A welding electrode is a metal wire coated with a material that has a similar composition to the metal that is being weld. It is quite easy to choose the right welding electrode for the job if you know the various types of electrodes and their applications.
Here is a brief look.
Electrodes come in two basic variants: consumable and non-consumable.
This category consists of bare electrodes, light coated electrodes and heavy coated electrodes that are consumed during the welding process. Bare electrodes are made with wire compositions that are required for different applications. These are specifically used with manganese steel and useful in applications where a coated electrode is required. Using these electrodes increases the stability of the arc. Also, the metal drops are more regular and consistent in size leading to a smoother welding.
These electrodes may be further defined by the nature of their coatings:
Non-consumable or refractory electrodes do not melt during the welding process. They consist of tungsten electrodes that are mostly used in TIG welding processes and carbon electrodes are used for welding and cutting.
The tungsten electrodes come in variants like pure tungsten, 1% and 2% thorium tungsten and 0.3-0.5% zirconium tungsten. Pure tungsten is used in less critical applications than alloyed tungsten. It has a low current carrying capacity and low resistance to contamination. Alloyed tungsten has better arc starting and better arc stability, high current carrying capacity, longer life and higher resistance to contamination. Among the alloyed versions, the thorium variants are usually considered better as they enable better arc control and are also easier to start. The carbon electrodes are made from carbon graphite and sometimes have a layer of copper.