JPH07278845A - Chromium-plated product and its production - Google Patents

Abstract

PURPOSE:To decrease the corrosion rate of a plating layer and to obtain excellent gloss appearance without using a brightener in a microporous chromium plating method by replacing a nickel plating layer with a nickel-phosphorus plating layer having higher potential. CONSTITUTION:After a metal base layer is formed by electroplating on a conductive base body, the base body is subjected to electroplating in an electrolytic soln. prepared and controlled by adding nonmetal inert fine particles in a nickel- phosphorus alloy plating bath compsn. containing nickel supply source and phosphorus supply source. Thus, a nickel-phosphorus alloy plating layer of 0.15-20mum thickness containing dispersion of the nonmetal of the nonmetal inert fine particles is formed. Then, a chromium plating film of 0.01-0.5mum is formed thereon. Thereby, a chromium-plated product having high corrosion resistance and excellent gloss appearance for a long time is obtd.

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 an excellent glossy appearance for a long period of time and is suitable as an exterior or exterior decoration for automobiles, buildings and the like, and a method for producing the same. More specifically, the present invention relates to a chrome-plated product that further improves the corrosion resistance of a product that has been subjected to so-called microporous plating and that has an appearance gloss without using a brightener, and a method for producing the same. .

[0002]

2. Description of the Related Art Copper, nickel and chrome or nickel and chrome are sequentially electroplated on base materials such as zinc die cast products, steel plate pressed products, aluminum die cast products and electroless plated synthetic resin molded products. These products are widely used for decoration of automobiles and exterior of buildings.

By the way, when chromium is electroplated on a nickel layer, as shown in FIG. 1A, due to defects such as pits and cracks penetrating the chromium layer generated during plating, the chromium side is the cathode. , 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, there is a phenomenon in which the chromium plating layer on the formed corrosion cavity is desorbed early and the appearance is impaired in a short time.

In order to improve such a defect, as shown in FIG. 1 (b), plating is performed in a nickel plating bath in which non-metal inert fine particles are dispersed, and the fine particles are deposited in the nickel plating layer. After making a composite nickel plating layer, chromium plating on it to form a large number of fine holes in the chromium plating layer to increase the area of the anode and reduce the corrosion current density, a method of improving corrosion resistance,
A so-called microporous chrome plating method is known. In this method, the nickel plating layer is a single layer of the bright nickel layer or a multi-layer of the bright nickel layer and the semi-bright nickel layer.

However, when the microporous chrome-plated product is exposed to a corrosive environment, the corrosive liquid penetrates into the micropores of the chrome-plated layer to form a battery between the chrome-plated layer and the composite nickel-plated layer. Then, the composite nickel plating layer that became the anode dissolves and disappears, and then the bright nickel plating layer dissolves in a circular shape, disappears and becomes hollow, and the chromium plating layer supports the composite nickel layer and the bright nickel layer that supported it. When it is lost, it breaks into fragments in the cavity or is washed away by the corrosive liquid. As a result, there are drawbacks that corrosion holes are scattered on the surface of the chrome plating and the appearance becomes marbling in a short period of time.

In order to improve such a defect, 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. A method of strictly adjusting the potential difference between the two (Japanese Patent Laid-Open No. 5-287579 and Japanese Patent Laid-Open No. 5-171468) has been proposed. The potential difference depends on the concentration of the brightening agent, the nonuniform current density, and the stirring condition. Since it depends on the presence or absence of impurities, it is difficult to keep this in a constant range on the manufacturing line at all times.

Further, a method of thickening the composite nickel plating layer to increase the strength so that the chromium plating layer can be supported even if the underlying bright nickel plating layer is hollow is considered. This method is unsuitable because it increases the thickness and causes the surface of the chrome-plated layer to fog, which reduces its decorative value.

[0008]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of conventional microporous plated products and has a high corrosion resistance and excellent gloss appearance for a long period of time even when used under severe conditions. It is made for the purpose of providing.

[0009]

Means for Solving the Problems As a result of intensive studies on the improvement of wear resistance and appearance gloss of microporous plated products, the present inventors have dispersed a composite nickel plating layer, that is, non-metal inert fine particles. By replacing the nickel plating layer with a higher potential nickel-phosphorus plating layer to reduce the potential difference from the chromium layer, the corrosion rate of this nickel-phosphorus alloy plating layer can be reduced, and in addition, a bright nickel plating layer. Corrosion initiation can be significantly delayed, and since the nickel-phosphorus alloy itself has high strength, it is possible to support the chromium layer for a long period of time even if cavities are created in the bright nickel layer due to corrosion,
Moreover, they have found that an excellent gloss appearance can be obtained without using a brightener, and have completed the present invention based on this finding.

That is, according to the present invention, a metal electroplating underlayer and a nickel-phosphorus alloy plating layer containing non-metal inert fine particles dispersed therein are sequentially provided on a conductive substrate, and chromium coating is further applied thereon. The present invention provides a microporous chrome plated product characterized by the above.

As the conductive substrate in the present invention, iron,
Metals such as zinc, copper and aluminum, alloys thereof, various ceramics and plastics which have been electroconductively treated by electroless plating, such as glass, iron oxide, ceramics, 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 an ordinary microporous chrome plated product. Used.

This bright nickel plating layer not only provides 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 underlying layer. It can be formed by adding a brightener to the Watts bath. In this case, examples of the brightener include primary brighteners such as sodium 1,5-naphthalene disulfonate, sodium 1,3,6-naphthalene trisulfonate and saccharin, and secondary brighteners such as 1,4-butynediol. , Propargyl alcohol, sodium allyl sulfonate and the like can be used. The content of the brightening agent is preferably in the range of 0.04 to 1.0% by weight.

Next, the semi-bright nickel plating layer improves the smoothness of the base material and improves the overall appearance, and since it is highly flexible, it absorbs deformation and thermal expansion of the base material and suppresses delamination. To fulfill. This semi-bright nickel plating layer is substantially free of sulfur. To form a noble semi-bright nickel plating layer of this potential, a brightener such as coumarin, formalin or chloral hydrate is used in a Watt bath. An electroplating bath to which is added 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, in addition to relaxing the electrodeposition stress of the semi-bright nickel plating layer and absorbing the thermal expansion of the base material, Usually, a metal underlayer such as a copper layer is provided,
This metal underlayer is not always necessary and may be omitted in some cases. In the present invention, it is necessary to have a nickel-phosphorus alloy plating layer containing non-metal inert fine particles dispersed therein as a layer in direct contact with the chromium coating.

This nickel-phosphorus alloy layer has good resistance to acids and alkalis, is not easily attacked by oxidizing acids such as nitric acid, and has a chemical resistance similar to that of gold. There are electroless and electrolytic methods for forming this nickel-phosphorus alloy plating layer. However, the deposition rate is large at low temperatures and the plating time is short, and the phosphorus supply source such as phosphorous acid or hypophosphorous acid. It is preferable to use the electrolysis method in the present invention because the phosphorus content in the plating layer produced can be controlled by the addition amount of, the consumption of the phosphorus supply source is small, and the bath life is long.

The nickel-phosphorus alloy layer containing non-metal inert fine particles according to the present invention is a known nickel-phosphorus alloy plating bath composition according to a known method, for example, the method described in Japanese Patent Publication No. 5-60000. In addition, a liquid to which non-metal inert fine particles are added can be used as an electrolytic solution. At this time, nickel sulfate, nickel chloride, as a nickel supply source in the nickel-phosphorus alloy plating bath composition,
A nickel salt such as nickel carbonate is used, and phosphorous acid, hypophosphorous acid or salts thereof are used as a phosphorus source. If desired, boric acid and a complexing agent may be added to the composition of the plating bath, and the pH may be adjusted.
PH with regulators such as phosphoric acid, sodium hydroxide
It is adjusted to 0.5 to 4.0.

An example of a plating bath composition suitable for forming a nickel-phosphorus alloy plating layer containing non-metal inert fine particles dispersed in the present invention is nickel sulfate 100 to 100
300 g / liter, nickel chloride 0-200 g / liter, nickel carbonate 0-100 g / liter, phosphorous acid or sodium hypophosphite 5-100 g / liter, phosphoric acid 0-100 g / liter, balance water composition You can

The phosphorus content in the nickel-phosphorus alloy plating layer of the present invention is preferably in the range of 3 to 19% by weight. If this amount is less than 3% by weight, it is difficult to obtain bright plating and the decorative value is lowered. If it exceeds 19% by weight, the gloss is lowered and the cathode current efficiency is lowered, so that the required plating thickness is obtained. It will take a long time. The electrochemical potential of the nickel-phosphorus alloy plating layer with respect to the above-mentioned bright nickel layer shows a noble value of 140 to 1150 mV in the range of the phosphorus content of 3 to 19% by weight.

The phosphorus content depends on the nickel concentration, the phosphorus source concentration, the pH and the current density, and decreases the amount of nickel salt, increases the amount of phosphorus source, or increases the pH.
By reducing or reducing the current density,
The phosphorus content in the nickel-phosphorus alloy plating layer can be increased. In addition, the cathode current efficiency decreases as the phosphorus content increases.

The non-metal inert fine particles added to the nickel-phosphorus plating bath are fine particles added to microporous chromium, which is widely used in the industry today, 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-metal 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 satin finish, which is not preferable for decoration with 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. Generally, if it is less than 0.001 g / liter, the remarkable effect of improving the corrosion resistance is small, and if it exceeds 30 g / liter, clouding occurs or it becomes difficult 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,
Further, since water leakage and dispersibility of fine particles are poor and it is difficult to uniformly co-deposit, it is desirable to add an anionic or nonionic surfactant having a low foaming property to improve the dispersibility. Cationic compounds are not preferred because they reduce the adhesion to the underlying nickel layer. These fine particles may be added directly to the nickel-phosphorus plating solution, but they may be prepared as a suspension by stirring with a small amount of water containing a surfactant or the nickel-phosphorus plating solution, and then ultrasonically. It is preferable to add it by adding. The stirring of the plating bath may employ mechanical stirring such as air stirring, propeller stirring, and pump stirring as in the case of conventional microporous chromium.

The plating thickness of the nickel-phosphorus plating layer thus formed has a great influence on the corrosion resistance, and the corrosion resistance increases as the thickness increases. However, considering productivity and economy, 0.15 to 20 μm is preferable. 0.15 μm
If it is less than 20 μm, the effect of improving corrosion resistance is small, and it is 20 μm.
If it exceeds, it is uneconomical because of excessive quality.

Next, the chromium coating applied on the nickel-phosphorus alloy plating layer containing the non-metal inert fine particles dispersed therein is formed in exactly the same manner as in the case of the conventional microporous chromium product. The thickness of the chromium plating is 0.01 to 0.5 μm, preferably 0.1 to 0.
It is in the range of 3 μm. When the thickness exceeds 0.5 μm,
It may cause cracks and worsen corrosion resistance,
If it is less than 0.01 μm, there is a problem in wear resistance.

[0027]

The present invention will be described in more detail with reference to Examples. The corrosion resistance test in each example is JIS H850.
Evaluation was made by the Cass test method according to the provisions of 2. The results are shown by rating numbers. Further, no rusting from the substrate was observed in any of the samples, so only surface corrosion was evaluated.

Example 1 (1) Formation of Metal Electroplating Underlayer An ABS resin plate (50 × 90) which has been electrically conductive by a conventional method.
mm), which was copper-plated with a thickness of 20 μm using a copper sulfate plating bath, was used as a conductive substrate, and a metal plating underlayer was formed according to the following composition and conditions.

That is, first, 300 g / liter of nickel sulfate, 60 g / liter of nickel chloride, and 45 g of boric acid.
/ Liter, coumarin 0.1g / liter including pH
Using electrolyte of 4.0, temperature 50 ℃, current density 3A / d
Electroplating was carried out under the condition of m ² to form a semi-bright nickel plating layer having a thickness of 12 μm.

Then, 300 g of nickel sulfate /
Liter, nickel chloride 60g / liter, boric acid 45
g / liter, saccharin 2 g / liter as a primary brightener, and 0.2% 1,4-butydiol as a secondary brightener.
Using an electrolytic solution containing g / l and having a pH of 4.0, a temperature of 5
Electrolytic plating was performed under conditions of 0 ° C. and 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 Dispersing Non-Metallic Inert Fine Particles 210 g / liter of nickel sulfate, 90 g / liter of nickel chloride, and phosphorous acid were placed on a sample provided with a metal electroplating underlayer. 20 g / liter, phosphoric acid 100 g / liter, silicon oxide fine particles (modal diameter 8.3 μm) 20 g / liter
Liter and 0.02 g / liter of nonionic surfactant, pH of 0.5 is used for electrolytic plating under conditions of temperature 55 ° C. and current density 3 A / dm ² , thickness 3 μm, phosphorus content A 9% by weight nickel-phosphorus alloy plating layer was formed.

(3) Formation of chrome plating layer Chromic anhydride 200
Using an electrolytic solution containing g / l, sulfuric acid 1.5 g / l, potassium silicofluoride 5 g / l, temperature 46
Electrolytic plating was carried out under 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. In this way, a microporous chrome plated product was manufactured.

Example 2 In step (2), 150 g / liter of nickel sulfate, 40 g / liter of nickel chloride, 20 g / liter of phosphorous acid, 5 g of finely divided zirconium oxide (modal diameter 4.5 μm)
/ L, 0.01 g / L of nonionic surfactant and pH 0.8, using an electrolyte solution at a temperature of 60 ° C. and a current density of 2.0 A / dm ² , a thickness of 3 μm,
A microporous chromium plated product was produced 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 In the step (2), 120 g / liter of nickel sulfate, 80 g / liter of nickel chloride, 15 g / liter of phosphorous acid, 30 g / liter of complexing agent, fine-grained titanium oxide (mode diameter 2.5 μm) To change the electrolysis time under conditions of a temperature of 50 ° C. and a current density of 2.5 A / dm ² , using an electrolyte solution containing 0.05 g / liter and 0.01 g / liter of a nonionic surfactant and having a pH of 2.5. Due to the phosphorus content 12
Thickness of nickel-phosphorus alloy plating layer of 1% by weight
A microporous chrome-plated product was manufactured in the same manner as in Example 1 except that (A), 3 μm (B) and 5 μm (C) were used.

Example 4 In step (2), nickel sulfate 250 g / liter, nickel chloride 5 g / liter, sodium hypophosphite 10 g
/ Liter, complexing agent 50 g / liter, finely divided silicon oxide (modal diameter 8.3 μm) 20 g / liter, anionic surfactant 0.03 g / liter, and an electrolytic solution having a pH of 3.5 and a temperature of 50 ° C. A microporous chromium plated product was manufactured in exactly the same manner as in Example 1 except that the nickel-phosphorus alloy plating layer having a phosphorus content of 7% by weight was formed with a thickness of 3 μm under the condition of a current density of 3 A / dm ^2. Was manufactured.

Example 5 In step (2), 150 g / liter of nickel sulfate, 150 g / liter of nickel chloride, 20 g / liter of phosphorous acid, 100 g / liter of phosphoric acid, 1 g of finely divided aluminum oxide (modal diameter 2.1 μm) / L, 0.05 g / L of an anionic surfactant, pH 0.5, using an electrolyte solution at a temperature of 55 ° C. and a current density of 5 A / dm ² , with a phosphorus content of 5% by weight and a thickness of Example 1 except that a 3 μm nickel-phosphorus alloy plating layer was formed.
A microporous chrome plated product was manufactured in exactly the same manner as in.

Comparative Example 1 In step (2), 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 (modal diameter 8.3 μm) and not containing phosphorus having a pH of 3.5,
Micropores were 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-metal 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. A chrome plated product was produced.

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 particulate titanium oxide from the electrolytic solution in Example 3 was used.
(A ′), 3 μm (B ′) and 5 μm (C ′) chrome plated products were produced.

Reference Example The cast samples of the samples obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were tested for up to 240 hours, and the results are shown in Table 1. Further, the results of Example 3 and Comparative Example 2 are shown in FIG. For comparison, data on a conventional microporous plated product is shown as D.

[0040]

[Table 1]

As is apparent from the above, the microporous chrome-plated product of the present invention has excellent corrosion resistance for a long period of time and does not cause deterioration of appearance due to corrosion holes unlike conventional products.

[0042]

EFFECTS OF THE INVENTION The conventional microporous chrome-plated product, when used for a long period of time under severe conditions, expands the corrosion pits and eventually causes a partial loss of the chrome coating layer. The chrome-plated product does not lose the chrome coating layer even when used for a long time under severe conditions, and therefore does not deteriorate in appearance.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view for explaining a state of progress of corrosion between a normal chrome 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.

Front Page Continuation (72) Inventor Kiyotaka Funada 2-10-4 Fukuura, Kanazawa-ku, Yokohama, Kanagawa Prefecture Kisai Co., Ltd. (72) Masatoshi Maruta 2-10-4 Fukuura, Kanazawa-ku, Yokohama, Kanagawa Stock In-house (72) Inventor Masanobu Tsuge 2-10-4 Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Within Kizai Co., Ltd.

Claims (7)

[Claims] 1. A conductive base material, on which a metal electroplating underlayer and a nickel-phosphorus alloy plating layer containing non-metal inert fine particles dispersed therein are sequentially provided, and a chromium coating is further applied thereon. Micro porous chrome plated product. 2. The microporous chromium plated product according to claim 1, wherein the phosphorus content in the nickel-phosphorus alloy plating is 3 to 19% by weight. 3. The microporous chrome plated product according to claim 1, wherein the nickel-phosphorus alloy plating layer containing non-metal inert fine particles dispersed therein has a thickness of 0.15 to 20 μm. 4. The chromium plating coating has a thickness of 0.01 to
The microporous chrome plated product according to claim 1, 2 or 3, which has a thickness of 0.5 μm. 5. The microporous chrome-plated product of claim 1, wherein the metal electroplating underlayer comprises a bright nickel layer and a semi-bright nickel layer. 6. A nickel-phosphorus alloy plating layer containing non-metallic inert fine particles dispersedly contained in an amount of 14 relative to a bright nickel layer.
6. An electrochemical potential of 0 to 1150 mV noble.
Microporous chrome plated product as described. 7. A non-metal inert fine particle is added to a nickel-phosphorus alloy plating bath composition containing a nickel source and a phosphorus source after a required metal underlayer is formed on the conductive substrate by electroplating. Electrolytic plating is performed in the prepared electrolytic solution to form a nickel-phosphorus alloy plating layer having a thickness of 0.15 to 20 μm and containing non-metal inert fine particles dispersed therein, and then having a thickness of 0.01 to 0. A method for producing a microporous chrome-plated product, which comprises applying a chrome-plating coating of 0.5 μm.