JPH0565700A - Resin coated zn-ni-cr-al2o3 type electroplated steel sheet and its production - Google Patents

Abstract

PURPOSE:To produce a resin coated Zn-Ni-Cr-Al2O3 type electroplated steel sheet having high corrosion resistance, excellent in surface smoothness and external appearance, and suitable for automotive body steel sheet. CONSTITUTION:The resin coated Zn-Ni-Cr-Al2O3 type electroplated steel sheet has a Zn-Ni-Cr-Al2O3 alloy plating layer, which has a composition consisting of, by weight, 6-16% Ni, 0.1-10.0% Cr, 0.01-5% Al, and the balance Zn and where the degree of gloss (60 deg.C) by JIS Z 8741 at the plating surface is regulated to >=50, at least on one side of the steel sheet and also has a resin layer on the alloy plating layer with or without a chromate later in-between. Further, this electroplated steel sheet has characteristics in the plating bath composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-coated Zn-Ni-Cr- which is suitable for use in a portion of an automobile body having a poor coating throwing property and which is excellent in corrosion resistance, particularly bare corrosion resistance.
The present invention relates to an Al ₂ O ₃ -based electroplated steel sheet and a method for manufacturing the same.

[0002]

2. Description of the Related Art Zn-Ni alloy-plated steel sheets are widely used as materials for automobiles, home appliances, building materials, etc. in fields requiring corrosion resistance. The corrosion resistance of Zn-Ni-based plating depends on the Ni content in the plating, and the corrosion resistance becomes suitable when the Ni content is 6 to 16% by weight. Even if the Ni content exceeds 16% by weight, not only the corrosion resistance is not improved but there is a tendency for deterioration, and further increase of the expensive Ni content is rather meaningless. .. Therefore, Zn and Ni
Only the alloys cannot improve the corrosion resistance to some extent.

Therefore, a third metal, especially Cr, is used,
A technique for improving the corrosion resistance of Zn-Ni based plating has been proposed.

First, Japanese Examined Patent Publication No. 59-38313 discloses a Zn-Ni-Cr alloy-plated steel sheet, in which a sulfuric acid bath is used to add Cr.
Those containing 0.1 to 1.0% by weight are disclosed.

Further, JP-A-02-310394 discloses a Zn-Ni-Cr alloy-plated steel sheet in which 1% by weight or more of Cr is contained in the Zn-Ni plating by using a chloride bath. Things are disclosed. JP 02-3
According to Japanese Patent No. 10394, particularly when the Cr content is 2% by weight or more, good corrosion resistance can be obtained. It is also disclosed that Pb should be 2.5 ppm or less in order to suppress the damage of Pb as an impurity.

[0006] In fact, the inclusion of Cr in the Zn-Ni plating is effective in improving the corrosion resistance. However, Japanese Examined Patent Publication No. 59-38313 describes that when the Cr content exceeds 1.0% by weight, the appearance of plating is impaired, and the inventors of the present invention disclose Japanese Patent Laid-Open No. 02-310394. When the technology of
A black streak pattern was generated with an increase in the content, and the appearance was also deteriorated. A surface analysis of this Zn-Ni plating revealed that Cr was concentrated in the black portion, and as a result, a Cr-concentrated layer appeared in a layered form.

Therefore, the present inventors have proposed Zn-Ni plating.
If Cr is uniformly co-deposited in the inside,
I think that the problem can be solved, and in Zn-Cr composite plating
A technique for uniformly co-depositing Cr, JP-A-63-15
Suitable for Zn-Ni-Cr plating of the technique of Japanese Patent No. 7900.
I tried to use it. In addition, in JP-A-63-157900
The disclosed technology is trivalent in Zn-Cr composite plating.
Cr ions of₂O ₃ / Cr molar ratio of 0.3 to 2
This is to use the positively charged alumina sol deposited. Only
In this method, the plating surface has irregularities of 0.1 to several μm.
Occurred and the glossiness became almost zero.

As described above, various attempts have been made to further improve the corrosion resistance of Zn-Ni alloy plating.
Not enough has been obtained yet.

Recently, on the plating layer, there is
Alternatively, a steel sheet having improved corrosion resistance has been developed by forming a thin film type organic resin film without intervention. Even in such a high corrosion-resistant steel plate, Zn-Ni plating is often used as the undercoat.

When an Zn-plated steel sheet with such an organic coating is applied to an automobile, when the thickness of the uppermost organic resin film exceeds 2.5 μm, the weldability (continuous It was revealed that the hitting point) was poor. Therefore, in general, an uppermost organic resin film having a thickness of 0.5 μm or more and 2.5 μm or less is used, which has relatively good press workability and weldability,
Regarding the corrosion resistance, it is not necessarily sufficient, probably because of the underlying plating.

[0011]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a resin coating suitable for use as a steel sheet for automobile bodies, which has high corrosion resistance and is excellent in surface smoothness and appearance. _{Zn-Ni-Cr-Al 2} O 3 based electroplated steel sheet and to provide a manufacturing method thereof.

[0012]

According to a first aspect of the present invention, at least one side of a steel sheet has 6 to 16% by weight of Ni, 0.1 to 10.0% by weight of Cr, and 0.01 to 5% of Al. % By weight, balance Zn, JIS Z 8 on plating surface
Z having a glossiness Gs (60 ° C.) of 741 of 50 or more
_{n-Ni-Cr-Al 2} O 3 based alloy plating layer, a resin film and having a resin layer on the alloy plating layer Z
is a _{n-Ni-Cr-Al 2} O 3 based electroplated steel sheet.

According to a second aspect of the present invention, at least one surface of the steel sheet contains 6 to 16% by weight of Ni and 0.1 to 10.0 of Cr.
% -Zn-Ni-Cr- containing 0.01 to 5% by weight of Al, the balance being Zn, and the glossiness Gs (60 ° C.) of the plating surface according to JIS Z 8741 of 50 or more.
A resin coating Zn-Ni-Cr-Al ₂ O ₃ -based electroplated steel sheet having an Al ₂ O ₃ -based alloy plating layer, a chromate layer on the alloy plating layer, and a resin layer on the chromate layer. ..

In a third aspect of the present invention, Zn ions are replaced with ZnCl ₂
100-300 g / l, Ni ions as NiCl ₂ 10-200 g / l, trivalent Cr ions 0.1-2
0 g / l and alumina sol 0.2 to 0.2 in terms of alumina
After electroplating the surface of the steel sheet with a chloride plating bath containing 20 g / l and further containing 0.1 g / l or more of polyvinyl alcohol as a brightener, a resin layer is formed on the plated layer. Resin coating Zn characterized by
A -Ni-Cr-Al ₂ O ₃ based method for manufacturing an electro-plated steel sheet.

In a fourth aspect of the present invention, Zn ions are replaced with ZnCl ₂
100-300 g / l, Ni ions as NiCl ₂ 10-200 g / l, trivalent Cr ions 0.1-2
0 g / l and alumina sol 0.2 to 0.2 in terms of alumina
After electroplating the surface of the steel sheet with a chloride plating bath containing 20 g / l and further containing polyvinyl alcohol 0.1 g / l or more as a brightener, a chromate layer is formed on the plating layer. And a resin layer Zn-N characterized by further forming a resin layer on the chromate layer.
This is a method for producing an i-Cr-Al ₂ O ₃ -based electroplated steel sheet.

The present invention will be described in detail below. Begin
And the resin-coated Zn-N according to the first and second aspects of the present invention.
i-Cr-Al₂O ₃ The electroplated steel sheet will be described.

In the steel sheet according to the first and second aspects of the present invention, the composition of the undercoat layer is such that Ni is 6 to 16% by weight, Cr is 0.1 to 10.0% by weight, and Al is 0. 01 ~
It contains 5% by weight and the balance is Zn.

Among the four kinds of metals constituting the undercoat plating layer, the action mechanism of the effects related to the corrosion resistance of Ni and Cr is mainly summarized in the following four points.

Depending on the corrosive environment, Ni, which is more noble than Zn,
When elements such as Cr and Cr are present in the plating layer, excessive activity of Zn plating is suppressed. Zn plating easily produces conductive ZnO as a corrosion product, but when Ni is present, Ni is non-conductive Zn (OH).
Stabilizes ₂ and exhibits plating protection. Generally, as chromate treatment improves corrosion resistance,
Cr plays a major role in improving corrosion resistance. Especially Cr
Forms a passive film at the initial stage of corrosion, prevents elution of plating, and also prevents redox reaction, which greatly contributes to corrosion resistance.

Even if the passivation film formed once is broken by uniformly depositing Ni or Cr in the plating layer, the broken portion has a slow elution rate of the plating due to the action of However, due to the effect of, non-conductive Zn (OH) ₂ is generated and a passive film is formed again (self-repairing action).

In order to effectively obtain the above effects (1) to (6), Ni in the alloy electroplating layer is 6 to 16% by weight and C
r is 0.1% by weight or more, preferably 2 to 10% by weight.

When the Ni content is less than 6% by weight, a large improvement in corrosion resistance is not observed even when a proper amount of Cr is co-deposited.
Even if it exceeds 16% by weight, not only the corrosion resistance is not improved but it tends to deteriorate.

When the Cr content is less than 0.1% by weight, red rust is generated by a salt spray test (SST) within 1000 hours, and corrosion resistance is deteriorated. Although 0.1% by weight or more is obviously effective, when the Cr content is increased, the corrosion resistance is further improved, and 2% by weight or more is preferable. However, when Cr in the plating layer exceeds 10% by weight, the plating becomes hard and brittle, cracks occur during processing, and the plating eventually separates. Therefore, the amount of Cr eutectoid in the plating layer is preferably 10% by weight or less.

Al is Zn-Ni- which is a base plating layer.
It is derived from an alumina sol used for stably and uniformly depositing a large amount of Cr when forming a Cr-Al ₂ O ₃ -based plating layer, and is contained in the plating layer in an amount of 0.01 to 5% by weight. Although the details will be described later, suitable Zn-Ni is preferable.
In order to form a --Cr--Al ₂ O ₃ system plating, the alumina sol is converted to alumina in the plating bath and the amount is 0.2 to 20 g /
It is advisable to add Al in this case, and in that case, the Al content in the plating layer is 0.01 to 5% by weight.

Further, Zn in the base plating layer is the main component of the plating layer and exhibits sacrificial corrosion resistance.

The base plating layer containing the above four metals has a gloss level G according to JIS Z 8741 of the plating surface.
s (60 ° C) must be 50 or more. this is,
This indicates that the plating surface is smooth and has metallic luster, and that the glossiness of less than 50 indicates that the plating surface has irregularities of several μm. And
If the unevenness is present, the plating surface is exposed by penetrating the chromate layer and the resin layer on the plating layer, and the corrosion resistance is reduced.

In the steel sheet of the first aspect of the present invention, the resin layer is provided on the undercoating layer, and in the steel sheet of the second aspect of the present invention, the resin layer is provided on the undercoating layer via a chromate layer described later. ..

As the organic resin which constitutes this resin layer,
Examples thereof include epoxy resins, acrylic resins, polyester resins, urethane resins, olefin acrylic resins and the like, or copolymer derivatives thereof. In addition to the organic resin, the resin layer usually also contains additives such as a rust preventive additive such as SiO ₂ , a surface tension viscosity modifier, and a lubricity imparting agent.

The steel sheet according to the second aspect of the present invention has a chromate layer between the base plating layer and the resin layer. The chromate layer has the effect of ensuring the adhesion between the base plating layer and the resin layer.

The chromate layer may be a layer of a known ordinary chromate film, and more specifically, for example, a mixed solution containing chromic anhydride, chromate salt, dichromic acid or the like as a main component,
This layer is mainly composed of a hydrated chromium, which is obtained by using a treatment liquid prepared by mixing colloidal silica, vapor phase silica and the like in the mixed liquid, and treating the mixture by a known ordinary method.

The structure of the coating layer of the steel sheet according to the first and second aspects of the present invention is as described above. The layer thickness of each layer is
Although not particularly limited, the following range is preferable.

That is, the base plating layer is 1 to 60 g /
m ² is preferred. If it is less than 1 g / m ² , sufficient corrosion resistance cannot be obtained, while if it is more than 60 g / m ² , it cannot be economically produced.

The resin layer preferably has a thickness of 0.5 to 2.5 μm. If it is less than 0.5 μm, the effect of improving the corrosion resistance by the resin does not exist, and if it is more than 2.5 μm, the weldability, the suitability for cationic ED, and the press workability may deteriorate.

The chromate layer preferably has an adhesion amount of 130 mg / m ² or less in terms of metallic chromium. If it exceeds 130 mg / m ² , the weldability deteriorates, which is not preferable in practice.

The steel sheet according to the first aspect of the present invention has, on at least one surface thereof, the above-mentioned base plating layer of Zn-Ni-Cr-.
It has an Al ₂ O ₃ alloy plating layer and a resin layer on the plating layer. If only one face has these two layers, the other face may have any configuration. Incidentally, suitable are steel sheet having a _{Zn-Ni-Cr-Al 2} O 3 alloy plating layer and the resin layer on both surfaces.

The steel sheet according to the second aspect of the present invention has, on at least one surface thereof, the above-mentioned base plating layer of Zn-Ni-Cr-.
It has an Al ₂ O ₃ based alloy plating layer, a chromate layer on the plating layer, and a resin layer on the chromate layer. If you have these three layers on only one side,
The other aspects may have any configuration. In addition, a steel sheet having a Zn-Ni-Cr-Al ₂ O ₃ alloy plating layer, a chromate layer and a resin layer on both surfaces is preferable.

Next, according to the third and fourth aspects of the present invention,
A method for producing a resin-coated Zn-Ni-Cr-Al ₂ O ₃ -based electroplated steel sheet will be described.

In the manufacturing methods of the third and fourth aspects of the present invention, the raw steel sheet (cold rolled steel sheet, high corrosion resistant steel sheet, etc.) is pretreated as necessary, and then a specific plating bath is used. Electroplating.

That is, the Zn ions are changed to ZnCl ₂ and
0-300g / l, Ni ion as NiCl ₂ 10-2
00 g / l, trivalent Cr ions of 0.1 to 20 g / l and alumina sol of 0.2 to 20 g / l in terms of alumina.
The surface of the raw steel sheet is electroplated using a chloride plating bath containing 0.1 g / l or more of polyvinyl alcohol as a brightening agent.

The reasons for limiting the content of each component in this plating bath are as follows. First, Zn ions, which are 100 to 300 g / l as ZnCl ₂ . ZnCl
_{When 2} is less than 100 g / l, there is a problem that plating efficiency is lowered and plating burn occurs, and when it exceeds 300 g / l, ZnCl ₂ is saturated in the liquid.

Ni ions in the plating bath are NiCl₂ As
10 to 200 g / l is added. NiCl ₂ Is less than 10 g / l
Then, the amount of Ni eutectoid in the plating layer decreases,
Corrosion resistance cannot be obtained. Moreover, when it exceeds 200 g / l,
The Ni eutectoid amount in the plating layer becomes too high, and in this case as well,
Corrosion resistance deteriorates.

As Cr ions in the plating bath, CrCl
₃ , Cr ₂ (SO ₄ ) ₃ , KCr (SO ₄ ) _{2 and the} like are used, and 0.1 to 20 g / l is added as trivalent Cr ions. When it is less than 0.1 g / l, the amount of Cr eutectoid in the plating layer is small, and sufficient corrosion resistance cannot be obtained. Moreover, when it exceeds 20 g / l,
The amount of Cr eutectoid in the plating layer becomes too high, the plating becomes hard and brittle, cracks occur during processing, and the plating finally separates.

Cr ions are prepared separately from Ni and Zn together with an alumina sol described later, and C is added onto the alumina sol.
It is necessary to adsorb and add r. At that time, the pH is 5
Below. When the pH exceeds 5, most of Cr ions are changed to chromium oxide and are not adsorbed on the alumina sol, so that the co-deposition of Cr in the plating layer becomes unstable.

Alumina sol is used for adsorbing the above-mentioned trivalent Cr, which is also contained in the plating bath, and for stably and uniformly depositing a large amount of Cr, which is generally said to be difficult to eutectoid. That is, when used in the form of pseudo-boehmite, the phenomenon that the trivalent Cr is adsorbed on the negatively charged alumina sol is utilized, and when there is no alumina sol, the amount of Cr eutectoid in the plating layer is 0.1 wt%. As described above, the streak pattern that occurs darkly is eliminated.

The amount of alumina sol added is 0.2 to 20 g / l in terms of alumina. When it is 0.2 g / l or less, uniform co-deposition of Cr in the plating layer is insufficient and streaks appear. On the other hand, if it exceeds 20 g / l, the viscosity of the plating bath increases and plating becomes difficult. When plating is performed with a plating bath containing alumina sol within this range, the Al concentration in the plated layer falls within the range of 0.01 to 5% by weight.

As the alumina sol, it is appropriate to use pseudo-boehmite particles having a particle size of 5 to 30 nm.

As mentioned above, the alumina sol contains trivalent Cr.
It is effective to stably and uniformly deposit a large amount of aluminum, but the addition of alumina sol to the plating bath causes unevenness of several μm on the surface of the plating layer, which eliminates the appearance of metallic luster and When chromate or resin is applied, non-uniformity occurs, and in some places plating penetrates through the resin layer and is exposed on the surface.

Therefore, an organic substance that smoothes the plating surface is added to the plating bath. As a result, the surface becomes smooth and the luster becomes metallic luster, and it becomes possible to uniformly apply the chromate or the resin on the plating layer, thereby improving the corrosion resistance.

In the present invention, as the brightener, polyvinyl alcohol (PVA, degree of polymerization = 20 to 1000) which does not impair the corrosion resistance and other plating performance is used.
Add 10 g / l. If the amount of PVA added is less than 0.1 g / l, the performance of smoothing the plating is weak and the surface gloss cannot be 50 or more. On the other hand, when it is added in excess of 10 g / l, the viscosity of the plating bath increases.

In the present invention, the above-mentioned chloride plating bath may be prepared by a known method. After the alumina sol is dispersed in a Cr ion-containing solution and Cr ions are adsorbed on the alumina sol, the chloride plating bath is not Preferred is the method of mixing with a solution containing the ions and additives.

The electroplating may be carried out by a known method using the above chloride plating bath. As an example, using a zinc plate as an anode and a base steel plate as a cathode, a bath temperature of 30 to 70 ° C.,
Bath pH 2.0-4.0, plating current density 20-200A /
dm ^2, energization amount of electricity 30~2000C / dm ² may be performed electroplating.

In the third aspect of the present invention, after electroplating,
The resin layer is formed.

The resin layer is formed by preparing a resin composition containing an organic resin such as an epoxy resin, an acrylic resin, a polyester resin, a urethane resin and an olefin acrylic resin as a main component, and applying the resin composition to a bar coater, a roll coater or the like. It may be applied by a method used, or by a method such as spray coating or dip coating, and dried by heating.

In the fourth aspect of the present invention, after electroplating,
The chromate layer is formed.

The formation of the chromate layer may be carried out by a known method. For example, coating type chromate treatment, reactive type chromate treatment and electrolytic type chromate treatment can be applied.
In addition, when performing coating type or reactive type chromate treatment, in addition to Cr (IV) and Cr (III), inorganic colloids,
A treatment liquid containing an acid such as phosphoric acid, a fluoride, or the like may be used. Then, after applying the treatment liquid to the steel plate after plating, it is about 80 to 200 ° C. (80 in the case of a BH steel plate or the like.
It may be dried at up to 150 ° C.

In the fourth aspect of the present invention, the resin layer is formed after the formation of the chromate layer. The method for forming the resin layer is the same as in the case of the third aspect of the present invention.

[0057]

EXAMPLES The present invention will be specifically described below based on examples.

(Example) (1) Preparation of test piece Plating treatment A cold-rolled steel sheet having a plate thickness of 0.7 mm was prepared and subjected to degreasing and pickling pretreatments for plating by a conventional method. next,
Using a plating bath having the composition shown in Table 1, one side was electroplated under the following conditions. [Plating conditions] Plating bath temperature: 60 ° C. Plating bath pH: 2.5-3 Plating current density: 100 A / dm ² Electricity supplied: 700 C / dm ² Anode: Zinc plate

Chromate Treatment After the plating treatment, a part of the test pieces was coated on the plating layer.
A coating type chromate treatment was performed under the following conditions. [Condition-type chromate treatment conditions] A treatment solution consisting of chromic anhydride 5%, zinc phosphate 1.5%, and phosphoric acid 1% was applied to a plated steel sheet with a roll coater, and at 120 ° C,
Drying was performed for 0 to 30 seconds.

Formation of Resin Layer Except for Comparative Example 7, any one of the following resin solutions was applied on the surface of the test piece after chromate treatment or not subjected to chromate treatment with a bar coater under the following conditions. It was baked and dried. (A) Conditions for forming acrylic resin layer [Resin liquid] Acrylic resin (acrylonitrile 1
0%, vinyl chloride 50%) 20%, silica 5% [baking conditions] 115 ° C., 10 to 30 seconds (b) Epoxy resin layer forming conditions [resin liquid] epichlorohydrin-bisphenol A type epoxy resin ( Mw> 2000) 10% silica 8% [Baking conditions] 120 ° C., 10 to 30 seconds (c) Urethane resin layer forming conditions [Resin liquid] Mw ≦ 4000 polyether urethane resin 15%, silica 10% content [Baking conditions] 110 ° C., 15 to 40 seconds The plating layer composition, the adhesion amount of the plating layer, the chromate layer and the resin layer of each test piece produced under the above conditions are as shown in Table 1. ..

(2) Test / Evaluation Method Test / Evaluation on Plating Layer (a) Glossiness JIS Z 8741 was used for the test piece after the plating treatment.
Was used to measure the glossiness in the optical path of 60 ° / 60 °.

(B) Roughness With respect to the test piece after the plating treatment, the roughness was evaluated by observation with a scanning electron microscope and shown as smooth or uneven.

(C) Pattern The appearance of the test pieces after the plating treatment was visually evaluated, and ◯ means no pattern and x means streak (striped pattern).

Test on test piece after resin layer formation
Evaluation (a) Salt water spray test The test was performed for 1000 hours according to JIS Z 2371, and evaluated by the area (%) in which red rust occurred.

(B) Complex corrosion test Salt water (5% saline solution) spraying for 2 hours, drying for 2 hours, wet (>)
Two cycles of 90% RH and 35 ° C.) for 2 hours and 2 hours for drying were performed for 200 cycles, and the reduction in plate thickness (mm) of the perforated corrosion portion was evaluated. The results are shown in Table 1, and the steel sheet of the present invention has excellent plating appearance, significantly improved corrosion resistance, and improved smoothness.

[0066]

[Table 1]

[0067]

[Table 2]

[0068]

As described above, according to the present invention,
In particular, the corrosion resistance of the steel sheet can be remarkably improved by plating with a light weight. Further, according to the present invention, a resin-coated steel sheet excellent in surface smoothness and appearance can be obtained. Therefore, when the steel sheet of the present invention is applied to materials for transportation vehicles including automobiles, materials for construction, materials for electric devices, etc., industrially excellent effects can be obtained.

Claims (4)

[Claims] 1. A steel sheet having at least one surface coated with Ni in an amount of 6 to 16
% By weight, 0.1 to 10.0% by weight of Cr, 0.0% of Al
1 to 5% by weight, the balance being Zn, and the plating surface has a gloss Gs (60 ° C.) of 5 according to JIS Z 8741.
And _{Zn-Ni-Cr-Al 2} O 3 alloy plating layer is 0 or more, resin coating _{Zn-Ni-Cr-Al 2} O 3 based electricity and having a resin layer on the alloy plating layer Plated steel sheet. 2. A steel sheet having at least one surface coated with Ni in an amount of 6 to 16
% By weight, 0.1 to 10.0% by weight of Cr, 0.0% of Al
1 to 5% by weight, the balance being Zn, and the plating surface has a gloss Gs (60 ° C) of 5 according to JIS Z 8741.
0 or in which _{Zn-Ni-Cr-Al 2} O 3 alloy plating layer, a resin film and having a chromate layer and resin layer on the chromate layer on the alloy plating layer Zn
-Ni-Cr-Al ₂ O ₃ based electroplated steel sheet. The 3. Zn ions as ZnCl ₂ 100 to 300
g / l, Ni ion as NiCl ₂ 10-200 g /
1, 0.1-20 g / l of trivalent Cr ions and 0.2-20 g / l of alumina sol in terms of alumina,
Furthermore, 0.1g of polyvinyl alcohol is used as a brightener.
/ After performing electroplating on the surface of the steel sheet with a chloride plating bath l containing more, resin coating _{Zn-Ni-Cr-Al 2} O , which comprises forming a resin layer on the plating layer
Manufacturing method of ₃ series electroplated steel sheet. 4. Zn ion is used as ZnCl.₂ As 100-300
g / l, Ni ion is NiCl₂ 10-200g /
1, trivalent Cr ions of 0.1 to 20 g / l and al
Minasol is contained in an amount of 0.2 to 20 g / l in terms of alumina,
Furthermore, 0.1g of polyvinyl alcohol is used as a brightener.
On the surface of steel sheet using a chloride plating bath containing more than 1 / l
After performing electroplating, a chromate layer on the plated layer
To form a resin layer on the chromate layer.
Resin coating Zn-Ni-Cr-Al characterized by ₂O₃ system
Manufacturing method of electroplated steel sheet.