Which of the following best describes the purity level of pure tungsten electrodes used in GTAW?

Pure tungsten electrodes used in Gas Tungsten Arc Welding (GTAW) are characterized by their high level of purity, typically defined as being composed of 99.5% tungsten or higher. This purity is essential because impurities can adversely affect the electrode's performance, particularly its electrical conductivity and arc stability. Pure tungsten is particularly advantageous for welding applications where the highest quality welds are required, such as in aerospace and nuclear industries.

The correct understanding of purity implies that while tungsten in its pure form is exceptionally effective for producing stable and consistent arcs, it does not retain any significant level of impurities. Other methods of enhancing performance, such as adding certain alloying elements like thorium, lead to other types of tungsten electrodes that are designed for specific applications but do not align with the definition of pure tungsten. Hence, the correct characterization of pure tungsten electrodes is that they can contain no impurities, highlighting their essential qualities in the context of GTAW.