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Mystery Metal

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  • Mystery Metal

    I was melting some aluminum over the weekend, and threw in a few chunks from an old Sears clothes dryer control panel. Some of the decorative front surfaces of the panel did appear more shiny than aluminum, and other areas had kind of tan, bronze coating, but a torch test had led me to believe it was aluminum nevertheless. (tho the torch test had been on the back side of it) Well as those chunks started melting there appeared a very bright yellowish glow in the furnace, and I could see a white fibrous foamy-like substance forming, and little white strands floating up from the flue. So I shut off the blast and let it cool some, then dumped it all out. At that point the white stuff had kinda congealed into a powdery white, crumbly mass.

    Needless to say I made sure I stayed well upstream of the fumes, and vowed not to melt any more of that!

    But I'm wondering if someone could offer a guess as to what the source metal might have been?
    Lynn (Huntsville, AL)

  • #2
    Could have been a zinc coating or annodizing. I have seen zinc coatings throw up "threads" in the melting process - good thing to have a very good ventilation system.

    Zinc is also used in many applications that you might think of as aluminum, in things such as car interior ornamentation (lighter bezels, handles, and one item that surprised me, glass cutter handles. I have seen face castings of types made in my area as well.

    We have a zinc molding company right in our fair city that makes these parts, thus my resource.



    • #3
      Lynn, I think you had an alloy of magnesium. In my foundry we run into a piece of mag scrap from time to time and it acted as you described. If I think a piece might be mag I grind the piece and throw the grindings in the open frame of the furnace and if the sparks look like a kid's sparkler it is magnesium.


      • #4
        Might have to agree with spope14, I read your post too quick and read only the very bright but not the yellowish color. Mag is very bright but brilliant in color. It also makes a white smoke but without the stringy strands which is more in line with zinc alloys. We see this when melting high zinc brass. Sorry for the misdirect.


        • #5
          When I dumped the stuff out and stirred around in it, some of the remaining small fragments did flare back up with a yellow flash, until they burned themselves out.
          Lynn (Huntsville, AL)


          • #6
            Zinc alloy of some such. Melts at a lower temperature than aluminum. Zinc chromate is yellow paint pigment I believe. Zinc turns white when oxidized, ever cut some galvanize with a torch?

            Best way to sort it out is by weight, it's heavier than steel. Scrap dealers will buy it mixed in with yellow brass, at least they did last time I sold some.

            Be careful not to get any Magnesium mixed up with melt, when it burns it really burns well. Magnesium oxidizes easy, you won't run onto any nice shiny scrap mag unless it's been polished recently, reason that mag wheels are actually usually made of aluminum.
            Cut a small sliver and apply torch, you will know real quick if it is magnesium, and make sure surface it is on isn't burnable, it will make a hole in concrete if chunk of mag is big enough.

            If it fumes yeller and smells bad it is zinc.


            • #7
              If it is Zinc, stay far away, the further the better. Zinc with some of the other metals can create a vapor that will do you in very fast.
              I tried to forge a piece of braided cable that had been galvanized, the vapor from it did damage to my forge. It's called "poisoning your forge" I talked to some other smithies and they said that I was lucky that I didn't get the vapor in my face.
              When I melt down scrap aluminum, I look for things like car pistons, cable TV amplifer housings, engine heads, and bunch more. I know that they are aluminum, many other things can be zinc based alloy, or what ever the factory in China has in the scrap bin that day.