JP3043336B1 - Electro-galvanized steel sheet excellent in white rust resistance and method for producing the same - Google Patents

Abstract

A non-chromate treated steel sheet having excellent white rust resistance,
Furthermore, the present invention provides a non-chromate treated steel sheet excellent in white rust resistance and blackening resistance and a method for producing the same. SOLUTION: In an electric Zn-plated steel sheet in which an inorganic and / or organic film substantially containing no Cr is formed on an upper layer of an electroplating layer containing Zn as a main component, Pb contained in the electroplating layer is provided. 5 ppm or less, Cu 10
When the content of Ag is set to 5 ppm or less and the total amount of these elements is set to 15 ppm or less, it is possible to obtain an electro-Zn plated steel sheet having excellent white rust resistance. Further, Ni,
By containing one or more metal elements selected from Co and In in the electroplating layer in the range of 50 to 700 ppm in the case of Ni and 0.5 to 50 ppm in the case of Co or In, the blackening resistance can be reduced. Can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electro-zinc plated steel sheet having excellent white rust resistance and a method for producing the same, and more particularly, to an electro-zinc plated steel sheet having an electroplated layer of pure Zn having a purity of 99.9% or more. White rust resistance of steel sheet (and blackening resistance)
It is related to the improvement technology.

[0002]

2. Description of the Related Art Zn-plated steel sheets exhibit excellent corrosion resistance (red rust resistance) due to the fact that Zn has a sacrificial anti-corrosion effect on the steel sheet and the corrosion products of Zn have an excellent protection effect. Since it is used in a wide range of fields, such as automobiles, building materials, and home appliances.

Conventionally, as a characteristic required for a Zn-plated steel sheet, the corrosion resistance (that is, red rust resistance) of the steel sheet itself is regarded as important from the viewpoint of preventing the strength of the steel sheet as a structure from being reduced by corrosion. It had been. Therefore, for example, a steel sheet for an automobile is coated after being subjected to a chemical conversion treatment represented by a chromate treatment.

In recent years, Zn-plated steel sheets have been frequently used for chassis and case parts of home electric appliances, OA equipment, and the like, and the proportion of Zn-plated steel sheets used without coating on the Zn-plated layer has increased significantly. As a result, the appearance of the Zn-plated steel sheet itself has become an important characteristic, and white rust, which is the rust of Zn itself, has come to be regarded as a problem. The chromate treatment film was originally developed for the purpose of preventing white rust of Zn, and the chromate treatment also exerts a white rust suppression effect by the self-repairing action of hexavalent chromium. However, recently, from the viewpoint of minimizing adverse effects on the environment, there has been a strong movement to abolish chromate treatment containing hexavalent chromium, and non-chromate treated steel plates that do not use chromate treatment have been developed. Since the non-chromate-treated steel sheet cannot be expected to have the effect of suppressing the white rust of hexavalent chromium, there has been a demand for the development of a technique for preventing the white rust of the electro-zinc plated steel sheet except for the chromate treatment.

Incidentally, there has been proposed a technique for improving the white rust resistance by forming an organic film or an inorganic film on the upper layer of the electro-Zn plating film. Was not yet enough.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a non-chromate treated steel sheet excellent in white rust resistance, and further excellent in white rust resistance and black discoloration resistance. An object of the present invention is to provide a non-chromate treated steel sheet and a method for manufacturing the same.

[0007]

Means for Solving the Problems The electro-zinc-coated steel sheet of the present invention which is excellent in white rust resistance and which solves the above-mentioned problems is an inorganic zinc-free electroplated layer containing substantially no Cr in the upper layer. Z on which an organic and / or organic coating is formed
An n-plated steel sheet, wherein Pb contained in the electroplating layer is 5 ppm or less, Cu is 10 ppm or less, and Ag is 5 ppm or less.
ppm or less, and the total amount of these elements is 15 pp
m or less.
one or more metal elements selected from i, Co, In
Blackening resistance can be improved by incorporating the electroplating layer in the range of 50 to 700 ppm for i and 0.5 to 50 ppm for Co or In.

Further, even in the case of an electro-zinc plated steel sheet in which a chromate treatment layer is formed on an electro-plating layer containing Zn as a main component, Pb contained in the electro-plated layer is reduced by 1%.
0 ppm or less, Cu 20 ppm or less, Ag 10 pp
m or less and the total amount of these elements is 30 ppm or less, it is possible to obtain an electro-galvanized steel sheet having excellent white rust resistance. In addition, when one or more metal elements selected from Ni, Co, and In are Ni, Is contained in the electroplating layer in the range of 50 to 1000 ppm, and in the case of Co or In in the range of 0.5 to 50 ppm, the blackening resistance can be improved.
Alternatively, it is more desirable to form an organic film.

In producing the electro-zinc-coated steel sheet of the present invention which is excellent in white rust resistance, the Pb in the plating solution is 0.1%.
5 ppm or less, Cu is 1 ppm or less, Ag is 0.5 pp
m or less and the total amount of these elements is 1.5 ppm or less, the electro-Zn plating may be performed. Further, one or more metal ions selected from Ni, Co, and In may be converted into Ni. In the case of 25 to 300 ppm, and in the case of Co or In, 0.1 to 30 ppm of an acidic plating solution is used to perform electro-Zn plating to produce an electro-Zn plated steel sheet having excellent white rust resistance and blackening resistance. be able to.

In producing an electro-galvanized steel sheet in which a chromate treatment layer is formed on an electroplating layer containing Zn as a main component, Pb in a plating solution is 1 ppm.
Hereinafter, by performing electro-Zn plating using an acidic plating solution in which Cu is 2 ppm or less, Ag is 1 ppm or less, and the total amount of these elements is 3 ppm or less, it is possible to produce an electric Zn-plated steel sheet having excellent white rust resistance. , And Ni, C
one or more metal ions selected from o, In
500 ppm, 0.1 to 30 p for Co or In
By performing electro-Zn plating using an acidic plating solution containing pm, the electro-Z plating is excellent in white rust resistance and black discoloration resistance.
An n-plated steel sheet can be manufactured.

Further, in producing the electro-zinc coated steel sheet according to the present invention, Pb, C is substantially used as an anode.
An iridium oxide electrode not containing u and Ag is used, and Pb is 15 ppm or less and Cu is 20 pp as impurity elements.
raw material Zn containing Ag in a range of 7 ppm or less.
It is recommended to perform the electro-Zn plating process using

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies on the prevention of white rust generated on a Zn plating layer of a non-chromate-treated steel sheet (an electrical Zn-plated steel sheet not subjected to a chromate treatment). As a result, among the impurity elements inevitably present due to the Zn plating raw material and the like, if the content of the specific component is limited, even if a chromate film is not formed on the electro-Zn plating layer, excellent resistance can be obtained. The present inventors have found that white rust properties can be obtained, and have reached the present invention.

More specifically, the amounts of Pb, Cu, and Ag contained in the electro-Zn plating layer may be controlled.
Excellent white rust resistance can be obtained by setting pm or less, Cu to 10 ppm or less, Ag to 5 ppm or less, and the total amount of these elements to 15 ppm or less. In order to obtain better white rust resistance, Pb is preferably 4 ppm or less, Cu is 8 ppm or less, and Ag is preferably 4 ppm or less, and the total amount is desirably 13 ppm or less. In producing the above-mentioned electric Zn-plated steel sheet, electric Zn
Pb in plating solution is 0.5ppm or less, Cu is 1ppm
Hereinafter, a method of performing electro-Zn plating using an acidic plating solution in which Ag is 0.5 ppm or less and the total amount of these elements is 1.5 ppm or less may be adopted.
4 ppm or less, Cu is 0.8 ppm or less, Ag is 0.4
ppm or less, and the total amount is desirably 1.3 ppm or less.

Further, in order to obtain an electric Zn-plated steel sheet which is excellent in blackening resistance in addition to white rust resistance, one or more metal elements selected from Ni, Co and In are contained in the electric Zn plating layer. It is desirable to contain Ni in the range of 50 to 700 ppm, and in the case of Co or In in the range of 0.5 to 50 ppm, and the Ni content is 100 to 400 pp.
More preferably, the content in the case of m, Co and In is 1 to 40 ppm.

In this case, at least one metal ion selected from Ni, Co, and In is used.
ppm, Co or In, it is recommended to perform electro-Zn plating using an acidic plating solution containing 0.1 to 30 ppm, and Ni is 50 to 250 ppm, Co or In.
Is desirably 0.5 to 20 ppm.

The reason why the white rust resistance is deteriorated when Pb, Cu, and Ag are contained in the plating layer is that these impurity elements are metals nobleer than Zn, and the standard electrode is more expensive than Zn. It is considered that the potential is high. Therefore, in a corrosive environment, a corrosion battery of these impurity elements and Zn is formed, the elution of Zn in the early stage of corrosion is promoted, and the formation of white rust is promoted. This phenomenon is caused by a potential difference from Zn. Is the most intense.

The black discoloration phenomenon is a phenomenon in which the plating surface turns black (brown), which occurs in a relatively mild corrosive environment, and is a corrosion phenomenon before (white) rust occurs. is there. The reason why it looks dark is that, during the oxidation reaction (corrosion) of Zn, an amorphous oxide having a stoichiometric composition of Zn _x O _{1 -x} is generated. The formation of the amorphous oxide is due to the fact that the oxidation reaction of Zn is incomplete. Therefore, in order to suppress the blackening phenomenon, the oxidation reaction may be accelerated to some extent. However, if promoted too much, then the white rust resistance is remarkably deteriorated. Therefore, it is effective to add Ni, Co, In, which is a noble element slightly more than Zn, as an additive element for appropriately promoting oxidation. It is. However, the amount of addition is P
Since it is determined based on a delicate balance with b, Cu, and Ag, care must be taken, and it is important to keep the range as described above.

Further, the technique for preventing white rust according to the present invention is effective not only for the non-chromate-treated steel sheet but also for improving the white rust resistance of the chromate-treated steel sheet. That is, even in the case of an electro-zinc plated steel sheet in which a chromate treatment layer is formed on an electro-plating layer containing Zn as a main component, Pb, Cu,
By suppressing the amount of Ag, white rust resistance can be further improved. When performing the chromate treatment, excellent white rust resistance can be obtained without reducing the amount of Pb or the like as compared with the case where the chromate treatment is not performed. 10 ppm or less, Cu is 2
0 ppm or less, Ag should be 10 ppm or less, and the total amount of these elements should be 30 ppm or less.
pppm or less, Cu is 15 ppm or less, Ag is 8 ppm
It is more preferable that the total amount be 15 ppm or less.

In addition, electric Zn for forming a chromate treatment layer
In the plating layer, 1 selected from Ni, Co, In
More than one kind of metal element, 50 to 1000 pp for Ni
In the case of m, Co or In, it is possible to improve the blackening resistance by adding it in the range of 0.5 to 50 ppm, and it is more preferable that Ni is 100 to 800 ppm and Co or In is 1 to 40 ppm. .

An organic film and / or an inorganic film may be formed on the chromate-treated layer for the purpose of further improving white rust resistance.

Electricity Z when forming a chromate treatment layer
When manufacturing an n-plated steel sheet, the P
b is 1 ppm or less, Cu is 2 ppm or less, Ag is 1 pp
m or less, and a method of performing electro-Zn plating using an acidic plating solution having a total amount of these elements of 3 ppm or less may be adopted.
Is 1.5 ppm or less, Ag is 0.8 ppm or less, and the total amount is desirably 1.5 ppm or less.

In order to produce an electro-galvanized steel sheet having excellent resistance to blackening in addition to white rust, Ni, C
It is recommended to perform electro-Zn plating using an acidic plating solution containing 25 to 500 ppm for Ni and 0.1 to 30 ppm for Co or In for at least one metal ion selected from o and In. And Ni is 50 to 400
It is desirable that ppm, Co or In be 0.5 to 20 ppm.

Pb, Cu, A which has an adverse effect on white rust resistance
g is an impurity contained in the raw material Zn, Pb
This is due to elution of the anode when an In-Ag alloy, a Pb-Sn alloy, or the like is used as the anode material. Therefore, even if the raw material Zn has an impurity amount of Pb of 15
It is preferable to carry out the electro-Zn plating using a material having a concentration of not more than 20 ppm, a content of not more than 20 ppm of Cu, and a content of not more than 7 ppm of Ag.
It is desirable that Cu be 15 ppm or less and Ag be 5 ppm or less. In addition, as an anode during electroplating, substantially P
It is recommended to use an iridium oxide electrode that does not contain b, Cu, Ag.

Further, hereinafter, a method for producing an electro-galvanized steel sheet according to the present invention will be described in detail.

Regarding plating conditions As the plating solution, an acidic bath (for example, a sulfate bath or a chloride bath) can be used. Regarding the current density, when plating is performed in a region where the current density is low, that is, in a state where the overvoltage required for the deposition of the metal element is low, Pb, Cu, and Ag having a “noble” potential than Zn have priority over Zn. Precipitate,
The content in the plating layer becomes relatively large. Therefore, it is preferable to perform plating at a high current density in view of the gist of the present invention, and specifically, it is recommended to perform plating at 30 A / dm ² or more, more preferably 50 A / dm ² or more. The upper limit is not limited from the viewpoint of white rust resistance, but if the current density is too high, the supply of Zn ions will not be able to keep up, and the “plating burn” phenomenon in which the plating appearance will change to a blackish color will occur. / D
m ² or less. Also, the pH of the plating solution
Is not particularly limited, but is preferably in the range of pH 0.5 to 4.0 from the relationship with the current efficiency and the plating burn phenomenon. Note that the plating solution contains Na ₂ SO ₄ ,
A conductive auxiliary such as (NH ₄ ) ₂ SO ₄ , KCl, or NaCl may be added.

With respect to other plating conditions (for example, plating solution temperature and relative flow rate), conditions that do not cause other problems such as plating burns may be appropriately selected and performed. The plating solution temperature is in the range of 30 to 70 ° C., and the relative flow rate is in the range of 0.3 to 5 m / s. Note that the relative flow velocity is a difference between the liquid flow velocity and the passing speed in consideration of the flow direction of the liquid and the passing direction of the steel plate as the plating original plate.

There is no particular limitation on the plating method. The plating base material may be subjected to a pretreatment such as degreasing or pickling according to a conventional method, and then subjected to electroplating in a vertical or horizontal plating cell. Good. The method of electroplating is not particularly limited, and a known direct current (constant current) plating method or pulse plating method can be adopted.

Regarding the coating weight of the plating The coating weight of the electro-Zn plating is not particularly limited, but if the coating weight is less than 3 g / m ² , the corrosion resistance in the as-plated state is insufficient. is there. Conversely, a high plating weight exceeding 100 g / m ² is inferior in economics. Therefore, it is desirable to select from the range of 3 to 60 g / m ² , more preferably 5 to 40 g / m ² . The plating may be applied to the required surface of the metal plate as the base material, and may be applied to only one surface or both surfaces.

Addition of Sr and Ba compounds In the present invention, it is possible to suppress Pb, Cu, and Ag in the plating solution within the range of the present invention by selecting the materials of the raw material Zn and the anode material. However, it is recommended to add a compound of Sr or Ba to the plating solution as a method of further suppressing the impurity element such as Pb to a low concentration or stably maintaining the low concentration. Further, when a raw material exceeding the upper limit of the impurity concentration in the raw material Zn is used, or when an anode material other than iridium oxide (for example, Pb-Sn alloy or Pb-I
Also when an n-Ag alloy is used, the concentration of Pb, Cu and Ag in the plating solution can be controlled within the range of the present invention by adding a compound of Sr or Ba to the plating solution.

Here, the compound of Sr or Ba is
Those added as soluble compounds such as carbonates and hydroxides to the plating solution are insolubilized (sulfate compounds: SrSO ₄ , Ba)
SO ₄ ), and these insoluble compounds reduce the concentration of these harmful impurities in the plating solution by adsorbing Pb, Cu, and Ag ions contained in the plating solution.

When adding the compound of Sr or Ba to the plating solution, a predetermined amount may be intermittently supplied to the plating solution, or a predetermined amount may be continuously supplied to the plating solution.

Analysis method for Pb, Cu, Ag (plating layer, plating solution) In analyzing trace impurities in the plating layer or plating solution, an atomic absorption analysis method or an inductively coupled plasma emission spectroscopy (ICP) method is used. Or inductively coupled plasma mass spectrometry (I
CP-MS) or the like may be employed. The solution used for dissolving the plating layer includes Pb, Cu,
Any solution that can completely dissolve Ag, Ni, Co, and In may be used, and examples thereof include hydrochloric acid and nitric acid solutions. When analyzing trace impurity elements in the plating solution, Zn,
In order to avoid interference by matrix elements such as Na and S, a method of analyzing after dilution is recommended. Regarding the dilution ratio, a dilution ratio of about 10 to 1000 times may be appropriately used depending on the concentration of the matrix element and the concentration of the element to be measured.

Chromate treatment method Typical examples of the chromate film treatment include a reaction type chromate film treatment, a coating type chromate treatment, an electrolytic chromate treatment, and the like. Various oxides such as silica and organic silane compounds, and various reaction accelerators such as phosphoric acid, nitric acid, fluoride, silicon fluoride, etc. were added as necessary for the purpose of improving characteristics such as blackening resistance. Chromate treatment may be performed.

The adhesion amount of the above chromate film is as follows:
In terms of a general chosen from the range of 5 to 300 mg / m ^2, considering also economical with effectively exhibiting耐白rust improving effect and the like, in the range of 5-60 mg / m ² It is more preferably in the range of 10 to 30 mg / m ² .

Regarding organic or inorganic film treatment For thin film treatment, when the film is mainly composed of organic resin, epoxy resin, polyester resin, polyurethane resin, ethylenically unsaturated carboxylic acid, etc. Those mainly composed of organic resin components such as an ethylene copolymer resin containing an acid as a polymerization component, a polyvinyl resin, a polyamide resin, and a fluorine resin, or having corrosion resistance, lubricity, scratch resistance, workability, etc. In order to improve the quality of weldability, electrodeposition coating properties, coating film adhesion, etc., if necessary, various oxide particles such as silica, inorganic pigments such as various phosphates, wax particles, organic silane compounds, naphthenates For example, application of a treatment liquid containing the same is exemplified.

When the film is mainly composed of an inorganic substance, it is mainly composed of a silicate such as sodium silicate, potassium silicate, lithium silicate or the like.
In order to improve the quality of corrosion resistance, lubricity, scratch resistance, workability, weldability, electrodeposition coating property, coating film adhesion, etc., various oxide particles such as colloidal silica and inorganic substances such as various phosphoric acids An example is to apply a treatment liquid containing a pigment, wax particles, and an organic silane compound.

The organic or inorganic coatings may be formed alone or in combination. The combination order may be arbitrarily determined, and an inorganic film may be provided as a lower layer and an organic film may be provided as an upper layer, or vice versa. Further, three or more layers may be laminated. Also, providing these films on the chromate film layer,
This is a more preferable method from the viewpoint of white rust resistance. The preferable amount of the organic or inorganic coating film is generally in the range of 0.05 to 20 μm in terms of the film thickness in consideration of the effect of improving the corrosion resistance and the like and the economy.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples do not limit the present invention, and any design changes based on the above and following gist will be described. Are included within the technical scope of

[0039]

EXAMPLE 1 An Al-killed cold-rolled steel sheet produced by a conventional method was used as a base material for plating. This was degreased and pickled, and then electroplated using a sulfate bath under the following conditions. <Electroplating Conditions> plating solution _{composition: ZnSO 4 · 7H 2 O 350g} / l Na 2 SO 4 70g / l H 2 SO 4 20g / l · Current density: 50 to 150 A / dm ² Plating bath temperature: 60 ± 5 ° C. ・ Plating solution flow rate: 1.3 m / sec ・ Electrode (anode): IrO _x electrode ・ Plating adhesion amount: 20 g / m ² .

In the above plating solution, Pb, Cu, and Ag were added in predetermined amounts of Pb for lead acetate, Cu for copper sulfate, and Ag for silver nitrate. Further, Ni, Co, and In were also added as sulfates.

The amount of impurity elements contained in the plating layer was analyzed by the following method. The electro-zinc plated steel sheet cut to a size of 50 × 50 mm was immersed in 1: 1 hydrochloric acid until the dissolution reaction of Zn was completed. P once dissolved
After the dissolution reaction of the plating layer, the steel sheet is quickly pulled up, and the steel sheet is once again put into a new 1: 1 hydrochloric acid in order to eliminate errors in the analysis values due to b, Cu, and Ag being substituted and precipitated on the surface of the steel sheet as the base material. Dipped for 30 seconds. Thereafter, both solutions were combined to a constant volume, and then an ICP-MS analyzer (VG
Pb and Ag were analyzed using PLASMAQUAD (manufactured by Company I). Cu was quantitatively analyzed using an ICP analyzer (ICPV-1000, manufactured by Shimadzu Corporation).

Without subjecting the plated steel sheet to a chromate treatment, an inorganic film mainly composed of lithium silicate and colloidal silica (as in Example 2) was applied as a lower layer, and a polyester resin was mainly used as an upper layer. (As in Example 2) was applied so that the total film thickness after drying was 0.7 μm.

The obtained chromate-plated steel sheet was evaluated for white rust resistance by a salt spray test according to JIS Z2371. 96 hours after the salt spray test, the white rust generation area ratio was determined according to the following criteria. In order to evaluate the resistance to blackening, the plated steel sheet was stored in a thermo-hygrostat at 50 ° C. × 95% or more relative humidity for 72 hours, and then the color difference (ΔE) before and after the test was determined. Judged. Further, a check for uneven appearance was also performed at the same time. Color difference (色 E)
Is the color tone (L, a, b value of the hunter) made by Nippon Denshoku
It measured at 0 and calculated using the following formula. _{△ E = {(L a -L} b) 2 + (a a -a b) 2 + (b a -b b) 2} 1/2 L a: L value after the test, L _b: before test L Value a _a : a value after test, a _b : a value before test b _a : b value after test, _bb : b value before test

The obtained results are summarized in Tables 1 and 2. <White rust resistance> ：: less than 5%: 5% or more and less than 10%: 10 or more and less than 50% ×: 50% or more <Blackening resistance (color difference)> ：: less than ΔE1 ○: △ E1 Or more and less than 3 Δ: ΔE 3 or more and less than 5 ×: ΔE 5 or more <Blackening resistance (uneven appearance)> ○: no unevenness or almost inconspicuous ×: uneven appearance is noticeable

[0045]

[Table 1]

[0046]

[Table 2]

From Tables 1 and 2, Pb, Cu, Ag and Ni, Co, In in the plating layer and the plating solution were found to be the same as those of Example No. within the range of the present invention. In the case of 1 to 34, it shows very excellent white rust resistance even without having a chromate treatment layer,
At the same time, blackening resistance is good. On the other hand, Pb,
Comparative Example No. 1 in which either or the total amount of Cu or Ag exceeds the upper limit of the present invention. In the case of 35 to 39, the white rust resistance is poor.
Also, Pb, Cu, and Ag are within the scope of the present invention.
Comparative Example No. i where Co, In was lower than the lower limit of the present invention.
In the case of 40 to 42, the white rust resistance was satisfactory, but the result was inferior to blackening resistance. Further, in Comparative Example No. where Ni, Co, and In exceeded the upper limit of the present invention. 43 to 45 are inferior in white rust resistance.

Example 2 In the same manner as in Example 1, Pb, Cu, Ag and N
An electrical Zn-plated steel sheet containing i, Co, and In was produced. A known reaction type chromate treatment was further performed on the obtained electroplated Zn steel sheet. The adhesion amount of the chromate film is adjusted according to the reaction time, and is 20 mg /
It was adjusted to m ^2.

Regarding the obtained chromate-plated steel sheet,
The white rust resistance and the blackening resistance were evaluated by the same test method as in Example 1. However, the test time was evaluated after 48 hours for white rust resistance and 72 hours for blackening resistance. The criteria are the same as in the first embodiment. The obtained results are summarized in Tables 3 to 5.

[0050]

[Table 3]

[0051]

[Table 4]

[0052]

[Table 5]

As is clear from Tables 3 to 5, Pb, Cu, Ag and Ni, Co,
In is Example No. within the scope of the present invention. In the case of 101 to 150, it has excellent resistance to white rust and blackening. On the other hand, in Comparative Example No. in which any one or the total amount of Pb, Cu and Ag exceeds the upper limit of the present invention. In the case of 151 to 159, the white rust resistance is poor. Further, Pb, Cu, and Ag are within the range of the present invention, but Ni, Co, and In are lower than the lower limit of the present invention. In the case of 160 to 163, the white rust resistance was satisfactory, but the result was inferior to blackening resistance. Furthermore, N
Comparative Example No. i, Co, In exceeds the upper limit of the present invention.
In the case of 164 to 167, the white rust resistance is poor.

Example 3 The chromate-treated electrical Zn-plated steel sheet produced in Example 2 was subjected to an organic film treatment. As an organic film,
A material obtained by adding colloidal silica and wax particles to a polyester resin was applied and baked by a roll coater so that the film thickness after drying was 0.5 μm.

The obtained organic resin-coated chromate-treated plated steel sheet was evaluated for white rust resistance and blackening resistance by the same test method as in Example 1. The test time was 360 hours for white rust resistance and 4 hours for blackening resistance.
Evaluation was performed after 80 hours. The criteria are the same as in the first embodiment. Tables 6 and 7 show the obtained results.
Are shown together.

[0056]

[Table 6]

[0057]

[Table 7]

As is clear from Tables 6 and 7, Pb, Cu, Ag and Ni, Co,
In is Example No. within the scope of the present invention. In the case of 201 to 227, even after 360 hours of spraying with salt water, it has extremely excellent white rust resistance, and also has good blackening resistance. On the other hand, in Comparative Example No. in which any one or the total amount of Pb, Cu and Ag exceeds the upper limit of the present invention. 228
In the case of ２232, the white rust resistance is poor. Pb, Cu,
Ag is within the range of the present invention, but Comparative Example No. where Ni, Co, and In are lower than the lower limit of the present invention. In the case of 233 to 235, the white rust resistance was satisfactory, but the result was inferior to blackening resistance. Further, in Comparative Example No. where Ni, Co, and In exceeded the upper limit of the present invention. In the case of 236 to 238, the white rust resistance is poor.

Example 4 A low-carbon aluminum-killed cold-rolled steel sheet coil produced by a conventional method was used as a plating base plate, subjected to alkaline electrolytic degreasing and pickling by a conventional method, and then a total of 11 liquid cushion type horizontal electroplating cells were prepared. Electro-Zn plating was performed in an electroplating line equipped with cells. As raw material Zn, P
Zn particles (diameter 5 to 8 mm) having different contents of b, Cu, and Ag are used, and the anode material is IrO
_x , Pb-Sn, and Pb-In-Ag were used alternately. In the test evaluation, the raw material Zn having the same impurity amount was used.
Alternatively, a plated steel sheet manufactured after continuously using the anode for 10 days was used. The plated steel sheet was coated with an organic resin mainly composed of polyester by an inline roll coater without being subjected to a chromate treatment, and baked and dried. The plating conditions are shown below. <Electroplating Conditions> plating solution _{composition: ZnSO 4 · 7H 2 O 250~350g} / l Ni 2+ 100~200ppm Na 2 SO 4 50~70g / l H 2 SO 4 15~30g / l · Current density: 30 ２００200 A / dm ²通 Passing speed: 50 to 200 mpm め っ き Plating solution temperature: 60 ± 5 ° C. め っ き Plating solution flow rate: 1.0 to 2.0 m / sec 電極 Electrode (anode): IrO _x electrode, Pb-Sn electrode , Pb-In-Ag electrode ・ Plating weight: 20 g / m ²・ Organic coating layer thickness: 0.5 μm

The obtained non-chromate (organic coated) coated steel sheet was evaluated for white rust resistance and blackening resistance by the same test method as in Example 1. The test time was 96 hours for white rust resistance and 4 hours for blackening resistance.
Evaluation was performed after 80 hours. The criteria are the same as in the first embodiment. Table 8 summarizes the obtained results.

[0061]

[Table 8]

From Table 8, it can be seen that IrO _x containing substantially no Pb was used as the anode material, and Pb, C
Example No. u, in which the Ag concentration is within the range of the present invention. 3
In the case of 01 to 304, it has excellent white rust resistance. On the other hand, in Comparative Example No. in which any one of the Pb, Cu, and Ag concentrations exceeded the upper limit of the present invention. Comparative Examples Nos. 305 to 307 and the anode material other than the present invention. In the case of 308 to 309, the white rust resistance is poor.

[0063]

As described above, according to the present invention, the white rust resistance of the non-chromated steel sheet can be greatly improved. Furthermore, the blackening resistance of the non-chromate treated steel sheet could be improved.

Further, the technique for preventing white rust resistance according to the present invention can be applied to a chromate-treated steel sheet, and the white rust resistance of the chromate-treated steel sheet can be further improved.
Improvement in blackening resistance has also become possible.

Continued on the front page (72) Inventor Kuniyasu Araga 1 Kanazawacho, Kakogawa-shi, Hyogo Prefecture Kobe Steel, Ltd. Kakogawa Works (72) Inventor Tomio Kajita 1 Kanazawacho, Kakogawa-shi, Hyogo Kobe Steel Co., Ltd. Kakogawa Works (72) Inventor Hiroo Shigeru 1 Kanazawacho, Kakogawa City, Hyogo Prefecture Kobe Steel, Ltd.Kakogawa Works (72) Inventor Takefumi Watase 1 Kanazawacho, Kakogawa City, Hyogo Prefecture Kobe Steel Works Kakogawa Works (56) Reference Document JP-A-9-276787 (JP, A) JP-A-9-276790 (JP, A) JP-A-8-325789 (JP, A) JP-A-7-70788 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C25D 1/00-7/12

Claims (10)

(57) [Claims] 1. An electro-zinc plated steel sheet in which an inorganic and / or organic film substantially free of Cr is formed on an upper layer of an electroplating layer containing Zn as a main component. Pb is 5 ppm or less and Cu is 10
An electro-zinc plated steel sheet having excellent white rust resistance, characterized in that the content of Ag is 5 ppm or less and the total amount of these elements is 15 ppm or less. 2. One or more metal elements selected from Ni, Co, and In, in the case of Ni, 50 to 700 ppm,
The electrolytic Zn-plated steel sheet according to claim 1, wherein, in the case of In, the resistance to blackening is improved by being contained in the electroplating layer in the range of 0.5 to 50 ppm. 3. An electro-galvanized steel sheet in which a chromate treatment layer is formed on an electroplating layer containing Zn as a main component, wherein Pb contained in the electroplating layer is 10 pp.
m, Cu is 20 ppm or less, Ag is 10 ppm or less, and the total amount of these elements is 30 ppm or less. 4. One or more metal elements selected from Ni, Co and In, in the case of Ni, 50 to 1000 ppm, C
4. The electro-zinc plated steel sheet according to claim 3, wherein in the case of o or In, the resistance to blackening is improved by being contained in the electroplating layer in a range of 0.5 to 50 ppm. 5. 5. The galvanized steel sheet according to claim 3, wherein an inorganic and / or organic film is formed on the chromate treatment layer. 6. The method according to claim 1, wherein Pb in the plating solution is 0.5 ppm or less, Cu is 1 ppm or less, and Ag is 0.5 ppm or less.
A method for producing an electro-galvanized steel sheet having excellent white rust resistance, wherein electro-zinc plating is performed using an acidic plating solution having a total amount of these elements of 1.5 ppm or less. 7. The method for producing an electro-zinc plated steel sheet according to claim 2, wherein at least one metal ion selected from Ni, Co, and In is 25 to 300 pp in the case of Ni.
A method for producing an electro-galvanized steel sheet having excellent resistance to white rust and blackening, wherein electro-zinc plating is performed using an acidic plating solution containing 0.1 to 30 ppm of m, Co or In. 8. The method according to claim 3, wherein Pb in the plating solution is 1 ppm or less.
Production of an electro-galvanized steel sheet excellent in white rust resistance, characterized in that electro-zinc plating is performed using an acidic plating solution containing 2 ppm or less of Cu, 1 ppm or less of Ag, and a total amount of these elements of 3 ppm or less. Method. 9. The method for producing an electro-galvanized steel sheet according to claim 4, wherein the content of one or more metal ions selected from Ni, Co, and In is 25 to 500 ppm. A method for producing an electro-galvanized steel sheet excellent in white rust resistance and blackening resistance, wherein electro-zinc plating is performed using an acidic plating solution containing 1 to 30 ppm. 10. An anode comprising substantially Pb, Cu, Ag
Using an iridium oxide electrode containing no Pb, as an impurity element, Pb of 15 ppm or less, Cu of 20 ppm or less,
An electro-Zn plating process is performed by using a raw material Zn containing Ag in a range of 7 ppm or less.
5. The method for producing an electric Zn-plated steel sheet according to item 5.