HK1175491B - Corrosion-proofing coating composition and process for production thereof, and method for prevention of corrosion in steel material - Google Patents

Description

Anticorrosive coating composition, method for producing same, and method for preventing corrosion of steel material

Technical Field

The present invention relates to an anticorrosive coating composition used as a primer for a steel surface, a method for producing the same, and a method for preventing corrosion of a steel.

The present application claims priority based on japanese patent application No. 2010-042285 filed in japan on 26/2/2010 and japanese patent application No. 2010-042298 filed in japan on 26/2/2010, the contents of which are incorporated herein by reference.

Background

Steel frame buildings or steel frame bridges and other steel structures are used for a long time. Therefore, surface coating has been conventionally performed on these steel structures for the purpose of ensuring corrosion resistance and appearance. In general, the coating is composed of three layers, i.e., an undercoat coating for rust resistance, a topcoat coating for weather resistance and appearance, and an intercoat coating for improving adhesion between the undercoat coating and the topcoat coating. The coating life is greatly affected by the coating material and the use environment, but in a severe environment, there are also examples in which the coating life of the modified epoxy-based coating is 6 years and the coating life of the epoxy urethane-based coating is 10 years. Therefore, several recoats are required during the service life of the steel structure.

Here, the mechanism of rust generation is explained in advance. When iron is exposed to rainwater or the like, moisture adsorbed on the iron surface takes electrons from the iron element, and chemically reacts with oxygen in the air to generate OH^-. On the other hand, Fe having lost electrons²⁺Dissolved in water to react with OH formed^-Binding to Fe (OH)₂Which is oxidized to FeOOH or Fe₂O₃·nH₂O、Fe₃O₄·nH₂Rust such as O.

As one of the rust-proof methods for iron, a method of passivating an iron surface while keeping the iron surface alkaline is known. Generally, Fe forms Fe at a pH of 9-12.5₂O₃Thereby becoming a stable state. As a technique for preventing rust by maintaining the iron surface alkaline, for example, patent document 1 discloses the following invention: a surface coating agent comprising a composite obtained by adding carbon fibers to a main material comprising a mixture of white cement and ultrafine silica particles, and a water-soluble curing agent comprising a mixture of a cationic styrene-butadiene copolymer and a cyclohexyl methacrylate copolymer.

Further, patent document 2 discloses an invention in which: a rust-proof coating composition free from environmental pollution, which comprises a resin solid component and slag containing a basic group, mica, and aluminum phosphomolybdate, which are produced in a refining process.

On the other hand, as an anticorrosive coating technique different from the above-mentioned basic anticorrosive coating, patent document 3 discloses the following invention: aA method for spraying mortar, characterized in that mortar obtained by mixing polymer cement, aggregate, water and a lithium nitrite solution is sprayed onto a predetermined portion of a concrete structure through a mortar spraying nozzle. In this process, lithium nitrite (LiNO) is passed through in the mortar₂) Nitrite ion (NO)₂ ^-) The following reaction occurs to form a passivation coating film (Fe)₂O₃) Thereby preventing the generation of rust.

Fe²⁺+2OH^-+2NO₂ ^-→2NO+Fe₂O₃+H₂O

Further, patent document 4 discloses an invention in which: a substrate cleaning material for a steel material, which positively removes anions in a nest (nest) formed at an interface between a rust layer and the steel material, which is formed by concentrating an anode part through electrochemical replenishment of anions by a corrosion cell formed on the steel surface due to corrosion of the steel, by incorporating an anion adsorbent in the substrate cleaning material.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 5-155649

Patent document 2: japanese laid-open patent publication No. 2002-80786

Patent document 3: japanese patent laid-open No. 2007-177567

Patent document 4: japanese laid-open patent publication No. 2004-299979

Disclosure of Invention

Problems to be solved by the invention

However, the surface coating agent described in patent document 1 uses carbon fibers as an expensive material. Furthermore, the increase in the coating thickness (700 to 800 μm) increases the effects of preventing cracks and suppressing the diffusion of moisture and oxygen in the coating film, thereby increasing the service life of the coating film, and therefore, the cost of the conventional epoxy coating material is required to be about three times as high.

The environmental pollution-free rust-proof coating composition described in patent document 2 is considered to be excellent in long-term rust resistance, but a passive coating film on the surface of a steel material formed from a component such as slag containing a basic group is broken by a corrosion factor entering from a portion of a flaw generated by deterioration of a coating film or external damage, rust progresses in a short time, and the life is shortened to about ten years.

On the other hand, in the invention described in patent document 3, when the passivation coating film is damaged by some external factor, the passivation coating film is reconstructed by the action of nitrite ions, but when the passivation coating film is coated as a corrosion preventing coating material for steel, the corrosion inhibitor is dissolved out because of solubility of nitrite. Therefore, there is a problem in corrosion resistance over a long period of time. In the invention described in patent document 4, the generation of corrosion of steel is suppressed by including an anion adsorbent such as calcium-aluminum composite hydroxide which is not consumed by the reaction with cement in the cement-based primer remover using an aqueous epoxy resin as an admixture, but the long-term corrosion resistance is not clear.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an anticorrosive coating composition which can reduce the number of primer treatments compared with the conventional one, and can reduce the diffusion rate of nitrite by appropriately sealing nitrite used as an anticorrosive agent, thereby maintaining the anticorrosive effect of a steel material for a long period of time, a method for producing the anticorrosive coating composition, and an anticorrosive method for a steel material.

Means for solving the problems

The present invention relates to an anticorrosion coating composition comprising: a composite containing cement, an inorganic powder material and an expanding material; a polymer emulsion selected from styrene/butadiene copolymer emulsions or acrylic acid/styrene copolymer emulsions; and a nitrite salt.

With the above configuration, workability and durability as a paint are ensured. Further, since an alkaline coating film is formed on the surface of the steel material, the surface of the steel material is passivated and corrosion does not progress. In the passivation coating film (Fe)₂O₃) Nitrite ion (NO) when damaged by an external factor₂ ^-) With Fe²⁺And OH^-Chemical reaction to the passivation coating film (Fe)₂O₃) And (4) reconstructing. Therefore, the steel structure can be significantly longer in life than the conventional steel structure. Furthermore, a dense structure can be constructed by setting the mass ratio of cement to the inorganic powder material to 1.0 to 1.4. This reduces the diffusion rate of the nitrite, and can maintain the rust-proof effect of the nitrite for a long period of time. As a result, the number of recoats during the service life of the steel structure is reduced, and the cost for recoating can be greatly reduced. On the other hand, when the mass ratio of cement to the inorganic powder material is less than 1.0 or exceeds 1.4, the diffusion rate of nitrite cannot be appropriately decreased.

The styrene/butadiene copolymer and the acrylic acid/styrene copolymer are excellent in adhesion to a substrate, have little temperature dependence, and have excellent elasticity even at low temperatures or in a high temperature region. Therefore, a coating film having excellent water permeability resistance and weather resistance can be obtained.

Although the cationic styrene-butadiene copolymer-based synthetic resin described in patent document 1 can expect a rust-proof effect, the coating film has a deformability (elongation) of 0.4%, and has a problem such as cracking of the coating film since the elongation when a bending axial force is applied to a steel material is 0.5% or more. In addition, the epoxy-based synthetic resin described in patent document 4 generally has a lower elongation than a cationic styrene-butadiene copolymer-based synthetic resin.

On the other hand, in the present invention, when a styrene/butadiene copolymer is used, the compatibility is combined in an emulsion (latex) in which the blending ratio of the styrene/butadiene copolymer is changed (the amount of styrene is reduced) and the blending ratio is changedA good composite, and a coating film having an elongation of 5% or more was successfully obtained. When the stability of the coating film is taken into consideration, the coating film formed from the anticorrosive coating composition of the present invention can sufficiently follow the deformation of a steel structure by setting the elongation to 5%. In addition, as another constitution, in order to promote nitrite ion (NO)₂ ^-) The solution was flowed to the anode, and an acrylic acid/styrene copolymer was used as an anionic synthetic resin.

Regarding the amount of nitrite (solid content) used in the conventional polymer cement mortar described in patent document 3 and the like, abnormal setting of cement occurs when the mixing ratio of the nitrite to the total composition is increased. Therefore, the amount of nitrite used is 5 mass% as the upper limit of the amount used in the case of lithium nitrite, and 1.25 mass% as the upper limit of the amount used in the case of calcium nitrite. However, in order to maintain the rust-proofing effect for a long period of time as the paint is applied, it is necessary to set the nitrite content to 2.5 mass% or more. Therefore, in the present invention, an increase in the nitrite is achieved by setting the amount of the styrene/butadiene copolymer to 5% by mass or more, or by setting the amount of the acrylic acid/styrene copolymer to 6% by mass or more. Further, by setting the cement amount to 26 mass% or more, the coating film has an alkaline atmosphere with a pH of 11.5 to 12.5, and thus reduction in the base treatment and corrosion prevention over a long period of time can be achieved. In order to ensure the tensile strength, the elongation following property, and the adhesion strength as the coating material, the inorganic powder material and the intumescent material are simultaneously contained in the composite.

The nitrite contained in the anticorrosive coating composition of the present invention is preferably 2.5% by mass or more.

When the nitrite is less than 2.5 mass%, the rust-proof effect is flush with the epoxy resin coating, and rust is generated at a cross cut (cross) portion in a salt spray test for 3000 hours. For example, when the nitrite amount in the present invention is 3 mass%, the nitrite amount is about 2.5 times as large as that of the conventional paint.

When a styrene/butadiene copolymer emulsion is selected as the polymer emulsion, the nitrite contained in the anticorrosive coating composition is preferably 7.5% by mass or less.

If the nitrite content exceeds 7.5 mass%, the amount of water in the mixture with the styrene/butadiene copolymer increases, and voids in cement water and cement are increased. Along with this, the water becomes easy to infiltrate into the voids, and the diffusion of nitrite in the cement water and the contents also becomes fast. As a result, a long-term rust-proof effect cannot be expected.

When an acrylic/styrene copolymer emulsion is selected as the polymer emulsion, the nitrite contained in the anticorrosive coating composition is preferably 9.0 mass% or less.

If the nitrite content exceeds 9.0 mass%, the amount of water in the mixture with the acrylic acid/styrene copolymer increases, and voids in cement water and cement are increased. Along with this, the water becomes easy to infiltrate into the voids, and the diffusion of nitrite in the cement water and the contents also becomes fast. As a result, a long-term rust-proof effect cannot be expected.

In the present invention, the styrene/butadiene copolymer may be contained in an amount of 5 to 18 mass% in the anticorrosive coating composition. When the styrene/butadiene copolymer content is less than 5% by mass, the styrene/butadiene copolymer emulsion content is less than 18 parts by mass per 100 parts by mass of cement, and the elongation and breaking strength of the coating film cannot be improved, and the ability to follow deformation of the steel material is lowered. Therefore, cracks of the coating film are likely to occur, and rust is likely to develop from the cracked portions. On the other hand, when the styrene/butadiene copolymer exceeds 18% by mass, the deformability required as a coating film is exceeded, and on the contrary, the adhesion strength of the coating film is insufficient and peeling of the coating film occurs.

Alternatively, the acrylic/styrene copolymer may be contained in an amount of 6 to 24 mass% in the anticorrosive coating composition. When the acrylic acid/styrene copolymer content is less than 6% by mass, the acrylic acid/styrene copolymer emulsion content is less than 11 parts by mass per 100 parts by mass of cement, and the elongation and breaking strength of the coating film cannot be improved, and the ability to follow deformation of the steel material is lowered. Therefore, cracks of the coating film are likely to occur, and rust is likely to develop from the cracked portions. On the other hand, when the acrylic/styrene copolymer exceeds 24% by mass, the deformability required as a coating film is exceeded, and on the contrary, the adhesion strength of the coating film is insufficient and peeling of the coating film occurs.

In the present invention, the anticorrosive coating composition contains 26 to 39 mass% of the cement, 20 to 28 mass% of the inorganic powder material, and 0.5 to 1.5 mass% of the swelling material.

When the styrene/butadiene copolymer emulsion is selected, the cement contained in the anticorrosive coating composition is preferably 26 mass% or more and 39 mass% or less.

When the cement content is less than 26% by mass, the water-cement ratio exceeds 1.4 when the nitrite and the styrene/butadiene copolymer are properly mixed, and the desired film strength cannot be obtained. Specifically, peeling of the coating film is caused due to insufficient adhesion strength, and cohesive failure occurs due to insufficient compressive strength.

On the other hand, if the amount exceeds 39 mass%, the required coating film strength can be expected, but the amount of cement increases too much, and the shrinkage increases, thereby causing cracks to form on the coating film surface.

When the acrylic/styrene copolymer emulsion is selected, the cement contained in the anticorrosive coating composition is preferably 26 mass% or more and 38 mass% or less.

When the cement content is less than 26% by mass, the water-cement ratio exceeds 1.0 when the nitrite and the acrylic acid/styrene copolymer are properly mixed, and the desired strength of the coating film cannot be obtained. Specifically, peeling of the coating film is caused due to insufficient adhesion strength, and cohesive failure occurs due to insufficient compressive strength. On the other hand, when the cement content exceeds 38 mass%, the required coating film strength can be expected, but the cement content is too large, the shrinkage increases, and cracks occur on the coating film surface.

When the inorganic powder material is less than 20% by mass, the coating film becomes rich in cement and the occurrence probability of cracking during drying increases. In addition, the amount of water increases and the strength of the coating film cannot be secured. On the other hand, when the inorganic powder material exceeds 28 mass%, the aggregate powder becomes too large, the viscosity of the cement hydrate decreases, and the adhesive force on the ground surface decreases.

The expansion material can be expected to have its effect at an appropriate amount of cement. When the amount of the expanding material is less than 0.5% by mass, the coating film becomes brittle when the amount of the styrene/butadiene copolymer or the acrylic acid/styrene copolymer is small, and thus cannot cope with shrinkage caused by cement. On the other hand, when the styrene/butadiene copolymer or the acrylic acid/styrene copolymer is large, the amount of water inevitably increases, and the coating film becomes too soft, and the effect of the swelling material cannot be expected. On the other hand, when it exceeds 1.5% by mass, SO in the composite₃The amount of (sulfur trioxide) increases to approach the use threshold (8% by mass to cement), which becomes a cause of expansion cracking.

When the styrene/butadiene copolymer emulsion is selected as the polymer emulsion, the water content is preferably 13 to 42 mass%. The water content here is the water content in the styrene/butadiene copolymer emulsion and in the aqueous nitrous acid solution. When the water content is less than 13% by mass, the nitrite content cannot be ensured to be 2.5% by mass, and when the water content exceeds 42% by mass, the nitrite content exceeds 7.5% by mass, which results in excessive specifications and increased costs.

When an acrylic acid/styrene copolymer emulsion is selected as the polymer emulsion, the water content is preferably 12 to 43% by mass. The water content here is the water content in the acrylic acid/styrene copolymer emulsion and in the aqueous nitrous acid solution. When the water content is less than 12% by mass, the nitrite content cannot be ensured to be 2.5% by mass, and when the water content exceeds 43% by mass, the nitrite content exceeds 9.0% by mass, which becomes an excessive specification. The cost increases.

In order to reduce white spots and pinholes on the surface of the coating film, the inorganic powder material is one or more selected from the group consisting of silica sand powder, calcium carbonate, magnesium silicate, slag powder (steel slag powder, etc.) and clay powder. In the case of thin coating work in summer, it is possible to prevent dry out (a phenomenon in which hydration reaction is suppressed due to loss of water in the base and curing failure or adhesion failure occurs) and to further improve the effect by further using clay powder in a methylcellulose-based thickener, thereby securing water retentivity.

In the anticorrosive coating composition according to the present invention, when the cement is ordinary portland cement, the nitrite is preferably lithium nitrite. In addition, when the nitrite is calcium nitrite, the cement is preferably blast furnace cement.

Clinker produced in the cement production process mainly includes a set cement (alite), belite cement (belite), an aluminate (aluminate) phase, and a ferrite phase. The present inventors have found that the aluminate phase in the clinker reacts with the calcium nitrite, causing abnormal setting of the cement. Therefore, in order to prevent abnormal setting of cement, when the cement is ordinary portland cement, it is set that lithium nitrite is used in the nitrite. In addition, when calcium nitrite is used as the nitrite, the blast furnace cement is used to achieve a reduction in the aluminate phase, thereby preventing abnormal coagulation of the cement.

In addition, when the blast furnace cement is combined with lithium nitrite, the setting time is prolonged, so that the coating material flows down during the application, and it is difficult to secure the thickness of the coating film.

Further, an anticorrosive coating film formed from the anticorrosive coating composition comprises: a composite containing cement, an inorganic powder material and an expanding material; a polymer selected from a styrene/butadiene copolymer or an acrylic acid/styrene copolymer; and a nitrite salt.

One embodiment of the above anticorrosive coating film is an anticorrosive coating film containing a styrene/butadiene copolymer as the polymer, characterized by containing 32.5 to 49 mass% of the cement (cement component), 25 to 35 mass% of the inorganic powder material, 0.6 to 1.9 mass% of the intumescent material, 6 to 23 mass% of the styrene/butadiene copolymer, 3.1 to 9.4 mass% of the nitrite, and 7 to 12 mass% of crystal water, wherein the inorganic powder material is one or more selected from the group consisting of silica sand powder, calcium carbonate, magnesium silicate, slag powder, and clay powder.

Another embodiment of the above anticorrosive coating film is an anticorrosive coating film containing an acrylic acid/styrene copolymer as the high component, characterized by containing 32.5 to 47.5 mass% of the cement (cement component), 25 to 35 mass% of the inorganic powder material, 0.6 to 1.9 mass% of the expansive material, 7.5 to 30 mass% of the acrylic acid/styrene copolymer, 3.1 to 11.2 mass% of the nitrite, and 7.8 to 12 mass% of crystal water, wherein the inorganic powder material is one or more selected from the group consisting of silica sand powder, calcium carbonate, magnesium silicate, slag powder, and clay powder.

In the above-described coating film structure, the content of cement, an intumescent material, a nitrite, and the like indicates the content of each raw material component of the coating film, and the content of crystal water corresponds to the amount of water taken into the coating film by hydration reaction with cement or the like.

In any of the above embodiments, according to the experimental results, the amount of water evaporated accompanying the curing of the anticorrosion coating composition is about 20% of the total mass of the anticorrosion coating composition. Therefore, the composition ratio of the anticorrosive coating film is a value obtained by dividing the composition ratio of the anticorrosive coating composition by 0.8.

Further, a method for producing an anticorrosive coating composition according to the present invention is a method for producing an anticorrosive coating composition, the method comprising: a first step of pretreating a mixed solution obtained by adding the styrene/butadiene copolymer emulsion or the acrylic acid/styrene copolymer emulsion to the aqueous solution of the nitrite at a constant temperature; and a second step of adding the composite containing the cement, the inorganic powder material, and the expansion material to the mixed solution pretreated at a constant temperature.

Here, "pretreatment at constant temperature" means that a mixed solution obtained by adding a styrene/butadiene copolymer emulsion or an acrylic acid/styrene copolymer emulsion to a nitrite aqueous solution is stirred at a low speed for a predetermined time while maintaining a predetermined temperature. The predetermined temperature is 30 to 60 ℃, for example, about 40 ℃ is preferable, and the predetermined time is 3 to 10 minutes, for example, about 5 minutes is preferable. Further, it is more preferable to add the complex to the mixed solution after the constant-temperature pretreatment by leaving the mixed solution to stand for 5 to 10 days, for example, about 7 days.

In the present invention, the mixed solution obtained by adding the styrene/butadiene copolymer emulsion or the acrylic acid/styrene copolymer emulsion to the nitrite aqueous solution is subjected to a pretreatment at a constant temperature, whereby the viscosity of the mixed solution can be reduced to about 1/40 of the viscosity of the styrene/butadiene copolymer emulsion or the acrylic acid/styrene copolymer emulsion alone. As a result, a significant improvement in kneading effect with the composite can be expected. Moreover, the liquid mixture is stable for a long period of time and can be stored for a long period of time.

Further, the present invention relates to a method for preventing corrosion of a steel material, which comprises removing rust from the surface of the steel material, applying an undercoat material comprising the anticorrosive coating composition to the surface of the steel material to form an undercoat layer, and applying a topcoat material comprising a coating film having an elongation of 5% or more to the undercoat layer to form a topcoat layer.

The coating layer according to the present invention is characterized by being formed from an undercoat layer formed from the corrosion-resistant coating film and a topcoat layer formed from a coating film having an elongation of 5% or more.

The elongation is a value obtained by a measurement method according to "3. tensile strength and elongation at break test" described in "method for testing quality of polymer cement based coating waterproof material" in reference 2, "which is written in" guide (case) of polymer cement based coating waterproofing works and description thereof "of the japan architecture society.

In the present invention, since the primer layer is made alkaline (pH11.5 or more) by the cement contained in the anticorrosive coating composition, a passivation coating film (Fe) is formed on the surface of the steel material₂O₃) Thereby preventing rusting (basic anticorrosion function). Thus, the surface of the steel material does not need to be highly cleaned, and the cost can be reduced. For example, the surface cleaning may be performed to a third ke' n (kern) level to remove the rust from the surface of the steel material. When the passivation coating film is damaged by some external factor, the nitrite is dissolved out, and the passivation coating film is reconstructed (self-repairing function). Further, flexibility is imparted to the undercoat layer by the styrene/butadiene copolymer or the acrylic acid/styrene copolymer, and the undercoat layer capable of following the deformation of the steel surface is formed.

As described above, the elongation of the anticorrosive coating film according to the present invention is set to 0.5% or more from the viewpoint that the elongation when a bending axial force acts on a steel material is 0.5% or more, and when the stability of the coating film is taken into consideration, it is necessary to set the elongation of the top coating film to 5% or more in order for the top coating film to follow the elongation of the coating film primer layer.

The topcoat layer may be composed of a coating film containing one or more selected from epoxy resin, urethane resin, polyurethane resin, acrylic silicone resin, acrylic urethane resin, HALS mixed resin, and the like. The top coat layer may be a single-layer coating film or may be composed of two or more coating films.

The total layer thickness of the top coat layer is not particularly limited, but is, for example, 60 to 130 μm. For example, the film may be composed of a first layer having a layer thickness of 60 to 80 μm and a second layer having a layer thickness of 20 to 40. Alternatively, the laminate may be composed of a first layer having a layer thickness of 40 to 70 μm and a second layer having a layer thickness of 30 to 40 μm.

ADVANTAGEOUS EFFECTS OF INVENTION

The anticorrosive coating composition of the present invention comprises: a composite containing cement, an inorganic powder material and an expanding material; styrene/butadiene copolymer emulsions or acrylic/styrene copolymer emulsions; and a nitrite salt. The nitrite content is set to 2.5 mass% or more, and the nitrite content is set to 5 mass% or more of a styrene/butadiene copolymer or 6 mass% or more of an acrylic acid/styrene copolymer emulsion. The cement content of the entire composition is 26 mass% or more. Thus, the coating film has an alkaline atmosphere with a pH of 11.5 to 12.5, and reduction in the number of base treatments and corrosion prevention over a long period of time can be achieved. Further, since the cured cement paste is appropriately sealed with a nitrite used as an anti-rust agent, the diffusion rate of the nitrite is reduced, and the effect of the nitrite can be maintained for a long period of time.

In the present invention, when producing the anticorrosive coating composition, a mixed solution obtained by adding a styrene/butadiene copolymer emulsion or an acrylic acid/styrene copolymer emulsion to a nitrite aqueous solution in advance is subjected to a pretreatment at a constant temperature. Therefore, the viscosity of the mixed solution can be reduced to about 1/40 of the viscosity of the styrene/butadiene copolymer emulsion alone or the viscosity of the acrylic acid/styrene copolymer emulsion alone. As a result, a significant improvement in kneading effect with the composite can be expected.

In the present invention, since the primer layer is alkaline, a passivation film is formed on the surface of the steel material to prevent rust. Thus, a high degree of surface cleaning of the steel surface is not required. When the passivation coating film is damaged by some external factor, the nitrite is dissolved out to reconstruct the passivation coating film. Further, flexibility is imparted to the undercoat layer by the styrene/butadiene copolymer or the acrylic acid/styrene copolymer, and the undercoat layer capable of following deformation of the steel surface is formed.

Detailed Description

Next, an embodiment in which the present invention is embodied will be described, but the present invention is not limited to the following embodiment at all, and includes other embodiments and modifications that are conceivable within the scope of the items described in the claims.

[ undercoating Material ]

The present invention relates to an anticorrosive coating composition for use as a primer coating material for steel surfaces, which is produced by adding a styrene/butadiene copolymer emulsion or an acrylic acid/styrene copolymer emulsion to a nitrite aqueous solution and pretreating the mixture at a constant temperature to obtain a mixed solution, and adding a composite containing cement, an inorganic powder material and an intumescent material. In this case, it is preferable that the styrene/butadiene copolymer is 5 to 18% by mass and the nitrite is 2.5 to 7.5% by mass. Alternatively, it is preferable that the acrylic acid/styrene copolymer is 6 to 24 mass% and the nitrite is 2.5 to 9.0 mass%.

In order to ensure durability without deteriorating rust-proof quality and to ensure a predetermined primer coating thickness (200 to 650 μm), it is more preferable to set the styrene/butadiene copolymer to 10 to 18 mass%, the nitrite to 3 to 4.5 mass%, or the acrylic acid/styrene copolymer to 10 to 20 mass%, and the nitrite to 4 to 6.5 mass%. In addition, if a mixed solution obtained by adding a styrene/butadiene copolymer emulsion or an acrylic acid/styrene copolymer emulsion to a nitrite aqueous solution is subjected to a pretreatment at a constant temperature in advance, the amount of nitrite can be easily increased.

When a styrene/butadiene copolymer is used, the amount of the compound is more preferably 50 to 70% by mass of the total composition. When an acrylic acid/styrene copolymer is used, it is more preferably 50 to 60% by mass of the total composition.

In addition, in order to prevent the cracking of the coating film, it is more preferable to set the inorganic powder material to 20 to 28 mass%, and to suppress the SO of the coating film₃The amount of (sulfur trioxide) is more preferably 0.5 to 1% by mass of the intumescent material.

Nitrite is a substance that imparts an anti-rust effect. Lithium nitrite, sodium nitrite, potassium nitrite, calcium nitrite, magnesium nitrite, barium nitrite, etc. can be used, but the compatibility of lithium nitrite and calcium nitrite with cement is good.

The cement keeps the coating film alkaline and has a function as a binder. The cement is not particularly limited, and various portland cements, various mixed cements, blast furnace cement, fly ash cement, and the like can be used, but when calcium nitrite is used as the nitrite, blast furnace cement is preferably used in order to improve fluidity.

The inorganic powder material enhances the dispersibility and adhesion of the composite. As the inorganic powder material, silica sand powder such as natural silica sand or regenerated silica sand, clay powder, or calcium carbonate or slag powder, etc. can be used, but among them, one or two or more selected from calcium carbonate, magnesium silicate, slag powder and clay powder are preferable.

When the composite is composed of only cement and an intumescent material, the thickness of the coating film cannot be ensured, and the coating film shrinks as the cement cures. For these reasons, it is necessary to add an inorganic powder material to the anticorrosive coating composition. In this case, if the particle size of the inorganic powder material is not set to about 1/3 of the minimum coating thickness, a stable coating cannot be obtained. Therefore, the minimum coating thickness of the particle size distribution of the inorganic powder material is 200 μm, and the proportion of the inorganic powder material having a thickness of 74 μm or less is 80% or more.

The intumescent material serves to prevent drying shrinkage of the composite. As the expanding material, commercially available products such as anhydrous gypsum can be used.

In addition to the above-mentioned materials, a water reducing agent for reducing water to improve fluidity, a thickener for increasing viscosity, and the like may be added as an admixture. When a styrene/butadiene copolymer is used, the amount of the blending agent is preferably 0.4 to 0.8% by mass, and more preferably 0.6% by mass. When an acrylic acid/styrene copolymer is used, the amount of the compounding agent is preferably 0.3 to 0.6% by mass, more preferably 0.4% by mass.

Regarding the coating and the epoxy resin coating using the anticorrosive coating composition according to the present invention, and the alkaline coating and the heavy anticorrosive coating using the anticorrosive coating composition according to the present invention, the total cost such as material cost and temporary cost is calculated assuming that the life expectancy of each coating is 30 years, 7 years, 8 years, and 10 years, and the total cost when the anticorrosive coating composition according to the present invention is used is 1, the epoxy resin coating time is 5.0, the alkaline coating time is 4.1, and the heavy anticorrosive coating time is 5.0. From this fact, it is also found that the life cycle cost of the steel structure can be greatly reduced by using the anticorrosive coating composition according to the present invention.

[ Top-coating Material ]

A coating film formed on a primer layer formed from the anticorrosive coating composition is required to have substrate-following properties, prevent elution of nitrite, and excellent weather resistance. Although a combination of an epoxy resin, a urethane resin, and the like having high deformability can be applied, a top-coat material having high weather resistance will be described here. For example, as a top coat material for a top coat layer formed directly on a base coat layer, a 2-component mixed type paint can be used in which a solution obtained by dissolving an acrylic silicone resin in a turpentine-based weak solvent is used as a main agent and isocyanate is used as a curing agent. The compounding ratio of the main agent and the curing agent is preferably 2 to 15 parts by mass of the main agent to 1 part by mass of the curing agent.

In the above-mentioned top coating material, by using an acrylic silicone resin having excellent weather resistance as a main component of the main agent and mixing an isocyanate as a curing agent, OH groups of the main agent are combined with isocyanate groups of the curing agent to form polyurethane crosslinks in the molecular structure of the coating film. This results in a three-dimensional network structure in the molecular structure of the coating film, and the sealing properties of the coating film are improved. That is, the nitrite contained in the undercoat layer can be prevented from dissolving out in the topcoat layer. In addition, when the polyurethane is crosslinked, softening (in terms of pencil hardness, H degree) is performed by setting the crosslinking density (the ratio of the number of crosslinking points to the whole structural units) to be slightly low, thereby ensuring the base-following property.

In addition, excellent weather resistance capable of maintaining gloss for a long time is required for the top coat layer. Therefore, as another example of the topcoat material used for forming the topcoat layer, a 2-component mixed type paint can be used in which a solution obtained by dissolving a HALS mixed resin in a strong solvent such as toluene or xylene is used as a main component and isocyanate is used as a curing agent. The compounding ratio of the main agent and the curing agent is preferably 2 to 15 parts by mass with respect to 1 part by mass of the curing agent, as in the case of the top coat material.

The HALS blend resin as the main component of the main agent is an acrylic polyol resin obtained by copolymerizing a hindered amine Light Stabilizer (hinderdamine Light Stabilizer) and cyclohexyl methacrylate. Hindered amine light stabilizers (hereinafter referred to as "HALS") inhibit autoxidative degradation reactions of a coating film by trapping radicals generated by ultraviolet rays (a phenomenon in which radicals, once generated, react with oxygen in the air to generate radicals in a chain manner, thereby degrading the coating film). On the other hand, cyclohexyl methacrylate does not have a benzene skeleton which easily absorbs sunlight to generate radicals and is highly hydrophobic. The HALS-mixed resin prevents bleeding (bleeding out) of the HALS by chemically bonding the HALS to the resin, suppresses the autoxidative deterioration reaction of the coating film for a long period of time, and realizes a long life of the coating film by virtue of high hydrophobicity of cyclohexyl methacrylate.

Further, when the main agent and the curing agent are mixed, OH groups of the main agent are bonded to isocyanate groups of the curing agent to form polyurethane crosslinks in the molecular structure, so that the molecular structure of the coating film has a three-dimensional lattice structure, and the sealing property of the coating film is improved.

[ method of preventing Corrosion of Steel Material ]

Next, a method of preventing corrosion of a steel material according to an embodiment of the present invention will be described by taking recoating of an existing structure in which corrosion has occurred as an example.

(1) The pressurized high-pressure water is jetted from the nozzle toward the surface of the steel material by a high-pressure water generator (not shown) at a water pressure of about 15 to 25MPa, thereby performing surface cleaning (base cleaning) of the surface of the steel material. The degree of surface cleaning was set to a third degree (SSPC-SP2 or the same degree as SIS St 2), that is, to a degree of removing old coating films and rust to develop the steel surface, and the living film portion was a clean surface obtained by removing powder and dirt. In addition, surface cleaning may also be performed using sandblasting or a power tool.

(2) The surface-cleaned steel material is coated with a primer material comprising the anticorrosive coating composition to form a primer layer. In this case, the thickness of the undercoat layer is set to 200 to 650 μm. The drying time is approximately 1 day, but varies depending on environmental conditions such as humidity.

(3) The first top coat layer is formed by applying a top coat material obtained by mixing and stirring a solution obtained by dissolving an acrylic silicone resin in a weak solvent with isocyanate onto a base coat layer. In this case, the thickness of the first topcoat layer is set to 60 μm to 80 μm. The drying time is approximately 1 day, but varies depending on environmental conditions such as humidity.

(4) A second topcoat layer is formed by applying a topcoat material obtained by mixing and stirring a solution obtained by dissolving a HALS mixed resin in a strong solvent with isocyanate onto a first topcoat layer. In this case, the thickness of the second topcoat layer is set to 20 μm to 40 μm. The drying time is approximately 1 day, but varies depending on environmental conditions such as humidity.

Further, each coating method of the undercoat and the first and second topcoats may be any one of brush coating, roll coating, and spray coating. In addition, when it rains after coating, the next coating is performed for about 3 days.

Examples

Next, examples according to the present invention will be explained.

[ first embodiment ]

In the first example, a styrene/butadiene copolymer was used.

[ Compound cycle test ]

A composite cycle test was performed on a test piece in which a surface-treated steel sheet with a plate shape was coated with a primer material and a topcoat material. The material compositions and the characteristics of the top coat materials of the examples and the reference examples subjected to the composite cycle test are shown in tables 1, 12, and 3, and the test results are shown in table 4. The material composition and test results of the comparative examples are shown in tables 5, 6, 7 and 8. Among these, in the reference examples, the anticorrosive coating composition according to the present invention was used as a primer, and a topcoat material having an elongation of less than 5% was used as a coating film.

In the examples, the reference examples, and the comparative examples, two test pieces were used, and after the top coat material was applied to each test piece, the surface of the test piece was scribed with a cutter knife.

Examples A1 to A6 used lithium nitrite in the nitrite contained in the primer, and examples A7 to A11 used calcium nitrite. In examples A1 to A6, ordinary portland cement was used as the cement, and blast furnace cement was used in examples A7 to A11. In this case, as inorganic powder materials, a composition of calcium carbonate, magnesium silicate and clay powder was used in examples a1 and A3 to a5, a composition of silica sand powder and clay powder was used in example A8, a composition of slag powder (steel slag powder) and clay powder was used in example a11, a slag powder was used in example 2, calcium carbonate and magnesium silicate were used in examples a6 and 9, silica sand powder was used in example a7, and clay powder was used in example a 10.

On the other hand, the top coat layer was formed in a two-layer structure composed of two different top coat materials in each example, and the total thickness was set to 80 μm or 100 μm. As regards the crosslink density of the top coat material, it is a value obtained by relatively evaluating the crosslink densities of examples A1 to A11 for the average value of the first top coat layer and the second top coat layer. The elongation of the top coat material is also the average of the first top coat and the second top coat.

In reference examples A1 to A4, lithium nitrite was used as the nitrite contained in the primer, and ordinary portland cement was used as the cement. Reference example a5 calcium nitrite was used as the nitrite contained in the primer, and the cement was blast furnace cement. As the inorganic powder material, calcium carbonate and magnesium silicate were used in reference examples a1, a4 and a5, a composition of slag powder and clay powder was used in reference example 2, and a composition of calcium carbonate, magnesium silicate and clay powder was used in reference example 3. On the other hand, as for the top-coat materials, epoxy resins were used in reference examples a1 and a2, weak-solvent silicone epoxy resin was used in reference example A3, and modified silicone epoxy resin was used in reference examples a4 and a 5.

TABLE 2

TABLE 3

TABLE 4

For the primers of comparative examples A1 to A3, a Mighty CF manufactured by Mighty chemical Co., Ltd., containing white cement and ultrafine silica as main components was used. For the primers of comparative examples a4 and a5, Tomoric (registered trademark) manufactured by Primet Technology corporation containing silicone resin and zinc powder as main components was used. The primers of comparative examples a6 and 7 were alkaline paints, the primer of comparative example A8 was a zinc-rich paint, and the primer of comparative example a9 was an epoxy resin paint. Comparative examples A10 to A12 are paints containing the same components as those of the present invention, but the mixing ratio is outside the range of the present invention.

On the other hand, as the top coating materials of comparative examples a1 to a12, only comparative example a7 used a chlorinated olefin based paint, and the other comparative examples used an epoxy resin.

Comparative examples A13, A14, A17 to A21, A23, A24, A29 and A30 used lithium nitrite as a nitrite contained in the primer and ordinary portland cement as cement. In comparative examples A15, A16, A22, A25 to A28, and A31 to 34, calcium nitrite was used as the nitrite contained in the primer, and blast furnace cement was used as the cement. As inorganic powder materials, compositions of calcium carbonate, magnesium silicate and clay powder were used in comparative examples a13, a14, a16, a25 and a26, compositions of silica sand powder and clay powder were used in comparative example a27, compositions of slag powder and clay powder were used in comparative examples a30 and a31, calcium carbonate and magnesium silicate were used in comparative examples a15, a19, a20 and a32 to a34, silica sand powder was used in comparative examples a17, a18 and a28, slag powder was used in comparative examples a21, a22 and a29, and clay powder was used in comparative examples a23 and a 24.

On the other hand, the top coating materials of comparative examples A13 to A34 were weak solvent urethane acrylate resins, and the thicknesses were all 180 μm.

The coating weight was 1.0kg/m in the case of the primer²In the case of a top coating material, 0.4 to 0.5kg/m². The thickness of each coating film in tables 2, 5 and 7 is a measured value obtained by a film thickness meter.

TABLE 6

TABLE 8

The combined cycle test was as follows: after a CASS spray test was performed at 35 ℃ for 4 hours, the test was dried at 60 ℃ under a temperature and humidity of 50% for 2 hours, and then a humidity resistance test was performed at 50 ℃ under a temperature and humidity of 95% for 2 hours, and the test for a total of 8 hours was performed in a plurality of cycles.

The CASS spray test is a test in which the test solution is changed from a saline solution to a CASS solution in the saline spray test method according to JIS Z2371. The CASS solution was prepared as an aqueous solution containing 40g/L sodium chloride and 0.205g/L cuprous chloride, and adjusted to pH3.0 with acetic acid.

The moisture resistance test was carried out in accordance with JIS K5600-7-3 for moisture resistance (discontinuous condensation method).

200 composite cycle tests were performed. In the examples, reference examples, and comparative examples, the state of rust generation (rust-preventive effect) on the surfaces of two test pieces was evaluated at 10 full points according to the criteria shown in table 9, and the average value of the scores of the two test pieces was determined. Among them, the comprehensive evaluations in tables 4, 6 and 8 are results of comprehensive evaluations for rust resistance effect, workability, substrate followability and weather resistance.

TABLE 9

The following can be understood from these tables.

a) The rust-proof effect in the examples was high, and in some cases, workability was poor, but overall high evaluation was obtained.

b) The reference example is excellent in both rust resistance and workability, but the elongation of the top coat layer is low less than 5%, so the substrate followability is poor. Therefore, the overall evaluation was low.

c) The rust-proofing effects in the comparative examples were all low, and the overall evaluation was also low.

d) As a result, the overall evaluation of the examples using the top coating material having a high crosslinking density and an elongation of 5% or more was high. That is, it is known that a coating material having both the sealing property and the base following property of a coating film is expected as a top coating material.

[ mixing stability ]

The properties of the mixed solution obtained by adding the styrene/butadiene copolymer emulsion to the lithium nitrite aqueous solution and the mixed solution obtained by adding the styrene/butadiene copolymer emulsion to the calcium nitrite aqueous solution were shown in table 10 by comparison immediately after the constant-temperature pretreatment and after standing for 7 days after the constant-temperature pretreatment. Wherein the mass ratio of the nitrous acid aqueous solution to the styrene/butadiene copolymer emulsion is 1: 4. The viscosity was measured at 20rpm using a BH viscometer. From the table, it is clear that no large change was observed in the concentration, viscosity and pH immediately after the pretreatment at constant temperature and after the standing for 7 days, and the properties were stable.

Further, the viscosity of the two mixed solutions was 40 to 50 mPas, and it was found that the fluidity was significantly improved compared with the viscosity of 600 to 800 mPas, which is the viscosity of the styrene/butadiene copolymer emulsion alone.

Watch 10

[ tensile test ]

This test is a test for judging the tensile strength of the coating film. The formulation of the anticorrosive coating composition of example A12 is shown in Table 11. When coating, it is required to be 0.5 to 1.0N/mm²The tensile strength above, but that of example A12 was 1.5N/mm²And has sufficient tensile strength as a coating film.

TABLE 11

[ elongation at Break test ]

This test is a test for judging the elongation at break of the coating film. The formulation of the examples was the same as that of the tensile test. In the case of steel, elongation of 0.5% or more is required to follow the deformation of the base material, but the elongation at break in the example is 5%, and the coating film can sufficiently follow the deformation of the base material. In addition, the elongation at break was at the level of 1.4% in the conventional products.

[ adhesion Strength test ]

This test is a test for determining the degree of adhesion between the base material and the coating film. This time, the production was carried out according to the definition of JIS A6203 "Polymer Dispersion for Cement mixing and reemulsified powder resin". Table 12 shows the formulation of the anticorrosive coating composition of example A13. Example A13 adhesion Strength of 1.1N/mm²0.5N/mm which is the adhesion strength of a thin coating material satisfying JIS A6916²And the adhesive strength of the thick coating material is 1.0N/mm²。

TABLE 12

[ second embodiment ]

In a second example, experiments were conducted using an acrylic/styrene copolymer.

[ Compound cycle test ]

A composite cycle test was performed on a test piece in which a surface-treated steel sheet with a plate shape was coated with a primer material and a topcoat material. Table 13, table 14, and table 15 show the material compositions and the characteristics of the top coat materials of the examples and reference examples subjected to the composite cycle test, and table 16 shows the test results. Table 17, table 18, table 19, and table 20 show the material configurations and test results of the comparative examples. Among them, the reference examples used the anticorrosive coating composition according to the present invention as a primer and used a top coating material having an elongation of less than 5% as a coating film.

In the examples, the reference examples, and the comparative examples, the test pieces were each divided into two pieces, and after the top coating material was applied to each test piece, the surface of the test piece was scribed with a cutter at a ruler ratio.

Examples B1 to B6 used lithium nitrite in the nitrite contained in the primer, and examples B7 to B11 used calcium nitrite. In examples B1 to B6, ordinary portland cement was used as the cement, and blast furnace cement was used in examples B7 to B11. In this case, as inorganic powder materials, a composition of calcium carbonate, magnesium silicate and clay powder was used in examples B1 and B3 to B5, a composition of silica sand powder and clay powder was used in example 8, a composition of slag powder (steel slag powder) and clay powder was used in example B11, a slag powder was used in example B2, calcium carbonate and magnesium silicate were used in examples B6 and B9, silica sand powder was used in example B7, and clay powder was used in example B10.

On the other hand, the top coat layer had a two-layer structure composed of two different top coat materials in each example, and the total thickness was set to 80 μm or 100 μm. The crosslink density of the top coat material was an average value of the first top coat layer and the second top coat layer, and it was a value obtained by relatively evaluating the crosslink densities of examples B1 to B11. The elongation of the top coat material is also the average of the first top coat and the second top coat.

In reference examples B1 to B4, lithium nitrite was used as the nitrite contained in the primer, and ordinary portland cement was used as the cement. Reference example B5 calcium nitrite was used as the nitrite contained in the primer, and the cement was blast furnace cement. As the inorganic powder material, calcium carbonate and magnesium silicate were used in reference examples B1, B4, and B5, a composition of slag powder and clay powder was used in reference example B2, and a composition of calcium carbonate, magnesium silicate and clay powder was used in reference example B3.

On the other hand, as for the top coat material, epoxy resins were used in reference examples B1 and B2, a weak solvent silicone epoxy resin was used in reference example B3, and a modified silicone epoxy resin was used in reference examples B4 and B5.

TABLE 14

Watch 15

TABLE 16

For the primers of comparative examples B1 to B3, a Mighty CF manufactured by Mighty chemical Co., Ltd., which contains white cement and ultrafine silica as main components, was used. For the primers of comparative examples B4 and B5, Tomoric (registered trademark) manufactured by Primet Technology corporation containing silicone resin and zinc powder as main components was used. The primers of comparative examples B6 and B7 were alkaline paints, the primer of comparative example 8 was a zinc-rich paint, and the primer of comparative example B9 was an epoxy resin paint. In addition, comparative examples B10 to B12 are coatings which are composed of the same components as those of the present invention but have a blending ratio outside the range of the present invention.

On the other hand, as the top coating materials of comparative examples B1 to B12, only comparative example B7 used the chlorinated olefin based paint, and the other comparative examples used the epoxy resin.

Comparative examples B13, B14, B17 to B21, B23, B24, B29 and B30 used lithium nitrite as the nitrite contained in the primer and ordinary portland cement as the cement. Comparative examples B15, B16, B22, B25 to B28, and B31 to B34 calcium nitrite was used as the nitrite contained in the primer, and blast furnace cement was used as the cement. As inorganic powder materials, compositions of calcium carbonate, magnesium silicate and clay powder were used in comparative examples B13, B14, B16, B25 and B26, compositions of silica sand powder and clay powder were used in comparative example B27, compositions of slag powder and clay powder were used in comparative examples B30 and B31, calcium carbonate and magnesium silicate were used in comparative examples B15, B19, B20 and B32 to B34, silica sand powder was used in comparative examples B17, B18 and B28, slag powder was used in comparative examples B21, B22 and B29, and clay powder was used in comparative examples B23 and B24.

On the other hand, the top coating materials of comparative examples B13 to B34 were weak solvent urethane acrylate resins, and the thicknesses were all 180 μm.

The coating weight was 1.0kg/m in the case of the primer²In the case of a top coating material, 0.4 to 0.5kg/m². The coating thicknesses in tables 13, 17 and 19 are measured by a film thickness meter.

Watch 18

Watch 20

The combined cycle test was as follows: after a CASS spray test was performed at 35 ℃ for 4 hours, the test was dried at 60 ℃ under a temperature and humidity of 50% for 2 hours, and then a humidity resistance test was performed at 50 ℃ under a temperature and humidity of 95% for 2 hours, and the test for a total of 8 hours was performed in a plurality of cycles.

The CASS spray test is a test in which the test solution is changed from a saline solution to a CASS solution in the saline spray test method according to JIS Z2371. The CASS solution was prepared as an aqueous solution containing 40g/L sodium chloride and 0.205g/L cuprous chloride, and adjusted to pH3.0 with acetic acid. The moisture resistance test was carried out according to JIS K5600-7-3 for moisture resistance (discontinuous condensation method).

200 composite cycle tests were performed. In the examples, reference examples, and comparative examples, the state of rust generation (rust-preventive effect) on the surfaces of two test pieces was evaluated at 10-point intervals according to the criteria shown in table 21, and the average of the scores of the two test pieces was determined. Among them, the comprehensive evaluations in tables 16, 18 and 20 are results of comprehensive evaluations for rust resistance effect, workability, substrate followability and weather resistance.

TABLE 21

The following can be understood from these tables.

a) The rust-proof effect in the examples was high, and in some cases, workability was poor, but a high evaluation was obtained in combination.

b) The reference example is excellent in both rust resistance and workability, but the elongation of the top coat layer is low less than 5%, so the substrate followability is poor. Therefore, the overall evaluation was low.

c) The rust-proofing effects in the comparative examples were all low, and the overall evaluation was also low.

d) As a result, the overall evaluation of the examples using the top coating material having a high crosslinking density and an elongation of 5% or more was high. That is, it is known that a coating material having both the sealing property and the base following property of a coating film is expected as a top coating material.

[ mixing stability ]

The properties of the mixed solution obtained by adding the acrylic acid/styrene copolymer emulsion to the lithium nitrite aqueous solution and the mixed solution obtained by adding the acrylic acid/styrene copolymer emulsion to the calcium nitrite aqueous solution were shown in table 22 by comparison immediately after the constant temperature pretreatment and after standing for 7 days after the constant temperature pretreatment. Wherein the mass ratio of the nitrous acid aqueous solution to the acrylic acid/styrene copolymer emulsion is 3: 4. The viscosity was measured at 20rpm using a BH viscometer. From the table, it is clear that the concentration, viscosity and pH immediately after the pretreatment at constant temperature and after the standing for 7 days did not change greatly, and the properties were stable.

Further, the viscosity of the two mixed solutions was 40 to 50 mPas, and it was found that the fluidity was significantly improved with respect to 600 to 800 mPas, which is the viscosity of the acrylic/styrene copolymer emulsion alone.

TABLE 22

[ tensile test ]

This test is a test for judging the tensile strength of the coating film. The formulation of the anticorrosion coating composition of example B12 is shown in Table 23. When coating, it is required to be 0.5 to 1.0N/mm²The tensile strength above, but that of example B12 was 1.5N/mm²And has sufficient tensile strength as a coating film.

TABLE 23

[ elongation at Break test ]

This test is a test for judging the elongation at break of the coating film. The formulation of the examples was the same as that of the tensile test. In the case of steel, elongation of 0.5% or more is required to follow the deformation of the base material, but the elongation at break in the example is 5%, and the coating film can sufficiently follow the deformation of the base material. In addition, the elongation at break was at the level of 1.4% in the conventional products.

[ adhesion Strength test ]

This test is a test for determining the degree of adhesion between the base material and the coating film. This time, the production was carried out according to the definition of JIS A6203 "Polymer Dispersion for Cement mixing and reemulsified powder resin". The formulation of the anticorrosion coating composition of example A13 is shown in Table 24. Example B13 had an adhesion strength of 1.1N/mm²0.5N/mm which is the adhesion strength of a thin coating material satisfying JIS A6916²And the adhesive strength of the thick coating material is 1.0N/mm²。

Watch 24

Industrial applicability

A coating film formed on the surface of a steel material by using the anticorrosive coating composition of the present invention has an alkaline atmosphere with a pH of 11.5 to 12.5. When a coating film layer using such a coating film as an undercoat layer is formed, a passivation film is formed on the surface of the steel material, thereby preventing rust from occurring. Further, since nitrite is appropriately retained by the cement paste, the rust-proof effect by nitrite can be maintained for a long period of time. In addition, the polymer formed of a styrene/butadiene copolymer or an acrylic acid/styrene copolymer imparts flexibility to the undercoat layer, and can follow deformation of the steel surface. Due to these effects, it is not necessary to perform high-level surface cleaning of the steel surface, and corrosion can be prevented for a long time.

Claims (13)

1. An anticorrosion coating composition for use as a primer for steel surfaces, characterized in that it comprises: a composite containing cement, an inorganic powder material and an expanding material; a polymer emulsion which is a styrene/butadiene copolymer emulsion; and a nitrite salt, and a salt of nitrogen,

wherein the inorganic powder material has a particle size distribution in which the minimum coating thickness is 200 μm and the proportion of the inorganic powder material having a thickness of 74 μm or less is 80% or more,

the anticorrosive coating composition comprises 26 to 39 mass% of the cement, 20 to 28 mass% of the inorganic powder material, 0.5 to 1.5 mass% of the intumescent material, 5 to 18 mass% of the styrene/butadiene copolymer, and 2.5 to 7.5 mass% of the nitrite,

and 13 to 42 mass% of water, wherein the inorganic powder material is one or more selected from silica sand powder, calcium carbonate, magnesium silicate, slag powder and clay powder.

2. An anticorrosion coating composition for use as a primer for steel surfaces, characterized in that it comprises: a composite containing cement, an inorganic powder material and an expanding material; a polymer emulsion which is an acrylic acid/styrene copolymer emulsion; and a nitrite salt, and a salt of nitrogen,

wherein the inorganic powder material has a particle size distribution in which the minimum coating thickness is 200 μm and the proportion of the inorganic powder material having a thickness of 74 μm or less is 80% or more,

the anticorrosive coating composition comprises 26-38 mass% of the cement, 20-28 mass% of the inorganic powder, 0.5-1.5 mass% of the intumescent material, 6-24 mass% of the acrylic/styrene copolymer, and 2.5-9.0 mass% of the nitrite,

and further contains 12 to 43 mass% of water, and the inorganic powder material is one or more selected from silica sand powder, calcium carbonate, magnesium silicate, slag powder, and clay powder.

3. The anticorrosion coating composition of claim 1 or 2 wherein the cement is blast furnace cement and the nitrite is calcium nitrite.

4. The anticorrosion coating composition of claim 1 or 2 wherein the cement is ordinary portland cement and the nitrite is lithium nitrite.

5. A method of producing an anticorrosion coating composition, which is used for producing the anticorrosion coating composition of claim 1 or 2, comprising: a first step of pretreating a mixed solution obtained by adding the polymer emulsion to the aqueous solution of nitrite at a constant temperature; and a second step of adding the composite containing the cement, the inorganic powder material, and the expansion material to the mixed solution pretreated at a constant temperature.

6. A method of making an anticorrosion coating composition for making the anticorrosion coating composition of claim 3 comprising: a first step of pretreating a mixed solution obtained by adding the polymer emulsion to the aqueous solution of nitrite at a constant temperature; and a second step of adding the composite containing the cement, the inorganic powder material, and the expansion material to the mixed solution pretreated at a constant temperature.

7. A method of making an anticorrosion coating composition for making the anticorrosion coating composition of claim 4 comprising: a first step of pretreating a mixed solution obtained by adding the polymer emulsion to the aqueous solution of nitrite at a constant temperature; and a second step of adding the composite containing the cement, the inorganic powder material, and the expansion material to the mixed solution pretreated at a constant temperature.

8. A method for preventing corrosion of a steel material, comprising removing rust from the surface of the steel material, applying a primer coating material comprising the anticorrosive coating composition according to claim 1 or 2 to the surface of the steel material to form a primer coating layer, and applying a topcoat coating material comprising a coating film having an elongation of 5% or more to the primer coating layer to form a topcoat layer.

9. A method for preventing corrosion of a steel material, comprising removing rust from the surface of the steel material, applying a primer coating material comprising the anticorrosive coating composition according to claim 3 to the surface of the steel material to form a primer coating layer, and applying a top coating material forming a coating film having an elongation of 5% or more to the primer coating layer to form a top coating layer.

10. A method for preventing corrosion of a steel material, comprising removing rust from the surface of the steel material, applying a primer coating material comprising the anticorrosive coating composition according to claim 4 to the surface of the steel material to form a primer coating layer, and applying a top coating material comprising a coating film having an elongation of 5% or more to the primer coating layer to form a top coating layer.

11. An anticorrosive coating film for forming a primer layer on a steel surface, characterized by comprising: a composite containing cement, an inorganic powder material and an expanding material; a polymer which is a styrene/butadiene copolymer; and a nitrite salt, and a salt of nitrogen,

wherein the inorganic powder material has a particle size distribution in which the minimum coating thickness is 200 μm and the proportion of the inorganic powder material having a thickness of 74 μm or less is 80% or more,

the anticorrosive coating film comprises 32.5-49 mass% of the cement, 25-35 mass% of the inorganic powder material, 0.6-1.9 mass% of the intumescent material, 6-23 mass% of the styrene/butadiene copolymer, and 3.1-9.4 mass% of the nitrite,

and 7-12% by mass of crystal water, wherein the inorganic powder material is one or more selected from silica sand powder, calcium carbonate, magnesium silicate, slag powder and clay powder.

12. An anticorrosive coating film for forming a primer layer on a steel surface, characterized by comprising: a composite containing cement, an inorganic powder material and an expanding material; a polymer which is an acrylic acid/styrene copolymer; and a nitrite salt, and a salt of nitrogen,

wherein the inorganic powder material has a particle size distribution in which the minimum coating thickness is 200 μm and the proportion of the inorganic powder material having a thickness of 74 μm or less is 80% or more,

the anticorrosive coating film comprises 32.5-47.5 mass% of the cement, 25-35 mass% of the inorganic powder material, 0.6-1.9 mass% of the intumescent material, 7.5-30 mass% of the acrylic acid/styrene copolymer, and 3.1-11.2 mass% of the nitrite,

and 7.8 to 12 mass% of crystal water, wherein the inorganic powder material is one or more selected from silica sand powder, calcium carbonate, magnesium silicate, slag powder and clay powder.

13. A coating film layer comprising a primer layer and a top coat layer, wherein the primer layer is formed from the anticorrosive coating film according to claim 11 or 12, and the top coat layer is formed from a coating film having an elongation of 5% or more.