JP2007016112A - Aqueous composition for use in formation of heat-resistant/corrosion-resistant coating film, and heat-resistant/corrosion-resistant coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for use in the formation of the coating film which is for the purpose of protecting a metal base material and has together the excellent heat-resistant and corrosion-resistant property. <P>SOLUTION: The aqueous composition for use in the formation of a heat-resistant/corrosion-resistant coating film contains as the effective components a combination of (A) a lowly water-soluble inorganic component, preferably potassium silicate, for contributing chiefly to the base material adhesion of a coating film and (B) a hardly water-soluble inorganic component, preferably fine titanium oxide, for contributing chiefly the denseness of the coating film. The heat-resistant/corrosion-resistent coating film comprises this composition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an aqueous composition for forming a heat and corrosion resistant coating, and a heat and corrosion resistant coating. More specifically, the present invention relates to an aqueous composition for forming a heat-resistant inorganic coating having a high heat resistance / corrosion-resistant coating, which is excellent in substrate adhesion and denseness, and also has a particularly high corrosion resistance. The present invention relates to a heat-resistant / corrosion-resistant film formed using the same.

  2. Description of the Related Art Conventionally, a coating film using a heat-resistant coating composition (a film forming composition) is formed on various metal structures, metal facilities, metal equipment, and the like that are exposed to high temperatures. As such a heat-resistant composition for forming a film, many of them are composed of an inorganic active ingredient.

JP, 7-26166, A For example, the invention of "water heat-resistant paint and heat-resistant coating layer" concerning the above-mentioned patent document 1 mixes silicon dioxide powder in water glass, thins it with water, and makes sodium silicate 7-20 weight. %, 5 to 30% by weight of a silicon dioxide powder, and a heat-resistant coating layer using this paint.

JP, 11-279488, A According to the above-mentioned patent document 2, the invention relates to a silicone resin of 20 to 60% by weight, glass powder of 1 to 25% by weight, glass fiber of 0.3 to 25% by weight, anticorrosive pigment of 0.1. Disclosed is a heat-resistant coating composition containing 10 to 10% by weight, 1 to 30% by weight of other pigments, and 20 to 60% by weight of a solvent.

  However, the film formed using the conventional inorganic-based heat-resistant film-forming composition, including the invention according to Patent Document 1 above, can ensure heat resistance that can withstand even in a high temperature range of 600 ° C, for example. However, it did not provide sufficient corrosion resistance to the metal substrate. That is also evident by the fact that these heat resistant coatings are vulnerable to corrosion resistance tests such as salt spray tests. Therefore, when these coating-forming compositions are used to form a coating on a metal substrate that is exposed to high temperatures and in contact with water (or in an environment under high humidity), the heat resistance and rust prevention properties are achieved. Was insufficient.

  On the other hand, the invention according to Patent Document 2 proposes a film-forming composition containing a silicone resin in addition to an inorganic component in consideration of the adhesion of the film to the substrate. However, for example, various metal structures / facilities / equipment and the like installed in a steel factory are exposed to a high temperature of 600 ° C. and are in contact with water or in a high humidity environment. A silicone resin that is not an inorganic component shows high heat resistance as a resin, but is eventually an organic substance, and at a high temperature level of, for example, 600 ° C., it deteriorates or decomposes and burns, and heat resistance cannot be expected.

  Therefore, the present invention provides heat and corrosion resistance that can form a film sufficiently exhibiting heat resistance and rust prevention against a metal substrate even in an environment (or an environment under high humidity) in contact with water in a high temperature range of 600 ° C. It is a technical problem to be solved to provide a film-forming composition and a heat- and corrosion-resistant film formed using this composition.

〔Viewpoints〕
Conventional inorganic heat-resistant coatings have poor adhesion to metal substrates, and can easily form fine pinholes. These points are the cause of the defect that the inorganic heat-resistant coating film has insufficient rust prevention (in other words, weak in the corrosion resistance test).

  The inventor of the present application has obtained the knowledge of the following 1) and 2) in the course of studying the means for solving the above technical problems, and only by selecting a specific inorganic component, a film excellent in heat resistance and rust prevention properties can be obtained. As a result, the present invention has been completed.

  1) Sodium silicate, which is widely used in conventional inorganic heat-resistant coatings, has a relatively high water solubility and is not necessarily preferable for ensuring the corrosion resistance of the coating. When an inorganic component having heat resistance equivalent to that of sodium silicate and water-resistant, for example, potassium silicate, is used, the adhesion of the inorganic heat-resistant film to the metal material can be enhanced.

  2) When the inorganic heat-resistant coating contains a fine inorganic component with high heat resistance and high water resistance, for example, fine powder of titanium oxide, the denseness of the coating is remarkably improved, and fine pinholes are effectively generated. Can be prevented.

(Configuration of the first invention)
The configuration of the first invention of the present application for solving the above problems is an aqueous composition for forming a heat and corrosion resistant coating, which contains potassium silicate and fine titanium oxide as active ingredients.

(Configuration of the second invention)
The configuration of the second invention of the present application for solving the above problem is that the potassium silicate according to the first invention is a molar ratio of silicon dioxide content to potassium oxide content (weight ratio of SiO ₂ / K ₂ O × 1.568). Is an aqueous composition for forming a heat- and corrosion-resistant coating film, which is at least one kind of potassium silicate having a value in the range of 2.0 to 3.8.

(Configuration of the third invention)
The configuration of the third invention of the present application for solving the above problem is that the molar ratio of the silicon dioxide content and the potassium oxide content in the potassium silicate according to the second invention is in the range of 2.7 to 3.7. It is an aqueous composition for forming a heat and corrosion resistant film.

(Configuration of the fourth invention)
The structure of the fourth invention of the present application for solving the above-mentioned problems is that the fine titanium oxide according to any one of the first to third inventions is a kind of rutile titanium oxide having an average particle diameter of 0.3 μm or less. This is the aqueous composition for forming a heat and corrosion resistant film.

(Structure of the fifth invention)
The structure of the fifth invention of the present application for solving the above-mentioned problems is that, with respect to 100 parts by weight of potassium silicate according to any of the first to fourth inventions, 30 to 60 parts by weight of titanium oxide, 10 to 10 parts of water. It is an aqueous composition for forming a heat- and corrosion-resistant coating film containing 80 parts by weight.

(Structure of the sixth invention)
The structure of the sixth invention of the present application for solving the above-described problem is that the aqueous composition for forming a heat- and corrosion-resistant coating film according to any one of the first to fifth inventions further comprises aluminum oxide, magnesium oxide, kaolin, mica. , An aqueous composition for forming a heat and corrosion resistant film, which contains at least one selected from the group of inorganic fillers consisting of talc, zeolite, sericite, clay and zirconia.

(Structure of the seventh invention)
The structure of the seventh invention of the present application for solving the above problem is that the aqueous composition for forming a heat- and corrosion-resistant coating film according to any one of the first to sixth inventions is further provided with a leveling agent, a dispersant and a coupling agent. It is an aqueous composition for forming a heat and corrosion resistant film, containing at least one selected from the group consisting of:

(Configuration of the eighth invention)
The structure of the eighth invention of the present application for solving the above-mentioned problem is that the aqueous composition for forming a heat and corrosion resistant film according to any one of the first to seventh inventions further contains a coloring pigment. -An aqueous composition for forming a corrosion-resistant film.

(Structure of the ninth invention)
The structure of the ninth invention of the present application for solving the above problems is a heat and corrosion resistant coating formed using the aqueous composition for forming a heat and corrosion resistant coating according to any one of the first to eighth inventions.

(Effect of the first invention)
The aqueous composition for forming a heat and corrosion resistant film of the first invention contains potassium silicate and fine titanium oxide as active ingredients.

  Potassium silicate has the same heat resistance as sodium silicate, which is widely used in conventional inorganic heat-resistant coatings. On the other hand, it is characterized by water resistance (low water solubility) compared to sodium silicate. ing. Therefore, the substrate adhesion of the coating is ensured mainly by potassium silicate.

  On the other hand, titanium oxide has high heat resistance and high water resistance (slightly water-soluble), and its fine powder remarkably improves the denseness of the film, and effectively prevents the generation of fine pinholes in the film. Therefore, the fineness of the coating is ensured mainly by fine titanium oxide.

  In view of the above, the use of the aqueous composition for forming a heat and corrosion resistant coating of the first invention effectively prevents the lack of adhesion to a metal substrate and the generation of fine pinholes as in the conventional inorganic heat resistant coating. The As a result, the film formed using the aqueous composition for forming a heat- and corrosion-resistant film according to the first invention is strong in corrosion resistance tests such as a salt spray resistance test, and can exhibit sufficient rust resistance against metal substrates. . At the same time, since potassium silicate and titanium oxide, which are effective components, are both heat-resistant inorganic components, it is a matter of course that they exhibit high heat resistance.

  In addition, since it is an aqueous composition, the familiarity of inorganic components, the absence of flammability and offensive odor as seen in oily compositions, the easy adjustment of the concentration that can be applied by spraying, and the adjustment of the coating film thickness There are advantages such as being easy.

(Effect of the second invention)
The molar ratio of silicon dioxide and potassium oxide in potassium silicate (weight ratio of SiO ₂ / K ₂ O × 1.568) is not necessarily limited, but the molar ratio is in the range of 2.0 to 3.8. It is particularly preferred to use one or more of potassium silicate.

  If the molar ratio is less than 2.0, there is a dissatisfaction that it is relatively difficult to form a glass film. On the other hand, when the above molar ratio exceeds 3.8, there is a dissatisfaction point that water resistance becomes relatively weak.

(Effect of the third invention)
When the above-mentioned molar ratio of the silicon dioxide content and the potassium oxide content in potassium silicate is in the range of 2.7 to 3.7, the contribution to the adhesion of the heat and corrosion resistant coating is particularly large.

(Effect of the fourth invention)
As the fine titanium oxide, one or more of rutile type titanium oxide having an average particle diameter of 0.3 μm or less is particularly preferable. The finer the average particle diameter of titanium oxide, the better. However, if the average particle diameter is 0.3 μm or less, the denseness of the coating can be sufficiently secured. When the average particle diameter of titanium oxide exceeds 0.3 μm, there is a dissatisfaction point that it is relatively difficult to sufficiently secure the denseness of the film. Anatase-type titanium oxide can also be used, but it is relatively unsatisfactory that optical resolution is generated as compared with rutile-type titanium oxide.

(Effect of the fifth invention)
It is preferable that the relative content of the potassium silicate and the fine titanium oxide, which are active ingredients of the heat-resistant / corrosion-resistant coating-forming aqueous composition, are within a certain range. That is, it is preferable to contain 30 to 60 parts by weight of titanium oxide and 10 to 80 parts by weight of water with respect to 100 parts by weight of potassium silicate as in the fifth invention.

  If the content of potassium silicate or titanium oxide deviates from the above range and is too small (in other words, the proportion of water is too large out of the above range), the lack of active ingredients It is difficult to form a uniform film, and it is difficult to ensure the desired effect due to the inclusion of these components. In addition, if the content of potassium silicate deviates from the above range and is excessively large, there is a problem that the retention of the film after film formation deteriorates, and the content of titanium oxide deviates from the above range. If it is too large, there is a problem that formation of a uniform glass film is likely to be hindered.

  Further, when the proportion of water is too small, the composition becomes highly viscous or difficult to flow, and there is a drawback that application to a film-forming substrate by, for example, spray coating tends to be inconvenient.

(Effect of the sixth invention)
The aqueous composition for forming a heat / corrosion-resistant coating film contains, in addition to the medium, water, potassium silicate, and fine titanium oxide, any necessary or useful optional component as long as the effects of the invention are not impaired. Can be included. Examples thereof include at least one selected from the group of inorganic fillers consisting of aluminum oxide, magnesium oxide, kaolin, mica, talc, zeolite, sericite, clay and zirconia.

(Effect of the seventh invention)
The aqueous composition for forming a heat-resistant / corrosion-resistant film can further contain one or more selected from a leveling agent, a dispersant, and a coupling agent. These components can be arbitrarily selected from, for example, commercially available products.

(Effect of the eighth invention)
The aqueous composition for forming a heat and corrosion resistant film can be used as a colored paint by further containing a coloring pigment.

(Effect of the ninth invention)
When a film is formed using the aqueous composition for forming a heat- and corrosion-resistant film according to any one of the first to eighteenth inventions, a heat- and corrosion-resistant film with the effects of any one of the first to eighth inventions is obtained. . This heat / corrosion resistant coating is a metal substrate in an environment (or an environment under high humidity) in contact with water in a high temperature range of 600 ° C., for example, various metal structures / equipment / equipment installed in a steel factory. Excellent heat resistance and corrosion resistance are exhibited even when a film is formed on a material.

  Next, modes for carrying out the first invention to the ninth invention will be described including the best mode. In the following, the term “present invention” refers to each invention of the present application as a whole.

[Aqueous composition for forming heat and corrosion resistant film]
The aqueous composition for forming a heat and corrosion resistant coating according to the present invention comprises (A) a heat resistant and water resistant inorganic component that mainly contributes to the adhesion of the coating to the substrate, and (B) a high heat resistance that mainly contributes to the denseness of the coating. It is characterized in that it contains a fine inorganic component with high water resistance and high water resistance as an active ingredient.

  About the amount ratio of (A) component, (B) component, and water in the aqueous composition for heat-resistant and corrosion-resistant film formation, 1 to 100 parts by weight of (B) component, 1 water for 100 parts by weight of (A) component It is preferable that it is -1000 weight part, and it is especially preferable that they are 30-60 weight part of (B) component and 10-80 weight part of water with respect to 100 weight part of (A) component.

  Although it does not limit about the kind of (A) component and (B) component, a potassium silicate can be illustrated preferably as (A) component, and a fine titanium oxide can respectively be illustrated as (B) component. And also about the amount ratio of potassium silicate, fine titanium oxide, and water in the aqueous composition for forming a heat and corrosion resistant coating, 1 to 100 parts by weight of titanium oxide and 1 to 1000 parts of water with respect to 100 parts by weight of potassium silicate. It is preferable to contain a weight part, and it is especially preferable to contain 30-60 weight part of titanium oxide and 10-80 weight part of water with respect to 100 weight part of potassium silicate.

[Component (A)]
Regarding the potassium silicate typically exemplified as the component (A), when the molar ratio of the silicon dioxide content and the potassium oxide content is defined as “weight ratio of SiO ₂ / K ₂ O × 1.568”, preferably , The molar ratio is in the range of 2.0 to 3.8, particularly preferably, one kind of potassium silicate having this molar ratio in the range of 2.7 to 3.7 is used alone, or Two or more kinds of such potassium silicates can be used in combination.

[(B) component]
About the fine titanium oxide typically illustrated as (B) component, a thing with a small average particle diameter is preferable, and a 0.3 micrometer or less thing is especially preferable. Further, rutile type titanium oxide is preferable. One kind of titanium oxide belonging to these preferred categories can be used alone, or two or more kinds of such titanium oxides can be used in combination.

[Other ingredients]
The aqueous composition for forming a heat / corrosion resistant coating according to the present invention is a coating of this type as long as the effect of the present invention is not impaired, in addition to the medium water and the components (A) and (B). Various components that may be contained in the forming composition can optionally be contained.

  Examples of such components include one or more selected from an inorganic filler group consisting of aluminum oxide, magnesium oxide, kaolin, mica, talc, zeolite, sericite, clay, and zirconia.

  Furthermore, 1 or more types chosen from a leveling agent, a dispersing agent, and a coupling agent can also be contained. Although the kind of dispersing agent is not limited, a polymeric dispersing agent etc. can be illustrated. Although the kind of coupling agent is not limited, a silane coupling agent etc. can be illustrated.

Furthermore, the heat-resistant / corrosion-resistant film-forming aqueous composition according to the present invention may contain a coloring pigment. Although the kind of pigment is not limited, a fired pigment is preferable in consideration of heat resistance. Examples of the calcined pigment include FeO (black), Fe ₂ TiO ₄ (brown), CoAl ₂ O ₄ (dark blue), and the like. Other types of pigments, such as anticorrosive pigments such as zinc phosphate, aluminum phosphate, calcium phosphate, zinc molybdate and calcium molybdate, scaly pigments such as mica and scaly iron oxide, kaolin, precipitated barium sulfate and carbonic acid Extender pigments such as calcium can also be used.

[Formation of heat and corrosion resistant coatings]
The heat-resistant / corrosion-resistant coating film according to the present invention can be formed on any film-forming substrate using any of the above-described aqueous compositions for forming a heat-resistant / corrosion-resistant coating film.

  The type of the film-forming substrate is not limited, but a metal substrate that exhibits the effects of the invention is preferable, and in particular, a metal substrate that is exposed to water or placed in a high-humidity environment while being exposed to high temperatures, for example, iron making Metals that come into contact with water or are exposed to high temperatures of 600 ° C, such as various metal structures installed in factories, metal facilities, metal equipment, etc. The substrate can be preferably exemplified.

  A method for forming a heat-resistant / corrosion-resistant film, that is, a method for forming a film for forming a heat-resistant / corrosion-resistant film-forming aqueous composition on various substrates such as a metal substrate is not limited, but can preferably be applied by spraying. In this case, it is preferable to make water into a ratio of about 10 to 30 parts by weight with respect to 100 parts by weight of the whole inorganic component. The thickness of the heat / corrosion resistant coating is not limited, but is preferably about 5 to 20 μm, for example.

  When rapid film formation is desired after spray coating, heating after film formation can be performed. For example, the film is formed by heating at 500 ° C. for about 3 minutes.

  It is a matter of course that other various film forming methods such as brush coating, dipping of the base material with respect to the aqueous composition for forming a heat and corrosion resistant film can be employed.

  The formed heat / corrosion-resistant coating is provided with excellent heat resistance and adhesion to the substrate mainly by the component (A) which is a heat-resistant and water-resistant inorganic component that mainly contributes to the substrate adhesion of the coating. Excellent heat resistance and film denseness are imparted by the component (B) which is a fine inorganic component having high heat resistance and high water resistance that contributes to the denseness of the film. As a result, an inorganic coating film that is highly heat resistant, adheres well to the substrate even in a high temperature region of 600 ° C., and has no fine pinholes and is excellent in the rust prevention property of the substrate. This good antirust property is also evident by the fact that it is strong in corrosion resistance tests such as salt spray test.

[Example A: Preparation of aqueous composition for forming heat and corrosion resistant film]
In each example and each comparative example according to Example A, as potassium silicate, 2K potassium silicate [trade name of Nippon Chemical Industry Co., Ltd .: molar ratio of silicon dioxide content and potassium oxide content is 3. Within the range of 4 to 3.7] was used. As the titanium oxide, TITANIX JR-800 [trade name of Taca Co., Ltd .: rutile type titanium oxide, average particle size 0.27 μm] was used. A commercially available polymer dispersant was used as the dispersant. A commercially available silane coupling agent was used as the coupling agent.

  In Example 1, 15 parts by weight of water was added to 100 parts by weight of potassium silicate, 50 parts by weight of titanium oxide, 4 parts by weight of a dispersant, and 1 part by weight of a coupling agent. The product was stirred and mixed for 30 minutes, and further 30 parts by weight of water was added to adjust the concentration to be suitable for spray coating.

  In Example 2, 15 parts by weight of water was added to 100 parts by weight of potassium silicate, 30 parts by weight of titanium oxide, 20 parts by weight of mica, 4 parts by weight of a dispersant, and 1 part by weight of a coupling agent. The mixture was stirred and mixed for 30 minutes, and 30 parts by weight of water was further added to adjust the concentration to be suitable for spray coating.

  In Example 3, 15 parts by weight of water was added to 100 parts by weight of potassium silicate, 30 parts by weight of titanium oxide, 10 parts by weight of mica, 10 parts by weight of talc, 4 parts by weight of a dispersant and 1 part by weight of a coupling agent. The mixture was stirred and mixed for 30 minutes in the same disperser, and 30 parts by weight of water was further added to adjust the concentration to be suitable for spray coating.

  In Comparative Example 4, 15 parts by weight of water was added to 100 parts by weight of potassium silicate, 50 parts by weight of mica, 4 parts by weight of a dispersant, and 1 part by weight of a coupling agent, and the mixture was stirred and mixed for 30 minutes using the same disperser. Further, 30 parts by weight of water was added to adjust the concentration to be suitable for spray coating.

  In Comparative Example 5, 15 parts by weight of water was added to 100 parts by weight of mica, 50 parts by weight of titanium oxide, 4 parts by weight of a dispersant, and 1 part by weight of a coupling agent, and the mixture was stirred and mixed for 30 minutes using the same disperser. Further, 30 parts by weight of water was added to adjust the concentration to be suitable for spray coating.

In Comparative Example 6, 15 parts by weight of water was added to 100 parts by weight of sodium silicate (water glass), 50 parts by weight of titanium oxide, 4 parts by weight of a dispersant, and 1 part by weight of a coupling agent. For 30 minutes by mixing and adding 30 parts by weight of water and adjusting to a concentration suitable for spray coating. For film formation according to each of the above Examples and Comparative Examples The composition after the concentration adjustment of the aqueous composition is shown in Table 1 below.

〔実施例Ｂ：評価用試料の作製〕
供試材としてφ４５×１５０×１．５ｍｍの鋼管材片（ＳＴＫＭ材）を採用し、この供試材に対して、上記の各実施例、比較例に係る被膜形成用水性組成物をそれぞれスプレー塗布した。このスプレー塗布は、スプレー圧３Ｋｇで、１流体アトマイザーにて、パイプ状供試材の内面に厚さ１５μｍの塗布膜を形成する設定で行った。

[Example B: Preparation of sample for evaluation]
A φ45 × 150 × 1.5 mm steel pipe material piece (STKM material) was adopted as the test material, and the film-forming aqueous compositions according to the above Examples and Comparative Examples were respectively sprayed on the test material. Applied. This spray coating was performed with a spray pressure of 3 kg and a setting of forming a coating film having a thickness of 15 μm on the inner surface of the pipe-shaped specimen with a single fluid atomizer.

[Example C: Sample evaluation test]
Samples for evaluation according to Examples and Comparative Examples in which a coating film was formed according to Example B above were taken out from the electric furnace after being placed in an electric furnace maintained at 600 ° C. for 5 minutes, and after cooling, the axial direction The paint surface was exposed in half along the side. Then, the cut edge portion of each halved sample was sealed with a rust preventive paint, and then subjected to the next salt spray test.

The salt spray test was carried out using a salt spray tester (type ISO type) manufactured by Suga Test Instruments Co., Ltd. The test conditions were as follows: temperature 35 ± 1 ° C., salt water concentration 5 ± 1%, salt spray amount 1.0-2.0 mL / hr. / 80cm was ^2.

  As evaluation items, first, the rust prevention property of the coating film was evaluated. That is, the presence or absence of rust on the surface of the coating film on the sample was checked after 6 hours, 12 hours, 24 hours, 36 hours, and 48 hours from the start of the salt spray test. The evaluation results were expressed by describing the check point at which rust was first observed in the column of “salt spray test” for each example and comparative example in Table 2. For example, when “24Hr” is written in the column, it means that “the occurrence of rust was recognized in the check after 24 hours from the start of the salt spray test”. Therefore, the longer the number of hours, the higher the rust prevention property of the coating film.

  The second evaluation item is an evaluation of the adhesion of the coating film by a cross-cut tape method. That is, for each of the evaluation samples according to each of the Examples and Comparative Examples after the 48-hour salt spray test, after the salt water was well wiped off, the coating film was cut with a cutter guide, and the cuts were made vertically and horizontally. 100 squares having a width of 1 mm were formed. And after making a cellophane tape contact | adhere so that these whole grids might be covered, this cellophane tape was peeled off and the number of the grids in which the coating film was not peeled in that case was counted. The evaluation results are indicated by numbers in the “cross-cut tape method” column for each example and comparative example in Table 2. This number is the number of squares in which the above-mentioned coating film has not been peeled off, with the number of human digits discarded. For example, when “50” is written in the column, it means that “the number of cells in which the above-mentioned coating film has not been peeled is within the range of 50 to 59”. Therefore, the larger the number, the higher the adhesion of the coating film.

  The column of “Comprehensive evaluation” in Table 2 is an evaluation of the rust prevention and adhesion of the coating film. The column of “Salt spray test” is “36 Hr” or more, and the column of “cross-cut tape method” Is evaluated as “◎”, “salt spray test” is “24Hr”, and “cross-cut tape method” is “10”. did. On the other hand, either the low evaluation condition that the “salt spray test” column is less than “24Hr” or the low evaluation condition that the “cross-cut tape method” column is less than “10” Applicable products were evaluated as “△”, and those applicable to both were evaluated as “X”.

〔試料の評価結果〕
表２に示す評価結果より、以下の点が認められる。まず、被膜形成用組成物がケイ酸カリウムを含有するか否かに関して、各実施例及び比較例４と、比較例５との対比から、ケイ酸カリウムの含有による塗膜密着性の改善が明瞭である。更に、実施例１と比較例６との対比から、塗膜の密着性（ひいては塗膜の防錆性）に関して、従来型の無機質耐熱被膜において汎用されているケイ酸ソーダに対する、ケイ酸カリウムの優位性が明瞭である。

[Sample evaluation results]
From the evaluation results shown in Table 2, the following points are recognized. First, as to whether or not the film-forming composition contains potassium silicate, the improvement in coating film adhesion due to the inclusion of potassium silicate is clear from the comparison between each Example and Comparative Example 4 and Comparative Example 5. It is. Further, from the comparison between Example 1 and Comparative Example 6, regarding the adhesion of the coating film (and consequently the rust prevention property of the coating film), potassium silicate with respect to sodium silicate widely used in conventional inorganic heat-resistant coating films The superiority is clear.

  Next, regarding whether or not the film-forming composition contains titanium oxide, Comparative Example 4 not containing titanium oxide has poor adhesion results of the coating film, but the result of the salt spray test is poor. The rustproofing property to the substrate is bad. This suggests that the inclusion of titanium oxide is effective in preventing the occurrence of fine pinholes in the coating film. On the other hand, Comparative Example 5, which contains titanium oxide but does not contain potassium silicate, has poor adhesion of the coating film, and also has a poor salt spray test result (rust prevention against a metal substrate). When these comparative examples are compared with the evaluation results of Examples 1 to 3, in Comparative Example 4, the antirust property is poor due to the occurrence of fine pinholes in the coating film, and in Comparative Example 5, the adhesion of the coating film. It is considered that the rust prevention property is poor due to the poor quality.

  In contrast to Examples 1 to 3, compared to Example 1 containing 50 parts by weight of titanium oxide, Example 2 containing 30 parts by weight of titanium oxide and 20 parts by weight of mica. However, the result of the salt spray test is good. In Example 3, which contains 30 parts by weight of titanium oxide, 10 parts by weight of mica, and 10 parts by weight of talc, the result of the salt spray test is even better.

  Regarding this point, when the coating thickness of the sample according to each example was re-examined after the evaluation was completed, in Example B, the coating thickness of 15 μm was uniformly set by the atomizer. The actual coating thickness was 18 μm in Example 2 and 20 μm in Example 3, which was thicker than the set coating thickness. The inventor of the present application believes that the difference in the results of the salt spray test between Example 1 and Examples 2 and 3 is due to the difference in the coating thickness.

According to the present invention, it is a coating preferably formed on a metal substrate, and has high heat resistance because it is composed exclusively of an inorganic active ingredient, and has a denseness and adhesion to a substrate that are not found in conventional inorganic heat-resistant coatings. Therefore, a composition for forming a heat / corrosion-resistant film excellent in rust resistance and a heat / corrosion-resistant film using the same are provided.

Claims (9)

An aqueous composition for forming a heat- and corrosion-resistant film, comprising potassium silicate and fine titanium oxide as active ingredients. The potassium silicate is one or more types of potassium silicate having a molar ratio of silicon dioxide content to potassium oxide content (weight ratio of SiO ₂ / K ₂ O × 1.568) within a range of 2.0 to 3.8. The aqueous composition for forming a heat- and corrosion-resistant coating film according to claim 1, wherein The aqueous composition for forming a heat- and corrosion-resistant coating film according to claim 2, wherein the molar ratio of the silicon dioxide content and the potassium oxide content in the potassium silicate is in the range of 2.7 to 3.7. The heat-resistant / corrosion-resistant coating film according to any one of claims 1 to 3, wherein the fine titanium oxide is one or more of rutile-type titanium oxide having an average particle size of 0.3 µm or less. Aqueous composition. 5. The heat and corrosion resistance according to claim 1, comprising 30 to 60 parts by weight of the titanium oxide and 10 to 80 parts by weight of water with respect to 100 parts by weight of the potassium silicate. An aqueous composition for film formation. The heat-resistant / corrosion-resistant coating-forming aqueous composition further contains one or more selected from the group of inorganic fillers consisting of aluminum oxide, magnesium oxide, kaolin, mica, talc, zeolite, sericite, clay, and zirconia. The aqueous composition for forming a heat and corrosion resistant film according to any one of claims 1 to 5. The said heat-resistant / corrosion-resistant film-forming aqueous composition further contains at least one selected from a leveling agent, a dispersant, and a coupling agent. An aqueous composition for forming heat and corrosion resistant films. The aqueous composition for forming a heat and corrosion resistant coating according to any one of claims 1 to 7, wherein the aqueous composition for forming a heat and corrosion resistant coating further contains a pigment for coloring. A heat-resistant / corrosion-resistant film formed using the aqueous composition for forming a heat-resistant / corrosion-resistant film according to any one of claims 1 to 8.