How to Best Join Aluminum: Fasteners, Brazing, Soldering or Welding?

In reply to Go_Gators (Forum Supporter) :

What ga. Al, and how long is your MIG hose?

Can't duct tape it.  Jb weld 

I'd like to hear the pros and cons of rivnuts

Brazing and welding can be disasterous if you use the wrong aluminum alloys, and unfortunately, most aluminum tubing is made from the wrong alloy - 6000 series.  This alloy will lose up to 2/3 of its strength when welded.  It needs to be heat treated in a heat treating oven after welding to bring it back to spec. 

There are stories on the corvette forum where guys are getting their forged aluminum wheels powder coated and if the powder coater heats the wheels just a little too much, they lose their temper.

If you want to weld aluminum, stick with a marine grade alloy - something in the 5000 series.  These alloys are not tempered.

In reply to JG Pasterjak :

Soldering and brazing appear to be similar but are actually quite different. Brazing uses an alloy rod that melts and dissolves a thin layer of the base materials forming a true metallic bond. Soldering is typically done at a lower temperature and the actual bonding is achieved by the formation of intermetallic compounds between the solder and the base material. These intermetallics are brittle and generally do not provide anywhere near the strength of a brazed joint. Soldering does provide a good electrical bond, which is why it is widely used in electronics.  

I've always wonder how these Cragar aluminum centers welded to steel rim shells works. They have been building them this way for some 60 years. (Edit: fixed the link to the right) CragarWheel.com: Series 61C S/S

Sorry, but soldering and brazing are not the same. With a braze joint, the filler metal actually dissolves the surface of the base material, forming a metallic bond. With soldering the filler material forms an intermetallic compound between it and the base material. Intermetallic compounds are brittle and weaker compared to true metallic joints. They do conduct electricity well.  This is the reason soldering is used in extensively in electronics, but only in relatively low stress mechanical applications like gutters or copper plumbing.