KR102007103B1 - Method for manufacturing steel sheet coated with zinc-based coating layer - Google Patents

Abstract

Provided the manufacturing method of a zinc-based plated steel sheet which can remove the oxide on the surface of a zinc-based plating layer by contact with alkaline aqueous solution, and can avoid the external trouble by the precipitate which precipitates in 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 An oxide layer containing a crystal structure represented by (CO ₃ ) _X (OH) ₆ nH ₂ O, and as a pretreatment for forming the reaction layer, sodium gluconate, sodium glucoheptonate, sodium citrate, tartaric acid, arabic acid, galac At least one chelating agent selected from tonic acid, sorbitol, mannitol, glycerin, EDTA, and sodium tripolyphosphate contains 0.050 mass% or more in total, and the zinc-based plated steel sheet is brought into contact with the alkaline aqueous solution having a pH of 10.0 or more for 1.0 second or more.

Description

Manufacturing method of galvanized steel sheet {METHOD FOR MANUFACTURING STEEL SHEET COATED WITH ZINC-BASED COATING LAYER}

The present invention relates to a method for producing a galvanized steel sheet having a reaction layer.

Zinc-based galvanized steel sheet is used for a wide range of applications mainly in automobile bodies, home appliances, and building materials. With respect to a zinc-based galvanized steel sheet in such a use, a technique is known in which a reaction layer is formed on the surface of a steel sheet to improve characteristics such as press molding, corrosion resistance, and appearance.

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

Increasing the reaction time is accompanied by an increase in equipment costs and line lengths, and also leads to an increase in running costs such as electricity and gas.

On the other hand, the technique which shortens reaction time by removing the unnecessary oxide layer which exists in the surface layer of a galvanized steel sheet by making it contact with alkaline aqueous solution before forming a reaction layer is known.

Patent Literature 1 describes a technique of treating a hot dip galvanized steel sheet with an alkaline aqueous solution and then treating the SiO ₂ -containing chromate solution.

Moreover, the technique of intentionally forming an oxide film after processing with alkaline aqueous solution is also known.

Patent Literatures 2 and 3 describe a technique of forming an oxide layer after contacting a hot dip galvanized steel sheet with an alkaline aqueous solution.

Patent Literature 4 describes 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 an oxide containing a crystal structure represented by Zn ₄ (SO ₄ ) _1-X (CO ₃ ) _X (OH) ₆ nH ₂ O after the surface of the hot-dip galvanized steel sheet is brought into contact with an alkaline aqueous solution. Techniques for forming a layer are described.

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

In the technique of patent documents 1-5, the reaction time for forming a reaction layer by contact with alkaline aqueous solution can be shortened. However, in the conventional continuous processing apparatus, Zn or Al precipitates deposited in alkaline aqueous solution adhere to the deflector rolls or support rolls, resulting in crushing scratches on the surface of the steel sheet, and further, appearance irregularities after reaction layer formation. In other cases, appearance problems may occur.

This invention is made | formed in view of such a situation. It is possible to remove an unnecessary oxide layer on the surface of a zinc-based plating layer by contact with an alkaline aqueous solution, and to provide a method for producing a zinc-based plated steel sheet, which can avoid an external trouble caused by precipitates precipitated in an alkaline aqueous solution. It aims to do it.

The inventors of the present invention have conducted intensive studies in order to solve the above problems. As a result, it was found out that the above problems can be solved by adding a specific chelating agent to the alkaline aqueous solution used before forming the reaction layer, thus 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 An oxide layer containing a crystal structure represented by (CO ₃ ) _X (OH) ₆ nH ₂ O, and as a pretreatment for forming the reaction layer, sodium gluconate, sodium glucoheptonate, sodium citrate, tartaric acid, arabic acid, galac It contains 0.050 mass% or more of 1 or more chelating agents selected from tonic acid, sorbitol, mannitol, glycerin, EDTA, and sodium tripolyphosphate, and the zinc-based plated steel sheet is brought into contact with the alkaline aqueous solution having a pH of 10.0 or more for at least 1.0 second. It is done.

The manufacturing method of the zinc-based galvanized steel sheet which concerns on the 2nd invention for solving the said subject is a manufacturing method of the zinc-based galvanized steel sheet as described in 1st invention, It is characterized by the pH of the said alkaline aqueous solution being 12.6 or more.

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

1: is a schematic diagram which showed the evaluation criteria for evaluating appearance nonuniformity.

Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment. In the present invention, a galvanized steel sheet is a steel sheet having a film 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 plated steel sheet, and a plated steel sheet in which particles are dispersed in zinc. do. That is, the zinc-based plating layer includes a zinc plating layer, a zinc alloy plating layer, a plating layer in which particles are dispersed in zinc, and the like.

The present invention provides a reaction layer capable of satisfactorily removing an unnecessary oxide layer present on the surface of a zinc-based plating layer, that is, Zn ₄ (SO ₄ ) _1-X (CO ₃ ) _X (OH) ₆ nH ₂ O ( However, X is a manufacturing method of the galvanized steel plate which has an oxide layer in which the crystal structure represented by 0 <X <1) is contained. The present invention includes, for example, a process of performing zinc-based plating, a process of contacting with an alkaline aqueous solution, and Zn ₄ (SO ₄ ) _1-X (CO ₃ ) _X (OH) ₆ nH ₂ O ( X is equipped with the process of forming the oxide layer in which the crystal structure represented by 0 <X <1) is contained. Each step will be described below.

Zinc Plating Process

First, the process of performing zinc plating is demonstrated. In the process of performing zinc plating, the method of galvanizing is not specifically limited, General methods, such as hot dip galvanization and an electrogalvanization, can be employ | adopted. Moreover, the process conditions of electrogalvanization and hot dip galvanization are not specifically limited, What is necessary is just to employ | adopt appropriate conditions suitably. In the case of performing hot dip galvanizing, it is preferable that Al is added in the plating bath from the viewpoint of the dross countermeasure. In this case, element components other than Al are not specifically limited. That is, even if Al contains Pb, Sb, Si, Sn, Mg, Mn, Ni, Ti, Li, Cu, etc., the effect of this invention is not impaired.

Here, the kind of steel of the steel plate to which zinc plating is given is not specifically limited, Various steel plates, such as a low carbon steel, an ultra low carbon steel, IF steel, and the high tensile steel plate which added various alloying elements, can be used. In addition, a hot rolled sheet steel and a cold rolled sheet steel can be used for the said steel plate. The thickness of the steel sheet is not particularly limited. Moreover, 0.4-5.0 mm is preferable from a viewpoint of using for uses, such as an automobile body, a household appliance, and building materials.

Furthermore, in the process of galvanizing, after performing hot dip galvanizing, it is good also as an alloying hot dip galvanized steel plate which performed the alloying process. In this invention, the conditions of alloying process are not specifically limited, What is necessary is just to employ | adopt appropriate conditions suitably.

Contact with alkaline aqueous solution

After performing zinc-based plating treatment, contact treatment using an alkaline aqueous solution is performed. The alkaline aqueous solution used by this contact treatment is pH 10.0 or more. Below pH 10.0, the removal of the oxide layer becomes insufficient. If pH is 12.6 or more, contact time with aqueous alkali solution can be shortened and it is effective and preferable.

On the other hand, pH 14.0 or less is preferable from a viewpoint of preventing melt | dissolution of a zinc type plating layer, and blackening of a surface appearance.

The alkaline aqueous solution contains 0.050 mass% or more of a specific chelating agent in total. When Al, the precipitate of Zn, etc. increase in alkaline aqueous solution, the external appearance of a liquid will become a suspension form. The present invention contains 0.050 mass% or more of a chelating agent in an alkaline aqueous solution to reduce precipitates of Al, Zn, and the like.

The chelating agent is at least one selected from sodium gluconate, sodium glucoheptonate, sodium citrate, tartaric acid, arabic acid, galactonic acid, sorbitan, mannitol, glycerin, EDTA and sodium tripolyphosphate. From the viewpoint of being able to chelate Al and Zn and inexpensive, the chelating agent is preferably sodium gluconate.

When content of the chelating agent in alkaline aqueous solution is less than 0.050 mass% in total, the solubility increase of Al and Zn in alkaline aqueous solution will become inadequate. 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, from the viewpoint of the drug cost, the amount of the chelating agent contained in the alkaline aqueous solution is preferably 10.0 mass% or less.

From a viewpoint of shortening the contact time of an alkaline aqueous solution and a steel plate, it is preferable that it is the range of 20 degreeC-70 degreeC, and 40 degreeC-70 degreeC is more preferable.

The kind of alkali builder is not limited. Moreover, it is preferable to use chemicals, such as NaOH, from a viewpoint of cost reduction. 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 substances other than elements contained in zinc-based plating solutions such as Zn, Al, Fe, or other components.

The method of bringing the alkaline aqueous solution into contact with the zinc-based galvanized steel sheet (particularly, the oxide layer of the surface layer) is not particularly limited, and the method of contacting by dipping the zinc-based galvanized steel sheet into the alkaline aqueous solution, spraying the alkaline aqueous solution to the zinc-based galvanized steel sheet Contact method;

The time for bringing the galvanized steel sheet into contact with the alkaline aqueous solution is 1.0 seconds or more. If the contact time is less than 1.0 second, since the oxide on the surface of the zinc-based plating layer cannot be sufficiently removed, the shortening of the reaction time for forming the reaction layer becomes insufficient. In terms of equipment cost and productivity, the time for bringing the galvanized steel sheet into contact with the alkaline aqueous solution is preferably 10.0 seconds or less.

In the present invention, after the step of performing zinc plating, temper rolling may be performed somewhere before and after the alkaline aqueous solution treatment. Since the site | part which contacted the tempered rolling roll in a steel plate removes unnecessary oxide layers of Al and Zn which exist in the surface of a zinc-based plating layer by contact with a roll, reactivity becomes high.

Process of forming reaction layer

Typically subjected to water washing and drying after contacting the plate with an alkaline aqueous solution, and then the crystal represented by the reaction layer, _{i.e., Zn 4 (SO 4) 1} -X (CO 3) X (OH) 6 · nH 2 O The process for forming the oxide layer containing a structure is performed.

In the present invention, the oxide layer containing the crystal structure represented by Zn ₄ (SO ₄ ) _1-X (CO ₃ ) _X (OH) ₆ .nH ₂ O means that the zinc-based plating and the chemical treatment liquid are in contact with each other to react chemically. This takes place, whereby it is a layer of reaction product formed on the steel plate surface. As a formation process of the oxide layer containing the crystal structure represented by Zn ₄ (SO ₄ ) _1-X (CO ₃ ) _X (OH) ₆ .nH ₂ O, for example, a zinc-based plated steel sheet is used as a sulfate ion. 0.5 second or more in the state which contacted with the alkaline aqueous solution the oxide layer formation process which carries out contact for the acidic solution to contain, and maintains for 1 to 60 second, and then washes with water, and the surface of the oxide layer formed in the said oxide layer formation process. It carries out, and the neutralization process of washing with water and drying is performed after that. The alkaline aqueous solution may contain 0.01 g / l or more of P ions as P concentration and 0.1 g / l or more as carbonate 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 may exist on the surface of the steel sheet, and the present invention is not limited to this treatment method.

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 examples.

Temper rolling was performed with respect to the steel plate obtained by performing a hot dip galvanizing process on the plate | board thickness 0.7 mm and the width 1100 mm cold rolled sheet steel. Subsequently, as a removal process of an oxide layer, after making a steel plate contact the alkaline aqueous solution adjusted on the conditions shown to Table 1-1, 1-2 for a predetermined time, it washed with water and dried.

Rough rolled steel sheets obtained by performing hot dip galvanizing and alloying treatment on a cold rolled steel sheet having a sheet thickness of 0.7 mm and a width of 1100 mm, and electrolytic zinc to a cold rolled steel sheet having a sheet thickness of 0.7 mm and a width of 1100 mm. The plating treatment was also brought into contact with the alkaline aqueous solution in the same procedure, followed by washing with water and drying.

With respect to the zinc-based plated steel sheet obtained above, the thickness of the unnecessary oxide layer on the surface of the zinc-based plating layer after the alkaline aqueous solution treatment and the appearance unevenness after the reaction layer formation were evaluated, and thus the suspended solids (SS) contained in the alkaline aqueous solution. The measurement was performed. In addition, pH of alkaline aqueous solution was measured with the commercially available glass electrode.

Subsequently, as an oxide layer formation process in which the crystal structure represented by Zn ₄ (SO ₄ ) _1-X (CO ₃ ) _X (OH) ₆ nH ₂ O is contained, 30 g / L of sodium acetate trihydrate is contained. The steel plate was immersed in a sulfuric acid acid solution adjusted to pH 1.5, woven into a roll, and held for 10 seconds. Next, it washed with water and dried. Subsequently, neutralization treatment was performed with a treatment liquid containing 9.8 g / L sodium pyrophosphate and 0.48 g / L sodium carbonate 10 hydrate.

(1) Measurement of thickness of unnecessary oxide layer

After contact with the alkaline aqueous solution, a fluorescent X-ray analyzer was used to measure the thickness of the unnecessary oxide layer formed on the galvanized steel sheet. If the thickness (oxide film thickness) of an oxide layer is 4 nm or less, it can be evaluated that the reaction time for forming a reaction layer was shortened. If it is 2 nm or less, it can be evaluated that reaction time was further shortened.

The voltage and current of the tube at the time of the measurement were set to 30 mA and 100 mA, and the spectral crystal was set to TAP to detect the O-Kα line. In the measurement of the O-Kα line, in addition to the peak position, the intensity at the background position was also measured to calculate the net strength of the O-Kα line. In addition, the integration time in a peak position and a background position was 20 second, respectively.

In the sample stage, a silicon wafer having a silicon oxide film having a thickness of 96 nm, 54 nm and 24 nm cleaved to an appropriate size is set together with these series of samples, and O-Kα is also obtained from these silicon oxide films. The strength of the line can be calculated. Using these data, calibration curves of oxide layer thickness and O-Kα line strength were prepared, and the thickness of the oxide layer of the specimen was calculated as the oxide layer thickness in terms of silicon oxide film conversion.

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

After the treatment of forming an oxide layer on the surface of the hot dip galvanized steel sheet, the alloyed hot dip galvanized steel sheet, and the electrogalvanized steel sheet subjected to contact treatment with an alkaline aqueous solution, the appearance unevenness was evaluated by visual 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 / 7 hydrate to pH 2.0 with sulfuric acid was prepared, and various treatments in which the treatment solution was subjected to contact treatment with an alkaline aqueous solution. After apply | coating so that it might become thickness of 3 micrometers to a plated steel plate, and hold | maintained for 10 second, it washed with water and dried, and the process which forms an oxide layer was performed. In addition, an observation area is 70 mm x 150 mm. Based on the external appearance sample shown in FIG. 1, the rating was given to 1-5 points and evaluated. Four points showed the favorable thing and five points showed the further favorable thing.

(3) Determination of Suspended Material (SS)

The alkaline aqueous solution after 100 tons of zinc-based galvanized steel sheet was collected, and suction filtered using a membrane filter having a pore size of 1 m. The filtered material was dried at 110 ° C. and then weighed, and converted to mg / L. The production amount at which this value exceeded 10 mg / L was recorded. If the steel plate throughput exceeding 10 mg / L is 3000 t or more, it can be evaluated as satisfactory in terms of productivity. Moreover, even after 5000 t process, about the thing which did not exceed 10 mg / L, it evaluated as having no suspension substance (it describes as "> 5000" in Table 1-1, 1-2). Nos. 1, 54 and 56 that did not undergo aqueous alkali solution treatment did not perform this measurement.

The results obtained from the above are shown in Tables 1-1 and 1-2. In addition, No.15 and No.41 are the same test conditions, and No.20 and No.28 are the same test conditions.

[Table 1-1]

[Table 1-2]

The following matters can be seen from Tables 1-1 and 1-2.

About No.1-57, the surface analysis after removing unnecessary oxide layer by aqueous alkali solution was performed.

In Comparative Examples Nos. 1, 54 and 56 which did not undergo contact treatment with alkaline aqueous solution, the thickness of the oxide layer was 7 to 10 nm and was not sufficiently removed.

Although No.2 and 3 contact with alkaline aqueous solution, it is an insufficient example (comparative example) in that the chelating agent is not added in alkaline aqueous solution. The oxide layer is sufficiently removable. However, when the yield of the steel sheet is increased, a suspended substance is formed in the alkaline aqueous solution, thereby deteriorating the appearance.

Nos. 4 and 11 are in contact with an alkaline aqueous solution containing a chelating agent, but are examples where the concentration of the chelating agent is insufficient (comparative example). The oxide layer is sufficiently removable. However, an increase in the yield of the steel sheet produces a suspended substance in the alkaline aqueous solution.

No. 19 and 23 contact with the alkaline aqueous solution containing a chelating agent, but are the example (comparative example) whose contact time is short. The oxide layer has a thickness of 6 to 7 nm and is not sufficiently removed.

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

No. 24 and 28-33 are the examples of this invention which confirmed the influence of pH in 1.0 second of contact time. If the pH is 12.6 or more, the oxide film can be removed to 2 nm or less even with a contact time of 1.0 second, and the reaction time for forming the reaction layer can be further shortened.

Example 2

With respect to the No.2 ~ 53, 55, 57, was subjected to _{Zn 4 (SO 4) 1-} X (CO 3) X (OH) 6 · analysis of the oxide layer which is a crystal structure containing indicated by the nH ₂ O.

(4) Confirmation of _{Zn 4 (SO 4) 1-} X (CO 3) X (OH) 6 · nH 2 O

The oxide layer containing the crystal structure represented by Zn ₄ (SO ₄ ) _1-X (CO ₃ ) _X (OH) ₆ .nH ₂ O was prepared by using a stainless brush and a ethanol of 0.15 mm in diameter and 45 mm in length. The film component was extracted as a powder component by rubbing and filtering the obtained ethanol liquid. The quantitative analysis of C was performed by carrying out temperature analysis of the film component extract | collected as a powder using the gas chromatograph mass spectrometer. A pyrolysis furnace was connected to the front end of the gas chromatograph mass spectrometer. About 2 mg of the powder sample collected in the pyrolysis furnace was inserted, and the gas generated in the pyrolysis furnace in which the temperature of the pyrolysis furnace was raised from 30 ° C to 500 ° C at a heating rate of 5 ° C / min was converted into helium gas. It returned to the chromatograph mass spectrometer and the gas composition was analyzed. The column temperature at the time of GC / MS measurement was set to 300 degreeC.

The form of C

In the same way, the powder component and the gas chromatograph mass spectrometry collected were analyzed, and the presence form of C was analyzed.

Presence form of Zn, S, O, H

X-ray photoelectron spectroscopy was used to analyze the presence forms of S, Zn, O. Using an Al Ka monochrome source, narrow measurement of the spectrum corresponding to Zn LMM and S 2p was performed.

The form of P

The presence of P was analyzed using an X-ray absorbing microstructure device. In the beam line BL27A of the high-energy accelerator research instrument Photon Factory, the measurement of ZAFS (X-ray absorption edge microstructure) was performed at room temperature. Monochromatic radiation was irradiated to the surface of the degreased sample, and the absorption edge XANES (structure near X-ray absorption edge) spectrum of the P-K angle was measured by the total electron quantity method (TEY) by sample absorption current measurement.

Quantification of Crystalline Water

Differential heat balance was used to measure the amount of weight reduction up to 100 ° C. About 15 mg of a powder sample was used for the measurement. After the sample was introduced into the apparatus, the temperature was raised from room temperature (about 25 ° C) to 1000 ° C at a temperature increase rate of 10 ° C / min, and the thermogravimetric change at the time of temperature increase was recorded.

Specific to crystal structure

In the same manner, X-ray diffraction was performed on the powder components obtained by powdering, and the crystal structure was estimated. As a target, measurement was carried out using Cu under conditions of an acceleration voltage of 40 mA, a tube current of 50 mA, a scan speed of 4 deg / min, and a scan range of 2 to 90 degrees.

Hereinafter, the result obtained about No.2-38, 40-53, 55, 57 is described.

As a result of gas chromatograph mass spectrometry, it was possible to confirm the release of CO ₂ between 150 ° C. and 500 ° C., and found that C was present as a carbonate.

As a result of analysis using an X-ray photoelectron spectrometer, a peak corresponding to Zn LMM was observed around 987 eV, and it was found that Zn exists as a zinc hydroxide state. Similarly, a peak corresponding to S 2p was observed around 171 eV, and it was found that S exists as a sulfate.

As a result of analysis using an X-ray absorption microstructure device, peaks were observed around 2153, 2158, and 2170 eV, and it was found that P exists as pyrophosphate.

From the result of the differential thermal balance, the weight loss of 11.2% was confirmed below 100 degreeC, and it turned out that it contains the crystal water.

As a result of the X-ray diffraction, diffraction peaks are observed around 2,5 °, 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 °. .

From the above results, composition ratio, and charge balance, it can be seen that the crystal structure material represented by Zn ₄ (SO ₄ ) _0.95 (CO ₃ ) _0.05 (OH) ₆ · 3.3H ₂ O is contained.

No. 39 was subjected to detailed film analysis.

As a result of gas chromatograph mass spectrometry, it was possible to confirm the release of CO ₂ between 150 ° C. and 500 ° C., and found that C was present as a carbonate.

As a result of analysis using an X-ray photoelectron spectrometer, a peak corresponding to Zn LMM was observed around 987 eV, and it was found that Zn exists as a zinc hydroxide state. Similarly, a peak corresponding to S 2p was observed around 171 eV, and it was found that S was present as a sulfate.

As a result of analysis using an X-ray absorption microstructure device, peaks were observed around 2153, 2158, and 2170 eV, and it was found that P exists as pyrophosphate.

From the result of the differential thermal balance, the weight loss of 9.4% was confirmed at 100 degrees C or less, and it turned out that it contains the crystal water.

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 °.

From the above results, the composition ratio and the charge balance, it can be seen that the crystal structure substance represented by Zn ₄ (SO ₄ ) _0.8 (CO ₃ ) _0.2 (OH) ₆ .2.7H ₂ O is contained.

Claims (2)

Method for producing a galvanized steel sheet having a reaction layer on the surface of the steel sheet, the following method steps:
0.050 mass% or more and 10.0 mass% or less of a total of one or more chelating agents selected from sodium gluconate, sodium glucoheptonate, sodium citrate, tartaric acid, arabic acid, galactonic acid, sorbitan, mannitol, glycerin, EDTA, and sodium tripolyphosphate A pre-treatment step of forming the reaction layer, the zinc-plated steel sheet being brought into contact with the alkaline aqueous solution having a pH of 12.6 or more for 1.0 seconds or more; And
Zn ₄ (SO ₄ ) _1-X (CO ₃ ) _X (OH) ₆ nH ₂ O (where X is an oxide layer containing a crystal structure represented by 0 <X <1) on the surface of the zinc-based galvanized steel sheet Forming the reaction layer;
Method for producing a galvanized steel sheet comprising a. delete

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