WO2009093499A1 - Trivalent chromium plating bath - Google Patents
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- WO2009093499A1 WO2009093499A1 PCT/JP2009/050300 JP2009050300W WO2009093499A1 WO 2009093499 A1 WO2009093499 A1 WO 2009093499A1 JP 2009050300 W JP2009050300 W JP 2009050300W WO 2009093499 A1 WO2009093499 A1 WO 2009093499A1
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- trivalent chromium
- chromium plating
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/04—Electroplating: Baths therefor from solutions of chromium
- C25D3/06—Electroplating: Baths therefor from solutions of chromium from solutions of trivalent chromium
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- the present invention relates to a plating bath containing a trivalent chromium compound, a plating method using the plating bath, and an article on which a chromium plating film is formed.
- Chrome plating is widely used in various fields such as decoration and industrial use.
- Conventionally used chromium plating baths contain a large amount of hexavalent chromium as a chromium component.
- the toxicity of hexavalent chromium has become a problem, and development of a plating solution with low toxicity is strongly desired from the viewpoint of work environment and wastewater treatment.
- chromium plating baths containing trivalent chromium that is less toxic than hexavalent chromium (see Patent Documents 1 to 3 and Non-Patent Documents 1 to 3 below).
- the valent chromium ion concentration is 0.4 mol or more, and at least one component selected from the group consisting of an aqueous aliphatic carboxylic acid and a salt thereof is added in an amount of 1.0 to 3.0 with respect to 1 mol of trivalent chromium ions.
- a chromium plating bath containing a molar range has been reported.
- Such a trivalent chrome plating bath has been partially put into practical use as a decorative chrome plating with a thin plating thickness.
- Plating baths such as Canning), trade name: trichlorite (Eugelite), trade name: trichrome plus (Atotech Japan) are commercially available.
- the plating film formed from the conventional trivalent chromium plating bath has a darker appearance and is inferior in decorativeness than the plating film formed from the hexavalent chromium plating bath. For this reason, there is a strong demand for a trivalent chromium plating bath that can form a chromium plating film having a white appearance similar to a chromium plating film obtained from a hexavalent chromium bath.
- the present invention has been made in view of the above-mentioned problems of the prior art, and its main object is the problem of the above-described conventional trivalent chromium plating bath, particularly plating formed from a hexavalent chromium bath.
- An object of the present invention is to provide a novel trivalent chromium plating bath that can be used effectively for industrial purposes by solving the problems that the appearance of the film is darker than the film and the decorativeness is poor.
- the trivalent chromium ion concentration in the plating bath is 0.003 to 0.12 mol / L, which is lower than the conventional trivalent chromium plating bath, and the concentration of the aqueous aliphatic carboxylic acids is trivalent.
- the amount By limiting the amount to 0.3 mol or less with respect to 1 mol of chromium ions, it is possible to form a chromium plating film having a white appearance with a high decorativeness similar to a chromium plating film formed from a plating bath containing a hexavalent chromium compound. I found it.
- the chrome plating bath has a good turnability even immediately after the building bath, can form a good chrome plating film in a wide current density range, and the formed chrome plating film has good corrosion resistance and high hardness. It has been found that it can be thickened and is highly industrially useful, and the present invention has been completed here.
- the present invention provides the following trivalent chromium plating bath, a plating method using the plating bath, and an article on which a chromium plating film is formed.
- 1. 3 comprising an aqueous solution containing a water-soluble trivalent chromium compound, a conductive salt and a pH buffer, wherein the concentration of trivalent chromium ions in the aqueous solution is 0.003 to 0.12 mol / L. Valent chromium plating bath.
- the trivalent according to Item 1 comprising an aqueous solution containing 0.003 to 0.12 mol / L of trivalent chromium ions, 50 to 400 g / L of conductive salt, and 60 to 120 g / L of pH buffering agent. Chrome plating bath. 3. 3. The trivalent chromium plating bath according to item 1 or 2, further comprising 1 to 10 g / L of at least one sulfur-containing compound selected from the group consisting of a compound having an SO 2 group and a compound having an SO 3 group. 4). Item 4.
- the trivalent chromium plating bath of the present invention contains a water-soluble trivalent chromium compound, a conductive salt, and a pH buffer as essential components.
- the trivalent chromium compound may be a water-soluble compound containing trivalent chromium, and for example, chromium sulfate, chromium nitrate, chromium acetate, basic chromium sulfate and the like can be used. These trivalent chromium compounds can be used individually by 1 type or in mixture of 2 or more types.
- the trivalent chromium ion concentration needs to be in the range of 0.003 to 0.12 mol / L.
- Conventional trivalent chromium plating baths usually contain about 0.4 mol / L or more of trivalent chromium ions.
- the trivalent chromium ion concentration in the plating bath increases, the film forming speed increases, but the color tone of the plating film becomes dark, while the trivalent chromium ion concentration is low. It became clear that although the color tone of the film became brighter, the film forming speed decreased.
- the valent chromium ion concentration needs to be in the range of about 0.003 to 0.12 mol / L, and preferably in the range of about 0.04 to 0.1 mol / L. became.
- the concentration of the water-soluble aliphatic carboxylic acid is 0.3 mol with respect to 1 mol of the trivalent chromium ion. It is necessary that: In conventional trivalent chromium plating baths, water-soluble aliphatic carboxylic acids are considered to be essential in order to maintain the stability of the plating bath, and usually about equimolar or more with respect to trivalent chromium ions. Water-soluble carboxylic acids are used.
- the trivalent chromium plating bath of the present invention by setting the trivalent chromium ion concentration to a relatively low concentration of about 0.003 to 0.12 mol / L, water-soluble aliphatic carboxylic acids can be obtained. Even if it is not included, the stability of the plating bath is not hindered.
- the plating film formed from such a low trivalent chromium ion concentration plating bath is hexavalent chromium. It has a white appearance excellent in decorativeness similar to a chromium plating film formed from a plating bath containing a compound, and further has good corrosion resistance and high hardness.
- the trivalent chromium plating bath of the present invention may contain water-soluble aliphatic carboxylic acids as long as the properties of the formed chromium plating film are not affected.
- water-soluble aliphatic carboxylic acids may be contained with respect to 1 mol of trivalent chromium ions.
- the amount of the water-soluble aliphatic carboxylic acids is preferably 0.2 mol or less with respect to 1 mol of trivalent chromium ions.
- the water-soluble aliphatic carboxylic acids are water-soluble aliphatic carboxylic acids or salts thereof, for example, aliphatic monocarboxylic acids such as formic acid and acetic acid; aliphatic dicarboxylic acids such as oxalic acid, malonic acid, and succinic acid.
- Aliphatic hydroxy monocarboxylic acid such as gluconic acid: Aliphatic hydroxy dicarboxylic acid such as malic acid; Carboxylic acid such as aliphatic hydroxy tricarboxylic acid such as citric acid, Water-soluble salt of these carboxylic acids, for example, sodium salt Examples thereof include alkali metal salts such as potassium salts, alkaline earth metal salts such as calcium salts and magnesium salts, ammonium salts and the like.
- the trivalent chromium plating bath of the present invention does not contain water-soluble aliphatic carboxylic acids at all, or its content is very small. Since the conventional trivalent chromium plating bath contains a relatively large amount of water-soluble aliphatic carboxylic acids, a long electrolytic treatment is required to stabilize the complex after the plating bath is constructed. However, since the plating bath of the present invention does not contain water-soluble aliphatic carboxylic acids or its content is very small, a good white chrome plating similar to a hexavalent chromium film immediately after the building bath is obtained. A film can be formed. This eliminates the need for long-term electrolytic treatment and greatly improves work efficiency. Further, when replenishing the chromium compound, time for stabilizing the complex is not required, and the management of the plating bath is easy.
- the conductive salt for example, sulfates such as potassium sulfate, sodium sulfate and ammonium sulfate, alkali metal chlorides such as potassium chloride and sodium chloride can be used. These conductive salts can be used singly or in combination of two or more.
- the concentration of the conductive salt is not particularly limited, but when the concentration is low, the bath voltage rises and the bath temperature rises during electrolysis, so that it is necessary to cool the electrolytic cell in order to maintain a constant temperature. In addition, when the conductive salt concentration is high, the bath voltage decreases, but it is difficult to dissolve at the time of bathing, and when the plating operation is stopped and the temperature of the plating bath decreases, precipitation or the like may occur. Will be generated. From these points, the concentration of the conductive salt is preferably about 50 to 400 g / L, and more preferably about 150 to 300 g / L.
- pH buffering agents that can be used include boric acid, sodium borate, potassium borate, phosphoric acid, disodium hydrogen phosphate, dipotassium hydrogen phosphate, sodium carbonate, sodium hydrogen carbonate, and the like.
- concentration of the pH buffering agent is preferably about 60 to 120 g / L, more preferably about 80 to 100 g / L.
- the trivalent chromium plating bath of the present invention may further contain at least one sulfur-containing compound selected from the group consisting of a compound having an SO 2 group and a compound having an SO 3 group, if necessary. These sulfur-containing compounds are effective components for providing a dense and good appearance to the formed chromium film.
- examples of the compound having an SO 2 group include saccharin and sodium saccharin
- examples of the compound having an SO 3 group include sulfobenzaldehyde, benzenesulfonic acid, toluenesulfonic acid, and salts thereof.
- sulfur-containing compounds can be used singly or in combination of two or more.
- the concentration of the sulfur-containing compound is not particularly limited, but is usually preferably about 1 to 10 g / L, and more preferably about 2 to 7 g / L.
- the trivalent chromium plating bath of the present invention is obtained by dissolving the above components in water, and the order of dissolving the components is arbitrary.
- the pH of the trivalent chromium plating solution bathed with each of the above components varies somewhat depending on the type of complexing agent used, but is usually preferably in the range of about pH 2-4. By setting the pH range to this level, it is possible to prevent the precipitation due to chromium hydroxide even when water-soluble aliphatic carboxylic acids are not included.
- the trivalent chromium plating of the present invention when the bath temperature during the plating operation is low, the throwing power is improved, but the film-forming speed tends to decrease. Conversely, when the bath temperature is high, the product is manufactured. Although the film speed is improved, the throwing power to the low current density region tends to decrease.
- An appropriate bath temperature may be determined in consideration of this point, but generally, a temperature range of about 30 to 60 ° C. is preferable as a bath temperature for industrial use.
- the anode used for plating is not particularly limited, and a known insoluble anode such as a Ti—Pt electrode can be usually used.
- a Ti electrode covered with an Ir—Ta composite oxide thin film it is advantageous in that generation of hexavalent chromium can be suppressed.
- the trivalent chrome plating bath of the present invention has good coverage, and can form a good chrome plating film even at a low current density of about 1 A / dm 2 , for example. Therefore, a chromium plating film having a good appearance can be formed in a wide cathode current density range of about 1 to 20 A / dm 2 .
- a good chromium plating film can be formed on the object to be plated by energizing the object to be plated as a cathode in the chromium plating bath according to a conventional method.
- chromium hydroxide may precipitate in the washing water after the plating treatment.
- the addition of a trivalent chromium complexing agent in the washing water immediately after the chromium plating treatment can prevent the precipitation in the washing water.
- any compound having a complexing power with respect to trivalent chromium can be used without particular limitation.
- the above-mentioned water-soluble aliphatic carboxylic acids can be used.
- Complexes such as tetraacetic acid, iminodiacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, water-soluble salts thereof and the like can be used.
- concentration of the complexing agent in the washing water is not particularly limited, but may be, for example, about 1 to 10 g / L.
- the trivalent chromium plating bath of the present invention the following remarkable effects are exhibited.
- a good white chromium plating film similar to a hexavalent chromium film can be formed immediately after the bathing. This eliminates the need for long-term electrolytic treatment and greatly improves work efficiency.
- It has excellent throwing power in a low current density region and can form a good chromium plating film in a wide current density range.
- the plating film grows according to the plating time, it is possible to apply a thickness exceeding 1 ⁇ m.
- a good chromium plating film having high film hardness and excellent corrosion resistance can be obtained.
- the plating test method is as follows. The results are shown in Table 2 below.
- (Plating test method) 1) Color tone evaluation of film Using each trivalent chrome plating bath immediately after the building bath, the color tone of the test piece formed in a 500 mL Haring cell was visually evaluated.
- the test piece is a 0.48 dm 2 brass plate with a bright Ni plating film of about 3 ⁇ m.
- the current density is 7.5 A / dm 2
- the plating time is 5 minutes
- the anode is an Ir—Ta composite oxide thin film.
- a coated Ti electrode was used.
- FIG. 1 the measurement result of a reflectance is shown in FIG. 1 about the chromium plating film formed from the hexavalent chromium plating bath, and the plating film obtained in Example 1 and Comparative Example 1.
- FIG. 1 the measurement result of a reflectance is shown in FIG. 1 about the chromium plating film formed from the hexavalent chromium plating bath, and the plating film obtained in Example 1 and Comparative Example 1.
- Hull cell test Using each trivalent chromium plating bath immediately after the building bath, a Hull cell test was performed using a product obtained by forming a bright Ni plating on a brass plate with a thickness of about 3 ⁇ m.
- the Hull cell test conditions were a cell current of 5 A and a plating time of 5 minutes, and a Ti electrode coated with an Ir—Ta composite oxide thin film was used as the anode.
- Vickers hardness measurement The Vickers hardness was measured about the to-be-plated object which could be thickened by the said test.
- the film forming speed is greatly reduced after about 60 minutes from the start of plating, and the chromium plating film is about 3 ⁇ m even if the film forming time is increased.
- the film could not be thickened.
Abstract
Disclosed is a trivalent chromium plating bath which is characterized by being composed of an aqueous solution containing a water-soluble trivalent chromium compound, a conductive salt and a pH buffering agent. The trivalent chromium plating bath is also characterized in that the aqueous solution has a trivalent chromium ion concentration of 0.003-0.12 mol/L. Also disclosed are a chromium plating method comprising a step of forming a chromium plating film on an object to be plated by using the object as a cathode in the trivalent chromium plating bath and then washing the plated object with a washing water containing a complexing agent for trivalent chromium ions, and an article having a chromium plating film formed by using the trivalent chromium plating bath. The chromium plating bath of the present invention is a commercially effective novel trivalent chromium plating bath which has solved various problems of conventional trivalent chromium plating baths.
Description
本発明は、３価クロム化合物を含むめっき浴、該めっき浴を用いるめっき方法及びクロムめっき皮膜が形成された物品に関する。
The present invention relates to a plating bath containing a trivalent chromium compound, a plating method using the plating bath, and an article on which a chromium plating film is formed.
クロムめっきは、装飾用、工業用等の各種の分野で広く利用されている。従来から主として用いられているクロムめっき浴は、クロム成分として６価クロムを多量に含むものである。しかしながら、近年、６価クロムの有害性が問題となっており、作業環境や排水処理などの点から、毒性の少ないめっき液の開発が強く望まれている。
Chrome plating is widely used in various fields such as decoration and industrial use. Conventionally used chromium plating baths contain a large amount of hexavalent chromium as a chromium component. However, in recent years, the toxicity of hexavalent chromium has become a problem, and development of a plating solution with low toxicity is strongly desired from the viewpoint of work environment and wastewater treatment.
６価クロムと比較して毒性の低い３価クロムを含むクロムめっき浴として、各種のめっき浴が知られており（下記特許文献１～３及び非特許文献１～３参照）、浴中の３価クロムイオン濃度が０．４モル以上であって、水溶液脂肪族カルボン酸及びその塩からなる群から選ばれた少なくとも一種の成分を３価クロムイオン１モルに対して１．０～３．０モル程度の範囲で含有するクロムめっき浴が報告されている。この様な３価クロムめっき浴については、めっき厚の薄い装飾用クロムめっきとして一部実用化が進んでおり、例えば、商標名：アレクラ３０００（アルブライトアンドウイルソン社），商標名：エンバイロクロム（カニング社）、商標名：トリクロライト（ユージライト社），商標名：トライクロムプラス（アトテックジャパン）などのめっき浴が市販されている。
Various plating baths are known as chromium plating baths containing trivalent chromium that is less toxic than hexavalent chromium (see Patent Documents 1 to 3 and Non-Patent Documents 1 to 3 below). The valent chromium ion concentration is 0.4 mol or more, and at least one component selected from the group consisting of an aqueous aliphatic carboxylic acid and a salt thereof is added in an amount of 1.0 to 3.0 with respect to 1 mol of trivalent chromium ions. A chromium plating bath containing a molar range has been reported. Such a trivalent chrome plating bath has been partially put into practical use as a decorative chrome plating with a thin plating thickness. Plating baths such as Canning), trade name: trichlorite (Eugelite), trade name: trichrome plus (Atotech Japan) are commercially available.
しかしながら、従来の３価クロムめっき浴から形成されるめっき皮膜は、６価クロムめっき浴から形成されるめっき皮膜と比較すると、皮膜外観が暗く装飾性において劣るものである。このため、６価クロム浴から得られるクロムめっき皮膜に類似した白色外観のクロムめっき皮膜を形成できる３価クロムめっき浴に対して強い要望がある。
表面技術 vol.56, No.6, 324p (2005) 表面技術 Vol.47, No.3, 245p (1996) 近畿アルミニウム表面処理研究会 平成18年度秋季特別講演 講演要旨集 特開55-119192号公報
特開平4-45598号公報
特開2002-285375号公報
However, the plating film formed from the conventional trivalent chromium plating bath has a darker appearance and is inferior in decorativeness than the plating film formed from the hexavalent chromium plating bath. For this reason, there is a strong demand for a trivalent chromium plating bath that can form a chromium plating film having a white appearance similar to a chromium plating film obtained from a hexavalent chromium bath.
Surface technology vol.56, No.6, 324p (2005) Surface Technology Vol.47, No.3, 245p (1996) Kinki Aluminum Surface Treatment Study Group Autumn 2006 Special Lectures Abstracts JP 55-119192 A Japanese Unexamined Patent Publication No. 4-45598 JP 2002-285375 A
表面技術 vol.56, No.6, 324p (2005) 表面技術 Vol.47, No.3, 245p (1996) 近畿アルミニウム表面処理研究会 平成18年度秋季特別講演 講演要旨集
Surface technology vol.56, No.6, 324p (2005) Surface Technology Vol.47, No.3, 245p (1996) Kinki Aluminum Surface Treatment Study Group Autumn 2006 Special Lectures Abstracts
本発明は、上記した従来技術の問題点に鑑みてなされたものであり、その主な目的は、上記した従来の３価クロムめっき浴の問題点、特に、６価クロム浴から形成されるめっき皮膜と比較すると皮膜外観が暗く、装飾性で劣るという問題点を解消して、工業用に有効に利用できる新規な３価クロムめっき浴を提供することである。
The present invention has been made in view of the above-mentioned problems of the prior art, and its main object is the problem of the above-described conventional trivalent chromium plating bath, particularly plating formed from a hexavalent chromium bath. An object of the present invention is to provide a novel trivalent chromium plating bath that can be used effectively for industrial purposes by solving the problems that the appearance of the film is darker than the film and the decorativeness is poor.
本発明者は、上記した目的を達成すべく鋭意研究を重ねてきた。その結果、めっき浴中の３価クロムイオン濃度を０．００３～０．１２モル／Ｌという従来の３価クロムめっき浴と比較して低い濃度とし、且つ水溶液脂肪族カルボン酸類の濃度を３価クロムイオン１モルに対して０．３モル以下に制限することによって、６価クロム化合物を含むめっき浴から形成されるクロムめっき皮膜に類似した装飾性の高い白色外観のクロムめっき皮膜を形成できることを見出した。しかも、該クロムめっき浴は、建浴直後においても付き回性が良好であり、広い電流密度範囲において良好なクロムめっき皮膜を形成でき、形成されるクロムめっき皮膜は、良好な耐食性と高い硬度を有し、厚付けも可能であり、工業的に有用性が高いものであることを見出し、ここに本発明を完成するに至った。
The present inventor has intensively studied to achieve the above-mentioned purpose. As a result, the trivalent chromium ion concentration in the plating bath is 0.003 to 0.12 mol / L, which is lower than the conventional trivalent chromium plating bath, and the concentration of the aqueous aliphatic carboxylic acids is trivalent. By limiting the amount to 0.3 mol or less with respect to 1 mol of chromium ions, it is possible to form a chromium plating film having a white appearance with a high decorativeness similar to a chromium plating film formed from a plating bath containing a hexavalent chromium compound. I found it. In addition, the chrome plating bath has a good turnability even immediately after the building bath, can form a good chrome plating film in a wide current density range, and the formed chrome plating film has good corrosion resistance and high hardness. It has been found that it can be thickened and is highly industrially useful, and the present invention has been completed here.
即ち、本発明は、下記の３価クロムめっき浴、該めっき浴を用いるめっき方法及びクロムめっき皮膜が形成された物品を提供するものである。
１． 水溶性３価クロム化合物、伝導性塩及びｐＨ緩衝剤を含有する水溶液からなり、該水溶液中の３価クロムイオンの濃度が０．００３～０．１２モル／Ｌであることを特徴とする３価クロムめっき浴。
２． ３価クロムイオンを０．００３～０．１２モル／Ｌ、伝導性塩を５０～４００ｇ／Ｌ、及びｐＨ緩衝剤を６０～１２０ｇ／Ｌ含有する水溶液からなる、上記項１に記載の３価クロムめっき浴。
３． 更に、SO2基を有する化合物及びSO3基を有する化合物からなる群から選ばれる少なくとも一種の含イオウ化合物を１～１０ｇ／Ｌ含有する上記項１又は２に記載の３価クロムめっき浴。
４． 水溶性脂肪族カルボン酸類の濃度が、３価クロムイオン１モルに対して、０．３モル以下である上記項１～３のいずれかに記載の３価クロムめっき浴。
５． 上記項１～４のいずれかに記載の３価クロムめっき浴中において被めっき物を陰極としてクロムめっき皮膜を形成した後、３価クロムイオンの錯化剤を含む水洗水中で該被めっき物の水洗処理を行う工程を含むクロムめっき方法。
６． 上記項１～４のいずれかに記載の３価クロムめっき浴を用いて形成されたクロムめっき皮膜を有する物品。 That is, the present invention provides the following trivalent chromium plating bath, a plating method using the plating bath, and an article on which a chromium plating film is formed.
1. 3 comprising an aqueous solution containing a water-soluble trivalent chromium compound, a conductive salt and a pH buffer, wherein the concentration of trivalent chromium ions in the aqueous solution is 0.003 to 0.12 mol / L. Valent chromium plating bath.
2. Item 3. The trivalent according to Item 1, comprising an aqueous solution containing 0.003 to 0.12 mol / L of trivalent chromium ions, 50 to 400 g / L of conductive salt, and 60 to 120 g / L of pH buffering agent. Chrome plating bath.
3. 3. The trivalent chromium plating bath according to item 1 or 2, further comprising 1 to 10 g / L of at least one sulfur-containing compound selected from the group consisting of a compound having an SO 2 group and a compound having an SO 3 group.
4). Item 4. The trivalent chromium plating bath according to any one of Items 1 to 3, wherein the concentration of the water-soluble aliphatic carboxylic acid is 0.3 mol or less with respect to 1 mol of trivalent chromium ions.
5). 5. After forming a chromium plating film in the trivalent chromium plating bath according to any one of the above items 1 to 4 using the object to be plated as a cathode, the object to be plated is washed in water containing a trivalent chromium ion complexing agent. A chromium plating method including a step of performing a water washing treatment.
6). An article having a chromium plating film formed by using the trivalent chromium plating bath according to any one of Items 1 to 4.
１． 水溶性３価クロム化合物、伝導性塩及びｐＨ緩衝剤を含有する水溶液からなり、該水溶液中の３価クロムイオンの濃度が０．００３～０．１２モル／Ｌであることを特徴とする３価クロムめっき浴。
２． ３価クロムイオンを０．００３～０．１２モル／Ｌ、伝導性塩を５０～４００ｇ／Ｌ、及びｐＨ緩衝剤を６０～１２０ｇ／Ｌ含有する水溶液からなる、上記項１に記載の３価クロムめっき浴。
３． 更に、SO2基を有する化合物及びSO3基を有する化合物からなる群から選ばれる少なくとも一種の含イオウ化合物を１～１０ｇ／Ｌ含有する上記項１又は２に記載の３価クロムめっき浴。
４． 水溶性脂肪族カルボン酸類の濃度が、３価クロムイオン１モルに対して、０．３モル以下である上記項１～３のいずれかに記載の３価クロムめっき浴。
５． 上記項１～４のいずれかに記載の３価クロムめっき浴中において被めっき物を陰極としてクロムめっき皮膜を形成した後、３価クロムイオンの錯化剤を含む水洗水中で該被めっき物の水洗処理を行う工程を含むクロムめっき方法。
６． 上記項１～４のいずれかに記載の３価クロムめっき浴を用いて形成されたクロムめっき皮膜を有する物品。 That is, the present invention provides the following trivalent chromium plating bath, a plating method using the plating bath, and an article on which a chromium plating film is formed.
1. 3 comprising an aqueous solution containing a water-soluble trivalent chromium compound, a conductive salt and a pH buffer, wherein the concentration of trivalent chromium ions in the aqueous solution is 0.003 to 0.12 mol / L. Valent chromium plating bath.
2. Item 3. The trivalent according to Item 1, comprising an aqueous solution containing 0.003 to 0.12 mol / L of trivalent chromium ions, 50 to 400 g / L of conductive salt, and 60 to 120 g / L of pH buffering agent. Chrome plating bath.
3. 3. The trivalent chromium plating bath according to item 1 or 2, further comprising 1 to 10 g / L of at least one sulfur-containing compound selected from the group consisting of a compound having an SO 2 group and a compound having an SO 3 group.
4). Item 4. The trivalent chromium plating bath according to any one of Items 1 to 3, wherein the concentration of the water-soluble aliphatic carboxylic acid is 0.3 mol or less with respect to 1 mol of trivalent chromium ions.
5). 5. After forming a chromium plating film in the trivalent chromium plating bath according to any one of the above items 1 to 4 using the object to be plated as a cathode, the object to be plated is washed in water containing a trivalent chromium ion complexing agent. A chromium plating method including a step of performing a water washing treatment.
6). An article having a chromium plating film formed by using the trivalent chromium plating bath according to any one of Items 1 to 4.
以下、本発明の３価クロムめっき浴について詳細に説明する。
Hereinafter, the trivalent chromium plating bath of the present invention will be described in detail.
本発明の３価クロムめっき浴は、水溶性３価クロム化合物、伝導性塩、及びｐＨ緩衝剤を必須成分として含有するものである。
The trivalent chromium plating bath of the present invention contains a water-soluble trivalent chromium compound, a conductive salt, and a pH buffer as essential components.
上記した成分の内で、３価クロム化合物は、３価クロムを含む水溶性の化合物であればよく、例えば、硫酸クロム、硝酸クロム、酢酸クロム、塩基性硫酸クロムなどを用いることができる。これらの３価クロム化合物は、一種単独又は二種以上混合して用いることができる。
Among the above-described components, the trivalent chromium compound may be a water-soluble compound containing trivalent chromium, and for example, chromium sulfate, chromium nitrate, chromium acetate, basic chromium sulfate and the like can be used. These trivalent chromium compounds can be used individually by 1 type or in mixture of 2 or more types.
本発明の３価クロムめっき浴では、３価クロムイオン濃度は、０．００３～０．１２モル／Ｌの範囲内にあることが必要である。従来の３価クロムめっき浴には、通常、３価クロムイオンは０．４モル／Ｌ程度以上含まれている。しかしながら、本願発明者の研究によれば、めっき浴中における３価クロムイオン濃度が高くなると製膜速度が高くなるものの、めっき皮膜の色調が暗くなり、一方、３価クロムイオン濃度が低い場合には皮膜の色調は明るくなるが、製膜速度が低下することが明らかとなった。この点を考慮して研究を重ねた結果、形成されるクロムめっき皮膜について、良好な白色外観と適度な製膜速度を両立して、工業的に使用に適したものとするためには、３価クロムイオン濃度が０．００３～０．１２モル/L程度の範囲内であることが必要であり、０．０４～０．１モル／Ｌ程度の範囲内であることが好ましいことが明らかとなった。
In the trivalent chromium plating bath of the present invention, the trivalent chromium ion concentration needs to be in the range of 0.003 to 0.12 mol / L. Conventional trivalent chromium plating baths usually contain about 0.4 mol / L or more of trivalent chromium ions. However, according to the study of the present inventor, when the trivalent chromium ion concentration in the plating bath increases, the film forming speed increases, but the color tone of the plating film becomes dark, while the trivalent chromium ion concentration is low. It became clear that although the color tone of the film became brighter, the film forming speed decreased. As a result of repeated research in consideration of this point, in order to make the formed chromium plating film compatible with a good white appearance and an appropriate film forming speed and suitable for industrial use, 3 It is clear that the valent chromium ion concentration needs to be in the range of about 0.003 to 0.12 mol / L, and preferably in the range of about 0.04 to 0.1 mol / L. became.
また、本発明の３価クロムめっき浴では、３価クロムイオン濃度が上記範囲内にあることに加えて、水溶性脂肪族カルボン酸類の濃度が３価クロムイオン１モルに対して０．３モル以下であることが必要である。従来の３価クロムめっき浴では、めっき浴の安定性を維持するために、水溶性脂肪族カルボン酸類が必須であると考えられており、通常、３価クロムイオンに対して等モル程度以上の水溶性カルボン酸類が使用されている。これに対して本発明の３価クロムめっき浴によれば、３価クロムイオン濃度を０．００３～０．１２モル/L程度という比較的低濃度とすることによって、水溶性脂肪族カルボン酸類が含まれない場合であってもめっき浴の安定性が阻害されることがなく、しかも驚くべきことに、この様な低い３価クロムイオン濃度のめっき浴から形成されるめっき皮膜は、６価クロム化合物を含むめっき浴から形成されるクロムめっき皮膜に類似した装飾性に優れた白色外観を有し、更に、良好な耐食性と高い硬度を有するものとなる。
Further, in the trivalent chromium plating bath of the present invention, in addition to the trivalent chromium ion concentration being within the above range, the concentration of the water-soluble aliphatic carboxylic acid is 0.3 mol with respect to 1 mol of the trivalent chromium ion. It is necessary that: In conventional trivalent chromium plating baths, water-soluble aliphatic carboxylic acids are considered to be essential in order to maintain the stability of the plating bath, and usually about equimolar or more with respect to trivalent chromium ions. Water-soluble carboxylic acids are used. On the other hand, according to the trivalent chromium plating bath of the present invention, by setting the trivalent chromium ion concentration to a relatively low concentration of about 0.003 to 0.12 mol / L, water-soluble aliphatic carboxylic acids can be obtained. Even if it is not included, the stability of the plating bath is not hindered. Surprisingly, the plating film formed from such a low trivalent chromium ion concentration plating bath is hexavalent chromium. It has a white appearance excellent in decorativeness similar to a chromium plating film formed from a plating bath containing a compound, and further has good corrosion resistance and high hardness.
本発明の３価クロムめっき浴では、形成されるクロムめっき皮膜の特性に影響がない範囲であれば、水溶性脂肪族カルボン酸類が含まれていてもよい。例えば、３価クロムイオン１モルに対して０．３モル以下の水溶性脂肪族カルボン酸類が含まれていても良い。特に、水溶性脂肪族カルボン酸類の量は、３価クロムイオン１モルに対して０．２モル以下であることが好ましい。
The trivalent chromium plating bath of the present invention may contain water-soluble aliphatic carboxylic acids as long as the properties of the formed chromium plating film are not affected. For example, 0.3 mol or less of water-soluble aliphatic carboxylic acid may be contained with respect to 1 mol of trivalent chromium ions. In particular, the amount of the water-soluble aliphatic carboxylic acids is preferably 0.2 mol or less with respect to 1 mol of trivalent chromium ions.
尚、水溶性脂肪族カルボン酸類とは、水溶性脂肪族カルボン酸又はその塩であり、例えば、ギ酸、酢酸等の脂肪族物モノカルボン酸；シュウ酸、マロン酸、コハク酸等の脂肪族ジカルボン酸；グルコン酸などの脂肪族ヒドロキシモノカルボン酸：リンゴ酸等の脂肪族ヒドロキシジカルボン酸；クエン酸等の脂肪族ヒドロキシトリカルボン酸などのカルボン酸、これらのカルボン酸の水溶性塩、例えば、ナトリウム塩、カリウム塩等のアルカリ金属塩、カルシウム塩、マグネシウム塩等のアルカリ土類金属塩、アンモニウム塩等を例示できる。
The water-soluble aliphatic carboxylic acids are water-soluble aliphatic carboxylic acids or salts thereof, for example, aliphatic monocarboxylic acids such as formic acid and acetic acid; aliphatic dicarboxylic acids such as oxalic acid, malonic acid, and succinic acid. Acid; Aliphatic hydroxy monocarboxylic acid such as gluconic acid: Aliphatic hydroxy dicarboxylic acid such as malic acid; Carboxylic acid such as aliphatic hydroxy tricarboxylic acid such as citric acid, Water-soluble salt of these carboxylic acids, for example, sodium salt Examples thereof include alkali metal salts such as potassium salts, alkaline earth metal salts such as calcium salts and magnesium salts, ammonium salts and the like.
本発明の３価クロムめっき浴は、上記した通り、水溶性脂肪族カルボン酸類を全く含まないか、或いは、その含有量が非常に少量である。従来の３価クロムめっき浴では、水溶性脂肪族カルボン酸類が比較的多量に含まれているために、めっき浴を建浴後、錯体を安定化させるために、長時間の電解処理が必要であったが、本発明のめっき浴では、水溶性脂肪族カルボン酸類を含まないか、或いは、その含有量が非常に少ないために、建浴直後においても６価クロム皮膜と類似した良好な白色クロムめっき皮膜を形成できる。このため、長時間の電解処理が不要となり、作業効率が大きく向上する。また、クロム化合物を補給する際にも錯体の安定化のための時間が不要であり、めっき浴の管理が容易である。
As described above, the trivalent chromium plating bath of the present invention does not contain water-soluble aliphatic carboxylic acids at all, or its content is very small. Since the conventional trivalent chromium plating bath contains a relatively large amount of water-soluble aliphatic carboxylic acids, a long electrolytic treatment is required to stabilize the complex after the plating bath is constructed. However, since the plating bath of the present invention does not contain water-soluble aliphatic carboxylic acids or its content is very small, a good white chrome plating similar to a hexavalent chromium film immediately after the building bath is obtained. A film can be formed. This eliminates the need for long-term electrolytic treatment and greatly improves work efficiency. Further, when replenishing the chromium compound, time for stabilizing the complex is not required, and the management of the plating bath is easy.
本発明の３価クロムめっき浴では、伝導性塩としては、例えば、硫酸カリウム、硫酸ナトリウム、硫酸アンモニウム等の硫酸塩、塩化カリウム、塩化ナトリウム等のアルカリ金属塩化物などを用いることができる。これらの伝導性塩は一種単独又は二種以上混合して用いることができる。
In the trivalent chromium plating bath of the present invention, as the conductive salt, for example, sulfates such as potassium sulfate, sodium sulfate and ammonium sulfate, alkali metal chlorides such as potassium chloride and sodium chloride can be used. These conductive salts can be used singly or in combination of two or more.
伝導性塩の濃度については特に限定されないが、濃度が低い場合には浴電圧が上昇して電解中に浴温が上昇するため一定温度に保持するために電解槽を冷却する必要が生じる。また，伝導性塩濃度が高い場合には浴電圧は低下するが建浴時に溶解させることが困難であり、しかも、めっき作業を中止してめっき浴の温度が低下した場合には、沈殿などが生成することになる。これらの点から伝導性塩の濃度は、５０～４００g/L程度とすることが好ましく、１５０～３００g/L程度とすることがより好ましい。
The concentration of the conductive salt is not particularly limited, but when the concentration is low, the bath voltage rises and the bath temperature rises during electrolysis, so that it is necessary to cool the electrolytic cell in order to maintain a constant temperature. In addition, when the conductive salt concentration is high, the bath voltage decreases, but it is difficult to dissolve at the time of bathing, and when the plating operation is stopped and the temperature of the plating bath decreases, precipitation or the like may occur. Will be generated. From these points, the concentration of the conductive salt is preferably about 50 to 400 g / L, and more preferably about 150 to 300 g / L.
本発明の３価クロムめっき浴には、ｐＨ緩衝剤を添加することが必要である。ｐＨ緩衝剤としては、例えば、ホウ酸、ホウ酸ナトリウム、ホウ酸カリウム，リン酸，リン酸水素2ナトリウム，リン酸水素２カリウム，炭酸ナトリウム，炭酸水素ナトリウムなどを使用することができる。ｐＨ緩衝剤の濃度が低い場合には陰極反応界面でのｐＨ上昇が起こり，クロムの水酸化物などが生成するため良好なクロムめっき皮膜が得られない。このことから，良好なクロムめっき皮膜を得るためには、ｐＨ緩衝剤の濃度は６０～１２０g/L程度とすることが好ましく、８０～１００g/L程度とすることがより好ましい。
It is necessary to add a pH buffer to the trivalent chromium plating bath of the present invention. Examples of pH buffering agents that can be used include boric acid, sodium borate, potassium borate, phosphoric acid, disodium hydrogen phosphate, dipotassium hydrogen phosphate, sodium carbonate, sodium hydrogen carbonate, and the like. When the concentration of the pH buffering agent is low, the pH rises at the cathode reaction interface, and chromium hydroxide and the like are produced, so that a good chromium plating film cannot be obtained. From this, in order to obtain a good chromium plating film, the concentration of the pH buffering agent is preferably about 60 to 120 g / L, more preferably about 80 to 100 g / L.
本発明の３価クロムめっき浴には、更に、必要に応じて、SO2基を有する化合物及びSO3基を有する化合物からなる群から選ばれる少なくとも一種の含イオウ化合物を添加することができる。これらの含イオウ化合物は、形成されるクロム皮膜を緻密で良好な外観とするために有効な成分である。
The trivalent chromium plating bath of the present invention may further contain at least one sulfur-containing compound selected from the group consisting of a compound having an SO 2 group and a compound having an SO 3 group, if necessary. These sulfur-containing compounds are effective components for providing a dense and good appearance to the formed chromium film.
これらの内でSO2基を有する化合物としては、サッカリン、サッカリンナトリウム等を例示でき、SO3基を有する化合物としは、スルホベンズアルデヒド、ベンゼンスルホン酸、トルエンスルホン酸、これらの塩等を例示できる。これらの含イオウ化合物は、一種単独又は二種以上混合して用いることが出来る。
Of these, examples of the compound having an SO 2 group include saccharin and sodium saccharin, and examples of the compound having an SO 3 group include sulfobenzaldehyde, benzenesulfonic acid, toluenesulfonic acid, and salts thereof. These sulfur-containing compounds can be used singly or in combination of two or more.
含イオウ化合物の濃度については、特に限定されないが、通常、1～10g/L程度とすることが好ましく、２～７g/L程度とすることがより好ましい。
The concentration of the sulfur-containing compound is not particularly limited, but is usually preferably about 1 to 10 g / L, and more preferably about 2 to 7 g / L.
本発明の３価クロムめっき浴は、上記した各成分を水に溶解したものであり、各成分を溶解する順序は任意である。
The trivalent chromium plating bath of the present invention is obtained by dissolving the above components in water, and the order of dissolving the components is arbitrary.
上記した各成分を用いて建浴した３価クロムめっき液のｐＨは、使用する錯化剤の種類により多少の変動があるが、通常、ｐＨ２～４程度の範囲内とすることが好ましい。この程度のｐＨ範囲とすることによって、水溶性脂肪族カルボン酸類を含まない場合であっても、水酸化クロムによる沈殿の発生を防止することができる。
The pH of the trivalent chromium plating solution bathed with each of the above components varies somewhat depending on the type of complexing agent used, but is usually preferably in the range of about pH 2-4. By setting the pH range to this level, it is possible to prevent the precipitation due to chromium hydroxide even when water-soluble aliphatic carboxylic acids are not included.
本発明の３価クロムめっきによれば、めっき作業時の浴温が低い場合にはつき回り性は向上するが製膜速度は低下する傾向があり、逆に浴温が高い場合には，製膜速度は向上するが低電流密度領域へのつき回り性は低下する傾向がある。この点を考慮して適切な浴温を決めればよいが、通常、工業的に使用する際の浴温としては、３０～６０℃程度の温度範囲が好ましい。
According to the trivalent chromium plating of the present invention, when the bath temperature during the plating operation is low, the throwing power is improved, but the film-forming speed tends to decrease. Conversely, when the bath temperature is high, the product is manufactured. Although the film speed is improved, the throwing power to the low current density region tends to decrease. An appropriate bath temperature may be determined in consideration of this point, but generally, a temperature range of about 30 to 60 ° C. is preferable as a bath temperature for industrial use.
めっき時に使用する陽極としては、特に限定的ではなく、通常は、Ｔｉ－Ｐｔ電極などの公知の不溶性陽極を用いることができる。特に、Ｉｒ－Ｔａ複合酸化物薄膜で被覆したＴｉ電極を用いる場合には、６価クロムの生成を抑制できる点で有利である。
The anode used for plating is not particularly limited, and a known insoluble anode such as a Ti—Pt electrode can be usually used. In particular, when a Ti electrode covered with an Ir—Ta composite oxide thin film is used, it is advantageous in that generation of hexavalent chromium can be suppressed.
本発明の３価クロムめっき浴は、付き回りが良好であり、例えば、１A/dm2程度の低電流密度においても良好なクロムめっき皮膜を形成できる。このため、１～20 A/dm2程度の広い陰極電流密度範囲において良好な外観のクロムめっき皮膜を形成できる。
The trivalent chrome plating bath of the present invention has good coverage, and can form a good chrome plating film even at a low current density of about 1 A / dm 2 , for example. Therefore, a chromium plating film having a good appearance can be formed in a wide cathode current density range of about 1 to 20 A / dm 2 .
本発明の３価クロムめっき浴によれば、常法に従って、該クロムめっき浴中において被めっき物を陰極として通電することによって、被めっき物上に良好なクロムめっき皮膜を形成できる。但し、水溶性脂肪族カルボン酸類を全く含まないか、或いは水溶性脂肪族カルボン酸類の含有量が少ない場合には、めっき処理後の水洗水中において水酸化クロムの沈殿が生じる場合がある。この様な場合には、クロムめっき処理の直後の水洗水中に３価クロムの錯化剤を添加することによって、水洗水中における沈殿の発生を防止することができる。この様な錯化剤としては、３価クロムに対して錯化力がある化合物であれば特に限定なく使用でき、例えば、上記した水溶性脂肪族カルボン酸類を用いることができ、その他に、エチレンジアミンテトラ酢酸、イミノジ酢酸、ジエチレントリアミンペンタ酢酸、トリエチレンテトラミンヘキサ酢酸などのコンプレクサン類、これらの水溶性塩等を用いることができる。水洗水中の錯化剤の濃度については特に限定的ではないが、例えば、１～１０ g/L程度とすればよい。
According to the trivalent chromium plating bath of the present invention, a good chromium plating film can be formed on the object to be plated by energizing the object to be plated as a cathode in the chromium plating bath according to a conventional method. However, when water-soluble aliphatic carboxylic acids are not contained at all or when the content of water-soluble aliphatic carboxylic acids is low, chromium hydroxide may precipitate in the washing water after the plating treatment. In such a case, the addition of a trivalent chromium complexing agent in the washing water immediately after the chromium plating treatment can prevent the precipitation in the washing water. As such a complexing agent, any compound having a complexing power with respect to trivalent chromium can be used without particular limitation. For example, the above-mentioned water-soluble aliphatic carboxylic acids can be used. Complexes such as tetraacetic acid, iminodiacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, water-soluble salts thereof and the like can be used. The concentration of the complexing agent in the washing water is not particularly limited, but may be, for example, about 1 to 10 g / L.
本発明の３価クロムめっき浴によれば、下記に示す顕著な効果が奏される。
（１）建浴直後においても６価クロム皮膜と類似した良好な白色クロムめっき皮膜を形成できる。このため、長時間の電解処理が不要となり、作業効率が大きく向上する。
（２）低電流密度領域での付き回り性に優れ、広い電流密度範囲において良好なクロムめっき皮膜を形成できる。
（３）めっき時間に応じてめっき皮膜が成長するので、１μｍを上回る厚付けが可能である。
（４）高い皮膜硬度を有し、耐食性にも優れた良好なクロムめっき皮膜を得ることができる。
（５）クロム酸浸漬処理を行わない場合にも良好な耐食性を有するクロムめっき皮膜を形成できる。 According to the trivalent chromium plating bath of the present invention, the following remarkable effects are exhibited.
(1) A good white chromium plating film similar to a hexavalent chromium film can be formed immediately after the bathing. This eliminates the need for long-term electrolytic treatment and greatly improves work efficiency.
(2) It has excellent throwing power in a low current density region and can form a good chromium plating film in a wide current density range.
(3) Since the plating film grows according to the plating time, it is possible to apply a thickness exceeding 1 μm.
(4) A good chromium plating film having high film hardness and excellent corrosion resistance can be obtained.
(5) Even when chromic acid immersion treatment is not performed, a chromium plating film having good corrosion resistance can be formed.
（１）建浴直後においても６価クロム皮膜と類似した良好な白色クロムめっき皮膜を形成できる。このため、長時間の電解処理が不要となり、作業効率が大きく向上する。
（２）低電流密度領域での付き回り性に優れ、広い電流密度範囲において良好なクロムめっき皮膜を形成できる。
（３）めっき時間に応じてめっき皮膜が成長するので、１μｍを上回る厚付けが可能である。
（４）高い皮膜硬度を有し、耐食性にも優れた良好なクロムめっき皮膜を得ることができる。
（５）クロム酸浸漬処理を行わない場合にも良好な耐食性を有するクロムめっき皮膜を形成できる。 According to the trivalent chromium plating bath of the present invention, the following remarkable effects are exhibited.
(1) A good white chromium plating film similar to a hexavalent chromium film can be formed immediately after the bathing. This eliminates the need for long-term electrolytic treatment and greatly improves work efficiency.
(2) It has excellent throwing power in a low current density region and can form a good chromium plating film in a wide current density range.
(3) Since the plating film grows according to the plating time, it is possible to apply a thickness exceeding 1 μm.
(4) A good chromium plating film having high film hardness and excellent corrosion resistance can be obtained.
(5) Even when chromic acid immersion treatment is not performed, a chromium plating film having good corrosion resistance can be formed.
以下、実施例および比較例を挙げて本発明を更に詳細に説明する。
Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples.
実施例１～４及び比較例１～２
下記表１に示す各成分を水に溶解して３価クロムめっき浴を調製し、表中に示すｐＨ値及び浴温で、下記の方法によってめっき試験を行った。 Examples 1 to 4 and Comparative Examples 1 to 2
Each component shown in Table 1 below was dissolved in water to prepare a trivalent chromium plating bath, and a plating test was performed by the following method at the pH value and bath temperature shown in the table.
下記表１に示す各成分を水に溶解して３価クロムめっき浴を調製し、表中に示すｐＨ値及び浴温で、下記の方法によってめっき試験を行った。 Examples 1 to 4 and Comparative Examples 1 to 2
Each component shown in Table 1 below was dissolved in water to prepare a trivalent chromium plating bath, and a plating test was performed by the following method at the pH value and bath temperature shown in the table.
めっき試験方法は以下の通りである。その結果を下記表２に示す。
（めっき試験方法）
１）皮膜の色調評価
建浴直後の各３価クロムめっき浴を用い、500 mLハーリングセルで製膜した試験片の色調を目視により評価した。試験片には0.48 dm2の真鍮板に光沢Niめっきを約3μm製膜したものを使用し電流密度7.5 A/dm2、めっき時間５分間とし、陽極としては、Ｉｒ－Ｔａ複合酸化物薄膜で被覆したＴｉ電極を用いた。 The plating test method is as follows. The results are shown in Table 2 below.
(Plating test method)
1) Color tone evaluation of film Using each trivalent chrome plating bath immediately after the building bath, the color tone of the test piece formed in a 500 mL Haring cell was visually evaluated. The test piece is a 0.48 dm 2 brass plate with a bright Ni plating film of about 3 μm. The current density is 7.5 A / dm 2 , the plating time is 5 minutes, and the anode is an Ir—Ta composite oxide thin film. A coated Ti electrode was used.
（めっき試験方法）
１）皮膜の色調評価
建浴直後の各３価クロムめっき浴を用い、500 mLハーリングセルで製膜した試験片の色調を目視により評価した。試験片には0.48 dm2の真鍮板に光沢Niめっきを約3μm製膜したものを使用し電流密度7.5 A/dm2、めっき時間５分間とし、陽極としては、Ｉｒ－Ｔａ複合酸化物薄膜で被覆したＴｉ電極を用いた。 The plating test method is as follows. The results are shown in Table 2 below.
(Plating test method)
1) Color tone evaluation of film Using each trivalent chrome plating bath immediately after the building bath, the color tone of the test piece formed in a 500 mL Haring cell was visually evaluated. The test piece is a 0.48 dm 2 brass plate with a bright Ni plating film of about 3 μm. The current density is 7.5 A / dm 2 , the plating time is 5 minutes, and the anode is an Ir—Ta composite oxide thin film. A coated Ti electrode was used.
尚、６価クロムめっき浴から形成されたクロムめっき皮膜と、実施例１と比較例１で得られためっき皮膜については、反射率の測定結果を図１に示す。
In addition, the measurement result of a reflectance is shown in FIG. 1 about the chromium plating film formed from the hexavalent chromium plating bath, and the plating film obtained in Example 1 and Comparative Example 1. FIG.
２）ハルセル試験
建浴直後の各３価クロムめっき浴を用い、被めっき物として、真鍮板に光沢Niめっきを約3μm製膜したものを使用して、ハルセル試験を行った。ハルセル試験条件は、槽電流５A、めっき時間５分間とし、陽極としては、Ｉｒ－Ｔａ複合酸化物薄膜で被覆したＴｉ電極を用いた。 2) Hull cell test Using each trivalent chromium plating bath immediately after the building bath, a Hull cell test was performed using a product obtained by forming a bright Ni plating on a brass plate with a thickness of about 3 μm. The Hull cell test conditions were a cell current of 5 A and a plating time of 5 minutes, and a Ti electrode coated with an Ir—Ta composite oxide thin film was used as the anode.
建浴直後の各３価クロムめっき浴を用い、被めっき物として、真鍮板に光沢Niめっきを約3μm製膜したものを使用して、ハルセル試験を行った。ハルセル試験条件は、槽電流５A、めっき時間５分間とし、陽極としては、Ｉｒ－Ｔａ複合酸化物薄膜で被覆したＴｉ電極を用いた。 2) Hull cell test Using each trivalent chromium plating bath immediately after the building bath, a Hull cell test was performed using a product obtained by forming a bright Ni plating on a brass plate with a thickness of about 3 μm. The Hull cell test conditions were a cell current of 5 A and a plating time of 5 minutes, and a Ti electrode coated with an Ir—Ta composite oxide thin film was used as the anode.
クロムめっき後の被めっき物（ハルセル板）について、電流密度分布スケールを基準としてどの電流密度に相当する部分までめっきが析出しているかを判定して、つき回り性を評価した。その後、電解式膜厚計を使用しハルセル板の各電流密度における膜厚を測定した。下記表２には１次電流密度で10A/dm2に相当する部分の膜厚を記載する。
About the to-be-plated object (Hull cell board) after chromium plating, it was determined to which part of the current density the plating was deposited on the basis of the current density distribution scale, and the throwing power was evaluated. Then, the film thickness in each current density of a hull cell board was measured using the electrolytic film thickness meter. Table 2 below shows the film thickness of the portion corresponding to 10 A / dm 2 in terms of primary current density.
３）製膜時間と膜厚の関係
各３価クロムめっき浴を用い、電流密度7.5A/dm2の条件でNiめっき真鍮板にめっき時間を変化させてクロムめっき皮膜を析出させ、製膜時間と膜厚の関係を調べた。膜厚は析出重量と面積から算出した。 3) Relationship between film forming time and film thickness Using each trivalent chromium plating bath, changing the plating time to Ni plated brass plate under the condition of current density 7.5A / dm 2 , depositing chromium plating film, film forming time The relationship between the film thickness and the film thickness was investigated. The film thickness was calculated from the precipitation weight and area.
各３価クロムめっき浴を用い、電流密度7.5A/dm2の条件でNiめっき真鍮板にめっき時間を変化させてクロムめっき皮膜を析出させ、製膜時間と膜厚の関係を調べた。膜厚は析出重量と面積から算出した。 3) Relationship between film forming time and film thickness Using each trivalent chromium plating bath, changing the plating time to Ni plated brass plate under the condition of current density 7.5A / dm 2 , depositing chromium plating film, film forming time The relationship between the film thickness and the film thickness was investigated. The film thickness was calculated from the precipitation weight and area.
４）ビッカース硬度測定
上記試験で厚膜化が可能であった被めっき物について、ビッカース硬度を測定した。 4) Vickers hardness measurement The Vickers hardness was measured about the to-be-plated object which could be thickened by the said test.
上記試験で厚膜化が可能であった被めっき物について、ビッカース硬度を測定した。 4) Vickers hardness measurement The Vickers hardness was measured about the to-be-plated object which could be thickened by the said test.
５）耐食性評価
各３価クロムめっき浴を用いて、光沢Niめっきを行なった真鍮板に約0.1μmの３価クロムめっき皮膜を形成した。水洗後、クロム酸浸漬処理を行うことなく、塩水噴霧試験（ＪＩＳ ２３７１）を行った。７２時間後に装置から取り出し、水洗後に目視による観察で腐食の進行状態をめっき品全体に対する白さびが発生した面積の割合で評価した。 5) Corrosion resistance evaluation About 0.1 micrometer trivalent chromium plating film was formed in the brass plate which performed bright Ni plating using each trivalent chromium plating bath. After washing with water, a salt spray test (JIS 2371) was conducted without chromic acid immersion treatment. After 72 hours, the product was taken out from the apparatus, and after rinsing with water, the progress of corrosion was evaluated by the ratio of the area where white rust was generated to the entire plated product.
各３価クロムめっき浴を用いて、光沢Niめっきを行なった真鍮板に約0.1μmの３価クロムめっき皮膜を形成した。水洗後、クロム酸浸漬処理を行うことなく、塩水噴霧試験（ＪＩＳ ２３７１）を行った。７２時間後に装置から取り出し、水洗後に目視による観察で腐食の進行状態をめっき品全体に対する白さびが発生した面積の割合で評価した。 5) Corrosion resistance evaluation About 0.1 micrometer trivalent chromium plating film was formed in the brass plate which performed bright Ni plating using each trivalent chromium plating bath. After washing with water, a salt spray test (JIS 2371) was conducted without chromic acid immersion treatment. After 72 hours, the product was taken out from the apparatus, and after rinsing with water, the progress of corrosion was evaluated by the ratio of the area where white rust was generated to the entire plated product.
以上の結果から次のことが明らかである。
（１）浴中の３価クロムイオン濃度が０．０３～０．１２モルであり、かつ、カルボン酸類濃度が３価クロムイオン１モルに対して０．２モル以下である実施例１～４の各３価クロムめっき浴から得られた皮膜は、６価クロムめっき皮膜に類似した白色外観を示した。これに対して、浴中３価クロムイオン濃度が０．２８８モルである比較例１のめっき浴およびカルボン酸類/浴中金属クロム比が１．０の比較例２のめっき浴からは、実施例１～４の場合と比較すると色調の暗いクロムめっき皮膜が形成された。 From the above results, the following is clear.
(1) Examples 1 to 4 in which the trivalent chromium ion concentration in the bath is 0.03 to 0.12 mol and the carboxylic acid concentration is 0.2 mol or less with respect to 1 mol of trivalent chromium ions. The films obtained from each of the trivalent chromium plating baths showed a white appearance similar to the hexavalent chromium plating film. On the other hand, from the plating bath of Comparative Example 1 having a trivalent chromium ion concentration of 0.288 mol in the bath and the plating bath of Comparative Example 2 having a carboxylic acid / metal chromium ratio in the bath of 1.0, Example Compared with the cases of 1-4, a chrome plating film having a darker color tone was formed.
（１）浴中の３価クロムイオン濃度が０．０３～０．１２モルであり、かつ、カルボン酸類濃度が３価クロムイオン１モルに対して０．２モル以下である実施例１～４の各３価クロムめっき浴から得られた皮膜は、６価クロムめっき皮膜に類似した白色外観を示した。これに対して、浴中３価クロムイオン濃度が０．２８８モルである比較例１のめっき浴およびカルボン酸類/浴中金属クロム比が１．０の比較例２のめっき浴からは、実施例１～４の場合と比較すると色調の暗いクロムめっき皮膜が形成された。 From the above results, the following is clear.
(1) Examples 1 to 4 in which the trivalent chromium ion concentration in the bath is 0.03 to 0.12 mol and the carboxylic acid concentration is 0.2 mol or less with respect to 1 mol of trivalent chromium ions. The films obtained from each of the trivalent chromium plating baths showed a white appearance similar to the hexavalent chromium plating film. On the other hand, from the plating bath of Comparative Example 1 having a trivalent chromium ion concentration of 0.288 mol in the bath and the plating bath of Comparative Example 2 having a carboxylic acid / metal chromium ratio in the bath of 1.0, Example Compared with the cases of 1-4, a chrome plating film having a darker color tone was formed.
（２）実施例１～４の各３価クロムめっき浴では、ハルセル試験において良好なつき回り性を示し、１A/dm２程度の低電流密度域まで良好なクロムめっき皮膜を形成できた。これに対して、比較例１及び２のめっき浴では、建浴直後においては低電流密度領域へのつき回り性が十分でなく、ハルセル試験においては4A/dm２に相当する部分にまでしかめっきが析出しなかった。
(2) Each of the trivalent chromium plating baths of Examples 1 to 4 showed good throwing power in the Hull cell test, and a good chromium plating film could be formed up to a low current density range of about 1 A / dm 2 . On the other hand, in the plating baths of Comparative Examples 1 and 2, the throwing power to the low current density region is not sufficient immediately after the building bath, and only the portion corresponding to 4 A / dm 2 is plated in the hull cell test. Did not precipitate.
（３）実施例１～４の各３価クロムめっき浴では、製膜時間とともに膜厚が増加し、５時間経過時点においても製膜時間と膜厚はほぼ直線関係を示し、製膜時間を延長することによって厚膜化が可能であった。また、厚膜化されたクロムめっき皮膜は、1000HV程度という高いビッカース硬度を示した。
(3) In each of the trivalent chromium plating baths of Examples 1 to 4, the film thickness increased with the film formation time, and the film formation time and the film thickness showed a substantially linear relationship even after 5 hours had elapsed. It was possible to increase the film thickness by extending the length. The thick chromium plating film showed a high Vickers hardness of about 1000 HV.
これに対して、比較例１及び２の３価クロムめっき浴では、めっき開始から６０分間程度経過後に製膜速度が大幅に低下し、製膜時間を長くしてもクロムめっき皮膜は３μm程度までしか成長せず、厚膜化が出来なかった。
On the other hand, in the trivalent chromium plating baths of Comparative Examples 1 and 2, the film forming speed is greatly reduced after about 60 minutes from the start of plating, and the chromium plating film is about 3 μm even if the film forming time is increased. However, the film could not be thickened.
（４）実施例１～４の各３価クロムめっき浴から形成されたクロムめっき皮膜は、クロム酸浸漬処理を行わない場合にも良好な耐食性を示した。
(4) The chromium plating films formed from the trivalent chromium plating baths of Examples 1 to 4 exhibited good corrosion resistance even when the chromic acid immersion treatment was not performed.
Claims (6)
- 水溶性３価クロム化合物、伝導性塩及びｐＨ緩衝剤を含有する水溶液からなり、該水溶液中の３価クロムイオンの濃度が０．００３～０．１２モル／Ｌであることを特徴とする３価クロムめっき浴。 3 comprising an aqueous solution containing a water-soluble trivalent chromium compound, a conductive salt and a pH buffer, wherein the concentration of trivalent chromium ions in the aqueous solution is 0.003 to 0.12 mol / L. Valent chromium plating bath.
- ３価クロムイオンを０．００３～０．１２モル／Ｌ、伝導性塩を５０～４００ｇ／Ｌ、及びｐＨ緩衝剤を６０～１２０ｇ／Ｌ含有する水溶液からなる、請求項１に記載の３価クロムめっき浴。 2. The trivalent according to claim 1, comprising an aqueous solution containing 0.003 to 0.12 mol / L of trivalent chromium ions, 50 to 400 g / L of conductive salt, and 60 to 120 g / L of pH buffering agent. Chrome plating bath.
- 更に、SO2基を有する化合物及びSO3基を有する化合物からなる群から選ばれる少なくとも一種の含イオウ化合物を１～１０ｇ／Ｌ含有する請求項１に記載の３価クロムめっき浴。 The trivalent chromium plating bath according to claim 1, further comprising 1 to 10 g / L of at least one sulfur-containing compound selected from the group consisting of a compound having an SO 2 group and a compound having an SO 3 group.
- 水溶性脂肪族カルボン酸類の含有量が、３価クロムイオン１モルに対して、０．３モル以下である請求項１に記載の３価クロムめっき浴。 The trivalent chromium plating bath according to claim 1, wherein the content of the water-soluble aliphatic carboxylic acid is 0.3 mol or less with respect to 1 mol of trivalent chromium ions.
- 請求項１に記載の３価クロムめっき浴中において、被めっき物を陰極としてクロムめっき皮膜を形成した後、３価クロムイオンの錯化剤を含む水洗水中で該被めっき物の水洗処理を行う工程を含むクロムめっき方法。 In the trivalent chromium plating bath according to claim 1, after forming a chromium plating film using the object to be plated as a cathode, the object to be plated is washed in water containing a complexing agent of trivalent chromium ions. A chromium plating method including a process.
- 請求項１に記載の３価クロムめっき浴を用いて形成されたクロムめっき皮膜を有する物品。 An article having a chromium plating film formed using the trivalent chromium plating bath according to claim 1.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPS5395134A (en) * | 1976-12-16 | 1978-08-19 | Ibm | Chrome or chrome alloy electroplating liquid |
| JPS57152483A (en) * | 1981-02-09 | 1982-09-20 | W Kiyaningu Materiaruzu Ltd | Chromium electrodeposition |
| JPS61588A (en) * | 1984-06-14 | 1986-01-06 | Nippon Kokan Kk <Nkk> | After-treatment of one-side electroplated steel sheet |
| JPS61235592A (en) * | 1985-02-06 | 1986-10-20 | ダブリユ− キヤニング マテリアルズ リミテツド | Improved electroplating method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5395134A (en) * | 1976-12-16 | 1978-08-19 | Ibm | Chrome or chrome alloy electroplating liquid |
| JPS57152483A (en) * | 1981-02-09 | 1982-09-20 | W Kiyaningu Materiaruzu Ltd | Chromium electrodeposition |
| JPS61588A (en) * | 1984-06-14 | 1986-01-06 | Nippon Kokan Kk <Nkk> | After-treatment of one-side electroplated steel sheet |
| JPS61235592A (en) * | 1985-02-06 | 1986-10-20 | ダブリユ− キヤニング マテリアルズ リミテツド | Improved electroplating method |
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