JP2002212765A - Rust preventive and coating material composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a rust preventive which is of a pollution-free type to take place of lead and chromium regarded to be harmful, is low in cost and is effectual for a long period of time and to obtain a coating material composition. SOLUTION: The rust preventive (C) is prepared by impregnating a porous base material (A) with a compound (B) of at least one kind selected from a gluconic acid-base compound, gluconate-base compound, triazole-base compound, pyrazole-base compound, thidiazole-base compound, a polyphosphoric acid-base compound and polyphosphate-base compound and/or including the compound described above into the base material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD [0001] The present invention relates to a method for preventing a compound having a rust-preventing action from impregnating and / or encapsulating a porous substrate such as clay or mineral in a paint or a formed coating film. The present invention relates to a rust preventive agent having a sustained release property such as adjusting the dissolution rate of a rust agent and exhibiting a rust preventive effect over a long period of time, and a coating composition containing the rust preventive agent.

[0002]

2. Description of the Related Art Rust-inhibiting pigments and rust-preventing agents are incorporated into paints such as organic solvent-based paints and water-based paints in order to improve the corrosion resistance of the metal material to be coated. Conventionally, lead (for example, lead red, basic lead silicate, cyanamide lead, calcium lead, lead acetate, etc.), chromium (for example, zinc chromate, Strontium chromate). However, these rust preventive pigments and rust preventives are extremely harmful substances, and their use is problematic in consideration of environmental problems, laws and regulations, and effects on the human body.

[0003] Therefore, non-toxic or low-toxic rust-preventive pigments and rust-preventive agents have been studied in place of the above-mentioned lead compounds and chromium compounds. In addition, there has been a demand for a low-cost rust inhibitor which has a long-lasting rust-preventing effect, good storage stability and low cost.

[0004]

Means for Solving the Problems The present inventors have developed a low-cost rust preventive agent that does not contain harmful metals such as lead compounds and chromium compounds, is non-toxic or low-toxic, and has excellent storage stability of paints. We worked diligently to find out. As a result, it was found that it is important to appropriately adjust the dissolution rate. From this, the compound having a rust-preventive action is impregnated and / or included in a porous base material such as clay or mineral, and the dissolution rate is adjusted by blending the rust-preventive agent into the coating composition for a long time. The present inventors have found that the migratory rust preventive effect is maintained, and have completed the present invention.

That is, the present invention provides: One or more compounds selected from a gluconate-based compound, a gluconate-based compound, a triazole-based compound, a pyrazole-based compound, a thiadiazole-based compound, a polyphosphate-based compound, and a polyphosphate-based compound on the porous substrate (A). 1. A rust preventive (C) obtained by impregnating and / or enclosing (B). When the porous substrate (A) is bentonite, montmorillonite, saponite, wollastonite, acid clay, activated clay, diatomaceous earth, kaolin, clay, clay, china clay, hydrotalcite, calcium carbonate, talc, mica, smectite, zeolite, silica 1 selected from
2. The rust preventive (C) according to item 1, which is at least one kind of inorganic material; 3. The rust inhibitor (C) according to item 1 or 2, wherein the gluconic acid-based compound of compound (B) is gluconic acid. The rust inhibitor (C) according to item 1 or 2, wherein the gluconate compound of the compound (B) is at least one of sodium gluconate, zinc gluconate, iron gluconate, and aluminum gluconate. ), 5. When the triazole compound of the compound (B) is 3-amino-1,2,4-triazole, 4-amino-1,2,2,
5. The rust inhibitor (C) according to item 1 or 2, wherein one or more types of 4-triazole are used. 6. The rust inhibitor (C) according to item 1 or 2, wherein the pyrazole compound of compound (B) is 3-amino-1,2,4-ethylpyrazole; 7. The rust inhibitor (C) according to item 1 or 2, wherein the thiadiazole-based compound of the compound (B) is 5-amino-2-mercapto-1,3,4-thiadiazole. 8. The rust preventive (C) according to item 1 or 2, wherein the polyphosphate compound of the compound (B) is at least one selected from the group consisting of pyrophosphoric acid, hexametaphosphoric acid, and tripolyphosphoric acid. 3. The polyphosphate compound of the compound (B) uses one or more of an alkali metal salt or an alkaline earth metal salt of the polyphosphoric acid compound according to item 8, wherein the compound (B) is a polyphosphate compound. 9. rust inhibitor (C); The compound (B) is mixed with a porous substrate (A) having a solid content of 100.
The rust preventive (C) according to any one of the items 1 to 9, wherein the rust preventive (C) is 1 to 100 parts by weight with respect to parts by weight, and is selected from the items of 11.1 to 10. A rust preventive (C) in an amount of 1 to 200 parts by weight per 100 parts by weight of the solid content of the coating composition.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

[0006] In the present invention, clays and minerals used as the porous substrate (A) have various shapes such as being porous and having a layered internal structure. A compound having a rust-preventing effect or a metal ion is impregnated or / included in the surface layer and / or the inner layer or the gap to form a composite compound, and chemically and physically different characteristics can be obtained. Sometimes called intercalation.

As a patent relating to the above method, there is disclosed a method in which a divalent metal ion or an inhibitor is added to a crystalline layered phosphate and applied to a paint as a rust preventive pigment.
No. 0). However, this compound has a problem that the inhibitory activity is insufficient and the stability of the paint is impaired.

In the present invention, the compound (B) having a high initial rust-preventing effect but having a high dissolution rate and a poor sustainability is used to convert the compound (B) into a surface layer or an internal layer of a porous substrate (A) such as clay or natural mineral. This is an inexpensive non-polluting rust preventive agent that inserts a compound with rust preventive effect into the gap to adjust the dissolution rate of the rust preventive agent and maintain the effect for a long time. The fact that the present invention has been developed as a rust preventive agent using a porous base material has been achieved by the present inventors after diligent studies.

In the present invention, the porous substrate (A) includes an acidic porous substrate, a basic porous substrate, and other porous substrates depending on the surface condition. Is appropriately selected depending on the combination of.

Examples of the acidic porous base material (A) include bentonite, montmorillonite, saponite, wollastonite, acid clay, activated clay, diatomaceous earth, kaolin family such as anoxite, clay, clay, china clay and the like. Examples of the basic porous substrate (A) include mica such as calcium carbonate, talc, and chlorite, smectite, and zeolite.

Other porous substrates (A) include allophane groups such as silica, graphite, kaolin and allophane; halosite groups such as metahalosite and halosite;
Serpentine family such as chrysotile, lizardite, antigolite, vermiculite mineral such as vermiculite, helite, sericite, attapulgite, sepioraipaigolskite, bentonite, kibushi clay, gailome clay, hisingelite, pyrophyllite, ryokuday Stone group and the like. The above-mentioned acidic, basic, and other porous substrates (A) may be used as a mixture.

The compound (B) having a rust-preventing effect is a gluconic acid compound, a gluconic acid or gluconate compound, sodium gluconate, zinc gluconate, iron gluconate, aluminum gluconate or a triazole compound. , 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole and pyrazole-based compound are 3-amino-1,2,4-ethylpyrazole and thiadiazole-based compound are 5- Amino-2-mercapto-
1,3,4-thiadiazole, a polyphosphate compound,
Examples of pyrophosphoric acid, hexametaphosphoric acid, tripolyphosphoric acid, and polyphosphate compounds include alkali metal salts and alkaline earth metal salts of the polyphosphoric acid compounds.

The above-mentioned compound (B) is impregnated and / or included in the surface layer of the porous substrate (A), the inner layer and the gap, and the rust inhibitor (C) is produced. Base material (A)
1 to 1 part by weight of the solid content of
00 parts by weight, preferably 5 to 50 parts by weight, is preferably impregnated and / or included in the surface layer of the porous substrate (A), the internal layers and gaps.

The amount of the compound (B) impregnated and / or included in the surface layer, the inner layer and the gap of the porous substrate (A) is 1
If the amount is less than 100 parts by weight, there is no effect on the anticorrosion property. If the amount exceeds 100 parts by weight, stability is impaired and production cost is increased.

For example, the step of producing the rust preventive (C) by impregnating and / or enclosing the compound (B) into the surface layer, the inner layer and the gap of the porous substrate (A) is as follows. There is, but is not limited to this.

Sol process: If it is an acidic compound (B), it is rapidly mixed with a basic substance such as an amine, and if it is a basic compound (B), it is rapidly mixed with an acidic substance such as a carboxylic acid and aggregated. A sol of the compound (B) is formed without generating a substance. Impregnation and / or inclusion step: Next, a suspension is prepared by dispersing and swelling the porous substrate (A) in water, and the suspension is stirred well in the sol of the compound (B). Added. As a result, a sediment, that is, a rust preventive (C) is obtained. Finishing process: The rust inhibitor (C) is completed as a product by filtration, washing, drying, and pulverization. Analysis of the rust preventive (C) by X-ray diffraction analysis or the like shows that the compound (B) impregnates and / or includes the surface layer of the porous base material (A), the inner layers and gaps, and / or inclusions. You can check.

In the present invention, a sediment, that is, a coating composition to which a rust preventive is applied can be selected from conventionally known coating systems without any particular limitation. Specific examples include an organic solvent and an aqueous coating composition depending on the solvent.

The rust preventive (C) can be used in either an organic solvent type coating composition or an aqueous coating composition. When used in an organic solvent coating composition, the rust inhibitor is often used by being dispersed together with other pigments, and is used as a pigment-dispersed paste in the coating composition.

Specific examples of the organic solvent paint composition include acrylic resin paints, alkyd resin paints, polyester paints, epoxy resin paints, amino resin paints (melamine resin, benzoguanamine resin, urea resin and amine resin). Paints using methylolated or alkyl etherified compounds of compounds), cellulose derivative paints (nitrocellulose lacquer, acetylcellulose lacquer, acetylbutylcellulose lacquer, ethylcellulose lacquer, etc.), urethane resin paint, vinyl chloride resin paint, fluorine resin Paints, vinyl acetate resin paints, styrene-butadiene resin paints, and vinyl chloride organosol paints.

As the cross-linking type, for example, any of a thermosetting type and a room temperature setting type can be used. For example, a hydroxyl group-containing resin (acrylic, epoxy, polyester, etc.) / Curing agent (amino resin, (Block) polyisocyanate compound), epoxy group-containing resin / polyamine / polyamide, polycarboxylic acid resin / epoxy curing agent, epoxy base resin / polycarboxylic acid curing agent, etc.
Conventional curing types can be used.

The solvent used in the organic solvent coating composition may be appropriately selected depending on the type of the coating, and specific examples thereof include hydrocarbons (hexane, heptane, etc.), alcohols (propanol, butanol, etc.), and ethers. Examples (e.g., ethyl cellosolve, butyl cellosolve, diethylene glycol monoethyl ether), ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone), and esters (e.g., ethyl acetate, propyl acetate, butyl acetate, cellosolve) can be used. Also,
The rust-preventing effect can be adjusted by changing the elution rate of the compound in the rust-preventing agent depending on the type and amount of the organic solvent.

If necessary, compounds, pigments, flow regulators, surfactants, pigment dispersants, plasticizers, curing catalysts, surface regulators, ultraviolet absorbers, viscosity regulators, compounds added to the rust preventive agent as required. An antifoaming agent, a pH adjusting agent and the like can be added.

As the above-mentioned pigments, those conventionally used can be used without limitation, for example, coloring pigments such as titanium oxide, carbon black, red iron oxide, aluminum paste, pearl powder, graphite, MIO, phthalocyanine blue; And extender pigments such as mica, barita, talc, calcium carbonate, and silica; and rust-preventive pigments such as zinc phosphate, iron phosphate, bismuth-based compounds, and zinc white.

The amount of the rust preventive (C) in the organic solvent type coating composition is preferably 1 to 200 parts by weight, more preferably 5 to 100 parts by weight, based on 100 parts by weight of the solid content of the resin. If the added amount is less than 1 part by weight, there is no effect on the anticorrosion property, and if it exceeds 200 parts by weight, the stability of the paint is impaired, which is not preferable.

The aqueous coating composition may be a conventionally known water-soluble, water-dispersible or emulsion-type one, and may be an anionic, cationic or nonionic type. The amount of the rust preventive (C) is often used as a pigment paste by dispersing it together with other pigments in the same manner as in the organic solvent type coating composition.

The amount of the rust inhibitor (C) is preferably 1 to 200 parts by weight, more preferably 5 to 100 parts by weight, based on 100 parts by weight of the resin solid content. If the added amount is less than 1 part by weight, there is no effect on the anticorrosion property, and if it exceeds 200 parts by weight, the stability of the paint is impaired, which is not preferable.

Examples of the aqueous paint composition include acrylic resin paints, alkyd resin paints, polyester paints, epoxy resin paints, amino resin paints (melamine resins, benzoguanamine resins, urea resins and amine compounds). Paints using a methylol compound or an alkyl ether compound), urethane resin paints, vinyl chloride resin paints, fluororesin paints, vinyl acetate resin paints, styrene-butadiene resin paints, and the like. If necessary, pigments, flow regulators, plasticizers, surfactants, curing catalysts, coating surface regulators, ultraviolet absorbers and the like can be added.

As the pigment, those conventionally used can be used without limitation. For example, coloring pigments such as titanium oxide, carbon black, red iron oxide, aluminum paste, pearl powder, graphite, MIO, phthalocyanine blue; Extenders such as mica, barita, talc, calcium carbonate, silica; zinc phosphate,
Rust preventing pigments such as iron phosphate can also be used in combination.

In addition to the above-mentioned organic solvent-based coating compositions and water-based coating compositions, they can also be used in solvent-free liquid coating compositions, active energy ray-curable and powder coating compositions.

The composition of the present invention can form a cured coating film by applying the above coating composition to a substrate and then subjecting the composition to room temperature, heating, or irradiation with active energy rays. Examples of objects to be coated include cold-rolled steel sheets, hot-dip galvanized steel sheets, electro-galvanized steel sheets, zinc alloy-plated steel sheets, aluminum-plated steel sheets, stainless steel sheets, copper-plated steel sheets, tin-plated steel sheets, and the like. A steel sheet which has been subjected to a chemical conversion treatment such as a phosphate treatment or a chromate treatment. Among them, a cold-rolled steel sheet, a galvanized steel sheet, a zinc alloy-plated steel sheet, and an aluminum-plated steel sheet which have been subjected to a chemical conversion treatment are preferable.

The coating method of the coating composition includes, for example, brush coating, spray spray coating, roll coater coating, roller coating, dip coating, electrostatic powder coating, flow coater,
Alternatively, the surface of the steel sheet can be coated by electrodeposition coating or the like. The thickness of the coating film varies depending on the type of coating material, coating means, purpose of use, etc., but is usually 1 to 300 μm, preferably 5 to 300 μm.
It is in the range of 100 μm.

The conditions for drying the coating film can be selected according to the type of the coating composition. For example, a coating composition containing a hydroxyl group-containing acrylic resin as a base resin and a (blocked) polyisocyanate compound or a melamine resin as a cross-linking agent can be heated to 120 ° C. in a drying facility such as a hot air electric drying oven or a hot air gas drying oven. 250 ° C. for 30 seconds to 18
It takes about 0 minutes.

[0033]

[Effect of the Invention] The product of the present invention is a non-polluting rust preventive agent that replaces conventional lead and chromium, and is inexpensive compared with rust preventive agents using alternative metals, and the cost of paint is low. It contributes to the conversion. Further, by adjusting the dissolution rate of the rust inhibitor in the coating film, it is useful for maintaining the coating film corrosion resistance for a long period of time even under severe conditions against corrosion such as automobile bodies and buildings. The reason for this is that the rust preventive is gradually impregnated and / or included with a compound having a rust preventive effect in the surface layer of clay or natural mineral having a complicated structure, the inner layer and gaps. Is eluted to produce an effect.

[0034]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited by this. Note that “parts” and “%” indicate “parts by weight” and “% by weight”.

Production Example of Rust Inhibitor 1 In a 5 L flask, 400 g of a 0.1% by weight aqueous solution of gluconic acid was heated to 90 ° C., and 100 g of 0.1% by weight octylamine was rapidly mixed. After that, a precipitate-free sol was formed, followed by stirring at 25 ° C. for 1 hour. Separately, a suspension was prepared by dispersing 100 g of calcium carbonate in 2000 mL of water and stirring at 25 ° C. for 1 hour, and added all at once to the sol solution with good stirring.
After stirring for 6 hours, the mixture was allowed to stand for 1 day. After filtering and washing the product, it was dried at 50 ° C. to obtain a rust preventive agent 1. X-ray diffraction analysis confirmed that gluconic acid was impregnated in calcium carbonate in a 50 nm layer.

Production Example of Rust Preventive Agent 2 In a 5 L flask, 0.1% by weight of 3-amino-1,
400 g of 2,4-triazole is heated to 100 ° C.
A precipitate-free sol was formed by rapidly mixing 20 g of 0.1% by weight acetic acid, followed by stirring at 25 ° C. for 1 hour. Separately, Kunipia-F. C. E. FIG. C (manufactured by Kunimine Industries Co., Ltd., trade name: Montmorillonii 100 g in water 200
A suspension was prepared which was dispersed in 0 mL and stirred at 25 ° C. for 1 hour, added to the sol solution at once with good stirring, further stirred at 25 ° C. for 8 hours, and allowed to stand for 1 day. . After filtering and washing the product, it was dried at 50 ° C. to obtain a rust preventive agent 2. According to X-ray diffraction analysis, 3
It was confirmed that -amino-1,2,4-triazole was impregnated in montmorillonite.

Example 1 Coating composition NO. 1 In 100 parts of Acridic A801 (manufactured by Dainippon Ink and Chemicals, acrylic resin) in a stirring and mixing vessel, add JR-
701 (manufactured by Teica Corporation, trade name, titanium white) 80
Parts, 120 parts of the rust preventive obtained in the Production Example and a xylene-based solvent were added and stirred for 60 minutes to obtain a pigment paste a having a solid content of 30% by weight. Next, 30 parts of the pigment paste a, OH
Sumidure N33 so that amount / NCO amount = 1/1
Add 170 parts of 00 (trade name, hexamethylene diisocyanate, trade name, manufactured by Sumitomo Bayer Urethane Co., Ltd.) and stir with a disper to obtain a solid content of 32% by weight in Example 1.
Of the coating composition NO. 1 was obtained.

Example 2 Coating composition NO. 2 Rust inhibitor NO. Rust inhibitor 2 instead of 1
Pigment paste b having a solid content of 30% by weight was obtained by the same blending and operation except that 20 parts were used. The subsequent formulation and operation were the same as in Example 3, except that the coating composition NO. 2 was obtained.

Comparative Example 1 3 100 parts of Acrydick A801 (manufactured by Dainippon Ink and Chemicals, Inc., acrylic resin) in a stirring and mixing container, and JR-
701 (manufactured by Teica Corporation, trade name, titanium white) 80
Parts, 5 parts of gluconic acid, 15 parts of calcium carbonate, and a xylene-based solvent were added and stirred to obtain a pigment paste c having a solid content of 30% by weight. Next, 30 parts of the above-mentioned pigment paste c, OH content /
Sumidur N3300 so that the NCO amount = 1/1
170 parts (trade name, hexamethylene diisocyanate, trade name, manufactured by Sumitomo Bayer Urethane Co., Ltd.) were added, and the mixture was stirred with a disper. 3 was obtained.

Comparative Example 2 4 100 parts of Acrydic A801 (manufactured by Dainippon Ink and Chemicals, acrylic resin) in a stirring and mixing vessel, and JR-
701 (manufactured by Teica Corporation, trade name, titanium white) 80
, 5 parts of 3-amino-1,2,4-triazole, 15 parts of montmorillonite, and a xylene-based solvent were added and stirred to obtain a pigment paste d having a solid content of 30% by weight. Next, the coating composition N having a solid content of 32% by weight in Comparative Example 2 was prepared by the same formulation and operation as in Comparative Example 1 with respect to 30 parts of the pigment paste d.
O. 4 was obtained.

Comparative Example 3 5 100 parts of Acrydick A801 (manufactured by Dainippon Ink and Chemicals, acrylic resin) in a stirring and mixing container, and JR-
701 (manufactured by Teica Corporation, trade name, titanium white) 80
, 20 parts of calcium carbonate and a xylene-based solvent were added and stirred to obtain a pigment paste e having a solid content of 30% by weight. next,
The same composition and operation as in Comparative Example 1 were applied to 30 parts of the pigment paste e, and the coating composition No. 3 having a solid content of 32% by weight in Comparative Example 3 was used. 5 was obtained. Tables 1 and 2 show the contents of the pigment paste and the coating composition of the examples and comparative examples.

[0042]

[Table 1]

[0043]

[Table 2]

Preparation of coating test plate 0.8 × 70 chemically treated with Palbond # 3020 (trade name, manufactured by Nippon Parkerizing Co., trade name, zinc phosphate treating agent)
The paints obtained in Examples and Comparative Examples were applied to a cold-rolled dull steel sheet of × 150 mm by spray coating so that the dry film thickness became 30 μm. The baking drying was performed using an electric hot air drying furnace at 120 ° C. for 30 minutes at the surface temperature of the object to be coated.
Table 3 shows the test results.

Test results

[0046]

[Table 3]

(Note 1) Salt spray test (SST): 12
On each coated plate obtained at 0 ° C. for 30 minutes, a cross-cut wound was made on the coating film with a cutter knife so as to reach the substrate, and this was subjected to a salt water spray test for 480 hours in accordance with JISZ-2371. Evaluated according to the following criteria according to the following criteria based on scratches from scratches, blister width, and coating condition of the general part (blister): Content ：: The maximum width of rust and blisters was less than 2 mm (one side) from the cut part, and no blister was generated △ : The maximum width of rust and blisters is 2 mm or more from the cut part, 3
mm (one side) and blisters are observed on a part of the painted surface. ×: The maximum width of rust and blisters is 3 mm or more from the cut part, and blisters are observed on the entire painted surface. (Note 2) Water-resistant secondary adhesion: Each test plate was exposed to warm water at 40 ° C.
After soaking for 68 hours, making a square cut of 2 mm square, peeling off Cellotape (registered trademark) and evaluating the remaining coating film Evaluation: Remaining number / 100 ○: 100/100 △: 90 to 99 Pcs / 100 pcs ×: 89 pcs or less / 100 pcs (Note 3) Outdoor baculo test: For the test plate with cross cut, the south side 30 according to JIS K-5409.9
The test was carried out for one year on the coast of Chikura, Chiba Prefecture under the conditions of degrees. With respect to the coated plate after each test, the maximum width of the peeling width and the rusting width on one side of the cross cut portion was measured.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4J038 BA021 CC041 CD021 CF021 CG001 DA161 DA171 DB001 DD001 DD121 DG001 HA286 HA406 HA446 HA466 HA526 HA536 HA556 JA44 JB32 JB35 JC22 KA05 KA08 KA22 MA08 MA10 NA03 NA27 PA18 PA19 PB05PB07A GA01 GA10

Claims (11)

[Claims] 1. The porous substrate (A) is selected from a gluconic acid compound, a gluconate compound, a triazole compound, a pyrazole compound, a thiadiazole compound, a polyphosphate compound, and a polyphosphate compound. A rust preventive (C) comprising one or more compounds (B) impregnated and / or included. 2. A porous substrate (A) comprising bentonite, montmorillonite, saponite, wollastonite, acid clay, activated clay, diatomaceous earth, kaolin, clay, porcelain clay, china clay, hydrotalcite, calcium carbonate, talc, mica, The rust preventive (C) according to claim 1, characterized in that it is at least one inorganic substance selected from smectite, zeolite and silica. 3. The rust inhibitor (C) according to claim 1, wherein the gluconic acid compound of the compound (B) is gluconic acid. 4. A gluconate compound of the compound (B),
The rust preventive (C) according to claim 1 or 2, wherein one or more of sodium gluconate, zinc gluconate, iron gluconate and aluminum gluconate are used. 5. The compound of claim 1, wherein the triazole compound of the compound (B) is
3-amino-1,2,4-triazole, 4-amino-
The rust inhibitor (C) according to claim 1 or 2, wherein one or more kinds of 1,2,4-triazole are used. 6. A compound of the formula (B) wherein the pyrazole compound is 3
The rust inhibitor (C) according to claim 1 or 2, which is -amino-1,2,4-ethylpyrazole. 7. The rust inhibitor (C) according to claim 1 or 2, wherein the thiadiazole compound of the compound (B) is 5-amino-2-mercapto-1,3,4-thiadiazole. 8. The rust preventive (C) according to claim 1, wherein the polyphosphoric acid compound of the compound (B) is at least one selected from the group consisting of pyrophosphoric acid, hexametaphosphoric acid and tripolyphosphoric acid. 9. The polyphosphate compound of the compound (B),
An alkali metal salt of the polyphosphate compound according to claim 8,
The rust preventive (C) according to claim 1 or 2, wherein one or more kinds of alkaline earth metal salts are used. 10. The compound according to claim 1, wherein the compound (B) is impregnated or included in an amount of 1 to 100 parts by weight with respect to 100 parts by weight of the solid content of the porous substrate (A). The rust inhibitor (C) according to item 1. 11. A coating composition comprising 1 to 200 parts by weight of a rust inhibitor (C) selected from the group consisting of 1 to 10 parts by weight based on 100 parts by weight of the solid content of the coating.