Beginner With DC TIG

[Bigblockscott]

I agree with Raustinss. Scotch bright your aluminum then wipe with acetone. I actually clean all my materials with scotch bright, I have a few dedicated SS toothbrushes I use if I need to get into little nooks and crannies.
Tungsten stick out and how close you are holding the torch to your material can make a major difference too.
I personally have not done much mild steel, I mostly do stainless exhaust, and I run 1 amp per thousandth of material thickness. 0.060 exhaust tubing = 60 amps on the welder.
I need to practice with aluminum more, my aluminum welds look like garbage.
Don't forget to wipe down your filler rod with a little acetone on a paper towel.