JP2009173996A - Coated steel product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated steel product that has a coating on the surface of a steel product and is chromium-free so as to be friendly to an environment while exhibiting excellent corrosion-resistant performance. <P>SOLUTION: The coated steel product has a coating formed on the surface of the steel product via an inorganic film which includes a silicon oxide in the range of 5-100 mg/m<SP>2</SP>in terms of a silicon content and substantially does not include chromium and an organic material. Though the coated steel product substantially does not include hexavalent chromium and trivalent chromium at all, that is, being so-called chromium-free, it has excellent corrosion-resistant performance and is a material friendly to an environment. Consequently, it can be safely used in a wide range of applications. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  This invention is applied to various kinds of materials such as cold-rolled steel material, hot-rolled steel material, stainless steel, zinc-based plated steel material, zinc-aluminum alloy-plated steel material, zinc-iron-based plated steel material, zinc-magnesium-based plated steel material, and aluminum-based plated steel material. The present invention relates to a coated steel material having a coating film excellent in corrosion resistance on the surface of the steel material.

  Conventionally, methods using a chromium-based surface treatment agent such as chromate treatment or phosphoric acid chromate treatment are well known for corrosion resistance treatment of steel materials, and these methods are still widely used today. However, the use of chromium-based surface treatment agents may be limited in the future due to the toxicity of chromium. Motivation to regulate the use of environmentally hazardous substances is increasing globally. For example, in the EU, laws and regulations relating to hexavalent chromium have begun due to the directive on scrapped automobiles. For this reason, it has been desired to develop a coated steel material that does not contain chromium and is a so-called non-chromium treatment and has excellent corrosion resistance.

  And as an example of the non-chromium-type coating treatment of the steel material, on the surface of a metal plate such as a galvanized steel plate, 50 to 90% by mass of a specific cross-linked resin matrix (A), colloidal silica, phosphoric acid, niobium oxide sol, etc. By forming a film containing 10-50% by mass of the inorganic rust preventive agent (B), a non-chromium type organic coated metal plate with excellent corrosion resistance, alkali resistance, solvent resistance, scratch resistance and adhesion is provided. It has been proposed (see Patent Document 1).

Further, zirconium and titanium-based chemical conversion treatments have been proposed as good non-chromium chemical conversion treatments for all metals (see Patent Document 2), and zinc-based plated steel sheets and aluminum materials are treated with sulfur compounds as non-chromium treatments. And a coating base treatment containing polyurethane has been proposed (see Patent Document 3). Furthermore, as a non-chromic treatment of a metal material, a coating containing a silane coupling agent, a urethane resin, and a zirconium compound is formed, thereby improving corrosion resistance. It has been proposed to provide a surface-treated film having excellent coating film adhesion (see Patent Document 4).
JP 2005-281,863 A JP 2004-218,070 A JP 2006-124,752 A JP 2006-328,445 A

  As a result of further investigation on the coated steel material in which the coating film having excellent corrosion resistance and environment-friendly non-chromium has been developed, the present inventor unexpectedly found that the surface of the coated steel material and the coated steel material The corrosion resistance of the resulting coated steel material is remarkably improved by interposing a film (inorganic film) containing a predetermined silicon oxide in a predetermined silicon amount and substantially not containing an organic substance. The present invention has been completed.

  Accordingly, an object of the present invention is to provide a coated steel material which has a coating film on the surface of the steel material, is non-chromium and is environmentally friendly and exhibits excellent corrosion resistance.

That is, according to the present invention, a coating film is formed on the surface of a steel material through an inorganic coating that contains silicon oxide in a silicon amount range of 5 to 100 mg / m ² and substantially does not contain chromium and organic substances. It is a painted steel material characterized by Here, “substantially free of chromium” means that chromium is below the detection limit (usually 0.5 mg / m ² or less) in fluorescent X-ray analysis of inorganic coatings. It means that it is not added, and “substantially free of organic substances” means less than a small amount of carbon (C amount) detected by surface contamination in fluorescent X-ray analysis (usually 10 mg / m ² or less) This means that, for example, an organic substance intended to remain in an inorganic film such as an organic resin binder is not added, and in the formation process of this inorganic film, it does not substantially remain in an inorganic film such as alcohols. The use of organic materials is not excluded.

  In the present invention, as the steel material, cold rolled, hot rolled steel material, stainless steel, zinc-based plated steel material, zinc-aluminum alloy-plated steel material, zinc-iron-based plated steel material, zinc-magnesium-based plated steel material, aluminum-based plated steel material, etc. Steel materials, processed materials obtained by appropriately processing these materials, and combined materials obtained by appropriately combining these materials. Examples of the zinc-based plated steel material include, for example, an electrogalvanized steel sheet, a hot-dip galvanized steel sheet, and the like, and examples of the zinc-aluminum-plated steel material include, for example, a hot-dip zinc-5% aluminum alloy-plated steel sheet, Examples include a molten 55% aluminum-zinc alloy plated steel sheet.

In the present invention, the inorganic coating formed on the surface of the steel material contains silicon oxide in a silicon amount of 5 mg / m ² or more and 100 mg / m ² or less, preferably 10 mg / m ² or more and 90 mg / m ² or less. is required. When the amount of silicon in the inorganic film is less than 5 mg / m ^2, there is a problem that corrosion resistance is poor, on the contrary, if larger than 100 mg / m ^2, a problem that adhesion is poor is caused.

  The inorganic film of the present invention usually has a film thickness of 5 nm to 500 nm, preferably 20 nm to 300 nm, and the silicon content in the film is 30% to 46.7% by weight. In the following, it is preferably 32% by weight or more and 46.7% by weight or less. If the film thickness of the inorganic film is less than 5 nm, the yarn rust resistance may be insufficient. Conversely, if the film thickness is greater than 500 nm, the adhesion may be insufficient. Further, if the silicon content in the film is less than 30% by weight, there is a problem that the corrosion resistance is inferior, and if it is more than 46.7% by weight, it is difficult to form a film with a general-purpose raw material and the cost is increased. .

  Furthermore, the inorganic film containing the silicon oxide of the present invention is preferably a film formed using water-dispersible silica as a raw material, and examples of the water-dispersible silica include colloidal silica and vapor phase silica. More preferably, it is colloidal silica. The colloidal silica is not particularly limited. Specifically, for example, spherical colloidal silica includes SNOWTEX-C, SNOWTEX-O, SNOWTEX-N, SNOWTEX-N, manufactured by Nissan Chemical Industries, Ltd. There are Tex-S, Snowtex-OL, Snowtex-XS, Snowtex-XL, etc. As chain colloidal silica, there are Snowtex-UP and Snowtex-OUP manufactured by Nissan Chemical Industries. Gas phase silica includes Aerosil 130, Aerosil 200, Aerosil 200CF, Aerosil 300, Aerosil 300CF, Aerosil 380, Aerosil MOX80, etc. manufactured by Nippon Aerosil Co., Ltd.

Furthermore, for the purpose of further improving the corrosion resistance, if necessary, the inorganic film has a predetermined value in addition to the silicon oxide in the film forming treatment liquid used in the film forming process for forming the inorganic film. In this way, the phosphorus compound is added into the inorganic film. The added phosphorus compound may be contained in the film when zinc or aluminum on the surface of the plated steel reacts with the phosphorus compound to form a phosphate such as zinc phosphate or aluminum phosphate during film formation. . The addition amount of the phosphorus compound added for this purpose in the inorganic coating, a phosphorus content of the coating in the 1 mg / m ² or more 15 mg / m ² or less, preferably 1.5 mg / m ² or more 10 mg / m ² or less It is preferable that the phosphorus content in the film is within 10% by weight or less. Regarding the amount of phosphorus compound added, if the amount of phosphorus in the film is less than 1 mg / m ² , the purpose of adding the phosphorus compound is not achieved, and if it exceeds 15 mg / m ² , poor adhesion occurs. In addition, when the phosphorus content in the film exceeds 10% by weight, there is a problem that the adhesiveness is lowered.

  The phosphorus compound added to the film-forming treatment solution for this purpose is not particularly limited, but preferably one or two selected from, for example, orthophosphoric acid, phosphonic acid, pyrophosphoric acid, tripolyphosphoric acid and salts thereof. Examples of the mixture include phosphoric acid, triammonium phosphate, trisodium phosphate, aluminum phosphate, zinc phosphate, and magnesium phosphate.

  In addition to the silicon oxide, an inorganic compound may be added to the inorganic film in the same manner as the phosphorus compound, if necessary, for the purpose of further improving corrosion resistance. The term “inorganic compound” as used herein refers to an inorganic compound other than the above silicon oxide and phosphorus compound, and the amount of the inorganic compound added to the film is preferably 35% by weight or less. When the added amount of the inorganic compound in the film exceeds 35% by weight, the corrosion resistance is lowered. Examples of inorganic compounds added to the film-forming treatment liquid include metal oxide sols such as alumina sol, zirconia sol, and titania sol, and inorganic pigments such as zinc oxide, titanium oxide, barium sulfate, alumina, kaolin, and iron oxide. Can be mentioned.

  In the present invention, the coating film formed on the surface of the steel material through the inorganic film is not particularly limited. Examples of the coating material for forming this coating film include acrylic paints and polyester paints. , Urethane paint, Acrylic urethane paint, Acrylic polyester paint, Epoxy paint, Fluorine paint, Acrylic silicone paint, Urethane silicone paint, Acrylic urethane silicone paint, Alkali silicate paint, Colloidal silica, etc. Examples thereof include paints, titanium oxide-based paints, ceramics-based paints, silicon-containing paints, and any of organic, inorganic, and organic / inorganic hybrid paints may be used.

  The coating film formed on the surface of the steel material through an inorganic coating is formed by applying a silicon-containing paint containing silicon element (Si), and the silicon-containing coating film containing silicon element (Si) in the coating film. The silicon-containing paint for forming the silicon-containing coating film is not particularly limited. The silicon-containing paint is specifically a paint containing a monomer or polymer having a siloxane bond, or a paint containing an alkoxysilane and / or silanol group. Specific examples of such paints include, for example, silicone paints, acrylic silicone paints, urethane silicone paints, acrylic urethane silicone paints, alkali silicate paints, silica sol paints, silica paints, ceramic paints, and the like. Examples of the paint system include solvent-based, water-based emulsion, and water-based paints.

  In the present invention, the coating film formed on the surface of the steel material through the inorganic film may itself be a top coating film that forms the outermost surface of the coated steel material. It may be a primer coating film that functions as a primer layer for lamination. And, the film thickness of the coating film formed on the inorganic film is appropriately selected according to the purpose of use of the coated steel material, etc., but the film thickness of the primer coating film that functions as the primer layer, Usually, it should be 0.1 μm or more and 20 μm or less, preferably 0.5 μm or more and 15 μm or less. If the thickness is less than 0.1 μm, sufficient corrosion resistance is not exhibited. There arises a problem that the performance is lowered.

  And, when the coating film of the present invention is used as a primer layer, a top coating is further formed on the coating film to form a top coating, but there is no particular limitation on the top coating used here, For example, acrylic paint, polyester paint, urethane paint, acrylic urethane, acrylic polyester, epoxy paint, fluorine paint, silicone paint, acrylic silicone paint, urethane silicone paint, acrylic urethane silicone paint, Examples include alkali silicate paints, silica sol paints using colloidal silica, titanium oxide paints, ceramic paints, and any organic, inorganic, or organic / inorganic hybrid paints may be used. . Further, the top coating film is not limited to a single layer coating film, and may be a multilayer coating film having two or more layers. Further, although the film thickness is not particularly limited, it is usually preferably 1 to 100 μm.

The coated steel material of the present invention was obtained by applying a film forming treatment liquid containing silicon oxide to the surface of the steel material to form an inorganic film having a silicon amount of 5 to 100 mg / m ² , and then obtained. It is manufactured by applying a paint on an inorganic film to form a film.

  In the production of the coated steel material of the present invention, preferably, prior to the film formation treatment, an acid treatment with an acid solution, preferably an acid solution having a pH of 6 or less, on the surface in advance for the purpose of degreasing, surface adjustment, and the like, and Alternatively, a pretreatment comprising an alkali treatment with an alkaline solution, preferably an alkaline solution having a pH of 8 or higher, may be performed.

  Here, examples of the acid solution used for this pretreatment include those prepared with commercially available acid degreasing agents, mineral acids such as sulfuric acid, nitric acid, hydrofluoric acid, and phosphoric acid, organic acids such as acetic acid and citric acid, and the like. What was prepared using acid reagents, such as mixed acid obtained by mixing acid of this, etc. can be used, Preferably it is an acid solution below pH 6, and as an alkaline solution, for example, Those prepared with a commercially available alkaline degreasing agent, those prepared with an alkaline reagent such as caustic soda, or those prepared by mixing these materials can be used, and preferably an alkaline solution having a pH of 8 or more. .

  Further, the acid solution and / or the alkali solution used for the pretreatment may contain a silicon compound. By performing the pretreatment using an acid solution and / or an alkali solution containing a silicon compound, an effect of strengthening the adhesion between the surface of the steel material and the inorganic film formed thereon is expected. Is done. Examples of such an acid solution and / or alkali solution containing a silicon compound include an acid solution containing colloidal silica and an alkali solution containing a silicate such as sodium metasilicate and sodium silicate. .

  Regarding the operation method and treatment conditions of the pretreatment performed using the above acid solution and / or alkali solution, the operation method and treatment conditions of the pretreatment conventionally performed using this kind of acid solution or alkali solution, and For example, by a method such as dipping or spraying, the temperature is from room temperature to 90 ° C., preferably from room temperature to 70 ° C., one step for about 1 second to about 15 minutes, preferably about 5 seconds to about 10 minutes. However, it is preferable that the time is 5 seconds to 3 minutes.

  And after pre-treating the surface of the steel material, it may be washed with water if necessary, and industrial water, ground water, tap water, ion-exchanged water, etc. can be used for this washing treatment, and the steel material to be produced It is appropriately selected depending on. Further, the pretreated steel material is subjected to a drying treatment as necessary. This drying treatment may be natural drying left at room temperature, or may be forced drying using an air blower, a dryer, an oven, or the like.

Next, the surface of the steel material or, if necessary, the surface of the steel material pretreated by the above acid treatment and / or alkali treatment, preferably contains a silicon oxide made of water-dispersible silica such as colloidal silica. Then, if necessary, a film forming treatment liquid to which a predetermined phosphorus compound or an inorganic compound is added is applied, and a film forming process for forming an inorganic film having a silicon amount of 5 to 100 mg / m ² is performed.

  The film forming solution is preferably an aqueous solution or an alcohol solution, and an organic substance such as an alcohol, a solvent, or a surface conditioner may be added as necessary. The organic substance added here is preferably one that vaporizes and disappears from the coating during the formation of the inorganic coating and does not substantially remain in the coating as a component of the coating. As an approximate standard, the organic substance that substantially disappears when vaporized from the film during film formation is one having a boiling point of 150 ° C. or lower.

  As for the operation method and processing conditions of the film forming process for forming the inorganic film by applying the above film forming treatment liquid on the surface of the steel material, for example, roll coating method, spray coating method, dipping method, bar coating method, electrostatic Even if it is a pre-coating method by a coating method or the like, or by a post-coating method by a spray coating method, a spin coating method, a dipping method, an electrostatic coating method or the like, usually from room temperature to 80 ° C., preferably from room temperature to 50 ° C. In this temperature range, one step is performed for about 1 second to about 10 minutes, preferably about 2 seconds to about 5 minutes, and after the coating, if necessary, the drying process is performed. Natural drying may be performed, or may be forced drying using an air blower, a dryer, an oven, or the like. In the case of forced drying, it is preferable to dry at room temperature to 250 ° C. for about 1 second to 10 minutes, preferably about 2 seconds to 5 minutes.

  After a predetermined inorganic film is formed on the surface of the steel as described above, a paint is applied on the inorganic film to form a coating film. As for the coating method of this paint, for example, a pre-coating method such as a roll coating method, a spray coating method, a dipping method, a bar coating method, an electrostatic coating method, etc., or a spray coating method, a spin coating method, a dipping method, A post-coating method such as an electrostatic coating method may be used. The drying process after painting may be performed by a drying method corresponding to the paint, for example, a method of performing air blowing, a dryer, an oven, etc. in the range of room temperature to 300 ° C. for 5 seconds to 24 hours. can do.

  In addition, when the above-mentioned coating film is used as a primer layer and a top coating film is provided thereon, the top coating film is applied to the conventional primer layer to form a top coating film. Post-coating by roll coating method, spray coating method, dipping method, bar coating method, electrostatic coating method, etc., spray coating method, spin coating method, dipping method, electrostatic coating method, etc. A top coating material may be applied by a coating method, and then dried by a drying method corresponding to the top coating material.

  ADVANTAGE OF THE INVENTION According to this invention, the coating steel material which has a coating film on the surface of steel materials, is non-chromium substantially free of chromium, and is environmentally friendly and exhibits excellent corrosion resistance can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail based on examples and comparative examples.

[Examples 1 to 17 and Comparative Examples 1 to 7]
In Examples 1 to 4 and Comparative Example 1, an electrogalvanized steel sheet having a size of 70 mm × 150 mm × 0.6 mm (weight per unit area 20 g / m ² ) was used. In Examples 5 to 9 and Comparative Examples 2, 3 and 7, the size was used. A hot-dip galvanized steel sheet of 70 mm × 150 mm × 0.6 mm (weight per unit area: 100 g / m ² ) was used in Examples 10 to 13 and Comparative Example 4 and was a zinc-5% aluminized steel sheet of 70 mm × 150 mm × 0.6 mm in size ( A basis weight of 50 g / m ² ), and in Examples 14 to 17 and Comparative Examples 5 and 6, a zinc-55% aluminum-plated steel sheet having a size of 70 mm × 150 mm × 0.6 mm (a basis weight of 150 g / m ² ) was used. Prepared as a steel material, pretreatment, film formation, and coating film formation were performed as follows.

〔Preprocessing〕
In Examples 1 to 9 and Comparative Examples 1 to 3, as an alkaline solution containing a silicon compound, 2% by weight of a degreasing agent containing sodium metasilicate (degreasing agent A: trade name manufactured by Nippon Paint Co., Ltd .: Surf Cleaner 53S) After spraying at 60 ° C. for 2 minutes using an aqueous solution, it was washed with water and dried.

  Moreover, in Examples 10-17 and Comparative Examples 4-7, 2 of the degreasing agent (degreasing agent A: Nippon Paint Co., Ltd. brand name: Surf cleaner 155) containing sodium metasilicate as an alkaline solution containing a silicon compound. After dipping at 60 ° C. for 30 seconds using a weight% aqueous solution, it was washed with water and dried.

[Film formation treatment]
Table 2 (Examples 1 to 8), Table 3 (Examples 9 to 16) and Table 4 (Example 17 and Comparative Examples) containing the water-dispersible silica shown in Table 1 as the treatment liquid containing silicon oxide. The film formation processing liquid of the composition shown to 1-6) was used.

In Examples 1 to 17 and Comparative Examples 1 to 6, after the pretreatment, a film forming treatment liquid having the composition shown in Table 2 was applied with a bar coater to 6 g / m ² and dried at 200 ° C. for 1 minute. .

  At this time, in Examples 2, 5, 8, 9, and 13 to 17 and Comparative Examples 2 and 5, in addition to water-dispersible silica, phosphoric acid (Wako Pure Chemical Industries, Ltd.) was used at the ratios shown in Tables 2 and 3. A reagent special grade manufactured by the company: phosphoric acid content 85 wt%) and / or aluminum phosphate (for reagent chemistry manufactured by Wako Pure Chemical Industries, Ltd.) was added.

  In Examples 5 and 11 to 15 and Comparative Examples 1, 2 and 6, in addition to water-dispersible silica, alumina sol (manufactured by Nissan Chemical Industries: Alumina Sol-100, solid content 10 wt%) or zirconia sol (Nissan Chemical Industry) Manufactured, solid content 30 wt%) or boehmite (manufactured by Nissan Chemical Industries: AS-100, solid content 10 wt%) was added.

    Furthermore, in Comparative Example 7, the film formation treatment for forming this inorganic film was not performed.

About the inorganic film | membrane of Examples 1-17 and Comparative Examples 1-6 formed as mentioned above, the silicon | silicone amount (Si amount: mg / m < ² >) contained in a film | membrane unit area, and phosphorus amount (P amount :) mg / m ² ) was measured by X-ray fluorescence analysis. For the measurement, an inorganic film was prepared on a 99.999% pure aluminum plate in the same manner as in Examples 1 to 17 and Comparative Examples 1 to 6, and the amount of silicon contained in the film unit area (Si Amount: mg / m ² ) and phosphorus amount (P amount: mg / m ² ) were quantitatively analyzed. Similarly, for chromium (Cr) and carbon (C), the amount of chromium (Cr amount) and the amount of carbon (C amount) are quantitatively analyzed by fluorescent X-ray analysis, and they are not detected (below the detection limit: the detection limit of Cr is 0.5. It was mg / m ² , and the detection limit of C was 10 mg / m ² ).

  Furthermore, regarding the silicon content (Si content: wt%) and phosphorus content (P content: wt%) in the inorganic film, a predetermined amount of the coating material forming the silicon-containing film was taken and 5% at 200 ° C. After heating for a minute, the weight of the formed silicon-containing film was measured, and the amount of Si and the amount of P were quantitatively analyzed by chemical analysis to determine the content.

[Formation of coating film]
The coating film formed through the inorganic film was formed using the paint shown in Table 5 below. For the formation of the silicon-containing coating film, paints F, G, H and I which are silicon-containing paints in Table 5 were used.

[Examples 1-7, 12-14, 16 and 17 and Comparative Examples 1-4, 6 and 7]
About each steel plate of each of Examples 1-7, 12-14, 16 and 17 and Comparative Examples 1-4, 6 and 7 after the above pretreatment and film formation treatment were performed, the coating film was formed by the following method. Each test piece (painted steel material) was prepared.

  In Example 1, the coating material A was bar-coated, baked for 40 seconds at a peak metal temperature (PMT) of 210 ° C. and dried to form a primer coating having a thickness of 5 μm. Next, paint J was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 20 μm, and a test piece (painted steel material) of Example 1 was prepared.

  In Example 2, paint B was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 10 μm, and a test piece (painted steel) of Example 2 was prepared. did.

  In Example 3, the coating material C was bar-coated, baked at PMT 210 ° C. for 40 seconds and dried to form a primer coating film having a thickness of 10 μm. Next, paint K was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 10 μm, and a test piece (painted steel material) of Example 3 was prepared.

  In Example 4, the coating material D was bar-coated, baked at PMT 210 ° C. for 40 seconds and dried to form a primer coating film having a thickness of 2 μm. Next, the paint C was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 10 μm, and a test piece (coated steel material) of Example 4 was prepared.

  In Example 5, paint E was bar-coated, baked at PMT 210 ° C. for 40 seconds and dried to form a primer coating film having a thickness of 1 μm. Subsequently, the coating material M was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 15 μm, and a test piece (coated steel material) of Example 5 was prepared.

  In Example 6, the coating material F was bar-coated, baked at PMT 230 ° C. for 40 seconds and dried to form a silicon-containing primer coating having a thickness of 0.5 μm. Next, the paint K was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 30 μm, and a test piece (painted steel material) of Example 6 was prepared.

  In Example 7, paint G was bar-coated, baked at PMT 230 ° C. for 100 seconds and dried to form a silicon-containing top coating film having a film thickness of 20 μm. ) Was prepared.

  In Example 12, the coating material F was bar-coated, baked at PMT 230 ° C. for 40 seconds and dried to form a silicon-containing primer coating having a thickness of 5 μm. Next, the paint K was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 10 μm, and a test piece (painted steel material) of Example 12 was prepared.

  In Example 13, the coating material C was bar-coated, baked at PMT 220 ° C. for 40 seconds and dried to form a primer coating film having a thickness of 10 μm. Subsequently, the coating material L was bar-coated, baked for 60 seconds at PMT 225 ° C. and dried to form a top coating film having a thickness of 20 μm, and a test piece (painted steel material) of Example 13 was prepared.

  In Example 14, paint F was bar-coated, baked at PMT 230 ° C. for 40 seconds and dried to form a silicon-containing primer coating having a thickness of 1 μm. Next, the paint J was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a film thickness of 15 μm, and a test piece (painted steel material) of Example 14 was prepared.

  In Example 16, the coating material C was bar-coated, baked at PMT 220 ° C. for 40 seconds and dried to form a primer coating film having a thickness of 10 μm. Subsequently, the coating material L was bar-coated, baked for 60 seconds at PMT 225 ° C. and dried to form a top coating film having a thickness of 20 μm, and a test piece (coated steel material) of Example 16 was prepared.

  In Example 17, paint F was bar-coated, baked at PMT 230 ° C. for 40 seconds and dried to form a silicon-containing primer coating having a thickness of 0.2 μm. Next, the paint K was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 10 μm, and a test piece (painted steel material) of Example 17 was prepared.

  In Comparative Example 1, paint C was bar-coated, baked at PMT 220 ° C. for 40 seconds and dried to form a primer coating film having a thickness of 10 μm. Next, the paint K was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 10 μm, and a test piece (coated steel) of Comparative Example 1 was prepared.

  In Comparative Examples 2 and 4, the coating material D was bar-coated, baked at PMT 220 ° C. for 40 seconds and dried to form a primer coating film having a thickness of 5 μm. Next, the paint K was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 10 μm, and test pieces (coated steel materials) of Comparative Examples 2 and 4 were prepared. .

  In Comparative Example 3, paint G was bar-coated, baked at PMT 230 ° C. for 40 seconds and dried to form a silicon-containing primer coating having a thickness of 2 μm. Next, paint K was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 10 μm, and a test piece (coated steel) of Comparative Example 3 was prepared.

  In Comparative Examples 6 and 7, the paint C was bar-coated, baked at PMT 230 ° C. for 40 seconds and dried to form a primer coating film having a thickness of 10 μm. Next, paint K was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 10 μm, and test pieces (coated steel materials) of Comparative Examples 6 and 7 were prepared. .

[Examples 8 to 11, 15 and Comparative Example 5]
In Example 8, paint H was spray-coated, baked at PMT 170 ° C. for 20 minutes, and dried to form a silicon-containing top coating film having a film thickness of 30 μm. Thus, a test piece (painted steel material) of Example 8 was prepared. .

  In Example 9, the coating material I was spray-coated, baked at PMT 100 ° C. for 20 minutes, and dried to form a silicon-containing primer coating film having a thickness of 5 μm. Next, the paint K was bar-coated, baked at PMT 225 ° C. for 60 seconds and dried to form a top coating film having a thickness of 10 μm, and a test piece (painted steel material) of Example 9 was prepared.

  In Examples 10 and 15, paint I was spray-coated, baked at PMT 100 ° C. for 20 minutes, and dried to form a silicon-containing top coating film having a film thickness of 50 μm. ) Was prepared.

  In Example 11, the paint I was spray-coated, baked at PMT 100 ° C. for 20 minutes and dried to form a silicon-containing top coating film having a thickness of 10 μm, and a test piece (painted steel material) of Example 11 was prepared. .

  In Comparative Example 5, paint I was spray-coated, baked at PMT 100 ° C. for 20 minutes, and dried to form a silicon-containing top coating film having a thickness of 50 μm, and a test piece (coated steel material) of Comparative Example 5 was prepared. .

[Corrosion resistance test]
About the test piece of each Example 1-17 and Comparative Examples 1-7 which were prepared as mentioned above, the following salt spray test, corrosion resistance performance, and adhesion performance were evaluated.

  The salt spray test was carried out for 1000 hours with a cross cut made according to the method of JIS K5600. The coating after 1000 hours has no corrosion, blistering, etc. in the cut part, and the cut part has good adhesion. Is evaluated as “Good”, and “C” indicates that the corrosion of the cut portion is 1 mm or more, or the occurrence of swelling or abnormalities such as poor adhesion occurs.

In the boiling water immersion test, the test piece was immersed in boiling water for 5 hours, and after the test was completed, abnormalities such as swelling and peeling were observed, and then the adhesion of the coating film was evaluated as a secondary physical property. Evaluation was made with no abnormality in the appearance after completion of the test, and with X where abnormality such as swelling or peeling occurred. Secondary physical properties are JIS K5600 adhesion (cross-cut method) ◎ when there is no peeling at all, ◯ 5 when the area of the cross-cut part where peeling occurs is 5% or less (class 1 or less) Those exceeding% were rated as x.
The results of the salt spray test and the boiling water immersion test are shown in Table 6 (Examples 1 to 17, Comparative Examples 1 to 7).

  The coated steel material of the present invention is a so-called non-chromium that contains substantially no hexavalent and trivalent chromium, and has excellent corrosion resistance, and is an environmentally friendly material. It can be used with confidence and has high industrial value.

Claims (7)

The surface of the steel material contains silicon oxide in a silicon amount range of 5 to 100 mg / m ² and is characterized in that a coating film is formed through an inorganic film substantially free of chromium and organic substances. Painted steel.   The coated steel material according to claim 1, wherein the inorganic film has a silicon content of 30 to 46.7% by weight.   The coated steel material according to claim 1 or 2, wherein the inorganic film is a film formed using water-dispersible silica as a raw material.   The coated steel material according to claim 3, wherein the water-dispersible silica is colloidal silica.   The coated steel material according to any one of claims 1 to 4, wherein the inorganic coating contains a phosphorus compound in addition to silicon oxide. Painted steel according to claim 5 phosphorus content of the inorganic coating is a 1-15 mg / m ^2.   The coated steel material according to claim 5 or 6, wherein the inorganic film has a phosphorus content of 10% by weight or less.