Re-magnetize after coating?
  • eggiteggit September 2016
    Is there a reason re-magnetizing a magnet after coating has not been considered? I know one of the main issues with TiN and similar coatings is that the coating process requires heat and that degrades the magnetic force. Neodymium magnets can be re-magnetized with another powerful magnet. Its my understanding that this requires a high powered industrial strength electromagnet and would not be practical on a DIY or home scale, but surely we could convince a magnet manufacturer to re-magnetize some coated magnets for us.
  • CassoxCassox September 2016
    Actually they do it with an electromagnet. One big nasty pulse. It isn't inconceivable to do at home. In fact, when Amal was talking about RFIDs at Defcon he talked about hitting it with a pulse.. I have a strong suspicion he's either purchased or has access to a pulse magnetizer but you'd have to ask him about it. I believe it's mostly a crep load of capacitors that all discharge at the same time.

    Anyhow, yeah I've had stuff re-magnetized a few times. If you're already working with a company sometimes you can get them to throw it in for free for you. Adam Magnetics charged me something like 250 or so for a huge batch; however, the remagnetization isn't really the problem with TiN coatings. If you wanted to do something like Teflon or something that requires high heat, then you could do this and then remag.. but TiN just seems to have a high number of failed coatings. I'm not saying this can't be remedied. I'm just acknowledging that I've never found a way to do it. It's a shame too because the ultra thin coating performs so much better.
  • eggiteggit September 2016
    I thought the high failure rate of the TiN coatings was in part because they are coated with a different process than what is standard to avoid heat.
  • AerisAeris September 2016
    Its quite easy to do on a DIY
    My current research project in university is about changing the polarity of magnets. With not much equipment, we can magnetize N52's easily, both directions and multiple times a second.

    Sadly, I can't share any of the plans since we'll be applying for a patent, but here's the gist of it:
    1-Connect high speed capacitors to a magnetization coil (more turns is better since you wont be getting currents in the thousands of amps that could burn the wire) with a thyristor acting as a switch between them.
    2-Load up capacitors as high as you can.
    3-Use the thyristor to discharge them as fast as possible into your coil.

    Since you don't need precise control or high frequency of pulses, a simple circuit like this will do quite easily. Forgive my shit drawing skills.
    image
    This thyristor worked out well for us, but do your research before buying anything.


    As always, be careful when magnetizing things. We operate at around 1.2kV and +300amps, this WILL kill you if you mess something up.