JP4416167B2 - Chemically treated ground treatment agent for anticorrosion coated steel, chemical groundwork treatment method for anticorrosive coated steel, and anticorrosive coated steel - Google Patents

Description

  The present invention is a non-chromium-based surface treatment for steel materials, and does not require washing such as washing after the surface treatment, and has excellent long-term anticorrosion properties with little peeling from the collar and end portions. The present invention relates to a coating-type base treatment agent, a base treatment method, and a corrosion-resistant coated steel material using the same.

  Conventionally, when long-term anticorrosion properties are required for offshore structures, line pipes, etc., a method of forming a thick film coating exceeding 300 μm has been adopted to improve long-term barrier anticorrosion performance. However, in the case of thick film coating, since the stress of the coating film is large, it is necessary to perform a base treatment on the surface of the steel material to ensure the adhesion between the steel material and the coating film. Conventionally, as a steel base treatment, first, descaling is performed by blasting or pickling, and then chromate conversion treatment containing chromic acid is performed as shown in Japanese Patent No. 2949681 (Patent Document 1). Even if this chromate treatment is applied and then dried, the adhesion is good and the peel resistance can be greatly improved.

  However, since the chromate treatment contains hexavalent chromium, it can be carried out only in a controlled environment, so that the treatment can be carried out only at the factory, for example, it cannot be applied at the construction site. . On the other hand, there is zinc phosphate treatment as a typical chemical conversion treatment not containing hexavalent chromium. Zinc phosphate treatment is a method in which a steel material is immersed in a heated treatment solution, and crystals of zinc phosphate are precipitated on the surface of the steel material to form a base treatment layer.

  However, after the immersion, water washing is performed so that the water-soluble component of phosphoric acid does not remain on the steel surface. Furthermore, although it is used also for the surface treatment after assembly welding of an automobile, as shown in Japanese Patent No. 1299463 (Patent Document 2), sufficient adhesion cannot be obtained unless further chromate treatment is performed. When chromate treatment and zinc phosphate treatment are difficult for large steel structures, etc., the performance is inferior, but the base treatment is to prevent peeling of the buttocks with an inorganic and organic zinc rich paint that uses the sacrificial anticorrosive effect of zinc powder. It was.

Japanese Patent No. 2949681 Japanese Patent No. 1299463 JP 2003-34881 A

  Zinc phosphate treatment has no environmental restrictions like chromate, but because it is an immersion method, it requires a treatment tank and requires water washing after immersion, requiring large-scale equipment and a long-term process. At the same time, it was a dipping type, so there was a problem that it was not suitable for large steel structures. Overseas, it may be used as a chemical conversion treatment method for line pipes other than chromate, but the anticorrosion properties such as water-resistant adhesion, water-peeling resistance, and cathode-peeling resistance are not as great as chromate treatment.

  On the other hand, a chemical conversion treatment containing ammonium molybdate and a silane coupling agent has been proposed as disclosed in Japanese Patent Application Laid-Open No. 2003-34881 (Patent Document 3) for heavy anticorrosion coating. However, the performance was not sufficient. In addition, the zinc rich paint used for the base treatment of general paint is also insufficient in performance because the adhesiveness tends to decrease. For this reason, the chemical conversion treatment of the steel material surface which is excellent in the anticorrosion performance which does not contain hexavalent chromium and has no restrictions on the process such as washing with water is required.

  The object of the present invention is to provide a chemical conversion treatment as a substitute for chromate in heavy-duty anti-corrosion coatings or painted steel materials, and the method does not require washing such as water washing only in the coating / drying process, and has performance comparable to chromate treatment. It is an object of the present invention to provide a surface treatment agent excellent in treatment workability, a surface treatment method, and a coated steel material using the same.

  As means for solving the above-mentioned problems, the present inventors have made the surface of a steel material with a treatment liquid containing, as a main component, a metal compound of phosphoric acid represented by magnesium and calcium as a treating agent for base treatment, and containing fine particle silica. It has been found that by forming a chemical conversion coating on the surface, it is possible to provide an anticorrosion-coated steel material excellent in the peeling resistance and adhesion of the coating. That is, in the heavy anticorrosion coated steel material according to the present invention, after forming a chemical conversion coating layer mainly composed of a metal phosphate compound and a fine particle silica component, a resin primer layer and an anticorrosion resin coating layer having a thickness of 0.3 mm or more are sequentially formed. Laminate. As the anticorrosion resin coating layer, a modified polyolefin alone, a two-layer coating of a modified polyolefin adhesive layer and a polyolefin, or a polyurethane resin coating is used.

The gist of the invention is that
(1) Water-dispersed silica fine particles in which primary particles having a diameter of 5 to 50 nm synthesized by a dry method are secondarily aggregated in a simple substance of magnesium biphosphate or calcium phosphate or a mixture thereof are 0.33 to 0.33 in mass ratio. A chemical base treatment for heavy anticorrosion-coated steel, which is an aqueous solution having a pH of 4 or less added at a ratio of 4.0.

( 2 ) The surface treatment agent according to the above (1) is applied to the surface of a steel material subjected to pickling or blasting, so that the amount of magnesium phosphate, calcium phosphate alone or a mixture thereof is 0.5 to 5 g / A chemical foundation treatment method for heavy anti- corrosion coated steel material having excellent adhesion and peeling resistance, characterized in that it is applied to m ² and then dried without washing.
(3) the surface of the steel material (2) surface treatment layer which has been subjected to surface treatment method described primer resin layer, excellent adhesion and peeling resistance which is characterized by comprising sequentially laminating an anticorrosive resin layer Weight In anticorrosion coated steel.

  As described above, according to the present invention, it is not necessary to use chromic acid as a chemical conversion base treatment agent for a steel material to be subjected to anticorrosion coating, and processing can be performed only by coating and drying which does not require washing with water. . As a result, it is possible to coat the base coat of the paint film without requiring special environmental measures for large steel structures such as steel sheet piles, steel pipe sheet piles, steel pipe piles, and steel pipes that are difficult to wash. Moreover, the anticorrosion coating steel material which has the water-resistant adhesiveness and peeling resistance of the outstanding coating film equivalent to chromium oxidation treatment by the process can be provided.

Hereinafter, the present invention will be described in detail.
FIG. 1 is a cross-sectional view of a coating structure of a heavy anticorrosion coated steel material showing an example of the present invention. As the steel material 1 used in the present invention, any steel type such as ordinary steel or high alloy steel can be applied. Conventionally, it can be applied to steel pipes to which heavy anti-corrosion coating is applied, and steel pipe piles, steel pipe sheet piles, steel sheet piles, H-section steel, wire rods and the like used in offshore structures and the like. Since other steel materials do not require special equipment, the present invention can be applied as a base treatment for general coating.

  Before performing the chemical conversion base treatment of the chromate alternative chemical conversion base treatment film 2 of the present invention, it is necessary to first remove the scale, contaminants, etc. on the surface of the steel material 1. Therefore, any pretreatment such as alkali degreasing to pickling, sand blasting, grid blasting, or shot blasting is performed. Then, after apply | coating the primer resin 3, the anti-corrosion coating layer 4 is formed.

In forming the chromate-substitute chemical conversion base treatment film, first, a chemical conversion base treatment agent is applied and dried. In that case, in the present invention, washing with water after applying the base treatment agent is not necessary. Hereinafter, the chemical conversion treatment agent of the present invention will be described in detail.
It is desirable to form an insoluble film on the metal surface in the coating treatment of heavy anticorrosive coating. This is because if a large amount of water-soluble components remain in the chemical conversion coating film, the adhesion tends to decrease when used in an aqueous environment. Moreover, in the case of the steel material surface, since the reactivity is inferior compared with the galvanized surface etc., in order to ensure the reactivity of the steel material surface and the processing liquid, the pH of the processing liquid needs to be at least 4 or less acidic. .

In order to form a compound with iron as an acid and to form a certain thickness, a phosphoric acid metal compound is suitable, so phosphoric acid is most preferable. However, since most metal phosphate compounds are insoluble in water, an excessive phosphate component is required to form a solution, such as metal zinc. Magnesium is suitable as a metal that does not leave an excessive phosphoric acid component and is stable as an aqueous solution and combined with phosphoric acid. Among them, magnesium diphosphate (magnesium dihydrogen phosphate) Mg (H ₂ PO ₄ ) An aqueous solution in which ₂ is dissolved is most suitable.

  On the other hand, as long as the acid does not become excessive, it is possible to add a part of other metal phosphate compounds and use them. For example, calcium phosphate may be used. Calcium forms a strong film of calcium phosphate. In this way, by using an acidic aqueous solution in which a specific metal phosphate compound is dissolved, the reactivity with the steel material is ensured, and an insoluble film is formed to improve the anticorrosion property, thereby improving the water-resistant adhesion and corrosion. The film peelability is greatly improved. However, since this method alone is not sufficient in coating dispersibility and coating film adhesion as compared with the conventional chromate treatment, a fine particle silica component is further added to the metal phosphate compound.

  As the fine particle silica, one obtained by secondary agglomeration of primary particles having a diameter of 5 to 50 nm synthesized by a dry method is used. By doing so, the fine particles aggregate and coalesce into a grape shape to form a porous coating layer, and the adhesion to the coating layer thereon is improved. Examples of the fine particle silica include AEROSIL 130, AEROSIL 200, AEROSIL 200V, AEROSIL 200CF, AEROSIL 200 FAD, AEROSIL 300, AEROSIL 300CF, AEROSIL 380, AEROSIL OX50, AEROSIL TT600, AEROSIL TIOSIL, etc., manufactured by Nippon Aerosil Co., Ltd.

The addition amount of the fine particle silica is added in a range of 0.33 to 4.0 in terms of mass ratio with respect to the total amount of the metal phosphate compound. This is because if it is less than 0.33 , the water adhesion and cathode peel resistance are lowered, and if it exceeds 4.0, the silica component becomes excessive and the cohesive strength of the film is lowered. The fine particle silica has an effect of improving the coverage of the steel material surface and improving the dispersibility of the metal phosphate compound.

  2 to 5 show examples of effects according to the present invention. FIG. 2 or FIG. 3 is an SEM photograph in the case where fine particle silica is not included, and a micrograph showing Mg distribution by EPMA. As can be seen from this figure, it can be seen that the treatment liquid is unevenly dispersed. On the other hand, FIG. 4 and FIG. 5 are SEM photographs and micrographs showing the distribution of Mg by EPMA when a treatment liquid containing fine particle silica is applied. As can be seen from FIG. 4 and FIG. 5, it can be seen that the steel material is uniformly dispersed on the surface.

In the ground treatment of the present invention, the ground treatment agent prepared so as to contain 1 to 15% of the metal phosphate compound is applied to the steel material so that the metal phosphate compound has an adhesion amount of 0.3 to 5 g / m ^2. Apply. This is because if the coating amount is less than 0.3 g / m ² , the coating cannot sufficiently cover the steel surface, and if it exceeds 5 g / m ² , the coating itself becomes bulky and brittle, resulting in a decrease in adhesion.

  The heavy anticorrosion coating to be applied after applying the ground treatment agent according to the present invention will be described below. The resin to be coated may be anything such as vinyl chloride, polyester, acrylic, epoxy, fluorine resin, etc. as long as it has excellent durability and barrier properties against water and oxygen. Polyolefin resins and polyurethane resins are often used for corrosion protection, which is inexpensive and expected to have a long life of several tens of years.

  In such a long-term anticorrosion coating, a primer treatment for improving the adhesion between the anticorrosion coating and the steel material, resistance to cathodic detachment, and anticorrosion is performed. A thermosetting resin is used for the primer used in the heavy anticorrosion-coated steel material, and an epoxy resin, polyurethane resin, or polyester resin to which a curing agent and an inorganic pigment are added is used as a main component. Typical examples of the polyurethane resin include a moisture curing type one-component type using a prepolymer, or a two-component curing type utilizing a reaction between an isocyanate and a polyol.

  In particular, for the demand for high heat resistance, it is preferable to use an epoxy resin as a primer. Generally, a bisphenol A type or bisphenol F type resin is used alone or in combination as a main component. Further, when high temperature characteristics are required, a multifunctional phenol novolac or halogenated resin is used in combination with the above bisphenol A type or bisphenol F type resin.

  When the curing agent is a two-component curing type amine curing agent, or an imidazole compound that is a latent curing agent, dicyandiamide or a phenol curing agent is used alone or in combination, the adhesion and corrosion resistance are excellent. In addition, when the inorganic pigment added to the primer is added in the range of 3 to 30 vol% with respect to the total volume, the shrinkage distortion is reduced, and the adhesion characteristics are greatly improved. Inorganic pigments include pigments such as silica, titanium oxide, wollastonite, mica, talc, kaolin, chromium oxide, zinc borate, zinc borate, zinc phosphate, or metal powder such as zinc or aluminum, or ceramic powder, In addition, a rust preventive pigment such as a vanadium phosphorus compound is appropriately used. In order to improve wettability with the resin, these pigments may be subjected to silane coupling treatment on the surface.

  By using the above-mentioned thermosetting resin primer and combining with the above-described base treatment, it is possible to provide a base treatment for a heavy anticorrosion coated steel material having excellent performance in peel resistance. When the resin primer is supplied as a liquid, a method such as roll or brush coating, ironing or air spray coating is used. When the powder is supplied, it is applied in the range of 20 to 1000 μm using a method such as electrostatic powder coating. When the film thickness is thinner than 20 μm, many pinholes are generated. On the other hand, although the upper limit of the film thickness varies depending on the type of resin, characteristics such as impact resistance at low temperatures are likely to deteriorate in thick film coating exceeding 1000 μm.

  The polyolefin resin used for heavy anticorrosion coating has as its main component conventionally known polyolefins such as low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, and ethylene-propylene block or random copolymer. It is a resin containing a known polyolefin copolymer such as a polymer, a polyamide-propylene block or a random copolymer.

  As other components, carbon black or other coloring pigments, filling reinforcing agents, antioxidants, ultraviolet absorbers, hindered amine-based weathering agents, and the like are added in any combination as heat resistance and weather resistance countermeasures. When a polyolefin resin is used for coating, an polyolefin-modified adhesive is used for the lower layer portion that comes into contact with the primer primer. This adhesive was prepared by modifying a known polyolefin such as polyethylene, polypropylene or nylon, or a known polyolefin copolymer resin with an unsaturated carboxylic acid such as maleic acid, acrylic acid or methacrylic acid or an acid anhydride thereof. Or a modified polyolefin known in the art such as a product obtained by appropriately diluting the product with a polyolefin resin. A method of combining a polyolefin resin layer having a thickness of 0.3 to 5 mm with a thin modified polyolefin adhesive layer having a thickness of 50 to 700 μm is preferable from the viewpoint of the balance between price and performance. You may coat | cover 3 mm or more and use it as an anticorrosion layer.

  As a polyolefin coating method, for example, an extrusion coating method is used in which a steel material is directly coated with a heat-melted resin using a die. Alternatively, there are a method of sticking a pre-formed polyolefin sheet to a heated steel material, and a method of forming a film by powder coating and melting the pulverized polyolefin. By these methods, a polyolefin anticorrosive coating layer having a film thickness of 0.3 mm or more is formed.

  There is also a method of applying a polyurethane resin to the heavy anticorrosion coating. The polyurethane resin is a two-component mixed coating of a main agent composed of a mixture of a polyol, a filled inorganic pigment and a color pigment, and a curing agent composed of an isocyanate compound. Polyols such as polyester polyols, polybutadiene polyols, and polypropylene glycols, acrylic polyols, castor oil derivatives, and other hydroxyl-containing compounds are used as the polyols. As the isocyanate, a commercially available isocyanate such as methylene diphenyl diisocyanate is used.

  In general, commercially available inorganic pigments such as silica, titanium oxide and kaolin clay are used as the filled inorganic pigment, and carbon black is generally used as the colored pigment in order to impart weather resistance to the resin. When other color pigments are used from the viewpoint of design, an ultraviolet absorber is added together. The coating thickness is preferably in the range of 0.5 to 6 mm in consideration of the function and economy as a heavy anticorrosion layer.

Hereinafter, the present invention will be specifically described with reference to examples.
As the ground treatment solution of the present invention, a magnesium biphosphate solution is adjusted to a concentration of 1 to 15%, and AEROSIL 200 manufactured by Nippon Aerosil Co., Ltd. is used with silica fine particles produced by a gas phase method. Then, a ground treatment solution was prepared by mixing and adding in a weight ratio of 0.33 to 4.0. The pH at this time was 2-3. Moreover, the thing which replaced magnesium diphosphate with calcium deuterium phosphate, and also what added magnesium hydrogen phosphate, calcium hydrogen phosphate, calcium citrate, etc. were prepared.

  A grid blast treatment was applied to a 9 mm × 100 mm × 150 mm hot-rolled steel sheet as a heavy anticorrosion coating sample. As an example of the present invention, the above-prepared surface treatment solution was applied and dried at room temperature. On the other hand, for comparison, Comparative Example No. When no chemical conversion treatment is performed as No. 29, Comparative Example No. No. 30, a process of applying partially dried chromate containing fine particle silica shown in Patent Document 1 and drying, Comparative Example No. 31 contains 0.05 mol / l ammonium molybdate, 0.02 mol / l γ-aminopropyltriethoxysilane, and 0.02 mol / l γ-mercaptopropyltrimethoxylane according to Example 5 of Patent Document 3. After immersion in the treatment liquid, chemical conversion treatment with water washing, Comparative Example No. No. 32 was subjected to zinc phosphate treatment requiring immersion and water washing.

  After heating the steel plate to 60 ° C., spray coating was carried out with an epoxy resin primer containing a pigment aimed at 50 μm. After curing and curing at room temperature for 1 day, the steel plate is heated again to 50 ° C, and the 2.5-mm thick polyurethane anticorrosive layer is applied by spraying the surface of the spray gun while mixing the polyol and isocyanate with pigment added to the surface. Formed. Furthermore, the polyurethane coating was cured by room temperature curing for 3 days to produce heavy corrosion-resistant coated steel materials of Examples and Comparative Examples of the present invention.

  For the purpose of simulating peeling in the long-term use, the produced heavy anti-corrosion steel material was stripped of 10 mm width from the end surface of the steel plate to expose the steel surface. On the other hand, the back surface was coated with an epoxy resin and immersed in artificial seawater at 50 ° C. for 180 days. Stirring and oxygen supply were performed by blowing air into the artificial seawater. After the test, the coating was removed, and the progress distance of the decrease in adhesive force from the coating end was measured as the distance of the portion where the steel surface was exposed. However, most of the exposed steel surface was not corroded even if the adhesive force was reduced unless the entire surface was peeled off, and no problem in corrosion prevention was observed. Adhesive strength of the test piece was bonded to the center of the steel plate with a 20 mmφ vertical tension bonding jig via an epoxy adhesive, and the coating was cut to the iron surface along the same circle, and then the tensile tester was used to 1 mm / Vertical adhesion was evaluated at a rate of minutes. In any case, the adhesion strength was evaluated as a retention rate relative to the initial adhesion strength.

Table 1 shows the results of the comparative examples and the examples using the components of the present invention. From the result of the comparative example, the required performance cannot be satisfied by the chemical conversion treatment other than the conventional chromate. Comparative Example No. No. 27 zinc phosphate-based treatment exhibits relatively good performance when washed with water. Comparative Example No. 31- No. Although the single treatment of magnesium biphosphate 36 does not require washing with water, Comparative Example No. The performance equivalent to 27 can be obtained. However, the conventional phosphoric acid-based treatment not containing silica did not reach the chromate treatment at all in terms of performance.

On the other hand, the results of the present invention example and the comparative example when the metal phosphate compound and the silica fine particles were mixed and added were shown as the present invention example Nos. 1 shows in 23. A combination of the two components and the present invention example No. in the claims of the present invention. 1,2 6-8, 11-14, 17-20, 22-23 it can be seen that particularly excellent water adhesion and peel resistance. The treatment condition range in which the fine particle water-dispersed silica is 0.33 to 4.0 and the converted adhesion amount of the metal phosphate compound is 0.5 to 5 g / m ² with respect to the metal phosphate compound component according to these claims. Then, high water adhesion and peeling resistance equivalent to chromate treatment were obtained.

It is coating | coated structure sectional drawing of the heavy-duty anticorrosion coating steel material which shows an example of this invention. It is a SEM photograph in case fine particle silica is not included, and a microscope picture showing Mg distribution by EPMA. It is a SEM photograph in case fine particle silica is not included, and a microscope picture showing Mg distribution by EPMA. It is a SEM photograph at the time of giving the processing liquid containing particulate silica, and a microscope picture showing distribution of Mg by EPMA. It is a SEM photograph at the time of giving the processing liquid containing particulate silica, and a microscope picture showing distribution of Mg by EPMA.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel material 2 Chromate substitute conversion base treatment film 3 Primer resin 4 Anticorrosion coating layer


Patent applicant: Nippon Steel Corporation
Attorney Attorney Shiina and others 1

Claims (3)

Water-dispersed silica fine particles in which primary particles having a diameter of 5 to 50 nm synthesized by a dry method are secondarily aggregated in a simple substance of magnesium biphosphate or calcium phosphate or a mixture thereof are 0.33 to 4.0 by mass ratio. The chemical | medical-treatment ground-treatment agent for heavy anti-corrosion coating | coated steel materials which is pH 4 or less aqueous solution added in the ratio. The surface treatment agent according to claim 1 is deposited on the surface of a steel material that has been pickled or blasted so that the amount of magnesium phosphate, calcium phosphate alone, or a mixture thereof is 0.5 to 5 g / m ^2. And then drying without washing , a chemical protection substrate treatment method for heavy anticorrosion coated steel materials having excellent adhesion and peel resistance. Surface treatment layer which has been subjected to surface treatment method according to claim 2, wherein the steel material surface, the primer resin layer, heavy anticorrosive coating steel with excellent adhesion and peeling resistance which is characterized by comprising sequentially laminating an anticorrosive resin layer.

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