Why is AC used on aluminium TIG welding?

What Is Aluminium Welding with Alternating Current (AC)?

Back in the day when I was at school, AC/DC was the name of a hard rock band* but it was also mentioned frequently in my physics class, to describe alternating current (AC) and direct current (DC).

But what is alternating current really all about? What does it have to do with aluminium?

AC Welding

Whenever aluminium is welded using the tungsten inert gas welding process, alternating current is used. Why?

When TIG welding aluminium, AC or alternating current is used due to the alternating current having a scrubbing effect on the surface, breaking up oxides that limit weld quality.

But it is still possible to TIG weld aluminium with direct current (also called “DC”).

TIG Weld Seam

It takes some practice to weld an even TIG seam.  Welding aluminium is particularly difficult because the material is surrounded by an oxide layer. This only melts at approximately 2015 degrees Celsius, but aluminium itself, depending on the alloy, melts at around 650 degrees.

This means that the aluminium would run away while the oxide layer was being melted, making welding impossible. The oxide layer needs to be destroyed or displaced in order for the process to work.

When welding using alternating current (AC), the electrode continues to change from plus to minus. When the electrode is set to positive, the negatively polarized electrons move from the work piece into the electrode, rupturing the oxide layer in the process. The electrode is then set to negative and the electrons moving into the work piece generate heat—this is how the penetration required for the weld seam occurs.

There are a number of good brands that produce equipment for alternating current and ideally suited to aluminium applications.

Our top 5 acdc tig GTAW models we buy & sell

Fronius Magicwave 3000 AC/DC water cooled TIG
ESAB Origo 4300 AC/DC water cooled TIG
Lincoln Precision 375 TIG AC DC
Miller Dynasty 300 ACDC TIG
Kemppi Mastertig 3500W AC/DC TIG

Are you the owner of AC/DC Aluminum TIG welding equipment?

Want to share your projects with us? We will promote your work. Send us images of TIG welding seams or weaves, your completed work, your equipment and a link back to your web site.

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*Fact
If like me you didn’t know – AC/DC are an Australian rock band formed in Sydney in 1973 by brothers Malcolm and Angus Young (who were born in Glasgow, Scotland)

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