When performing GTAW on magnesium, which polarity is typically used?

When performing GTAW on magnesium, which polarity is typically used?

• A. DC+
• B. DC-
• C. AC
• D. Multipolar

Answer: (C)

When performing Gas Tungsten Arc Welding (GTAW) on magnesium, the typical polarity used is alternating current (AC). This choice is significant because AC allows for better cleaning action on the surface of magnesium, which is crucial for achieving a good weld. Magnesium is an exotic metal that tends to oxidize quickly when exposed to air, creating a layer of oxide that can negatively affect the welding process if not properly managed. Using AC introduces a cleaning effect during the positive half of the AC cycle, where the positive electrode helps to remove the oxide layer from the surface of the magnesium. Additionally, the negative half-cycle allows for the effective penetration of the weld in the underlying base metal. This dual action of AC is why it is favored over direct current options, which may not provide the same level of cleaning and can lead to poor weld quality. In contrast, direct current options have specific advantages in other scenarios, but they do not effectively manage the surface oxide layer on magnesium in the same way that AC does. Therefore, AC is the most reliable and effective polarity choice for GTAW when welding magnesium.

When performing Gas Tungsten Arc Welding (GTAW) on magnesium, the typical polarity used is alternating current (AC). This choice is significant because AC allows for better cleaning action on the surface of magnesium, which is crucial for achieving a good weld. Magnesium is an exotic metal that tends to oxidize quickly when exposed to air, creating a layer of oxide that can negatively affect the welding process if not properly managed.

Using AC introduces a cleaning effect during the positive half of the AC cycle, where the positive electrode helps to remove the oxide layer from the surface of the magnesium. Additionally, the negative half-cycle allows for the effective penetration of the weld in the underlying base metal. This dual action of AC is why it is favored over direct current options, which may not provide the same level of cleaning and can lead to poor weld quality.

In contrast, direct current options have specific advantages in other scenarios, but they do not effectively manage the surface oxide layer on magnesium in the same way that AC does. Therefore, AC is the most reliable and effective polarity choice for GTAW when welding magnesium.