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Don Foreman
 
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On Fri, 13 May 2005 19:23:54 -0400, rich brenz
wrote:

I have some small pieces of aluminum I wish to join, and have Al solder
and flux. The flux has no directions but does say to apply to parts and
do not overheat. Should the flux be wiped off before attempting to
solder? When I try to leave the flux in place, it turns dark brown,
smokes a lot, and seems to prevent the solder from adhering? Any useful
suggestions?(Other than "try brazing" or "get a welder"...)

Rich


That sounds like the organic flux used with Harris Alsolder500 and
Allstate Strongset 509. The flux must be present when soldering for
the solder to wet the aluminum These materials work well if you can
avoid burning the flux, but that's not easy to do. The trick is to
keep flame away from the flux. If the flame ever touches the flux,
yer screwed. Either heat by conduction from an unfluxed area, or use
a hot air gun.

Some easier-to-use aluminum solders a
aerosolder , see
http://www.tinmantech.com/html/alumi..._brazing_.html

#33 from http://www.aladdin3in1.com/catalog2.htm use #585 flux

The fluxes used with these materials work OK with a torch. I like
the aerosolder best. That flux turns water clear at about the right
heat for soldering, which is about 780F. It's a lot easier to use
than the organic stuff. There is no sodium flare with these
fluxes, so you don't need special goggles as in aluminum brazing.

I don't like the "miracle rod" or "rub on rod" , as Aladdin #31
"three-in-one" and others for aluminum, though they do work well on
whitemetal. They basically are whitemetal! I think the other
materials mentioned here make much better and stronger joints.

As others have mentioned, buy a stainless "toothbrush" from a welding
store for cleaning the metal. They're under 2 bux. Anchor is one
good brand. The Chinese ones are so soft they're about useless.