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platinized titanium anodes


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#1 MadMat

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Posted 02 April 2019 - 10:24 PM

I have been doing experiments trying to make solid lead anodes with lead dioxide formed on the surface for the production of Chlorate/perchlorate. I continue to have problems with the coating "flaking off" after an extended time. Meanwhile, I want to make some perchlorate! I have been looking at various anodes and noticed platinized titanium anodes on Ebay. Does anyone know about these? I am certain the platinum coating on these anodes is very thin and am concerned with the coating failing. Many years ago, I worked in the lab at an electroplating company and was put in charge of the operation and maintenance of a device which removed chrome out of rinse water by way of a semi-permeable membrane and electrolysis. This device had platinized titanium electrodes and I distinctly remember the platinum peeling off those electrodes (much to the dismay of my boss, who had authorized the $15,000 purchase of that device.)  I am wondering if it is possible that a new technique has been developed which makes these anodes more durable?


Edited by MadMat, 02 April 2019 - 10:27 PM.

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#2 Arthur

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Posted 03 April 2019 - 12:48 AM

First if it's from ebay there is little certainty that it's platinum. Second if you get one try to run it at half the suggested current. 

Do you have a local (state or continent) supplier of jewellery supplies -just buy a piece of platinum sheet say 25 x 25 mm x 0.25mm. hide the connection in a fused glass tube.



#3 dagabu

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Posted 03 April 2019 - 07:47 AM

Didn't WSM do a full writeup on this some time back? Pretty sure he worked all the bugs out.
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#4 MadMat

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Posted 03 April 2019 - 10:53 AM

If he did a write up on them, I missed it. Now, from what I have read platinum is not the preferred anode material for the conversion of chloride to chlorate, bit is preferred for chlorate to perchlorate. Granted it would seem rather cumbersome (ridiculous?) to change out anodes in the middle of  the process, but platinum is a very expensive material to be wasted to electrolytic corrosion.  By the way, I do have a source for MMO anodes, which is what I'm probably going to use. I was just interested in what a platinized titanium anode would do.


Edited by MadMat, 03 April 2019 - 10:57 AM.


#5 MadMat

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Posted 03 April 2019 - 11:03 AM

Oh yeah, um.... Now I'm not afraid of math (went up to a semester of calculus in college), but it seems like an exercise in futility trying to calculate the surface area of "expanded metal" anodes. Does anyone know of a simple, concise formula for calculating the surface area for them? I suppose I could whip out the dial caliper, take dimensions of everything and manually calculate everything out, but not my idea of a fun time.               I should have engaged my brain before typing this... I did a simple google search and found exactly what I was looking for from a metals supplier


Edited by MadMat, 03 April 2019 - 11:07 AM.


#6 Arthur

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Posted 03 April 2019 - 11:17 AM

Yes Pt erodes badly when there are low chloride concentrations in solution, so normally MMO / DSA is used for stage one then the chlorate is boiled and extracted, then (almost) chloride free chlorate  is electrolysed with one Pt electrode and one CP Titanium electrode. Fortunately the Pt cell can run well at a few amps, the chloride to chlorate  cell does best running hot with lots of current.



#7 dagabu

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Posted 04 April 2019 - 04:47 PM

Mad, depending on the size of the mesh, 1/4" expanded metal is 4:1.
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#8 MadMat

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Posted 04 April 2019 - 05:22 PM

This website gave me everything I needed to know:  https://www.dexmet.com/technology

Like I posted earlier, I worked in the laboratory for an electroplating company and during that time learned a lot about electrochemistry. One of the things of importance is current density.  One thing that isn't mentioned much about creating perchlorate/chlorate is that the current density must be higher on the anode than the cathode. If the surface area of the cathode and anodes are the same, or worse, higher on the anode than the cathode (more surface area, lower current density). reduction rather than oxidation will be the majority reaction in the cell and you will get no chlorate/perchlorate produced. If the current density on the cathode is kept low enough no reduction occurs. Unfortunately, I have never found what current density is optimum for the production of chlorate or perchlorate. I will bet companies that have industrial production of these chemicals would know. I remember, in hard chrome plating a current density of around 2 Amps per square inch was optimal, too much more than that and the plating was rough and "burned", too much less than that and no plating would occur.


Edited by MadMat, 04 April 2019 - 05:24 PM.


#9 Arthur

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Posted 05 April 2019 - 12:37 AM

All of the current figures and densities are in the huge post started by gods knight and completed by Swede and WSM. The important detail about the chlor alkali process is the temperature, at low temps the product are the lower oxidised chlor species, the temp must be higher to get the higher oxidised chlor compounds -so cool makes bleach and hot makes chlorate. While the current density matters don't go too far, or the small electrode will erode.



#10 WSM

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Posted 09 April 2019 - 01:00 PM

I used low current with a platinized titanium anode, to convert sodium chlorate solution to sodium perchlorate solution.

Somewhere in the neighborhood of 1-2 A/cm2. The ozone production seemed minimal and at the projected end-of-run,
I had lots of NaClO4.

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#11 LardmanAttack

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Posted 10 April 2019 - 12:11 AM

Yeah, ebay and Aliexpress have a huge reputation for ripping people off with bad quality electrodes, sometimes they are even fakes, Amazon is better for that kind of stuff, although it is possible you may still be ripped off there.



#12 WSM

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Posted 06 May 2019 - 01:00 PM

One important thing to remember when shopping for platinized titanium electrodes, is the thickness of the platinum layer.

The better electrodes are those with a platinum layer 50 to 100 microns thick.

Many of the cheap imports have much thinner layers, and therefore won't last nearly as long (or at all).

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