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How To Tell If It's Really Titanium

Posted by Zonk on Tue Dec 25, 2007 01:26 PM
from the hold-your-credit-card-to-a-grinder dept.
Science
With the growing popularity of titanium, some disreputable merchandisers are passing off other materials as the more expensive metal. Popular Science looks at a surefire way to prove what that credit card/crowbar/ring is really made of. "Hold any genuine titanium metal object to a grinding wheel (even a little grindstone on a Dremel tool will do), and it gives off a shower of brilliant white sparks unlike any softer common metal. The sparks are tiny pieces of cut titanium--the friction of the grinder heats them till they burn white-hot. Hold a grindstone to the shackle of a "titanium" padlock from Master Lock, however, and you'll instead see the telltale fine, long, yellow sparks of high-carbon steel."
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How To Tell If It's Really Titanium 25 Comments More /

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  • is there a better way? (Score:5, Insightful)

    by pwizard2 (920421) on Tuesday December 25 2007, @01:29PM (#21815428)
    The method in TFA sounds like it would really scratch up whatever you're trying to test. Is there a way to run a test without damaging the object?

    • Re:is there a better way? (Score:5, Funny)

      by Dan East (318230) on Tuesday December 25 2007, @02:13PM (#21815716) Homepage
      Yes, there is a better way, and your concern about damaging expensive objects - particularly jewelry - is quite justified. Simply send the object to one of my two testing centers (conveniently covering both hemispheres - one is located in Russia, the other in Africa) and we will send you a full report of the object's composition.

      Dan East

      • Re:is there a better way? (Score:5, Informative)

        by necro81 (917438) on Tuesday December 25 2007, @04:39PM (#21816546) Journal
        How much are you paying for that service? For $30,000-40,000, you can buy a handheld x-ray fluorescence analyzer [niton.com]. These things got started in testing for lead paint, and now get used to test and check for lots of things - including alloy composition verification. An XRF shines x-rays of a known energy at the test sample, then detects and analyzes the spectrum that is reflected back. Each element has a characteristic x-ray emission spectrum based on the energy of electrons dropping into lower shells. In 10-20 seconds, you can get a really good breakdown of the elements in the test sample.

    • Re:is there a better way? (Score:5, Informative)

      by ByteSlicer (735276) on Tuesday December 25 2007, @03:11PM (#21816076)
      A laser spectrometer [wikipedia.org] can do this for you. It will still create microscopic damage though.

      • Re:a magnet? (Score:5, Informative)

        by LynnwoodRooster (966895) on Tuesday December 25 2007, @03:01PM (#21816018) Journal
        Nope. Get above 0.15% carbon or so and you lose almost all the magnetic properties of iron. It's one reason that loudspeakers are made with low carbon steel (usually 1006, 1008, or 1010 grade) since you get too much carbon and the flux no longer flows well, meaning you need a LOT more magnet and a higher grade magnet to get the same flux in the gap.

        And yes, I am a loudspeaker engineer... ;)

        MERRY CHRISTMAS!

        • Re:a magnet? (Score:5, Informative)

          by Kazymyr (190114) on Tuesday December 25 2007, @02:42PM (#21815900) Journal
          ...iron is always magnetic.

          That is a big fallacy. There are some alloys in which iron is around 98-99% which are non-magnetic (think unusual alloying elements like niobium and rhenium).

              • Re:a magnet? (Score:5, Insightful)

                by budgenator (254554) on Tuesday December 25 2007, @03:24PM (#21816158) Journal
                Iron isn't always magnetic, when heated to or above it's normalization temperature it loses it's magnetic properties, you can hold a piece of steel suspended with an electrimagnet in a kiln and heat it, when it reaches it's normalization temp it will fall to the kiln floor.

                • Re:a magnet? (Score:5, Informative)

                  by Gordonjcp (186804) on Tuesday December 25 2007, @05:35PM (#21816822) Homepage
                  And in fact, some soldering iron thermostats use this property. When the iron is cold, a magnet pulls the contact closed. Once it heats above the Curie point, the magnet lets go and the contact breaks.

                  • Re:a magnet? (Score:5, Informative)

                    by Grishnakh (216268) on Wednesday December 26 2007, @03:49AM (#21819720)
                    Sorry, that's not my understanding of the metal's properties. I guess for digging around in the sand, you don't really need a fine edge, but nothing to my knowledge compares to the ability of steel (esp. high-carbon steel) to hold an edge. High-carbon steel is very brittle, which helps it to hold an extremely sharp edge; this is why Japanese samurai swords were forged to have one side harder than the other side, so the sharp side would be extremely hard, but the other side would be less hard and more strong (done by using clay on one side during quenching) so that the blade as a whole wouldn't break easily.

                    There's a reason no other knives are made of titanium, or anything besides steel for that matter.

                    Titanium is known to be a very strong metal. If you know anything about metallurgy and its terminology, strong and hard are different properties, and usually work against each other: a metal is usually strong, but not hard, or vice versa, not both. Steel can be made to be hard, but brittle, or strong (which is more flexible) but not very hard.

                    Anyone with a titanium ring knows that it's not a hard metal at all: it's easily scratched unless it has a protective coating (usually diamond). Sure, it might prevent a automatic pressure door on an undersea rig from locking you in, but it doesn't hold a sharp edge at all.

  • Oh great... (Score:5, Funny)

    by grassy_knoll (412409) on Tuesday December 25 2007, @01:30PM (#21815440) Homepage
    Think the store will mind if I bring a dremel with grinding wheel to the store with me? For testing purposes of course...

  • Good news (Score:5, Funny)

    by Anonymous Coward on Tuesday December 25 2007, @01:34PM (#21815470)
    Apparently my wife's jewelry was all genuine titanium!

  • He also runs periodictable.com (Score:5, Informative)

    by Ed Pegg (613755) * <ed@mathpuzzle.com> on Tuesday December 25 2007, @01:41PM (#21815524) Homepage
    The author of this Popular Science article, Theo Gray, also recently relaunched http://www.periodictable.com/ [periodictable.com] Thousands of elemental pictures and videos are available there, all linked in with his Popular Science series.

  • Ow! Shit! (Score:5, Funny)

    by schon (31600) on Tuesday December 25 2007, @01:56PM (#21815610) Homepage
    Man, I just tried this with a new package of Energizer Tianium, and the spray burned a hole through my skin!

    You can be sure I'll be returning these "titanium" batteries just as soon as I'm back from Emergency!

  • A few simple ones (Score:5, Informative)

    by BlueParrot (965239) on Tuesday December 25 2007, @02:01PM (#21815642)
    a: Titanium is not ferromagnetic, and hence it is not attracted by magnets as strongly as iron is ( the difference in force should be orders of magnitude ).
    b: Titanium's density is 4.5g/cm^3 , iron is 7.8g/cm^3
    c: Titanium is corrosion resistant to dillute sulfuric and hydrochloric acid, iron is not.

  • Interesting! (Score:5, Funny)

    by Poromenos1 (830658) on Tuesday December 25 2007, @02:02PM (#21815654) Homepage
    Next up: Test if your explosives have gone bad by detonating them.

    • Re:Titanium: not recommended for rings (Score:5, Funny)

      by Nexzus (673421) on Tuesday December 25 2007, @02:47PM (#21815936)
      About 18 years ago, I was on an underwater oil-drilling rig, when the mission we were "tasked" to perform by the navy went horribly wrong, and the rig started taking on water. I was running frantically running through cold freezing water towards a closing hydraulic door. I didn't make it in time, but I stuck my hand in the opening, and the door was stopped by my titanium wedding band. A colleague had found me, cut the hydraulic power to the door, and saved me. Earlier I had almost flushed it down the toilet. Good thing I didn't.

      Couple hours later I met some aliens.

      (Yeah, I know, but it sounds better in 1st person.)

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