Inert Anode Research Articles

Influence of CO2 Gas in the Electro-Carburisation Process of Mild Steel

In the attempt to develop a clean process, study has been conducted to determine the effect of absorbed CO2 gas as source of carbon to the case hardening of treated mild steels in the recently developed process of electro-carburisation in non-toxic molten carbonate salts. The concentration of CO2 in the process was varied by purging a CO2 and N2 mixture at flow rate ratios of CO2:N2 of 200:0, 150:50, 100:100, 50:150 and 0:200 mL.min -1 . Electro-carburisation was performed in two types of molten salt electrolyte i.e. a mixed anion Na2CO3-NaCl (mole ratio 4:1) and a pure carbonate Li2CO3-K2CO3 (1:1 mole ratio). A voltage of 2.5V was applied between mild steel cathode and an inert SnO2 anode at a carburisation temperature of 800 o C for 60 minutes. The results show that greater CO2 concentration produced samples with greater surface hardness and thicker case-hardening, attributed to the increased availability of the electro-active carbon source which was generated by absorption of CO2. Electro-carburisation in Li2CO3-K2CO3 and Na2CO3-NaCl gave surface hardness of 1075 ± 25 HV, however Li2CO3-K2CO3 (540 thickness) gave thicker case depth compared to Na2CO3-NaCl (500 thickness). This is thought to be due to the amount of carbon deposited in each salt; 12.70 wt.% C in Li2CO3-K2CO3 and 11.10 wt.% C in Na2CO3-NaCl.

Pd-catalytic hydrodechlorination of chlorinated hydrocarbons in groundwater using H2 produced by a dual-anode system

Water electrolysis has been employed for in situ supplying H2 to Pd-catalytic treatment of groundwater, but the treatment efficiency is greatly inhibited by the concomitant production of O2. In this study, a new dual-anode system is proposed to improve the efficiency. An inert anode and an iron anode are used simultaneously to produce O2 and Fe(II), respectively. The quick oxidative precipitation of Fe(II) by O2 removes both Fe(II) and O2, improving the utilization of cathodic H2 for the subsequent Pd-catalytic hydrodechlorination. Feasibility tests in the lab show that Pd-catalytic hydrodechlorination of trichloroethylene (TCE) was considerably increased by the addition of an iron anode to the conventional two-electrode system. Scale-up tests at an abandoned chemical site demonstrated that chlorobenzenes in the groundwater were largely hydrodechlorinated to benzene, showing a maximum efficiency with the currents of 0.24 and 0.16 A applied to the inert and iron anodes, respectively, at the flow rate of 6 L/h. In a 3-month intermittent field test, Pd normalized rate constants of hydrodechlorinating three chlorobenzenes are comparable to the conventional means of H2 supply, while the cost for hydrodechlorination normalized by one mole [H] is much lower. The dual-anode system is an effective means to supplying H2 in situ for Pd-catalytic treatment.

Electrosynthesis of Al/Pb/α-PbO2 composite inert anode materials

The α-PbO2 deposition layers were prepared on the surface of Al/Pb substrates by constant current electrosynthesis from an alkaline bath, and Al/Pb/α-PbO2 composite inert anode materials were obtained. The effects of the bath composition and bath temperature on the electrosynthesis of α-PbO2 were investigated by means of anodic polarization method, the phase structures and surface microstructures of Al/Pb and α-PbO2 deposition layers were tested by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The experimental data have shown that the process of α-PbO2 formation have several stages. The appropriate conditions can effectively improve the formation rate of α-PbO2 and avoid the occurrence of oxygen evolution reaction. The α-PbO2 deposition layer obtained in alkaline bath possesses rhombic structure, and it is composed of well developed spherical unit cells.

Enhanced Electrokinetic Transport of Sulfate in Saline Soil

The electrokinetic transport of sulfate was investigated as a means of treating and restoring a sulfate-accumulating saline soil. The electrokinetic treatment decreased the electrical conductivity of the soil, an indicator of soil salinity, to 58.6, 73.1, and 83.5 % for 7, 14, and 21 days, respectively. More than 96 % of the chloride and nitrate were removed within 7 days. However, the removal of sulfate was highly influenced by the anode material. An iron anode removed sulfate effectively, whereas sulfate was hyper-accumulated in the anodic region when an inert anode was used. The iron anode was oxidized in a sacrificial anodic reaction, which competed with the electrolysis reaction of water at the anode, and finally, the reaction prevented the severe acidification of the soil in the anodic region. However, the competing reactions produced hydrogen ions at the anode and the ions were transported toward the cathode, which, in turn, acidified the soil, especially in the anodic region. The acidification switched the surface charge of the soil from negative to positive, increasing the interaction between the soil surface and sulfate and thus inhibiting the transport of sulfate under the electric field. The zeta potential analysis of the soil provided an explanation. The results indicate that preventing severe acidification is an important factor which influences the transport of anions and iron anode for the enhanced removal of anionic pollutants by electrokinetic remediation.

Anodic Corrosion Behavior of NiFe2O4-Based Cermet in Na3AlF6-K3AlF6-AlF3 for Aluminum Electrolysis

A (Cu,Ni)/(10NiO-NiFe2O4) cermet was tested as an inert anode for aluminum electrolysis in Na3AlF6-K3AlF6-AlF3 melt at 1173 K (900 °C), and its corrosion behavior was studied. The results show that the low-temperature Na3AlF6-K3AlF6-AlF3 bath is beneficial, improving the service conditions. With the combined effects of the electrolyte composition and the nascent oxygen during electrolysis, the metal phase (Cu,Ni) at the surface of anode will not be leached preferentially, but be transferred into the aluminates including FeAl2O4, NiAl2O4 and CuAl2O4. This is helpful for the anode to improve its corrosion resistance.

ANODE BEHAVIOR OF NIO–FE2O3–CR2O3–CU COMPOSITE AT LOW-TEMPERATURE ELECTROLYSIS OF ALUMINUM

To produce 25,3NiO–41,2Fe2O3–13,5Cr2O3–20Cu oxide-metal composite (wt.%), the temperature and sintering duration (1350 °С, 30 min.) have been determined, which provide the formation of chromium oxide solid solution in nickel ferrite phase. The composite has been tested as an anode during low-temperature (800 °C) alumina saturated 12,0NaF–36,8KF–51,2AlF3 (wt.%) melt electrolysis. The amount of oxygen gas evolved from the anode was measured. The oxygen gas evolution is shown to be the main reaction on the anode at current density of 0,015 to 1,0 A·сm–2, and a substantial increase in the oxidation rate of the composite anode is observed at i = 0,015÷1,0 A·сm–2. The electrolyzer voltage (4,5±0,5 V) and the anode potential (2,43±0,2 relatively to the Al-reference electrode) during a long-term experiment (89 h, i = 0,4 A·сm–2) show stable and admissible composite electric conductivity; and the dissolution rate calculated from the mass loss (0,6 cm/year) and volume loss (0,7 cm/year) meets the requirements to inert anodes.

An investigation into dissolution behavior of pre-oxidized Ni-6Al-10Cu-11Fe-15Cr nickel base alloy in molten cryolite

Purpose– The purpose of this paper was the investigation of corrosion behaviour of Ni-6Al-10Cu-11Fe-15Cr alloy, as a candidate material for inert anodes in aluminium electrolysis industries.Design/methodology/approach– The samples were prepared by casting, and then were oxidized at 1,000°C for 30, 70 and 100 hours, respectively. To determine corrosion resistant of the samples, they were exposed to molten cryolite at 930°C for 70 hours. Then the surface layers were studied.Findings– Results showed that by extension of corrosion time, thickness of oxide layers increases. In addition, it was found that Al2O3 and Cr2O3 are the major oxide compounds that appear on the surface of the sample.Originality/value– In this paper, the Ni-6Al-10Cu-11Fe-15Cr nickel base alloy has been selected to study its corrosion behaviour in molten cryolite as a candidate for inert anodes. It was found out that by addition Al and Cr into the alloy composition, due to formation of Al2O3 and Cr2O3 following oxidation, the substrate was protected from corrosion attacks.

Cobalt Powder Production by Electro-Reduction of Co3O4 Granules in Molten Carbonates Using an Inert Anode

Electrochemical splitting of Co3O4 into cobalt powder and oxygen was realized by electrolysis in molten Na2CO3-K2CO3 at 1023 K using a solid oxide pellet cathode and a Ni11Fe10Cu alloy inert anode. The electro-reduction mechanism of Co3O4 was investigated in details by cyclic voltammetry measurements and potentiostatic electrolysis in a three-electrode cell combining with the composition and morphology characterization of the electrolytic products. The electro-reduction of Co3O4 in Na2CO3-K2CO3 melt mainly involves two steps by electrochemical formation of intermediate product of CoO and then the CoO is reduced to cobalt metal. NaxCoO2 intermediate was not detected by XRD measurements and EDX analysis, different from the electro-reduction of Fe2O3 in this melt. However, the particle size and morphology of the intermediate CoO is found to be dependent of the applied potential in the range of −0.35 V to −0.75 V vs. Ag/Ag2SO4 reference electrode. Metallic cobalt powder was prepared by potentiostatic electrolysis at potential more negative than −1.25 V (vs. Ag/Ag2SO4) or by constant cell voltage electrolysis under a cell voltage higher than 1.7 V using a Ni11Fe10Cu inert anode. A high current efficiency of 95.3% and a low electrolysis energy consumption of 2.16 kW·h/kg-Co represents a novel high efficiency and green process for Co extraction. The Co product is a mixture of FCC and HCP structure, which is affected by the applied cell voltage and deserves further investigation to recognize the structure controllable condition and mechanism.

纳米增韧Φ100 mm圆柱形NiFe<sub>2</sub>O<sub>4</sub>基惰性阳极的电解腐蚀行为研究

采用粉末冶金两步烧结法制备纳米增韧Φ100 mm圆柱形NiFe2O4基惰性阳极，通过10 h电解实验研究其电解腐蚀行为与机理。研究结果表明纳米增韧Φ100 mm圆柱形NiFe2O4基惰性阳极高温稳定性好，金属导杆和惰性阳极通过固相烧结扩散连接具备足够的高温强度和导电性能，电解过程中槽电压保持相对稳定。电解10 h后阳极没有发生开裂、肿胀、表面起层等现象，表现出较好的抗热震性能和耐腐蚀性能；产品铝纯度为98.02%，其中杂质主要为Fe、Ni和Cu，耐腐蚀性能需要进一步提升。NiFe2O4纳米粉的添加能够有效地增强阳极材料的晶界结合强度和降低气孔率，降低电解质组成渗入阳极内部几率，从而有效提高NiFe2O4基惰性阳极的耐熔盐腐蚀能力。 Nano toughened Φ100 mm cylindrical NiFe2O4 based inert anodes was prepared by powder me-tallurgy two-step sintering method. The electrolytic corrosion behavior and mechanism of NiFe2O4 based inert anodes were investigated by 10 h electrolysis experiment. The results show that the cell voltage keeps relatively stable, which is attributed to the good high temperature stability of nano toughened cylindrical NiFe2O4 based inert anode as well as the adequate high-temperature strength and conductivity of the solid state sintered connection between metal rod and inert anode. The electrolyzed inert anode has not undergone cracking or swelling, showing a suitable thermal shock resistance and corrosion resistance. The corrosion resistance should be enhanced for the purity of product aluminum was 98.02%, where the main impurities were Fe, Ni and Cu. The enhanced grain boundary bonding strength and decreased porosity, derived from the adding of NiFe2O4 nanopowder, can reduce the probability of electrolyte infiltration into the anode inside. As a result, the corrosion resistance of nano toughened NiFe2O4 based inert anodes has been improved effectively.

Metallic Nickel Preparation by Electro-Deoxidation in Molten Sodium Hydroxide

The preparation of nickel powders by electro-deoxidation of nickel oxide in molten sodium hydroxide at 550°C has been investigated. Cyclic voltammetry on different electrodes was applied to study the electrochemical reaction mechanism of the reduction of NiO in the melt. In addition, NiO pellets were reduced by constant voltage electrolysis for different times. The results disclose that the reduction of nickel oxide is a one-step reaction and the side reaction, hydrogen evolution, may lower the current efficiency during the constant voltage electrolysis. The current efficiency increases from 25.9% to 87.2% with the addition of sodium oxide which leads to a higher cathodic potential for the hydrogen evolution reaction and, therefore, prevents it occurring. With using an inert nickel anode, oxygen gas emits during the electrolysis.

Influence of the operating parameters over the current efficiency and corrosion rate in the Hall–Heroult aluminum cell with tin oxide anode substrate material

A systematic laboratory study was conducted on current efficiency and corrosion obtained in cryolite–alumina melts with SnO2–Sb2O3–CuO ceramic inert anodes. The current efficiency (CE) was determined by measuring the total amount of oxygen evolved at the anode and was found to be ~95%. The influence of operating parameters (inter-electrode distance, temperature and current density) was evaluated. The quantitative interdependencies as well as the ranges of CE optimal values were established (2–3cm, 940–960°C and 0.7–0.8A·cm−2). The corrosion process of these anodes was evaluated by the mass loss method. The evaluation also took care of the corrosion data, as the problem of the anode corrosion appeared to be the main obstacle for the use of those anodes in the commercial cells. Lowering of the ACD up to 2cm did not aggravate anode corrosion.

Electrochemical Conversion of CO2 into Negative Electrode Materials for Li‐Ion Batteries

AbstractThe capture and electrochemical conversion of CO2 in molten LiCl–Li2CO3 salt is proposed. By using an inert platinum anode and a tungsten cathode, the CO32− could be easily converted into carbon and oxygen gas, as well as O2−. The released O2− was responsible for the further capture of CO2. Also, CO2 could be effectively absorbed in such chloride melts with a low content of oxygen ion dissolved. In addition, the produced carbon displayed good performance as a negative electrode material for Li‐ion batteries, suggesting that the process is an environmentally friendly way to convert CO2 into energy‐storage materials.

Cold sprayed Cu–Ni–Fe anode for Al production

Inert anodes for Al electrolysis were produced by cold spray deposition of mechanical alloyed 65Cu20Ni15Fe powder. No structural change of the 65Cu20Ni15Fe alloy was observed during the cold spray processing apart from a small crystallite size increase. The electrochemical characterization was performed at 700°C in a potassium cryolite-based electrolyte. A progressive increase of the cell voltage was observed during the 50h of electrolysis. This is thought to reflect a decrease of the electrical conductivity of the anode attributed to the accumulation of electrolyte at the oxide/alloy interface and to the formation of insulating FeF2 precipitates in the bulk alloy.

Further Development on NiFe2O4-Based Cermet Inert Anodes for Aluminum Electrolysis

The new aluminum electrolysis technology based on inert electrodes has received much interest for several decades because of the environment and energy advantages. The key to realize this technique is the inert anode. This article presents China’s recent developments of NiFe2O4-based cermet inert anodes, which include the optimization of material performance, the joint between the cermet inert anode and metallic bar, as well as the results of 20 kA pilot testing for a large-size inert anode group. The problems NiFe2O4-based cermet inert anodes face are also discussed.

Consumable Anode Process for SnAg Electroplating

Near eutectic tin-silver (SnAg) is currently the alloy of choice for electroplated lead-free solder bumping and Cu pillar capping. While lead-tin (PbSn) is still used in some applications, there has been considerable momentum in moving away from the use of lead in semiconductor packaging. Both solders are normally electroplated as alloys with specific compositions to target a desired melting point. Since the deposition potentials of lead and tin are very close together, they plate with similar characteristics. This makes it possible for PbSn plating systems to use a consumable anode system where the anode composition matches the desired deposit composition. Metals are replenished into the bath in much the same ratio they are consumed. In a SnAg plating bath, the deposition potential of Ag is much more positive than Sn, so very low potential is required for Ag deposition. The plating rate of Ag is generally mass transfer limited. The plating rate of Sn is current controlled. While similar in concept to systems using consumable anodes for plating other metals, the SnAg alloy system presents some unique challenges. Because it is more noble, the Ag+ will deposit onto the Sn anode material by displacement reaction, and passivation will occur. Thus, the Sn anodes cannot come in contact with the Ag+ in the bath. Historically this problem is overcome by using an inert anode and metals replenishment by liquid concentrate. This paper outlines a method for plating SnAg using a consumable Sn anode, thereby reducing cost of ownership (CoO) and increasing bath stability compared to conventional SnAg wafer level packaging (WLP) plating.

Oxygen-evolving SnO2-based ceramic anodes in aluminium electrolysis

This study deals with SnO2-based ceramic anodes doped with Sb2O3 and CuO, aiming at contributing new data regarding their electrochemical behavior in cryolite melts. The performances of the anodes were evaluated by anodic polarization, cyclic voltammetry, and current efficiency and corrosion measurements. The investigation proves that the anodic process of SnO2-based inert anodes occurs at a low overvoltage and the oxygen discharge takes place in one step with an exchange of two electrons. The current efficiency and corrosion were proved to be dependent on the electrolysis parameters and composition of electrolysis bath. For a long term electrolysis, the dissolution of the anode in the cryolite-alumina melt produced small aluminium contamination(ca. 0.2%, mass fraction).

Porous Carbon Anodes for the Supply of Methane during Electrowinning of Aluminium

Currently consumable carbon anodes are utilized in the aluminium production process. The major drawback of this type of anodes is the high amount of CO2 emissions. Furthermore, due to the consumption of the anodes during the electrolysis it is necessary to adjust the anode – cathode distance continuously and finally replace the anode. Introduction of hydrogen or natural gas through the anode can decrease the CO2 emissions significantly and reduce the consumption of the anode. The use of inert porous anodes is interesting since the energy demand will be reduced due to natural gas/hydrogen participating in the anode reaction. However, due to unavailability of a sufficiently inert anode for aluminium electrolysis until now, carbon anodes seem to be more attractive. When natural gas/hydrogen is purged through the porous carbon anode, there will be competing anodic reactions depending on whether carbon from the anode or the CH4/H2 reacts with the oxygen ions from the bath. Previous studies using porous carbon anodes showed 0.3 V depolarization as well as 20% decrease in carbon anode consumption using methane compared to passing argon through the anode1. On the other hand, using CH4/H2 can lead to the formation and evolution of additional hydrogen fluoride. This was studied before and some ideas on how to deal with this extra HF evolution were presented2. In this study, further laboratory experiments were performed and the effect of carbon anodes with different porosities and designs were studied. Besides, off-gas analysis was performed and HF evolution will be discussed.

Physical-Chemical Properties of Potassium Cryolite-Based Melts Containing KBF4

Recent developments in the field of low-temperature aluminum electrolysis utilizing oxygen-evolving inert anodes prove the efficiency of potassium cryolite-based electrolytes. Such electrolytes give an opportunity to perform electrolysis at temperature below 800 °C. The potassium cryolite-based electrolytes can be used as prospective media for other electrochemical and chemical technological processes including aluminum alloys production. However, the introduction to the electrolytic bath the metal-containing additives along with alumina can result in electrolysis violation. It is a consequence of significant change in electrolyte properties with varied composition. In present work the KBF4impact on the physical-chemical properties of the potassium cryolite-based melts was studied.Liquidus temperature, electrical conductivity, density, alumina solubility in the KF-AlF3 and KF-NaF(15.9 mol%)-AlF3 molten mixtures containing KBF4 were determined. Cryolite ratio (CR), the ratio between molar concentrations of the alkali metal fluoride and aluminum fluoride (CR=NMF/NAlF3), was varied from 1.3 to 1.5. It should be mentioned that the cryolite ratio for the mixed KF-NaF-AlF3 cryolite melts was calculated as CR=(NKF+NNaF)/NAlF3. Elemental composition of the molten mixtures being studied was controlled by ICP analysis and X-ray fluorescence spectroscopy on XRF-1800 (Shimadzu).The liquidus temperature of the cryolite melts was measured by the specially developed thermal analysis technique. The data obtained in the KF-AlF3-KBF4 and KF-NaF(15.9 mol%)-AlF3-KBF4 systems showed that the liquidus temperature rises with the KBF4 content. It should be noted that the NaF, LiF, and CaF2, potential additives to the electrolyte for low-temperature electrolysis, being added to the KF-AlF3 melts with low CR, impact the liquidus temperature the same manner as KBF4.The alumina additions to the potassium cryolite-based melts decrease the liquidus temperature as it is shown in Fig.1. The quasi-binary “cryolite mixture”– alumina phase diagrams are simple eutectics. The KBF4 presence in the KF-NaF-AlF3-Al2O3 electrolytes shifts the eutectic point to the right and increases the alumina solubility in these melts. The eutectic points were found equal to 759 and 761°C at the Al2O3 content 4 and 5 mol%, respectively, in the [KF-NaF(15.9mol%)-AlF3+KBF4 (3mol%)]-Al2O3 and [KF-NaF(15.9 mol%)-AlF3+KBF4(5 mol%)]-Al2O3 mixtures with CR=1.3. The Al2O3addition of 6 mol% to the both electrolytes results in significant rise of the liquidus. The bend point on the cooling curves corresponding to the temperature of primary crystallization was not detected because the beginning temperature of the cooling process in these tests was below the liquidus. The presence of not dissolved deposit at the bottom of crucible at 850 °C was also confirmed by visual observation.The original technique to study the electrical conductivity of aggressive fluoride and oxide-fluoride melts was developed. It consists in combination of two types cells: capillary (BN) and with parallel electrodes (Mo). The resistivity of electrolyte was measured by means of impedancemeter (Zahner electrik IM6E) in a frequency range from 100 Hz to 1 MHz using a signal with amplitude 5 mV/s. The electrical conductivity of the potassium and potassium-sodium cryolites was measured in the capillary-type cell whereas the electrical conductivity of electrolytes with KBF4 and Al2O3additions was studied in the cell with parallel electrodes. The temperature dependence of a cell constant was taken into account that made the electrical conductivity measurements more accurate in a wide temperature range.The density of cryolite melts was measured using the Archimedean method. A platinum sphere suspended with platinum wire and attached to an electronic balance unit (Mettler AT20) was immersed into the electrolyte located in the glassy carbon crucible. The measurements were performed in the temperature range 700-800 °C. The temperature dependence of the Pt sphere volume was considered and determined in the calibration test with FLiNaK (eutectic). The density of the KF-AlF3-KBF4 melts decreases with increasing the KBF4 content. So, the addition of the KBF4 3 mol% reduces the density of the molten mixture on about 5%.

Density and Molar Volume of KF-NaF-AlF3 Melts with Al2O3 and CaF2 Additions

The ability to dissolve alumina makes the sodium cryolite melt applicable for the primary aluminum production despite the high liquidus temperature of the melt. Numerous cryolite based compositions are used by aluminum smelters nowadays. The majority of industrial baths contain various salt additions intended to improve physical and chemical properties of the melt, as well as the overall process parameters. Nevertheless, the question of an appropriate medium for the inert anode application remains relevant in the aluminum industry because of high corrosion activity of fluoride melts at temperatures around 950 ºC. Lowering the operating temperature by means of reducing the liquidus temperature seems an advantageous approach to extend the implementation of the technology with the oxygen evolving inert anode.Recently KF-NaF-AlF3 melts with low cryolite ratio have been recognized a prospective medium for the new environmentally benign technology for the primary aluminum production [1,2]. The change in the chemical composition of the melt affects noticeably its physical and chemical properties. The electrolyte density is one of the properties dramatically affecting the technological parameters of the electrolytic cell.The density of conventional electrolytes for the aluminum production has been well studied [3,4] however, the need to scrutinize the physical and chemical properties of low melting electrolytes is clearly warranted. Yan with coauthors [5] addressed the KF-NaF-AlF3 melt with a different NaF content at (([KF] + [NaF])/[AlF3]) 1.3 and 1.41 but data presented concerning the influence of alumina and calcium fluoride are scarce.The aim of the present work was to study the density and molar volume of the KF-NaF-AlF3 system at CR=1.3, 1.5, with Al2O3 and CaF2 additions by the Archimedean method in the temperature range 920–1150 K.In the present work the cryolite ratio was defined as a ratio between molar concentrations of the alkali metal fluoride and aluminum fluoride (CR=NMF/NAlF3) – for the mixed cryolite melts (KF-NaF-AlF3) was calculated as CR=(NKF+NNaF)/NAlF3.Analysis of the data obtained for the density of low-melting cryolite mixtures illustrates the existence of some general regularities and specific features of the melts under study. Over a broad interval of the SCR, the molar volume of the melt rises upon the replacement of sodium fluoride with the potassium one (Fig. 1). The molar volume was shown to decrease with the CR rise. The calcium fluoride additives cause the density increase and molar volume depression (Fig. 2). The alumina additions up to 6 mol.% did not show to significantly change either the density or the molar volume of the melts.References Redkin, A.; Apisarov, A.; Dedyukhin, A.; Kovrov, V.; Zaikov, Yu.; Tkacheva O.; and Hryn J. Recent Developments in Low-Temperature Electrolysis of Aluminum. ECS Trans. 2013, 50 (11), 205-213.Tkacheva, O. J. Hryn, J. Spangenberger, B. Davis, T. Alcorn Operating parameters of aluminum electrolysis in KF-AlF3 based electrolytes. Light Metals. – 2012. - P. 675-680Fellner, P.; Haarberg, G.M.; Hives, J.; Kvande, H.; Sterten A.;, Thonstad, J. Aluminium Electrolysis. 3 rd Edition – Aluminium; Verlag: Dusseldorf, 2001.Fernandez, R.; Ostvold, T. Surface Tension and Density of molten Fluorides and Fluoride Mixtures Containing Cryolite. Acta Chemica Scandinavica 1989, 43, 151-159.Yan, H.; Yang, J.; Li, W. Surface Tension and Density in the KF-NaF-AlF3-Based Electrolyte. J. Chem. Eng. Data 2011, 56, 4147-4151.

Current Efficiency, Corrosion and Structural Changes in SnO2-Sb2O3-CuO Inert Anodes for Aluminium Electrolysis

A systematic study was conducted on current efficiency (CE), corrosion and structural changes in SnO2-based inert anodes (made of 96wt%SnO2+2wt%Sb2O3+2wt%CuO) on a laboratory Hall-Heroult aluminium cell. The influence of operating parameters and electrolyte composition on the CE and corrosion process were evaluated. The CE was found to be more than 90% and catastrophic corrosion took place at low percent of Al2O3, high percent of LiF, low cryolite ratio and high current densities. From all the structural changes that took place in the SnO2-based inert anodes, we assumed that the most important contribution was due to the migration of CuO towards the outer limits of the constituent grains of SnO2 based ceramic. The complex process occurred during the formation of various phases and their sintering ability both directly depended on Cu/Sb molar ratio.