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Thread: Homemade Solder for Aluminum

  1. #1

    Homemade Solder for Aluminum

    Ive been interested in this subject for a while, and while there is a ton of commercial aluminum brazing rods (alumiweld, etc). I was wanting to see how it worked, and a while ago, I found someone on here that had used zinc to fill in some blowholes in castings. I was also wanting to find/make a solder besides silver solder that can stick to pretty much all metals, including aluminum, and could withstand the temps of steam. The temp I needed was needing to get was over 350 degrees to be safe, and after a little bit of research and tinkering around in my spare time, I eventually found a good mix. I went with 60/40 tin/zinc and the little bit of copper from the solder. I was just messing around with different mixes to see what worked for almost all metals. I had problems getting it to wet to aluminum and to non magnetic stainless, but this batch seemed to wet to the stainless fairly easily and aluminum even easier. The tin that I used is from lead free solder, the 99.3% tin, 0.6% copper stuff.

    I tried it on 6061, 7075, A356 aluminum, I tried mild steel, 316 and 303 stainless, and I tried it on brass so far. It seemed to wet very easily to everything, even aluminum with no flux or anything. I just poked at it was all with a rod, then it almost instantly started flowing underneath of the oxides and such.

    I figured this was really interesting and imo, it's actually comparable to medium silver solder, but melts at around 700F degrees, so well under the range of melting temps of the aluminum and such, and also high enough temps to not be affected by steam temps without needing to go buy silver solder and flux for it. I was just trying to find a replacement for S&Gs really, but it seems to work so far. I just need to find some sort of flux to use with the solder, but atm, I dont think thats really much of an issue really. I may just crush up some of my low temp flux that I made a while back into a powder and use that as a flux.

    The flux is made of equal portions of sodium chloride, potassium chloride, and calcium chloride. The sodium and potassium salt, when mixed together and melted, it drops the melting temps to around 1000F degrees from what Ive found, and if you mix it with calcium chloride (sold as damp rid, just keep salt mix in airtight container or it will absorb moisture), it'll drop the melting temp even more creating a eutectic that melts at around 600-700 degrees. I believe that if you mix it with magnesium chloride also, it'll drop it even further into 400-500 degrees.

    I figured that it was interesting and might come in handy or of interest to you guys on here. I'll post a video of this last batch that Ive made and the experiments.

    I thought this would be handy for things made of softer aluminum and such that had threads in it that kept stripping out or something, just drill it out oversize, fill it with the solder,drill and tap it, and your good to go. It's actually much harder than the aluminum, so would hold threads really well imo. It would be awesome for little blow holes in castings that are just cosmetic, just melt it into the holes and machine it flush.

    Edit: here's the video of it on aluminum parts.
    Last edited by cae2100; 06-03-2017 at 07:36 AM.

  2. #2
    Join Date
    Mar 2016
    Tornado alley, USA
    That sounds like some pretty useful stuff.

  3. #3
    It actually is, I was doing some other experiments with it, and it actually works much better than I expected that it would, lol. I havent tried it on cast iron, mainly because I dont have any extra cast iron to experiment with, but everything else, it seems to stick to. I'll be using it on brass sometime soon to make a piece for my steam engine, I just dont feel like casting the piece out again, lol.

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