Tungsten electrodes carry the TIG arc and are graded by the oxide added to the tungsten, which changes arc starting, current capacity and arc stability. The colour code on the end of the electrode identifies the type.
Thoriated tungsten (red band) contains thorium oxide and gives the best arc starting and stability at high amperage on DC. It is the traditional choice for steel and stainless, but thorium is mildly radioactive, which has pushed many shops toward alternatives for grinding dust and disposal reasons.
Lanthanated (gold band) is the general replacement — comparable or better arc starting than thoriated, good current capacity, and usable on both AC and DC. Ceriated (grey band) starts well at low amperage and is favoured for thin material. Pure tungsten (green band) is used for aluminium on AC because it forms a balled tip, but it has lower current capacity than the alloyed types. Zirconiated (brown band) is a middle ground for AC aluminium work with better resistance to contamination.
Diameter sets the amperage range — 1/16 in covers roughly 70-150 A, 3/32 in covers 150-250 A, 1/8 in covers 250-400 A. Electrode tip preparation matters as much as the type: a pointed tip for DC work on steel, a balled or truncated tip for AC aluminium.
