Energy-saving nano ceramic anti-oxidation coating applied to electrolytic aluminum anode carbon block and preparation method of energy-saving nano ceramic anti-oxidation coating

Abstract

The invention relates to the technical field of anti-oxidation coatings, in particular to energy-saving nano ceramic anti-oxidation coating slurry applied to an electrolytic aluminum anode carbon block, which is prepared from the following raw materials in parts by mass: 100 parts of deionized water, 30-50 parts of water glass, 30-50 parts of alpha-alumina powder, 20-30 parts of gamma-alumina powder, 5-10 parts of aluminum dihydrogen phosphate and 1-2 parts of carboxymethyl cellulose. 0.5 to 1 part of triethanolamine; and 3 parts of a carbon-containing antioxidant. According to the energy-saving nano ceramic anti-oxidation coating disclosed by the invention, a composite bonding system taking the water glass and the aluminum dihydrogen phosphate as cores is constructed, and the alpha-alumina powder and gamma-alumina powder bimodal refractory aggregate is matched, so that stable and tough combination is realized in the whole process from room-temperature curing to high-temperature sintering; cracking and stripping at high temperature are fundamentally avoided; meanwhile, long-term homogeneous stability of the slurry is ensured by an optimized slurry formula and a simple preparation process, solid-liquid separation is avoided, the construction uniformity and efficiency are remarkably improved, and the comprehensive cost is reduced.

Description

Energy-saving nano-ceramic anti-oxidation coating applied to carbon blocks of electrolytic aluminum anodes and its preparation method Technical Field

[0001] This invention belongs to the field of anti-oxidation coating technology, specifically relating to an energy-saving nano-ceramic anti-oxidation coating applied to electrolytic aluminum anode carbon blocks and its preparation method. Background Technology

[0002] In the industrial production of electrolytic aluminum, anode carbon blocks are not only a crucial conductive material but also participate in the electrolysis process as a reaction component. However, under high-temperature conditions, anode carbon blocks undergo oxidation, a chemical reaction that significantly increases carbon consumption and directly drives up production costs for enterprises. More seriously, the oxidation reaction also brings a series of environmental pollution problems, such as the emission of harmful gases and increased difficulty in waste disposal, all of which pose a significant threat to environmental protection. Therefore, how to effectively mitigate the oxidation reaction of anode carbon blocks at high temperatures has become an urgent technical challenge to be solved in the electrolytic aluminum industry.

[0003] To suppress anodizing, various anti-oxidation coating solutions have been developed in the industry. Among existing technologies, Chinese invention patent application number 202310786198X, entitled "An Electrolytic Prebaked Anode Anti-oxidation Microcrystalline Protective Slurry and its Preparation Method," discloses a microcrystalline protective slurry mainly composed of glass powder, alumina powder, and water glass. While it possesses a certain anti-oxidation capability, the coating is prone to cracking at high temperatures and has insufficient adhesion to the carbon matrix. Furthermore, it is susceptible to solid-liquid separation after long-term storage, affecting the uniformity of application. Chinese invention patent application number 2022100706620, entitled "An Anti-oxidation Coating for Aluminum Electrolytic Carbon Anode and its Preparation Method," also presents... The invention patent proposes to use a system of aluminum hydroxyfluoride and auxiliary sintering agent to form a protective layer containing phases such as lapis lazuli and mullite after sintering. However, the coating composition is complex and the cost is high. Moreover, the density of low-temperature sintering is limited, and there is still room for improvement in the antioxidant durability. The Chinese invention patent with application number 2021104773935, entitled "Ceramic-based Coating Protective Material for Electrolytic Aluminum Prebaked Anode Steel Claws and Its Preparation Method", focuses on the protection of the steel claw part. It prepares the coating by using alumina base material and grain activation process. However, its process steps are cumbersome and the ball milling and activation treatment are time-consuming, making it difficult to meet the rapid coating needs of large-scale anode carbon block surfaces.

[0004] While existing technologies have made some progress, they still suffer from common problems such as insufficient adhesion strength between the coating and the substrate, susceptibility to high-temperature cracking, complex preparation processes, high costs, and unsatisfactory long-term oxidation resistance. These issues hinder their widespread application in the electrolytic aluminum industry and further improvement of energy-saving benefits. Therefore, overcoming these technical problems and defects is a key issue that needs to be addressed. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects described in the background art and to disclose an energy-saving nano-ceramic anti-oxidation coating for use on electrolytic aluminum anode carbon blocks and its preparation method, so as to solve the problems of easy cracking, poor adhesion, complex process and insufficient anti-oxidation effect of existing coatings.

[0006] To achieve the above-mentioned objectives, the present invention discloses an energy-saving nano-ceramic anti-oxidation coating slurry for use on electrolytic aluminum anode carbon blocks, which is made from raw materials comprising the following parts by weight: 100 parts deionized water, 30-50 parts water glass, 30-50 parts α-alumina powder, 20-30 parts γ-alumina powder, 5-10 parts aluminum dihydrogen phosphate, 1-2 parts carboxymethyl cellulose, 0.5-1 parts triethanolamine, and 3 parts carbon-containing antioxidant; wherein the α-alumina powder has a particle size of 4 micrometers and the γ-alumina powder has a particle size of 2 micrometers.

[0007] The raw materials also include modified powder comprising 0.5%-5% of the total mass of the α-alumina powder, γ-alumina powder, and antioxidant.

[0008] A method for preparing an energy-saving nano-ceramic anti-oxidation coating slurry as described above includes the following steps:

[0009] S1. Preparation of liquid matrix: Carboxymethyl cellulose, triethanolamine and aluminum dihydrogen phosphate are added to deionized water, stirred until completely dissolved, and allowed to stand for aging to obtain a homogeneous liquid.

[0010] S2. Dry powder premixing: Mix α-alumina powder, γ-alumina powder, antioxidant and modified powder evenly to obtain a dry powder mixture.

[0011] S3. Mixing and homogenizing: Add the liquid obtained in step S1 to the dry powder mixture obtained in step S2, stir and grind until a paste-like slurry is formed.

[0012] Specifically, the settling and aging time in step S1 is 30 minutes.

[0013] The stirring and grinding described in step S3 specifically involves stirring with a glass rod while grinding with a mortar and pestle until a toothpaste-like or cream-like slurry is formed.

[0014] Preferably, the method further includes step S4: letting the slurry stand for 10-20 minutes to defoam.

[0015] This invention also discloses a coating protection method for electrolytic aluminum anode carbon blocks, comprising the following steps:

[0016] A. Grind and clean the surface of the anode carbon block.

[0017] B. Apply the above-mentioned energy-saving nano-ceramic anti-oxidation coating slurry to the surface of the treated anode carbon block.

[0018] C. Cure the coated anode carbon block at room temperature first, and then dry it at a low temperature of 60-80℃.

[0019] Specifically, in step B, a brush coating method is used. First, a thin layer is applied. After the first thin layer is surface dry, a second layer is applied. After the second layer is applied, its surface is smoothed.

[0020] The room temperature curing time in step C is 24 hours, and the low temperature drying conditions are 70°C drying for 3 hours.

[0021] This invention discloses an electrolytic aluminum anode carbon block coated with an energy-saving nano-ceramic anti-oxidation coating. The coating is formed by coating, curing, and drying the slurry as described above. The coating amount is 1.6-1.85 kg / m²; the coating can withstand a high-temperature oxidation environment of 900℃.

[0022] The energy-saving nano-ceramic anti-oxidation coating of the present invention is applied to the electrolytic aluminum anode carbon block in the production of electrolytic aluminum.

[0023] The energy-saving nano-ceramic anti-oxidation coating applied to electrolytic aluminum anode carbon blocks and its preparation method of the present invention have the following beneficial effects:

[0024] 1. The energy-saving nano-ceramic anti-oxidation coating of the present invention, applied to the anode carbon block of electrolytic aluminum, achieves a stable and tough bond throughout the entire process from room temperature curing to high temperature sintering by constructing a composite bonding system with water glass and aluminum dihydrogen phosphate as the core, and combining it with α-alumina and γ-alumina bimodal refractory aggregates, fundamentally avoiding cracking and peeling at high temperatures. At the same time, the optimized slurry formula and simple preparation process ensure the long-term homogeneity and stability of the slurry, avoid solid-liquid separation, significantly improve the uniformity and efficiency of construction, and reduce the overall cost.

[0025] 2. The coating provided by this invention exhibits superior protective performance and long-lasting oxidation resistance under extreme operating conditions. The dense nano-ceramic protective layer formed on the surface of the anode carbon block effectively blocks the penetration of oxygen and corrosive electrolytes, maintaining structural integrity even in high-temperature oxidizing environments above 900°C, significantly reducing the oxidation consumption rate of the anode carbon block. Simultaneously, the introduction of functional modified powders further strengthens the microstructure of the coating, significantly improving its thermal shock resistance, molten salt corrosion resistance, and high-temperature dimensional stability, thus meeting the protection requirements of various complex operating conditions, from conventional electrolytic cells to high-temperature and highly corrosive environments.

[0026] 3. The application of this invention brings significant comprehensive benefits to electrolytic aluminum production. Industrial applications show that using this coating can effectively maintain the regularity of the anode geometry, extend the anode replacement cycle, and directly reduce carbon block consumption and production costs. Simultaneously, the coating has no negative impact on the quality of primary aluminum and helps reduce harmful gas emissions and solid waste generated by excessive anode oxidation, thus possessing both good economic and environmental benefits. Based on an annual electrolytic aluminum production capacity of 600,000 tons, the long-term application of the anode anti-oxidation coating material can bring direct economic benefits of approximately RMB 23.6 million per year. Its wide process adaptability facilitates large-scale, rapid coating, providing a reliable solution for energy conservation, emission reduction, and green production in the electrolytic aluminum industry. Attached Figure Description

[0027] Figure 1 is a SEM image of the microstructure of the energy-saving nano-ceramic anti-oxidation coating of the present invention applied to the carbon block of electrolytic aluminum anode;

[0028] Figure 2. SEM image of the microstructure of the nano-ceramic protective layer of the energy-saving nano-ceramic anti-oxidation coating applied to the carbon block of electrolytic aluminum anode according to the present invention.

[0029] Figure 3 is a curve comparing the oxidation burn-off rate of the energy-saving nano-ceramic anti-oxidation coating of the present invention applied to the anode carbon block of electrolytic aluminum with the change of the uncoated carbon block over time after being kept at 900°C in air atmosphere for 7 hours.

[0030] Figure 4 is a schematic diagram of the state of the electrolytic aluminum anode carbon block with an energy-saving nano-ceramic anti-oxidation coating on its surface before it is put into the tank.

[0031] Figure 5 is a schematic diagram of the state of the electrolytic aluminum anode carbon block coated with an energy-saving nano-ceramic anti-oxidation coating after it is placed in the tank according to the present invention.

[0032] Figure 6 is a schematic diagram of the actual state of the residual anode of the electrolytic aluminum anode test cell with an energy-saving nano-ceramic anti-oxidation coating on its surface.

[0033] Figure 7 is a schematic diagram of the actual state of the anode residue in the comparison tank (without coating) at the same time period as in Figure 6;

[0034] Figure 8 is a comparison of the actual consumption height of each anode in the second cycle of industrial application of the energy-saving nano-ceramic anti-oxidation coating of the present invention applied to the carbon block of electrolytic aluminum anode, sorted by the date of electrode exit.

[0035] Figure 9 is a comparison of the actual consumption height of each anode in the second cycle of industrial application of the energy-saving nano-ceramic anti-oxidation coating of the present invention applied to the carbon block of electrolytic aluminum anode, sorted by consumption height.

[0036] Figure 10 is a comparison of the actual consumption height of each anode in the third cycle of industrial application of the energy-saving nano-ceramic anti-oxidation coating of the present invention applied to the carbon block of electrolytic aluminum anode, sorted by the date of electrode exit.

[0037] Figure 11 is a comparison of the actual consumption height of each anode in the third cycle of industrial application of the energy-saving nano-ceramic anti-oxidation coating applied to the electrolytic aluminum anode carbon block of the present invention, sorted by consumption height. Detailed Implementation

[0038] The present invention will now be described in more detail through specific embodiments.

[0039] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship shown, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0040] Example 1

[0041] This embodiment discloses an energy-saving nano-ceramic anti-oxidation coating applied to electrolytic aluminum anode carbon blocks and its preparation method. By using water glass as a binder, combined with α-alumina and γ-alumina powders of specific particle sizes as refractory aggregates, and supplemented with additives such as aluminum dihydrogen phosphate and carboxymethyl cellulose to form a uniform and stable slurry system, a dense and strongly adherent nano-ceramic protective layer can be constructed on the surface of the anode carbon block. This effectively improves the structural stability, oxidation resistance and durability of the coating at high temperatures and the adaptability of the construction process, thereby solving the problems of existing coatings such as easy cracking, poor adhesion, complex process and insufficient anti-oxidation effect.

[0042] The energy-saving nano-ceramic anti-oxidation coating slurry applied to the anode carbon block of electrolytic aluminum in this embodiment is made from raw materials comprising the following parts by weight: 100 parts deionized water, 30-50 parts water glass, 30-50 parts α-alumina powder, 20-30 parts γ-alumina powder, 5-10 parts aluminum dihydrogen phosphate, 1-2 parts carboxymethyl cellulose, 0.5-1 parts triethanolamine, and 3 parts carbon-containing antioxidant. The α-alumina powder has a particle size of 4 micrometers, and the γ-alumina powder has a particle size of 2 micrometers. The antioxidant is mainly composed of carbon-containing materials, including but not limited to modified calcined petroleum coke powder and boron carbide.

[0043] In this embodiment, a composite bonding system is constructed using water glass and aluminum dihydrogen phosphate. During drying and heating, a stable silicon-aluminum-phosphorus network skeleton is formed through chemical cross-linking and dehydration condensation, endowing the coating with excellent initial adhesion and final structural strength. Simultaneously, α-alumina powder with a particle size of 4 micrometers and γ-alumina powder with a particle size of 2 micrometers are selected as bimodal refractory aggregates. The gradation and filling effect of particles with different sizes increases the packing density of the coating slurry before sintering. At high temperatures, the high surface activity of γ-alumina promotes sintering densification, while α-alumina ensures the dimensional stability and corrosion resistance of the coating in the high-temperature environment of the electrolytic cell.

[0044] The coating slurry was prepared using the above-mentioned raw materials and proportions. The composite bonding system avoids the brittleness or insufficient temperature resistance problems associated with single binders, achieving stable bonding throughout the entire process from room temperature curing to high-temperature sintering. Simultaneously, the combination of dual-particle-size alumina not only optimizes the slurry's rheological properties for easier application but also lays the material foundation for the coating's dense structure at the microscopic level, effectively blocking the penetration of oxygen and corrosive gases. Furthermore, the carbon-containing antioxidants and triethanolamine introduced into the formulation further enhance the coating's resistance to oxidation-reduction atmospheres and improve powder dispersibility. Through the targeted design and synergistic effect of the functions of each component, the above proportions ultimately achieve long-term, stable antioxidant protection for the anode carbon block under complex high-temperature environments.

[0045] Example 2

[0046] The similarities with the above embodiments will not be repeated, the differences are as follows:

[0047] The raw materials also include modified powder comprising 0.5%-5% of the total mass of the α-alumina powder, γ-alumina powder, and antioxidant.

[0048] In this embodiment, modified powder accounting for 0.5%-5% of the total mass of α-alumina powder, γ-alumina powder and antioxidant is introduced. Through surface modification and / or the introduction of functional micro-nano particles, the interfacial compatibility and dispersion stability of solid particles in the coating matrix are further optimized, thereby enhancing the overall structure and performance of the coating at the microscopic level.

[0049] Modified powder can effectively coat or bond to the surface of the main alumina particles, reduce powder agglomeration, ensure high homogeneity of slurry components, and improve the uniformity of coating application. In addition, during high-temperature sintering, the modifier can promote mass transfer between particles and the formation of sintering necks, reduce the sintering temperature of the ceramic phase, and help form a denser nano-ceramic protective layer with fewer defects on the surface of the anode carbon block, thereby more effectively blocking the erosion of the oxidizing medium.

[0050] In this embodiment, the modified powder includes, but is not limited to, nano-alumina or nano-silica.

[0051] Example 3

[0052] The similarities with the above embodiments and their combinations will not be repeated, the differences being:

[0053] This embodiment discloses a method for preparing an energy-saving nano-ceramic anti-oxidation coating slurry as described in the above embodiment, including the following steps:

[0054] S1. Preparation of liquid matrix: Carboxymethyl cellulose, triethanolamine and aluminum dihydrogen phosphate are added to deionized water, stirred until completely dissolved, and allowed to stand for 30 minutes to obtain a homogeneous liquid.

[0055] S2. Dry powder premixing: Mix α-alumina powder, γ-alumina powder, antioxidant and modified powder evenly to obtain a dry powder mixture.

[0056] S3. Mixing and homogenizing: Add the liquid obtained in step S1 to the dry powder mixture obtained in step S2, stir and grind, using a glass rod to stir and grind with a mortar and pestle until a toothpaste-like or cream-like slurry is formed.

[0057] In this embodiment, through sequential control and mechanical synergy, multi-level homogenization from the molecular scale to the macroscopic scale is achieved, thereby constructing a slurry system with stable structure and reliable performance.

[0058] In the liquid phase preparation stage, by fully dissolving carboxymethyl cellulose, triethanolamine and aluminum dihydrogen phosphate in deionized water and allowing them to stand and age, the polymer chains are fully extended and the inorganic precursors are evenly distributed, forming a homogeneous liquid matrix with specific viscoelasticity and reactivity. This lays the chemical foundation for the good wetting and bonding of the subsequent powders.

[0059] By employing a mixing and homogenization process that combines dry powder premixing with stirring and grinding, the initial macroscopic homogenization of solid components such as α-alumina powder, γ-alumina powder, antioxidants, and trace modified powders is ensured, avoiding agglomeration and uneven dispersion that are prone to occur during direct wet mixing. When the liquid matrix is ​​added to the dry powder mixture, a combined operation of stirring with a glass rod and grinding with a mortar and pestle is used to exert a strong dispersing force on the powder agglomerates (especially nano-sized modified powders), ultimately forming a highly homogeneous paste with ideal rheological properties resembling toothpaste or cream.

[0060] In addition, this embodiment also includes step S4: letting the slurry stand for 10-20 minutes to defoam. In stage S3, the synergistic effect of stirring with a glass rod and grinding with a mortar and pestle achieves the ultimate uniformity and nanoscale dispersion of the solid and liquid components. However, the intense mechanical motion will inevitably entrain air into the viscous slurry in the form of bubbles. By letting the slurry stand for 10-20 minutes, most of the harmful bubbles can be effectively eliminated, and problems such as slurry sedimentation or surface film formation that may be caused by excessively long standing time can be avoided. This makes the entire preparation process ensure coating performance while also having good production feasibility and operational stability.

[0061] It should be noted that during large-scale production, air bubbles in the slurry can be defoamed using equipment, including but not limited to vacuum defoamers or ultrasonic defoamers.

[0062] Example 4

[0063] The similarities with the above embodiments will not be repeated, the differences are as follows:

[0064] This embodiment discloses a coating protection method for electrolytic aluminum anode carbon blocks, characterized by comprising the following steps:

[0065] A. Grind and clean the surface of the anode carbon block.

[0066] In this step, the surface of the anode carbon block is polished and cleaned. Mechanical polishing removes the oxide layer, loose particles, and contaminant film from the surface, exposing a fresh, rough carbon matrix with higher surface energy, providing excellent physical anchoring points for subsequent coatings.

[0067] B. Apply the energy-saving nano-ceramic anti-oxidation coating slurry as described in the previous embodiment to the surface of the treated anode carbon block. The coating is done by brushing. First, apply a thin layer. After the first thin layer is dry, apply a second layer. After the second layer is applied, smooth the surface.

[0068] In this step, the aforementioned nano-ceramic slurry is coated onto the treated surface. The toothpaste-like rheological properties of the slurry ensure uniform coating and controllable thickness, while effectively filling microscopic pits on the surface, achieving a tight bond between the coating and the substrate at the microscale.

[0069] Furthermore, a brush coating method is adopted, which involves applying a thin base coat, followed by a top coat after surface drying, and finally smoothing the surface. This multi-coating strategy optimizes the interface between the coating and the carbon substrate in stages. The first thin layer acts as a penetration layer; its low thickness and high fluidity allow it to fully penetrate the micropores and unevenness of the cleaned anode carbon block surface, achieving maximum close contact and initial anchoring. After surface drying, a preliminary but stable bonding interface is formed between the coating and the substrate. Applying the second layer, which bears the main protective thickness, at this point effectively avoids problems such as sagging, uneven thickness, and interface stress concentration caused by rapid solvent evaporation that are common with thick coatings applied in one go. The final smoothing operation ensures a smooth and uniform macroscopic morphology of the coating, improving aesthetics and ensuring consistent coating thickness, thereby guaranteeing the uniformity and reliability of the protective performance during subsequent sintering.

[0070] C. After coating, the anode carbon block is first cured at room temperature for 24 hours, and then dried at a low temperature of 60-80℃ for 3 hours at 70℃.

[0071] In this step, a two-stage curing process is adopted, consisting of room temperature curing followed by low-temperature drying. Room temperature curing provides a gentle environment for the evaporation of moisture in the slurry, allowing the binder system, mainly composed of water glass and aluminum dihydrogen phosphate, to initially form a network structure through the sol-gel process, thus avoiding stress cracking caused by excessively rapid drying. The low-temperature drying at 60-80℃ further promotes the dehydration condensation and strengthening of the binder network under gentle heat drive, and gradually removes residual crystal water and bound water. This ensures that the coating has sufficient mechanical strength and cohesion before being subjected to high temperatures in the bath, thereby ensuring that the coating can be completely and densely sintered into a ceramic protective layer under subsequent extreme thermal shock, rather than powdering or peeling off.

[0072] The 24-hour room temperature curing provides sufficient and gentle reaction time for the chemical bonding in the slurry, allowing the bonding network to form slowly and the internal stress to be released gradually. The subsequent 70°C, 3-hour low-temperature drying strengthens the structure while removing moisture. Without excessively impacting the nascent network structure, it effectively removes the remaining moisture in the gel network, further promoting the condensation reaction and enabling the coating to reach a pre-sintered stable state with excellent strength and toughness before entering the bath.

[0073] In addition, this embodiment also discloses an electrolytic aluminum anode carbon block with an energy-saving nano-ceramic anti-oxidation coating on its surface. The coating is formed by coating, curing, and drying the slurry described in the previous embodiment. The coating amount is 1.6-1.85 kg / m²; the coating can withstand a high-temperature oxidation environment of 900℃.

[0074] By applying the aforementioned specific formulation slurry to the anode surface at a coating rate of 1.6-1.85 kg / m², and then subjecting it to standardized curing and drying, a ceramic protective layer that combines physical insulation and high-temperature stability is constructed on the carbon block. This coating amount ensures the formation of a continuous, defect-free, and appropriately thick protective film on the complex surface of the anode, effectively blocking the erosion of oxygen and electrolytes while avoiding the risk of cracking or peeling under thermal shock due to mismatched coefficients of thermal expansion caused by excessively thick coatings.

[0075] The energy-saving nano-ceramic anti-oxidation coating of the present invention, when applied to the electrolytic aluminum anode carbon block, establishes an active, stable and durable physicochemical barrier for the anode in the extreme environment of high temperature and strong corrosion inside the electrolytic cell.

[0076] Example 5

[0077] The similarities with the above embodiments will not be repeated, the differences are as follows:

[0078] In this embodiment, an energy-saving nano-ceramic anti-oxidation coating and its preparation method are disclosed. By mass, the coating slurry composition is as follows: 100 parts deionized water, 40 parts water glass, 40 parts α-alumina powder (4μm), 25 parts γ-alumina powder (2μm), 8 parts aluminum dihydrogen phosphate, 1.5 parts carboxymethyl cellulose, 0.8 parts triethanolamine, 3 parts carbon-containing antioxidant (calcined petroleum coke powder), and 2% nano-alumina modified powder accounting for 2% of the total mass of α-alumina, γ-alumina and antioxidant.

[0079] In the preparation process, carboxymethyl cellulose, triethanolamine, and aluminum dihydrogen phosphate are first added sequentially to deionized water, stirred and dissolved, and then allowed to stand for 30 minutes to form a homogeneous liquid phase. Then, α-alumina, γ-alumina, antioxidants, and nano-alumina are premixed evenly in a mortar. The liquid phase is then slowly poured into the dry powder, stirred with a glass rod, and ground in a mortar for 15–20 minutes to form a uniform toothpaste-like slurry. This slurry is then allowed to stand for 15 minutes to defoam. Before coating, the surface of the anode carbon block is polished and cleaned. During application, a brush coating method is used, first uniformly applying a thin layer, allowing it to dry slightly before applying a second layer, and finally smoothing the surface. The coated anode carbon block is then cured at room temperature for 24 hours, followed by drying in a 70℃ oven for 3 hours to obtain a firmly adhered, dense, energy-saving nano-ceramic anti-oxidation coating.

[0080] In this embodiment, 40 parts of water glass and 8 parts of aluminum dihydrogen phosphate together constitute a composite bonding system. During drying and heating, a silicon-aluminum-phosphorus network is formed through a chemical cross-linking reaction, thereby providing excellent initial adhesion and high-temperature structural strength. α-alumina and γ-alumina utilize the gradation and filling effect of the 4μm α phase and 2μm γ phase to significantly improve the bulk density of the slurry. Furthermore, the high activity of the γ phase promotes densification during sintering, while the α phase ensures the dimensional stability of the material under high-temperature conditions. Referring to Figure 1, electron microscopy reveals a dense coating without through-cracks. 3 parts of carbon-containing antioxidant and 0.8 parts of triethanolamine not only enhance the coating's resistance to redox atmospheres but also improve powder dispersibility; no abnormalities were found after water boiling resistance testing. 2% nano-alumina modification further improves the compatibility and dispersion stability of the particle interface, lowers the sintering temperature, and promotes the formation of a denser ceramic protective layer.

[0081] The experimental data for the coatings prepared according to the above proportions are shown in Table 1 below:

[0082] Test Items, Test Conditions, Methods, Results, and Explanation: Adhesion: Tape Peeling Method, Grade 0, no peeling, meets industrial coating requirements; Water Resistance: Boiling in water for 2 hours, coating intact, no peeling or chalking; Weather Resistance: Good; High-Temperature Oxidation Weight Loss: 900℃ air atmosphere, heat preservation for 7 hours, average weight loss 2.3%, approximately 30% lower than the uncoated sample; Coating Porosity: Scanning Electron Microscopy Image Analysis, <8%, dense structure, effectively blocking oxygen; Industrial Residual Electrode Thickness Comparison: A 400kA cell in an aluminum plant in Henan, third cycle test cell residual electrode thickness 0.6cm > control cell; Electrode replacement cycle extended by 1 day. surface

[0083] Table 1

[0084] This formulation underwent an industrial trial for three electrode replacement cycles in a 400kA electrolytic cell at an aluminum plant in Henan Province from September 25, 2022 to January 5, 2023. Four test cells (4321#-4324#) and four control cells (4315#-4318#) were set up. In the first cycle (34 days), the original anodes were gradually replaced with coated anodes. In the second cycle (34 days), the residual electrode dimensions were measured daily, and data showed that the average thickness of the coated anode residual electrode was 1.5cm higher. In the third cycle, the electrode replacement cycle in the test cells was extended to 35 days (the control cells remained at 34 days), and the residual electrode thickness after removal was still 0.6cm higher. During the trial, the average coating application was 1.85kg / m², approximately 1.76kg per ton of aluminum. It is expected that this can be controlled below 1.6kg after large-scale promotion. The results show that the coating can effectively reduce carbon block oxidation and slag shedding, maintain the anode geometry, and extend the service life by 1 day.

[0085] The electrolytic aluminum anode carbon block prepared by the above process and formula, with an energy-saving nano-ceramic anti-oxidation coating on its surface, has been fully verified in industry. It has balanced comprehensive performance, good workability, and excellent slurry stability. It is suitable for continuous large-scale coating and has a high cost performance. It is suitable for prebaked anode electrolytic cells with conventional electrolysis temperature (850–920℃) and relatively stable atmosphere.

[0086] Example 6

[0087] The similarities with the above embodiments will not be repeated, the differences are as follows:

[0088] In this embodiment, an energy-saving nano-ceramic anti-oxidation coating and its preparation method are disclosed. By mass, the coating slurry composition is as follows: 100 parts deionized water, 50 parts water glass, 30 parts α-alumina powder (4μm), 30 parts γ-alumina powder (2μm), 10 parts aluminum dihydrogen phosphate, 2 parts carboxymethyl cellulose, 1 part triethanolamine, 3 parts carbon-containing antioxidant (boron carbide), and nano-silica modified powder accounting for 3% of the total mass of the above dry powder.

[0089] In preparation, carboxymethyl cellulose, triethanolamine, and aluminum dihydrogen phosphate are first dissolved in water, stirred, and allowed to stand for 30 minutes to age. Then, all powder raw materials are premixed evenly in a mixer. The liquid phase is added to the dry powder and transferred to a planetary grinder for grinding for 30 minutes to form a fine, creamy slurry, which is then degassed under vacuum. The coating application also adopts a layered brushing method: after the anode surface is sanded and cleaned, a thin layer is first applied as a penetrating primer. After surface drying, a second layer is applied and smoothed. After coating, the anode is cured at room temperature for 24 hours and then dried at 70°C for 3 hours to form a nano-ceramic coating with extremely high adhesion strength and impact resistance.

[0090] In this embodiment, 50 parts of water glass and 10 parts of aluminum dihydrogen phosphate form a denser network skeleton, giving the coating excellent initial adhesion and high-temperature bonding strength. 30 parts of α-alumina and 30 parts of γ-alumina, while ensuring refractoriness, increase the proportion of highly active γ-phase, promote medium- and low-temperature sintering, and ensure that the coating forms a strong whole before being subjected to mechanical stress, significantly increasing the bulk density of the slurry.

[0091] The experimental data for the coatings prepared according to the above proportions are shown in Table 2 below:

[0092] Test Item Test Conditions and Methods Results Description Adhesion (Cross-cut Test) 1mm cross-cut test, tape peeling grade 0, no peeling Excellent bonding strength Thermal shock resistance 900℃↔room temperature water quenching, 5 cycles, coating no cracking or peeling Resistance to rapid temperature changes High temperature oxidation weight loss 900℃ air atmosphere, heat preservation for 7 hours, average weight loss rate 2.1% High bonding system Effective oxygen barrier Bending strength Three-point bending test Coating specimen ≥15MPa High mechanical strength Industrial application performance Same factory test, high vibration tank section residual thickness Comparison Tank height 0.8cm still maintains integrity under mechanical vibration surface

[0093] Table 2

[0094] The SEM image of the nano-ceramic protective layer is shown in Figure 2. Under the same industrial testing framework as Example 5, this high-strength formulation performed exceptionally well in the second cycle under conditions of high mechanical vibration and anode assembly stress, with no instances of coating cracking or peeling. In the third cycle, the electrode replacement cycle of the test tank was extended to 35 days. Measurements after electrode removal showed that the residual electrode thickness was on average 0.8 cm thicker than that of the control tank, indicating a superior protective effect compared to the standard formulation. This demonstrates that the formulation maintains high-strength adhesion without sacrificing its antioxidant properties, making it particularly suitable for production environments with unstable tank conditions and strong mechanical interference.

[0095] The electrolytic aluminum anode carbon block prepared by the above process and formula, with a surface coated with an energy-saving nano-ceramic anti-oxidation coating, has been fully verified in industry to have excellent ultimate bonding strength and impact resistance, good thermal shock resistance, and is not easily damaged under vibration or thermal shock; it is suitable for electrolytic cells with high current density, high mechanical stress during anode assembly or operation, and frequent thermal shock.

[0096] Example 7

[0097] The similarities with the above embodiments will not be repeated, the differences are as follows:

[0098] In this embodiment, an energy-saving nano-ceramic anti-oxidation coating and its preparation method are disclosed. By mass, the coating slurry composition is as follows: 100 parts deionized water, 30 parts water glass, 50 parts α-alumina powder (4μm), 20 parts γ-alumina powder (2μm), 5 parts aluminum dihydrogen phosphate, 1 part carboxymethyl cellulose, 0.5 parts triethanolamine, 3 parts carbon-containing antioxidant (calcined petroleum coke powder), and 5% nano-alumina modified powder accounting for 5% of the total dry powder mass.

[0099] The preparation process is as follows: First, a liquid phase containing carboxymethyl cellulose, triethanolamine, and aluminum dihydrogen phosphate is prepared and aged; then, all powder components are thoroughly mixed in a three-dimensional mixer; after mixing the liquid phase and dry powder, the mixture is sequentially subjected to high-speed shear dispersion and fine rolling with a three-roll mill to form a paste-like slurry with extremely high solid content and density, and finally defoamed by ultrasonication. The coating process adopts the same layered brush coating and curing procedure as in Example 6 (grinding → two layers of brush coating and smoothing → room temperature curing for 24 hours → drying at 70°C for 3 hours), ultimately forming an ultra-dense ceramic protective layer with high refractory properties on the anode surface.

[0100] The experimental data for the coatings prepared according to the above proportions are shown in Table 3 below:

[0101] Test Items, Test Conditions, Methods, Results, Explanation: High-Temperature Oxidation Weight Loss: 950℃ air atmosphere, 7-hour heat treatment, average weight loss 2.0%. Suitable for ultra-high temperature oxidation environments. Resistant to electrolyte corrosion. Immersed in molten cryolite (Na3AlF6) for 2 hours: no penetration, no peeling. Extremely strong resistance to fluoride salt corrosion. Coating porosity: <5% (SEM image analysis). Highly dense structure. Thermal expansion coefficient measured by a high-temperature horizontal dilatometer. Good matching with anode carbon block, reducing the risk of thermal stress cracking. Industrial residual electrode morphology: High-corrosion tank conditions. Long-term monitoring shows that the residual electrode geometry is regular, with no localized pitting. Suitable for extreme corrosion conditions. surface

[0102] Table 3

[0103] In comparative tests conducted under high-temperature, high-fluoride-concentration conditions, this highly refractory formulation demonstrated unparalleled protective capabilities. During months of follow-up experiments, the coated anode maintained a complete ceramic protective layer even at temperatures above 950°C, effectively resisting the penetration and erosion of the molten salt electrolyte. After tapping, the residual anode surface was smooth and flat, with clear edges and corners, showing no localized burning or erosion. Primary aluminum quality analysis showed that the iron content decreased due to reduced corrosion, while the silicon content slightly increased and then stabilized, confirming that the coating not only extended anode life under extreme conditions but also had no negative impact on the purity of the molten aluminum.

[0104] The electrolytic aluminum anode carbon block prepared by the above process and formula, with an energy-saving nano-ceramic anti-oxidation coating, has been fully verified in industry to have top-notch fire resistance, resistance to molten salt corrosion and high-temperature structural stability, and the longest coating life. It is suitable for extreme electrolytic cells with electrolysis temperatures above 900℃, strong electrolyte corrosiveness (high fluoride content) or local overheating areas.

[0105] Furthermore, it should be noted that in specific implementations, the structures or processes described in this specification are not fixed or unchanging embodiments. The components of the embodiments of the present invention described and shown herein can be arranged and designed in various different configurations. These are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Additionally, this specification is for illustrative purposes only and does not represent the specific structure or actual quantity in a concrete implementation.

[0106] Unless otherwise defined, the technical or scientific terms used herein should be understood in their ordinary sense as would be understood by one of ordinary skill in the art to which this invention pertains. The use of terms such as "a" or "an" in this specification and claims does not necessarily indicate a limitation of quantity. Terms such as "comprising" or "including" mean that the element or component preceding the word encompasses the element or component listed following the word and its equivalents, without excluding other elements or components. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0107] The exemplary embodiments of the present invention have been described in detail above with reference to preferred embodiments. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of the present invention, and various combinations can be made to the various technical features and structures proposed in the present invention without exceeding the protection scope of the present invention.

Claims

1. An energy-saving nano-ceramic anti-oxidation coating slurry applied to electrolytic aluminum anode carbon blocks, characterized in that, It is made from raw materials comprising the following parts by weight: 100 parts deionized water, 30-50 parts water glass, 30-50 parts α-alumina powder, 20-30 parts γ-alumina powder, 5-10 parts aluminum dihydrogen phosphate, 1-2 parts carboxymethyl cellulose, 0.5-1 parts triethanolamine, and 3 parts carbon-containing antioxidant; wherein the α-alumina powder has a particle size of 4 micrometers and the γ-alumina powder has a particle size of 2 micrometers.

2. The energy-saving nano-ceramic anti-oxidation coating slurry according to claim 1, characterized in that, The raw materials also include modified powder comprising 0.5%-5% of the total mass of the α-alumina powder, γ-alumina powder, and antioxidant.

3. A method for preparing the energy-saving nano-ceramic anti-oxidation coating slurry as described in claim 2, characterized in that, Includes the following steps: S1. Liquid matrix preparation: Carboxymethyl cellulose, triethanolamine and aluminum dihydrogen phosphate are added to deionized water, stirred until completely dissolved, and allowed to stand for aging to obtain a homogeneous liquid; S2. Dry powder premixing: α-alumina powder, γ-alumina powder, antioxidant and modified powder are mixed evenly to obtain a dry powder mixture; S3. Mixing and homogenization: The liquid obtained in step S1 is added to the dry powder mixture obtained in step S2, stirred and ground to form a paste slurry.

4. The method for preparing the energy-saving nano-ceramic anti-oxidation coating slurry according to claim 3, characterized in that, The settling and aging time in step S1 is 30 minutes; the stirring and grinding in step S3 specifically involves stirring with a glass rod while grinding with a mortar and pestle until a toothpaste-like or cream-like slurry is formed; and step S4 is also included: let the slurry stand for 10-20 minutes to defoam.

5. A coating protection method for electrolytic aluminum anode carbon blocks, characterized in that, Includes the following steps: A. Grind and clean the surface of the anode carbon block; B. Apply the energy-saving nano-ceramic anti-oxidation coating slurry as described in claim 1 or 2 to the surface of the treated anode carbon block; C. Cure the coated anode carbon block at room temperature first, and then dry it at a low temperature of 60-80℃.

6. The coating protection method for electrolytic aluminum anode carbon blocks according to claim 5, characterized in that, In step B, a brush coating method is used. First, a thin layer is applied. After the first thin layer is surface dry, a second layer is applied. After the second layer is applied, its surface is smoothed. In step C, the room temperature curing time is 24 hours, and the low temperature drying conditions are 70°C drying for 3 hours.

7. An electrolytic aluminum anode carbon block with a surface coated with an energy-saving nano-ceramic anti-oxidation coating, characterized in that, The coating is formed by coating, curing and drying the slurry as described in claim 1 or 2.

8. The electrolytic aluminum anode carbon block according to claim 7, characterized in that, The coating has a coating weight of 1.6-1.85 kg / m²; the coating can withstand a high-temperature oxidation environment of 900℃.

9. The application of an electrolytic aluminum anode carbon block with an energy-saving nano-ceramic anti-oxidation coating as described in any one of claims 7 to 8 in the production of electrolytic aluminum.

Images