YT2095
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Plating out Chromium metal
As some may already know, I tried to obtain Chrome metal by a thermit reaction (it wasn`t ideal).
my Next course of action is to try and Plate some out as a foil, as I did with Tin metal a year or so ago from 60/40 Solder.
I have Chrome Alum, Potassium dichromate and also Ammonium Dichromate as the donor sources.
in addition I also have many of the common Lab reagents available to me.
Currently (excuse the pun) I`m trying Chrome alum with a little sulphuric acid at 7.3 volts (just enough to get a "Fizz" at the cathode) I`m using
Carbon electrodes and there is a Slight greyness to the Cathode, but Nothing even remotely ressembles Chrome metal.
anyone have any ideas as to what may be the most effective method to use?
I`m after about 100mg (minimum) of the metal for my Element collection.
EDIT: turns out that grey on the cathode isn`t grey when dry, it `s just a great way to make Cr2O3 
[Edited on 27-9-2006 by YT2095]
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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not_important
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Head over to the library section and get the file that is Mellor's chromium section, it has a lot of references to various routes to the metal,
although you most likely will end up chasing down the original reference as well.
As I remember, the solution must be acid, and neutral sulfates help too - thus sodium or potassium bisulfate might do. Current density is important,
as is bath temperature.
Chrome plating is one of the trickier metal plating procedures, as I remember. I looked for but don't seem to have at hand a book on metal plating; I
remember it using chromium anodes to keep the concentration constant; that would mean going back to Goldschmidt for the impure metal.
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12AX7
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You also need the basics of electroplating, levelers and brighteners and such.
Chrome is typically plated from an acid CrO3 solution, at atrocious efficiency (~20%). AFAIK, chrome anodes are not used but CrO3 is added.
And don't forget that stereotypical chrome plating is on top of polished base metal, and the plating itself is polished a lot too.
Tim
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chromium
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Classic way:
250 g/l CrO3 (can be made from dichromates),
1.25 ... 2.5 g/l H2SO4
temperature 45 ... 55C
current density 0.35 ... 0.55 A/cm2
Use lead anode. Graphite will also work but you need large surface area.
Do not change concentrations without good reason as this may well ruin the preparation. You can not plate out all chromiumm from your CrO3 this way
but more likely 20% or so. Good luck!
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ethan_c
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| Quote: | Originally posted by chromium
Classic way:
250 g/l CrO3 (can be made from dichromates),
1.25 ... 2.5 g/l H2SO4
temperature 45 ... 55C
current density 0.35 ... 0.55 A/cm2
Use lead anode. Graphite will also work but you need large surface area.
Do not change concentrations without good reason as this may well ruin the preparation. You can not plate out all chromiumm from your CrO3 this way
but more likely 20% or so. Good luck! |
This is good procedure. Also, if you even want to consider an even (unflaky) coating, whatever you are plating should be polished to a ridiculous
degree, cleaned of oils, and preferably plated with nickel first. IIRC, industrial auto bumpers are plated with somewhere around 7 millionths of an
inch nickel and then 7 billionths of an inch chromium.
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not_important
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Given that the goal is bulk chromium, not just a thin coat, Cr anodes may still be useful. Even just a tenth of a gram of chromium will cover a lot of
surface at the thicknesses normally done with those baths.
Note that for taking Cr(6+) to Cr metal, you'll need almost 200 amp-hours for every 52 grams of metal produced. (I didn't take my shoes off, but I
think I calculated that correctly)
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