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Alumaloy review

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Alumaloy review

Unread postAuthor: Fnord » Sun Mar 10, 2013 8:29 am

Alumaloy/durafix is a pot-metal alloy for soldering material that cannot be joined with normal tin/lead solders.

I bought a pound of it a while back and have had a chance to do some test projects recently

Metals it will stick to:
Galvanized(aka zinc plated) steel

Physical properties:
Significantly harder than common aluminum alloys (estimate maybe 40-50kpsi tensile?) Will not stretch much before breaking. Seems to fail by separating from the workpiece in most cases, but usually does so after significant deformation of the workpiece occurs.

Contrary to what the demo videos say, you do not need a stainless wire brush to prep the surface - anything abrasive will work fine. You actually don't need to sand it at all, but it will adhere much easier when there is less of an oxide layer to dissolve. Note that it is important to work the solder into the metal a bit with a steel rod if you want the most possible surface adhesion. Just 'globing it on' may leave patches underneath that have not bonded completely.

The situations you should use this stuff in are similar to when you would use a normal mig/tig welder but high-strength is not critical.
It has very high surface tension and will *not* wick into a crack or sweat fittings like normal solder. You can create roughly a 3/16 (4.5mm) 'weld bead' on a horizontal/vertical joint before it starts to puddle at the bottom. If you need anything thicker, angle your workpiece so the surface of the bead is level with the ground.
It is possible to patch holes, though anything larger than 3/8 will probably need backing to avoid drips.

Important engineering notes:
Alumaloy is extremely caustic in its liquid state. Soldering a beer can is possible, but the can will quickly dissolve into the alloy. For metal less than 1/16” (1.5mm) thick, you should keep your hot-working time under five minutes to avoid thinning the material.

When clamping a workpiece, do not use excessive force. Aluminum loses significant strength at 700F and your clamp may deform it after heat is applied. Back your vise/clamping surfaces with a larger steel plate if possible.
Heating aluminum much higher than the melting point of alumaloy will destroy heat treatment and return the metal to its annealed state (The simple DIY way to anneal aluminum is by rubbing a bar of soap on it and applying heat until the soap turns black. Cool slowly).

Complex parts may warp slightly when cooled, so plan your joints in a way that will alloy you to bend them back a bit before finalizing everything.

Localized heat:

It's possible to do precise work without causing surrounding joints to liquefy again. For 1/4” aluminum plate, I was able to work with a heated area around 2” diameter without affecting the surrounding metal. Note that nearly molten joints may 'run' slightly even when in an apparent solid state.

Aesthetic notes:
Alumaloy will darken significantly after being exposed to the atmosphere, making it plainly visible next to bare aluminum. It is also not as corrosion resistant, so apply a clearcoat if you're not going to paint it later.

For the best possible finish, scrape the surface of the molten solder with a smooth piece of metal, or cotton cloth/glove before allowing it to cool. This will leave a nearly oxide-free surface and will only require light sanding to clean up. Practice a bit and you can easily match or best the look of a professional tig weld.

Health/safety notes:
Obviously a melting point of 700 degrees makes it a little more dangerous than soft solders, and thick aluminum will conduct heat to other areas very quickly. The “Everything-is-Always-Hot” mantra is pretty much literal here.
I've also noticed that this alloy appears to have a significant amount of zinc in it, so set up your ventilation/work area as you would for welding galvanized steel. Assume it also has traces of lead (i.e, probably causes cancer in California/ don't use it for cookware. Do not apply alumaloy to children under three years).
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A tripod mount for my camera. This was the first project I attempted. You can see the darkening obviously after several months.
A kinda-neat but rough joint, prior to sanding
Example of what a 'nice' joint looks like when the oxides are skimmed off the liquid surface. I went over this with some 220 grit sandpaper/steel wool.
A nearly finished frame that is of course non-spudgun related and definitely does not involve the number '3' in any way.
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Unread postAuthor: cammyd32 » Sun Mar 10, 2013 10:27 am

Looks like your results turned out a lot better than when I tried the stuff! I'm interested in what kind of torch did you use? The one I usually use for plumbing (prop-butane) didn't seem to heat 3mm aluminium sufficiently for it to adhere well, even after about fifteen minutes going at with the torch, when it cooled it was really patchy, and only really stuck in the hottest places.
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Unread postAuthor: POLAND_SPUD » Sun Mar 10, 2013 11:50 am

thx fnord
I always wanted to know if this product is any good

could you post a vid of you using it?
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