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Magnesiumn Question

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  • CCWKen
    replied
    There's only a few of the aluminum alloys that don't contain magnesium. Even 6061 has it. The sad part of using the magnesium alloys is that it must be coated. Well, not must, but if you want to keep looking nice it needs to be coated. It turns a dark grey and looks ugly in pretty short order. You won't have any problems machining it but I would stick to the aluminum alloys just because it's easier to get.

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  • topct
    replied
    I just found some 7075 "magnesium" aluminum lug nuts on the net.

    Yes 7075 contains magnesium. But that kind of magnesium won't catch fire.

    Is it getting like that other tricky word, billet?

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  • CCWKen
    replied
    It's pretty hard to "light" Magnesium unless it's in powder or thin sheet form. I've got some large pieces of it that took an acetylene torch to get started. The base on my vertical lathe is made out of it. I've drilled it and cut it with with no problems. You just need to take care of swarf and powder and not leave it laying around--About the same as Aluminum dust.

    It burns brighter than the sun so don't play with it. But it does make cool blobs of melted dirt and sand.

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  • garagemark
    replied
    May be a tad hard to set magnesium on fire, but depending on the quantity of material, a paltry class D extinguisher wouldn't kill it. Especially if there were sufficient piles of shavings lying about. Ever see a landing gear fire? I watched an entire landing gear burn/melt down on a C-5A due to hot brakes (read- stupid pilot). Caught the wheel on fire. They foamed, and foamed, and foamed, and foamed the fireā€¦. And FINALLY put it out. But not before the front left main gear was all but gone, along with a lot of sheet metal and structure in the wheel well.

    I have a little coil of it that I tear a piece off and light for the grandson once in a while. It is BRIGHT, SMOKEY, and COOL! But is also short lived and controlled.

    I would opt for a good alloy of aluminum if it were me.

    Just another $000,000,000.02

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  • ADGO_Racing
    replied
    Machining Magnesium is not a big deal. We machine center sections and side bells of quick change rears, as well as weld to repair cracks. We have never set the stuff on fire. However it IS POSSIBLE. A class D fire extinguisher is an absolute must have item. We have four of them in the shop, two in the fab section, and two in the machining section. Although I doubt you will have any trouble machining the stuff. We also make wheel nuts for sprint cars out of Magnesium, front steering and rear drive hubs are also a magnesium casting. Also wheel centers for sprint cars and late models are also magnesium. I think if magnesium was as easy to burn as people think, racers would accomplish the task on a regular basis.

    Having seen a good number of race cars drag a broken hub on the asphalt for over a mile, with sparks flying from the chassis dragging on the track, I tend to think the fire issue in a shop environment is a little over rated.

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  • fasto
    replied
    The O.P. may be thinking about "intergranular corrosion" which I assure you can happen internally, though I don't know if it happens in magnesium.

    Some Piper PA-28 and PA-32 airplanes had issues with intergranular corrosion of the extruded aluminum wing spars. Needless to say, it was not a good thing! Topical corrosion prevention does no good against intergranular corrosion, of course, because the electrical circuit is built into the metal.

    As I recall, the root of the problem was traced to some kind of a production issue at Alcoa in the mid 70's, of course that was no help to the people who had to replace their wing spars.

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  • Guest's Avatar
    Guest replied
    The answer to his question is no. All metals corrode due to exposure to oxygen (air and/or water). He may have heard of hollow magnesium corroding on the inside due to oxygen exposure.

    As to machining mag, I'm with Evan. A class D fire is no fun.

    Leave a comment:


  • topct
    replied
    This is interesting. It's only 5 pages, the last one being very important.

    http://www.magnesium-elektron.com/da...20Brochure.pdf

    The stuff is just to strange to consider it for this application. Most of it is used for casting where strength can be gained by making it thicker where needed. Even then I would be surprised to see it being used as a mount for a vehicles brakes.

    In fact I think I have heard somewhere where it is illegal for use in certain applications, in and or around brakes for one.

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  • Evan
    replied
    Do you have a Class D fire extinguisher? Magnesium burns really well, especially when you put water on it. I won't machine magnesium even though I have some. The last thing I want is a metal fire.

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  • JoeLee
    replied
    It can cause the metal it is in contact with or bolted to to corrode.
    Especially if there is moisture and if a voltage is induced. Remember al the junk GM cars of the late 70's and early 80's where the bumpers would corrode right off the car. the bumper mounts where they were bolted to the frame just disolved. I would check the chart of galvanic reaction to see where that alloy stands.

    JL.........................

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  • topct
    replied
    Unless you know exactly which alloy of magnesium you have I would tend to go for some 7075 instead. You could compensate for the weight difference by using thinner sections of the stronger alloy.

    Leave a comment:


  • madman
    started a topic Magnesiumn Question

    Magnesiumn Question

    Is it true that Magnesiumn corrodes form ther Inside out? I faintly recall reading this many years ago. I am not sure though. I have some blocks of this stuff and thought of making some brake caliper hangers from it for my new Motorcycle.
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