https://www.tokentools.com.au/wp-content/uploads/AC-Frequency.png

AC current is used for aluminium and it’s alloys. When electrons flow from the workpiece to the positively charged tungsten during the cleaning half cycle, they remove the oxide layer from the surface of the aluminium by blowing it off from beneath and the gas shield of inert argon prevents new oxide forming thus allowing the molten pool of pure aluminium to fuse.

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ac for tig aluminium, ac or dc for tig, difference ac dc tig welding, why ac on tig