Corrosion and Passivation of Cermet Inert Anodes in Cryolite‐Type Electrolytes

Tarcy, Gary P.

doi:10.1002/9781118647745.ch145

Cited by 3 publications

(4 citation statements)

References 2 publications

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“…ALCOA studied cermets composed of copper as metallic phase and a mixture of NiFe 2 O 4 and NiO [12] [13]. Anodes were tested in cryolite at 0.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Degradation Mechanism of a Cermet Anode for Aluminum Production

Meyer¹,

Massot²,

Gibilaro³

et al. 2019

MSA

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Tests on (Ni x Fe y O 4-Ni 1−x Fe x O)/(Cu x Ni y Fe z) cermets, considered as promising anode for the aluminium production, were performed under electrolysis at 0.8 A•cm −2 in molten mixture of cryolite at 960˚C. In order to predict phase compositions, a thermodynamic study was performed and experimentally verified by SEM-EDS analysis. The metallic phase oxidation leads to the formation of different phases such as FeF 2 , Ni 0.90 Fe 0.10 O, NiF 2 and Cu 2 O phases, while Ni x Fe 3−x O 4 spinel is continuously enriched up to x = 0.90, the thermodynamically stable nickel composition. When the cermet material is fully oxidized, metallic and oxide phases are converted into soluble or non-conductive phases, leading to the end of anode service life.

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“…ALCOA studied cermets composed of copper as metallic phase and a mixture of NiFe 2 O 4 and NiO [12] [13]. Anodes were tested in cryolite at 0.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Degradation Mechanism of a Cermet Anode for Aluminum Production

Meyer¹,

Massot²,

Gibilaro³

et al. 2019

MSA

View full text Add to dashboard Cite

show abstract

“…The increase of the metallic phase content can reduce the thermal expansion mismatch of the conductor and the cermets, and improve the conductivity of cermets anodes. Meanwhile, high metallic phase content can maintain the corrosion resistance by using Cu rich Cu–Ni alloy . However, it is hard to increase the Cu content because Cu can exude easily during sintering .…”

Section: Introductionmentioning

confidence: 99%

“…However, it is hard to increase the Cu content because Cu can exude easily during sintering . Although, the addition of Ni in the metallic phase could increase the solidus temperature of the metallic phase and improve the wettability, the Ni content in Cu–Ni alloy should be low since Ni is anodically dissolvable in the electrolysis process . Until recently, little information about the sintering process of NiFe 2 O 4 based cermets containing high content of Cu or Cu alloy and the morphology of the exudates is available in literature.…”

Section: Introductionmentioning

confidence: 99%

Microstructural Evolution of a Nickel Ferrite–Copper Alloy Cermet During Sintering and High‐Temperature Oxidation

Yuqiang

Zhang

et al. 2012

J. Am. Ceram. Soc.

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The microstructural evolution during sintering and high-temperature oxidation of a cermet comprised of (wt%) a 40/60 ratio of an alloy of composition 80% Cu/20% Ni and a ceramic of composition 90% NiFe 2 O 4 /10% NiO has been studied as a function of processing temperature. The porosity of the cermet reduced significantly without undue coarsening of the microstructure during sintering up to the melting temperature of the alloy phase (T m % 1160°C), whereas at sintering temperatures higher than T m , the ferrite rapidly coarsened with little additional reduction in porosity, and the alloy phase formed a continuous interconnected network while partially extruding from the composite. Upon oxidation in air at temperatures between 850°C and 1000°C, the cermet developed a multilayered oxidized scale, comprising a thin copper-rich outer oxide layer formed via external oxidation and a thicker zone of internal oxidation. The external oxide scale transformed from CuO to Cu 2 O with increasing oxidation temperature. Out-diffusion of the copper to the externally oxidized layer led to significant porosity at the internal interface between oxide and unoxidized cermet. P. Joy-contributing editor

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“…However, the nickel metallic phase is anodically dissolvable in electrolysis process, which would result in the failure of electrolysis and the contamination of Al product . Tarcy reported that Cu was passivated in the electrolysis, and considered that cermet anodes with continuous wormy copper metallic phase would be very conductive, corrosion resistance anodes. However, it is very difficult to prepare this type anode for the bad wettability between Cu and NiFe 2 O 4 .…”

Section: Introductionmentioning

confidence: 99%

Preparation of Nickel Ferrite–Copper Composite by Pressureless Infiltration

Yuqiang

Zhang

et al. 2012

J. Am. Ceram. Soc.

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Pressureless infiltration was used to prepare a dense Cu/NiFe 2 O 4 -10NiO composite with interlocking microstructure. The results showed that the addition of Cu 2 O in Cu could improve the wettability between Cu and NiFe 2 O 4 . The metallic phase content and densification of the resulting composite were 34 wt% and 99.2%, respectively. The resulting composite had a flexural strength of 200 ± 20 MPa, a room-temperature thermal diffusivity of 0.12 cm 2 /s, and an electrical conductivity of 1503 S/cm at 900°C.

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Corrosion and Passivation of Cermet Inert Anodes in Cryolite‐Type Electrolytes

Cited by 3 publications

References 2 publications

Electrochemical Degradation Mechanism of a Cermet Anode for Aluminum Production

Electrochemical Degradation Mechanism of a Cermet Anode for Aluminum Production

Microstructural Evolution of a Nickel Ferrite–Copper Alloy Cermet During Sintering and High‐Temperature Oxidation

Preparation of Nickel Ferrite–Copper Composite by Pressureless Infiltration

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