Methods of acquiring gold and TiN coated N52 + implantation idea + new method of testing coated N52

135

Comments

  • edited July 2017
    Or, I have another idea of how to make this useful.

    Here's the thing.. nickel copper nickel has been done and it fails; however, as long as all of these units are the same size I don't think it would matter what the undercoating will be. They probably will refuse zinc.. it'll make a toxic gas.. but there are many other materials that may work.

    Why not send a batch with say 30 of magnet a, 30 of magnet b, 30 of c and so on? In fact, I have about 2k phosphate coated n52 that are not yet magnetized. You could try TiN on that. We could try it over gold. We could try it over nickel copper nickel gold. Etc.

    I honestly believe that if you want TiN to work you're going to actually need a stronger denser undercoat then the nickel copper nickel... 

    Why not try electroplating over the final product? No.. nothing will bond to the titanium but if there are flaws will it fill them?

    C'mon people, what ideas do you have?
  • edited July 2017
    I'll consider Electroplating of Platinum. Cassox it's seems like you misunderstood me, I didn't say you 4 didn't correctly test, I said most users don't have the capabilities to test. I never said that you had them performed incorrectly either. I said a majority of magnets seem to have that issue, and from what I have been able to gather the biggest cause of failed magnets is that they are improperly coated by the manufacturers.

    If i'm incorrect then correct me, but I wasn't accusing you at all. My point was that I am working very hard to get a working testing method and high quality coats. I would argue that the combination of coats I have presented is the best in regards to functionality and cost feasibility.

    I avoided using gold due to the fact it doesn't bond well with other coatings. Nickel bonds really well with copper, which is another material we can chemically test for. The nickel bonds very well with the titanium, which in terms of tensile strength, biocompatibility, and chemical resistance outcompetes TiN. The nickel is required by my manufacturer because it coats over NdFeB better than copper and the tensile strength is also beneficial.

    I do recognize that the more material it is coated with it begins to lose it's magnetism, that is why I am specifically requesting to decrease the size of the nickel and copper coats.

    Cassox I am currently in and have been in the process of getting information regarding their coating method. The magnet is being remagnetized and isn't going to go past 310 C. it is being heavily tested before it's shipped out.

    I appreciate your input on the gradual decrease of magnetism, I guess the magnets could potentially last allot longer than I thought, especially with the titanium coating.
  • edited July 2017
    @Cassox I would consider doing that but I am paying $360 for 25 magnets coated in Ni+Cu+Ti. The cost to perform all those coatings would be incredibly expensive.

    Would you mind sharing why you think the magnets would fail if they are coated in this combination?
  • It's just how I talk man. Lol. I'm not being an asshole. I don't feel accused.. I'm playing the devils advocate. Nothing would be better then for this to work out. Are you on the slack boards?

    Ok, sometime next week like maybe Monday would you like to have a chat about this? I'd love to review your stuff. If I have a better vendor for any of it I'll share it. Obviously you don't need my go ahead for anything but I believe you could alter how you go about it slightly and get better results.
  • You might consider asking the cost to coat 100. Usually, these companies charge by the run. It doesn't matter if you coat 20 or 1k as long as they fit. Also, does the company intend to flip them? Are they going to pay for the mounts?
  • I'm confused, are you doing TiN or straight Ti?
  • edited July 2017
    I don't really have anything to review, all my research is in this thread. I would talk to you next Monday but I'm not sure when i'll reach $360. What do you recommend I reconsider to get better results? Also, what are the slack boards?

    I am going straight Ti. The company does reduce the price if I raise the amount but it would cost $500 for double. According to them, "Most coatings are done in a bath. But depending on the magnet size and the type of coating, our production team will determine the best method to coat them."
  • The problem with that is that titanium isn't something you can electroplate on. Ask them what method they plan to use.
  • Where is the company? It's not in China right? You might ask to talk to one of their engineers. Sometimes you get a salesman who doesn't actually know what he's doing.

    https://www.finishing.com/331/83.shtml

    This site is great. It's full of engineers. Titanium can't be applied via electroplating because if it's electronegativity. In fact it's used as the anode is playing baths.
  • edited July 2017
    That's a good point, i'll look into that... thanks for pointing it out. The company is based here in the U.S. and I'm currently waiting for a response from one of their engineers
  • edited July 2017
    This company does coatings for many different kinds of objects, two categories being aerospace and medical implant plating. According to finishing, "titanium cannot be a 'plator' from a conventional aqueous plating bath," which is alright because according to the manufacturers "Most coatings are done in a bath. But depending on the magnet size and the type of coating, our production team will determine the best method to coat them." Because of this it is likely they will coat the titanium outside of an aqueous solution.

    This solves the electroplating issue, but I am still waiting for their official response to the exact questions.

    Look at this link for more information:
  • Hilarious. This conversation was incredibly fruitful. I figured out with 95 percent certainty why this design fails. I've spoken with Amal about it and he's cool if I discuss it. I need to sleep right now but I'm super excited and promise to get back to you.
  • The short answer is that the layers are electrically coupled and cause galvanic corrosion. They destroy themselves from there inside out.
  • edited July 2017
    That sounds promising except what's the layer and cause of the chemical reaction the corrosion would originate from? Could you explain further?
  • This does sound promising and I hope the conversation can take place here where others can see it,  

    One suggestion (constructive criticism) If you need to edit a post, maybe consider using the strikethrough instead of just deleting the information in case that idea or information turns out to be important or to help others who may read this thread in the future know what has been tried or thought of before.


  • edited July 2017
    The manufacturer who I am using just contacted me and told me they can no longer do titanium coatings because of the difficulty and cost of the procedure. Instead I am now getting TiN coatings.

    Cassox can you give any more information on the corrosion's source?

    The popular vote was 3x1mm.

  • Did they say the methods used?
  • For the Ti or the TiN?
  • For whatever you're going to be using.. so TiN I guess.
  • Yes, galvanic corrosion it's a process where a material with two different metal layers selectively breaks down the less Noble metal in the presence of an electrolyte. So, it's the metal under the Ti or TiN breaking down. If you can figure out how to put a non-conductive layer down this should be prevented.

    So here's my suggestion to you regarding this. I would first contact a number of other coating services. You can find better pricing. That amount for 25 magnets is way too much. I'd use this as an excuse to coat a bunch of different magnets.. for example, gold under titanium. People speak about it but I've never seen it done and gold is resistant to galvanic corrosion. Also phosphate. I'll give you the phosphate coated magnets if you'd like. The corrosion resistance would be super high.. but I have no idea how well the metals will bond. Also.. pure neo magnets shipped directly from the manufacturer packed in oil.

    Go ahead and do all the other tests you can think of.. but make sure one of them is a saline test. I'd bet money they pass all the other tests.. but fail in saline. And if they don't, great. You've made a huge contribution to grinding.
  • edited July 2017
    Galvanic corrosion effects the anode/less noble metal which in this case is the titanium/TiN instead of the gold. I sent a message to Cassox and am hoping we can come to a conclusion on how to make the magnets and what manufacturers/coaters I can use.

    I am still trying to get magnets coated in Au+Ti as it's the most ideal coating combination is regards to biocompatibility, tensile strength, ease and efficiency of testing, chemical resistance, and the least amount of galvanic corrosion possible.

    Cassox, why is that you think it will fail the saline test? What's the concentration of the saline in the solution? I know saline is incredibly acidic, meaning putting a coated magnet in a concentrated saline solution would be a very useless test unless you balanced the pH in-between the degradation point of titanium and gold. This is exactly what I'm doing with bleach just on the acidic side of the spectrum. Our blood is only pH 7.35-7.45 so anything past 7.5 is useless unless we are intentionally trying to degrade the undercoats.

  • As far as I can tell, the saline solution should be about 0.9%.  This would be 9 grams per liter or around 1/2 tsp in 240 ml (~8 ounces) of water.

    I don't think normal table salt (sodium chloride) changes the pH.
     
    Adding a little bit of dish soap to help break the surface tension MIGHT change it a little but probably not enough to worry about.


  • According to multiple sources a .9% solution of saline is only pH 5.5-6 in salt water and 7 in distilled water. This test is not nearly as harsh as the diluted bleach test, if it passed that I still don't see a reason it couldn't reasonably pass this.
  • Yeah that's the weird thing. Traditional corrosion simply isn't an issue. TiN can withstand a month of soaking in highly concentrated Sulfuric Acid. Sodium Hypochlorite is a little bit different.. In solution it's still giving you an electrolyte leading to galvanic corrosion.
    Ok, so I'll backtrack on a few things: One is titanium. Nothing I'm talking about is related to pure titanium coatings simply because I've never been able to find a vendor able or willing to apply it. I've been working almost entirely with variants of TiN. A quick note about that too.. you really need to speak to the engineers regarding the process because sometimes they have other metals as additives.. for example Chromium.. that they won't mention to you. Just ask them to make sure it's not a variant.

    Anyhow, an undercoating of Gold MAY work. I don't know. The thing is.. usually it's gold over nickel/copper/nickel... in which case we would probably end up with the same Galvanic Corrosion problem. One option that I discussed with a vendor at one point is having them ship the magnets uncoated.. in oil.. and then having the TiN applied directly to the magnet. No undercoat. I didn't follow up because these magnets are weak. It's like trying to coat a dirt clod. Also, would this lead to Galvanic corrosion of the magnet material? Idk.

    So, my working theory is that these things are failing due to the g corrosion. There is a way to test this idea.. we need an electrolyte bath and to pass current through it. It should speed up the process and they should break down really rapidly. This test would be great because we could then use it on every magnet before implantation.
  • Oh, and I had kind of offered to talk about vendors but I realized I can't. The thing is, I worked with Amal on magnets and so there are some issues.. He's totally cool about it, but I feel as if talking about vendors/capital etc. is kind of crossing the line. Amal is very supporting of our community so the last thing I want to do is make enemies.
  • That's alright, thank you for your help Cassox. I'll go ahead and put the message I PM'd you on here.

    I'll do some research on whether the galvanic corrosion will effect the NdFeB and put my findings on this thread. I'll continue speaking to as many manufacturers as possible and question their coating methods and materials in order to be certain the magnets and coatings will be high quality. When I eventually receive the order I will do more research and physical testing on your galvanic corrosion theory.

    I will make sure to get magnets manufactured that do not have the nickel/copper layers unless I decide to forego the Au which is unlikely because I am attempting to solve the potential galvanic corrosion issue.

    The manufacturer I am most likely going to use can't coat the magnets in titanium otherwise I would heavily consider a direct coat of titanium over the NdFeB.
  • "There are a couple issues I could use your help with. I've come to the conclusion the best materials to use for the magnets is Au+TiN. Gold is higher in the galvanic series than titanium, making gold the cathode and titanium the anode. In order to reduce the corrosion rate we can factor in the cathode/anode ratio as the smaller this ratio is, the better as it's proportional to the reduction of the galvanic corrosion rate. Fortunately the cathode/anode ratio is low

    In my thread you mentioned gold is resistant to galvanic corrosion, could you give me more information on that? There's also another issue, galvanic corrosion effects the anode/less noble metal which in this case is the titanium/TiN.

    In my magnet design I don't have to worry about the nickel and copper corroding drastically, but there is a massive difference between copper and titanium in the galvanic series. Since I am using TiN, titanium with an extra nitrogen/oxygen depending on purity, the corrosion resistance of the material and the oxide film is lowered. I'm trying to calculate the galvanic corrosion potential between TiN and Cu (a sacrificial layer anyways) by finding the electrode potential. Do you happen to have access to that information?

    One issue I am still trying to work out is the cause of the galvanic corrosion. Galvanic corrosion needs an electrolyte to be present and also needs to be broken down in a polar solvent. Both of these things are abundant in our blood which is one potential cause of the electrical current. Do you have any ideas on how we can prevent the current from causing the galvanic corrosion?

    Do you have any coaters/manufacturers that you trust their methods? Titanium coatings are very difficult to do and most coating companies don't have the money or equipment to do it. TiN and Au is honestly our most feasible option, unless you have any ideas.

    I am exploring alternative coating materials such as phosphate, which looks promising."
  • I have seen tests on TiN magnets in very harsh tests and not fail, but once put into the body will fail in 6 months. Just because you have a few good tests does not mean you are good. The bodies just is to kill that thing and it will. Being that you said it's a method you haven't seen before it freaky. You might not have seen it because it's a bad test. If you get one of these magnets and have it in a human for a year and after taking it out can see no issues in the magnet then you have past the test and can move on to selling not beta units.
  • edited July 2017
    Benbeezy I would appreciate it if you would read everything in the thread before you make up your mind.

    If you think logically about the conditions the magnet will be in while it's in the body you can easily make tests that mirror that environment. The blood has a pH of 7.35-7.45 making the pH not an issue and the bioinert, or "biocompatible" metals I will be using (Gold and titanium+nitride) won't invoke an immune response.

    The cause of the quick degradation is galvanic corrosion as was explained in the last few comments. When a magnet is implanted it is in an environment that has a large amount of electrolytes, which are what the energy that causes galvanic corrosion comes from. 

    I am in the process of solving this issue before I proceed in manufacturing the magnets and am looking into using parylene as a dielectric (Doesn't conduct electricity) and biocompatible material in between Cu and TiN.  It is possible I will still use Au instead of Cu however gold has a very slick surface and the copper may bond with the parylene better.

    The tests are going to have harsher conditions than are found in the body and I am looking into solving the cause of the corrosion you are mentioning. I am also looking into a chemical test that the manufacturers perform before I receive the magnets and continue to do other chemical testing.

    It is also potentially possible I can get the magnets observed under a microscope by the manufacturers however I am still discussing it and the tests with the manufacturers. 
  • Benbeezy What is your opinion on using the Atom Adhesives medical grade epoxy as an outer coating on these coated magnets or other cheap magnets to help insure they stay good for as long as possible?

    Does the added thickness make a big difference in the sensations of the magnet?  I'm sure it does but is there still enough sensation to make it worth doing?

    Have you found anything other than parchment paper that the epoxy doesn't stick to?  I contacted that company and they said "This product does not stick very well to rubber and very hard plastics."

    I'd like to figure out how to make a mold to make the coating smoother and make cleaning it up easy.  I've never used the epoxy so I don't know how hard it would be to work with.  Labor cost would probably be too high if you wanted to sell them but time wouldn't be a factor for someone wanting to coat their own personal magnets or other implants.

    I don't know exactly how the corrosion problem is happening.  It must be pinholes or some other defect in the outer TiN coating letting moisture (blood or body fluids) inside where it can contact two different coatings. 
Sign In or Register to comment.