KR101332477B1 - METHOD FOR MANUFACTURING Cr-FREE BLACKING ELECTROPLATED STEEL SHEET WITH EXCELLENT SURFACE APPEARANCE - Google Patents

Abstract

Disclosed are a chromium-free blackened electroplated steel sheet excellent in surface appearance and a method of manufacturing the same.
Method for producing a black electroplated steel sheet according to the present invention comprises the steps of (a) forming an electroplating layer comprising a Zn-Ni alloy on the base steel sheet; And (b) forming a blackening electroplating layer including Zn-Ni alloy but not containing chromium (Cr) on the electroplating layer, wherein step (b) comprises sodium nitrate (NaNO ₃ ). Characterized in that the electrolyte is carried out by a cathodic plating method.

Description

Method for manufacturing chromium-free blackened electroplated steel sheet with excellent surface appearance {METHOD FOR MANUFACTURING Cr-FREE BLACKING ELECTROPLATED STEEL SHEET WITH EXCELLENT SURFACE APPEARANCE}

The present invention relates to a blackening electroplating steel sheet used for the purpose of decoration or absorbance in copying machines, air conditioners, cameras, automobiles, etc. In more detail, the surface appearance is excellent, while the blackening electroplating layer does not contain chromium and is environmentally friendly. The present invention relates to a chromium-free blackened electroplated steel sheet capable of simplifying the process and a method of manufacturing the same.

In general, the surface-treated steel sheet produced by continuous plating is manufactured for various uses by applying various post-treatment techniques. In particular, black steel sheet (black steel sheet) is widely used as a steel sheet for home appliances, such as audio, video.

The black steel sheet is manufactured through blacking treatment in a plating process or a painting process.

Since blackening in the coating process requires the use of a separate black paint, the production cost of black steel sheet is relatively high. Therefore, many studies on the blackening treatment in the plating process has been made, and the black steel sheet manufactured by electroplating during plating is called blackening electroplating steel sheet.

Conventional black plating is generally performed by black chromium plating, black chromate treatment, etc., as disclosed in Korean Patent Publication No. 1996-0002637 (1996.02.24.).

However, the chromium is a component that adversely affects the environment, and in recent years, the use of chromium has been refrained. Korean Patent Publication No. 10-2005-0089076 (published on September 7, 2005) discloses a black zinc-based plated steel sheet that does not contain hexavalent chromium. However, the above document proposes a technique for forming a black film through the anode electrolytic treatment.

However, as described in the above document, the black film formed by the anodic electrolytic treatment has poor corrosion resistance, and to compensate for this, phosphate ions, vanadium ions, metal ions, α, β-unsaturated carboxylic acid are added to the black film. And a separate composite film containing glycol uril resin, resulting in an increase in steel sheet manufacturing cost.

An object of the present invention does not require a separate black coating process, it is possible to form a blackening electroplating layer directly in the electroplating process by improving the plating conditions of the rear end of the electroplating line, and also contains chromium (Cr) in the blackening electroplating layer It is to provide a method for producing a chromium-free blackening electroplating steel sheet.

Another object of the present invention is to provide a chromium-free blackening electroplating steel sheet produced by the above method excellent in surface appearance.

The blackening electroplated steel sheet manufacturing method according to an embodiment of the present invention for achieving the one object comprises the steps of (a) forming an electroplating layer including a Zn-Ni alloy on the base steel sheet; And (b) forming a blackening electroplating layer including Zn-Ni alloy but not containing chromium (Cr) on the electroplating layer, wherein step (b) comprises sodium nitrate (NaNO ₃ ). Characterized in that the electrolyte is carried out by a cathodic plating method.

At this time, it is preferable that the electrolyte solution contains NaNO ₃ at a concentration of 2 to 5 g / L. In addition, the step (b) is most preferably carried out with a current density of 40 ~ 60 ℃, pH 1.5 ~ 2.0, 10 ~ 60A / dm ² and adhesion amount of 2 ~ 4g / m ² .

In addition, the method of manufacturing a blackening electroplating steel sheet according to the present invention may further comprise the step (c) forming a fingerprint resin layer on the blackening electroplating layer.

Blackening electroplating steel sheet according to an embodiment of the present invention for achieving the above another object is a base steel plate; An electroplating layer formed on the base steel sheet including a Zn-Ni alloy; And a blackening electroplating layer formed on the electroplating layer including Zn-Ni alloy and not including chromium (Cr), wherein the blackening electroplating layer is one of zinc oxide (ZnO) and nickel oxide (NiO). It is characterized by containing at least one oxide and at least one sulfide among zinc sulfide (ZnS) and nickel sulfide (NiS).

The method for producing blackened electroplated steel sheet according to the present invention does not include chromium, which is environmentally friendly and has the advantage of manufacturing blackened electroplated steel sheets having excellent blackness and peeling process without a separate black coating process.

In addition, the manufactured blackening electroplating steel sheet can be utilized as a material in various fields requiring design and luxury surface appearance such as home appliances, acoustic equipment, copiers, cameras, and the like through a uniform surface appearance.

Figure 1 schematically shows a chromium-free blackening electroplating steel sheet according to an embodiment of the present invention.
Figure 2 schematically shows a method for producing a chromium-free blackening electroplating steel sheet according to an embodiment of the present invention.
Figure 3 shows an example of an electroplating line that can be applied to the present invention.
4 to 6 show the change in the surface whiteness according to the concentration of the additive contained in the blackening electrolyte.
Figure 7 shows the change in surface whiteness according to the electrolysis time when the composite additive is applied to the blackening electrolyte.

Hereinafter, a chromium free blackening electroplating steel sheet having excellent surface appearance and a method of manufacturing the same will be described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Figure 1 schematically shows a chromium-free blackening electroplating steel sheet according to an embodiment of the present invention.

Referring to FIG. 1, the chromium free blackening electroplating steel sheet according to the present invention includes a base steel plate 110, an electroplating layer 120, and a blackening electroplating layer 130. The base steel sheet 110 may be used a variety of steel sheets without particular limitation, preferably a cold rolled steel sheet that is easy to electroplating may be used.

The electroplating layer 120 may be formed on the base steel sheet 110 including a Zn-Ni alloy.

The blackening electroplating layer 130 is formed on the electroplating layer 120 by including a Zn-Ni alloy, it does not contain chromium (Cr). In this case, the blackening electroplating layer 130 includes at least one oxide of zinc oxide (ZnO) and nickel oxide (NiO), and at least one sulfide of zinc sulfide (ZnS) and nickel sulfide (NiS).

In addition, referring to Figure 1, the chromium-free blackening electroplating steel sheet according to the present invention may be further formed on the chromium-free blackening electroplating layer 130 to the fingerprint resin layer 140. When the anti-fingerprint layer 140 is further formed, corrosion resistance, chemical resistance, lubricity, and the like may be further improved.

The to-fingerprint layer may be formed in various compositions, but preferably does not contain chromium, and the amine-based resin 10 to 30% by weight, the silica and silane mixture of silica and silane in a weight ratio of 1: 0.2 to 0.8 10 ~ It is preferable to form in the composition containing 50 weight%, an inorganic sol 1-10 weight%, and a residual amount of epoxy resin.

The amine resin plays a role of imparting adhesive force by crosslinking. Such amine-based resin is preferably contained in 10 to 30% by weight of the total weight of the anti-fingerprint resin layer. When the amine resin is added in less than 10% by weight, the adhesive strength due to crosslinking is insufficient, and when it exceeds 30% by weight, the workability is lowered.

Silica-silane mixtures are added to improve storage stability, adhesion, corrosion resistance and processability. The silica-silane mixture is preferably contained in 10 to 50% by weight of the total weight of the fingerprint resin layer. If the silica-silane mixture is added at less than 10% by weight, the conductivity is deteriorated, and if it exceeds 50% by weight, the workability is lowered.

The silica may be colloidal silica, fumed silica, or the like, and the silane may be clicside oxypropyl ethoxysilane, aminopropyl ethoxysilane, methoxyoxypropyl drimethoxysilane, or the like. Silica and silane can be used mixed in a weight ratio of 1: 0.2 ~ 0.8. When the silica and the silane are mixed in a weight ratio of less than 1: 0.2, crosslinkability is lowered, and when the amount is mixed in excess of 1: 0.8, workability may be reduced.

Inorganic sol is included to improve adhesion and corrosion resistance. As the inorganic sol, zirconia sol, alumina sol, titanium sol and the like can be used. The inorganic sol is preferably contained in 1 to 10% by weight of the total weight of the anti-fingerprint layer. If the inorganic sol is less than 1% by weight, the effect of the inorganic sol may not be obtained. If the inorganic sol is more than 10% by weight, corrosion resistance may be improved.

Epoxy resin acts as a binder resin, forms a dense barrier coating, is resistant to corrosion factors such as salt and oxygen, and has excellent corrosion resistance and chemical resistance because hydroxyl groups in the molecule have excellent adhesion to the substrate.

Figure 2 schematically shows a method for producing a chromium-free blackening electroplating steel sheet according to an embodiment of the present invention.

Referring to FIG. 2, the illustrated method for manufacturing a chromium-free blackening electroplating steel sheet includes an electroplating layer forming step S210 and a blackening electroplating layer forming step S220, and after forming the blackening electroplating layer, a step of forming a fingerprint resin layer (S230). ) May be further included.

3 illustrates an example of an electroplating line that may be applied to the present invention, and includes an electroplating unit 310 and a blackening electroplating unit 320. In describing the electroplating layer forming step S210 and the blackening electroplating layer forming step S220 illustrated in FIG. 2, reference is made to FIG. 3.

In the electroplating layer forming step (S210), the electroplating layer is formed on the base steel sheet through the continuous electroplating in the electroplating unit 310 illustrated in FIG. 3. The electroplating layer may be performed by a cathode plating method using a base steel sheet as a cathode and using an insoluble anode.

In the blackening electroplating layer forming step (S220), a blackening electroplating layer is formed on the electroplating layer in the blackening electroplating part. This step is performed in the same manner as the electroplating step of the electroplating method including the Zn-Ni alloy in the electroplating method after the electroplating layer forming unit 310 shown in Figure 3 by the cathode plating method, sodium nitrate (NaNO ₃ ) additive in the electrolyte Included, but does not contain chromium (Cr).

At this time, the electrolyte solution preferably contains NaNO ₃ at a concentration of 2 to 5 g / L. When the NaNO ₃ concentration is less than 2 g / L, the blackening electroplating layer does not grow sufficiently. On the contrary, when the NaNO ₃ concentration exceeds 5g / L, the blackening plating layer becomes coarse due to the overgrowth of the blackening plating layer. May occur.

Most preferably, the electrolyte solution contains ZnSO ₂ · 6H ₂ O 100 to 200 g / L, NiSO ₂ · 6H ₂ O 150 to 250 g / L, Na ₂ CO ₃ 70 to 90 g / L, and NaNO ₃ 2 to 5 g / L. Do. When the concentrations of ZnSO ₂ · 6H ₂ O and NiSO ₂ · 6H ₂ O correspond to the above ranges, appropriate adhesion amount and solution stability can be ensured, and the balance of zinc and nickel can be maintained. Na ₂ CO ₃ improves the conductivity during plating, and if it is added below 70 g / L, it does not play a role of improving conductivity. When it is added above 90 g / L, it is easy to form zinc hydroxide at the cathode interface. As a result, edge burning of the plated material may occur.

In addition, it is preferable that blackening electroplating is performed at 40-60 degreeC. When the blackening electroplating temperature is less than 40 ℃, the plating layer growth rate can be greatly reduced. On the contrary, when the blackening electroplating temperature exceeds 60 ° C, it is difficult to form a uniform blackening electroplating layer, and solution stability may decrease.

In addition, it is preferable to use the electrolyte solution of pH 1.5-2.0 for blackening electroplating. When the pH of the electrolyte is less than 1.5, problems such as plating stain may occur due to problems of solution stability. In contrast, when the pH of the electrolyte exceeds 2.0, the electroplating rate may be significantly slowed.

In addition, blackening electroplating is preferably carried out at a current density of 10 ~ 60A / dm ² . If the current density is less than 10A / dm ² , the degree of blackening may be insufficient. On the contrary, when the current density exceeds 60 A / dm ² , cracking of the blackening electroplating layer may occur.

In addition, it is preferable that blackening electroplating is performed by the adhesion amount of 2-4 g / m <^2> . When blackening electroplating amount is less than 2g / m ² , the degree of blackening may be insufficient, on the contrary, when blackening electroplating amount exceeds 4g / m ² , due to overplating may cause cracks in the blackening electroplating layer.

In the anti-fingerprint layer forming step (S230), the anti-fingerprint layer is formed on the blackening electroplating layer in order to improve the corrosion resistance, chemical resistance, lubricity, and the like of the blackening electroplating layer. The anti-fingerprint layer may be formed with an adhesion amount of about 1 g / m ² and a thickness of about 1 μm by a 1 coating 1 baking method.

Example

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Details that are not described herein will be omitted since the description can be inferred by those skilled in the art.

1. Preparation of specimens

As the blackening electroplating solution, blackening electroplating was performed using various additives in plating solutions containing ZnSO ₂ · 6H ₂ O 150g / L, NiSO ₂ · 6H ₂ O 200g / L, Na ₂ CO ₃ 80g / L.

A Zn-Ni plated layer was formed at an adhesion amount of 20 g / m ² on a 0.8 mm thick cold rolled steel sheet degreased, washed with water and pickled. After the final washing, blackening electroplating was performed on the Zn-Ni plating layer using the above electroplating solution under the conditions shown in Tables 1 to 3. All blackening electroplating was carried out at 53 ° C. The electrolyte also contained 150 g / L of ZnSO ₂ · 6H ₂ O, 200 g / L of NiSO ₂ · 6H ₂ O, and 80 g / L of Na ₂ CO ₃ .

Table 1 shows the anodized blackening electroplating conditions and the whiteness (Lightness, L) of each specimen after plating when HNO ₃ and H ₃ PO ₄ are applied as additives, and FIGS. 4 to 6 are included in the blackening electrolyte solution. It shows a change in surface whiteness according to the concentration of the additive.

In Table 1 and FIGS. 4 to 6, the lower the whiteness L, the higher the degree of blackening.

 [Table 1]

Referring to Table 1, the case where nitric acid (HNO ₃ ) was applied as an additive was generally superior to the case where phosphoric acid (H 3 PO 4) was applied as an additive. In addition, in the case of nitric acid, the higher the addition amount, the better the degree of blackness, but in the case of phosphoric acid, the degree of blackness was not significantly lowered. In addition, when the blackening electroplating was higher than the current density is low, the degree of black was better.

In addition, in the case of liquid flow, the blackening degree was better when the air injection was stopped while stirring and air injection were performed simultaneously, and the surface appearance showed a tendency to be stable.

When nitric acid and phosphoric acid are used in combination, when the addition amount of phosphoric acid is fixed at 0.5 g / L, the longer the electrolysis time, the higher the degree of blackness.

However, when air was also applied for liquid flow, the appearance was uneven.

In addition, the same electroplating conditions as Specimen 1-7, but further pickling pretreatment before blackening electroplating, whiteness was 24.8, indicating that the pickling pretreatment does not significantly affect the whiteness.

Figure 7 shows the change in surface whiteness according to the electrolysis time when the composite additive is applied to the blackening electrolyte.

Referring to FIG. 7, the whiteness was lowered up to 10 seconds of the electrolysis time under the conditions of 0.5 g / L phosphoric acid and 3 g / L nitric acid, but there was no significant change thereafter.

However, when blackening electroplating was carried out under the conditions shown in Table 1, that is, anodization, cracking of the plating layer occurred in many cases.

Table 2 shows the blackening electroplating conditions and plating of anodizing method when an ammonium sulfate ((NH4) 2.SO4), sodium chlorate (NaClO3), sodium sulfate (Na2SO4) and sodium nitrate (NaNO3) other than acid were added as an additive. The whiteness (L) of each specimen is shown.

[Table 2]

Referring to Table 2, when ammonium sulfate was applied as an additive, sufficient blackening plating layer was not formed, and an undissolved phenomenon occurred when the amount of ammonium sulfate was increased. In addition, when sodium chlorate or sodium sulfate was applied as an additive, blackening degree was obtained, but it was difficult to obtain a uniform surface appearance. In addition, the lower the pH, the lower the degree of blackening, which appears to be a solution stability problem.

In addition, when sodium nitrate was added as an additive, blackness was obtained. In particular, in the case of 2-10 specimens, the surface appearance was excellent with low whiteness. However, when sodium thiosulfate (Na ₂ S ₂ O ₃ ) was added together, the surface appearance was not good.

Appearance was observed after the Danny Moon treatment on specimens 2-5, 2-9 and 2-10. As a result, specimens 2-9 and 2-10 showed better surface appearance. In addition, as a result of the tape peeling test after the Ericsson process, the peeling rate of 50% and the fingerprint resin was peeled off in the case of Specimen 2-5, but in the case of specimens 2-9 and 2-10, the tape peeling rate of 0% and the fingerprint resin layer were It did not peel off.

Therefore, it can be said that it is most preferable to add sodium nitrate as an additive.

Table 3 shows the blackening plating conditions and the whiteness (L) when sodium nitrate is applied as an additive.

[Table 3]

Referring to Table 3, when the additive is sodium nitrate, it can be seen that the whiteness is generally excellent under various plating conditions. However, when the addition amount was only 1g / L, blackening did not proceed, and when the addition amount was 6g / L, some cracking occurred in the blackening electroplating layer, and the most preferable addition amount of sodium nitrate was 2-5g / L. .

On the other hand, in the case of specimens 3-3 to 3-10, oxygen (O) of about 20% by weight was detected on the surface of the blackening electroplating layer, and sulfur (S) component was detected as high as about 10% by weight. This blackening electroplating layer is Zn, Ni and O, each of the S can be combined to include zinc oxide, nickel oxide, zinc sulfide, nickel sulfide.

On the other hand, the anti-fingerprint resin coating was applied to the specimens 3-5 to 3-7, showing good appearance.

Table 4 shows the results of friction coefficient and chemical resistance after blackening plating and anti-fingerprint coating when sodium nitrate was applied as an additive.

[Table 4]

Referring to Table 4, the coefficient of friction was found to be low for all specimens.

In addition, in order to see the chemical resistance, the MEK solution was applied to the specimen surface, and then tested using a wear resistance tester (500 g / cm 2, 50 round trips). As a result, all specimens showed good results (standard: ΔE <1.5), and in particular, specimens 3-2 to 3-6 showed very good results.

In addition, in order to confirm the peeling of the plating layer by processing, Ericsson test was performed. After raising the processed part to 6 mm, the processed part was peeled off using a scotch tape. In addition, a 10 × 10 cross cut test was performed to examine blackening plating peelability.

As a result of the Ericsson test and the cross cut test, it was found that both the specimens 3-2 to 3-6 and the specimen 3-8 did not have tape peeling, and thus had good adhesion and workability.

Although the above description has been made with reference to the embodiments of the present invention, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible.

Accordingly, the true scope of protection of the present invention should be defined by the following claims.

110: base steel plate
120: electroplating layer
130: blackening electroplating layer
140: anti-finish resin layer
310: electroplating part
320: blackening electroplating
S210: electroplating layer forming step
S220: blackening electroplating layer forming step
S230: forming an anti-fingerprint layer

Claims (12)

(a) forming an electroplating layer including a Zn-Ni alloy on the base steel sheet; And
(b) forming a blackening electroplating layer including Zn-Ni alloy but not containing chromium (Cr) on the electroplating layer;
The step (b)
ZnSO ₂ · 6H ₂ O 100-200 g / L, NiSO ₂ · 6H ₂ O 150-250 g / L, Na ₂ CO ₃ 70-90 g / L and NaNO ₃ 2-5 g / L by cathodic plating The blackening electroplating steel sheet manufacturing method characterized in that it is carried out.
delete delete The method of claim 1,
The step (b)
The blackening electroplating steel sheet manufacturing method characterized in that it is carried out at 40 ~ 60 ℃.
The method of claim 1,
The step (b)
The blackening electroplating steel sheet manufacturing method characterized in that carried out at pH 1.5 ~ 2.0.
The method of claim 1,
The step (b)
The blackening electroplated steel sheet manufacturing method characterized by being carried out at a current density of 10 ~ 60A / dm ² .
The method of claim 1,
The step (b)
Process for producing blackening electroplated steel sheet, characterized in that it is carried out with an adhesion amount of 2 ~ 4g / m ²
The method of claim 1,
(c) forming an anti-fingerprint layer on the blackening electroplating layer; the method of manufacturing a blackening electroplating steel sheet further comprising a.
9. The method of claim 8,
The anti-finger resin layer is
10 to 30% by weight of the amine resin, 10 to 50% by weight of the silica-silane mixture of silica and silane in a weight ratio of 1: 0.2 to 0.8, 1 to 10% by weight of the inorganic sol and the balance of the epoxy resin Blackening electroplating steel sheet manufacturing method to be.
delete delete delete

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