Electroplating from tungsten via phosphate salt?

[jrodatus]

At the bottom of page 54 of Tungsten: Properties, Chemistry, Technology of the Elements, Alloys, and Chemical Compounds by Lassner and Schubert:

Phosphoric acid (H3PO4): Tungsten is highly resistant to diluted phosphoric acid as long as air is excluded. It dissolves easily in concentrated acid.

I'm presuming the reaction goes something like 2H_{3}PO_{4} + 2W → 3H_{2} + 2WPO_{4}

Since I'm pretty sure copper phosphate works just fine for electroplating, why wouldn't tungsten phosphate? What's the difference? The absence of any Google info on this makes me think there must be some good reason why it won't work.

But it sure would be useful for a particular project. Would appreciate input!

 

[SteamKing]

I think the result is more like W(PO4)2, since phosphate is -3 while W can be +6. Since tungsten has several oxidation states running from +6 to -2, there may be different compositions.

 

[jrodatus]

I think the result is more like W(PO4)2, since phosphate is -3 while W can be +6. Since tungsten has several oxidation states running from +6 to -2, there may be different compositions.

Okay, assuming W loses all 6 electrons like it can, that sounds like a pretty strong bond. I suppose it would be insoluble in pretty much anything. Thank you.

 

[SteamKing]

Sections 3.7 and 3.8 of your reference also discuss some aspects of electroplating with tungsten. Apparently, not much is known about tungsten compounds and this lack of information makes it difficult to determine which compounds are the most suitable.

 

[jrodatus]

Sections 3.7 and 3.8 of your reference also discuss some aspects of electroplating with tungsten.

Doh, thank you again. From page 123:

In aqueous solution, no oxygen-free tungsten cation exists but only monomeric or dimeric species like WO^{2+}_{2}. Tungsten, due to its great affinity to oxygen, may never form a metal/metal ion electrode system but always a metal/metal oxide/metal ion system, which is quite irreversible.

(Just posting it here for reference. Hope that's not a copyright violation.)

 

[SteamKing]

Nope. You aren't claiming the work is your own, and it falls under what is known as 'fair use'.