JP2002180007A - Method for preventing corrosion of weather-resistant steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing corrosion of a weather-resistant steel in reduced steps by which rust preventing properties and weather resistance are held for a long period and optional coloring can be carried out. SOLUTION: This method for preventing corrosion of the weather-resistant steel comprises coating the surface of the weather-resistant steel with an anticorrosive coating containing particles of at least one kind selected from the group consisting of aluminum, zinc and alloys thereof so as to provide 30-80 μm dried film thickness, drying the coating film, then coating the top surface with a color finish coating containing a nonpollution rust preventing coating and capable of forming a film having >=80% gloss retention after irradiation for 300 h in an accelerated weathering test sunshine weatherometer so as to provide 20-40 μm dried film thickness and drying the resultant coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel coating method for weather-resistant steel, and more particularly, to a method for preventing flow rust (red rust) of weather-resistant steel and imparting various colors in harmony with the environment. Further, the present invention relates to a method for preventing corrosion of a weather-resistant steel that provides long-term weather resistance and rust resistance in a reduced process.

[0002]

2. Description of the Related Art In general, carbon steel is often used for steel structures due to its low cost. However, carbon steel generates red rust in a short period of time when moisture (rainfall, moisture, etc.) and oxygen in the air come into contact with the steel material surface. As a method of preventing the occurrence of red rust, a method of applying a paint is generally used. In this method, in order to minimize repainting, it is common to apply a paint having good durability. For example, inorganic zinc rich paint coating → epoxy resin paint mist coat → epoxy resin paint undercoating (2
Times) → intermediate coating of epoxy resin paint → top coat of polyurethane resin paint is a typical steel coating system having a durability of 15 years or more. This coating system has the advantage of maintaining aesthetics with long-lasting anticorrosion and a color that is in harmony with the environment. It takes time and cost. Therefore, recently, the use of weather-resistant steel having good corrosion resistance for steel structures has been increasing.

[0003] Weathering steels are generally P, Cu, Cr, N
It is a low alloy steel to which elements such as i are added. This steel material has the property of forming rust (hereinafter referred to as "protective rust") that has a protective action against corrosion in the outdoors for more than ten years, making the rust prevention work unnecessary, so-called maintenance-free. Have. Rust that has a protective action against this corrosion is what controls so-called rust, and is mainly made of amorphous iron oxyhydroxide containing a large amount of water of crystallization,
It is believed that this contributes to the formation of a dense and highly adherent protective rust.

[0004]

However, if a weather-resistant steel material is used without any treatment, floating rust such as red rust and yellow rust and flowing rust occur during the period until protective rust is formed. This is not only unfavorable in appearance, but also causes pollution of the surrounding environment.
Further, in the conventional example, there is a surface treatment method by painting to obtain protective rust on the surface of the weathering steel, but it still takes a long period of several years until protective rust is formed, during which time the coating film itself is used. This causes problems such as whitening, blistering and peeling. Further, in order to make the generated rust less conspicuous, the color tone is unified to rust, and no consideration has been given to imparting various colors in harmony with the environment like coating on carbon steel.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, by applying an anticorrosive paint containing aluminum particles, zinc particles, and the like to the surface of a weather-resistant steel, rust prevention has been achieved. The long-term maintenance of the weather-resistant steel, which has a long-lasting weather resistance by applying a topcoat containing a resin and a coloring agent with good weather resistance, maintains the weather resistance for a long time, and enables any coloring. The anticorrosion method was completed. That is, the present invention applies a corrosion-resistant paint containing at least one kind of particles selected from the group consisting of aluminum, zinc and their alloys to a weather-resistant steel surface so as to have a dry film thickness of 30 to 80 μm, After drying, a colored top coat containing a non-polluting rust-preventive pigment and having a gloss retention of 80% or more after 300 hours of irradiation with an accelerated weather resistance test sunshine weather meter was dried. The present invention relates to a method for preventing corrosion of weather-resistant steel, which is coated to a thickness of 20 to 40 μm and dried.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The weathering steel used in the present invention is referred to as a SPA material or an SMA material, which is specified by JIS. If rust or the like is adhered, a blast or pickling as a pretreatment is performed. preferable. Next, the anticorrosion paint used in the present invention will be described. The anticorrosion paint is made of resin, particles made of aluminum, zinc or their alloys and a solvent to be blended as necessary, furthermore, a dispersant, an antibacterial agent, various additives such as an anti-cissing agent and a silane coupling agent. Be composed. The form of the paint may be any of a solvent type, a water type and a non-solvent type.

[0007] It is necessary to use a resin which is a binder constituting the coating material and has good adhesion and is hardly permeable to water or oxygen which causes corrosion. Specific examples of such a resin include an epoxy resin, a modified epoxy resin, a moisture-curable urethane resin, an acrylic resin, a polyester resin, an acrylic silicone resin, an epoxy silicone resin, and a resin in which a curing agent is used in combination. No.
The aluminum particles, zinc particles, or their alloy particles that constitute the paint have a so-called sacrificial anticorrosion action that corrodes instead of steel when water or oxygen, which causes corrosion, penetrates. The product forms a dense film and has an effect of preventing water and oxygen from penetrating and contacting the steel material surface.

The average particle size of these particles is usually 2
２５25 μm, preferably 5-15 μm.
The mixing amount of these particles is 100 (resin and its curing agent).
5 to 800 parts by mass, preferably aluminum, or alloy particles containing aluminum as a main component, 8 to 200 parts by mass, zinc, or alloy particles containing zinc as a main component with respect to parts by mass. , 100 to 600 parts by weight are suitable. If the amount is less than the above range, the rust resistance is insufficient, while if the amount is excessive, the storage stability of the anticorrosion paint and the physical properties of various coating films tend to deteriorate.

The thickness of the anticorrosion paint is 30 to 8 in terms of dry film thickness.
0 μm, preferably 35 to 60 μm is suitable. 3
If the thickness is less than 0 μm, the rust prevention property is insufficient.
If it exceeds 0 μm, it is not preferable because, when it is applied to a vertical surface, the paint tends to sag and the drying tends to be slow. Next, the top coat used in the present invention will be described. Topcoat paint is resin, pollution-free rust-proof pigment,
It is composed of a coloring agent, a solvent to be blended as required, a silane coupling agent, and various additives such as a dispersant, an ultraviolet absorber, an antibacterial agent, and an anti-cissing agent. The form of the paint may be any of a solvent type, an aqueous type, and a non-solvent type.

It is necessary to use a resin having good weather resistance as a resin constituting a paint. That is, accelerated weathering test Sunshine weather meter irradiation 300
The gloss retention after the time is 80% or more, preferably 90%
It is a resin that forms the above coating film. 80% gloss retention
If the amount is less than the above, it is not preferable because whitening, blistering, peeling and the like occur in the coating film. Specific examples of the resin include a chlorinated rubber resin, an acrylic resin, a polyester resin, a urethane resin,
An acrylic silicone resin, a fluororesin, and a combination of these resins with a curing agent, more preferably a moisture-curable urethane resin, an acrylic silicone resin, a fluororesin, and a combination of these resins with a curing agent. In the present invention, as a part of the resin, an epoxy equivalent of 120 to 5000 g / eq, in order to improve the adhesion of the coating film,
Preferably, an epoxy resin having a bisphenol skeleton of 400 to 2000 g / eq, or a resin obtained by modifying the epoxy resin with a urethane resin, an acrylic resin, a rubber, a basic nitrogen compound, a polybasic acid compound, or the like is used as the total resin. Of these, 0 to 40% by mass, preferably 5 to 30% by mass is used in combination.

The accelerated weathering test sunshine weather meter referred to here is a sunshine carbon arc lamp type accelerated weathering resistance tester defined by JIS K5400, which has a correlation with actual outdoor exposure, and has a gloss retention rate. The term refers to the degree of gloss remaining calculated from the 60-degree specular gloss defined by JIS K5400 by the following equation. Gloss retention = (Sunshine weather meter irradiation 30
Gloss after 0 hours) × 100 / Initial gloss (%) In addition, the non-polluting rust-preventive pigments constituting the coating material include aluminum phosphate, aluminum tripolyphosphate, zinc phosphate, zinc phosphite, and potassium phosphite. Anticorrosive pigments such as calcium phosphite, aluminum phosphite, zinc calcium phosphate, zinc aluminum phosphate, zinc molybdate, zinc phosphomolybdate, aluminum phosphomolybdate, calcium molybdate, hydrocalumite, and the like. Is used alone or as a mixture of two or more. However, chromium and lead are not preferred from the viewpoint of toxicity.

These non-polluting rust-preventive pigments are compounded in order to adjust the dissolution rate of particles in the anticorrosion paint film and thereby to improve long-term rust resistance.
1 to 80 parts by mass, preferably 5 to 60 parts by mass is added to 100 parts by mass of the resin (and the curing agent). 1
If the amount is less than 10 parts by mass, the rust resistance is insufficient, while if it exceeds 80 parts by mass, the paint stability tends to be poor. Constituting paint, as a coloring pigment for applying a color that meets the demand, specifically, titanium dioxide, white pigments such as zinc oxide, carbon black, black pigments such as graphite, molybdate orange, permanent carmine, Red pigments such as quinacridone red, yellow pigments such as quinophthalene yellow and permanent yellow, phthalocyanine green, greens such as phthalocyanine blue, and blue pigments, etc. Can be Further, extenders may be used in combination. The coloring pigment is
Depending on the type, it is appropriate to add 0.1 to 70 parts by mass with respect to 100 parts by mass of the resin.

As the silane coupling agent constituting the coating material, γ-chloropropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyl tris (β-
Methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-amino Propyltriethoxysilane, N-β- (aminoethyl) aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyldimethyl, γ-gly Sidoxypropyldimethylethoxysilane and the like are typical examples. The silane coupling agent is compounded with the particles in the anticorrosion paint film to improve the adhesion between the anticorrosion paint film and the colored topcoat paint film. It is desirable to add 0 to 20 parts by mass, preferably 1 to 5 parts by mass with respect to 100 parts by mass of the curing agent. If the amount exceeds 20 parts by mass, the paint stability tends to decrease.

The thickness of the top coat is 20 to 40 μm on a dry basis.
m, preferably 25 to 35 μm. 20 μm
When it is less than 30%, the concealing property and the weather resistance become insufficient. on the other hand,
If it exceeds 40 μm, foaming and poor curing are likely to occur,
In the case of painting on a vertical surface, problems such as paint dripping occur. Next, a method of coating weather-resistant steel will be described. The above-mentioned anticorrosive paint is applied to the weather-resistant steel by means of brush, spray, roller or the like so that the dry film thickness is 30 to 80 μm, and is naturally dried or forcibly dried at a temperature of 100 ° C. or less. Next, the above top coat is applied by the same means so that the dry film thickness becomes 20 to 40 μm, and dried in the same manner.

[0015]

(Anti-corrosion paint)

<Main agent component> Epoxy resin solution ^{Note 1)} 200.0 parts Zinc particles (average particle size: 5 μm) 800.0 parts Xylene 75.0 parts

Note 1) Bisphenol A type epoxy resin having an epoxy equivalent of 450, solid content 70% <Curing agent component> Polyamide amine resin solution ^{Note 2)} 101.6 parts Xylene 172.4 parts Note 2) Amine value 75 mg KOH / g, 65% solids

[Top coating composition] <Main ingredient> Fluororesin solution ^{Note 3)} 153.8 parts γ-glycidoxypropyltrimethoxysilane 6.4 parts Aluminum tripolyphosphate 18.0 parts Quinacridone red 32.3 parts Xylene 61. 5 parts Note 3) Hydroxyl value of resin 45 mgKOH / g, number average molecular weight 7,000, solid content 65% <Curing agent component> Hexamethylene diisocyanate 17.5 parts 53.5 parts butyl acetate

Example 2 Alumina blasted 3 × 100 × 300 (mm) having an average surface roughness of 30 μm as in Example 1.
The following moisture-curable urethane resin-based anticorrosive paint was applied once on a surface of a weather-resistant steel (SMA400) specified by JIS G3141 to a dry film thickness of 50 μm, and was naturally dried for one day. Next, the same fluororesin-based topcoat as in Example 1 was applied once thereon to a dry film thickness of 35 μm, the back and side surfaces were sealed with an epoxy resin paint, and air-dried for 7 days. Table 1 shows the evaluation results of the weather resistance and corrosion resistance of the coated steel.

[Anticorrosion paint] Xylene resin ^{Note 4)} 39.0 parts Aromatic polyisocyanate ^{Note 5)} 91.0 parts Zinc particles (average particle size 8 μm) 770.0 parts Dehydrating agent ^{Note 6)} 16.0 parts Xylene 680 0.0 part Note 4) Trade name of Mitsubishi Gas Chemical Industry Co., Ltd .; Nicanol 3L (xylene / formaldehyde resin) Note 5) Trade name of Sumitomo Bayer Urethane Co., Ltd .; Sumidur E21-1 Note 6) Sumitomo Bayer Urethane Brand name; Additive T1 (tosyl isocyanate)

Example 3 The following epoxy resin-based anticorrosive paint was dried on the surface of a 3 × 100 × 300 (mm) weather-resistant steel (SMA400) specified in JIS G3141 having an average surface roughness of 30 μm and subjected to alumina blasting. Once painted to a thickness of 50μm,
It was air-dried for one day. Next, the following acrylic silicone resin-based topcoat was applied once to a dry film thickness of 35 μm, the back and side surfaces were sealed with an epoxy resin paint, and air-dried for 7 days. Table 1 shows the evaluation results of the weather resistance and corrosion resistance of the coated steel.

[Anti-corrosion paint] <Main ingredient> Epoxy resin solution ^{Note 7)} 200.0 parts Aluminum paste ^{Note 8)} 35.6 parts Mineral spirit 200.0 parts Note 7) Bisphenol A type epoxy resin having an epoxy equivalent of 210, solid Note 8) Average particle size of aluminum particles 12 μm, solid content 75%

<Curing agent component> Polyamideamine resin solution ^{Note 9)} 102.8 parts Xylene 69.6 parts Note 9) Amine value 255 mgKOH / g, solid content 76%

[Top coating composition] <Main ingredient> Acrylic silicone resin solution ^{Note 10)} 200.0 parts Acrylic modified epoxy resin ^{Note 11)} 15.0 parts Zinc phosphite 8.0 parts γ-glycidoxypropyltrimethoxysilane 10.5 parts Quinophthalein yellow 32.0 parts Xylene 80.0 parts * 10) An acrylic resin containing an alkoxysilyl group, number average molecular weight 10,000, solid content 50% * 11) Hydroxyl value 100 mgKOH / g, solid content 100%

<Curing Agent Component> Dibutyltin dilaurate 12.8 parts Hexamethylene diisocyanate 1.5 parts Xylene 80.0 parts

Comparative Example 1 The same weather-resistant steel as in Example 1 was evaluated without any coating at all, and the weather resistance and corrosion resistance were evaluated. The results are shown in Table 1.

COMPARATIVE EXAMPLE 2 In Example 1, an anticorrosive paint containing no zinc powder or aluminum powder was used, and a fluffy resin-based topcoat containing no rust preventive pigment and no silane coupling agent was applied. Table 1 shows the results of evaluation of the weather resistance and corrosion resistance of the sample. Table 1 Results of evaluation of weather resistance and corrosion resistance and tint and gloss retention Color tint gloss retention ^{Note 12)} Weather resistance ^{Note 13)} Corrosion resistance ^{Note 14)} Example 1 Red 98 Good Good Example 2 Red 96 Good Good Example 3 Yellow 97 Good Good Comparative Example 1--Red rust after 48H Full red rust Comparative Example 2 Red 95 Red rust 300H Red rust after 300H

Note 12) Gloss retention after 300 hours of sunshine weather meter (%) Note 13) One year of outdoor exposure Note 14) Salt spray test 1000 hours As is clear from Table 1, in Examples of the present invention,
It could be colored in any color and had excellent weather resistance and corrosion resistance. On the other hand, in Comparative Example 1 where no paint was applied and in Comparative Example 2 where no rust preventive agent was contained, red rust was generated.

[0028]

According to the method of the present invention, it is possible to maintain the rust resistance and weather resistance for a long period of time, and furthermore, it is possible to arbitrarily color, and it is possible to prevent the corrosion of weather-resistant steel in a reduced process.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Wataru Kutoku 3-1172-4 Shimonaga, Nishinasuno-machi, Nasu-gun, Tochigi Prefecture (72) Inventor Hiroyuki Tanabe 8-15 Asahimachi, Nishinasuno-machi, Nasu-gun, Tochigi F-term (reference) 4D075 CA32 CA33 EC10 EC15 4J038 CD021 CD091 CG001 DB001 DD001 DG001 DL001 HA066 JC32 KA05 KA08 NA03 PB03

Claims (2)

[Claims] An anticorrosive paint containing at least one kind of particles selected from the group consisting of aluminum, zinc and their alloys on the surface of a weather-resistant steel is coated with a dry film having a thickness of 30 to 80 μm.
And then dried, then containing a non-polluting rust preventive pigment, and having an accelerated weather resistance test having a gloss retention of 80% after 300 hours irradiation with a sunshine weather meter.
Apply the colored top coat which forms the above coating film to a dry film thickness of 20 to 4
An anticorrosion method for weather-resistant steel, which is coated to a thickness of 0 μm and dried. 2. The anticorrosion method according to claim 1, wherein the colored top coat contains a silane coupling agent.