Iron Diffusion and Corrosion Behavior of Ni-Fe-Co Alloy Anodes During High-temperature Oxidation and Aluminum Electrolysis with Addition of Cobalt AITranslate
Abstract AITranslate
The current aluminum smelting technology adopts Hall-Héroult molten salt electrolysis method. During the electrolysis process, a large amount of carbon anode materials is consumed to generate CO2 and strong greenhouse gas perfluorocarbon （PFC）. The average direct current （DC） power consumption per ton of aluminum produced is about 13500 kWh. In recent years, the carbon-free aluminum smelting technology with non-consumable anode （also known as inert anode） has become the main direction of technological innovation and industrial upgrading of the aluminum industry. Due to its nickel ferrite film forming characteristics, Ni-Fe based alloy has become one of the most promising anode material. However, during the high temperature oxidation process, the external diffusion of Fe in Ni-Fe alloy is much higher than that of Ni, which leads the oxidation and corrosion resistance of the alloy in molten salt are poor. Aiming at the problem of rapid external diffusion of Fe in the nickel-iron-based alloy during high temperature oxidation and aluminum electrolysis process, （Ni1.67Fe）100-xCox （x=0, 5, 10, 20； %, mass fraction） alloys with different additions of Co were prepared by vacuum melting investment casting method in this study. The effects of different Co contents on the surface roughness, microstructure and structure of （Ni1.67Fe）100-xCox alloys after high temperature oxidation at 850 ℃, as well as Fe diffusion and electrolytic corrosion behavior in NaF-KF-AlF3-Al2O3 molten salt were studied by high temperature oxidation kinetics test, laser confocal microscopy, Scanning electron microscopy/energy dispersive X-ray spectroscopy （SEM/EDS） and X-ray diffraction （XRD） analysis. The high temperature oxidation experiments of the alloy were carried out in 1atm oxygen atmosphere at 850 ℃ for 48 h. The results showed that the oxidation of the samples were divided into three stages and followed the parabolic law. With the increasement of Co, the high temperature oxidation rate constant of the alloy decreased first and then increased, and the oxidation rate constants were 9.18×10-8, 6.33×10-8, 8.64×10-8 and 12.82×10-8 g2·cm-4·h-1 respectively. After linear fitting, the oxidation rate of （Ni1.67Fe）100-xCox alloys with 5%Co content was significantly lower than that of the other three alloys. Moreover, the alloys were accompanied by different degrees of film bulge and spalling during oxidation. With the increasement of Co content, the bulge and peeling of the membrane layer are gradually intensified. The results of laser confocal microscopy on the surface of high temperature oxide film of （Ni1.67Fe）100-xCox alloys showed that the higher the Co content, the more serious of the film surface undulation and bulge, and the higher of the surface roughness （Sa） value, which were 2.584, 2.994, 3.208 and 7.419 μm respectively. The peak distance difference （ΔZ） also gradually increased with the increasing content of Co, which were 11.693, 14.422, 19.849 and 43.355 μm, respectively. XRD results of the scales showed that the film was mainly composed of （NiCo）Fe2O4, Fe2O3 and NiO oxides. The higher the content of Co and its oxide, the higher the Co-oxide formed in the oxidation process of the alloy. Due to the larger Pilling Bedworth ratio （PBR） value of Co element, the film growth produces greater stress, and the film was easy to crack or peel off from the substrate. The results of low-temperature NaF-KF-AlF3 molten salt aluminum electrolysis test of the alloys showed that the maximum voltages of （Ni1.67Fe）100-xCo alloys with different Co contents during the electrolysis process were 3.92, 3.62, 4.32 and 5.14 V respectively. After electrolysis for 5 h, the voltage of （Ni1.67Fe）100-xCo alloy with 5%Co content was always lower than that of the other three alloys and had been in a stable state. The cross-section SEM/EDS results of the electrolytic corrosion showed that the film of all the four alloys after electrolysis presented a three-layer structure：the outermost oxide layer, the intermediate fluoride layer, and the internal corrosion transition layer of the metal matrix. With the increasement of Co content, the degree of erosion of the corrosion transition layer inside the metal matrix gradually decreased. This was mainly due to the addition of a certain amount of Co, which led to the formation of （NiCo）Fe2O4 composite spinel structure film during the high temperature oxidation of the alloy. On the one hand, it inhibited the external diffusion of Fe in the alloying elements. On the other hand, it prevented the internal diffusion and erosion of the electrolyte molten salt to the alloy matrix. The corrosion resistance of the alloy was greatly improved and the content of Fe impurities in the produced aluminum was reduced. Comprehensively considering the high temperature oxidation and electrolytic corrosion properties of the alloy, the addition of Co in （Ni1.67Fe）100-xCo alloys was not more than 10%, which was beneficial to the improvement of the comprehensive performance of Ni-Fe alloy anode. The addition of Co combined with low temperature Na-KF-AlF3 electrolysis technology played a dual role in improving the high temperature oxidation and molten salt corrosion resistance of Ni-Fe alloy anode, which was conducive to accelerate the industrial application of this alloy anode.
KeyWords AITranslate
［1］（田林，李传斌，赵鸿滨，袁学韬，尹延西. 热分解温度对Ti/Mn2O3-Co3O4涂层阳极的析氧电催化性能影响 ［J］. 稀有金属，2024，48（4）：467.）
L Tian，C B Li，H B Zhao，X T Yuan，Y X Yin. Electrochemical properties of Ti/Mn2O3-Co3O4 coating anodes prepared with different thermal decomposition temperatures ［J］. Chinese Journal of Rare Metals，2024，48（4）：467.
［2］（武天恒，刘蕊，韩雪，刘日嘉，孙源. BiOI/g-C3N4修饰电极伏安法检测磺胺甲噁唑 ［J］. 分析试验室，2024，43（1）：1.）
T H Wu，R Liu，X Han，R J Liu，Y Sun. Detection of sulfamethoxazole by cyclic voltammetric method based on BiOI/g-C3N4 modified electrode ［J］. Chinese Journal of Analysis Laboratory，2024，43（1）：1.
［3］Sadoway D R. Inert anode for the Hall-cell：the ultimate materials challenge ［J］. JOM，2001，53（5）：34.
［4］（吴静，刘永长，李冲，伍宇婷，夏兴川，李会军. 高Fe、Cr含量多相Ni3Al基高温合金组织与性能研究进展 ［J］. 矿物、金属与材料学会期刊，2020，56（1）：21.）
J Wu，Y C Liu，C Li，Y T Wu，X C Xia，H J Li. Research progress on microstructure and properties of multiphase Ni3Al based high-temperature alloys with high Fe and Cr content ［J］. The Journal of The Minerals，Metals & Materials Society，2020，56 （1）：21.
［5］（吴栋，王鑫，董文超，陆善平. 焊接热循环及时效处理对一种Ni-Fe基高温合金的组织和力学性能的影响 ［J］. 矿物、金属与材料学会期刊，2014，50（3）：313.）
D Wu，X Wang，W Dong，S P Lu. The effect of welding thermal cycle and aging treatment on the microstructure and mechanical properties of a Ni Fe based high-temperature alloy ［J］. The Journal of The Minerals，Metals & Materials Society，2014，50（3）：313.
［6］Vivien C. Nickel-Iron-Based Metallic Inert Anodes for Aluminium Electrolysis ［D］. Sydney，Australia：School of Chemical Engineering University of New South Wales，2012. 1.
［7］Vivien C，Barry J W，Maria S. Anodic behaviour of oxidised Ni-Fe alloys in cryolite-alumina melts ［J］. Electrochimica Acta，2011，56（3）：1227.
［8］Jentoftsen T E，Lorentsen O A，Dewing E W，Haarberg G M，Thonstad J. Solubility of some transition metal oxides in cryolite-alumina melts：Part I. solubility of FeO，FeAl2O4，NiO，and NiAl2O4 ［J］. Metallurgical and Materials Transactions B，2002，V33B：901.
［9］（刘英，梁志敏，王立伟，彭珍珍，汪殿龙. Al对Cu-20Ni-19Fe合金微观组织和高温抗氧化性能的影响 ［J］. 河北科技大学学报，2021，42（3）：296.）
Y Liu，Z M Liang，W Wang，Z Z Peng，D L Wang. The effect of Al on the microstructure and high-temperature oxidation resistance of Cu-20Ni-19Fe alloy ［J］. Journal of Hebei University of Science and Technology，2021，42（3）：296.
［10］Liu Y，Zhang Y A，Wang L W，Dong S，Ma J Y，Du J. Effect of La on oxidation and corrosion resistance of Cu52Ni30Fe18 alloy for aluminum electrolysis ［J］. Journal of Arabic Language Science and Engineering，2018，43（11）：6285.
［11］（郭兴龙. 铁锌尖晶石基铝用惰性阳极及镍基底氧化物膜惰性阳极的研究 ［D］. 济南：山东师范大学，2004. 1.）
X L Guo. Research on Inert Anodes for Iron Zinc Spinel Based Aluminum and Nickel Based Oxide Film Inert Anodes ［D］. Jinan：Shandong Normal University，2004. 1.
［12］（刘英，张永安，王卫，李冬生，王俊伟，梁玉冬. Fe对（Cu-Ni-Fe）100-xNiFe2O4复合惰性阳极低温铝电解成膜机制的影响 ［J］. 材料工程，2019，47（2）：107.）
Y Liu，Y A Zhang，W Wang，D S Li，J W Wang，Y D Liang. The effect of Fe on the mechanism of low-temperature aluminum electrolysis film formation on （Cu-Ni-Fe）100-xNiFe2O4 composite inert anode ［J］. Materials Engineering，2019，47（2）：107.
［13］Gavrilova E，Goupil G，Davis B，Guay D，Roué L. On the key role of Cu on the oxidation behavior of Cu-Ni-Fe based anodes for Al electrolysis ［J］. Corrosion Science，2015，101：105.
［14］Vivien S，Barry J W，Maria S. Influence of cobalt additions on electrochemical behavior of Ni-Fe-based anodes for aluminium electrowinning ［J］. Light Metals，2011，190：1137.
［15］（熊聪，王建，郑海忠，马盼盼，李贵发，鲁世强. Ti2AlNb基合金制备方法研究进展 ［J］. 特种铸造及有色合金，2020，40（10）：1072.）
C Xiong，J Wang，H Z Zheng，P P Ma，G F Li，S Q Lu. Research progress on preparation methods of Ti2AlNb based alloys ［J］. Special Casting and Nonferrous Alloys，2020，40（10）：1072.
［16］Zheng J，Chen A K，Zheng W，Zhou X J，Bai B，Wu J，Ling W，Ma H P，Wang W. Effectiveness analysis of resources consumption，environmental impact and production efficiency in traditional manufacturing using new technologies：case from sand casting ［J］. Energy Conversion and Management，2020，V209：112671.
［17］（陈志鹏，朱冬冬，王刚，董多，王晓红. 高压凝固原位自生Al2O3/Al复合材料微观组织与热膨胀性能研究 ［J］. 稀有金属，2024，48（4）：477.）
Z P Chen，D D Zhu，G Wang，D Dong，X H Wang. Microstructure on thermal expansion coefficient of in-situ Al2O3/Al composites by high pressure solidification ［J］. Chinese Journal of Rare Metals，2024，48（4）：477.
［18］（黄立强. NaF-KF-AlF3低温电解质体系的研究 ［D］. 昆明：昆明理工大学，2020. 1.）
L Q Huang. Research on NaF-KF-AlF3 Low Temperature Electrolyte System ［D］. Kunming：Kunming University of Technology，2020. 1.
［19］Liu Y，Chai D P，Wang W，Li D S，Shi Z R. Effect of heat treatment on oxidation and corrosion behavior of copper-nickel metal inert anode for aluminum electrolysis ［J］. Journal of Alloys and Compounds，2020，832（8）：154.
［20］Deněk V，Gaustavsen T，Ostvold T. Structure of the MF-AlF3-Al2O3 （Mg，La，Na，K） melts ［J］. Can. Metall. Q.，2000，39（2）：153.
［21］Liu Y，Zhang Y A，Wang W，Li D S，Shi Z R. The organization and electrolysis behavior of aluminum electrochemical copper nickel iron composite noble anode ［J］. The International Journal of Minerals，Metallurgy，and Materials，2018，V25（10）：1208.
［22］Lacassagne V，Bessada C，Florian P，Bouvet S，Ollivier B，Coutures J P，Massiot D. Structure of high temperature NaF-AlF3-Al2O3 melts：a multinuclear NMR study ［J］. J. Phys. Chem. B，2002，106（8）：1862.
［23］Gallino I，Kassner M E，Busch R. Oxidation and corrosion of highly alloyed Cu-Fe-Ni as inert anode material for aluminum electrowinning in as-cast and homogenized conditions ［J］. Corrosion Science，2012，63：293.
Basic Information:
DOI：10.13373/j.cnki.cjrm.XY24040001
Chinese Library Classification Number:TG146.21
Citation Information:
The current aluminum smelting technology adopts Hall-Héroult molten salt electrolysis method. During the electrolysis process, a large amount of carbon anode materials is consumed to generate CO2 and strong greenhouse gas perfluorocarbon （PFC）. The average direct current （DC） power consumption per ton of aluminum produced is about 13500 kWh. In recent years, the carbon-free aluminum smelting technology with non-consumable anode （also known as inert anode） has become the main direction of technological innovation and industrial upgrading of the aluminum industry. Due to its nickel ferrite film forming characteristics, Ni-Fe based alloy has become one of the most promising anode material. However, during the high temperature oxidation process, the external diffusion of Fe in Ni-Fe alloy is much higher than that of Ni, which leads the oxidation and corrosion resistance of the alloy in molten salt are poor. Aiming at the problem of rapid external diffusion of Fe in the nickel-iron-based alloy during high temperature oxidation and aluminum electrolysis process, （Ni1.67Fe）100-xCox （x=0, 5, 10, 20； %, mass fraction） alloys with different additions of Co were prepared by vacuum melting investment casting method in this study. The effects of different Co contents on the surface roughness, microstructure and structure of （Ni1.67Fe）100-xCox alloys after high temperature oxidation at 850 ℃, as well as Fe diffusion and electrolytic corrosion behavior in NaF-KF-AlF3-Al2O3 molten salt were studied by high temperature oxidation kinetics test, laser confocal microscopy, Scanning electron microscopy/energy dispersive X-ray spectroscopy （SEM/EDS） and X-ray diffraction （XRD） analysis. The high temperature oxidation experiments of the alloy were carried out in 1atm oxygen atmosphere at 850 ℃ for 48 h. The results showed that the oxidation of the samples were divided into three stages and followed the parabolic law. With the increasement of Co, the high temperature oxidation rate constant of the alloy decreased first and then increased, and the oxidation rate constants were 9.18×10-8, 6.33×10-8, 8.64×10-8 and 12.82×10-8 g2·cm-4·h-1 respectively. After linear fitting, the oxidation rate of （Ni1.67Fe）100-xCox alloys with 5%Co content was significantly lower than that of the other three alloys. Moreover, the alloys were accompanied by different degrees of film bulge and spalling during oxidation. With the increasement of Co content, the bulge and peeling of the membrane layer are gradually intensified. The results of laser confocal microscopy on the surface of high temperature oxide film of （Ni1.67Fe）100-xCox alloys showed that the higher the Co content, the more serious of the film surface undulation and bulge, and the higher of the surface roughness （Sa） value, which were 2.584, 2.994, 3.208 and 7.419 μm respectively. The peak distance difference （ΔZ） also gradually increased with the increasing content of Co, which were 11.693, 14.422, 19.849 and 43.355 μm, respectively. XRD results of the scales showed that the film was mainly composed of （NiCo）Fe2O4, Fe2O3 and NiO oxides. The higher the content of Co and its oxide, the higher the Co-oxide formed in the oxidation process of the alloy. Due to the larger Pilling Bedworth ratio （PBR） value of Co element, the film growth produces greater stress, and the film was easy to crack or peel off from the substrate. The results of low-temperature NaF-KF-AlF3 molten salt aluminum electrolysis test of the alloys showed that the maximum voltages of （Ni1.67Fe）100-xCo alloys with different Co contents during the electrolysis process were 3.92, 3.62, 4.32 and 5.14 V respectively. After electrolysis for 5 h, the voltage of （Ni1.67Fe）100-xCo alloy with 5%Co content was always lower than that of the other three alloys and had been in a stable state. The cross-section SEM/EDS results of the electrolytic corrosion showed that the film of all the four alloys after electrolysis presented a three-layer structure：the outermost oxide layer, the intermediate fluoride layer, and the internal corrosion transition layer of the metal matrix. With the increasement of Co content, the degree of erosion of the corrosion transition layer inside the metal matrix gradually decreased. This was mainly due to the addition of a certain amount of Co, which led to the formation of （NiCo）Fe2O4 composite spinel structure film during the high temperature oxidation of the alloy. On the one hand, it inhibited the external diffusion of Fe in the alloying elements. On the other hand, it prevented the internal diffusion and erosion of the electrolyte molten salt to the alloy matrix. The corrosion resistance of the alloy was greatly improved and the content of Fe impurities in the produced aluminum was reduced. Comprehensively considering the high temperature oxidation and electrolytic corrosion properties of the alloy, the addition of Co in （Ni1.67Fe）100-xCo alloys was not more than 10%, which was beneficial to the improvement of the comprehensive performance of Ni-Fe alloy anode. The addition of Co combined with low temperature Na-KF-AlF3 electrolysis technology played a dual role in improving the high temperature oxidation and molten salt corrosion resistance of Ni-Fe alloy anode, which was conducive to accelerate the industrial application of this alloy anode.
quote
| GB/T 7714-2015 | [1] Lin Yang, Ying Liu, Zihan Liu, et al. Iron Diffusion and Corrosion Behavior of Ni-Fe-Co Alloy Anodes During High-temperature Oxidation and Aluminum Electrolysis with Addition of Cobalt[J]. Chinese Journal of Rare Metals, 2026, 50(8): 1287-1298. DOI:10.13373/j.cnki.cjrm.XY24040001. |
| MLA | [1] Lin Yang, et al., "Iron Diffusion and Corrosion Behavior of Ni-Fe-Co Alloy Anodes During High-temperature Oxidation and Aluminum Electrolysis with Addition of Cobalt." Chinese Journal of Rare Metals, vol. 50, no. 8, 2026, pp. 1287-1298, https://doi.org/10.13373/j.cnki.cjrm.XY24040001. |
| APA | [1] Lin Yang, Ying Liu, Zihan Liu, Zhe Liu, & Zhimin Liang. (2026). Iron Diffusion and Corrosion Behavior of Ni-Fe-Co Alloy Anodes During High-temperature Oxidation and Aluminum Electrolysis with Addition of Cobalt. Chinese Journal of Rare Metals, 50(8), 1287-1298. https://doi.org/10.13373/j.cnki.cjrm.XY24040001 |
| IEEE | [1] Lin Yang, Ying Liu, Zihan Liu, Zhe Liu, and Zhimin Liang, "Iron Diffusion and Corrosion Behavior of Ni-Fe-Co Alloy Anodes During High-temperature Oxidation and Aluminum Electrolysis with Addition of Cobalt," Chinese Journal of Rare Metals, vol. 50, no. 8, pp. 1287-1298, 2026, doi: 10.13373/j.cnki.cjrm.XY24040001. keywords: {high-temperature oxidation;corrosion;inert anode;aluminum electrolysis} |