Tungsten electrodes are used when arc welding or plasma welding using the tungsten inert gas (TIG) process. In both processes, the electrodes, arc and molten pool are protected from atmospheric contamination by an inert gas. A tungsten electrode is used because it can withstand very high temperatures with minimal melting or corrosion.
Tungsten electrodes are classified according to their chemical composition, i.e. the main oxide used and its percentage of the total mass of the electrode. All the different tungsten electrodes are assigned different codes and colors for easy identification.
The oxides are mainly thorium, lanthanum, cerium and zirconium. Their additions can vary from 0.7% to 4%. The color chart below summarizes the types of TIG tungsten electrodes: