puppycock
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Fe2O3 from Scrap Iron and Nitric Acid
I was looking for methods of producing Fe2O3 in large quantities from scrap Iron and found a patent about using these reactants:
Scrap Iron
Nitric Acid 25-60%
Water and Air
I have easy access to dilute nitric acid from local suppliers and Scrap Iron can be easily obtained from scrap yards. I'm a total amateur in
chemistry, but I have been lurking this and other forums for about two years so I have an idea of how stuff works.
Anyway the patent states that "With the help of oxygen, heating process and application of small pressure, the speed of the chemical reaction suddenly
become vigorous when iron turns into hydrated Ferric Oxide Fe2O3.H2O dispersion in acid-water media". However all the literature I have found only has
Fe(NO3)3 as the resulf of Fe+HNO3 and the patent is very vague and never mentions the Temperature and "Small Pressure" required to achieve Fe2O3 from
this reaction.
Any help would be appreciated since I don't see how this could work, but if it does it would be a very good source of Iron Oxide and the Nitric Acid
can be recycled from the NO2 that would be released from the reaction.
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12AX7
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The sulfate is usually used, because it's cheaper (= almost free).
Adding any electrolyte will enhance corrosion. The redox reaction of iron in solution tends to help corrode things quite well, resulting in a finely
dispersed Fe(OH)3 product which can be used as pigment. The counterion doesn't really matter, if sulfate, nitrate, chloride, etc.
Tim
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chief
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What does form upon electrolysis of Fe, using it as an anode ?
==> Some hydroxides, for sure, but there are various modifications of those ...
Probably these could be heated, to remove the hydrogen, and Fe2O3 or Fe3O4 would remain ...
Then producing a lage quantity migh just be as easy as throwing Iron-scrap into some electrolyte and connecting some power-supply ...
==> The rate, at which Iron can be dissolved this way, is quite high ...
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not_important
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What you want is rust. Simply pump water containing a little HCl over the scrap iron, making sure there is ready access of air; chloride ions are good
at promoting corrosion of ferrous metals.
An air lift pump, basically a wide tube with its lower end in the liquid and with a jet of air blown into that end, works well for this; these are
used for aquariums as part of the under-gravel filtration system. Plastic water or drain pipe would work, perforated plastic pipe could be used to
distribute the water over the top of the metal, and a plastic basic - from dish pan to childs pool size - could be used to contain the liquid and
metal/rust.
Just keep adding water to it to male up that consumed by rusting and lost through evaporation. As the metal corrodes, try to move remaining pieces of
metal to the top of the rust; when it's mostly rust stir or rake it to insure good exposure of all of it to O2.
Or as chief says, you can use electrolysis with an iron anode in a mildly alkaline electrolyte to make the hydroxide. You might even be able to use a
pair of iron electrodes and AC power in a well stirred electrolyte; I've never tried that so it's just a guess.
When it's done, heating to a bit above 200 C converts the hydroxides to the oxide.
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bquirky
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Oh man are they ever.. dont try this in your tool shed !!
the stuff gets in the air and goes everywhere im still wire brushing and oiling things down 
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puppycock
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not_important: Thanks a lot for the information , I can surely do that for very cheap, I don't need to get it to rust very fast as long as it does.
Will I get Iron chlorides as side reactions with this method?
12AX7: Do you mean using Sulfuric Acid? can you please elaborate a little more on your method. I have to mention that I want to keep it as cheap as
possible so electrolysis would be last resort.
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12AX7
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Sulfuric acid, ferrous sulfate, whatever.
Electrolysis is certainly not required, indeed, iron generates 0.4V when dissolved in acid. You could power more rusting cells by rusting iron in
cells!
Tim
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not_important
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Yes, you get iron chlorides. They will most remain in solution, and the solution can be used on the next batch of metal to rust. Chloride seems to be
more agressive towards iron than does sulfate, in my opinion, but either should work.
Just wash the rust several times. The first time just barely cover it with water and stir well, you can stir and let settle repeatedly. Pour off the
wash water and add it it the recovered chloride containing solution. Do several more washings, these can be discarded.
If there's a tendency for some of the rust to float off with the water as you drain it off, pour the water through a filter but don't intentionally
dump the rust onto the filter; this will keep the filtering rate up as only a small amount of solids should be ending up on the filter.
Remember that the alloying metals may show up in the rust, as will calcium and magnesium in the water. There also may be some Fe3O4. Likely it's
good enough for thermite, maybe even for pigment use, but it's not lab grade.
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