KR20170067834A - Method for manufacturing galvanized steel sheet - Google Patents

Abstract

The present invention provides a method of manufacturing a zinc-based plated steel sheet which is capable of removing oxides on the surface of a zinc-based plated layer by contact with an alkaline aqueous solution and avoiding apparent troubles due to precipitates precipitated in an alkaline aqueous solution. Method of manufacturing a zinc-based plated steel sheet according to the first invention for solving the aforementioned problems is a zinc-based method of manufacturing a coated steel strip having the reaction layer on the surface of the steel plate, the reaction layer is _{Zn 4 (SO 4) 1-} X (CO ₃ ) _X (OH) ₆ .nH ₂ O, and as the pretreatment for forming the reaction layer, an aqueous solution containing sodium gluconate, sodium gluconate, sodium citrate, tartaric acid, arabic acid, The zinc plated steel sheet is brought into contact with an alkaline aqueous solution containing at least 0.050 mass% of a total of at least one chelating agent selected from among sulfuric acid, sulfuric acid, sorbitol, mannitol, glycerin, EDTA and sodium tripolyphosphate in a total amount of not less than 1.0.0 and not less than 1.0 second.

Description

METHOD FOR MANUFACTURING GALVANIZED STEEL SHEET [0002]

The present invention relates to a method for producing a zinc-plated steel sheet having a reaction layer.

The galvanized steel sheet has been used for a wide range of purposes, mainly in automobile bodies, home appliances, and building materials. BACKGROUND ART With respect to zinc-plated steel sheets for such applications, there is known a technique for forming a reaction layer on the surface of a steel sheet to improve properties such as press molding, corrosion resistance and appearance.

However, the zinc-based plated steel sheet before forming the reaction layer has conventionally had an undesirable oxide layer such as Zn with a thickness of less than 10 nm on the outermost layer and Al, which is an impurity element. This unnecessary oxide layer hinders the reactivity of the conversion treatment such as, for example, zinc phosphate treatment or chromate treatment, and it is necessary to set a long reaction time in order to form a sufficient reaction layer.

The increase in the reaction time accompanies an increase in the equipment ratio and the line length, and also causes an increase in the running cost of electricity, gas and the like.

On the other hand, there is known a technique in which an unnecessary oxide layer present in the surface layer of a zinc-based plated steel sheet is removed by contacting it with an alkaline aqueous solution before forming the reaction layer, thereby shortening the reaction time.

Patent Document 1 discloses a technique in which a hot-dip galvanized steel sheet is brought into contact with an alkaline aqueous solution and then treated with a chromate solution containing SiO ₂ .

Further, there is also known a technique of intentionally forming an oxide film after treatment with an alkaline aqueous solution.

Patent Documents 2 and 3 disclose a technique in which a hot-dip galvanized steel sheet is brought into contact with an alkaline aqueous solution to form an oxide layer.

Patent Document 4 discloses a technique of forming an oxide layer after bringing the surface of an alloyed hot-dip galvanized steel sheet into contact with an alkaline aqueous solution.

Patent Document 5 discloses a method in which after the surface of a hot-dip galvanized steel sheet is brought into contact with an alkaline aqueous solution, an oxide containing a crystal structure represented by Zn ₄ (SO ₄ ) _{1 -X} (CO ₃ ) _X (OH) ₆ .nH ₂ O A layer forming method is disclosed.

Japanese Patent Application Laid-Open No. 5-279868 Japanese Laid-Open Patent Publication No. 2006-183074 Japanese Laid-Open Patent Publication No. 2006-233280 Japanese Patent Application Laid-Open No. 2005-97741 Japanese Patent Application No. 2015-530230

In the techniques of Patent Documents 1 to 5, the reaction time for forming the reaction layer by contact with the alkaline aqueous solution can be shortened. However, in a commonly used continuous treatment apparatus, deposits of Zn or Al precipitated in an alkaline aqueous solution are adhered to a deflector roll or a support roll, resulting in a pressed scratch on the surface of the steel sheet, and further appearance unevenness occurs after formation of the reactive layer Resulting in appearance problems.

The present invention has been made in view of such circumstances. There is provided a method of manufacturing a zinc-based plated steel sheet which can remove an unnecessary oxide layer on the surface of a zinc-based plated layer by contact with an alkaline aqueous solution and can avoid apparent troubles due to precipitates precipitated in an alkaline aqueous solution .

The inventors of the present invention have conducted intensive studies in order to solve the above problems. As a result, it has been found that the above problems can be solved by adding a specific chelating agent to the alkaline aqueous solution used before forming the reaction layer, thereby completing the present invention. More specifically, the present invention provides the following.

Method of manufacturing a zinc-based plated steel sheet according to the first invention for solving the aforementioned problems is a zinc-based method of manufacturing a coated steel strip having the reaction layer on the surface of the steel plate, the reaction layer is _{Zn 4 (SO 4) 1-} X (CO ₃ ) _X (OH) ₆ .nH ₂ O, and as the pretreatment for forming the reaction layer, an aqueous solution containing sodium gluconate, sodium gluconate, sodium citrate, tartaric acid, arabic acid, Characterized in that the zinc-plated steel sheet is contacted with an alkaline aqueous solution having a pH of not less than 10.0 for not less than 1.0 seconds in total not less than 0.050 mass% in total of at least one chelating agent selected from the group consisting of sulfuric acid, nitric acid, sulfuric acid, sorbitol, mannitol, glycerin, EDTA and sodium tripolyphosphate .

A method of manufacturing a zinc-plated steel sheet according to a second invention for solving the above-mentioned problems is characterized in that the alkaline-based aqueous solution has a pH of 12.6 or more.

According to the present invention, it is possible to satisfactorily remove the oxide on the surface of the zinc-based plated layer by contact with the alkaline aqueous solution. Further, in the alkali treatment for shortening the reaction layer formation time, precipitates of Al and Zn can be reduced, and a zinc-based plated steel sheet having a reaction layer having a good appearance can be obtained.

Fig. 1 is a schematic diagram showing evaluation criteria for evaluating appearance unevenness.

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments. In the present invention, the zinc plated steel sheet is a steel sheet having a coating mainly composed of zinc on the surface of the steel sheet regardless of the manufacturing method, and includes a galvanized steel sheet, a zinc alloy coated steel sheet and a coated steel sheet in which particles are dispersed in zinc do. That is, the zinc plated layer includes a zinc plated layer, a zinc alloy plated layer, a plated layer in which particles are dispersed in zinc, and the like.

The present invention relates to a method of manufacturing a semiconductor device, which comprises a reaction layer capable of satisfactorily removing an unnecessary oxide layer present on the surface of a zinc-based plated layer, that is, Zn ₄ (SO ₄ ) _{1 -X} (CO ₃ ) _X (OH) ₆ .nH ₂ O Wherein the oxide layer contains a crystal structure showing a crystal structure showing a crystal structure. The present invention relates to a method for manufacturing a semiconductor device, which comprises, for example, a step of performing zinc plating, a step of bringing into contact with an alkaline aqueous solution, a step of forming a crystal represented by Zn ₄ (SO ₄ ) _{1 -X} (CO ₃ ) _X (OH) ₆ .nH ₂ O And a step of forming an oxide layer containing the structure. Each step will be described below.

- Process to conduct zinc plating -

First, the process of zinc plating is described. In the step of zinc plating, the method of zinc plating is not particularly limited, and general methods such as hot dip galvanizing and electro-galvanizing may be employed. The conditions for the treatment of electro-galvanizing and hot-dip galvanizing are not particularly limited, and any suitable conditions may be employed as appropriate. Further, in the case of performing hot dip galvanizing, it is preferable that Al is added to the plating bath from the viewpoint of dealing with the dross. In this case, an element component other than Al is not particularly limited. That is, even if Pb, Sb, Si, Sn, Mg, Mn, Ni, Ti, Li, Cu and the like are contained in addition to Al, the effect of the present invention is not impaired.

Here, the type of steel of the steel sheet to be galvanized is not particularly limited, and various steel sheets such as low carbon steel, ultra low carbon steel, IF steel, and high tensile steel with various alloying elements can be used. The steel sheet may be a hot-rolled steel sheet or a cold-rolled steel sheet. The thickness of the steel sheet is not particularly limited. Further, it is preferably 0.4 to 5.0 mm from the viewpoint of use for automobile bodies, household electrical appliances, building materials and the like.

Further, in the step of zinc-based plating, an alloyed hot-dip galvanized steel sheet subjected to galvannealing after hot-dip galvanizing may be used. In the present invention, the conditions of the alloying treatment are not particularly limited, and suitable conditions may be appropriately employed.

- contacting with an alkaline aqueous solution -

After zinc plating, a contact treatment using an alkaline aqueous solution is carried out. The alkaline aqueous solution used in this contact treatment has a pH of 10.0 or more. When the pH is less than 10.0, removal of the oxide layer becomes insufficient. When the pH is 12.6 or more, the contact time with the alkaline aqueous solution can be shortened, which is effective and preferable.

On the other hand, from the viewpoints of prevention of dissolution of the zinc plated layer and prevention of blackening of the surface appearance, the pH is preferably 14.0 or less.

The alkaline aqueous solution contains a total of 0.050 mass% or more of a specific chelating agent. When precipitates of Al or Zn in the alkaline aqueous solution increase, the appearance of the liquid becomes a suspension phase. In the present invention, 0.050 mass% or more of a chelating agent is contained in an alkaline aqueous solution to reduce precipitates of Al and Zn.

The chelating agent is at least one selected from the group consisting of sodium gluconate, sodium gluconate, sodium citrate, tartaric acid, arabic acid, galactonic acid, sorbitol, mannitol, glycerin, EDTA and sodium tripolyphosphate. From the viewpoint that it is possible to chelate Al and Zn and from an inexpensive point of view, the chelating agent is preferably sodium gluconate.

If the content of the chelating agent in the alkaline aqueous solution is less than 0.050 mass% in total, increase in solubility of Al or Zn in the alkaline aqueous solution becomes insufficient. From the viewpoint of reducing the precipitate in the alkaline aqueous solution, the amount of the chelating agent contained in the alkaline aqueous solution is preferably 0.100 mass% or more. On the other hand, the amount of the chelating agent contained in the alkaline aqueous solution is preferably 10.0 mass% or less from the viewpoint of pharmaceutical cost.

From the viewpoint of shortening the contact time between the alkaline aqueous solution and the steel sheet, the temperature of the alkaline aqueous solution is preferably in the range of 20 ° C to 70 ° C, more preferably 40 ° C to 70 ° C.

The type of alkali builder is not limited. From the viewpoint of cost reduction, it is preferable to use a chemical such as NaOH. In order to realize the pH of the desired alkaline aqueous solution, the alkali builder amount is appropriately adjusted. The alkaline aqueous solution may contain a substance other than the element contained in the zinc-based plating solution such as Zn, Al, Fe, or other components.

The method of bringing the alkaline aqueous solution into contact with the zinc plated steel sheet (particularly, the oxide layer of the surface layer thereof) is not particularly limited, and a method of contacting the zinc plated steel sheet with an alkaline aqueous solution and contacting the same, or a method of spraying an alkaline aqueous solution, And the like.

The time for which the zinc plated steel sheet is brought into contact with the alkaline aqueous solution is 1.0 second or more. If the contact time is less than 1.0 second, the oxide on the surface of the zinc-based plated layer can not be sufficiently removed, so that the reduction of the reaction time for forming the reaction layer becomes insufficient. From the viewpoint of facility cost and productivity, the time for which the zinc plated steel sheet is brought into contact with the alkaline aqueous solution is preferably 10.0 seconds or less.

In the present invention, after the step of zinc-based plating, temper rolling may be performed somewhere before or after the alkaline aqueous solution treatment. Since the unnecessary oxide layer of Al or Zn existing on the surface of the zinc-based plated layer is removed by contact with the roll at the portion of the steel sheet which is in contact with the temper rolling roll, the reactivity is increased.

- Step of forming reaction layer -

Usually, the steel sheet is contacted with an alkaline aqueous solution and then washed and dried. Thereafter, a reaction layer, that is, a crystal represented by Zn ₄ (SO ₄ ) _{1 -X} (CO ₃ ) _X (OH) ₆ .nH ₂ O A treatment for forming an oxide layer containing the structure is performed.

In the present invention, an oxide layer containing a crystal structure represented by Zn ₄ (SO ₄ ) _{1 -X} (CO ₃ ) _X (OH) ₆ .nH ₂ O is a layer in which a zinc- And thus a layer of the reaction product formed on the surface of the steel sheet. Examples of the treatment for forming an oxide layer containing a crystal structure represented by Zn ₄ (SO ₄ ) _{1 -X} (CO ₃ ) _X (OH) ₆ .nH ₂ O include a method in which a zinc- And the surface of the oxide layer formed in the oxide layer forming step is contacted with the alkaline aqueous solution for 0.5 seconds or more And thereafter, a neutralization treatment step of washing and drying is carried out. The alkaline aqueous solution may contain 0.01 g / L or more of P ion in terms of P concentration and 0.1 g / L or more in terms of carbonic acid ion concentration. In the present invention, a crystal structure represented by Zn ₄ (SO ₄ ) _{1 -X} (CO ₃ ) _X (OH) ₆ .nH ₂ O exists on the surface of the steel sheet, and the present invention is not limited thereto.

Example 1

Hereinafter, the present invention will be described by way of examples. The technical scope of the present invention is not limited to the following embodiments.

The cold-rolled steel sheet was subjected to hot-dip galvanizing to a steel sheet having a thickness of 0.7 mm and a width of 1100 mm. Subsequently, as a treatment for removing the oxide layer, the steel sheet was brought into contact with the alkaline aqueous solution adjusted under the conditions shown in Tables 1-1 and 1-2 for a specified time, washed with water and dried.

A hot rolled steel sheet obtained by performing hot dip galvanizing and alloying treatment on a cold rolled steel sheet having a thickness of 0.7 mm and a width of 1100 mm and a cold rolled steel sheet having a thickness of 0.7 mm and a width of 1100 mm, Plating treatment was also carried out in the same order as above with the alkaline aqueous solution, followed by washing with water and drying.

The zinc-plated steel sheet thus obtained was evaluated for the thickness of the unnecessary oxide layer on the surface of the zinc-based plated layer after the treatment with the alkaline aqueous solution and the appearance unevenness after the formation of the reaction layer to measure the appearance unevenness of the suspended material SS contained in the alkaline aqueous solution . Further, the pH of the alkaline aqueous solution was measured with a commercially available glass electrode.

Subsequently, as an oxide layer formation treatment containing a crystal structure represented by Zn ₄ (SO ₄ ) _{1 -X} (CO ₃ ) _X (OH) ₆ .nH ₂ O, 30 g / l of sodium acetate trihydrate The steel sheet was immersed in an acidic sulfuric acid solution adjusted to pH 1.5, kneaded with a roll, and then held for 10 seconds. Next, after being washed with water, it was dried. Subsequently, neutralization treatment was carried out with a treatment liquid containing 9.8 g / l sodium pyrophosphate and 0.48 g / l sodium carbonate decahydrate.

(1) Measurement of unnecessary thickness of oxide layer

A fluorescent X-ray analyzer was used for measurement of the thickness of the unnecessary oxide layer formed on the zinc plated steel sheet after contact with the alkaline aqueous solution. When the thickness of the oxide layer (oxide film thickness) is 4 nm or less, it can be estimated that the reaction time for forming the reaction layer is shortened. If it is 2 nm or less, it can be estimated that the reaction time is further shortened.

The voltage and current of the tube at the time of measurement were 30 kV and 100 mA, and the spectroscopic crystal was set to TAP to detect the O-Kα line. At the time of measuring the O-K alpha line, the intensity at the background position was measured in addition to the peak position, so that the intensity of the O-K alpha line could be calculated. The integration time at the peak position and the background position was 20 seconds, respectively.

In the sample stage, a series of samples and a silicon wafer having a 96 nm, 54 nm, and 24 nm thick silicon oxide film, which were cleaved to an appropriate size, were set. From these silicon oxide films, O- So that the strength of the wire can be calculated. Calibration curves of the oxide layer thickness and the O-K alpha ray intensity were made using these data, and the thickness of the oxide layer of the disclosed material was calculated as the oxide layer thickness in terms of the silicon oxide coating.

(2) Evaluation of appearance unevenness and oxide film thickness after surface oxidation treatment

A hot-dip galvanized steel sheet, a galvannealed galvanized steel sheet, and an electro-galvanized steel sheet which had been subjected to a contact treatment with an alkaline aqueous solution were subjected to a treatment for forming an oxide layer on the surface, and appearance unevenness was evaluated by visual observation and microscopic observation. That is, a solution prepared by adjusting an aqueous solution containing 5.0 g / l of ferrous sulfate and 50 g / l of sodium acetate · tetrahydrate to pH 2.0 with sulfuric acid was prepared, and the resulting solution was contacted with an alkaline aqueous solution Coated steel sheet so as to have a thickness of 3 占 퐉 and maintained for 10 seconds, followed by washing with water and drying to form an oxide layer. The observation area is 70 mm x 150 mm. Evaluation was made by assigning a rating of 1 to 5 on the basis of the appearance sample shown in Fig. 4 points are good, and 5 points are better.

(3) Measurement of suspended solids (SS)

Alkaline aqueous solution after 100 t treatment of zinc plated steel sheet was collected and subjected to suction filtration using a membrane filter having a pore size of 1 탆. The filtrate was dried at 110 DEG C and then weighed and converted into mg / l. A production amount exceeding 10 mg / L was recorded. If the throughput of the steel sheet exceeding 10 mg / L is 3000 t or more, it can be evaluated as good in terms of productivity. After 5,000 t treatment, no suspension substance was observed in the case of not exceeding 10 mg / L ("5000" in Table 1-1, 1-2). Nos. 1, 54 and 56, which were not subjected to the alkali aqueous solution treatment, were not subjected to this measurement.

The results obtained from the above are shown in Tables 1-1 and 1-2. Nos. 15 and 41 are the same test conditions, and Nos. 20 and 28 are the same test conditions.

[Table 1-1]

[Table 1-2]

The following can be seen from Table 1-1, 1-2.

Nos. 1 to 57 were subjected to surface analysis after removal of an unnecessary oxide layer by an aqueous alkali solution.

In the comparative examples of Nos. 1, 54 and 56 in which the contact treatment with the alkaline aqueous solution was not performed, the thickness of the oxide layer was 7 to 10 nm and was not sufficiently removed.

Nos. 2 and 3 are contacted with the alkaline aqueous solution, but they are insufficient (Comparative Example) in that no chelating agent is added to the alkaline aqueous solution. The oxide layer is sufficiently removable. However, when the production amount of the steel sheet is increased, a suspended material is generated in the alkaline aqueous solution and deteriorates the appearance.

Nos. 4 and 11 are contacted with an alkaline aqueous solution containing a chelating agent, but are examples in which the concentration of the chelating agent is insufficient (Comparative Example). The oxide layer is sufficiently removable. However, when the production amount of the steel sheet increases, a suspended material is produced in the alkaline aqueous solution.

Nos. 19 and 23 are contacted with an alkaline aqueous solution containing a chelating agent, but the contact time is short (comparative example). The oxide layer has a thickness of 6 to 7 nm and is not sufficiently removed.

Nos. 27 and 34 are contacted with an alkaline aqueous solution containing a chelating agent, but they are low in pH (Comparative Example). The thickness of the oxide layer is 7 nm and is not sufficiently removed.

Nos. 24 and 28 to 33 show the effect of the pH at the contact time of 1.0 second. If the pH is 12.6 or more, the oxide film can be removed to 2 nm or less even when the contact time is 1.0 second, and the reaction time for forming the reaction layer can be further shortened.

Example 2

An oxide layer containing a crystal structure represented by Zn ₄ (SO ₄ ) _{1 -X} (CO ₃ ) _X (OH) ₆ .nH ₂ O was analyzed for Nos. ₂ to 53, 55 and 57.

(4) Identification of Zn ₄ (SO ₄ ) _{1 -X} (CO ₃ ) _X (OH) ₆ .nH ₂ O

An oxide layer containing a crystal structure represented by Zn ₄ (SO ₄ ) _{1 -X} (CO ₃ ) _X (OH) ₆ .nH ₂ O was applied to the surface by using a stainless steel brush having a diameter of 0.15 mm and a length of 45 mm and ethanol And the resulting ethanol solution was subjected to suction filtration to extract the film component as a powder component. The component of the film collected as a powder was subjected to a temperature elevation analysis using a gas chromatograph mass spectrometer to quantitatively analyze the C content. A thermal decomposition furnace was connected to the front end of the gas chromatograph mass spectrometer. Approximately 2 mg of the powder sample collected in the thermal decomposition furnace was introduced, and the temperature of the thermal decomposition furnace was raised from 30 DEG C to 500 DEG C at a heating rate of 5 DEG C / min. Transferred into a chromatographic mass spectrometer, and analyzed for gas composition. The column temperature during GC / MS measurement was set at 300 캜.

The existence form of C

The powder components obtained by pulverization in the same manner were analyzed using mass spectrometry of gas chromatograph, and the presence of C was analyzed.

The presence of Zn, S, O, H

An X-ray photoelectron spectrometer was used to analyze the presence of S, Zn, and O. Using the Al Ka monochrome source, narrow measurements of spectra corresponding to Zn LMM and S 2p were performed.

The presence of P

The presence of P was analyzed using an X-ray absorption microstructure device. Measurements of ZAFS (X-ray absorption edge microstructure) were carried out at room temperature with beam line BL27A of Photon Factory, a high-energy accelerator research institute. The surface of the degreased sample was irradiated with monochromatic radiation, and the absorption XANES (X-ray absorption edge near structure) spectrum of the P-K angle was measured by the total electron quantity method (TEY) by measuring the absorption current of the sample.

Quantity of crystal water

A weight loss of 100 DEG C or less was measured using a differential thermal balance. About 15 mg of a powder sample was used for the measurement. After introducing the sample into the apparatus, the sample was heated from room temperature (about 25 ° C) to 1000 ° C at a temperature raising rate of 10 ° C / min, and the change in thermogravity at the time of temperature rise was recorded.

Specification of crystal structure

X-ray diffraction of the film components sampled and pulverized in the same manner was carried out to estimate the crystal structure. Cu was used as the target, and measurement was performed under conditions of an acceleration voltage of 40 kV, a tube current of 50 mA, a scan speed of 4 deg / min, and a scan range of 2 to 90 degrees.

Hereinafter, results obtained for Nos. 2 to 38, 40 to 53, 55, and 57 will be described.

As a result of the gas chromatograph mass spectrometry, the emission of CO ₂ was confirmed between 150 ° C and 500 ° C, indicating that C exists as a carbonate.

As a result of analysis using an X-ray photoelectron spectrometer, a peak corresponding to Zn LMM was observed near 987 eV, indicating that Zn existed as a zinc hydroxide state. Similarly, a peak corresponding to S 2p was observed in the vicinity of 171 eV, and S was found to exist as a sulfate.

As a result of analysis using an X-ray absorption microstructure device, peaks were observed in the vicinity of 2153, 2158 and 2170 eV, indicating that P exists as pyrophosphate.

From the results of the differential thermal scales, a weight reduction of 11.2% was confirmed at 100 占 폚 or lower, and it was found that the crystals contained therein.

As a result of X - ray diffraction, diffraction peaks were observed near 2θ in the vicinity of 8.5 ˚, 15.0 ˚, 17.4 ˚, 21.3 ˚, 23.2 ˚, 26.3 ˚, 27.7 ˚, 28.7 ˚, 32.8 ˚, 34.1 ˚, 58.6 ˚ and 59.4 ˚ .

It can be seen from the above results that the composition ratio and charge balance contain a crystal structure material represented by Zn ₄ (SO ₄ ) _0.95 (CO ₃ ) _0.05 (OH) ₆ .3.3H ₂ O.

No.39 was subjected to detailed film analysis.

As a result of the gas chromatograph mass spectrometry, the emission of CO ₂ was confirmed between 150 ° C and 500 ° C, indicating that C exists as a carbonate.

As a result of analysis using an X-ray photoelectron spectrometer, a peak corresponding to Zn LMM was observed near 987 eV, indicating that Zn existed as a zinc hydroxide state. Similarly, a peak corresponding to S 2p was observed in the vicinity of 171 eV, and S was found to exist as a sulfate.

As a result of analysis using an X-ray absorption microstructure device, peaks were observed in the vicinity of 2153, 2158 and 2170 eV, indicating that P exists as pyrophosphate.

From the results of the differential thermal scales, a weight loss of 9.4% was confirmed at 100 占 폚 or less, and it was found that the crystals contained therein.

As a result of X - ray diffraction, diffraction peaks were observed in the vicinity of 2θ of 8.8 ˚, 15.0 ˚, 17.9 ˚, 21.3 ˚, 23.2 ˚, 27.0 ˚, 29.2 ˚, 32.9 ˚, 34.7 ˚ and 58.9 ˚.

It can be seen from the above results that the composition ratio and the charge balance contain a crystal structure material represented by Zn ₄ (SO ₄ ) _0.8 (CO ₃ ) _0.2 (OH) ₆ · 2.7H ₂ O.

Claims (2)

A process for producing a zinc-based plated steel sheet having a reaction layer on the surface of a steel sheet, wherein the reaction layer contains a crystal structure represented by Zn ₄ (SO ₄ ) _{1 -X} (CO ₃ ) _X (OH) ₆ .nH ₂ O Wherein at least one selected from the group consisting of sodium gluconate, sodium gluconate, sodium citrate, tartaric acid, arabic acid, galactonic acid, sorbitol, mannitol, glycerin, EDTA and sodium tripolyphosphate And a chelating agent in an amount of not less than 0.050 mass% in total and having a pH of not less than 10.0 with a zinc-based plated steel sheet for at least 1.0 second. The method according to claim 1,
Wherein the alkaline aqueous solution has a pH of 12.6 or more.

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