JP2000144446A - Organic-coated steel sheet excellent in corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic-coated steel sheet capable of giving excellent corrosion resistance and most suitably used for automobile use, household electrical appliance use, building material use or the like. SOLUTION: A chromate film having (1 to 1,000) mg/m2 chromium coating weight expressed in terms of metal chromium is formed on the surface of a galvanized steel sheet or an aluminum coated steel sheet. Further, an organic film of 0.1-5 μm film thickness, containing ion exchange silica (a) in an amount of 1-100 pts.wt. (solid content) based on 100 pts.wt. (solid content) of film forming organic resin (A) is formed on the above chromate film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organically coated steel sheet having excellent corrosion resistance and suitable for use in automobiles, home appliances, building materials and the like.

[0002]

2. Description of the Related Art For the purpose of improving corrosion resistance (white rust resistance, red rust resistance) on the surface of a zinc-based steel sheet or an aluminum-based steel sheet as a steel sheet for home appliances, a steel sheet for construction materials, and a steel sheet for automobiles. BACKGROUND ART A surface-treated steel sheet having a chromate film and an organic film thereon is widely used.

[0003] In recent years, waste disposal of products such as home electric appliances and automobiles has become a major problem due to environmental problems, and reducing the amount of waste is becoming a social issue. In particular, since the processing capacity of the final disposal site for waste is becoming limited, demands for recycling and reuse of parts are increasing. Against this background, there is an increasing demand for a surface-treated steel sheet as a material, which is capable of being reused, that is, a steel sheet having a long life and excellent corrosion resistance.

[0004] Against this background, the following techniques have been disclosed for the purpose of improving the corrosion resistance of galvanized steel sheets. (1) A chromate film, a resin such as an ethylene-acrylic copolymer, and a blocked isocyanate have a particle size of 2-1.
Steel plate (Japanese Patent Publication No. 8-11215) having a resin layer containing a water-dispersed sol such as ₂ μm of SiO ₂ , (2) a chromate film, a resin obtained by copolymerizing olefin and acrylic acid, and a particle diameter of 1 to 10 μm Steel sheet having a film containing colloidal silica (JP-A-8-243488)

[0005]

However, sufficient corrosion resistance cannot be obtained only by specifying the particle size of the organic resin and silica as in the prior arts (1) and (2).
That is, the corrosion resistance obtained with these surface-treated steel sheets is as follows:
It does not exceed the level of corrosion resistance of the conventionally used organic composite film composed of organic resin and silica, and therefore does not significantly extend the life of the steel sheet.
Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide an organic-coated steel sheet having excellent corrosion resistance.

[0006]

Means for Solving the Problems As a result of intensive studies by the present inventors to solve the above-mentioned problems, a chromate film is formed on the surface of a zinc-based steel sheet or an aluminum-based steel sheet and specified as an upper layer. It has been found that an organic coated steel sheet having extremely excellent corrosion resistance can be obtained by forming an organic film containing a rust preventive additive. The present invention has been made based on such knowledge, and the characteristic configuration thereof is as follows.

[1] A chromate film having a chromium equivalent of 1 to 1000 mg / m ^{2 in} terms of metallic chromium is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. A) 100 parts by weight (solid content) of ion-exchanged silica (a) is 1 to 1
An organic coated steel sheet having excellent corrosion resistance, characterized by having an organic film having a thickness of 0.1 to 5 μm containing 00 parts by weight (solid content).

[2] A chromate film having a chromium equivalent of 1 to 1000 mg / m ^{2 in} terms of chromium metal is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. A) The ion-exchanged silica (a) contains the ion-exchanged silica (a) and the fine particle silica (b) in a total amount of 1 to 100 parts by weight (solids) with respect to 100 parts by weight (solids). Characterized in that it has an organic coating film having a weight ratio (a) / (b) of 1/99 to 99/1 with respect to the content (solid content) of the fine silica (b) and the fine particle silica (b) and a film thickness of 0.1 to 5 μm. Organic coated steel sheet with excellent corrosion resistance.

[3] A chromate film having a chromium equivalent of 1 to 1000 mg / m ^{2 in} terms of chromium metal is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. A) 100 parts by weight (solid content) of ion-exchanged silica (a) is 1 to 1
An organic coating having excellent corrosion resistance, characterized by having an organic film having a thickness of 0.1 to 5 μm containing 00 parts by weight (solid content) and 1 to 80 parts by weight (solid content) of the solid lubricant (c). steel sheet.

[4] A chromate film having a chromium equivalent of 1 to 1000 mg / m ^{2 in} terms of metallic chromium is formed on the surface of a zinc-based or aluminum-plated steel sheet, and a film-forming organic resin ( A) 100 parts by weight (solid content), ion-exchanged silica (a) and fine-particle silica (b) in a total of 1 to 100 parts by weight (solid content), and solid lubricant (c) in 1 to 100 parts by weight. 80 parts by weight (solid content), and the weight ratio (a) / (b) of the content (solid content) of the ion-exchanged silica (a) and the fine particle silica (b) is 1
An organic-coated steel sheet having excellent corrosion resistance, comprising an organic film having a thickness of 0.1 to 5 μm, which is / 99 to 99/1.

[5] In the organic-coated steel sheet according to any one of the above [1] to [4], the film-forming organic resin (A) has an OH group and / or
Or an organic coated steel sheet having excellent corrosion resistance, which is an organic polymer resin having a COOH group. [6] The organic coated steel sheet having excellent corrosion resistance, wherein the organic polymer resin is a thermosetting resin in the organic coated steel sheet according to the above [5].

[7] The organically coated steel sheet according to the above [6], wherein the thermosetting resin is an epoxy resin and / or a modified epoxy resin. [8] In the organic-coated steel sheet according to any one of the above [1] to [7],
An organic coated steel sheet having excellent corrosion resistance, wherein the chromate film is formed by a chromate treatment composition having a hexavalent Cr / total Cr concentration of 0.1 or less. [9] In the organic-coated steel sheet according to any one of the above [1] to [8],
An organic-coated steel sheet having excellent corrosion resistance, wherein the ion-exchanged silica in the organic coating is Ca-exchanged silica. [10] The organic-coated steel sheet according to [9], wherein the Ca-exchanged silica has an average particle size of 4 μm or less, and has excellent corrosion resistance. [11] The organic-coated steel sheet according to the above [9] or [10], wherein
An organic-coated steel sheet having excellent corrosion resistance, wherein the Ca concentration of the exchanged silica is 2 to 8 wt%.

The basic features of the organic coated steel sheet of the present invention are as follows:
A chromate film is formed on a surface of a galvanized steel sheet or a galvanized steel sheet with a predetermined adhesion amount, and a film-forming organic resin (A), preferably an organic polymer resin having an OH group and / or a COOH group, is formed thereon. (More preferably a thermosetting resin, particularly preferably an epoxy resin and / or a modified epoxy resin) to form an organic film in which an appropriate amount of ion exchange silica (a) is added as a rust preventive additive.

By incorporating ion-exchanged silica (a) as an anticorrosive additive into the organic film, a self-healing function at the film defect can be imparted to the organic film. That is, when cations such as Na ions enter in a corrosive environment, Ca ions and Mg ions on the silica surface are released by an ion exchange action, and further, OH ions are generated by a cathode reaction in a corrosive environment, and the vicinity of the plating interface is generated. Rises, the Ca ions (or Mg ions) released from the ion-exchanged silica become Ca (O
H) ₂ or Mg (OH) ₂ precipitates in the vicinity of the plating interface, blocks defects as a dense and poorly soluble product, and suppresses the corrosion reaction. Further, it is also considered that the eluted zinc ions are exchanged for Ca ions (or Mg ions) and fixed on the silica surface.

Further, in addition to the anticorrosive action of the ion-exchanged silica as described above, a film-forming organic resin (A)
By using an organic polymer resin having an OH group and / or a COOH group (preferably a thermosetting resin, more preferably an epoxy resin and / or a modified epoxy resin), the organic polymer resin can be used as a crosslinking agent. A dense barrier film is formed by the reaction, and this barrier film is
It has excellent ability to suppress permeation of corrosion factors such as oxygen, and OH groups and COOH groups in the molecule provide a strong bonding force to the substrate, so that particularly excellent corrosion resistance is obtained.

Further, in the organic coated steel sheet of the present invention, the ion exchange silica (a) and the fine particle silica (b) are contained in the organic film.
Is added to further improve the corrosion resistance. Since ion-exchange silica is mainly composed of porous silica and generally has a relatively large particle diameter of 1 μm or more, a rust-preventing effect as silica cannot be expected after Ca ions are released. For this reason, fine particle silica having a large specific surface area such as fumed silica or colloidal silica (primary particle diameter of 5 to 50 nm, preferably 5 to 20 n
m, more preferably 5 to 10 nm) is considered to promote the production of dense and stable corrosion products such as basic zinc chloride and suppress the production of zinc oxide (white rust). It is presumed that a particularly excellent anticorrosion effect can be obtained by such a composite rust prevention mechanism of ion exchange silica and fine particle silica.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention and the reasons for limiting the same will be described below. The zinc-coated steel sheet serving as a base of the organic coated steel sheet of the present invention includes a zinc-coated steel sheet, Zn-Ni
Alloy plated steel sheet, Zn-Fe alloy plated steel sheet (electroplated steel sheet and galvannealed steel sheet), Zn-Cr
Alloy plated steel sheet, Zn-Mn alloy plated steel sheet, Zn-C
o alloy plated steel sheet, Zn-Co-Cr alloy plated steel sheet,
Zn-Cr-Ni alloy plated steel sheet, Zn-Cr-Fe alloy plated steel sheet, Zn-Al alloy plated steel sheet (for example, Z
n-5% Al alloy plated steel sheet, Zn-55% Al alloy plated steel sheet), Zn-Mg alloy plated steel sheet, Zn-Al-
Mg-plated steel sheets, and zinc-based composite plated steel sheets (eg, Zn—SiO ₂ dispersed plated steel sheets) in which metal oxides, polymers, and the like are dispersed in the plating films of these plated steel sheets can be used.

[0018] Of the above-mentioned platings, a multi-layer plated steel sheet obtained by plating two or more layers of the same type or different types may be used. In addition, as the aluminum-plated steel sheet serving as the base of the organic-coated steel sheet of the present invention, an aluminum-plated steel sheet, an Al—Si alloy-plated steel sheet, or the like can be used. Further, the plated steel sheet may be one in which thin steel plating such as Ni is previously applied to the surface of the steel sheet and various platings as described above are applied thereon. As a plating method, any practicable method can be adopted among an electrolysis method (electrolysis in an aqueous solution or electrolysis in a non-aqueous solvent), a melting method, and a gas phase method.

In order to prevent the occurrence of film defects and unevenness when a chemical conversion film or an organic film is formed on the surface of the plating film, if necessary, the surface of the plating film is previously subjected to alkali degreasing, solvent degreasing, surface conditioning. A treatment such as a treatment (alkaline surface conditioning treatment or acidic surface conditioning treatment) can be performed. Further, in order to prevent blackening (a kind of oxidation phenomenon on the plating surface) in the use environment of the organic coated steel sheet, if necessary, an iron group metal ion (Ni
Surface treatment with an acidic or alkaline aqueous solution containing ions, Co ions, and Fe ions) can also be performed. When an electrogalvanized steel sheet is used as a base steel sheet, an iron group metal ion (Ni ion, Co ion, Fe ion) is added to the electroplating bath for the purpose of preventing blackening.
And these metals can be contained in the plating film in an amount of 1 ppm or more. In this case, there is no particular upper limit on the iron group metal concentration in the plating film.

A chromate film is formed as a first layer film on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. The chromate film may be any of a reaction type chromate treatment film, an electrolytic type chromate treatment film, and a coating type chromate treatment film. The coating type chromate-treated film is composed of a partially reduced aqueous solution of chromic acid as a main component, and, if necessary, a chromate treatment solution to which one or more components selected from the following components are added. It can be obtained by applying the treatment liquid to a plated steel sheet and drying it without washing with water.

Water-soluble or water-dispersible organic resins such as acrylic resins and polyester resins Colloids of oxides such as silica, alumina, titania, zirconia, and zinc oxide and / or powders such as molybdic acid, tungstic acid, and vanadic acid Acids and / or salts thereof Phosphoric acids such as phosphoric acid and polyphosphoric acid Zirconium fluorides, fluorides such as silicon fluorides, titanium fluorides, and phosphate fluorides Metal ions such as zinc ions, nickel ions, cobalt ions, and iron ions Phosphorylation Conductive fine powder such as iron and antimony-doped tin oxide Hydrogen fluoride Silane coupling agent

In this coating type chromate treatment, 6
It is effective to increase the reduction ratio in the chromate treatment liquid in order to suppress the content of valent Cr. In particular, it is effective to use a chromate treatment solution in which the proportion of hexavalent chromium in the treatment solution is reduced and the ratio (solid content) of hexavalent Cr / total Cr is 0.1 or less, preferably 0.01 or less. It is. As a method of adjusting such a chromate treatment solution, an excess oxalic acid and / or oxycarboxylic acid is added as a reducing agent to an aqueous solution of chromic anhydride to increase the reduction rate, and the reduction product is obtained by increasing the pH. It is effective to lower the pH with phosphoric acid or the like to prevent precipitation of trivalent Cr, whereby a chromate film containing trivalent Cr as a main component can be stably obtained. In the application type chromate treatment, the treatment liquid is usually applied by a roll coater method, but after applying by a dipping method or a spray method, it is also possible to adjust the application amount by an air knife method or a roll drawing method.

The electrolytic chromate treatment film contains, for example, a partially reduced aqueous solution of chromic acid and sulfuric acid as main components and, if necessary, metal ions (for example, Zn, Ni, Co, Fe, M).
g, ions of Mn, Al, Ca, etc.), oxide colloids and / or fine powder (silica, alumina, titania, zirconia, magnesia, zinc oxide, tin oxide, antimony oxide, etc.) chloride ion, fluorine ion, nitric acid Ions, phosphate ions and other anions Zirconium fluoride, silicide fluoride, titanium fluoride, boron borofluoride, fluoride such as phosphate fluoride One or more selected from organic compounds such as polyethylene glycol and aqueous acrylic resin Was added, and the plated steel sheet was adjusted to 30 to 30% using a chromate treatment solution adjusted to pH 1 to 5.
It can be obtained by performing cathodic electrolysis at a temperature of 70 ° C. and an amount of electricity of 0.5 to 40 C / dm ² .

The reaction type chromate film contains, for example, chromic anhydride and sulfuric acid as main components, and the content of trivalent Cr in all Cr is 50% by weight or less, preferably 20 to 35% by weight. A chromate treatment solution to which an appropriate amount of metal ions (for example, Zn ions, Co ions, Ni ions, Fe ions, etc.) or other mineral acids (for example, phosphoric acid, hydrochloric acid, hydrofluoric acid, etc.) is added, It can be obtained by treating a plated steel sheet with a chromate treatment solution.

The amount of these chromate films deposited is 1 to 1000 mg / m ^{2 in} terms of chromium metal, preferably 5 to 1000 mg / m ² .
200 mg / m ² , particularly preferably 10 to 100 mg / m ²
and m ^2. When the amount is less than 1 mg / m ² , the corrosion resistance is insufficient. On the other hand, when the amount is more than 1000 mg / m ² , problems such as formation of cracks in the chromate film and deterioration of weldability occur.

As an upper layer of the chromate film, an organic film containing a specific rust preventive additive is formed. The base resin of the organic film is not particularly limited, and any of a water-soluble resin, a water-dispersible resin, and an organic solvent-soluble resin can be used. From the viewpoint of corrosion resistance, an organic resin having an OH group and / or a COOH group is particularly preferable. It is preferable to use the polymer resin (A). Among them, a thermosetting resin is preferable, and an epoxy resin or a modified epoxy resin is most preferable. Examples of the organic polymer resin having an OH group and / or a COOH group include an epoxy resin, a polyhydroxy polyether resin, an acrylic copolymer resin,
Ethylene-acrylic acid copolymer resin, alkyd resin,
Examples thereof include polybutadiene resin, phenol resin, polyurethane resin, polyamine resin, polyphenylene resin, and a mixture or addition polymer of two or more of these resins.

(1) Epoxy resin As the epoxy resin, epoxy resin obtained by glycidyl etherification of bisphenol A, bisphenol F, novolak, etc., propylene oxide to bisphenol A,
Epoxy resins added with ethylene oxide or polyalkylene glycol and converted to glycidyl ether, furthermore, aliphatic epoxy resins, alicyclic epoxy resins, polyether epoxy resins, and the like can be used. These epoxy resins desirably have a number average molecular weight of 1500 or more, particularly when curing at a low temperature is required. The above epoxy resins can be used alone or in combination of different types.

Examples of the modified epoxy resin include resins in which various modifiers are reacted with an epoxy group or a hydroxy group in the epoxy resin. For example, an epoxy ester resin obtained by reacting a carboxyl group in a drying oil fatty acid,
Epoxy acrylate resin modified with acrylic acid, methacrylic acid, etc., urethane modified epoxy resin obtained by reacting isocyanate compound, amine-added urethane modified epoxy resin obtained by adding alkanolamine to urethane modified epoxy resin obtained by reacting isocyanate compound with epoxy resin, etc. Can be mentioned.

The above polyhydroxy polyether resin is
A polymer obtained by polycondensing a mononuclear or dinuclear phenol or a mixture of mononuclear and dinuclear phenols with an approximately equimolar amount of epihalohydrin in the presence of an alkali catalyst. . Representative examples of mononuclear dihydric phenols include resorcin, hydroquinone, and catechol. Representative examples of dinuclear phenols include bisphenol A. These may be used alone or in combination of two or more. You may.

(2) Urethane resin Examples of the urethane resin include an oil-modified polyurethane resin, an alkyd-based polyurethane resin, a polyester-based polyurethane resin, a polyether-based urethane resin, and a polycarbonate-based polyurethane resin. (3) Alkyd resin Examples of the alkyd resin include oil-modified alkyd resin, rosin-modified alkyd resin, phenol-modified alkyd resin,
Styrenated alkyd resin, silicon-modified alkyd resin,
Acrylic-modified alkyd resins, oil-free alkyd resins, high-molecular-weight oil-free alkyd resins, and the like can be given.

(4) Acrylic resin Examples of the acrylic resin include polyacrylic acid and its copolymer, polyacrylic ester and its copolymer, polymethacrylic ester and its copolymer, and polymethacrylic ester. And a copolymer thereof, a urethane-acrylic acid copolymer (or urethane-modified acrylic resin), a styrene-acrylic acid copolymer, and the like. Further, these resins may be used in other alkyd resins, epoxy resins,
A resin modified with a phenol resin or the like may be used.

(5) Ethylene resin (polyolefin resin) Examples of the ethylene resin include ethylene-based copolymers such as ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, and carboxyl-modified polyolefin resin; Examples thereof include a saturated carboxylic acid copolymer and an ethylene ionomer. Further, a resin obtained by modifying these resins with another alkyd resin, an epoxy resin, a phenol resin, or the like may be used. (6) Acrylic silicone resin As the acrylic silicone resin, for example, a resin containing a hydrolyzable alkoxysilyl group in a side chain or a terminal of an acrylic copolymer as a main component, and a curing agent added thereto is exemplified. When these acrylic silicone resins are used, excellent weather resistance can be expected.

(7) Fluororesins Fluororesins include fluoroolefin copolymers, for example, monomers such as alkyl vinyl ether, synchroalkyl vinyl ether, carboxylic acid-modified vinyl ester, hydroxyalkyl allyl ether, tetrafluoropropyl There is a copolymer obtained by copolymerizing vinyl ether or the like with a fluorine monomer (fluoroolefin). When using these fluororesins,
Excellent weather resistance and excellent hydrophobicity can be expected.

Further, in order to lower the drying temperature of the resin, the core portion and the shell portion of the resin particles have different resin types or cores made of resins having different glass transition temperatures.
A shell-type water-dispersible resin can be used. In addition, by using a water-dispersible resin having self-crosslinking properties, for example, by providing an alkoxysilane group to the resin particles, a silanol group is generated by hydrolysis of the alkoxysilane during heating and drying of the resin, and a silanol group between the resin particles is formed. Cross-linking between particles using a dehydration condensation reaction of the above can be used. Further, as a resin used for the organic film, an organic composite silicate obtained by compounding an organic resin with silica via a silane coupling agent is also suitable.

In the present invention, in order to improve the corrosion resistance and workability of the organic film, it is particularly preferable to use a thermosetting resin. In this case, urea resin (butylated urea resin etc.), melamine resin (butylated melamine resin), butylated urea
Amino resins such as melamine resin and benzoguanamine resin,
A curing agent such as a blocked isocyanate, an oxazoline compound, and a phenol resin can be blended.

Among the organic resins described above, epoxy resins and ethylene resins are preferable in consideration of corrosion resistance, workability, and paintability. Particularly, thermosetting resins having excellent barrier properties against corrosion factors such as enzymes. Particularly preferred are epoxy resins and modified epoxy resins. As these thermosetting resins, a thermosetting epoxy resin, a thermosetting modified epoxy resin, an acrylic copolymer resin copolymerized with an epoxy group-containing monomer, a polybutadiene resin having an epoxy group,
Examples thereof include polyurethane resins having an epoxy group, and adducts or condensates of these resins. One type of these epoxy group-containing resins may be used alone, or two or more types may be used in combination.

In the present invention, ion exchange silica (a) is blended as a rust preventive additive in the organic film. Ion-exchanged silica is one in which metal ions such as calcium and magnesium are fixed on the surface of a porous silica gel powder, and the metal ions are released under a corrosive environment to form a precipitated film. Any Ca-exchanged silica can be used,
Those having an average particle diameter of 6 μm or less, desirably 4 μm or less are preferable. For example, those having an average particle diameter of 2 to 4 μm can be used. The average particle size of the Ca-exchanged silica is 6
If it exceeds μm, the corrosion resistance decreases and the dispersion stability in the coating composition decreases. Ca in Ca-exchanged silica
The concentration is preferably 1 wt% or more, and more preferably 2 to 8 wt%. If the Ca concentration is less than 1% by weight, the rust prevention effect due to the release of Ca cannot be sufficiently obtained.

The surface area, pH and oil absorption of the Ca-exchanged silica are not particularly limited. Examples of such Ca-exchanged silica include WRGrace & Co. SHIEEL
DEX C303 (average particle size 2.5 to 3.5 μm, C
a concentration 3 wt%), SHIELDEX AC3 (average particle diameter 2.3 to 3.1 μm, Ca concentration 6 wt%), SHI
ELDEX AC5 (average particle size of 3.8 to 5.2 μm,
Ca concentration 6 wt%), S by Fuji Silysia Chemical Ltd.
HIELDEX (average particle diameter 3 μm, Ca concentration 6 to 8 w
t%), SHIELDEX SY710 (average particle size 2.2 to 2.5 μm, Ca concentration 6.6 to 7.5 wt%)
Etc. can be used. The anticorrosion mechanism when the ion-exchanged silica (a) is added to the organic film is as described above, and an extremely excellent anticorrosion effect is exhibited by the effect of the ion-exchanged silica to suppress corrosion in the cathode reaction section.

The amount of ion-exchanged silica (a) in the organic resin film is 1 to 100 parts by weight (solid content), preferably 5 to 8 parts by weight, per 100 parts by weight (solid content) of the base resin.
0 parts by weight (solid content). If the amount of the ion-exchanged silica (a) is less than 1 part by weight, the effect of improving corrosion resistance after alkali degreasing is small. On the other hand, if the amount is more than 100 parts by weight, the coatability and processability are undesirably reduced.

In the present invention, particularly excellent corrosion resistance can be obtained by adding ion-exchanged silica (a) and fine-particle silica (b) to the organic film in combination. That is, by adding the ion-exchanged silica (a) and the particulate silica (b) in combination, a particularly excellent anticorrosion effect can be obtained by the composite rust prevention mechanism of the two as described above.

The fine particle silica (b) is colloidal silica,
Any of fumed silica may be used. When colloidal silica is based on an aqueous film-forming resin,
For example, Snowtex O, Snowtex N, Snowtex 20, Snowtex 30, Snowtex 4
0, Snowtex C, Snowtex S (all manufactured by Nissan Chemical Industries, Ltd.), Cataloid S, Cataloid SI-
350, Cataloid SI-40, Cataloid SA, Cataloid SN (manufactured by Catalysis Chemical Industry Co., Ltd.), Adelaite AT-20-50, Adelaite AT-20N, Adelaite AT-300, Adelaite AT-300S, Adelaite AT20Q (all And Asahi Denka Kogyo Co., Ltd.) can be used.

When the solvent-based film-forming resin is used as a base, for example, the organosilica sol MA-ST-
M, organosilica sol IPA-ST, organosilica sol EG-ST, organosilica sol E-ST-ZL,
Organosilica Sol NPC-ST, Organosilica Sol DMAC-ST, Organosilica Sol DMAC-ST-
ZL, organosilica sol XBA-ST-MIBK-S
T (all manufactured by Nissan Chemical Industries, Ltd.), OSCAL-11
32, OSCAL-1232, OSCAL-1332,
OSCAL-1432, OSCAL-1532, OSC
AL-1632 and OSCAL-1722 (all manufactured by Catalyst Chemical Industry Co., Ltd.) can be used.

Examples of the fumed silica include AEROSIL R971 and AEROSIL R81.
2, AEROSIL R811, AEROSIL R97
4, AEROSIL R202, AEROSIL R80
5, AEROSIL 130, AEROSIL 200,
AEROSIL 300, AEROSIL 300CF
(Above, manufactured by Nippon Aerosil Co., Ltd.) and the like.

The fine-particle silica contributes to the formation of a dense and stable zinc corrosion product in a corrosive environment, and the corrosion product is formed densely on the plating surface, thereby suppressing the promotion of corrosion. It is considered possible. From the viewpoint of corrosion resistance, it is preferable to use fine-particle silica having a particle diameter of 20 nm or less, more preferably 15 nm or less.

When the ion exchange silica (a) and the fine particle silica (b) are combined and added to the organic film, the amount of the ion exchange silica (a) and the fine particle silica is 100 parts by weight (solid content) of the base resin. 1 in total amount of silica (b)
-100 parts by weight (solid content), preferably 5-80 parts by weight (solid content), and the weight ratio (a) of the compounding amount (solid content) of ion-exchanged silica (a) and fine-particle silica (b) /
(B) is from 99/1 to 1/99, preferably from 95/5 to 4
0/60, more preferably 90/10 to 60/40.

If the total amount of the ion-exchanged silica (a) and the finely divided silica (b) is less than 1 part by weight, the effect of improving the corrosion resistance after alkali degreasing is small. On the other hand, if the total compounding amount exceeds 100 parts by weight, the coatability and workability deteriorate, which is not preferable. If the weight ratio (a) / (b) of the ion-exchanged silica (a) and the fine particle silica (b) is less than 1/99, the corrosion resistance is poor, while the weight ratio (a) / (b) is 9
If it exceeds 9/1, the effect of the composite addition of the ion exchange silica (a) and the fine particle silica (b) cannot be sufficiently obtained.

Further, in the organic film, in addition to the above-mentioned rust preventive additive, a polyphosphate (for example, aluminum polyphosphate: Teika K-WHIT manufactured by Teica Co., Ltd.) may be used as a corrosion inhibitor.
E80, Takeka K-WHITE84, Takeka K-WHI
TE105, Takeka K-WHITEG105, Takeka K
-WHITE90, etc.), phosphates (eg, zinc phosphate, aluminum dihydrogen phosphate, zinc phosphite, etc.), molybdate, phosphomolybdate (eg, aluminum phosphomolybdate), organic phosphoric acid and salts thereof (For example,
Phytic acid, phytate, phosphonic acid, phosphonate and their metal salts, alkali metal salts, alkaline earth metal salts), organic inhibitors (eg, hydrazine derivatives, thiol compounds, etc.) can be added.

If necessary, a solid lubricant (c) may be added to the organic film for the purpose of improving the processability of the film. Examples of the solid lubricant applicable to the present invention include the following. (1) Polyolefin wax, paraffin wax:
For example, polyethylene wax, synthetic paraffin, natural paraffin, microwax, chlorinated hydrocarbon, etc. (2) Fluororesin fine particles: For example, polyfluoroethylene resin (polytetrafluoroethylene resin, etc.), polyvinyl fluoride resin, polyvinylidene fluoride Resin, etc.

In addition, other fatty acid amide compounds (eg, stearic acid amide, palmitic acid amide,
Methylenebisstearamide, ethylenebisstearamide, oleic amide, esylamide, alkylenebisfatty acid amide, etc., metal soaps (eg, calcium stearate, lead stearate, calcium laurate, calcium palmitate, etc.), metals Sulfide (molybdenum disulfide, tungsten disulfide), graphite,
Graphite fluoride, boron nitride, polyalkylene glycol,
You may use alkali metal sulfate etc.

Among the above solid lubricants, polyethylene wax, fluororesin fine particles (among others, poly 4
Fluorinated ethylene resin fine particles) are preferred. Examples of the polyethylene wax include Seridust 9615A, Seridust 3715, Seridust 3 manufactured by Hoechst Inc.
620, Seridust 3910, Sunwax 131-P and Sunwax 161-P manufactured by Sanyo Chemical Co., Ltd., Chemipearl W-100, Chemipearl W-200, Chemipearl W-500, Chemipearl W-500, Chemipearl manufactured by Mitsui Petrochemical Co., Ltd.
W-800, Chemipearl W-950 and the like can be used.

As the fluororesin fine particles, tetrafluoroethylene fine particles are most preferable. For example, Lubron L-2 and Lubron L- manufactured by Daikin Industries, Ltd.
5. MP1100, MP12 manufactured by Mitsui DuPont
00, Fluon Dispersion AD1, Fluon Dispersion AD2, Fluon L141J, Fluon L15 manufactured by Asahi ICI Fluoropolymers Co., Ltd.
0J, Fullon L155J and the like are preferable. Among these, a particularly excellent lubricating effect can be expected by using a combination of polyolefin wax and fine particles of tetrafluoroethylene.

The amount of the solid lubricant (c) in the organic film is 1 to 80 parts by weight (solid content) with respect to 100 parts by weight of the base resin.
Parts by weight (solid content), preferably 3 to 40 parts by weight (solid content). If the amount of the solid lubricant (c) is less than 1 part by weight, the lubricating effect is poor. On the other hand, if the amount is more than 80 parts by weight, the coatability is undesirably reduced.

The organic coating of the organic coated steel sheet of the present invention comprises a coating-forming organic resin (A) as a base resin, and ion-exchanged silica (a) mixed therein. A lubricant (c), a curing agent, and the like are added. If necessary, an organic coloring pigment (for example, a condensed polycyclic organic pigment, a phthalocyanine-based organic pigment, or the like) or a coloring dye (for example, Organic solvent-soluble azo dyes, water-soluble azo metal dyes, etc.), inorganic pigments (eg, titanium oxide), chelating agents (eg, thiol, etc.), conductive pigments (eg, metal powders such as zinc, aluminum, nickel, etc.) Iron phosphide, antimony-doped tin oxide, etc.), coupling agents (eg, silane coupling agents, titanium coupling agents, etc.), melamine / cyanuric acid adducts, etc. Can.

The coating composition for forming a film containing the above-mentioned base resin and additive components usually contains a solvent (organic solvent and / or water), and if necessary, a neutralizing agent or the like is added. . The dry thickness of the organic film is 0.1 to 5 μm, preferably 0.3 to 3 μm, more preferably 0.5 to 2 μm.
μm. When the thickness of the organic film is less than 0.1 μm, the corrosion resistance is insufficient. On the other hand, when the thickness exceeds 5 μm, the conductivity and workability deteriorate.

Next, a method for producing the organic coated steel sheet of the present invention will be described. The organic-coated steel sheet of the present invention is obtained by subjecting the surface of a zinc-based steel sheet or an aluminum-based steel sheet to a chromate treatment, adding ion-exchanged silica (a) to the above-mentioned film-forming organic resin (A), and optionally adding fine particles. It is manufactured by applying a coating composition to which silica (b), a solid lubricant (c) and the like are added, and drying by heating.
The surface of the plated steel sheet may be subjected to an alkali degreasing treatment as required before applying the treatment liquid, and may be subjected to a pretreatment such as a surface conditioning treatment in order to improve adhesion and corrosion resistance.

In the case of forming a chromate film on the surface of a plated steel sheet, any of the above-mentioned coating type, electrolytic type, and reactive type chromate treatments is performed, and if necessary, washed with water and then dried by heating. The treatment liquid may be coated on the surface of the plated steel sheet by any of a coating method, a dipping method, and a spray method. The coating method may be any of a roll coater (three-roll method, two-roll method, etc.), a squeeze coater, a die coater, and the like. May be used. In addition, after the coating, dipping, and spraying with a squeeze coater or the like, it is also possible to adjust the coating amount, make the appearance uniform, and make the film thickness uniform by an air knife method or a roll drawing method.

The method of heating and drying after the chromate treatment is arbitrary, and for example, means such as a dryer, a hot air oven, a high frequency induction heating oven, and an infrared oven can be used. This heat drying treatment is performed at a temperature of 40 to 150 ° C.,
It is preferable to carry out in the range of 0 to 140 ° C. If the heating and drying temperature is lower than 40 ° C., a large amount of water remains in the film, and the corrosion resistance becomes insufficient. On the other hand, when the heating and drying temperature exceeds 150 ° C., not only is it uneconomical, but also defects such as cracks tend to occur in the coating, and the corrosion resistance is reduced.

After the formation of the chromate film as described above, a coating composition for forming an organic film is applied. As a method for applying the coating composition, any method such as an application method, a dipping method, and a spray method can be adopted. As a coating method, any method such as a roll coater (three-roll system, two-roll system, etc.), a squeeze coater, a die coater, and the like may be used. In addition, after the coating, dipping, or spraying with a squeeze coater or the like, it is also possible to adjust the coating amount, uniform the appearance, and uniform the film thickness by an air knife method or a roll drawing method.

After application of the coating composition, drying by heating is usually carried out without washing with water, but a washing step may be carried out after application of the coating composition. For the heating and drying treatment, a dryer, a hot blast furnace, a high-frequency induction heating furnace, an infrared furnace, or the like can be used. Heat treatment is 50-350 ° C at ultimate plate temperature,
It is desirable to carry out the reaction in the range of preferably 80 ° C to 250 ° C. If the heating temperature is lower than 50 ° C., a large amount of water in the film remains, and the corrosion resistance becomes insufficient. The heating temperature is 350 ° C
When it exceeds, it is not only uneconomical, but also there is a possibility that a defect occurs in the film and the corrosion resistance is reduced.

The present invention includes a steel sheet having the above-described chromate film and organic film on both surfaces or one surface. Therefore, examples of the form of the steel sheet of the present invention include the following. (1) One side: plating film-chromate film-organic film,
One side: Plating film (2) One side: Plating film-Chromate film-Organic film,
One side: Plating film-Other chemical conversion coating (3) Both surfaces: Plating film-Chromate film-Organic film (4) One surface: Plating film-Chromate film-Organic film,
One side: plating film-organic film

[0061]

EXAMPLE As an organic resin for forming an organic film, a resin shown in Table 2 was used. Ion exchange silica, fine particle silica shown in Table 3, and a solid lubricant shown in Table 4 were appropriately blended with this resin composition, It was dispersed for a required time using a dispersing machine (sand grinder) to obtain a desired coating composition. The ion exchange silica is Ca exchange silica WRGrace &
SHIELDEX C303 (average particle size 2.
5-3.5 μm, Ca concentration 3 wt%).

In order to obtain an organically coated steel sheet for home appliances, building materials and automobile parts, the sheet thickness: 0.8 mm and the surface roughness Ra: 1.0
μm cold-rolled steel sheet was subjected to various zinc-based or aluminum-based plating, and the coated steel sheet shown in Table 1 was used as a treatment base sheet. The surface of the plated steel sheet was subjected to alkali degreasing treatment, washing and drying, and then coating type chromate treatment described below. Chromate treatment was performed by any one of electrolytic chromate treatment and reactive chromate treatment to form a chromate film. Next, a coating composition for forming an organic film was applied by a roll coater and dried by heating to form an organic film, thereby producing organic-coated steel sheets of Examples of the present invention and Comparative Examples. The thickness of the organic film was adjusted according to the solid content (heating residue) of the coating composition or the application conditions (roll rolling force, rotation speed, etc.).

Reaction type chromate treatment Chromic anhydride: 30 g / l, phosphoric acid: 10 g / l, Na
Using a treatment liquid containing 0.5 g / l of F and 4 g / l of K ₂ TiF _{6, the} mixture was sprayed at a bath temperature of 40 ° C., and then washed with water and dried. The amount of chromium deposited was adjusted by changing the treatment time and the free acidity.

Electrolytic Chromate Treatment Cathodic electrolysis treatment was carried out using a treatment solution of chromic anhydride: 30 g / l, sulfuric acid: 0.2 g / l, and bath temperature of 40 ° C., followed by washing and drying. The amount of chromium deposited was adjusted by controlling the amount of electricity in the electrolytic treatment.

Coating-type chromate treatment (a) Chromic anhydride aqueous solution: 100 g / l of a reducing agent (starch) is added to the mixture, the temperature is adjusted to 80 ° C., and the mixture is left for 2 hours to reduce a part of the chromic anhydride. An aqueous solution of hexavalent Cr / 3 trivalent Cr: 3/2 was prepared. Next, a silica sol was added to this aqueous solution so that silica / total Cr: 6/1, and further, a zinc phosphate aqueous solution obtained by dissolving zinc oxide and phosphoric acid was added to PO ₄ ion / total Cr: A chromate treatment solution was prepared by adding １ ／, divalent Zn / 6 hexavalent Cr: 3/20. This chromate treatment solution was diluted to a predetermined concentration, applied to the surface of various plated steel sheets by a roll coater, and dried by heating at a sheet temperature of 70 to 250 ° C. without washing with water. The amount of chromium adhered was adjusted by changing the concentration of the processing solution and the coating conditions.

Coating type chromate treatment (b) A reducing agent (oxalic acid saturated aqueous solution: 1 L) and phosphoric acid: 100 ml were gradually added to chromic anhydride aqueous solution: 20 g / l (1 L), and the mixture was left at room temperature for 24 hours. Chromic acid was reduced to prepare a chromate treatment solution having hexavalent Cr / total Cr <0.1, pH = 1. This chromate treatment solution was diluted to a predetermined concentration, applied to the surface of various plated steel sheets by a roll coater, and dried by heating at a sheet temperature of 70 to 250 ° C. without washing with water. The amount of chromium adhered was adjusted by changing the concentration of the processing solution and the coating conditions.

The resulting organic coated steel sheets were evaluated for quality performance (chromium elution resistance, white rust resistance, white rust resistance after alkali degreasing, paint adhesion, workability). Table 5 shows the results together with the composition of the chemical conversion coating and the organic coating.
To Table 17 below. The evaluation of the quality performance of the organic coated steel sheet was performed as follows.

(1) Chromium elution resistance (chromium fixation rate) Each sample was subjected to degreasing treatment under standard conditions using a degreasing agent PALCLEAN N364S manufactured by Nippon Parkerizing Co., Ltd., and the fixation rate of chromium before and after degreasing was measured. did.
Chromium fixation rate = {(chromium adhesion before degreasing-chromium adhesion after degreasing) / chromium adhesion before degreasing} × 100
(%). The evaluation criteria are as follows. ：: Chromium fixing rate 100% ○: Chromium fixing rate 90% or more and less than 100% △: Chromium fixing rate 80% or more and less than 90% ×: Chromium fixing rate less than 80%

(2) White rust resistance For each sample, salt spray test (JIS-Z-23)
71) was carried out, and evaluated by the area ratio of white rust occurrence after a predetermined time. The evaluation criteria are as follows. ◎: No white rust generated ○ +: White rust generation area ratio less than 5% ○: White rust generation area ratio 5% or more and less than 10% ○-: White rust generation area ratio 10% or more and less than 25% △: White rust Generated area rate 25% or more, less than 50% ×: White rust generated area rate 50% or more

(3) White rust resistance after alkali degreasing For each sample, an alkali treatment liquid CLN-364S manufactured by Nippon Parkerizing Co., Ltd. (60 ° C., spray 2
Min), and then a salt spray test (JIS)
-Z-2371), and evaluated by a white rust area ratio after a predetermined time. ◎: No white rust generated ○ +: White rust generation area ratio less than 5% ○: White rust generation area ratio 5% or more and less than 10% ○-: White rust generation area ratio 10% or more and less than 25% △: White rust Generated area rate 25% or more, less than 50% ×: White rust generated area rate 50% or more

(4) Paint Adhesion For each sample, a melamine-based baking paint (film thickness 30
μm), immersed in boiling water for 2 hours, immediately cut in a grid (10 × 10 grids at 1 mm intervals), adhered and peeled with an adhesive tape, and peeled area of the coating film Rate was evaluated. The evaluation criteria are as follows. ：: No peeling ○: Peeling area rate less than 5% △: Peeling area rate 5% or more, less than 20% ×: Peeling area rate 20% or more

(5) Workability Deep drawing was performed with a blank diameter of φ120 mm and a die diameter of φ50 mm (oil-free condition), and the evaluation was made based on the molding height until cracking occurred. The evaluation criteria are as follows. ◎: Draw-out ○: Molding height 30 mm or more △: Molding height 20 mm or more, less than 30 mm ×: Molding height less than 20 mm

[0073]

[Table 1]

[0074]

[Table 2]

[0075]

[Table 3]

[0076]

[Table 4]

[0077]

[Table 5]

[0078]

[Table 6]

[0079]

[Table 7]

[0080]

[Table 8]

[0081]

[Table 9]

[0082]

[Table 10]

[0083]

[Table 11]

[0084]

[Table 12]

[0085]

[Table 13]

[0086]

[Table 14]

[0087]

[Table 15]

[0088]

[Table 16]

[0089]

[Table 17]

As a conventional reactive chromate treated steel sheet,
Chromic anhydride: 30 g / l, phosphoric acid: 10 g / l, Na
F: 0.5 g / l, K ₂ TiF ₆ : Spray treatment at a bath temperature of 40 ° C. using a treatment solution containing 4 g / l, followed by washing and drying to obtain the chromium deposition amount (in terms of chromium metal). Manufactured a chromate-treated steel sheet of 20 mg / m ² . When this was subjected to a salt spray test under the same conditions as in this example, white rust was generated in about 24 hours. Therefore,
From these results and the results of this example, it can be seen that the organic-coated steel sheet of the present invention can provide much better corrosion resistance than the conventional chromate-treated steel sheet.

[0091]

As described above, the organic coated steel sheet of the present invention has extremely excellent corrosion resistance as compared with the conventional steel sheet.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihiko Furuta 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Masaru Sagiyama 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor Masaaki Yamashita 1-2-1 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 4K026 AA02 AA07 AA08 AA12 AA13 AA22 BA06 BA12 BB04 BB06 BB08 BB09 BB10 CA16 CA19 CA20 CA21 CA26 CA28 CA39 CA41 DA15 DA16 EB08

Claims (11)

[Claims] 1. A chromate film having a chromium equivalent of 1 to 1000 mg / m ^{2 in} terms of metallic chromium is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet;
On top of this, ion-exchanged silica (a) was added in an amount of 1 to 100 parts by weight (solid content) to 100 parts by weight (solid content) of the film-forming organic resin (A).
An organic coated steel sheet having excellent corrosion resistance, characterized by having an organic film having a thickness of 0.1 to 5 [mu] m containing parts by weight (solid content). ^2. A chromate film having a chromium equivalent of 1 to 1000 mg / m ^{2 in} terms of chromium metal is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet;
On top of this, ion-exchanged silica (a) and fine-particle silica (b) are added in a total amount of 1 to 100 parts by weight (solid content) based on 100 parts by weight (solid content) of the film-forming organic resin (A).
And the weight ratio (a) / (b) of the content (solid content) of the ion-exchanged silica (a) and the particulate silica (b) is 1
An organic-coated steel sheet having excellent corrosion resistance, comprising an organic film having a thickness of 0.1 to 5 μm, which is / 99 to 99/1. 3. A chromate film having a chromium equivalent of 1 to 1000 mg / m ^{2 in} terms of chromium metal is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet.
On top of this, ion-exchanged silica (a) was added in an amount of 1 to 100 parts by weight (solid content) to 100 parts by weight (solid content) of the film-forming organic resin (A).
An organic coated steel sheet having excellent corrosion resistance, comprising an organic film having a thickness of 0.1 to 5 μm containing 1 to 80 parts by weight (solid content) of a solid lubricant (c) by weight (solid content). . 4. A chromate film having a chromium equivalent of 1 to 1000 mg / m ^{2 in} terms of chromium metal is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet.
On the upper part, ion-exchanged silica (a) and fine-particle silica (b) were added in a total amount of 1 to 100 parts by weight (solid content) with respect to 100 parts by weight (solid content) of the film-forming organic resin (A). The solid lubricant (c) is contained in an amount of 1 to 80 parts by weight (solid content), and the weight ratio (a) / (b) of the content (solid content) of the ion exchange silica (a) and the fine particle silica (b) is: 1
An organic-coated steel sheet having excellent corrosion resistance, comprising an organic film having a thickness of 0.1 to 5 μm, which is / 99 to 99/1. 5. The organic material having excellent corrosion resistance according to claim 1, wherein the film-forming organic resin (A) is an organic polymer resin having an OH group and / or a COOH group. Coated steel sheet. 6. The organically coated steel sheet having excellent corrosion resistance according to claim 5, wherein the organic polymer resin is a thermosetting resin. 7. The thermosetting resin according to claim 6, wherein the thermosetting resin is an epoxy resin and / or a modified epoxy resin.
Organic coated steel sheet having excellent corrosion resistance according to 1. 8. The chromate film according to claim 1, wherein the chromate treatment composition has a hexavalent Cr / total Cr concentration ratio (molar ratio) of 0.1 or less. The organic-coated steel sheet excellent in corrosion resistance according to 3, 4, 5, 6, or 7. 9. The method according to claim 1, wherein the ion exchange silica in the organic film is Ca exchange silica.
The organic-coated steel sheet excellent in corrosion resistance according to 4, 5, 6, 7 or 8. 10. The average particle diameter of the Ca-exchanged silica is 4 μm.
The organic-coated steel sheet excellent in corrosion resistance according to claim 9, characterized in that: 11. A Ca-exchanged silica having a Ca concentration of 2 to 8 watts.
The organic-coated steel sheet excellent in corrosion resistance according to claim 9 or 10, wherein the content is t%.