Iron migration from the anode surface in alumina electrolysis


Тип публикации: статья из журнала

Год издания: 2013

Идентификатор DOI: 10.1016/j.apsusc.2012.11.113

Ключевые слова: Corrosion mechanism, Alumina electrolysis, Metallic inert anodes in aluminum production, Aluminum production, Anode corrosion, Anode surfaces, Corrosion mechanisms, Corrosion products, Electrochemical polarization, Electrolyte penetration, Electronic conductors, High purity aluminum, High temperature, Iron atoms, Iron ions, Iron-based alloy, Oxyfluorides, Rate-limiting steps, Two-component, Alumina, Aluminum, Electrolysis, Electrolytes, Electron probe microanalysis, Iron, Iron compounds, Iron oxides, Manganese, Metal ions, Scanning electron microscopy, X ray diffraction, Corrosion

Аннотация: Corrosion destruction of two-component iron-based alloys used as an anode in high-temperature alumina electrolysis in the melt of NaF/KF/AlF3 electrolyte has been considered. Ni, Si, Cu, Cr, Mn, Al, Ti in the amount of up to 10% have been tested as the dopants to an anode alloys. The composition of the corrosion products has been sПоказать полностьюtudied using X-ray diffraction, scanning electron microscopy and electron microprobe analysis. It has been established that the anode corrosion is induced by a surface electrochemical polarization and iron atom oxidation. Iron ions come into an exchange interaction with the fluoride components of the melted electrolyte, producing FeF2. The last interacts with oxyfluoride species transforming into the oxide forms: FeAl2O4, Fe3O4, Fe2O3. Due to the low solubility, the iron oxides are accumulated in the near-electrode sheath. The only small part of iron from anode migrates to cathode that makes an production of high purity aluminum of a real task. The alloy dopants are also subjected to corrosion in accordance with electromotive series resulting corrosion tunnels on the anode surface. The oxides are final compounds which collect in the same area. The corrosion products form an anode shell which is electronic conductor at electrolysis temperature. The electrolysis of alumina occurs beyond the corrosion shell. The rate limiting step in the corrosion is the electrolyte penetration through corrosion shell to the anode surface. The participation of the released oxygen in the corrosion has not been observed. (c) 2012 Elsevier B.V. All rights reserved.

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Выпуск журнала: Vol. 265

Номера страниц: 790-795

ISSN журнала: 01694332

Место издания: AMSTERDAM