JPH0376828B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a painted laminate with excellent weldability, workability, and corrosion resistance, and particularly to a painted laminate with excellent continuous spot weldability, high workability, and high corrosion resistance suitable for steel materials for automobile bodies. 2. Description of the Related Art Generally, various types of equipment, parts, etc. that are painted and put into actual use are painted entirely after being processed and assembled. However, with such processing and painting after assembly, a sufficient coating may not be obtained in some areas. In order to eliminate this disadvantage,
Pre-painted steel sheets, so-called painted steel sheets, are widely used. However, resistance welding is usually not possible with this type of painted steel plate, and the assembly requires methods other than welding.
For example, fixing means such as bolts and nuts must be used, which is disadvantageous in terms of workability and assembly cost. From the point of view of spot weldability of coated steel sheets, it is necessary that the coating film has electrical conductivity, and conventionally, this purpose has generally been achieved by using conductive pigments. However, continuous spot welding is an important issue in high-speed, large-volume, labor-saving lines such as automobile body production lines. Continuous spot welding performance is determined by the fact that as the number of welding increases, the electrode
Since it is contaminated with plating film, coating composition, etc. and requires cleaning or replacement, it is evaluated by the number of times welding until cleaning or replacement is required. Techniques for imparting conductivity to paint films using conductive pigments (for example, Japanese Patent Publication No. 52-44569, Japanese Patent Application Laid-Open No. 58-138758)
Spot welding is possible with techniques such as JP-A No. 58-174582, etc.) or technology that further improves the conductivity of the coating film by devising pigments (e.g. JP-A No. 51-79138, JP-B No. 58-19706). However, there is no consideration given to the requirements for ensuring continuous spot welding of 2000 points or more, that is, electrode contamination, resulting in unsatisfactory results. Moreover, in recent automobile production processes, continuous spot welding of as large as possible, for example 2000 to 5000 points, is required. In addition, when pressing or deep drawing painted materials, the road film may peel off into powder during processing and adhere to the press machine, causing processing scratches, requiring frequent cleaning of the press machine, or The coating must not peel off from the base or crack, which may reduce the corrosion resistance of the area.
It is known to add an inorganic or organic lubricant for the purpose of improving the workability of this coating film. However, originally, weldable coatings tend to have a pigment-rich composition to ensure conductivity.
For example, there is a problem in that blending inorganic pigments such as molybdenum disulfide, carbon, and lead oxide in amounts sufficient to exhibit their effects may lead to a decrease in the strength and processability of the coating film. In addition, in the production of automobiles, body parts such as car panels, doors, fenders, etc. are usually made from steel plates by perez processing, assembled by spot welding, and then degreased, treated with phosphate, and then electrodeposited. In addition to workability and spot weldability, it is required to have good adhesion to electrodeposited coatings and corrosion resistance. Corrosion resistance also becomes an issue in areas where electrodeposition coating is insufficient, such as the joints and edges of parts.
Generally, when a paint containing a relatively large amount of conductive pigment or lubricant is applied, the corrosion resistance of the paint film tends to decrease, and in some cases, the conductive pigment itself or its decomposition products may exhibit a corrosion-promoting effect. The type and conditions of use are particularly important in obtaining highly corrosion-resistant coatings. Furthermore, the above-mentioned coating film adhesion and corrosion resistance of the coated steel sheet largely depend on the properties of the base metal. Conventional painted steel sheets are made by applying a coating containing hexavalent chromium to a general cold-rolled steel sheet base material, and then applying a paint containing electrically conductive substances such as Zn and Al (Special Publications Co., Ltd.
-6882), and one using a Zn-plated steel plate as the base material and coated with paint containing various conductive substances (Japanese Patent Publication No. 11331/1982). However, none of these conventional weldable coated steel sheets can be said to be sufficient for the above-mentioned applications. The former method, which uses cold-rolled sheets, has problems with paint film adhesion, and when it cools down, there is a high risk that the paint film will peel off because the molding process for automobile fenders and the like is very highly processed. This is because the adhesion between the cold-rolled base material and the chromate film as a coating base is not sufficient in the first place. Furthermore, with this coated steel sheet, if the coating film is damaged during processing or use, red rust will develop on the base material at an early stage, resulting in a loss of commercial value, which is a problem in terms of corrosion resistance. The latter, which uses galvanized steel sheets, is intended to solve the problem of corrosion resistance of the above-mentioned painted steel sheets, so to speak, and is certainly superior in terms of red rust resistance. However, the corrosion resistance of galvanized steel sheets originally depends on so-called sacrificial corrosion protection, in which zinc preferentially dissolves in a corrosive environment and prevents corrosion of the steel sheet base, and the rate at which zinc dissolves in a corrosive environment depends on the corrosion resistance of galvanized steel sheets. As a result, zinc dissolution under the paint film progresses in the vicinity of scratches or end faces, and there is a tendency for paint film blisters (hereinafter referred to as blisters) to occur at an early stage. This blister is a major problem because it significantly impairs the commercialization value of this type of coated steel sheet. In recent years, electrolytic galvanized steel sheets containing nickel (Ni
-Zn alloy plated steel sheets) are being put into practical use. This Ni-Zn alloy plated steel sheet also has sacrificial corrosion resistance, but its properties are thin and its electrochemical corrosion protection function is much stronger, and its bare corrosion resistance surpasses that of ordinary galvanized steel sheets. Anything can happen. By using this Ni-Zn plated steel plate,
It is expected that the blister resistance after painting will be the same as when cold-rolled sheets are used, and the corrosion resistance will also be significantly improved compared to when galvanized steel sheets are used. However, the highly corrosion-resistant nature of the Ni-Zn alloy plating layer conversely reduces its reactivity with chemicals commonly used for painting base treatment, reducing the adhesion between the formed base film and the substrate, resulting in insufficient There are many cases where the quality after painting cannot be obtained, and this is a particularly serious problem in the case of base treatment containing hexavalent chromium, which has a strong passivating power for metals. Therefore, one of the objects of the present invention is to provide a painted laminate which has excellent synergistic workability, corrosion resistance, and continuous spot weldability by laminating a chromate film and a paint film on a specific plated steel plate. The purpose of the present invention is to provide excellent workability, corrosion resistance, and continuous spot weldability, as well as excellent coating film adhesion during post-coating such as electrodeposition coating, and corrosion resistance in areas where coating is insufficient, especially for automobiles, etc. The purpose is to provide a prepainted steel sheet suitable for production. As a result of research into the relationship between continuous spot weldability and coating film composition, the present inventors have found that the thermal decomposition of the coating film binder resin is greatly involved in this continuous spot weldability, and that the thermal decomposition property is It changes depending on the aromatic ring content of It has been found that weldability is significantly improved. In addition, in order to improve processability, since a considerable amount of inorganic pigment coexists, it is preferable to use a lubricant with a small amount, low specific gravity, and large volume, that is, an organic lubricant, which is suitable for high-level processing such as automobile bodies. I learned that it is important to select the appropriate type and amount of lubricant, as well as the total amount of conductive pigments and other inorganic pigments. In order to make it weldable, a conductive pigment is naturally included, but the present inventors greatly improved the corrosion resistance of the laminate by providing a specific corrosion-resistant chromate layer and plating layer under the paint layer containing the conductive pigment. In addition, conductive pigments, especially those containing iron phosphide as the main component, have little negative effect on corrosion resistance and workability, and have a stable and low electrical resistance, and do not melt during welding and have high hardness. Being excellent;
Furthermore, by using an iron phosphide decomposition inhibitor and controlling the inorganic pigment concentration, it is possible to obtain a laminate with higher corrosion resistance and excellent processability, weldability, paint film adhesion, and especially corrosion resistance after processing. This discovery led to the completion of the present invention. That is, according to the present invention, a nickel-containing electrogalvanized phase consisting of a single γ phase is formed on a cold rolled steel sheet, and at least one compound containing hexavalent chromium having a solubility of 20 to 10 ^-5 , aqueous silica and/or or aqueous resin binder, further 2 to 6% by weight of a water-soluble chromium compound with solubility greater than 20
A corrosion-resistant layer and a conductive paint layer of a composition containing a phosphoric acid compound of % Organic lubricant 4-30% by weight Conductive pigment mainly composed of iron phosphate 15-85% by weight Iron phosphide decomposition inhibitor 1-71% by weight Other inorganic pigments 0-70% by weight However, conductive pigments, iron phosphide Decomposition inhibitor and
A corrosion resistant paint laminate is provided, the layer comprising a composition having a total amount of other inorganic pigments of 35 to 86% by weight. The metal base material in the laminate of the present invention is a cold-rolled steel plate on which a Ni--Zn alloy plating layer consisting of a single γ phase is formed. In the present invention, the Ni-Zn alloy plating layer of the plated steel sheet is made of a single γ phase because other types, such as η+γ phase and γ+α phase, have poor corrosion resistance and blister resistance. The Ni-Zn alloy plating layer consisting of a single γ phase has both moderate sacrificial corrosion protection and the above-mentioned electrochemical corrosion protection function, and has extremely excellent corrosion resistance.Moreover, the dissolution rate of the plating layer is low. Since it is sufficiently small, it can also solve the problem of blistering after painting. In the case of a single γ phase, the Ni content of the Ni-Zn alloy plating layer is 9~
20%. A Ni--Zn alloy plating layer containing 9 to 20% Ni can be obtained by substituting about 70% of the Zn amount in the bath with nickel sulfate, nickel chloride, etc. in generally known Zn electroplating. Although this basis weight is not particularly specified, it is preferably 1 g/m ² or more from the viewpoint of corrosion resistance. However, a thickness exceeding 60 g/m ² is practically unnecessary, uneconomical, and undesirable from the viewpoint of weldability. Even when the Ni--Zn alloy plating layer contains Co content of 1% by weight or less or iron content of 3% by weight or less, the same improvement in corrosion resistance and weldability as described above can be achieved. These metal base materials are degreased if necessary. This is a common degreasing process that is well known to those skilled in the art, and there is no need to explain its details. In the present invention, the solubility is
At least one chromium compound containing hexavalent chromium of 20 to 10 ^-5 , an aqueous silica and/or an aqueous resin binder, a water-soluble chromium compound with a solubility of more than 20, and a phosphoric acid compound of 2 to 6% by weight. A corrosion-resistant layer of a composition comprising: The solubility here refers to the number of grams of a compound dissolved to saturation in 100 ml in a pure frame at 20°C. Typical hexavalent chromium-containing chromium compounds with a solubility of 20 to 10 ^-5 contained in this corrosion-resistant layer include calcium chromate with a solubility of 20 to 10;
These include potassium zinc chromate and strontium chromate with solubility of 10 to 10 ^-1 , barium chromate and lead chromate with solubility of ¹⁰ to ^{10 -5} . Further, it is a mixture of a hexavalent chromium compound and another metal or a reaction product with an organic substance and has a solubility of 20 to 10 ^-5 . Compounds with a solubility of more than 20 are too active and may be inactivated by contact with the coating composition during coating film formation, or may become inactivated over time even after coating film formation, resulting in insufficient improvement in corrosion resistance; Chromium compounds with a content of less than 10 ^-5 have insufficient anticorrosion ability. Such chromium compounds are usually present in the corrosion-resistant layer singly or in combination of two or more. Furthermore, the corrosion-resistant layer contains a water-soluble chromium compound with a solubility of over 20, such as CrO ₃ , K ₂ CrO ₄ ,
Cr(NO ₃ ) ₃ ·9H ₂ O, Cr ₂ (SO ₄ ) ₃ ·18H ₂ O, other chromates, dichromates, etc. are added. These water-soluble chromium compounds form a strong layer incorporating chromium compounds containing hexavalent chromium with a solubility of 20 to 10 ^-5 by reacting with water-based silica and/or water-based resin, which will be described later. Demonstrates corrosion resistance. In order to form such a strong layer, it is preferable to use a mixture of a water-soluble hexavalent chromium compound and a water-soluble trivalent chromium compound. For example, CrO ₃ and Cr
(NO ₃ ) It can be obtained by using _{3.9H 2} O together or by partially reducing CrO ₃ with formalin, etc. The ratio of hexavalent chromium compounds is the total water-soluble chromium in terms of chromium metal.
Maximum corrosion resistance is achieved at 10-90% by weight, especially 50-80% by weight. The ratio of a chromium compound containing hexavalent chromium (A ₁ ) with a solubility of 20 to 10 ^-5 and a water-soluble chromium compound (A ₂ ) with a solubility exceeding 20 is 0.25/Cr in A ₂ / Cr in A ₂
1.75 to 1/1 is preferable. If it is less than 0.25/1.75, corrosion resistance tends to decrease, and if it exceeds 1/1, the layer tends to become brittle and the coating film adhesion tends to decrease. In addition, the chromium compounds (A ₁ and A ₂ ) contained in this corrosion-resistant layer are 0.01 to 1 g/m ² in terms of metallic chromium.
is preferred. If it is less than 0.01 g/m ² , corrosion resistance will be insufficient, and if it exceeds 1 g/m ² , coating film adhesion will decrease. Typical water-based silica is colloidal silica or water-dispersible silica with a particle size of 100 mμ or less. Specific examples of such colloidal silica include Snowtex 0 (Colloidal Silica, product name of Nissan Chemical Co., Ltd., solid content 20%, average particle size 20 μm, PH3.0),
Snowtex N (same, PH9), Snowtex
PL (particle size 40 to 50 mμ, PH3), and water-dispersible silicas include Aerosil 300 (particle size 100 mμ or less), manufactured by Nippon Aerosil Co., Ltd., and Aerosil TT-600r (particle size 0.1 to 0.3 μ). , Imcil A108
(particle size 5μ, trade name manufactured by Illinois Minerals), etc. are preferably used. In addition, water-based resins include water-soluble resins and water-dispersible resins that are compatible with chromium, and specific examples of water-soluble resins include polyvinyl alcohol, alkylhydroxyalkyl cellulose, polyacrylic acid and its derivatives, polyacrylamide and its derivatives. derivatives, polyvinylpyrrolidone, reactants of polyvinylmethylmaleic anhydride and vinyl or acrylic compounds, etc. Specific examples of water-dispersible resins include alkyd resins, phenolic resins, amino resins, vinyl acetate diameter emulsion polymers, styrene, Examples include butadiene-based synthetic latex polymers, acrylic-based emulsion polymers, and natural and synthetic rubber-based emulsion polymers. These binders can be used alone or in combination of two or more, and are effective in closely fixing the chromium compound to the metal surface. The suitable content of these binders in the corrosion-resistant layer is such that the weight ratio of metallic chromium in the binder/chromium compound (A ₁ +A ₂ ) is 1/10 to 5/1.
If it is less than 1/10, the adhesion of the paint film after painting will decrease,
When it exceeds 5/1, corrosion resistance decreases. As already mentioned, the metal base material of the present invention is a cold-rolled steel sheet on which a Ni--Zn alloy plating layer consisting of a single γ phase is formed. As mentioned above, the plating layer itself exhibits a high degree of corrosion resistance, but because of this, the chromate film formed thereon cannot sufficiently react with the plating surface, resulting in a decrease in adhesion. In such a case, the processability of the coating film after painting is reduced. This is particularly noticeable in high-strength press working, such as the application of the coated steel sheet of the present invention, and this appears as a decrease in the corrosion resistance of the processed part, and the advantage of the high corrosion resistance of the metal material is not fully exhibited. In the present invention, in order to solve the above problem, a phosphoric acid compound is contained in the corrosion-resistant layer. The compound is added as phosphoric acid to a chemical solution for forming a corrosion-resistant layer. This phosphoric acid also reacts with the inert Ni--Zn alloy plating layer during the formation of the corrosion-resistant layer, improving the adhesion of the formed layer to the substrate. The content of the phosphoric acid compound in the corrosion-resistant layer is 2 to 6% by weight as phosphoric acid based on the total weight of the corrosion-resistant layer. 2
If it is less than 6% by weight, sufficient adhesion of the corrosion-resistant layer to the substrate cannot be obtained, and if it exceeds 6% by weight, the same problem occurs, and the corrosion resistance also decreases. In the method for forming a corrosion-resistant layer of the present invention, an aqueous chemical solution that satisfies the above conditions is prepared, applied in a predetermined amount onto the surface of a metal substrate by spraying, dipping, roll coating, etc., and then heated and dried. Heating is preferably carried out at a relatively high temperature in order to cause a sufficient reaction between the chemical solution and the metal base material. The temperature is preferably 150 to 250°C as the highest temperature reached by the metal base material. The laminate of the present invention has processability,
A specific conductive coating layer with excellent weldability, corrosion resistance, etc. is created. This coating layer is used as a binder resin, such as paint resins with aromatic ring content in the molecule of 0 or up to 50% by weight, such as epoxy resins, alkyd resins, acrylic resins, melamine resins, and urethane resins. resin, phenolic resin, vinyl resin,
It is characterized by using polyvinyl butyral resin, polyvinyl acetate resin, chlorinated rubber, oil-free polyester resin, phthalic acid resin, styrene resin, polyolefin resin, etc. in organic solvent type or water-based type. These resins can be used alone or in combination of two or more, but in the case of a combination, the aromatic ring content expressed as an average content is 50% by weight or less, most preferably not 0%, as described above. must not. The present inventors found that the aromatic ring content in the resin molecule is closely related to continuous spot weldability, and that when it exceeds 50%, the thermal decomposition rate is determined by the following measurement method. Previous resin weight) x 100 Resin weight after heating... Raise the temperature of the resin from room temperature to 550℃ at a rate of 20℃/min (in a _N2 gas flow), and calculate the weight when the sample temperature reaches 550℃. Measurement with a gravimetric analyzer (sample amount: 5-10 mg) is significantly reduced, and continuous spot weldability is also significantly reduced. Aromatic ring content is 0-50
In weight percent, the weight loss rate due to pyrolysis of the resin is 70
It was found that at ~100%, it can sufficiently withstand continuous spot welding of up to 5,000 points. In addition, the content of the resin in the coating layer is 10 to 35% by weight,
It has been found that the content is preferably 15 to 25% by weight, and if it is less than 10% by weight, workability is significantly reduced, and if it exceeds 35% by weight, continuous spot weldability is reduced. The coating layer contains an organic lubricant as a second component. Organic lubricants are known as slip agents, which reduce the friction between the processing jig and the paint film, weaken the force applied to the paint film, and reduce damage to the paint film during processing. Not only is it an organic substance with a low specific gravity and a large volume fraction in the coating film, but it also has good thermal decomposition properties (decomposition temperature 300-500℃)
It is preferable to use a substance that exhibits an exothermic reaction in the welding process and promotes the thermal decomposition of the coexisting resin without leaving behind carbon that exerts most of its energy and adversely affects continuous spot welding.In this sense, polyolefin compounds such as polyethylene, Polymers of unsaturated aliphatic olefin hydrocarbons such as isotactic polypropylene and polybutene (preferably with a molecular weight of 1000
~10,000); Carboxylic acid ester compounds such as stearic acid, oleic acid, adipic acid, azelaic acid,
Carboxylic acids such as sebacic acid, n-butanol,
sec.-butanol, 3-methylbutanol, 2-
Mona-, di- or poly-esters with alcohols such as ethylhexanoate and neopentyl alcohol; polyalkylene glycol compounds such as polypropylene glycol and polyethylene glycol are particularly recommended. From the viewpoints of processability, thermal decomposition, corrosion resistance, adhesion of top coat, etc., polyethylene wax is particularly preferred, and the most preferred is polyethylene fine powder with a molecular weight of 1,000 to 10,000 and a particle size of 50 μm or less. Such organic lubricants can be used alone or in combination of two or more, and the amount added is 4 to 4 in the coating layer.
30% by weight, preferably 4-20% by weight, 4% by weight
If the weight is less than 30%, the processability decreases and no effect on promoting thermal decomposition of the resin is observed.On the other hand, if the weight exceeds 30%, no further improvement in processability is observed, and as the weight increases, corrosion resistance tends to decrease. is recognized. The coating layer of the present invention also contains a conductive pigment for the purpose of imparting conductivity, and such a conductive pigment has a stable and low electrical resistance, and a sufficient current carrying effect can be obtained with a small amount, and it is necessary to weld. It is a high melting point material that does not melt due to the heat generated during welding, and does not have disadvantages such as melting, increased contact area, reduced current density, and electrode adhesion contamination.It is also highly hard, and conductive particles are insulated by pressure during welding. It goes without saying that it is preferable that the material can destroy the body coating resin layer and improve the conductivity, and that it can be supplied in large quantities at as low a price as possible. The present inventors developed a pigment with iron phosphide (Fe ₂ P) as a main component that has the above advantages and is also inert and has excellent corrosion resistance compared to other metal particles.
Hereinafter, it has been found that a pigment having an average particle size of preferably 10 μm or less is optimal. Various conductive pigments containing iron phosphide as a main component are commercially available as Ferrophos and the like, and these can be used alone or in combination. The conductive pigment containing iron phosphide as a main component is used in the coating layer in an amount of 15 to 85% by weight, preferably 30 to 70% by weight. I mean
If it is less than 30% by weight, the conductivity may be insufficient if the coating thickness is 10 μm or more, and if it is less than 15% by weight, the conductivity is clearly insufficient and spot welding cannot be performed. If it exceeds 70% by weight, the processability of the coating may deteriorate, and if it exceeds 85% by weight, the processability will clearly deteriorate and become impractical. As described above, one of the foundations of the present invention is the discovery that among the known conductive pigments, pigments mainly containing iron phosphide give the most excellent results for the purpose of the invention. It has been found that in a corrosive environment, particularly when a coating film is placed in an acidic atmosphere, iron phosphide decomposes and corrosion is accelerated by the decomposed products. Whether or not the coating film becomes an acidic atmosphere depends on the coating composition, base metal,
Although it depends on the corrosive environment conditions, Ni-
The above-mentioned phenomenon is likely to occur when a Zn alloy plating layer or corrosion-resistant layer is provided under the coating. Therefore, it is necessary to suppress the decomposition of iron phosphide or to render the decomposed products harmless, and for this purpose, the present inventors have investigated the coexistence of pigments whose suspended water pH is 6 to 13, preferably 7 to 11. It has been found that this is an extremely effective means as it allows the coating film to be kept on the neutral or alkaline side continuously. Therefore, the coating composition of the present invention contains an iron phosphide decomposition inhibitor as an essential component along with a conductive pigment mainly composed of iron phosphide. Specific examples of such decomposition inhibitors include the following compounds. Alkaline earth metal petroleum sulfonates Chromate pigments such as zinc chromate, potassium zinc chromate, barium chromate, basic lead chromate, calcium chromate, strontium chromate, etc. Zinc phosphate, iron phosphate, aluminum tripolyphosphate, etc. Phosphate pigments Lead compound pigments such as calcium leadate and lead silicate Extender pigments such as talc, calcium carbonate, and silica Zinc dust (less than the same amount as iron phosphide) However, this pigment should be used at a content of less than 1% by weight in the coating film. The amount shall not exceed the total amount of inorganic pigments described below. Although these compounds are sometimes classified as antirust pigments or extender pigments, they are recognized as iron phosphide decomposition inhibitors in the present invention in terms of the pH of suspended water. The coating layer of the present invention may optionally contain other inorganic pigments, such as chromium pigments (zinc chromate, lead chromate, calcium chromate, strontium chromate pigments, etc.) for improving corrosion resistance.
Phosphate pigments (zinc phosphate, iron phosphate, aluminum tripolyphosphate pigments, etc.), lead compound pigments (calcium leadate, lead silicate, etc.): Adjustment of resin amount,
Extender pigments (silica, calcium carbonate, talc, alumina, etc.) and coloring pigments (chromium oxide, iron oxide, lead oxide, etc.) can be added to adjust the pH of the paint film. When adding such inorganic pigments, the total amount of inorganic pigments listed below must not be exceeded. That is, in the coating layer used in the present invention, the total amount of the conductive pigment mainly composed of iron phosphide, the iron phosphide decomposition inhibitor, and other inorganic pigments added as desired is 35-86% by weight, preferably is 35
It is important that the content be within the range of -70% by weight. This is because when the total amount is less than 35% by weight, the processability of the coating film decreases, and even when it exceeds 70% by weight, a decrease in processability may be observed, and when it exceeds 86% by weight, there is a clear decline in the processability. This is because a decrease in mechanical properties is observed. The thickness of the coating layer is 1-20μ, preferably 2-20μ.
It is 10μ. If the thickness is less than 1μ, corrosion resistance will be insufficient, and if it exceeds 20μ, continuous spot weldability will deteriorate. The coating layer is formed by baking, and the conditions are appropriately selected depending on the type of resin, and the maximum board temperature is 100-300°C for about 20 seconds to 5 minutes. The laminate of the present invention exhibits extremely excellent workability, corrosion resistance, continuous spot weldability, and coating adhesion, and is particularly useful for use in industrial production lines for automobiles and the like. The present invention will be explained below with reference to Examples. In the following examples, the following metal substrates were used. Except for Comparative Examples 1 and 2, a plating bath in which 70% of the Zn content of a generally known electrolytic galvanizing bath was replaced with nickel sulfate was used on a surface-cleaned cold-rolled steel plate (plate thickness 0.8 mm). Ni11wt%, Zn89wt% basis weight 20
A single ^- phase γ-phase Ni-Zn alloy plated steel sheet was obtained. In Comparative Example 1, a cold-rolled steel sheet was used as it was, and in Comparative Example 2, an electrolytic galvanized steel sheet having a basis weight of 40 g/m ² obtained using the above-mentioned known electrolytic galvanizing bath was used. Example 1 The above Ni-Zn alloy plated steel sheet was treated with alkaline degreasing, washed with water, dried, coated with the following chromate treatment solution by roll coating, and then heated to the highest temperature in a gas furnace.
It was dried for 1 minute at 150°C to form a corrosion-resistant layer with a chromium content of 200 mg/m ² . The chromate treatment solution is a chromate anhydride aqueous solution reduced with formalin.
Prepare a solution with a total chromium content of 20 g/Cr ⁶⁺ /Cr ³⁺ = 7/3, add Aerosil 300 (manufactured by Nippon Aerosil Co., Ltd., Huumed Silica) to a concentration of 20 g/g/, and add chromium with a solubility of 10 to 10 ^-1 . Zinc chromate C, an acid zinc potassium pigment (manufactured by Kikuchi Shiki Kogyo Co., Ltd., abbreviated as ZPC)
was added in an amount of 15g/converted to Cr, and further phosphoric acid was added in an amount of 3% based on the solid content of the chromate treatment solution, and 15g was added using a paint shaker.
A solution obtained by dispersing glass beads for a period of time was used. The following coating composition was also prepared separately. As resin B, 16 parts by weight (in terms of solid content) of urethane-modified epoxy resin (prepared according to JP-A-57-30717, Example 3, benzene ring content in molecule 45 wt%), and as resin C, resol type phenol resin ( 4 parts by weight (in terms of solid content) of BKS-316 (manufactured by Showa Union Gosei Co., Ltd., benzene ring content in the molecule: 55 wt%) was melted in cyclohexanone, and Ferrophos HRS2132 (manufactured by Hooker Chemicals and Plastics Co., Ltd., mainly made of iron phosphide) was dissolved in cyclohexanone. 60 parts by weight of strontium chromate N (conductive pigment), strontium chromate N (Kikuchi pigment products,
Add 5 parts by weight of chromate pigment, an iron phosphide decomposition inhibitor, and disperse with steel beads for 2 hours using a paint shaker. Filter the paint and seli dust
Add 15 parts by weight of 3620 (manufactured by Hoechst, micronized polyethylene wax), mix uniformly with a disper, and reduce the non-volatile content to approximately 60 wt% with cyclohexanone.
Adjust so that it becomes. The coating composition was applied to the chromate-treated steel plate by a roll coating method, and baked in a gas furnace at a maximum plate temperature of 200°C for 1 minute to form a film with a coating thickness of 7 μm to obtain a corrosion-resistant painted laminate. Ta. Examples 2 to 6 and Comparative Examples 1 to 11 Painted laminates were obtained in the same manner as in Example 1, except that the metal base material, corrosion-resistant layer composition, and paint composition were changed as shown in Table 1 below. In Table 1, yellow lead 5G-DH, lead chromate pigment with solubility of 10 ^-1 to 10 ^-5 , zinc powder manufactured by Kikuchi Shiki Kogyo Co., Ltd. zinc powder for paints, Sicor Zmp/manufactured by Mitsui Kinzoku Kogyo Co., Ltd. S Zinc phosphate pigment Resin D manufactured by BASF Co. Epoxy resin with an epoxy equivalent of 950 and a benzene ring content of 54% in the molecule Epototo YD-D14 manufactured by Toto Kasei Co., Ltd. For the layered bodies obtained in each example and comparative example, The following performance tests were conducted for each, and the results shown in Table 2 were obtained. Test method and evaluation criteria 1 Continuous spot welding Spot welding was carried out under the conditions of an electrode diameter of 5 mm, a pressing force of 200 Kg, a current application time of 10 cycles, and a current of 8000 A, and the number of continuous spots that could be made was determined. Evaluation ◎: 5000 points or more, little electrode dirt ○: 5000 points or more, a lot of electrode dirt △: 3000 points to 5000 points ×: Less than 3000 points 2 Cylindrical deep drawing processability Cylindrical deep drawing tester (manufactured by Eriksen, model
B1-142 type), wrinkle presser pressure 3 tons, punch diameter 50mmφ, die diameter 52.4mmφ, drawing depth 40
mm, blank diameter 95 mm), scratches on the paint film,
Checked for peeling. Evaluation ◎: No abnormality on the painted surface ○: There are scratches on the painted surface (not reaching the base metal) (10% or less) △: There are scratches that reach the base metal, and there are many scratches on the painted surface ×: Original plate crack 3 Corrosion resistance Combined corrosion test (1) Cycle = salt spray (5
%NaCl, 35℃), 2 hours → drying (60℃), 2
Time → Humidity (98%RH≦, 50℃) 4 hours 200
We investigated the occurrence of red rust and white rust on the flat surface after cycling. Evaluation ◎: No white rust, no red rust ○: Less than 5% white rust, no red rust △: 6% or more, ×: 1% or more red rust Salt water spray resistance (according to JIS-Z2371) 2500
After some time, the state of red rust and white rust on the flat surface was examined. Evaluation ◎: No white rust, no red rust ○: Less than 5% white rust, no red rust △: 6% or more, ×: 1% or more red rust Salt water spray resistance after cylindrical processing Item 2 After cylindrical deep drawing under the following conditions, it was kept indoors for 2 months and then subjected to a salt spray test (JIS-Z-
2371) for a period of time, the state of rust occurrence on the machined surface was examined and evaluated using a 3- standard.

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Claims (1)

[Claims] 1. A nickel-containing electrogalvanized layer consisting of a single γ phase is formed on a cold-rolled steel sheet, and the solubility is 20 to 10 ^-5 .
At least one chromium compound containing hexavalent chromium of
seeds and an aqueous silica and/or aqueous resin binder, a water-soluble chromium compound with a solubility greater than 20,
Furthermore, a corrosion-resistant layer and a conductive paint layer of a composition containing 2 to 6% by weight of a phosphoric acid compound are laminated in sequence, and the coating layer is a paint having an aromatic ring content in the molecule of 0 to 50% by weight. Resin for use 10-35% by weight Organic lubricant 4-30% by weight Conductive pigment mainly composed of iron phosphate 15-85% by weight Iron phosphide decomposition inhibitor 1-71% by weight Other inorganic pigments 0-70% by weight However, A corrosion-resistant painted laminate, characterized in that the layer comprises a conductive pigment, an iron phosphide decomposition inhibitor, and other inorganic pigments in a total amount of 35 to 86% by weight. 2. The laminate according to claim 1, wherein the nickel-containing electrogalvanized layer contains a Co content of 3% by weight or less or an iron content of 3% by weight or less. 3 Corrosion-resistant layer contains chromium compound in terms of metallic chromium
The laminate according to claim 1, containing 0.01 to 1 g/m ² . 4. The laminate according to claim 1, wherein hexavalent chromium accounts for 10 to 90% by weight of the total chromium in the chromium compound having a solubility of more than 20 in the corrosion-resistant layer. 5. The laminate according to claim 1, wherein the paint layer has a thickness of 1 to 20 μm. 6 Paint resins include epoxy resins, alkyd resins,
Claim 1: Acrylic resin, melamine resin, urethane resin, phenolic resin, vinyl resin, polyvinyl butyral resin, polyvinyl acetate resin, chlorinated rubber, oil-free polyester resin, phthalic acid resin, styrene resin, polyolefin resin The described laminate. 7. The laminate according to claim 1, wherein the organic lubricant is a compound selected from polyolefin compounds, carboxylic acid ester compounds, and polyalkylene glycol compounds. 8. The laminate according to claim 6, wherein the organic lubricant is a compound that exhibits exothermic decomposition at 300 to 500°C. 9. The laminate according to claim 1, wherein the iron phosphide decomposition inhibitor is a pigment exhibiting a suspension pH of 6 to 13. 10. The laminate according to claim 1, wherein the other inorganic pigment is a chromium pigment, a phosphate pigment, a lead pigment, or a colored pigment. 11. The laminate according to claim 1, wherein the total amount of the conductive pigment, iron phosphide decomposition inhibitor, and other inorganic pigments is 35 to 70% by weight based on the solid content of the paint.