WSM Posted October 30, 2012 Posted October 30, 2012 (edited) Sorry, it was some chinese stuff with no diagrams, how do I shunt it? The stuff is rated up to 30A Unless the meter has an internal shunt, you may be stuck. Most of the Chinese ammeters I have use a shunt rated for 75mA. Try a search on eBay for a 30A DC shunt and see what's available. I expect you'll find lots of hits. Good luck. WSM Edited October 31, 2012 by WSM
taiwanluthiers Posted October 30, 2012 Posted October 30, 2012 I guess it probably have an internal shunt. All it has is a diagram on the box that lists the dimension of the meter itself, has absolutely no other instructions. There is 2 terminal in the back with + and - on it, I assume + is where the current comes in?
pdfbq Posted October 30, 2012 Posted October 30, 2012 (edited) If it works, it works! There's no arguing with success. Dont get me wrong.. If I had a spotwelder I'd spot weld . I find it very interesting though that in a cell just a tight fit between the Ti and the MMO anode can handle those currents. Probably due to the hydrogen doping of the TiO2. @taiwanluthiers About a half year ago I wrote here (this thread) how to measure big amps with a cheap meters. I'm to lazy to look it up for you though. Edited October 30, 2012 by pdfbq
WSM Posted October 31, 2012 Posted October 31, 2012 I guess it probably have an internal shunt. All it has is a diagram on the box that lists the dimension of the meter itself, has absolutely no other instructions. There is 2 terminal in the back with + and - on it, I assume + is where the current comes in? Be careful, if you're wrong you'll fry the meter . Be sure before you connect it to power. WSM
taiwanluthiers Posted October 31, 2012 Posted October 31, 2012 I made a test cell today. I took a plastic beaker and filled it with water and dissolved sodium chloride (table salt) into it. Then I connected the ammeter in series with the cell, and touched the lead to a battery for a few seconds. The cell drew about 3 amps, and gases began to bubble from the plates. So the meter is shunted and should work correctly. The solution smelled like bleach only after a few seconds of run. It was a test cell and wasn't meant to be run for an extended period of time... the Ti plate where it was in the solution turned a little dark compared to bare Ti.
Swede Posted October 31, 2012 Posted October 31, 2012 If a monolithic ammeter designed for, say, 75 amps, has BIG terminals in the back, it has a built-in shunt. If it has small or tiny terminals, what you really have is a volt meter to be used with a matched external shunt. As WSM says, these things come standardized (but there are a few standards), so if you have a KNOWN shunt, you simply wire it in series (in line) with your heavy current, and apply a volt meter across the shunt. WHat you are doing is measuring voltage drop across a very small (but known and precise) resistance.
taiwanluthiers Posted November 1, 2012 Posted November 1, 2012 One question (I am sure it was already addressed somewhere). What prevents people from selling ready made lead dioxide anode? Is it because they are too fragile to ship? Would you be interested in selling pre plated LD or can I send you a piece of MMO to plate in LD?
WSM Posted November 1, 2012 Posted November 1, 2012 (edited) One question (I am sure it was already addressed somewhere). What prevents people from selling ready made lead dioxide anode? Is it because they are too fragile to ship? Would you be interested in selling pre plated LD or can I send you a piece of MMO to plate in LD? There are companies in China that do sell LD anodes, but so far our use of them has not gone well. We have yet to figure out why. This has motivated Swede and I to try to work out how we can make our own MMO and research various ways to coax it to produce perchlorates (including different methods of applying LD to them). It may take us a long time or we may get lucky with some sort of breakthrough. We're having fun learning though. LD is fragile, but fragile things are shippable if you prepare them properly. WSM Edited November 1, 2012 by WSM
taiwanluthiers Posted November 1, 2012 Posted November 1, 2012 I've been reading the blogs to figure out how I can make my own LD but it just seems difficult. Most of the required chemicals are cheaply obtainable but things like bismuth nitrate is very expensive for me to obtain. Then it looks like I needed a fully equipped chemistry lab in order to do this properly, which was why I asked if I could possibly send you a MMO to plate. What is your suggestion for producing perchlorate? Should I just buy some platinized titanium mesh from ebay?
Swede Posted November 1, 2012 Posted November 1, 2012 First off, get rid of Bismuth in any form from lead dioxide plating processes. I tried it based upon an old patent, and all it did was screw things up. Eventually, the plan is to have a lead dioxide plating process that produces working anodes of reasonable durability. MMO for chlorates has spoiled us in that it seems to last forever and works so well. Perchlorate is a different process, and there is ALWAYS some anode erosion. The goal is to minimize it to the point where the perchlorate yield is acceptable vs. any erosion. The problem with LD seems to be mechanical strength and durability over the substrate. Hobbyists years ago attempted LD over bare Ti, and this proved very challenging. I'm confident that this is how the Chinese LD anodes are made. I don't know how they prep the titanium, but that part of the process seems to be a bit of a voodoo art. By starting with MMO, which isn't an electroplating process, we have a surface that CAN be plated with LD. The process isn't trivial, as you've seen, you'll need a number of pretty toxic chems in some quantity. If/when I do LD plating again, once the rig is set up, I'm going to plate a number of anodes, not just one. And the anode shape is going to be engineered to maximize mechanical strength of the LD plating, with possibly a thinner coating. If all you want to do is play a bit and get some very clean, easy perchlorate, look for a platinized Ti anode off eBay. You'll have perc in short order, but the anodes are obviously expensive, and the Pt will wear off after some time. I haven't personally run a Pt anode to destruction so I can't comment on the economy of it, but it does work.
taiwanluthiers Posted November 2, 2012 Posted November 2, 2012 I ran the MMO anode I have in a small test cell just to see how things work. I at first tested it with a battery and about 3 amps went through it, but only for a few seconds. I may have connected the plates in the wrong polarity because the first time the titanium plate turned darker and I noticed in some area the MMO seem to have fallen off and exposed bare Ti. I did it again using a wall wart and this time used the right polarity. I notice the coating coming off in one small strip only on one side regardless of where it faces. What can cause the MMO coating to come off?
WSM Posted November 3, 2012 Posted November 3, 2012 (edited) I ran the MMO anode I have in a small test cell just to see how things work. I at first tested it with a battery and about 3 amps went through it, but only for a few seconds. I may have connected the plates in the wrong polarity because the first time the titanium plate turned darker and I noticed in some area the MMO seem to have fallen off and exposed bare Ti. I did it again using a wall wart and this time used the right polarity. I notice the coating coming off in one small strip only on one side regardless of where it faces. What can cause the MMO coating to come off? If run with reverse polarity, I think the titanium substrate is attacked so it won't support the MMO coating, physically or (eventually) electrically. It's like if you have severe gum disease, what's going to hold your teeth in? So we need to be absolutely certain the MMO anode is connected to the positive (+) lead of the power supply. Test it with a Volt-Ohm meter if you're not sure (this isn't a guessing game, know what you're doing, electrically). WSM edit: What is the source of your MMO anode? Is it possible it may have been damaged before you got it and tested it? Edited November 3, 2012 by WSM
taiwanluthiers Posted November 3, 2012 Posted November 3, 2012 The MMO is from laserred on ebay. The anode was large enough for 2 so if it gets really bad I have another one. I ran it again at a about 500mA for a few hours and noticed more of the coating coming off. I was wondering if it was too low of a chloride level because I dissolved only a few grams of salt in a cup of water. The stripping only occurred on one side and the other side is good as always.
Arthur Posted November 3, 2012 Posted November 3, 2012 Usually the start point is a hot saturated solution of salt. Try more like 500g made up to a litre at about 50C. Low chloride content kills electrodes too.
WSM Posted November 4, 2012 Posted November 4, 2012 The MMO is from laserred on ebay. The anode was large enough for 2 so if it gets really bad I have another one. I ran it again at a about 500mA for a few hours and noticed more of the coating coming off. I was wondering if it was too low of a chloride level because I dissolved only a few grams of salt in a cup of water. The stripping only occurred on one side and the other side is good as always. Does the liquid change color or is it still clear when the coating comes off? WSM
taiwanluthiers Posted November 4, 2012 Posted November 4, 2012 (edited) its still clear, it smells like bleach though. Edited November 4, 2012 by taiwanluthiers
WSM Posted November 4, 2012 Posted November 4, 2012 its still clear, it smells like bleach though. It remaining clear eliminates iron contaminants on the surface of the anode as the source of the material coming off the anode. Iron on the anode surface would likely turn the cell liquor yellow to brown. The liquid smelling like bleach is correct. When the cell runs it breaks down the water, the hydrogen bubbles off and the oxygen is driven onto the salt, first making hypochlorite and then hypochlorous acid. The pH control has as its goal (for "bulk reactions" in the cell) a 2:1 ratio of hypochlorous acid to hypochlorite; which is achieved at or near a pH of 6.8 (the "sweet spot", if you will). I don't know if your anode is defective or the reverse polarity at the beginning caused a dramatic failure. If you try the second electrode with the correct polarity and the same thing happens, I suspect your anode has a defect (or your setup is uniquely destructive (?) to the anodes). I've never seen them come apart like that, but I haven't seen everything. Let us know how this turns out. WSM 1
WSM Posted November 4, 2012 Posted November 4, 2012 Usually the start point is a hot saturated solution of salt. Try more like 500g made up to a litre at about 50C. Low chloride content kills electrodes too. Arthur makes a good point. Running a cell with a low chloride content is destructive to the electrodes. Some formulations of MMO can handle it better than others, but overall it's hard on all of them and will shorten the anode's life. See how the anode works with a saturated salt solution rather than a weak solution. WSM
WSM Posted November 4, 2012 Posted November 4, 2012 The MMO is from laserred on ebay. The anode was large enough for 2 so if it gets really bad I have another one. I ran it again at a about 500mA for a few hours and noticed more of the coating coming off. I was wondering if it was too low of a chloride level because I dissolved only a few grams of salt in a cup of water. The stripping only occurred on one side and the other side is good as always. This comment sounds more like the anode has a defect. Did you use two cathodes (one on each side of the anode mesh)? If not, which side showed the failure? Thanks for helping us help you solve this mystery. WSM
taiwanluthiers Posted November 4, 2012 Posted November 4, 2012 I used only one cathode. The anode stripping only appeared on one side even if I flipped the bad side away from the cathode, same thing happened. Interestingly it only happened on the surface of the mesh, it did not progress inside the mesh itself. At first I wasn't even sure it was the MMO coming off because the Ti was very smooth and I thought it was simply the anode getting a glaze. I figure I will run it normally like it is until it quits producing chlorate. How can I know if the anode is in itself defective, and how can I be sure that the next anode I buy isn't going to be defective? What if Laserred actually just sells Ti thats painted black (meaning its not actually MMO but a fake one)?
WSM Posted November 4, 2012 Posted November 4, 2012 (edited) I used only one cathode. The anode stripping only appeared on one side even if I flipped the bad side away from the cathode, same thing happened. Interestingly it only happened on the surface of the mesh, it did not progress inside the mesh itself. At first I wasn't even sure it was the MMO coming off because the Ti was very smooth and I thought it was simply the anode getting a glaze. I figure I will run it normally like it is until it quits producing chlorate.How can I know if the anode is in itself defective, and how can I be sure that the next anode I buy isn't going to be defective? What if Laserred actually just sells Ti thats painted black (meaning its not actually MMO but a fake one)? If it produces chlorate, it is MMO. I don't believe plain titanium will make chlorate at all, or we'd have no need to go after the MMO coated titanium, neither would industry bother with it. I think if we tried a cell with two titanium electrodes, the "anode" (or positive plate) would self destruct. As Swede has mentioned, the MMO, though physically fragile or able to be scraped off, is electrically and chemically very tough. It's also much more electrically conductive than the titanium substrate. I would recommend using the anodes till they quit producing chlorate. Any defect you observe may only involve the particular anode material you got this time. I wouldn't judge all of laserred's MMO by the one you got. The next one may be perfect. The low price overcomes a lot of negative features if it works for our purposes. WSM edit: Swede has found several of the anodes to have a brown "smut" on them which a 15-30 minute soak in HCl removed without any affect on the MMO coating. We believe the brown to be iron oxide because the acid turned yellow to brown, often indicating ferric chloride was produced. Edited November 5, 2012 by WSM
taiwanluthiers Posted November 5, 2012 Posted November 5, 2012 So if a Ti anode would self destruct what prevents any exposed Ti on the MMO and the strap from being attacked? I do notice a lot of brown smut on the anode but I was afraid to do anything to it because I might scratch off the coating, and it looks easy to scratch off. In fact the places where it looks like the coating came off looked as though it was scratched off. I don't know how this works but maybe there could be MMO elements embedded within the Ti and even though it may look like bare Ti it's not?
WSM Posted November 5, 2012 Posted November 5, 2012 (edited) So if a Ti anode would self destruct what prevents any exposed Ti on the MMO and the strap from being attacked? I do notice a lot of brown smut on the anode but I was afraid to do anything to it because I might scratch off the coating, and it looks easy to scratch off. In fact the places where it looks like the coating came off looked as though it was scratched off. I don't know how this works but maybe there could be MMO elements embedded within the Ti and even though it may look like bare Ti it's not? Good catch. You're right. But even though it doesn't self destruct, it still won't produce chlorate. Titanium tends to self heal and is very corrosion resistant in marine environments. Where the MMO in a working cell is compromised, the exposed titanium is unaffected. One exception is fluorides. The least amount of soluble fluorides tends to tear up titanium immediately, which is why I shy away from tap water in my cells. If they fluoridate your drinking water, it can trash your MMO by attacking the titanium substrate and separating it from the MMO coating. Physical abrading will damage MMO, but it won't be affected by HCl, so a good soak will clean off the brown smut. Try it, it sure worked for me (and yes, the acid turned yellow; but the brown smut was gone). I gave it about a 30 minute soak in full strength pool acid and rinsed it off with pure water... good as new! WSM Edited November 5, 2012 by WSM
taiwanluthiers Posted November 5, 2012 Posted November 5, 2012 Tap water in Taiwan is supposedly drinkable but nobody drinks them, it has a heavy chlorine taste and I do not know if they add fluoride to it. So then I am supposed to use distilled water? Is there any way of telling distilled water from any other water because while I see bottled water, I can't really tell which one is distilled or which one is mineral water. I will be using the potassium chloride with the red stuff in them (whatever they may be) because they're the cheapest one I can get.
WSM Posted November 5, 2012 Posted November 5, 2012 (edited) Tap water in Taiwan is supposedly drinkable but nobody drinks them, it has a heavy chlorine taste and I do not know if they add fluoride to it. So then I am supposed to use distilled water? Is there any way of telling distilled water from any other water because while I see bottled water, I can't really tell which one is distilled or which one is mineral water. I will be using the potassium chloride with the red stuff in them (whatever they may be) because they're the cheapest one I can get. A TDS meter will let you know if it's distilled or not. They cost about $15 US at the lowest and are worth having. A reading of 0.00 ppm is distilled. TDS stands for Total Dissolved Solids. WSM Edited November 5, 2012 by WSM
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