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Author: Subject: More on PbO2 electrodes
Rosco Bodine
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[*] posted on 1-6-2007 at 10:33


Quote:
Originally posted by dann2
Quote:
Originally posted by Rosco Bodine
Industry patents have in general proven to be sources of good information for me anyway , although there are a few
exceptions ...some of which can be debunked with a little effort .

BTW , on your website there is an interesting
article , JES Vol.104, No. 7 (July 1957) page 448
Electrolytic Production of Bromates , which describes
the deposition of massive PbO2 anode material on *iron*
substrate from a *neutral* pH lead nitrate bath . It would hardly get any simpler than that , if a piece of low carbon soft steel would work as well . I am thinking cold rolled bar stock could do the trick as a substrate . or possibly even a soft cast iron , or mild steel .

http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...


[Edited on 1-6-2007 by Rosco Bodine]


This set up uses 5 tanks, two stirrers, a pump and constant pH monitoring. Not impossible but not too simple either.


Think outside the box for a minute and realize that 5 separate tanks are not required , just because that is how they accomplished the desired result for an industrial scale apparatus . An aquarium power filter with the neutralizing salts in the filter would accomplish the same thing . Two tanks only would be convenient , and actually one of those
could be the filter tank compartment of the power filter itself .
Quote:

Most people only want to bother with one tank. Perhaps thats the problem.
If you are going to plate any substrate that is attackable by nitric acid from a nitrate bath you must plate with a neutral or near neutral bath. This will require two tanks. It is difficult to keep pH close to neutral as it will drop rapidly as plating commences due to formation of nitric acid.
You cannot do it in a one tank set up IMHO.
DANN2


Actually a one tank setup is possible if you have one of those miniature submersible magdrive pumps like are used for tabletop fountains .

http://www.pondland.com/product_info.php/cPath/1/products_id...

You would simply put the submersible pump in the bottom of the plating tank , and bring a discharge tube straight up from it to discharge into a receiving vessel above , which has a bottom drain , and an overflow tube also coming down to the drain would be good . The vessel would be a percolation
funnel having a wad of polyester filter fiber in the bottom ,
maybe a layer of diatomaceous earth filter aid above that ,
and then a loose wad of filter fiber whose space is loaded with solid particles of lead oxide or basic lead nitrate , for
neutralization of the electrolyte which percolates by gravity
through the vessel . Something like this could be made from
an empty plastic bottle with the bottom cut off and inverted ,
or from an old filter housing or plastic cannister , or even a section of PVC pipe . The setup would function in the same way as the drawing of Fig.#4 in the patent US2492206 .
This is something that could be done for a small scale cell , perhaps even for a gallon jar sized plating tank .

[Edited on 1-6-2007 by Rosco Bodine]
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[*] posted on 1-6-2007 at 17:35
Palladium vs Ruthenium


When I first started looking into this, Ru was cheaper than Pd!

Going by the Englehard data that Eclectic linked to, it looks like Ru really took off last year for some reason, but prior to 2006, AFAIK, Ru was usually significantly cheaper than Pd.

Anyway I'm attaching a patent that you might find interesting. It looks like an attempt to find an alternative to Beer's MMO patents. According to these inventors, Pd is better than Ru as far as electrocatalytic activity is concerned. They find that PdO by itself didn't adhere well to the titanium.

And they ended up with a PdO/Pt-Pt alloy or something like that.

[Edited on by jpsmith123]

[Edited on by jpsmith123]

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[*] posted on 1-6-2007 at 23:27


The processes described in that patent sound really complicated, with baking at defined temperatures and for defined time.
I also consider my platinum too valuable to use it in a way that is so uncertain of success. If the electrode doesnt work, I'm left with the work of recovering and separating the Pd and Pt from the solution and surface of the failed electrode which is going to be very tedious.

Oh well, I probably wont get around ordering two or three grams of Ru. One try with a pure PdO coating, and if it fails its time for ordering Ru and TiCl4.




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jpsmith123
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[*] posted on 2-6-2007 at 03:55


If it were me I don't think I would bother with the process in that patent...I think that was mainly an attempt to find a proprietary alternative to Beer's MMO technology.

What I thought most interesting about that patent was the brief discussion comparing the catalytic activity of the various PGMs.

Maybe you could try a PdO/TiO2 (electrodeposited or baked on) coating in the molar ratio suggested by Beer? Seems to me that's the logical place to start. You can get 5 grams of PdCl2 on ebay for $80.00.

http://cgi.ebay.com/Palladium-Chloride-ACS-pure-Photo-5g_W0Q...
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Rosco Bodine
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[*] posted on 2-6-2007 at 07:39
All you need is iron


All you need is iron ,
All you need is iron ,

All you need is iron , iron .....

Iron is all you need
Iron is all you need
Iron is all you need

:D:D:D:P:D;):cool::cool::cool::D:D:D:D


http://www.youtube.com/watch?v=Z05zPJKasDw

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[*] posted on 2-6-2007 at 08:13


I think all you need is lead free 95/5 solder, Muriatic acid, and a self cleaning oven to make Sn/Sb oxide coated titanium, coated or not with PbO2. Oh, and maybe some oxalic acid to strip the oxide off of the Ti first.

If you use a closed end Ti tube, you could pour molten aluminum around a copper bus bar in the center and never have to worry about making a good electrical connection. :D
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Rosco Bodine
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[*] posted on 2-6-2007 at 08:39


Iron , Iron , Iron
Iron , Iron , Iron
Iron , Iron , Iron

Iron is all you need ! :D

Spend the money you would spend for your titanium
on a fountain pump instead :) And save a bit for
a silver bullion coin , for plating a contact surface .


BTW , a bit of background for the youngsters
concerning that video clip from forty years ago ....

It was the first live global television broadcast from
linked satellite feeds .....and the subject matter
was the rock and roll group called The Beatles
offering a message of peace and love to planet earth :D

Here is an interview about the broadcast .

http://www.youtube.com/watch?v=ef-6zix0YNg&mode=related&...

Pretty cool .......huh ? :D

Also cool was that it was an unrehearsed and never
performed song , which was improvised for the occasion
and performed for a world audience .....
which is something requiring a lot of talent and
a major set of balls :D

But the songs performance came off very well ,
and it became a very famous song .
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[*] posted on 2-6-2007 at 17:47


All you need is love, and a nice -big- PbO2 anode... :) (sigh).

-Alan
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[*] posted on 3-6-2007 at 04:19


3 anodes burst into flames. damn

Finaly i made 3 nice anodes on plastic subtrce, conected them with the silver paint.. started to run nicely, after couple of hours .. puff no anode.

is there a minimal thickness of the coating? maximum current? is the paint good enough contact? what is the best way to connect to the paint?

anyone made the paint by himself? im starting to run out of paint(and it isnt cheap)
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[*] posted on 3-6-2007 at 04:37


Quote:
Originally posted by hashashan
3 anodes burst into flames. damn

Finaly i made 3 nice anodes on plastic subtrce, conected them with the silver paint.. started to run nicely, after couple of hours .. puff no anode.

is there a minimal thickness of the coating? maximum current? is the paint good enough contact? what is the best way to connect to the paint?

anyone made the paint by himself? im starting to run out of paint(and it isnt cheap)


Hello Hashashan,

What sort of power supply are you using with the anodes.
(You probably answered this before :()

It is strange that they are going on fire!!
Usually if the anode fails due to a bad connection or cracked Dioxide or bad/discontinous Dioxide the current simply decreased to the point where it is very low or non existant.
The only time I had a problem like this was when I used a welder to put current into cell. You program the current but if you start to get a bad connection somewhere the voltage will rise and rise (up to approx. 100V) accross connection, a huge amount of power will be dissipated (it will go red hot.).
Are you getting smooth, good quality coatings on the anodes or are they bad quality nodular coatings.

Dann2
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[*] posted on 3-6-2007 at 05:04


The PSU is a computer supply. i conect the 12V conection and the current is held at about 10 amps.
the anode heats a lot and then it just catches fire.

the coating is quite smooth although not perfect

Do you use the paint? what do you connect to the paint? i used a platinum wire, or several silver wires.
for some reason the silver wires dont drive current when they are conected to the dioxide directly.

what can be my problem?
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[*] posted on 3-6-2007 at 05:29


Quote:
Originally posted by hashashan
The PSU is a computer supply. i conect the 12V conection and the current is held at about 10 amps.
the anode heats a lot and then it just catches fire.

the coating is quite smooth although not perfect

Do you use the paint? what do you connect to the paint? i used a platinum wire, or several silver wires.
for some reason the silver wires dont drive current when they are conected to the dioxide directly.

what can be my problem?


The coating of Lead Dioxide is probable too thin and/or off too low a quality, though if you say it is smooth it would appear that the quality is OK. Try putting on a thicker coating.
What is the dimensions of the anode/coating?

When I used a silver paint at the top of a massive anode I put copper braid on top of the silver and then clamped that or wound copper wire around the wad of braid to hold it tightly against the silver. You can get copper braid from TV type cable (co-axial cable).

The fact that you need 12 volts to drive current into cell and through anode + connections is an indication that there is a bad current path somewhere.
The anode I guess since it is igniting!

Lead Dixoide has a conductivity better than most metals. Thats if it is good/fairly good quality coating.

The 'sock' substrate anode that you posted pictures of some time ago had a Lead Dioxide coating that was not of high quality. If you coatings are of similar quality I would expect trouble.

Dann2
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hashashan
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[*] posted on 3-6-2007 at 05:36


Well i plated at very low currents and the next ones were of much better quality, i didnt understand what you said about my 12V.
i am connecting it to the 12V supply, what is the problem with that?

the dimensions are 10*5 and the thickness is about 1mm(maybe a bit less)
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[*] posted on 3-6-2007 at 18:49


Hello,

The 5 volt output should be enough voltage to drive a sensible current into a Chlorate cell.
The fact that you need 12 volts seems to me to be an indication that there is something wrong.
Where in the circuit is the 12 volts getting dropped.
When the Anode is working OK most of the voltage is probably getting dropped accross the bulk of the Chlorate solution where that is able to take the generated heat. When a connection (or the Lead Dioxide skin on the anode) in your case starts to become a higher resistance you start to get the voltage dropped accross that section. The power associated with the voltage drop at, say, a crack in the anode is causing it to heat up and ignite.
Try the 5 volt setting, but this is not going to cure the bad anodes. At least the current flow will (hopefully) decrease to a level where you may be able to acertain where the problem is before whole lot goes up in smoke.

Cheers,
Dann2
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Rosco Bodine
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[*] posted on 3-6-2007 at 19:10
Inline Pump Idea


There is a fairly cheap but good quality magdrive pump which is made for use as a powerhead *or* can optionally be run unsubmerged as an inline pump . They are called Resun King pumps and there are several variants or rebadged versions
available . I have been looking mainly at the Resun King 1 , the smallest , a 10 watt pump , and the Resun King 2 , a bit larger 20 Watt pump .

The pump can double as a plating bath stirrer and pH / lead ion maintainer , performing the circulation task for both simultaneously .

They look like this. The slotted cowling contains a filter sponge which covers an intake hose barb for use when the
pump is used non-submerged , as an external inline pump .
This would be necessary to allow pump cooling if warm liquids were being pumped for example . It also allows for
intake from a tube dropped to the bottom of a vessel and
connected to the intake hose barb on the pump , in cases
where there is not room at the bottom of the vessel or the
presence of the pump would be unsightly or otherwise inconvenient and remote location in inline configuration is necessary .





The pumps have more flow than is needed for circulating
the bath through a pH neutralizing funnel , and the flow would need to be restricted by a valve to keep it from
continuously overflowing the percolation filter with the excess flow . So I figured that the easiest way to manage the flow from the pump would be to split the flow using a Y on the discharge , simply returning most of the pump output along the sidewall of the beaker in which the plating bath is held , to keep it swirling ......serving the function of a stirrer
using the excess flow . A globe valve could be used to restrict the open flow adjustably , and the back pressure at
the Y would divert some of the flow upwards to the percolation funnel above the plating bath . A soxhlet extractor or a pressure equalized addition funnel could be used for the percolation funnel , or one could be improvised .
The discharge flow from the bottom of the percolation funnel
could be delivered through a drop tube near the discharge
of the stirring jet to provide good mixing .

I was looking at what appears to be a knockoff or variant
of the Resun King that is the cheapest one I have found .
The WP22 here at 12.6 Watts is $12.95 plus postage .

http://www.aquaticeco.com/index.cfm/fuseaction/product.detai...

And the cheapest genuine Resun King pumps I found here

http://www.americanaquariumproducts.com/Kingwaterpump.html

$15.99 for the Resun King 1A and $17.99 for the Resun King 2 , plus $7.45 postage for either .

In regards to a different , but related matter ....

These sintered alumina cylinders also caught my notice ,
as the largest one would make a 25 Amp anode if it was
a ceramic substrate . What I thought was if the inside diameter is not too large , it might make a good sleeve around the outside of a rod form massive PbO2 core
having been grown on a wire , for building up its surface
area quickly . The finished anode would be something
shaped like a broomstick concentrically mounted in a soup can . It might also make a good diameter buildup substrate as a wrap for the lower end section of a graphite EDM rod .



http://www.aquaticeco.com/index.cfm/fuseaction/product.detai...

BTW there is another magdrive pump which is cheap and also
is reportedly good quality , called a Maxi-jet ......and one of
the descriptions says that it has inline capability , but other
descriptions say that it must be at least partly submerged ,
so I am not sure whether it is inline capable or not .

The Sen 300 is inline capable .

http://www.aquacave.com/detail.aspx?ID=969

Also the Azoo 1800 at about $20 is inline capable

http://www.drsfostersmith.com/product/prod_display.cfm?pcati...

And BTW these inline capable pumps are useful for water cooling recirculation pumps , like for cooling condensers , water block heatsinks for CPU's ect .


[Edited on 3-6-2007 by Rosco Bodine]
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hashashan
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[*] posted on 3-6-2007 at 23:56


Quote:
Originally posted by dann2
Hello,

The 5 volt output should be enough voltage to drive a sensible current into a Chlorate cell.
The fact that you need 12 volts seems to me to be an indication that there is something wrong.
Where in the circuit is the 12 volts getting dropped.
When the Anode is working OK most of the voltage is probably getting dropped accross the bulk of the Chlorate solution where that is able to take the generated heat. When a connection (or the Lead Dioxide skin on the anode) in your case starts to become a higher resistance you start to get the voltage dropped accross that section. The power associated with the voltage drop at, say, a crack in the anode is causing it to heat up and ignite.
Try the 5 volt setting, but this is not going to cure the bad anodes. At least the current flow will (hopefully) decrease to a level where you may be able to acertain where the problem is before whole lot goes up in smoke.

Cheers,
Dann2


I use the 12V because my electrodes are at a quite large distance, they are about 10cm away from each other. When i connect th 5V i get only about 4 amps, which is not enough to make perchlorate.
However you might be right about the cracks thing, ill try to grow my anode a bit thicker and ill see what is going on there.
I actually do get the connection are quite hot and i dont know why. I pasted a quite large area with the silver paint and there is no reason for it not to drive the current along the crack even if it exists.


PS. does anybody know how to make the silver paint, i.e. what is the glue that holds the silver pieces together?
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Rosco Bodine
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[*] posted on 4-6-2007 at 00:45


An electrode spacing of 5 to 8 mm would seem
more reasonable .....10 mm at the most ,
not ten times that . One of the coaxial electrode
arrangements described in a patent was 4 mm spacing ,
but that was in a precisely aligned fixture and using
a pumped electrolyte moving quickly through the gap .
Every time you double the number of mm's distance
for the electrode spacing ......you also double
the voltage drop for keeping the same current .

For example if you have plates 10 mm apart
and the cell is drawing 20 Amps at 6 volts ,
if you move the plates to 20 mm apart then
it should take 12 volts to produce the same current ,
but you are dumping the wasted power as heat ,
not making any more perchlorate , because it is the
Amperes passed that does the work . So for best
power efficiency , you want the voltage as low as you can use and still achieve the 1.3 amps per square inch
of anode current ..or more , that you want for a PbO2
anode .....about 0.2 A per square cm of anode surface .

Sheesh , I bet that cell you are using runs hot .
It would have to be dumping 90+% of its real
power as heat instead of making anything .
You wrote your anode is about 1 mm thick , and
it needs to be at least 5 times that thick probably
to carry the current . Thicker is better .


[Edited on 4-6-2007 by Rosco Bodine]
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hashashan
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[*] posted on 4-6-2007 at 01:05


Good to know, thanks that really mightbe my problem.
I was told to take a big gap in order to avoid cathodic reduction. I dont have a persulfates or Flurides so i need some way to avoid reduction.

Ill try to make a short gap. And my cell does get hot but not too much, it reaches about 60c but doesnt go above that(Hey it is in a bucket full of cooling water :D)
Ill try to combine all that you have said, thanks a lot :)
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Rosco Bodine
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[*] posted on 4-6-2007 at 01:29


You could sort of reverse engineer what is the cross sectional area of the PbO2 needed per Ampere of
current required for the surface area of the anode ,
and determine how thick the anode needs to be in
relation to its surface area to safely conduct the current .

If you take that Bromate patent for example and look at
the dimensions of the anodes compared to their thickness , that will get you in the ball park for what a production electrode requires . You know what they state
as the current density at which the cell is being run in production , so you just do the math .....and you can figure out what you will need to adapt that scenario
to your own . The folks who applied for the patent
already did the work .....so just steal their numbers as
a starting point for copying success into your own design .

Even though that is a bromate cell , it shouldn't matter ,
as too much current would burn up an anode regardless
of what sort of cell it is in or what is being made . So in that respect the bromate cell data is transferable to any
other cell using a massive PbO2 anode .
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hashashan
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[*] posted on 4-6-2007 at 02:08


i just left the plating running and when to study :). i guess when ill get back home ill have a nice 1cm thick anode and that will be 100% enough
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Rosco Bodine
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[*] posted on 4-6-2007 at 09:45


The art of plating , no matter what is the material being plated .....from everything I have read describes a process which must be closely controlled within certain
limits to produce a structurally sound deposit . The pH
and the temperature and the concentration of the material in the plating bath which is being consumed by the process , and the plating current must *all* be kept controlled to achieve the best plating . The conditions
in the plating cell have to be optimized and then kept constant .....with the exception of the current which might be deliberately varied for fixed periods . Otherwise , if you haven't set up a cell with something in the way of automatic controls , then you have to manually baby sit the process , or have a cell set up so
that as the process runs , the changes do not exceed
a certain permitted range of change in the composiition
for the electrolyte .

That is exactly why I am looking at *pumps* in order to
set up a tank where I can regulate everything in order
to remove the variables as much as possible from the
process . I figure if there was an easier way to get good results , then the penny wise folks in industry wouldn't have ever bothered with all the extra work and detailing
what was required to achieve success . I may simplify
the configuration considerably for a smaller scale process , but the idea is to keep the reaction conditions as close to identical as I can make them to what was reported to work . That will rule out a lot of variables
when it comes to troubleshooting any problems , or tweaking the process later .

Keeping the bath circulating by some method is necessary , and a stirrer or a pump is unavoidable unless
the electrode assembly itself functions as a pump of sorts to keep the liquid flowing . That is why my attention very
quickly was drawn to little magdrive pumps . I think it is possible to do a labscale duplication of the industrial scale methods , since those methods were almost certainly piloted and prototyped on a labscale first and then scaled up for the plant scale tanks . With plating methods having been around for more than a hundred years , and the basics having been pretty well established , there is no need for us to try to reinvent the wheel .....but more for us to *copy* what works ,
and maybe see little refinements which may be possible .

Concerning surfactants or plating "conditioners" which might improve the density of the plating , there are a few others
which might be worth a try . Phenolpthalein , ethanolamine ,
and betaine are things that might be worth a try as small
percentage additives . Sulfanilic acid is another amino organic compound I didn't see mentioned , but also might be worth trying , as it also has surfactant properties .

[Edited on 4-6-2007 by Rosco Bodine]
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[*] posted on 4-6-2007 at 14:05


*Shrug* copper is effortless to plate, given some thiourea. Strong (about half strength of saturated) solution of CuSO4, dash of sulfuric acid, couple drops of thiourea solution, add a moderate current and go.

But on the other hand, I've discovered zinc is a bitch to plate. It really likes water and either foamy or crystalline deposits...you may be on to something about control...

And that's to say nothing of PbO2, but that's something still completely differentER...

Tim

[Edited on 6-4-2007 by 12AX7]




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Rosco Bodine
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[*] posted on 4-6-2007 at 17:18


Quote:
Originally posted by 12AX7
*Shrug* copper is effortless to plate, given some thiourea. Strong (about half strength of saturated) solution of CuSO4, dash of sulfuric acid, couple drops of thiourea solution, add a moderate current and go.


Copper might also plate out well from the same sort of amine or ammonia complexation baths as would silver and probably nickel and probably zinc also since they all form polyamino complexes . Ammonium acetate or possibly ammonium nitrate and free ammonium hydroxide are additives to the alkaline plating baths . The problem I think with the close to neutral pH baths would be hydrolysis causing some metals like Tin for example to precipitate , as their basic salts are nearly insoluble .

No problem in that regard for basic lead nitrate , as it is nearly half as soluble as the normal nitrate . It would seem that PbO2 should plate onto copper , since it plates onto iron ....
but I never saw it described and it may just not work at all
or it may work fine ...I don't know . But there is one way to find out , try it and see what happens . There is also a technique of amalgamating the surface of some metals which
may be difficult to plate , and then plating onto the amalgam
which breaks the surface oxide . Whole books and sets of books have been written on plating as part of the metal finishers industry .
Quote:

But on the other hand, I've discovered zinc is a bitch to plate. It really likes water and either foamy or crystalline deposits...you may be on to something about control...

Yeah at the very least a good flow of fresh electrolyte across the surface is required since that is the conveyor that keeps the ions supplied that are being plated out . If you don't have a steady flow of electrolyte then it is left to chance what is the composition of the relatively stagnant liquid which
may set up its own peculiar laminar flows having swirls and eddies and variable composition depending only on where bubbles are forming and thermal currents are flowing by chimney effect . But a forced flow of electrolyte takes those variables out of the picture .
Quote:

And that's to say nothing of PbO2, but that's something still completely differentER...

Tim

[Edited on 6-4-2007 by 12AX7]


Yeah it is different being that the plating of PbO2 is actually anodizing ....exactly the opposite of metal plating which is a cathode process . But the same rules apply to doing good chemistry , and the same surfactants good for a cathodic
process may also be good for the opposite polarity . In fact some of these processes are entirely reversible by the flip of a switch .

One of the things about which I have been wondering concerning the plating of PbO2 and maintaining the Pb ion
relates to using a sacrificial " pH - trode " , perhaps amalgamate the surface of some lead sheet using mercuric nitrate in dilute nitric acid and hang these amalgamated lead sheets as spectator "neutrodes" in the electrolyte for maintenance of the pH and replenishment of the lead ions . This amalgamation should break the oxide which would normally be on the sheet lead and render it sufficiently vulnerable to increasing acidity of the bath ....
so that an equilibrium might be established in a pH range
moderate enough for good plating performance . The idea is
that the "neutrode" sheet lead would simply be eaten away by the increasing acidity of the electrolyte as the lead in solution is plated out as the dioxide , and this would eleminate having to use any lead oxide or basic lead salt separately for pH control .

Many metal plating processes use an anode made from the metal that is being plated and it is sacrificed and corroded away as the plating proceeds . Of course this is straightforward when the metal plating uses that polarity ,
as the anode is conventionally the sacrificial part . But hydrogen evolution on the surface of the cathode would likely
protect a sheet lead cathode from attack in a nearly neutral pH bath , so it may not just work to use an amalgamated lead sheet cathode . Maybe ...maybe not ....I don't know .
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dann2
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[*] posted on 4-6-2007 at 17:58


Quote:
Originally posted by hashashan
Good to know, thanks that really mightbe my problem.
I was told to take a big gap in order to avoid cathodic reduction. I dont have a persulfates or Flurides so i need some way to avoid reduction.

Ill try to make a short gap. And my cell does get hot but not too much, it reaches about 60c but doesnt go above that(Hey it is in a bucket full of cooling water :D)
Ill try to combine all that you have said, thanks a lot :)


I have never heard of keeping the electrodes apart to stop reduction at the cathode.
I do not think that the spacing of the electrodes will make any difference to reduction at the cathode.

Where did you hear that?

60C is hot.

Cheers,
DANN2
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hashashan
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[*] posted on 4-6-2007 at 22:54


Never mind, one of my friends told me that, usually he does know what he's talking about.
But if you say that it doesnt really matter ill try to take about 1cm distance with 5V(damn there's going to be a high current)
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