TWI731335B - Coating with oxidation resistance at high temperature and method for coating surface of carbon steel - Google Patents

Abstract

The present invention relates to a coating with oxidation resistance at high temperature and a method for coating a surface of a carbon steel. The coating with oxidation resistance at high temperature is firstly coated on the surface of the carbon steel, and then being subjected to a drying process to form a protective layer on the surface. The coating with oxidation resistance at high temperature comprises an inorganic binder, an aluminum pigment and an organic solvent. The inorganic binder includes a silane coupling agent and a compound having a crosslinked network structure formed with Si-O-Si bonding. After a hot stamping process is performed to the carbon steel with the protective layer, the protective layer is not broken, thereby efficiently preventing from forming rust. Moreover, the protective layer has excellent welding property and coating property.

Description

Surface coating method of anti-high temperature oxidation coating composition and carbon steel

The present invention relates to a coating composition, and particularly provides a high-temperature oxidation-resistant coating composition and a coating method for coating the surface of carbon steel using the high-temperature oxidation-resistant coating composition.

Because steel has good mechanical strength, and its properties can be easily improved by adjusting the element composition to meet various needs, steel systems are widely used. Among them, the automobile industry is more heavily used in steel. In order to form various structural parts of the car body, the steel plate can be formed into various shapes of steel objects by a hot stamping process. When the hot stamping process is performed, the steel plate can be heated to the state of austenitic iron, and then transferred to the mold to be formed into a structural part by the stress applied by the stamping equipment, and the tensile strength can be more than 1470MPa. And has a car body structure with a uniform Asada scattered iron structure.

However, the temperature of the hot stamping process is generally greater than 900 ℃, so the steel without surface treatment is easy to oxidize to produce surface rust, which must be formed after forming Additional sandblasting and rust removal process. Secondly, the rust on the surface of the structure will also contaminate and wear the mold, which will affect the production process and increase the production cost.

In order to solve the defect of the rust skin of steel at high temperature, before the hot stamping process, the surface of the steel can be formed with an aluminum-silicon coating on the surface of the steel by a hot-dip aluminum-silicon process. However, the hot-dip galvanizing production line commonly used in general steel plants cannot perform the hot-dip aluminum-silicon plating process, and the equipment must be modified, which in turn increases the production cost. In addition, the hot-dip aluminum-silicon plating process has the disadvantage of high energy consumption, so it is difficult to meet the cost requirements of steel plants.

In order to solve the defect of high temperature scale produced by the hot stamping process of steel, a conventional method is to coat the surface of the steel with a paint containing organic-inorganic compound, metal material and dispersant to form a protective coating. Among them, the organic-inorganic mixture contains a liquid aluminum alkoxide, a chelating agent and a solvent. Although this protective coating can effectively improve the high-temperature oxidation resistance of steel, the liquid alkoxide in the coating is a highly reactive compound, and it is easy to react with moisture in the environment and produce a melt-gel reaction, thereby increasing The viscosity of the paint. Accordingly, the coating is not easy to store, and cannot be recycled and reused, and has poor storage stability, and increases the coating cost.

Another conventional method is to form a double coating on the steel surface by a two-coating process. In this method, a thin silicate layer is formed on the surface of the steel, and then a paint containing pigment is applied. Among them, the coating contains a binder dissolved in a liquid phase and a particle type aluminum metal pigment and a bismuth metal salt material. Although the double coating contributes to the corrosion resistance of the steel, it is generally known that the coating production line only has one coating and one baking equipment, so the equipment must be additionally modified, which increases the manufacturing cost. Furthermore, The double coating has high insulation, and it is easy to produce welding defects such as electrode tip sticking and weld nugget burrs during spot welding.

In view of this, it is urgent to provide a surface coating method for high temperature oxidation resistant coating composition and carbon steel in order to improve the defects of the conventional steel in the hot stamping process.

Therefore, one aspect of the present invention is to provide a high-temperature oxidation-resistant coating composition. The high-temperature oxidation-resistant coating composition has good storage stability, and the formed protective layer can effectively withstand the hot stamping process, and has a good Its resistance to high temperature oxidation and spot welding.

Another aspect of the present invention is to provide a surface coating method for carbon steel, which uses the aforementioned high temperature oxidation resistant coating composition to coat the surface of carbon steel.

According to one aspect of the present invention, a high temperature oxidation resistant coating composition is provided. The high temperature oxidation resistant coating composition includes inorganic binder, aluminum metal pigment and organic solvent. Among them, the inorganic binder includes a silane coupling agent and/or a compound having a network cross-linked structure formed by Si-O-Si bonds. The compound includes a cross-linking compound and/or polysiloxane, wherein the cross-linking compound is formed by a reaction of a silane coupling agent, and the polysiloxane has aliphatic functional groups and/or aromatic functional groups.

According to an embodiment of the present invention, the aforementioned cross-linking compound is formed by hydrolyzing and condensing the silane coupling agent, and/or the cross-linking compound The material system is formed by cross-linking a silane coupling agent, and in the cross-linking reaction, the silane coupling agent contains an epoxy group and/or an amino group.

According to another embodiment of the present invention, in the aforementioned cross-linking reaction, the molar ratio of the epoxy group to the amino group is 0.5 to 5.0.

According to another embodiment of the present invention, when the aforementioned inorganic binder includes at least one of a silane coupling agent and a crosslinking compound and polysiloxane, the mass ratio of the total amount of silane coupling agent to the polysiloxane is Greater than 0 and less than or equal to 0.2.

According to another embodiment of the present invention, the aforementioned aluminum metal pigment includes flake-shaped aluminum metal, wherein the thickness of the aluminum metal is not more than 1 μm, and the length of the aluminum metal is 5 μm to 30 μm.

According to yet another embodiment of the present invention, the mass ratio of the aluminum metal of the aluminum metal pigment to the solid content of the inorganic binder is 0.5 to 2.5.

According to another aspect of the present invention, a surface coating method of carbon steel is provided. In this coating method, the aforementioned high temperature oxidation resistant coating composition is first coated on the surface of carbon steel to form a coating layer. Then, the coating layer is dried to form a protective layer on the surface of the carbon steel.

According to an embodiment of the present invention, the aforementioned carbon steel includes manganese-boron-carbon steel.

According to another embodiment of the present invention, the drying temperature of the aforementioned drying process is 200°C to 400°C.

According to another embodiment of the present invention, the thickness of the protective layer is 1.0 μm to 4.0 μm.

By applying the high temperature oxidation resistant coating composition and the surface coating method of carbon steel of the present invention, the high temperature oxidation resistant coating composition has good coating stability and construction convenience. Secondly, the high-temperature oxidation resistant coating composition can be coated on the surface of carbon steel to form a dense protective layer that adheres well to the surface of carbon steel, thereby improving the corrosion resistance of the surface of carbon steel. Moreover, after the hot stamping process, the protective layer does not peel off, so it has good high temperature oxidation resistance, and can effectively prevent the carbon steel from rusting after the hot stamping process. In addition, because the protective layer has an appropriate resistance value, the carbon steel object formed by the hot stamping process also has good spot weldability.

100‧‧‧Method

110/120/130/140‧‧‧Operation

In order to have a more complete understanding of the embodiments of the present invention and its advantages, please refer to the following description and the corresponding drawings. It must be emphasized that the various features are not drawn to scale and are for illustration purposes only. The contents of the relevant drawings are described as follows: [FIG. 1] is a schematic flow diagram of a carbon steel surface coating method according to an embodiment of the present invention.

The manufacture and use of the embodiments of the present invention are discussed in detail below. However, it can be understood that the embodiments provide many applicable inventive concepts, which can be implemented in various specific contents. The specific embodiments discussed are for illustration only, and are not intended to limit the scope of the present invention.

Please refer to FIG. 1, which is a schematic flow chart of a surface coating method for carbon steel according to an embodiment of the present invention. In the method 100, the high temperature oxidation resistant coating and carbon steel are provided first, and the high temperature oxidation resistant coating is coated on the surface of the carbon steel to form a coating layer, as shown in operation 110 and operation 120.

The high temperature oxidation resistant coating composition includes inorganic binder, aluminum metal pigment and organic solvent. The inorganic binder may include a silane coupling agent and/or a compound having a network cross-linked structure formed by Si-O-Si bonds. Among them, the compound having a network cross-linking structure formed by Si-O-Si bonds may include a cross-linking compound, polysiloxane, or any mixture of the above materials. Wherein, the cross-linking compound is formed by the reaction of a silane coupling agent, and the polysiloxane has aliphatic functional groups and/or aromatic functional groups.

It should be noted that the aforementioned silane coupling agent as an inorganic binder is not particularly limited, and it only needs to be a silane compound. It is understood that the silane coupling agent used as an inorganic binder may be the same as or different from the silane coupling agent used to react to form a crosslinking compound and/or the silane coupling agent used to form polysiloxane.

In some embodiments, the aforementioned cross-linking compound can be obtained by subjecting the silane coupling agent to a hydrolysis condensation reaction, a cross-linking reaction, and other reactions that can cause the silane coupling agent to react to form a network cross-linked structure with Si-O-Si bonds. Mechanism, or any combination of the above reaction mechanisms. It is understandable that in the hydrolysis condensation reaction, the crosslinking compound can be formed by hydrolysis and condensation reaction of the silane coupling agent, so the silane coupling agent used is not particularly limited, but the crosslinking compound formed must have A network cross-linked structure formed by Si-O-Si bonds. Secondly, in the aforementioned cross-linking reaction, the silane coupling agent is The epoxy group and the amino group generate a cross-linking reaction, wherein the molecular structure of each silane coupling agent may have an epoxy group and an amino group, or the molecular structure of each silane coupling agent may independently have an epoxy group or an amino group. In some embodiments, the molar ratio of epoxy group to amino group may be 0.5 to 5.0, and preferably 1.0 to 4.8. When the molar ratio of the epoxy group to the amino group is in the aforementioned range, the formed high temperature oxidation resistant coating can have a more appropriate degree of polymerization, and has better storage stability. According to the needs of the back-end application, the degree of polymerization of the cross-linking compound formed by the silane coupling agent can be appropriately adjusted to meet the demand.

In some specific examples, the silane coupling agent used in the aforementioned crosslinking reaction may include, but is not limited to, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-propylene oxide propyl Trimethoxysilane, γ-glycidylpropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyl diethoxysilane, N-β(aminoethyl)- γ-Aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltriethoxysilane, γ-glycidylpropylmethyldiethoxysilane, other appropriate silanes Coupling agent, or any mixture of the above-mentioned compounds.

The aforementioned polysiloxane can be formed by performing a condensation reaction on a silane coupling agent, wherein the silane coupling agent contains aliphatic functional groups and/or aromatic functional groups. Preferably, the polysiloxane may be a T-type polysiloxane, and the aliphatic functional group and/or the aromatic functional group are the side chain groups of the network crosslinked structure formed by the Si-O-Si bond. When the polysiloxane has aliphatic functional groups and/or aromatic functional groups as side chain groups, the subsequent protective layer formed may have better heat resistance.

In some embodiments, when the inorganic binder includes at least one of the aforementioned silane coupling agent and crosslinking compound and polysiloxane, the silane coupling agent and/or the silane coupling agent forming the crosslinking compound are reactive Side chain groups (such as the aforementioned epoxy groups and/or amino groups), which can make the formed anti-high temperature oxidation coating have better adhesion when coated on the surface of carbon steel, or can make the inorganic binder It has better adhesion to aluminum metallic pigments, which can improve the compactness of the protective layer formed by the subsequent drying process. In some specific examples, when the inorganic binder contains at least one of the aforementioned silane coupling agent and crosslinking compound and polysiloxane, the total amount of the silane coupling agent (ie, the silane coupling agent and the /Or the mass ratio of the total amount of silane coupling agent used to form the crosslinking compound) to polysiloxane can be greater than 0 and less than or equal to 0.2, preferably 0 to 0.19. It is understandable that the total amount of the aforementioned silane coupling agent does not include the usage amount of the silane coupling agent used to form polysiloxane. If the total amount of silane coupling agent and the mass ratio of polysiloxane meets this range, in addition to helping to improve the compactness of the protective layer, the formed anti-high temperature oxidation coating also has a more appropriate viscosity, and has a better Storage stability, and therefore not easy to solidify, and easy to construct.

The aluminum metal pigment may be aluminum metal powder and/or aluminum metal paste. Among them, the aluminum metal paste contains aluminum metal powder and a pigment solvent. In some embodiments, the pigment solvent may include, but is not limited to, petroleum solvents, aromatic solvents, other suitable solvents, or any mixture of the above solvents. For example, the pigment solvent may include, but is not limited to, petroleum ether, n-hexane, heptane, pentane, benzene, toluene, xylene, ethyl acetate, butyl acetate, isobutyl acetate, ethylene glycol Monobutyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, other suitable solvents, or any mixture of the above solvents.

The aluminum metal powder may be flake-shaped aluminum metal. For example, the aluminum metal powder may be polygonal flake aluminum metal, disk-shaped flake aluminum metal, or other aluminum metal powder with a suitable shape. In some specific examples, the thickness of the aluminum metal is not greater than 1 μm, and the length can be 5 μm to 30 μm. It is understandable that when the aluminum metal powder is a disc-shaped flake aluminum metal, its radial length (ie diameter) can be 5 μm to 30 μm. If the thickness of the aluminum metal powder is greater than 1μm, the dispersibility of the aluminum metal powder in the anti-high temperature oxidation coating or aluminum metal paste will be poor, and the thicker aluminum metal powder will easily lead to stacking gaps, which will reduce the subsequent formation of the protective layer The density. Furthermore, because aluminum metal powder has a very small size, and aluminum metal powder has high activity, it is easy to induce dust explosion in the preparation process of high temperature oxidation coating, so the aluminum metal pigment is preferably aluminum metal Slurry.

In some embodiments, in order to reduce the surface activity of the aluminum metal powder, the surface of the aluminum metal powder can be modified to passivate the surface of the aluminum metal powder, thereby avoiding the aforementioned dust risk. In addition, in the subsequent preparation process of high temperature oxidation resistant coatings, compared to aluminum metal pastes containing aluminum metal powders that have not been surface-modified, aluminum metal pastes containing surface-modified aluminum metal powders are easier to disperse in In high temperature oxidation resistant coatings, it has better dispersibility, and the surface-modified aluminum metal powder (that is, the surface-passivated aluminum metal powder) can effectively inhibit the agglomeration of aluminum metal powder.

In some embodiments, the mass ratio of the aluminum metal powder in the aluminum metal pigment to the solid content of the inorganic binder can be 0.5 to 2.5, and preferably can be From 0.5 to 2.0. When the mass ratio of the aluminum metal powder and the solid content of the inorganic binder in the aluminum metal pigment is within the aforementioned range, the formed high temperature oxidation resistant coating can have better viscosity performance, which is helpful for the workability of the back-end application .

Since the inorganic binder produces alcohols during the hydrolysis process, and the formed inorganic binder is dissolved in the liquid phase (ie alcohols), the aforementioned organic solvents may include solvents that have good compatibility with alcohols . In some specific examples, the organic solvent may include, but is not limited to, alcohol solvents, ketone solvents, aliphatic solvents, ester solvents, aromatic solvents, alcohol ether solvents, other suitable organic solvents, or any of the above solvents. Mix arbitrarily. For example, the organic solvent may be isopropanol, acetone, toluene, xylene, and/or glycol ether. In some embodiments, in order to improve the appearance quality of the formed protective layer, the boiling point of the organic solvent may be greater than 100° C., and may be slowly volatilized in the subsequent drying process. It is understandable that the amount of organic solvent used is not particularly limited. In some embodiments, the amount of organic solvent used can be adjusted appropriately, and the combination of inorganic binder and aluminum metal pigment in the high temperature oxidation resistant coating can be adjusted. The concentration and storage stability of the coating can meet the requirements of back-end applications (such as the thickness requirements of the protective layer) and the requirements of operation and construction.

In some embodiments, the high temperature oxidation resistant coating composition of the present invention may optionally include additives to enable the aluminum metal pigment to be uniformly dispersed in the high temperature oxidation resistant coating and to slow down the sedimentation of the aluminum metal powder. Among them, the additives may include wetting and dispersing agents, anti-settling additives, other appropriate additives, or any mixture of the above additives. In some specific examples, the wetting and dispersing agent may include, but is not limited to, anionic dispersant, cationic dispersant, neutral dispersant and/ Or a polymer dispersant, and the anti-settling aid may include, but is not limited to, polyamide wax and/or polyethylene wax.

For example, the wetting and dispersing agent can be sulfate compound (RO-SO ₃ Na), sulfonate compound (R-SO ₃ Na), carboxylate compound, sodium oleate (C ₁₇ H ₃₃ COONa), amine Salt compound, pyridine amine salt compound, quaternary amine salt compound, oil amino oleate (C ₁₈ H ₃₅ NH ₃ OOCC ₁₇ H ₃₃ ), block copolymer composed of polycaprolactone polyol and polyethylenimine (block copolymer), acrylate polymer dispersant, polyester dispersant and/or polyurethane dispersant.

In some specific examples, after uniformly mixing the aforementioned inorganic binder, aluminum metal pigment and organic solvent, the high temperature oxidation resistant coating of the present invention can be prepared. Secondly, based on application requirements, the aforementioned additives can be additionally added to the high temperature oxidation resistant coating. In some embodiments, based on the anti-high temperature oxidation coating 100 weight percent, the solid content is 15 weight percent to 40 weight percent. When the solid content of the high temperature oxidation resistant coating is in the aforementioned range, the high temperature oxidation resistant coating may have better storage stability.

In some embodiments, the aforementioned carbon steel may include manganese boron carbon steel. For example, the manganese-boron-carbon steel may include 0.5 wt% to 3.5 wt% manganese and 0.0005 wt% to 0.015 wt% boron.

The coating method of the high temperature oxidation resistant coating of the present invention is not particularly limited, and it only needs to be able to completely coat the high temperature oxidation resistant coating on the surface of carbon steel.

In some embodiments, before coating the anti-high temperature oxidation coating on the surface of the carbon steel, the carbon steel can be selectively cleaned and degreasing process to clean The surface of carbon steel can improve the adhesion of anti-high temperature oxidation coating. Among them, the cleaning and degreasing process can be carried out by using cleaning agents or cleaning operations well known to those with ordinary knowledge in the technical field of the present invention, so it will not be repeated here. For example, the cleaning agent may be an alkaline compound, and the cleaning operation may be alkaline washing and drying operations.

After coating the anti-high temperature oxidation coating on the surface of the carbon steel, the formed coating layer is dried to form a protective layer on the surface of the carbon steel, as shown in operation 130 and operation 140.

The parameters of the drying process of the present invention are not particularly limited, but it should be noted that when the drying process is performed, in order to ensure that the protective layer after drying is good and not damaged, the organic solvent in the anti-high temperature oxidation coating will not violently evaporate and boil. Reduce the appearance quality of the protective layer. In some specific examples, the drying temperature of the drying process can be 200°C to 400°C, and the drying time does not exceed 90 seconds. When the drying temperature and drying time are in the aforementioned range, the drying process can more effectively remove the organic solvent in the high temperature oxidation resistant coating, and the formed protective layer can have better appearance quality, thereby improving the formation of the high temperature oxidation resistant coating The adhesion of the protective layer to the surface of carbon steel.

In some specific examples, the thickness of the protective layer formed by the anti-high temperature oxidation coating may be 1.0 μm to 4.0 μm. When the thickness of the anti-high temperature oxidation coating is within this range, the formed protective layer has good corrosion resistance and high temperature oxidation resistance, and has an appropriate resistance value, so that the carbon steel object after the hot stamping process still has good Weldability. Secondly, after the hot stamping process, the protective layer formed by the anti-high temperature oxidation coating of the present invention is not damaged, but can effectively protect the carbon steel. In other specific examples, the thickness of the formed protective layer may be 1.5 μm to 2.5 μm.

In some application examples, after the hot stamping process, the manufactured carbon steel object can be directly subjected to the welding process and/or the paint process. In other words, after the hot stamping process, the protective layer of the formed carbon steel object may not be removed. Accordingly, the protective layer formed by the anti-high temperature oxidation coating of the present invention also has good adhesion to the baking paint.

The following examples are used to illustrate the application of the present invention, but they are not intended to limit the present invention. Anyone who is familiar with the art can make various changes and modifications without departing from the spirit and scope of the present invention.

Production of high temperature oxidation resistant coatings and carbon steel materials Example 1

First, a silane coupling agent containing an epoxy group and an amino group is used to make an inorganic binder, wherein the molar ratio of the epoxy group to the amino group is 5.0. Then, mix the inorganic binder, aluminum metal pigment (aluminum metal powder with a D50 diameter of 15μm) and n-butanol (boiling point of 117°C) to obtain the high temperature oxidation resistant coating of Example 1 (solid content of 15 Weight percentage). Among them, the aluminum metal pigment used is aluminum metal paste, and the mass ratio of the aluminum metal powder and the solid content of the inorganic binder in the aluminum metal pigment is 0.5.

Then, a No. 7 coating rod was used to roll coat the high-temperature oxidation-resistant paint of Example 1 on the surface of the manganese-boron steel plate, where the manganese-boron steel plate had been previously subjected to a degreasing process, a water washing process and a drying process. Next, place the manganese-boron steel plate coated with anti-high temperature oxidation paint in a thermal cycle oven and dry it at a temperature of 300°C Manganese boron steel plate. After drying for 60 seconds, the surface-treated carbon steel material of Example 1 can be obtained.

The obtained high-temperature oxidation resistant paint was evaluated by the evaluation method of paint stability, and the results are shown in Table 1, wherein the evaluation method of paint stability will be described later.

The prepared carbon steel materials were evaluated by the following evaluation methods. The results are shown in Table 1. The evaluation methods of coating appearance, corrosion resistance, high temperature oxidation resistance and spot weldability will be described later.

Example 2 to Example 4 and Comparative Example 1 and Comparative Example 2

Examples 2 to 4 and Comparative Example 1 and Comparative Example 2 use the same preparation method as the high temperature oxidation resistant coating composition of Example 1, except that Example 2 to Example 4 and Comparative Example 1 and Comparative Example 2 is to change the type of the composition of the anti-high temperature oxidation coating. The inorganic binder of Comparative Example 2 is a polysiloxane blended polyester resin. Its composition and evaluation results are as shown in Table 1, and will not be repeated here.

Secondly, Example 2 to Example 4 and Comparative Example 1 and Comparative Example 2 use the same preparation method as the carbon steel material of Example 1, except that Example 2 to Example 4 and Comparative Example 1 and Comparative Example 2 is to coat manganese-boron steel plate with anti-high temperature oxidation coating made by individual. The evaluation results are as shown in Table 1, and will not be repeated here.

Evaluation item 1. Paint stability

First, measure the viscosity of the anti-high temperature oxidation coatings of Examples 1 to 4 and Comparative Example 1 and Comparative Example 2 with Ford No. 4 cups. Then, using the anti-high temperature oxidation coating as 100% by weight, add 1% by weight of deionized water to the beaker, and stir in an open cup (rotating speed: 250 rpm). After stirring for 24 hours, pour the anti-high temperature oxidation paint into a sample bottle for storage.

After one month of storage, take out the anti-high temperature oxidation coating, and after stirring for 1 hour, measure the viscosity of the anti high temperature oxidation coating to compare the viscosity change of the anti high temperature oxidation coating after one month of storage. The stability of the coating was evaluated according to the following standards:

◎: Measured with Ford No. 4 cup, and the viscosity change is less than 5 seconds.

△: Measured with Ford No. 4 cup, and the viscosity change is 5 seconds to 10 seconds.

×: Measured with Ford No. 4 cup, and the viscosity change is greater than 10 seconds.

2. Appearance of coating film

The appearance of the carbon steel materials prepared in Examples 1 to 4 and Comparative Example 1 and Comparative Example 2 were inspected and evaluated according to the following standards:

◎: The appearance of the carbon steel material presents a uniform silver color, and the surface feels smooth to the touch.

○: The appearance of the carbon steel material presents a uniform silver color, but the surface touch is slightly grainy.

△: The appearance of the carbon steel material presents a slight white mist or matte color, and the surface feels slightly grainy.

×: The appearance of the carbon steel material is obviously white fog or matte color, and the surface feels obviously rough to the touch.

3. Corrosion resistance

The salt spray test was performed on the carbon steel materials prepared in Examples 1 to 4 and Comparative Example 1 and Comparative Example 2 by the standard method of Japanese Industrial Standards (JIS) No. Z-2371. After 5 hours of testing, visually evaluate the corrosion area on the surface of the carbon steel material. If the rusted area is smaller, the carbon steel material has better corrosion resistance. Among them, the corrosion resistance is evaluated according to the following standards:

◎: Corrosion area <10%.

○: 10%≦corrosion area≦30%.

△: 30%≦corrosion area≦50%.

×: 50%<corroded area.

4. High temperature oxidation resistance

First, the carbon steel materials prepared in Examples 1 to 4 and Comparative Example 1 and Comparative Example 2 were baked at a high temperature of 930°C. After 4 minutes, the carbon steel material is subjected to a hot stamping process to form a carbon steel object with a specific shape. Then, tape the surface of the carbon steel object to perform a peel test, and evaluate it according to the following standards:

◎: No coating peeling off, and there is no residual peeling material on the tape.

○: No coating peeling off, and a slight peeling material remains on the tape.

△: The coating is slightly peeled off, and the tape remains peeled off.

×: The coating is obviously peeled off, and the carbon steel object has oxidized scale.

5. Spot weldability

According to the specification of American Welding Society (AWS) No. D8.9M, 7.0kA The high current up to 8.0kA was used to perform spot welding tests on the aforementioned hot stamped carbon steel objects, and evaluated according to the following standards:

◎: During the spot welding test, there was no flying explosion and welding head adhesion.

○: During the spot welding test, there was a slight flying explosion, but no welding head adhesion phenomenon occurred.

△: During the spot welding test, a slight flying explosion and bonding of the welding head occurred.

×: Obvious flying explosion and bonding of the welding head occurred during the spot welding test.

The high-temperature oxidation-resistant coating compositions of the foregoing Examples 1 to 4 and Comparative Example 1 and Comparative Example 2 and their evaluation results are summarized in the following table.

According to the content of Table 1, the anti-high temperature oxidation coating composition prepared in Example 1 to Example 4 all have good coating stability, so The formed protective layer has good appearance quality, and can completely cover the manganese-boron steel plate, and can improve the corrosion resistance of the manganese-boron steel plate. Secondly, after the hot stamping process, the protective layer formed by the high temperature oxidation resistant coating composition prepared in Example 1 to Example 4 still has good high temperature oxidation resistance and spot weldability.

Among them, it should be additionally noted that although the evaluation result of the coating stability of the high temperature oxidation resistant coating of Example 3 is only "△", the other evaluation items all have excellent evaluation results. Therefore, the high temperature oxidation resistant coating composition of Example 3 can still meet the needs of back-end applications.

In Comparative Example 1, the coating of Comparative Example 1 not only has poor coating stability, but also has poor high temperature oxidation resistance. Therefore, the coating prepared in Citation 1 cannot provide good hot stamping protection for carbon steel. In addition, in Comparative Example 2, although the coating of Comparative Example 2 has good coating stability, its high temperature oxidation resistance is extremely poor, so it is difficult to effectively protect the surface of carbon steel during the hot stamping process.

Accordingly, the high temperature oxidation resistant coating composition of the present invention has good stability and can adhere well to the surface of carbon steel to form a dense protective layer, thereby improving the corrosion resistance of carbon steel. Secondly, after the hot stamping process, the protective layer formed by the anti-high temperature oxidation coating composition is not damaged, so it can effectively protect the coated carbon steel. Therefore, the carbon steel coated with the anti-high temperature oxidation coating composition of the present invention can have good high temperature oxidation resistance. In addition, the protective layer formed by the anti-high temperature oxidation coating of the present invention has appropriate resistance, so that the carbon steel after the hot stamping process still has good spot weldability, so it can meet the needs of back-end applications.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field of the present invention can make various changes and modifications without departing from the spirit and scope of the present invention. Retouching, therefore, the scope of protection of the present invention shall be subject to the scope of the attached patent application.

100‧‧‧Method

110/120/130/140‧‧‧Operation

Claims (8)

A high-temperature oxidation resistant coating composition, comprising: an inorganic binder, comprising a silane coupling agent and/or a compound having a network cross-linked structure formed by Si-O-Si bonds, wherein the compound comprises a cross-linking Linking compound and/or polysiloxane, wherein the crosslinking compound is formed by a reaction of the silane coupling agent, the polysiloxane has aliphatic functional groups and/or aromatic functional groups, and the crosslinking compound is The silane coupling agent is formed by a hydrolysis condensation reaction and/or the cross-linking compound is formed by a cross-linking reaction of the silane coupling agent, and in the cross-linking reaction, the silane coupling agent contains epoxy And an amino group, and one molar ratio of the epoxy group to the amino group is 0.5 to 5.0; aluminum metal pigment; and an organic solvent. As for the high temperature oxidation resistant coating composition described in item 1 of the scope of patent application, when the inorganic binder includes at least one of the silane coupling agent and the crosslinking compound and the polysiloxane, the silane coupling agent The mass ratio of a total amount to the polysiloxane is greater than 0 and less than or equal to 0.2. The high-temperature oxidation resistant coating composition described in item 1 of the scope of patent application, wherein the aluminum metal pigment comprises flake-shaped aluminum metal, one of the aluminum metal has a thickness of not more than 1 μm, and one of the aluminum metal has a length of 5 μm to 30 μm . According to the anti-high temperature oxidation coating composition described in item 1 of the scope of patent application, a mass ratio of the aluminum metal of the aluminum metal pigment to a solid content of the inorganic binder is 0.5 to 2.5. A method for surface coating of carbon steel, comprising: coating the anti-high temperature oxidation coating composition as described in any one of items 1 to 4 in the scope of the patent application on a surface of the carbon steel to form a coating layer And a drying process for the coating layer to form a protective layer on the surface. The surface coating method of carbon steel as described in item 5 of the scope of patent application, wherein the carbon steel comprises manganese boron carbon steel. The surface coating method of carbon steel as described in item 5 of the scope of patent application, wherein a drying temperature of the drying process is 200°C to 400°C. The surface coating method of carbon steel as described in item 5 of the scope of patent application, wherein one of the protective layers has a thickness of 1.0 μm to 4.0 μm.

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