Thoriated

Thoriated refers to materials containing thorium, most commonly thoriated tungsten electrodes used in tungsten inert gas welding. Thoriated tungsten is tungsten doped with thorium oxide (ThO2), typically around 2% by weight. The thorium oxide improves electron emission from the electrode, lowers work function, reduces the tendency to arc-strike, and allows stable arc initiation at higher current levels. This makes thoriated tungsten favorable for direct current (DC) welding, particularly DCEN, and for welding thicker sections where high current is used.

However thorium is radioactive, presenting health and safety considerations. When heated in welding, thorium-containing compounds may be emitted in fumes. Grinding or machining thoriated electrodes can generate radioactive dust; appropriate ventilation, fume extraction, and protective equipment are advised. Used electrodes should be disposed of according to local radioactive waste regulations, and many jurisdictions restrict disposal in ordinary waste streams. Due to these concerns and the availability of non-radioactive alternatives, some welding operations now prefer cerium- or lanthanum-doped tungstens or zirconiated varieties for many applications, especially in situations with health and regulatory concerns or where alternating current (AC) welding is required.

Thoriated tungstens remain in use in certain DC welding applications, particularly where a stable arc at high current is needed and operators are trained to manage thorium-related risks. Proper handling and compliance with safety guidelines are essential.