ANSI Classifications System - Airgas.com

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ANSI Classification
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Tungsten electrodes are classified on the basis of their chemical compositions.

E: Stands for Electrode
W: stands for the chemical symbol for tungsten (also called Wolfram) The final letter indicates the alloying element or oxide additions.
P: Pure
Zr: Zirconiated
Th: Thoriated
Ce: Ceriated
La: Lanthanated
G: stands for unspecified oxide additions

The numbers specify the nominal alloying composition (in weight by percent). For instance, EWTH-2 is a thoriated tungsten electrode that contains nominally 2% thoria.