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Table 2 Special shielding gas mixtures used in arc welding of aluminium and key gas characteristics (based on (Regis 2008))

From: Investigation of weld defects in friction-stir welding and fusion welding of aluminium alloys

Shielding gas mixtures Resultant positive weld features Gas characteristics
Argon and helium (80 %) Improvements in bead profile and fusion Argon—low cost and better protection as its density is higher than air.
Argon and chlorine Significant reduction in porosity & improved process tolerance Chlorine—extreme toxicity limits its suitability for many applications.
Argon and Freon Improved arc stability and weld bead geometry Argon/Freon mixtures—non-toxic so Freon can substitute chlorine yet obtain similar effects to argon/chlorine mixtures.
Helium Greater penetration Helium—welding Al leads to high levels of ozone. Small amounts of nitric oxide can control ozone formation.