JPH1161432A - Metal plate surface-treated with inorganic/organic composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a surface treated metal sheet as an alternative for a chromated metal sheet by forming a first layer of a film essentially comprising an oxo-acid or an oxo-acid hydrogen compd. of a rare earth element and/or a group IV element or their mixture as a first layer and forming a second layer essentially comprising a resin to coat a metal sheet. SOLUTION: The film as the first layer essentially consists of a compd. of La, Y, Zn, Ti, Ce and an oxo-acid anion such as phosphoric acid ion, tungstic acid ion and vanadic acid ion, and/or a compd. containing hydrogen as a part of a cation. The amt. of the compd. of the rare earth metal element/the group IV element in the film is preferably >=1 mg/m<2> and the film thickness is preferably >=0.05 μm. The resin component to form the second layer is not especially limited as far as it has adhesion property to the compd. of the rare earth metal element/the group IV element in the first layer, and is preferably formed to >=0.1 μm film thickness. The whole film thickness of the first and second layers is specified to >=0.2 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated metal sheet having a coating layer having excellent corrosion resistance and containing no hexavalent chromium at all, and a treating solution therefor.

[0002]

2. Description of the Related Art Conventionally, cold-rolled steel sheets, galvanized steel sheets, zinc-based alloy-coated steel sheets, aluminum-coated steel sheets, and the like used for automobiles, home appliances, building materials, etc., are used for imparting rust resistance. In general, a chromate film is coated on the surface of the steel sheet. Examples of the chromate treatment include electrolytic chromate and coating chromate. Electrolytic chromate has been performed by subjecting a metal plate to cathodic electrolysis using, for example, a bath containing chromic acid as a main component and various anions such as sulfuric acid, phosphoric acid, boric acid, and halogen. In addition, the coating type chromate has a problem of elution of chromium from a chromate-treated metal plate, and therefore, a solution in which a part of hexavalent chromium is reduced to trivalent in advance or a solution in which the ratio of hexavalent chromium to trivalent chromium is specified in advance. It has been carried out by adding an inorganic colloid or inorganic anion to a treatment liquid, immersing a metal plate therein, or spraying the treatment liquid onto the metal plate.

[0003] Of the chromate films, the chromate film formed by electrolysis has little elution of hexavalent chromium, but does not have sufficient anticorrosion properties. In particular, when the film damage is large during processing or the like, the corrosion resistance is reduced. . On the other hand, the corrosion resistance of the metal plate coated with the coating type chromate film is high,
Particularly, the corrosion resistance of the processed portion is excellent, but the elution of hexavalent chromium from the chromate film is a serious problem. If the organic polymer is coated, the elution of hexavalent chromium is considerably suppressed but not sufficient. Further, although a method generally called resin chromate as disclosed in Japanese Patent Application Laid-Open No. 5-230666 is effective in suppressing the dissolution of hexavalent chromium, a small amount of dissolution cannot be avoided. In order to completely suppress the elution of hexavalent chromium as described above, it is necessary to develop a rust-preventive film having no function and no equivalent to the conventional chromate film containing hexavalent chromium without using any hexavalent chromium. .

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and to provide a surface-treated metal plate which can be substituted for a chromate film and a treating solution therefor.

[0005]

Means for Solving the Problems In order to design a general-purpose chemical conversion coating instead of the current chromate treatment with a system containing no hexavalent chromium, the inventors have conducted intensive studies and as a result, have found that rare earth metal An inorganic / organic composite surface-treated metal plate coated with a compound of an element and / or a group IVA element or a mixture thereof as a first layer, and further coated as a second layer with a coating mainly composed of a resin on the surface of the first layer. We found that it had excellent anticorrosion performance.

The gist of the present invention is as follows: (1) Rare earth metal element and / or IVA
Inorganic / organic, characterized in that a coating mainly composed of a compound of a group element or a mixture thereof is coated as a first layer, and a coating mainly composed of resin is coated as a second layer on the surface. Composite surface treated metal plate. (2) The compound of a rare earth metal element and / or a group IVA element or a mixture thereof contains the rare earth metal element and / or
Alternatively, the surface-treated metal plate according to the above (1), which is an oxygen acid compound or a hydrogen oxyoxy compound of a Group IVA element or a mixture thereof. (3) The surface-treated metal plate according to (1) or (2), wherein the rare earth metal element and / or the IVA element is lanthanum, cerium, yttrium, and / or zirconium.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Rare earth metal elements and / or IV
The group A element has an anticorrosion function although the mechanism is not clear. The rare earth metal element used in the present invention and / or
Alternatively, all the rare earth metal elements and / or IVA elements can be used for the compound of the IVA element or a mixture thereof (hereinafter, abbreviated as “rare earth metal element and / or IVA element compound”), and the valence of the metal can be used. Is not particularly limited. From the viewpoint of ease of handling, lanthanoid, yttrium, zirconium, titanium, and more preferably lanthanum or cerium, more preferably tetravalent cerium having an oxidizing power. Cerium is also effective in suppressing the cathodic reaction, and the use of tetravalent cerium further enhances the effect.

The rare earth metal element and / or group IVA element compound used in the present invention may be a rare earth metal element and / or
Alternatively, an oxygen acid compound or a hydrogen oxyoxygen compound of a Group IVA element or a mixture thereof (hereinafter, abbreviated as “a rare earth metal element and / or an oxygen acid compound of a Group IVA element”) is preferable. The oxyacid compound of the rare earth metal element and / or the IVA element refers to a compound of the oxyacid anion such as a phosphate ion, a tungstate ion, and a vanadate ion with the rare earth metal element and / or the IVA element. An oxyhydrogen compound refers to a compound containing hydrogen as part of a cation.

Since these oxyacid compounds and / or hydrogenoxygen compounds form a paste-like and possibly non-crystalline (amorphous) inorganic polymer, they have a process-following property even when formed into a film. In addition, the barrier effect suppresses corrosion, and an excess of oxyacid can form a passivation film of an oxyacid salt film type, and a passive film of an oxide film type can be formed. It is possible to obtain an inorganic corrosion-resistant chemical conversion treatment film having higher corrosion resistance.
Suitable oxyacid compounds are phosphoric acid compounds and / or hydrogen phosphate compounds, and the phosphoric acid species are orthophosphoric acid, metaphosphoric acid, polyphosphoric acid. Particularly, a hydrogen polyphosphate compound is preferable.

The rare earth metal element and / or IVA element compound used in the present invention is preferably poorly water-soluble in order to impart long-term corrosion resistance. The solubility of the rare earth metal element and / or IVA compound in water is preferred. Is pH 6
It is preferably 0.01 mol / l or less in terms of metal element in the range of 7 to 7. More preferably, when the solubility is 0.01 mol / l or less in terms of a metal element at pH 5 to 8, corrosion resistance can be maintained for a long time. When the solubility in water at a pH of 6 to 7 is more than 0.01 mol / l, the rare earth metal element and / or the IVA element compound are easily eluted from the film under a humid environment such as rainwater or dew. The long-term corrosion resistance is reduced.

In order to impart corrosion resistance to a worked portion or a damaged portion, a rare earth metal element and / or a group IVA compound which becomes water-soluble in an acidic region is preferable. In particular,
PH of rare earth metal element and / or IVA group compound
The solubility at 3 or less is 0.1 mol /
It is preferably at least 1. By adjusting the concentration to 0.1 mol / l or more, the rare earth metal element and / or the IVA element compound dissolves in response to the pH decrease at the location where the corrosion occurs, and selectively repair the corrosion progressing part such as the processed part and the damaged part. Function can be provided. If it is less than 0.1 mol / l, when the film is damaged by severe processing and is exposed to an extremely severe corrosive environment, the supply of the rare earth metal element and / or the IVA element compound to the corroded portion becomes insufficient, Corrosion resistance decreases.

The rare earth metal element and / or group IVA compound used in the present invention can be used by adding one kind in the same film. However, the rare earth metal element and / or group IVA element or A plurality of rare earth metal elements and / or group IVA element compounds in which the oxyacid is changed can be used. The addition of a plurality of rare earth metal elements and / or oxyacid compounds of Group IVA elements enables a wide variety of corrosive environments to be accommodated. However, in practice, the film thickness depends on film properties such as manufacturing cost and weldability. The amount and type must be optimized because the absolute amount of the rare earth metal element and / or group IVA element compound added to the film per unit area is limited.

[0013] The amount of the rare earth metal element and / or the group IVA element compound contained in the coating on the metal plate cannot be limited because the required addition amount varies depending on the required corrosion resistance, but it is 1 mg / metal equivalent. m ² or more. If it is less than 1 mg / m ² , the effect of addition is insufficient and no improvement in corrosion resistance as a film is observed. In addition, 10 g / m
^Even if added in excess of ² , the effect of improving corrosion resistance is saturated, so that 10 g / m ² is sufficient in consideration of economy.

The presence form of the rare earth metal element and / or IVA element compound in the treatment solution depends on the solvent used and the p
Although it depends on H, temperature, and concentration, a colloidal state which is dissolved or finely dispersed in a processing solution is preferable. Other than these, when the film is formed, the dispersed state of the rare earth metal element and / or the group IVA element compound becomes non-uniform, and the place where the rare earth metal element and / or the group IVA element compound is present in a small amount tends to be corroded. When the rare earth metal element and / or IVA element compound is finely dispersed in a colloidal form, the average particle diameter is preferably 1 μm or less,
Further, the thickness is preferably 0.5 μm or less, particularly preferably 0.2 μm or less. When the particle diameter is 1 μm or more, not only the dispersion state of the rare earth metal element and / or the IVA element compound in the treatment liquid or the film becomes non-uniform, but also the film tends to be broken starting from the particles when processed. And the corrosion resistance is significantly deteriorated.

The resin component coated as the second layer in the present invention includes a rare earth metal element and / or IVA in the first layer.
There is no particular limitation as long as it has adhesion to the group element compound. In general, acrylic, epoxy, and olefin-based organic resins are given as examples.
As the form, water-soluble, emulsion resin dispersed in water, latex, and the like can be appropriately selected.

The coating of the first and second layers of the present invention has
Corrosion inhibitor to improve the passivation, formation of passivation film
Surfactants such as dispersants, dispersants and defoamers, and other additives.
It can be used in combination. Passivation film forming aid
As phosphoric acid and polyphosphoric acid, and as an additive
Calcium, calcium carbonate, calcium oxide, phosphoric acid
Zinc, potassium phosphate, calcium phosphate, calcium silicate
Cium, zirconium silicate, aluminum phosphate, glue
Zirconium phosphate, TiO_Two, SiO_Two, Al _TwoO_ThreeWhat
Etc. can be added.

According to the method for producing a surface-treated metal sheet of the present invention, a treatment liquid containing a rare earth metal element and / or a group IVA element compound as a main component is applied to the surface of the metal sheet and dried.
What is necessary is just to apply | coat and dry the chemical | medical solution which has resin as a main component, and specific conditions and means are not specifically limited. For example, the currently used coating equipment for chromate treatment and coating equipment for paint can be used as they are, and no special equipment is required.
Further, a film can also be formed by applying manually by using a brush coating or a bar coater and then drying.

Although the thickness of the first layer cannot be limited because it varies depending on the application, the thickness of the first layer is preferably 0.05 μm or more. More preferably, it is 0.1 μm or more. In addition, the thickness of the second layer is preferably 0.1 μm or more, and more preferably 0.4 μm or more. The total thickness of the first layer and the second layer is preferably 0.2 μm or more. More preferably, it is 0.5 μm or more. If it is less than 0.2 μm, the effect of inhibiting corrosion is recognized but not sufficient.
However, even if the film thickness exceeds 10 μm, the effect of improving corrosion resistance is saturated, so that 10 μm is sufficient in consideration of economy.

The metal sheet to which the present invention is applied is not particularly limited. For example, hot-dip galvanized steel sheet, hot-dip zinc-iron alloy coated steel sheet, hot-dip zinc-aluminum-magnesium alloy coated steel sheet, hot-dip aluminum-silicon alloy coated steel sheet, hot-dip Hot-dip galvanized steel sheet such as lead-suzu alloy-plated steel sheet, surface-treated steel sheet such as electro-galvanized steel sheet, electro-zinc-nickel alloy-plated steel sheet, electro-zinc-iron alloy-plated steel sheet, electro-zinc-chromium alloy-plated steel sheet, etc. It can be applied to steel plates and metal plates such as zinc, aluminum and magnesium.

[0020]

EXAMPLES Rare earth metal elements and IVA group compounds (1) Nd ₂ O ₃ (2) La ₂ O ₃ (3) CeO ₂ (4) LaPO ₄ (1) to (3) are manufactured by Kanto Chemical Co., Ltd. In 4), a commercially available reagent manufactured by High Purity Chemical Co., Ltd. was pulverized and atomized to 1 μm or less.

(5) Vanadic acid / lanthanum compound (abbreviation: V-La) An aqueous lanthanum chloride solution and an aqueous ammonium vanadate solution are mixed at a molar ratio La / P at a ratio of 1/18, and then mixed.
Heat at 00 ° C. for 12 hours. (6) phosphate / lanthanum compound (abbreviation: P-La) lanthanum chloride solution and ortho phosphoric acid (H ₃ PO _4, 85
(% By weight) with a molar ratio of La / P at a ratio of 1/6, and then heated at 200 ° C. for 12 hours.

(7) Polyphosphoric acid / lanthanum compound (abbreviation: PP-La) A lanthanum chloride aqueous solution and polyphosphoric acid (manufactured by Showa Chemical Co., Ltd .: average molecular weight: about 338) are mixed at a molar ratio La / P of 1/6. Then, the mixture was heated at 200 ° C. for 12 hours. (8) Polyphosphoric acid / cerium (III) compound (abbreviation: PP
-Ce) A cerium chloride aqueous solution and polyphosphoric acid (manufactured by Showa Chemical Co., Ltd .; average molecular weight: about 338) were sufficiently mixed at a molar ratio Ce / P of 1/6, and then heated at 200 ° C. for 12 hours.

(9) Polyphosphoric acid / cerium (IV) compound (abbreviation: PP-CeIV) Diammonium cerium (IV) nitrate is dissolved in polyphosphoric acid (Showa Chemical Co., Ltd .; average molecular weight: about 338) (molar ratio). Ce
/ P, and heated at 200 ° C. for 12 hours. (10) Polyphosphoric acid / titanium compound (abbreviation: PP-T
i) Titanium sulfate aqueous solution and polyphosphoric acid (manufactured by Showa Chemical Co., Ltd .: average molecular weight: about 338) were sufficiently mixed at a molar ratio of Ti / P at a ratio of 1/6, and then heated at 200 ° C. for 12 hours. (11) Polyphosphoric acid / zirconium compound (abbreviation: PP
-Zr) A zirconium chloride aqueous solution and polyphosphoric acid (manufactured by Showa Chemical Co., Ltd .: average molecular weight: about 338) are converted to a molar ratio Zr / P of 1 /
After sufficiently mixing at a ratio of 6, the mixture was heated at 200 ° C. for 12 hours.

Resin (A) Block copolymer poly (methacrylic acid, hydroxyethyl acrylate,
Hydroxyethyl methacrylate) -poly (styrene,
A methyl methacrylate, butyl methacrylate, butyl acrylate) -poly (methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate) block copolymer (solvent: tetrahydrofuran) was produced by a living anion polymerization method.

(B) Acrylic emulsion Commercially available water-dispersible carboxyl group-containing acrylic emulsion resin (manufactured by Nippon Synthetic Rubber Co., Ltd .: resin solid content 50% by weight)
It was used. (C) SBR latex A commercially available water-dispersed carboxyl group-containing SBR latex (manufactured by Nippon Synthetic Rubber Co., Ltd .: resin solid content: 50% by weight) was used.

Preparation of Treatment Solution The above rare earth metal element or Group IVA element compound as a treatment solution for forming the first layer, and orthophosphoric acid or colloidal silica solution as an additive (ST-O, manufactured by Nissan Chemical Industries, Ltd.)
Are blended, each concentration is a rare earth metal element or
The IVA element compound was 100 g / 1 in terms of metal, orthophosphoric acid was 20 g / 1 in terms of H ₃ PO ₄ , and colloidal silica was 5 g / l in terms of SiO ₂ . Further, as the processing liquid for forming the second layer, the resin which was boiled up was 100 g / 1 in terms of solid content, and the colloidal silica solution was 5 g / l.
It was dispersed in water and used. The composition of each bath is shown in the table.

Film forming method Each of the above-mentioned treatment baths was applied on a steel plate and dried to form a film. The amount of application to the steel sheet was uniformed to about 0.5 μm for the first layer and about 0.5 μm for the second layer in terms of film thickness. The steel sheets used were GI (galvanized steel sheet, coating weight: 90 g / m ² ), EG (electrogalvanized steel sheet,
Coating weight 20: g / m ² ), SZ (hot-dip zinc-aluminum alloy coated steel sheet, plating weight: 90 g /
m ² , Zn / Al = 95.2 / 4.8), AL (hot-dip aluminum-silicon alloy plated steel sheet, coating weight:
120 g / m ² , Al / Si = 90/10), and CR (cold rolled steel plate). In order to make a comparison with a chromate-treated steel sheet, a partially reduced chromic acid by starch was 30 g / 1 in terms of CrO ₃ and SiO ₂ was 4
A treatment solution containing 0 g / 1 and 20 g / 1 orthophosphoric acid was bathed, applied on a steel plate so as to be about 50 mg / m ^{2 in} terms of chromium metal, and dried to form a film. The first layer and the second layer were coated using a bar coater, and the first layer was dried at an ambient temperature of 200 ° C. for 30 seconds, and the second layer was dried at an ambient temperature of 200 ° C. for 15 seconds.

Evaluation Method of Coating Performance (I) The corrosion resistance of a flat plate was evaluated by the rust generation rate after spraying 5% salt water at 35 ° C. on a sample. The spraying period is GI, E
G and SZ are 10 days, AL is 15 days
CR measured the occurrence rate of red rust in 5 days.

(II) The sample was processed for Erichsen 7 mm, and the corrosion resistance of the processed portion was evaluated on the rust generation area after spraying 5% salt water at 35 ° C. The spraying period is GI, E
G and SZ were 10 days, AL was 15 days, and the white rust occurrence rate was measured, and CR was 5 days, and the red rust occurrence rate was measured.

(III) Melt-alkyd paint having a thickness of about 20 μm was applied to the sample and baked, and immersed in boiling water for 30 minutes.
(10 cuts and tape peeling). Tables 1 and 2 show the performance test results. As is clear from Tables 1 and 2, the inorganic / organic composite surface-treated metal sheet according to the present invention has performance equal to or higher than that of the chromate film of the comparative example. Therefore, it exhibits excellent performance as a chemical conversion coating containing no hexavalent chromium at all.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

As described above, as described above, the inorganic / organic material of the present invention
The organic composite surface-treated metal plate exhibits performance equal to or higher than that of a film containing hexavalent chromium. Thereby, it is possible to provide a surface-treated metal plate and a metal surface treatment liquid having performance equivalent to that of a chromate film and significantly reducing the environmental load.

Claims (3)

[Claims] 1. A metal plate surface coated with a film mainly composed of a compound of a rare earth metal element and / or a group IVA element or a mixture thereof as a first layer, and a film mainly composed of a resin is further coated on the surface thereof. An inorganic / organic composite surface-treated metal plate, which is coated as a second layer. 2. The compound of a rare earth metal element and / or a group IVA element or a mixture thereof is an oxygen acid compound or a hydrogen oxyoxy compound of a rare earth metal element and / or a group IVA element or a mixture thereof. The surface-treated metal plate according to claim 1. 3. The surface-treated metal plate according to claim 1, wherein the rare earth metal element and / or the IVA element is lanthanum, cerium, yttrium and / or zirconium.