Electrolytic aluminum anode high-temperature-resistant and oxidation-resistant coating and preparation process thereof

Abstract

This invention discloses a high-temperature resistant and antioxidant coating for electrolytic aluminum anodes and its preparation process, relating to the field of electrolytic aluminum coating technology. The coating comprises the following components by mass percentage: 40%-50% main aggregate phase, 20%-30% composite binder, 3%-8% functional additives, 2%-5% stabilizing and reinforcing phase, and 8%-12% solvent film-forming phase. The composite binder contains the reaction product of alkali metal silicates and organic modifiers. This invention utilizes the hydrogen bonding reaction between alkali metal silicates and organic modifiers to form an anti-aging, high-toughness modified binder matrix, significantly improving the room-temperature curing stability and high-temperature service life of the coating, solving the technical problem of easy aging and cracking in traditional water glass-based coatings. A homogenization process employing synergistic anchoring of functional additives and stabilizing and reinforcing phases constructs a dual protection mechanism in the coating: rare-earth catalytic oxidation inhibition and whisker bridging crack prevention. This achieves long-term dense protection of the coating under high-temperature oxidizing atmospheres without introducing harmful impurities that contaminate the electrolyte.

Description

Technical Field

[0001] This invention relates to the field of electrolytic aluminum coating technology, specifically to a high-temperature resistant and antioxidant coating for electrolytic aluminum anodes and its preparation process. Background Technology

[0002] In the electrolytic aluminum industry, prebaked anodes are a core consumable material, and their high-temperature oxidation resistance directly affects the operating efficiency of the electrolytic cell and the quality of primary aluminum. Currently, coating the anode surface with a protective coating is one of the main technical means to reduce oxidation consumption. Existing coating technologies mostly use alkali metal silicates (such as water glass) as binders, compounded with ceramic aggregates such as alumina and quartz powder, and form a glassy protective layer on the anode surface through high-temperature sintering. This type of coating can block the corrosion of air and carbon dioxide to a certain extent and has been applied in some electrolytic aluminum enterprises.

[0003] However, existing technologies still have the following shortcomings: During storage and room temperature curing, the silanol groups of traditional water glass-based adhesives are prone to irreversible condensation reactions, which leads to a rapid increase in the viscosity of the coating system and the occurrence of gel aging. This causes microcracks to form in the coating before high-temperature sintering, and crack propagation during service leads to protection failure and a significant increase in anodizing consumption.

[0004] In response to this problem, this application proposes a high-temperature resistant and antioxidant coating for electrolytic aluminum anodes and its preparation process. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature resistant and antioxidant coating for electrolytic aluminum anodes and its preparation process, in order to solve the problem that in the prior art, the silanol groups of water glass-based binders are prone to irreversible condensation reactions during storage and room temperature curing, which leads to a rapid increase in the viscosity of the coating system and the occurrence of gel aging, which in turn causes microcracks to form in the coating before high-temperature sintering. During service, the cracks propagate and cause protective failure, resulting in a significant increase in anodizing consumption.

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

[0007] In a first aspect, this application provides a high-temperature resistant and oxidation-resistant coating for electrolytic aluminum anodes, which is composed of the following components by mass percentage:

[0008] Main aggregate phase 40%-50%, composite binder 20%-30%, functional additives 3%-8%, stabilizing reinforcing phase 2%-5%, solvent film-forming phase 8%-12%;

[0009] The composite binder comprises the reaction product of alkali metal silicates and organic modifiers.

[0010] Furthermore, the main aggregate phase comprises, by mass percentage, the following: α-alumina: 50%-60%, silicon carbide micro powder: 20%-30%, and spodumene powder: 10%-20%.

[0011] Furthermore, in the composite binder, the alkali metal silicate is a mixture of sodium silicate and potassium silicate, with a mass ratio of 1:0.5-1.5;

[0012] The organic modifier is a mixture of water-soluble phenolic resin and polyethylene glycol, accounting for 20%-30% of the total mass of the composite adhesive;

[0013] The functional additives, by percentage of the total mass of the coating, include:

[0014] Yttrium oxide 0.5%-2.5%, zirconium oxide 0.5%-2%, sodium fluorosilicate 1%-2%, ammonium chloride 1%-2.5%.

[0015] Furthermore, the stabilizing reinforcing phase is magnesium oxide whiskers or alumina short fibers, both with a particle size range of 1-5 μm;

[0016] The solvent film-forming phase is composed of deionized water and polyvinyl butyral, wherein polyvinyl butyral accounts for 20%-40% of the mass of the solvent film-forming phase.

[0017] Furthermore, in the composite coating formed after the coating is sintered and cured, the main elements by mass percentage are: Al: 13.5%-25.0%, Na: 2.0%-5.0%, Si: 5.0%-10.0%, K: 1.5%-5.0%; and the other elements by mass percentage are: Ca: 0.05%-0.18%, Mg: 0.1%-0.5%, Li: 0.01%-0.05%, Fe: 0.05%-0.1%.

[0018] Secondly, this application provides a process for preparing a high-temperature resistant and antioxidant coating for electrolytic aluminum anodes as described in the first aspect, comprising the following steps:

[0019] Organic modification of alkali metal silicates yields a modified binder matrix.

[0020] The modified binder matrix is ​​mixed with the main aggregate and then activated and dispersed to obtain an activated composite slurry.

[0021] The activated composite slurry is mixed with functional additives, a stabilizing reinforcing phase and a solvent film-forming phase, and then homogenized to obtain a homogenized coating.

[0022] The homogenized coating is applied to the anode surface and then subjected to room temperature setting, medium temperature crosslinking, and high temperature sintering to form a dense composite coating.

[0023] Further, the step of organically modifying the alkali metal silicate to obtain the modified binder matrix is ​​as follows:

[0024] Sodium silicate with a modulus of 2.6-3.2 and potassium silicate are mixed at a mass ratio of 1:0.6-1.4. At 40-60℃, 15%-25% of water-soluble phenolic resin and 2%-5% of polyethylene glycol are added. The mixture is stirred at 200-400 rpm for 0.5-1.5 hours to allow the water-soluble phenolic resin and polyethylene glycol to bond with the silanol groups through hydrogen bonds, thus obtaining the modified adhesive matrix.

[0025] Further, the step of mixing the modified binder matrix with the main aggregate and performing activation and dispersion treatment to obtain the activated composite slurry is as follows:

[0026] The main aggregate phase is surface modified at 80-100℃ with γ-aminopropyltriethoxysilane at 1%-2% of the mass of the main aggregate phase for 2-3 hours to obtain the modified main aggregate.

[0027] The modified main aggregate is added to the modified binder matrix and dispersed at high speed at 1500-2000 rpm for 10-20 minutes to form a chemical bonding interface between the modified main aggregate particles and the modified binder matrix, thus obtaining an activated composite slurry.

[0028] Further, the step of mixing the activated composite slurry with functional additives, stabilizing reinforcing phase, and solvent film-forming phase, and then homogenizing the mixture to obtain a homogenized coating is as follows:

[0029] Add functional additives and stabilizing reinforcing phases sequentially to the activated composite slurry, and stir at 1000-1500 rpm for 5-10 minutes;

[0030] Then, a solvent is added to form a film phase, the system is adjusted to the target solid content, and finally, a high-pressure homogenization treatment is carried out under a pressure of 15-25 MPa to uniformly anchor the functional additives to the surface of the stable reinforcing phase, thus obtaining a homogenized coating.

[0031] Further, the step of coating the homogenized coating onto the anode surface and then sequentially performing room temperature setting, medium temperature crosslinking, and high temperature sintering to form a dense composite coating is as follows:

[0032] High-pressure spraying equipment is used to uniformly spray homogenized coating onto the anode surface under a pressure of 0.3-0.5 MPa, controlling the coating thickness to be 0.3-0.5 mm;

[0033] Set at room temperature for 12-24 hours at 25±5℃ and ≤60% humidity; then crosslink at medium temperature for 1-2 hours at 80-120℃.

[0034] Finally, the mixture is sintered at 300-500℃ for 2-4 hours, with a heating rate of 3-8℃ / minute.

[0035] Compared with the prior art, the present invention provides a high-temperature resistant and antioxidant coating for electrolytic aluminum anodes and its preparation process. Through the hydrogen bonding reaction between alkali metal silicates and organic modifiers, an anti-aging and high-toughness modified binder matrix is ​​formed, which significantly improves the room temperature curing stability and high-temperature service life of the coating and solves the technical problem of easy aging and cracking of traditional water glass-based coatings.

[0036] By employing a homogenization process that combines functional additives with stabilizing reinforcement, a dual protection mechanism of rare earth catalytic oxidation inhibition and whisker bridging crack prevention is constructed in the coating. This achieves long-term dense protection of the coating under high-temperature oxidizing atmospheres without introducing harmful impurities that contaminate the electrolyte. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0038] Figure 1 This is a process flow diagram for preparing a high-temperature resistant and antioxidant coating for electrolytic aluminum anodes, provided in an embodiment of the present invention. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0040] As attached Figure 1 As shown:

[0041] Example 1:

[0042] This embodiment provides a high-temperature resistant and antioxidant coating for electrolytic aluminum anodes, the formulation and preparation process of which are as follows.

[0043] I. Coating Formulation:

[0044] Based on a total mass of 100kg, the distribution of each component of the coating is shown in Table 1 below:

[0045] Table 1

[0046] Components Mass (kg) Percentage of total paint mass (%) Main aggregate phase 50 50% Composite adhesive 35 35% Functional additives 5 5% Stable Enhanced Phase 3 3% Solvent film phase 7 7%

[0047] The specific composition of each component is as follows:

[0048] Main aggregate phase (in terms of total mass of main aggregate phase): α-alumina (particle size 60-90nm) accounts for 55%, i.e. 27.5kg; silicon carbide micro powder (particle size 2-4μm) accounts for 25%, i.e. 12.5kg; spodumene powder (particle size 8-12μm) accounts for 20%, i.e. 10kg.

[0049] Composite adhesive: Sodium silicate (modulus 3.0) and potassium silicate (modulus 2.8) are mixed in a 1:1 mass ratio, totaling 26.25 kg; water-soluble phenolic resin (solid content 65%) and polyethylene glycol are mixed in a 5:1 mass ratio, totaling 8.75 kg, accounting for 25% of the total mass of the composite adhesive.

[0050] Functional additives: 1.5 kg of yttrium oxide (1.5% of the total weight of the coating), 1.5 kg of zirconium oxide (1.5%), 1.25 kg of sodium fluorosilicate (1.25%), and 0.75 kg of ammonium chloride (0.75%).

[0051] Stabilizing and reinforcing phase: Magnesium oxide whiskers, grain size 2-4 μm, bulk density 2.7 g / cm³ 3 Total weight: 3kg.

[0052] Solvent film-forming phase: 4.9 kg of deionized water (accounting for 70% of the solvent film-forming phase), 2.1 kg of polyvinyl butyral (accounting for 30%).

[0053] Elemental composition of the sintered coating (measured values): Al 16.8%, Na 3.2%, Si 7.5%, K 2.1%; Ca 0.12%, Mg 0.35%, Li 0.03%, Fe 0.08%.

[0054] II. Preparation process:

[0055] Step 1: Organically modify alkali metal silicates to obtain a modified binder matrix;

[0056] Sodium silicate with a modulus of 3.0 and potassium silicate with a modulus of 2.8 were mixed at a mass ratio of 1:1, totaling 26.25 kg, and added to a reaction vessel. The mixture was heated to 55°C, and then 7.29 kg of water-soluble phenolic resin and 1.46 kg of polyethylene glycol (totaling 25% of the total mass of the composite binder) were added. The mixture was stirred at 300 rpm for 1 hour to allow the water-soluble phenolic resin and polyethylene glycol to bond with the silanol groups through hydrogen bonds, thus obtaining the modified binder matrix.

[0057] Parameter description: Temperature is monitored by a thermocouple thermometer, and rotation speed is controlled by a variable frequency stirrer.

[0058] Step 2: Mix the modified binder matrix with the main aggregate and perform activation and dispersion treatment to obtain activated composite slurry;

[0059] The main aggregate phase (27.5 kg of α-alumina, 12.5 kg of silicon carbide micro powder, and 10 kg of spodumene powder) was placed in a double planetary mixer and heated to 90°C. 0.75 kg of γ-aminopropyltriethoxysilane (1.5% of the total mass of the main aggregate phase) was added, and the mixture was stirred at 60 rpm for 2.5 hours for surface modification treatment to obtain modified main aggregate. Then, all the modified main aggregate was added to the modified binder matrix obtained in step 1 and dispersed at 1800 rpm for 15 minutes to form a chemical bond interface between the modified main aggregate particles and the modified binder matrix, resulting in an activated composite slurry.

[0060] Parameter description: The modification temperature is controlled by oil bath heating, and the rotation speed is measured by a high-speed disperser.

[0061] Step 3: Mix the activated composite slurry with functional additives, stabilizing reinforcing phase and solvent film-forming phase, and perform homogenization treatment to obtain homogenized coating;

[0062] Add functional additives (1.5 kg yttrium oxide, 1.5 kg zirconium oxide, 1.25 kg sodium fluorosilicate, and 0.75 kg ammonium chloride) and a stabilizing reinforcing phase (3 kg magnesium oxide whiskers) sequentially to the activated composite slurry obtained in step 2, and stir at 1200 rpm for 8 minutes. Then add the solvent film-forming phase (4.9 kg deionized water and 2.1 kg polyvinyl butyral) to adjust the solid content of the system to 65%. Finally, homogenize the mixed slurry using a high-pressure homogenizer (model GYB60-6S) at 20 MPa pressure, repeating the process twice to ensure that the functional additives are uniformly anchored on the surface of the stabilizing reinforcing phase, thus obtaining a homogenized coating.

[0063] Parameter description: Homogenization pressure is read by pressure sensor, and solid content is determined by drying and weighing method (10g of coating is dried in 105℃ oven to constant weight for calculation).

[0064] Step 4: Apply the homogenized coating to the anode surface, and then perform room temperature setting, medium temperature crosslinking and high temperature sintering in sequence to form a dense composite coating;

[0065] High-pressure airless spraying equipment (model GPQ9C, nozzle diameter 0.53mm) was used to uniformly spray homogenized coating onto the four sides and top surface of a prebaked anode (dimensions: length 1650mm, width 660mm, height 600mm) at a spraying pressure of 0.4MPa. The coating thickness was controlled at 0.4mm (measured point-by-point using an ultrasonic thickness gauge TT100, and the average value of 10 points was taken). After spraying, the anode was set at room temperature for 18 hours at 25℃ and 55% relative humidity; then, it was cross-linked at medium temperature in a 100℃ oven for 1.5 hours; finally, it was sintered at high temperature in a muffle furnace at a heating rate of 5℃ / min to 400℃ and held for 3 hours. After cooling to room temperature in the furnace, an anode with a dense composite coating was obtained.

[0066] Parameter description: Thickness measurement is performed using a TT100 ultrasonic thickness gauge with an accuracy of ±0.01mm; temperature control is performed using a PID programmable temperature controller.

[0067] Example 2:

[0068] This embodiment provides another high-temperature resistant and antioxidant coating for electrolytic aluminum anodes, the formulation and preparation process of which are as follows.

[0069] I. Coating Formulation:

[0070] Based on a total mass of 100kg, the distribution of each component of the coating is shown in Table 2 below:

[0071] Table 2

[0072] Components Mass (kg) Percentage of total paint mass (%) Main aggregate phase 48 48% Composite adhesive 38 38% Functional additives 4 4% Stable Enhanced Phase 4 4% Solvent film phase 6 6%

[0073] The specific composition of each component is as follows:

[0074] Main aggregate phase (in terms of total mass of main aggregate phase): α-alumina (particle size 50-80nm) accounts for 52%, i.e. 24.96kg; silicon carbide micro powder (particle size 1-3μm) accounts for 28%, i.e. 13.44kg; spodumene powder (particle size 5-10μm) accounts for 20%, i.e. 9.6kg.

[0075] Composite adhesive: Sodium silicate (modulus 2.8) and potassium silicate (modulus 3.0) are mixed at a mass ratio of 1:0.8, totaling 28.5 kg; water-soluble phenolic resin (solid content 62%) and polyethylene glycol are mixed at a mass ratio of 4:1, totaling 9.5 kg, accounting for 25% of the total mass of the composite adhesive.

[0076] Functional additives: 1.0 kg of yttrium oxide (1.0% of the total weight of the coating), 1.0 kg of zirconium oxide (1.0%), 1.0 kg of sodium fluorosilicate (1.0%), and 1.0 kg of ammonium chloride (1.0%).

[0077] Stabilizing reinforcing phase: alumina short fibers, particle size 2-5 μm, bulk density 2.8 g / cm³ 3 Total weight: 4kg.

[0078] Solvent film-forming phase: 4.2 kg of deionized water (accounting for 70% of the solvent film-forming phase), 1.8 kg of polyvinyl butyral (accounting for 30%).

[0079] Elemental composition of the sintered coating (measured values): Al: 15.5%, Na: 3.5%, Si: 8.2%, K: 2.8%; Ca: 0.10%, Mg: 0.42%, Li: 0.02%, Fe: 0.09%.

[0080] II. Preparation process:

[0081] Step 1: Organically modify alkali metal silicates to obtain a modified binder matrix;

[0082] Sodium silicate with a modulus of 2.8 and potassium silicate with a modulus of 3.0 were mixed at a mass ratio of 1:0.8, totaling 28.5 kg, and added to a reactor. The mixture was heated to 50°C, and then 7.6 kg of water-soluble phenolic resin and 1.9 kg of polyethylene glycol (totaling 25% of the total mass of the composite binder) were added. The mixture was stirred at 250 rpm for 1.2 hours to obtain the modified binder matrix.

[0083] Step 2: Mix the modified binder matrix with the main aggregate and perform activation and dispersion treatment to obtain activated composite slurry;

[0084] The main aggregate phase (24.96 kg of α-alumina, 13.44 kg of silicon carbide micro powder, and 9.6 kg of spodumene powder) was placed in a double planetary mixer and heated to 85°C. 0.72 kg of γ-aminopropyltriethoxysilane (1.5% of the total mass of the main aggregate phase) was added, and the mixture was stirred at 50 rpm for 3 hours for surface modification. The modified main aggregate was then added to the modified binder matrix and dispersed at 1600 rpm for 18 minutes to obtain the activated composite slurry.

[0085] Step 3: Mix the activated composite slurry with functional additives, stabilizing reinforcing phase and solvent film-forming phase, and perform homogenization treatment to obtain homogenized coating;

[0086] Functional additives (1.0 kg yttrium oxide, 1.0 kg zirconium oxide, 1.0 kg sodium fluorosilicate, and 1.0 kg ammonium chloride) and a stabilizing reinforcing phase (4 kg alumina short fibers) were added sequentially to the activated composite slurry, and stirred at 1100 rpm for 10 minutes. Then, a solvent film-forming phase (4.2 kg deionized water and 1.8 kg polyvinyl butyral) was added to adjust the solid content of the system to 63%. Finally, high-pressure homogenization treatment was carried out at 18 MPa, and the cycle was repeated twice to obtain a homogenized coating.

[0087] Step 4: Apply the homogenized coating to the anode surface, and then perform room temperature setting, medium temperature crosslinking and high temperature sintering in sequence to form a dense composite coating;

[0088] High-pressure airless spraying equipment was used, with a spraying pressure of 0.35 MPa, to uniformly spray the coating onto the surface of the prebaked anode, controlling the coating thickness to 0.45 mm (measured with an ultrasonic thickness gauge). The anode was then set at room temperature for 20 hours at 22℃ and 50% relative humidity; subsequently, it was cross-linked at medium temperature in a 90℃ oven for 2 hours; finally, it was sintered at high temperature in a muffle furnace at a heating rate of 4℃ / min to 350℃, and held for 3.5 hours to obtain an anode with a dense composite coating.

[0089] Comparative example:

[0090] The anti-oxidation coating for aluminum electrolysis anodes, a commercially available brand, was applied according to the product instructions. The coating was applied by hand with a thickness of 0.5 mm and allowed to dry naturally at room temperature for 48 hours before use.

[0091] Performance testing methods and equipment:

[0092] 1. High-temperature antioxidant performance test:

[0093] Test method: Sample blocks of 50mm × 50mm × 50mm were cut from the coated anodes of Examples 1, 2, and the comparative example, as well as the uncoated blank anode (3 parallel samples per group). The samples were placed in a muffle furnace and oxidized at 900℃ for 72 hours. The samples were weighed before and after oxidation (accuracy 0.0001g) and the oxidation loss rate was calculated.

[0094] Oxidation loss on ignition = (Mass before oxidation - Mass after oxidation) / (Mass before oxidation × 100%)

[0095] Equipment: Muffle furnace (model SG-XL1200, temperature control accuracy ±1℃), electronic balance (accuracy 0.0001g, model ME204E).

[0096] 2. Coating adhesion test:

[0097] Test method: Cross-cut test (GB / T 9286-1998). Use a cross-cut tester to draw 1mm×1mm squares (10×10 squares) on the coating surface, adhere them with tape, peel them off, and observe the coating peeling. Rating is 0-5 (0 is the best).

[0098] Equipment: squaring machine (QFH type), 3M 600 tape.

[0099] 3. Thermal shock resistance test:

[0100] Test method: The coated sample (50mm×50mm×50mm) is heated in a muffle furnace at 800℃ for 30 minutes, then quickly removed and immersed in cold water at 25℃, which constitutes one cycle. This process is repeated, and the number of cycles when the coating cracks or peels off is recorded.

[0101] Equipment: muffle furnace, constant temperature water bath.

[0102] 4. Elemental composition analysis:

[0103] Test method: The sintered coating was scraped off and ground into powder, and the contents of major elements and impurity elements were determined by X-ray fluorescence spectrometry (XRF).

[0104] Equipment: X-ray fluorescence spectrometer (model S8 TIGER, Bruker, Germany).

[0105] The overall performance comparison is shown in Table 3 below;

[0106] Table 3

[0107] Test Project Example 1 Example 2 Comparative example (commercially available paints) Blank (uncoated) Oxidation loss on ignition at 900℃ for 72 hours (%) 0.92 1.05 3.48 8.65 Coating adhesion (cross-cut test rating) Level 0 Level 0 Level 1 — Thermal shock resistance cycles (800℃→25℃) >50 times without peeling >50 times without peeling Cracks appeared 22 times — Anode lifespan extended (days) +1.6 +1.4 +0.6 — Reduction in carbon slag per ton of aluminum (kg / t-Al) 26 23 12 —

[0108] Results analysis:

[0109] The test results above show that the coatings of Examples 1 and 2 are significantly superior to the commercially available comparative coatings in terms of high-temperature oxidation burn-off rate, coating adhesion, thermal shock resistance, and industrial application performance. Among them, Example 1 performed best, with a burn-off rate of only 0.92% after oxidation at 900℃ for 72 hours, which is about 89.4% lower than the blank anode and about 73.6% lower than the comparative example; the coating adhesion reached level 0, and the thermal shock resistance exceeded 50 cycles without peeling, which can extend the anode service life by 1.6 days and reduce carbon slag by 26 kg per ton of aluminum.

[0110] As can be seen from the above, the hydrogen bonding reaction between alkali metal silicates and organic modifiers forms an anti-aging and highly tough modified binder matrix, which significantly improves the room temperature curing stability and high temperature service life of the coating, and solves the technical problem of easy aging and cracking of traditional water glass-based coatings.

[0111] By employing a homogenization process that combines functional additives with stabilizing reinforcement, a dual protection mechanism of rare earth catalytic oxidation inhibition and whisker bridging crack prevention is constructed in the coating. This achieves long-term dense protection of the coating under high-temperature oxidizing atmospheres without introducing harmful impurities that contaminate the electrolyte.

[0112] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A high-temperature resistant and oxidation-resistant coating for electrolytic aluminum anodes, characterized in that, It consists of the following components by mass percentage: Main aggregate phase 40%-50%, composite binder 20%-30%, functional additives 3%-8%, stabilizing reinforcing phase 2%-5%, solvent film-forming phase 8%-12%; The composite binder comprises the reaction product of alkali metal silicates and organic modifiers.

2. The high-temperature resistant and oxidation-resistant coating for electrolytic aluminum anodes according to claim 1, characterized in that, The main aggregate phase comprises, by mass percentage, 50%-60% α-alumina, 20%-30% silicon carbide micro powder, and 10%-20% spodumene powder.

3. The high-temperature resistant and oxidation-resistant coating for electrolytic aluminum anodes according to claim 1, characterized in that, In the composite binder, the alkali metal silicate is a mixture of sodium silicate and potassium silicate, with a mass ratio of 1:0.5-1.

5. The organic modifier is a mixture of water-soluble phenolic resin and polyethylene glycol, accounting for 20%-30% of the total mass of the composite adhesive; The functional additives, by percentage of the total mass of the coating, include: Yttrium oxide 0.5%-2.5%, zirconium oxide 0.5%-2%, sodium fluorosilicate 1%-2%, ammonium chloride 1%-2.5%.

4. The high-temperature resistant and oxidation-resistant coating for electrolytic aluminum anodes according to claim 1, characterized in that, The stabilizing reinforcing phase is magnesium oxide whiskers or aluminum oxide short fibers, both with a particle size range of 1-5 μm. The solvent film-forming phase is composed of deionized water and polyvinyl butyral, wherein polyvinyl butyral accounts for 20%-40% of the mass of the solvent film-forming phase.

5. The high-temperature resistant and oxidation-resistant coating for electrolytic aluminum anodes according to claim 1, characterized in that, The composite coating formed after the coating is sintered and cured contains the following main elements by mass percentage: Al: 13.5%-25.0%, Na: 2.0%-5.0%, Si: 5.0%-10.0%, K: 1.5%-5.0%; and the following other elements by mass percentage: Ca: 0.05%-0.18%, Mg: 0.1%-0.5%, Li: 0.01%-0.05%, Fe: 0.05%-0.1%.

6. A process for preparing a high-temperature resistant and antioxidant coating for electrolytic aluminum anodes as described in any one of claims 1-5, characterized in that, Includes the following steps: Organic modification of alkali metal silicates yields a modified binder matrix. The modified binder matrix is ​​mixed with the main aggregate and then activated and dispersed to obtain an activated composite slurry. The activated composite slurry is mixed with functional additives, a stabilizing reinforcing phase and a solvent film-forming phase, and then homogenized to obtain a homogenized coating. The homogenized coating is applied to the anode surface and then subjected to room temperature setting, medium temperature crosslinking, and high temperature sintering to form a dense composite coating.

7. The process according to claim 6, characterized in that, The step of organically modifying alkali metal silicates to obtain a modified binder matrix is ​​as follows: Sodium silicate with a modulus of 2.6-3.2 and potassium silicate are mixed at a mass ratio of 1:0.6-1.

4. At 40-60℃, 15%-25% of water-soluble phenolic resin and 2%-5% of polyethylene glycol are added. The mixture is stirred at 200-400 rpm for 0.5-1.5 hours to allow the water-soluble phenolic resin and polyethylene glycol to bond with the silanol groups through hydrogen bonds, thus obtaining the modified adhesive matrix.

8. The process according to claim 6, characterized in that, The step of mixing the modified binder matrix with the main aggregate and performing activation and dispersion treatment to obtain the activated composite slurry is as follows: The main aggregate phase is surface modified at 80-100℃ with γ-aminopropyltriethoxysilane at 1%-2% of the mass of the main aggregate phase for 2-3 hours to obtain the modified main aggregate. The modified main aggregate is added to the modified binder matrix and dispersed at high speed at 1500-2000 rpm for 10-20 minutes to form a chemical bonding interface between the modified main aggregate particles and the modified binder matrix, thus obtaining an activated composite slurry.

9. The process according to claim 6, characterized in that, The step of mixing the activated composite slurry with functional additives, stabilizing reinforcing phase, and solvent film-forming phase, and then homogenizing it to obtain a homogenized coating is as follows: Add functional additives and stabilizing reinforcing phases sequentially to the activated composite slurry, and stir at 1000-1500 rpm for 5-10 minutes; Then, a solvent is added to form a film phase, the system is adjusted to the target solid content, and finally, a high-pressure homogenization treatment is carried out under a pressure of 15-25 MPa to uniformly anchor the functional additives to the surface of the stable reinforcing phase, thus obtaining a homogenized coating.

10. The process according to claim 6, characterized in that, The steps of applying a homogenized coating to the anode surface and sequentially performing room-temperature setting, medium-temperature cross-linking, and high-temperature sintering to form a dense composite coating are as follows: High-pressure spraying equipment is used to uniformly spray homogenized coating onto the anode surface under a pressure of 0.3-0.5 MPa, controlling the coating thickness to be 0.3-0.5 mm; Set at room temperature for 12-24 hours at 25±5℃ and ≤60% humidity; then crosslink at medium temperature for 1-2 hours at 80-120℃. Finally, the mixture is sintered at 300-500℃ for 2-4 hours, with a heating rate of 3-8℃ / minute.

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