A new electrode configuration
Entry posted by Swede
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Do you like the new board better? Worse?
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I am a typical experimenter who tends to mess with things even if they are not broken. Such was the case with my MMO anode / Titanium cathode electrode set. The original cell, made from a "Lock & Lock" plastic container, had a pretty healthy spacing of the anode and cathode, and required about 7 volts to push 20 amps through the system. I've got a killer power supply, capable of 80 amps, but it only goes to 10 volts. I thought by decreasing the spacing, and surrounding the anode with cathode material, I could get greater current flow at a reduced voltage.
Not much survives the hell that is the inside of a chlorate cell. Teflon is an ideal material, and is what I put to use for a new electrode configuration. The project starts with a 1' length of 1/2" virgin PTFE rod. In the lathe, I turned grooves every 0.200"
The MMO anode is 1/16" thick. The plan was to position two sections of the turned PTFE rod on either edge of the anode. This required a 1/16" slot to be cut on both rod sections:
Additionally, one of the rods was slotted on the opposite side to secure the 1/16" diameter pure titanium wire which was going to be used as the cathode. The wire was routed in the outer channel from top to bottom, and given a 90 degree bend:
From there, the wire was wrapped around the entire assembly, using the turned grooves as guides. The wire was not dead soft, and if I ever attempt something like this again, I am going to anneal it first. It had quite a bit of spring, and it was pretty challengng to get it properly wrapped around both PTFE rods. My hands cramped badly, and if I let go of the wire, it would come unraveled off the teflon rods very quickly.
At the top, I used a couple of twist ties to temporarily hold the Ti wire in place, while I dithered on how to take both ends of the wire through the top to form a junction for the power supply lead.
In the end, I simply created two bends in both wires, joined them at a spot about 1" away from the anode shank, and routed them upwards. the Lock & Lock lid was cut and drilled for the anode shank, and the much smaller hole to handle the two Ti cathode wires.
In the previous runs, hot glue worked well to seal the electrodes to the lid. While not especially strong, it is temporary, and as the system heats up, actually softens a bit, flexes, and keeps the gap(s) nicely sealed. The lids and the containers themselves seem pretty durable, but I noticed a definite bit of discoloration and hardening on the previous lid, especially the silicone gasket. Hint: Buy one or two of the 3.5 liter containers for the actual cells, but buy several of the smallest containers just for the lids. The lids on the small square containers seem universal, and will fit all of them, the only variation being the height. The lids, definitely, get the brunt of the abuse from the harsh chemistry of these cells.
The generated gasses are noxious, especially Cl2, and some means is needed to vent the chlorine from the cell AND the room. A length of tubing is best, with 1/4" OD being the minimum; wider would be better. Nylon has been holding up well with previous runs, but I did buy a short section of PTFE tube (all PTFE is expensive) if needed. To truly secure the tube to the container, some sort of fitting is required. The fitting here is a commercial nylon fitting of the type you can buy at any big-box hardware store. PTFE fittings of this sort are available, but the cost about $25 apiece. This nylon job was $2. If it hardens, cracks, and dies, I can replace it. I can buy a lot of nylon fittings for the price of one made of PTFE.
The threaded shank of the fitting is a tapered pipe thread. The thickness of plastic on the lid is too small to take a thread, and nuts for such a thread are pretty-much non-existent... so I created one from a short section of PTFE.
Ready to go!
Two copper clamps were set up on the electrodes to recieve the current from the power supply. These are pretty cheap, easy to find at Lowe's, and are infinitely preferable to alligator-style clamps. They create a very secure connection, which permits higher current flow with reduced temperatures.
The odd configuration of the cathode wires and the electrical connection - I wanted (needed, actually) to keep the Ti wire leads straight so that when this lid wears out, which it will eventually do, by scraping the hot glue away, the electode unit can be pulled straight through the old lid, and reinstalled on a fresh one.
The new electrode is ready to go. The teflon should last forever, and I can't imagine an electrode set being made with a lower voltage potential... the gap between anode and cathode is nowhere greater than about 0.250", and the anode is completely surrounded in a cage of Ti cathode wire. I have lost a little bit of anode surface area near the edges. My main concern is the possibility of excess heat in the Ti wire itself. The thick bar shank of the original Ti cathode carries current well, and even at 25 amps, did not heat appreciably. The wires, definitely less so. Ti conducts well, but not nearly as well as Cu.
It lives... and my fears were realized. While the voltage requirement did in fact go down, any current much above 18 amps makes the cathode frighteningly hot. I may end up eventually tearing this down, but a better answer is to buy another MMO anode, to be paired with the now orphaned Ti mesh cathode, and run two sets.
To get a really efficient, bulk-production system set up, I really need a larger cell. With 80 amps available, my power supply right now is loafing along at 18 amps. 25 amps seems about the maximum with this 1 gallon container - much above that, and the electrolyte would get too hot. Two sets of electrodes immersed in about 4 gallons of electrolyte, running at 60 amps, would be awesome!
Do you think ebay would have a problem with 55 gallon fibre drums of KClO3 being sold? 
As I've mentioned previously, the chlorate is purely an intermediate on the way to perchlorate. I will keep a small amount of chlorate on hand, but I can't see it being used much with my limited skill set.
As always, be safe, stay safe; life, limbs, eyesight, all are awesome things to retain. A message to Noobs, from a Noob himself - stay away from flash. It is scary stuff. Don't make perc with flash in mind, make it for stars and other colorful comps. The fastest way to get in serious legal trouble is with an illegal salute. Please, don't do it.
Adios, amigos. 
TWO Days Later...
This electrode SUCKS. 
A lot of work for nothing except the knowledge. The main problem was the cathode's inability to carry a decent current. 18 amps was the maximum, and for reference, the cathode's cross-section was 0.024 inches squared, or 4 mm squared. The original (commercial) Ti cathode shank was 20mm squared, a five-fold increase. So keep those numbers in mind if you are making a Ti cathode... you're going to need at least 20mm squared to do 25 to 40 amps without overheating.
Another observation... Hot glue SUCKS as well to seal the electrode shank. The lid to this cell makes use of a soft, silicone gasket. I noticed that the silicone was in great shape, and relatively unaffected after two runs. After I tore this electrode down, for the new cell lid, I used pure GE silicone rubber from a tube to seal the electrode shanks to the plastic lid. This glue too is flexible, temporary, and best of all, does not soften as badly as the hot glue as the system heats up. It seals well. Conclusion - silicone rubber is relatively long-lived in a chlorate system, and is useful to seal gaps and secure electrodes.
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