Choosing between them requires matching four properties to the application: strength, corrosion resistance, formability and welding behavior. Cost and availability then narrow the field further.
This guide walks through each series in turn so that a designer can move from a load requirement or a service environment to a short list of practical grades.
Non-Heat-Treatable Series: 1xxx, 3xxx and 5xxx
The 1xxx series is commercially pure aluminum with at least 99 percent aluminum, offering the highest conductivity and reflectivity and the best formability but the lowest strength. Grade 1060 is a typical example used for foil stock, reflectors and electrical work.
The 3xxx series adds manganese. Alloy 3003 is stronger than the pure grades while remaining highly formable, which makes it the standard for roofing, cookware and heat exchanger components. The 5xxx series adds magnesium, giving good strength with outstanding corrosion resistance; 5052 and 5083 are the leading grades for marine, transport and pressure applications.
Heat-Treatable Series: 2xxx, 6xxx and 7xxx
The 2xxx series uses copper as the main addition and offers high strength with good fatigue performance, but it has lower corrosion resistance and is the basis of 2024 for aerospace structures. The 6xxx series uses magnesium and silicon to give moderate strength with good corrosion resistance, weldability and machinability; 6061 and 6082 are the workhorse grades.
The 7xxx series combines zinc, magnesium and copper to reach the highest strengths available, with 7075 reaching beyond 500 MPa. These alloys are less weldable and need protective finishing, so they are reserved for the most demanding weight-critical components.
Tempers and Their Effect on Properties
Non-heat-treatable alloys use the O and H tempers. O is fully annealed and most formable, while H12 through H18 indicate increasing amounts of strain hardening and H22 through H24 indicate partially annealed strain-hardened material.
Heat-treatable alloys use the T system. T4 is naturally aged, T5 is cooled from forming and artificially aged, T6 is solution treated and artificially aged to peak strength, T73 is overaged for corrosion resistance, and T8 combines cold work with artificial aging for maximum strength.
Practical Selection Logic
Start with the service environment. If seawater or aggressive chemicals are involved, a 5xxx grade such as 5052 or 5083 is the natural choice. If a structural load must be carried economically, 6061 or 6082 in T6 is usually the answer. If weight saving outweighs all else, 7075 or 2024 enters consideration.
Then confirm the fabrication route. Bending favors softer tempers, welding favors 5xxx and 6xxx grades, and heavy machining favors 6061 or 6082. Finally, check availability in the required thickness so that the specification is one a mill can actually deliver.
Frequently Asked Questions
Q: Which aluminum series is the strongest?
The 7xxx series offers the highest strength, with 7075 in the T6 temper reaching tensile strengths above 500 MPa, followed by the 2xxx series used in aerospace applications.
Q: Which aluminum is most corrosion resistant?
The 5xxx series, and particularly 5083 and 5052, provides the best overall corrosion resistance, including excellent performance in seawater environments.
Q: What is 1060 aluminum used for?
Grade 1060 is commercially pure aluminum used for foil stock, lighting reflectors, electrical conductors and other applications that need high conductivity, reflectivity and formability.
Q: Which alloy is easiest to weld?
The 5xxx and 6xxx series weld most readily, with 5083 joined by 5183 or 5356 filler and 6061 joined by 4043 or 5356 filler.
Q: What does the T6 temper mean?
T6 indicates that the alloy was solution heat treated, quenched and then artificially aged to peak strength, which is the most commonly specified condition for 6061 and 6082.
Q: How do I choose between 6061 and 5052?
Choose 6061 when heat-treatable structural strength and machinability matter, and 5052 when superior corrosion resistance and formability matter more than peak strength.