JP7415160B2 - Rust prevention treatment liquid and surface treated steel plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to an anti-corrosion treatment liquid for end surfaces and a surface-treated steel plate.

BACKGROUND ART Conventionally, steel plates and plated steel plates whose surfaces are subjected to Zn-based plating have been used in various applications such as exterior building materials. Since these plated steel sheets may not have sufficient corrosion resistance or discoloration resistance as they are, a chemical conversion film containing an organic resin may be formed on the surface thereof.

Further, the above-mentioned plated steel sheet is often used as a molded product. When forming a galvanized steel sheet, a chemical conversion film is formed on the end surface or the exposed area after forming to improve the corrosion resistance of the end face or exposed area of the base steel plate caused by the forming process. Sometimes.

A method of increasing the corrosion resistance of a steel plate by forming a phosphate film is known (for example, Patent Document 1). According to Patent Document 1, zinc (Zn) is usually added to the treatment liquid used for forming a phosphate film in addition to a phosphate compound. Furthermore, Patent Document 1 discloses that, in addition to Zn, iron (Fe), nickel (Ni), cobalt (Co), chromium (Cr), antimony (Sb), manganese (Mn), and various alkaline earth metals are It is stated that they may be combined.

Japanese Patent Application Publication No. 01-263280

It is known to form a phosphate film on the end face or exposed portion of a steel plate using a treatment solution containing a phosphate compound and the optionally added other elements. However, there is a desire to further improve the corrosion resistance of steel sheets with respect to the conventional phosphate coatings formed on the end faces of steel sheets.

In view of the above circumstances, an object of the present invention is to provide a rust prevention treatment liquid that can further improve the corrosion resistance on the end face of a steel plate, and a surface-treated steel sheet that can further improve the corrosion resistance on the end face.

One embodiment of the present invention for solving the above problems contains a phosphate ion, at least one type of metal atom or ion thereof selected from the group consisting of Ca, Zn, Mg, and Mn, and an organic resin. The present invention relates to an anti-corrosion treatment liquid for the end surface of steel plates. In the rust prevention treatment liquid, the ratio of the content of the metal atoms or their ions to the content of phosphorus atoms (P) is 1.0 or more in molar ratio, and the organic resin is a cationic urethane. Contains resin or nonionic urethane resin.

Another aspect of the present invention for solving the above problems is a steel sheet containing phosphate ions, at least one type of metal atom or ion thereof selected from the group consisting of Ca and Zn, and an organic resin. This invention relates to an anti-rust treatment liquid for end faces of. In the rust prevention treatment liquid, the ratio of the content of Zn or its ions to the content of Ca or its ions is 0.2 or more and 1.2 or less in molar ratio, and The ratio of the content of the metal atoms or their ions to the content is 1.5 or more in mass ratio, and the organic resin includes a cationic urethane resin or a nonionic urethane resin.

One aspect of the present invention for solving the above problems relates to a surface-treated steel plate having a base steel plate and a surface treatment layer disposed on an end surface or a cut surface of the base steel plate. The surface treatment layer contains a phosphate and at least one type of metal atom selected from the group consisting of Ca, Zn, Mg, and Mn, and the metal atom is The molar ratio of the contents is 1.0 or more.

One aspect of the present invention for solving the above problems relates to a surface-treated steel plate having a base steel plate and a surface treatment layer disposed on an end surface or a cut surface of the base steel plate. The surface treatment layer contains phosphate, Zn, and Ca, and the ratio of the Zn content to the Ca content is 0.2 or more and 1.2 or less in molar ratio. The ratio of the total content of Zn and Ca to the content of phosphorus (P) is 1.5 or more in terms of mass ratio.

According to the present invention, it is possible to provide a rust-preventing treatment liquid that can further improve the corrosion resistance on the end face of a steel plate, and a surface-treated steel sheet that can further improve the corrosion resistance on the end face.

An embodiment of the present invention will be described below.

[Rust prevention treatment liquid]
One embodiment of the present invention relates to a rust prevention treatment liquid for treating the end face of a steel plate.

The rust prevention treatment liquid contains a phosphate compound or phosphate ion, and metal atoms such as Ca, Zn, Mg, and Mn or ions thereof, and may further contain an organic resin.

The above-mentioned phosphoric acid compound is deposited on the end face of the steel plate to which the above-mentioned rust prevention treatment liquid has been applied and dried. As a result, the phosphoric acid compound is contained as granular phosphate crystals in the surface treatment layer formed by the antirust treatment solution, thereby improving the corrosion resistance of the end face of the steel sheet.

The above-mentioned phosphoric acid compound may be water-soluble or water-insoluble as long as it can precipitate a phosphate that exhibits a rust-preventive effect on steel sheets. The phosphoric acid compound may be phosphoric acid or a phosphate. The above phosphoric acid may be a normal phosphoric acid such as orthophosphoric acid, or a complex phosphoric acid such as pyrophosphoric acid. Examples of cations that serve as counter ions to phosphate ions in phosphate compounds include hydrogen ions, alkali metal ions, alkaline earth metal ions, ammonium ions, manganese ions, aluminum ions, titanium ions, zirconium ions, hafnium ions, and Contains zinc ions.

A part of the metal atoms are co-precipitated with phosphoric acid. In addition, some of the metal atoms that were not consumed by the co-precipitation become oxides or hydroxides, filling the voids between the phosphate crystals and densifying the surface treatment layer. . By densifying the surface treatment layer in this way, the penetration of water through the surface treatment layer is suppressed, the number of starting points for red rust in the steel sheet is reduced, and the corrosion resistance of the steel sheet is increased.

The metal atoms can be added to the rust prevention treatment solution in the form of phosphates, nitrates, sulfates, carbonates, acetates, oxalates, and the like. The metal atoms are usually dissociated and ionized in the rust prevention treatment solution, but some of them may be contained in the rust prevention treatment solution as a salt.

In order to fill the spaces between the phosphates with the oxide or hydroxide, the content of the metal atoms or their ions (metal content/P amount) is preferably 1.0 or more in molar ratio. Note that the phosphorus atom is usually derived from the phosphoric acid compound. From the above viewpoint, the molar ratio of the amount of metal/the amount of P is more preferably 1.2 or more, and even more preferably 1.5 or more. Although the upper limit of the molar ratio of the amount of metal/the amount of P is not particularly limited, it is preferably 4.0 or less from the viewpoint of preventing formation defects of the surface treatment layer due to excessive metal ions.

Preferably, the metal atoms include Ca and Zn. According to the new findings of the present inventors, at this time, by adjusting the amount of Zn added to Ca, the corrosion resistance of the end face of the steel plate can be further improved. Specifically, the molar ratio of the content of Zn or its ions to the content of Ca or its ions (Zn/Ca) is preferably 0.2 or more and 1.2 or less. By setting the above molar ratio to 0.2 or more, the effect of improving corrosion resistance by Zn becomes remarkable. Further, by setting the molar ratio to 1.2 or less, it is possible to prevent formation defects of the surface treatment layer due to excess metal ions from occurring. From the above viewpoint, the molar ratio is more preferably 0.2 or more and 1.0 or less, even more preferably 0.2 or more and 0.5 or less, and 0.2 or more and 0.35 or less. is particularly preferred.

Further, at this time, the content of the metal atoms or their ions (metal content/P content) with respect to the content of phosphorus atoms (P) in the rust prevention treatment liquid should be 1.5 or more in mass ratio. is preferred. By keeping the molar ratio of Zn/Ca within the above range and the mass ratio of metal amount/P amount to 1.5 or more, a sufficient amount of the above metal atoms or ions thereof are contained in the rust prevention treatment solution, By filling the spaces between the phosphates with the oxide or hydroxide, the effect of improving the corrosion resistance of the steel sheet can be made more pronounced. From the above viewpoint, the mass ratio of the amount of metal/the amount of P is more preferably 1.5 or more, and even more preferably 2.0 or more. Although the upper limit of the mass ratio of the amount of metal/the amount of P is not particularly limited, it is preferably 6.0 or less from the viewpoint of preventing formation defects of the surface treatment layer due to excessive metal ions.

The organic resin mainly constitutes the film structure of the surface treatment layer formed by applying and drying the rust prevention treatment liquid. The organic resin may be one type or more than one type. Examples of the organic resins include urethane resins, polyesters, acrylic resins, epoxy resins, polyolefins, and fluororesins.

Among these organic resins, the rust prevention treatment liquid contains a nonionic urethane resin or a cationic urethane resin. The above-mentioned nonionic urethane resin or cationic urethane resin makes it difficult for the above-mentioned phosphate and metal atoms to be eluted from the surface layer, thereby increasing the corrosion resistance of the steel plate over a long period of time. In addition, since the nonionic urethane resin or cationic urethane resin has high miscibility with the phosphate ion or metal component ion, it is possible to further improve the storage stability and processability of the rust prevention treatment solution. can.

Further, the above-mentioned rust prevention treatment liquid usually has a pH of 4 or less. In such an acidic treatment solution, the nonionic urethane resin or cationic urethane resin is stable and difficult to gel the rust prevention treatment solution, further improving the storage stability and applicability of the rust prevention treatment solution. be able to.

By the way, when attempting to form a film on the cut end surface of a steel plate, residual processing oil and dirt applied during processing may repel the rust prevention treatment solution, resulting in the formation of a discontinuous film. Such a discontinuous film tends to cause red rust to occur from the gaps in the film, making it difficult to sufficiently improve corrosion resistance. On the other hand, nonionic urethane resins or cationic urethane resins can improve the spreadability of the antirust treatment solution, and therefore can also suppress the formation of the discontinuous film.

Nonionic urethane resins are more preferred from the viewpoint of improving the corrosion resistance of the steel plate over a long period of time, improving storage stability, processability, and coating properties, and further enhancing the effect of suppressing the formation of discontinuous films.

The nonionic urethane resin has a structure as a reaction product of an organic polyisocyanate compound and a polyol compound, for example. The nonionic urethane resin is preferably a water-soluble or water-dispersible urethane resin, more preferably a water-dispersible urethane resin, from the viewpoint of ease of manufacturing the surface treatment layer and safety. .

The nonionic urethane resin preferably has a polyoxyalkylene group such as a polyoxyethylene group and a polyoxypropylene group as a nonionic group. The above-mentioned polyoxyalkylene group tends to improve the spreadability of the antirust treatment liquid. Such a nonionic urethane resin may be synthesized by reacting the organic polyisocyanate compound, the polyol compound having a polyoxyalkylene group, and the polyol compound not having a polyoxyalkylene group. . Alternatively, it may be synthesized by reacting polyether alcohol and isocyanurate and then reacting with a polyol compound.

Examples of the organic polyisocyanate compounds include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Examples of aliphatic diisocyanates include tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, and trimethylhexamethylene diisocyanate. Examples of cycloaliphatic diisocyanates include cyclohexane diisocyanate, isophorone diisocyanate, norbornane diisocyanate, xylylene diisocyanate and tetramethylxylylene diisocyanate. Examples of aromatic diisocyanates include phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate and naphthalene diisocyanate.

The isocyanurate is preferably a trimerized isocyanurate of the various diisocyanates, more preferably a trimerized isocyanurate of aliphatic diisocyanates.

Examples of the polyol compounds include polyolefin polyols. Examples of polyolefin polyols include polyester polyols, polyether polyols, polycarbonate polyols, polyacetal polyols, polyacrylate polyols, and polybutadiene polyols.

Examples of the polyether alcohol include alkylene oxide adducts of monoalkyl ethers of alcohols having 1 to 18 carbon atoms and alkylene glycols having 1 to 18 carbon atoms.

The content of the organic resin in the rust prevention treatment liquid is preferably 10% by mass or more based on the total mass of solids in the rust prevention treatment liquid. Within the above range, the effect of improving corrosion resistance by containing a sufficient amount of organic resin in the surface treatment layer to be formed and making it difficult for the phosphates and metal atoms to be eluted from the surface treatment layer can be achieved more fully. It can be demonstrated. From the above viewpoint, the content of the organic resin is more preferably 15% by mass or more, and even more preferably 20% by mass or more. The upper limit of the content of the organic resin is not particularly limited, but from the viewpoint of improving the applicability of the rust prevention treatment liquid, it is preferably 80% by mass or less. Preferably, the content of the nonionic urethane resin or cationic urethane resin is within the above range, and more preferably, the content of the nonionic urethane resin or cationic urethane resin is within the above range.

The solvent of the anti-corrosion treatment liquid is preferably an aqueous medium from the viewpoint of explosion-proofing during production of the surface treatment layer. When preparing the rust prevention treatment liquid, an aqueous emulsion or a water-soluble treatment solution of the organic resin can be suitably used in blending the organic resin. Since such an aqueous composition does not have a flash point, using the aqueous composition as a material for the above-mentioned anti-rust treatment liquid makes it possible to manufacture the surface treatment layer even in drying equipment without explosion-proof equipment. It is preferable because

The aqueous medium is a liquid medium containing water as a main component, and is, for example, water or a mixture of water and a water-soluble organic solvent. The content of the liquid medium can be determined as appropriate within the above-mentioned solid content concentration range suitable for application of the anticorrosive treatment liquid.

Further, the rust prevention treatment liquid may further contain a valve metal compound, a rheology control agent, an etching agent, an inorganic compound, a lubricant, and the like.

The above-mentioned valve metal compound imparts self-healing properties to the surface treatment layer and contributes to further improving the corrosion resistance of the surface treatment layer. Examples of the above valve metals include Ti, Zr, Hf, V, Nb, Ta, Mo and W. The valve metal compound may be any valve metal salt, including valve metal oxides, hydroxides, and fluorides. Note that the above-mentioned content of metal atoms or ions thereof does not include the content of these valve metals or ions thereof.

The above-mentioned rheology control agent, for example, prevents the solid content from settling in the above-mentioned rust prevention treatment liquid, and contributes to improving the dispersibility of the solid content. Examples of the above rheology control agents include urethanes, acrylics, polyolefins, amides, anionic activators, nonionic activators, polycarboxylic acids, cellulose, Metrose, and urea.

The etching agent activates the surface of the steel plate and contributes to improving the adhesion of the surface treatment layer to the steel plate. Examples of etchants include fluoride. The inorganic compound further densifies the surface treatment layer and contributes to improving the water resistance of the surface treatment layer. Examples of inorganic compounds include oxides and nitrates and phosphates of Mg, Sr, V, W, Mn, Ni, B, Si and Sn. The above lubricant improves the lubricity of the surface treatment layer. Examples of such lubricants include inorganic lubricants such as molybdenum disulfide and talc.

The above-mentioned rust prevention treatment liquid can be applied to the end face of a steel plate and dried to form a surface treatment layer. At this time, a surface treatment layer may be formed with the rust prevention treatment liquid that does not contain the organic resin, and then an organic resin layer covering the surface treatment layer may be formed with the treatment liquid containing the organic resin. However, a surface treatment layer containing the phosphate and metal atoms may be formed using the rust prevention treatment liquid containing the organic resin.

The type of steel plate to be coated is not particularly limited. Examples of the steel plates include low carbon steel, medium carbon steel, high carbon steel, and alloy steel. It is preferable that the steel sheet is a deep drawing steel sheet such as low carbon Ti-added steel or low carbon Nb-added steel from the viewpoint of improving the workability of the steel sheet.

The steel plate may be a plated steel plate in which a plating layer is formed on the surface of the base steel plate. Examples of the plated steel sheet include galvanized steel sheet, Zn-Al alloy plated steel sheet, Zn-Al-Mg alloy plated steel sheet, Zn-Al-Mg-Si alloy plated steel sheet, and aluminum plated steel sheet. At this time, the anti-rust treatment liquid is applied to the end surface of the base steel plate exposed by processing and dried.

The rust prevention treatment liquid can be applied to the surface of the steel plate by a known coating method such as a roll coating method, a curtain flow method, a spin coating method, a spray method, or a dipping/pulling method. Drying of the anti-rust treatment liquid applied to the surface of the steel plate can be carried out at room temperature, but from the viewpoint of productivity (continuous operation), it is preferably carried out at a temperature of 50°C or higher, and it is preferably carried out at a temperature of 100°C or higher. It is more preferable. The drying temperature is preferably 300° C. or lower from the viewpoint of preventing thermal decomposition of the components in the antirust treatment liquid.

[Surface treated steel sheet]
Another embodiment of the present invention relates to a surface-treated steel sheet having a surface-treated layer formed on the cut surface.

The surface-treated steel sheet has the above-described steel sheet (or plated steel sheet) as a base steel sheet, and a surface treatment layer is formed on the end surface of the base steel sheet. In addition, when the said base material steel plate is a plated steel plate, the said plated steel plate has a cut surface formed by processing. The surface treatment layer is formed on the cut surface.

The surface treatment layer contains a phosphate and metal atoms such as Ca, Zn, Mg, and Mn, and may further contain an organic resin.

The phosphate is phosphate particles deposited on the surface of the steel plate.

The particles of the phosphate salt preferably have an average particle size of 0.1 μm or more and 5.0 μm or less. When the average particle size is 0.1 μm or more, the effect of improving corrosion resistance by the phosphate particles can be more fully exerted. Further, when the average particle size is 5.0 μm or more, cohesive failure of the phosphate compound particles is less likely to occur when the surface-treated steel sheet according to the present embodiment is formed.

Further, it is preferable that the phosphate particles cover 20% or more of the surface of the end face of the steel plate on the surface where the surface treatment layer is disposed. When the coverage is 20% or more, the effect of improving corrosion resistance by the phosphate particles can be more fully exerted. The upper limit of the coverage is not particularly limited, but from the viewpoint of suppressing cohesive failure of phosphate particles during further molding processing, it can be set to 98%. The coverage of the surface of the end face by the phosphate compound particles can be measured by image analysis of a scanning electron microscope (SEM) photograph of the surface of the end face.

The metal atoms are co-precipitated with the phosphate and contained within the particles, and form a dense chemical conversion layer filling the spaces between the particles as the oxide or hydroxide. .

In order to fill the spaces between the phosphates with the oxide or hydroxide, the content of the metal atoms (metal content/P content) relative to the phosphorus atom (P) content in the surface treatment layer is as follows: It is preferable that the molar ratio is 1.0 or more. Note that the phosphorus atom is usually derived from the phosphate. From the above viewpoint, the metal amount/P amount is more preferably 1.2 or more, and even more preferably 1.5 or more. The upper limit of the amount of metal/the amount of P is not particularly limited, but is preferably 4.0 or less from the viewpoint of preventing formation defects of the surface treatment layer due to excessive metal ions.

Preferably, the metal atoms include Ca and Zn. By adjusting the amount of Zn added to Ca, the corrosion resistance of the end face of the steel plate can be further improved. Specifically, the molar ratio of the Zn content to the Ca content (Zn/Ca) is preferably 0.2 or more and 1.2 or less. By setting the above molar ratio to 0.2 or more, the effect of improving corrosion resistance by Zn becomes remarkable. Further, by setting the molar ratio to 1.2 or less, formation defects of the surface treatment layer can be made less likely to occur. From the above viewpoint, the molar ratio is more preferably 0.2 or more and 1.0 or less, even more preferably 0.2 or more and 0.5 or less, and 0.2 or more and 3.5 or less. is particularly preferred.

Further, at this time, the content of the metal atoms (metal amount/P amount) with respect to the content of phosphorus atoms (P) is preferably 1.5 or more in mass ratio. By keeping the molar ratio of Zn/Ca within the above range and the mass ratio of metal amount/P amount to 1.5 or more, the above oxide or hydroxide fills the space between the phosphates. , the effect of improving the corrosion resistance of the steel plate can be made more pronounced. From the above viewpoint, the mass ratio of the amount of metal/the amount of P is more preferably 1.5 or more, and even more preferably 2.0 or more. Although the upper limit of the mass ratio of the amount of metal/the amount of P is not particularly limited, it is preferably 6.0 or less from the viewpoint of preventing formation defects of the surface treatment layer due to excessive metal ions.

The above-mentioned surface treatment layer may contain the above-mentioned organic resin, or may not substantially contain it. Note that "substantially not containing" means, for example, that the amount of the organic resin adhered to the surface treatment layer is 0.1 g/m ² or less.

The organic resin may be one type or more than one type. Examples of the organic resin include urethane resin, polyester, acrylic resin, epoxy resin, polyolefin, and fluororesin.

When the surface treatment layer contains an organic resin, it contains a nonionic urethane resin or a cationic urethane resin among these organic resins. The above-mentioned nonionic urethane resin or cationic urethane resin makes it difficult for the above-mentioned phosphate and metal atoms to be eluted from the surface treatment layer, thereby increasing the corrosion resistance of the steel sheet over a long period of time.

In addition, the above-mentioned nonionic urethane resin or cationic urethane resin increases the spreadability of the rust-preventing treatment liquid, and the remaining machining oil and dirt applied to the cut end surface of the steel plate during processing are removed by the rust-preventing treatment liquid. It is possible to suppress the formation of a discontinuous film due to

When the surface treatment layer contains the organic resin, the amount of the organic resin attached is preferably 0.1 g/m ² or more. If the amount of adhesion is 0.1 g/m ² or more, the organic resin has a significant effect of inhibiting elution of the phosphate and metal atoms from the surface treatment layer. From the above viewpoint, the amount of the organic resin adhered is more preferably 0.2 g/m ² or more, and even more preferably 0.3 g/m ² or more. The upper limit of the amount of the organic resin deposited is not particularly limited, but if it is 3.0 g/m ² or less, the applicability of the antirust treatment liquid for forming the surface treatment layer is good.

The surface-treated steel sheet may have an organic resin layer covering the surface-treated layer, regardless of whether the surface-treated layer contains the organic resin.

The organic resin layer suppresses the elution of the phosphate and metal atoms from the surface treated layer, thereby making the corrosion resistance of the surface treated steel sheet more remarkable.

The organic resin constituting the organic resin layer may be one type or more than one type. Examples of the organic resin include urethane resin, polyester, acrylic resin, epoxy resin, polyolefin, and fluororesin.

The surface treatment layer contains a nonionic urethane resin or a cationic urethane resin among these organic resins. The above-mentioned nonionic urethane resin or cationic urethane resin makes it difficult for the above-mentioned phosphate and metal atoms to be eluted from the surface treatment layer, thereby increasing the corrosion resistance of the steel sheet over a long period of time.

In addition, the above-mentioned nonionic urethane resin or cationic urethane resin increases the spreadability of the rust-preventing treatment liquid, and the remaining machining oil and dirt applied to the cut end surface of the steel plate during processing are removed by the rust-preventing treatment liquid. It is possible to suppress the formation of a discontinuous film due to
In addition, when the above-mentioned nonionic urethane resin or cationic urethane resin comes into contact with a rust prevention treatment liquid that is typically acidic, the rust prevention treatment liquid dissolves into the organic resin and gels, resulting in whitening of the resin. Or coloring is less likely to occur.

The amount of the organic resin layer covering the surface treatment layer is preferably 0.1 g/m ² or more. If the amount of adhesion is 0.1 g/m ² or more, the organic resin has a significant effect of inhibiting elution of the phosphate and metal atoms from the surface treatment layer. From the above viewpoint, the amount of the organic resin adhered is more preferably 0.2 g/m ² or more, and even more preferably 0.3 g/m ² or more. The upper limit of the amount of the organic resin deposited is not particularly limited, but if it is 3.0 g/m ² or less, the coating properties of the treatment liquid for forming the organic resin layer are good.

Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited by these Examples.

1. Experiment 1
[Production of plated steel sheet]
A hot-dip 6% Al-3% Mg-Zn plated steel plate was prepared by applying molten alloy plating of a molten Zn-6% Al-3% Mg alloy to a cold rolled steel plate (SPCC). The plate thickness of the plated steel plate was 3.2 mm, and the coating weight on one side was 60 g/m ² .

When the above-mentioned plated steel plate was cut into a piece with a width of 50 mm and a length of 100 mm, approximately 20% of the surface area of the end face produced by cutting was covered with the plating layer, and the remaining approximately 80% area was exposed to the base steel. Was.

[Preparation of treatment liquid]
A treatment solution containing the materials listed in Table 1 was prepared.

The organic resins used include Hydran APX-601 manufactured by DIC as a nonionic urethane resin, Superflex 650 manufactured by Daiichi Kogyo Seiyaku as a cationic urethane resin, and Superflex 650 manufactured by Daiichi Kogyo Seiyaku as an acrylic resin. Boncoat 8430 was prepared, and one of these was blended.

Further, the pH of the adjusted treatment liquid was adjusted to 2.0 by adding nitric acid. The pH of the treatment solution was measured using a Horiba pH meter F-71.

Table 1 shows the types and concentrations of phosphoric acid, metals, and organic resins added to Treatment Solutions 1 to 15, as well as the metal amount/P amount, Zn amount/Ca amount, and the pH of each treatment solution.

[evaluation]
(Storability)
Treatment liquids 1 to 15 were stored at room temperature for 60 days. The amount of change in viscosity of each aqueous treatment liquid before and after storage (the value obtained by subtracting the viscosity before storage from the viscosity after storage) was measured using Ford Cup No. 4, and the storage stability was evaluated based on the following criteria.
◎ The amount of viscosity change was less than 10 seconds 〇 The amount of viscosity change was more than 10 seconds, but there was no problem with use × The amount of viscosity change was more than 30 seconds, and it was difficult to apply due to thickening

(corrosion resistance)
6 ml/m ² of treatment liquids 1 to 15 were applied to the end face of the plated steel sheet and dried at room temperature to obtain a surface-treated steel sheet, which was used as a test piece.

The test piece was exposed to the atmosphere for 3 months, and after 1 month, 2 months, and 3 months, the area ratio of red rust generated on the end face of the test piece was measured, and the area where red rust occurred out of the total area of the end face was measured. The ratio WR (area where red rust occurred/total area of the end face) was determined, and the end face corrosion resistance was evaluated based on the following criteria.
◎ Red rust occurrence area rate WR was 10% or less 〇 Red rust occurrence area rate WR was more than 10% and less than 30% △ Red rust occurrence area rate WR was more than 30% and less than 50% × Red rust occurrence area rate WR was 50 It was over %

Table 2 shows the type of treatment liquid used to form the surface treated layer, the amount of metal/P amount (molar ratio and mass ratio) in the surface treated layer, and the evaluation of each surface treated steel sheet.

In this experiment, those whose corrosion resistance was evaluated as "△" after two months were deemed to have practical corrosion resistance and were passed.

2. Experiment 2

[Adjustment of organic treatment liquid]
The organic treatment liquid used was Hydran APX-601 manufactured by DIC Corporation as an organic treatment liquid containing a nonionic urethane resin (organic treatment liquid 1), and an organic treatment liquid containing a cationic urethane resin (organic treatment liquid 2). Superflex 650 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. was used as an organic treatment liquid containing an acrylic resin (organic treatment liquid 3), Boncoat CM-8403 manufactured by DIC was used as an organic treatment liquid containing an anionic urethane resin (organic treatment liquid 3), As the treatment liquid 4), Superflex 130 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. was prepared.

[evaluation]
(exterior)
A treatment liquid 13 of 6 ml/m ² was applied to the end surface of the plated steel sheet and dried at room temperature to form a surface treatment layer. Thereafter, 6 ml/m ² of any of organic treatment liquids 1 to 4 was applied to the surface of the surface treatment layer, and the degree of change in the appearance of the plated steel sheet after application was evaluated using the following criteria.
◎ No noticeable change in appearance was observed ○ Whitening or discoloration was observed in 10% or more but less than 30% of the area where the organic resin liquid was applied △ Of the area where the organic resin liquid was applied, 30% Whitening or discoloration was observed in % or more and less than 50% of the area x Whitening or discoloration was observed in 50% or more of the area where the organic resin liquid was applied

(corrosion resistance)
A treatment liquid 13 of 6 ml/m ² was applied to the end surface of the plated steel sheet and dried at room temperature to form a surface treatment layer. Thereafter, 6 ml/m ² of any of organic treatment liquids 1 to 4 was applied to the surface of the surface treatment layer and dried at room temperature to form an organic resin layer.

The test piece was exposed to the atmosphere for 3 months, and after 1 month, 2 months, and 3 months, the area ratio of red rust generated on the end face of the test piece was measured, and the area where red rust occurred out of the total area of the end face was measured. The ratio WR (area where red rust occurred/total area of the end face) was determined, and the end face corrosion resistance was evaluated based on the following criteria.
◎ Red rust occurrence area rate WR was 10% or less 〇 Red rust occurrence area rate WR was more than 10% and less than 30% △ Red rust occurrence area rate WR was more than 30% and less than 50% × Red rust occurrence area rate WR was 50 It was over %

Table 3 shows the type of treatment liquid used to form the surface treated layer, the amount of metal/the amount of P (molar ratio and mass ratio) in the surface treated layer, the amount of Zn/the amount of Ca, and the evaluation of each surface treated steel sheet.

The treatment liquid and surface-treated steel sheet of the present invention can further improve the corrosion resistance at the end face of the steel sheet and at the end face of the plated steel sheet where the base steel sheet is exposed by forming or the like. For example, the treatment liquid and surface-treated steel sheet of the present invention can be applied to 1) steel pipes, shaped steel, supports, beams, and conveyance members for vinyl greenhouses or agricultural greenhouses, 2) sound insulation walls, soundproof walls, sound absorption walls, snow walls, guardrails, It can be suitably used for steel plates used in applications such as handrails, protective fences, supports, 3) railway vehicle members, overhead wire members, electrical equipment members, safe environment members, structural members, and solar mounts.

Claims (9)

phosphate ion,
At least one metal atom or ion thereof selected from the group consisting of Ca and Zn;
organic resin,
Contains
The ratio of the content of Zn or its ions to the content of Ca or its ions is 0.2 or more and 1.2 or less in molar ratio,
The ratio of the content of the metal atoms or ions thereof to the content of phosphorus atoms (P) is 1.5 or more in mass ratio,
The organic resin includes a cationic urethane resin or a nonionic urethane resin,
Anti-corrosion treatment liquid for the edge of steel plates. The rust prevention treatment liquid according to claim 1 , wherein the organic resin includes a nonionic urethane resin . The rust prevention treatment liquid according to claim 1 or 2 , wherein the content of the organic resin is 10% by mass or more based on the total mass of the solid content. The antirust treatment liquid according to any one of claims 1 to 3 , which has a pH of 4.0 or less. base steel plate,
a surface treatment layer disposed on the end surface or cut surface of the base steel plate;
has
The surface treatment layer contains phosphate, Zn, and Ca,
The ratio of the Zn content to the Ca content is 0.2 or more and 1.2 or less in molar ratio,
The ratio of the total content of Zn and Ca to the content of phosphorus (P) is a mass ratio,
is 1.5 or more,
Surface treated steel plate. The surface-treated steel sheet according to claim 5 , wherein the surface-treated layer contains a cationic urethane resin or a nonionic urethane resin. The surface-treated steel sheet according to claim 6 , wherein the surface-treated layer contains a nonionic urethane resin. The surface-treated steel sheet according to any one of claims 5 to 7 , comprising an organic resin layer containing a cationic urethane resin or a nonionic urethane resin, covering the surface treatment layer. The surface-treated steel sheet according to claim 8 , wherein the organic resin layer contains a nonionic urethane resin.