JP2000226691A - Production of surface treated steel sheet and surface treated steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel sheet excellent in corrosion resistance and forming workability by using a sol-gel method, in which a galvanized steel sheet is subjected to cathodic treatment or anodic treatment in an aq. soln. of specified pH composed of one or more kinds among binding agents composed of inorganic compds. and one or more kinds among water soluble or water dispersible organic resins and is dried, and forming an organic/inorganic hybrid film. SOLUTION: One or more kinds among inorganic compds. such as sodium silicate and one or more kinds among water soluble or water dispersible organic resins such as an alkyd resin are dissolved into water by each 5 to 40 wt.% solid content concn., which is added with modifying agent such as chromium, and pH therein is adjusted to 2 to 11 to form into a treating soln. A galvanized steel sheet such as a hot dip plated steel sheet obtd. by plating a low carbon steel sheet annealed after cold rolling with a zinc alloy under heating and melting is subjected to electrolytic treatment at 0.1 to 50 A/dm2 current density and at 20 to 40 deg.C to form an organic/inorganic hybrid film of 0.01 to 5 μm thickness. In the case the treating soln. is charged to a plus, cathodic treatment is executed, and in the case of a minus, anodic treatment is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a surface-treated steel sheet and a surface-treated steel sheet prepared by using the method. More specifically, the present invention relates to a method for producing a surface-treated steel sheet, a post-treatment method for forming an organic / inorganic hybrid film on a zinc-based plated steel sheet using a sol-gel method, and an organic / inorganic method using this post-treatment method. The present invention relates to a galvanized steel sheet having a hybrid film and excellent in corrosion resistance, molding workability, and coating film adhesion.

[0002]

2. Description of the Related Art Galvanized steel sheets have a drawback that they are easily rusted when left in the air due to their high activity of zinc. In practical use, many troubles occur in characteristics such as molding processability and coating film adhesion. Therefore, as a countermeasure, after a steel sheet is plated with zinc, a post-treatment such as a chemical conversion treatment such as a phosphate treatment and a chromate treatment, a metal oxide coating treatment, and an organic resin coating treatment is performed.

However, many disadvantages are inherent in such conventional post-processing, and improvement is required.
For example, in the conventional chromate treatment after galvanizing, zinc reacts with a chemical conversion treatment agent in a treatment tank to generate sludge, and it is necessary to improve work environment conservation and economy. As a remedy, a coating type chromate treatment that does not require a treatment tank has been developed.
In addition, properties such as moldability are not satisfactory, and further improvements are required.

[0004] A method of coating a metal oxide after galvanizing is to form a hydrated oxide film of a metal such as cobalt or molybdenum by a chemical reaction with zinc by immersion treatment. Has a tendency to be inferior to the corrosion resistance as compared with the chromate treatment.

In the method of coating an organic resin after galvanizing, the corrosion resistance is improved by increasing the thickness of the film, but corrosion progresses from a defective portion of the film, and improvement is required. When the resin film is thick, drying after coating takes a long time and productivity is poor, and a method of coating a thick resin film is not practical. For this reason, methods such as adding a metal oxide to the resin film have been tried, and although some improvement effect is recognized, the moldability deteriorates, and further improvement is required.

[0006]

SUMMARY OF THE INVENTION In the present invention, in order to solve the above-mentioned drawbacks of the prior art, a surface treatment which is excellent in the preservation of working environment and excellent in corrosion resistance, molding workability and coating film adhesion. It is an object of the present invention to provide a method for manufacturing a steel sheet and a surface-treated steel sheet prepared using the manufacturing method.

[0007]

According to the present invention, there is provided a method for producing a surface-treated steel sheet, comprising a method of preparing a steel sheet having a pH of at least 1 comprising at least one binder composed of an inorganic compound and at least one water-soluble or water-dispersible organic resin.
In the aqueous solutions of Nos. 1 to 11, the organic / inorganic hybrid film is formed by subjecting the zinc-based plated steel sheet to either a cathodic treatment or an anodizing treatment, and then drying it with or without washing with water using a sol-gel method. It is characterized by being formed. The binder composed of the inorganic compound is preferably any one of an alkali metal salt, an acidic metal salt, a colloid metal oxide, a metal alkoxide, a metal acylate, and an organic / inorganic hybrid resin. The water-soluble or water-dispersible organic resin is preferably any one of an alkyd resin, a vinyl acetate resin, an acrylic resin, an epoxy resin, a urethane resin, and a polyester resin. Further, the modifier may include a modifier composed of a supply material of ions derived from any of chromium, molybdenum, tambusten, titanium, zirconium, and vanadium. In addition, the surface-treated steel sheet of the present invention may be formed on a steel sheet by using any one of the above-described methods for producing a surface-treated steel sheet.
It is characterized in that an organic / inorganic hybrid film having a thickness of μm is formed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a binder composed of an inorganic compound and an organic / inorganic hybrid (combined organic resin and inorganic compound at a molecular level) film composed of a water-soluble or water-dispersible organic resin are used. With electrolytic treatment or sol-
It has been found that the object of the present invention can be achieved by forming a galvanized steel sheet using the gel method. Hereinafter, the present invention will be described in detail. First, as a zinc-coated steel sheet to be subjected to surface treatment, a low-carbon steel sheet subjected to normal cold rolling and annealed, a zinc alloy containing zinc as a main component, aluminum, manganese, magnesium, etc. was heated and melted and plated. Hot-dip coated steel sheet, electroplated steel sheet containing zinc, iron, cobalt, nickel, manganese, chromium, silica, etc .; electroplated steel sheet with zinc and eutectoid inorganic and organic particles; and vapor-deposited steel sheet And so on.

Examples of the binder composed of an inorganic compound used in the surface treatment solution include silicates such as sodium silicate, potassium silicate and lithium silicate; alkali metal salts such as zirconium salts such as alkali zirconium; Colloidal metal oxides, which are oxides of metals that form hydrated oxides, such as acidic metal salts such as aluminum oxide, colloidal silica, colloidal alumina, and tin, nickel, cobalt, zinc, vanadium, and zirconium;
Organopolysiloxanes including silicone resin,
Metals such as organoalkoxysilanes such as methyltrimethoxysilane, metal alkoxides such as alkoxy metals such as tetrabutylzirconate and tetrabutyltitanate, and metals such as silicon acylate and silicon stearate and aluminum stearate. Organic / inorganic hybrid resins such as metal acylates such as acylates and alkyl metals such as triethyl aluminum, zirconia silicon such as tetrabutyl zirconate and silicone resins, and acrylic silicates such as amine silicate and acrylic resins. included. Many of these compounds are generally used as a binder for inorganic paints, and these inorganic compounds can be applied as they are to the surface treatment solution used in the present invention.

The water-soluble or water-dispersible organic resin used in the surface treatment liquid is, for example, an alkyd resin, a vinyl acetate resin, an acrylic resin, an epoxy resin, a urethane resin, or a polyester resin, which is soluble in water. Alternatively, any resin that can be dispersed in water can be applied, and it is desirable that the resin has ionicity. An emulsifier or a surfactant may be added to stabilize the dispersion state. These resins are used as an organic / inorganic hybrid resin in combination with a binder comprising the above-mentioned inorganic compound,
An organic / inorganic hybrid resin which is originally an amine silicate and an acrylic resin, and tetrabutyl silicate and a silicon resin may be used.

By combining a binder comprising the above-mentioned inorganic compound with a water-soluble or water-dispersible organic resin,
Although a surface treatment liquid for forming an organic / inorganic hybrid film is obtained, a modifier, a pigment, or a dye may be further added to the surface treatment liquid. Chromium,
A supply material of ions derived from any of molybdenum, tambusten, titanium, zirconium, and vanadium can be used. In the solution, these ion supply materials are chromate ions such as ammonium chromate, molybdate ions such as ammonium molybdate, tambusate ions such as ammonium tambusteate, respectively.
It exists as a titanate ion such as ammonium titanate, a zirconate ion such as ammonium zirconate, a vanadate ion such as ammonium vanadate, or a compound with these ions.
These modifiers are considered to be involved in the formation of an organic / inorganic hybrid film when performing treatment such as electrolytic treatment.
It promotes the formation of strong films and improves properties such as corrosion resistance, moldability, and coating film adhesion.

In order to color the inorganic / organic hybrid film, a pigment or dye may be further added to the above surface treatment liquid. Any of these pigments or dyes can be applied as long as they can be used for water-soluble or water-dispersible paints.

The concentration of the binder composed of an inorganic compound, which is the main component of the surface treatment solution, and the concentration of the water-soluble or water-dispersible organic resin are 5 to 40 as solids from the viewpoint of the stability and workability of the treatment solution. % By weight. If the amount is less than 5% by weight, the deposition efficiency of the film decreases. Meanwhile, 4
If it exceeds 0% by weight, the treatment liquid tends to gel and the stability is poor. The concentrations of the modifying agent, the pigment, and the dye can be arbitrarily selected as long as they are not particularly high. The ratio of each component is not particularly limited, but the inorganic /
In the organic hybrid film, when the ratio of the binder mainly composed of an inorganic compound increases, the corrosion resistance and the coating film adhesion improve, but the moldability tends to deteriorate. The ratio of other components is not particularly limited.

The pH of the treatment liquid is preferably in the range of 2 to 11, and the precipitation efficiency is particularly favorable in the range of 3 to 10. When the pH is less than 2 or more than 11, the precipitation efficiency of the binder composed of an inorganic compound is decreased, which is not preferable. It is also possible to add an acidic or alkaline substance to the treatment liquid in order to adjust the pH of the treatment liquid to the range of 2 to 11, but these acidic or alkaline substances remain on the treated film and the Since the characteristics may be deteriorated, it is necessary to wash the film after the film forming process.

Next, a processing method will be described. First, the temperature of the processing liquid affects the stability of the processing liquid, and the higher the temperature of the processing liquid, the more the gelation tends to occur. At a low temperature, the deposition efficiency of the film decreases, so that the temperature of the treatment liquid is preferably in the range of 20 to 40 ° C. In the electrolytic treatment, either the anodic treatment or the cathodic treatment is appropriately selected according to the state of the treatment solution, that is, the ionicity of the treatment solution at the pH. However, the polarity of the ionicity of the binder composed of an inorganic compound and the polarity of the water-soluble or water-dispersible organic resin may be different, and it is necessary to know in advance which substance governs the ionicity or polarity during the electrolytic treatment. Need to be kept. Cathode treatment when the treatment liquid is positively charged,
When negatively charged, anodizing is performed. The current density is practically in the range of 0.1 to 50 A / dm ² . The thickness of the treatment film is adjusted by the energization time. A thickness of 0.01 to 5 μm is practical. If it is less than 0.01 μm, sufficient corrosion resistance cannot be obtained, and if it exceeds 5 μm, moldability deteriorates, and it takes a long time to dry and solidify the film, which hinders high-speed productivity.

As described above, the film obtained by the electrolytic treatment exhibits excellent corrosion resistance, but the reason has not been sufficiently elucidated.
In the immersion treatment, a film in which an inorganic substance and an organic substance are simply mixed is obtained, whereas in the electrolytic treatment, the surface of a zinc-based plated steel sheet, which is a substrate to be treated, is activated, and the inorganic substance is removed by electrolysis. This is presumed to be due to the fact that organic substances combine at the molecular level to form a strong organic / inorganic hybrid film.

[0017]

The present invention will be described in more detail with reference to the following examples. (Example) [Zinc-coated steel sheet] As the zinc-coated steel sheet used in the present invention, a hot-dip coated steel sheet having a thickness of 0.3 mm (zinc-coated steel sheet, Zn-5% Al alloy-coated steel sheet, hereinafter referred to as H
G, HGAl), electroplated steel sheet having a thickness of 0.5 mm (galvanized steel sheet, Zn-11% Ni alloy coated steel sheet, Zn-2% Co-0.5% Mo alloy coated steel sheet, hereinafter referred to as EG, EGNi, EGCo), thickness:
A 0.5 mm-diameter galvanized steel sheet (hereinafter referred to as VG) was used. These zinc-coated steel sheets were buffed before being subjected to the surface treatment of the present invention, and then subjected to electrolytic alkali degreasing and pickling to clean the surfaces.

An organic / inorganic hybrid film was formed on the zinc-coated steel sheet whose surface was cleaned as described above, using the surface treatment shown in Tables 1 and 2 under the conditions shown in Tables 1 and 2.

[0019]

[Table 1]

[0020]

[Table 2]

[Evaluation of Characteristics] The corrosion resistance, coating film adhesion, and moldability of the organic / inorganic hybrid film-coated steel sheet obtained as described above were evaluated under the following conditions. Corrosion resistance After a salt spray test was performed for 48 hours based on JIS Z 2371, the surface was visually observed and evaluated according to the following rating. ：: No problem in practical use. ×: White rust of a practically problematic level is observed.

Coating Adhesion An organic solvent-based acrylic resin was baked on a steel sheet coated with an organic / inorganic hybrid coating so that the coating thickness after curing was 15 μm. This painted steel sheet was drawn at a drawing ratio of 2.2.
Then, the coating film on the side surface of the cup was forcibly peeled off with an adhesive tape, the degree of peeling of the coating film was visually observed, and evaluated according to the following rating. ：: No problem in practical use. ×: Peeling to a degree that is problematic in practical use is observed.

Formability The organic / inorganic hybrid coated steel sheet was coated with a DuPont impact tester.
(The weight of the impact-applied part: 500 g; the drop height: 50 cm), and then the organic / inorganic hybrid film of the processed part was forcibly peeled off with an adhesive tape, and the degree of peeling of the film was visually observed. The score was evaluated. ：: No problem in practical use. ×: Peeling to a degree that is problematic in practical use is observed. Table 3 shows the results of the above characteristic evaluation.

[0024]

[Table 3]

As shown in Table 3, the surface-treated steel sheet coated with the organic / inorganic hybrid film of the present invention has excellent corrosion resistance, coating film adhesion, and moldability.

[0026]

According to the present invention, a zinc-plated steel sheet is treated in an aqueous solution containing a binder made of an inorganic compound and a water-soluble or water-dispersible organic resin, and an organic / inorganic hybrid is produced using a sol-gel method. A method for producing a surface-treated steel sheet for forming a film, and a surface-treated steel sheet obtained by using the method, the production method of the present invention is excellent in work environment preservation, and the surface-treated steel sheet obtained by using the method is Corrosion resistance,
Excellent molding processability and coating film adhesion.

Claims (6)

[Claims] 1. A binder comprising at least one inorganic compound,
PH comprising at least one water-soluble or water-dispersible organic resin
An organic / inorganic hybrid film is formed by subjecting the galvanized steel sheet to either cathodic treatment or anodizing treatment in an aqueous solution of Nos. 2 to 11 and then drying it with or without water washing. Forming a surface-treated steel sheet. 2. A binder comprising one or more inorganic compounds,
A zinc-coated steel sheet is subjected to either cathodic treatment or anodizing treatment in an aqueous solution of at least one water-soluble or water-dispersible organic resin and a modifier at pH 2 to 11, and then after or after water washing A method for producing a surface-treated steel sheet, wherein an organic / inorganic hybrid film is formed by using a sol-gel method of drying without drying. 3. The method according to claim 1, wherein the binder comprising the inorganic compound is any one of an alkali metal salt, an acidic metal salt, a colloid metal oxide, a metal alkoxide, a metal acylate, and an organic / inorganic hybrid resin. The method for producing a surface-treated steel sheet according to the above. 4. The water-soluble or water-dispersible organic resin is any one of an alkyd resin, a vinyl acetate resin, an acrylic resin, an epoxy resin, a urethane resin, and a polyester resin. 4. The method for producing a surface-treated steel sheet according to any one of Items 1 to 3. 5. The surface according to claim 2, wherein the modifying agent is a modifying agent comprising a source of ions derived from any of chromium, molybdenum, tambusten, titanium, zirconium, and vanadium. Manufacturing method of treated steel sheet. 6. A surface-treated steel sheet obtained by forming an organic / inorganic hybrid film having a thickness of 0.01 to 5 μm on a steel sheet by using the method for producing a surface-treated steel sheet according to any one of claims 1 to 5.