The major alloy in 2000 series is Copper, it's unweldable with TIG. As far as I know. You can resistance weld it. If your wanting to learn to weld Aluminum try to find 6000 series, can be welded with most processes.

Welding aircraft components without a class 1 repair doccument approved by the manufacturer is a bad practice at best.

If your job is aircraft aluminum that won't fly ever, thats another story.

Finding out the material type is very important. As mentioned, 2000 series aluminum is not going to be sound after welding. 7075 is the other primary alloy used for aircraft structures, this is also unweldable. Your aircraft mechanic friend can do the research to find out what material that component.

If you find that your material is 6061 sheet than you can do a few things that will make those butt welds go just fine.

First is surface prep. Oxides must be removed, for that thin material I suggest an aluminum oxide scotchbrite disc 11/2 inch dia. mounted on a 12-18thousand rpm angle die grinder.

Next. No gap in the butt joint. It must be *cleanly* sheared with no roughness at the mating surfaces. There must be very little mismatch when you tack it (less than 0.010 max mismatch). Hold it up to a light, it must be tight.

Next, do a trial on 1.5 x 4 inch coupons

Set dynasty balence control to 60

Set frequency to 120

Set amps at 25-30, you won't need it all but its nice to have a little juice at the beginning.

Sharpen your tungsten and keep it perfectly clean. Stop at once if you dip it even a little and redress. 0.040 may work, so will 1/16

Technique. Tightly tack at each end, 6061 requires filler even for the tacks.

After tacking, make a slight tent out of your coupon so that your reenforcement will not get heat sinked on the table. Just enough to keep the root about 1/8 inch off the table.

Torch angle should be practically perpendicular, maybe 5 to 10 degrees push angle. Strike an arc on the joint line 1/4 inch inside of the tack and don't add wire until you see the line between your work pieces both melt. If your piece is prepped properly it will melt together rather than seperate. add wire to the pool as soon as you see it sink, than move forward and repeat until you reach the end.

Making the assumption the purpose of this repair is so this aircraft can fly again I have to agree with Lawrence. It’s just not a wise move to proceed without being approved to do such repairs. Proper material identification (statement from a mechanic doesn’t count) is paramount to any structural repair, welded or not. In addition to proper welding technique, some form of post weld inspection is almost certainly mandatory. This inspection, in most cases, requires NDT equipment and someone w/ an A&P cert qualified (usually by the repair station) to conduct such an inspection. Being new to TIG welding isn’t going help either.

During my years as a structural mechanic with a heavy jet repair station we only made a handful of welding repairs. Out of those few instances the components were mainly titanium or inconel and not structural members.