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Aluminum Workshop: How to Identify Aluminum Types

Q: Most of my aluminum welding involves the repair of components my customers bring me. How do I know which alloy they are made of and which filler metal to use?

A: This is a good question and one to which there is no easy answer. There is no quick, cheap test that will tell you which aluminum alloy you have. Some equipment can perform chemical analysis without destroying the part, but it is very expensive. The best I can do is provide you with guidelines.

Types of Aluminum Alloys

Castings. While there are many different types of aluminum casting alloys available, the most common castings you will encounter are AlSiMg alloys. The best filler metal for these alloys is 4043.

Extrusions.Extrusions should be easy to recognize. Anything that is an open section, such as an angle or channel shape, or a closed section, such as a round tube or more complex section, is probably an extrusion. Solid shapes, such as round or square bar, can be extruded as well. If you look at the surface of an extrusion, you should see a pattern of fine lines along the long axis. These result from the extrusion process. Aluminum extrusions made In North America or Europe are almost always 6061, 6063, 6082, or 6005. All of these alloys can be welded easily using 4043 or 5356. However, extrusions made in Asia usually are made from 7005, an AlZnMg alloy. You can be fairly sure the extrusions are 7005 if you are working on a motorcycle, bicycle, or car made in Japan or China. The preferred filler for this alloy is 5356.

Bar. Most solid shapes, such as rod or squares, are made by rolling bar. In North America, these are most often made from 6XXX alloys and can be welded using 4043 or 5356 filler.

Sheet and Plate. The most common sheet and plate alloys in North America are the 3XXX and 5XXX series, for which 5356 filler is preferred. However, 6061 is commonly available as a plate alloy, as are the 2XXX and 7XXX alloys, which should not be welded because most of them are considered unweldable.

There is really no easy test to find out which sheet or plate alloy you have.

About the Author
Aluminum Consulting Inc.

Frank Armao

President

Aluminum Consulting Inc.

440-479-0239

Frank Armao was an active member of the AWS D1 Committee, chairman of the AWS D1 Aluminum Subcommittee, and member of the Aluminum Association Committee on Welding and Joining. He also was the author of The WELDER's "Aluminum Workshop" column from 2001 to 2020.