Tungsten inert gas (TIG) welding, also known as gas tungsten arc welding (GTAW), is an arc welding process that uses a tungsten electrode to transmit the electric arc to the work piece. Unlike other arc welding methods, the tungsten electrode does not provide material to the weld, so a separate filler rod is needed for that purpose. Some tungsten electrodes are made with a small amount of thorium,namely thoriated tungsten electrodes, which is a radioactive material and improves the welding qualities of the electrode.
Thoriated tungsten electrodes are made from tungsten combined with 1 to 2 percent thorium in the form of thorium dioxide. Thoriated tungsten electrodes result in improved welding properties over pure tungsten electrodes. By using thoriated tungsten electrodes, welders find it easier to start the arc and maintain the arc, reduce weld contamination, carry a higher level of current, and achieve a longer electrode life through reduction in wear. Therefore, thoriated tungsten electrodes are preferred by welders in tungsten insert gas welding.
There is one point should be mentioned that thorium is a radioactive element, so thoriated tungsten electrodes do emit some radioactivity, but the amount is relatively low. Thorium mainly emits alpha particles, which can't pass through a sheet of paper, but could potentially damage skin tissue with prolonged exposure. Thoriated tungsten electrodes should be stored in a steel container marked with the radiation trefoil as an identifier.