Electrodeposition of Rhenium and its Alloys

Electrolysis has been applied primarily to extract metallic Re from solutions, and to produce Re coatings. In electrolytic extraction, the metal can be obtained in the form of a bright deposit or a black powder, depending on the conditions of electrolysis. The 

An early, relatively short, review on electrodeposition of Re alloys with iron-group metals was presented by Breimer. In an acid perrhenate solution, the overall reaction can be written as 

Typical bath compositions and operating conditions for electrodeposition of Re are listed in Appendix C. An acid sulfate solution, based on potassium perrhenate, was suggested by Fink and Deren. Netherton and Holt worked with similar baths, to which they added either citric acid or ammoniacal citrate. Sligh and Brenner used more concentrated solutions of perrhenate, but still could not increase the FE significantly. Their deposits exfoliated when produced thicker than 10 pm, and oxidized rapidly upon exposure to air. Therefore, it was hypothesized that the elec-trodeposited metal was not pure, but contained oxide inclusions. 

It should be noted that at low pH citric acid exists in its fully protonated, uncharged form (cf, Fig. la). In this form, it is not a good complexing agent. 

Root and Beach also found that the as-deposited Re was not stable in air and moisture, because of the inclusion of rhenium hydride impurities. The quantity of hydride depends on the pH of 

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There are only a few studies on the electrochemical behaviour of rhenium in molten salts [1-6]. Most investigations dealt with electrodeposition of rhenium and its alloys. The absence of reliable data on the electrochemical reduction of rhenium in molten salts greatly impedes further progress in the field of rhenium galvanoplastics and hinders interpretation of the experimental results. 

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