JP5154348B2 - Chemical conversion steel sheet - Google Patents

Description

The present invention relates to a chemical conversion treated steel sheet using an aqueous emulsion treatment liquid .

  Plated steel sheets having good corrosion resistance are used for exterior materials, interior materials, exterior materials, vehicle steel plates, and the like. However, when the plated steel sheet is exposed to a humid atmosphere, exhaust gas atmosphere, sea salt particle flying atmosphere, etc. for a long time, white rust is generated on the surface of the plated steel sheet. The appearance of white rust significantly deteriorates the appearance.

In order to improve the corrosion resistance of the plated steel sheet, for example, Patent Document 1 discloses a plated steel sheet treated with a chemical conversion solution containing an organic resin, a valve metal compound, an ammonium salt and / or an amine. This chemical conversion treated steel sheet is characterized in that the ratio (nitrogen ratio) of nitrogen constituting the NCO group to the total nitrogen in the chemical conversion coating is in the range of 0.8 to 0.95, and is excellent in corrosion resistance and alkali resistance. Is done.
JP 2005-226155 A

  The inventors conducted a preliminary corrosion resistance test on the chemical conversion treated steel sheet described in Patent Document 1. As a result, the chemical conversion treated steel sheet described in Patent Document 1 can maintain good corrosion resistance in a salt spray test at an atmospheric temperature of less than 50 ° C. according to JIS Z237. It was revealed that the corrosion resistance is inferior in a high-temperature and high-humidity environment in which the atmosphere temperature simulating ship storage is 50 ° C. or higher and the relative humidity is 90% or higher. The reason why the corrosion resistance decreased in a high temperature and high humidity environment was presumed to be that water easily penetrated from the interface between the resin and the valve metal compound in the chemical conversion coating.

That is, although a chemical conversion treated steel sheet having excellent corrosion resistance in a high temperature and high humidity environment has been desired, there is still no satisfactory chemical conversion treated steel sheet.
The present invention has been made in view of such a point, and when a plated steel sheet is subjected to a chemical conversion treatment, it gives a chemical conversion steel sheet having excellent corrosion resistance in a high temperature and high humidity environment (simply referred to as “corrosion resistance in a high temperature and high humidity environment”). It is an object of the present invention to provide an aqueous emulsion treatment liquid, and a chemical conversion treated steel sheet subjected to chemical conversion treatment thereby.

  As a result of intensive studies, the present inventors have found that the above-described problems can be solved by an aqueous emulsion treatment liquid containing polyether-modified silicone and having a particle size of the organic resin emulsion in a specific range. That is, the said subject is solved by the following aqueous | water-based emulsion process liquids and the chemical conversion treatment steel plate using the same.

[1] (A) organic resin,
(B) valve metal compound,
An aqueous emulsion treatment liquid comprising (C) a polyether-modified silicone, and (D) water,
The emulsion particle diameter of the (A) organic resin is 10 to 100 nm,
The content of the (B) valve metal compound is 0.1 to 5 parts by mass with respect to 100 parts by mass of the (A) organic resin,
Content of the said (C) polyether modified silicone is an aqueous | water-based emulsion processing liquid which is 0.01-3.0 mass parts with respect to a total of 100 mass parts of said (A) organic resin and (D) water.
[2] The (C) polyether-modified silicone according to [1], wherein the ratio of the number of Si atoms and the number of polyether groups in the molecule is 1: 0.001-1 in terms of a molar ratio. Treatment liquid.
[3] The processing liquid according to [1] or [2], wherein the (A) organic resin is a urethane resin or an acrylic resin.
[4] A chemical conversion treated steel sheet having a chemical conversion treatment film formed by applying the treatment liquid according to any one of [1] to [3] to the surface of the plated steel sheet and drying it.
[5] The chemical conversion film has a different concentration of the (C) polyether-modified silicone in the thickness direction, and the (C) polyether-modified silicone is concentrated in the vicinity of the surface layer of the chemical conversion film, [4] ] The chemical conversion treatment steel plate of description.

  According to the present invention, when a steel sheet is subjected to chemical conversion treatment, an aqueous emulsion treatment liquid that provides a chemical conversion treated steel sheet having excellent corrosion resistance in a high-temperature and high-humidity environment, and a chemical conversion-treated steel sheet treated thereby.

1. The aqueous emulsion treatment liquid of the present invention The aqueous emulsion treatment liquid of the present invention is
(A) organic resin,
(B) valve metal compound,
(C) a polyether-modified silicone, and (D) an aqueous emulsion treatment liquid comprising water, wherein the aqueous emulsion treatment liquid comprises:
The emulsion particle diameter of the (A) organic resin is 10 to 100 nm,
The content of the (B) valve metal compound is 0.1 to 5 parts by mass with respect to 100 parts by mass of the (A) organic resin,
Content of said (C) polyether modified silicone is 0.01-3.0 mass parts with respect to a total of 100 mass parts of said (A) organic resin and (D) water, It is characterized by the above-mentioned.
The aqueous emulsion treatment liquid is a treatment liquid in which (A) an organic resin is mainly dispersed as fine particles in water as a dispersion medium. In the aqueous emulsion treatment liquid, (B) the valve metal compound and (C) the polyether-modified silicone may be dispersed as fine particles or may be dissolved in water. Hereinafter, the aqueous emulsion treatment liquid of the present invention is also simply referred to as “treatment liquid”.

(1) (A) Organic resin An organic resin is an organic polymer compound. The organic resin is applied to the plated steel sheet to form a chemical conversion treatment film. Examples of the organic resin include urethane resin, epoxy resin, polyethylene resin, polypropylene resin, ethylene-acrylic acid copolymer, polystyrene resin, or modified products thereof. In the present invention, two or more of the organic resins may be used in combination.

The organic resin of the present invention is preferably a urethane resin or an acrylic resin. This is because it is easy to obtain and easy to prepare an emulsion. The urethane resin is a general term for resins having a urethane bond in the molecule, and is usually obtained by reacting a polyol and a polyisocyanate.
Examples of polyisocyanates include the following.
Aliphatic diisocyanates such as phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, or naphthalene diisocyanate.
Cycloaliphatic diisocyanates such as cyclohexane diisocyanate, isophorone diisocyanate, norbornane diisocyanate, xylylene diisocyanate, or tetramethylxylylene diisocyanate;

  Examples of the polyol compound include polyester polyols, polyether polyols, polycarbonate polyols, polyacetal polyols, polyacrylate polyols, polyester amide polyols, or polyolefin polyols such as polybutadiene.

  An acrylic resin is a general term for a polymer of a compound having (meth) acrylic acid or a methyl (meth) acrylate acrylic group. (Meth) acryl means acryl or methacryl. Examples of the acrylic resin include a polymer of (meth) acrylic acid or (meth) acrylic alkyl ester. Examples of (meth) acrylic alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, (meth) acrylic Acid hexyl, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, and stearyl (meth) acrylate are included.

  The organic resin (A) of the present invention is dispersed as an emulsion in the treatment liquid, and the particle diameter thereof is 10 to 100 nm, more preferably 20 to 60 nm. In the present invention, the symbol “˜” includes numerical values at both ends thereof. As will be described later, the emulsion particle diameter affects the movement of the (C) polyether-modified silicone in the film when a chemical conversion film is formed.

  The treatment liquid of the present invention is applied to the surface of the steel sheet and then dried to form a chemical conversion treatment film. At that time, the polyether-modified silicone moves to the film surface. As a result, a concentrated layer of polyether-modified silicone is formed near the surface of the chemical conversion coating. Since the polyether-modified silicone has high hydrophobicity, this concentrated layer makes it difficult for water to enter the chemical conversion film. As a result, the chemical conversion treated steel sheet treated with the treatment liquid of the present invention is excellent in water resistance under high temperature and high humidity.

At this time, if the emulsion particle diameter of the organic resin in the treatment liquid is less than 10 nm, the number of organic resin particles in the treatment liquid increases and the total surface area of the particles also increases. Therefore, when the polyether-modified silicone moves to the surface layer of the film, the movement is hindered due to a long path of movement or adsorption to the surface of the organic resin. As a result, it is difficult to obtain a chemical conversion treated steel sheet having excellent water resistance under high temperature and high humidity.
On the contrary, when the emulsion resin particle diameter of the organic resin in the treatment liquid exceeds 100 nm, the denseness of the chemical conversion treatment film to be formed is lowered, so that the corrosion resistance and workability of the chemical conversion treatment steel plate are lowered.

  The particle diameter of the emulsion may be measured by a known method, but is preferably measured by a “dynamic light scattering method” in which the average particle diameter is measured by measuring the speed at which the particles in the liquid diffuse due to Brownian motion.

  10-40 mass parts is preferable with respect to 100 mass parts of water, and, as for content of the organic resin in the process liquid of this invention, 20-30 mass parts is more preferable. When the content of the organic resin is less than 10 parts by mass, water evaporation during the drying process is remarkably increased, and the film formability and denseness of the film are not sufficient, and the corrosion resistance of the chemical conversion treated steel sheet may be lowered. Moreover, when content of organic resin exceeds 40 mass parts, the storage stability of a chemical conversion liquid may fall.

(2) (B) Valve metal compound Valve metal refers to a metal whose oxide exhibits high insulation resistance, and a compound containing a valve metal element is referred to as a valve metal compound. Examples of the valve metal include Ti, Zr, Hf, V, Nb, Ta, Mo, and W. Examples of the valve metal compound include salts of these metals and organometallic compounds, and specific examples thereof include the following compounds.

K _n TiF ₆ (K is an alkali metal or alkaline earth metal, n is 1 or 2), K ₂ [TiO (COO) ₂ ], (NH ₄ ) ₂ TiF ₆ [ammonium fluoride titanate] Ti compounds such as TiCl ₄ , TiOSO ₄ , Ti (SO ₄ ) ₂ , and Ti (OH) ₄ .

Zr compounds such as (NH ₄ ) ₂ ZrF ₆ , Zr (SO ₄ ) ₂ , (NH ₄ ) ₂ ZrO (CO ₃ ) ₂ [zirconium carbonate].

Mo compounds such as (NH ₄ ) ₆ Mo ₇ O ₂₄ [ammonium molybdate] and K ₂ (MoO ₂ F ₄ ).

Other compounds such as Na ₂ WO ₄ (NH ₄ ) ₂ TiF ₆ , TiOSO ₄ VF ₄ , and K ₅ NbF ₇ .

  Among these, from the viewpoint of easy availability, the valve metal compound is preferably ammonium fluoride titanate, ammonium zirconium carbonate, or ammonium molybdate. As the valve metal compound, two or more of the above compounds may be used in combination.

  Content of a valve metal compound is 0.1-5 mass parts with respect to 100 mass parts of (A) organic resin. When the content of the valve metal compound is less than 0.1 parts by mass, the corrosion resistance of the steel sheet is insufficient. When the content exceeds 5 parts by mass, the area of the interface between the valve metal compound and the resin in the coating increases, so that water easily enters the coating, and the corrosion resistance of the chemical conversion treated steel sheet at high temperature and high humidity decreases. .

  A valve metal compound undergoes a chemical change by chemical conversion treatment, and generates a valve metal oxide or a valve metal hydroxide (hereinafter referred to as “valve metal oxide etc.”) in a chemical conversion treatment film formed on the surface of the steel sheet. . Since the valve metal oxide or the like hinders the movement of electrons, the oxidation reaction between the base steel of the chemical conversion treated steel sheet and the dissolved oxygen contained in the moisture in the atmosphere where the chemical conversion treated steel sheet is placed is suppressed. As a result, the corrosion resistance of the steel sheet is improved.

  However, in the chemical conversion treatment film, a film defect portion is formed in the chemical conversion treatment or processing, and corrosion may occur based on that portion. Therefore, in the present invention, it is preferable to contain a water-soluble fluoride (also referred to as “valve metal fluoride”) of the valve metal compound in the chemical conversion coating. Valve metal fluoride imparts a self-repairing function to the chemical conversion coating. Specifically, the valve metal fluoride dissolves in moisture in the atmosphere and re-deposits as a poorly soluble oxide or hydroxide on the surface of the underlying steel exposed from the film defects, resulting in film defects. Cover the part.

In order to include the valve metal fluoride in the chemical conversion coating, the valve metal fluoride may be included in the chemical conversion solution. That is, as the valve metal compound, it is preferable to use a compound containing a valve metal element and a fluorine element, such as K _n TiF ₆ or (NH ₄ ) ₂ ZrF ₆ .
Alternatively, a chemical conversion treatment liquid containing a fluorine compound and the valve metal compound may be prepared, and fluorine and valve metal may be reacted during the chemical conversion treatment to produce valve metal fluoride in the coating. Examples of the fluorine compound in this case include NH ₄ F and MF ₆ (M is a metal element). The content of NH ₄ F or MF ₆ is preferably 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the organic resin.

(3) (C) Polyether-modified silicone Polyether-modified silicone is a silicone having a main chain composed of a polysiloxane bond and having a polyether group at the terminal or side chain. Examples of the silicone having a main chain composed of a polysiloxane bond include polydimethylsiloxane and silicones in which some methyl groups in the polydimethylsiloxane are other alkyl groups or arylene groups.

The polyether group plays a role of enhancing the hydrophilicity of the silicone and stabilizing the dispersibility of the silicone in the treatment liquid of the present invention.
In addition, amino groups, carboxyl groups, and mercapto groups are known as groups used for modifying silicone. These groups are easy to react with the valve metal compound of the present invention although they serve to increase the hydrophilicity of the silicone. For this reason, the treatment liquid containing silicone modified with the component (A), the component (B), an amino group, or the like is less likely to move through the film when it is converted into a chemical conversion film. On the other hand, since the treatment liquid of the present invention employs silicone modified with a polyether group, it hardly reacts with the valve metal compound, and the silicone easily moves to the surface layer portion of the film.

Examples of the polyether group include an alkoxyl group and a polyoxyalkylene group. Specific examples of the alkoxyl group include —OC ₂ H ₅ , —OC ₃ H ₇ , —OC ₄ H ₉ . In this example, the alkyl group also includes its isomers.
Specific examples of the polyoxyalkylene group include —OCH ₂ — (OCH ₂ ) _n and —OC ₂ H ₅ — (OC ₂ H ₅ ) _n . In this example, n represents an integer of 1 or more.

(C) Preferred specific examples of the polyether-modified silicone include the following compounds.

  In the above formula, n and m are positive integers, and are numbers determined as appropriate depending on the molecular weight of the polyether-modified silicone and the number of polyether groups.

  The content of the polyether-modified silicone is 0.01 to 3.0 parts by mass with respect to 100 parts by mass in total of the (A) organic resin and (D) water.

  The molar ratio of the number of Si atoms and the number of polyether groups in the polyether-modified silicone is preferably 0.001 to 1.0. When this molar ratio is less than 0.001, dispersibility in the treatment liquid may be lowered. Moreover, when this molar ratio exceeds 1.0, a chemical conversion treatment film may become excessively hydrophilic and water resistance may be lowered. This molar ratio is sometimes referred to as the “modified amount”.

(D) Water The water used in the present invention is not particularly limited as long as it is water normally used in emulsions.

2. Method for Producing Aqueous Emulsion Treatment Liquid of the Present Invention The treatment liquid of the present invention is optionally produced within a range that does not impair the effects of the invention. Hereinafter, a preferred production method will be described.
The treatment liquid of the present invention is
(A) preparing a water-dispersible organic resin emulsion;
(B) It is preferable that the water-dispersible organic resin emulsion includes a step of mixing a valve metal compound and a polyether-modified silicone.

(1) Step (a) In this step, a water-dispersible organic resin emulsion is prepared. The water-dispersible organic resin emulsion may be commercially available, but is preferably prepared by the method described below.
1) A surfactant method in which an emulsion is obtained by high-shear stirring a resin solution obtained by dissolving an organic resin in a solvent, a surfactant, and water.
2) An emulsion polymerization method in which an emulsion in which a monomer is dispersed in water is prepared and the monomer is polymerized.
3) A self-emulsification method in which an organic resin having a hydrophilic group introduced into the molecule is prepared and dispersed in water.

  In the surfactant method 1), a cationic surfactant, an anionic surfactant, or a nonionic surfactant can be used. The cationic surfactant is a surfactant that ionizes hydrophilic groups in the surfactant into cations. Similarly, an anionic surfactant is a surfactant that ionizes a hydrophilic group in the surfactant into an anion. A nonionic surfactant is a surfactant that does not ionize hydrophilic groups in the surfactant.

  Known cationic surfactants may be used, but examples include monoalkylamine salts, dialkylamine salts, trialkylamine salts, and amine salts such as alkylbenzyldimethylammonium chloride.

  Known anionic surfactants may be used. Examples thereof include carboxylates such as aliphatic monocarboxylates, sulfonates such as alkylbenzene sulfonates, sulfate esters such as alkyl ether sulfates, and phosphoric acid. Phosphate esters such as (mono or di) alkyl salts are included.

  Known nonionic surfactants may be used, but examples include fatty acid esters such as glycerin fatty acid esters, ethers such as polyoxyethylene alkyl ether, ester ethers such as fatty acid polyethylene glycol, and fatty acid alkanolamides. Of the alkanolamide.

  A known means may be adopted as the means for high shear stirring in the surfactant method. Examples of known means include dispersers.

  In the surfactant method, the larger the shear rate or the longer the stirring time, the smaller the particle size of the emulsion. By optimizing the shear rate and the like, the particle size of the emulsion of the present invention is reduced as described above. Can be a value. Moreover, although mentioned later in detail, when an organic resin has hydrophilic groups, such as a carboxyl group, a particle diameter will become small. Therefore, the particle diameter of the emulsion can be adjusted to the above range by optimizing the content (acid value) of the carboxyl group and the like of the organic resin.

  The emulsion polymerization method 2) is a suitable method when an organic resin is an acrylic resin. In emulsion polymerization, an emulsion in which monomers are dispersed in water is prepared using a surfactant, and this emulsion is then polymerized. In preparing the emulsion, it is preferable to use the aforementioned surfactant. Also in emulsion polymerization, the larger the shear rate or the longer the stirring time, the smaller the particle size of the emulsion in which the monomer is dispersed in water. That is, the particle diameter of the emulsion of the present invention can be set to the above-mentioned value by optimizing the shear rate at the time of preparing the monomer emulsion.

  The self-emulsification method 3) is a suitable method when the organic resin is a urethane resin. Examples of the hydrophilic group introduced into the urethane resin include a hydroxyl group, a sulfonic acid (salt) group, a carboxyl (salt) group, and an ether group. In order to introduce these hydrophilic groups into the urethane resin, a polyol or polyisocyanate having these hydrophilic groups may be used as a raw material. For example, when ethylene glycol is used as the polyol, a urethane resin having an ether group in the molecule can be obtained.

  The urethane resin introduced with a hydroxyl group is anionic, the urethane resin introduced with a sulfonic acid (salt) group or carboxyl (salt) group is cationic, and the urethane resin introduced with an ether group is nonionic. In the present invention, it is preferable to introduce a sulfonic acid (salt) group or a carboxyl (salt) group into the urethane resin. This is because the particle size of the emulsion obtained is small.

  In the present invention, the emulsion obtained by any of the above methods may be used, but the emulsion obtained by the self-emulsification method in which the organic resin having the hydrophilic group introduced in 3) is prepared and dispersed in water is prepared. Is preferred.

(2) Step (b) In this step, a valve metal compound and a polyether-modified silicone are mixed with the water-dispersible organic resin emulsion prepared in the previous step. The means for mixing the two is not particularly limited, but it is preferable to mix the two using a stirrer or three rolls. The mixing temperature is not particularly limited, but it is preferable to mix at room temperature.

3. Chemical conversion treated steel sheet The chemical conversion treated steel sheet subjected to chemical conversion treatment with the treatment liquid is obtained by applying the treatment liquid of the present invention to the steel sheet and drying it.
A steel plate is a plate-shaped steel. Examples of the steel plate include a normal steel plate, a plated steel plate, and a stainless steel plate. Examples of plated steel sheets include steel sheets that have been subjected to hot dipping, electroplating, vapor deposition plating, or the like. Examples of hot dipped steel sheets include a molten Zn bath, a molten Zn-Al alloy bath, a molten Zn-Al-Mg alloy bath, a molten Zn-Mg alloy bath, a molten Al bath, a molten Al-Si alloy bath, and the like. Those obtained by plating or immersion plating are included. Alternatively, an alloyed hot dip plated steel sheet that has been alloyed after hot dip plating may be used as the steel sheet.

  Examples of electroplated steel sheets are obtained by continuous plating using a normal electric Zn plating solution, an electric Zn alloy plating solution, an electric Cu plating solution, an electric Sn plating solution, or by immersion plating (individual electroplating method). Is included.

  The steel sheet used in the present invention may be subjected to chemical conversion treatment such as degreasing treatment or phosphate treatment using an alkaline solvent as a pretreatment for improving corrosion resistance and adhesion.

  The chemical conversion treatment film refers to a film obtained by applying a treatment liquid on a steel plate and drying it. In the present invention, the film before drying is referred to as “coating film”, and the dried film is referred to as “chemical conversion film”.

  The thickness of the chemical conversion film is preferably 0.1 to 5 μm. When the thickness of the chemical conversion film is within this range, the balance between the above performance and cost is excellent. Since the effect of the thickness of the chemical conversion coating is saturated at about 5 μm, no further improvement in performance can be expected with an increase in thickness beyond 5 μm.

  In the chemical conversion film of the present invention, the concentration of the polyether-modified silicone is different in the thickness direction, and the polyether-modified silicone is preferably concentrated in the vicinity of the surface layer of the chemical conversion film. FIG. 1 is a diagram showing an example of a chemical conversion treated steel sheet of the present invention. In FIG. 1, 1 is a chemical conversion treatment film, 2 is a c layer in which polyether-modified silicone is concentrated, 3 is a layer other than the c layer in the chemical conversion treatment film, 4 is a plated steel sheet, and 5 is a c layer and a c layer. It is an interface of other layers.

  It is preferable that the interface 5 exists in the area | region of 0.2 to 2% of thickness from the surface layer of the chemical conversion treatment film of this invention.

  The c layer can be identified by surface analysis of the chemical conversion treatment film. In the present invention, the chemical conversion treatment film surface is analyzed by an X-ray photoelectron spectrometer (XPS), and the main component of each layer can be obtained from the change over time of the obtained peak. For example, what is necessary is just to analyze the peak resulting from the silicon atom peculiar to polyether modified silicone.

4). Chemical conversion treatment method Although chemical conversion treatment may be performed by a known method, a preferable chemical conversion treatment method will be described below.
Chemical conversion treatment using the chemical conversion liquid of the present invention,
(C) preparing a plated steel sheet;
(D) Applying the chemical conversion treatment liquid of the present invention to the plated steel sheet and heating it is preferable.

(1) Step (c) In this step, a plated steel sheet is prepared. The means for preparing is not particularly limited, but it is preferable to prepare by the method as already described. Or you may purchase a commercial item and prepare a plated steel plate.

(2) Step (d) In this step, the chemical conversion solution of the present invention is applied to the plated steel plate prepared in the previous step and dried. The process of applying is also referred to as an application process, and the process of drying is also referred to as a drying process.
The chemical conversion solution is prepared by the method described above. The prepared treatment liquid is applied onto the plated layer of the plated steel sheet by a roll coating method, a spin coating method, a spray method or the like. After coating, the coating film is dried without washing with water, and a chemical conversion film is formed on the plating layer.

  Although the drying temperature of a coating film is not specifically limited, In order to accelerate | stimulate reaction of a valve metal compound, Preferably it is 100 degreeC or more, More preferably, it is 120-200 degreeC. If the drying is performed at an excessively high temperature, the organic resin is decomposed and the performance of the chemical conversion film is deteriorated. Therefore, the upper limit of the drying temperature is preferably 200 ° C.

[Example 1]
An aqueous urethane resin emulsion having a nonvolatile content of 30% by mass and an average particle size of the emulsion of 10 nm was prepared. For 100 parts by mass of organic resin, 0.7 parts by mass of ammonium zirconium carbonate (0.33 parts by mass in terms of ZrO ₂ ) as a valve metal compound, polyether-modified silicone (made by Toray Dow Corning Co., Ltd., product name FZ-) 77), 0.2 parts by mass was added to 100 parts by mass of the total amount of the organic resin and water and mixed by a conventional method to obtain a treatment liquid.

  This treatment liquid was directly applied to a galvalume steel plate (aluminum 55% -containing galvanized steel plate) and dried at a plate temperature of 150 ° C. to obtain a chemical conversion treated steel plate with a chemical conversion coating having a thickness of 1.0 μm. The obtained chemical conversion treated steel sheet was evaluated by the following method. The evaluation results are summarized in Tables 1 and 2. In the table, the valve metal compound is 100 parts by mass of the organic resin, and the silicone is mass parts with respect to 100 parts by mass of the total of the organic resin and water.

(1) Corrosion resistance 1) Salt spray test A test piece (150 mm x 70 mm) was cut out from the chemical conversion treated steel sheet and end face sealed. Using this test piece, a salt spray test (based on JIS Z2371) 240 h was performed, and the white rust generation area ratio of the flat portion was evaluated.
When the white rust generation area ratio is less than 5%, it is evaluated as ◎ when it is 5% or more and less than 10%, △ when it is 10% or more and less than 20%, and × when it is 20% or more. .

2) High-temperature and high-humidity test A test piece (150 mm x 70 mm) was cut out from the chemical conversion-treated steel sheet and subjected to end face sealing. This test piece was left in a high-temperature and high-humidity tank with an atmospheric temperature of 50 ° C. and RH of 98% for 480 h, and the white rust generation area of the flat part was evaluated.
When the white rust generation area ratio is less than 5%, it is evaluated as ◎ when it is 5% or more and less than 10%, △ when it is 10% or more and less than 20%, and × when it is 20% or more. .

(2) Scratch resistance A test piece (30 mm × 250 mm) was cut out from the chemical conversion treated steel sheet and subjected to end face sealing. Using this test piece, a draw bead test (mold: bead height: 4 mm, pressure: 3000 N, drawing speed: 8.3 × 10−2 m / sec) was performed to determine the residual rate of the chemical conversion film on the mold sliding portion. It was measured.
When the film remaining rate was 80% or more, it was evaluated as ◎, when it was 60% or more and less than 80%, ◯, when it was 40% or more and less than 60%, and when it was less than 40%, it was evaluated as ×.

[Examples 2 to 14]
The types and addition amounts of the organic resin emulsion, the valve metal compound and the polyether-modified silicone were changed as shown in Table 1, and a chemical conversion treated steel sheet was obtained in the same manner as in Example 1. About the obtained chemical conversion treatment steel plate, evaluation similar to Example 1 was performed.

[Comparative Examples 1 to 10]
The types and addition amounts of organic resin emulsion, valve metal compound and silicone were as shown in Table 1, and a chemical conversion treated steel sheet was obtained in the same manner as in Example 1. About the obtained chemical conversion treatment steel plate, evaluation similar to Example 1 was performed.

  As shown in Tables 1 and 2, it was revealed that the chemical conversion treated steel sheets of Examples 1 to 14 all have good salt spray test corrosion resistance and high temperature and high humidity test corrosion resistance, and are sufficiently useful for practical use.

  The chemical conversion treated steel sheets of Comparative Example 3 in which the addition amount of the valve metal compound is less than 0.1 parts by mass and Comparative Example 4 in which the addition amount exceeds 5.0 parts by mass are corrosion resistance in the salt spray test and the high temperature and high humidity test. There was a tendency for galling resistance to decrease. This is because the chemical conversion treated steel sheet of Comparative Example 3 has a small amount of valve metal compound in the chemical conversion film, and the chemical conversion steel sheet of Comparative Example 4 has a total area of the interface between the valve metal compound and the resin in the chemical conversion film. It was speculated that the increase in

  The chemical conversion treated steel sheet of Example 5 in which the ratio of Si to the polyether group in the polyether-modified silicone molecule was less than 0.01 in terms of molar ratio was slightly lowered in corrosion resistance in the high temperature and high humidity test. This was presumably because the water resistance of the film was insufficient because the hydrophilicity of the polyether-modified silicone was not sufficient and was not stably dispersed in the treatment liquid. In addition, the chemical conversion treated steel plate of Example 8 with the ratio exceeding 1.0 showed a tendency that the corrosion resistance in the high-temperature and high-humidity test was lowered, which is presumed that the hydrophilicity of the film became excessive. It was done.

  The chemical conversion treatment steel plate of Comparative Example 6 in which the addition amount of the polyether-modified silicone was less than 0.01 parts by mass showed a tendency that the corrosion resistance in the high temperature and high humidity test was lowered. This is presumably because the water resistance of the film is not sufficient. In the chemical conversion treated steel sheet of Comparative Example 7 in which the addition amount exceeds 3.0 parts by mass, the corrosion resistance and galling resistance tend to decrease. This is presumably because the amount of the polyether-modified silicone in the film became excessive, hindering the bonding between the resin emulsions, and the denseness of the dried coating film was reduced.

  Since the chemical conversion treatment steel plate of the comparative example 1 whose average particle diameter of an organic resin emulsion is less than 10 nm lacks the concentration amount in the coating-film surface layer of polyether modified silicone, the corrosion resistance in a high temperature, high humidity test fell. Moreover, since the chemical conversion treatment steel plate of the comparative example 2 whose average particle diameter exceeds 100 nm reduces the compactness of a chemical conversion treatment film, corrosion resistance and the galling resistance at the time of a process fell.

  The chemical conversion treated steel sheet of Comparative Example 5 containing no polyether-modified silicone was inferior in corrosion resistance in a high-temperature and high-humidity test because the water resistance of the film was insufficient.

The chemical conversion treated steel sheet of Comparative Example 8 using unmodified silicone was inferior in compatibility with the resin emulsion, and silicone was unevenly distributed in the coating film, so that the corrosion resistance in the high temperature and high humidity test was inferior.
The chemical conversion treated steel sheets of Comparative Examples 9 and 10 using silicone modified with an amino group or a mercapto group were inferior in corrosion resistance in a high-temperature and high-humidity test because of insufficient silicone concentration on the coating surface layer.

  The treatment liquid of the present invention provides a chemical conversion treated steel sheet having excellent corrosion resistance under a high temperature and high humidity environment. Therefore, this invention is suitable for the chemical conversion treatment of the steel plate which requires corrosion resistance.

Sectional drawing which shows an example of the chemical conversion treatment steel plate of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chemical conversion film 2 Polyether modified silicone c layer 3 Layers other than c layer 4 Plated steel sheet 5 Interface between layers other than c layer and c layer

Claims (3)

The surface of the plated steel sheet is a chemical conversion-treated steel sheet having a chemical conversion film formed by applying an aqueous emulsion treatment liquid and drying it,
The aqueous emulsion treatment liquid comprises (A) an organic resin, (B) a valve metal compound containing a valve metal selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Mo and W, and (C) poly Ether-modified silicone, and (D) water,
The emulsion particle diameter of the (A) organic resin is 10 to 100 nm,
The content of the (B) valve metal compound is 0.1 to 5 parts by mass with respect to 100 parts by mass of the (A) organic resin,
The content of the (C) polyether-modified silicone is 0.01 to 3.0 parts by mass with respect to a total of 100 parts by mass of the (A) organic resin and (D) water,
The chemical conversion treatment film has a different concentration of the (C) polyether-modified silicone in the thickness direction, and the (C) polyether-modified silicone is concentrated in the vicinity of the surface layer of the chemical conversion treatment film.
Chemical conversion steel sheet. The said (C) polyether modified silicone is a chemical conversion steel plate of Claim 1 whose ratio of the number of Si atoms in a molecule | numerator and the number of polyether groups is 1: 0.001-1 in molar ratio. . The said (A) organic resin is a chemical conversion treatment steel plate of Claim 1 which is a urethane resin or an acrylic resin.

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