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Posted by Neon John on April 1, 2009, 7:27 am

Big honking soldering gun.  Weller or equiv
Xacto knife or equiv
Small file
Aforementinoed flux.

Use the file to remove any anodizing or other coatings.  bright shiny
metal is required.  Arrange the surface to be level.  Puddle on a
little flux. Take the Xacto knife and scrape the surface of the
aluminum while it is submerged and covered in the flux.  This is
critical, as it prevent the aluminum from instantly oxidizing.

Get the iron very hot.  apply some solder to the iron so that it hangs
from the bottom.  Plunge the iron into the flux and immediately scrub
the surface with the iron.  Keep the area covered in flux.  I use a
flux applicator that has a blunt hypodermic needle to dispense the

As you scrub the surface with the iron tip, you'll notice that solder
starts to wet the surface in spots.  Rub between the spots to spread
the wetting to one solid puddle.  When the puddle is large enough to
receive the wire, apply the fluxed wire to the puddle.  Heat well,
then allow to cool.

The critical parts are:

- aluminum is always submerged in flux to protect it from oxidization
- Iron is very hot so that solder starts wetting the aluminum before
it can oxidize once the flux is vaporized.
- Work fast.  Have everything at hand so that you can immediately
apply the solder after scraping the surface with the knife.  Even
under flux, aluminum will oxidize in a short period.  If you have to
stop for any reason, go back and re-establish the puddle and then
scrape again.


Posted by Morris Dovey on April 1, 2009, 10:41 am
Neon John wrote:

I've saved /two/ copies, just in case. :)

I'd always heard that it couldn't be done - and this is info that I can
put to use.

Thank you!

Morris Dovey
DeSoto Solar
DeSoto, Iowa USA

Posted by Ulysses on April 1, 2009, 11:03 pm

I was sure it couldn't be done so I've never even tried to solder aluminum.

Posted by Bob F on April 2, 2009, 6:14 pm
 Ulysses wrote:

Posted by Jim Wilkins on April 1, 2009, 11:54 am
That technique works well on copper and brass, too, for instance when
repairing old equipment. It can damage the plating on the tip of the
iron, so don't try it with a temperature-controlled iron unless you
have a source for spare tips. They usually don't hit the second-hand
market until they are obsolete.

One place to look:

Jim Wilkins

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