Electroplating from tungsten via phosphate salt?

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Discussion Overview

The discussion centers on the feasibility of electroplating tungsten using phosphate salts, specifically exploring the chemical reactions involved and the properties of tungsten in relation to phosphoric acid. Participants examine the potential compounds formed and the challenges associated with tungsten electroplating.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests a reaction involving phosphoric acid and tungsten, proposing a possible equation for the dissolution of tungsten in phosphoric acid.
  • Another participant proposes that the resulting compound might be W(PO4)2, considering the oxidation states of tungsten and phosphate, and notes the potential for different compositions due to tungsten's multiple oxidation states.
  • A participant mentions that if tungsten loses all six electrons, the resulting bond would likely be strong and possibly insoluble.
  • References to sections in the source material indicate that there is limited knowledge about tungsten compounds, complicating the determination of suitable compounds for electroplating.
  • It is noted that in aqueous solutions, tungsten does not exist as a simple cation but rather in more complex forms, which may affect electroplating processes.

Areas of Agreement / Disagreement

Participants express differing views on the specific compounds formed during the electroplating process and the implications of tungsten's chemical behavior. The discussion remains unresolved regarding the practical application of tungsten phosphate in electroplating.

Contextual Notes

There are limitations in the understanding of tungsten compounds and their behavior in electroplating, as well as the specific conditions under which these reactions occur. The discussion highlights the complexity of tungsten's oxidation states and the nature of its interactions with phosphoric acid.

jrodatus
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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!
 
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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.
 
SteamKing said:
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.
 
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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.
 
SteamKing said:
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.)
 
Nope. You aren't claiming the work is your own, and it falls under what is known as 'fair use'.
 

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