JP6525216B2 - Undercoating material for steel corrosion protection - Google Patents

Description

  The present invention relates to a primer for corrosion protection of steel.

Today, many steel products are used in public facilities such as bridges, road fences and footbridges, housing construction materials such as handrails, balconies, fences and gates, industrial facilities such as tanks, and many other fields. However, steel materials inherently have the property of rusting.
The rusting of steel materials is caused by moisture and oxygen in air, but is promoted by sulfate ions derived from plant exhaust gas and chloride ions derived from sea salt particles. In addition, in cold district road facilities, it is also promoted by the deicing agent (calcium chloride) sprayed in winter.
Therefore, anticorrosion coating is usually applied to the steel surface. In order to enhance the anticorrosion effect, in many cases, after the undercoating, a multilayer coating such as an intermediate coating and an overcoating is applied.

  A polymer cement-based paint is known as one of the anticorrosion paint (for example, Japanese Patent Application Laid-Open No. 60-243169 (hereinafter referred to as Patent Document 1)). Polymer cement paint is water-curable and can be flexible depending on the choice of polymer, so it can sufficiently follow the expansion and contraction of steel materials, so it is difficult to generate cracks etc., and long-term corrosion protection Although it is considered to be excellent, the coating film itself does not have a chloride ion capturing function, so the anticorrosion performance was not sufficient.

  On the other hand, Japanese Patent Application Laid-Open No. 05-043282 (hereinafter referred to as Patent Document 2) describes hydrocalumite (in particular, a nitrite-type hydrocalumite) as a compound having a function of capturing chloride ions. Further, JP-A-11-92692 (hereinafter referred to as Patent Document 3), JP-A-2007-191385 (hereinafter referred to as Patent Document 4), and Japanese Patent No. 3859 731 (hereinafter referred to as Patent Document 5) An anticorrosion paint composition incorporating the above hydrocalumite is disclosed.

  Japanese Patent Application Laid-Open No. 2004-299979 (hereinafter referred to as Patent Document 6) discloses a substrate adjusting material for steel material in which hydrocalumite is contained in a cement-based substrate adjusting material. More specifically, there is disclosed a base adjusting material for steel materials in which hydrocalumite as an anion adsorbent and a water-based epoxy resin as a polymer admixture are mixed with a water-curable component containing cement.

  The anticorrosion paint compositions of Patent Documents 3 to 5 and the base conditioning material of Patent Document 6 contain hydrocalumite having a chloride ion capturing function as a component thereof, and therefore, the corrosion protection is better than that of the conventional anticorrosion coating material The function was expected to be high.

Japanese Patent Application Laid-Open No. 60-243169 JP 05-043282 A Japanese Patent Application Laid-Open No. 11-92692 JP 2007-191385 A Patent No. 3589731 gazette Unexamined-Japanese-Patent No. 2004-299979

  Then, when the present inventors evaluated the performance about the antirust coating composition of patent documents 3-5, it turned out that the antirust effect is not enough yet. Although the reason for this is not clear, the rustproof coating composition described in Patent Documents 3 to 5 is one in which hydrocalumite is added to a paint vehicle containing an organic polymer as a base component, and therefore nitrite / The present inventors estimate that ions such as chloride ion / hydroxide ion are difficult to move and the function of hydrocalumite is not sufficiently exhibited.

  Moreover, as a result of the present inventors after carrying out evaluation examination in more detail about the base adjustment material of patent document 6, it turned out that the anti-corrosion effect of steel materials is not yet enough. Moreover, since the said base | substrate adjusting material is high in viscosity, it is easy to produce coating nonuniformity, Therefore, in order to fully ensure an anti-corrosion effect, it also became clear that there existed a problem of requiring excessive recoating.

Therefore, the inventors of the present invention have made investigations on the problem of completing an undercoat material for corrosion protection of a steel material excellent in corrosion resistance and paintability, making the most of the chloride ion capturing function of hydrocalumite.

As a result of intensive studies, the present inventors
1. Composition containing cement-based water-hardening material (A), fine aggregate (B), nitrous acid type hydrocalumite (C), re-emulsifiable powder resin (D) and thickener (E) is the anticorrosive effect of steel materials Become a water-curable primer having excellent paintability and good paintability, and when the water-curable primer further contains an antifoam (F) and a fluidity improver (G), the anticorrosion effect and the paint Become a more superior undercoating material, and the thickener (E) is a powder thickener (E1) and the antifoam (F) is a powder antifoam (F1); By using the powder type flowability improver (G1) as the property improver (G), the anticorrosion performance is further enhanced, and it becomes a powder type water curable primer which can be coated only by adding water thereon.
2. When applying anticorrosion coating to steel materials, the method of forming an undercoat layer with a water-cured product of the above-mentioned undercoat material and then applying a weak solvent epoxy paint to form an intermediate coating layer can impart excellent corrosion resistance performance to steel materials. ,
3. A subbing layer consisting of a water-cured product of the above subbing material is formed on the surface of the steel material, then the subbing layer is overlaid to form an intermediate coating layer made of a weak solvent epoxy resin coating, and further overlaid on the intermediate coating layer The steel material that forms the top coat layer becomes an excellent corrosion resistant steel material,
The present invention has been completed.

That is, the present invention provides a primer for corrosion protection of steel according to the following aspects (1) to (5);
(1) Cement-based water-hardening material (A), fine aggregate (B), nitrous acid hydrocalumite (C), re-emulsifiable powder resin (D) and thickener (E) for corrosion protection of steel materials Material.
(2) The undercoat material for steel corrosion prevention according to the above (1), wherein the re-emulsifiable powder resin (D) is an acrylic acid ester re-emulsifiable resin.
(3) The primer for corrosion protection of steel according to the above (1), which further comprises an antifoaming agent (F) and a fluidity improver (G).
(4) The primer for corrosion protection of steel according to the above (2), which further comprises an antifoaming agent (F) and a flowability improving agent (G).
(5) Cement based water curing material (A) 100 parts by mass, fine aggregate (B) 50 to 150 parts by mass, nitrous acid type hydrocalumite (C) 10 to 100 parts by mass, re-emulsifiable powder resin (D) 5-30 parts by mass, thickener (E) 0.05 parts by mass to 1 part by mass, antifoaming agent (F) 0.05-0.5 parts by mass and fluidity improver (G) 0.05-0 (7) The primer for corrosion protection of steel according to the above (3) or (4), which comprises 7 parts by mass.

Further, according to the present invention, as a preferred embodiment of the undercoat material for steel corrosion prevention according to the above (1) to (5), all of the constituent components are powder, and the following constituent (6) And 7) provide a powder base primer for corrosion protection of steel materials. Since these steel powder base coats for corrosion protection are water hardened only by adding water, they become coat coats excellent in handling property and on-site workability;
(6) In the above embodiments (1) to (5), powder thickener (E1) as thickener (E), powder antifoam (F1) as antifoam (F), flowability improvement Powder based primer for corrosion protection of steel material, which comprises powder based fluidity improver (G1) as agent (G).
(7) The powder based undercoating material as set forth in (6), wherein the powder-based thickener (E1) is a cellulose-based thickener or a polysaccharide-based thickener.
(Hereinafter, the undercoat material for steel corrosion prevention according to the embodiments of the above (1) to (7) is referred to as "the present invention undercoat material", and the powder based undercoat material for corrosion protection of steel according to the embodiments of (6) and (7) The undercoat layer formed by the water-cured product of the undercoating material of the present invention may be referred to as the "inventive powder-based undercoating material", and may be referred to as the "substituent layer of the present invention".

Hereinafter, the present invention will be described in detail.
<Steel coating for corrosion protection>
The undercoating material of the present invention described in the above (1) to (7) is a cement-based water-hardening material (A), fine aggregate (B), re-emulsifiable powder resin (C), nitrous acid type hydrocalumite (D And thickener (E) as essential components. The undercoating material of the present invention, when mixed with water, becomes a water-curable undercoating material for steel corrosion protection, which has good paintability, excellent adhesion to steel materials, and excellent corrosion resistance performance.

The primer of the present invention can not achieve its purpose even if it lacks any of the components (A) to (E).
Hereinafter, the undercoating material of the present invention will be described for each component thereof.
(A) Cement-Based Water-Hardening Material The primer of the present invention comprises a cement-based water-hardening material as an essential component.
The cement-based water-hardening material referred to in the present invention means a water-curable composition containing cement as a main component, and imparts water-hardening properties to the primer of the present invention. Thus, by applying a mixture of the primer of the present invention and water to a steel material, a strong water-curable coating can be formed on the surface thereof. In addition, the cement-based water-hardening material generates calcium hydroxide by hydration reaction, and as a result, exhibits alkalinity, thereby suppressing rusting of the steel material.

In the present invention, unlike the cement component in a concrete structure, the cement-based water-hardening material is not only simply water-hardened, but as the undercoating material, it is more preferable to form a coating film of high strength and uniform on the steel sheet surface. .
Therefore, as the cement-based water hardener in the present invention,
(A1) Besides cement alone,
(A2) cement and pozzolanic active material,
(A3) cement and latent hydraulic material, or (A4) cement, pozzolanic active material and latent hydraulic material can be mentioned.
The cement-based water-curable materials of (A1) to (A4) can all form a strong water-curable coating on the surface of the steel material, but some of the cement is substituted with a pozzolanic active material (A2), cement In the case where part of the cement is replaced with latent hydraulic material (A3), and the part of cement is replaced with pozzolanic active material and latent hydraulic material (A4), a denser film is formed than in the case of cement alone As a result, the antirust effect is further enhanced, which is preferable.

  The cement in (A1) to (A4) is typically, but not limited to, Portland cement. Further, as types of Portland cement, in addition to ordinary Portland cement, there are early-strength Portland cement, ultra-early-strength Portland cement, moderate heat Portland cement, low-heat Portland cement, sulfate resistant Portland cement, and any of these in the present invention. Can also be used. Among the above, early-strength Portland cement and ultra-early-strength Portland cement can be suitably used.

The pozzolanic active material referred to in the above (A2) and (A4) is a fine powdery substance containing silicon dioxide as a main component, and although it itself does not harden by water, calcium hydroxide formed upon hydration of cement And the above-mentioned siliceous substance (referred to as pozzolanic reaction) to form calcium silicate hydrate of a compact structure. When the cement-based water-hardening material contains a pozzolanic active material, the subbing layer of the present invention improves coating film strength, steel sheet adhesion strength, chloride ion shielding properties more than cement alone, and as a result, its antirust effect is further enhanced. Increase.
Examples of pozzolanic active materials include silica fume, fly ash, volcanic ash, siliceous clay and the like. Among these, silica fume and fly ash are particularly preferable because they have high silicon dioxide content and fine particle size.
In addition, since both the silica fume and fly ash have spherical particle shapes, the bearing effect enhances the fluidity of the primer and also improves the paintability of the primer of the present invention. That is, the adhesion to the roller and the brush is good, and the coating unevenness after the roller coating is eliminated.
The proportion of the pozzolanic active material represented by the above-mentioned silica fume or fly ash in the cement-based water-hardening material is preferably in the range of 5 to 20% by mass.

The latent hydraulic material referred to in the above (A3) and (A4) is one containing calcium oxide and silicon dioxide as main components, and exhibiting hydraulicity under alkaline conditions, and as a representative example, ground granulated blast furnace slag Can be mentioned. When an alkaline atmosphere is generated by calcium hydroxide generated by hydration of cement, calcium oxide and silicon dioxide in the latent hydraulic material gradually elute to form a compact hydrate of silicon dioxide. The above reaction is continued for a long time.
Therefore, when the cement-based water-hardening material contains a latent hydraulic material as a component, the primer of the present invention forms a layer of a high-strength and dense hardened film over a long period of time, so the chloride ion shielding effect Retained for many years months.
As for the ratio for which the potential hydraulic material represented by the said blast-furnace slag fine powder accounts for a cement-type water-hardening material, the range of 10-40 mass% is preferable.
The fine blast furnace slag fine powder preferably has a brane specific surface area of 4000 (g / cm ² ) or more, more preferably 6000 (g / cm ² ) or more, as an index of its particle size. Here, the Blaine specific surface area refers to the specific surface area measured using a Blaine air permeation device defined in JIS R 5201 (Physical test method for cement) (the same applies hereinafter).

(B) Fine Aggregate The primer of the present invention contains fine aggregate as an essential component.
If the primer material lacks fine aggregate, the coating film strength of the primer layer will be low, and if the steel material is subjected to vibration or impact, cracks will easily occur, resulting in poor corrosion resistance of the steel material.

  As fine aggregate, both natural fine aggregate and artificial fine aggregate can be used suitably. Natural fine aggregate includes river sand, land sand, sea sand, natural silica sand and the like. However, when using sea sand, it is important that the salt be sufficiently removed. As an artificial fine aggregate, a blast furnace slag fine aggregate, a ferro nickel slag fine aggregate, a copper slag fine aggregate, an electric furnace oxidation slag fine aggregate etc. can be used.

As for the quantity of the fine aggregate contained in this invention undercoat, 50-150 mass parts is preferable with respect to 100 mass parts of cement-type water-hardening materials.
When the fine aggregate is contained in an amount of 50 parts by mass or more based on 100 parts by mass of the cement-based water-hardening material, higher strength is imparted to the undercoat layer of the present invention. The amount of fine aggregate is preferably 60 parts by mass or more, and more preferably 80 parts by mass or more, with respect to 100 parts by mass of the cement-based water-hardening material.

  On the other hand, when the fine aggregate is contained in an amount of 150 parts by mass or less based on 100 parts by mass of the cement-based water-hardening material, the mixture of the primer of the present invention and water has excellent paintability (workability). . 120 mass parts or less are more preferable with respect to 100 mass parts of said cement type water-hardening materials, and, as for a fine aggregate amount, 100 mass parts or less are still more preferable.

  In the fine aggregate, the proportion of components having a particle diameter of 500 μm or more in the total mass of the fine aggregate component is preferably 30% by mass or less. When the component having a particle diameter of 500 μm or more is 30% by mass or less, the surface of the finally obtained undercoat layer is smoothed, which is preferable. The proportion of the component having a particle diameter of 500 μm or more is more preferably 10% by mass or less, and still more preferably 5% by mass or less. In addition, the measurement of particle size distribution is calculated | required according to the sieve method defined in JISZ8011.

(C) Nitrite-Type Hydrocalumite The primer of the present invention contains nitrite-type hydrocalumite as an essential component.
The nitrite-type hydrocalumite not only adsorbs chloride ions, which are the cause of corrosion of steel materials, but also has the function of releasing nitrite ions that have a corrosion inhibiting effect on steel materials. In the case where the primer material lacks the nitrite type hydrocalumite, the steel corrosion resistance of the primer layer becomes extremely inferior, and the object of the present invention can not be achieved.

The nitrite-type hydrocalumite referred to in the present invention is Ca represented by a chemical formula of the general formula: 3CaO.Al ₂ O ₃ .Ca (NO ₂ ) ₂ .nH ₂ O (n represents a natural number of 20 or less). -Al-based composite hydroxide, having a plate-like crystal structure.

The nitrite type hydrocalumite is produced, for example, by a method of reacting and crystallizing a raw material system comprising sodium aluminate and a soluble calcium salt and / or an alkali metal salt and slaked lime (Japanese Patent Application Laid-Open No. 07-033340), CaO · Al ₂ It can be obtained in a powder form by a method of reacting / crystallizing an O ₃ -based compound and a soluble calcium salt and / or slaked lime in a liquid (JP-A-07-033341).

  The amount of the nitrite-type hydrocalumite contained in the undercoating material of the present invention is preferably 10 to 100 parts by mass with respect to 100 parts by mass of the cement-based water-curable material.

  By containing 10 parts by mass or more of the nitrite-type hydrocalumite per 100 parts by mass of the cement-based water-hardening material, the water-cured product of the undercoating material of the present invention has chloride ion adsorption capacity and nitrite ion release capacity. It will be excellent. As a result, the primer layer formed by the water-cured product exhibits excellent anticorrosion performance.

  Even if the nitrous acid type hydrocalumite is added in excess of 100 parts by mass with respect to 100 parts by mass of the cement-based water-hardening material, the chloride ion adsorption capacity corresponding to the increment of the addition amount is not recognized and it is economical In addition, the paintability (workability) of the mixture of the primer of the present invention and water tends to decrease, and the coating strength of the primer layer of the present invention tends to decrease, which is not preferable. The amount of the nitrous acid type hydrocalumite is more preferably 50 parts by mass or less with respect to 100 parts by mass of the cement-based water-hardening material.

  Nitrite-type hydrocalumite is usually obtained as a powder substance in the range of 5 to 100 μm by the reaction and crystallization method described above, but by optimizing the reaction conditions, small particles and a narrow particle size range are obtained. It can be obtained as a powder.

  In the present invention, commercially available powdered nitrous-type hydrocalumite can be suitably used. As powdery nitrous acid type hydrocalumite which can be obtained, for example, “Solkat” (Nippon Chemical Industry Co., Ltd. registered trademark) manufactured by Nippon Chemical Industry Co., Ltd. can be mentioned.

(D) Re-emulsifiable powder resin The primer of the present invention comprises a re-emulsifiable powder resin as an essential component.
The re-emulsifiable powder resin improves the tensile strength and elongation of the water-cured product of the primer of the present invention and at the same time enhances the adhesion to steel materials. If the primer material lacks the re-emulsifiable powder resin, the primer layer can not resist the distortion caused by the difference in thermal expansion coefficient with that of the steel material, and as a result, peeling and cracking occur, and it can withstand a severe temperature change environment. Absent.
In the present invention, the reason why the re-emulsifiable powder resin is employed as the resin component for reinforcing the undercoat layer is as follows. That is, a cement-based water-hardening material as a water-hardening component which forms the main component of the present invention, a fine aggregate as a strength-imparting component to a water-hardening layer, hydrocalumite as a chloride ion-trapping component, and re-emulsification It is possible to pre-mix the powdery resin component in a powdery state with a mixer as it is, and as a result, each component is micro-dispersed in the undercoat layer. As a result, the paintability of the primer material is improved, and the anticorrosion function of the water-cured primer layer is also enhanced.
In addition, when using resin components that are not in powder form, such as resin emulsions, for the purpose of reinforcing the undercoat layer, many coating operations are required to secure the coating thickness, and coating workability and coating are required. Membrane quality is degraded.

  The above re-emulsifiable powder resin has a glass transition temperature of 10 ° C. or less from the viewpoint of the film formation temperature of the mixture of the primer of the present invention and water and the strength retention of the primer of the present invention at low temperature. Is preferred.

  As the re-emulsifiable powder resin, a known re-emulsifiable powder resin can be used. Specifically, the base resin is a (meth) acrylic acid ester copolymer, an ethylene vinyl acetate copolymer (EVA) or Mention may be made of those which are vinyl acetate / vinyl versatate copolymers. Further, in order to enhance the re-emulsification performance, it is also possible to use one in which a part of the base resin is bonded to a polyvinyl alcohol chain.

In the undercoating material of the present invention, among the above re-emulsifiable powder resins, those in which the base resin is an acrylic ester resin (hereinafter referred to as an acrylic ester re-emulsifiable powder resin) are formed of a water-cured product. It is particularly preferable because the coating film of the undercoat layer is excellent in water resistance.
As the above-mentioned acrylic acid ester type re-emulsifiable powder resin, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, (meth) acrylic acid n-butyl, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate or two of these The thing comprised from the above monomer unit can be mentioned, You may contain (meth) acrylic acid as a structure monomer unit.

  It is preferable that the quantity of re-emulsifiable powder resin contained in this invention undercoat is 5 mass parts-30 mass parts with respect to 100 mass parts of cement-type water-hardening materials.

  By containing the re-emulsifiable powder resin in an amount of 5 parts by mass or more based on 100 parts by mass of the cement-based water-hardening material, the adhesion between the water-cured product of the undercoating material of the present invention and the steel material is further improved. The anticorrosion effect increases. The amount of re-emulsifiable powder resin is more preferably 10 parts by mass or more with respect to 100 parts by mass of the cement-based water-hardening material.

  Further, by setting the amount of re-emulsifiable powder resin to not more than 30 parts by mass with respect to 100 parts by mass of cement-based water-hardening material, the water of the present invention undercoat material of cement-based water-curing material which is a carrier component of nitrite hydrocalumite. Since the proportion of the cured product can be kept high, the anticorrosion performance of the undercoat layer of the present invention is not impaired. The re-emulsifiable powder resin is more preferably 20 parts by mass or less with respect to 100 parts by mass of the cement-based water-hardening material.

(E) Thickener The primer of the present invention contains a thickener as an essential component.
The thickener imparts an appropriate viscosity to the mixture of the primer of the present invention and water to enhance the paintability on the steel surface. If the primer lacks a thickener, thin coating becomes extremely difficult.

  Examples of the thickener include various water-soluble polymers such as cellulose ethers such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose and carboxymethyl cellulose, polyacrylamide, polyethylene oxide, polyvinyl alcohol and casein, and polymers such as xanthan gum, welan gum and dutan gum. Saccharides can be mentioned, and one or two or more of these can be used in combination.

  By employing a powder-based thickener (E1) as a thickener, it can be used as a water-curable powder-based undercoat material for steel corrosion prevention by using in combination with other powder-based constituents of the present invention. A commercial item can be used suitably as a powdery thickener (E1). As such a thing, a methylcellulose type powder thickener, a polyacrylic acid type powder thickener, etc. are mentioned.

  It is preferable that the quantity of the thickener contained in this invention undercoat is 0.05 mass part-1 mass part with respect to 100 mass parts of cement-type water-hardening material.

  When the thickener content is 0.05 parts by mass or more with respect to 100 parts by mass of the cement-based water-hardening material, the mixture of the primer of the present invention and water is easily extended, and good brush coatability is imparted. The amount of thickener is more preferably 0.1 parts by mass or more.

  On the other hand, by setting the amount of thickener to 1 part by mass or less with respect to 100 parts by mass of the cement-based water curing material, the viscosity of the mixture of the primer of the present invention and water does not become too high. The amount of the thickener is more preferably 0.5% by mass or less with respect to 100 parts by mass of the cement-based water curing material.

(F) Antifoamer The primer of the present invention may contain an antifoamer as an optional component.
The antifoaming agent suppresses foaming and air entrainment when mixing the primer of the present invention with water. As a result, the formation of micropores (pinholes) in the subbing layer of the present invention is suppressed, and as a result, the anticorrosion function of the subbing layer of the present invention is further enhanced.

  Examples of the antifoaming agent that can be used in the present invention include various antifoaming agents such as alcohols, polyols, fatty acid esters, ethylene oxide-propylene oxide and silicones, and one or more of these antifoaming agents may be used. It can be used in combination.

  By employing a powder-based antifoaming agent (F1) as the antifoaming agent, it can be used as a powder-based undercoating material for steel corrosion prevention by using in combination with other powder-based constituents of the present invention. A commercial item can be used conveniently as a powder type antifoamer (F1).

  It is preferable that the addition amount of an antifoamer sets it as 1 mass part or less with respect to 100 mass parts of cement-type water-hardening materials. Even if it is added in excess of 1 part by mass, the defoaming effect is difficult to improve any more and is not economical. From the balance of the defoaming effect and economic efficiency, the addition amount of the antifoaming agent is more preferably 0.05 to 0.5 parts by mass, and further preferably 0.1 to 0.4 parts by mass.

(G) Flowability improver The primer of the invention may contain a flowability improver as an optional component. In the present invention, the fluidity improver suppresses aggregation of cement-based water-hardening particles by its dispersing effect, and has the effect of enhancing the fluidity of the mixture of the primer and water of the present invention. The fluidity improver of the present invention may be a mixture of a cement-based water curing agent and water, in addition to those known to those skilled in the art as a water reducing agent, an AE water reducing agent, and a high performance AE water reducing agent. An admixture (known to those skilled in the art as a fluidizing agent) is included, which has the effect of increasing the fluidity of the kneaded product by post-addition mixing and stirring.

  Examples of the water reducing agent include those containing lignin sulfonate and oxycarboxylate as main components. As an AE water reducing agent, the thing of a polyol type can be mentioned. Examples of the high performance AE water reducing agent include polycarboxylic acids, naphthalenes, melamines and aminosulfonic acids. Examples of the fluidizing agent include naphthalene sulfonic acid formaldehyde high condensate salt, melamine sulfonic acid formaldehyde condensate salt, water-soluble salt of polycarboxylic acid, and styrene sulfonic acid copolymer salt.

Among these, polycarboxylic acid salts are preferable because they exhibit high dispersion and fluidity improvement effects in small amounts.
As polycarboxylic acid salts, polyacrylates, polyacrylamide partial hydrolysates, olefin-maleic acid copolymers, styrene-maleic acid copolymers, styrene-maleic acid (polyoxyethylene) ester copolymers, allyl Examples include (EO) ether-maleic anhydride-styrene copolymer, allyl (EO) ether-maleic acid-styrene copolymer and the like.

  By employing a powder type flowability improver (G1) as a flowability improver, it can be made into a powder type undercoat material for steel corrosion prevention by using in combination with other powder type components of the present invention. A commercial item can be used suitably as a powder type | system | group fluidity | liquidity modifier (G1).

  The addition amount of the flowability modifier is preferably 1 part by mass or less with respect to 100 parts by mass of the cement-based water-hardening material. Even if it is added in excess of 1 part by mass, the fluidity is hardly improved further and is not economical. From the balance of the improvement of fluidity and economy, the addition amount of the fluidity improver is more preferably 0.05 to 0.7 parts by mass, and further preferably 0.1 to 0.5 parts by mass.

<Powder composition for steel corrosion prevention>
Each essential component of said (A)-(D) which comprises this invention undercoat is a powdery component. Therefore, when each of the above optional components (E) to (G) is in powder form, these powder components are blended beforehand in a desired ratio to obtain a powder based undercoat material for corrosion protection of steel material which has been premixed. I can do it. As a mixer for premixing, mixers, such as a tumbler mixer and a V-type mixer, can be used suitably. Such a powder-based undercoating material is excellent in on-site workability because a water-curable coating material for corrosion protection of a steel material can be prepared only by mixing the powder-based undercoating material with water when painting.

In the undercoating material of the present invention, the effect of the thickener is that the coating liquid is well-stretched on the coating surface, and a uniform coating film having a constant film thickness is obtained, the coating property becomes good, and brush coating, roller coating, etc. The usual painting method can be adopted. In addition, since the primer of the present invention is excellent in paintability, a uniform and smooth primer layer can be formed without recoating.

  For the purpose of the present invention, the thickness of the undercoat layer is preferably in the range of 50 to 500 μm, and more preferably in the range of 100 to 400 μm.

    After the primer is applied, it is preferably allowed to cure in water for 24 hours or more.

  By the undercoating material, the anticorrosion coating method, and the anticorrosion steel material of the present invention, the steel material can be prevented from salt damage, and the life of the steel structure can be extended.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic cross section of the corrosion- resistant steel material which provided the undercoat of this invention. It is a photograph which shows the state of the test piece of Example 1, the comparative example 1, and the reference example 1 before a salt spray test start. It is a photograph which shows the state of the test piece of Example 1, the comparative example 1, and the reference example 1 after salt-water spray 500 hours progress. It is a photograph which shows the state of the test piece of Example 1, the comparative example 1, and the reference example 1 after salt-water spray 1500 hours progress.

Hereinafter, the contents of the present invention will be specifically described by way of examples.
In the following examples and comparative examples, the following test methods were used.

<Steel steel for testing>
A polished steel plate specified in JIS K5600 1-4, which is 150 mm long, 100 mm wide, and 1 mm thick, is used as a test steel material.

<Salt spray test>
A cross cut is put on a test piece in which a primer, an intermediate coat and a top coat are sequentially applied to a steel for test (a test piece having a cut is referred to as a "cross cut test piece"). The crosscut test piece is placed in a temperature-controlled room maintained at a temperature of 35 ° C., and a 5% saline solution is sprayed. The condition of the test piece after 300 hours, 500 hours, 800 hours, 1000 hours, 1500 hours and 2000 hours is observed.

Example 1
1) Preparation of undercoating material and formation of undercoating layer Each component was compounded according to the following composition and uniformly mixed by a mixer to prepare a powder-based undercoating material;
-Early strength Portland cement: 100 parts by mass,
90 parts by mass of silica sand (commercially available product having a particle diameter of 500 μm or more and 10% by mass or less)
Nitrite type hydrocalumite (manufactured by Nippon Chemical Industrial Co., Ltd.): 15 parts by mass,
-14 parts by mass of acrylic ester-based re-emulsifiable powder resin (glass transition temperature 10 ° C.)
Cellulose-based thickener (powder): 0.2 parts by mass,
Powder antifoaming agent: 0.2 parts by mass,
Powder system flowability improver: 0.3 parts by mass.
35 parts by mass of water was added to the total amount of the prepared powder base primer and uniformly mixed with a mixer. The blend was applied to a test steel to form a primer layer. The coatability of the undercoating material was good, and it was possible to form a uniform and smooth undercoating layer by one brushing without requiring recoating. The thickness of the undercoat layer was 300 μm. After undercoating, it was water cured for 48 hours.
2) Formation of middle coat layer and top coat layer It piled up on the above-mentioned ground coat layer, middle coat coating was performed by using a weak solvent 2-liquid epoxy resin paint (Epolo MP primer, manufactured by Isam Paint Co., Ltd.) as a middle coat material. The thickness of the middle coat layer was 60 μm. Ten hours after the formation of the middle coat layer, it was overlaid on the middle coat layer and coated with a strong solvent two-component urethane resin paint (Hyart 3000, manufactured by Isam Paint Co., Ltd.) as a top coat material. The thickness of the overcoat layer was 30 μm. Thus, corrosion resistance test pieces were prepared.
3) Salt spray test A crosscut was placed on the above anticorrosion performance test piece, the crosscut test piece was placed in a thermostatic chamber maintained at a temperature of 35 ° C., and a 5% saline solution was sprayed. The surface condition of the test piece was observed after 300 hours, 500 hours, 800 hours, 1000 hours, 1500 hours, and 2000 hours. The results are shown in Table 1 and FIGS.

Comparative Example 1
A primer was prepared in the same manner as in the preparation of the primer of Example 1, except that no nitrite type hydrocalumite was added. Subsequently, using the same middle coat material and top coat material as used in Example 1, a corrosion resistance test specimen and then a crosscut test specimen were similarly prepared and subjected to a salt spray test. The results are shown in Table 1 and FIGS.

Comparative Example 2
A primer was prepared in the same manner as in Example 1 except that no cellulose thickener was added. Then, anticorrosion performance test pieces and then cross cut test pieces were prepared and subjected to a salt spray test. The results are shown in Table 1. The paintability of the undercoating material was poor. That is, it was difficult to form a uniform coated surface on the surface of the steel material because the coating solution did not stretch well, and three overcoatings were required to form an undercoat layer having an average thickness of 300 μm.

[Test Example 3]
In Example 1, in place of the weak solvent epoxy resin paint as the middle coat material and using the aqueous epoxy resin paint in the same manner, an anticorrosive performance test piece and then a cross cut test piece are prepared and a salt spray test is conducted. The The results are shown in Table 1.

[Test Example 4]
In Example 1, in place of the weak solvent epoxy resin paint and using a strong solvent epoxy resin paint as the middle coat material, a corrosion protection test specimen and then a cross cut test specimen are prepared in the same manner as in the salt spray test. went. The results are shown in Table 1.

Example 2
In Example 1, an anticorrosion performance test piece and then a cross cut test piece were prepared in the same manner as in Example 1 except that a silicone resin paint was used as a top coat material, and a salt spray test was conducted. No change was observed on the surface of the test piece even after 2000 hours.

[Example 3]
In Example 1, an anticorrosive performance test piece and then a cross cut test piece were prepared in the same manner as in Example 1 except that a fluorine resin paint was used as a top coat material, and a salt spray test was conducted. No change was observed on the surface of the test piece even after 2000 hours.

[Reference Example 1]
In Example 1, in place of 14 parts by mass of re-emulsifiable powder resin, 14 parts by mass of acrylic acid ester resin emulsion (in terms of solid content) were used, and in the same manner, test pieces for corrosion resistance and then crosscuts It made and did salt spray test. After 1000 hours, rust (rust width: 1.6 mm) was observed at the cross cut portion. After 1500 hours, swelling was observed along with rust growth (rust width 3.0 mm). After 2000 hours, as rust further grew (rust width 5.2 mm), blistering further increased. The results are shown in FIGS.
The paintability of the undercoating material was poor. That is, it was difficult to form a uniform coated surface on the surface of the steel material due to the poor elongation of the coating solution. That is, at the time of brush coating, a uniform coating film could not be formed, and there were places where the base was transparent and the coating was extremely thin. Therefore, three or more overcoatings were required to form a uniform undercoat layer with a thickness of 300 μm.

1. Steel 2. Subbing layer 3. Middle coat layer 4. Top layer

Claims (8)

100 parts by mass of cement-based water-hardening material (A), 50 to 150 parts by mass of fine aggregate (B), 10 to 100 parts by mass of powdered nitrite hydrocalumite (C), acrylate ester re-emulsifiable powder resin (D) 5 to 30 parts by mass, powder based thickener (E) 0.05 to 1 part by mass, powder based antifoamer (F) 0.05 to 0.5 parts by mass, and powder based fluidity improver (G) Powder based primer for corrosion protection of steel material comprising 0.05 to 0.7 parts by mass. The cement-based water-hardening material (A) is portland cement, The powder base primer for corrosion protection of steel materials according to claim 1. The cement-based water-hardening material (A) comprises Portland cement and pozzolanic active material. The cement-based water-hardening material (A) is made of portland cement and a latent hydraulic material. The cement-based water-hardening material (A) comprises portland cement, a pozzolanic active material, and a latent hydraulic material, and the powder-based undercoat material for corrosion protection of steel according to claim 1. The powder-based primer according to claim 3, wherein the pozzolanic active material is silica fume or fly ash. The powder base primer for corrosion protection of steel according to claim 5, wherein the pozzolanic active material is silica fume or fly ash. The powder base primer for corrosion protection of steel according to any one of claims 4, 5 or 7, wherein the latent hydraulic material is ground granulated blast furnace slag.