75/25 is not good to use on aluminum. Always tig with straight argon. I usually weld at around 100 amps A/C when I do catch cans. Don't worry about the tungsten too much, just use a red 3/32 and you will be good to go. The red won't really ball up like the green and it seems to weld better.
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Don't bother giving me "rep", I won't return it and I think it is stupid.
Gracie Barra Clearwater
Gyms in Clearwater, St. Pete and Port Richey
pm me if you are interested in trying a free class at any of the gyms.