Dave Plowman (News) wrote:

I need to secure a boss made from aluminium rod into a hole made in the
wall of an aluminium tube. Of course welding would be ideal - but there's
little load on it. And I'm not sure I can be bothered finding an aluminium
welder. Unless I could do it myself with my MIG. Which I'm not much good
with on steel. ;-)
Car body filler? Epoxy? Any special precautions?

http://www.weldguru.com/braze-aluminum.html

You can use Araldite, but you need to thoroughly de-grease and I find it
better to abrade away the surface oxide before applying the adhesive. I
once made a whole load of microscope slide racks from aluminium extruded
sections and glued them with araldite. It was obvious which ones were
not succesfully glued. A slight tap on the desk and they fell apart.

I was told when I worked with a group that developed composite structure
for aircraft that epoxy glued aluminium degrades fairly rapidly over
time and that over-the-counter epoxy gues really don't bond well to
aluminium. The preferred adhesives for aluminium are a hybrid epoxy
adhesive such as epoxy-nylon and specialist polyurethane glues. Some of
these glues require special primers or activators to be applied to the
surface before bonding.

If I wanted to make a permanent job I'd braze it, using the appropriate
aluminium brazing rod.