Selection and Preparation of Tungsten Electrodes
Types of Tungsten Electrodes
2% Cerium-Alloyed Tungsten Electrode (AWS Classification: EWCe-2, Color Code: Gray)
Cerium-alloyed tungsten electrodes are preferred for welding carbon and stainless steels, nickel alloys, titanium, pipes, and thin sheet materials due to their excellent arc initiation. These electrodes deliver high performance particularly in DC current but can also be used in AC current. Containing a minimum of 97.30% tungsten and 1.8–2.2% cerium, these electrodes can also be used as a substitute for pure tungsten electrodes because they have a 30–40% higher current capacity in AC.
1.5% Lanthanum-Alloyed (AWS Classification: EWLa-1.5, Color Code: Gold) and 2% Lanthanum-Alloyed (AWS Classification: EWLa-2, Color Code: Blue) Tungsten Electrodes
1.5% and 2% lanthanum-alloyed tungsten electrodes provide excellent arc initiation at low currents and offer a long-lasting, stable structure that reduces tip wear. 2% lanthanum-alloyed electrodes are used in critical industries such as aerospace and can replace 2% thorium-alloyed tungsten electrodes. Both types can be used for welding carbon and stainless steels, nickel and aluminum alloys, and titanium. 1.5% lanthanum-alloyed electrodes contain 97.8% tungsten and 1.3–1.7% lanthanum, while 2% lanthanum-alloyed electrodes contain 97.3% tungsten and 1.8–2.2% lanthanum. With their round tip shape, they are also a preferred choice for AC power sources.
Pure Tungsten Electrode (AWS Classification: EWP, Color Code: Green)
Containing 99.5% pure tungsten, these electrodes offer a more economical option compared to alloyed types. They are particularly preferred for AC welding applications and form a round tip when heated, providing a stable arc. While they offer good arc stability when welding aluminum and magnesium alloys with AC power sources, they should not be used with DC inverter power sources.
2% Thorium-Alloyed Tungsten Electrode (AWS Classification: EWTh-2, Color Code: Red)
These electrodes feature good arc initiation and high current-carrying capacity. Thanks to an alloy containing a minimum of 97.3% tungsten and 1.7–2.2% thorium, they maintain arc stability with a low consumption rate and prevent contamination of the weld metal. They can be used for both AC welding and DC (-) welding of materials such as carbon steel, stainless steel, nickel alloys, and titanium. Due to its thorium content, it contains a small amount of radioactive material; therefore, operators must follow the instructions for use and the Material Safety Data Sheet (MSDS) guidelines.
Zirconium-Alloyed Tungsten Electrode (AWS Classification: EWZr-1, Color Code: Brown)
Designed for welding aluminum and magnesium alloys, this electrode contains 98.6% tungsten and 0.7–0.9% zirconium. It produces a reliable arc by forming a rounded tip in AC applications. Compared to other types, it has a higher current-carrying capacity without breaking and ensures minimal tungsten carryover into the weld metal. It also offers superior arc stability and a reliable arc start.
Electrode Preparation
Depending on the electrode type, two different tip shapes can be achieved using appropriate preparation methods: round and pointed tips.
Round-Tip Tungsten Electrodes
The round tip shape is particularly suitable for pure tungsten electrodes and is preferred for welding operations performed with AC sinusoidal waveform or traditional square-wave TIG power sources. To round the tip of the tungsten electrode, AC current values appropriate for the electrode diameter must be applied; this allows the round tip to form naturally. To prevent tip breakage and arc instability, the diameter of the round tip should not exceed 1.5 times the electrode diameter.
Pointed-Tip Tungsten Electrodes
Pointed-tip tungsten electrodes are particularly preferred for pure, cerium-alloyed, lanthanum-alloyed, and thorium-alloyed electrodes in inverter AC and DC welding applications. They are also ideal for welding thin materials at low currents. The fact that the electrode tip focuses the arc and prevents distortion makes this application a preferred choice. However, these electrodes should be avoided at high currents due to the risk of them penetrating the weld metal. To properly grind a tungsten electrode, it should be rubbed against the grinding wheel with a back-and-forth longitudinal motion. To ensure arc focusing and easy arc initiation, the length of the pointed tip should not exceed 2.5 times the electrode diameter. Take care to remove any dust generated while grinding thorium-alloyed tungsten electrodes from the work area.
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