JP2006281710A - Coated steel plate excellent in film adhesion and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated steel plate having an excellent coating film adhesion even after being severely formed e.g. being subjected to deep drawing under the condition that a chromium-free chemical treatment is being applied to the plate, and its manufacturing method. <P>SOLUTION: The coated steel plate comprises a hexavalent chromium-free chemically treating layer on at least one side of a base steel plate and, in addition, at least one coating film on its topmost layer, wherein the chemically treating layer is mainly made of silica and a silane coupling agent and substantially contains no phospheric acid group. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coated steel sheet having excellent coating film adhesion and a method for producing the same, and more particularly to a coated steel sheet used for a part for forming a product and a method for producing the same.

  In the case of using a coated steel plate as an outer plate of home appliances, furniture, building materials, automobile parts, etc., conventionally, it has been used only for applications in which simple processing such as flat plate portions and bending processing that are not processed is performed. On the other hand, for applications where drawing is performed, a cold-rolled steel plate or a plated steel plate is used, and post-coating is performed after forming. However, in recent years, with the increase in the spread rate of coated steel sheets, coated steel sheets (so-called precoated steel sheets) have come to be used for applications where drawing is performed.

  In applications where drawing is performed, it is well known to apply, for example, a coated steel sheet having improved lubricity of the outermost coating layer. In addition, in order to comply with recent environmental regulations, chrome-free processing as a chemical conversion treatment is being promoted in coated steel sheets.

  At this time, as a chromium-free chemical conversion treatment instead of chromate, for example, Patent Document 1 describes a coated steel sheet using a ternary chromium-free chemical conversion treatment of a silane coupling agent, a resin, and silica. Patent Document 1 describes that phosphoric acid is added as a pH adjuster, and in the examples, the adhesion of a coated steel sheet based on a ternary system is evaluated.

Patent Document 2 describes a coated steel sheet using a metal ion-phosphoric acid-silane coupling agent-resin chromium-free chemical conversion treatment, and paragraph 0038 describes that silica sol may be added. There is also.
Japanese Patent Laid-Open No. 11-256096 JP-A-11-106945 JP 9-324282 A

  In the coated steel sheet applied to the application to be formed, the adhesion of the coating film needs to be maintained not only before forming but also after forming. In the conventional chemical conversion treatment of the silica-phosphoric acid-organic resin composite system, the coating film adhesion after severe molding such as drawing is not always good. When this phenomenon was investigated, it was found that peeling occurred at the interface between the plating and the chemical conversion treatment. As a method for improving coating film adhesion at the plating interface, when the chemical conversion treatment is chromate, a method in which fine cracks are provided in advance in the plating film as in Patent Document 3 is also conceivable. However, sufficient paint adhesion cannot be obtained only by this method.

  Accordingly, the present invention provides a coated steel sheet having excellent coating film adhesion even after severe forming such as drawing when a chromium-free chemical conversion treatment is performed, and a method for producing the same. Let it be an issue.

  The inventors of the present invention have studied based on the chemical conversion treatment of the silica-phosphoric acid-organic resin composite system, and that the application of a silane coupling agent may be effective in improving coating film adhesion. I found it. However, with such a treatment liquid, the coating film adhesion may not always be good. On the other hand, when treated with a chemical conversion treatment liquid that does not substantially contain phosphoric acid, the coating film adhesion is improved, and the stability over time of the chemical conversion treatment liquid itself is better than when using a liquid containing phosphoric acid. It was good.

  The present invention has been completed based on the above findings, and the gist thereof is as follows.

  The invention according to claim 1 is a coated steel plate having a chemical conversion treatment layer not containing hexavalent chromium on at least one surface of the base steel plate, and further comprising one or more coating films on the upper layer, wherein the chemical conversion treatment layer is silica. And a coated steel sheet characterized by containing a silane coupling agent as a main component and containing substantially no phosphate radical. Here, “main component” means that the mass of the component is 50 or more when the mass of the entire chemical conversion treatment layer is 100 (the same applies hereinafter).

  The invention according to claim 2 is a coated steel plate having a chemical conversion treatment layer containing no hexavalent chromium on at least one surface of the base steel plate, and further comprising one or more coating films on the upper layer, wherein the chemical conversion treatment layer is made of silica. And a coated steel sheet characterized by containing a silane coupling agent and a resin as main components and substantially not containing phosphate groups.

  The invention according to claim 3 is the coated steel sheet according to claim 1 or 2, characterized in that the chemical conversion treatment layer contains at least one of a zirconium salt and benzothiazole or a derivative thereof.

Invention of Claim 4 is the coated steel plate of any one of Claims 1-3, The adhesion amount of a chemical conversion treatment layer is 10 mg / m < ² > or more as Si in the said film | membrane, It is characterized by the above-mentioned. To do.

The invention according to claim 5 is the coated steel sheet according to any one of claims 1 to 4, wherein the base steel sheet is an electrogalvanized alloy-plated steel sheet having cracks on the surface, and per 1 mm ^{2 of} the steel sheet surface. The number of regions surrounded by cracks is 1000 to 15000.

  Invention of Claim 6 is a manufacturing method of the coated steel plate provided with the chemical conversion treatment process which forms a chemical conversion treatment layer in at least one surface of a base steel plate, and the coating process which coats one or more layers on a chemical conversion treatment layer. The chemical conversion treatment step uses an aqueous chemical conversion treatment liquid mainly containing colloidal silica and a silane coupling agent and substantially free of phosphate radicals. The ratio (B / C) of the mass (C) of the silane coupling agent to the mass (B) of the colloidal silica is 1.5 to 10, which is a method for producing a coated steel sheet.

  According to a seventh aspect of the present invention, in the method for producing a coated steel sheet according to the sixth aspect, the aqueous chemical conversion treatment solution further contains a resin, and the dry mass ratio indicates that colloidal silica and silane with respect to the mass (A) of the resin. The ratio (A / (B + C)) of the total mass (B + C) with the coupling agent is 0.01 to 0.5.

  The invention according to claim 8 is the coated steel sheet manufacturing method according to claim 6 or 7, wherein the base steel sheet is an electrical zinc alloy plated steel sheet, and the plated steel sheet is brought into contact with an acidic aqueous solution before the chemical conversion treatment step. A process is provided.

  The coated steel sheet of the present invention has good coating film adhesion even after forming, and can be applied to applications where particularly severe forming is performed. In addition, it is a chromium-free coated steel sheet, and the application range of the coated steel sheet can be expanded from the environmental aspect.

The present invention provides a coated steel sheet on which a coating film of one or more layers is further formed after a chemical conversion treatment containing silica and a silane coupling agent and containing substantially no phosphoric acid on a coated base steel sheet, and a method for producing the coated steel sheet It is. FIG. 1 is a perspective view schematically showing an example of the layer structure of the coated steel sheet. In FIG. 1, in order to facilitate understanding, the thickness of each layer is shown to the same level (which is actually different). In the coated steel sheet of FIG. 11, the layers are usually laminated in the same order on both sides of the steel sheet. In the present invention, these layers may be formed on at least one side. Paying attention to one side of the steel plate (for example, the upper surface side in FIG. 11), the coated steel plate is
Steel plate / Zinc-based plating layer / Chromium-free chemical conversion treatment layer / Undercoat / Topcoat
Each layer is laminated in this order.

1. Base Steel Sheet In the present invention, the base steel sheet used for the coating base is not particularly limited. Usually, zinc-based plated steel sheets are often used from the viewpoint of corrosion resistance. In addition, when applied to a draw forming application, a steel plate having excellent drawability, for example, a carbonitride-forming element such as Ti and / or Nb is added at an equivalent amount or more with respect to the amount of C and N. Carbon-based IF (Interstitial Free) steel is preferably used.

Also, the plating type is not particularly limited. However, when there are fine cracks on the surface as will be described later, the coating film adhesion is improved. In hot dip plating, an alloyed hot dip galvanized steel sheet is preferable, and in electroplating, Zn—Ni alloy plated steel or Zn—Fe alloy plated steel sheet having fine cracks on the surface is preferable. After the plating, the fine cracks are brought into contact with, for example, an acid aqueous solution (in the case of electroplating, the acidic plating solution may be passed without current), so that the fine cracks can be relatively easily formed on the plating film. Can be generated. As an indication of cracks, the number of regions surrounded by cracks per 1 mm ² is in the range of 1000 to 150,000. The range is preferably 2000 to 50000.

  On the other hand, when an alloyed hot-dip galvanized steel sheet is used as the base steel sheet, the gloss, gloss, and sharpness after coating may be reduced due to fine irregularities on the surface. Therefore, in order to achieve both the gloss and the above-described coating film adhesion, it is preferable to use an electric Zn—Ni alloy plated steel plate or a Zn—Fe alloy plated steel plate having fine cracks as the base steel plate.

2. Chemical conversion treatment 2-1) Components of chemical conversion treatment liquid In the present invention, as a chromium-free chemical conversion treatment, a chemical conversion treatment using a chemical conversion treatment liquid containing silica and a silane coupling agent and substantially free of phosphoric acid is performed. .

  In the present invention, silica and a silane coupling agent are further essential components. By containing these, the coating film adhesion is improved.

  Colloidal silica is used as the silica. This is because it is advantageous in terms of dispersion in an aqueous solution and stability over time of the dispersion as compared with the case of using dry silica. However, dry silica may be used in combination with colloidal silica as long as performance permits.

The silane coupling agent forms a film having a crosslinked siloxane bond as a skeleton by hydrolyzing an alkoxy group into hydroxyl groups and condensing the hydroxyl groups. When there are few alkoxy groups, a crosslinking reaction may be delayed and adhesiveness with a base | substrate may fall. On the other hand, when there are few organic functional groups, adhesiveness with the clear coating film of an upper layer may fall. From these points, the silane coupling agent is preferably a trialkoxyl type. Specific examples of the silane coupling agent suitable for use in the present invention include the following compounds (including common names), but are not limited thereto.
: Vinylethoxysilane, vinylmethoxysilane, N- (2-aminomethyl) 3-aminopropylmethyldimethoxysilane, N- (2-aminomethyl) 3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3 -Glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane , Tetraethoxysilane, tetramethoxysilane

  These preferred blending ratios are dry mass ratios, where the mass of colloidal silica is B, and the mass of the silane coupling agent is C, B / C is a blending ratio of 1.5 to 10, more preferably B / C is in the range of 2-3.

  When the said compounding ratio is too large, a coating-film adhesiveness will worsen on the contrary. On the other hand, if the blending ratio is too small, the stability of the treatment liquid itself is greatly impaired, for example, the chemical conversion treatment liquid is easily gelled.

  In this invention, phosphoric acid is not substantially contained in a chemical conversion liquid. This is because the coating film adhesion is not always good when using a chemical conversion treatment solution that has passed a certain amount of time after blending. The reason for this is not clear, but it is thought that phosphoric acid has an adverse effect on the dispersibility of silica and silane coupling agents in the chemical conversion treatment solution and agglomeration occurs. In addition, as a standard of the content upper limit of the phosphate radical permitted as an impurity, it is thought that it is 0.01 by the dry mass ratio of the phosphate radical with respect to the dry mass ratio of a silica.

  In the present invention, an organic resin can be blended in the chemical conversion solution to be used to further improve coating adhesion, corrosion resistance, and the like. Preferred organic resins include water-dispersed resins or resin emulsions that can be dispersed in water. As these water-dispersed resins, acrylic resin emulsions, water-dispersed polyester resins, and water-dispersed urethane resins are preferable because they are heat curable and have excellent processability and chemical resistance. Moreover, as a compounding ratio, mass ratio A / (B + C) is 0.01-0.0 when the mass of organic resin is A and the total amount of silica and a silane coupling agent is (B + C) by dry mass ratio. 5 is preferable, and more preferably 0.1 to 0.3.

  Moreover, in this invention, in order to improve corrosion resistance, you may add a rust prevention additive as needed. Preferable rust preventive additives include, for example, zirconium salts, vanadium compounds, thiazole compounds and the like.

  Furthermore, as long as the performance of the present invention is not impaired, hydrofluoric acid radicals (including fluoride ions as well as complex fluoride ions such as fluoride titanate ions) for improving the adhesion to the underlying steel sheet, and various types. A rust preventive additive, a coating workability, a thickener for improving liquid stability, a surfactant, a pH adjuster, and the like can be added.

  The chemical conversion treatment solution used in the present invention is preferably an aqueous treatment solution from the viewpoint of work environment and safety. However, if necessary, a slight amount of alcohol or other solvent-based solvent may be mixed.

2-2) Adhesion amount of chemical conversion liquid and application method Regarding the adhesion amount of the chemical conversion treatment film, as the adhesion amount increases, not only the corrosion resistance but also the coating film adhesion after molding tends to be better. Specifically, in the case of using the treatment liquid composition described above without taking a long time after blending, it is preferable to deposit 10 mg / m ² or more as Si in the chemical conversion coating. On the other hand, if the adhesion amount is too large, the film thickness of the chemical conversion film itself becomes large and there is a risk of cohesive failure in the chemical conversion film. Therefore, Si in the chemical conversion film is preferably 50 mg / m ² or less. .

  The method for applying the chemical conversion liquid is not particularly limited. Examples of the continuous operation include a roll coating method and a method of squeezing the adhesion amount with a ringer roll after immersing the substrate in the treatment liquid or spraying the treatment liquid onto the substrate.

3. Coating In the present invention, one or more coating films are formed on the chemical conversion coating. Usually, in a pre-coated steel sheet, two layers of undercoat and topcoat are applied to the surface that guarantees performance, particularly appearance. If desired, the coating may be one layer, or three or more layers. The components and thickness of the coating film may be designed according to the required performance. Hereinafter, the preferable form in the case of two-layer coating is demonstrated.

  As an undercoat for two-layer coating, a so-called primer, a polyester resin, a urethane resin, or an epoxy resin is often used from the viewpoint of coating film adhesion and corrosion resistance. At this time, the coating film adhesion is generally better when a resin having a low glass transition temperature (Tg) is used. This is considered to be because the internal stress in the coating film is reduced and the adhesion is improved. It is preferable to use a resin having a Tg of 30 ° C. or lower. However, in the coated steel sheet of the present invention, the coating film adhesion is good even with a primer using a resin having a Tg of 35 ° C., as shown in Examples described later.

  In the present invention, the top coat film is not particularly limited. In the present invention, examination is mainly focused on the coating film adhesion of the coated steel sheet in high processing applications, but when applied to such applications, high workability containing a lubricant such as wax. It is also preferable to use a coating film.

(1) Preparation of coated steel plate test piece 1-1. Paint base steel sheet A 12% Ni—Zn electroplated steel sheet (plating adhesion amount: 20 g / m ² ) based on a cold-rolled steel sheet having a thickness of 0.60 mm was used as a base material. This plated steel sheet was immersed in an acidic plating solution as it was without being energized as it was after plating, thereby forming a region surrounded by about 1000 to 50000 cracks per mm ^{2 in} the plating film.

By plating the surface of such an electroplated steel sheet with an alkaline nickel treatment solution after alkaline degreasing, plating cracks were further increased. The treated steel sheet had a region surrounded by about 3000 to 150,000 cracks per 1 mm ^{2 in the} plating film. Then, after further washing with water and drying, a chemical conversion treatment described later was performed immediately.

1-2. Chemical treatment Treatment liquid 1 preparation (aqueous chemical treatment solution used in Invention Example 1)
As a colloidal silica dispersion (liquid B), Snowtex N (average particle diameter of colloidal silica: 10 to 20 nm, silica content: 20% by mass) manufactured by Nissan Chemical Industries, Ltd. was used. 3-Glycidoxypropyltrimethoxysilane (Cyrus Ace S510 manufactured by Chisso Corporation) was gradually added as a silane coupling agent (solution C) to the solution obtained by adding water to the aqueous solution while stirring. The mass ratio of this liquid mixture was set as B liquid: water: C liquid = 6.0: 93.5: 0.5.
In mixing the silane coupling agent, it was gradually added over about 15 minutes. In this way, an aqueous chemical conversion treatment liquid 1 was obtained.

Preparation of treatment liquid 2 (aqueous chemical conversion treatment liquid used in Invention Example 2)
First, a polyester resin emulsion-containing liquid (liquid A) was prepared as follows.
2,5-dimercapto-1,3,4-thiadiazole (manufactured by Wako Pure Chemical Industries, Ltd.) is added to 1 part by weight of a dispersion of water-dispersed polyester resin (MD-1400, byronal Toyobo Co., Ltd., 30% resin content). ) 0.34 parts by mass and 0.85 parts by mass of ammonium zirconium carbonate (manufactured by Sigma-Aldrich Japan Co., Ltd.) were added, and water was further added to make a total of 93.5 parts by mass.
Next, the colloidal silica dispersion (liquid B) was gradually added while gently stirring the liquid A. The mixing ratio of A liquid: B liquid was A liquid: B liquid = 93.5: 6. As the B liquid, the above-mentioned Snowtex N manufactured by Nissan Chemical Industries, Ltd. was used.
Further, immediately after mixing the liquid A and the liquid B, 3-glycidylpropyltrimethoxysilane (S510 Sailer Ace Chisso Corporation) is gradually added as a silane coupling agent-containing liquid (liquid C) while stirring the liquid mixture. Added. The mixing ratio of the A and B liquid mixture and the C liquid was A and B mixed liquid: C liquid = 99.5: 0.5. In mixing the liquid C, it was gradually added over about 15 minutes to obtain an aqueous chemical conversion liquid 2.

Preparation of treatment liquid 3 (aqueous chemical treatment liquid used in comparative examples)
First, a mixed liquid (liquid A) of a polyester resin emulsion and phosphoric acid was prepared as follows.
Dispersion of water-dispersed polyester resin (MD-1400 Vylonal Toyobo Co., Ltd., 30% resin content) 1 part by weight Sodium phosphate (Wako Pure Chemical Industries, Ltd.) 0.37 parts by weight and 2,5- Dimercapto-1,3,4-thiadiazole (manufactured by Wako Pure Chemical Industries, Ltd.) 0.34 parts by mass and zirconium carbonate ammonium sigma-manufactured by Aldrich Japan Co., Ltd.): 0.85 parts by mass, and water was added. The total amount was 93.5 parts by weight.
Next, the colloidal silica dispersion (liquid B) was gradually added while the liquid A was gently stirred. The mixing ratio of A liquid: B liquid was A liquid: B liquid = 93.5: 6. As the B liquid, the above-mentioned Snowtex N manufactured by Nissan Chemical Industries, Ltd. was used.
Furthermore, 3-glycidylpropyltrimethoxysilane (S510 Sailor Ace Chisso Corporation) was gradually added as a silane coupling agent-containing liquid while stirring the liquid mixture immediately after mixing the liquid A and the liquid B. The mixing ratio (mass ratio as the liquid) of the A and B liquid mixture and the C liquid was 99.5: 0.5, and when mixing the C liquid, it was gradually added over about 15 minutes, Treatment liquid 3 was obtained.
Table 1 shows the dry mass of each component in 100 parts by mass of these treatment liquids 1 to 3.

The following coating operations were carried out using these chemical conversion treatment liquids immediately after production, 3 days later, and 90 days later. In applying the chemical conversion treatment solution, the bar coating method was used, and the chemical conversion treatment adhesion amount was changed in the range of 0.5 to 45 g / m ^{2 in} terms of the Si adhesion amount in the film. After applying the treatment liquid, it was dried in a hot air oven so that the plate temperature was about 100 ° C. About some, it dried so that plate | board temperature might be 230 degreeC, and it washed and dried after the temperature fell after that.

1-3 Coating After the chemical conversion treatment, a coating film was formed on both surfaces of the plated steel sheet subjected to the chemical conversion treatment by the method described below.
a) Undercoat film: Polyester resin paint having a Tg of 35 ° C. (containing 100 parts by mass of the polyester resin, 18 parts by mass of the melamine-based crosslinking agent, and 15 parts by mass of aluminum phosphate and calcium phosphate as pigments). Applied. This was dried under the condition that the maximum temperature of the steel sheet was 200 ° C. in 45 seconds to form an undercoat coating film.
b) Top coat film: After forming the undercoat film, a polyester resin paint (18 parts by mass of melamine-based crosslinking agent, 25 parts by mass of titania as a pigment, 15 parts by mass of silica, and 100 parts by mass of polyester resin) Containing 3 parts by weight of polyethylene wax). This was dried under conditions such that the maximum temperature of the steel sheet was 230 ° C. in 60 seconds to form a top coat film. The average film thickness of the top coat film was 15 μm.

(2) Evaluation 2-1 Time-dependent change of processing liquid The transmittance | permeability in visible region was measured about the chemical conversion liquid from which the elapsed time after mixing differs. When colloidal silica, which is a component in the treatment liquid, is aggregated, light that should be transmitted is scattered, and thus the transmittance is considered to be lower than that in the initial state. By this method, although it is simple, the aggregation state of the treatment liquid, that is, the change with time of the treatment liquid over time from the preparation was measured.

2-2 Paint adhesion The cylindrical deep drawing was performed under the following conditions using the coated steel sheet specimen prepared by the method described in (1) above.
Deep drawing conditions Punch diameter: 50mm Punch shoulder R: 5mm Dice diameter: 52.5mm Dice shoulder R: 5mm
Wrinkle holding power: 14700N
Aperture speed: 10 mm per minute
Lubricant: Not used.
The coating surface was the die side and the organic coating surface was the punch side.
The drawn sample prepared under such conditions was immersed in boiling water for 24 hours, and the peeled state of the subsequent coating film was evaluated. As shown in FIG. 4, “5 (good)” indicates that there is almost no change in the state of the coating film, and hereinafter, “1” depending on the abnormal state such as swelling of the coating film and peeling of the coating film from the end surface. The rating was from 1 to 5 with the lowest "
(Evaluation criteria)
5 points: No peeling of the coating film on the drawing flange surface and others.・ ・ ・ Acceptance level 4 points: Slightly small peeling on the flange surface.・ ・ ・ Acceptance level 3 points: There are many small peelings on the diaphragm flange surface.
2 points: There is peeling of the coating film on the drawing flange surface and the drawing wall.
1 point: Most of the coating film peeled off at the drawing flange surface and drawing wall.

2-3 Corrosion resistance About the deep drawn sample which carried out the cylindrical deep drawing on the said conditions, the change after 120 hours was observed by the salt spray test prescribed | regulated to JISZ2371. “5 (good)” indicates that there is almost no change from before the test. Hereinafter, “1” is the minimum of “1” to “5” depending on the abnormal state such as swelling of the coating film or peeling of the coating film from the end face. Evaluated by rating.
(Evaluation criteria)
5 points: No peeling or swelling of the paint film on the diaphragm flange surface, etc.・ ・ ・ Acceptance level 4 points: There is a slight peeling and swelling of the paint film on the diaphragm flange surface.・ ・ ・ Acceptance level 3 points: There are many small peelings on the diaphragm flange surface.
2 points: There is peeling of the coating film on the drawing flange surface and the drawing wall.
1 point: Most of the coating film peeled off at the drawing flange surface and drawing wall.

(3) Evaluation results 3-1 Change with time of treatment liquid FIGS. 1 to 3 show the treatment liquids 1 to 3 in the visible light region within 1 day after preparation, 3 days after preparation, and 90 days after preparation. The transmittance was measured by changing the wavelength. The tendency of the transmittance | permeability of the chemical conversion liquid in the same wavelength of the processing liquid 3 containing a phosphate radical to fall with the elapsed time after preparation was recognized (FIG. 3). On the other hand, almost no change in the transmittance was observed in the treatment liquid 1 and the treatment liquid 2 (the treatment liquid according to the present invention) that did not contain phosphate groups (FIGS. 1 and 2).

3-2 Paint adhesion FIGS. 5 to 7 use the three kinds of treatment liquids 1 to 3 shown in Table 1 within one day after preparation, three days after preparation, and 90 days after preparation. This is a comparison of coating film adhesion after cylindrical squeezing of a sample that has been subjected to chemical conversion treatment and adjusted so that the Si adhesion amount in the film is in the range of 0.5 to 45 g / m ² . In the present invention example 1 subjected to the chemical conversion treatment with the treatment liquid 1 and in the present invention example 2 chemical conversion treated with the treatment liquid 2, there is almost no influence of the time after the preparation, and the chemical treatment adhesion of 10 mg / m ² or more is achieved in any condition. It was an acceptable level (4 or more) in quantity (Figs. 5 and 6). On the other hand, in the comparative examples subjected to the chemical conversion treatment with the treatment liquid 3, only those using the liquid within one day after the preparation were treated with the treatment liquids 1 and 2, and Invention Example 1 and Invention Example 2 were performed. It was confirmed that the adhesiveness decreased with the passage of time, 3 days after blending and 90 days after blending (FIG. 7).

3-3 Corrosion Resistance FIGS. 8 to 10 show the chemical conversion treatment liquids 1 to 3 shown in Table 1 within 1 day after preparation, 3 days after preparation, and 90 days after preparation. This is a comparison of the corrosion resistance after cylindrical squeezing of the samples that were processed and adjusted so that the Si adhesion amount in the film was in the range of 0.5 to 45 g / m ² . In the present invention example 1 subjected to the chemical conversion treatment with the treatment liquid 1 and in the present invention example 2 subjected to the chemical conversion treatment with the treatment liquid 2, there is almost no influence after the preparation, and in any conditions, the chemical conversion treatment adhesion amount is 10 mg / m ² or more. It was a pass level (4 or more) (FIGS. 8 and 9). However, it was confirmed that Example 1 of the present invention (FIG. 8) was slightly inferior in corrosion resistance compared to Example 2 of the present invention (FIG. 9). Compared with the treatment liquid 2 used in the present invention example 2, the treatment liquid 1 used in the present invention example 1 contains only silica in the chemical conversion treatment liquid component and contains a rust preventive additive. It can be inferred that this is not the case. In comparative examples, only those using the chemical conversion treatment liquid 3 within 1 day after blending showed the same results as those of Invention Example 1 and Invention Example 2, with 3 days after blending and 90 days after blending, with the passage of time. It was confirmed that the corrosion resistance was lowered (FIG. 10).

  From these facts, it is presumed that in the treatment liquid 3, the silica in the treatment liquid is agglomerated due to the influence of phosphoric acid over time. 7 and 10, the deterioration in adhesion and corrosion resistance after aging in the comparative examples including phosphate radicals is considered to be caused by the aggregation of silica, which is a chemical conversion liquid component, due to the influence of phosphate radicals. It is done.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. However, the invention can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification, and the coated steel sheet and the manufacturing method thereof are also within the technical scope of the present invention. It must be understood as included.

It is a figure which shows the relationship between the wavelength in the visible region, and the transmittance | permeability at the time of changing the days after chemical conversion liquid 1 preparation. It is a figure which shows the relationship between the wavelength in a visible region, and the transmittance | permeability at the time of changing the days after chemical conversion liquid 2 preparation. It is a figure which shows the relationship between the wavelength in the visible region, and the transmittance | permeability at the time of changing the days after chemical conversion liquid 3 preparation. It is a figure showing the coating-film adhesiveness standard of a coated steel plate. It is a figure which shows the relationship between the amount of Si adhesion in a film, and chemical-coating film adhesiveness of the coated steel plate concerning the example 1 of this invention. It is a figure which shows the relationship between the amount of Si adhesion in a film, and chemical-coating film adhesiveness of the coated steel plate concerning the example 2 of this invention. It is a figure which shows the relationship between the amount of Si adhesion in a film, and chemical conversion coating film adhesiveness of the coated steel plate concerning a comparative example. It is a figure which shows the relationship between the adhesion amount of Si in a film, and corrosion resistance of the coated steel plate concerning the example 1 of this invention. It is a figure which shows the relationship between the amount of Si adhesion in a film, and corrosion resistance of the coated steel plate concerning the example 2 of this invention. It is a figure which shows the relationship between the amount of Si adhesion in a film, and corrosion resistance of the coated steel plate concerning a comparative example. It is the schematic which shows the layer structure of a coated steel plate.

Claims (8)

A coated steel plate comprising a chemical conversion treatment layer containing no hexavalent chromium on at least one side of the base steel plate, and further comprising one or more coating films on the upper layer,
The said chemical conversion treatment layer has a silica and a silane coupling agent as a main component, and is a thing which does not contain a phosphate radical substantially, The coated steel plate characterized by the above-mentioned. A coated steel plate comprising a chemical conversion treatment layer containing no hexavalent chromium on at least one side of the base steel plate, and further comprising one or more coating films on the upper layer,
The said chemical conversion treatment layer has a silica, a silane coupling agent, and resin as a main component, and is a thing which does not contain a phosphate radical substantially, The coated steel plate characterized by the above-mentioned. The coated steel sheet according to claim 1 or 2, wherein the chemical conversion treatment layer contains at least one of a zirconium salt and benzothiazole or a derivative thereof. The coated steel sheet according to any one of claims 1 to 3, wherein an adhesion amount of the chemical conversion treatment layer is 10 mg / m ² or more as Si in the film. The base steel plate is an electrogalvanized alloy-plated steel plate having cracks on its surface, and the number of regions surrounded by cracks per 1 mm ^{2 of the} steel plate surface is 1000 to 15000. The coated steel plate of any one of -4. A method for producing a coated steel sheet comprising a chemical conversion treatment step for forming a chemical conversion treatment layer on at least one side of a base steel plate, and a coating step for coating one or more layers on the chemical conversion treatment layer,
The chemical conversion treatment step is to use an aqueous chemical conversion treatment liquid containing, as main components, colloidal silica and a silane coupling agent and substantially free of phosphate radicals,
The ratio (B / C) of the mass (C) of the silane coupling agent to the mass (B) of the colloidal silica in the aqueous chemical conversion treatment liquid is 1.5 to 10 in a dry mass ratio. A method for producing a coated steel sheet. Resin is further contained in the aqueous chemical conversion treatment liquid, and the ratio (A / (B + C)) of the total mass (B + C) of the colloidal silica and the silane coupling agent to the mass (A) of the resin in a dry mass ratio. The manufacturing method of the coated steel plate of Claim 6 characterized by the above-mentioned. The method for producing a coated steel sheet according to claim 6 or 7, wherein the base steel sheet is an electric zinc alloy plated steel sheet, and includes a step of bringing the plated steel plate into contact with an acidic aqueous solution before the chemical conversion treatment step. .

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