Study On The Corrosion Resistance Of Eu₂O₃-magnesium Aluminum Spinel Side Wall Material For Aluminum Electrolysis Cel

The current method for melting primary aluminum is still the well-known Hall-Héroult process.To protect this sidewall material,the electrolysis process usually extends the life of the sidewall and the aluminum electrolytic cells by continuously forming and maintaining the furnace gang.The heat dissipated through the sidewall for the formation and maintenance of the furnace gang is huge,about 35%of the total energy consumption of the electrolysis process,which seriously affects the energy efficiency of the aluminum electrolytic cells.In order to achieve the goal of dual control of energy consumption in the aluminum electrolysis industry,furnaceless electrolytic cell aluminum smelting has become the first choice,which puts forward extremely high requirements for the corrosion resistance of sidewall materials.Magnesia aluminum spinel is seen as a potential sidewall material.However,on the basis of sintering additives synergistically enhancing the sinterability and corrosion resistance of MgAl₂O₄,there are few studies on the thermodynamics and corrosion behavior dynamics in low-temperature electrolytes.Therefore,this paper aims to study the effect of sintering additives on the corrosion resistance of MgAl₂O₄,the corrosion behavior of MgAl₂O₄ in different electrolytes,and the influence of different corrosion times on the corrosion resistance behavior of MgAl₂O₄ under different superheat,and the following conclusions are drawn by characterizing its relative density,phase composition,microstructure,cross-sectional microstructure and XRF content in electrolyte:（1）During the sintering process of MgAl₂O₄ samples with Eu₂O₃ added,Eu³⁺will enter the lattice of MgAl₂O₄to form a solid solution,strengthen the lattice structure of MgAl₂O₄,promote mass transfer and diffusion,improve the growth rate and uniformity of MgAl₂O₄ grains during sintering,and improve the density and hardness of the samples.In addition,Eu₂O₃ reacts with MgAl₂O₄ to form a second phase Al Eu O₃ that fills the grain gap of MgAl₂O₄,strengthening the interaction between grains.The optimal amount of Eu₂O₃ added was 3 wt.%.It was confirmed by pre-corrosion experiments that the corrosion depth of MgAl₂O₄ added with Eu₂O₃ was significantly reduced.The corrosion depth of MgAl₂O₄ at the optimum Eu₂O₃ addition amount（3 wt.%）was effectively reduced by 75.3%compared with that without addition,and the corrosion resistance was significantly improved.（2）The samples analysis of MgAl₂O₄ after corrosion in 6 different electrolytes was showed in SEM-EDS and XRF,it can be concluded that the E1 electrolyte（41.30%KF-2.20%Na F-50.00%Al F3-5.00%Al2O3）has a low initial crystal temperature and the lowest corrosion degree to MgAl₂O₄,and its corrosion depth is 54.08μm;from the EDS line scan results and reaction equation,it can be concluded that the reaction between MgAl₂O₄ and electrolyte is actually reacted with Al F₃ in the electrolyte to generate metal fluoride-MgF₂.Thermodynamic analysis showed that MgAl₂O₄ had excellent chemical stability in each electrolyte system.（3）Under different corrosion temperatures,the micromorphology of the corrosion sample becomes rough with the increase of corrosion time,the corrosi on rate is faster in the early stage of corrosion,and the corrosion rate slowly decreases after 6 hours,which may be due to the loss of magnesium in the spinel on the surface,and the electrolyte may slowly develop in the direction parallel to the surface of the sample through some pores of the surface corrosion,so the average corrosion rate slows down.Corrosion behavior kinetic studies have shown that at a temperature of 790°C,the initial corrosion rate is the fastest,the corrosion depth is the deepest,and the magnesium content in the electrolyte solution is also high.