JP5649021B2 - Surface-treated galvanized steel sheet, pre-coated galvanized steel sheet, and production methods thereof - Google Patents

Description

  The present invention relates to a surface-treated galvanized steel sheet, a pre-coated galvanized steel sheet, and methods for producing them.

  For home appliances, building materials, automobiles, and the like, pre-coated metals coated with a colored coating film have been used instead of post-painted products that have been painted after processing. This metal plate is obtained by coating a metal plate that has been subjected to metal pretreatment, and is generally used after being cut and press-molded after the paint is applied. Therefore, the corrosion resistance of the cut end face part where the metal not coated with the coating film is exposed and the coating film peeling at the time of press processing were problems of the pre-coated metal plate, but the chromate treatment was applied as a pretreatment for metal, and These problems have been solved by including a hexavalent chromium-based rust preventive pigment in the coating film, and it is currently used for general purposes.

  However, due to the environmental problems of hexavalent chromium that may be eluted from the paint film containing chromate treatment and hexavalent chromium-based anticorrosive pigments, recently, non-chromate chemical conversion treatments that do not contain hexavalent chromium and non-chromate paint films The demand is growing. Patent Document 1 discloses a technique for providing a pre-coated metal sheet having excellent workability part adhesion and corrosion resistance by using a chemical conversion treatment that simultaneously contains tannin and tannic acid, a silane coupling agent, and fine silica instead of chromate treatment. It is disclosed. On the other hand, in Patent Document 2, instead of the hexavalent chromium-based rust preventive pigment, the corrosion resistance of the cut end face portion is obtained by using a polyester-based and epoxy-based paint in which a phosphate-based rust preventive pigment and an ion-exchange silica-based rust preventive pigment are used in combination. A technology for providing a precoated steel sheet excellent in the above is disclosed. However, these technologies have a problem in that long-term corrosion resistance, in particular, long-term corrosion resistance in a corrosive environment having a high wet rate such as a salt spray test is inferior to conventional precoated metal plates containing hexavalent chromium. . For example, when trying to improve the corrosion resistance in a corrosive environment with a high wet rate using the technology of Patent Document 1 and the technology of Patent Document 2, the amount of rust preventive pigment added in the coating film described in these Patent Documents It needs to be increased greatly. However, if the amount of the anticorrosive pigment added in the coating is greatly increased, the adhesion of the coating with the metal plate is impaired, and the coating may be easily peeled off at the processed part when the precoated metal plate is molded. When the precoated metal plate is exposed to a high humidity environment such as a moisture resistance test for a long period of time, blisters are generated from the surface of the coating film or the coating film is easily peeled off.

JP 2001-89868 A Japanese Patent Laid-Open No. 9-12931

The object of the present invention is to solve the above-mentioned problems in the prior art and to provide a surface-treated galvanized steel sheet excellent in long-term corrosion resistance and a method for producing the same.
Another object of the present invention is to provide a precoated galvanized steel sheet having excellent long-term corrosion resistance and excellent coating film adhesion, and a method for producing the same.
A further object of the present invention is to provide a surface-treated galvanized steel sheet and pre-coated galvanized steel sheet that do not contain hexavalent chromium, which is an environmentally hazardous substance, and methods for producing them.

When the present inventors diligently investigated about the improvement of the corrosion resistance of the zinc plating layer of a galvanized steel sheet, it discovered that a specific substituent showed high affinity with a zinc plating layer. And it discovered that the surface-treated galvanized steel plate excellent in long-term corrosion resistance was obtained by forming a self-organization film | membrane with the compound provided with such a specific substituent.
It has also been found that the formation of this self-assembled film improves the adhesion of a chemical conversion film such as a non-chromate film, and further improves the corrosion resistance.

The present invention has been completed based on such knowledge, and the gist of the present invention is as follows.
(1) A surface-treated galvanized film characterized in that a self-assembled film formed by applying a compound represented by the chemical formula of R ¹ —X or Y—R ² —X is formed on the surface of a galvanized layer. steel sheet.
[However, R ¹ is a linear alkyl group having 3 to 20 carbon atoms, R ² is a linear alkylene group having 3 to 20 carbon atoms, and X is either a PO (OH) ₂ group or an OH group. And Y is any one of PO (OH) ₂ group, imidazolium group, pyridinium group, and SO ₃ H group. ]
( 2 ) The surface-treated galvanized steel sheet according to (1), wherein a multilayer film made of PSS / PDDA is formed on the self-assembled film.
( 3 ) A precoated galvanized steel sheet comprising a chemical conversion film and a coating film laminated on the self-assembled film of the surface-treated galvanized steel sheet according to (1) .
(4) on the surface of the galvanized layer, it is coated with the compound represented by the chemical formula R 1 ^-X or Y-R 2 ^-X, by drying or washing, characterized by forming a self-assembled monolayer A method for producing a surface-treated galvanized steel sheet.
[However, R ¹ is a linear alkyl group having 3 to 20 carbon atoms, R ² is a linear alkylene group having 3 to 20 carbon atoms, and X is either a PO (OH) ₂ group or an OH group. And Y is any one of PO (OH) ₂ group, imidazolium group, pyridinium group, and SO ₃ H group. ]
( 5 ) The method for producing a surface-treated galvanized steel sheet according to ( 4 ), wherein a mutual laminated film made of PSS / PDDA is formed on the self-assembled film.
( 6 ) A method for producing a pre-coated galvanized steel sheet, wherein a chemical conversion treatment film and a coating film are laminated on the self-assembled film of the surface-treated galvanized steel sheet produced by the production method according to ( 4 ). .

ADVANTAGE OF THE INVENTION According to this invention, the surface treatment galvanized steel plate excellent in long-term corrosion resistance and its manufacturing method can be provided.
Moreover, according to this invention, the precoat galvanized steel plate which is excellent in long-term corrosion resistance and has the outstanding coating-film adhesiveness, and its manufacturing method can be provided.
Furthermore, according to this invention, the surface treatment galvanized steel plate and precoat galvanized steel plate which do not contain the hexavalent chromium which is an environmental load substance, and these manufacturing methods can be provided.

The surface-treated galvanized steel sheet of the present invention comprises a self-assembled film in which a compound represented by R ¹ —X or Y—R ² —X is applied to the surface of a galvanized layer of a galvanized steel sheet. Has been.
In the precoated galvanized steel sheet of the present invention, the self-assembled film is formed on the surface of the galvanized layer of the galvanized steel sheet, and further, a chemical conversion treatment film, a rust preventive coating film, and a coating film are sequentially laminated thereon. Configured. In addition, when the corrosion resistance requested | required of a precoat galvanized steel plate is not high, you may abbreviate | omit a rust prevention coating film.
Hereinafter, the configuration of the present invention will be sequentially described.

Zinc-plated steel sheets include zinc-plated steel sheets such as hot-dip galvanized steel sheets and electrogalvanized steel sheets, zinc-plated steel sheets, zinc-nickel alloy-plated steel sheets, hot-dip alloyed galvanized steel sheets, and aluminum-zinc alloyed steel sheets. And an alloy-plated steel plate with other metals can be used. Among these galvanized steel sheets, galvanized steel sheets such as hot dip galvanized steel sheets and electrogalvanized steel sheets are more suitable because they have a large sacrificial anticorrosive effect and excellent corrosion resistance. In addition, it is more preferable that the coating amount of these zinc-based plated steel sheets is 10 to 120 g / m ² per side because both workability and corrosion resistance are compatible. If the coating amount per side is less than 10 g / m ² , the corrosion resistance may be inferior, and if it exceeds 120 g / m ² , plating cracks may occur during processing and the workability may be inferior.
These galvanized steel sheets are subjected to general surface cleaning treatments such as alkali degreasing with orthosilicate sodium, caustic soda, etc., organic solvent degreasing with alcohols, ketones, etc., ultrasonic cleaning treatment, or a combination thereof. Can be used.

Next, the self-assembled film formed on the galvanized layer is configured by applying a compound represented by the chemical formula of R ¹ —X or Y—R ² —X. Here, R ¹ is a linear alkyl group having 3 to 20 carbon atoms, R ² is a linear alkylene group having 3 to 20 carbon atoms, X is an SH group, PO (OH) ₂ group, COOH group, OH group, NH ₂ group, Si (OCH ₃ ) ₃ group, Y is Si (OC ₂ H ₅ ) ₃ group, PO (OH) ₂ group, imidazolium group, pyridinium group, SO ₃ H group , NH ₂ group, or COOH group.

The self-assembled film formed of R ¹ —X or Y—R ² —X is a so-called monomolecular film. This monomolecular film forms a monomolecular film in the form in which the substituent X of R ¹ —X or Y—R ² —X is adsorbed to the galvanized layer. Thereby, the substituent R ¹ or the substituents R ² and Y are present on the outermost surface of the self-assembled film.

Since the substituent R ¹ exhibits hydrophobicity, when the self-assembled film is composed of R ¹ -X, hydrophobicity is imparted to the galvanized layer. By imparting hydrophobicity to the galvanized layer, the corrosion resistance of the galvanized layer is enhanced. In addition, since the substituent R ² has hydrophobicity similar to the substituent R ¹ , even when a self-assembled film is composed of Y—R ² —X, hydrophobicity is imparted to the galvanized layer. The corrosion resistance of the layer is increased.

R ¹ is preferably a linear alkyl group having 3 to 20 carbon atoms, and R ² is preferably a linear alkylene group having 3 to 20 carbon atoms. When the number of carbon atoms of R ¹ or R ² is less than 3, it is not preferable because the hydrophobicity of the self-assembled film is lowered and the corrosion resistance of the galvanized layer is lowered. Further, the carbon number of R ¹ or R ² is more than 20, since the solubility in a solvent of the compound consisting of R 1 ^-X or Y-R 2 ^-X is decreased, using the processing solution containing these compounds applied This is not preferable because it is difficult to form a self-assembled film by the method.

Further, the substituent X is preferably any one of SH group, PO (OH) ₂ group, COOH group, OH group, NH ₂ group, Si (OCH ₃ ) ₃ group, SH group, PO (OH) ₂ group, A COOH group is particularly preferred. All of these substituents have high adsorptivity to the galvanized layer, and exhibit a hydrophobic property as a dense monomolecular film within a short time after application. Therefore, in the manufacturing process of the galvanized steel sheet, another process can be performed immediately after the formation process of the self-assembled film. In addition, the adsorptivity with respect to a galvanization layer can be calculated | required from the relationship between the elapsed time from immediately after formation of a self-assembled film, and the contact angle of the water droplet with respect to a self-assembled film.

Furthermore, since the substituent Y has various chemical properties, when the self-assembled film is composed of Y—R ² —X, the strength of the self-assembled film can be improved, or the surface of the self-assembled film can be improved. The ionicity can be freely designed, and for example, it is possible to improve the adhesion with a chemical conversion treatment film or the like laminated on the self-assembled film.

The substituent Y is preferably any one of Si (OC ₂ H ₅ ) ₃ group, PO (OH) ₂ group, imidazolium group, pyridinium group, SO ₃ H group, and NH ₂ group. Among these, the Si (OC ₂ H ₅ ) ₃ group is a self-organized monomolecular film in which Y groups of adjacent Y—R ² —X compounds are hydrolyzed to form Si—O—Si bonds. Increase the strength of the structured membrane. Moreover, you may use the functional group which has a carbon triple bond as Y group. In this case, the surface of the film is irradiated with, for example, ultraviolet light after the formation of the self-assembled film to cause a photopolymerization reaction with a diacetylene derivative having a carbon-carbon triple bond, and Y groups are chemically bonded to each other to form a self-organized structure. Increase the strength of the chemical film.

In addition, since imidazolium group and pyridinium group have N atoms having a positive charge in the substituent group, electrostatic interaction can be expressed, and thus, a chemical conversion film or PSS / PDDA is used. Adhesiveness with a mutual laminated film etc. can be improved. PSS is poly (sodium 4-styrenesulfonate), and PDDA is poly (diallyldimethylammonium) chloride.
Similarly, the SO ₃ H group has an O atom having a negative charge in the substituent, and the NH ₂ group becomes an NH ₃ group and has a positive charge in the substituent. It can be expressed, and the adhesion to the chemical conversion treatment film and the mutual laminated film made of PSS / PDDA can be enhanced. Furthermore, since the imidazolium group, pyridinium group, SO ₃ H group, and NH ₂ group impart water solubility to the Y—R ² —X compound, an aqueous solvent can be used when forming a self-assembled film. Is easy to form.

YR ² -X can also form a self-assembled film made of a bimolecular film. That is, the metal ion is coordinated to the Y group of the monomolecular film consisting of Y-R 2 ^-X, be to further coordinating the Y group of another Y-R 2 ^-X in the metal ion, the metal ion A bilayer film as a center can be formed. In this case, the outermost surface of the bimolecular film is an X group. As a metal ion, any one kind of metal of Hf, Ti, and Zn can be illustrated. There are no particular restrictions on the substituents X and Y in the case of constituting a bimolecular film, but a PO (OH) ₂ group is particularly preferred.

Next, various non-chromate films can be used as the chemical conversion treatment film.
As an example, a film (coating (1)) containing two or more of silica, a silane coupling agent, tannin or tannic acid, a zirconium compound, and a titanium compound and a resin can be used.
As another example, a film (film (2)) containing an aqueous resin and a silane coupling agent can also be used.
As still another example, a film (film (3)) containing an aqueous resin and tannin or tannic acid can be used.
By forming the chemical conversion treatment film, the coating film adhesion can be improved and the corrosion resistance can be improved. Moreover, since these chemical conversion treatment films are all non-chromate films, the problem of toxicity of hexavalent chromium can be avoided. The chemical conversion treatment film is not limited to the above example.

If the film (1) does not contain a resin, the coating film adhesion during molding may be inferior. Moreover, there is a possibility that the coating film adhesion may be inferior even if only one of silica, silane coupling agent, tannin or tannic acid, zirconium compound, and titanium compound and the resin are used.
As the resin used for the film (1), generally known resins such as a polyester resin, an acrylic resin, a urethane resin, and an epoxy resin can be used. These resins are more preferably water-soluble or water-dispersed types because the treatment liquid is easy to handle.

  A silica having a particularly fine particle size as the coating (1) is more preferable because it can maintain stability when dispersed in a chemical conversion solution. For example, silica gel such as `` Snowtex N '', `` Snowtex C '', `` Snowtex UP '', `` Snowtex PS '' (all manufactured by Nissan Chemical Industries), `` Adelite AT-20Q '' (produced by Asahi Denka Kogyo), Alternatively, powdered silica such as Aerosil # 300 (manufactured by Aerosil Japan) can be used.

  The tannin or tannic acid used for the film (1) may be a tannin that can be hydrolyzed or a condensed tannin, or a part of them may be decomposed. Tannin or tannic acid is not particularly limited, such as Hamametatannin, pentaploid tannin, gallic tannin, myrobalan tannin, dibibi tannin, argaroviran tannin, valonia tannin, catechin, etc., but `` tannic acid: AL '' ( When using Fuji Chemical Industry Co., Ltd., the processing adhesion of the coating film is particularly improved.

Examples of the silane coupling agent used for the film (1) include γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, and γ- (2-aminoethyl). Aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropylmethyldiethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyl Dimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (N- Vinylbenzylaminoethyl) -γ-aminopropylmethyldimethoxysilane, N-β- (N-vinylbenzylamino) Minoethyl) -γ-aminopropyltriethoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyl Dimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltriethoxysilane, γ- Mercaptopropylmethyldiethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane , Γ-chloropropyltriethoxysilane, γ-chloropropylmethyldiethoxysilane, hexamethyldisilazane, γ-anilinopropyltrimethoxysilane, γ-anilinopropylmethyldimethoxysilane, γ-anilinopropyltriethoxysilane , Γ-anilinopropylmethyldiethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride, octadecyldimethyl [ 3- (methyldimethoxysilyl) propyl] ammonium chloride, octadecyldimethyl [3- (triethoxysilyl) propyl] ammonium chloride, octadecyldimethyl [3- (methyldiethoxysilyl) propyl] ammoni Mukuroraido, .gamma.-chloropropyl methyl dimethoxy silane, .gamma.-mercaptopropyl methyl dimethoxy silane, methyl trichlorosilane, dimethyl dichlorosilane, trimethyl chlorosilane or the like.

  Zirconyl ammonium carbonate, zircon hydrofluoric acid, zircon ammonium fluoride, zircon fluoride, sodium zircon fluoride, zirconium acetylacetonate, zirconium butoxide 1-butanol solution, zirconium n-propoxide Etc. can be used.

  Titanium compounds used in the coating (1) include titanium hydrofluoric acid, ammonium titanium fluoride, potassium potassium oxalate, titanium isopropoxide, isopropyl titanate, titanium ethoxide, titanium 2-ethyl 1-hexanolate, and tetra titanate. Isopropyl, tetra n-butyl titanium potassium titanate fluoride, sodium titanium fluoride, etc. can be used.

The blending ratio of the resin and the two or more kinds of silica, silane coupling agent, tannin or tannic acid, zirconium compound, and titanium compound contained in the film (1) is not particularly specified, It can be appropriately selected as necessary. When the chemical conversion treatment solution is water-soluble, the resin addition amount is 1.0 to 100 g / L, and any two or more of silica, silane coupling agent, tannin or tannic acid, zirconium compound, and titanium compound are 0.01 to 100 g / L, respectively. What was dried by applying the chemical conversion solution contained on a metal plate is excellent. If the amount of resin added is less than 1.0 g / L, there is a possibility that the effect on corrosion resistance and coating film adhesion may not be exerted, and if it exceeds 100 g / L, the stability as a chemical conversion treatment solution becomes poor and gelation tends to occur. Similarly, the addition amount of silica, silane coupling agent, tannin or tannic acid, zirconium compound, and titanium compound may not exert an effect on corrosion resistance and coating film adhesion if it is less than 0.01 g / L, and it exceeds 100 g / L. The stability as a chemical conversion treatment solution becomes poor and gelation tends to occur.
The amount of the coating (1) attached is not particularly specified, but it is more preferable that the total solid weight is in the range of 10 to 500 mg / m ² . If it is less than 10 mg / m ² , the corrosion resistance may be inferior or the adhesion of the coating film may be reduced. If it exceeds 500 mg / m ² , the adhesion of the coating film may be reduced.

  Next, the film (2) contains a silane coupling agent based on an aqueous resin. The aqueous resin includes, in addition to water-soluble resins, those that are essentially water-insoluble but can be in a state in which the insoluble resin is finely dispersed in water, such as emulsions and suspensions (water-dispersible resins). Examples of water-based resins include polyolefin resins, acrylic olefin resins, polyurethane resins, polycarbonate resins, epoxy resins, polyester resins, alkyd resins, phenol resins, and other thermosetting resins. It is desirable that the resin be crosslinkable. Particularly preferred resins are acrylic olefin resins, polyurethane resins, and mixed resins thereof. Two or more of these aqueous resins may be mixed or polymerized for use.

  The silane coupling agent dramatically improves the coating film adhesion in the presence of the aqueous resin, and consequently improves the corrosion resistance. As the silane coupling agent, those similar to the coating (1) can be used.

  It is preferable that content of a silane coupling agent is 0.1-3000 weight part with respect to 100 weight part of aqueous resin in conversion of solid content. If it is less than 0.1 part by weight, sufficient coating film adhesion cannot be obtained during processing, and the corrosion resistance is not sufficient. When it exceeds 3000 parts by weight, the adhesion of the coating film decreases.

  When fine silica is further added to the film (2), the rust prevention action (corrosion resistance) is promoted. As the fine silica, the same silica as in the case of the film (1) may be used. The content of the fine silica is preferably 1 to 2000 parts by weight, more preferably 10 to 400 parts by weight, based on 100 parts by weight of the aqueous resin, in terms of solid content. If it is less than 1 part by weight, the effect of addition is small, and if it exceeds 2000 parts by weight, the effect of improving corrosion resistance is saturated, which is uneconomical.

  Moreover, when an etching fluoride is added to the film (2), the coating film adhesion is improved. Here, as the etching fluoride, zinc fluoride tetrahydrate, zinc hexafluorosilicate hexahydrate, or the like can be used. The content of the etching fluoride is preferably 1 to 1000 parts by weight with respect to 100 parts by weight of the aqueous resin in terms of solid content. If it is less than 1 part by weight, the effect of addition is small, and if it exceeds 1000 parts by weight, the effect of improving the adhesion of the coating film is saturated, which is uneconomical.

The amount of the coating (2) when it is dried is preferably 10 mg / m ² or more. If it is less than 10 mg / m ² , the rust preventive power is insufficient. On the other hand, if the adhesion amount is too large, it is not only uneconomical as a chemical conversion film, but also the adhesion of the coating film is lowered. The upper limit of the film thickness is preferably 3000 mg / m ² or less.

  Next, the film (3) is a film containing tannin or tannic acid based on an aqueous resin. As the aqueous resin, tannin and tannic acid, the same materials as those described in the film (1) or film (2) may be used. Furthermore, fine silica may be added in the same manner as the coating (2).

  Further, as the chemical conversion treatment film, JP-A-9-828291, JP-A-10-251509, JP-A-10-337530, JP-A2000-17466, JP-A-2000-248385, JP2000-2000A. Chemical conversion treatment films described in JP-A Nos. 273659 / 2000-282252 and the like may be used.

  The chemical conversion film can be formed by applying the chemical conversion liquid to the galvanized steel sheet after forming the self-assembled film by a coating method such as dip coating, roll coater coating, ringer roll coating, brush coating or spray coating. . After application, forced drying or baking may be performed as necessary.

  Next, the anticorrosive coating is one or more of (A) calcium ion exchanged silica, (B) aluminum dihydrogen phosphate, and (C) magnesium phosphate or magnesium tripolyphosphate phosphated. Are essential components, and the total amount of (A), (B), (C) is preferably 60 parts by mass or more and 160 parts by mass or less with respect to 100 parts by mass of the resin solid content in the anticorrosive coating.

  Calcium ion-exchanged silica is very effective for improving corrosion resistance, but is not suitable by itself because it is highly soluble in water and easily elutions from the coating film in a highly humid environment. In addition, when aluminum tripolyphosphate is used alone, regardless of the presence or absence of magnesium treatment, in a corrosive environment with a high wet rate, a large coating bulge is likely to occur in spots from the end face of the galvanized steel sheet.

  On the other hand, aluminum dihydrogen tripolyphosphate has the effect of suppressing the excessive elution of rust-preventing pigments that use this together, so combining them together achieves a certain degree of compatibility between corrosion resistance and planar blister suppression in a highly humid environment. However, there is a limit to the amount of addition in the coating film, and if it is added too much, the flat blister resistance in a highly humid environment decreases. Therefore, the combined use of a compound containing magnesium, aluminum dihydrogen tripolyphosphate and calcium ion exchanged silica is essential. As the compound containing magnesium, magnesium phosphate and aluminum dihydrogen tripolyphosphate subjected to magnesium treatment are effective in suppressing excessive dissolution of the rust preventive pigment.

  Furthermore, if the total amount of these rust inhibitors is less than 60 parts by mass with respect to 100 parts by mass of the resin solid content in the rust-preventive coating film, the corrosion resistance in a high wet environment is lowered, which is inappropriate. If the content is more than part by mass, the organic resin content in the coating film decreases, so that the adhesion between the coating film and the steel sheet, particularly the adhesion at the processed part, is unsuitable.

  The ratio of calcium ion exchanged silica, aluminum tripolyphosphate, magnesium phosphate and aluminum dihydrogen tripolyphosphate treated with magnesium is not particularly defined and can be appropriately selected as necessary. In order to prevent the corrosion resistance from being lowered, it is preferable that 10 mass% or more of calcium ion-exchanged silica is added to the anticorrosive coating film, and 30 mass% or more is more preferable. Further, in order to prevent the occurrence of flat blisters in a highly humid environment, it is preferable that 1% by mass or more of aluminum tripolyphosphate subjected to magnesium treatment is added to the anticorrosive coating film, and 5% by mass or more is preferable. More preferred.

  In addition to calcium ion-exchanged silica and magnesium-treated aluminum dihydrogen phosphate, the rust-preventing coating film of the present invention may contain other rust-preventing pigments. However, rust preventive pigments containing hexavalent chromium are environmentally hazardous substances and are not suitable. Furthermore, if the total addition amount of these rust preventive pigments is less than 60 parts by mass with respect to 100 parts by mass of the resin solid content in the rust preventive coating film, it is unsuitable because the corrosion resistance in a high wet environment decreases. If it exceeds 160 parts by mass, the organic resin content in the coating film decreases, so that the adhesion between the coating film and the metal plate, particularly the adhesion at the processed part, is unsuitable.

  Non-hexavalent chromium-based rust preventives other than calcium ion exchanged silica, aluminum trihydrogen phosphate, magnesium phosphate, magnesium tripolyphosphate treated with magnesium, such as zinc phosphate, Zinc phosphate, molybdate, calcium phosphate, vanadic acid / phosphoric acid combination pigment (generally called VP pigment), and the like can be used.

  As the resin binder of the anticorrosive coating, for example, a resin for paint such as a polyester resin, an epoxy resin, a urethane resin, an acrylic resin, or a fluorine resin can be used. In particular, a polyester-based resin is more preferable because it has excellent processability. In addition, a polyester resin having a number average molecular weight of 3000 to 30000 and a glass transition temperature of 0 to 60 ° C. is more preferable because it has better processability. Examples of the polyester resin include oil-free polyester resin, alkyd resin, linear polymer polyester resin, and branched polymer polyester resin.

It is more preferable to add an epoxy resin to the polyester resin because the coating film adhesion is greatly improved. As the epoxy resin, an epoxy resin “Epicron ^™ ” manufactured by Dainippon Ink & Chemicals, Inc. can be used. It is preferable that the addition amount of the epoxy resin solid content is 0.1 to 20 mass parts with respect to 100 mass parts of the polyester resin solid content. If it is less than 0.1 parts by mass, the adhesion may not be effective, and if it exceeds 20 parts by mass, the workability may be inferior.

  Moreover, the resin binder of a rust prevention coating film can use a melamine resin or isocyanate as a crosslinking agent. In the case of the melamine resin, 5 to 70 parts by mass is preferable with respect to 100 parts by mass of the main resin such as a polyester resin in a solid content ratio. If it is less than 5 parts by mass, the coating film may be uncured and the adhesion may be reduced. If it exceeds 70 parts by mass, the coating film may become too hard and the workability may be reduced. In addition, the amount added in the case of isocyanate is more preferably [NCO group equivalent of isocyanate] / [OH group equivalent of polyester resin] = 0.8 to 1.2. When the value of [NCO group equivalent of isocyanate] / [OH group equivalent of polyester resin] is less than 0.8 or more than 1.2, the film may be uncured during film formation. When these crosslinking agents are used, a catalyst can be added as necessary.

  Next, the coating film can use what added the color pigment etc. to the resin for coating materials, and can use the above-mentioned resin for rust prevention coating films. In particular, a type in which a polyester resin is cross-linked with a melamine resin or an isocyanate is more preferable because it is excellent in processability. The thickness of the coating film is not particularly specified, but is preferably 1 to 30 μm. If it is less than 1 μm, the function as a top coat film (for example, coloring property) may not be obtained, and if it exceeds 30 μm, a coating defect called “WAKI” may occur during baking. To these top coat films, generally known color pigments, leveling agents, pigment dispersants, waxes, matting agents and the like can be added as necessary. The type and amount of these additives are not particularly defined and can be appropriately selected as necessary.

Examples of coating methods for rust-preventive coatings and coatings include roll coating, curtain flow coating, roller curtain coating, die coating, air spray, airless spray, electrodeposition coating, powder coating, dipping, bar coating, brush coating, etc. Can be done. However, it is more suitable to apply on a continuous coating line called a general coil coating line or sheet coating line complete with roll coat, curtain flow coat, and roller curtain coat, because the painting work efficiency is high and mass production is possible. . As a method for drying and baking the paint, generally known drying and baking methods such as a hot air oven, a direct flame oven, a salt infrared oven, an induction heating oven, and the like can be used.
In addition, when the corrosion resistance requested | required of a precoat galvanized steel plate is not high, you may abbreviate | omit a rust prevention coating film.

Next, the manufacturing method of the surface treatment galvanized steel plate of this embodiment is demonstrated.
First, in order to form a self-assembled film on a galvanized layer of a galvanized steel sheet, a compound represented by the chemical formula of R ¹ —X or Y—R ² —X is added to a solvent to prepare a treatment solution. . Examples of the solvent include alcohols such as water, methyl alcohol, and ethyl alcohol. The adjusted treatment liquid is applied to the galvanized layer of the steel sheet. As a coating method, means such as a spray method or a roll coating method can be used. After application of the treatment liquid, the solvent may be removed by drying, or after application, the excess treatment liquid may be washed away with water and dried. A few minutes after applying the treatment liquid, a self-assembled film made of R ¹ —X or Y—R ² —X is formed. As described above, the surface-treated galvanized steel sheet according to this embodiment is manufactured.

  Furthermore, the precoat galvanized steel sheet of this embodiment is manufactured by forming a chemical conversion treatment film, a rust prevention coating film, and a coating film in order as needed.

According to the surface-treated galvanized steel sheet of this embodiment, the self-assembled film is formed on the galvanized layer. Since the surface of this self-assembled film is hydrophobic, the corrosion resistance of the galvanized steel sheet can be improved. Further, R ¹ -X or YR ² -X constituting the self-assembled film is provided with an X group, and this X group is strongly adsorbed on the galvanized layer of the steel sheet. Adhesion can be increased.
Furthermore, according to the precoated galvanized steel sheet of the present embodiment, the adhesion of the chemical conversion film to the steel sheet can be enhanced by forming the chemical conversion film on the self-assembled film. In particular, by forming a self-assembled film composed of Y—R ² —X and selecting a functional group having an affinity for the chemical conversion treatment film as the Y group, the adhesion of the chemical conversion treatment film can be further enhanced. I can do it.

Further, by forming a self-assembled film composed of Y—R ² —X and selecting a functional group having affinity for the chemical conversion treatment film as the Y group, the adhesion of the chemical conversion treatment film can be further enhanced. I can do it.
For example, when a functional group having a Si (OC ₂ H ₅ ) ₃ group or a carbon triple bond is used as the substituent Y, adjacent Y groups form a chemical bond, and are self-organized as a monomolecular film. The strength of the chemical film can be further increased.
In addition, when an imidazolium group, a pyridinium group, a SO ₃ H group, or an NH ₂ group is used as the substituent Y, an electrostatic interaction is expressed with another film laminated on the self-assembled film. It is possible to improve the adhesion to the chemical conversion film or the mutual laminated film made of PSS / PDDA.

Moreover, according to the manufacturing method of the surface-treated galvanized steel sheet and pre-coated galvanized steel sheet according to the present embodiment, self-organization can be achieved simply by applying a treatment liquid containing R ¹ -X or Y-R ² -X to the galvanized layer. A film is formed, and depending on the concentration of the treatment liquid, the formation speed is as fast as several tens of seconds to several minutes, so that the treatment time is shortened and productivity can be increased. Moreover, since processing time is short, another process can be performed immediately after formation of a self-organization film | membrane, and the productivity of a precoat galvanized steel sheet can be improved more.

1. Galvanized steel sheet The following galvanized steel sheets were used as test materials.
Low-weight galvanized steel sheet (GI low) :
Plate thickness 0.6mm, zinc adhesion 60g / m ² per side (plating on both sides)

2. Treatment liquid for self-assembled film The following was prepared as a treatment liquid for the self-assembled film used for the test specimens.
Treatment liquid for self-assembled film (A) :
1-octanol (C ₈ H ₁₇ OH) methanol solution (concentration 0.5 mmol / L)
Treatment liquid for self-assembled film (B) :
n-octanoic acid (C ₇ H ₁₅ COOH) in methanol solution (concentration 0.5 mmol / L)
Treatment liquid for self-assembled film (C) :
1-octylamine (C ₈ H ₁₇ NH ₂ ) methanol solution (concentration 0.5 mmol / L)
Treatment liquid for self-assembled film (D) :
Methanol solution (concentration 0.5 mmol / L) of octyltrimethoxysilane (C ₈ H ₁₇ Si (OCH ₃ ) ₃ )
Treatment liquid for self-assembled film (E) :
n-octylphosphonic acid (C ₈ H ₁₇ PO (OH) ₂ ) in methanol solution (concentration 0.5 mmol / L)
Processing solution for self-assembled film (F) :
1-octanethiol (C ₈ H ₁₇ SH) in methanol solution (concentration 0.5 mmol / L)

3. Chemical conversion liquid The following chemical conversion liquids were prepared for the test materials.
Chemical conversion solution (A) :
“CTE300N” manufactured by Nippon Parkerizing Co., Ltd., which is a commercially available coating chromate treatment, was used.
Chemical conversion solution (B) :
“Palbond” manufactured by Nippon Parkerizing Co., Ltd., which is a commercially available zinc phosphate treatment, was used.

4. anticorrosive coating is manufactured by Toyobo amorphous polyester resin "Vylon ^TM 270", an organic solvent (cyclohexanone at a weight ratio:: Solvesso 150 = 1 the use of a mixture in 1), a resin solids It dissolved so that a density | concentration might be 30 mass%. Next, a melamine resin “Cymel ^™ 303” manufactured by Mitsui Cytec was added as a curing agent. The addition amount of the melamine resin was added so that the mass ratio of the resin solid content was polyester resin solid content: melamine resin solid content = 80: 20. In addition, 5 parts by mass of an epoxy resin “Epicron ^TM 1000” manufactured by Dainippon Ink Co., Ltd. with respect to 100 parts by mass of the polyester resin solid content was added to the mixed solution of the polyester resin and the melamine resin. “Epiclon ^™ 1000” was added in advance after being mixed with an organic solvent (using a mixture of cyclohexanone: solvesso 150 = 1: 1 by mass). Further, 0.5% by mass of an acidic catalyst “Catalyst ^™ 600” manufactured by Mitsui Cytec Co., Ltd. was added to the mixed solution of the polyester resin and the melamine resin, and these were stirred to obtain a clear paint.

  Next, in this clear paint, Teca's Mg-treated aluminum dipolyphosphate "K-WHITE K-G105" (hereinafter referred to as Mg-P-Al), Grace's calcium ion-exchanged silica `` Shieldex C303 '' (hereinafter referred to as Ca-Si), Zn-treated aluminum dihydrogen triphosphate `` K-WHITE K- # 105 '' (hereinafter referred to as Zn-P-Al), reagent phosphoric acid 2 A required amount of magnesium hydrogen (hereinafter referred to as P-Mg) was added and stirred to obtain a rust preventive paint. In addition, as a comparison, a rust-preventing paint to which commercially available strontium chromate (hereinafter referred to as Cr) was added was also prepared. The details of the prepared primer paint, the added pigment type and the added amount are shown in Table 1.

5. Top coat “FL100HQ” made by Nippon Paint Co., Ltd., which is a commercially available polyester top coat. The color used was white.
6. Back side paint “FL100HQ” made by Nippon Paint Co., Ltd., a commercially available polyester-based top coat was used. The color used was gray.

7. Preparation of surface-treated galvanized steel sheet The galvanized steel sheet was degreased by ultrasonic cleaning in isopropanol for 5 minutes and then washed with methanol.
Then, the washed galvanized steel sheet was immersed in the treatment liquids (A) to (F) for the self-assembled film, washed with ultrapure water, and dried in nitrogen. In this way, a surface-treated galvanized steel sheet was prepared.

The obtained surface-treated galvanized steel sheet was subjected to surface elemental analysis by XPS, contact angle to water, evaluation of membrane resistance by AC impedance measurement.
The contact angle with respect to water was evaluated with ultrapure water using a FACE CA-X type manufactured by Kyowa Interface Science Co., Ltd.
The AC impedance measurement is performed using a surface-treated galvanized steel sheet as a working electrode, a platinum wire as a counter electrode, Ag / AgCl as a reference electrode, a 0.1 M Na2SO4 solution as a solvent, an amplitude potential of ± 10 mV at an open circuit potential, and a frequency of It carried out at 0.01-1.0 * 10 < ⁶ > Hz.
In the XPS analysis, Al monochrome X-ray was used as the X-ray source, and correction was performed with C1s (285 eV). The measurement chamber was 1 × 10 ⁻⁹ torr.
Table 2 shows the evaluation results of the contact angle with respect to water.

Moreover, corrosion resistance was evaluated about the obtained surface-treated galvanized steel sheet.
The evaluation was performed according to the following procedure. Each sample was cut into a size of 50 mm × 100 mm and the end face was sealed (planar plate). Further, each sample was cut into a size of 50 mm × 100 mm, and a center part subjected to 7 mm Erichsen extrusion from the back surface was prepared (Ericsen plate). These were used as test pieces.
About these test pieces, the salt spray test was implemented by the method of 9.1 of JISK5400. The test time was 24 hours. The evaluation was carried out at the ratio of the area where rust was generated in each of the flat part and the elixir part. The flat portion was evaluated as ◎ when the rust generation area was less than 1%, ◯ when it was 1% or more and less than 10%, Δ when it was 10% or more and less than 50%, and × when it was 50% or more. The Erichsen part was evaluated as ◎ when the rust generation area was less than 10%, ◯ when it was 10% or more and less than 30%, Δ when it was 30% or more and less than 70%, and × when it was 70% or more. The results are shown in Table 3.

As shown in Table 2, a particularly high contact angle was obtained when the X group was COOH, PO (OH) ₂ or SH.
In the AC impedance measurement, when the membrane resistance values are arranged in descending order, PO (OH) ₂ , SH, OH, COOH, Si (OMe) ₃ , NH ₂ are in this order, and PO (OH) ₂ , SH is particularly high. Showed resistance. It is considered that a good film was formed for PO (OH) ₂ and SH.
Further, from XPS measurement, the presence of P = O bonds in P2p orbits and O1s orbitals was confirmed in PO (OH) ₂ , and the presence of S—H and S—Zn bonds in S2p orbitals was confirmed in SH.

  Moreover, as shown in Table 3, the sample in which the self-assembled film was formed had good corrosion resistance. Furthermore, when a chemical conversion treatment film was further formed on the self-assembled film, the corrosion resistance was further improved. On the other hand, the corrosion resistance of the sample that did not form the self-assembled film was not improved.

8. Preparation of pre-coated galvanized steel sheet Various surface-treated galvanized steel sheets were manufactured in the same manner as in 7. above.
Next, a chemical conversion treatment liquid (A) or (B) was applied onto these surface-treated galvanized steel sheets with a coating bar and dried in a hot air drying furnace to obtain a chemical conversion treatment film. The dry adhesion amount of chemical conversion treatment (A) is
100 mg / m ² . The ultimate plate temperature during chemical conversion treatment drying was 60 ° C. The amount of chemical conversion treatment (B) was such that the amount of zinc phosphate deposited was 2 g / m ² . The ultimate plate temperature during the chemical conversion treatment drying was 60 ° C.

  Next, the rust preventive paint is applied with a roll coater so that the film thickness after drying is 10 μm, and the other side is coated with a back coat with a roll coater so that the film thickness after drying is 5 μm. The coating layer was obtained by drying and curing under the condition that the ultimate temperature of the metal plate was 210 ° C. in an induction heating furnace in which hot air was blown. Water was sprayed on the metal plate painted after dry baking, and then cooled with water. Furthermore, on top of the anti-corrosion coating, the top coat is applied with a roll coater so that the film thickness after drying is 15 μm, and the ultimate temperature of the metal plate is 230 ° C. in an induction heating furnace blown with hot air. Dry baking was performed under the conditions. The pre-coated galvanized steel sheet as the test material was obtained by wiping water on the metal plate coated after dry baking with a spray and cooling with water.

  The following evaluation test was carried out on the precoated galvanized steel sheet thus produced. In addition, about any test, the test was implemented by making the surface which has a rust prevention coating film into an evaluation surface.

I. Coating Film Processability Test The prepared precoated galvanized steel sheet was subjected to 180 ° folding, and the coating film in the processed part was observed with a 20-fold loupe to examine whether the coating film was cracked. The bending process was 0T in an atmosphere of 20 ° C.
Evaluation of coating film cracking was evaluated as ◯ when there was no coating film cracking, △ when there was a very small crack in the coating film, and x when there was a clear large crack on the entire processed part visually. . Furthermore, after a tape was affixed on the coating film of a process part, the coating film was peeled and the coating film residual state after peeling was observed. The evaluation after peeling is ○ when the coating film is not peeled at all over the processed part, △ when the coating film is peeled off at a part of the processed part, and when the entire coating film is peeled off X was evaluated.

II. Corrosion resistance test The prepared pre-coated galvanized steel sheet was cut into a size of 70 mm in width and 150 mm in length, and for the end face of the long side, the return (burr) at the time of cutting came to the surface coated with the back coating (below A sample for corrosion resistance test was prepared by cutting (to form burrs) and sealing the lateral end face portions with tape. And the salt spray test was implemented by the method of 9.1 of JIS K 5400. The salt water was sprayed so as to wipe the surface having the anticorrosive coating film. The test time was 500 hours. In this experiment, cut scratches that reach the base of the test piece from above the coating film were not provided.

  After completion of the test, measure the average bulge width of the end face of the vertical side where the end face is not tape-sealed, ◎ if the average bulge width is 2 mm or less, ○ if it is more than 2 mm and 3 mm or less, if it is more than 3 mm and 5 mm or less In the case of Δ and over 5 mm, it was evaluated as ×.

  The average bulge width of the end face is divided into 10 mm sections (total of 15 sections) with a 150 mm vertical side, the maximum bulge width in each section is measured, and the maximum bulge width in each section is the total number of sections. The value obtained by dividing by was used as the average swelling width.

III. Moisture resistance test The prepared pre-coated galvanized steel sheet was cut into a size of 70 mm x 150 mm, and all cut end surfaces were sealed with tape to prepare a sample for corrosion resistance test. Then, a moisture resistance test was performed by the method described in 9.2 of JIS K 5400. The moisture resistance test was conducted for 1000 hours. In this experiment, cut scratches that reach the base of the test piece from above the coating film were not provided.

  After the test, observe the degree of blistering on the surface of the coating film. If no blistering was observed, ◯, if several very small blisters were observed, △, blistering on the front of the test piece. When it was recognized, it evaluated as x.

  Next, the adhesive cross-cut tape method described in 8.5.2 of JIS K 5400 is carried out. If the evaluation standard of the same JIS is 6 points or more, ○, if 4 points, △, 0 points to 2 points The case of was evaluated as x.

Details of the evaluation results will be described below.

  Table 4 shows the evaluation results of the precoated galvanized steel sheet. It turns out that the precoat galvanized steel plate of an Example is excellent in all of workability, corrosion resistance, and moisture resistance compared with a comparative example.

Claims (6)

A surface-treated galvanized steel sheet, wherein a self-assembled film formed by applying a compound represented by a chemical formula of R ¹ —X or Y—R ² —X is formed on the surface of a galvanized layer.
[However, R ¹ is a linear alkyl group having 3 to 20 carbon atoms, R ² is a linear alkylene group having 3 to 20 carbon atoms, and X is either a PO (OH) ₂ group or an OH group. And Y is any one of PO (OH) ₂ group, imidazolium group, pyridinium group, and SO ₃ H group. ] 2. The surface-treated galvanized steel sheet according to claim 1 , wherein a mutual laminated film made of PSS / PDDA is formed on the self-assembled film. A precoated galvanized steel sheet comprising a chemical conversion film and a coating film laminated on the self-assembled film of the surface-treated galvanized steel sheet according to claim 1 . A surface characterized by forming a self-assembled film by applying a compound represented by the chemical formula of R ¹ —X or Y—R ² —X to the surface of a galvanized layer and then drying or washing with water. A method for producing a treated galvanized steel sheet.
[However, R ¹ is a linear alkyl group having 3 to 20 carbon atoms, R ² is a linear alkylene group having 3 to 20 carbon atoms, and X is either a PO (OH) ₂ group or an OH group. And Y is any one of PO (OH) ₂ group, imidazolium group, pyridinium group, and SO ₃ H group. ] 5. The method for producing a surface-treated galvanized steel sheet according to claim 4 , wherein a mutual laminated film made of PSS / PDDA is formed on the self-assembled film. A method for producing a pre-coated galvanized steel sheet, comprising: laminating a chemical conversion film and a coating film on the self-assembled film of the surface-treated galvanized steel sheet produced by the production method according to claim 4 .