JPH10251870A - Chrome plate products - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide chrome plated products which exhibit high corrosion resistance and excellent gloss appearance over a long period and are adequate as exterior parts and outdoor ornaments of automobiles, buildings, etc. SOLUTION: The chrome plated products are formed by successively providing the surface of a conductive based with a metallic electroplating ground surface layer and a nickel-phosphorus alloy plating layer dispersedly contg. nonmetallic inert particulates (exclusive of titanium oxide) having a thickness of 0.15 to 3μm or a phosphorus contents of 3 to 7wt.% and thickness of 0.15 to 20μma and further, applying a chrome coating thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chrome-plated product which exhibits high corrosion resistance and excellent gloss appearance over a long period of time and is suitable for exterior decoration and exterior decoration of automobiles and buildings. More specifically, the present invention relates to a chromium-plated product which has a further improved corrosion resistance in a product subjected to so-called microporous plating and has a glossy appearance 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 is formed as 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 this is to provide.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the improvement of corrosion resistance and gloss appearance of microporous plated products. The corrosion rate of the nickel-phosphorus alloy plating layer is reduced by replacing the layer with a nickel-phosphorus alloy plating layer having a higher potential and a predetermined thickness or a predetermined phosphorus content to reduce the potential difference from the chromium layer. In addition, the initiation of corrosion of the bright nickel plating layer can be greatly delayed, and the nickel-phosphorus alloy itself has a high strength, so even if a cavity is formed in the bright nickel layer due to corrosion, They have found that they can support the chromium layer and can provide an excellent gloss appearance without using a brightener. It has led to the completion of the present invention have.

That is, according to the present invention, the conductive base material has a metal electroplating underlayer and a thickness of 0.15 to 3 μm, or a phosphorus content of 3 to 7% by weight and a thickness of 0.15%. A microporous nickel-phosphorus alloy plating layer having a dispersion of non-metallic inert fine particles (excluding titanium oxide) of up to 20 μm, and a chromium coating thereon; Provide chrome plated products.

[0011] In the present invention, the conductive substrate may be iron,
Metals such as zinc, copper, aluminum and their alloys, various ceramics and plastics which have been made conductive by electroless plating, such as glass, iron oxide, ceramics, and AB
S 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 provides a mirror surface to the layer and coating thereon and plays the 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 conventional nickel electroplating bath, for example, 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. The content of this brightener is 0.0
A range of 4 to 1.0% by weight is suitable.

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 dispersed non-metallic inert fine particles (excluding titanium oxide) as a directly contacting layer of the chromium coating.

The nickel-phosphorus alloy plating layer is made of an acid,
It has good resistance to alkali, 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 plating layer containing non-metallic inert fine particles can be formed by a known nickel-phosphorus alloy plating bath according to a known method, for example, a method described in Japanese Patent Publication No. 5-600000. The composition can be formed by using a liquid obtained by adding nonmetallic inert fine particles to the composition as an electrolytic solution. In this case, a nickel salt such as nickel sulfate, nickel chloride or nickel carbonate is used as a nickel supply source in the nickel-phosphorus alloy plating bath composition, and phosphorous acid, hypophosphorous acid or a salt thereof is used as a phosphorus supply source. Used respectively. If necessary, boric acid and a complexing agent are added to the plating bath composition as a buffer, and the pH is adjusted to 0.5 to 4.0 with a pH adjuster such as phosphoric acid or sodium hydroxide.

Examples of the plating bath composition suitable for forming a nickel-phosphorus alloy plating layer in which non-metallic inert fine particles are dispersed and contained in the present invention include nickel sulfate 100 to 100%.
300 g / l, nickel chloride 0-200 g / l, nickel carbonate 0-100 g / l, appropriate amount of phosphoric acid or sodium hypophosphite 5 g / l or more, phosphoric acid 0-100 g / l, balance water Can be mentioned.

The nickel-phosphorus alloy plating layer of the present invention has a thickness of 0.15 to 3 μm or a phosphorus content of 3 to 7% by weight and a thickness of 0.15 to 20%.
It needs to be μm. This thickness is 0.15μm
If it is less than 3, the effect of improving the corrosion resistance is small, and if the phosphorus content is less than 3% by weight or the thickness is more than 20 μm, it is difficult to obtain bright plating and the decorative value is reduced.

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 alloy plating bath, silicon oxide, aluminum oxide, barium sulfate, zirconium oxide, aluminum silicate, calcium silicate and the like are used.

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 added amount of the non-metallic inert fine particles is 0.001.
-30 g / liter, and the addition amount is adjusted according to the type and particle size of the fine particles. In general, when the content is less than 0.001 g / liter, the effect of significantly improving corrosion resistance is small,
On the other hand, if it exceeds 30 g / liter, it becomes cloudy or it becomes difficult to maintain a uniform concentration by stirring.

Since the specific gravity of the non-metallic inert fine particles is relatively large, they are easy to settle in a nickel-phosphorus alloy plating bath, and because the fine particles have poor water leakage and dispersibility and are difficult to uniformly eutect, the dispersion is difficult. In order to improve the property, it is desirable to add an anionic or nonionic surfactant having a low foaming property. The cationic type is not preferred because it lowers the adhesion to the underlying nickel layer.

The non-metallic inert fine particles may be directly added to the nickel-phosphorus alloy plating solution, but may be stirred with a small amount of water or a nickel-phosphorus alloy plating solution to which a surfactant has been added, or by a method such as ultrasonic waves. It is preferable to add a suspension prepared in advance. Stirring of the plating bath is similar to that of the conventional microporous chrome plating method.
Mechanical stirring such as propeller stirring and pump stirring can be employed.

Next, the chromium coating applied to the nickel-phosphorus alloy plating layer containing non-metallic inert fine particles dispersed therein is formed in exactly the same manner as in the case of the conventional microporous chromium product. The plating thickness of the chromium coating 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 condition 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-butynediol 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 a nonionic surfactant 0.02 g / liter, using an electrolytic solution having a pH of 0.5, performing electroplating at a temperature of 55 ° C. and a current density of 3 A / dm ² , and dispersing fine particles to a thickness of 3 μm. 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 under the conditions of a temperature of 15 ° C. and a current density of 15 A / dm ² , and a chromium 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.
/ L, using an electrolytic solution containing 0.01 g / L of a nonionic surfactant and having a pH of 0.8 under the conditions of a temperature of 60 ° C. and a current density of 2.0 A / dm ² , and a thickness of 3 μm in which fine particles are dispersed. 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 phosphorus content of 16% by weight was formed.

Example 3 Step (2) was carried out using 250 g / liter of nickel sulfate, 5 g / liter of nickel chloride, and 10 g of sodium hypophosphite.
/ G, complexing agent 50 g / l, fine-grained silicon oxide (mode diameter 8.3 µm) 20 g / l, anionic surfactant 0.03 g / l, pH 3.5 electrolyte, temperature 50 ° C Exactly the same as Example 1 except that the current density was changed to 3 A / dm ² to form a nickel-phosphorus alloy plating layer having a thickness of 3 μm in which fine particles were dispersed and a phosphorus content of 7% by weight. Thus, a microporous chrome-plated product was manufactured.

Example 4 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 finely divided aluminum oxide (mode diameter 2.1 μm) 1 g. / L, containing 0.05 g / L of an anionic surfactant, using an electrolyte having a pH of 0.5, at a temperature of 55 ° C. and a current density of 5 A / dm ² , and having a thickness of 3 μm in which fine particles are dispersed. 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 phosphorus content of 5% by weight was changed.

COMPARATIVE EXAMPLE Step (2) was carried out using 210 g / liter of nickel sulfate, 90 g / liter of nickel chloride, 40 g / liter of boric acid,
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.
Performed under conditions of a temperature of 55 ° C. and a current density of 4 A / dm ² ,
A microporous chrome-plated product was manufactured in the same manner as in Example 1 except that a nickel plating layer having a thickness of 0.25 μm in which fine particles were dispersed was changed.

Reference Example The Cass test was performed on the samples obtained in Examples 1 to 4 and Comparative Example for up to 240 hours. Table 1 shows the results.

[0038]

[Table 1]

As is apparent from the above, the microporous chrome-plated product 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.

[0040]

According to the conventional microporous chrome-plated product, when used under severe conditions for a long period of time, the corrosion pits are enlarged and eventually the chromium coating layer is partially lost. The chromium-plated product does not lack the chromium coating layer even when used under severe conditions for a long period of time, and therefore does not deteriorate 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.

Continued on the front page (72) Inventor Kiyotaka Funada 2-10-4 Fukuura, Kanazawa-ku, Yokohama City, Kanagawa Prefecture Inside (72) Inventor Masatoshi Maruta 2-10-4, Fukuura, Kanazawa-ku, Yokohama City, Kanagawa Prefecture Kizai Stock Inside the company (72) Inventor Masanobu Tsuge 2-10-4 Fukuura, Kanazawa-ku, Yokohama, Kanagawa

Claims (6)

[Claims] The present invention relates to a method for producing a conductive base material comprising a metal electroplating base layer and nickel-dispersed non-metallic fine particles (excluding titanium oxide) having a thickness of 0.15 to 3 μm.
A microporous chrome-plated product comprising a phosphorus alloy plating layer sequentially provided and a chromium coating thereon. 2. An electroconductive substrate comprising a metal electroplating underlayer and a phosphorus content of 3 to 7% by weight and a thickness of 0.15 to 2
Microporous chromium, characterized in that a nickel-phosphorus alloy plating layer having a dispersion of non-metallic inert fine particles (excluding titanium oxide) having a thickness of 0 μm is sequentially provided, and a chromium coating is further provided thereon. Plating products. 3. The microporous chrome-plated product according to claim 1, wherein the nickel-phosphorus alloy plating layer according to claim 1 has a phosphorus content of 3 to 7% by weight. 4. The thickness of the chromium coating is 0.01 to 0.5 μm.
4. The microporous chrome-plated product according to claim 1, wherein m is m. 5. The microporous chrome-plated product according to claim 1, wherein the metal electroplating underlayer comprises a bright nickel layer and a semi-bright nickel layer. 6. The microporous chrome-plated product according to claim 1, wherein the nonmetallic inert fine particles are silicon oxide, aluminum oxide, barium sulfate, zirconium oxide, aluminum silicate, and calcium silicate.