What happens if the red hot end of the filler rod is outside the shielding gas?

When the red hot end of the filler rod is outside the shielding gas, it is exposed to the surrounding atmosphere. One of the major advantages of shielding gas in Gas Tungsten Arc Welding (GTAW) is to protect the molten metal, including the filler rod, from atmospheric contaminants. If the filler rod is not shielded, it can react with oxygen and moisture in the air, leading to oxidation.

Oxidation can cause undesirable effects on the quality of the weld, such as the formation of oxides that can weaken the final joint, create inclusions, or lead to porosity in the weld. Furthermore, oxidation can negatively affect the appearance of the weld bead, resulting in a rougher and less aesthetically pleasing finish. Thus, the lack of shielding gas directly impacts the rod's integrity and the overall quality of the weld. This is why the correct answer focuses on the oxidation of the filler rod when it is not protected by shielding gas.