There are two shielding gases commonly used for arc welding aluminum, and these are argon and helium. These gases are used as pure argon, pure helium and various mixtures of both argon and helium.
Excellent welds are often produced using pure argon as a shielding gas. Pure argon is the most popular shielding gas and is often used for both gas metal arc and gas tungsten arc welding of aluminum. Mixtures of argon and helium are probably the next common, and pure helium is generally only used for some specialized GTAW applications.