2014-Sustainable Industrial Processing Summit
SIPS 2014 Volume 6: Rare Earths & Ionic Liquids
| Editors: | Kongoli F |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2014 |
| Pages: | 432 pages |
| ISBN: | 978-1-987820-08-9 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Relationship between the passivation properties of noble and refractory metals and their electrochemical behavior in low-temperature ionic liquids
Nelly Tumanova1; Svetlana Kochetova2; Viktor Malyshev1; Dmytro Shakhnin2; Marcelle Gaune-Escard3;1IGIC NASU, Kyiv, Ukraine; 2V.I. VERNADSKY INSTITUTE OF GENERAL AND INORGANIC CHEMISTRY OF THE NATIONAL ACADEMY OF SCIENCES OF UKRAINE, Kyiv, Ukraine; 3ECOLE POLYTECHNIQUE, MECANIQUE ENERGETIQUE, CNRS UMR, Marseille, France;
Type of Paper: Regular
Id Paper: 119
Topic: 11
Abstract:
It was found that low-temperature melts based on urea, acetamide, imidazole and tetraalkylammonium chlorides are stable and have low melting point (<100oC).
Based on study results of electrochemical behavior of noble and refractory metals in these melts, a relationship between the passivation properties of these metals and their electrochemical behavior was established. Metals which are not passive (Ag, Cu, Pt, and Pd) are deposited on cathode in form of powder or galvanic coating. Galvanic coatings of Pt (from urea), Pd (from acetamide), Cu, Ag (from urea, acetamide, and imidazole) of different thickness were deposited with good adhesion to substrate. Pd powders were deposited from urea having spherical and needle structure. The electropolishing of such metals is unprofitable due to a high consumption of metal during unimpeded dissolution.
Metals which are poorly passive (Ru, Rh, Ir, Ti, Mo, and W) are deposited on cathode in form of metal or metal-like deposit containing mainly oxihalide complexes and small amount of pure metals. In case of metals which are well passive (Nb and Ta), it is not possible to obtain a cathode deposit.
Metals which are passive are suitable for electropolishing. The passivation degree of metal is the lowest, the process efficiency (polishing conditions - time, current density, and surface quality) is the highest. With weak passivation of metal, the metal-like deposit is deposited on cathode (containing small amount of metal and mainly its insoluble compounds).
The relationships obtained allow predicting the possibility of applying solutions realization, i.e. obtaining a cathodic deposit and its purity and also efficiency of anodic surface treatment of metals.