JP2003013284A - Manufacturing method of surface treated steel sheet with excellent corrosion resistance - Google Patents

Abstract

(57) [Summary] PROBLEM TO BE SOLVED: To form a film containing no chromium.
To provide a method for producing a surface-treated steel sheet having excellent corrosion resistance.
That. SOLUTION: For electrolytic treatment using a steel sheet as a cathode in an electrolytic solution.
Production of surface-treated steel sheet that forms a protective treatment layer on the steel sheet surface
In the manufacturing method, one selected from Y, La, and Ce or
Two or more metal cations are converted to Y, La, and Ce in a total of 0.01
~ 3mol / L, Silica fine particle is SiO_Two0.001 to 3 mol / L conversion
Subjecting steel sheet to electrolytic treatment using aqueous solution as electrolyte
Method for producing surface-treated steel sheet with excellent corrosion resistance
Is used. In addition, Y, L
a, of one or more metal components selected from Ce
Adhesion amount is 5-3000mg / m in Y, La, Ce conversion^Two, Silica adhesion
Amount is SiO _Two10-1000mg / m in conversion^TwoForming a protective treatment layer
I do.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a surface-treated steel sheet having excellent corrosion resistance, which is suitable for use in automobiles, home appliances, building materials and the like.

[0002]

2. Description of the Related Art In order to improve the corrosion resistance of a surface-treated steel sheet, a chromate treatment for forming a protective treatment layer containing chromium on the surface of the steel sheet has hitherto been widely performed. However, in recent years, various technologies have been proposed for a protective treatment layer that does not use harmful Cr ⁶⁺ from the viewpoint of reducing environmentally hazardous substances. Among them, the fact that a hydroxide film of a rare earth element is dense and has corrosion resistance is used. The technology that has been done is attracting attention. As a method of forming such a protective treatment layer, electrolytic treatment has advantages such as easier control of the adhesion amount as compared with the method of forming a protective treatment layer by reaction, and therefore, for example, Japanese Patent Application Laid-Open No. H9-96952.
No. 249990 and Japanese Patent Laid-Open No. 2000-64090 disclose a technique of coating a metal surface with a rare earth hydroxide film by electrolytic treatment with an aqueous solution containing a rare earth element.

[0003]

In any of the above techniques, a protective treatment layer containing these components is formed on a surface of a metal material by electrolysis from an aqueous solution containing a rare earth metal ion or the like to obtain a dense rare earth water. Although it forms an oxide film, there is a problem that the corrosion resistance level does not improve as expected. It is considered that this is because the rare earth hydroxide can delay the corrosion of the underlayer due to its barrier effect, but once the corrosion starts, the corrosion proceeds rapidly.

The present invention has been made to solve the above problems of the prior art, and an object thereof is to provide a method for producing a surface-treated steel sheet having excellent corrosion resistance by forming a coating film containing no chromium. To do.

[0005]

The features of the present invention for solving the above problems are as follows.

(1) In the method for producing a surface-treated steel sheet in which a protective treatment layer is formed on the steel sheet surface by electrolytic treatment using a steel sheet as a cathode in an electrolytic solution, selected from Y, La, and Ce.
0.01 to 3 mol / L in terms of Y, La, and Ce in terms of one or more types of metal cations, and 0.001 to 3 mo in terms of SiO _{2 in} terms of silica fine particles.
A method for producing a surface-treated steel sheet having excellent corrosion resistance, which comprises subjecting a steel sheet to an electrolytic treatment using an aqueous solution containing l / L as an electrolytic solution.

(2) Y, L on the surface of the steel sheet by electrolytic treatment
a, one or more metal components selected from Ce
Adhesion amount is 5 to 3000 mg / m in terms of Y, La and Ce²Adhesion of silica
Amount of SiO ₂10-1000 mg / m in conversion²Forming a protective layer
A table excellent in corrosion resistance according to (1), characterized in that
Method for manufacturing surface-treated steel sheet.

(3) The electrolyte solution further contains nitrate ions, nitrite ions, chlorate ions, perchlorate ions, permanganate ions, bromate ions, vanadate ions,
Excellent corrosion resistance according to (1) or (2), characterized by containing 0.001 to 3 mol / L in total of one or more selected from molybdate and P oxygenate. Method for manufacturing surface-treated steel sheet.

(4) After subjecting the steel sheet to the electrolytic treatment according to any one of (1) to (3), an aqueous solution containing 0.001 to 3 mol / L of vanadate ion as V is used as an electrolytic solution. The method for producing a surface-treated steel sheet having excellent corrosion resistance, which is characterized in that the electrolytic treatment is performed.

(5) The protective layer formed by the electrolytic treatment according to any one of (1) to (3) by the second electrolytic treatment contains V of vanadium oxide and / or vanadium hydroxide. The amount of adhered components is 5 to 1000 mg / m in terms of V
It is characterized by forming a protective treatment layer which is ² (4)
The method for producing a surface-treated steel sheet having excellent corrosion resistance according to 1.

(6) The method for producing a surface-treated steel sheet according to any one of (1) to (5), wherein the steel sheet is a zinc-based plated steel sheet.

(7) A coating layer is formed on the surface of the surface-treated steel sheet obtained by the manufacturing method according to any one of (1) to (6), and the coating layer has a thickness of 0.05 to 3 μm. A method for producing a surface-treated steel sheet, comprising: Same as claim

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a method for producing a surface-treated steel sheet having excellent corrosion resistance, which comprises forming a protective treatment layer on at least one surface of the raw steel sheet by electrolytic treatment in an electrolytic solution. There is no limitation on the type of the material steel sheet to be subjected to the electrolytic treatment, and for example, a hot rolled steel sheet, a cold rolled steel sheet, a zinc-based plated steel sheet, or the like can be used. As the zinc-based plated steel sheet, electrogalvanized steel sheet, hot-dip galvanized steel sheet, alloyed hot-dip galvanized steel sheet, Zn-Ni, Zn-Co, Zn-
Co-Mo, Zn-Cr and other alloy electroplated steel sheets, Z
There are n-SiO ₂ dispersion electroplated steel sheet, hot-dip zinc-aluminum alloy-plated steel sheet, hot-dip zinc-aluminum-magnesium alloy-plated steel sheet, hot-dip zinc-magnesium alloy-plated steel sheet and the like. In addition, in order to prevent film defects and unevenness when a protective layer or organic film is formed on the plating film surface, alkaline degreasing, solvent degreasing, surface conditioning treatment (alkaline Surface conditioning treatment, acid surface conditioning treatment) and the like.

The present inventors have studied the formation of a protective treatment layer by electrolysis, and as a result of studying a method for enhancing the corrosion resistance of a coating film made of a rare earth hydroxide, as a result, the corrosion resistance can be improved by precipitating silica together with the rare earth hydroxide by cathodic electrolysis. The present invention has been completed with the finding that the above-mentioned increase dramatically.
That is, by using an aqueous solution satisfying the following (a) and (b) as a component of the aqueous solution for electrolysis (electrolytic solution),
It is possible to obtain a protective treatment layer exhibiting excellent corrosion resistance.

(A) 1 selected from Y, La and Ce
One or two or more kinds of metal cations are contained in a total amount of 0.01 to 3 mol / L in terms of Y, La and Ce. (Y, La, Ce conversion means that Y, La, and Ce contained in the electrolytic solution are all metal cations, and Y and L in the analyzed electrolytic solution are
a, the amount of metal cation calculated from the amount of Ce. ) There are no particular restrictions on the supply source of the metal cations of Y, La, and Ce, and when Y, La, and Ce are deposited, the electrolytic solution does not necessarily include nitrate ions, nitrite ions, chlorate ions,
No oxidizer components such as bromate ion and hydrogen peroxide are required, and electrolysis is performed in an aqueous solution obtained by dissolving water-soluble rare earth salts such as sulfates, halides, carboxylates, perchlorates and carbonates. A film containing a rare earth oxide and / or a hydroxide can be formed only by treating. There are no particular restrictions on the hydration number of sulfates, halides, carboxylates, perchlorates, carbonates, etc., which serve as cation supply sources. Examples of carboxylates include acetate, lactate, citrate, and oxalate. The total concentration of one or more metal cations selected from Y, La and Ce is 0.01 to 3 mol / L. If less than 0.01 mol / L,
A film with excellent corrosion resistance cannot be obtained. Also, 3mo
If it exceeds l / L, it is uneconomical because the amount of adhesion corresponding to the concentration cannot be obtained. Preferably 0.05-0.5
It is mol / L. Since the sulfate salt is easy to handle, it is preferable to use a system in which a carboxylate salt is mixed with the sulfate salt as a base.

(B) 0.001 to 3 of silica fine particles in terms of SiO ₂
Contains mol / L.

An electrolytic solution containing only metal cations of Y, La and Ce has insufficient corrosion resistance of the formed film,
Corrosion resistance can be improved by co-depositing silica. Although the reason is not clear, it is considered that the effect of the silica inhibitor is added to the barrier property of the rare earth hydroxide. The addition of silica stabilizes the corrosion product and makes the progress very slow even when corrosion begins. In order to deposit silica in the film, an electrolytic solution containing silica fine particles of an appropriate concentration is required, and 0.001 to 3 mol /
When L is contained, silica precipitates stably. 0.001m
If it is less than ol / L, it is not sufficiently precipitated, and if it exceeds 3 mol / L, the stability of the liquid is lowered. More preferably 0.01 to 0.5
mol / L. The fine silica particles can be added by a method using an aqueous dispersion such as silica sol or a method of directly adding fine silica particles such as fumed silica and white carbon. In this case, the primary particle size of silica (the smallest particle size that can be physically divided), the shape, etc. are not particularly specified, but in order to form a dense protective treatment layer, those with a small primary particle size are preferred. More preferable.

The protective treatment layer formed by electrolytic treatment with the electrolytic solution containing (a) and (b) contains an oxide and / or hydroxide containing Y, La and Ce as main components. Although it may be crystalline or amorphous, a film having excellent denseness is obtained especially when it is amorphous.

Description will be made on the preferable adhesion amount of the protective treatment layer.
To do. As described above, the structure of the protective treatment layer obtained by the present invention
Structure is not clear enough, but the inclusion of each component in the protective layer
The amount (adhesion amount) is one selected from Y, La, and Ce
Or, two or more kinds of metal components are 5 in total in terms of Y, La, and Ce.
~ 3000mg / m², The silica component is SiO₂10-10 in conversion
00 mg / m², Is preferred. (Y, La, Ce
Conversion means that Y, La, and Ce contained in the protective treatment layer film
Y, L in the analyzed film, assuming that they are all metals
a, the amount of metal calculated from the amount of Ce. ) Of metal components
Adhesion amount is 5 mg / m ²If less than, corrosion resistance may be insufficient.
On the other hand, 3000 mg / m²If it exceeds, the film will be easily peeled off.
And problems such as deterioration of conductivity occur. Furthermore
Preferably 10 to 500 mg / m²Is. Silica component
Adhesion amount of 10mg / m²If less than, corrosion resistance may be insufficient
Yes, while 1000 mg / m²If it exceeds, the conductivity will decrease.
Problems occur. Note that electrolysis conditions (current density and
That in the protective layer by changing the charging time)
Optimizing corrosion resistance by controlling the amount of each component deposited
You can

Further, as the electrolytic solution, the above (a), (b)
In addition to the above, by using an aqueous solution satisfying (c), it is possible to obtain a protective treatment layer exhibiting further excellent corrosion resistance.

(C) 1 selected from nitrate ion, nitrite ion, chlorate ion, perchlorate ion, permanganate ion, bromate ion, vanadate ion, molybdate ion, P oxygenate ion 1 It contains 0.001 to 3 mol / L in total of one kind or two or more kinds.

By adding the above-mentioned components, the denseness of the coating in the rare earth + silica system can be improved, and a coating excellent in corrosion resistance can be obtained. Although the mechanism of improving the denseness of the film by adding these components is not clear, it is presumed that the effect of increasing the pH due to the consumption of hydrogen ions at the time of reduction, the effect of eutectoid to the film, and the like.

The above-mentioned ion supply method is not particularly limited, and a metal salt such as a water-soluble alkali metal salt containing these ions or an ammonium salt may be added. Further, as the oxygen acid of P, phosphoric acid, primary phosphate,
Polycondensation phosphates such as dibasic phosphate, tertiary phosphate, pyrophosphate, pyrophosphate, tripolyphosphate, tripolyphosphate, phosphorous acid, phosphite, hypophosphite, hypophosphite One or more such as acid salts can be added.

The above-mentioned ions in total of 0.001 to 3 mol /
Effective when L is contained. If it is less than 0.001 mol / L, the effect is not sufficient. Further, if it exceeds 3 mol / L, the stability of the liquid decreases. It is preferably 0.01 to 2 mol / L, more preferably 0.01 to 1 mol / L.

The pH of the electrolytic solution containing the above (a), (b) and preferably (c) is not particularly limited as long as it can stably disperse the components in the aqueous solution, but the stability of the solution Moreover, pH 1-9 is preferable. More preferably p
H3-8, particularly preferably pH 4-8.

In addition to the above, components that enhance electric conductivity, such as sodium sulfate and ammonium sulfate, a pH buffering agent such as sodium acetate and sodium citrate, and a water-soluble organic resin for the purpose of further densifying the film, are used in the electrolytic solution. You may add.

Further, after the lower protective treatment layer is formed by performing electrolytic treatment using the electrolytic solution containing the above (a) and (b), preferably (c), the following (d) is further performed. By performing the second electrolytic treatment with the contained electrolytic solution to form the upper protective treatment layer to form a two-layer protective treatment layer, the corrosion resistance can be further dramatically improved.

(D) 0.001 in terms of V of vanadate ion
Contains ~ 3mol / L. Here, the V conversion means that V in the electrolytic solution depends on the amount of V in vanadate ions contained in the electrolytic solution.
It is a definition of concentration.

As the vanadate ion source, metavanadic acid, orthovanadic acid sodium salt, potassium salt, ammonium salt or the like can be used. The concentration of vanadate ion is 0.001 to 3 mol / L. 0.00
If it is less than 1 mol / L, a film having excellent corrosion resistance cannot be obtained. On the other hand, if it exceeds 3 mol / L, it is uneconomical because the amount of adhesion corresponding to the concentration cannot be obtained. It is preferably 0.05 to 0.5 mol / L.

By forming a rare earth hydroxide + silica film which is the lower protective treatment layer, and further performing a second electrolytic treatment in an aqueous solution containing vanadate ions to form the upper protective treatment layer, corrosion resistance is improved. Although the mechanism for dramatically improving it is not necessarily clear, it is considered that a dense film is formed due to the oxidation action at the time of precipitation of vanadium oxide to improve the corrosion resistance. The film obtained by the above electrolytic treatment is a film containing vanadium oxide and / or hydroxide. Although it may be either crystalline or amorphous, a film having excellent denseness is obtained particularly when it is amorphous.

The preferred adhesion amount when the protective treatment layer is formed into the two-layer structure of the lower protective treatment layer + the upper protective treatment layer with the electrolytic solution using (d) will be described. The upper protective layer preferably contains V in an amount of 5 to 1000 mg / m ^{2 in} terms of V.
If it is less than 5 mg / m ² , corrosion resistance may be insufficient, and 100
If it exceeds 0 mg / m ² , problems such as easy peeling of the film and deterioration of conductivity occur. More preferably, 1
It is set to 0 to 500 mg / m ² .

Silica fine particles were added to the electrolytic solution using (d) as Si.
Addition of 0.001 to 3 mol / L in terms of O ₂ further improves the corrosion resistance. If it is less than 0.001 mol / L, the effect is not sufficient. Further, if it exceeds 3 mol / L, the stability of the liquid decreases. More preferably, it is 0.01 to 0.5 mol / L. The preferable amount of silica attached is 10 to _{1 in} terms of SiO _2.
It is 000 mg / m ² . If it is less than 10 mg / m ^2, the corrosion resistance may be insufficient, while if it exceeds 3000 mg / m ² , there is a problem such as a decrease in conductivity.

The electrolytic solution using (d) further contains nitrate ion, nitrite ion, chlorate ion, perchlorate ion, permanganate ion, bromate ion, molybdate ion, P oxygenate ion. When one or two or more selected from the above are contained in a total amount of 0.001 to 3 mol / L, the denseness of the film is improved and a more excellent film can be obtained.
If the amount of the above ions is less than 0.001 mol / L, the effect is not sufficient. On the other hand, if it exceeds 3 mol / L, the stability of the liquid decreases. It is preferably 0.01 to 2 mol / L, more preferably 0.01 to 1 mol / L. Although the mechanism of improving the denseness of the film by adding these components is not clear,
PH increase effect due to consumption of hydrogen ions during reduction,
The effect of eutectoid on the film can be considered. The method for supplying these ions is not particularly limited, and a metal salt such as a water-soluble alkali metal salt containing these ions or an ammonium salt may be added. As the oxygen acid of P, phosphoric acid, primary phosphate, secondary phosphate,
One or more of polycondensation phosphates such as tertiary phosphate, pyrophosphate, pyrophosphate, tripolyphosphate, tripolyphosphate, phosphorous acid, phosphite, hypophosphite, hypophosphite, etc. Can be added.

The pH of the electrolytic solution using (d) is not particularly limited as long as it can stably disperse the components in the aqueous solution, but from the stability of the solution, it is preferably pH 5 to 14, and more preferably pH 7. ~ 12.

In addition to the above, the electrolytic solution using (d) is
A component such as sodium sulfate or ammonium sulfate that enhances electrical conductivity, a pH buffering agent such as sodium acetate or sodium citrate, or a water-soluble organic resin may be added for the purpose of further densifying the film.

Next, preferable electrolytic conditions for manufacturing will be described. The following conditions are the same in the second electrolytic treatment for forming the upper protective treatment layer.

In the present invention, a protective treatment layer is formed on a steel sheet by electrolysis, and the electrolysis method is not particularly limited, but in one embodiment, a strip is usually passed through a cell in which anodes are arranged in parallel. The electrolysis cell can be used. In this case, both vertical cells and horizontal cells can be applied. The counter electrode of the steel sheet is not particularly limited, but any of a Pb alloy system, an insoluble anode such as an electrode coated with iridium oxide, and a self-fluxing anode that can replenish the components of the electrolytic bath are applicable.

The conditions for forming the protective treatment layer by electrolysis of the present invention are not particularly limited except for the current density, but when a zinc-based plated steel sheet is used, the zinc-based plated steel sheet is used as the cathode and electrolysis is performed at a constant current. Are particularly preferable in that the protective treatment layer can be effectively formed without elution of zinc. Even when a normal steel plate is used, electrolysis at a constant current with the steel plate as the cathode can effectively form the protective layer with less elution of iron.

The current density of the electrolytic treatment in the present invention is preferably 1 to 20 A / dm ² when the electrolytic treatment is performed using a steel sheet as the cathode. This is because hydrogen gas is generated as a side reaction when a film is formed by cathodic electrolysis, and when the current density is 20 A / dm ² or more, hydrogen is strongly generated and the denseness of the film is greatly reduced. On the other hand, if it is less than 1 A / dm ² , the film is not sufficiently deposited and a film effective for corrosion resistance cannot be obtained. The current density is more preferably 1 to 10 A / dm
^Set to ² . The electrolysis time is not particularly limited, and a pattern in which there are a plurality of electrolysis cells and the energization is in multiple stages may be used. In this case, the total energizing time is 30
Seconds or less are preferable. When energized for 30 seconds or more, not only the production efficiency becomes a problem, but also the protective treatment layer becomes thick and may be easily missing. A more preferable energization time is 0.1 to 5 seconds. The temperature of the electrolytic solution is not particularly limited, but is preferably 40 to 60 ° C.

The method of washing with water after electrolysis is not particularly limited, and ordinary spray washing is suitable. The washing temperature is not particularly limited, either, and is preferably room temperature to 80 ° C. Also, the drying method is not particularly limited, and any method such as drying by high frequency induction heating, drying by hot air, or drying by infrared rays can be used.

Although a steel sheet having excellent corrosion resistance is obtained as described above, the corrosion resistance can be further improved by coating the upper part of the protective treatment layer. A coating layer of an organic or inorganic type or a mixture thereof is formed on the protective treatment layer of a zinc-based plated steel sheet having a protective treatment layer or a cold-rolled or hot-rolled steel sheet. The coating layer may be a single layer, but for example, an inorganic coating layer is dipped on the protective treatment layer, formed by spraying, and an organic coating layer is further formed thereon to form a two-layer structure. A multilayer structure is also possible.

The coating layer will be described in detail below. The coating layer is a film on the protective treatment layer, which is an inorganic type,
Any organic type may be used. The coating composition is not particularly limited, but when an inorganic coating is formed as a coating layer, for example, water glass, a silicic acid-based aqueous solution such as lithium silicate, methyl silicate, ethyl silicate or the like silicate ester is ethanol, methyl cell. An organic solvent such as sorb, or a solution dissolved in a mixed solution of an organic solvent and water, a solution of a silane coupling agent in water or an organic solvent, a solution of a silicone resin dissolved in a solvent, an aqueous phosphate solution, Alternatively, silica in these solutions,
A dispersion of an oxide such as alumina, magnesia, titania or zirconia may be dipped or sprayed, or after coating, it may be dried.

Next, the organic coating layer will be described. The base resin for the organic coating layer (organic film) is not particularly limited, and any of water-soluble resin, water-dispersible resin, and organic solvent-soluble resin can be used. Epoxy resin, urethane resin, acrylic resin, acrylic resin -Ethylene copolymers,
Although an acrylic-styrene copolymer, an alkyd resin, a polyester resin, an ethylene resin, etc. can be used, it is preferable to use an organic polymer resin having an OH group and / or a COOH group particularly from the viewpoint of corrosion resistance.

Examples of the organic polymer resin having an OH group and / or a COOH group include epoxy resin, polyhydroxypolyether resin, acrylic copolymer resin, ethylene-acrylic acid copolymer resin, alkyd resin and polybutadiene. Examples thereof include resins, phenol resins, polyurethane resins, polyamine resins, polyphenylene resins, and mixtures or addition polymers of two or more kinds of these resins. Of these, thermosetting resins are preferable, and epoxy resins or modified epoxy resins are most preferable. Thermosetting epoxy resin, thermosetting modified epoxy resin, acrylic copolymer resin copolymerized with epoxy group-containing monomer, polybutadiene resin having epoxy group, polyurethane resin having epoxy group, and addition products of these resins or Condensates and the like may be mentioned, and one of these epoxy group-containing resins may be used alone or 2
A mixture of two or more species can be used.

As the epoxy resin, bisphenol A, bisphenol F, novolac, etc. are glycidyl etherified epoxy resin, bisphenol A is added with propylene oxide, ethylene oxide or polyalkylene glycol, and glycidyl etherified epoxy resin is further added. A group epoxy resin, an alicyclic epoxy resin, a polyether epoxy resin, or the like can be used. These epoxy resins preferably have a number average molecular weight of 1500 or more, especially when curing at low temperature is required. The epoxy resins may be used alone or as a mixture of different types.

Examples of the modified epoxy resin include resins obtained by reacting various modifying agents with the epoxy group or bidroxyl group in the above 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 made to react with isocyanate compound, amine added urethane modified epoxy resin made by adding alkanolamine to urethane modified epoxy resin made to react epoxy compound with isocyanate compound, etc. Can be mentioned.

The polyhydroxypolyether resin is a mononuclear type or dinuclear type divalent phenol or a mixed divalent phenol of mononuclear type and dinuclear type with an approximately equimolar amount of epihalohydrin in the presence of an alkali catalyst. It is a polymer obtained by polycondensation. Representative examples of mononuclear dihydric phenols include resorcin, hydroquinone, and catechol, and representative examples of dinuclear phenols include bisphenol A. These may be used alone or in combination of two or more. May be.

Examples of the urethane resin include oil-modified polyurethane resin, alkyd polyurethane resin, polyester polyurethane resin, polyether urethane resin, polycarbonate polyurethane resin and the like.

Examples of the alkyd resin include oil-modified alkyd resin, rosin-modified alkyd resin, phenol-modified alkyd resin, styrenated alkyd resin, silicone-modified alkyd resin, acrylic-modified alkyd resin, oil-free alkyd resin, and high-molecular-weight oil-free alkyd. Resin etc. can be mentioned.

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

Examples of the ethylene resin include ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene-based copolymers such as carboxyl-modified polyolefin resin, ethylene-unsaturated carboxylic acid copolymers,
Examples thereof include ethylene ionomers, and resins obtained by modifying these resins with other alkyd resins, epoxy resins, phenol resins and the like may be used.

Examples of the acrylic silicone resin include those containing a hydrolyzable alkoxysilyl group at the side chain or terminal of an acrylic copolymer as a main component, and a curing agent added thereto. When these acrylic silicone resins are used, excellent weather resistance can be expected.

As the fluororesin, there is a fluoroolefin copolymer, and examples thereof include alkyl vinyl ether, synchroalkyl vinyl ether, carboxylic acid modified vinyl ester, hydroxyalkyl allyl ether, tetrafluoropropyl vinyl ether, etc. There is a copolymer obtained by copolymerizing a monomer (fluoroolefin). When these fluororesins are used, excellent weather resistance and excellent hydrophobicity can be expected.

In order to lower the drying temperature of the resin,
Different resin types in the core part and shell part of the resin particles,
Alternatively, a core-shell type water-dispersible resin composed of resins having different glass transition temperatures can be used. Further, using a water-dispersible resin having a self-crosslinking property, for example, by providing an alkoxysilane group to the resin particles, the silanol group is generated by the hydrolysis of the alkoxysilane during the heating and drying of the resin, and the silanol group between the resin particles is generated. Inter-particle cross-linking utilizing the dehydration condensation reaction of can be used. Also,
As the resin used for the organic film, an organic composite silicate in which an organic resin is composited with silica via a silane coupling agent is also suitable.

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), Amino resins such as butylated urea-melamine resin and benzoguanamine resin, hardeners such as blocked isocyanates, oxazoline compounds, and phenol resins can be added.

Further, the organic and inorganic coating layers described above contain fine oxide particles (for example, silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, and oxide) as a rust preventive additive for further improving the corrosion resistance. cerium,
Antimony oxide, etc.), polyphosphate, phosphate (eg, zinc phosphate, aluminum dihydrogen phosphate, zinc phosphite, etc.), vanadate, molybdate, phosphomolybdate (aluminum phosphomolybdate, etc.) ), Organic phosphoric acid and salts thereof (for example, phytic acid, phytate, phosphonic acid, phosphonate and metal salts thereof, alkali metal salts), organic inhibitors (for example, hydrazine derivatives, thiol compounds, dithiocarbamate salts, etc.) ), One or more compounds selected from organic compounds (polyethylene glycol) and the like may be added to the coating composition.

Furthermore, in the above-mentioned coating layer, as other additives, organic coloring pigments (for example, condensed polycyclic organic pigments, phthalocyanine organic pigments, etc.), coloring dyes (for example, organic solvent-soluble azo dyes, Water-soluble azo metal dyes, etc.), inorganic pigments (titanium oxide), chelating agents (thiols, etc.), conductive pigments (for example, metal powders of zinc, aluminum, nickel, etc., iron phosphide, antimony-doped tin oxide, etc.) , A coupling agent (for example, a silane coupling agent, a titanium coupling agent, etc.), a melamine / cyanuric acid adduct and the like can be added.

Further, in order to prevent blackening (a kind of oxidation phenomenon of the plating surface) under the use environment of the organic coated steel sheet having the above organic coating layer, iron group metal ions (Ni Ion, Co ion, Fe ion), preferably Ni ion. The upper limit of the concentration of the iron group metal ion is not particularly specified, but it is set to such an extent that the corrosion resistance is not affected as the concentration increases.

If desired, a solid lubricant may be added to the coating layer for the purpose of improving the processability of the coating. Examples of the solid lubricant applicable to the present invention include the following. Polyolefin wax, paraffin wax (for example, polyethylene wax, synthetic paraffin, natural paraffin, microwax, chlorinated hydrocarbon), fluororesin fine particles (for example, polyfluoroethylene resin (polytetrafluoroethylene resin, etc.), polyvinyl fluoride resin , Poly (vinylidene fluoride resin, etc.), fatty acid amide compounds (for example, stearic acid amide, palmitic acid amide, methylene bis stearoamide, ethylene bis stearoamide, oleic acid amide, esyl acid amide, alkylene bis fatty acid amide, etc.), Metal soaps (eg calcium stearate,
Lead stearate, calcium laurate, calcium palmitate, etc., metal sulfides (molybdenum disulfide, tungsten disulfide), graphite, fluorinated graphite, boron nitride, polyalkylene glycol, alkali metal sulfates and the like can be used.

Among the above solid lubricants, polyethylene wax, fluororesin fine particles (poly 4
Fluorinated ethylene resin fine particles) are suitable. Examples of the polyethylene wax include Celidust 9615A, Celidust 3715, and Celidust 362 manufactured by Hoechst.
0, Ceridust 3910, Sun Wax 131P, San Wax 161P manufactured by Sanyo Kasei Co., Ltd., Chemipearl W100, Chemipearl W200 manufactured by Mitsui Petrochemical Co., Ltd.
Chemipearl W500, Chemipearl W800, Chemipearl W950, etc. can be used.

Further, as the fluororesin fine particles, tetrafluoroethylene fine particles are most preferable, and for example, Lubron L2 and Lubron L5 manufactured by Daikin Industries, Ltd., MP1100, MP1200 manufactured by Mitsui-Dupont Co., and Asahi IC Eye Fluoro. Fullon Dispersion AD1 and Fullon Dispersion AD manufactured by Polymers Co., Ltd.
2, full-on L141J, full-on L150J, full-on L155J and the like are preferable. Also, among these,
A particularly excellent lubricating effect can be expected by the combined use of polyolefin wax and tetrafluoroethylene fine particles.

The blending amount of the solid lubricant in the coating layer is 1 to 80 mass% (solid content), preferably 3 to the base resin.
-40 mass% (solid content). If the blending amount of the solid lubricant is less than 1 mass%, the lubricating effect is poor, while the blending amount is 8
If it exceeds 0 mass%, the coating property is deteriorated, which is not preferable.

The coating composition for forming the coating layer is
Usually, it contains a solvent (organic solvent and / or water), and if necessary, a neutralizing agent and the like are added. The dry film thickness of the coating layer is 0.05 to 3 μm, preferably 0.1 to 1 μm. If it is thinner than 0.05 μm, the corrosion resistance is not improved. On the other hand, if it exceeds 3 μm, there is a problem that welding is not possible because the corrosion resistance is good but the conductivity is poor.

The production method of the present invention having a coating layer will be described. In the present invention, formation of a protective treatment layer by electrolysis,
A film is formed by a process of washing with water, drying, and formation of a coating layer, and if necessary, formation of a protective treatment layer by electrolysis,
The sealing treatment may be carried out immediately after the formation of the protective treatment layer, such as washing with water (or no washing), sealing treatment, drying, formation of a coating layer and the like. The sealing treatment is performed by a method such as spraying treatment, dipping treatment, and coating. As the coating layer used for sealing, the composition for the coating layer described in the present invention can be used. Further, in this case, although the film thickness of the sealing layer is not particularly specified, sufficient performance can be obtained even with a film thinner than the coating layer from the viewpoint of closing defects in the protective treatment layer,
Further, if the film thickness is too thick, the adhesion to the coating layer will decrease, so it is preferably 0.05 to 1 μm, more preferably 0.1.
05-0.5 μm is suitable.

The method for forming the coating layer on the protective treatment layer is not particularly limited, but any of a coating method, a dipping method, an electrolytic method and a spray method may be used, and the coating method may be a roll coater (three roll method). 2 roll method), a squeeze coater, a die coater, or the like may be used. 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 squeezing method after coating, dipping, and spraying with a squeeze coater or the like.

The formation of the coating layer is carried out following the steps of forming a protective layer by electrolytic treatment, contacting with an electrolytic solution without electricity (if necessary), washing with water, and drying. Formation of layers may be performed.

Further, the temperature at the time of applying the raw material resin for the coating layer is not particularly limited, but an ordinary temperature to 60 ° C. is suitable. If the temperature is lower than room temperature, it is uneconomical because equipment for cooling or the like is required. On the other hand, if the temperature exceeds 60 ° C., water is evaporated and liquid management becomes difficult.

After forming the coating layer, heating and drying are usually carried out without washing with water, but it is also possible to carry out washing with water after forming the coating layer. The method for drying the coating layer is not particularly limited, and any of drying by high frequency induction heating, drying by hot air, and drying by infrared rays can be used. The heat drying temperature in this case is 50 to 300 ° C., preferably 8 at the ultimate plate temperature.
It may be carried out in the range of 0 to 200 ° C, more preferably 80 to 160 ° C.

[0069]

EXAMPLE An electrolytic solution adjusting chemical having a concentration shown in Tables 1 and 2 was dissolved in ion-exchanged water to prepare an electrolytic solution for lower protective treatment layers A to P and upper protective treatment layers a to i. And the electrolytic solution of. The pH of each electrolytic solution is also shown in Tables 1 and 2. The ICP method was used to quantify the amount of metal cations in the electrolytic solution. The pH of the electrolytic solution is a value at 50 ° C., and in the case of a sulfate salt, an acid having basically the same anion, such as sulfuric acid, was used. When raising pH, it adjusted appropriately using diluted sodium hydroxide. In Tables 1 and 2, special grade reagents manufactured by Wako Pure Chemical Industries, Ltd. were used as chemicals other than silica sol (silica fine particles). The silica sol added to the electrolytic solution was Snowtex OS from Nissan Kagaku, and the silica sol concentration in the table was Si.
It is the molar concentration in terms of O ₂ .

[0070]

[Table 1]

[0071]

[Table 2]

Reference numerals A to H, M, N, a to f shown in Tables 1 and 2
Is within the range of the components of the electrolytic solution used in the present invention, but the symbol I
~ L, O, P, g ~ i are out of range. Code O is Y, Ce, L
The cation of a is not contained, the code P does not contain fine silica particles, and the code i does not contain vanadate ion.

Further, as the composition for obtaining the organic coating layer, the resin compositions (symbols A to O) shown in Table 3 were prepared. Fine silica particles were added to each of the resin compositions shown in Table 3 so as to be 10 mass% with respect to the solid content of the resin composition, and dispersed using a paint disperser (sand grinder) to obtain a paint composition. In addition, as the composition for obtaining the inorganic coating layer, the resin compositions (symbols A to C) shown in Table 4 were prepared.

[0074]

[Table 3]

[0075]

[Table 4]

As the original plate for forming the protective treatment layer, various galvanized steel sheets and cold-rolled steel sheets (codes EG, GI, shown in Table 5)
GA, EN, GL, GF, CR) were used.

[0077]

[Table 5]

The various steel sheets shown in Table 5 were subjected to alkaline degreasing treatment, washed with water and dried, and these steel sheets were used as a cathode to electrolytically treat the steel sheets with the various electrolytic solutions shown in Table 1 (bath temperature 50 ° C.), followed by washing with water. Then, hot-air drying was performed to form a protective treatment layer. For some of the samples, following the formation of the above-mentioned protective treatment layer (lower protective treatment layer), a second electrolytic treatment was performed on the steel sheet in various electrolytic solutions (bath temperature 50 ° C) shown in Table 2 to protect the upper layer. A treatment layer was formed to form two protective treatment layers. In this way, the samples Nos. 1 to 64 shown in Tables 6 and 7 were prepared.

Amount of silica, Y, La, Ce in the protective layer
As for the amount and V amount, each sample was dissolved in the acid as it was, and the amount of silica, Y, La, Ce amount, and V amount in the solution were obtained, and the original plate without the electrolytic protection treatment layer was previously dissolved in the acid as a blank. Then, these values were obtained by dividing the measured values. However, when the original plate having plating was used, only the plated film was dissolved in acid, and when the cold-rolled steel plate was used as the original plate, the whole steel plate was dissolved in acid and the measurement was performed. These values are also shown in Tables 6 and 7.

Further, for the samples of Nos. 32 to 64, the coating layer was formed after the protective treatment layer was washed with water and dried. To form the coating layer, a roll coater was used to apply a treatment liquid comprising the resin composition of Table 3 and additional components or the resin composition of Table 4 and heat-dry to form. The film thickness of the film was adjusted by the solid content of the treatment composition, the roll rolling force, the rotation speed, and the like.

The surface-treated steel sheet thus obtained was evaluated for corrosion resistance and conductivity. The results are also shown in Tables 6 and 7.

[0082]

[Table 6]

[0083]

[Table 7]

The corrosion resistance was evaluated by salt spray test (JIS
Z2371), and the corrosion occurrence area ratio after 36 hours was measured. 5 points without corrosion, 1 to 3% area ratio
4.5 points, 3-5% 4 points, 5-10% 3.5 points, 10-1
5% for 3 points, 15-30% for 2.5 points, 30-50% for 2 points
50 to 70% was 1.5 points, and 70% or more was 1 point.

For the conductivity, the interlayer insulation resistance value (JIS C2
It was evaluated by measuring 550). Interlayer insulation resistance value is 1Ω
cm ² / sheet or less is ◎, 1 to 5 Ωcm ² / sheet is ○, 5Ωcm ² /
The number exceeding the number of sheets was set to x, and ◎ and ◯ were set to have preferable conductivity.

In this example, a cold rolled steel sheet (C
R) and galvanized steel sheet (EG) were also subjected to chromate treatment. Nippon Paint on the surface of each steel plate
Surf Coat S-7 manufactured by Co., Ltd. was applied using a bar coater and dried at an ultimate plate temperature of 100 ° C. to obtain a Cr adhesion amount of 30 mg / m ^2.
As the above, the same evaluation as above was performed. Both of these chromate steel sheets had corrosion resistance of 3 points and conductivity of ⊚.
Therefore, in this example, a surface-treated steel sheet having a corrosion resistance of 3 points or more was regarded as having a performance equivalent to or higher than that of the chromate treatment and passed.

It was found that the samples Nos. 1 to 8, 13, 14, 17 to 64 in which the protective treatment layer was formed by the production method of the present invention exhibited excellent corrosion resistance. In Nos. 17 to 22, since the upper protective treatment layer was formed by the production method of the present invention, the corrosion resistance was greatly improved. Nos. 23, 24, and 25 have good corrosion resistance because the lower protective treatment layer uses the manufacturing method of the present invention, but the amount of adhesion and components of the upper protective treatment layer are outside the scope of the present invention. Nos. 23 and 25 did not have much improved corrosion resistance, and No. 24 had poor conductivity. Since No. 50 also uses the manufacturing method of the present invention, the corrosion resistance is good, but the conductivity is inferior because the coating layer is thick.

[0088]

As described above, according to the present invention, a galvanized steel sheet and a cold-rolled or hot-rolled steel sheet can be electrolytically formed with a film containing no harmful chromium, thus polluting the environment. Steel plate with excellent corrosion resistance can be obtained efficiently without Further, when the steel sheet obtained by the present invention is used for automobiles, home appliances, and building materials, it is possible to reduce the risk of impairing the health of the users of those products, including the handlers during manufacturing and after disposal.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshiharu Sugimoto             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Takahiro Kubota             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Naoto Yoshimi             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Akira Matsuzaki             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Masaaki Yamashita             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. F-term (reference) 4K044 AA03 AB02 BA10 BA12 BA14                       BB01 BB03 BB04 BC02 CA11                       CA17 CA18

Claims (7)

[Claims] 1. A method for producing a surface-treated steel sheet, wherein a protective treatment layer is formed on a steel sheet surface by electrolytic treatment using a steel sheet as a cathode in an electrolytic solution, in one or more kinds selected from Y, La and Ce. 0.01 in total of Y, La, and Ce as metal cations
A method for producing a surface-treated steel sheet having excellent corrosion resistance, which comprises subjecting a steel sheet to electrolytic treatment with an aqueous solution containing ˜3 mol / L and fine silica particles in an amount of 0.001 to 3 mol / L in terms of SiO ₂ as an electrolytic solution. 2. The amount of one or more metal components selected from Y, La and Ce deposited on the surface of the steel sheet by the electrolytic treatment is
5 to 3000 mg / m ^{2 in} terms of Y, La and Ce, and the amount of silica attached is SiO ₂
The method for producing a surface-treated steel sheet having excellent corrosion resistance according to claim 1, wherein a protective treatment layer having a conversion of 10 to 1000 mg / m ² is formed. 3. The electrolytic solution further comprises nitrate ion, nitrite ion, chlorate ion, perchlorate ion, permanganate ion, bromate ion, vanadate ion, molybdate ion, and P oxygenate ion. The method for producing a surface-treated steel sheet having excellent corrosion resistance according to claim 1 or 2, characterized in that one or more selected from the above are contained in a total amount of 0.001 to 3 mol / L. 4. A vanadate ion is added to a V steel after subjecting the steel sheet to the electrolytic treatment according to any one of claims 1 to 3.
A method for producing a surface-treated steel sheet excellent in corrosion resistance, which comprises subjecting a second electrolytic treatment to an aqueous solution containing 0.001 to 3 mol / L in conversion as an electrolytic solution. 5. The protective treatment layer formed by the second electrolytic treatment according to any one of claims 1 to 3 contains V component of vanadium oxide and / or vanadium hydroxide. Adhesion amount is 5 to 1000 mg / m ^{2 in} terms of V
5. A protective treatment layer is formed.
The method for producing a surface-treated steel sheet having excellent corrosion resistance according to 1. 6. The method for producing a surface-treated steel sheet according to claim 1, wherein the steel sheet is a zinc-based plated steel sheet. 7. A coating layer is formed on the surface of the surface-treated steel sheet obtained by the production method according to claim 1, and the coating layer has a thickness of 0.05 to 3 μm. A method for producing a characteristic surface-treated steel sheet.