Editors: | Vayenas Intl. Symp. / Physical Chemistry and its applications for sustainable development Edited by: F. Kongoli, E. Aifantis, C. Cavalca, A. de Lucas Consuegra, A. Efstathiou, M. Fardis, D. Grigoriou, A. Lemonidou, S.G. Neophytides, Y. Roman, M. Stoukides, M. Sullivan, P. Vernoux, X. Verykios, I. Yentekakis |
Publisher: | Flogen Star OUTREACH |
Publication Year: | 2019 |
Pages: | 249 pages |
ISBN: | 978-1-989820-09-4 |
ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
The term "induced codeposition" was already coined by Brenner in 1963 to describe a process where certain elements such as tungsten (W),that cannot be deposited alone from their aqueous solutions, are readily codeposited with iron-group metals. Indeed, alloys of W with iron-group metals can readily be formed using, for example, a solution of NiSO4 and Na2WO4, with citric acid added as a complexing agent. In this particular case, it was shown that the NiW alloy is deposited from an adsorbed complex containing both metals, while Ni is also deposited in parallel reactions from its complex with citrate. The term induced codeposition may also be used to describe a process where a metal, that can barely be deposited alone, with a low current efficiency (FE) and poor adherence of the deposit, is readily deposited in the presence of other metal ions. This is the case of rhenium (Re), which can be electroplated alone at FE a ≤ 7% and poor coating quality. By adding a suitable iron-group metal salt to the bath, we have obtained coatings with a Re content as high as 93 at.% and a FE as high as 96%.
In this plenary presentation, we review our study of the electrodeposition and electroless plating of Re-based alloys. Issues such as the catalytic effect of iron-group metals on the deposition of Re, the early stages of deposition, the effects of bath additives and pulse plating, electroless plating, and the associated microstructures are discussed. We also discuss the effect of other alloying elements (e.g. Sn or Ir) on the resulting deposition process and microstructure. Similarities and differences compared to induced codeposition of W are discussed. The fundamental aspects are complemented by some applied aspects, e.g. with respect to thermal barrier coatings and catalysis.