KR102295705B1 - Heat resistant Coating Composition For Protection of Metal And Manufacturing Methods For The Same - Google Patents

Abstract

Disclosed is a coating composition coated on a metal surface to improve thermal properties and provide corrosion resistance. The present invention is a ceramic precursor binder containing a silane compound 30 to 60% by weight; 30-60 wt% of heat-resistant metal oxide powder; and 5 to 20% by weight of the metal active filler powder. According to the present invention, it is possible to provide a coating composition that has good adhesion to the carbon steel surface, imparts heat resistance and corrosion resistance, and can suppress cracking of the coating film.

Description

Heat resistant coating composition for metal coating and manufacturing method thereof

The present invention relates to a coating composition coated on a metal surface to improve thermal properties and provide corrosion resistance, and more particularly, to a ceramic-based heat-resistant and corrosion-resistant coating composition for protecting a metal surface.

The heat exchanger of an industrial boiler needs to be operated at a high temperature for efficient heat recovery. However, due to the high-temperature corrosion problem of the boiler water pipe at high temperature, there is a limit (300℃, about 30atm) depending on the temperature and pressure of the steam, which limits the increase in the energy recovery rate. Due to these limitations, in the case of incinerators, the current generation efficiency is only 10 to 15%. However, when operated at a higher temperature and pressure, the heat exchange efficiency increases proportionally, and when steam is generated at 400° C. and 40 atmospheres, the power generation efficiency can be increased by 20 to 25%.

For the production of high-temperature and high-pressure steam, technology development has been carried out on the material of the boiler tube and the coating material that protects the boiler tube. Among them, ceramic material has heat and corrosion resistance and is strong in overcoming extreme conditions, but there is a limit to its application as a coating material for high-temperature boilers due to the difference in coefficient of thermal expansion between metal and ceramic. In addition, when a ceramic material is used as a coating material as in the prior art, there is a problem in that cracks occur due to oxidative decomposition of a binder used for attachment.

For example, Patent Registration No. 728468 provides a plated steel sheet having high heat resistance and corrosion resistance in which discoloration or visual observation is not observed at a surface temperature of about 450 degrees. The composition of this patent inevitably causes cracks due to decomposition of the binder at high temperatures.

(1) Registered Patent KR 728468

In order to solve the problems of the prior art, an object of the present invention is to provide a coating composition for surface protection having good adhesion to a metal surface such as carbon steel.

Another object of the present invention is to provide a coating composition for protecting the surface of a metal such as carbon steel having heat resistance and corrosion resistance.

Another object of the present invention is to provide a coating composition for protecting the surface of a metal, such as carbon steel, which can prevent the generation of cracks in the coating film due to the decomposition of the binder.

Another object of the present invention is to provide a method for preparing the above-described coating composition.

In order to achieve the above technical problem, the present invention provides a ceramic precursor binder containing a silane compound in an amount of 30 to 60% by weight; 30-60 wt% of heat-resistant metal oxide powder; and 5 to 20% by weight of the metal active filler powder.

In the present invention, the binder includes an organic solvent, and the solid content in the binder is adjusted to be included in an amount of 15 to 30 parts by weight based on 100 parts by weight of the binder.

In the present invention, the binder preferably includes polysiloxane. In this case, the polysiloxane is prepared from at least two or more silane compounds, and the silane compound preferably includes at least two selected from the group consisting of MTMS, TEOS and GPTMS. In addition, in the present invention, the binder is characterized in that a hydrolyzed silane hydrolyzate and a polysiloxane oligomer resin obtained by partially polymerizing the silane hydrolyzate are mixed.

In addition, in the present invention, the metal active filling powder may include at least one metal selected from the group consisting of Al, Si, Ti, Zr, Cr, and B.

In addition, the composition of the present invention may further include an inorganic viscosity modifier in an amount of 2 to 5% by weight. In addition, the composition of the present invention may further include a glass frit.

In order to achieve the above another technical problem, the present invention comprises the steps of preparing a ceramic precursor binder including a silane compound; preparing a coating solution by mixing 30 to 60 wt% of the heat-resistant metal oxide powder and 5 to 20 wt% of the active filling metal powder in 30 to 60 wt% of the ceramic precursor binder; applying the coating solution to the carbon steel surface; And it provides a carbon steel coating method comprising the step of drying the coating solution.

In the present invention, the application step is preferably performed by dip coating.

According to the present invention, it is possible to provide a coating composition that has good adhesion to the carbon steel surface, imparts heat resistance and corrosion resistance, and can suppress cracking of the coating film.

1 is a graph showing the results of measuring the weight loss characteristics of the coating composition according to Preparation Example 1 of the present invention.
2 is a graph showing the results of measuring the weight loss characteristics of the coating composition according to Preparation Example 2 of the present invention.
3 is a graph showing the results of measuring the weight loss characteristics of the coating composition according to Preparation Example 3 of the present invention.
4 is a graph showing the results of measuring the weight loss characteristics of the coating composition according to Preparation Example 4 of the present invention.
5 is a graph showing the results of measuring the weight loss characteristics of the coating composition according to Preparation Example 5 of the present invention.

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention with reference to the drawings.

The carbon steel coating composition of the present invention is a composition in which a heat-resistant ceramic powder, a ceramic precursor binder containing a silane compound, and an active filling metal powder are mixed.

The carbon steel coating composition of the present invention comprises a heat-resistant ceramic powder. The ceramic powder protects the metal coating. In the present invention, as the ceramic powder, a metal oxide powder such as silicon oxide or alumina may be used. In the present invention, the powder may be crystalline or amorphous powder. In the present invention, the ceramic powder may be included in 30 to 60% by weight of the carbon steel coating composition.

In the present invention, the carbon-valent coating composition includes a ceramic precursor binder (pre-ceramic binder). The ceramic precursor binder may include an organic silane compound, a surfactant, and an organic solvent.

In the present invention, the ceramic precursor binder facilitates adhesion of the coating composition to a metal surface such as carbon steel. In addition, the ceramic precursor binder is oxidized in a high-temperature atmospheric environment after coating on the metal surface to be converted into ceramics.

In the present invention, polycarbosilane or polysiloxane may be used as the organosilane compound. In the present invention, the ceramic precursor binder is preferably included in an amount of 30 to 60% by weight based on the total weight of the coating composition.

In an exemplary embodiment of the present invention, polysiloxane is used as the silane compound. The polysiloxane binder is a mixture of a hydrolyzed silane hydrolyzate and a polysiloxane oligomer resin obtained by partially polymerizing the hydrolyzed silane. In this type of material, after the solvent is volatilized during application, the oligomer resin and the hydrolyzate of silane are polycondensed with each other to cause curing shrinkage, and a coating film with high mechanical strength can be formed.

In the present invention, in the preparation of polysiloxane, a silane capable of hydrolysis and having three or more alkyl groups may be used. Preferably, the polysiloxane may be obtained from two or more silane compounds.

According to an embodiment of the present invention, the organosilane compound is selected from the group consisting of methyltrimethoxysilane (MTMS), tetraethoxysilane (TEOS) and 3-glycidoloxypropyl-trimethoxysilane (GPTMS). The two selected species may be used in combination.

The greater the curing shrinkage, the greater the capacity is applied and the surface hardness increases, but there is a risk of cracking of the coating film. The types of silanes used in this embodiment are shown in Table 1. As shown in Table 1, the organic/inorganic content in the binder can be controlled with silane. In this embodiment, the composition of the binder may be determined at a level at which cracks do not occur in the coating film using the silane hydrolyzate and polysiloxane oligomer resin.

silane Molecular Weight Solids (%) Organic (%) weapon (%) GPTMS 236.34 70.76 69 31 MTMS 136.22 49.27 22 78 TEOS 208.33 28.84 0 100

In the present invention, the MTMS is a chemical monomer constituting silanetriol and methanol by reacting with water. When used to prevent the inorganic surface from being easily absorbed by water, it has excellent dispersibility with other silanes.

In the present invention, the MTMS preferably contains 50 to 70 parts by weight when the total amount of the silane compound in the binder composition is 100 parts by weight. If it is less than 50 parts by weight, the organic ratio of MTMS in the binder component constituting the coating film may be lowered, thereby reducing adhesion or dispersibility with other silanes.

In the TEOS, silica bonds and silanols are formed by hydrolysis and polycondensation reactions, and when the coating film is cured, all of the remaining silanols are converted to silica bonds and the curing density increases to significantly improve the strength of the finally formed coating film, and heat resistance and durability This is excellent and helps to prevent cracks in the coating film.

The TEOS preferably includes 30 to 50 parts by weight based on 100 parts by weight of the total amount of the silane compound. If it is less than 30 parts by weight, the content of inorganic substances in the binder component constituting the coating film is reduced, and the curing density synergistic effect is small, so that the hardness may be reduced. When it exceeds 50 parts by weight, there is a problem in that adhesion strength is lowered or cracks occur due to stress caused by curing shrinkage due to residual silanol that has not undergone a condensation reaction during curing.

The GPTMS contains a glycidoxy reactive organic group and an inorganic trimethoxysilyl group, so it is used as a coupling agent with glass or inorganic fillers, improves adhesion, and improves strength, appearance and processability. The GPTMS is preferably used in an amount of 0 to 30 parts by weight based on 100 parts by weight of the total amount of the silane compound.

In the present invention, distilled water may be included for hydrolysis and polycondensation of the organosilane compound. The distilled water preferably contains 20 to 40 parts by weight based on 100 parts by weight of the silane compound.

In the present invention, the ceramic precursor binder (pre-ceramic binder) includes the organic solvent to disperse the organic silane compound or to appropriately adjust the viscosity. In the present invention, as the organic solvent, an alcohol-based, ether-based, or ketone-based organic solvent may be used, and a mixture of two or more may be used.

In addition, in the present invention, an inorganic binder may be additionally used in addition to the ceramic precursor binder. Since glass frit melts at 500~800℃ condition, it is possible to form a dense heat-resistant ceramic coating film at high temperature when various glass frits are selected and used depending on the application field of the coating material. In addition, when a glass frit is used, it is possible to manufacture a ceramic coating film having uniform surface properties, so that deposition of ash inside the boiler can be minimized.

In the present invention, the organic solvent is added so that the total amount of the solid content in the binder is 15 to 30% by weight. When the organic solvent is less than 15% by weight, the viscosity increases and it is difficult to form a coating film, and when it exceeds 30% by weight, there is a problem that the coating film is greatly contracted during drying after forming the coating film.

In the present invention, the ceramic precursor binder may include a surfactant as the other additive. The surfactant serves to improve the leveling property of the coating surface and prevent defects that may appear in the coating film after coating, for example, pinholes and crater phenomena. In the present invention, the surfactant is preferably included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the silane compound in the binder.

Additionally, in the present invention, the binder may include a liquid nano-colloidal sol. The liquid nano-colloidal sol is preferably surface-treated to be hydrophobic. The liquid nano-colloidal sol may be included in 150 to 200 parts by weight based on 100 parts by weight of the silane compound. The liquid nano-colloidal sol is selected in consideration of improving heat resistance, corrosion resistance, and adhesion at high temperatures, and compatibility and reactivity with an organosilane compound. In the present invention, as the nano colloidal sol, alumina sol, silica sol, etc. may be used.

In the present invention, the coating composition comprises a metal active filler. The metal active filler compensates for pores and cracks occurring in the coating composition at high temperatures.

In the present invention, the active filler may include at least one metal powder selected from the group consisting of Al, Si, Ti, Zr, Cr, and B. Preferably, the active filler comprises 10 to 15% by weight based on the total amount of the coating composition. If it is out of the above range, there is a problem that the material swells at high temperatures.

In addition, the coating composition of the present invention may further include a viscosity modifier. When a viscosity modifier is further included to control the viscosity of the coating composition, the viscosity modifier is preferably an inorganic viscosity modifier. Bentonite, etc. may be used as the inorganic viscosity modifier in the present invention.

The coating composition of the present invention described above may be coated on a metal surface in an appropriate manner. For example, conventional wet coating methods such as flow coating, spin coating, bar coating, dip coating and spray coating may be used. It is preferable to select and use an appropriate coating method according to the type or shape of the material to be coated and the desired coating film thickness.

The coating film formed by an appropriate coating method is dried at room temperature for at least 10 minutes, and then heat-treated at 150° C. to 200° C. for at least 1 hour. Sufficient hardness is imparted to the coating film by heat treatment.

<Preparation of ceramic precursor binder>

A. Preparation of PCS binder

Polycarbosilane having a molecular weight of 2000-5500 was dissolved in an organic solvent such as benzene or toluene to prepare polycarbosilane. At this time, the concentration of polycarbosilane in the solution was set to 20% by weight.

B. Preparation of polysiloxane binder

Meanwhile, a polysiloxane binder was prepared separately from this. In this example, two kinds of polysiloxane binders (#1, #2) were prepared. A method of manufacturing the polysiloxane binder in this embodiment is as follows.

Polysiloxane Binder #1

A binder was prepared with two types of silane compounds using MTMS and TEOS. The binder was manufactured through a two-step process. First, 66.7 parts by weight of IPA, an organic solvent, was mixed with respect to 100 parts by weight of methyltrimethoxysilane, reacted at 65° C. for 4 hours or more, and then aged at room temperature for 12 hours or more.

Then, after mixing 30 parts by weight of tetraethoxysilane to the prepared coating solution, 19 parts by weight of distilled water as a catalyst was added, mixed for 4 hours or more, 1 part by weight of surfactant was added, and mixed for 2 hours or more until completely mixed. IPA was added to the prepared binder to dilute the solid content to 20% by weight.

Polysiloxane Binder #2

After mixing 450 parts by weight of hydrophobic surface-treated aluminasol and 50 parts by weight of IPA as an organic solvent, 100 parts by weight of methyltrimethoxysilane was mixed, reacted at 65° C. for 4 hours or more, and then aged at room temperature for 12 hours or more.

After mixing 150 parts by weight of tetraethoxysilane to the prepared coating solution, 190 parts by weight of distilled water as a catalyst was added and mixed for 4 hours or more, then 10 parts by weight of a surfactant was added and mixed for 2 hours or more until completely mixed. IPA was added to the prepared binder to dilute the solid content to 20% by weight.

<Coating composition Preparation Example 1>

A coating composition was prepared by using the previously prepared PCS binder (PCS) and polysiloxane binder #1 (PSX) as a ceramic precursor binder, and mixing the ceramic powder and the filling powder thereto. The binder, ceramic powder and filling powder used and their contents are shown in the table below. In Sample A4, a mixture of Al2O3 (32 wt%) and TiO2 (15 wt%) was used as the ceramic powder.

division bookbinder ceramic powder filling powder A1 Furtherance PCS Al2O3 ZrO2 content (wt%) 50 38.5 11.5 A2 Furtherance PSX Al2O3 TiO2 content (wt%) 50 38.5 11.5 A3 Furtherance PSX Al2O3 Si content (wt%) 50 38.5 11.5 A4 Furtherance PSX Al2O3/TiO2 Zr content (wt%) 50 32/15 3

A coating film was formed by dip coating a carbon steel substrate on the prepared coating composition solution, and the coating film was dried at room temperature for at least 10 minutes, and then heat-treated at 150° C. to 200° C. for at least 1 hour. Sufficient hardness was imparted to the coating film by heat treatment. The weight loss of the obtained coating film was measured according to the method for removing corrosion products from corrosion test pieces of KSD ISO 8407 metals and alloys.

1 is a graph showing a weight loss measurement result according to Preparation Example 1. FIG.

Referring to Figure 1, looking at the weight loss at a temperature of 800 °C, it was found that the sample (A3, A4) using Si or Zr as the filling powder had a decrease in weight loss than the samples (A1, A2) using the ceramic powder as the filling powder. Able to know. In addition, it can be seen that sample A9 exhibits the best properties when the temperature is increased to 900°C, and a significant weight loss occurs in all samples overall when the temperature is further increased to 1000°C.

<Coating composition Preparation Example 2>

A coating film was formed in the same manner using PCS binder (PCS) and polysiloxane binder #2 (New PSX) as binders. For comparison, a coating film was formed using water glass (W/G) and TEOS as binders. Manufacturing conditions except for the mixing ratio were the same as in Preparation Example 1.

The weight loss of the obtained coating film was measured. The formulation of the coating composition of this example is shown in the following table.

division bookbinder ceramic powder filling powder B1 Furtherance New PSX Al2O3 Si content (wt%) 50 40 10 B2 Furtherance PCS Al2O3 Si content (wt%) 50 40 10 B3 Furtherance W/G Al2O3 - content (wt%) 50 50 - B4 Furtherance TEOS Al2O3 Si content (wt%) 50 40 10

2 is a graph showing a weight loss measurement result according to Preparation Example 2. FIG. Referring to FIG. 2 , samples B1 and B2 show a loss of less than 1% by weight over the entire temperature range. In addition, it is shown that the binder composed of two types of silane compounds according to the present invention exhibits superior coating properties than those composed of one type of silane compound such as TEOS.

In addition, compared to the PSX binder of Preparation Example 1, the New PSX binder exhibits good weight loss characteristics in the entire temperature range. This is considered to be due to the coating film having better adhesion and heat resistance by the alumina nano-sol contained in the New PSX binder.

<Coating composition preparation example 3>

A viscosity modifier was added to the coating composition and the effect on weight loss according to the type of the viscosity modifier was investigated. As a viscosity modifier, hydroxypropyl cellulose (product name: Klucel M Ind) was used as an organic viscosity modifier, and Benton 54 was used as an inorganic viscosity modifier. Organic thickeners (hydroxypropyl cellulose (product name: Klucel M Ind)) and inorganic thickeners (Benton 54) can increase the thickness of the coating.

Manufacturing conditions except for the mixing ratio were the same as in Preparation Example 1. The formulation of the coating composition of this example is shown in the following table.

division bookbinder ceramic powder filling powder viscosity modifier C1 Furtherance New PSX Al2O3 Si OVA content (wt%) 50 39.75 10 0.25 C2 Furtherance New PSX Al2O3 Si OVA content (wt%) 50 39.5 10 0.5 C3 Furtherance PCS Al2O3 Si InVA content (wt%) 50 37 10 3.0 C4 Furtherance PCS Al2O3 Si InVA content (wt%) 50 35 10 5.0

3 is a graph showing a weight loss measurement result according to Preparation Example 3. FIG. Referring to FIG. 3 , it can be seen that when an inorganic thickener is used, the overall weight loss is lower than when an organic thickener is used.

<Coating composition preparation example 4>

Using polysiloxane binder #2 (New PSX) as a binder, weight loss according to the content of the filling powder was measured. Manufacturing conditions except for the mixing ratio were the same as in Preparation Example 1. The formulation of the coating composition of this example is shown in the following table.

division bookbinder ceramic powder filling powder D1 Furtherance New PSX Al2O3 Si content (wt%) 50 45 5 D2 Furtherance New PSX Al2O3 Si content (wt%) 50 40 10 D3 Furtherance New PSX Al2O3 Si content (wt%) 50 35 15 D4 Furtherance New PSX Al2O3 Si content (wt%) 50 30 20

4 is a graph showing a weight loss measurement result according to Preparation Example 4. Referring to FIG. 4 , good weight loss characteristics are exhibited in the Si content range, but it can be seen that the weight loss characteristics are slightly changed according to the Si content, and the Si content is about 10% by weight, preferably 8 to 12% by weight. When added in a range, it showed good weight loss properties.

<Coating composition Preparation Example 5>

Polysiloxane binder #2 (New PSX) was used as a binder to measure the weight loss according to the type of filling powder. Manufacturing conditions except for the mixing ratio were the same as in Preparation Example 1. The formulation of the coating composition of this example is shown in the following table. In sample E6, a mixture of Si (10% by weight) and glass frit (3% by weight) was used as the filling powder.

division bookbinder ceramic powder filling powder E1 Furtherance New PSX Al2O3 Si content (wt%) 50 40 10 E2 Furtherance New PSX Al2O3 Cr content (wt%) 50 40 10 E3 Furtherance New PSX Al2O3 Zr content (wt%) 50 40 10 E4 Furtherance New PSX Al2O3 Al content (wt%) 50 40 10 E5 Furtherance New PSX Al2O3 SiC content (wt%) 50 40 10 E6 Furtherance New PSX Al2O3 Si/Glass frit content (wt%) 50 37 10/3

5 is a graph showing a weight loss measurement result according to Preparation Example 5; Referring to FIG. 5 , it can be seen that when Si or Al is used as the filling powder, better results are obtained. Furthermore. It can be seen that when glass frit is added as a filling powder, good weight loss properties are exhibited at a temperature of 900°C.

Claims (11)

30-60 wt % of ceramic precursor binder;
30-60 wt% of heat-resistant metal oxide powder; and
Al, Si, Ti, Zr, Cr, and at least one metal active filling powder selected from the group consisting of 5 to 20% by weight,
The ceramic precursor binder includes a hydrophobic surface-treated liquid nano colloidal sol, polysiloxane, and an organic solvent,
The solids in the binder include 15 to 30 parts by weight based on 100 parts by weight of the binder,
wherein the polysiloxane is prepared from at least two silane compounds selected from the group consisting of MTMS, TEOS and GPTMS.
delete delete delete delete According to claim 1,
The binder is a metal coating composition, characterized in that hydrolyzed silane hydrolyzate and polysiloxane oligomer resin obtained by partially polymerizing silane hydrolyzate. delete According to claim 1,
Metal coating composition, characterized in that it further comprises 2-5% by weight of an inorganic viscosity modifier. According to claim 1,
Metal coating composition, characterized in that it further comprises a glass frit. preparing a ceramic precursor binder;
30-60 wt% of heat-resistant metal oxide powder and 5-20 wt% of at least one active filled metal powder selected from the group consisting of Al, Si, Ti, Zr, Cr and B to 30-60 wt% of the ceramic precursor binder mixing to prepare a coating solution;
applying the coating solution to the carbon steel surface; and
Drying the application solution at 150 ~ 200 ℃,
The ceramic precursor binder includes a hydrophobic surface-treated liquid nano colloidal sol, polysiloxane, and an organic solvent,
The solids in the binder include 15 to 30 parts by weight based on 100 parts by weight of the binder,
wherein the polysiloxane is prepared from at least two silane compounds selected from the group consisting of MTMS, TEOS and GPTMS. 11. The method of claim 10,
The metal coating method, characterized in that the coating step is carried out by dip coating.

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