Aluminum electrolysis carbon anode anti-oxidation coating and preparation method thereof

Abstract

The invention relates to the technical field of aluminum electrolysis metallurgy, in particular to an aluminum electrolysis carbon anode anti-oxidation coating and a preparation method thereof. The coating is prepared from the following raw materials in percentage by mass: 45-60% of aluminum oxide powder; 15 to 25% of water glass; 8-12% of potassium feldspar powder; 0.5 to 2% of sodium fluoride; 7-11% of sodium acetate trihydrate; 8-12% of ionized water; the preparation method comprises the following steps: S1, preparing the catalytic compact component; s2, mixing the coating; s3, coating and drying; and S4, carrying out high-temperature calcination. The product provided by the invention has good oxidation resistance, adhesive force and compactness, and the preparation method provided by the invention has the advantages of simple process and low cost.

Description

An anti-oxidation coating for aluminum electrolysis carbon anode and its preparation method Technical Field

[0001] This application relates to the field of aluminum electrolytic metallurgy technology, specifically to a high-temperature anti-oxidation coating for protecting prebaked carbon anodes in aluminum electrolytic cells and its preparation method. Background Technology

[0002] In aluminum electrolysis production, prebaked carbon anodes undergo severe oxidation reactions at high temperatures (approximately 950℃) and in highly oxidizing atmospheres (containing CO2 and O2), leading to excessive consumption. Theoretically, producing 1 ton of aluminum requires only 334 kg of carbon anodes, but in reality, consumption reaches 460-500 kg, accounting for over 15% of the total aluminum production cost. This not only increases production costs but also generates a large amount of carbon slag, affecting the stable operation of the electrolytic cell.

[0003] To reduce oxidation consumption of carbon anodes, coating the anode surface with an anti-oxidation coating is an economical and effective method. Various coating formulations exist in the current technology, but they generally suffer from problems such as easy cracking, poor adhesion, unstable structure at high temperatures, and unsatisfactory anti-oxidation effects. For example, some coatings cannot form a stable ceramic phase at high temperatures, resulting in limited protective effects; others are prone to peeling due to a mismatch in thermal expansion coefficients with the carbon anode substrate.

[0004] Therefore, developing a coating material that can form a stable, dense, and firmly adhered ceramic phase at high temperatures and significantly reduce carbon anodizing consumption is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an aluminum electrolytic carbon anode anti-oxidation coating with excellent anti-oxidation properties, strong adhesion, and good high-temperature stability, as well as its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An anti-oxidation coating for aluminum electrolysis carbon anodes is prepared from the following raw materials in the indicated mass percentages:

[0008] Alumina (Al2O3): 45-60%, used as the ceramic matrix for coatings, and is the main component for forming high-temperature stable phases;

[0009] Water glass (Na2O·nSiO2): 15-25%, as a binder and film-forming agent, provides initial adhesion and participates in the reaction;

[0010] Potassium feldspar powder (KAlSi3O8): 8-12%, as a catalytic densifying component, promotes the formation of a eutectic glass phase at high temperatures, fills pores, and improves densification;

[0011] Sodium fluoride (NaF): 0.5-2%, as a flux and catalytic densifying component, lowers the melting temperature of the system and accelerates the sintering densification process;

[0012] Sodium trihydrate (CH3COONa·3H2O): 7-11%, as an alkali metal co-catalytic component, provides active alkali metal ions during the heating decomposition process, promoting phase transformation;

[0013] Deionized water: 8-12%, used as a solvent to adjust the viscosity of the coating.

[0014] Preferably, the raw materials are in the following mass percentages: alumina: 50%, water glass: 20%, potassium feldspar powder: 10%, sodium fluoride: 1%, sodium acetate trihydrate: 9%, and deionized water: 10%.

[0015] Preferably, after high-temperature calcination, the main phase of the coating is corundum phase α-Al2O3.

[0016] Another object of the present invention is to provide a method for preparing the above-mentioned coating, a method for preparing an anti-oxidation coating for an aluminum electrolytic carbon anode, comprising the following steps:

[0017] S1. Preparation of catalytic compacting component: Weigh sodium fluoride and sodium acetate trihydrate according to the formula, pour them into a mortar and grind them together. Then pour the ground powder and potassium feldspar powder into a container, add the formula amount of deionized water, stir evenly, and obtain catalytic compacting component.

[0018] S2. Coating Mixing: The catalytic dense component obtained in step S1 is mixed with alumina powder and water glass. The mixture is stirred thoroughly with a mechanical stirrer (such as an egg beater) until it is homogeneous and free of lumps, thus obtaining the desired antioxidant coating.

[0019] S3. Coating and Drying: Apply the coating obtained in step S2 evenly to the pretreated carbon anode surface using a brush. Dry using a segmented drying process.

[0020] S4. High-temperature calcination: The dried carbon anode coated with paint is placed in a high-temperature furnace and calcined in an air atmosphere at 900-1000℃ for 0.5-2 hours. Then it is naturally cooled to room temperature, which forms a dense and firmly adhered antioxidant coating on the surface of the carbon anode.

[0021] Preferably, the specific process in step S3 is as follows: First, coat the top and bottom surfaces of the carbon anode with a coating thickness of approximately 0.5 mm, then place it in a forced-air drying oven at 40-50℃ and dry for 10-20 minutes. After the bottom surface is dry, coat the sides of the carbon anode and dry them at 40-50℃ for 10-20 minutes. This process is repeated to ensure that each surface of the carbon anode is coated twice and dried twice, thus ensuring the uniformity and adhesion of the coating.

[0022] Preferably, the calcination temperature in step S4 is 950°C and the holding time is 1 hour.

[0023] In summary, this application has the following beneficial effects:

[0024] 1. Excellent oxidation resistance: Through a unique formulation design, this invention transforms the main phase of the coating into the corundum phase α-Al₂O₃ after high-temperature calcination. The corundum phase possesses extremely high thermal stability and chemical inertness, effectively preventing oxygen and CO₂ from contacting the carbon anode, significantly reducing the oxidation weight loss rate of the anode. Experiments show that the average oxidation weight loss rate of this coating can be reduced by approximately 67%, far superior to other comparative formulations.

[0025] 2. Excellent adhesion and density: Using water glass as a binder, combined with a segmented coating and drying process, the coating adheres tightly to the carbon anode substrate, exhibiting no cracking or peeling after high-temperature calcination. Potassium feldspar powder and sodium fluoride, as catalytic densifying components, form a glassy phase at high temperatures, effectively filling the coating pores, resulting in a dense structure and barrier effect.

[0026] 3. Simple process and low cost: All raw materials are common industrial raw materials, resulting in low cost. The preparation process is simple and easy to operate, making it very suitable for industrial production and application.

[0027] 4. Improved overall performance: The coating of this invention can effectively extend the service life of carbon anodes and reduce carbon consumption per ton of aluminum, which is of great practical significance for energy conservation, emission reduction and green production in the aluminum electrolysis industry. Attached Figure Description

[0028] Figure 1 is a line graph showing the oxidation weight loss rate of different formulations in this application.

[0029] Figure 2 shows the morphology of calcined carbon blocks with different formulations in this application; where A is the calcined carbon block of formulation 1; B is the calcined carbon block of formulation 2; and C is the calcined carbon block of formulation 3.

[0030] Figure 3 is the XRD analysis diagram of formulation 1 in this application, where A is the main XRD phase of formulation 1 before calcination; and B is the main XRD phase of formulation 1 after calcination. Detailed Implementation

[0031] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] Example 1

[0033] An anti-oxidation coating for aluminum electrolysis carbon anodes is prepared from the following raw materials in the indicated weight percentages: alumina powder: 50%; water glass: 20%; potassium feldspar powder: 10%; sodium fluoride: 1%; sodium acetate trihydrate: 9%; deionized water: 10%.

[0034] A method for preparing an anti-oxidation coating for carbon anodes in aluminum electrolysis includes the following steps:

[0035] S1. Preparation of catalytic compaction component: Weigh 1g of sodium fluoride and 9g of sodium acetate trihydrate, mix them and grind them in a mortar. Then put the ground powder into a planetary ball mill and ball mill it until the particle size is about 100 mesh. Weigh 10g of potassium feldspar powder and pour it into the mixed powder. Add 10ml of deionized water and stir evenly to obtain catalytic compaction component.

[0036] S2. Coating mixing: Weigh 50g of alumina powder and 20g of water glass (about 12ml) and mix with the catalytic densifying component obtained in step S1. Use a whisk to stir the mixture evenly to obtain an antioxidant coating.

[0037] S3. Coating and Drying: Apply the coating evenly to the cylindrical carbon anode sample with a diameter of 50mm × 50mm. First, coat the top and bottom surfaces and dry at 45℃ for 15 minutes. After the bottom surfaces are dry, coat the sides and dry at 45℃ for 15 minutes. Repeat this process once.

[0038] S4. High-temperature calcination: The dried carbon anode coated with paint is placed in a muffle furnace and heated to 950°C at a certain heating rate. After holding at this temperature for 1 hour and then naturally cooling, the antioxidant coating is formed on the surface of the carbon anode.

[0039] Example 2

[0040] An anti-oxidation coating for aluminum electrolysis carbon anode is prepared from the following raw materials in weight percentages: alumina powder: 45%; water glass: 15%; potassium feldspar powder: 8%; sodium fluoride: 0.5%; sodium acetate trihydrate: 7%; deionized water: 8%.

[0041] A method for preparing an anti-oxidation coating for carbon anodes in aluminum electrolysis includes the following steps:

[0042] S1. Preparation of catalytic compacting component: Weigh 0.5g sodium fluoride and 7g sodium acetate trihydrate, mix them and grind them in a mortar. Then put the ground powder into a planetary ball mill and ball mill it until the particle size is about 100 mesh. Weigh 8g potassium feldspar powder and pour it into the mixed powder. Add 8ml deionized water and stir evenly to obtain catalytic compacting component.

[0043] S2. Coating mixing: Weigh 45g of alumina powder and 15g of water glass and mix them with the catalytic densifying component obtained in step S1. Use a whisk to stir the mixture evenly to obtain an antioxidant coating.

[0044] S3. Coating and Drying: Apply the coating evenly to the cylindrical carbon anode sample with a diameter of 50mm × 50mm. First, coat the top and bottom surfaces and dry at 40℃ for 10 minutes. After the bottom surfaces are dry, coat the sides and dry at 40℃ for 10 minutes. Repeat this process once.

[0045] S4. High-temperature calcination: The dried carbon anode coated with paint is placed in a muffle furnace and heated to 900°C at a certain heating rate. After holding at this temperature for 0.5 hours and then naturally cooling, the antioxidant coating is formed on the surface of the carbon anode.

[0046] Example 3

[0047] An anti-oxidation coating for aluminum electrolysis carbon anodes is prepared from the following raw materials in the following weight percentages: alumina powder: 60%; water glass: 25%; potassium feldspar powder: 12%; sodium fluoride: 2%; sodium acetate trihydrate: 11%; deionized water: 12%.

[0048] A method for preparing an anti-oxidation coating for carbon anodes in aluminum electrolysis includes the following steps:

[0049] S1. Preparation of catalytic compaction component: Weigh 2g of sodium fluoride and 11g of sodium acetate trihydrate, mix them and grind them in a mortar. Then put the ground powder into a planetary ball mill and ball mill it until the particle size is about 100 mesh. Weigh 12g of potassium feldspar powder and pour it into the mixed powder. Add 12ml of deionized water and stir evenly to obtain catalytic compaction component.

[0050] S2. Coating mixing: Weigh 60g of alumina powder and 25g of water glass and mix with the catalytic densifying component obtained in step S1. Use a whisk to stir the mixture evenly to obtain an antioxidant coating.

[0051] S3. Coating and Drying: Apply the coating evenly to the cylindrical carbon anode sample with a diameter of 50mm × 50mm. First, coat the top and bottom surfaces and dry at 50℃ for 20 minutes. After the bottom surfaces are dry, coat the sides and dry at 50℃ for 20 minutes. Repeat this process once.

[0052] S4. High-temperature calcination: The dried carbon anode coated with paint is placed in a muffle furnace and heated to 1000°C at a certain heating rate. After holding at this temperature for 2 hours and then naturally cooling, the antioxidant coating is formed on the surface of the carbon anode.

[0053] After calcination of the above three embodiments, it was found that the coating surface of Example 1 was dense and without cracks or peeling, thus concluding that the coating formulation in Example 1 was the optimal formulation.

[0054] Comparative Example 1

[0055] The difference from Example 1 is as follows:

[0056] An anti-oxidation coating for aluminum electrolysis carbon anodes has the following formulation: 28% alumina powder, 21% potassium feldspar powder, 7% sodium fluoride, 12% sodium hydroxide, 1% yttrium oxide powder, and 31% deionized water.

[0057] Preparation method: First, weigh 1g of yttrium oxide powder, 21g of potassium feldspar powder, and 7g of sodium fluoride powder and put them into a ball mill at room temperature. Ball mill until the particle size is about 200 mesh to obtain a mixture of catalytic dense component and rare earth catalytic component. Then, weigh 28g of alumina powder and 12g of sodium hydroxide powder and add them to the mixture. Mix and ball mill until the particle size is about 100 mesh. Finally, weigh 31ml of deionized water and add it to the mixed powder. Stir evenly with a whisk to obtain an antioxidant coating.

[0058] Comparative Example 2

[0059] The difference from Example 1 is as follows:

[0060] An anti-oxidation coating for aluminum electrolysis carbon anodes has the following formulation: 43% alumina powder, 25% potassium feldspar powder, 22% sodium hydroxide, 8% water glass, and 2% sodium fluoride.

[0061] Preparation method: Weigh 25g of potassium feldspar powder, 22g of sodium hydroxide and 2g of sodium fluoride into a container, mix and ball mill until the particle size is about 100 mesh to obtain a mixture of catalytic dense component and alkali metal synergistic catalytic component. Then weigh 43g of alumina powder and pour it into the above mixture. Finally, weigh 8g of water glass (about 6ml) into the mixed powder and stir evenly with a whisk to obtain an antioxidant coating.

[0062] Performance testing

[0063] I. Experimental Materials and Equipment

[0064] 1. The materials required for the experiment are shown in Table 1 below:

[0065] Item No. Raw Material Specifications or Purity Remarks 1 Anode Carbon Block Φ50×50mm Provided by an aluminum electrolysis company in Qinghai 2 Alumina Powder 8000 Mesh Purchased 3 Industrial Grade Water Glass Provided by an aluminum electrolysis company in Qinghai 4 Potassium Feldspar Powder 325 Mesh Purchased 5 Sodium Fluoride Chemically Pure Purchased 6 Sodium Hydroxide Chemically Pure Purchased 7 Sodium Acetate Trihydrate Chemically Pure Purchased 8 Yttrium Oxide Powder Chemically Pure Purchased 9 Deionized Water Chemically Pure (Made in-house) surface

[0066] 2. The equipment required for the experiment is shown in Table 2 below:

[0067] Item No. Name Specifications or Model Application 1. Electric Heating Blower Drying Oven DHG-9030A for Drying Carbon Blocks 2. High Temperature Muffle Furnace KSL-1100X-S for Calcining Carbon Blocks 3. X-ray Diffractometer D-max2500PC for XRD Detection of Coatings 4. Planetary Ball Mill MSK-SF-1S for Grinding Coating Raw Materials surface

[0068] II. Test Methods

[0069] Antioxidant coatings were prepared by sequentially using Examples 1, 1, and 2 as Formulations 1, 2, and 3, respectively. Each coating was applied to five carbon blocks. Since the experimental anode carbon blocks were cylindrical, the top and bottom surfaces of the carbon blocks were first coated with a brush to a thickness of approximately 0.5 mm. The blocks were then placed in an electric heating drying oven at 45°C for 15 minutes. After both surfaces were dry, the sides of the carbon blocks were coated, and the drying temperature was also 45°C for 15 minutes. This process was repeated to ensure that each side of the anode carbon block was coated twice and dried twice.

[0070] 1. Coating oxidation weight loss rate

[0071] The dried anode carbon blocks were weighed and then placed in a muffle furnace for high-temperature calcination at 950°C for 1 hour. The calcined anode carbon blocks were then cooled to room temperature and weighed again to obtain the final weight. The oxidation weight loss rate of each anode carbon block for each coating was calculated. The average oxidation weight loss rate of five anode carbon blocks for each formulation was then calculated to obtain the average oxidation weight loss rate for each formulation. Adhesion analysis was performed to determine the optimal formulation.

[0072] The formula for calculating the oxidation weight loss rate is as follows:

[0073] Oxidation weight loss rate = [(mass before calcination - mass after calcination) / mass before calcination] × 100%

[0074] 2. Coating adhesion

[0075] Adhesion is a core factor in the performance of anti-oxidation coatings for aluminum electrolysis carbon anodes, directly affecting the coating's anti-oxidation effect and service life. Its strength depends on the synergistic effect of binders, fillers, and additives in the coating formulation. In high-temperature oxidizing environments, insufficient adhesion between the coating and the carbon anode substrate can lead to coating cracking and peeling, exposing the carbon anode to the oxidizing atmosphere and accelerating its consumption. This experiment used visual inspection to observe whether the surface of the calcined anode carbon block had peeled off and whether there were cracks to determine the degree of coating adhesion.

[0076] 3. XRD phase analysis

[0077] From both the perspectives of antioxidant properties and adhesion, Formula 1 is clearly the optimal formula. Therefore, the experiment determined Formula 1 to be the final optimal formula. To better understand the phase changes of Formula 1 before and after calcination, XRD phase analysis was performed on the coating powder of Formula 1 before and after calcination.

[0078] III. Analysis of Experimental Results

[0079] 1. Oxidative weight loss analysis

[0080] Table 3 below shows the oxidation weight loss rate of three antioxidant coating formulations after being calcined at 950°C for 1 hour after being applied to the anode carbon block. Figure 1 shows a line graph of the oxidation weight loss rate of the three formulations.

[0081] Table 3 Oxidative weight loss rate of different formulations

[0082] Formulas No. 1, 2, 3, 4, and 5: Formula 1: 2.21%, 2.56%, 2.81%, 2.77%, 3.01%; Formula 2: 4.36%, 4.11%, 3.99%, 3.45%, 3.56%; Formula 3: 3.87%, 3.67%, 3.56%, 3.21%, 3.76%. surface

[0083] From the oxidation weight loss rate data of different formulations in Table 1, the average weight loss rates of each formulation can be calculated as follows: Formulation 1: 2.672%; Formulation 2: 3.894%; Formulation 3: 3.614%. Since the oxidation weight loss rate of the coating is also related to the coating thickness and uniformity, in order to reduce the influence of other factors on the oxidation weight loss rate and obtain more accurate weight loss rate data, five anode carbon blocks were coated for each formulation in the experiment, and their average oxidation weight loss rates were compared to reduce the influence of errors. In addition, Figure 1 also shows that the overall oxidation weight loss rate of Formulation 1 is lower than that of the other two formulations.

[0084] Compared to Formula 3, Formula 1 uses sodium acetate trihydrate as the alkali metal co-catalyst, while Formula 3 uses sodium hydroxide. The main function of the co-catalyst is to promote the reaction between the substrate ceramic component and the catalytically dense component, forming a highly dense coating phase, reducing the direct contact between the carbon anode and oxygen, and thus reducing the oxidation weight loss rate of the anode carbon block. Therefore, it can be inferred that sodium acetate trihydrate has a better co-catalytic effect than sodium hydroxide.

[0085] Oxidation weight loss rate reflects the proportion of weight lost by the anodic carbon block protected by the coating in a high-temperature oxidizing environment. A low weight loss rate indicates a dense coating structure with low porosity, effectively blocking oxygen penetration. If the coating is loose and porous, oxygen can easily penetrate, leading to accelerated anodizing and a higher weight loss rate. Under the same conditions, coating formulation 1 has a lower oxidation weight loss rate, proving that formulation 1 has better antioxidant properties than the other two coatings. This also indicates that the coating structure is dense, making it difficult for oxygen to penetrate. The above analysis concludes that formulation 1 is the optimal formulation based solely on the antioxidant properties of the coating, which also indirectly reflects the better density of the coating.

[0086] 2. Coating adhesion analysis

[0087] Referring to Figure 2, the anode carbon blocks after calcination at 950 °C with different formulations are, from left to right, formulation 1, formulation 2, and formulation 3. It can be seen that the coating of formulation 1 is tightly bonded to the carbon block after calcination, with no cracks or peeling, and has the best adhesion. After calcination, the surface of the anode carbon block of formulation 3 has a small number of cracks, and the coating of formulation 2 has a large number of cracks, with a small amount of peeling off from the edge of the cylindrical carbon block.

[0088] Compared to Formula 2, Formula 3 lacks the rare earth catalyst component yttrium oxide powder and deionized water. However, it contains water glass. Formula 3 exhibits better adhesion than Formula 2, suggesting that anode carbon blocks using water glass as a binder have better adhesion than those without. The binder is a key factor determining whether the coating bonds tightly to the carbon block.

[0089] Therefore, in terms of coating adhesion, Formula 1 is the best, followed by Formula 3, and Formula 2 is the worst. Thus, it can be concluded that, from the perspective of both coating adhesion and thermal stability, Formula 1 is the optimal formula.

[0090] 3. XRD phase analysis

[0091] Referring to Figure 3, XRD phase analysis of the coating material of Formulation 1 before and after calcination shows the phase composition of the coating material after calcination at room temperature and at 950℃. The coating material was dried and ground before analysis.

[0092] Referring to Figure 3-A, the XRD results of the coating of Formulation 1 at room temperature show that the main phases in the dried coating are SiO2 and Al2O3, with relatively high peak intensity and sharp peak shape, indicating that the content and crystallinity of SiO2 and Al2O3 in this material are both high. However, it is worth noting that the baseline of the XRD pattern is not flat, which suggests that in addition to SiO2 and Al2O3, there are also poorly crystallized or amorphous components in the coating material.

[0093] The XRD results of formulation 1 after high-temperature treatment are shown in Figure 3-B. The main phases of the coating material changed after high-temperature treatment; the SiO2 peak disappeared, and the Na peak appeared.4.4 Si 134.11 And Al 1.98 Cr 0.02O3 The presence of two new phases indicates that SiO2 and Al2O3 reacted at high temperature to form a new phase. The Al phase... 1.98 Cr 0.02O3 The formulation is α-Al₂O₃ (corundum, containing a small amount of chromium). Corundum is a high-hardness, high-melting-point, and chemically extremely stable oxide crystal, with a Mohs hardness of 9, second only to diamond, and excellent wear resistance. Corundum has a melting point as high as 2050℃, while the temperature inside an aluminum electrolysis cell is 940℃-980℃ during operation, making it a suitable protective layer for the carbon anode. Corundum maintains structural stability at high temperatures and possesses good thermal conductivity and electrical insulation, making it suitable for extreme thermal environments and high-voltage insulation scenarios. In summary, the new phase formed after calcination of Formula 1 is extremely suitable for the aluminum electrolysis environment.

[0094] IV. Conclusion

[0095] 1. Through oxidation weight loss rate testing and coating adhesion studies on three different formulations, the preliminary optimal formulation was determined to be 50% alumina powder, 20% water glass, 10% potassium feldspar powder, 1% sodium fluoride, 9% sodium acetate trihydrate, and 10% deionized water.

[0096] 2. XRD phase analysis of the optimal formulation revealed that after calcination, the main components of the coating, SiO2 and Al2O3, underwent changes, producing Na. 4.4 Si 134.11 And Al 1.98 Cr 0.02O3 Two new phases were identified. One of these phases, Al, was... 1.98 Cr 0.02O3 It is α-Al2O3 (corundum phase) containing a small amount of chromium. The various physical properties of the corundum phase are suitable for the electrolytic cell environment.

[0097] In summary, the optimal formula obtained from the experiment meets the requirements for anti-oxidation of aluminum electrolytic carbon anodes in terms of both antioxidant properties and coating adhesion.

[0098] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An anti-oxidation coating for carbon anodes in aluminum electrolysis, characterized in that, It is prepared from the following raw materials in the indicated weight percentages: alumina powder: 45-60%; water glass: 15-25%; potassium feldspar powder: 8-12%. Sodium fluoride: 0.5-2%; Sodium acetate trihydrate: 7-11%; Ionized water: 8-12%.

2. The aluminum electrolysis carbon anode anti-oxidation coating according to claim 1, characterized in that, The raw materials are as follows by mass percentage: alumina powder: 50%; water glass: 20%; potassium feldspar powder: 10%; sodium fluoride: 1%; sodium acetate trihydrate: 9%; deionized water: 10%.

3. The aluminum electrolysis carbon anode anti-oxidation coating according to claim 1 or 2, characterized in that, After being calcined at high temperature, the main phase of the coating is corundum phase α-Al2O3.

4. A method for preparing an anti-oxidation coating for an aluminum electrolytic carbon anode according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Preparation of the catalytic densifying component: Sodium fluoride and sodium acetate trihydrate are mixed and ground, then mixed with potassium feldspar powder and deionized water, and stirred evenly to obtain the catalytic densifying component; S2. Mixing of the coating: The catalytic densifying component obtained in step S1 is mixed with alumina powder and water glass, and stirred thoroughly until uniform to obtain the antioxidant coating; S3. Coating and drying: The antioxidant coating obtained in step S2 is coated on the surface of the carbon anode and dried in stages; S4. High-temperature calcination: The dried carbon anode coated with the coating is calcined at 900-1000℃ and held at that temperature for 0.5-2 hours. After natural cooling, the antioxidant coating is formed on the surface of the carbon anode.

5. The method for preparing an anti-oxidation coating for an aluminum electrolytic carbon anode according to claim 4, characterized in that, The specific process in step S3 is as follows: First, coat the top and bottom surfaces of the carbon anode, then dry them at 40-50℃ and keep them warm for 10-20 minutes; after the bottom surfaces are dry, coat the sides of the carbon anode and dry them at 40-50℃ for 10-20 minutes; repeat the above operation at least twice to ensure that each surface is coated twice and dried twice.

6. The method for preparing an anti-oxidation coating for an aluminum electrolytic carbon anode according to claim 4, characterized in that, The calcination temperature in step S4 is 950℃, and the holding time is 1 hour.

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