dann2
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Accidental Anode
Hello,
I got around to making another Magnetite anode by melting Magnetite with a welder and quickly putting into an annealing oven at about 800C for 24
hours (with the temperature being reduced to room).
When all had cooled I opened oven took out the anode.
The thick piece of mild steel that had been sitting in the oven along with the Magnetite anode had grown/formed a large piece of Magnetite scale on
its surface. It was smooth and consistant and was about 1.3 by 5 by .05 inches. It would remind you of a large microscope slide but was of course
opaque. I was about to discard it when I decided to pop it into a cell where it is working quite well.
It would seem that may be a much easier way to make Magnetite anodes. All you need is the hot oven and a piece of mild steel and feed in some steam.
Water vapour is needed I believe.
A patent along the lines of this is US 2,727,842
I have seen others.
If Magnette proves to be a suitable substrate for PbO2 it may come in useful.
Dann2
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dann2
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Hello,
The anode above was put into a cell containing mostly Chlorate just to see how long it would last. It broke at the liquid air interfact after about 4
days. It was run at about 40mA per square cm.
The thinkness of anode was about 0.48mm.
I am currently attempting to make Magnetite anode by heating mild steel at about 800C and feeding water vapour into oven.
Steel is about 8mm thick.
There are some patents on this.
Dann2
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Pyridinium
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Interesting. I don't know if anyone mentioned it in another thread or not yet, but it's also possible to obtain an Fe3O4 finish on mild steel by
heating it in a solution of NaOH (about 0.8 g per ml in water) at 140 C for 20 minutes or so. (Face shield, lab coat, & gloves a must.)
I have had some success with dark blue finishes on steel by immersion in molten KNO3. Of course, you want it for a different purpose (in my case,
it's just doing the experiment for its own sake) so I don't know how this would work for that.
EDIT: I just found out the coating for the alkali method is something like only 0.000030 inch thick. This from the Birchwood Casey website.
However, surface-treatment methods probably don't give thick coatings in general. The oxidation only affects the outermost layer of the metal, so
you're limited from the start.
[Edited on 30-6-2007 by Pyridinium]
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12AX7
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Eh, you can do the same by heating to circa 300C for a period of time. Steel goes through the interference colors (straw, red, purple, blue, that
sort of thing) as the oxide layer forms through a combination of time and temperature. At higher temperatures (near and above incandescence), you can
see a fainter, darker repeat of the same pattern.
I've already tried oxidized steel, and it produced a little chlorine, but the pinholes were quite effectively pitted out. As a substrate for PbO2 it
may be okay.
Tim
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Rosco Bodine
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Wonder if any of the selenium based "bluing salts" like
gunsmiths use could have any usefulness in regards to anode coatings ....perhaps by itself or further treated
with something else like a chromate or phosphate .
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dann2
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Hello,
Got around to firing up my oven for to attempt to make Magneite anode by way OF Mild Steel (note I do not refer to this as *Iron*) and Steam (beat
THAT with OTC'S).
The first attempt failed as the steam did not seem to go into oven. I am using a domestic kettle + variac to boil the water.
Second time around I got the oven to run for about 6 hours before it stopped. A copper connection failed. I should have used nichrome through out.
The whole thing is very sloppily constructed. I am using an Iron + Copper/Nickle wire thermocouple which is good to only about 850C. It went all the
way up to 50mV (the output of the thermocouple) which means the temperature of oven got to about 1000C. The thermocouple then failed and give out low
reading from then on.
In the meantime the tiles that formed the oven warped and the fiber glass melted somewhat.
The piece of steel had about 1.4 mm of it's outside concerted to Magnetite. The 1.4mm increased in size as the Magneite seems to be more volumous
that the parent metal.
(Mild Steel). Other thinner pieces of steel in the oven (that I was using as 'furniture' for the anode proper where entirely converted to Mangetite.
I think this is a good way to make Magnetite anode. Handier and more convenient that having to use (and own) a welder to meld the Magneitte. The anode
are consistant and not too delicate. I still have not got around to trying to put a good coating of LD on one of them.
The Nicrome wire in the heating elements was uneffected by the steam.
I will have to construct the whole thing in a more professional manner. Some alumina bricks would be great. I am using tiles surrounded by Perlite
(volcanic rock) in a Steel box wrapped in fiber glass.
I need to get a Aluminium/Nickle + Copper/Nickle thermocouple, they are good to about 1100C or so.Anyone know where you can purchase Aluminal
(Aluminium Nicle alloy) wire.
Dann2
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Eclectic
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There is a lot of type K thermocouple (1300+) stuf on ebay:
K thermocouple on Ebay
The non contact IR thermometer stuff is getting really cheap too.
You can pick up process controllers that drive solid state relays for under $50 that have thermocouple inputs.
[Edited on 7-3-2007 by Eclectic]
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dann2
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Hello,
Thanks for reply. I got some K type thermocouple wire on ebay for 2 quid per meter. Should do the trick.
Some picks of my half baked anodes (NOT half baked ideas by any means  )
It would seem that Steel, when converted to Magnetite expands by about 43%. A 0.7mm steel thickness going up to 1mm.
The surface of the Magnetie (not shown) is fairly smooth but it would not be 'electrolyte proof' I would think.
It is some what pocked marked where the steam tube entered the oven. Some water (actual liquid) dripped onto it and this may have caused the marks.
The pieces in the pictures were cut (the big one) and the other broken (the piece of oven Furniture) . It takes quite a blow to break the 'Furniture'
anode. This stuff is not delicate.
Next time I will start with a far thinner piece of Steel. The piece I chose last time was far too thick.
http://i168.photobucket.com/albums/u200/anodes_2007/MagF.jpg
http://i168.photobucket.com/albums/u200/anodes_2007/MagB.jpg
Dann2
[Edited on 5-7-2007 by dann2]
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dann2
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Another failed attempt but getting there.
Hello,
Put together new furnace using fire bricks and Perlite in a steel box. Fire bricks are a bad choice as they will take lots of heat but are not so good
at insulating, therefor my furnace only got up to about 700C. I fed in steam for about 12 hours anyways and opened.
The steel looked 100% the same as when I put into furnace. I put the 'piece of steel' to one side.
I picked it up the other day only to discover that it was very easy to bend. On taking a closer look it turnes out that most of the steel has
converted to Magnetite (even at the low temperature of oven) and only a thin sliver of Steel is left in the interior. I have put it into a Chlorate
cell to see if steel will be attacked through the Magnetite coating.
I have since remade the furnace using sliced up firebrick and Perlite. The fire brick it in thin slices so most of the insulating will be performed by
Perlite. Too stingy to purchase Alumina bricks.
Hopefully this is the final time I will have to do this and will be able to make Magnetite anodes at will so long as I don't run out of scrap steel,
steam and electricity.
I am putting in approx. 950 Watts into furnace. The steam goes in using a domestic kettle connected to a variac.
Are computer frames/boxes made from ordinary steel. A piece cut from one of them will probably be thick enough for an anode.
If one were to use an alloy of Iron containing Cobalt or coat Iron with Cobalt (easy to do) would Cobalt Oxide (Co3O4) form on the ouside. This would
surely be the simplest anode possible 
Dann2
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12AX7
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A lot of sheet metal is galvanized.
...Any place in all this for zinc ferrite? If it works, you wouldn't have to strip off the galvy.
Tim
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