Sciencemadness Discussion Board - MMO anode degradation

MMO anode degradation

dischem - 5-8-2014 at 02:47

Hey all,

I recently ordered a MMO mesh anode for chlorate production. It's got quite a bit of surface area, so I'm planning on taking advantage of that and setting up a fairly large scale chlorate cell (roommate wants to make a rocket fuel...). I know 5v is usually used for chlorate cells to prevent damage to the anode. However, I'm using an old ATX power supply that's rated for a higher amperage on the 12v rail than on the 5v rail.

My question is, is damage to the anode caused by overvoltage, too high of a current density, or both? I read somewhere (I'll find it later, on my phone) that MMO electrodes shouldn't be used at a current density greater than 0.2 A/cm^2. Can I use the 12v rail on my power supply as long as the current doesn't exceed 0.2A/cm^2, or will higher voltages damage the anode regardless of current density?

Many thanks

Bert - 5-8-2014 at 05:18

Before getting to the issues of electrode parameters, tell room mate he really wants perchlorates for rocket fuel? Chlorate is better as an oxidizer for an explosive or pyrotechnic colored stars, it tends to make overly sensitive propellant.

Your over voltage power supply output is perhaps a resource for conversion of the chlorate from first reaction to perchlorate?

Zyklon-A - 5-8-2014 at 05:48

Using over 7 volts tends to make perchlorate rather than chlorate, which inevitably corrodes MMO.
I suggest using something to lower the voltage to 4-7 volts or else buy a Pt anode and make perchlorate.

And like Bert said, you don't want a chlorate based rocket - they tend to explode!

Brain&Force - 5-8-2014 at 08:40

Also, you can't make potassium perchlorate through electrolysis of potassium chloride - potassium chlorate tends to crystallize, preventing conversion to perchlorate. You have to make sodium perchlorate and then precipitate it with a potassium salt if you want potassium perchlorate.

dischem - 5-8-2014 at 12:09

Well, rockets would be cool, but honestly he and I just want to make something cool that's cheap to produce. We were planning on just using chlorate and sugar to keep the reaction relatively mild. If it does end up exploding...that works too. :-P

As brain&force mentioned, since the potassium chlorate precipitates out, could I use a higher voltage, or would there still be degradation at the anode? The real thing I'm trying to understand is the mechanism which damages the anode. Overvoltage, or over current.

Zyklon-A - 5-8-2014 at 12:17

Well, both I think. Over current shouldn't be a problem though right, cause you said you have a big piece of MMO.

MrHomeScientist - 5-8-2014 at 12:47

Quote: Originally posted by dischem

If it does end up exploding...that works too. :-P

Not if it's in your hand at the time!

I am not an expert in electrolysis at all, but what I've heard around here suggests it's excess voltage that is the killer. I still don't fully understand why everyone wants to make boatloads of chlorate. So many threads on chlorate production, but almost no threads on chlorate use. Pyrotechnics, or as a feedstock to perchlorate I suppose?

Mailinmypocket - 5-8-2014 at 12:50

It's sort of fun to run a cell you made and can operate. At least for me it is. Do a few runs and although it's more than I need for my uses, it is cool to have around for campfires, making demos for friends outdoors etc. For the chemistry I do I rarely use it though.

Edit- I have used it as an exceptionally effective weed killer actually!

[Edited on 5-8-2014 by Mailinmypocket]

MrHomeScientist - 5-8-2014 at 13:22

Hah! That's pretty interesting. Massage finely ground chlorate into leaves and ignite?

[Edited on 8-5-2014 by MrHomeScientist]

Mailinmypocket - 5-8-2014 at 14:48

Lol not that spectacular! It was something like a 10% solution poured on the base of the plant. They wither and die pretty fast within a few hours, never bothered to read why though.

Manifest - 5-8-2014 at 15:00

I have made chlorate rockets before but I haven't 'cooked' it with sugar, for obvious reasons.
It worked as well as KNO3.

Do not ram the Chlorate/Sugar into the rocket tube or it may explode.
I have done hammer tests with Chlorate/sugar and it's hard to get it to detonate but it certainly does.

On topic, remember to keep the pH low to minimise corrosion of the anode, the best way to do this is with Sodium Bisulfate.

[Edited on 5-8-2014 by Manifest]

Bert - 5-8-2014 at 16:17

Sodium chlorate/Sugar is too touchy for casual propellant use by the inexperienced. It had a reputation for maiming and killing those who thought to use it in pipe bombs & etc. in the various countries where Sodium chlorate was freely available as a weed killer.

Potassium chlorate + nearly any organic fuel + Sulfur has killed fire workers and powder hands a-plenty, starting with the very first people who tried to harness the improvement in specific impulse over Potassium nitrate oxidized mixtures and created chlorate based black powder analogues.

hyfalcon - 5-8-2014 at 17:14

Quote: Originally posted by Brain&Force

Also, you can't make potassium perchlorate through electrolysis of potassium chloride - potassium chlorate tends to crystallize, preventing conversion to perchlorate. You have to make sodium perchlorate and then precipitate it with a potassium salt if you want potassium perchlorate.

Strange, I didn't have any trouble with perchlorates, but I was using a platinized titanium anode in a small vessel running a 12v battery charger. Temperatures stayed upwards of 65C keeping my chlorate in solution.

dischem - 5-8-2014 at 17:36

Huh, I didn't realize it was that touchy, thanks for the info. I've seen fairly mild reactions with sugar on YouTube, but I imagine the reaction changes when compacted into a smaller space.

Thanks for the info on all this, very useful.

arkoma - 5-8-2014 at 17:55

Quote: Originally posted by MrHomeScientist

Hah! That's pretty interesting. Massage finely ground chlorate into leaves and ignite?

[Edited on 8-5-2014 by MrHomeScientist]

I remember barrels of sodium chlorate solution in the farm shop in Arkansas. We sprayed it on soybeans and rice about a week before harvest as a "dessicant". Helps deal with green bean syndrome in soybeans.

Whatever it does to plants to kill/dry them, it does WELL.

gdflp - 5-8-2014 at 18:03

Yeah when I tried a mix of potassium chlorate and sugar in a pyrex test tube, the bottom of the tube shattered in about two seconds. I wouldn't call that mild

dischem - 5-8-2014 at 18:29

Quote: Originally posted by gdflp

Yeah when I tried a mix of potassium chlorate and sugar in a pyrex test tube, the bottom of the tube shattered in about two seconds. I wouldn't call that mild

Damn, 2 seconds after heating it up? It didn't just spontaneously explode did it?

Zyklon-A - 6-8-2014 at 09:55

Quote: Originally posted by dischem

Huh, I didn't realize it was that touchy, thanks for the info. I've seen fairly mild reactions with sugar on YouTube, but I imagine the reaction changes when compacted into a smaller space.

Thanks for the info on all this, very useful.

Well, yes. It generally depends on quantity and confinement. If you have a five gram mixture and light it in the open, chances are it will just burn quickly, but if you pound three hundred grams into a rocket motor, it might explode while pounding, or it might explode when lit, either way it's quite dangerous.

dischem - 10-8-2014 at 17:23

Just an update, there's a ton of useful information I found here.

http://www.oocities.org/capecanaveral/Campus/5361/chlorate/c...

jock88 - 12-8-2014 at 14:35

That page is now at this address

http://oxidizing.typhoonguitars.com/

[Edited on 12-8-2014 by jock88]