Re: aluminum solder?

"brassbend" <waldhorn@xxxxxxxxxxxx> wrote in message
news:1dPSe.399$wR4.38097@xxxxxxxxxxxxxxxxxxxxxx
> What 'zacky is in aluminum solder? Will it only work on Aluminum only
> or will it solder other materials? Is it a strong bond?

Depends on what it is...

Aluminum solder is anything that wets aluminum. This includes most metals
on the periodic table with a melting point less than aluminum's. Zinc, tin,
gallium, mercury and some of the alkaline metals (maybe just lithium). The
heavy white metals thallium, lead, indium and bismuth probably don't stick
too well. Gallium and mercury amalgamate (aluminum amalgam is used in
various chemical reactions), but they just weaken and oxidize it at room
temperature. Cadmium is similar to zinc so may wet it well, but it is more
of a "heavy metal" than zinc, so may not.

Of the "good" metals, zinc and tin are the cheapest and thus most practical.
Coincidentially, they happen to be the most used. Pure tin, maybe with some
copper or silver to strengthen it, would work well enough. Lead-tin may
work, the tin holding it to the aluminum. I've done it before, but due to
the poor joint (I don't have the fluxes), it's hard to say how well it
works.

As for zinc, it alloys very well with aluminum so is more like brazing, and
as a matter of fact its melting point is somewhere around 800°F so it's
pretty much brazing by definition anyways.

The "magic solder" stuff that comes with a flux (probably based on corrosive
fluorides) and melts at a low temperature is probably tin and zinc, possibly
with cadmium and lead. The "miracle rod" product that "doesn't" require a
flux (because you rub the rod against the work to break the oxide) is either
pure zinc or an alloy with up to 12% aluminum.

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms


.

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