Anodic behaviour of oxidised Ni–Fe alloys in cryolite–alumina melts

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• 作者：Vivien Chapman ; Barry J. Welch ; Maria Skyllas-Kazacos
• 关键词：Inert anodes ; Aluminium electrolysis ; Oxygen evolution ; Nickel anodes ; Metal oxidation
• 刊名：Electrochimica Acta
• 出版年：2011
• 出版时间：1 January 2011
• 年：2011
• 卷：56
• 期：3
• 页码：1227-1238
• 全文大小：2378 K

文摘

Nickel-iron alloys have been identified as promising inert anode candidates for the Hall–Héroult process. In this study, binary Ni–Fe alloys of various compositions were subjected to short-term galvanostatic electrolysis in a cryolite–alumina bath at 960 °C. Prior to electrolysis, the anodes were oxidised at 800 °C for 48 h, forming a protective scale. Fe₂O₃, Ni_xFe_3−xO₄ and Ni_xFe_1 − xO were identified as the major scale components using a combination of X-ray diffraction (XRD) analysis and energy dispersive X-ray spectroscopy (EDX). Anodes having Ni content of 50–65 wt % performed adequately during short-term electrolysis, operating at a steady potential of 3–3.5 V vs. AlF₃/Al. Overall, it was found that the pre-formed oxide scale was effective in reducing anode wear and fluoridation. In the absence of a pre-formed scale, anodes were shown to undergo appreciable internal corrosion and/or passivation due to metal fluoride formation. Analysis of the anodes following electrolysis was performed using XRD and electron microprobe analysis (EPMA).