JPH05171457A - Organic composite type alloying galvannealed steel sheet - Google Patents

Abstract

PURPOSE:To improve a bare corrosion resistance, adhesion and coating suitability of a steel sheet by specifying the compsn. in a plating layer or specifying the roughness, grain size or the like on the surface of the plating layer in the case of low iron, furthermore limiting specified alloy elements in the plating layer and their content and applying it with specified colloid-contg. organic resin. CONSTITUTION:On the surface of a steel sheet, a galvannealing layer in which the average iron content in the plating layer is regulated to, by weight, 8 to 15% and Al content is regulated to 0.1 to 0.5% or the iron content is regulated to 1 to 8% as well as 0.1 to 2% in the topmost surface layer and the Al content is regulated to 0.1 to 0.5% and the average roughness on the surface of the plating layer is regulated to 2.2 to 3.5mu and the average grain size is regulated to 50 to 200mu is formed. In the galvanizing layer, 0.01 to 5% of one or more kinds of alloy elements among Mg, Sb or the like may be incorporated. The surface of the plating layer is coated with chromate by 10 to 150mg/m<2> as Cr content, which is coated with an organic film obtd. by incorporating colloids of SiO2, Cr2O3 or the like having 1 to 12mum grain size by 5 to 100 pts. to 100 pts. resinous solid content into water-base resin having 10 to 200mu grain size such as ethylene-acrylic acid copolymer resin, poly(meta)acrylic acid and its copolymer resin or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alloyed molten Z compounded with an organic resin excellent in bare corrosion resistance, adhesiveness, paintability and workability.
It relates to an n-plated steel sheet.

[0002]

2. Description of the Related Art Alloyed hot-dip galvanized steel sheets are already known as surface-treated steel sheets for automobiles, building materials, and home appliances, which are excellent in coating film adhesion, corrosion resistance after coating, and the like. In recent years, in particular, the demand for surface-treated steel sheets having excellent corrosion resistance has become stronger and stronger, and it is considered that this tendency will increase in the future. Various surface-treated steel sheets have been proposed to meet this demand, but recently, Japanese Patent Publication No. 61-287.
As disclosed in Japanese Patent No. 51, a method for surface treatment of an alloyed Zn-plated steel sheet is proposed, in which after performing a chromate treatment on the alloyed Zn-plated steel sheet, chromium containing an aqueous solution of a water-soluble organic substance is further applied. There is.

[0003]

The alloyed hot-dip galvanized steel sheet is often used after being coated, but it may be used in an uncoated state for the purpose of omitting the coating process. Further, since the coating does not go around in the portion where the steel plates are joined together or the portion having the bag structure, the unpainted portion remains, so that the bare corrosion resistance is particularly important. On the other hand, as a method of improving the corrosion resistance, there is a method of performing chromate treatment on the steel sheet. However, since rust preventive oil is applied for the purpose of rust prevention of the steel plate after shipping, and press oil is applied during the forming process of the steel plate, degreasing containing caustic soda or caustic potash as the main component in the process before coating. These oils are removed by the agent. At this time, the degreasing agent elutes the chromate coating applied to the galvannealed steel sheet, which deteriorates the corrosion resistance and the coating property. For the purpose of solving this problem, Japanese Patent Publication 6
Japanese Patent Laid-Open No. 1-28751 proposes a surface treatment method for an alloyed hot-dip galvanized steel sheet in which a non-etching chromate treatment containing a water-soluble organic substance is performed after the etching chromate treatment. Alloyed molten Z produced by this method
Although the corrosion resistance of n-plated steel sheet is improved compared to the conventional one, the chromate film containing organic substances still elutes, and the elution amount is large depending on the degreasing conditions. As a result, the degreasing conditions partially differ. In such a case, the amount of chromium eluted in the same coil is different, which causes a difference in corrosion resistance. Further, since chromium is eluted, there is a problem of wastewater treatment accompanying this. Further, it has been known that when the steel sheet is processed by press forming, the chromate film is destroyed and the bare corrosion resistance after processing has almost no effect of chromate, and there is a problem in the powdering property due to peeling of the plating during processing. As described above, the alloyed hot-dip galvanized steel sheet produced by the conventional technique is insufficient in terms of bare corrosion resistance before processing, bare corrosion resistance after processing, workability, and wastewater treatment.

[0004]

Therefore, the present inventors have
In order to solve the above problems, the composition or structure of the lower alloyed hot-dip Zn coating layer was changed variously, and various combinations of the upper layer chromate deposition amount and the type of the organic resin on the chromate were examined, and the alloyed hot melt The composition in the Zn plating layer is in the range of 8 to 15% of Fe and 0.1 to 0.5% of Al, or even if the Fe content is as low as 1 to 8%, the average roughness of the plating layer surface and the crystal grains. By limiting the specific range of diameter, etc., as well as the specific alloying elements and content that coexist in the plating layer, the bare corrosion resistance and workability of the plating layer are secured, and a specific amount of chromate and chromate is added to this upper layer. A specific organic resin containing a specific colloid is applied on the top to suppress the elution of chromium, suppress the entry of corrosion factors into the chromate film and plating layer, and also to the plating layer and chromate layer during processing. By protecting the
It was found that even with the same amount of chromate as in JP-A 1-28751, excellent corrosion resistance is exhibited, and workability, adhesion, and paintability are remarkably improved. The present invention provides an organic composite type alloyed hot dip galvanized steel sheet excellent in bare corrosion resistance, workability, adhesiveness and coatability by applying a chromate and an organic film layer on the alloyed hot dip galvanized steel sheet as described above. To do.

The present invention is based on the average Fe in the plating layer on the surface of the steel sheet.
On the surface of the hot-dip Zn coating layer or the steel sheet having a content rate of 8 to 15% and an Al content of 0.1 to 0.5%, F in the plating layer
e content is 1 to 8% on average in the plated layer and 0.1 to 0.1 in the outermost layer
2%, Al content is 0.1-0.5% on average in the plating layer
And the average roughness Ra of the plating layer surface is 2.2 to 3.5.
μm, fused Zn having an average crystal grain size of 50 to 200 μm
The lowermost layer is a molten Zn plating layer containing 0.01 to 5% of Mg, Sb, Pb, Ti, Sn alone or in combination as an alloying element in the plating layer or the described Zn plating layer, and the amount of chromium is 10 ~ 150 mg / m ² chromate-coated steel sheet with ethylene / acrylic acid copolymer resin, polyacrylic acid and its copolymer resin, polyacrylic acid ester and its copolymer resin and polymethacryl having a particle diameter of 10 to 200 mμ One or more aqueous organic resin dispersions of an aqueous organic resin dispersion of an acid and a copolymer resin thereof, a polymethacrylic acid ester and a copolymer resin thereof, and a copolymer resin of bisphenol A and the acrylic resin. the solid content 100 parts by weight of the body, SiO ₂ particle size of 12mμ from _{1mμ, Cr 2 O 3, Fe} 2 O 3, Fe 3 O 4, Mg
Bare corrosion resistance is obtained by coating one or more colloids (sols) of O, ZrO ₂ , SnO ₂ , Al ₂ O ₃ , and Sb ₂ O ₅ with an organic film containing 5 to 100 parts by weight of solid content. , The workability, the adhesion, and the paintability are remarkably improved.

The present invention will be described in detail below. First, the structure of the plating layer will be described. Within this range, the average Fe content in the plating layer is set to 8 to 15%.
This is because the plated layer itself has the best corrosion resistance (blister resistance of the scratched portion) and workability (powdering resistance) after coating. If it is less than 8%, the corrosion resistance after coating will be somewhat insufficient, and if it exceeds 15%, the alloying of the plating layer will proceed too much, and the Γ phase (Fe ₅ Zn ₂₂ ) at the base iron interface will develop too much. Becomes insufficient. A in the plating layer
The appropriate amount of l is 0.1 to 0.5%. Al in the plating layer changes depending on the amount of Al added to the molten Zn bath, and Al combines with the base iron during the plating reaction to form a Fe-Al-Zn ternary barrier layer that is strong against the Zn-Fe alloying reaction. Known to form. When Al in the plating layer is less than 0.1%, the Fe—Al—Zn barrier layer is not sufficiently formed, and the Γ phase of the alloy layer develops too much, resulting in poor plating adhesion. Further, when it exceeds 0.5%, Zn-
Fe alloying is difficult to proceed. Further, even if Fe in the plating layer is in the range of 1 to 8% on average in the plating layer, Fe in the surface layer portion of the plating layer is 0.1 to 2% and Al content is 0.1 in the plating layer on average. ~ 0.5%, average roughness Ra of the plating layer surface
Is 2.2 to 3.5 μm, and the average crystal grain size is 50 to 200 μm.
In the case of m, the corrosion resistance after coating is good. Further, as alloy elements in the plating layer, Mg, Sb, Pb,
In the case of containing 0.01 to 5% of Ti and Sn alone or in combination, particularly the corrosion resistance after coating is further improved, and these trace elements form a corrosion product of Zn under the coating film in a corrosive environment. It is considered that this is due to the effect of stabilizing and suppressing the cathode reaction.

Next, the chromate layer and the organic layer will be described. The deposition amount of Cr was 10-150 mg / m ^2, when the Cr content is 10 mg / m ² or less, since it is impossible to sufficiently cover the material, it is impossible to organic coating to ensure a strong bond strength The part that comes into contact with the plating base appears, and the adhesion of the organic film is reduced.
This is because if the amount exceeds mg / m ² , the chromate film itself causes cohesive failure, resulting in a total decrease in adhesion. As the chromate treatment, a coating type, a reaction type, an electrolytic type or the like can be used. The organic layer is composed of colloid and organic resin. Examples of the organic resin include ethylene / acrylic acid copolymer resin, polyacrylic acid and its copolymer resin, polyacrylic acid ester and its copolymer resin,
Polymethacrylic acid and its copolymer resin, polymethacrylic acid ester and its copolymer resin, bisphenol A
And a copolymer resin of the above acrylic resin is suitable,
In order to stably coexist with the colloid, it must be an emulsion, dispersion or water-soluble water-based organic resin in which the solvent is water. The particle size of the organic resin is 10
It is suitable that the particle size is 200 mμ and the particle size of the colloid is 1 to 12 mμ. If the resin particle diameter exceeds 200 mμ and the colloid particle diameter exceeds 12 mμ, the total surface area of the resin and the colloid becomes small, so that the bonding force between the resin and the resin, the resin and the colloid, and the colloid and the chromate becomes weak. For this reason, the organic coating becomes brittle, and the bare corrosion resistance and the adhesiveness when unprocessed are reduced. Furthermore, since the organic film peels off during processing due to the decrease in adhesion, build-up of the film on the molding die occurs, and bare corrosion resistance after processing decreases. Further, when the particle size of the resin is less than 10 mμ and the particle size of the colloid is less than 1 mμ, although the mechanism is not clear, bare corrosion resistance in unprocessed deteriorates. The amount of colloid added is 5 to 100 parts of the coexisting organic resin.
100 parts is appropriate. If the amount is less than 5 parts, the bonding strength between the colloid and the chromate is weak, so that the adhesiveness is lowered and the corrosion resistance and the processability are greatly affected. Further, if it exceeds 100 parts, it is considered that this is due to the polarity of the colloid, especially in a humid environment, but as a result of the increased water absorption, the adhesion between the chromate layer and the organic layer decreases. The effects of the colloid described above are SiO ₂ , Cr ₂ O ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ , and Mg.
The same applies to O, ZrO ₂ , SnO ₂ , Al ₂ O ₃ , and Sb ₂ O ₅ , and the kind of colloid is not particularly limited.

The base steel sheet can be a hot-rolled steel sheet or a cold-rolled steel sheet, and may be an Al-killed steel sheet, an Al-Si-killed steel sheet, or a T-rolled steel sheet.
i-added ultra-low carbon steel sheet, P-Ti-added ultra-low carbon steel sheet, high S
Materials such as i and Mn-based high-tensile steel plates can be applied. Further, as the hot-dip Zn plating method, various methods such as a normal Sendzimer method, a non-oxidizing furnace method, and a flux method can be used. Although the present invention has been described with respect to the plating layer and the chromate layer / organic layer, respectively, the present invention finds excellent bare corrosion resistance, workability, and adhesion by finding the individual effects of these layers and their synergistic effects. It is intended to provide a surface-treated steel sheet that retains paintability.

The present invention will be specifically described below. Hot-rolled steel sheet was used as a base, and hot-dip Zn coating was performed at a coating amount of 60 g / m ² . After hot-dip galvanizing, it is allowed to cool, alloyed and then sprayed with water, or at 470-520 ° C for 1-
Alloying treatment was performed within a range of 40 seconds to produce various alloyed hot-dip galvanized steel sheets. Chromate treatment was performed on the alloyed hot-dip Zn-plated steel sheet thus produced, and then dried to apply an organic coating of 1.0 g / m ² . In FIG. 1, the average Fe content in the plating layer is 8.1%, A
l content 0.4%, chromium adhesion amount 72.8 mg / m ² ,
Ethylene-acrylic acid copolymer 100 having a particle size of 93 mμ
A sample obtained by applying an organic resin containing 30 parts of 5 mμ colloidal silica to the solid weight part and a plating layer were similarly prepared according to JP-B-61-28751 (first-stage chromate: 58). Chromium elution amount when 3 mg / m ² , second-stage chromate: 72.1 mg / m ² ) was immersed in a bath of Ridrin 270TO (trade name, manufactured by Nihon Parkerizing Co., Ltd.) at a liquid temperature of 60 ° C. showed that. As shown in the figure, in the sample according to the present invention, chromium was not eluted even if the degreasing time was changed, and the chromate film was retained. However, in the sample according to Japanese Patent Publication No. 61-28751, the longer the degreasing time, the longer the degreasing time. Chromium is eluted, and it can be seen that in the present invention, there is no drainage problem associated with the elution of chromium.

FIG. 2 shows the adhesion of the coating when the treatment was carried out under the same conditions as above and only the amount of chromium deposited was changed. 3 to 11 are treated under the same conditions as above (however, the chromium deposition amount is 68 to 76 mg /
m ² ), resin particle size, colloidal silica particle size, and number of parts of colloidal silica added were changed to show bare corrosion resistance after processing, paint adhesion and processability. 12 and 13 show the corrosion resistance and workability after coating when the average Fe content in the plating layer was changed by performing the treatment under the same conditions as described above. FIG. 14 shows the workability when the treatment was performed under the same conditions as above and the average Al content in the plating layer was changed. FIG. 15 shows the corrosion resistance after coating when the treatment was performed under the same conditions as above, Mg was added as an alloying element to the plating layer, and the content rate was changed. Further, for the condition of claim 2 of the present invention,
Average crystal grain size, average roughness (Ra), Fe in plating surface layer
Content, average Al content in plating layer, average F in plating layer
Corrosion resistance after coating when the content of e was changed is shown in FIGS. 16 to 20.

Regarding the evaluation of the adhesion of the film, the test piece was dipped in boiling water for 30 minutes, and then the film was cut at 2 mm intervals and the tape was peeled off. ◎, ○, △, ×, ×
The evaluation was made in 5 grades of x, and ⊚ is the best. ◎: Film peeling area 0% ○: Film peeling area 0 to 1% △: Film peeling area 1 to 10% ×: Film peeling area 10 to 50% XX: Film peeling area 50% or more

Regarding the corrosion resistance after processing, the test piece was dipped in the above-mentioned Rydrin 270TO for 120 seconds and then pressed to check the corrosion resistance of the processed portion. Evaluation is JIS-Z-23
According to the salt spray test according to the standard of 71,
%, In-bath temperature 35 ° C., spray pressure 20 psi) The rusting condition after 5000 hours was investigated and evaluated in 5 grades of ◎, ○, △, ×, XX, and ◎ is the best. ◎: Red rust occurrence 0% ○: Red rust occurrence 0 to 1% △: Red rust occurrence 1 to 10% ×: Red rust occurrence 10 to 50% XX: Red rust occurrence 50% or more

For the evaluation of paint adhesion, a melamine-based paint was applied to a thickness of 20 μm, drawn according to JIS-K-5400, and each test of scoring, elixir, impact, and 2T bending was performed. In addition, in the burdock eye Erichsen test, the sample after being immersed in warm water at 50 ° C. for 240 hours was also evaluated. The evaluation was made in five grades of ⊚, ○, Δ, ×, and XX, and ⊚ is the best. ◎: coating film peeling area 0% ○: coating film peeling area 0 to 1% △: coating film peeling area 1 to 10% ×: coating film peeling area 10 to 50% xx: coating film peeling area 50% or more

Regarding the evaluation of the corrosion resistance after coating, a melamine-based paint was coated to a thickness of 20 μm, a cross cut reaching the base of the coated steel sheet was inserted, and then a salt spray test in accordance with the standard of JIS-Z-2371 was applied to determine the alloy elements. The blister resistance of the cross-cut portion was evaluated after 840 hours for the effect and after 672 hours for the other. Evaluation is ◎, ○,
The evaluation was made in 5 grades of Δ, ×, and XX, and ◎ is the best. ◎: Blister width 3 mm or less ○: Blister width 3 to 4 mm or less Δ: Blister width 4 to 5 mm or less ×: Blister width 5 to 6 mm or less XX: Blister width 6 mm or more

For workability, continuous pressing was performed 500 times, and the build-up property and mold galling property of the coating on the way were investigated.
The evaluation was made in 5 grades of ○, △, ×, and XX, and ◎ is the best. ◎: After 500 continuous presses, no build-up or powdering, no mold galling ○: 400-500 continuous presses, no build-up or powdering, no mold galling △: 200-400 continuous presses, build-up Or partial powdering, partial mold galling, ×: Build-up after 100 to 200 times of continuous press, or build-up or partial powdering, partial mold galling XX: Continuous press after 0 to 200 times, build-up Or part of powdering, part of mold scraping

As is clear from FIG. 2, when the amount of chromium deposited is less than 10 mg / m ² or more than 150 mg / m ² , the adhesion of the coating tends to be slightly lowered. As is clear from FIG. 3, the corrosion resistance after coating changes depending on the resin particle size,
When the particle size is 10 to 200 mμ, it shows excellent corrosion resistance after processing, and when it is less than 10 mμ or exceeds 200 mμ,
Corrosion resistance is reduced after processing. As is clear from FIG. 4, the paint adhesion varies depending on the resin particle size, and the particle size is 10 to 20.
When it is less than 10 mμ or more than 200 mμ, the paint adhesion is significantly reduced. As is apparent from FIG. 5, the continuous workability (pressability) changes depending on the resin particle size, and the particle size is 10 to 200.
When it is less than 10 mμ or more than 200 mμ, the workability is significantly reduced and buildup occurs.

As is clear from FIG. 6, the corrosion resistance after processing varies depending on the particle size of the colloidal silica.
When μ, the corrosion resistance after processing is extremely excellent, and when it is less than 1 mμ or more than 12 mμ, the corrosion resistance after processing decreases.
As is clear from FIG. 7, the coating adhesion varies depending on the particle size of the colloidal silica, and the coating adhesion is extremely excellent at 1 to 12 mμ, and the coating adhesion decreases when it is less than 1 mμ or more than 12 mμ. As is clear from FIG. 8, the continuous workability changes depending on the particle size of the colloidal silica, and when the particle size is 1 to 12 mμ, the workability is extremely excellent, and when the particle size is less than 1 mμ or more than 12 mμ, the workability decreases, Build up. As is clear from FIG.
Corrosion resistance after processing changes depending on the number of parts of colloidal silica added, and excellent corrosion resistance after processing is exhibited at 5 parts or more, and corrosion resistance after processing is reduced when it is less than 5 parts.

As is clear from FIG. 10, the coating adhesion varies depending on the number of parts of colloidal silica added, and it is 5 to 10
Excellent paint adhesion at 0 parts, less than 5 parts or 10 parts
If it exceeds 0 part, the adhesiveness of the coating material is significantly reduced. 11
As is clear from the above, the continuous workability changes depending on the number of added parts of colloidal silica, and excellent workability is exhibited at 5 to 100 parts, and if less than 5 parts or more than 100 parts, the workability decreases and buildup occurs. .. As is clear from FIG. 12, the corrosion resistance after coating changes depending on the average Fe content in the plating layer, and 8% or more shows excellent corrosion resistance after coating,
If it is less than 1, the corrosion resistance after coating is lowered. As is clear from FIG. 13, continuous workability changes depending on the average Fe content in the plating layer, and excellent workability is exhibited at 15% or less.
If it exceeds 5%, workability deteriorates and powdering occurs. As is clear from FIG. 14, the continuous workability changes depending on the average Al content in the plating layer, showing excellent workability at 0.1 to 0.5%, and less than 0.1% or more than 0.5%. Then, the workability deteriorates and powdering occurs. As is clear from FIG. 15, the corrosion resistance after coating changes depending on the Mg content in the plating layer, and 0.01 to 5% shows excellent corrosion resistance after coating, and when it is less than 0.01% or more than 5%, Corrosion resistance decreases after painting.

As is clear from FIG. 16, the corrosion resistance after coating varies depending on the average grain size of the plated layer, and the average grain size of the plated layer varies from 50 to 20.
When 0 μm, excellent corrosion resistance after coating is exhibited, and when it is less than 50 μm or more than 200 μm, the corrosion resistance after coating decreases.
As is clear from FIG. 17, the corrosion resistance after coating changes depending on the average roughness of the plating layer, and shows excellent corrosion resistance after coating at 2.2 to 3.5 μm, which is less than 2.2 μm or 3.5 μm.
If it exceeds m, the corrosion resistance after coating is lowered. As is clear from FIG. 18, the corrosion resistance after coating changes depending on the Fe content in the plating surface layer portion, and shows excellent corrosion resistance after coating at 0.1 to 2%, and when less than 0.1% or more than 2%, Corrosion resistance decreases after painting. As is clear from FIG. 19, the corrosion resistance after coating changes depending on the Al content in the plating layer, and
If the content is less than 0.1% or more than 0.5%, the corrosion resistance after coating is deteriorated. As is clear from FIG. 20, the corrosion resistance after coating changes depending on the Fe content in the plating layer, and excellent corrosion resistance after coating is exhibited at 1 to 8%, and if it is less than 1%, the corrosion resistance after coating is reduced.

[0020]

EXAMPLES Table 1 shows examples of steel sheets obtained under the conditions of the plating layer, the chromate layer and the organic layer of the present invention. The manufacturing method and the evaluation method are the same as the methods described in the section specifically describing the present invention. * Indicates a sample that deviates from the conditions of the present invention. Further, * is a comparative material produced according to Example 1 of Japanese Examined Patent Publication No. 61-28751. No. 1 to
As shown in No. 44, in the organic composite type alloyed hot dip galvanized steel sheet satisfying the conditions of the present invention, No. Compared with the conventional hot-dip galvannealed steel sheet shown in No. 56, it is clear that the bare corrosion resistance, the paint adhesion, and the post-coating corrosion resistance are all significantly improved. As shown in Nos. 45 to 55, in the case of a plated steel sheet that deviates from the conditions of the present invention, all of the above performances are inferior. In addition, No. 57-59, a non-etching chromate treatment containing a water-soluble organic substance is performed after the etching chromate treatment.
Alloyed fused Zn produced by the method of 1-28751
It can be seen that the above performance is remarkably improved as compared with the plated steel sheet.

[0021]

[Table 1A]

[0022]

[Table 1B]

[0023]

[Table 1C]

[0024]

[Table 1D]

[0025]

As described above, the organic composite type alloyed hot dip galvanized steel sheet according to the present invention has unprecedented bare corrosion resistance,
Since it has paint adhesion and corrosion resistance after painting, its industrial significance is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between degreasing time and chromium elution amount,

FIG. 2 is a diagram showing the adhesion of the film when the amount of deposited chromium is changed,

[Figure 3]

FIG. 11 is a diagram showing bare corrosion resistance after processing, coating adhesion and processability when the resin particle size, the colloidal silica particle size, and the number of colloidal silica added parts are changed,

FIG. 12 is a diagram showing corrosion resistance and workability after coating when the average Fe content in the plating layer is changed,

FIG. 13 is a diagram showing corrosion resistance and workability after coating when the average Fe content in the plating layer is changed,

FIG. 14 is a diagram showing workability when the average Al content in the plating layer is changed,

FIG. 15 is a diagram showing that Mg is added as an alloying element in the plating layer,
Diagram showing the corrosion resistance after coating when changing this content rate,

FIG. 16

FIG. 20 shows the average crystal grain size,
It is the figure which showed the corrosion resistance after coating when changing average roughness (Ra), Fe content of a plating surface layer part, average Al content rate in a plating layer, and average Fe content rate in a plating layer, respectively.

Claims (3)

[Claims] 1. A molten Zn plating layer having an average Fe content of 8 to 15% and an Al content of 0.1 to 0.5% in the plating layer on the surface of a steel sheet is the lowermost layer, and the amount of chromium is 10 to 15%.
10 to 200 on 0 mg / m ² chromate-coated steel sheet
Ethylene acrylic acid copolymer resin, polyacrylic acid and its copolymer resin, polyacrylic acid ester and its copolymer resin, polymethacrylic acid and its copolymer resin, polymethacrylic acid ester and their of mμ particle size 1% of one or two or more aqueous organic resin dispersions of an aqueous organic resin dispersion of a copolymer resin, a copolymer resin of bisphenol A and the above acrylic resin, relative to 100 parts by weight of the solid content of 1
SiO ₂ , Cr ₂ O ₃ , Fe ₂ O with a particle size of mμ to 12 mμ
₃ , Fe ₃ O ₄ , MgO, ZrO ₂ , SnO ₂ , Al ₂ O ₃ ,
An organic composite-type alloyed hot-dip Zn-plated steel sheet, characterized in that one or more Sb ₂ O ₅ colloids (sols) are coated with an organic coating containing 5 to 100 parts by weight of solid content. 2. The Fe content in the plating layer on the surface of the steel sheet is 1 to 8% on average in the plating layer, 0.1 to 2% in the outermost layer, and Al.
A hot-dip Zn plating layer having an average content of 0.1 to 0.5% in the plating layer, an average roughness Ra of the plating layer surface of 2.2 to 3.5 μm, and an average crystal grain size of 50 to 200 μm. As the lowermost layer, and the amount of chromium is 10 to 150 mg / m ²
Chromate-coated steel sheet having a particle size of 10 to 200 μm, ethylene acrylic acid copolymer resin, polyacrylic acid and its copolymer resin, polyacrylic acid ester and its copolymer resin, polymethacrylic acid and its copolymer resin,
To 100 parts by weight of solid content of one or two or more water-based organic resin dispersions of polymethacrylic acid ester and its copolymer resin, water-based organic resin dispersion of copolymer resin of bisphenol A and the acrylic resin. On the other hand, from 1 mμ to 12
SiO ₂ , Cr ₂ O ₃ , Fe ₂ O ₃ , Fe with mμ particle size
₃ O ₄ , MgO, ZrO ₂ , SnO ₂ , Al ₂ O ₃ , Sb ₂ O ₅
One or two or more of the colloids (sols) of 5 in solid content
An organic composite-type alloyed hot-dip Zn-plated steel sheet, which is coated with an organic coating containing 100 to 100 parts by weight. 3. The Zn plating layer according to claim 1 or 2, further comprising Mg, Sb, Pb, Ti and S as alloying elements.
Molten Z containing 0.01 to 5% of n alone or in combination
The n-plated layer is the bottom layer, and the chromium amount is 10 to 15
10 to 200 on 0 mg / m ² chromate-coated steel sheet
Ethylene acrylic acid copolymer resin, polyacrylic acid and its copolymer resin, polyacrylic acid ester and its copolymer resin, polymethacrylic acid and its copolymer resin, polymethacrylic acid ester and their of mμ particle size 1% of one or two or more aqueous organic resin dispersions of an aqueous organic resin dispersion of a copolymer resin, a copolymer resin of bisphenol A and the above acrylic resin, relative to 100 parts by weight of the solid content of 1
SiO ₂ , Cr ₂ O ₃ , Fe ₂ O with a particle size of mμ to 12 mμ
₃ , Fe ₃ O ₄ , MgO, ZrO ₂ , SnO ₂ , Al ₂ O ₃ ,
An organic composite-type alloyed hot-dip Zn-plated steel sheet, characterized in that one or more Sb ₂ O ₅ colloids (sols) are coated with an organic coating containing 5 to 100 parts by weight of solid content.