If you have the gear, you can weld aluminum, but it takes experience and just the right gear. One part of the skill is aluminum melts before it gets red hot. You can't tell the temperature from the color.
Standard solder won't stick to aluminum no matter what you do.
OTOH, there are several aluminum brazing products out there that work with a standard propane torch. Basically they are a zinc alloy and flux. I've actually never tried it, but those products have been on the market for decades so they must work. I've also seen a salesman demo where he brazed the butts of 2 coke cans together. All he did for prep was scrub with a stainless brush.
The big problem with aluminum is it quickly develops a thin oxide. For what little aluminum welding I've done, I scrub the area with a stainless wire brush (sand paper will work too) then clean it with rubbing alcohol, then I get the flux on it right away. The flux in the brazing kits may be aggressive enough to eat right though the oxide.