JP2741126B2 - Nickel-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 nickel-chromium plated product having excellent corrosion resistance and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, nickel-chromium plating has been used as decorative plating for automobile parts and the like, and microporous chromium plating has been widely used as a method for improving its corrosion resistance. This microporous chromium plating method is a method of forming a large number of micropores invisible to the naked eye on the surface of the chromium plating layer to effectively disperse the corrosion current, and therefore has excellent corrosion resistance.
In the microporous chromium plating method, the corrosion resistance increases as the number of micropores increases. However, for sufficient corrosion resistance, the number is preferably about 10,000 / cm ² or more.

In general, a microporous chromium plating method is a method in which a plating material is preliminarily nickel-plated and then non-conductive fine particles such as SiO ₂ and TiO ₂ are dispersed and suspended in a nickel plating bath. It can be obtained by performing eutectoid nickel (hereinafter referred to as "eutectoid nickel") plating and then chromium plating.

[0004] As the base nickel plating, a single layer of bright nickel is used.
Nickel plating or three-layer plating is employed, and copper plating is performed under the nickel plating as necessary. The following is a general example of the configuration of two-layer nickel plating and three-layer nickel plating capable of improving corrosion resistance as the base nickel.

(2 layer nickel plating) Semi-bright nickel plating (sulfur content: less than 0.005%) + bright nickel plating (sulfur content: 0.05%) (3 layer nickel plating) semi-bright nickel plating (sulfur Content: less than 0.005%) + Nickel plating with high sulfur content (sulfur content: 0.1 to 0.2%) + Bright nickel plating (sulfur content: about 0.05%)

[0006] The corrosion prevention mechanism of the two-layer and three-layer nickel plating described above is described as follows: "The electrochemically base nickel plating layer containing more sulfur is sacrificed by corrosion, and the electrochemically noble semi-bright nickel plating is performed. To prevent corrosion of the layer ".

[0007]

Conventionally, corrosion prevention of a material is most important as a function of plating, and the object has been achieved if the material is not corroded.
The demand for corrosion resistance is increasing, and it is required to prevent not only the material but also the plating film itself from preventing corrosion.

It is known that corrosion of a plating film in nickel-chromium plating starts at a defective portion of the chromium plating film, and a nickel plating film having a lower potential than the chromium plating film is preferentially dissolved. . As a result, corrosion holes of nickel are formed, and the plating appearance is deteriorated.

In the case of the microporous chromium plating described above, a number of defective portions of the chromium plating film are intentionally formed on the chromium plating surface, and the corrosion current is dispersed to promote mild corrosion. It is possible to delay the time until the corrosion reaches the material, but it is inevitable that many minute corrosion holes will be formed on the plating surface,
For this reason, the plating appearance deteriorates.

[0010] Such corrosion occurring in the plating layer can be prevented by using the above-described two-layer or three-layer nickel plating, which is excellent in base corrosion protection, as the underlying nickel plating. Since corrosion is used, there is little meaning in preventing corrosion in the plating layer.

[0011]

In order to prevent the corrosion in the plating layer as described above, the present inventors have developed a microporous chrome plating employing a two-layer nickel plating as the underlying nickel to reduce the corrosion in the plating layer. The generation and progress mechanism were examined. As a result, the nickel-chromium plated product obtained by maintaining the potentials of the semi-bright nickel plating layer, the bright nickel layer and the eutectoid nickel plating layer in a constant relation can effectively prevent the material from being corroded and increase the content in the plating layer. The present inventors have found that the corrosion of steel is extremely slow, and completed the present invention.

That is, according to the present invention, a base material to be plated is provided with a semi-bright nickel plating layer substantially free of sulfur,
A bright nickel plating layer having an electrochemical potential of 100 to 170 mV lower than the semi-bright nickel plating film, 60 to 120 mV lower than the semi-bright nickel plating film, and 10 to 60 mV to the bright nickel plating film.
A nickel-chromium plated product characterized by being sequentially coated with a non-conductive fine particle eutectoid nickel plating layer having a mV noble electrochemical potential and a chromium plating film, and a method for producing the same.

In the production of the nickel-chromium plated product of the present invention, it is extremely important to control the relationship between the potentials of the nickel plating layers within the above-mentioned fixed range.
The measurement of the potential of the nickel plating layer is generally performed using a device in which a silver-silver chloride electrode is attached as a reference electrode to an electrolytic plating thickness measuring device, and this type of potential measuring device is commercially available. .

In the product of the present invention, the semi-bright nickel plating applied first does not substantially contain sulfur in the nickel coating. For example, the sulfur content is 0.005%.
Less than can be used. Such a semi-bright nickel plating uses a known composition, for example, a bath in which a brightener such as coumarin or butynediol is added to a Watt bath, or a commercially available brightener for semi-bright nickel, for example, B It is prepared by using mu, BTL (both manufactured by Ebara Ujilight Co., Ltd.). There is no particular limitation on the thickness of this semi-bright nickel plating,
In order to obtain sufficient corrosion resistance, the thickness is desirably 5 μm or more.

The bright nickel plating applied as the intermediate nickel layer is 100
It is necessary to have a potential lower than 170 mV. The sulfur contained in this plating layer is generally considered to be about 0.05 to 0.08%, but since the electrochemical potential of the nickel plating film is not uniquely determined only by the sulfur content, There is no point in replacing the above potential range with the sulfur content.

When the potential difference between the bright nickel plating layer and the semi-bright nickel plating layer is 100 mV or less, the anti-corrosion effect of the semi-bright nickel plating layer is not sufficiently exerted, and the base corrosion prevention occurs at an early stage. If it is 170 mV or more, excessive dissolution of the bright nickel plating layer occurs as the corrosion progresses, and the plating tends to swell. The thickness of the bright nickel plating of the intermediate layer is not particularly limited, but is preferably 5 μm or more in order to obtain sufficient corrosion resistance.

Further, the eutectoid nickel plating applied on the bright nickel plating layer has a potential lower by 60 to 120 mV with respect to the semi-bright nickel plating layer and 10 to 60 mV with respect to the bright nickel plating layer. It is necessary to have a noble potential. The eutectoid nickel plating layer needs to be base to the semi-bright nickel plating layer, but if the potential difference between them is 120 mV or more, the dissolution of the non-conductive fine particle eutectoid nickel plating layer in the anticorrosion process proceeds excessively. However, a sufficient effect of preventing surface corrosion cannot be obtained. If the potential difference is 60 mV or less, chromium plating having a good appearance cannot be obtained.

On the other hand, if the potential difference between the non-conductive fine particle eutectoid nickel plating layer and the bright nickel plating layer is 10 mV or less, the effect of delaying the surface corrosion is small, and if it is 60 mV or more, the plating tends to swell. The thickness of the non-conductive fine particle eutectoid nickel plating layer is desirably 1 μm or more in order to obtain sufficient corrosion resistance.

As described above, in the production of the nickel-chromium plating product of the present invention, it is essential to control the potential difference between the nickel plating layers within a certain range. As long as it deposits a nickel film having the above-mentioned potential difference, a conventionally provided one can be used as it is.

When a known bright nickel plating or eutectoid nickel plating bath is used, examples of the means for adjusting the potential of the nickel film noblely include the following methods.

(1) Addition or supplementation of a chemical known as a secondary brightener for bright nickel plating, such as butynediol, hexynediol, propargyl alcohol, sodium allyl sulfonate, to the plating bath. (2) Addition or supplementation of a chemical known as a brightener for semi-bright nickel plating such as formalin and chloral hydrate to the plating bath. (3) Increase in plating bath temperature.

Conversely, in order to adjust the potential of the bright nickel plating or eutectoid nickel plating film to a low value, the following method can be used in addition to the above-mentioned reverse method. (1) Addition or replenishment of a chemical known as a brightener for nickel plating with high sulfur such as sodium benzenesulfinate to a plating bath.

The nickel-chromium product of the present invention is obtained by performing two-layer nickel plating, eutectoid nickel plating, and then chromium plating using the nickel plating baths adjusted as described above in accordance with a conventional method. Manufactured. Although the chromium plating of the uppermost layer may be obtained by a known method, the plating layer is desirably 0.1 μm or more in order to obtain sufficient corrosion resistance. Further, the material to be plated may be subjected to copper plating before the semi-bright nickel plating is performed, and the plated product thus obtained is also included in the present invention.

[0024]

According to the nickel-chromium plating product of the present invention, the electrochemical potential of each nickel plating layer is controlled within a certain range, and the corrosion current is well dispersed in the bright nickel layer and the eutectoid nickel layer. Compared to the same nickel-chromium products obtained by the conventional method,
Since corrosion in the plating layer hardly appears in the appearance and a beautiful appearance can be maintained for a long period of time, it is industrially extremely useful.

[0025]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, Comparative Examples and Test Examples, but the present invention is not limited to these Examples. The common plating conditions employed in the examples are as follows.

[0026] (Materials Used) Test material: copper plate (50 × 100 mm) semi-bright nickel base plating bath: Nickel sulfate _{(N i SO 4 · 6H 2} O) 280 g / l nickel chloride _{(N i Cl 2 · 6H 2} O 45 g / l boric acid (H ₃ BO ₃ ) 45 g / l brightener B-mu ^* 10 ml / l brightener BTL ^* 1.5 ml / l lubricant # 62 ^* 2 ml / l pH 4.0 bath temperature 55 ° C.

The bright nickel base plating bath: Nickel sulfate _{(N i SO 4 · 6H 2} O) 280 g / l nickel chloride _{(N i Cl 2 · 6H 2} O) 45 g / l boric acid (H ₃ BO ₃₎ 45 g / L Brightener # 610 ^* 5ml / l Brightener # 63 ^* 10ml / l Lubricant # 62 ^* 2ml / l pH 4.0 Bath temperature 55 ° C

The eutectoid nickel base plating bath: Nickel sulfate _{(N i SO 4 · 6H 2} O) 300 g / l nickel chloride _{(N i Cl 2 · 6H 2} O) 60 g / l boric acid (H ₃ BO ₃₎ 45 g / l brightener DN-301 ^* 3 ml / l brightener DN-303 ^* 8 ml / l additive DN-MP ^* 10 g / l additive DN-307 ^* 0.5 g / l pH 4.0 bath temperature 55 ° C

Chromium plating bath: Chromium anhydride solution (CrO ₃ ) 240 g / l Sulfuric acid (H ₂ SO ₄ ) 1 g / l Additive Chlolite KC-40 ^* 4 g / l Bath temperature 45 ° C. In the bath composition, those marked with ^* are products manufactured by Ebara Ugelight Co., Ltd.

(Plating process conditions) Semi-bright nickel: 4 A / dm ² , 20 minutes (plating thickness: 12 μm) Bright nickel: 4 A / dm ² , 20 minutes (plating thickness: 12 μm) Eutectoid nickel plating: 4 A / dm ² 3 minutes (plating thickness: 1.8 μm) Chrome plating: 15 A / dm ² , 5 minutes (plating thickness: 0.5 μm) (Number of micropores: 20000 / cm ² )

Example 1 Except for changing the following conditions, plating was performed in accordance with the above-mentioned materials and plating conditions. As a comparison, plating was performed in accordance with the above-mentioned materials and plating conditions (Comparative Example 1; conventional standard process). Sodium benzenesulfinate (8 mg / l) was added to the bright basic nickel plating bath. Raise the bath temperature of the eutectoid nickel basic plating bath to 60 ° C,
1.5 g / l of sodium allyl sulfonate was added.

Example 2 Plating was performed in accordance with the above-mentioned materials and plating conditions, except that the following conditions were changed. 15 mg / l of sodium benzenesulfinate was added to the bright nickel basic plating bath. Raise the bath temperature of the eutectoid nickel basic plating bath to 60 ° C,
1 g / l of sodium allyl sulfonate was added.

Example 3 Except for changing the following conditions, plating was performed in accordance with the above-mentioned materials and plating conditions. 15 mg / l of sodium benzenesulfinate was added to the bright nickel basic plating bath. 0.4 g / l of sodium allyl sulfonate was added to the eutectoid nickel basic plating bath.

Example 4 Except for changing the following conditions, plating was performed in accordance with the above-mentioned materials and plating conditions. Sodium benzenesulfinate (25 mg / l) was added to the bright nickel basic plating bath. 1 g / l of sodium allyl sulfonate was added to the eutectoid nickel basic plating bath.

Example 5 Plating was performed in accordance with the above-mentioned materials and plating conditions, except that the following conditions were changed. Sodium benzenesulfinate (50 mg / l) was added to the bright nickel basic plating bath. 1 g / l of sodium allyl sulfonate was added to the eutectoid nickel basic plating bath.

Comparative Example 2 Plating was performed in accordance with the above-mentioned materials and plating conditions, except that the following conditions were changed. The bright nickel plating bath was changed to the following (for high sulfur content nickel plating). The sulfur contained in the nickel plating film obtained from this plating bath was about 0.1%.
Met. Nickel sulfate _{(N i SO 4 · 6H 2} O) 300 g / l nickel chloride _{(N i Cl 2 · 6H 2} O) 80 g / l boric acid _{(H 3 BO 3) 35 g} / l additive Toriraito ^* 10 ml / l Wetting agent # 62 ^* 2 ml / l pH 3.0 Bath temperature 50 ° C ^* Product of Ebara Uzilite Co., Ltd. 1 g / l of sodium allyl sulfonate was added to the eutectoid nickel basic plating bath.

Test Example The potential of each nickel plating layer of the plating films obtained from the above Examples and Comparative Examples was measured, and JIS-
Corrosion resistance was compared in the Cas test of Appendix D0201.
The measurement of the potential difference between the nickel plating layers is as follows.
The measurement was performed using an electrolytic plating thickness measuring instrument and a multilayer nickel plating corrosion resistance measuring instrument manufactured by Chuo Seisakusho Co., Ltd. Table 1 shows the potential of each nickel plating and Table 2 shows the results of the corrosion resistance test.
Shown in

[0038] ^{* The} potential of the nickel plating film was expressed assuming that the potential of the semi-bright nickel plating film was 0 mV.

[0039] ^** Rating number is expressed as surface rating number indicating the degree of corrosion of the plating surface. If no corrosion is seen on the surface, the rating number is 10.

As is evident from the results, only those having a potential difference between the nickel coatings within a certain range exhibited excellent corrosion resistance.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tatsuhiko Hatanaka 1-1-6 Yoshiyukizaka, Fujisawa-shi, Kanagawa Prefecture Ebara Eugerite Co., Ltd. Central Research Laboratory (72) Inventor Hitoshi Wada 1-1-Yoshiyukizaka, Fujisawa-shi, Kanagawa Prefecture 6. Inside the Central Research Laboratory, EBARA Eugerite Co., Ltd. (72) Inventor Manabu Ozawa 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (56) References JP-B 62-52039 (JP, B2) "Field engineer Practical Plating for Metals, ”First Edition, (53-9-25), edited by the Japan Plating Technology Research Group, Maki Bookstore, pp. 243-261

Claims (3)

(57) [Claims] A semi-bright nickel plating layer substantially free of sulfur, a bright nickel plating layer having an electrochemical potential of 100 to 170 mV lower than that of a semi-bright nickel plating film, and a semi-bright nickel The non-conductive fine particle eutectoid nickel plating layer which is 60 to 120 mV base to the plating film and has a noble electrochemical potential of 10 to 60 mV to the bright nickel plating film is sequentially coated with the chromium plating film. Characterized nickel-chrome plated products. 2. The nickel-chromium plated product according to claim 1, wherein the substrate to be plated is copper-plated. 3. An electroplating method for forming a semi-bright nickel plating layer substantially free of sulfur on a product to be plated, and a bright nickel plating layer having an electrochemical potential lower than that of the semi-bright nickel plating film by 100 to 170 mV. Electroplating for forming a semi-bright nickel plating film
Electroplating to form a non-conductive fine particle eutectoid nickel plating layer having a noble electrochemical potential of 10 to 60 mV with respect to the bright nickel plating film, and electroplating to form a chromium plating film. A method for producing a nickel-chromium plated product, wherein the method comprises: