Which of the following shielding gases is NOT typically used in GTAW?

In Gas Tungsten Arc Welding (GTAW), shielding gases play a crucial role in protecting the weld area from atmospheric contamination, which can adversely affect the quality of the weld. Among the commonly used shielding gases in GTAW, argon and helium are the most prevalent due to their inert properties and effectiveness in preventing oxidation and contamination.

Argon is the most widely used shielding gas because it is economical, readily available, and provides good arc stability, making it highly effective for a variety of materials. Helium is also used, particularly for thicker sections or high heat applications, as it can provide a hotter arc and higher penetration.

While hydrogen can be used in specific GTAW applications, such as welding certain types of stainless steels, it is not commonly used as a primary shielding gas for general welding.

Carbon dioxide, on the other hand, is not typically used in GTAW. While carbon dioxide is more commonly associated with other welding processes, like Gas Metal Arc Welding (GMAW), it is not suitable for the GTAW process due to its reactive nature, which can lead to weld contamination and defects. Therefore, the correct answer indicates that carbon dioxide is the shielding gas that is not typically used in GTAW.