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Thread: Aluminum or pewter or magnesium

  1. #1

    Aluminum or pewter or magnesium

    How do you tell the difference on all these? I know you dont want the mag in your alum. But how do you tell the diff. Harold

  2. #2
    Senior Member metalmelter2693's Avatar
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    I know what pewter is. Pewter is made up of tin, antimony, bismuth, copper, or my favorite, lead. It can contain any combination of these metals. Pewter melts at a very low temperature of 500F or less and is heavier than magnesium or aluminum. Pewter is a dull gray if old or a shiny color. Aluminum is light weight and has a dull gray color to it or is shiny when polished. Magnesium is lighter than aluminum. It has a density of about 1.83g/cc while aluminum is about 3g/cc. Magnesium also will burn if heated to a high temp. I may not be 100% correct but it is a vague and general description.

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    Senior Member Rugerdude's Avatar
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    No idea about pewter. It's heavier, darker, and has significantly lower melting point than the other two metals you're talking about. I don't think it's much of a concern, getting pewter confused with Al or Mg.

    Magnesium has a density about 2/3 than that of aluminum (it's lighter). Also, if you file the surface of the scrap to expose bare metal and put some mild acid (acetic acid works well) on it, it should fizz if it's magnesium. As metalmelter2693 mentioned, magnesium burns in air to form magnesium oxide (MgO), but you wouldn't want to figure that out the hard way since it'll react with a good bit of hobby-scale fire extinguishing substances. (e.g. CO2 extinguishers, sand, water etc). To quote Anon's book,

    Magnesium burns in air, water, and even the carbon dioxide used in common fire extinguishers. It can also react with sand, so even burying it in sand won't put it out (and, indeed, any moisture in the sand can cause a dangerous explosion, more so than an ordinary steam explosion, from the magnesium, sand, and water reacting to release a highly explosive mixture of hydrogen and silane (SiH4) gases). The only sure-fire way to put out a magnesium fire is with inert gas such as argon or sulfur hexafluoride.
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  4. #4
    To add to what Rugerdude wrote, compared to aluminium, magnesium has a much stronger reaction when exposed to a mild acid like vinegar, if you can, find a piece of something which you know to be magnesium and something known to be aluminium, clean a spot on each, put a few drops of vinegar on each of the clean spots and compare the reactions, that'll give you a good benchmark against which you can compare unknown alloys.

    As for pewter, it's dull, grey and heavy for its size, especially compared to aluminium or magnesium.

  5. #5
    Ok, but what might be some of the items made of magnesium that a melter might run into? Sorry about all the questions but this is the easiest way to learn. Harold

  6. #6
    Probably the most common place the average bymc is might to encounter magnesium are parts from old aircooled VW's , its also commonly used in exotic or specialty auto parts for race cars, dune buggies etc.

  7. #7
    Senior Member Jammer's Avatar
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    I have some hotfoil printing plates that are Mg. I originally thought they were aluminum and sold about 100# to the scrapper.
    Some Aluminum alloys have a little Mg in them so some Al may react with vinagar.
    Mg is fun to make some thermite to play with.

  8. #8
    Senior Member metalmelter2693's Avatar
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    Don't forget magnesium is in cheap drills and cheap low quality lightweight tools.

  9. #9
    Magnesium is NOT all that common, it's more difficult and expensive to make stuff out of than aluminium so it's generally only used where the manufacturer deems light weight to be very critical.

  10. #10
    Senior Member metalmelter2693's Avatar
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    Isn't there any metals lighter than magnesium that won't explode when it is exposed to air or water?

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