JP2000000519A - Surface-treated steel plate with high white rust resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-treated steel plate which is free from environmental pollution and is corrosion-resistant without performing a chromate treatment with significant adverse effects by forming a protecting skin composed mainly of a water-dispersive and/or a water-soluble resin and a polymer chelating agent, on the surface of a galvanized or aluminum-plated steel plate. SOLUTION: A protecting skin consisting of a composition (A) which contains a water-dispersive and/or a water-soluble resin (a) and a polymer chelating agent (b) with a chelate-forming group in a polymer matrix and shows the weight ratio of the solid contents in (a) and (b) specified as 99/1-1/99. In addition, 1-100 pts.wt. rust prevention additive (B) selected from among silica, polyphosphate, phosphate and the like and 1-80 pts.wt. solid lubricant (C) selected from among a hydrocarbon compound such as polyolefin wax, a fluororesin compound and others may be blended to 100 pts.wt. the composition (A).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated steel sheet most suitable for use in automobiles, home appliances, and building materials, and has an effect on workers and users who handle products, measures against wastewater treatment during production, and products in use environments. Environmentally-friendly surface treatment that does not contain any heavy metals such as chromium, lead, cadmium, and mercury that are harmful to the environment and the human body in coating compositions and films to adapt to environmental problems such as volatilization and elution of harmful substances from the environment. It relates to a steel plate.

[0002]

2. Description of the Related Art Steel sheets for home appliances, building materials, and automobiles have been used to improve the corrosion resistance (white rust resistance, red rust resistance) on the surface of a zinc-based steel sheet or an aluminum-based steel sheet. A steel sheet which has been subjected to chromate treatment with a treatment liquid containing chromic acid, bichromic acid or salts thereof as a main component is widely used. This chromate treatment is an economical treatment method that has excellent corrosion resistance and can be performed relatively easily.

[0003] However, since chromate treatment uses hexavalent chromium, which is a pollution control substance, it is difficult for chromate salts to have an adverse effect on the human body in the treatment process, and it is difficult to dispose of chromium sludge after wastewater treatment. In addition, there are various problems, for example, that hexavalent chromium may be eluted from the product after the chromate treatment. For this reason, as the use control standards for chromic acids have become stricter, the management of chromate treatment plants, wastewater treatment, and secondary contamination by chromate treatment have become problems, and in response to this, each plant has closed drainage relations. In addition, measures are taken to minimize the emission of chromium ions to the outside.
In addition, in the process of degreasing the rust-preventive oil and press oil attached to the chromate-treated steel sheet by the user, when using an alkaline degreasing solution, the elution of chromium into the degreasing solution is considerably increased. Dechrome treatment is required.

[0004] In view of such circumstances, in order to prevent the generation of white rust on a zinc-based plated steel sheet, many pollution-free treatment techniques not based on chromate treatment have been proposed. For example,
There is a method of using an inorganic compound, an organic compound, an organic polymer material, or a combination thereof to form a thin film by a method such as immersion, coating, or electrolytic treatment. In particular,
The following methods are known. (1) A method using an oxide of a metal such as molybdenum or tungsten (for example, JP-A-57-5875). (2) A method using tannic acid (for example, JP-A-51-5875).
(3) A pollution-free chromate treatment method comprising only trivalent chromium and not containing hexavalent chromium (for example, see JP-A-61-5).
No. 87)

[0005]

However, in the above method (1), the stable area against corrosion of metal oxides such as molybdenum and tungsten is narrower than that of chromium.
It is impossible to obtain the same level of corrosion resistance as chromate treatment. In the method (2), only a film having insufficient corrosion resistance and having uneven coloring is obtained.
Furthermore, in the above method (3), since soluble chromium is used, it cannot fundamentally meet the need for chromium-free. Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a surface-treated steel sheet which can obtain excellent corrosion resistance without containing hexavalent chromium in a film.

[0006]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors to solve the above-mentioned problems, a water-dispersible resin and / or a water-soluble resin was coated on the surface of a zinc-based steel sheet or an aluminum-based steel sheet. By forming a protective film mainly composed of a resin and a polymer chelating agent having a chelating group in a polymer matrix, without performing chromate treatment that may adversely affect the environment and the human body, it is pollution-free. It has also been found that a surface-treated steel sheet having excellent corrosion resistance can be obtained.

The present invention has been made based on such findings, and the features thereof are as follows. (1) A water-dispersible resin and / or a water-soluble resin (a) and a polymer chelating agent (b) having a chelate-forming group in a polymer matrix are coated on the surface of a zinc-based or aluminum-based steel sheet. And the weight ratio (a) / (b) of the solid content of (a) and (b) is 99/1 to 1
A surface-treated steel sheet having excellent white rust resistance, characterized by forming a protective film of / 99.

(2) A surface excellent in white rust resistance, characterized in that a protective film containing the following components (A) and (B) is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. Treated steel sheet. (A) water-dispersible resin and / or water-soluble resin (a)
And a polymer chelating agent (b) having a chelating group in the polymer matrix, wherein (a) and (b)
Weight ratio (a) / (b) of 99/1 to 1/99
100 parts by weight (solid content ratio) of (B) silica, polyphosphate, phosphate, phosphite,
1 to 100 parts by weight (solid content) of one or more rust preventive additives selected from molybdate, phosphomolybdate, phytic acid, phytate, phosphonic acid, and phosphonate

(3) A surface excellent in white rust resistance, characterized in that a protective film containing the following components (A) and (C) is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. Treated steel sheet. (A) water-dispersible resin and / or water-soluble resin (a)
And a polymer chelating agent (b) having a chelating group in the polymer matrix, wherein (a) and (b)
Weight ratio (a) / (b) of 99/1 to 1/99
(C) a hydrocarbon-based compound such as a polyolefin wax,
One or more solid lubricants selected from fluororesin compounds, fatty acid amide compounds, metal sulfides, metal soaps, graphite, fluorinated graphite, boron nitride, polyalkylene glycols, and alkali metal sulfates 1 to
80 parts by weight (solid content ratio)

(4) White rust resistance characterized in that a protective film containing the following components (A), (B) and (C) is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. Excellent surface treated steel sheet. (A) water-dispersible resin and / or water-soluble resin (a)
And a polymer chelating agent (b) having a chelating group in the polymer matrix, wherein (a) and (b)
Weight ratio (a) / (b) of 99/1 to 1/99
100 parts by weight (solid content ratio) of (B) silica, polyphosphate, phosphate, phosphite,
1 to 100 parts by weight (solid content) of one or more rust preventive additives selected from molybdate, phosphomolybdate, phytic acid, phytate, phosphonic acid, and phosphonate C) hydrocarbon compounds such as polyolefin wax;
One or more solid lubricants selected from fluororesin compounds, fatty acid amide compounds, metal sulfides, metal soaps, graphite, fluorinated graphite, boron nitride, polyalkylene glycols, and alkali metal sulfates 1 to
80 parts by weight (solid content ratio)

(5) In the surface-treated steel sheet according to any one of the above (1) to (4), the chelating group of the polymer chelating agent may be an amino acid group, a carboxyl group, a dithiocarbamic acid group, a polyamino group, a thiol group. Excellent in white rust resistance characterized in that it is at least one member selected from a phosphomethylamino group, a thioureido group, a dithioic acid group, a phosphoric acid group, a β-diketone group, and a hydroxamoxime group. Surface treated steel sheet.

(6) In the surface-treated steel sheet according to any one of the above (1) to (5), the polymer matrix of the polymer chelating agent is polyethylene, polyvinyl alcohol, polyethylene glycol, polyethylene imine, a polyamino compound, a polychlorinated compound. Vinyl, polyacrylic acid, epoxy resin,
A surface-treated steel sheet having excellent white rust resistance, comprising one or more selected from phenol resin, styrene-divinylbenzene resin, and acrylic resin.

(7) The surface-treated steel sheet according to any of (1) to (6) above, wherein the number average molecular weight of the polymer matrix of the polymer chelating agent is 300 or more. Excellent surface treated steel sheet. (8) In the surface-treated steel sheet according to any one of the above (1) to (6),
A surface-treated steel sheet having excellent white rust resistance, wherein the number average molecular weight of the polymer matrix of the polymer chelating agent is 1,000 or more. (9) In the surface-treated steel sheet according to any of (1) to (8),
A surface-treated steel sheet having excellent white rust resistance, wherein the protective film has a thickness of 0.01 to 5 μm.

In such a surface-treated steel sheet of the present invention, a protective film containing a water-dispersible resin and / or a water-soluble resin and a polymer chelating agent formed on the surface of a galvanized steel sheet or an aluminum-coated steel sheet. In addition to covering the plating film in the same way as a general organic resin film and suppressing its corrosion, the chelating group forms a dense protective film layer by adsorbing or reacting on the surface of the plating film, The chelate-forming group captures metal ions eluted from the plating film during film formation to form a complex structure and forms a dense barrier layer, which exhibits a rust-preventive effect. Free chelate-forming groups in the film capture the metal ions eluted from the film, forming a stable metal complex structure Exert an effect of suppressing promoting food, excellent corrosion resistance by these effects is obtained.

[0015]

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 as a base of the surface-treated 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), and a zinc-based composite coated steel sheet (for example, Zn-SiO ₍₂ dispersion-plated steel sheet) or the like can be used.

Further, among 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. Further, as the aluminum-plated steel sheet serving as a base of the surface-treated steel sheet of the present invention, an aluminum-plated steel sheet, an Al-Si alloy-plated steel sheet, or the like can be used. Alternatively, the steel plate surface may be preliminarily plated with a thin coating of Ni or the like, and the various platings as described above may be performed 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.

Next, a water-dispersible resin and / or a water-soluble resin and a polymer chelating agent having a chelating group in a polymer matrix are formed on the surface of the zinc-based steel sheet or the aluminum-based steel sheet. The protective film as a main component will be described. The chelating group contained in the polymer chelating agent forms a dense protective film layer by chemisorption or reaction on the plating film surface, and further reacts with metal ions eluted from the plating film during film formation to form an insoluble Has a function of forming a dense chelate complex on the plating surface.

Techniques for protecting a metal surface by a chemical adsorption method using such a corrosion inhibitor (inhibitor) have been known for a long time. Cooling water systems, boiler systems, water supply / hot water supply are mainly used as corrosion prevention methods for iron. A method of adding an amine-based or phosphoric acid-based adsorbent to water in an environment such as a water-based system where water and metal are in constant contact has been put to practical use.

The purpose of the present invention is to prevent corrosion of steel pipes for water pipes, and of course, the purpose and application of the present invention are different. However, heretofore, as a surface treatment film of such a rust-preventive steel plate, there has been almost no practical application of a film mainly composed of a compound having a chelate-forming group. This is because (1) the adsorption capacity differs depending on the type of metal, and it is difficult to obtain a stable and dense adsorption film from a zinc-based plated steel sheet and an aluminum-based plated steel sheet. (2) The chelating agent generally has a low molecular weight. (Normal,
The molecular weight is less than 300), so that it is difficult to form a continuous film such as a polymer resin for a coating, and a sufficient anticorrosion function cannot be obtained due to the reason.

The present inventors have conducted intensive studies to overcome the above-mentioned problems, and as a result, have found that an aqueous resin such as a water-dispersible resin and a polymer chelating agent having a chelating group added to an organic polymer matrix are used. It has been found that a coating containing the same has an excellent anticorrosion function as a surface treatment film of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. The feature of the present invention is that a conventionally known low molecular weight chelating agent such as EDTA is not applied to rust prevention, but a chelating group is formed on an aqueous resin such as a water dispersible resin and an organic polymer matrix. The point is that the protective film containing the imparted polymer chelating agent is applied to a zinc-based plated steel sheet or an aluminum-based plated steel sheet. Another preferable feature of the present invention is that the chelating group contained in the polymer chelating agent and the organic polymer matrix of the polymer chelating agent are selected from specific types.

Although the mechanism of anticorrosion by a protective film containing such a polymer chelating agent is not always clear, (1) it is mainly composed of an organic polymer instead of a low molecular weight chelating agent as conventionally used. By using a polymer chelating agent, an organic film such as a resin for paint can be formed. (2) Stable and strong adsorption on the surface of a zinc-based steel sheet or an aluminum-based steel sheet by a chelating group.
The formation of a reaction film (a film formed by the chelate-forming group adsorbing or reacting to the surface of the plating film); and (3) the chelate-forming group capturing metal ions eluted from the plating film during film formation. (4) The chelating group is eluted at the time of film formation by using a polymer chelating agent having an organic polymer as a matrix instead of a low molecular weight chelating agent as in the prior art. (3) forming a film having a three-dimensional polymer complex structure to form a dense and stable three-dimensional ion-crosslinked structure film when forming a complex structure film by capturing the metal ions thus formed; When the steel sheet having the coated film is exposed to a corrosive environment, the metal ions eluted by the dissolution of the anode are captured by the chelate-forming group, and the above-mentioned (4)
It is considered that an excellent anticorrosive effect can be obtained by suppressing the progress of corrosion by generating an electrically neutralized polymer complex structure similar to that described above.

In the polymer chelating agent, the chelating group imparted to the organic polymer matrix includes an amino acid group, a carboxyl group, a dithiocarbamic acid group, a polyamino group, a thiol group, a phosphomethylamino group, a thioureido group, a dithioic acid group. , A phosphoric acid group, a β-diketone group, or a hydroxamoxime group. The amino acid group includes, for example, a glycine group, a β-alanine group, an iminodiacetic acid group, and the like.

In the polymer chelating agent, there is no particular limitation on the type of the organic polymer matrix to which the chelating group is provided, but polyethylene, polyvinyl alcohol,
Polyethylene glycol, polyethylene imine, polyamino compound, polyvinyl chloride, polyacrylic acid, epoxy resin, phenol resin, styrene-divinylbenzene resin, and acrylic resin are particularly preferred, and one or more selected from these are used. Is preferred.

The number average molecular weight of the organic polymer matrix is not particularly limited, but is preferably 300 or more, more preferably about 1000 or more, and further preferably 100 or more.
00 or more. When the number average molecular weight is less than 300, the effect of improving corrosion resistance is small. The upper limit of the number average molecular weight is not particularly limited. However, if the molecular weight is too large, a problem such as gelation of the coating composition occurs, so that the number average molecular weight is preferably 100.
10,000 or less.

Next, a water-dispersible resin and / or a water-soluble resin (hereinafter collectively referred to as “aqueous resin”), which is another main component of the protective film of the present invention, is uniformly used as a binder of the film. To form a strong film and enhance the rust prevention effect. As the aqueous resin, for example, the following can be used.

(1) Acrylic resin For example, polyacrylic acid and its copolymer, polyacrylic ester and its copolymer, polymethacrylic ester and its copolymer, polymethacrylic ester and its copolymer, It is possible to use urethane-acrylic acid copolymer (or urethane-modified acrylic resin), styrene-acrylic acid copolymer, and the like, and further, resins obtained by modifying these resins with other alkyd resins, epoxy resins, phenol resins, and the like. it can.

(2) Ethylene resin (polyolefin resin) For example, ethylene copolymers such as ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, carboxyl-modified polyolefin resin, and ethylene-unsaturated carboxylic acid copolymer For example, a resin obtained by modifying these resins with another alkyd resin, an epoxy resin, a phenol resin, or the like can be used.

(3) Alkyd resin For example, oil-modified alkyd resin, rosin-modified alkyd resin, phenol-modified alkyd resin, styrenated alkyd resin, silicon-modified alkyd resin, acrylic-modified alkyd resin, oil-free alkyd resin, high-molecular-weight oil-free alkyd Resin or the like can be used.

(4) Epoxy resin For example, straight epoxy resin such as epichlorohydrin type, glycidyl ether type, etc., fatty acid modified epoxy resin (epoxy ester resin), polybasic acid modified epoxy resin, acrylic resin modified epoxy resin, alkyd (or polyester) ) Modified epoxy resins, polybutadiene-modified epoxy resins, phenol-modified epoxy resins, amine or polyamine-modified epoxy resins, urethane-modified epoxy resins, and the like can be used. (5) Urethane resin For example, a polycarbonate-based polyurethane resin, a polyester-based polyurethane resin, a polyether-based urethane resin, or the like can be used.

In addition, 2 selected from the above aqueous resins
Two or more types of aqueous resins may be mixed and used. Further, for the purpose of lowering the drying temperature of the film, a core-shell type water-dispersible resin in which the core portion and the shell portion of the resin particles are formed of different resin types or resins having different glass transition temperatures can be used. Further, by providing an alkoxysilane group to a water-dispersible resin having a self-crosslinking property, for example, resin particles, a silanol group is generated by hydrolysis of the alkoxysilane during heating and drying of the film, and dehydration of the silanol group between the resin particles. A water-dispersible resin in which cross-linking between particles utilizing a condensation reaction occurs can also be used.

In addition, among the above aqueous resins, corrosion resistance,
In consideration of workability and coatability, an ethylene resin is most preferable.
Preference is given to ethylene copolymers such as acrylic acid copolymers, ethylene-methacrylic acid copolymers, carboxyl-modified polyolefin resins, ethylene-unsaturated carboxylic acid copolymers, ethylene ionomers and the like. Among them, ethylene ionomers exhibit excellent blackening resistance in addition to excellent corrosion resistance and workability. In addition, a water-dispersible epoxy resin, acrylic resin, urethane resin or the like can be used in combination with these ethylene resins.

Further, in addition to the water-based resins described above, one kind of water-soluble epoxy resin, water-soluble phenol resin, water-soluble butadiene rubber (SBR, NBR, MBR), melamine resin, block isocyanate, oxazoline compound, etc. It is effective to use the above as a crosslinking agent. The mixing ratio of the water-based resin (a) to the polymer chelating agent (b) is 99/1 to 1 in terms of the weight ratio of solids (a) / (b).
/ 99, preferably 95/5 to 5/95. When the amount of the polymer chelating agent (a) is less than the lower limit of the above-mentioned compounding ratio, the corrosion inhibitory effect due to chelate formation is insufficient, so that white rust resistance is poor. On the other hand, when the content of the aqueous resin (b) is less than the lower limit of the above-mentioned compounding ratio, the barrier effect is insufficient, and in this case, the white rust resistance is also poor.

For the purpose of further increasing the anticorrosion effect, silica, polyphosphate, and the like may be added to the protective film containing the aqueous resin (a) and the polymer chelating agent (b) as main components.
Contains one or more rust preventive additives selected from phosphate, phosphite, molybdate, phosphomolybdate, phytic acid, phytate, phosphonic acid, phosphonate, etc. can do.

As the silica, either colloidal silica or fumed silica may be used. Examples of the colloidal silica include Snowtex O, Snowtex N, Snowtex 20, Snowtex 30,
Snowtex 40, Snowtex C, Snowtex S (all manufactured by Nissan Chemical Industries, Ltd.) and the like can be used. Also, as a fume dredica, for example, A
EROSIL R971, AEROSIL R812, A
EROSIL R811, AEROSIL R974, A
EROSIL R202, AEROSIL R805, A
EROSIL130, AEROSIL 200, AER
OSIL 300, AEROSIL 300CF (or more,
Nippon Aerosil Co., Ltd.) can be used.

The silica added to the film contributes to the formation of dense and stable metal corrosion products in a corrosive environment, and the corrosion products are densely formed on the plating surface to promote corrosion. Is considered to be suppressed. In addition, as a rust preventive additive other than silica, known polyphosphates (for example, aluminum polyphosphate: Teica K-WHITE80,
Takeka K-WHITE 84, Takeka K-WHITE 1
05, Takeka K-WHITE G105, Takeka K-W
HITE 90 (all manufactured by Teica Corporation)), phosphates (eg, zinc phosphate, aluminum dihydrogen phosphate, zinc phosphite, etc.), molybdates, phosphomolybdates (eg, phosphomolybdic acid) Aluminum), phytic acid, phytate, phosphonic acid, phosphonate and the like can also be used.

The amount of the rust preventive additive is based on 100 parts by weight of the main component [(a) + (b)] composed of the water-based resin (a) and the polymer chelating agent (b) in a solid content ratio. 1-100
Parts by weight. If the amount is less than 1 part by weight, the effect of improving corrosion resistance is small. On the other hand, if the compounding amount exceeds 100 parts by weight, the corrosion factor advances due to agglomeration in the film, so that the white rust resistance is lowered and the coating property is lowered. The more preferable amount of the rust preventive additive is 5 to 80 parts by weight.

Further, a solid lubricant can be added to the protective film for the purpose of improving the processability of the film. Examples of the solid lubricant include the following. (1) Hydrocarbon compounds such as polyolefin wax:
For example, polyethylene wax, synthetic paraffin, natural paraffin, microwax, chlorinated hydrocarbon, etc. (2) Fluororesin compounds: For example, polyfluoroethylene resin (polytetrafluoroethylene resin, etc.), polyvinyl fluoride resin, polyfluoride (3) Fatty acid amide compounds: for example, stearic acid amide, palmitic acid amide, methylenebisstearamide, ethylenebisstearamide, oleic acid amide,
Esylamide, alkylenebisfatty acid amide, etc.

(4) Metal soaps: for example, calcium stearate, lead stearate, calcium laurate, calcium palmitate, etc. (5) Metal sulfides: for example, molybdenum disulfide, tungsten disulfide (6) Others: for example, graphite , Fluorinated graphite, boron nitride, polyalkylene glycol, alkali metal sulfate, etc.

Among the above solid lubricants, polyethylene wax, fluororesin compounds (among others, poly-4
Fluorinated ethylene resin fine particles) are preferred. Examples of polyethylene wax include Celidust 96 manufactured by Hoechst.
15A, Seridust 3715, Seridust 3620,
Celidust 3910, Sunwax 131-P, Sunwax 161-P, manufactured by Sanyo Chemical Co., Ltd., Chemipearl W-100, Chemipearl W-, manufactured by Mitsui Petrochemical Co., Ltd.
200, Chemipearl W-500, Chemipearl W-80
0, Chemipearl W-950 or the like can be used.

As the fluororesin compound, fine particles of tetrafluoroethylene are preferable, and Daikin Industries, Ltd.
Lubron L-2, Lubron L-5, MP1100, MP1200, Mitsui DuPont, Fluon Dispersion AD1, Fluon Dispersion AD2, Fluon L140J, Fluon L150J, Fluon L15, Asahi ICI Fluoropolymers Co., Ltd.
5J or the like can be used.

Further, by adding a polyolefin wax and tetrafluoroethylene in combination among these solid lubricants, a particularly excellent lubricating effect can be expected. The compounding amount of the solid lubricant is 1 to 80 parts by weight based on 100 parts by weight of the main component [(a) + (b)] composed of the aqueous resin (a) and the polymer chelating agent (b) in a solid content ratio. Department. If the amount of the solid lubricant is less than 1 part by weight, the lubricating effect is poor. On the other hand, if it exceeds 80 parts by weight, the paintability is reduced. The preferred compounding amount of the solid lubricant is 3 to 40 parts by weight.

Further, as another additive to the protective film,
Coloring dyes (eg, water-soluble azo metal complex dyes), organic coloring pigments (eg, condensed polycyclic organic pigments, phthalocyanine organic pigments, etc.), and inorganic pigments (eg, titanium oxide,
Powders or colloids of aluminum oxide, magnesium oxide, tin oxide, iron oxide (Fe ₂ O ₃ , Fe ₃ O ₄ ), zirconium oxide and the like, chelating agents (eg, thiols,
Pyridines, virazines, pyrophosphoric acid, etc.), conductive pigments (e.g., metal powders such as zinc, aluminum, nickel, etc., iron phosphide, antimony-doped tin oxide, etc.), coupling agents (e.g., silane coupling agents, Titanium coupling agent), melamine / cyanuric acid adduct, and the like.

The above-mentioned protective film is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet without a chromate-treated film. The dry film thickness of the protective film is optional, but is preferably 0.01 to 5 μm.
m. When the film thickness is less than 0.01 μm, the corrosion resistance is insufficient. On the other hand, when the weldability is required, the film thickness is 5 μm.
If it exceeds m, the weldability will decrease. More preferably, the thickness is 0.05 to 3 μm, and still more preferably 0.1 to 2 μm. Furthermore, an organic resin film is placed on top of this protective film,
A silica-containing organic resin film or an organic composite silicate film may be formed.

The surface-treated steel sheet of the present invention is obtained by applying a coating composition containing the above-mentioned aqueous resin (a) and polymer chelating agent (b) as main components to the surface of a zinc-based steel sheet or an aluminum-based steel sheet. It is manufactured by drying. Before applying the coating composition, the surface of the plated steel sheet may be subjected to an alkali degreasing treatment, if necessary, and may be subjected to a pretreatment such as a surface conditioning treatment in order to improve adhesion and corrosion resistance.

The method of applying the coating composition containing the aqueous resin (a) and the polymer chelating agent (b) as main components to the surface of a zinc-coated steel sheet or an aluminum-plated steel sheet includes a coating method, a dipping method, Any method such as 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, heating and drying are usually performed without washing with water. However, since the film containing the polymer chelating agent is bonded to the surface of the plated steel sheet as the base by chemical adsorption or reaction, a water washing step may be performed 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. The heat treatment is performed at a plate temperature of 50 to 30.
It is desirably performed at 0 ° C., preferably in the range of 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. When the heating temperature is 3
If the temperature is higher than 00 ° C., 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-mentioned protective film on both sides or one side. Therefore, examples of the form of the steel sheet of the present invention include the following. (1) One side: Plating film-Protective film, One side: Plating film (2) One side: Plating film-Protective film, One side: Known phosphate treatment film, etc. (3) Both surfaces: Plating film-Protective film

[0048]

[Example] As a surface-treated steel sheet for home appliances, building materials, and automobile parts, the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet is subjected to alkali degreasing treatment, washed with water, and dried.
The coating composition for forming a protective film was applied by a roll coater and dried by heating. About the obtained surface-treated steel sheet,
Evaluation of the appearance of the film and each evaluation test of corrosion resistance (white rust resistance), paint adhesion and workability were performed. The results are shown in Tables 7 to 20, and 22, together with the type of the plated steel sheet used, the composition of the protective film, the film thickness, and the drying temperature.

The conditions for producing the surface-treated steel sheet in this embodiment are shown below. (1) Plated steel sheet A cold-rolled steel sheet having a thickness of 0.8 mm and a surface roughness (Ra) of 1.0 μm was subjected to various types of zinc-based plating or aluminum-based plating and used as a base-plated steel sheet. Table 1 shows the used plated steel sheets. (2) a coating composition containing a water-based resin and a polymer chelating agent as a main component.
If necessary, a rust preventive additive and a solid lubricant were added thereto, and the mixture was dispersed for a required time using a coating disperser (sand grinder) to obtain a coating composition.

(2-1) Aqueous resin Various water-dispersible resins or water-soluble resins shown in Table 2 were used. (2-2) Polymer chelating agent 1 to No. 4 and Table 21 6-N
o. 21 polymer chelating agent aqueous solution was used. Also,
As a comparative example, No. 3 in Table 3 was used. ED, which is a low molecular weight chelating agent conventionally used as a rust inhibitor, shown in FIG.
A TA (ethylenediaminetetraacetic acid) aqueous solution was used. (2-3) Rust Prevention Additives Rust prevention additives such as silica shown in Table 4 and polyphosphate shown in Table 5 were used as needed. (2-4) Solid lubricant A solid lubricant shown in Table 6 was used as required.

The quality performance of the surface-treated steel sheet was evaluated as follows. (1) Appearance of Film For each sample, the uniformity of the film appearance (with or without unevenness) was visually evaluated. The evaluation criteria are as follows. ：: uniform appearance without any unevenness △: appearance with some unevenness ×: appearance with unevenness

(2) White rust resistance For each sample, a salt spray test (JIS-Z-23)
71) was carried out, and evaluated by the area ratio of white rust occurrence after a predetermined time. In addition, the film formed without the rust-preventive additive was evaluated by the white rust resistance after 96 hours, while the film containing the rust-preventive additive (silica or a rust-preventive additive other than silica) was formed. As for those obtained, the white rust resistance after 96 hours alone did not show a difference superior to that without the rust-preventive additive. Therefore, the white rust resistance after 120 hours, which is a more severe test condition, was also evaluated. In addition, the plated steel sheet No. 2-N
o. 12 was also used as a base plated steel sheet, and the white rust resistance after 96 hours and 120 hours was evaluated, respectively. 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) Adhesion of paint For each sample, a melamine 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

(4) Workability Deep drawing was performed with a blank diameter of φ120 mm and a die diameter of φ50 mm (without oiling), 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

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

[Table 4]

[0059]

[Table 5]

[0060]

[Table 6]

[0061]

[Table 7]

[0062]

[Table 8]

[0063]

[Table 9]

[0064]

[Table 10]

[0065]

[Table 11]

[0066]

[Table 12]

[0067]

[Table 13]

[0068]

[Table 14]

[0069]

[Table 15]

[0070]

[Table 16]

[0071]

[Table 17]

[0072]

[Table 18]

[0073]

[Table 19]

[0074]

[Table 20]

[0075]

[Table 21]

[0076]

[Table 22]

[0077]

As described above, the surface-treated steel sheet of the present invention does not contain any hexavalent chromium in the processing solution at the time of production or in the film component of the product, and furthermore, the surface treatment for applications such as building materials, home appliances and automobiles. It has high corrosion resistance as a steel sheet,
Excellent paint adhesion.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaru Sagiyama 1-2-1 Marunouchi, Chiyoda-ku, Tokyo F-term in Nihon Kokan Co., Ltd. 4D075 AE03 CA43 DA06 DB05 DB07 DC02 DC12 DC18 EA06 EA37 EB15 EB14 EB15 EB17 EB19 EB22 EB32 EB39 EB52 EB56 EC01 EC03 EC07 EC54 4K026 AA02 AA07 AA09 AA12 AA13 BA01 BB04 BB06 BB08 BB09 CA16 CA18 CA23 CA25 CA29 CA33 CA37 CA38 CA39 CA41 DA15 DA16

Claims (9)

[Claims] 1. A water-dispersible resin and / or a water-soluble resin (a) on the surface of a galvanized steel sheet or an aluminum-plated steel sheet, and a polymer chelating agent (b) having a chelating group in a polymer matrix. And the weight ratio (a) / (b) of the solid content of (a) and (b) is 99.
A surface-treated steel sheet having excellent white rust resistance, characterized in that a protective film having a thickness of from 1/1 to 1/99 is formed. 2. A surface treatment excellent in white rust resistance, characterized in that a protective film containing the following components (A) and (B) is formed on the surface of a galvanized steel sheet or an aluminum-coated steel sheet. steel sheet. (A) water-dispersible resin and / or water-soluble resin (a)
And a polymer chelating agent (b) having a chelating group in the polymer matrix, wherein (a) and (b)
Weight ratio (a) / (b) of 99/1 to 1/99
100 parts by weight (solid content ratio) of (B) silica, polyphosphate, phosphate, phosphite,
1 to 100 parts by weight (solid content) of one or more rust preventive additives selected from molybdate, phosphomolybdate, phytic acid, phytate, phosphonic acid, and phosphonate 3. A surface treatment excellent in white rust resistance, characterized in that a protective film containing the following components (A) and (C) is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. steel sheet. (A) water-dispersible resin and / or water-soluble resin (a)
And a polymer chelating agent (b) having a chelating group in the polymer matrix, wherein (a) and (b)
Weight ratio (a) / (b) of 99/1 to 1/99
(C) a hydrocarbon-based compound such as a polyolefin wax,
One or more solid lubricants selected from fluororesin compounds, fatty acid amide compounds, metal sulfides, metal soaps, graphite, fluorinated graphite, boron nitride, polyalkylene glycols, and alkali metal sulfates 1 to
80 parts by weight (solid content ratio) 4. The following (A), (B) and (C) are provided on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet.
Surface treated steel sheet with excellent white rust resistance, characterized by forming a protective film containing the following components: (A) water-dispersible resin and / or water-soluble resin (a)
And a polymer chelating agent (b) having a chelating group in the polymer matrix, wherein (a) and (b)
Weight ratio (a) / (b) of 99/1 to 1/99
100 parts by weight (solid content ratio) of (B) silica, polyphosphate, phosphate, phosphite,
1 to 100 parts by weight (solid content) of one or more rust preventive additives selected from molybdate, phosphomolybdate, phytic acid, phytate, phosphonic acid, and phosphonate C) hydrocarbon compounds such as polyolefin wax;
One or more solid lubricants selected from fluororesin compounds, fatty acid amide compounds, metal sulfides, metal soaps, graphite, fluorinated graphite, boron nitride, polyalkylene glycols, and alkali metal sulfates 1 to
80 parts by weight (solid content ratio) 5. The chelating group of the polymer chelating agent has an amino acid group, a carboxyl group, a dithiocarbamic acid group, a polyamino group, a thiol group, a phosphomethylamino group, a thioureido group, a dithioic acid group, a phosphoric acid group, β 1 selected from a diketone group and a hydroxamoxime group
Claim 1, characterized in that it is a species or two or more species
The surface-treated steel sheet having excellent white rust resistance according to 2, 3, or 4. 6. The polymer matrix of the polymer chelating agent is polyethylene, polyvinyl alcohol, polyethylene glycol, polyethylene imine, polyamino compound, polyvinyl chloride, polyacrylic acid, epoxy resin,
6. Excellent in white rust resistance according to claim 1, 2, 3, 4, or 5, comprising one or more selected from phenol resin, styrene-divinylbenzene resin, and acrylic resin. Surface treated steel sheet. 7. The white rust resistance according to claim 1, 2, 3, 4, 5, or 6, wherein the number average molecular weight of the polymer matrix of the polymer chelating agent is 300 or more. Surface treated steel sheet. 8. The white rust resistance according to claim 1, wherein the number average molecular weight of the polymer matrix of the polymer chelating agent is 1,000 or more. Surface treated steel sheet. 9. The method according to claim 1, wherein the thickness of the protective film is 0.01 to 5 μm.
Or a surface-treated steel sheet excellent in white rust resistance according to 8.