Tungsten electrodes are classified on the basis of their chemical compositions:
E	stands for electrode, which is used for one terminal of the arc welding circuit
W	stands for the chemical symbol of tungsten
The final letters indicate the alloying element (oxide additions):
P	designates a pure tungsten electrode without alloying elements
Zr	is for zirconiated
Th	is for thoriated
Ce	is for ceriated
La	is for lanthanated
The numbers specify the nominal alloying composition (in weight-percent). Thus, EWTh-2 is a thoriated tungsten electrode containing nominally 2 wt-% thoria.

Approximate Current Ranges for Tungsten Electrodes for GTAW
	Straight	Reverse
Electrode Diameter (inches)	Polarity Direct Current Amps	Polarity Direct Current Amps	Unbalanced Wave AC	Unbalanced Wave AC	Balanced Wave AC	Balanced Wave AC
	EWP	EWP	EWP	EWCe-2	EWP	EWCe-2
	EWCe-2	EWCe-2		EWLa-1		EWLa-1
	EWLa-1	EWLa-1		EWTh-1		EWTh-1
	EWTh-1	EWTh-1		EWTh-2		EWTh-2
	EWTh-2	EWTh-2		EWZr-1		EWZr-1
0.010	Up to 15	N/A	Up to 15	Up to 15	Up to 15	Up to 15
0.020	5-20	N/A	5-15	5-20	10-20	5-20
0.040	15-80	N/A	10-60	15-80	20-30	20-60
0.060	70-150	10-20	50-100	70-150	30-80	60-120
0.093	150-250	15-30	100-160	140-235	60-130	100-180
0.125	250-400	25-40	150-210	225-325	100-180	160-250
0.156	400-500	40-55	200-275	300-400	160-240	200-320
0.187	500-750	55-80	250-350	400-500	190-300	290-390
0.250	750-1000	80-125	325-450	500-630	250-400	340-325