Corrosion-resistant inorganic composite resin coating for silicon carbide rod and preparation method of corrosion-resistant inorganic composite resin coating

Abstract

The invention relates to a corrosion-resistant inorganic composite resin coating for a silicon carbide rod and a preparation method of the corrosion-resistant inorganic composite resin coating. The coating comprises a group A inorganic resin mixed solution and a group B inorganic high-temperature-resistant material, the inorganic composite resin mixed solution comprises aluminum sol, silica sol, a potassium silicate solution, a siloxane modifier, deionized water and hydrochloric acid; the inorganic high-temperature-resistant material is one or a combination of more than two of silicon carbide, mullite, silicon nitride, magnesium oxide and carbon nanotube water slurry; the mass ratio of the two is (2-3): 1. According to the corrosion-resistant inorganic composite resin coating for the silicon carbide rod, provided by the invention, silica sol, alumina sol and potassium silicate are mainly used as a binding agent together and permeate into micropores in the surface of the silicon carbide rod to seal the micropores, so that the acid and alkali resistance of the coating under a high-temperature condition is improved, and the adhesive force of the coating on the surface of the silicon carbide rod is enhanced. And a compact high-temperature-resistant layer is formed on the silicon carbide rod, so that the high temperature resistance and corrosion resistance of the silicon carbide rod are improved, and the service life of the silicon carbide rod is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of corrosion-resistant inorganic composite resin coating for silicon-carbon rod and its preparation method, belong to high-temperature resistant anticorrosion coating field. BACKGROUND

[0002] Silicon-carbon rod is mainly used as heating element in float glass electric tank, optical glass melting furnace, glass deep processing furnace, and is also widely used in high-temperature resistance furnace, high-temperature electric kiln, low-temperature electric kiln and other fields. Since silicon-carbon rod is used at high temperature for a long time, the silicon carbide (SiC) on the surface of silicon-carbon rod will chemically react with oxygen and water vapor, causing the SiC on the surface of silicon-carbon rod to eventually become SiO2 and gradually transfer from the surface to the deep layer, resulting in an increase in the resistance of silicon-carbon rod and eventually leading to a decrease in its performance; at a high temperature of 1500℃, acid-base mist and corrosive liquid often cause corrosion to silicon-carbon rod.

[0003] The coating formed by sodium silicate or potassium silicate and silicon nitride has relatively poor oxidation resistance and bonding force when used at a high temperature of up to 1500℃ for a long time. Chinese patent document CN109081707A discloses a high-temperature-resistant coating for silicon-carbon rod prepared from silicon carbide and sodium silicate, which uses sodium silicate as a bonding agent. However, the coating is prone to peeling under high-temperature conditions when sodium silicate is used as a single bonding agent, making silicon-carbon rod susceptible to corrosion and leading to a shortened service life.

[0004] Chinese patent document CN113800950A discloses a preparation method for a glass coating on the surface of silicon-carbon rod, which involves immersing the silicon-carbon rod in an aluminum-silicon sol and then coating the surface of the silicon-carbon rod with a layer of glass liquid formed by high-temperature melting of high-temperature-resistant powder. However, separately coating the bonding agent and high-temperature-resistant glass paste can cause the outer layer of high-temperature-resistant glass paste to peel off, resulting in a coating that does not meet the requirements for high-temperature resistance and corrosion resistance, and the preparation process is complex, involves many control parameters, is not conducive to the control of product consistency, and has high energy consumption in the preparation process. SUMMARY

[0005] To overcome the shortcomings of coatings using water glass as the main bonding agent, such as low bonding force and poor oxidation resistance at high temperatures, the present application provides a corrosion-resistant inorganic composite resin coating for silicon-carbon rod and a preparation method thereof.

[0006] The technical solution of the present application is as follows: A corrosion-resistant inorganic composite resin coating for silicon-carbon rod, comprising a group A inorganic resin mixture and a group B inorganic high-temperature-resistant material. The group A inorganic composite resin mixture comprises aluminum sol, silicon sol, potassium silicate solution, siloxane modifier, deionized water and hydrochloric acid. The B group inorganic high-temperature-resistant material is one or a combination of two or more of silicon carbide, mullite, silicon nitride, magnesium oxide, and carbon nanotube water slurry. The mass ratio of the A group inorganic resin mixed solution to the B group inorganic high-temperature-resistant material is (2-3):1.

[0007] According to the present application, the A group inorganic composite resin includes, by weight, 60-70 parts of aluminum sol, 15-25 parts of silicon sol, 5-8 parts of potassium silicate solution, 5-8 parts of siloxane modifier, 7-10 parts of deionized water, and 0.2-0.3 parts of hydrochloric acid.

[0008] Further preferably, the aluminum sol has a solid content of 15-20 wt%, a pH of 4-6, and a colloidal particle size of 15-25 nm in the aluminum sol. The aluminum sol can be purchased on the market.

[0009] Further preferably, the silicon sol has a solid content of 19-21 wt%, a pH of 9-11, and a SiO2 particle size of 10-15 nm in the silicon sol. The silicon sol can be prepared by a conventional silicon powder hydrolysis method.

[0010] Further preferably, the potassium silicate solution has a solid content of 30 wt% and a modulus of 3.5-3.9.

[0011] Further preferably, the siloxane modifier is one or a combination of two or more of methyltrimethoxysilane, methyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0012] According to the present application, the B group inorganic high-temperature-resistant material includes, by weight, 15-30 parts of silicon carbide, 20-30 parts of mullite, 15-25 parts of silicon nitride, 10-20 parts of magnesium oxide, and 3-5 parts of carbon nanotube water slurry.

[0013] Further preferably, the silicon carbide has a particle size of 320 mesh and a purity of ≥90%; The mullite has a particle size of 320 mesh and Al2O3≥72%; The silicon nitride has a particle size of 2000 mesh and a nitrogen content of 40-45%; The magnesium oxide has a particle size of 320 mesh and MgO≥85%; The carbon nanotube water slurry is a multi-walled carbon nanotube water slurry having a multi-walled carbon nanotube content of 5-10 wt%, a diameter of 5-15 nm, and a length of 10-30 μm.

[0014] According to the present application, the preparation method of the A group inorganic resin mixed solution includes the following steps: According to the proportion, the deionized water and hydrochloric acid are mixed to obtain a dilute hydrochloric acid solution; then the silica sol, potassium silicate and siloxane modifier are added into the dilute hydrochloric acid solution while stirring, and after reaction at 50-70℃ for 2-3h, the temperature is lowered to 20-30℃, and the acid solution is obtained after filtration; the aluminum sol is continuously added into the acid solution and stirred uniformly to obtain the A group inorganic resin mixture.

[0015] Further preferably, the reaction temperature is 60℃, and the reaction time is 2.5h.

[0016] Further preferably, the filtration is treated by using 732 cation exchange resin; and the stirring speed is 300-400r / min.

[0017] According to the present application, the preparation method of the corrosion-resistant inorganic composite resin coating for silicon-carbon rods comprises the following steps: (1) according to the proportion, the B group inorganic high-temperature-resistant material is sequentially added into the A group inorganic resin mixture, and high-speed stirring is performed for 25-35min to obtain the corrosion-resistant inorganic composite resin; (2) the corrosion-resistant inorganic composite resin obtained in step (1) is uniformly coated on the surface of the silicon-carbon rod, and the silicon-carbon rod is dried in a clean room at 20-30℃ for 4-8h, and then is dried and solidified at 160-200℃ for 15-25min; (3) the operation in step (2) is repeated for 2-4 times, and the coated silicon-carbon rod is naturally cooled to 20-30℃, and then is dried at 160-200℃ for 2-4h; then the temperature is increased to 300℃ at a rate of 5℃ / min, and is kept for 2-3h, and then is increased to 1500℃ at a rate of 10℃ / min, and is kept for 3-5h, and finally is naturally cooled to 200℃, to obtain the corrosion-resistant inorganic composite resin coating for silicon-carbon rods.

[0018] According to the present application, in step (1), the silicon-carbon rod can be one or more of equal-diameter silicon-carbon rods, U-shaped silicon-carbon rods or threaded silicon-carbon rods, and the coating of the present application can be suitable for various shapes of silicon-carbon rods.

[0019] According to the present application, in step (1), the high-speed stirring is treated by using a high-speed stirring dispersion machine, and the stirring speed is 600-800r / min.

[0020] According to the present application, in step (2), the coating method can be dip coating, spray coating or brush coating, and the formed film thickness is about 15-25μm.

[0021] Technical features of the present application: The application innovatively introduces silica sol, potassium silicate and aluminum sol together as a binder under high temperature conditions in the inorganic composite resin coating. Among them, the silica sol and potassium silicate are modified by siloxane, which can improve the compatibility with the aluminum sol, improve the adhesion to the substrate, and facilitate the dispersion of inorganic high-temperature-resistant powder. After high-temperature treatment, the aluminum sol is almost completely converted into alpha-Al2O3, which has excellent high-temperature resistance and can effectively protect the silicon-carbon rod from aging at a temperature above 1500℃, has excellent oxidation resistance and corrosion resistance in acid and alkali atmosphere, and has good bonding force, which can greatly prolong the service life of the silicon-carbon rod and reduce the cost and resource waste caused by replacing the silicon-carbon rod. And a variety of inorganic high-temperature-resistant materials can improve the high-temperature resistance of the coating, and carbon nanotubes can enhance the acid and alkali corrosion resistance of the coating under high temperature conditions.

[0022] Advantages: 1. The corrosion-resistant inorganic composite resin coating for silicon-carbon rods provided by the application mainly uses silica sol, aluminum sol and potassium silicate together as a binder to penetrate into the micropores on the surface of the silicon-carbon rod, seal the micropores, improve the acid and alkali resistance of the coating under high temperature conditions, and the generated Si-O-Si bond enhances the adhesion of the coating on the surface of the silicon-carbon rod. And high-temperature-resistant powder is also added to form a dense high-temperature-resistant layer on the silicon-carbon rod, improve the high-temperature resistance and corrosion resistance of the silicon-carbon rod, and prolong the service life of the silicon-carbon rod.

[0023] 2. The application improves the compatibility of silica sol and potassium silicate with aluminum sol by using a siloxane modifier, and improves the flexibility of the coating, which can provide a thermal expansion coefficient matching the silicon-carbon rod, improve the adhesion of the coating between high and low temperatures, and facilitate the formation of a complete protective layer on the surface of the silicon-carbon rod.

[0024] 3. The application uses silica sol, potassium silicate and aluminum sol together as a binder to form a dense high-temperature-resistant protective coating with inorganic high-temperature-resistant materials. Al2O3 in the aluminum sol is almost completely converted into alpha-Al2O3 with higher temperature resistance under high temperature conditions, so that the coating has a high temperature resistance coefficient, which can protect the silicon-carbon rod under high temperature conditions of 1500℃, avoid aging of the coating, and prolong the service life.

[0025] 4. The application adds carbon nanotube components to the corrosion-resistant inorganic composite resin coating for silicon-carbon rods, which can improve the high-temperature resistance and acid and alkali corrosion resistance of the coating, and improve the use stability of the silicon-carbon rod under extreme conditions. And the coating preparation process of the application is simple and feasible, the construction is simple, the raw material cost is low, and it is green and energy-saving. DETAILED DESCRIPTION

[0026] The technical solutions of the present application will be further described below in combination with examples, but the protection scope of the present application is not limited to this. The reagents and materials involved in the examples are all ordinary commercially available products if not otherwise specified.

[0027] Example 1 A corrosion-resistant inorganic composite resin coating for silicon-carbon rods is composed of an A group inorganic resin mixture and a B group inorganic high-temperature-resistant material; The A group inorganic composite resin includes, in terms of weight parts, aluminum sol 60 parts, silicon sol 15 parts, potassium silicate solution 10 parts, siloxane modifier 5 parts, deionized water 9.8 parts, and hydrochloric acid 0.2 part; The B group inorganic high-temperature-resistant material includes, in terms of weight parts, silicon carbide 30 parts, mullite 25 parts, silicon nitride 20 parts, magnesium oxide 20 parts, and carbon nanotube water slurry 5 parts. The mass ratio of the A group inorganic resin mixture to the B group inorganic high-temperature-resistant material is 3:1.

[0028] The preparation method of the above-mentioned corrosion-resistant inorganic composite resin coating for silicon-carbon rods includes the following steps: S1. Mix deionized water and hydrochloric acid according to the ratio to obtain a dilute hydrochloric acid solution; then add silicon sol, potassium silicate, and siloxane modifier to the dilute hydrochloric acid solution while stirring, and react at 60℃ for 2.5h, then cool to 25℃, filter to obtain an acidic solution; continue to add aluminum sol to the acidic solution and stir uniformly to obtain an A group inorganic resin mixture; S2. Under high-speed stirring and dispersion, add silicon carbide, mullite, silicon nitride, magnesium oxide, and carbon nanotube water slurry to the A group inorganic resin mixture according to the ratio under high-speed stirring at 700r / min, and disperse for 25-35min to obtain a corrosion-resistant inorganic composite resin; S3. Uniformly brush the corrosion-resistant inorganic composite resin on the surface of a U-shaped silicon-carbon rod, and dry in a clean room at 25℃ for 6h, and then dry and solidify at 180℃ for 20min; S4. After repeating the operation in S3 for 3 times, naturally cool to 25℃, dry the brushed silicon-carbon rod at 180℃ for 3h, then increase the temperature to 300℃ at a rate of 5℃ / min, keep for 2.5h, then increase the temperature to 1500℃ at a rate of 10℃ / min, keep for 4h, and finally naturally cool to 200℃ to obtain a corrosion-resistant inorganic composite resin coating for silicon-carbon rods.

[0029] Example 2 A corrosion-resistant inorganic composite resin coating for silicon-carbon rods is composed of an A group inorganic resin mixture and a B group inorganic high-temperature-resistant material; The A group inorganic resin mixture includes, by weight parts: aluminum sol 50 parts, silica sol 20 parts, potassium silicate solution 5 parts, siloxane modifier 5 parts, deionized water 9.8 parts, hydrochloric acid 0.2 parts; The B group inorganic high-temperature-resistant material includes, by weight parts: silicon carbide 30 parts, mullite 25 parts, silicon nitride 20 parts, magnesium oxide 20 parts, carbon nanotube water slurry 5 parts; The mass ratio of the A group inorganic resin mixture to the B group inorganic high-temperature-resistant material is 2:1.

[0030] The specific preparation method is the same as that of Example 1.

[0031] Comparative Example 1 A coating for a silicon-carbon rod, which is composed of an A group inorganic resin mixture and a B group inorganic high-temperature-resistant material; The A group includes, by weight parts: silica sol 75 parts, potassium silicate solution 10 parts, siloxane modifier 5 parts, deionized water 9.8 parts, hydrochloric acid 0.2 parts; The B group includes, by weight parts: silicon carbide 30 parts, mullite 25 parts, silicon nitride 20 parts, magnesium oxide 20 parts, carbon nanotube water slurry 5 parts.

[0032] The mass ratio of the A group inorganic resin mixture to the B group inorganic high-temperature-resistant material is 3:1.

[0033] Compared with Example 1, the present comparative example does not add aluminum sol.

[0034] Then, the coating for a silicon-carbon rod is prepared according to the method described in Example 1.

[0035] Comparative Example 2 A coating for a silicon-carbon rod, which is composed of an A group inorganic resin mixture and a B group inorganic high-temperature-resistant material; The A group includes, by weight parts: aluminum sol 70 parts, silica sol 15 parts, potassium silicate solution 10 parts, siloxane modifier 5 parts, deionized water 9.8 parts, hydrochloric acid 0.2 parts; The B group includes, by weight parts: silicon carbide 35 parts, mullite 25 parts, silicon nitride 20 parts, magnesium oxide 20 parts.

[0036] The mass ratio of the A group inorganic resin mixture to the B group inorganic high-temperature-resistant material is 3:1.

[0037] Compared with Example 1, the present comparative example does not add carbon nanotube water slurry.

[0038] Then, the coating for a silicon-carbon rod is prepared according to the method described in Example 1.

[0039] Comparative Example 3 A coating for a silicon-carbon rod, which is composed of an A group inorganic resin mixture and a B group inorganic high-temperature-resistant material; The A group inorganic composite resin includes, by weight parts: aluminum sol 65 parts, silica sol 15 parts, potassium silicate solution 10 parts, deionized water 9.8 parts, hydrochloric acid 0.2 parts; The B group inorganic high-temperature resistant material includes, by weight parts: silicon carbide 30 parts, mullite 25 parts, silicon nitride 20 parts, magnesium oxide 20 parts, carbon nanotube water slurry 5 parts; The mass ratio of the A group inorganic resin mixed solution to the B group inorganic high-temperature resistant material is 3:1.

[0040] Compared with Example 1, this comparative example does not add a siloxane modifier.

[0041] Then, the coating for silicon-carbon rods is prepared according to the method described in Example 1.

[0042] Comparative Example 4 A coating for silicon-carbon rods is composed of an A group inorganic resin mixed solution and a B group inorganic high-temperature resistant material; The A group inorganic composite resin includes, by weight parts: aluminum sol 65 parts, silica sol 15 parts, potassium silicate solution 10 parts, deionized water 9.8 parts, hydrochloric acid 0.2 parts; The B group inorganic high-temperature resistant material includes, by weight parts: silicon carbide 30 parts, mullite 25 parts, silicon nitride 20 parts, magnesium oxide 20 parts, carbon nanotube water slurry 5 parts; The mass ratio of the A group inorganic resin mixed solution to the B group inorganic high-temperature resistant material is 1:1.

[0043] Compared with Example 1, this comparative example changes the mass ratio of the A group inorganic resin mixed solution to the B group inorganic high-temperature resistant material.

[0044] Then, the coating for silicon-carbon rods is prepared according to the method described in Example 1.

[0045] Test Example The corrosion-resistant inorganic composite resin coating for silicon-carbon rods prepared in Examples 1-2 and the coating for silicon-carbon rods prepared in Comparative Examples 1, 2 and 4 are aged at 1500℃ for 200h, and the process is repeated 20 times. After 20 times of aging test, the resistance growth rate is measured and the coating integrity is observed. The results are shown in Table 1.

[0046] Resistance growth rate = (R-R0) / R0, R0 is the initial resistance, and R is the resistance after aging.

[0047] Table 1 As shown in Table 1, the resistivity of the coating prepared in Example 1 for the silicon-carbon rod is increased by 8%, and the coating does not fall off, the resistivity of the coating prepared in Example 2 for the silicon-carbon rod is increased by 10%, and the coating does not fall off. The resistivity of the coating prepared in Comparative Example 1 for the silicon-carbon rod is increased by 30%, and the coating falls off, because the ordinary binder can withstand 1400℃ temperature resistance strength, and the present application can improve the high temperature resistance of the coating by adding aluminum sol. The resistivity of the coating prepared in Comparative Example 2 for the silicon-carbon rod is increased by 25%, and the coating surface is corroded, which shows that the addition of carbon nanotubes in the present application can improve the acid and alkali corrosion resistance of the silicon-carbon rod, and further protect the silicon-carbon rod. In Comparative Example 3, since siloxane is not added, when the A group inorganic resin mixed solution is prepared, the aluminum sol colloidal particles are positively charged, the silica sol colloidal particles are negatively charged, and after the combination, the mixture is quickly in the form of jelly and is precipitated, so that the preparation of the inorganic composite resin cannot be carried out. In Comparative Example 4, the A group inorganic resin mixed solution and the B group inorganic high temperature resistant material are changed to have a mass ratio of 1:1, compared with Example 1, the addition ratio of the B group inorganic high temperature resistant material is increased, which leads to the decrease of the wrapping property of the final inorganic composite resin, the powder particles cannot be uniformly dispersed on the surface of the silicon-carbon rod, which leads to the increase of the resistance of the coating after 20 times of aging test, and the coating falls off.

[0048] The above described examples are only preferred specific embodiments of the present application, and are not used to limit the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A corrosion-resistant inorganic composite resin coating for a silicon carbon rod, characterized in that: It includes group A inorganic resin mixed liquid and group B inorganic high temperature resistant material; The inorganic composite resin mixture of group A comprises: aluminum sol, silica sol, potassium silicate solution, siloxane modifier, deionized water and hydrochloric acid; The inorganic high temperature resistant material of group B is one or a combination of two or more of silicon carbide, mullite, silicon nitride, magnesium oxide, and carbon nanotube aqueous slurry; The mass ratio of the inorganic resin mixture of group A to the inorganic high-temperature resistant material of group B is (2-3):

1.

2. The corrosion-resistant inorganic composite resin coating for silicon carbon rods according to claim 1, wherein: In parts by weight, the inorganic composite resin group A includes: 60-70 parts of aluminum sol, 15-25 parts of silica sol, 5-8 parts of potassium silicate solution, 5-8 parts of siloxane modifier, 7-10 parts of deionized water, and 0.2-0.3 parts of hydrochloric acid.

3. The corrosion-resistant inorganic composite resin coating for silicon carbon rods according to claim 2, wherein: The aluminum sol has a solid content of 15-20 wt %, a pH of 4-6, and a colloidal particle size of 15-25 nm. The silica sol has a solid content of 19-21 wt %, a pH of 9-11, and a particle size of SiO2 in the silica sol of 10-15 nm; The potassium silicate solution has a solid content of 30 wt % and a modulus of 3.5 to 3.9; The siloxane modifier is one or a combination of two or more of methyltrimethoxysilane, methyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-methacryloxypropyltrimethoxysilane.

4. The corrosion-resistant inorganic composite resin coating for silicon carbon rods according to claim 1, wherein: In parts by weight, the inorganic high-temperature resistant material group B includes: 15-30 parts of silicon carbide, 20-30 parts of mullite, 15-25 parts of silicon nitride, 10-20 parts of magnesium oxide, and 3-5 parts of carbon nanotube aqueous slurry.

5. The corrosion-resistant inorganic composite resin coating for silicon carbon rods according to claim 4, characterized in that: The silicon carbide has a particle size of 320 mesh and a purity of ≥90%; The mullite has a particle size of 320 mesh and Al2O3 ≥ 72%; The silicon nitride has a particle size of 2000 mesh and a nitrogen content of 40-45%; The magnesium oxide has a particle size of 320 mesh and MgO ≥ 85%; The carbon nanotube aqueous slurry is a multi-walled carbon nanotube aqueous slurry, with a multi-walled carbon nanotube content of 5-10 wt%, a diameter of 5-15 nm, and a length of 10-30 μm.

6. A corrosion-resistant inorganic composite resin coating for a silicon carbon rod, characterized in that: The preparation method of the inorganic resin mixed solution of group A comprises the following steps: Deionized water and hydrochloric acid are mixed according to the ratio to obtain a dilute hydrochloric acid solution; then, silica sol, potassium silicate and siloxane modifier are added to the dilute hydrochloric acid solution while stirring, and the mixture is reacted at 50-70°C for 2-3 hours, then cooled to 20-30°C, and filtered to obtain an acidic solution; Continue to add aluminum sol to the acidic solution and stir evenly to obtain Group A inorganic resin mixed solution.

7. The corrosion-resistant inorganic composite resin coating for a silicon carbon rod according to claim 6, wherein: The reaction temperature is 60° C., and the reaction time is 2.5 h. The filtration is performed using 732 cationic exchange resin. The stirring speed is 300-400 r / min.

8. The method for preparing the corrosion-resistant inorganic composite resin coating for silicon carbon rods according to any one of claims 1 to 7, characterized in that: The steps are as follows: (1) According to the proportion, add the inorganic high temperature resistant material of group B to the inorganic resin mixture of group A in sequence, and stir and disperse at high speed for 25 to 35 minutes to obtain a corrosion-resistant inorganic composite resin; (2) The corrosion-resistant inorganic composite resin obtained in step (1) is evenly coated on the surface of the silicon carbon rod, dried in a clean room at 20-30°C for 4-8 hours, and then dried and cured at 160-200°C for 15-25 minutes; (3) Repeat the operation in step (2) 2 to 4 times and then cool naturally to 20 to 30 ° C. Dry the coated silicon carbon rod at 160 to 200 ° C for 2 to 4 hours; then increase the temperature to 300 ° C at a rate of 5 ° C / min, keep it warm for 2 to 3 hours, then increase the temperature to 1500 ° C at a rate of 10 ° C / min, keep it warm for 3 to 5 hours, and finally cool it naturally to 200 ° C to obtain a corrosion-resistant inorganic composite resin coating for silicon carbon rods.

9. The preparation method according to claim 8, wherein In step (1), the silicon carbide rod can be one or more of a constant diameter silicon carbide rod, a U-shaped silicon carbide rod or a threaded silicon carbide rod. The coating of the present invention can be applied to silicon carbide rods of various shapes. The high-speed stirring is carried out by using a high-speed stirring disperser, and the speed of the high-speed stirring is 600-800 r / min.

10. The preparation method according to claim 8, characterized in that In step (2), the coating method can be dipping, spraying, or brushing, and the thickness of the formed film is about 15-25 μm.

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