JP2019127645A - Electrolytic nickel plating method including heat treatment process - Google Patents

Abstract

To provide a technology for obtaining a nickel plating film with high hardness of such a level that conventional electrolytic nickel plating technologies cannot have attained using an electrolytic nickel plating and a heat treatment.SOLUTION: There is provided a heat treatment method for an electrolytic nickel plating in which, after a nickel plating film is formed while stirring using an electrolytic nickel plating solution to which a primary brightener and a secondary brightener are added in a suitable concentration, the obtained plated-product is heat-treated. In addition, by using a method in which a surfactant is further added into the electrolytic nickel plating solution and/or a method in which micro bubbles are supplied into the solution to stir together, the nickel plating film with higher hardness can be formed.SELECTED DRAWING: None

Description

  The present invention relates to a nickel electroplating and heat treatment method, and more particularly to an electroplating and heat treatment method for increasing nickel plating film hardness.

Because the plating film is thin and difficult to measure various mechanical properties, it is generally measured using a Vickers hardness tester or a micro Vickers hardness tester specified in JIS Z 2244 to represent the mechanical properties of plating. Vickers hardness is used. The Vickers hardness Hv is used as a symbol, and is expressed as "Hv is 150". In general, improvement in abrasion resistance is important because abrasion resistance tends to improve as the hardness of the material increases.
The electrolytic nickel plating film usually has a Vickers hardness of about 400 or less, but the film plated with a plating solution to which a brightener is added has a high hardness. As a result of studying various compounds as additives for electrolytic nickel plating, it was reported that using sodium allyl sulfonate, which has been used as a brightener, a plating film with a hardness Hv of about 600 was obtained. (Non-Patent Document 1).
Thus, in the case of electrolytic nickel plating, the Hv is limited to about 600 even for the optimum selection of brighteners. In addition, it is generally said that the hardness does not increase even when heat treatment is performed for the electrolytic nickel plating film, and the hardness of the electrolytic nickel plating film currently produced industrially is 600 or less.

  There is also a method called alloy plating to increase the hardness of the nickel plating film. It is said that hardness of around Hv700 is possible for alloy plating such as nickel / cobalt plating, and hardness of around Hv800 is possible for composite plating of nickel and tungsten carbide, but the management of the plating process is complicated and the cost is high.

In the case of electroless plating, it is said that a considerable amount of phosphorus, boron or the like is co-deposited in the plating film, which also increases the hardness. In practice, the hardness of the film obtained by electroless nickel-phosphorus plating is about 600, and the hardness of the electroless nickel-boron film is about 700. However, when these films are heat-treated at a temperature of 300 ° C. or higher Vickers hardness is said to improve to about 1000 and about 1100, respectively. However, since electroless plating is performed by chemically reducing metal ions contained in the plating solution, it has a life due to consumption of the reducing agent, and it is necessary to discard the plating solution every time a certain amount of plating is performed. And therefore the cost is significantly higher compared to electroplating.
Also in electrolytic nickel plating, hypophosphorous acid or the like is added to a watt bath or a sulfamic acid bath, phosphorus is co-deposited in the nickel film to be electrodeposited, and further heat treatment is performed on the nickel plating film co-deposited with phosphorus. There is also research to increase the hardness of the plating film. However, this method of adding hypophosphorous acid takes time and effort to distribute phosphorus as uniformly as possible, and it is costly because phosphorus is never a cheap element. Research has not been done. Moreover, the above method imitates the method of increasing the hardness by co-depositing phosphorus and boron in conventional electroless nickel plating and further performing heat treatment at 300 ° C. or higher, and is similar to alloy plating. ing. On the other hand, even if heat treatment at 300 ° C. or higher is applied to an electrolytic nickel plating film formed without adding hypophosphorous acid or the like, the hardness does not increase and the heat treatment effect cannot be obtained.

As described above, electrolytic nickel plating does not require large-scale equipment, and the complexity of the processing steps is small, so there is a great advantage that the cost is significantly low, but the film hardness is only up to about Hv 600 even when using a brightener. It was said that it did not go up, and it tended to be avoided in terms of durability, wear resistance, etc.
From such a situation, it is practically significant if a high hardness nickel plating film can be obtained without largely changing the equipment of the usual electrolytic nickel plating and without changing the composition of the plating film.

Japanese Patent Laid-Open No. 5-112898 Japanese Patent No. 4941998 Japanese Patent No. 4991472 Japanese Patent No. 5858428

Kishimoto, K. et al. “Surface Technology” Vol.54, No.10, 2003 p.710-713 “Effects of various additives on the properties of electrodeposited nickel films” Takashi Kase “Metal Surface Technology” vol.12, No.2 (1961) p.53-58. “Some Properties of Brighteners and Electrodeposits in Bright Nickel Plating”

  The present invention is a technique for obtaining a nickel plating film having a level of hardness not obtained by the conventional electrolytic nickel plating, without largely changing the equipment for ordinary electrolytic nickel plating and without changing the composition of the plating film. It is to provide. Specifically, a method of obtaining a nickel electrolytic plating film with high hardness is provided by examining a plating method and heat treatment conditions when performing nickel plating using a normal electrolytic nickel plating solution to which a brightening agent is added.

By the way, electroplating technology using air bubbles is known as a technology to obtain a plating film with gloss and few pinholes, and plating with surface tension adjusted to 45 dyn / cm or less by adding a surfactant. A method of plating while generating fine bubbles (microbubbles) having a diameter of 10 to 1000 μm (for example, 100 μm) in a bath (Patent Document 1) or a method of plating in a foam layer formed by continuously generating bubbles Patent Document 2) is known.
The present inventors have also developed a technique for obtaining a glossy plating film with few pinholes by electroplating in a foam layer of a plating solution to which a brightener is added together with a surfactant (patent document). 3, 4). These techniques are mainly performed by plating in foam as an aggregate of only bubbles.

The present inventors recalled the use of electroplating while generating these air bubbles in developing a method for obtaining a nickel electroplating film having high hardness, and increase the hardness in the case of conventional electrolytic nickel plating. We decided to consider applying heat treatment that had a negative opinion on the effect.
Specifically, an appropriate amount of each of the primary brightening agent and the secondary brightening agent is added to a nickel electrolytic plating solution, and a small amount of sodium dodecyl sulfate (SDS) as a surfactant is further added, and microbubbles having a diameter of 500 microns or less are added. Electrolytic nickel plating was carried out while being fed, dispersed and stirred in a plating solution, and then the test piece was subjected to heat treatment at 200 ° C. for 1 hour.
As a result, the Vickers hardness (Hv) measured on the plating surface was able to provide a nickel plating film having a hardness as high as about 800, rather than 600, which has hitherto been considered impossible to achieve by electroplating.
Next, experiments were conducted on the case where the addition of a small amount of the surfactant was omitted and the case where the microbubbles were omitted. As a result, a nickel plating film having a high hardness of around 750 could be provided.
Having obtained the above findings, the present invention has been completed.
The hardness value described here is a value measured from the surface side using a Micro Vickers hardness tester FM-ARS9008 manufactured by Futuretec Co., Ltd. with a test load of 50 gf and a holding time of 15 seconds. The hardness may be measured on the side of the plating film. In this case, the plating film is plated thickly to a thickness of several tens of μm, the object to be plated is cut, the cross section is polished, and the hardness is increased. taking measurement. Therefore, not only the problem of whether the crystal orientation in the plating film is the same as when the plating film is thin, but also gives a strong history of cutting and polishing, so the hardness measured from the surface side of the tens of μm plating film And can not compare.

The present invention is a method for obtaining a nickel plating film having high hardness, and using a nickel plating solution prepared by adding an appropriate amount of a primary brightening agent and a secondary brightening agent to an electrolytic plating solution of nickel, electrolytic nickel plating is performed while stirring. A method is provided comprising the steps of conducting and subjecting the obtained nickel plated product to a heat treatment at 100 ° C. or more and less than 300 ° C.
The present invention is a method for obtaining a nickel plating film having a further increased level of hardness, and a nickel plating solution to which a small amount of surfactant is added together with a primary brightening agent and a secondary brightening agent is used in the above electroplating step. A method, or a method of performing plating while stirring while feeding microbubbles having the largest diameter of 500 microns or less, is provided.
In order to obtain a nickel plating film of the highest hardness, using an electrolytic plating solution containing a primary brightening agent, a secondary brightening agent and a surfactant, microbubbles are fed and electrolytic nickel plating is carried out while stirring, and then It is preferable to provide a step of performing heat treatment.

That is, the present invention is as follows.
[1] A heat treatment method of electrolytic plating of nickel
(1) A step of preparing by adding a primary brightening agent and a secondary brightening agent as an electrolytic nickel plating solution,
(2) forming a nickel film on the surface of the object to be plated while stirring the electrolytic nickel plating solution;
(3) applying a heat treatment to the plated material having the electrolytic nickel film formed thereon at a temperature of 100 ° C. or more and less than 300 ° C. for 5 minutes or more,
A method comprising the steps of:
[2] In the step of forming an electrolytic nickel film, microbubbles having a largest diameter of about 500 microns or less are fed into the electrolytic nickel plating solution, and the nickel film is formed on the surface of the object while stirring. The method according to [1] above.
[3] The method according to [1] or [2], wherein the electrolytic nickel plating solution is prepared by adding a surfactant together with a primary brightener and a secondary brightener.

  Conventionally, the upper limit of the Vickers hardness of the electrolytic nickel plating film is about 600, but according to the present invention, it has become possible to obtain a nickel plating film having a Vickers hardness of about 700 to 800.

Influence of heat treatment temperature on hardness of electrolytic nickel plated pieces

1. Plating apparatus The electroplating apparatus for carrying out the present invention is not particularly limited. For example, a plating tank formed of stainless steel or the like equipped with a stirrer, a DC power supply, and an anode electrically connected to the positive electrode side of the DC power supply It is necessary that the apparatus is equipped with a cathode which is a member to be plated which is electrically connected to the negative electrode side, and further equipped with equipment capable of forming microbubbles when microbubbles are fed. There are various methods of generating micro bubbles such as rotational shear, pressure bubbling, cavitation and venturi, but it is not limited to any of these methods, and equipment that can form micro bubbles of the required size. It is good if it is.
The object to be plated by the electrolytic nickel plating of the present invention is generally a metal such as iron or copper, but may be a plastic, ceramic or the like as long as the surface has electrical conductivity or is provided with it. Good.

2. Heat treatment apparatus There is no particular restriction on equipment for heat treatment, and an electric furnace or the like capable of appropriately managing the temperature may be used.
The heat treatment of the plating film is generally used to prevent hydrogen embrittlement of the material by the plating treatment, to improve the adhesion of the plating film to a special metal, to improve the mechanical properties, etc. It has been said that the hardness of the plating film decreases with heating due to the relaxation, the generation and coarsening of unstrained crystals by recrystallization, the release of occluded gas, the condensation of impurities, and the like.
In electroless nickel plating, the hardness of the plated film is greatly increased by heat treatment of 300 ° C. or higher, but it is said that the hardness does not become high even if the same heat treatment is applied to the film obtained by electrolytic plating. It is not performed that the heat treatment is performed on the nickel plating film obtained by the electrolytic plating.

3. Plating Solution There are also sulfamic acid bath and strike bath (wood bath) as a plating solution used for electrolytic nickel plating, but a watt bath mainly composed of nickel sulfate, nickel chloride and boric acid is the most common and practical. This can be used. The plating film obtained using a watt bath has good adhesion to the substrate, is semi-gloss, is corrosion resistant, and forming a mirror gloss film with a plating solution obtained by adding a brightening agent to a watt bath is also performed. It is known that when a brightener is used, the hardness of the plated film also increases to about Hv600.

4. Brighteners Brighteners for bright nickel plating include primary and secondary brighteners (Non-patent Document 2). In the present invention, a compound generally known as a brightener may be used or a commercially available brightener may be used.
(4-1) Primary Brightening Agent The primary brightening agent is said to work to impart gloss by refining the crystal particles in the plating film. Since the structure having a size just below the wavelength of visible light is mainly controlled, mirror gloss is often not obtained, and it is also called a semi-gloss agent.
Sulfur compounds used for primary brighteners include aromatic sulfonic acids benzene sulfonic acid, p-toluene sulfonic acid and their sodium salts, sodium 1,5-naphthalenedisulfonate (DNS), 1,3,6- Sodium naphthalene trisulfonate (TNS) and the like; benzenesulfonamide of aromatic sulfonamides, p-toluenesulfonamide and the like; orthobenzene sulfoneimide (saccharin) of aromatic sulfonimides and the sodium salt thereof and the like is there. In general, saccharin, benzene sulfonate or sodium naphthalene disulfonate (DNS) is used.
The primary brightening agent used in the present invention may be a single substance of these compounds, or a mixture of these compounds, or a compound obtained by adding some additives thereto, and is a commercially available primary brightening agent formulated as a primary brightening agent. May be

  The addition amount of the primary brightening agent to the plating solution in the present invention may be an addition amount in the range recommended as a normal addition amount. When the specific compounds shown here or a mixture thereof are used as the primary brightener, the addition amount is usually 3 to 9 mmol (3 to 9 mmol / L) of the primary brightener or a mixture thereof per 1 liter of plating solution. A range of degree is said to be appropriate, and in the present invention, it may be appropriately increased or decreased within such a range. When a commercially available primary brightener supplied in the form of a solution is used, it may be appropriately increased or decreased within the range of the addition amount recommended by the primary brightener manufacturer.

(4-2) Secondary Brightener The secondary brightener is used to smooth small areas which can not be reached by the primary brightener, thereby obtaining a specular gloss.
As the mechanism of action, a sulfur-based compound which is a primary brightening agent such as saccharin adsorbed on the surface controls crystallization at a level one digit lower than the wavelength of light to roughly roughen it, and a secondary such as butynediol It is believed that the brightener smoothes and imparts gloss to the fine irregularities created by the crystalline particles as it is reduced at the plating surface and reduced to butanediol.
Substances used as secondary brighteners include aldehydes such as formaldehyde (formalin); allyl sulfonic acids such as allyl or vinyl compounds and vinyl sulfonic acids; butyne diols such as acetylene compounds; ethylene cyanohydrin such as nitriles Others include propargyl alcohol, coumarin, gelatin, thiourea and the like. In general, since secondary alcohols such as butynediol and propargyl alcohol are used, the secondary brighteners are also referred to as unsaturated alcohol components.
The secondary brightener used in the present invention may be a compound obtained by adding these compounds, a mixture thereof, or some additives, or a commercially available secondary brightener prepared as a secondary brightener. You may use.

  The addition amount of the secondary brightening agent to the plating solution in the present invention may be an addition amount in the range recommended as a normal addition amount. When the specific compounds shown here or a mixture thereof are used as the secondary brightener, the amount added is usually in the range of about 0.4 to 1.8 mmol of secondary brightener or a mixture thereof per liter of plating solution ( It is said that 0.4 to 1.8 mmol / L) is appropriate, and in the present invention, it may be appropriately increased or decreased within such a range. When a commercially available secondary brightener supplied in the form of a solution is used, it may be appropriately increased or decreased within the range of the addition amount recommended by the secondary brightener manufacturer.

5. Surfactant As a surfactant, sodium dodecyl sulfate (SDS, also called sodium lauryl sulfate), which is generally versatile and inexpensive, is preferable, and is often used in practice, but other anionic surfactants are also used. Also usable are agents, cationic surfactants, nonionic surfactants, and further zwitterionic surfactants.
Anionic surfactants are typically alkyl sulfates such as sodium dodecyl sulfate (SDS), but also α-olefin sulfonates, alkyl benzene sulfonates, phosphates thereof, perfluoroolefins. Sulfonate, perfluoroalkylbenzene sulfonate, perfluoroether sulfonate and the like can be mentioned. In addition, as a cation of the salt of these anionic anionic surfactant, sodium, potassium, diethyldimethyl ammonium, tetramethyl ammonium etc. are mentioned, for example.
As a nonionic surfactant, carbon number C4-C25 alkylphenol type | system | group, carbon number C4-C20 alkanol, polyalkylene glycol type | system | group etc. are mentioned, for example. Examples of cationic surfactants include lauryl trimethyl ammonium salt, lauryl dimethyl ethyl ammonium salt, dimethyl benzyl lauryl ammonium salt and the like.
Examples of the zwitterionic surfactant include betaine, sulfobetaine, ethylene oxide and / or a sulfated or sulfonated adduct of a condensation product of propylene oxide and an alkylamine or diamine.

  When adding a surfactant to the plating solution, the addition amount must be at least one-tenth of the critical micelle concentration, but adding a concentration that exceeds or exceeds the critical micelle concentration is problematic. There is no. Depending on the type of surfactant, in the case of SDS, 0.1 to 10 g / L, preferably 0.5 to 5 g / L is added.

6. Microbubbles Microbubbles are generated by attaching a facility for generating microbubbles to a plating tank and operating it (see Patent Document 1 and the like). There are various types of equipment for generating microbubbles, such as pressurizing / swirling, pressurizing foaming, swirling / shearing, cavitation, and venturi, any of which may be used.
The bubble size of the microbubbles needs to be at the peak or largest diameter of the bubble diameter distribution of about 500 μm or less.

Before starting the plating, it is necessary to send a gas to the nozzle to cause a certain amount of microbubbles to be present in the plating solution. For this purpose, for example, about 1 to 0.2 liters of gas per minute of plating solution may be sent to the nozzle for about 2 to 3 minutes, but the gas flow rate may be increased to shorten the time. You can slow down and increase the time.
Since the microbubbles have small buoyancy and remain in the plating solution during plating, for example, for 10 minutes, the microbubbles may be continuously generated during plating, and the microbubbles Generation may be decelerated or stopped.

The embodiments of the present invention will be described in detail below based on examples. However, the embodiment of the present invention is not limited to these examples.
Other terms and concepts in the present invention are based on the meanings of terms that are conventionally used in the field, and various techniques used to implement the present invention include those that clearly indicate the source. Those skilled in the art can easily and surely carry out the present invention based on known documents and the like except for the above. In addition, various analyzes and the like were carried out using the methods described in the instruction manuals and catalogs of the analytical instruments or reagents used.
The contents of the prior art documents, patent publications and patent applications cited in this specification are to be referred to as the contents of the present invention.

EXAMPLE 1 Electrolytic Nickel Plating Method Including Heat Treatment Step (1-1) Electrolytic Nickel Plating Step and Heat Treatment Step In 1000 parts of water, 240 parts of nickel sulfate, 45 parts of nickel chloride and 30 parts of oxalic acid are dissolved, pH 4 to 5 Adjusted to To this, 16 mmol of saccharin per liter of plating solution as a primary brightening agent and 5.8 mmol per liter of plating solution as a secondary brightening agent were added to obtain a nickel plating solution used in this example.
The prepared plating solution is placed in a plating tank provided with a stirrer and a cyclone type (venturi type) micro bubble forming nozzle, and generation of micro bubbles is continued while stirring is performed for 10 minutes at an average current density of 5 A / dm ^2. Electrolytic nickel plating was performed on the Hull cell iron plate.
After completion of plating, the prepared plating test piece was washed with water and dried, and then the hardness was measured. The hardness of the plated film was measured at three points by changing the position with a micro Vickers hardness tester, and the average value was determined.
Further, the test pieces plated under the same conditions were heat-treated at 200 ° C. for 1 hour using an electric furnace. The hardness of the plated test piece after heat treatment was also measured in the same manner.

(1-2) Effects of Heat Treatment Step The Vickers hardness of the plated film of the test piece in the state not subjected to heat treatment is 583, which is substantially the same as the hardness obtained by ordinary nickel electrolytic plating, but after heat treatment The hardness of the plating film is 722 and it can be seen that the hardness is considerably high.

(1-3) Effect of Surfactant Formulation When using the nickel plating solution shown in this example (1-1) and performing plating treatment under the same plating conditions in which microbubbles coexist, and in the nickel plating solution The same heat treatment process as in (1-1) was performed for each case where plating was performed under the condition that only stirring was performed without coexisting microbubbles using a plating solution to which sodium dodecyl sulfate was added at a ratio of 0.1% by weight. gave.
About both, when the hardness of the plating film before and after heat processing was measured on the same measurement conditions as (1-1), both hardness after heat processing was substantially equivalent. That is, it was found that by adding a small amount of surfactant to the plating solution, the same effect as in the case of coexistence of microbubbles can be obtained.

(Example 2) Plating treatment step and heat treatment step in the presence of microbubbles with a surfactant-containing plating solution To a nickel plating solution prepared in the same manner as in Example 1 (1-1), sodium dodecyl sulfate was further added as a surfactant. 0.1 wt% was added. Using the prepared plating solution, electrolytic nickel plating was performed on a hullel iron plate while stirring in the presence of microbubbles under the same conditions as in Example 1. The Vickers hardness of the obtained plated test piece after washing with water and drying was 622.
The hardness of the test piece plated under the same conditions after heat treatment at 200 ° C. for 1 hour was 794, and the hardness after heat treatment significantly increased.

Example 3 Influence of Heat Treatment Temperature on Electrolytic Nickel Plating Film Hardness With respect to the test piece after the plating treatment step obtained in Example 2, 100 ° C., 150 ° C., 200 ° C., 250 ° C. The temperature was changed to 300 ° C., and a heat treatment process was performed for 1 hour. The hardness of the plated film is 718 at 100 ° C, 744 at 150 ° C, 794 at 200 ° C and 791 at 250 ° C, both of which are significantly higher than the hardness 622 before heat treatment, and the higher the temperature, the higher the hardness. It tended to be higher, but it decreased to 443 at 300 ° C, unlike in the case of electroless nickel plating. (Figure 1)

Claims (3)

A nickel electrolytic plating heat treatment method,
(1) A step of preparing by adding a primary brightening agent and a secondary brightening agent as an electrolytic nickel plating solution,
(2) forming a nickel film on the surface of the object to be plated while stirring the electrolytic nickel plating solution;
(3) applying a heat treatment to the plated material having the electrolytic nickel film formed thereon at a temperature of 100 ° C. or more and less than 300 ° C. for 5 minutes or more,
A method comprising the steps of:   In the step of forming the electrolytic nickel film, microbubbles having the largest diameter of about 500 microns or less are fed into the electrolytic nickel plating solution, and the nickel film is formed on the surface of the object while stirring. Item 2. The method according to Item 1.   The method according to claim 1, wherein the electrolytic nickel plating solution is prepared by adding a surfactant together with a primary brightener and a secondary brightener.