FragranceLover89
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Electroless plating Re on Mg
I attempted electroless deposition of Re on Mg to make a corrosion resistant Mg ring. I bought a sintered Re metal cylinder on ebay (XRD showed it
matched Re) and put it in an ammonia/H2O2 solution to produce perrhenic acid. A gold colored iridescent film formed on the Mg after contact with the
solution, which may have been a layer of Re. The ring later (4 months) oxidized in air and became rough. Adding vitamin c to the plating solution
seemed to make an Re complex (red/orange color), however this did not effect plating on Mg. Mg and Re have similar crystal structures (hcp) and
lattice constants. I don't know how safe Re is. Apparently tungsten and tungsten carbide are carcinogenic but Re seems more like manganese chemically
so it might be safer?
I got the chance to melt some of the Re powder in a vacuum arc furnace and made a cool pellet (photo below).
* I just remembered I was inspired to do this after depositing a black (CuS) layer on Mg with copper/ammonia with some sulfide(?) while I was trying
to de-tarnish silver. It was a really cool looking texture and surprisingly durable. If I remember correctly that solution was kind of a witches brew.
It had borax, copper, gallium (very small amount), ammonia, magnesium, aluminum, and tarnished silver. The coating was really slick like boron but
probably not boron. IDK.
 
[Edited on 30-10-2020 by FragranceLover89]
[Edited on 30-10-2020 by FragranceLover89]
[Edited on 30-10-2020 by FragranceLover89]
[Edited on 30-10-2020 by FragranceLover89]
[Edited on 30-10-2020 by FragranceLover89]
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FragranceLover89
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Here is the rhenium coating ~1 year later. Note the golden yellow color.
 
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woelen
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I had a similar experience with zinc metal, added to an acidic solution of ammonium perrhenate. I added granules of very pure zinc to such a solution,
hoping to get a nicely colored lower oxidation state compound in solution, but instead, the zinc became covered by a gold-colored (albeit much lighter
than real gold) layer and the reaction quickly came to a standstill.
Rhenium metal does not have such a gold color. I have sintered rhenium pellets, 0.75 grams each, and these are grey. I also have a few square cm of
rhenium foil. This has a silvery color. Maybe the mix of rhenium and the base metal on which the rhenium is plated has a more yellowish color?
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chornedsnorkack
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Rhenium trioxide is also described as a red solid with a metallic lustre resembling copper, insoluble in water and dilute acids and bases.
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FragranceLover89
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I forgot to mention that this metal cylinder was originally clean white Mg. The dark spots also contain Rhenium. To get a lower oxidation state I
would try adding vitamin C to perrhenates. I definitely saw a red/orange colored solution.
[Edited on 3-11-2020 by FragranceLover89]
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chornedsnorkack
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Rhenium dioxide is described as gray to black.
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FragranceLover89
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I am guessing you are right. It is likely a mixture of ReO2 and ReO3 in a super thin layer. It is iridescent so the gold color is likely due to thin
film interference.
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