JP2008111174A - Organic resin-coated phosphate treated galvanized steel sheet, and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic resin-coated phosphate treated galvanized steel sheet having corrosion resistance and blackening resistance higher than those of the conventional corrosion protective coated steel, and in which the adhesion of an organic resin film upon the deformation of the steel sheet is excellent, and to provide its production method. <P>SOLUTION: A galvanized steel sheet is treated with a phosphate treatment liquid comprising Zn<SP>2+</SP>: >2.0 to 5.0 g/L and Mg<SP>2+</SP>: 2.0 to 5.0 g/L, and in which the ratio of the Mg<SP>2+</SP>density to the Zn<SP>2+</SP>, Mg<SP>2+</SP>/Zn<SP>2+</SP>lies in the range of 0.4 to 2.5, and the ratio of free acidity to the total acidity in the treatment liquid is 0.020 to <0.15, thus a phosphate film comprising 0.2 to <2.0 mass% Mg and a coating weight of 0.2 to 1.0 g/m<SP>2</SP>is formed on the surface of the galvanized steel sheet, and further, an organic resin film is formed thereon. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a surface-treated steel sheet coated with an organic resin, does not contain chromium in the surface-treated film, and is an organic resin-coated phosphate-treated zinc-based plated steel sheet with excellent adhesion of the organic resin film, and a method for producing the same It is about.

  Organic resin-coated steel sheets such as painted steel sheets and laminated steel sheets are widely used in parts that require corrosion resistance in the use of building materials, home appliances, and the like. In general, zinc-plated steel sheets are used as the base steel sheet for organic resin-coated steel sheets, and phosphate treatment, chromate treatment, etc. are performed to ensure the adhesion between the organic resin film and the zinc-based plating layer. Is done.

  The chromate treatment is a treatment method that is excellent in corrosion resistance and paint adhesion and can be formed with relatively simple equipment such as a roll coater. For example, as shown in Patent Document 1, an oxide sol or the like is added to a chromate film. This is a technology that provides unevenness on the surface of the film and realizes excellent adhesion to the organic resin film by strengthening the anchor effect and interfacial bonding force.

  However, since the technique of Patent Document 1 uses hexavalent chromium, which is an environmentally hazardous substance, in the chromate treatment solution, it is not preferable for environmental conservation, and the corrosion resistance and paint adhesion of the zinc-based plated steel sheet without using hexavalent chromium. Many phosphate-treated zinc-based plated steel sheets that can improve the temperature are disclosed.

    For example, as shown in Patent Document 2, after forming an amorphous film by coating and drying a mixed aqueous solution of a polyvalent metal primary phosphate and a metal oxide sol, an organic resin film is formed, An organic resin-coated phosphate-treated zinc-based plated steel sheet having corrosion resistance and organic resin film adhesion is disclosed.

  Furthermore, as shown in Patent Document 3 and Patent Document 4, a composite oxide film containing oxide fine particles, phosphoric acid and / or a phosphoric acid compound, and one or more metals selected from Mg, Mn, and Al. In addition, an organic resin-coated phosphate-treated zinc-based plated steel sheet having excellent corrosion resistance is disclosed by forming an organic resin film on the composite oxide film.

However, the method of forming the phosphate film as in Patent Document 2, Patent Document 3 and Patent Document 4 is when the film thickness of the organic resin film in the organic resin-coated phosphate-treated galvanized steel sheet is 100 μm or more. There is a problem that the adhesiveness when processing the steel sheet is not sufficient. In particular, an organic resin film having a film thickness of 100 μm or more has high strength, and thus a strong shearing force acts on the interface between the organic resin film and the phosphating treatment during deformation, and peeling is likely to occur.

Further, as a phosphate-treated zinc-based plated steel sheet that can improve the corrosion resistance and paint adhesion of a zinc-based plated steel sheet without using hexavalent chromium, there are many known techniques for containing Mg in zinc phosphate. It is shown in the patent literature. For example, as shown in Patent Document 5, a zinc phosphate film containing Mg of 2.0% or more and one or more elements selected from Ni, Co, and Cu in an amount of 0.01 to 1% has an adhesion amount of 0.7 g / m. ^A zinc phosphate-treated zinc-based plated steel sheet excellent in corrosion resistance and color tone that is formed to be ² or more is disclosed.

However, in the technique of Patent Document 5, since the zinc phosphate film contains a large amount of Mg, there is a risk that the blackening resistance is deteriorated such that the surface turns black in a high-temperature and high-humidity environment. There is a problem that the color tone of the zinc phosphate coating becomes dark by containing Ni, Co, and Cu in a high concentration in the coating.
Japanese Patent Laid-Open No. 10-306381 JP 2000-129460 A JP 2002-53979 A JP 2002-53980 A JP 2002-285346 A

  An object of the present invention is to provide an organic resin-coated phosphate-treated zinc-based plated steel sheet having corrosion resistance and blackening resistance and having excellent adhesion of an organic resin film during deformation of the steel sheet, and a method for producing the same. is there.

  As a result of repeated studies to solve the above problems, the present inventors have prescribed the zinc ion concentration and the magnesium ion concentration, and the ratio of the magnesium ion concentration to the zinc ion and the free acidity in the treatment liquid. Manufactured using a phosphating solution that optimizes the ratio to the total acidity, so that it has corrosion resistance and blackening resistance, and has excellent adhesion between the organic resin film and the zinc-based plating layer during steel plate deformation. It has been found that an organic resin-coated phosphate-treated zinc-based plated steel sheet can be obtained.

The present invention has been made based on such findings, and the gist thereof is as follows.
(1) An organic resin-coated phosphorus that treats a zinc-based plated steel sheet with a phosphate treatment solution, forms a phosphate film on the surface of the zinc-based plated steel sheet, and forms an organic resin film on the phosphate film. A method for producing an acid-treated galvanized steel sheet, wherein the phosphate treatment liquid contains Zn ²⁺ : more than 2.0 g / L and 5.0 g / L or less, Mg ²⁺ : 2.0 to 5.0 g / L. and wherein the range ratio Mg ²⁺ / Zn ²⁺ is 0.4 to 2.5 of the concentration of Mg ²⁺ for Zn ^2+, relative to the total acidity of the free acidity in the treatment solution is less than 0.020 to 0.15 A method for producing an organic resin-coated phosphatized zinc-based plated steel sheet.

(2) The surface of the zinc-based plated steel sheet has a phosphate film containing Mg: 0.2% by mass or more and less than 2.0% by mass and having an adhesion amount of 0.2 to 1.0 g / m ^2. An organic resin-coated phosphate-treated zinc-based plated steel sheet produced by the method for producing an organic resin-coated phosphate-treated zinc-based plated steel sheet according to (1) above, which has an organic resin film.

(3) The organic resin-coated phosphate-treated zinc-based plated steel sheet according to (2) above, wherein the thickness of the organic resin film is 100 μm or more.

According to the present invention, the zinc-based plated steel sheet contains Zn ²⁺ : more than 2.0 g / L and 5.0 g / L or less, Mg ²⁺ : 2.0 to 5.0 g / L, and Mg ^{2 with} respect to Zn ²⁺ . in the range of ratio Mg ²⁺ / Zn ²⁺ is 0.4 to 2.5 of the density of ^+, treated with phosphate treatment solution ratio is less than 0.020 or 0.15 to the total acidity of the free acidity in the treatment solution, Corrosion resistance and blackening resistance are reduced by forming a phosphate film containing Mg: 0.2% by mass or more and less than 2.0% by mass on the surface of galvanized steel sheet and having an adhesion amount of 0.2 to 1.0 g / m ^2. It has become possible to provide an organic resin-coated phosphatized zinc-based plated steel sheet and a method for producing the same, which are excellent in adhesion of the organic resin film when the steel sheet is deformed.

Hereinafter, the configuration of the present invention and the reasons for limitation will be described.
The organic resin-coated phosphate-treated zinc-based plated steel sheet according to the present invention contains Mg: 0.2% by mass or more and less than 2.0% by mass on the surface of the zinc-based plated steel sheet, and the adhesion amount is 0.2 to 1.0 g / m ² . An organic resin-coated phosphatized zinc-based plated steel sheet produced by a production method described later, comprising a phosphate film and having an organic resin film on the phosphate film.

(Zinc-based plating)
Examples of the zinc-based plated steel sheet to be the base steel sheet of the steel sheet of the present invention include a hot-dip galvanized steel sheet, an electrogalvanized steel sheet, an alloyed hot-dip galvanized steel sheet, and an aluminum-zinc alloy-plated steel sheet (for example, hot-dip zinc-55% by mass). Aluminum alloy-plated steel sheet, hot-dip zinc-5 mass% aluminum alloy-plated steel sheet), iron-zinc alloy-plated steel sheet, nickel-zinc alloy-plated steel sheet, various zinc-based plated steel sheets such as blackened nickel-zinc alloy-plated steel sheet, etc. Can be used. Moreover, the base steel plate which is a board | substrate will not be specifically limited if it is a steel plate which can be applied as a zinc-plated steel plate, and can be suitably selected according to a use. Furthermore, although the adhesion amount of a galvanization layer can be suitably selected according to a use, it is preferable to set it as 1-100 g / m < ² > or more. Adhesion amount are not corrosion resistance sufficient for less than 1 g / m ^2, because the 100 g / m ² by weight, the resistance to plating peeling resistance is lowered. A more preferable adhesion amount is 5 to 70 g / m ² .

(Phosphate coating)
At least one surface of the galvanized steel sheet has a phosphate film containing Mg: 0.2% by mass or more and less than 2.0% by mass and having an adhesion amount of 0.2 to 1.0 g / m ² .

  The phosphate film is formed mainly for improving the adhesion between the galvanized layer and the coating film, and more preferably one that can improve not only the adhesion but also the corrosion resistance. Further, the content of Mg in the phosphate film needs to be 0.2% by mass or more and less than 2.0% by mass. If it is less than 0.2% by mass, the corrosion resistance is not sufficient, and if it is 2.0% by mass or more, the blackening resistance decreases. A more preferable content of Mg is 0.5 to 1.0% by mass. Moreover, Ni, Mn, Co, etc. can be contained in the said phosphate film as an unavoidable impurity if it is 0.01-0.4 mass%.

In addition, the adhesion amount of the said phosphate film needs to be 0.2-1.0 g / m < ² >. If it is less than 0.2 g / m ² , the corrosion resistance is not sufficient, and if it exceeds 1.0 g / m ² , the phosphate crystals in the phosphate film become coarse, resulting in low peel strength when the steel sheet is deformed and adhesion of the organic resin film. This is because the property decreases. The phosphate film is formed by bringing the galvanized layer and a phosphating solution described later into contact with each other by a conventional method such as spraying or dipping. Furthermore, the treatment time with the phosphate treatment liquid varies depending on the treatment method, but for example, in the case of spray treatment, it is preferably 3 to 15 seconds. If it is less than 3 seconds, the phosphate film cannot be formed sufficiently, and if it exceeds 15 seconds, it is etched by the phosphating solution and macro unevenness is likely to occur, so the formation of the phosphate film is uneven. It is because it becomes.

  Prior to the formation of the phosphate film, it is preferable to perform a surface adjustment treatment of the galvanized layer using a titanium colloidal active treatment agent. As a titanium colloid type active treating agent, for example, trade name “Prevalene ZN” manufactured by Nippon Parkerizing Co., Ltd. can be mentioned, and can be performed by spraying the treating agent on the surface of the galvanized layer.

(Organic resin film)
An organic resin film is formed on the phosphate film. The organic resin contained in the organic resin film is not particularly limited, and examples thereof include vinyl chloride-based and polyester-based films that are usually used for laminated steel sheets. It is preferable to use a non-vinyl chloride film such as a film. Furthermore, it is preferable to use a cross-linking agent such as melamine resin, urea or isocyanate in order to cure the organic resin in terms of the balance between processability and chemical resistance.

  The film thickness of the organic resin film is preferably 100 μm or more. One of the effects of the present invention is that the zinc phosphate-treated film has good film adhesion even when the film thickness of the organic resin film is increased, and the effect is most effective at a film thickness of 100 μm or more. This is because it appears prominently.

The method for producing an organic resin-coated phosphate-treated zinc-based plated steel sheet according to the present invention comprises treating a zinc-based plated steel sheet with a phosphate treatment liquid to form a phosphate film on the surface of the zinc-based plated steel sheet, An organic resin-coated phosphating-treated galvanized steel sheet for forming an organic resin coating on a phosphate coating, wherein the phosphating solution is Zn ²⁺ : more than 2.0 g / L and 5.0 g / L L or less, Mg ^2+: containing 2.0～5.0G / L, and the ratio Mg ²⁺ / Zn ²⁺ concentration of Mg ²⁺ with respect to the Zn ²⁺ is in the range of 0.4 to 2.5, the treatment solution The ratio of the free acidity to the total acidity is 0.020 or more and less than 0.15, which is a method for producing an organic resin-coated phosphate-treated zinc-based plated steel sheet.

・ Zn ²⁺ : More than 2.0g / L and less than 5.0g / L
Since Zn ²⁺ is an essential component for forming phosphate crystals, the Zn ²⁺ concentration in the phosphating solution exceeds 2.0 g / L and is 5.0 g / L or less, more preferably 3.0 to 5.0. It is necessary to control appropriately within the range of g / L. This is because at 2.0 g / L or less, phosphate is difficult to precipitate, and a non-uniform phosphate film in which phosphate crystals are not locally generated is formed. On the other hand, if it exceeds 5.0 g / L, a high concentration phosphoric acid component is required to stabilize the phosphating solution, so that it becomes difficult to set the free acid concentration described later low. This is because, since the sparse portion of the acid salt crystal increases, a sufficient effect of the corrosion resistance by the phosphate film cannot be obtained.

・ Mg ²⁺ : 2.0 ~ 5.0g / L
Since Mg ²⁺ is an essential component for improving the corrosion resistance of the phosphate coating, the Mg ²⁺ concentration in the phosphating solution is 2.0 to 5.0 g / L, more preferably 2.5 to 5.0 g / L. It is necessary to control appropriately within the range of L. If the amount is less than 2.0 g / L, the corrosion resistance of the zinc phosphate coating is reduced due to less uptake of the magnesium component, and if it exceeds 5.0 g / L, the content of the magnesium component is too high, so the resistance of the zinc phosphate coating is reduced. This is because blackening is reduced. In addition, since the Mg ²⁺ concentration differs depending on the Mg ²⁺ concentration ratio (Mg ²⁺ / Zn ²⁺ ) to Zn ²⁺ in the phosphate aqueous solution described later, Mg ²⁺ / Zn ²⁺ It is necessary to adjust the concentration within an appropriate range.

· Zn ratio of the concentration of Mg ²⁺ for ^{2+ (Mg 2+ / Zn 2+)} : 0.4~2.5
In order to contain an appropriate amount of Mg in the phosphate coating, in the present invention, the ratio Mg ²⁺ / Zn ²⁺ of zinc ion concentration to zinc ion concentration in the phosphating solution is 0.4 to 2.5, more preferably It is specified in 0.8-1.2. When Mg ²⁺ / Zn ²⁺ is less than 0.4, the Mg ²⁺ concentration in the treatment liquid is less than 2.0 g / L, so that the Mg content in the phosphate film is insufficient (less than 0.2% by mass), and phosphoric acid There is a possibility that the erodibility of the zinc film may decrease, and if Mg ²⁺ / Zn ²⁺ exceeds 2.5, the Mg ²⁺ concentration in the treatment liquid exceeds 5.0 g / L, so Mg in the phosphate film This is because the content is outside the proper range (over 2.0% by mass), and the blackening resistance of the zinc phosphate film may be reduced.

  In addition to the above conditions, the phosphating treatment solution dissolves the Mg salt in the phosphating treatment solution at an appropriate concentration. Therefore, the treatment solution has a liquid temperature of 30 to 70 ° C. and a pH of 1.0 to 2.5. It is preferable to set it as the range. This is for the following reason. When the liquid temperature is less than 30 ° C., since the reactivity is low, it is difficult to form a uniform film in a short time. On the other hand, if the liquid temperature is too high, the etching property becomes high and the phosphate is difficult to precipitate, so that it is very difficult to control the treatment time. On the other hand, when the pH is less than 1.0, the etching property is high and the film is difficult to be deposited, so that it is difficult to control the treatment time. On the other hand, when the pH exceeds 2.5, the stability of the treatment liquid is low and precipitation is likely to occur.

Furthermore, it is important to select an anion that is paired with Mg ²⁺ in the treatment solution. Here, when hydroxide ion, carbonate ion, sulfate ion, etc. are used, there is a tendency that sufficient solubility of Mg salt cannot be obtained, and when chloride ion is used, the solubility is sufficient, but Mg ^{At the} same time as ^{2+, a} high concentration of chlorine ions is mixed into the phosphating solution, which adversely affects the formation of the phosphate film. On the other hand, nitrate ions have an oxidizing action and are less likely to remain in the film components compared to other anions such as chloride ions and sulfate ions, so that the components soluble in the formed film can be minimized, and the phosphate film Since it has an effect of improving performance, nitrate ion is suitable as the anion, and magnesium nitrate is preferably used as the Mg ion source in the treatment liquid. As the phosphate treatment solution used in the present invention, a commercial treatment solution containing zinc ions and phosphate ions and further containing an accelerator, for example, trade name “PB3312M” manufactured by Nippon Parkerizing Co., Ltd. For example, a solution in which a predetermined amount of the nitrate ion is added is used.

-Ratio of free acidity to total acidity: 0.020 or more and less than 0.15 In the phosphate film, the etching action of free orthophosphoric acid (free acid) increases the pH at the solid-liquid interface of the treatment liquid, and the first in the treatment liquid Since there is a difference in the concentration equilibrium between zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) and orthophosphoric acid (H ₃ PO ₄ ), the primary zinc phosphate precipitates as zinc phosphate crystals containing magnesium. Thus, the free acid plays a very important role in the formation of the phosphate treatment layer. Therefore, the present inventors pay attention to the etching action of free acid, and form a uniform phosphate film in a short time (about 3 to 15 seconds) to improve the adhesion of the organic resin film when the steel sheet is deformed. Intensive study was conducted on the production method of the excellent organic resin-coated phosphate-treated galvanized steel sheet.

As a result, when the free acid concentration is increased, the etching property to galvanization increases, and the surface condition becomes non-uniform in the degreasing and surface finishing process that is a pretreatment of the phosphate treatment. When the free acid concentration rises, the zinc phosphate crystals are difficult to precipitate, and in the case of short-time treatment at the level of several seconds, a portion where a phosphate film is not locally formed occurs. I found out. And as a result of further investigation, by setting the ratio of free acidity to total acidity lower than before and optimizing it, it is possible to precipitate phosphate crystals equivalent to conventional technology while suppressing etching property The present inventors have found that a uniform phosphate film can be formed in a short time and that the adhesion of the organic resin film is improved by forming a uniform phosphate film.
The free acid (orthophosphoric acid) concentration is preferably in the range of 0.5 to 3.4 in terms of free acidity. More preferably, it is the range of 1.0-3.0. The total acidity is preferably in the range of 20 to 26, but it is necessary to have a ratio with the free acidity described later.

  The ratio of the free acidity to the total acidity (free acidity / total acidity) must be controlled to 0.020 or more and less than 0.15, more preferably 0.035 to 0.120. If it is less than 0.020, the free acid concentration is too low, so the etching property to zinc is poor, the reaction necessary for precipitation of phosphate crystals is less likely to occur, and a sufficient phosphate film is not formed. This is because the stability of the phosphating solution is lowered, and a solid content that is considered to be a phosphate compound containing zinc and iron present as impurities is precipitated and dispersed in the processing solution. On the other hand, at 0.15 or more, when a short time treatment of several seconds level is performed, unevenness of the phosphate film due to the non-uniformity of the surface state of zinc is likely to occur, and the adhesion of the organic resin film may be reduced. Because there is.

  Here, the free acidity refers to the amount of 0.1N caustic soda (ml) required for neutralization by adding several drops of bromophenol blue as an indicator to 10ml of phosphating solution and titrating with 0.1N caustic soda. Represent as Furthermore, the total acidity is the same with the addition of a few drops of phenolphthalein as an indicator for 10 ml of the phosphate treatment solution, titration with 0.1 normal caustic soda, and the amount of 0.1 normal caustic soda (ml) required for neutralization as a point. To express.

  The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

  Examples of the present invention will be described.

(Examples 1-12 and Comparative Examples 1-12)
On both surfaces of a cold-rolled steel sheet having a plate thickness of 1.0 mm, a hot dip zinc plating layer having an adhesion amount per side of 90 g / m ² was formed by CGL. Phosphate treatment was performed on one side.

  As a pretreatment for phosphating, the surface of the galvanized layer is surface-treated with a surface conditioner (manufactured by Nihon Parkerizing Co., Ltd .: trade name “Plenpalen Z”). Liquid ((Nippon Parkerizing Co., Ltd .: product name “PB3312M”) with magnesium nitrate added) Spray treatment at different times in the range of 2 to 10 seconds, rinse with water, and dry to form a phosphate coating Formed. The solution temperature of the phosphating solution is 60 ° C., and the pH is 2.1 to 2.7, although it varies depending on each example. Each treatment solution contains Ni in the range of 0.1 to 0.4 g / L. Yes.

The Zn ²⁺ concentration, Mg ²⁺ concentration, free acidity and total acidity in the phosphating solution should be appropriately added with the concentration of the “PB3312M” and aqueous sodium hydroxide, orthophosphoric acid and nitric acid. Thus, the Zn concentration was changed according to the initial concentration of “PB3312M”, and the magnesium concentration was changed by changing the amount of magnesium nitrate added.
A test piece (size: 90 × 90 mm) was cut out from the phosphate-treated zinc-based plated steel sheet produced as described above, and a general polypropylene film adhesive was applied so that the dry film thickness was 3 μm. After baking in a furnace with a furnace temperature of 100 ° C., a polypropylene film with a film thickness of 150 μm was pressed against the steel sheet surface with a roll and bonded by thermocompression bonding to produce an organic resin-coated phosphate-treated galvanized steel sheet.
In addition, the Mg content in the phosphate film was measured by dissolving the phosphate-treated layer with an aqueous ammonium dichromate solution and measuring the dissolved solution by ICP analysis (inductively coupled plasma emission analysis). The adhesion amount of was changed by changing the contact time with the phosphating solution (4 to 12 seconds). Further, the amount of the phosphate coating adhered was measured by a gravimetric method after being dissolved in an ammonium dichromate aqueous solution.
Zn ²⁺ concentration, Mg ²⁺ concentration, Mg ²⁺ / Zn ²⁺ ratio, free acidity, total acidity and free acidity / total acidity ratio in the phosphating solution used in Examples and Comparative Examples, and preparation Table 1 shows the Mg content and the adhesion amount of the phosphate coating of the organic resin-coated phosphate-treated galvanized steel sheet.

  Various tests were performed on the organic resin-coated phosphate-treated zinc-based plated steel sheet obtained as described above. The evaluation method of the test conducted in this example is shown below.

(Evaluation methods)
(1) Adhesiveness Adhesiveness of the organic resin-coated phosphate-treated galvanized steel sheet test material is JIS K6744-1992 (polyvinyl chloride metal plate). In accordance with the described adhesion test (Ericsen test), the test piece 90 x 90 mm, Erichsen height 6 mm, cut section length 50 mm was pressed and visually checked for the occurrence of peeling of the organic resin film. Evaluation was made according to the criteria.
○: No peeling occurred ×: Peeling occurred

(2) Adhesion (immersion in boiling water)
Prior to the adhesion test, tests and evaluations were performed in the same process as the above (1) adhesion except that the test piece was immersed in boiling ion exchange water for 1 hour.
○: No peeling occurred ×: Peeling occurred

(3) Corrosion resistance Corrosion resistance is determined by cutting a test piece (size: 50 x 100 mm) from the prepared organic resin-coated phosphate-treated galvanized steel sheet, tape-sealing the end and back of the test piece, and then JIS Z The salt spray test was conducted for 1000 hours in accordance with 2371-2000. Then, the test piece surface state was observed and corrosion resistance was evaluated in accordance with the following evaluation criteria.
○: No rust ×: Rust

(4) Blackening resistance Blackening resistance is obtained by cutting out a test piece (size: 100 x 50 mm) from the prepared organic resin-coated phosphate-treated zinc-plated steel sheet, and using a spectroscopic color difference meter SQ2000 (Nippon Denshoku Industries ( The initial L value (brightness) of the test piece was measured. Next, after leaving the test piece in a constant temperature and humidity chamber at 80 ° C. and 95% relative humidity for 24 hours, the L value of the test piece was measured in the same manner, and the change ΔL from the initial L value was obtained. Evaluation was performed according to the evaluation criteria.
A: ΔL ≧ −1
○: −1> ΔL ≧ −2
Δ: −2> ΔL ≧ −4
×: ΔL <−4

Table 1 shows the evaluation results of the above tests.
According to this, the organic resin-coated phosphate-treated zinc-based plated steel sheets of Examples 1 to 12 all have good adhesion, corrosion resistance, and blackening resistance. It was also found that sufficient performance was obtained even when the phosphate film was formed in a short time.

According to the present invention, the zinc-based plated steel sheet contains Zn ²⁺ : more than 2.0 g / L and 5.0 g / L or less, Mg ²⁺ : 2.0 to 5.0 g / L, and Mg ^{2 with} respect to Zn ²⁺ . in the range of ratio Mg ²⁺ / Zn ²⁺ is 0.4 to 2.5 of the density of ^+, treated with phosphate treatment solution ratio is less than 0.020 or 0.15 to the total acidity of the free acidity in the treatment solution, on the surface of the galvanized steel sheet, Mg: contain less than 0.2 wt% to 2.0 wt%, the adhesion amount to form a phosphate film is 0.2 to 1.0 g / m ^2, further forming an organic resin film that Thus, it is possible to provide an organic resin-coated phosphate-treated zinc-based plated steel sheet having corrosion resistance and blackening resistance and excellent adhesion of the organic resin film when the steel sheet is deformed, and a method for producing the same. .

Claims (3)

An organic resin-coated phosphating treatment in which a galvanized steel sheet is treated with a phosphating solution to form a phosphate film on the surface of the galvanized steel sheet, and an organic resin film is formed on the phosphate film. A method for producing a galvanized steel sheet,
The phosphate treatment solution contains Zn ²⁺ : more than 2.0 g / L and 5.0 g / L or less, Mg ²⁺ : 2.0 to 5.0 g / L, and the concentration of Mg ²⁺ with respect to Zn ²⁺ The ratio Mg2 ⁺ / Zn2 ⁺ in the range of 0.4 to 2.5, and the ratio of the free acidity to the total acidity in the treatment solution is 0.020 or more and less than 0.15 Manufacturing method of a galvanized steel sheet. The surface of the galvanized steel sheet has Mg: 0.2% by mass or more and less than 2.0% by mass, and has a phosphate coating with an adhesion amount of 0.2 to 1.0 g / m ² , and the phosphate coating is organic. The organic resin-coated phosphate-treated zinc-based plated steel sheet produced by the method for producing an organic resin-coated phosphate-treated zinc-based plated steel sheet according to claim 1, which has a resin film.   The organic resin-coated phosphate-treated zinc-based plated steel sheet according to claim 2, wherein the thickness of the organic resin film is 100 µm or more.