Anti-oxidation coating for anode of aluminum electrolysis cell and preparation method of anti-oxidation coating

Abstract

The invention discloses an anti-oxidation coating for an anode of an aluminum electrolysis cell. The anti-oxidation coating comprises the following raw materials in percentage by mass: 40-55% of a refractory base material, 15-25% of a high-temperature binder, 5-15% of a filler, 2-8% of an auxiliary agent and the balance of a water solvent, the base material, the silicon carbide powder and the zirconium oxide powder are compounded, and the high-temperature binder is added, so that the high-temperature oxidation resistance of the coating is improved, cracking and stripping caused by thermal stress can be resisted, and the service life of the coating is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of aluminum electrolysis cell technology, and particularly relates to an antioxidant coating for the anode of aluminum electrolysis cells and its preparation method. Background Technology

[0002] In the aluminum electrolysis production process, the anode, as a conductive material and a core component participating in the electrochemical reaction, needs to operate continuously at temperatures as high as approximately 950°C. Furthermore, at these high temperatures, the anode surface undergoes oxidation reactions with O2 and CO2, leading to excessive anode consumption and the generation of large amounts of carbon slag. This not only increases net anode consumption and production costs but also disrupts the thermal balance and stability within the electrolytic cell, affecting current efficiency.

[0003] To slow down anode oxidation, existing technologies often involve spraying or brushing an anti-oxidation coating onto the anode surface. Currently, commonly used coatings are mainly divided into two categories: one type is based on inorganic materials such as aluminum powder and glass powder, which forms a dense oxide layer or molten glassy isolation layer on the anode surface to block oxygen; the other type uses phosphates, silicates, etc., as binders, combined with refractory aggregates.

[0004] In the existing technology, some coatings use inorganic materials such as aluminum powder and glass powder as base materials, which have poor thermal shock resistance and are prone to cracking and peeling during the heating and cooling process of the electrolytic cell; some coatings use silicate binders, which are prone to glass transition and loss of strength at high temperatures and cannot withstand electrolyte corrosion for a long time.

[0005] Therefore, it is necessary to develop an anodizing anti-oxidation coating with strong adhesion, excellent antioxidant properties, and good high-temperature stability to overcome the shortcomings of existing technologies. Summary of the Invention

[0006] Purpose of the invention: The technical problem to be solved by the present invention is to provide an anti-oxidation coating for the anode of aluminum electrolytic cells and its preparation method, so as to solve the problems of easy peeling and poor high temperature resistance of the coating in the prior art.

[0007] Technical solution: The anti-oxidation coating for aluminum electrolytic cell anodes described in this invention comprises the following raw materials by mass percentage: 40%-55% refractory base material, 15%-25% high-temperature binder, 5%-15% filler, 2%-8% additives, and the balance being water solvent.

[0008] Furthermore, the refractory base material includes one or both of nano-sized α-Al2O3 powder and nano-sized silicon dioxide.

[0009] Furthermore, the high-temperature adhesive comprises water glass and water-soluble phenolic resin, wherein the water-soluble phenolic resin accounts for 10-15% of the mass of the high-temperature adhesive.

[0010] Furthermore, the filler comprises silicon carbide powder and zirconium oxide powder in a mass ratio of 1:(0.3-1).

[0011] Furthermore, the additives include rare earth oxides, dispersants, and defoamers in a mass ratio of 1:(0.5-0.75):(0.25-0.5).

[0012] Furthermore, the rare earth oxide is one or more of Y2O3 and CeO2.

[0013] Furthermore, the dispersant is sodium polyacrylate.

[0014] Furthermore, the defoamer is an organosilicone defoamer.

[0015] The present invention also provides a method for preparing the above-mentioned antioxidant coating for the anode of aluminum electrolytic cells, comprising the following steps:

[0016] (1) Mix the refractory base material and filler evenly and add water solvent, mix and stir evenly to form a slurry;

[0017] (2) Mix the high-temperature adhesive evenly at a temperature of 60-70℃ to form a sol;

[0018] (3) Add the sol to the slurry and mix evenly. Then add the additives to disperse and defoam to form a coating.

[0019] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are: by combining the base material with silicon carbide powder and zirconium oxide powder and adding a high-temperature binder, the high-temperature oxidation resistance of the coating is improved, while resisting cracking and peeling caused by thermal stress, thus improving the service life of the coating. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0021] All materials used in this invention are commercially available. The water glass consists of sodium water glass (NaO·3SiO2) and potassium water glass (K2O·3SiO2) in a mass ratio of 1:1.

[0022] Example 1

[0023] An anti-oxidation coating for the anode of an aluminum electrolytic cell, comprising:

[0024] The rare earth oxides used are as follows. The specific preparation method is as follows: 5 kg α-Al₂O₃, 2.25 kg water glass, 0.25 kg water-soluble phenolic resin, 1 kg silicon carbide, 0.5 kg zirconium oxide, 0.4 kg Y₂O₃, 0.2 kg sodium polyacrylate, and 0.2 kg organosilicon defoamer, with the balance being deionized water. The preparation method of the antioxidant coating for the anode of the aluminum electrolytic cell is as follows:

[0025] (1) Place α-Al2O3 powder, silicon carbide and zirconium oxide in a planetary ball mill, add water, and ball mill at 350 rpm for 4 hours to obtain a slurry;

[0026] (2) Sodium silicate and potassium silicate are heated to 60°C in a water bath and then mixed and stirred to form silicate. Then, water-soluble fractional resin is added and stirred for 3 hours to obtain a sol formed by high-temperature binder.

[0027] (3) Add sol, rare earth oxides and sodium polyacrylate to the slurry and stir to disperse. Then add organosilicon defoamer to defoam and stir evenly to obtain coating.

[0028] Example 2

[0029] An anti-oxidation coating for the anode of an aluminum electrolytic cell, comprising:

[0030] The rare earth oxides used are as follows. The specific preparation method is as follows: 4 kg α-Al₂O₃, 1.7 kg water glass, 0.3 kg water-soluble phenolic resin, 0.5 kg silicon carbide, 0.5 kg zirconium oxide, 0.3 kg Y₂O₃, 0.2 kg sodium polyacrylate, and 0.1 kg organosilicon defoamer, with the balance being deionized water. The preparation method of the antioxidant coating for the anode of the aluminum electrolytic cell is as follows:

[0031] (1) Place α-Al2O3 powder, silicon carbide and zirconium oxide in a planetary ball mill, add water, and ball mill at 400 rpm for 4 hours to obtain a slurry;

[0032] (2) Sodium silicate and potassium silicate are heated to 70°C in a water bath and then mixed and stirred to form silicate. Then, water-soluble fractional resin is added and stirred for 3 hours to obtain a sol formed by high-temperature binder.

[0033] (3) Add sol, rare earth oxides and sodium polyacrylate to the slurry and stir to disperse. Then add organosilicon defoamer to defoam and stir evenly to obtain coating.

[0034] Example 3

[0035] An anti-oxidation coating for the anode of an aluminum electrolytic cell, comprising:

[0036] The rare earth oxides used are as follows. The specific preparation method is as follows: 5.5 kg α-Al₂O₃, 1.7 kg water glass, 0.3 kg water-soluble phenolic resin, 0.5 kg silicon carbide, 0.5 kg zirconium oxide, 0.4 kg CeO₂, 0.2 kg sodium polyacrylate, and 0.2 kg organosilicon defoamer, with the balance being deionized water. The preparation method of the antioxidant coating for the anode of the aluminum electrolytic cell is as follows:

[0037] (1) Place α-Al2O3 powder, silicon carbide and zirconium oxide in a planetary ball mill, add water, and ball mill at 350 rpm for 4 hours to obtain a slurry;

[0038] (2) Sodium silicate and potassium silicate are heated to 60°C in a water bath and then mixed and stirred to form silicate. Then, water-soluble fractional resin is added and stirred for 3 hours to obtain a sol formed by high-temperature binder.

[0039] (3) Add sol, rare earth oxides and sodium polyacrylate to the slurry and stir to disperse. Then add organosilicon defoamer to defoam and stir evenly to obtain coating.

[0040] The coatings prepared in Examples 1-3 were uniformly sprayed onto the surface of industrial prebaked anode test blocks of the same size, with the coating thickness controlled at 0.5 mm. After drying at 150°C for 2 hours, the following tests were performed:

[0041] 1. High-temperature oxidation resistance test: The coated anode specimens were placed in a muffle furnace at 950℃ and oxidized at a constant temperature in air for 10 hours. After cooling, they were weighed, and the oxidation weight loss rate of the anodes was calculated. The lower the oxidation weight loss rate, the better the oxidation resistance.

[0042] 2. Thermal shock resistance test: The coated anode specimen was kept at 950℃ for 15 minutes, then quickly removed and cooled to room temperature in air. This constitutes one cycle. The coating was observed to determine whether cracking, peeling, or flaking occurred after 10 cycles. The properties of the coatings prepared in Examples 1-3 are shown in Table 1.

[0043] Table 1 sample Oxidative weight loss rate (%) thermal shock resistance Example 1 1.8 The coating is intact and no cracks are visible. Example 2 2.3 Minor microcracks at the edge of the coating Example 3 2.0 The coating is intact and no cracks are visible.

[0044] This solution uses water glass and water-soluble resin to form a high-temperature binder, which can form an interpenetrating network structure at high temperatures, improving the material's high-temperature resistance and adhesion. The addition of rare earth oxides significantly improves the antioxidant properties. The filler fills the voids in the coating at high temperatures, improving its density. Furthermore, zirconium oxide can inhibit coating crack propagation through the martensitic phase transformation toughening effect at high temperatures. As can be seen from the performance data in Table 1, the system of this invention can make the coating have superior antioxidant properties, while also reducing cracking and further peeling caused by thermal stress.

Claims

1. An antioxidant coating for the anode of an aluminum electrolytic cell, characterized in that, It includes the following raw materials by weight percentage: 40%-55% refractory base material, 15%-25% high-temperature binder, 5%-15% filler, 2%-8% additives, and the balance being water solvent.

2. The anti-oxidation coating for the anode of an aluminum electrolytic cell according to claim 1, characterized in that, The refractory base material includes one or both of nano-sized α-Al2O3 powder and nano-sized silicon dioxide.

3. The anti-oxidation coating for the anode of an aluminum electrolytic cell according to claim 1, characterized in that, The high-temperature adhesive comprises water glass and water-soluble phenolic resin, wherein the water-soluble phenolic resin accounts for 10-15% of the mass of the high-temperature adhesive.

4. The anti-oxidation coating for the anode of an aluminum electrolytic cell according to claim 1, characterized in that, The filler comprises silicon carbide powder and zirconium oxide powder in a mass ratio of 1:(0.3-1).

5. The anti-oxidation coating for the anode of an aluminum electrolytic cell according to claim 1, characterized in that, The additives include rare earth oxides, dispersants, and defoamers in a mass ratio of 1:(0.5-0.75):(0.25-0.5).

6. The anti-oxidation coating for the anode of an aluminum electrolytic cell according to claim 1, characterized in that, The rare earth oxide is one or more of Y2O3 and CeO2.

7. The anti-oxidation coating for the anode of an aluminum electrolytic cell according to claim 1, characterized in that, The dispersant is sodium polyacrylate.

8. The anti-oxidation coating for the anode of an aluminum electrolytic cell according to claim 1, characterized in that, The defoamer is an organosilicone defoamer.

9. A method for preparing an antioxidant coating for the anode of an aluminum electrolytic cell as described in any one of claims 1-8, characterized in that, Includes the following steps: (1) Mix the refractory base material and filler evenly and add water solvent, mix and stir evenly to form a slurry; (2) Mix the high-temperature adhesive evenly at a temperature of 60-70℃ to form a sol; (3) Add the sol to the slurry and mix evenly, then add the additives to disperse and defoam to form a coating.