JP6927061B2 - Manufacturing method of plated structure - Google Patents

Description

The present invention relates to a method for manufacturing a plated structure including a chromium plating layer.

In Patent Document 1, a trivalent chromium plating layer having a thickness of 0.05 to 2.5 μm formed by using basic chromium sulfate as a metal source and formed on the trivalent chromium plating layer by a cathode acidic electrolytic chromate treatment. A chrome-plated component having a chrome compound film having a thickness of 7 nm or more is disclosed. The cathode acidic electrolytic chromate treatment is carried out in a bath having a pH of 1.0 to 5.5 and a temperature of 20 to 70 ° C. containing at least one of dichromate, chromate and chromic anhydride at 20 to 40 g / l. It is said that the treatment is performed at a current density of 0.1 to 1.0 A / dm ^{2 under the condition of 10 to 90 seconds.}

As described above, for the cathode acidic electrolytic chromate treatment, it was necessary to use an electrolytic solution containing hexavalent chromium, which is completely different from the plating solution for the trivalent chromium plating layer. Hexavalent chromium has a problem of environmental pollution.

Regarding the film thickness of the chromium compound film formed by the cathode acidic electrolytic chromate treatment, Patent Document 1 states that "FIG. 2 ... As is clear from the figure, the film thickness of the chromium compound film 7 is 7 nm. The composition (at%) of each element tends to be stabilized in the region where the amount is large, especially in the region where the size is larger than 9 nm. ”However, the film thickness shown in FIG. 2 is up to 12 nm. Therefore, it is not assumed that the film thickness is as thick as 20 nm or more, and it is considered difficult to form the film.

In recent years, plating in which the color tone of a metal color is changed, such as so-called blue plating, has been preferred. Cannot be changed.

Japanese Unexamined Patent Publication No. 2009-74168

Accordingly, a first object of the present invention, by using a trivalent chromium plating solution, chromium plating layer, so that a high film thickness 20nm or more corrosion thereon chromium oxide layer can efficiently on preferred and readily formed To be.
The second purpose is to allow the chromium oxide layer to change the color tone of the appearance of the plated structure.

( 1 ) For the first purpose, the method for producing a plating structure of the present invention is to form a chromium plating layer by electrolytically treating with a trivalent chromium plating solution at a current density of 3 A / dm ^{2 or more.} ,
The current density is reduced to 0.05 to 2.5 A / dm ² by continuously using the same trivalent chromium plating solution or by using a trivalent chromium plating solution obtained by adding a material to the trivalent chromium plating solution. It is characterized in that a chromium oxide layer having a thickness of 20 nm or more is formed on the surface of the chromium plating layer by electrolytic treatment.

Generally, the hexavalent chromium chemical conversion treatment is referred to as a chromate treatment, and the chromium oxide layer formed by the treatment is referred to as a chromate layer. Therefore, in the present invention, the chromium oxide layer formed by the trivalent chromium electrolysis treatment is referred to as a chromate layer. I won't say it.

[Action]
Until now, it has not been known that a chromium oxide layer is formed by trivalent chromium electrolysis treatment, but this has been made possible by the present invention. The mechanism by which a chromium oxide layer is formed on the surface of the chromium plating layer by electrolytic treatment with a trivalent chromium plating solution at a current density of 0.05 to 2.5 A / dm ^{2 is related to the redox potential.} It seems, but the details are unknown.
As shown in Sample 1 described later, even if the surface of the nickel plating layer was electrolyzed with a trivalent chromium plating solution, the chromium oxide layer was not formed regardless of the current density, so that the chromium plating layer was present. Is considered essential for the formation of the chromium oxide layer.

In the current hexavalent chromium chemical conversion treatment (chromate treatment) or trivalent chromium chemical conversion treatment, the film formation rate of the chromium oxide layer is slow, it is difficult to increase the film thickness, and a chemical conversion treatment bath different from the plating bath is required. In the case of hexavalent chromium, there is a problem that yellowing due to ^{Cr 6+ is generated.}

On the other hand, the present invention has the following advantages.
-The film formation rate of the chromium oxide layer is faster than that of the chemical conversion treatment, and it is easy to make the film thickness 20 nm or more.
-For the second purpose, the film thickness of the chromium oxide layer can be set to 30 nm or more so as to exhibit an interference color, and the color tone of the appearance of the plated structure can be changed. The interference color can be changed by changing the film thickness of the chromium oxide layer at 30 nm or more. By making the chromium oxide layer exhibit a blue interference color at a film thickness of 45 to 90 nm, a so-called blue-plated plating structure can be obtained.
-The chromium plating layer and the chromium oxide layer can be formed by continuously electrolyzing in one plating bath (trivalent chromium plating solution).
^-Since Cr 6+ is not used, yellowness does not occur.

According to the inventions according to claims 1 and 2, using a trivalent chromium plating solution, a chromium plating layer and a chromium oxide layer having a film thickness of 20 nm or more and having high corrosion resistance are continuously formed, which is preferable and easily efficient. Can be formed.
According to the invention of claim 3, the color tone of the appearance of the plated structure can be changed by the chromium oxide layer.
According to the invention of claim 4, it can be a so-called blue-plated plating structure.

1A is a schematic cross-sectional view of the plating structure manufactured in Sample 1, FIG. 1B is Sample 2, FIG. 1C is a schematic cross-sectional view of Examples 1 and 2, and FIG. 1D is Example 3. FIG. 2 (a) is a perspective view showing a Hull cell test, FIG. 2 (b) is sample 1, (c) is sample 2, (d) is plating in Example 1, and (e) is plating using a Hull cell plate in Example 2. It is a front view of the structure. FIG. 3 is a graph showing XPS data of the first embodiment. FIG. 4 is a graph showing XPS data of the second embodiment. FIG. 5 is a graph showing the relationship between the film thickness of the chromium oxide layer of Example 1 and the reflection wavelength. FIG. 6 is a graph showing the relationship between the integrated current value and the film thickness of the chromium oxide layers (and the hexavalent chromate layer of Comparative Example) of Examples 1 and 2. FIG. 7 is a scanning electron micrograph of a comparative example.

1. 1. Base material of the object to be treated The material of the base material is not particularly limited, and examples thereof include metals and resins (surface conductivity). In the case of a resin base material, the resin may be thermoplastic or thermosetting, and is not particularly limited, but is limited to acrylonitrile / butadiene / styrene copolymer (ABS) resin, polycarbonate (PC) resin, PC / ABS resin, acrylic resin, and styrene. Examples thereof include resins, polyamide resins, polycarbonate resins, polypropylene resins, vinyl chloride resins, and polyurethane resins.

2. Base plating layer The base plating layer under the chrome plating layer is not essential and is not particularly limited, but a nickel plating layer is preferable. This is because the nickel-plated layer retains the aesthetic appearance of the chrome-plated layer and is electrochemically anticorrosive. The specific configuration of the nickel plating layer is not particularly limited, and may be one layer or a plurality of layers.
When the base material is a resin base material, the base plating layer preferably includes a copper plating layer under the nickel plating layer. This is because the copper plating layer is highly ductile and therefore follows the resin base material well.

3.3 Chromium Chromium Plating Solution The trivalent chromium compound used in the trivalent chromium plating solution is not particularly limited, but is chromium sulfate (Cr ₂ (SO ₄ ) ₃ ), chrome alum (CrK (SO ₄ ) ₂ ), and the like. Examples include chromium nitrate (Cr (NO ₃ ) ₃ ), chromium chloride (CrCl ₃ ), chromium acetate (Cr (CH ₃ COO) ₃ ), and the like.
As the trivalent chromium plating solution, the same one may be used continuously at the time of forming the chromium plating layer and at the time of forming the chromium oxide layer, or at the time of forming the chromium oxide layer, a material is added to the composition at the time of forming the chromium plating layer. It is preferable for efficiency to use the ones having different degrees .

4. Chromium plating layer The type of chrome plating layer is not particularly limited, but when the interference color due to the chromium oxide layer is expected, the darker the color underneath, the clearer the interference color can be seen. Is preferable.
The film thickness of the chromium plating layer is not particularly limited, but is preferably 0.1 μm or more in terms of durability, preferably 2 μm or less, and more preferably 1.5 μm or less in terms of preventing an increase in internal stress of the film.

5. Chromium oxide layer There is no particular upper limit on the film thickness of the chromium oxide layer, but if it is dared, it is preferably 200 nm or less, and more preferably 150 nm or less in terms of not overly extending the treatment time.

6. Applications of plated structures The applications of plated structures are not particularly limited, but are limited to vehicle decorative parts (radiator grills, fenders, garnishes, hubcaps, back panels, air spoilers, emblems, etc.), electrical products (mobile phones, smarts, etc.) Examples of housing parts for (phones, mobile information terminals, game machines, etc.) can be exemplified.

Prior to the embodiment, a plating structure [Sample 1] using the Hull cell plates shown in FIGS. 1 (a) and 2 (b) and the Hull cell plates shown in FIGS. 1 (b) and 2 (c) were used. The plated structure [Sample 2] was prepared on a trial basis by the following method.

[Sample 1]
(1) Pretreatment of Halcel plate and formation of glossy nickel plating layer A brass Halcel plate (dimensions 100 mm × 75 mm × 0.3 mm) was pretreated (defatted, pickled, washed with water, etc.).
A bright nickel plating layer was formed as a base plating layer on the surface of the Halcel plate. The base plating was performed by putting a nickel plating solution in a nickel plating tank, immersing the hull cell plate and the anode plate in parallel, and performing electrolytic plating.

(2) Attempt to Form Chromium Oxide Layer by New Method An attempt was made to form a chromium oxide layer by a new method of electrolyzing the surface of the bright nickel plating layer with a trivalent chromium plating solution at a low current density. Specifically, the Halcel test will be used, and as shown in FIG. 2A, the Halcel plate 1 taken out from the nickel plating tank is set as a cathode on the inclined wall of the Halsel tank 4 (267 ml) and confronted therewith. An anode plate 2 is set on the wall, and a trivalent chromium plating solution 3 (the trivalent chromium compound is basic chromium sulfate contained in trichromium azitibu) composed of an aqueous solution containing the following components is placed in a tank. It was carried out by electrolytic plating under the treatment conditions of a bath temperature of 35 ° C., a current of 2 A, and a treatment time of 300 seconds.
Boric acid 10g / L
Atotech Trichrome Agitib 400g / L
Atotech Trichrome Stabilizer 90ml / L
Atotech Trichrome Collector 3ml / L
Atotech Trichrome Regulator 3.5ml / L
Atotech Trichrome Graphite Makeup 90ml / L
The pH value was adjusted to 3.2 using hydrochloric acid.

In the Halsel test, the current density is high in the high electric portion 1a of the Halcel plate having a short distance between the anode plate and low, and the current density is low in the low electric portion 1b of the Halcel plate having a long distance between the electrode plate and the anode plate. FIG. 2B shows sample 1, and each distance (mm) from the edge of the high-voltage portion 1a of the Hull cell plate to the plurality of analysis points is entered. Table 1 shows the current densities and precipitates at each of these analysis points. In both the analysis points with a current density of 10 to 3 A / dm ^{2 and} the analysis points with a current density of ^{2 to} 0.1 A / dm 2, the lower glossy nickel plating layer is visually covered with black plating, and the analysis shows metallic chromium (black chrome). The plating layer) was deposited. That is, when the layer directly below is a bright nickel-plated layer, the attempt to form the chromium oxide layer by the new method has not been realized.

[Sample 2]
(1) Pretreatment of Halcel plate and formation of glossy nickel plating layer Same as (1) of Sample 1.

(2) Formation of Black Chrome Plating Layer by Trivalent Chrome Plating A black chrome plating layer having a film thickness of 0.3 μm was formed on the surface of the glossy nickel plating layer by trivalent chrome plating. For trivalent chrome plating, a trivalent chrome plating solution (same as the solution composition used in (2) of Sample 1) is placed in a chrome plating tank, and the Halcel plate and the anode plate are immersed in parallel, and the bath temperature is 35 ° C. The process was performed by electrolytic plating under the treatment conditions of a current of 2 A and a plating time of 150 seconds.

(3) Formation of Chromium Oxide Layer by New Method A chromium oxide layer was formed on the surface of the black chromium plating layer by a new method of performing electrolytic treatment with a trivalent chromium plating solution at a low current density. Specifically, the Halcel test was used, and as shown in FIG. 2A, the Halcel plate 1 taken out from the chromium plating tank was set as a cathode on the inclined wall of the Halsel tank 4 (267 ml), and the cathode was set. The anode plate 2 is set on the facing wall, the trivalent chromium plating solution 3 (same as the solution composition used in (2) of sample 1) is put in the tank, the bath temperature is 35 ° C., the current is 2A, and the processing time is 300 seconds. It was carried out by electrolytic plating under the treatment conditions of.

FIG. 2C shows sample 2, and each distance (mm) from the edge of the high-voltage portion 1a of the Hull cell plate to the plurality of analysis points is entered. Table 2 shows the current densities and precipitates at each of these analysis points. At the analysis site having a current density of 10 to 3 A / dm ² , there was no change in the color tone of the lower black chromium plating layer visually, and metallic chromium (black chromium plating layer) was deposited in the analysis. ^{At the analysis site with a current density of 2 to} 0.1 A / dm 2, the color tone of the lower black chrome plating layer changed visually, and chromium oxide was precipitated in the analysis.

[Examples 1 and 2]
Next, plating using the plating structure [Example 1] using the Hull cell plate shown in FIGS. 1 (c) and 2 (d) and the Hull cell plate shown in FIGS. 1 (c) and 2 (e). The structure [Example 2] was produced by the following method.

(1) Pretreatment of Halcel plate and formation of glossy nickel plating layer Same as (1) of Sample 1.

(2) Formation of Black Chromium Plating Layer by Trivalent Chromium Plating The same as (2) of Sample 2.

(3) Formation of Chromium Oxide Layer by New Method Example 1 was different from Sample 2 in that the treatment conditions were changed such that the current was 0.5 A and the treatment time was 120 seconds, and the other steps were the same as in Sample 2. FIG. 2D shows Example 1, and each distance (mm) from the edge of the high-voltage portion 1a of the Hull cell plate to the plurality of analysis points is entered.
Example 2 was different from sample 2 in that the processing conditions were changed such that the current was 0.5 A and the processing time was 30 seconds, and the other steps were the same as in sample 2. FIG. 2E shows Example 2, and each distance (mm) from the edge of the high-voltage portion 1a of the Hull cell plate to the plurality of analysis points is entered.
Table 3 below shows the current densities at each of the analysis points of Examples 1 and 2.

The elements (particularly O, Cr and C) present at each of the analysis points of Examples 1 and 2 were analyzed by XPS (X-ray photoelectron spectroscopy). Specifically, the element is analyzed every time the etching is performed at a depth of 5.4 nm at an X-ray spot size of 400 μm and an etching rate of 0.09 nm / sec × 60 seconds, and a total of about 160 nm (5.4 nm × 30 times) is performed. Etched. FIG. 3 shows XPS data of each analysis point of Example 1, and FIG. 4 shows XPS data of each analysis point of Example 2. From this XPS data, chromium oxide was precipitated at each analysis site of Examples 1 and 2, and a plating structure as shown in FIG. 1 (a) was formed. It can be seen that the degree is as shown in Table 3.

Further, the precipitated chromium oxide layer itself was transparent, and as shown in Table 3, the color tone of the lower black chromium plating layer did not change when the film thickness was 20 nm. However, as the film thickness changed from 30 to 50 to 60 to 110 to 140 nm, the color tone of the appearance of the plated structure changed from brown to blue to light blue to yellow to red. It is considered that the color is developed by the interference of the reflected light on both sides of the chrome layer.

The Lab chromaticity of this observed color tone was measured using a color difference meter. Further, the reflection wavelength was measured using a spectrophotometer MCPD3700 manufactured by Otsuka Electronics Co., Ltd. (reference: AL, vertical incidence (incident angle θ = 0 °)). The results of these measurements are shown in Table 3. Further, FIG. 5 shows the relationship between the film thickness of the chromium oxide layer of Example 1 and the reflection wavelength. From this result, it is possible to easily obtain an arbitrary interference color by controlling the current density in the range of 2.5 to 0.05 A / dm ² and changing the film thickness of the chromium oxide layer, which has been particularly preferred in recent years. It can be seen that the so-called blue plating can be easily realized.

Bragg's reflection type λpeak = 2d (n _eff ^2- sin 2θ) ^0.5
(Θ: incident angle, λpeak: reflection wavelength, d: surface spacing, n _eff : refractive index)
And from the measurement result of vertical incidence (θ = 0 °)
λpeak (nm) = 5.9149 x film thickness (nm)
Refractive index of chromium oxide layer n _eff = 2.96
Is calculated.

Further, FIG. 6 shows the relationship between the integrated current value and the film thickness of the chromium oxide layer at each analysis site of Examples 1 and 2, and as a comparative example, when forming a chromate layer by the current hexavalent chromium chemical conversion treatment. The relationship (example) between the integrated current value and the film thickness is shown. In addition, FIG. 7 shows a scanning electron microscope (SEM) photograph of a comparative example in which a chromate layer is formed. From these, it can be seen that in the current hexavalent chromate treatment, the film formation rate is slow and the chromate layer is thin, whereas in the new method of the example, the film formation rate is high and the chromium oxide layer is thick.

[Example 3]
A plating structure [Example 3] using the resin base material shown in FIG. 1 (d) was produced by the following method.

(1) Pretreatment of resin base material and formation of glossy nickel plating layer A plate-shaped resin base material made of ABS resin was pretreated (defatting, acid treatment, washing with water, etc.).
An electroless nickel plating layer was formed on the surface of the resin base material.
On the electroless nickel plating layer, a copper plating layer, a semi-bright nickel plating layer, a bright nickel plating layer, and a corrosion-dispersed nickel plating layer having a microporous structure were formed in this order as a base plating layer. The base plating was performed by putting each metal plating solution in each plating tank, immersing the resin base material and the anode plate in parallel, and electrolytically plating.

(2) Formation of Black Chrome Plating Layer by Trivalent Chrome Plating A black chrome plating layer having a film thickness of 0.3 μm was formed on the surface of the corrosion-dispersed nickel plating layer by trivalent chromium plating. For trivalent chrome plating, a trivalent chrome plating solution (same as the solution composition used in (2) of Sample 1) is placed in a chrome plating tank, and the resin base material and the anode plate are immersed in parallel, and the bath temperature is 35. This was performed by electrolytic plating under the treatment conditions of ° C., current 2A, and plating time 150 seconds.

(3) Formation of Chromium Oxide Layer by New Method Subsequently, a chromium oxide tank having a film thickness of 70 nm was formed on the surface of the black chromium plating layer by electrolytic treatment. In the electrolytic treatment, the bath temperature was lowered to 35 ° C. and the current was 0.5 A while the resin base material and the anode plate were immersed in the trivalent chrome plating solution of the chrome plating tank of (2) above in parallel, and the plating time was 120 seconds. Under the treatment conditions of (1), the same electrolytic treatment as the electrolytic plating was continued.

In order to evaluate the corrosion resistance of the prepared plated structure of Example 3, a CASS test (JIS H 8502) was carried out under the following conditions.
Test solution: sodium chloride 40 g / L, cupric chloride 0.205 g / L, pH value 3.0
Saturator temperature 63 ° C
Test tank temperature 50 ° C
Spray volume 1.5 ml / 80 cm ² / h
Compressed air pressure 0.98 MPa
Sample placement angle 30 °
Test time 80 hours After the CASS test was completed, the rating number was 8 or more, and no visual corrosion was observed.

The present invention is not limited to the above-described embodiment, and can be appropriately modified and embodied without departing from the spirit of the invention.

1 Halcel plate 2 Anode plate 3 Trivalent chromium plating solution 4 Halcel tank

Claims (6)

After forming a chromium plating layer by electrolytic treatment with a trivalent chromium plating solution at a current density of 3 A / dm ^{2 or more,}
The current density is reduced to 0.05 to 2.5 A / dm ² by continuously using the same trivalent chromium plating solution or by using a trivalent chromium plating solution obtained by adding a material to the trivalent chromium plating solution. A method for producing a plating structure in which a chromium oxide layer having a thickness of 20 nm or more is formed on the surface of a chromium plating layer by electrolytic treatment. The trivalent chromium compound used in the trivalent chromium plating solution is chromium sulfate (Cr). ₂ (SO _Four ) ₃ ), Chrome alum (CrK (SO) _Four ) ₂ ), Chromium nitrate (Cr (NO) ₃ ) ₃ ), Chromium chloride (CrCl) ₃ ) Or chromium acetate (Cr (CH) ₃ COO) ₃ ). The method for manufacturing a plated structure according to claim 1. The method for producing a plated structure according to claim 1 or 2, wherein the chromium oxide layer has a film thickness of 30 nm or more. The method for producing a plating structure according to claim 1 or 2, wherein the chromium oxide layer exhibits a blue interference color at a film thickness of 45 to 90 nm. The method for manufacturing a plating structure according to any one of claims 1 to 4, wherein the chrome plating layer is a black chrome plating layer. The method for producing a plating structure according to any one of claims 1 to 5, wherein the thickness of the chrome plating layer is 0.1 to 2 μm.

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