Coated and plated steel sheets

Abstract

To provide a coated plating steel plate having excellent end-face corrosion resistance without using a chromate antirust pigment.SOLUTION: A coated plating steel plate 1 has a steel plate 2, a plating layer 3 that covers the steel plate 2 and contains aluminum and zinc, and a coating layer 4 that covers the plating layer 3 and contains an antirust pigment having vanadium pentoxide as the main component. The antirust pigment has been surface-treated with a silane coupling agent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates generally to coated-plated steel sheets, and more particularly to coated-plated steel sheets having a plating layer and a coating layer covering the plating layer. [Background technology]

[0002] Conventionally, coated-plated steel sheets have been known in which a coating layer is provided on the plating layer of a coated steel sheet. In order to improve the corrosion resistance (edge ​​corrosion resistance) of the edge surface exposed when the coated-plated steel sheet is cut, the coating layer has been made to contain an anti-rust pigment.

[0003] For example, Patent Document 1 discloses a coated steel sheet having, on at least one side of the plated steel sheet, a first coating layer containing a chromate-based rust-preventive pigment and a second coating layer formed on the first coating layer. In the coated steel sheet of Patent Document 1, chromate ions derived from the chromate-based rust-preventive pigment are eluted from the edge surface, thereby improving the corrosion resistance of the edge surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-185259 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in order to reduce the burden on the global environment, there is a need to reduce the amount of chromate-based rust-preventive pigments used, and therefore there is a need to improve the edge corrosion resistance of coated / plated steel sheets without using chromate-based rust-preventive pigments.

[0006] An object of the present disclosure is to provide a coated / plated steel sheet that has excellent edge corrosion resistance without using a chromate-based rust-preventive pigment. [Means for solving the problem]

[0007] The coated-plated steel sheet according to the present disclosure includes a steel sheet, a plating layer covering the steel sheet and containing aluminum and zinc, and a coating layer covering the plating layer, wherein the coating layer contains an anti-rust pigment whose main component is vanadium pentoxide. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a coated-plated steel sheet having excellent edge corrosion resistance. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing a painted plated steel sheet according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1. Overview of this Disclosure 1, the coated plated steel sheet 1 according to this embodiment includes a steel sheet 2, a plating layer 3 containing aluminum and zinc that covers the steel sheet 2, and a coating layer 4 that covers the plating layer 3. The coating layer 4 contains an anti-rust pigment whose main component is vanadium pentoxide.

[0011] In this embodiment, the main component of the rust-preventive pigment contained in the coating layer 4 is vanadium pentoxide, so that the coated-plated steel sheet 1 has excellent edge corrosion resistance.

[0012] 2.Details The configuration of the coated-plated steel sheet 1 of this embodiment will be described in more detail below. The coated-plated steel sheet 1 shown in Fig. 1 includes a steel sheet 2, a plating layer 3 covering the steel sheet 2, and a coating layer 4 covering the plating layer 3. The coated-plated steel sheet 1 may further include a top coat layer 5 covering the coating layer 4.

[0013] 2-1. Steel plate There is no particular limitation on the steel plate 2. The steel plate 2 may be, for example, a low-carbon steel plate, a high-carbon steel plate, or a high-tensile steel plate.

[0014] 2-2. Plating layer As described above, the plating layer 3 covers the steel sheet 2. The plating layer 3 can be formed by, for example, hot dip plating.

[0015] The plating layer 3 contains aluminum and zinc. The plating layer 3 may further contain components other than aluminum and zinc. The plating layer 3 may contain, for example, one or both of magnesium and silicon. The plating layer 3 may contain one or more components selected from the group consisting of strontium, iron, alkaline earth elements, scandium, yttrium, lanthanoid elements, titanium, and boron. Examples of alkaline earth elements include beryllium, calcium, barium, and radium. Examples of lanthanoid elements include lanthanum, cerium, praseodymium, neodymium, promethium, samarium, and europium. The plating layer 3 may contain one or more of these components. The plating layer 3 may or may not contain chromium.

[0016] The amount of aluminum contained in the plating layer 3 is preferably 25% by mass or more and 75% by mass or less, and more preferably 45% by mass or more and 65% by mass or less.

[0017] When the plating layer 3 contains magnesium, the amount of magnesium contained in the plating layer 3 is preferably 0.5 mass % or more and 10 mass % or less, and more preferably 1 mass % or more and 3 mass % or less. In this case, the edge corrosion resistance of the coated-plated steel sheet 1 can be improved.

[0018] When plating layer 3 contains silicon, the amount of silicon relative to the amount of aluminum contained in plating layer 3 is preferably 0.5 mass % or more and 10 mass % or less, and more preferably 1.0 mass % or more and 5.0 mass % or less.

[0019] 2-3.Coating layer As described above, the coating layer 4 covers the plating layer 3. In this embodiment, the coating layer 4 is in direct contact with the plating layer 3. The coating layer 4 in this embodiment is a cured product of a coating paint.

[0020] The coating paint of this embodiment contains an anti-rust pigment (A) and a resin component (B). The coating paint may contain a component other than the anti-rust pigment (A) and the resin component (B) (hereinafter also referred to as component (C)).

[0021] (1) Anti-rust pigment (A) Since the coating paint contains the rust-preventive pigment (A), the coating layer 4, which is the cured product of the coating paint, also contains the rust-preventive pigment (A), thereby improving the edge corrosion resistance of the coated-plated steel sheet 1.

[0022] In this embodiment, the main component of the anti-rust pigment (A) is vanadium pentoxide. The term "main component" as used herein means a component that accounts for 70% or more of the total amount of the anti-rust pigment (A). Therefore, the proportion of vanadium pentoxide to the total amount of the anti-rust pigment (A) is 70% or more. The proportion of vanadium pentoxide relative to the total amount of the pigment (A) is preferably 80% or more, more preferably 90% or more, and particularly preferably 100%. If the proportion of vanadium pentoxide in the rust-preventive pigment (A) is less than 70%, i.e., if the main component of the rust-preventive pigment (A) is not vanadium pentoxide, the edge corrosion resistance of the coated-plated steel sheet 1 may not be sufficiently ensured. In contrast, by making vanadium pentoxide the main component of the rust-preventive pigment (A) and increasing the proportion of vanadium pentoxide in the rust-preventive pigment (A), the edge corrosion resistance of the coated-plated steel sheet 1 can be sufficiently ensured.

[0023] In this embodiment, it is also preferable that the rust-preventive pigment (A) contains only vanadium pentoxide, in which case the edge corrosion resistance of the coated-plated steel sheet 1 can be particularly improved.

[0024] The average particle size of vanadium pentoxide contained as the anti-rust pigment (A) may be 15 μm or less, and preferably 10 to 15 μm. In this case, the adhesion of the coating layer 4 can be stabilized, and peeling of the coating layer 4 and the occurrence of enamel hair can be suppressed. The average particle size of vanadium pentoxide is a volume-based median diameter calculated from particle size distribution measurements obtained by laser diffraction / scattering, and can be obtained using a commercially available laser diffraction / scattering particle size distribution analyzer.

[0025] The anti-rust pigment (A) may contain components other than vanadium pentoxide. The anti-rust pigment (A) may contain, for example, a vanadium compound. Examples of vanadium compounds include metavanadate, calcium vanadate, magnesium vanadate, ammonium metavanadate, vanadium oxytrichloride, vanadium trioxide, vanadium dioxide, vanadium oxysulfate, vanadium oxyacetylacetonate, vanadium acetylacetonate, and vanadium trichloride. The anti-rust pigment (A) may also contain, for example, a known chromate-free anti-rust pigment. Examples of chromate-free anti-rust pigments include phosphate-based anti-rust pigments such as zinc phosphate, iron phosphate, aluminum phosphate, and magnesium phosphate; molybdate-based anti-rust pigments such as zinc molybdate, calcium molybdate, aluminum molybdate, and barium molybdate; and fine silica particles such as water-dispersible silica and fumed silica.

[0026] The anti-rust pigment (A) may be surface-treated with a silane coupling agent. In other words, the anti-rust pigment (A) may be treated with a silane coupling agent. In this case, the amount of debris (enamel hair) generated from the coating layer 4 when the coated metal sheet 1 is cut can be reduced.

[0027] The weight ratio of the anti-rust pigment (A) to the total weight of the coating paint (PWC: Pigment Weight Concentration) is preferably 4% by weight or more and 30% by weight or less. The paint preferably contains the rust-preventive pigment (A) in a proportion of 4% by weight to 30% by weight, in which case the edge corrosion resistance of the coated-plated steel sheet 1 can be effectively improved.

[0028] (2) Resin component (B) Resin component (B) may contain any resin that is blended into a primer coating for plated steel sheets, and preferably contains a resin that can thicken the coating layer 4 formed from the coating coating. For this reason, resin component (B) may contain a polyester isocyanate resin (B1) or an amine-isocyanate resin (B3). Resin component (B) particularly preferably contains a polyester isocyanate resin (B1). When resin component (B) contains a polyester isocyanate resin (B1), resin component (B) preferably contains an epoxy resin (B2).

[0029] (i) Polyester-isocyanate resin (B1) The polyester-isocyanate resin (B1) contains a polyester resin (b1) having a hydroxyl group (hereinafter also referred to as polyester resin (b1)) and a blocked isocyanate compound (b2).

[0030] The polyester resin (b1) can be produced, for example, by polycondensation of a polycarboxylic acid or an ester-forming derivative thereof with a polyhydric alcohol or an ester-forming derivative thereof.

[0031] The polycarboxylic acid may contain, for example, one or more selected from the group consisting of terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, 1,4-cyclohexanedicarboxylic acid, and trimellitic anhydride, etc. Examples of ester-forming derivatives of polycarboxylic acids include carboxylic acid anhydrides and carboxylic acid chlorides.

[0032] The polyhydric alcohol may contain, for example, one or more selected from the group consisting of ethylene glycol, propanediol, butanediol, pentanediol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, pentaerythritol, hydroquinone, styrene glycol, and glycerin.

[0033] The polyester resin (b1) may be a commercially available polyester resin blended into polyester resin paints used to paint plated steel sheets. Examples of commercially available polyester resins include Becolite GS-15 manufactured by DIC and Arakid 7036 manufactured by Arakawa Chemical Industry Co., Ltd.

[0034] The number average molecular weight of the polyester resin (b1) is preferably 1,000 or more and 10,000 or less. When the number average molecular weight of the polyester resin (b1) is 1,000 or more, the processability of the coating layer 4 formed from the coating paint can be improved. When the number average molecular weight of the polyester resin (b1) is 10,000 or less, the weather resistance of the coating layer 4 formed from the coating paint can be improved. The number average molecular weight of the polyester resin (b1) can be measured by gel permeation chromatography using a calibration curve of standard polystyrene.

[0035] The hydroxyl equivalent of the polyester resin (b1) is preferably 500 g / eq or more and 2000 g / eq or less. In this case, a urethane bond (-NHCOO-) can be effectively formed by the reaction between the isocyanate group (-NCO) derived from the blocked isocyanate compound (b2) described below and the hydroxyl group (-OH) derived from the polyester resin (b1). This can improve the scratch resistance of the coating layer 4 formed from the coating paint.

[0036] The proportion of the polyester resin (b1) in the coating paint is preferably 10% by weight or more and 50% by weight or less, in which case the coating paint can have improved coating workability.

[0037] The blocked isocyanate compound (b2) can be produced, for example, by reacting the isocyanate group of a polyisocyanate with a blocking agent. By using such a blocked isocyanate compound (b2), the coating paint can be made into a one-component type. The polyisocyanate and the blocking agent can be reacted by a known method.

[0038] Polyisocyanates are fatty acids such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and hydrogenated diphenylmethane diisocyanate. The polyisocyanate may contain one or more selected from the group consisting of aliphatic polyisocyanates, aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, and hydrogenated diphenylmethane diisocyanate. The polyisocyanate preferably contains an aromatic polyisocyanate that has excellent reactivity with a blocking agent. Furthermore, the polyisocyanate preferably contains a multifunctional isocyanate that easily forms a three-dimensional network structure when reacting with hydroxyl groups derived from the polyester resin (B). The polyisocyanate may contain a prepolymer, an adduct, an isocyanurate, or a biuret.

[0039] The blocking agent may contain, for example, one or more selected from the group consisting of active methylene-based blocking agents, amine-based blocking agents, oxime-based blocking agents, and caprolactam-based blocking agents.

[0040] As the blocked isocyanate compound (b2), commercially available products may be used. Examples of commercially available blocked isocyanates include Karenz MOI-BM manufactured by Showa Denko K.K., TRIXENE BI7950 manufactured by BAXENDEN, and TRIXENE BI7951 manufactured by BAXENDEN.

[0041] Heating the blocked isocyanate compound (b2) dissociates the blocking agent, forming an isocyanate group (-NCO). This isocyanate group (-NCO) reacts with a hydroxyl group (OH) derived from the polyester resin (B) to form a urethane bond (-NHCOO-). In particular, the polyisocyanate used in producing the blocked isocyanate is a multifunctional isocyanate, which allows the formation of a three-dimensional network crosslinked structure. Therefore, the reaction between the polyester resin (b1) and the blocked isocyanate compound (b2) can thicken the coating layer 4 formed from the coating paint, improving the scratch resistance of the coating layer 4. Furthermore, the inclusion of a reaction product of the blocked isocyanate compound (b1) and the polyester resin (b2) in the coating paint can also improve the chemical resistance of the coating layer 4. Furthermore, the urethane bond formed by the reaction between an isocyanate group and a hydroxyl group has a higher cohesive energy than chemical bonds such as ether bonds and ester bonds. Therefore, by including a reaction product of the polyester resin (b1) and the blocked isocyanate compound (b2) in the coating paint, the elasticity of the coating layer 4 can be improved, and the bending processability of the coated-plated steel sheet 1 can be improved.

[0042] The blocked isocyanate compound (b2) is preferably blended into the coating material so that the equivalent ratio (isocyanate group / hydroxyl group, NCO / OH) of the isocyanate group (-NCO) derived from the blocked isocyanate compound (b2) to the hydroxyl group (-OH) derived from the polyester resin (b1) is 0.5 / 1 or more and 2 / 1 or less. In this case, the weather resistance and processability of the coating layer 4 formed from the coating material can be effectively improved.

[0043] The number average molecular weight of the blocked isocyanate compound (b2) is preferably 1000 or more and 10000 or less. In this case, it is possible to impart appropriate processability to the coating layer 4 formed from the coating paint.

[0044] (ii) Epoxy resin (B2) As described above, when the resin component (B) contains the polyester-isocyanate resin (B1), the resin component (B) preferably contains the epoxy resin (B2). In this case, the adhesion between the coating layer 4 formed from the coating paint and the plating layer 3 can be improved.

[0045] Epoxy resin (B2) is compounded in epoxy resin-based paints used in the production of coated steel sheets. The epoxy resin (B2) may contain one or more of these epoxy resins. Examples of epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, cresol novolac epoxy resins, phenol novolac epoxy resins, bisphenol A-novolac epoxy resins, naphthalene epoxy resins, biphenyl epoxy resins, biphenyl aralkyl epoxy resins, and alicyclic epoxy resins. The epoxy resin (B2) may contain one or more of these epoxy resins. When the coating paint contains the epoxy resin (B2), the adhesion of the coating layer 4 formed from the coating paint to the plating layer 3 can be improved. The number average molecular weight of the epoxy resin (B2) is not particularly limited, but is preferably 100 or more and 5,000 or less.

[0046] The ratio of the epoxy resin (B2) to the coating paint is preferably 5% by weight or more and 10% by weight or less, which can effectively improve the adhesion between the coating layer 4 formed from the coating paint and the plating layer 3.

[0047] (iii) Amine-isocyanate resin (B3) The amine-isocyanate resin (B3) contains a polyamine resin (b3) and a blocked isocyanate compound (b4).

[0048] The polyamine resin (b3) may contain one or more selected from the group consisting of aliphatic polyamines, alicyclic polyamines, and aromatic polyamines. The polyamine (b1) preferably contains an alicyclic polyamine. Examples of alicyclic polyamines include 1-cyclohexylamino-3-aminopropane, diaminocyclohexanes, bis(4-aminocyclohexyl)methane, bis(4-aminocyclohexyl)sulfone, 3,3'-dimethylaminopropane, bis(4-aminocyclohexyl)methane, bis(4-aminocyclohexyl)sulfone ... The polyamine resin (b3) may contain one or more of these alicyclic polyamines. The polyamine resin (b3) may be 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, isophoronediamine, etc. It is particularly preferred that the polyamine resin (b3) contains methyl methyl ether. The polyamine resin (b3) may contain two or more components.

[0049] The blocked isocyanate compound (b4) may be the same as the blocked isocyanate compound (b3) described above.

[0050] Therefore, when the blocked isocyanate compound (b4) is heated, the blocking agent dissociates to form an isocyanate group (-NCO). This isocyanate group (-NCO) reacts with the amine group (-NH2) derived from the polyamine resin (b3) to form a urea bond (-NHCONH-). Therefore, the reaction between the polyamine resin (b3) and the blocked isocyanate compound (b4) can thicken the coating layer 4 formed from the coating paint, thereby improving the scratch resistance of the coating layer 4.

[0051] The polyamine resin (b3) and the blocked isocyanate compound (b4) are preferably blended into the coating paint so that the equivalent ratio of isocyanate groups to amine groups (isocyanate groups / amine groups, NCO / NH2) is 0.6 or more and 2.0 or less, and more preferably 0.8 or more and 1.2 or less.

[0052] When the coating paint contains the amine-isocyanate resin (B3), it is better not to blend the epoxy resin (B3) into the coating paint, because the reaction between the polyamine resin (b3) contained in the amine-isocyanate resin (B3) and the epoxy resin (B2) may cause the coating paint to gel.

[0053] (3) Component (C) As described above, the coating paint may contain component (C) other than the anti-rust pigment (A) and the resin component (B). Component (C) includes liquid anti-rust agents, solvents, additives, etc.

[0054] The coating paint preferably further contains a liquid rust inhibitor as component (C). In this case, the edge corrosion resistance of the coated-plated steel sheet 1 can be improved. Examples of liquid rust inhibitors include Rasmin A (product number, manufactured by Kyoeisha Chemical Co., Ltd.) and NACORR 1151 and NACORR 1351 (product numbers, manufactured by KING INDUSTRY). The ratio of the liquid rust inhibitor to the coating paint is preferably 0.1% by weight or more and 5.0% by weight or less. In this case, the edge corrosion resistance of the coated-plated steel sheet 1 can be effectively improved.

[0055] The coating paint preferably contains a solvent as component (C). In this case, the coating paint can be easily applied, facilitating the formation of the coating layer 4. Examples of the solvent include water; hydrocarbon solvents such as toluene and xylene; ester solvents such as ethyl acetate and butyl acetate; ethyl solvents such as cellosolves; and ketone solvents such as methyl isobutyl ketone, methyl ethyl ketone, isophorone, and cyclohexanone. The coating paint can contain one or more of these solvents.

[0056] The coating paint may contain an additive as component (C). Examples of the additive include an antifoaming agent, a pigment dispersant, an anti-sagging agent, a leveling agent, a silane coupling agent, and an extender pigment. Examples of the extender pigment include silica, alumina, talc, calcium carbonate, and titania. The coating paint may contain one or more of these additives.

[0057] (4) Preparation of the coating layer The coating paint can be prepared by mixing the anti-rust pigment (A), the resin component (B), and, if necessary, the component (C).

[0058] The coating layer 4 can be produced, for example, by applying a coating paint onto the plating layer 3 and then heating and curing the paint. Appropriate coating methods such as roll coating, curtain flow coating, and spray coating can be used to apply the coating paint onto the plating layer 3. The heating temperature for the coating paint is preferably 190°C or higher and 250°C or lower. The heating time for the coating paint film is preferably 40 seconds or higher and 120 seconds or lower.

[0059] The coating layer 4 thus produced contains the rust-preventive pigment (A) containing vanadium pentoxide as its main component, thereby improving the corrosion resistance of the edge of the coated-plated steel sheet 1. This is thought to be because the vanadium eluted from the edge of the coated-plated steel sheet 1 acts as an inhibitor (corrosion-suppressing substance) to suppress the progression of edge creep.

[0060] Furthermore, by including a polyester-isocyanate resin (B1) or an amine-isocyanate resin (B3) as the resin component (B) in the coating paint used to prepare the coating layer 4, the coating layer 4 can be made thicker, thereby improving the scratch resistance and chemical resistance of the coated-plated steel sheet 1. Furthermore, the bending workability of the coated-plated steel sheet 1 can be improved.

[0061] Furthermore, the coating paint used to prepare the coating layer 4 contains an epoxy resin (B3) as the resin component (B), so that the adhesion between the plating layer 3 and the coating layer 4 can be improved.

[0062] The thickness of the coating layer 4 made of the coating paint is preferably 5 μm or more and 50 μm or less. It is preferable that the thickness of the coating layer 4 is 5 μm or more. This ensures the edge corrosion resistance and rust prevention properties of the coated-plated steel sheet 1. Furthermore, when a general-purpose primer paint is applied by a method such as roll coating, gasification of the organic solvent contained in the paint film can cause crater-like defects (also known as popping) in the paint film during the drying process of the paint film. Although increasing the thickness of the paint film can improve rust prevention, increasing the thickness of a general-purpose primer paint tends to cause popping, making it difficult to increase the thickness. In contrast, the coating paint of this embodiment is less likely to cause popping, so the upper limit of the thickness of the coating layer 4 can be set to 50 μm. This makes it easier to improve the edge corrosion resistance and rust prevention properties of the coated-plated steel sheet 1. The thickness of the coating layer 4 is preferably 10 to 40 μm, more preferably 15 to 35 μm, and particularly preferably 20 to 30 μm. In this case, the edge corrosion resistance and rust prevention properties of the coated-plated steel sheet 1 can be effectively improved.

[0063] 2-4. Top coat layer As described above, the top coat layer 5 covers the coating layer 4. In this embodiment, the top coat layer 5 is in direct contact with the coating layer 4. That is, the coating layer 4 is interposed between the plating layer 3 and the top coat layer 5, and can function as a primer layer. Therefore, the coating layer 4 can conceal the plating layer 3.

[0064] The topcoat layer 5 is a cured product of a topcoat paint. As the topcoat paint, any paint that is used to form a topcoat layer on a painted plated steel sheet can be used without any particular limitation.

[0065] The topcoat layer 5 can be formed by applying a topcoat paint onto the coating layer 4 to form a coating film and then curing this coating film. If the topcoat paint contains a thermosetting resin, the topcoat layer 5 can be formed by curing the topcoat paint film by heating. If the topcoat paint contains a photocurable resin, the topcoat layer 5 can be formed by irradiating the topcoat paint film with light to cure it.

[0066] 2-5. Painted and plated steel sheets As described above, the coating layer 4 is provided on the plating layer 3 covering the steel sheet 2, and the topcoat layer 5 is further provided on the coating layer 4, thereby producing the painted plated steel sheet 1 of this embodiment.

[0067] 2-6. Variations The configuration of the paint-plated steel sheet 1 is not limited to the above-described configuration.

[0068] For example, while Fig. 1 shows a plating layer 3, a coating layer 4, and a topcoat layer 5 provided on one surface of the steel sheet 2, the plating layer 3, the coating layer 4, and the topcoat layer 5 may also be provided on the other surface of the steel sheet 2. In other words, the plating layer 3, the coating layer 4, and the topcoat layer 5 may be provided on both surfaces of the steel sheet 2.

[0069] For example, the painted plated steel sheet 1 may include only the steel sheet 2, the plating layer 3, and the coating layer 4, and may not include the topcoat layer 5. For example, the steel sheet 2 may have the plating layer 3 and the coating layer 4 on one side thereof, and the plating layer 3 and the coating layer 4 on the other side thereof.

[0070] For example, the painted plated steel sheet 1 may have layers other than the steel sheet 2, the plating layer 3, the coating layer 4, and the topcoat layer 5. For example, a chemical conversion coating produced by chemically treating the plating layer 3 may be provided between the plating layer 3 and the coating layer 4. For example, an alloy layer may be provided between the steel sheet 2 and the plating layer 3. For example, a layer different from the topcoat layer 5 may be provided between the coating layer 4 and the topcoat layer 5. For example, one or more layers may be provided on the topcoat layer 5. [Example]

[0071] The present disclosure will now be described in detail with reference to examples.

[0072] (Examples 1 to 22, Comparative Examples 1 and 2) As a plated steel sheet having a steel sheet and a plating layer, "Galvalume Steel Sheet (registered trademark)" (manufactured by Nippon Steel & Sumitomo Metal Steel Sheet Co., Ltd., sheet thickness: 0.8 mm, double-sided plating coating weight: 150 g / m 2 , hereinafter referred to as GL) was prepared.

[0073] Coating paints having the compositions shown in Tables 1 and 2 below were prepared.

[0074] A coating paint was applied to the plating layer using a bar coater to form a coating film, which was then heated for 60 seconds to a maximum temperature of 216°C to harden the coating film and form a coating layer with a thickness of 25 μm.

[0075] In this manner, coated plated steel sheets of Examples 1 to 19 and Comparative Examples 1 and 2 were prepared.

[0076] (Examples 23 to 43, Comparative Example 3) As a coated steel sheet having a steel sheet and a coating layer, "SGL (registered trademark)" (manufactured by Nippon Steel & Sumikin Steel Sheet Co., Ltd., sheet thickness: 0.5 mm, coating weight on both sides: 150 g / m 2 , hereinafter referred to as SGL) was prepared.

[0077] Undercoat paints and topcoat paints having the compositions shown in Tables 3 and 4 below were prepared.

[0078] A coating paint was applied to the plating layer using a bar coater to form a coating film, which was then heated for 60 seconds to a maximum temperature of 216°C to harden the coating film and form a coating layer with a thickness of 25 μm.

[0079] In this manner, coated plated steel sheets of Examples 20 to 41 and Comparative Examples 3 and 4 were prepared.

[0080] The details of each component contained in the coating paints shown in Tables 1 to 4 are as follows. Polyester-isocyanate resin: A mixture of polyester resin and blocked isocyanate (equivalent ratio of isocyanate group to hydroxyl group (NCO / OH): 0.5~1.5 / 1). Amine-isocyanate resin: A mixture of polyamine and blocked isocyanate (equivalent ratio of isocyanate group to amine group (NCO / NH 2) :0.8~1.2 / 1). Epoxy resin: Bisphenol A epoxy resin (number average molecular weight 500-1000). Vanadium pentoxide: Shinko Scientific product number FF-J (average particle size: 10 μm). Vanadium pentoxide (silane treated): Shinko Scientific product number FF-J (average particle size: 10 μm) treated with a silane coupling agent (BRB product number Silanil 442). Calcium phosphate: Toho Pigment product number NP-530 (average particle size: 15 μm). Zinc molybdate: ZNF08PB manufactured by Kanae Kogyo (average particle size: 10 μm, crushed in a mortar if necessary). Strontium chromate: Strontium chromate (average particle size: 10 μm) manufactured by Junsei Chemical. Liquid rust inhibitor A: Kyoeisha Chemical's product number Rasmin A. Liquid rust inhibitor B: Additive TI, manufactured by Borches. Liquid rust inhibitor C: Product number NACORR 1151 manufactured by KING INDUSTRY.

[0081] (evaluation) (1) Edge corrosion resistance The coated steel sheets of Examples 1 to 43 and Comparative Examples 1 to 3 were cut to obtain samples measuring 70 mm × 150 mm in plan view. The short edges (70 mm long edges) of these samples were sealed to obtain samples for evaluating edge corrosion resistance. These samples were subjected to a combined cycle testing (CCT) to evaluate edge corrosion resistance. Specifically, the combined cycle testing (CCT) consisted of SST (5% NaCl salt spray: 35°C; 2 hours), dry (60°C; 4 hours), and wet (constant temperature wet: 50°C; 95% RH; 2 hours), and was performed 120 times. The length (mm) of white rust formed on the edge of the sample after the test was measured, and the results were evaluated according to the following criteria. The evaluation results of edge corrosion resistance are shown in Tables 1 to 4. A: The length of the white rust is less than 2 mm B: White rust length is 2mm or more but less than 5mm C: White rust length is 5mm or more but less than 10mm D: White rust is 10mm or longer

[0082] (2) Adhesion The coated / plated steel sheets of Examples 1 to 43 and Comparative Examples 1 to 3 were cut approximately 5 cm from the edge, and the presence or absence of thread-like debris (enamel hair) derived from the coating layer was confirmed. The results were evaluated according to the following criteria. The evaluation results for adhesion are shown in Tables 1 to 4. A: No thread-like debris (enamel hair) originating from the coating layer has been generated, and the coating layer has not peeled off. B: No thread-like debris (enamel hair) originating from the coating layer is generated.

[0083] (3) Solvent resistance The coated / plated steel sheets of Examples 1 to 43 and Comparative Examples 1 to 3 were rubbed 50 times with gauze moistened with xylene, and the coating films were observed. The results were evaluated according to the following criteria. The evaluation results for solvent resistance are shown in Tables 1 to 4. A: The coating layer remained. B: The coating layer was dissolved and the plating layer was exposed.

[0084] [Table 1]

[0085] [Table 2]

[0086] [Table 3]

[0087] [Table 4] [Explanation of symbols]

[0088] 1. Coated and plated steel sheets 2 steel plate 3 plating layer 4 Covering layer 5 Top coat layer

Claims

1. a steel plate, a plating layer, and a coating layer laminated in this order, the plating layer containing aluminum and zinc, the coating layer containing an anti-rust pigment whose main component is vanadium pentoxide, and the coating layer being a cured product of a coating paint; the anti-rust pigment is surface-treated with a silane coupling agent, the silane coupling agent comprises 3-mercaptopropyltrimethoxysilane; The vanadium pentoxide has an average particle size of 15 μm or less. Coated galvanized steel sheet.

2. The coating paint contains the anti-rust pigment in an amount of 4% by weight or more and 30% by weight or less. The coated plated steel sheet according to claim 1.

3. The coating paint contains a polyester resin having a hydroxyl group and a blocked isocyanate compound. The coated plated steel sheet according to claim 2.

4. The coating paint contains an epoxy resin. The coated plated steel sheet according to claim 3.

5. The ratio of the epoxy resin to the total amount of the coating paint is 5% by weight or more and 10% by weight or less. The coated plated steel sheet according to claim 4.

6. The thickness of the coating layer is 5 μm or more and 50 μm or less. The coated plated steel sheet according to any one of claims 1 to 5.

7. Further comprising a topcoat layer covering the coating layer. The coated plated steel sheet according to any one of claims 1 to 6.

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