EWP (Pure) are unalloyed tungsten electrodes (99.5%tungsten minimum) and are non radioactive.  Their current-carrying capacity is lower than those of other tungsten electrodes.  They provide good stability when used with AC, either balanced wave or continuously high frequency stabilized.  They may be used with DC and also with either Ar or He, or a combination of both, as a shielding gas.  They maintain a clean, balled end, which is preferred for aluminum and magnesium welding.  These electrodes have reasonably good resistance to contamination of the weld metal by the electrode, although the oxide containing electrodes are superior in this respect.  EWP electrodes are generally used on less critical applications, except for welding Al and Mg.  The lower cost EWP electrodes can be used for less critical applications where some tungsten contamination of welds is acceptable.

Chemical Composition Requirements

AWS A5.12M/A5.12:2009