NOCTI Welding Practice Test

The cause of tungsten "frosting" or discoloration primarily results from inadequate shielding gas. In TIG welding, the purpose of the shielding gas, usually argon, is to protect the tungsten electrode and the weld area from atmospheric contamination. When the gas coverage is insufficient, oxygen and nitrogen can react with the tungsten electrode, leading to discoloration or "frosting." This condition indicates a loss of clean, stable arc characteristics, which can negatively affect the quality of the weld.

Other factors, like excessive heat input or incorrect gas flow rate, can lead to other issues in the welding process but are not the direct causes of tungsten frosting. Similarly, while contamination of the tungsten could result from various sources, the specific term "frosting" is more directly associated with the failure to adequately shield the tungsten from the environment.