2% Thoriated (Color Code: Red)
2% thoriated tungsten electrodes (AWS classification EWTh-2) contain a minimum of 97.30% tungsten and 1.70 to 2.20% thorium. They are the most commonly used electrodes today and are preferred for their longevity and ease of use. Thorium increases the electron emission qualities of the electrode, which improves arc starts and allows for a higher current carrying capacity. This electrode operates far below its melting temperature, which results in a considerably lower rate of consumption and eliminates arc wandering for greater stability. It also features a lower level of weld contamination than other electrodes.
Unlike pure tungsten, these electrodes are only for specialty type AC welding (thin gauge aluminum or materials less than .060-in.), but they are exceptional for DC electrode negative or straight polarity on carbon and stainless steel, nickel and titanium applications.
During manufacturing, thorium is evenly dispersed throughout the electrode. This evenness allows the electrode to maintain a sharpened edge—the ideal electrode shape for welding thin steel. Sharpening the electrode's point, however, should be done with great care. Thorium is radioactive; therefore, you must always follow manufacture's warnings, instructions and the MSDS (Material Safety Data Sheet) for its use.

2% Ceriated (Color Code: Orange)
2% ceriated tungsten electrodes (AWS classification EWCe-2) contain a minimum of 97.30% tungsten and 1.80 to 2.20% cerium. These electrodes perform best in DC welding at low current settings but can be used proficiently in AC or DC processes. With its excellent arc starts at low amperages, ceriated tungsten has become popular in such applications as orbital tube and pipe manufacturing, thin sheet metal work or jobs where small and delicate parts are welded. Like thorium, it is best used to weld carbon and stainless steels, nickel alloys and titanium, making it an obvious replacement for 2% thoriated electrodes.
Ceriated tungsten features slightly different electrical characteristics than thorium but most operators won't be able to tell the difference. Using ceriated electrodes at higher amperages is not recommended. In these situations, the oxides will migrate quickly to the heat at the tip, removing the oxide content and nullifying its process benefits.

1.5% Lanthanated (Color Code: Gold)
1.5% lanthanated tungsten electrodes (AWS classification EWLa-1.5) contain a minimum of 97.80% tungsten and 1.30 to 1.70% lanthanum, or lanthana. These electrodes have excellent arc starting, low-burn-off rate, good arc stability and excellent re-ignition characteristics—many of the same advantages as ceriated electrodes. 1.5% lanthanated electrodes also closely resemble the conductivity characteristics of 2% thoriated tungsten, meaning, in some cases, it can replace 2% thoriated without having to make significant welding program changes.
1.5% lanthanated tungsten electrodes are ideal if you want to optimize your welding capabilities. Lanthanated electrodes work well on AC or DC electrode negative with a pointed end or they can be balled for use with AC sine wave power sources. The lanthana is dispersed evenly throughout the entire length of the electrode during manufacturing. It also maintains a sharpened point well, which is an advantage for welding steel and stainless steel on DC or the AC from squarewave power sources.
Unlike thoriated tungsten, these electrodes are suitable for AC welding and, like ceriated electrodes, allow for the arc to be started and maintained at lower voltages. AC Compared to pure tungsten, the addition of 1.5% lanthana increases the maximum carrying capacity by approximately 50% for a given size electrode.

Zirconiated (Color Code: Brown)
Zirconiated tungsten electrodes (AWS classification EWZr-1) contain a minimum of 99.10% tungsten and .15 to .40% zirconium. A Zirconiated tungsten electrode produces an extremely stable arc and resists tungsten spitting. It is ideal for AC welding as it retains a balled tip and has a high resistance to contamination. Its current carrying capability is equal to or greater than thoriated tungsten. Under no circumstances is zirconiated recommended for DC welding.

Rare Earth (Color Code: Gray)
Rare earth tungsten electrodes (AWS classification EWG) contain unspecified additives of rare earth oxides or hybrid combinations of different oxides, but manufacturers are required to identify each additive and its percentage on the package. Depending on the additives, desired results can include: a stable arc in both AC and DC processes, greater longevity than thoriated tungsten, the ability to use a smaller size diameter tungsten for the same job, use of a higher current for similar sized tungsten and less tungsten spitting.