designation. For alloys with no letter prefix, the next numeric digit after A9 is a 0; for those with A, the next digit is 1, for B, it is 2, and so forth. Thus in UNS system, 356.0 becomes A90356, A356.0 becomes A91356, C356.0 becomes A93356 etc.