platinized titanium anodes

[MadMat]

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 April 3, 2019 by MadMat

[Arthur]

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.

[dagabu]

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

[MadMat]

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 April 3, 2019 by MadMat

[MadMat]

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 April 3, 2019 by MadMat

[Arthur]

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.

[dagabu]

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

[MadMat]

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 April 4, 2019 by MadMat

[Arthur]

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.

[WSM]

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.

 

WSM

[LardmanAttack]

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.

[WSM]

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).

 

WSM

[WSM]

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.

WSM

 

I forgot to mention, I used a variable power supply with constant current (CC) capability.

 

Running the sodium perchlorate cell on CC mode and low current, plus at about 4-4.5 volts DC; the inexpensive and thin-layered platinum over CP titanium mesh anode worked quite well with no discernable breakdown of the Pt layer.

 

I avoided using full theoretical power on the Pt or LD anodes due to the many reports of anode failure by amateurs trying to make perchlorates for the first time. My guess was that they attempted to do so in a similar manner as chlorate is made and overpowered the anodes, causing the premature failures reported.

 

It worked for me but, of course, your milage may vary...

 

WSM

Edited June 14, 2019 by WSM

[markx]

For those especially inclined towards materials manipulation, one can produce platinized Ti substrate anodes in rather clandestine conditions. I have been doing a lot of tinkering around the development of the process and have had excellent results. There is no need to electroplate the platinum coating onto substrate. This approach can be tedious, complicated and not very easily reproduced. Instead simple pyrolysis of hexachloroplatinic acid solution in temperature controlled environment can be used and it shall yield a very satisfactory result considering the cost and simple reproducibility of the results.

 

Step 1. Take grade 1 or grade 2 Ti material, as the substrate used for anode must not be alloyed titanium, for it shall not hold up to the anodic potential in a cell without starting to dissolve and disintegrate. Sand the oxide coating off the titanium with emery paper. About 240-400 grit is fine enough. If one tries to polish the surface to a high sheen, it shall become highly hydrophobic and become unusable in later steps of the process. Store the cleaned substrates under alcohol to prevent premature oxide formation that block the surface. Try not to store the substrates for long periods of time (longer than a few hours) in the uncoated condition.

 

 

 

Step 2. Obtain hexachloroplatinic acid solution. Take one of the substrates, dry it from the alcohol and apply a thin coating of the hexachloroplatinic solution on the surface of Ti. Literally a fraction of a drop shall suffice to coat the size of substrate displayed (about 8cm2 in surface area). Take utter care to work with the solution! Protect your skin and surroundings from coming into contact with the platinic solution, it is very hazardous and the most potent sensitizer known. The effects on human body are permanent and irreversible.

 

 

 

 

Step 3. For this one needs a temperature controlled kiln that can achieve and hold a temperature of about 600C. Take the coated substrate and place it into the kiln for 10 minutes using a suitable support stand or other means. The kiln has to be vented as the hexachloroplatinic acid shall pyrolyse quickly with the release of fumes and fine Pt dust. It must be evacuated by the vent so as to not be breathed into ones lungs.

 

 

 

Step 4. After 5 minutes in the kiln, the substrate shall have a platinic coating on it. Take the sample out of the kiln and cool it (it can be cooled by tucking into water, or by means of an air flow). Wash the sample under running water to scrub off loose Pt particulate. Then wipe with paper and alcohol until no residues can be seen to come off. Do not be alarmed if the coating looks uneven and lots of it seem to come off during the scrubbing. It is a totally normal course of events. Dispose of the paper with Pt particulate on it in a wet condition. It might selfignite if left unchecked as the Pt dust is very fine and could display a catalytic effect. I have not yet observed such a mishap, but it pays to be aware of the danger.

 

 

 

Step 5. Repeat the steps of coating the substrate with another layer of hexachloroplatinic acid and the pyrolysis followed by cleaning off the loose particulates. Keep going until 4-5 coats of Pt have been applied at 600C. It shall yield an anode that will have a lifespan of about 700 hours in a perchlorate cell at the approximate current density of 100mA/cm2.

 

 

 

Step 6. Subject the anode to operation in a cell. Try to keep the applied voltage across the cell under 5V. There is no need to go high, as it shall passivate the anode prematurely and cut a good deal of lifespan off. The process of perchlorate formation works very nicely at low voltages on Pt coated anodes (thusly also at low anodic potential, which shall prevent excessive passivation of the Ti substrate).

 

 

 

 

One can upscale the process to larger substrates and acquire anodes of desired size for a larger setup:

 

 

 

 

 

[WSM]

Very nice, markx.

 

I would like to duplicate your demonstration, but hmmm, where to find some hexachlororoplatinic acid?!!!

 

Well, if I ever get some, I'll certainly give your process a try.

 

Thanks for sharing.

 

WSM

Edited June 18, 2019 by WSM

[Arthur]

http://www.prepchem.com gives a synthesis assuming normal lab chems and a bar of platinum.

https://www.cooksongold.com is a UK supplier of platinum and other bullion/jewelery metals in wire and sheet form =Look for a hobby jewelry supplier in the USA or your country.

[markx]

 

I would like to duplicate your demonstration, but hmmm, where to find some hexachlororoplatinic acid?!!!

 

 

 

WSM

 

The solution can be made by dissolving Pt in aqua regia, so if you happen to have some form of metallic Pt it becomes a rather easy task. Still care has to be taken when working with soluble platinic salts to avoid dispersing droplets into air during dissolution or spilling the stuff on your skin.

[WSM]

The solution can be made by dissolving Pt in aqua regia, so if you happen to have some form of metallic Pt it becomes a rather easy task. Still care has to be taken when working with soluble platinic salts to avoid dispersing droplets into air during dissolution or spilling the stuff on your skin.

 

Well, if I ever bother to buy a Pt bullion piece, I can make it myself. Thanks for the info and caution warnings.

 

WSM

[WSM]

http://www.prepchem.com gives a synthesis assuming normal lab chems and a bar of platinum.

https://www.cooksongold.com is a UK supplier of platinum and other bullion/jewelery metals in wire and sheet form =Look for a hobby jewelry supplier in the USA or your country.

 

Thanks, Arthur.

 

If I ever get my hands on some pure platinum, I'll try the system described using hexachloroplatinic acid of my own make, following markx's description.

 

WSM

Edited June 22, 2019 by WSM

[Arthur]

Cookson certainly sell small amounts of platinum you can buy inches or mm of Pt wire for a fair price based on UK bullion price and (iirc) UPS carriage.

 

https://www.ottofrei.com/jewelry-metals/shapes-sheets-stock/metal-stock is just google's first offering of a supplier selling platinum bar and rod stock in small quantities and small prices! no recommendation of this one supplier made or inferred, but nothing known against either.

[WSM]

Cookson certainly sell small amounts of platinum you can buy inches or mm of Pt wire for a fair price based on UK bullion price and (iirc) UPS carriage.

https://www.ottofrei.com/jewelry-metals/shapes-sheets-stock/metal-stock is just google's first offering of a supplier selling platinum bar and rod stock in small quantities and small prices! no recommendation of this one supplier made or inferred, but nothing known against either.

 

I'll hold off for now. I can't afford such an extravagant expenditure at this time, but perhaps later...

 

For now, I'm content to work out the details of pure sodium chlorate production, which, if I can get a good supply of, I'll continue my perchlorate research.

 

WSM

Edited June 22, 2019 by WSM

[markx]

I moved along the same path..........first trying to get a stable procedure to yield chlorate, after it had become a nobrainer I tryied my hand on perchlorate electrosynthesis. Both of them I can now yield on demand, but to be honest I have no reasonable use for the product. It piles up faster than can be consumed for practical purposes. But it feels good to be able to have such capability

 

The neat thing I found about the platinized anodes during my experiments is that the popular belief about chloride contamination extinguishing their soul quickly, does not really seem to be a major issue. In fact I have used the diy platinized anodes to perform a full conversion starting from plain sodium chloride and going all the way up to perchlorate. Damage shall start to manifest itself at the end of the perchlorate conversion stages when anode potential rises due to chlorate depletion and starts to promote passivation. When starting from chlorate, the chloride contamination in stock solution is not a problem and trying to purify it makes really no sense at all. The electrochemical processes in the perchlorate cell shall yield an equilibrium chloride concentration anyways (even if one starts out with perfectly pure chlorate).

 

What seems to be a major issue is high anode potential (polarisation due to the electrochemical processes not being able to keep up with the power supply and hence yielding a charge difference on the electrodes). In my experience, if one keeps the current density around 100-150mA/cm² and does not apply more than 5V across the cell, then usually the polarisation is not strong enough to cause problems with anode damage or passivation until the very end of conversion. But cranking up the cell voltage over an excess of 5V and letting current density on the anode rise sky high will quickly end in full passivation of the Ti substrate. So it is a waltz of balance....

[davidh]

I wonder about buying several one gram platinum bars, and making a titanium structure to mount them in. Then you always have the option of selling the worn bars as scrap platinum. And it would be easy to calculate the surface area.

 

https://www.apmex.com/category/33210/1-gram-platinum-bars-rounds

Edited June 27, 2019 by davidh

[WSM]

I wonder about buying several one gram platinum bars, and making a titanium structure to mount them in. Then you always have the option of selling the worn bars as scrap platinum. And it would be easy to calculate the surface area.

https://www.apmex.com/category/33210/1-gram-platinum-bars-rounds

 

If you have a spot welder (resistance welding), I see no reason you couldn't spot weld some one gram bullion pieces to CP titanium and use that as an anode for perchlorate production.

 

Other means (I'm thinking of mechanical fastening) of fixing Pt to a compatible substrate would likely also work.

 

Let us know which one you use and how it works.

 

WSM

[WSM]

When I commented on the expense of platinum, I was unaware that the price has dropped to nearly $800 USD/Troy Ounce (31.1 grams).

 

If I can find a reasonable seller of pure platinum, I may try to get 3 grams to experiment with. I hope the cost is under $100 USD.

 

WSM

Edited June 27, 2019 by WSM