Electrodeposition of alloys of rhenium with iron-group metals from aqueous solutions

Rhenium (Re) is a refractory metal, which exhibits unique combination of properties, making it an attractive material in a variety of applications. The mechanism of Re electrodeposition is still unknown. However, there are clear indications that codeposition of alloys with iron-group metals may lead to higher-quality coatings and higher Faradaic efficiencies (FE's). Re-Me alloys, where Me=Ni, Fe or Co, were deposited galvanostatically. The bath solution consisted of ammonium perrhenate, nickel or cobalt sulfamate or iron sulfate, citric acid, and magnesium sulfamate. The effects of bath chemistry and deposition time on the FE, Re content and partial deposition currents were determined. Rhenium contents as high as 93 at.% and FE values as high as 96% were attained. The results are discussed with emphasis on routes to increase the FE and Re content in the coating. The possible role of the 2^nd metal in electrodeposition of Re is presented.