Tests for Resistance to Cryolite: Methods and Comparative Evaluation

Simakov, Dmitry A.; Proshkin, A. V.; Polyakov, P. V.

doi:10.1023/b:refr.0000036728.31305.55

Cited by 4 publications

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“…There is information about tests of refractory materials for cryolite resistance. Different test procedures, their characteristics and comparisons are provided in [1,2].…”

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“…There is information about tests of refractory materials for cryolite resistance. Different test procedures, their characteristics and comparisons are provided in [1,2].Data from laboratory studies are provided in this article for the resistance of aluminosilicate refractories ShA-5, ShPD-43 and ShPD M -45 [3] to the action of a commercial electrolyte with a cryolite ratio (c.r.) of 2.4.…”

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Prospects for using aluminosilicate refractories for aluminum electrolyzers. Part 2. Resistance of aluminosilicate refractories to the action of commercial electrolyte

et al. 2007

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Data are provided for laboratory studies of the resistance of aluminosilicate refractories to the action of commercial electrolyte. It is established that refractory ShPD M -45, prepared using a mullite-corundum chamotte, is most resistant to electrolyte action. Results are provided for studies in the change of mineral composition and phase transformations in aluminosilicate refractories during reaction with commercial electrolyte. It is shown that long-prismatic titanium-containing mullite is more resistant to the action of the fluoride ion than short-prismatic material.The service life of an aluminum electrolyzer is mainly governed by the resistance of refractory linings of the cathode assembly to the action of an incoming corrosive medium. There is information about tests of refractory materials for cryolite resistance. Different test procedures, their characteristics and comparisons are provided in [1,2].Data from laboratory studies are provided in this article for the resistance of aluminosilicate refractories ShA-5, ShPD-43 and ShPD M -45 [3] to the action of a commercial electrolyte with a cryolite ratio (c.r.) of 2.4. Tests were performed by a petrographic method in reflected and transmitted light in MBI-6 and MIN-8 microscopes respectively. The resistance of aluminosilicate refractories in contact with molten commercial electrolyte was determined with a steady-state method by heating test articles in a Tamman furnace followed by a study of the change in mineral and phase composition of the refractories. Cylindrical holes of identical diameter and depth were made in articles, and they were filled with a uniform amount of commercial electrolyte with c.r. of 2.4 containing, apart from the main components, calcium and magnesium fluorides. The prepared samples were placed in a hermetically sealed alundum crucible and heated in a Tamman furnace to 1000°C with isothermal soaking at 1000°C for 1 h. Cooling took place in the furnace.After testing refractory specimens changed in color. At the surface of specimens from the side of the opening reaction zones were seen in the form of concentric circles of different color. The diameter of the original hole increased (Fig. 1), and its relative increase for specimens of ShA-5, ShPD-43, and ShPD M -45 was 47.5, 33.3 and 16.1% respectively.A specimen of ShA-5 after testing had a dingy lilac color. Over its surface (at the top of the hole and over the side) glassy new formations were seen in the form of circles with a diameter of 4 mm and leakages from the direction of the depression (hole), i.e. coarse pores with a diameter of 1.0 -1.5 mm. The electrolyte was converted into glass. With separation over the length of the depression two zones seen: a working zone 5 -10 mm thick of green color, and a glassy and transition zone yellow in color. The base of the specimen was the least changed zone (Fig. 2a ).A specimen of ShPD-43 after testing had a gray color. At its surface from the direction of the hole in the form of circles there was a working zone green in color and then t...

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“…There is information about tests of refractory materials for cryolite resistance. Different test procedures, their characteristics and comparisons are provided in [1,2].…”

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confidence: 99%

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confidence: 99%

Prospects for using aluminosilicate refractories for aluminum electrolyzers. Part 2. Resistance of aluminosilicate refractories to the action of commercial electrolyte

et al. 2007

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“…In accordance with the procedure described in [8], a specimen with a through hole 36 mm in diameter was placed on a specimen of a product with an area of 100´100 and a thickness of 64 mm. The hole in the upper specimen was drilled with a diamond bit and filled with electrolyte with a CR = 6.2.…”

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Comprehensive solution for lining the socle of an electrolyzer with contemporary refractories and heat insulating materials

Sakulin¹,

Skurikhin²,

Migal³

et al. 2007

Refract Ind Ceram

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“…Many aluminum manufacturers rely on the in-house methods of testing refractory materials for resistance to molten fluorides. Various testing methods have been described in some detail in [4].In this paper we are concerned with a method that has been in use over more than two years at the RUSAL Co. and Legkie Metally Research and Technology Center to test refractory materials for cryolitic resistance. The method is based on the direct attack of molten fluorides on test specimen that has formerly been suggested by Allaire and coworkers [5].…”

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Barrier materials tested for cryolitic resistance methodology and expertise

et al. 2006

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A method for testing barrier materials for cryolitic resistance to corrosive attack by molten fluoride and aluminum has been described. The method allows good reproducibility of measurements; an error analysis is given, factors affecting the accuracy of experiment are discussed, and ways of its improvement are suggested.As soon as an aluminum electrolysis cell is put in operation, its cathode blocks are fed with sodium and electrolyte. The electrolyte transfer is greatly assisted by sodium, which is formed by the reactions Al(liq) + 3NaF = 3Na (in C) + AlF 3 ,Na + + e -® Na (in Al).Sodium penetrates into the bottom block to render it wettable by molten fluoride; in this process, the front of molten fluoride is followed by a sodium front [1].The rate at which sodium penetrates into the bottom block is controlled by the blocks's material. Increasing the degree of graphitization of bottom blocks causes a significant decrease in sodium penetration rate [1]. A laboratory study has shown that the rate at which sodium penetrates into graphite is high enough -from 10 to 30 mm/h at 900°C [2]. For an amorphous graphite it was still higher, reaching 40 to 60 mm/h [2]. It is seen therefore that the life of a electrolysis cell is mainly controlled by the resistance to aggressive attack of barrier materials of the lining underlying the bottom blocks. Consequently, the choice of an appropriate barrier material is a major concern for technologists. Many aluminum manufacturers rely on the in-house methods of testing refractory materials for resistance to molten fluorides. Various testing methods have been described in some detail in [4].In this paper we are concerned with a method that has been in use over more than two years at the RUSAL Co. and Legkie Metally Research and Technology Center to test refractory materials for cryolitic resistance. The method is based on the direct attack of molten fluorides on test specimen that has formerly been suggested by Allaire and coworkers [5]. EXPERIMENTAL CELL AND TESTING UNITA schematic diagram of the cell for testing refractory materials is shown in Fig. 1. A specimen of refractory material 80 AE 54 AE 68 15 4 3 2 1 Fig. 1. Schematic diagram of a cell for testing refractory material for corrosive attack by electrolyte and aluminum: 1 ) graphite beaker; 2 ) specimen; 3 ) aluminum; 4 ) electrolyte.

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Tests for Resistance to Cryolite: Methods and Comparative Evaluation

Cited by 4 publications

References 2 publications

Prospects for using aluminosilicate refractories for aluminum electrolyzers. Part 2. Resistance of aluminosilicate refractories to the action of commercial electrolyte

Prospects for using aluminosilicate refractories for aluminum electrolyzers. Part 2. Resistance of aluminosilicate refractories to the action of commercial electrolyte

Comprehensive solution for lining the socle of an electrolyzer with contemporary refractories and heat insulating materials

Barrier materials tested for cryolitic resistance methodology and expertise

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