They are Zinc based rods that melt at 700* instead of 1200 for Al. I got some from True Value, marketed as Oxy-Acetylene Aluminum Welding rods. I'd hoped they'd be better than the Alumiweld and Duraweld stuff everyone hates. They're not.
They don't stick to anything. They melt, ball up into spheres, and roll off whatever you were trying to repair. And if you actually TRY to use then with an oxy-acetylene torch, they'll not only still not work, but you'll also probably ruin whatever you were repairing even more.
I saw some Aluminum Solder at ACE hardware a while ago which looks a lot more promising. I can't remember what it was called, but it was a very small spool of fluxed wire with a melting point of around 1100 degrees. Expensive, but worth if it works.
I've also tried brazing with an oxy-propane torch with TIG rods. Didn't work very well either, but without using any flux I didn't expect it to.
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