Which factor best determines the choice of filler rod in GTAW?

The choice of filler rod in Gas Tungsten Arc Welding (GTAW) is predominantly influenced by the type and thickness of the base material being welded. This is because different types of base materials require specific filler rods to ensure compatibility in terms of chemical composition, mechanical properties, and melting temperatures. For instance, when welding stainless steel, it's essential to select a filler rod that matches the alloy composition to maintain corrosion resistance, strength, and weld integrity.

Additionally, the thickness of the base material impacts the selection, as thicker materials might necessitate a different diameter or type of filler rod to achieve adequate penetration and stability during the welding process. Therefore, understanding the properties of the base material is crucial for making an informed decision about filler rod selection, ensuring that a high-quality weld is achieved.