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Why are noble gases used when refining aluminum and other hot metals?

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Neon — noble gas A road in Tokyo lined with neon signs.

Noble gases, such as argon and helium, are used during the refining and welding of aluminum and other hot metals because they provide a protective, chemically unreactive environment.1

When metals are heated to high temperatures, they become highly reactive and can easily combine with atmospheric oxygen, and sometimes nitrogen or carbon dioxide. This reaction is detrimental because it forms an oxide layer that can prevent proper bonding, create brittle joints, or alter the intended composition of the metal.12

By using noble gases to displace the air around the hot metal, industries create an inert atmosphere. Because these gases are chemically indifferent, they do not react with the metal, effectively shielding it from the damaging effects of the surrounding atmosphere during processing.12