It needs alternating current, and the reason for that is that it needs to blow off the oxide that forms instantly over raw aluminum. I did wonder at one time if there wasn't a way to DC weld aluminum, because frankly everything is possible with welding, and was probably typical at some point. Recently I came across infor that said it was possible to DC weld aluminum, but whatever the trick was it require something other than Argon to do it. So for me I wouldn't want to go a whole other rental. It is also possible to gas weld aluminum if you have that gear, get the right flux from Tinmantech, though proceed with caution and be sure you can do what you want with the alloys you want. Often one needs to heat treat the aluminum frame after welding which sounds like a pain. I had a friend who welded aluminum and got the frames heat treated in exchange for more Al welding.

Also, Al likes the higher end welders that have stuff like square wave, etc... because they give better efficiency and aluminum needs a lot of power to get the job done. Not much of a concern at our thicknesses.