What is the main disadvantage of using scratch start?

The main disadvantage of using scratch start in Gas Tungsten Arc Welding (GTAW) is that it can damage the tungsten electrode. This technique involves physically scratching the tungsten against the workpiece to initiate the arc. When this happens, it's possible for the tip of the tungsten to become contaminated with material from the workpiece or to experience wear and tear, leading to a less effective or unstable arc.

Using scratch start can also lead to issues such as increased risk of inclusions in the weld, as debris from the scratch can become trapped in the molten weld pool. Additionally, this method may require a bit of speed and precision to initiate the arc without damaging the electrode, and in some cases, it can take longer to initiate the arc. However, the direct damage to the tungsten and the contamination are particularly critical concerns that can affect the overall quality of the weld.