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Xenoid
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Quote: | Originally posted by jpsmith123
If you make another, I'd like to suggest adding some TiO2 to the solution before painting it on the titanium (see patent #4222842, example #2; 1g
Co(NO3)2, 1cc H2O, and 1cc isopropyl alcohol + TiO2 in suspension).
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@ jpsmith123 - Take another careful look at that patent and you will note that it is NOT TiO2 that is being used, but TiO ...!!! Specifically TiOx
where x = .45 to 1.2 and preferably where x = 0.9 to 1.2.
I will try and find out how easy or not it is to make TiO.
Edit: Well, you can buy it from a few places, and hereis a description of titanium(II) oxide:
http://www.webelements.com/webelements/compounds/text/Ti/O1T...
Edit: Well it looks like the boys in the anode manufacturing department are out of luck!
I've searched high and low for information on making this and all I have managed to find was a snippet in an abstract saying to effect, fuse Ti metal
with titanium dioxide in an argon arc furnace.
Ti + TiO2 ---> 2TiO
Given TiO has a melting point of 1750 oC. this would seem a fairly brutal operation to carry out in the kitchen. I guess it will have to be purchased!
Regards, Xenoid
[Edited on 4-12-2007 by Xenoid]
[Edited on 4-12-2007 by Xenoid]
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jpsmith123
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Yeah, I know that particular patent specifically says "TiOx where x = .45 to 1.2 and preferably where x = 0.9 to 1.2".
And if you look at patent #3399966, for example, you might get the idea that the cobalt compound involved simply HAS TO BE "CoOm.nH2O wherein m is
from 1.4 to 1.7 and n is from 0.1 to 1".
At this point however, after having looked at so many patents, I say, in general, *bullshit*. IOW, I'm very skeptical of patents, and I think it's
easy to let the trees block your view of the forest. Frankly I think that much of the detail in a lot of these patents has to do more with trying to
distinguish themselves from prior art than with some new indispensible technical innovation.
Seriously, if I hadn't read so many other, related patents (primarily those of Beer), I would probably get hung up on that detail, but as it is I
don't think it's much of a concern for our purposes.
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Xenoid
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Well, I've pulled the plug on the cobalt oxide anode after almost 3 days. There wasn't much point in continuing to run it (other than making
chlorate.. ). It is obvious that a single coat is not thick enough to form a
practical anode. I also wanted to leave a bit of the coat in tact so I could have a good look at it.
Just to confirm, however, it is well bonded to the Ti. It's actually a bit difficult to describe what it is like, perhaps a bit like a sooty or smoke
coating on metal. It's not really hard, but you can't rub it off either.... anyway, more later.
Regards, Xenoid
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Rosco Bodine
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There's new ideas worth exploring with experiments here . And if nothing else it may be prophylactic regarding
the experimenters risk of potential antimony and/or lead poisoning Heck I was
about to suggest the possibility
for the mixed valency precursor with stannic oxide , having
cobalt nitrate as the bivalent metal component . Or perhaps the possible complexation of cobalt nitrate in an ammonium stannate mixture , or perhaps
a cobalt nitrate
mixture with stannic oxalate . Even looked a bit at the
possibilty of a stannic nitrate derived mixture in combination with cobalt nitrate . There's plenty of novel experiments which could be done along
new lines ,
rather than just trying to copy any one process which may be incomplete in its method or disclosure .
Looks like what you had going there is very promising .
Nothing to be discouraging there for the one coat .
Try three Got tin? maybe try a sandwich coating .
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chloric1
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Mmmmmm sandwich...turkey & bacon(gargling and drooling)
Seriously, Rosco is right, tin with cobalt would be quite nice. I thought it was mentioned somewhere about vanadium with cobalt. Vanadium is an
efficient oxidation catalyst. By the way how would one know if a spinel was going to be conductive or not?
Fellow molecular manipulator
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Rosco Bodine
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Something I recall from a process for manufacturing
electrolytic capacitors , where manganese nitrate was
being used as a baked coating precursor for manganese oxide , was that 10% of the carbonate could be added
to the molten nitrate hydrate as a thixotropic thickener
which would also decompose to the oxide on baking .
This may be operative here as an easy method of thickening the cobalt nitrate coating . Some of the
hyrated oxide formed separately and mixed back in with
the molten nitrate might also serve to thicken the nitrate
to help get a faster thickness build with the baked coatings .
[Edited on 5-12-2007 by Rosco Bodine]
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chloric1
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Well...many of the metallic salts have covalent character and oxides if don't dissolve into the solutions surely for intricate oxycompounds to
polymerize and thickening the mix.
I like it! Ten or fifteen percent stannic chloride added would help this to as it would yield oxide and oxy compounds a little easier than cobalt
nitrate. Don't forget magnetite. It is not much help on its own but mixed with cobalt? You might get a cobalt ferrite or simular.
Fellow molecular manipulator
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Rosco Bodine
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using tin oxide alone may not be so simple
My earlier hopes about cobalt spinel doping of tin oxide are now abandoned . It appears the usefulness of cobalt alone
in doping tin oxide is for producing an *insulator* rather than a more conductive layer .
Anyway it looks like the antimony can't be avoided with
the tin . I have some new information that while the
cobalt and tin oxide spinel does form very readily , it is non-conductive , so that is certainly not helpful . See US4308319 . Evidently not all
cobalt spinels are necessarily conductive . And it is a sad development that the cobalt and tin spinel is one of these . Evidently I misinterpreted
the
graphical results shown in one of the patents where tin oxide alone or DTO was being used in combination with
a *substituted* Cobalt and Zinc *bimetal* spinel , and
plain Co3O4 does not help the conductivity of the tin oxide
but hurts it instead . What the graphical results of US4369105 show is the breakpoint of 425C where the
existing conductivity of plain SnO2 or DTO is compromised
by the formation of the Cobalt and Tin spinel , a situation
which worsens with temperature and time .
It is a bimetal cobalt spinel with zinc that is showing the
acceptable conductivity used on top of plain tin oxide , and I am still not sure how to interpret that . I don't recall if plain cobalt spinel was
tested with plain tin oxide in any of the other patents , so I will go back and look for that specific combination . It may be that only the
substituted bimetal spinels are capable of doping the tin oxide towards better
conductivity , or something else may be occuring there to
explain the anomaly .
It could prove to be as simple as following a rule that you can't mix the precursors for the Tin and cobalt , and you don't exceed a certain
temperature for separately formed layers , putting the higher heat developing layer on first .
What earlier seemed like a good idea , for mixing the unsubstituted cobalt spinel and tin oxide precursors plainly isn't a good idea , so pardon my
huge brainfart if that's what it turns out to be . It may be that it only works for the limited case where the DTO goes on first , followed by the
bimetal spinel , but is not a scenario which will work with alternating layers or a mixture .
[Edited on 5-12-2007 by Rosco Bodine]
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Xenoid
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When pool chlorinators go bad!
Ho, ho, ho! Christmas arrived early for me this year, and I finally got a present I wanted!
This is a bit off topic, but doing the rounds of the swimming pool maintenance companies looking for used pool chlorinators has finally paid off. I
went to a small company I hadn't visited before, the guys were sitting around having morning tea (as they do). I explained what I was after and why I
wanted them, only to be greeted with blank looks. Then one guy said "Oh, didn't we just throw one in the skip over there'! We had a look and it was
still there. They said they didn't get many, but when I said I would give them $10 for one they seemed quite enthusiastic and took my name, phone
number and email. I got the one in the skip for free. They said it was a "self cleaning model" but something obviously went very wrong with the
circuitry. It's a 6 electrode model and the electrodes still "look" OK, nice and black. I'm not sure what the pale blue stuff is, I assumed it was
copper stained salt, but it didn't taste very salty! Anyway I don't particularly care. As a first step in cleaning it up I've left it soaking in
water, I'll see how that goes!
Edit: I think the gunk is Na2CO3, it fizzes when a few drops of HCl are poured on it. Here in NZ, Na2CO3 is used as a "pH increase", the pool owners
probably added too much. I think the blue colour (which is fairly superficial) is just a water colouring to make the pool look better.
All the electrodes appear to be coated, I guess thats the case with a self-cleaning chlorinator, in that the polarity is switched on a regular basis.
It has 25 stamped on the top and the leads are pretty grunty so it may be a 25 Amp model.
I think I'll sit it in some vinegar to clean it up, nice and mild!
Ho, ho, ho, Xenoid
[Edited on 5-12-2007 by Xenoid]
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jpsmith123
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Well the Co Acetate solution doesn't work too well for painting and baking...it's just not soluble enough...I'd literally have to be there all night
with it.
Xenoid how did you go about making up your Co Nitrate?
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chloric1
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@jpsmith Well I don't feel good about acetates anyway because they may form CO or metane/ethane. These might produce Co metal instead or only CoO.
Fellow molecular manipulator
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jpsmith123
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Hello Chloric1,
Co Acetate apparently does decompose in air to CoO.
J. Mater. Chem., 1991, 1, 461 - 468, DOI: 10.1039/JM9910100461
Thermal decomposition of cobalt(II) acetate tetrahydrate studied with time-resolved neutron diffraction and thermogravimetric analysis
Robin W. Grimes and Andrew N. Fitch
The thermal decomposition of cobalt acetate tetrahydrate has been studied using time-resolved powder neutron diffraction. By using selectively
deuterated samples, the loss of water or the breakdown of the acetate group can be identified by following the decrease in the incoherent background
of the diffraction pattern as the hydrogen atoms are lost. The results suggest that by 150 °C dehydration is complete and a glass-like phase is
formed. Crystallization of this anhydrous acetate occurs at 200 °C. Further heating initiates a two-stage decomposition of the anhydrous acetate
terminated by the formation between 275–310 °C of a tetrahedrally co-ordinated cubic zinc blende form of CoO. This transforms at 310 °C to a
rock-salt structure. The neutron diffraction data have been complemented by thermogravimetric and chemical analyses from which we have been able to
propose some possible intermediate decomposition products and suggest an explanation for the formation of the unusual zinc blende form of CoO.
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Xenoid
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Quote: | Originally posted by jpsmith123
Xenoid how did you go about making up your Co Nitrate? |
From the "More on PbO2 electrodes" thread
Quote:
Originally posted by dann2
How might one make Co Nitrate from Co Sulphate?
Hi Dann2, I have had absolutely no success with Patent 3,399,966 nor with the hydriding process, I've tried all sorts of combinations!
We must be thinking along similar lines, I'm having a look at Patent 4,366,042 - the substituted cobalt spinel paper.
I am at this very moment making some cobalt nitrate by reacting some calcium nitrate with cobalt sulphate. One gets a pretty thick goopy result like
strawberry yoghurt, but I've put it through my pressure filter and I now have a nice red cobalt nitrate solution. This is the same process I used for
making manganese nitrate, but this time I'm going to concentrate and recrystallise it to get a purer product. I'm going to make some zinc nitrate by
the same process, and have a go at a simple zinc cobalt spinel coat on Ti.
The reaction precipitates CaSO4 which you have to remove. It is actually slightly soluble so there will be some left in the cobalt nitrate soln. Thats
why I have been trying to purify my nitrate in the earlier posts. Try to use stoichiometric amounts of the reactants and add the Ca nitrate carefully
until no more ppt. forms. Someone earlier mentioned using fairly dilute solutions, because the CaSO4 is hard to filter out (its so thick and goopy).
Fortunately I built myself a pressure filter some time back and I filter the mixture at about 20psi which leaves an almost dry "cake" of CaSO4
remaining in the filter. You may find it easier to do in a stepwise fashion ppt, filter, ppt, filter, etc.
Nitric acid and the carbonate would of course be much simpler, but I don't have any nitric acid, but I do have plenty of cheap Ca(NO3)2 fertilizer I
got from a hydroponics shop.
Regards, Xenoid
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Xenoid
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Quote: | Originally posted by jpsmith123
Crystallization of this anhydrous acetate occurs at 200 °C. Further heating initiates a two-stage decomposition of the anhydrous acetate terminated
by the formation between 275–310 °C of a tetrahedrally co-ordinated cubic zinc blende form of CoO. This transforms at 310 °C to a rock-salt
structure. The neutron diffraction data have been complemented by thermogravimetric and chemical analyses from which we have been able to propose some
possible intermediate decomposition products and suggest an explanation for the formation of the unusual zinc blende form of CoO.
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Yes, but CoO is not desirable, we want Co3O4 in the spinel form. Above 475 oC. Co2O3 and CoO tend to form from the nitrate, thats why the baking
temperature is ideally about 375 oC.
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Rosco Bodine
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The anomaly involving the non-conductive cobalt-tin spinel of US4308319 appears to be related to untypical elevated proportions of the cobalt to tin .
The non-conductive "spinel" material has a cobalt to tin ratio of 5:1 to 11:1 which is not really the conventional spinel , and the title of that
patent misled me to distrust my first conclusions based on the Dow patents , which don't tell the whole story on the tin cobalt interaction .
The conductive cobalt - tin spinel or cobalt doping of tin oxide inferenceed by Dow may still be perfectly operable . And I have found another
reference to cobalt being used at 3% as an additive to ATO baked films where the cobalt functions as a catalyst to allow the ATO baked anode to
function as a working coating , rather than just a substrate . So it seems that so long as the ratio for the tin oxide to cobalt oxide is much
richer in tin oxide , then the conductivity problem as occurs with the reversed ratio
does not occur .
More encouraging is the information in the Dow patents
that when the second oxide present along with the cobalt spinel is in great excess to that amount capable of forming the bimetal spinel , that the
spinel does not
form as a separate structure but remains in solid solution
in the excess oxide . That mechanism is what usually does the job of "doping" tin oxide in the direction of conductivity , so there may be no worries
here after all , within certain proportion limits . Again it seems when the doping of SnO2 is contemplated a small amount of the dopant is more
useful , and there is a larger percentage of dopant which becomes counterproductive . What the conductivity curve looks like for the cobalt spinels
and SnO2 , I haven't yet found charted .
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jpsmith123
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Quote: | Originally posted by Xenoid
Yes, but CoO is not desirable, we want Co3O4 in the spinel form. Above 475 oC. Co2O3 and CoO tend to form from the nitrate, thats why the baking
temperature is ideally about 375 oC.
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Well to be honest I'm not sure of exactly what we want.
According to the paper I think I previously upoaded here somewhere (Desalination 126 (1999) 77–82; "Production of sodium hypochlorite in an
electrolyser equipped with a ceramic membrane"; S.Yu. Bashtana*, V.V. Goncharuka, R.D. Chebotarevaa, V.N. Belyakovb, V.M. Linkovc):
"A VT-1 titanium was used as anode material; it was
surface-coated with cobalt oxide by means of
high temperature (t>900°C) plasma deposition.
Fig. 1. Photograph of electrochemical installation for sodium
hypochlorite generation.
Prior to the deposition, the titanium anode was
brush-cleaned and chemically degreased. Cobalt
tetroxide (Co3O4) powder was used as precursor
material in the plasma deposition operation.
According to the literature [10,11] high
temperature plasma deposition results in the
thermal dissociation of cobalt tetroxide with the
formation of a cobalt monoxide (CoO) layer on
the support surface. The final activation
treatment of the anode coating was carried out
under the conditions of the sodium hypochlorite
generation experiment at a current density of
6 mA/cm2 for 15 h. During the first 5 h of
treatment the hypochlorite current efficiency
increased from 18 to 65%, where it remained
until the end of the treatment. A change in the
coating colour from dark blue to black and a
comparison of the galvanostatic polarization
curves and hypochlorite current efficiencies were
used as indicators of the termination of the
oxidation processes in the anode coating."
Sounds like they specifically wanted CoO for their anode.
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jpsmith123
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Xenoid with regard to your baked on coating, I'm trying to get an idea of how well it stuck to the titanium. Did you really try to rub it off with a
rag, for example?
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Rosco Bodine
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For a gaggle of various spinels of possible interest not necessarily just cobalt spinels , see US3711382 . Sheesh
there is a couple of pages long list of these spinels , enough to keep a minerologist busy for a lifetime .
I read a brief mention that spinels can be baked directly onto hydrided titanium , in a patent from a different source than the patent jpsmith123
posted in starting the TiH2 thread .
@jpsmith123 , Did you try to do any of the baked coatings onto hydrided Ti ? The interface layer is everything ,
and once that is sealed off nicely by the first coating ,
and retaining conductivity , then you should be able to apply whatever else sort of wear coating you want ,
by whatever method . Maybe the MnO2 plus PbO2
low baked onto the TiH2 , then followed by the Co
acetate or nitrate as subsequent coatings could give
good results .
@Xenoid , About the open circuit gassing that you observed
from the spinel put back into the brine , it is probably the
catalytic decomposition of hypochlorite to free oxygen and NaCl . That's what happens if the spinel is in contact with
hypochlorite , and it may even hapen with other oxidizers ,
so when the current is off , you probably don't want to leave
the "decomposition catalyst" in the cell , because it makes
the powered on reaction run backwards when the power is off ![:D](./images/smilies/biggrin.gif)
[Edited on 5-12-2007 by Rosco Bodine]
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Xenoid
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Quote: | Originally posted by jpsmith123
Xenoid with regard to your baked on coating, I'm trying to get an idea of how well it stuck to the titanium. Did you really try to rub it off with a
rag, for example? |
Well I didn't try to rub it off before I put it in the cell, I just touched the surface with my finger and it made a smudge. It actually looked like
it had been given a light coat with a flat, black, spray paint. After I took it out, I have had a good go at it. There appears to be an extremely thin
black "stain" attached to the Ti which doesn't rub off, but the bulk of the coat does. It is soft, black and very fine so I guess it has an extremely
high surface area. In no way does it fall off, you can rinse it for example. In the cell I didn't see flakes lifting off like with some of my other
efforts. The coating just literally wore away. It is not a hard, shiny coating, I would more imagine it as being hard at the Ti interface and grading
outwards to what is essentially a bonded powder!
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Xenoid
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Quote: | Originally posted by Rosco Bodine
@Xenoid , About the open circuit gassing that you observed
from the spinel put back into the brine , it is probably the
catalytic decomposition of hypochlorite to free oxygen and NaCl . That's what happens if the spinel is in contact with
hypochlorite , and it may even hapen with other oxidizers ,
so when the current is off , you probably don't want to leave
the "decomposition catalyst" in the cell , because it makes
the powered on reaction run backwards when the power is off ![:D](./images/smilies/biggrin.gif)
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Rosco, I guess you are right about this! One of the first things I did was to put the anode in plain water, the result was nought, zero, nil, nothing,
nada! So I guess no free energy for all, at least not yet...
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R.P.Wang
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I think the Ti/PbO2 anode is best choice to produce perchloric acid, long service life and high oxygen evolution potential .
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Xenoid
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Quote: | Originally posted by R.P.Wang
I think the Ti/PbO2 anode is best choice to produce perchloric acid, long service life and high oxygen evolution potential . |
Yes! You are probably correct, but members of this forum are having a very difficult time trying to plate PbO2 on to Ti. This can be seen in the 31
page "More on PbO2 electrodes" thread and others. If you have a suitable procedure, please share your wisdom with us, because I can assure you it will
be much appreciated!
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Rosco Bodine
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Where's the cheapest place to get lead now ,
Toys 'R Us ?
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jpsmith123
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Xenoid the way you describe your baked on coating...well it sounds exactly like my best electrodeposited coatings...and I have to say I don't like it
.
I think Rosco's right in his implication that the trick (if there is one) is in the interface layer.
Rosco I haven't tried anything recently with a hydrided layer, but I'm preparing one now (it's been cathodized all night at about 30 mA/cm^2).
Anyway, I know when I plated a layer of plain cobalt (from Co Acetate solution) it was extremely adherent to the Ti (only sandpaper would take it
off), but I was not able to oxidize it just by heating it with the heat gun. It would apparently have to be baked for 8 hours or so at 350 degrees
Centigrade to accomplish that.
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Rosco Bodine
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You might try coating that plated cobalt with molten cobalt nitrate and then taking a propane torch to it . I don't have a lot of confidence in the
heat gun treatment .
Like I said before , some sort of on part heat indicator
like a strip of sheet lead and a strip of sheet zinc battery scrap , twist tied with wire around the rod will tell you when you have the heat range
over a burner and between the mp of lead and the mp of zinc is where you need to be . Hot enough to melt the lead , not quite hot enough to melt the
zinc .
With a nitrate coated onto the thin Co metal , the corrosiveness of the nitrate would probably expedite
the oxidation of the metal and develop the interface .
For such metal strike platings you don't want to plate on
very much at all , because that just gives you more to
decompose when the bake hits it . You want just a barely visible flash plating , not a hard coating but a fragile
very thin coat that will oxidize through when the heating is applied . An ammonium salt like sal ammoniac or ammonium nitrate would probably
facilitate the oxidation
on heating of the cobalt because cobalt complexes readily with ammonia and the complex is not heat stable , plus the oxidizer effect of the nitrate
would enhance the decomposition to the oxide .
With the hydride , you probably don't need to plate on
the metal cobalt too , at least not as a continuous flash ,
as that would probably be overkill , where the hydride alone is going to resist decomposition . The cobaltous acid derived from H2O2 plus cobalt
hydroxide just might
react directly with the hydride at ordinary temperature
or very slight heating to produce a "cobaltating" , chemically produced interface . This could be a good
initial treatment , coated over with cobalt nitrate and baked .
[Edited on 6-12-2007 by Rosco Bodine]
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