JP5407787B2 - Chrome plating solution - Google Patents

Description

  The present invention relates to a chromium plating solution.

  It is well known that nickel is plated on a base made of aluminum or an aluminum alloy in manufacturing a hard disk or the like. Here, the plating includes electroplating and electroless plating, but the electroless plating is industrially effective because it does not require a special apparatus.

  Here, electroless plating refers to reducing and depositing a metal based only on an electrochemical redox reaction without using an external power source. This plating method is characterized by using a solution containing metal ions and reducing ions as means for depositing metal.

  Electroless nickel plating is a type of electroless plating in which a metal nickel film is deposited on an object to be plated by impregnating the liquid with electrons released by oxidation of a reducing agent contained in the plating liquid.

  By the way, since aluminum or aluminum alloy reacts with oxygen in the air to form a thin oxide film on the surface, it is not possible to place a plating film with good adhesion on aluminum as it is. Therefore, pretreatment before plating, that is, a step of removing the aluminum oxide film is required. As such pretreatment, for example, a zinc replacement step called zincate treatment is known in addition to a degreasing step, an etching step, and a smut removing step. The etching step is a step of removing a thin oxide film on the aluminum surface using hydrofluoric acid or the like.

  Although this nickel nickel plating method has been practiced for many years, it has many problems and is still being improved.

  For example, since the zincate treatment causes great damage to aluminum, a replacement nickel plating method has been proposed (see Non-Patent Document 1). Further, as an alternative to etching using hydrofluoric acid, a method using a mixed solution of nitric acid and phosphoric acid has been proposed (see Non-Patent Document 1).

  In addition, a method in which a base material is pretreated with a fluoride of zinc, titanium or zirconium and then treated with an electroless plating solution (see Patent Document 1), a catalyst solution containing a palladium compound instead of a zincate and a phosphate. A method to be used (see Patent Document 2), a method in which an anodized film is formed on an aluminum surface, a catalyst nucleus is attached, and electroless plating is performed (see Patent Document 3) are proposed.

  However, both of these methods still require pretreatment. For this reason, in order to plate the aluminum surface, a large number of tanks (baths) containing a chemical solution have to be installed, and a large number of steps are required, which requires a lot of time.

JP 2006-144095 A JP 2003-313671 A JP-A-7-286296

Kanto Gakuin University Faculty of Engineering Research Report Vol. 51-1 (2007), p. 25

  The present invention has been made in view of the above-described background art, and an object of the present invention is to provide a plating solution capable of chromium plating aluminum or an aluminum alloy without pretreatment.

  As a result of intensive studies on an aluminum or aluminum alloy plating solution instead of the electroless nickel plating solution, the present inventors have pretreated a liquid containing hydrofluoric acid and / or a salt thereof, a chromium salt and water. Thus, the inventors have found that chromium can be plated on aluminum (or aluminum alloy), and have completed the present invention.

  That is, the present invention is a chromium plating solution as shown below.

  [1] A plating solution for chromium plating of aluminum or an aluminum alloy without going through a pre-process for removing an aluminum oxide film, which contains hydrofluoric acid and / or a salt thereof, a chromium salt and water A plating solution characterized by that.

  [2] The hydrofluoric acid and / or salt thereof is one or more selected from the group consisting of an aqueous hydrofluoric acid solution, ammonium fluoride, potassium fluoride, and sodium fluoride. 1].

  [3] The chromium salt is acetate, citrate, oxalate, sulfosalicylate, dimethylglyoximate complex, acetylacetonate complex, ethylenediamine complex, diethylenetriamine complex, triethylenetetramine complex, ethylenediaminetetraacetic acid complex, cyanide The above, characterized in that it is one or more selected from the group consisting of acid salts, thiocyanates, metaphosphates, pyrophosphates, chloride salts, fluoride salts, sulfates, ammine complex salts, and hydrazine complex salts The plating solution according to [1] or [2].

  [4] Any of the above [1] to [3], wherein the content of hydrofluoric acid and / or a salt thereof is 1 ppm by weight or more and 10% by weight or less based on the entire plating solution. The plating solution described in 1.

  [5] The plating solution according to any one of [1] to [4], wherein the chromium salt content is 1 ppm by weight or more and 1% by weight or less based on the entire plating solution.

  [6] The plating solution according to any one of [1] to [5], wherein the plating solution has a pH of 2 or more and less than 7.

  [7] The plating solution according to any one of [1] to [6], further comprising a surfactant and / or a chelating agent.

  [8] The plating solution according to [7], wherein the surfactant is one or more selected from the group consisting of a cationic surfactant and a nonionic surfactant.

  [9] A polyamine selected from the group consisting of oxalic acid, citric acid, malic acid, and polyacrylic acid, wherein the chelating agent is selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, and polyethyleneimine. And one or more selected from the group consisting of amino acids selected from the group consisting of glycine, alanine, aspartic acid, ethylenediaminetetraacetic acid, and diethylenetriaminepentaacetic acid. 8].

  [10] A plating method comprising chromium plating of aluminum or an aluminum alloy using the plating solution according to any one of [1] to [9].

  If the plating solution of the present invention is used, aluminum or an aluminum alloy can be chromium-plated without pretreatment, which is extremely useful industrially.

  The plating solution of the present invention is used for chromium plating of aluminum or an aluminum alloy, and has a feature that no pretreatment is required. In the present invention, the pretreatment refers to the treatment of aluminum or an aluminum alloy before plating with a chemical solution other than a plating solution, such as a zincate treatment, in addition to an etching step and a smut removing step, to remove the aluminum oxide film.

  There is no restriction | limiting in particular as an aluminum alloy, Al-Cu type alloy, Al-Mn type alloy, Al-Si type alloy, Al-Mg type alloy, Al-Mg-Si type alloy, Al-, which are generally distributed A Zn—Mg alloy or the like can be used, but it can be used in any other alloy.

  The plating solution of the present invention contains hydrofluoric acid and / or a salt thereof, a chromium salt, and water.

  In the plating solution of the present invention, hydrofluoric acid and / or a salt thereof is not particularly limited. For example, an aqueous hydrofluoric acid solution may be used, and ammonium fluoride, potassium fluoride, sodium fluoride, etc. A salt or an aqueous solution thereof may be used. These may be used alone or in combination of two or more.

  In the plating solution of the present invention, the chromium salt is not particularly limited, but a salt that dissolves in water is preferable. The chromium salt may be a complex salt in the plating solution. Examples of salts or complex salts that dissolve in water are acetate, citrate, oxalate, sulfosalicylate, dimethylglyoximate complex, acetylacetonate complex, ethylenediamine complex, diethylenetriamine complex, triethylenetetramine complex, ethylenediamine tetra Acetic acid complex salts, cyanate salts, thiocyanate salts, metaphosphate salts, pyrophosphate salts, chloride salts, fluoride salts, sulfate salts, ammine complex salts, hydrazine complex salts, and the like can be used. . These salts may be used alone or in combination of two or more.

  In the plating solution of the present invention, hydrofluoric acid and / or a salt thereof and a chromium salt are used by dissolving in water. Furthermore, an organic solvent soluble in water may be used in combination.

  In the plating solution of the present invention, the content of hydrofluoric acid and / or a salt thereof is not particularly limited, but is usually 1 ppm by weight or more and 10% by weight or less, preferably 10% by weight based on the whole plating solution. ppm to 5% by weight. The addition effect can be increased by setting the content of hydrofluoric acid and / or a salt thereof to 1% by weight or more. That is, the oxide on the surface of aluminum (or aluminum alloy) can be efficiently removed, and the chromium plating rate can be set to an industrial speed. Moreover, the damage of aluminum or aluminum alloy can be suppressed by making content of hydrofluoric acid and / or its salt into 10 weight% or less.

  The chromium salt content in the plating solution of the present invention is not particularly limited, but is usually 1 ppm by weight to 1% by weight, preferably 5 ppm by weight to 0.5% by weight, based on the entire plating solution. It is. If the chromium salt content is less than 1 ppm by weight, the chromium plating rate may be extremely slow, which is not industrial. On the other hand, if the amount of the chromium salt exceeds 1% by weight, chromium may be unevenly plated.

  The plating solution of the present invention is usually used after being acidified. A preferred pH is 2 or more and less than 7, and a more preferred pH is 3 or more and 6 or less. By setting the pH to 2 or more, damage to the aluminum or aluminum alloy can be suppressed, and by setting the pH to less than 7, the chromium plating film can be formed uniformly.

  In order to adjust the pH of the plating solution of the present invention, an acid or a base can be added as a pH adjuster. Examples of the acid include hydrochloric acid, hydrobromic acid, sulfuric acid, sulfurous acid, nitric acid, nitrous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid and other inorganic acids, formic acid, acetic acid, propionic acid, oxalic acid, Organic acids such as citric acid, methane sulfonic acid, benzene sulfonic acid, toluene sulfonic acid and the like can be mentioned, but other acids may be used. Examples of the base include inorganic bases such as ammonia, alkali metal hydroxides, alkali metal salts, alkaline earth metal hydroxides, alkaline earth metal salts, and organic bases such as amines and quaternary ammonium salts. However, other bases may be used in any way. Moreover, these may be used independently and may mix and use 2 or more types.

  In order to form a smoother chrome plating, a surfactant or a chelating agent may be further added to the plating solution of the present invention.

  Examples of the surfactant include cationic, anionic, and nonionic surfactants. Of these, cationic or nonionic surfactants are preferable.

  Although it does not specifically limit as a cationic surfactant, For example, a quaternary ammonium salt, pyridinium salt, etc. are mentioned, Specifically, tetra lower alkyl ammonium halide, alkyl trimethyl ammonium halide, hydroxyethyl alkyl Imidazoline, polyoxyethylene alkylmethylammonium halide, alkylbenzalkonium halide, dialkyldimethylammonium halide, alkyldimethylbenzylammonium halide, alkylamine hydrochloride, alkylamine acetate, alkylamine oleate, alkylaminoethylglycine, alkylpyridinium Examples include halides.

  Further, the nonionic surfactant is not particularly limited, and examples thereof include polyoxyalkylene alkyl ether (or ester), polyoxyalkylene phenyl (or alkylphenyl) ether, polyoxyalkylene naphthyl (or alkyl naphthyl). ) Ether, polyethylene glycol fatty acid ester, polyoxyalkylene alkylamine, polyoxyalkylene condensate adduct of ethylenediamine, polyoxyalkylene aliphatic amide and the like.

  Examples of the chelating agent include polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, and polyethyleneimine, polycarboxylic acids such as oxalic acid, citric acid, malic acid, and polyacrylic acid, glycine, alanine, aspartic acid, and ethylenediamine. Examples include amino acids such as tetraacetic acid and diethylenetriaminepentaacetic acid. These may be used alone or in combination of two or more.

  By using the plating solution of the present invention, aluminum or an aluminum alloy can be chrome plated without going through a pre-process for removing the aluminum oxide film.

  A method for using the plating solution of the present invention may be a conventionally known method and is not particularly limited, and examples thereof include a dipping method and a spraying method. Furthermore, ultrasonic waves can be used in combination as necessary.

  The plating solution of the present invention can be used without any particular heating. The preferred use temperature is in the range of 10 ° C to 80 ° C. By setting the operating temperature to 10 ° C. or higher, the removal rate of the oxide film on the aluminum (or aluminum alloy) surface is increased, and the plating rate can be improved. Moreover, the damage of aluminum or aluminum alloy can be suppressed because use temperature shall be 80 degrees C or less.

  After using the plating solution of the present invention, unnecessary plating solution can be easily removed simply by washing the plated aluminum or aluminum alloy with water. In order to speed up drying, it can be washed with an organic solvent such as alcohol.

  The plating solution of the present invention can be used in the atmosphere. In order to prevent the formation of an oxide film on the aluminum surface, the aluminum alloy surface, or the chromium plating surface, plating may be performed in an inert gas such as nitrogen.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In order to simplify the notation, the following abbreviations were used.

Chromium sulfate: CS,
Chromium chloride: CC,
Ammonium fluoride: AF,
Sodium fluoride: SF,
Sulfuric acid: SA,
Hydrochloric acid: HA,
Citric acid: CA,
Ammonia: AM,
Polyoxyalkylene alkyl ether (nonionic surfactant): POAE,
Benzyltrimethylammonium chloride (cationic surfactant): BMAC,
Triethylenetetramine (chelating agent): TETA.

Example 1.
Sulfuric acid was added to an aqueous solution containing chromium sulfate 100 wt ppm, hydrogen fluoride 0.25 wt%, ammonia 0.5 wt%, and triethylenetetramine 50 wt ppm to adjust to pH 6. An aluminum-copper alloy plate was immersed in this solution at 25 ° C. for 1 minute. The aluminum alloy plate was taken out, washed with water, dried, and elementally analyzed by XPS (X-ray photoelectron spectroscopy, ESCA-3400, manufactured by Shimadzu Corporation) (X-ray source: MgKα ray, 12 kV, 20 mA). As a result, it was found that chromium was detected and plating was formed.

  Next, the surface of the aluminum alloy plate was observed with an electron microscope. As a result, it was found that chromium was uniformly plated. The plating conditions and results are shown in Table 1.

Comparative Example 1
Sulfuric acid was added to an aqueous solution containing 100 wt ppm of chromium sulfate, 0.5 wt% of ammonia, and 50 wt ppm of triethylenetetramine to adjust the pH to 6. An aluminum-copper alloy plate was immersed in this solution at 25 ° C. for 1 minute. The aluminum alloy plate was taken out, washed with water, dried and subjected to elemental analysis by XPS. As a result, no chromium was detected and no plating was formed.

Example 2 to Example 9, Reference Example .
A pure aluminum plate was immersed in the liquid having the composition described in Table 1 at the temperature described in Table 1. The immersion time was 1 minute in all cases. The aluminum plate was taken out, washed with water, dried and subjected to elemental analysis by XPS. In both cases, chromium was detected and chrome plating was formed.

  Next, the surface of the aluminum plate was observed with an electron microscope, and the plating state was evaluated as follows.

Uniform plating: ◎ 、
Slightly observed chromium fine particles: ○,
Chromium particles observed: △,
No chrome plating formed: x.

  The above results are also shown in Table 1.

なお、表中のｐｐｍ、％は、いずれも重量ｐｐｍ、重量％を表し、残部は水である。

In addition, ppm and% in a table | surface represent weight ppm and weight%, respectively, and the remainder is water.

Claims (8)

A plating solution for chromium plating of aluminum or an aluminum alloy without going through a pre-process for removing the aluminum oxide film, containing hydrofluoric acid and / or a salt thereof, a chromium salt and water , The plating solution, wherein the chromium salt content is 1 ppm by weight or more and 0.5% by weight or less with respect to the entire plating solution, and the pH of the plating solution is 3 or more and 6 or less . The hydrofluoric acid and / or salt thereof is one or more selected from the group consisting of an aqueous hydrofluoric acid solution, ammonium fluoride, potassium fluoride, and sodium fluoride. Plating solution. Chromium salt is acetate, citrate, oxalate, sulfosalicylate, dimethylglyoximate complex, acetylacetonate complex, ethylenediamine complex, diethylenetriamine complex, triethylenetetramine complex, ethylenediaminetetraacetic acid complex, cyanate, The thiocyanate, metaphosphate, pyrophosphate, chloride, fluoride, sulfate, ammine complex, and hydrazine complex are selected from the group consisting of one or two or more The plating solution according to claim 2. 4. The plating according to claim 1, wherein the content of hydrofluoric acid and / or a salt thereof is 1 wt ppm or more and 10 wt% or less with respect to the entire plating solution. liquid. Further, the plating solution according to any one of claims 1 to 4, characterized in that it contains a surfactant and / or chelating agents. The plating solution according to claim 5 , wherein the surfactant is one or more selected from the group consisting of a cationic surfactant and a nonionic surfactant. A polyamine selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, and polyethyleneimine, a polycarboxylic acid selected from the group consisting of oxalic acid, citric acid, malic acid, and polyacrylic acid, and glycine , alanine, aspartic acid, according to claim 5 or claim 6, characterized in that it is ethylenediaminetetraacetic acid, and one or more selected from the group consisting of amino acids selected from the group consisting of diethylenetriaminepentaacetic acid Plating solution. A plating method comprising chromium plating of aluminum or an aluminum alloy using the plating solution according to any one of claims 1 to 7 .