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How to Solder Aluminum


#1

How does Aluminum do when soldiered? Does it work ok? Will Silver
Solder work?

Thanks ahead of time
Laura


#2

No! Do not attempt to use silver solder. You will end up with a mess!
I am not sure of an alternative.

Sincerely,
Andrea Streicher
510-528-1911


#3

The main problem with Aluminum is the oxide coating (AlO2 ?) which
melts at a higher temp. than the metal underneath. It also has very
little color change when heated making it difficult to tell if it’s
about to flow. There are special techniques, fluxes and solders to
work Aluminum. Could one of the resident Chemists comment on the Oxide?


#4

This is what I think I’ve learned about soldering. The solder, is a
filler metal. It works by creating by creating an electrostatic bond
between itself and then base metals when in the liquid state (it
"wets" the metal). That bond cannot happen if the metal is dirty or
oxidized. Aluminum oxides very easuly with heat. In fact it oxidizes
even without heat, the oxide layer is so strong that it protects the
surface.

So unless you are a pro who can provide an oxygen free environment,
you just might be out of luck. Why not consider cold joining (rivets,
tabs, and staples) and use them as part of the design?

Legamin


#5

As far as I know Aluminum does not solder with lead (soft) or
silver(hard) solder. There are some special rods available that will
join aluminum as in solder and it can be welded with special rod and
gas torch or TIG welded.

The special “solder” rods can oftem be found at agricultural
irrigation stores, farm supplies, farm equipment stores, welding
outlets and boat supply stores (chandleries… spelling). These
are the deep water boating suppliers, not the sports boats outlets. I
have some rod (Aluminu) that you can “weld” a hole in a beer/soda can
closed and if you try to remove the weldment, you destroy the can
before the weldment comes loose. This stuff cost about $2.00 for a
12" rod aobur 1/4" in diameter.

Hope this helps…
John Dach
MidLife Crisis Enterprises
C.T. Designs
Cynthias sculptures are at: http://www.mlce.net
Maiden Metals,
A small bronze foundry, no web site yet!!


#6
  How does Aluminum do when soldiered? Does it work ok? Will Silver
Solder work? 

Laura,

Aluminum is a very different metal from silver. One key difference
is that it has an extreme affinity for oxygen. Any aluminum exposed
surface forms an instant, impervious oxide layer, which then prevents
further oxygen from reaching the surface, and this is why the metal
retains it’s metallic nature. But that oxide layer prevents normal
soldering. Silver or gold solders will not work at all. In fact,
many of them melt at a higher temp than the aluminum itself, which
wouldn’t do you much good.

however, there ARE solders designed for aluminum. Generally they are
a combination of a fairly solid stick of the solder, and a specially
formulated flux. In use, you “scrub” the solder stick onto the joint,
which mechanically helps the flux displace that very tough oxide layer
enough for the solder to stick. The solders behave much more like the
tin based solders we jewelers call “soft” or “lead” solders. But they
do work. Still, these things usually are designed for repairing your
porch railing, not making jewelry scale objects. If you’re thinking
of carefully placing little paillons of aluminum solder around your
aluminum bezel while you solder it to your aluminum ring, you’re out
of luck. You’ll probably not get that to work… Note that
generally, these solders are designed to bond aluminum to aluminum.
Not aluminum to other metals.

Aluminum is generally fastened using so-called "cold bonding"
techniques, like rivits, screws, mechanically formed joints, or the
like. One technique which does actually fuse the metals is fusion
welding, which requires a specific machine. Usually this is used for
things like earring posts or similar findings being attached to the
aluminum. They are made specially for this use, with a tiny “nib” of
metal protruding down from the area which is intended to bond to the
aluminum. The machine places an electric charge between the finding
and the piece to be bonded to, and slams themtogether. As that little
nib just touches the other piece of metal, it causes a spark to jump.
The spark treats that little nib just like a fuse, blowing it. In
essence, it does the same thing as that screwdriver you accidentally
touched a live wire with once. Remember? vaporized half the tip of
the screwdriver when it arced? Will, this is controlled, but that
little “nib” of metal vaporizes just as the two larger surfaces are
brought together. This creates a very hot plasma for just a moment
between the metals, which not only drives off all atmospheric gas,
including oxygen, but also melts the surfaces enough so they can mix
and bond as they contact each other.

Fusion welding is, as I noted, usually used to put earring posts and
other findings on. but it can be used as a more versatile bonding
technique if you consider that a well bonded earring post can also be
considered as a rivet, ready to be inserted through a hole in another
piece of metal, and peened over… Getting any ideas?

The machines, start with the little “sparky” fusion welders sold for
about 400 bucks…

And if you’ve got access to regular electric arc welding equipment,
there are also welding techniques designed for aluminum. Usually they
require some sort of gas shielding of the weld zone, such as with TIG
or MIG welding. Again, this is not normally jewelry scale, but who
knows…

Hope this helps.

Peter Rowe


#7

Aloha, There is a product called Durafix, I used it to repair some
broken parts (serious and major), on a fishing boat. It is really
amazing stuff. Their web site is,
http://www.pagebiz.com/durafix/index.html. You will like this product
and you can use a torch. Have fun!

Best Regards,
Christian Grunewald
Precision Modelmaking Technologies
Hawaii
(808) 622-9005


#8

The only viable methods of joining aluminum parts either cold joints
(rivets, etc.) or TIG welding, which is a pretty refined skill in its
self.

Hank Paynter
Brook Hollow Studio
@brookhol


#9
        No! Do not attempt to use silver solder. You will end up
with a mess!   I am not sure of an alternative. 

G’day; I completely agree with the above. However, I do know of a
very good alternative to join two pieces of aluminium together. You
go to your friendly neighbourhood welding supplier and ask for
aluminium brazing rod. This is usually sold as thin wires about 16
inches long and 1/16" thick. It is an aluminium alloy. NOT brass! At
the same time you should buy some special aluminium welding/brazing
flux. The rods are very cheap; the flux is relatively expensive. I
made all our fly screens with aluminium strip 1/8 thick and 5/8 wide.
As the screen material had to be sandwiched between two of my
aluminium frames, there were two identical frames for each opening
window - heaps of joins. I made a jig for cutting 45 angles, and
another for holding firmly in position the two pieces to be joined.
Fairly heavy chamfers were filed on each joining edge so the two
together made a Vee groove. A little oxy propane torch was used as
propane air, though hot enough to melt aluminium itself, wasn’t
concentrated enough as heat is conducted away along aluminium very
similarly to silver. One heats the end of a rod, dips it in the flux
and applies it to the hot join so the join is just covered. The
moment the white flux clears is the moment to apply the rod, to fill
the Vee with aluminium solder, similarly to gas welding or brazing.
As the aluminium melts at a temperature only a little above that of
the rod, you have to be careful. After practice on a few bits of
scrap you are ready to go. Really, it is quite easy and simple. But
don’t try and use it the same way as you would use silver solder: it
won’t work. Those frames of ours were made 17 years ago, and I’ve
only had to do repairs to 3 joints in that time. (12 screens, 24
frames! We certainly couldn’t afford to buy window screens at that
time) Of course, the really professional way to join aluminium
pieces is to weld using a very hot argon shrouded flame, or there is
an aluminium MIG welding system available. Both methods require real
expertise. There is an aluminium joining method using very low
melting temperature aluminium solder, and an ordinary soldering iron.
I’ve never had much joy with it, and the results I have seen from
other people were not much good either, in my opinion. If you weren’t
13,000 miles away I’d give you a demo! And if you’re wondering,
ALUMINIUM is the proper British way to spell it! AND colour, labour,
sulphur, phantasy, tomAHto …Oh, let’s give the whole thing up.
(British War Time song, when American soldiers were taking British
girls back home!)

John Burgess; @John_Burgess2 of Mapua Nelson NZ


#10

To Everyone who so graciously answered my questions about this, THANK
YOU!

I have decided to try some rivets and other methods, and not try
soldering…

Maybe later in the future I will give it a try…it has been very
interesting reading!

Oh now for another quesiton…I came accross some sheet pewter…I
know pewter is very soft and it melts very easily, can this stuff be
soldered? I haven’t tried and won’t until I get the ok…

Thank you all again!
Laura


#11

Laura, you use Bismuth to solder Pewter but if you use a torch you
have to be extremely careful or you will melt through. I found using a
heavy duty electric soldering iron was much easier but as in all
things practice on scrap first.
Bill from Long Island


#12

Hello. There are complete set to repair and solder aluminum. It is
very simple to do at low temperatures… And it is often used in
restoration old aluminum motorbike parts. You use sticks of a Barium
Aluminum alloy. Each part who needed to be solder is heated up to 380
deg. Celsius, and covered with the alloy. You scratch with an
stainless steel pin into the surface to penetrate the alloy trough the
aluminum oxide layer. If both parts are covered with a thin layer of
alloy you can melt them together. It is a very strong bond approx. 325
N/mm2. This is stronger than low alloyed aluminum. Now the Question
where can I buy it. In Germany for me. But I think it should be
available in every country. By the name “Techno Weld” Otherwise Phone
or fax to : A. Braeckman-Breidbentenstrasse 22- D52080 Aachen- Tel +49
241 554719 fax +49 241 552079

Martin Niemeijer


#13

Hi Laura; My father was a pewtersmith at Greenfield Village (an
historical park). My first experiments in jewelry were with pewter.
I’m not perticularly an authority on it, however. I don’t remember
if Fred Fenster has written a book on techniques but you can get a
copy of Oppi Untracht’s “Metal Techniques for Craftsmen” and see his
chapter on it.

Pewter used to contain lead. The stuff used now called pewter is
actually Brittania metal, an alloy of tin and antimony. It certainly
can be soldered, but it takes a light touch, as it starts melting
around 475 degrees F (471 F. solidus, 563 F liquidus). There are
solders made for pewter, but I don’t know a source. I’m sure my
fellow Orchidians will come up with them, right? :slight_smile:

I used to fuse my seams, as did early american pewtersmiths in some
cases. You can use a padding of linen for support since the metal
begins to sag at the fusing temperature. On old porringers, you can
still see the “linen mark” where the molten metal settled against the
cloth. Linen has a higher ignition temperature than other fibers, so
don’t try using anything else. The flux that is used is usually a
mixture of glycerin and hydrochloric acid. Please don’t use any
lead containing solders for seams if the article is to be used for
food or beverage or worn against the skin. Better to fuse or use
pure tin (melts at about 450 F.) for solder. Tin is hard to tarnish,
so it will usually show a seam after a while, meaning there are cases
where you don’t want to use it, like to seam a cylinder for a vessel.
For some real historical perspective, try using a blowpipe and
alcohol lamp. (OK, oil lamp for the hard-cores).

It’s a lot of fun to work with it, just make sure you don’t
contaminate any areas where you work with gold or silver with pewter
filings or scraps. Probably wise to use seperate buffs too. It will
eat holes in harder metals when you heat them, just like lead.

David L. Huffman