JP2781362B2 - Manufacturing method of chrome plated products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a chrome-plated product which exhibits high corrosion resistance and excellent gloss appearance over a long period of time and is suitable as an exterior or outdoor decoration of automobiles and buildings. More specifically, the present invention relates to a method for producing a chromium-plated product, which has improved corrosion resistance in a product having been subjected to so-called microporous plating and has an appearance gloss without using a brightener.

[0002]

2. Description of the Related Art Copper, nickel and chromium or nickel and chromium are sequentially electroplated on a base material such as a zinc die-cast product, a steel plate pressed product, an aluminum die-cast product, or a synthetic resin molded product subjected to electroless plating to impart conductivity. These are widely used as exterior decorations for automobiles and exteriors for buildings.

In the case where chromium is electroplated on a nickel layer, as shown in FIG. 1A, the chromium side has a negative electrode due to defects such as pits and cracks penetrating the chromium layer generated during plating. The nickel side becomes the anode, and current flows between them, but since the anode area on the nickel side is small, the corrosion current density of the nickel layer increases,
As a result of the rapid progress of corrosion, a phenomenon is observed in which the chromium plating layer on the formed corrosion cavities is detached at an early stage and the appearance is impaired in a short time.

In order to improve such disadvantages, as shown in FIG. 1B, plating is performed in a nickel plating bath in which non-metallic inert fine particles are dispersed, and the fine particles are deposited in a nickel plating layer. After forming a composite nickel plating layer, chromium plating is performed thereon to form a large number of micropores in the chromium plating layer, thereby increasing the area of the anode, reducing the corrosion current density, and improving the corrosion resistance.
A so-called microporous chrome plating method is known. In this method, the nickel plating layer provided as an underlayer is a single layer of a bright nickel layer or a multilayer of a bright nickel layer and a semi-bright nickel layer.

However, when the microporous chromium-plated product is exposed to a corrosive environment, a corrosive liquid penetrates into the micropores of the chromium plating layer and forms a battery between the chromium plating layer and the composite nickel plating layer. Then, the composite nickel plating layer serving as the anode dissolves and disappears, and then the bright nickel plating layer dissolves and disappears in a circular shape and becomes hollow, and the chromium plating layer removes the composite nickel layer and the bright nickel layer that supported it. By losing it, it will be broken into pieces in this cavity or will be washed away by the corrosive liquid. As a result, there is a defect that corrosion holes are scattered on the chromium plating surface and the appearance becomes marbling in a short time.

[0006] In order to remedy such drawbacks, it is necessary to reduce the distance between the chromium plating layer and the composite nickel plating layer, between the composite nickel plating layer and the bright nickel plating layer, and between the bright nickel plating layer and the semi-bright nickel plating layer. (JP-A-5-287579 and JP-A-5-171468) have been proposed, but the potential difference is determined by the concentration of the brightener, the unevenness of the current density, and the stirring conditions. Since it depends on the presence or absence of impurities, it is difficult to always keep it in a certain range in a production line.

Further, a method of increasing the strength by thickening the composite nickel plating layer so as to support the chromium plating layer even when the underlying bright nickel plating layer is hollowed out is considered. This method is unsuitable because as the thickness increases, the surface of the chromium plating layer becomes fogged and its value as a decoration decreases.

[0008]

SUMMARY OF THE INVENTION The present invention overcomes the drawbacks of the conventional microporous plated products, and has high corrosion resistance and excellent gloss appearance over a long period of time even under severe conditions. The purpose of the present invention is to provide a production method.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies on the improvement of corrosion resistance and appearance gloss of microporous plated products, and as a result, have found that a nickel-phosphorus alloy plated layer in which non-metallic inert fine particles are dispersed is formed. By forming in a plating bath containing a surfactant and reducing the potential difference between the nickel-phosphorus alloy plating layer containing non-metallic inert fine particles and the chromium layer, the corrosion rate of this nickel-phosphorus alloy plating layer is reduced and , Greatly delaying the start of corrosion of the bright nickel plating layer, and since the nickel-phosphorus alloy itself has a high strength, the chromium layer can be supported for a long time even if the bright nickel layer has a cavity due to corrosion, Moreover, they have found that an excellent gloss appearance can be obtained without using a brightener, and based on this finding, the present invention has been accomplished.

That is, the present invention provides a method for producing a nickel-phosphorus containing a nickel supply source, a phosphorus supply source, and an anionic or nonionic surfactant after forming a required metal base layer on a conductive substrate by electroplating. Electroplating is performed in an electrolytic solution prepared by adding non-metallic inert fine particles to an alloy plating bath composition to form a nickel-phosphorus alloy plating layer containing dispersed non-metallic inert fine particles having a thickness of 0.15 to 20 μm. And then a thickness of 0.01 to 0.5 μm
And a method for producing a microporous chrome-plated product characterized by applying a chromium plating coating.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The conductive substrate used in the method of the present invention includes metals such as iron, zinc, copper, and aluminum, alloys thereof, and various ceramics and plastics such as glass, which have been made conductive by electroless plating. ,iron oxide,
Porcelain, ABS resin, polycarbonate resin, polyacetal resin, polyamide resin, polypropylene resin, polyphenylene oxide resin, epoxy resin, polyurethane resin, urea resin and the like are used.

As a metal electroplating underlayer provided on these conductive substrates, a combination of a bright nickel plating layer and a semi-bright nickel plating layer is generally used as in the case of a normal microporous chrome plating product. Used.

This bright nickel plating layer not only gives a mirror surface to the chromium coating applied thereon but also plays a role of anodic corrosion protection for the semi-bright nickel plating layer of the underlayer. It can be formed by adding a brightener to a watt bath. As a brightener at this time, for example, sodium 1,5-naphthalenedisulfonic acid, sodium 1,3,6-naphthalenetrisulfonate, saccharin and the like as a primary brightener, and 1,4-butynediol as a secondary brightener, Combinations of propargyl alcohol, sodium allyl sulfonate and the like can be used. An appropriate content of the brightener is in the range of 0.04 to 1.0% by weight.

Next, the semi-bright nickel-plated layer improves the smoothness of the substrate to improve the overall appearance, and because it is rich in flexibility, absorbs deformation and thermal expansion of the substrate and suppresses delamination. It fulfills. This semi-bright nickel plating layer is substantially free of sulfur. To form a noble semi-bright nickel plating layer of this potential, for example, a brightening agent such as coumarin, formalin, chloral hydrate is added to a watt bath. Is used.

Between the semi-bright nickel plating layer and the conductive base material of the substrate, in addition to smoothing the surface of the base material, to alleviate the electrodeposition stress of the semi-bright nickel plating layer and to absorb the thermal expansion of the base material, Usually, a metal base layer such as a copper layer is provided,
This metal underlayer is not always necessary and can be omitted in some cases. In the present invention, it is necessary to have a nickel-phosphorus alloy plating layer containing non-metallic inert fine particles dispersed therein as a layer in direct contact with the chromium coating.

The nickel-phosphorus alloy layer has good resistance to acids and alkalis, is not easily attacked by oxidizing acids such as nitric acid, and has chemical resistance close to that of gold. The nickel-phosphorus alloy plating layer can be formed by an electroless method or an electrolytic method. However, the deposition rate at a low temperature is large, the plating time is short, and a phosphorus supply source such as phosphorous acid or hypophosphorous acid is used. In the present invention, it is preferable to use an electrolysis method because the phosphorus content in the plating layer generated can be controlled by the addition amount of P, the consumption of the phosphorus supply source is small, and the bath life is long.

In the present invention, the nickel-phosphorus alloy layer containing the nonmetallic inert fine particles can be formed by a known nickel-phosphorus alloy plating bath composition according to a known method, for example, the method described in Japanese Patent Publication No. 5-600000. Alternatively, a solution to which non-metal inert fine particles are added can be used as an electrolytic solution. In this case, nickel sulfate, nickel chloride,
A nickel salt such as nickel carbonate is used, and as a phosphorus source, phosphorous acid, hypophosphorous acid or a salt thereof is used. In addition, boric acid and a complexing agent may be added to the plating bath composition as a buffering agent, if desired.
PH adjuster, such as phosphoric acid, sodium hydroxide
It is adjusted to 0.5-4.0.

Examples of a plating bath composition suitable for forming a nickel-phosphorus alloy plating layer in which non-metallic inert fine particles are dispersed and formed by the method of the present invention include nickel sulfate 100 to 300 g / liter and nickel chloride. 0-200
g / liter, nickel carbonate 0-100 g / liter,
Examples of the composition include phosphoric acid or sodium hypophosphite, 5 to 100 g / liter, phosphoric acid, 0 to 100 g / liter, and the balance of water.

The phosphorus content in the nickel-phosphorus alloy plating layer formed by the method of the present invention is preferably in the range of 3 to 19% by weight. If the amount is less than 3% by weight, it is difficult to obtain bright plating and the decorative value is reduced. If it exceeds 19% by weight, the gloss is reduced and the cathode current efficiency is reduced.
It takes a long time to obtain the required plating thickness.
Then, the electrochemical potential of the nickel-phosphorus alloy plating layer with respect to the bright nickel layer is set to a phosphorus content of 3 to
It shows a value of 140 to 1150 mV in the range of 19% by weight.

The phosphorus content depends on the concentration of nickel, the concentration of the phosphorus source, the pH and the current density, and can be used to reduce the amount of the nickel salt, increase the amount of the phosphorus source,
Or by reducing the current density,
The phosphorus content in the nickel-phosphorus alloy plating layer can be increased. Also, cathode current efficiency decreases with increasing phosphorus content.

As the non-metallic inert fine particles added to the nickel-phosphorus plating bath, fine particles added to microporous chromium which are currently widely used industrially, that is, silicon oxide, titanium oxide, aluminum oxide, sulfuric acid Barium, zirconium oxide, aluminum silicate,
Calcium silicate or the like can be used as it is.

The particle diameter of the non-metallic inert fine particles dispersed in the plating solution is preferably 0.01 to 20 μm, and the mode particle diameter is preferably 1 to 9 μm. If it exceeds 20 μm, the plating layer becomes cloudy or has a matte finish, which is not preferable for decorative use having a glossy appearance.

The addition amount is in the range of 0.001 to 30 g / liter, and the addition amount is adjusted according to the type and particle size of the fine particles. In general, if it is less than 0.001 g / liter, the effect of remarkably improving corrosion resistance is small, and if it exceeds 30 g / liter, it becomes difficult to maintain clouding or to maintain a uniform concentration by stirring.

Since the specific gravity of these fine particles is relatively large, they tend to settle in a nickel-phosphorus plating bath,
In addition, the method of the present invention uses a low foaming anionic or nonionic type in order to improve the dispersibility of the fine particles in the nickel-phosphorus plating bath because the water leakage and the dispersibility of the fine particles are poor and the uniform eutectoid is difficult. It is necessary to add a surfactant. The cationic type is not preferred because it lowers the adhesion to the underlying nickel layer. These fine particles may be added directly to the nickel-phosphorus plating solution.However, they are prepared in advance as a suspension using a small amount of surfactant-added water or nickel-phosphorus plating solution, stirring, ultrasonic waves, etc. It is preferable to add them. As with the conventional microporous chromium, mechanical stirring such as air stirring, propeller stirring, and pump stirring can be employed for stirring the plating bath.

The plating thickness of the nickel-phosphorus plating layer formed in this way has a great influence on the corrosion resistance, and as the thickness increases, the corrosion resistance improves. However, in consideration of productivity and economy, 0.15 to 20 μm is preferable. 0.15μm
If less than 20 μm, the effect of improving corrosion resistance is small.
Exceeding the limit results in excessive quality and is uneconomical.

Next, the chromium coating applied to the nickel-phosphorus alloy plating layer containing the non-metallic inert fine particles dispersed therein is formed in exactly the same manner as in the case of a conventional microporous chromium product. The thickness of the chromium plating is 0.01 to 0.5 μm, preferably 0.1 to 0.5 μm.
The range is 3 μm. When the thickness exceeds 0.5 μm,
Cracks may occur and corrosion resistance may worsen,
If it is less than 0.01 μm, there is a problem in terms of wear resistance.

[0027]

Next, the present invention will be described in more detail by way of examples. The corrosion resistance test in each example is based on JIS H850.
According to the provisions of 2, evaluation was made by the Cass test method. This result is indicated by a rating number. In addition, in any of the samples, no rust was found from the substrate, so only the surface corrosion was evaluated.

Example 1 (1) Formation of metal electroplating underlayer ABS resin plate (50 × 90
mm), a copper plating having a thickness of 20 μm using a copper sulfate plating bath was used as a conductive base, and a metal plating underlayer was formed under the following composition and conditions.

That is, first, nickel sulfate 300 g / l, nickel chloride 60 g / l, boric acid 45 g
/ Liter, pH including coumarin 0.1g / liter
Using an electrolytic solution of 4.0 at a temperature of 50 ° C. and a current density of 3 A / d
Electroplating was performed under the conditions of m ² to form a semi-bright nickel plating layer having a thickness of 12 μm.

Next, 300 g of nickel sulfate /
Liter, nickel chloride 60g / liter, boric acid 45
g / l, saccharin 2 g / l as primary brightener, 1,4-butydiol 0.2% as secondary brightener
g / liter and an electrolyte of pH 4.0 at a temperature of 5
Electroplating was performed at 0 ° C. and a current density of 3 A / dm ² to form a bright nickel layer having a thickness of 8 μm.

(2) Formation of nickel-phosphorus alloy plating layer in which non-metallic inert fine particles are dispersed On a sample provided with a metal electroplating underlayer, nickel sulfate 210 g / l, nickel chloride 90 g / l, phosphorous acid 20 g / liter, phosphoric acid 100 g / liter, silicon oxide fine particles (mode diameter 8.3 μm) 20 g / liter
Liter and nonionic surfactant [Nippon Yushi Co., Ltd.
Nonion NS-210], electroless plating was carried out at a temperature of 55 ° C. and a current density of 3 A / dm ² using an electrolytic solution having a pH of 0.5 and a thickness of 3 μm.
m, a nickel-phosphorus alloy plating layer having a phosphorus content of 9% by weight was formed.

(3) Formation of chromium plating layer A sample having the above-mentioned electrolytic plating layer was prepared by using chromic anhydride 200
g / l, 1.5 g / l sulfuric acid, 5 g / l potassium silicofluoride, at a temperature of 46
Electroplating was performed at a temperature of 15 ° C. and a current density of 15 A / dm ² , and a chrome plating coating having a thickness of 0.2 μm was applied. Thus, a microporous chrome-plated product was manufactured.

Example 2 Step (2) was carried out using nickel sulfate 150 g / l, nickel chloride 40 g / l, phosphorous acid 20 g / l, and finely divided zirconium oxide (mode diameter 4.5 μm) 5 g.
/ Liter, nonionic surfactant [manufactured by Sanyo Kasei Kogyo Co., Ltd .; Newpole PE-64] containing 0.01 g / liter of an electrolytic solution having a pH of 0.8 at a temperature of 60 ° C. and a current density of 2.0 A / dm. Perform under the conditions of ²
A microporous chrome-plated product was manufactured in exactly the same manner as in Example 1 except that a nickel-phosphorus alloy plating layer having a m and phosphorus content of 16% by weight was formed.

Example 3 Step (2) was carried out using nickel sulfate 120 g / l, nickel chloride 80 g / l, phosphorous acid 15 g / l, complexing agent 30 g / l, fine titanium oxide (mode diameter 2.5 μm). 0.05 g / liter, nonionic surfactant [manufactured by Sanyo Chemical Industry Co., Ltd .; Newpole PE-6]
4] By using an electrolytic solution containing 0.01 g / liter and having a pH of 2.5 and changing the electrolysis time under the conditions of a temperature of 50 ° C. and a current density of 2.5 A / dm ² , a phosphorus content of 12% by weight was obtained. The thickness of the nickel-phosphorus alloy plating layer is 1 μm
(A) A microporous chrome-plated product was manufactured in exactly the same manner as in Example 1 except that the thickness was changed to 3 μm (B) and 5 μm (C).

Example 4 Step (2) was carried out using 250 g / liter of nickel sulfate, 5 g / liter of nickel chloride, and 10 g of sodium hypophosphite.
/ Liter, complexing agent 50 g / liter, finely divided silicon oxide (mode diameter 8.3 μm) 20 g / liter, anionic surfactant [manufactured by Toho Chemical Industry Co., Ltd .; Alscope LN
-90] using an electrolytic solution containing 0.03 g / liter and a pH of 3.5 under the conditions of a temperature of 50 ° C. and a current density of 3 A / dm ² , to form a nickel-phosphorus alloy plating layer having a phosphorus content of 7% by weight. A microporous chrome-plated product was manufactured in exactly the same manner as in Example 1 except that the product was formed to a thickness of 3 μm.

Example 5 Step (2) was carried out using nickel sulfate 150 g / l, nickel chloride 150 g / l, phosphorous acid 20 g / l, phosphoric acid 100 g / l, and fine aluminum oxide (mode diameter 2.1 μm) 1 g. / Liter, anionic surfactant [Toho Chemical Industry Co., Ltd .; Alscope LN-
90] using an electrolytic solution containing 0.05 g / liter, pH 0.5, at a temperature of 55 ° C. and a current density of 5 A / dm ² , and having a phosphorus content of 5% by weight and a thickness of 3 μm.
A microporous chrome-plated product was manufactured in exactly the same manner as in Example 1 except that a phosphorus alloy plating layer was formed.

Comparative Example 1 Step (2) was carried out using nickel sulfate 210 g / l, nickel chloride 90 g / l, boric acid 40 g / l,
An electrolytic solution containing 20 g / liter of finely divided silicon oxide (mode diameter: 8.3 μm) and not containing phosphorus having a pH of 3.5 was used.
A microporous film was prepared in the same manner as in Example 1 except that a nickel plating layer having a thickness of 0.25 μm in which non-metallic inert fine particles were dispersed was formed under the conditions of a temperature of 55 ° C. and a current density of 4 A / dm ^2. Chrome plated products were manufactured.

Comparative Example 2 The nickel-phosphorus alloy plating layer had a thickness of 1 μm in the same manner as in Example 3 except that an electrolytic solution having a composition obtained by removing fine-grained titanium oxide from the electrolytic solution in Example 3 was used.
(A ′), 3 μm (B ′) and 5 μm (C ′) chromium plated products were manufactured.

REFERENCE EXAMPLE The samples obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were subjected to the Cass test for up to 240 hours, and the results are shown in Table 1. FIG. 2 shows a comparison between the results of Example 3 and Comparative Example 2 on a graph. For comparison, data on a conventional microporous plated product is shown as D.

[0040]

[Table 1]

As is clear from the above, the microporous chrome-plated product obtained by the method of the present invention maintains excellent corrosion resistance for a long period of time, and does not cause deterioration in appearance due to corroded holes unlike conventional products.

[0042]

The conventional microporous chrome-plated product, when used under severe conditions for a long period of time, enlarges the corrosion pits and eventually causes a partial loss of the chromium coating layer. The resulting microporous chromium-plated product does not have a chromium coating layer missing even when used under severe conditions for a long period of time, and therefore does not have any deterioration in appearance.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining the progress of corrosion of a normal chromium-plated product and a microporous chrome-plated product.

FIG. 2 is a graph comparing changes in appearance rating numbers of an example of the present invention and a comparative example.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyotaka Funada 2-10-4 Fukuura, Kanazawa-ku, Yokohama, Kanagawa Prefecture Inside (72) Inventor Masatoshi Maruta 2-10-4, Fukuura, Kanazawa-ku, Yokohama, Kanagawa Prefecture Inside (72) Inventor Masanobu Tsuge 2-10-4 Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Inside Kizai Corporation (56) References JP-A-6-240490 (JP, A) JP-A-1-294896 (JP) (A) JP-A-4-371597 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C25D 5/00-5/56 C23C 28/02 C25D 11/38 C25D 15/02

Claims (1)

(57) [Claims] 1. A nickel-phosphorus alloy plating bath composition containing a nickel supply source, a phosphorus supply source, and an anionic or nonionic surfactant after a required metal underlayer is formed on a conductive substrate by electroplating. Electrolytic plating is performed in an electrolyte solution prepared by adding non-metallic inert fine particles to a nickel-phosphorus alloy plating layer containing non-metallic inert fine particles having a thickness of 0.15 to 20 μm in a dispersed manner. A method for producing a microporous chrome-plated product, wherein a chromium plating coating having a thickness of 0.01 to 0.5 μm is provided thereon.