JP2024076911A - Non-cyan brass plating bath and plating method - Google Patents

Abstract

To provide a non-cyan brass plating bath and a plating method capable of suppressing coloration (redness) derived from copper and obtaining stable film uniformity and conformality.SOLUTION: A plating method comprises brass plating an object using a non-cyan brass electroplating bath containing a divalent copper salt, a divalent zinc salt, a hydroxy acid salt, a hydantoin compound, a conductive salt and any of a tin salt, a manganese salt, a cobalt salt or a nickel salt and a non-cyan brass electroplating bath containing a divalent copper salt, a divalent zinc salt, a hydroxy acid salt, a hydantoin compound and any of a tin salt, a manganese salt, a cobalt salt or a nickel salt.SELECTED DRAWING: None

Description

The present invention relates to a non-cyanide brass plating bath and plating method.

Cyanides have been widely used in plating because they are excellent complexing agents, but they are harmful to living organisms and require strict management to prevent water pollution, air pollution, and worker health, so there is a demand for plating solutions that are cyanide-free and in the weak acid to alkaline range.

A known example of a non-cyanide brass plating bath is a non-cyanide brass plating bath mixture (Patent Document 1) that contains copper, zinc, metal polyphosphate, and orthophosphate, and does not contain cyanide.

Japanese Patent Application Laid-Open No. 09-217193

The invention in Patent Document 1 is a method for depositing a brass barrier layer onto copper foil, but the gloss, uniformity, and coverage are insufficient for use in decorative applications.

In addition, when plating using a non-cyanide brass plating bath, there is generally an unavoidable problem of coloring (reddish) caused by the copper. In particular, when barrel plating buttons, zippers, hooks, and other small parts, reddish plating is mixed in at low current density areas, resulting in a noticeable lack of uniformity and throwing power, making this plating bath unusable for decorative purposes.

The inventors of the present invention have conducted extensive research into non-cyanide brass plating baths that suppress copper-derived coloring (redness) and provide stable coating uniformity and throwing power, and have discovered that the above problems can be solved by using a combination of a hydroxy acid salt and a hydantoin compound as a complexing agent, thus completing the present invention.

That is, the present invention is a non-cyanide brass electroplating bath that contains a divalent copper salt, a divalent zinc salt, a hydroxy acid salt, a hydantoin compound, a conductive salt, and either a tin salt, a manganese salt, a cobalt salt, or a nickel salt.

The present invention is also characterized in that the hydroxy acid salt is a hydroxy acid having 2 or 4 carbon atoms, and the hydantoin compound is hydantoin, alkylhydantoin, or phenylhydantoin.

The present invention also provides a plating method that involves plating an object with brass using a non-cyanide brass electroplating bath that contains a divalent copper salt, a divalent zinc salt, a hydroxy acid salt, a hydantoin compound, and either a tin salt, a manganese salt, a cobalt salt, or a nickel salt.

According to the present invention, by adjusting the ratio of tin salts, manganese salts, cobalt salts or nickel salts in addition to hydroxy acid salts and hydantoin compounds, it is possible to provide a non-cyanide brass plating bath that provides stable uniformity and throwing power even in barrel plating.

Furthermore, the non-cyanide brass plating bath of the present invention provides stable uniformity and adhesion not only in rack plating but also in barrel plating, making it suitable for plating when producing decorative plated products.

In addition, the non-cyanide brass plating bath of the present invention provides stable uniformity and throwing power, so plating can be performed at a low bath temperature of about 40°C, which not only improves the appearance of the plating film but also improves workability.

Additionally, by adding conductive salts to the plating bath, further uniformity and throw can be achieved, and the current density range can be expanded.

The present invention is a non-cyanide brass electroplating bath that contains a divalent zinc salt, a divalent copper salt, a hydroxy acid salt, a hydantoin compound, a conductive salt, and either a tin salt, a manganese salt, a cobalt salt, or a nickel salt.

In the present invention, both hydroxy acid salts and hydantoin compounds are used as complexing agents.

Examples of hydroxy acid salts include hydroxy acid salts having 2 or 4 carbon atoms, and specific examples thereof include gluconates, tartrates, citrates, malates, etc., with tartrates and citrates being particularly preferred.

Examples of salts of hydroxy acids include alkali metal salts and alkaline earth metal salts of hydroxy acids, such as potassium salts, sodium salts, and calcium salts. The above-mentioned hydroxy acid salts may be used alone or in combination of two or more kinds.

The hydroxy acid salt is preferably contained in the plating bath at 50 to 400 g/L, and more preferably at 100 to 300 g/L.

Examples of hydantoin compounds include hydantoin, alkyl hydantoins such as 1-methylhydantoin, 5-ethylhydantoin, and 5,5-dimethylhydantoin, and 5-phenylhydantoin. Hydantoin and alkyl hydantoins are preferred, and hydantoin and 5,5-dimethylhydantoin are particularly preferred. The hydantoin compounds may be used alone or in combination of two or more of them.

Hydantoin compounds are preferably contained in the plating bath at 10 to 150 g/L, and more preferably at 10 to 150 g/L.

In the plating bath of the present invention, the hydroxy acid salt and the hydantoin compound are preferably used in a weight ratio of 0.15 to 0.6 parts by weight of the hydantoin compound to 1 part by weight of the hydroxy acid salt.

Divalent copper salts include salts of divalent copper with inorganic or organic acids, such as copper (I) sulfate, copper (I) pyrophosphate, copper (I) oxalate, copper (I) oxide, and copper (I) chloride. In the plating bath of the present invention, oxides and chlorides of divalent copper can also be used. The divalent copper salts mentioned above can be used alone or in combination of two or more kinds.

The divalent copper salt is preferably contained in the plating bath at 1 to 30 g/L, and more preferably at 3 to 15 g/L.

Divalent zinc salts include salts of divalent zinc with inorganic or organic acids, such as zinc sulfate, zinc acetate, zinc hydroxide, zinc oxide, zinc chloride, etc. In the plating bath of the present invention, oxides and chlorides of divalent zinc can also be used. The divalent zinc salts may be used alone or in combination of two or more.

The divalent zinc salt is preferably contained in the plating bath at 1 to 30 g/L, and more preferably at 1.5 to 7.0 g/L.

To obtain a brass-colored plating film, the weight ratio of metallic copper to metallic zinc in the plating bath is important, and it is preferable to use a divalent zinc salt and a divalent copper salt so that the metallic zinc is in the range of 0.3 to 0.9 parts by weight per 1 part by weight of metallic copper.

In the present invention, by adding any one of tin salts, manganese salts, cobalt salts, and nickel salts to the plating bath, the plating metal becomes a ternary alloy and the gloss is increased. Such metal salts include salts of tin, manganese, cobalt, and nickel with alkali metals, alkaline earth metals, inorganic acids, or organic acids, and specific examples include sodium stannate, manganese sulfate, cobalt sulfate, and nickel sulfate.

The metal salt is preferably contained in the plating bath at 0.1 to 2 g/L.

In the plating bath of the present invention, by further adding conductive salt, the uniformity and adhesion of the plating film are improved and the current density range is expanded, so more favorable results can be obtained.

The conductive salt is preferably a chloride of an alkali metal, an alkaline earth metal, or ammonia, and specific examples include potassium chloride, sodium chloride, calcium chloride, and ammonium chloride. The divalent copper salt may be used alone or in combination of two or more of the above.

The conductive salt is preferably contained in the plating bath at 5 to 50 g/L.

The non-cyanide brass plating bath of the present invention can be produced by dissolving the above-mentioned divalent copper salt, divalent zinc salt, hydroxy acid salt, hydantoin compound, conductive salt, and any of tin salt, manganese salt, cobalt salt, and nickel salt in water.

The present invention is a plating method for plating an object with brass using a non-cyanide brass electroplating bath containing a divalent copper salt, a divalent zinc salt, a hydroxy acid salt, a hydantoin compound, a conductive salt, and either a tin salt, a manganese salt, a cobalt salt, or a nickel salt.

Plating may be carried out by a conventional method for electroplating, for example, the object to be plated may be subjected to pretreatment such as degreasing, washing, acid immersion, electrolytic degreasing, acid activation, etc., and then plated by a method such as a rack method or a barrel method. For example, plating may be carried out under conditions of a bath temperature of 30 to 50°C, a current of 0.2 to 2.0 A/ ^dm2 , and a plating time of 0.5 to 3 minutes when using the rack method, and a current of 5 to 10 A/kg, a plating time of 5 to 15 minutes, and a rotation speed of 4 to 15 rpm when using the barrel method.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Example 1
A plating bath of 10 L was prepared using 150.0 g/L of potassium sodium tartrate, 30.0 g/L of hydantoin, 5.0 g/L of copper (II) sulfate pentahydrate, 3.0 g/L of zinc (II) sulfate heptahydrate, 20.0 g/L of sodium chloride, and 0.5 g/L of sodium stannate (IV) trihydrate.

250 copper-plated zinc die castings (3.2 g/piece) were electrolytically degreased using 50.0 g/L of Activator Cu (product name: manufactured by Shimizu Corporation), and after pretreatment with water rinsing, acid cleaning, and water rinsing, they were plated in a mini barrel (manufactured by Kondo) under the following conditions.

Plating conditions: Anode = carbon plate (100 cm x 100 cm x 1 cm) x 2 sheets, current value = 7 A/kg, current application time = 10 minutes, bath temperature = 40°C
Barrel rotation speed = 6 revolutions per minute Plating thickness = approx. 0.4m
After plating, the plated object was promptly taken out of the barrel, washed with water, and dried in a centrifugal dryer.

Evaluation method Color:
Using a color difference meter (CM-3500d, manufactured by Konica Minolta, Inc.), the L value, a value, b value SCI (including specular reflection) of the flat surface of the plated object were measured (n=10), and the average value was calculated as ΔE from the cyan brass plated object. The lower the value, the closer the color is to the cyan brass color.
The cyanide-based brass plating was performed by plating 250 copper-plated zinc die castings (3.2 g/piece) with "Brass Salt" (product name, manufactured by Nippon Kagaku Sangyo Co., Ltd.) under the following plating conditions.
Plating conditions: Anode = brass plate (100 cm x 100 cm x 0.5 mm) x 2 sheets, current value = 5 A/Kg, current application time = 10 minutes, bath temperature = 40°C
Barrel rotation speed: 6 revolutions per minute

Throwing power uniformity:
Measurements were made with a color difference meter (n=100), and ΔE from the average of the L, a, and b values of all samples to be plated was calculated using the individual L, a, and b values. The standard deviation was calculated using the calculated ΔE of n=100 to evaluate throwing power and uniformity. The lower the standard deviation, the better the throwing power and uniformity of the finish.
◎: Standard deviation is 0.3 or less. ○: Standard deviation is between 0.3 and less than 0.7. △: Standard deviation is 0.7 or more.

Glossiness:
Similarly, measurements were made using a color difference meter (n=10), and evaluation was performed using the average L value. A higher average L value indicates a more glossy finish.
◎: Average L value is 83.5 or more. ○: Average L value is less than 83.5 to more than 82.4. △: Average L value is 82.4 or less.

Examples 2 to 9
Plating was carried out in the same manner as in Example 1, except that the plating baths shown in Tables 1 and 2 were used.
In Examples 2 to 9, the plating bath contained 5.0 g/L of copper(II) sulfate pentahydrate as the divalent copper salt, 3.0 g/L of zinc(II) sulfate heptahydrate as the divalent zinc salt, and 20.0 g/L of sodium chloride as the conductive salt.

Comparative Examples 1 and 2
Plating was carried out in the same manner as in Example 1, except that the plating shown in Table 3 was used.
In Comparative Examples 1 and 2, the plating bath contained 5.0 g/L of copper(II) sulfate pentahydrate as the divalent copper salt, 3.0 g/L of zinc(II) sulfate heptahydrate as the divalent zinc salt, and 20.0 g/L of sodium chloride as the conductive salt.
The results are shown in Tables 1 to 4.

Results and Observations As can be seen from Tables 1 to 4, in the plating baths containing hydroxy acids, hydantoin compounds, and photochromic agents, the ΔE value of the cyan brass color standard was low, and the throwing power and uniformity were similar or close to those of the cyan brass plating used for comparison. However, in the comparative examples, the ΔE value increased, the color became redder than the brass color, and the throwing power and uniformity were also worse.

That is, the present invention relates to a non-cyanide copper-zinc alloy electroplating bath comprising a divalent copper salt, a divalent zinc salt, a hydroxy acid salt, a hydantoin compound , and a conductive salt, and further comprising any one of a tin salt, a manganese salt, a cobalt salt, and a nickel salt.

The present invention also relates to a plating method, characterized in that an object to be plated is plated with a copper-zinc alloy using a non-cyanide copper-zinc alloy electroplating bath containing a divalent copper salt, a divalent zinc salt, a hydroxy acid salt, a hydantoin compound, and a conductive salt, and further containing any one of a tin salt, a manganese salt , a cobalt salt, and a nickel salt.

Claims (3)

A non-cyanide brass electroplating bath comprising a divalent copper salt, a divalent zinc salt, a hydroxy acid salt, a hydantoin compound, a conductive salt, and either a tin salt, a manganese salt, a cobalt salt, or a nickel salt. The non-cyanide brass electroplating bath according to claim 1, characterized in that the hydroxy acid salt is a hydroxy acid salt having 2 or 4 carbon atoms, and the hydantoin compound is hydantoin, alkylhydantoin, or phenylhydantoin. A plating method characterized by plating an object with brass using a non-cyanide brass electroplating bath containing a divalent copper salt, a divalent zinc salt, a hydroxy acid salt, a hydantoin compound, a conductive salt, and either a tin salt, a manganese salt, a cobalt salt, or a nickel salt.