what gas for DCEP GTAW?

I believe that argon is recommended for all GTAW work. I personally use it extensively for AC GTAW and it works extremely well.

Straight Ar.

Use a Argon/Helium mix. The Helium will boost the arc heat and make it so you don't need as many amps. This in turn will help your tungsten last a little longer.

Remember that with DCEP TIG on Aluminum you need to use a tungsten at least as thick as your base metal, preferably thicker.

Ernie Leimkuhler wrote in news:260320050237487597% snipped-for-privacy@stagesmith.com:

Based on your previous posts I bought 5/32 dia., 2% Lanthanated electrodes. This is the largest collet I could find. I'm only going to weld fairly thin Al, maybe 1/16 or 3/32.

Do you recommend any particular mix ratio?

I'm thinking of trying straight He, maybe it will conduct more heat from the electrode to the work. What do you think?

Thanks

Argon 75% / Helium 25% should be fine.

Pure Helium is a bitch, and the welds will not look as nice. Yes it is hotter, but the arc is erratic, harsh and hard to initiate.