JP2009173977A - ELECTRIC Al OR Al-ALLOY PLATING BATH USING ROOM TEMPERATURE MOLTEN SALT BATH AND PLATING METHOD USING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric Al or Al-alloy plating bath which (i) has no risk of explosion, (ii) can be safely handled, (iii) can provide a smooth and uniform plated film with good covering power properties even on a part where the electrical current density is low, and (iv) can provide a plated film having high corrosion resistance. <P>SOLUTION: The electric Al or Al-alloy plating bath includes: (A) an aluminum halide; (B) one or more compounds selected from the group consisting of N-alkylpyridinium halides, N-alkylimidazolium halides, N,N'-alkylimidazolium halides, N-alkylpyrazolium halides, N,N'-alkylpyrazolium halides, N-alkylpyrrolidinium halides, and N,N-alkylpyrrolidinium halides; and (C) a high boiling point aromatic hydrocarbon solvent. The molar ratio of the aluminum halide (A) to the compound(s) (B) is from 1:1 to 3:1, and the electric Al or Al-alloy plating bath has a flash point of 50°C or higher. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric Al or Al alloy plating bath that can be used at room temperature. In particular, the present invention relates to an electric Al or Al alloy plating bath for forming an electric Al or Al alloy plating layer that can be used as a general surface treatment for preventing corrosion.

It is well known that an aluminum metal material has excellent corrosion resistance, but aluminum has a high affinity for oxygen and a reduction potential is lower than that of hydrogen, so that electrodeposition from an aqueous solution is difficult. Therefore, conventionally, aluminum electroplating is performed in an organic solvent plating bath or a high-temperature molten salt bath. Typical examples of the organic solvent-based plating bath include a solution in which AlCl ₃ and LiAlH ₄ or LiH are dissolved in ether, a solution in tetrahydrofuran, and a toluene solution of NaF · 2Al (C ₂ H ₅ ) _3. . However, these baths have a problem that they are explosive when they come into contact with air or water and are difficult to handle. Therefore, a mixed molten salt bath of an aluminum halide and an alkylpyridinium halide has been proposed as a bath without risk of explosion (Patent Document 1). A molten salt bath in which zirconium halide is mixed with aluminum halide and alkylimidazolium halide has also been proposed (Non-patent Document 1). However, plating from such an Al—Zr alloy plating bath has non-uniform electrodeposition and poor smoothness. In particular, when the film thickness is increased or when the current density is increased, there is a problem that the high current density portion becomes dendritic precipitation and the precipitate easily falls off. Further, when the current density is lowered, there is a problem that the throwing power is lowered and plating is not deposited. Furthermore, the obtained plating film is easy to dissolve without performing chromate treatment with hexavalent chromium when subjected to a salt spray test or the like, and it is difficult to obtain the expected rust preventive power, and highly corrosion-resistant Al or Al It was difficult to obtain an alloy plating film. The present inventors have previously proposed a method of diluting a molten salt bath by adding a general-purpose aromatic solvent such as benzene, toluene and xylene in order to solve such a problem of the molten salt bath (Japanese Patent Application No. 2007). -030553). Addition of benzene, toluene, xylene, etc. improves the throwing power without reducing the conductivity of the molten salt, but for industrial handling, safety measures for the human body due to high volatility, There is a problem that measures for the risk of ignition due to low flash point are necessary.

JP-A 62-70592 Journal of The Electrochemical Society, 151 (7) C447-C454 (2004)

  In the present invention, (i) there is no risk of explosion even in contact with air or water, (ii) it can be handled industrially safely, and (iii) dendrite precipitation occurs even at high current density portions. In addition, it is possible to obtain a uniform plating film that is smooth and has good throwing power up to a low current density portion, and (iv) an electric Al or Al that can provide a plating film that can provide high corrosion resistance without chromate treatment. An object is to provide an alloy plating bath.

The present invention relates to (A) aluminum halide, (B) N-alkylpyridinium halides, N-alkylimidazolium halides, N, N′-alkylimidazolium halides, N-alkylpyrazolium halides, N One or more compounds selected from the group consisting of N, N'-alkylpyrazolium halides, N-alkylpyrrolidinium halides and N, N-alkylpyrrolidinium halides, (C) high boiling point An electric Al or Al alloy plating bath containing an aromatic hydrocarbon solvent, wherein the molar ratio of (A) aluminum halide to (B) compound is 1: 1 to 3: 1 and the flash point is 61 ° C. or higher. An electrical Al or Al alloy plating bath is provided.
The present invention also provides an electroplating method using the above-described electric Al or Al alloy plating bath.

  The plating bath of the present invention has no danger of explosion, can be handled industrially safely, and can obtain a smooth and dense Al or Al alloy plating film. Further, since the coating has high corrosion resistance even if it is chrome-free, it can be used in a wide range of applications such as automobile parts and home appliance parts for environmental use.

The electric Al or Al alloy plating bath of the present invention comprises (A) aluminum halide, (B) N-alkylpyridinium halides, N-alkylimidazolium halides, N, N′-alkylimidazolium halides, N— One or more selected from the group consisting of alkyl pyrazolium halides, N, N′-alkyl pyrazolium halides, N-alkyl pyrrolidinium halides and N, N-alkyl pyrrolidinium halides (C) An electric Al or Al alloy plating bath containing a high-boiling aromatic hydrocarbon solvent.
The (A) aluminum halide used in the present invention is represented by AlX ₃ , where X is a halogen such as fluorine, chlorine, bromine or iodine, with chlorine or bromine being preferred. In view of economy, chlorine is most preferable.

（式中、Ｒ₁は炭素原子数１〜１２の直鎖状、分岐鎖状又は環状のアルキル基であり、好ましくは炭素原子数１〜５の直鎖又は分岐鎖状のアルキル基であり、Ｒ₂は水素原子又は炭素原子数１〜６の直鎖状、分岐鎖状又は環状のアルキル基であり、好ましくは炭素原子数１〜３の直鎖又は分岐鎖状のアルキル基であり、Ｘはハロゲン原子であり、ハロゲン原子としては反応性を考慮すると臭素原子が最も好ましい。）
具体的なＮ−アルキルピリジニウムハライド類としては、例えばＮ−メチルピリジニウムクロライド、Ｎ−メチルピリジニウムブロマイド、Ｎ−エチルピリジニウムクロライド、Ｎ−エチルピリジニウムブロマイド、Ｎ−ブチルピリジニウムクロライド、Ｎ−ブチルピリジニウムブロマイド、Ｎ−ヘキシルピリジニウムクロライド、Ｎ−ヘキシルピリジニウムブロマイド、２−メチル−Ｎ−プロピルピリジニウムクロライド、２−メチル−Ｎ−プロピルピリジニウムブロマイド、３−メチル−Ｎ−エチルピリジニウムクロライド、３−メチル−Ｎ−エチルピリジニウムブロマイドなどが挙げられる。 As the N-alkylpyridinium halides used as the compound (B) in the present invention, an alkyl group may be substituted on the pyridium skeleton, and for example, it is represented by the following general formula (I).

(Wherein R ₁ is a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, preferably a linear or branched alkyl group having 1 to 5 carbon atoms, R ₂ is a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, preferably a linear or branched alkyl group having 1 to 3 carbon atoms, Is a halogen atom, and a bromine atom is most preferable as a halogen atom in consideration of reactivity.)
Specific N-alkylpyridinium halides include, for example, N-methylpyridinium chloride, N-methylpyridinium bromide, N-ethylpyridinium chloride, N-ethylpyridinium bromide, N-butylpyridinium chloride, N-butylpyridinium bromide, N -Hexylpyridinium chloride, N-hexylpyridinium bromide, 2-methyl-N-propylpyridinium chloride, 2-methyl-N-propylpyridinium bromide, 3-methyl-N-ethylpyridinium chloride, 3-methyl-N-ethylpyridinium bromide Etc.

（式中、Ｒ₃は炭素原子数１〜１２の直鎖状、分岐鎖状又は環状のアルキル基であり、好ましくは炭素原子数１〜５の直鎖又は分岐鎖状のアルキル基であり、Ｒ₄は水素原子又は炭素原子数１〜６の直鎖状、分岐鎖状又は環状のアルキル基であり、好ましくは水素原子又は炭素原子数１〜３の直鎖又は分岐鎖状のアルキル基であり、Ｘはハロゲン原子であり、ハロゲン原子としては反応性を考慮すると臭素原子が最も好ましい。）
具体的なＮ−アルキルイミダゾリウムハライド類及びＮ，Ｎ’−アルキルイミダゾリウムハライド類としては、例えば１−メチルイミダゾリウムクロライド、１−メチルイミダゾリウムブロマイド、１−エチルイミダゾリウムクロライド、１−エチルイミダゾリウムブロマイド、１−プロピルイミダゾリウムクロライド、１−プロピルイミダゾリウムブロマイド、１−オクチルイミダゾリウムクロライド、１−オクチルイミダゾリウムブロマイド、１−メチル−３−エチルイミダゾリウムクロライド、１−メチル−３−エチルイミダゾリウムブロマイド、１，３−ジメチルイミダゾリウムクロライド、１，３−ジメチルイミダゾリウムブロマイド、１，３−ジエチルイミダゾリウムクロライド、１，３−ジエチルイミダゾリウムブロマイド、１−メチル−３−プロピルイミダゾリウムクロライド、１−メチル−３−プロピルイミダゾリウムブロマイド、１−ブチル−３−ブチルイミダゾリウムクロライド、１−ブチル−３−ブチルイミダゾリウムブロマイドなどが挙げられる。 The N-alkylimidazolium halides and N, N′-alkylimidazolium halides used as the compound (B) in the present invention are represented by, for example, the following general formula (II).

(Wherein R ₃ is a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, preferably a linear or branched alkyl group having 1 to 5 carbon atoms, R ₄ is a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, preferably a hydrogen atom or a linear or branched alkyl group having 1 to 3 carbon atoms. X is a halogen atom, and a bromine atom is most preferable as the halogen atom in consideration of reactivity.)
Specific N-alkylimidazolium halides and N, N′-alkylimidazolium halides include, for example, 1-methylimidazolium chloride, 1-methylimidazolium bromide, 1-ethylimidazolium chloride, 1-ethylimidazole. Lilium bromide, 1-propylimidazolium chloride, 1-propylimidazolium bromide, 1-octylimidazolium chloride, 1-octylimidazolium bromide, 1-methyl-3-ethylimidazolium chloride, 1-methyl-3-ethylimidazole Rium bromide, 1,3-dimethylimidazolium chloride, 1,3-dimethylimidazolium bromide, 1,3-diethylimidazolium chloride, 1,3-diethylimidazolium bromide, 1 -Methyl-3-propylimidazolium chloride, 1-methyl-3-propylimidazolium bromide, 1-butyl-3-butylimidazolium chloride, 1-butyl-3-butylimidazolium bromide and the like.

（式中、Ｒ₅は炭素原子数１〜１２の直鎖状、分岐鎖状又は環状のアルキル基であり、好ましくは炭素原子数１〜５の直鎖又は分岐鎖状のアルキル基であり、Ｒ⁶は水素原子又は炭素原子数１〜６の直鎖状、分岐鎖状又は環状のアルキル基であり、好ましくは水素原子又は炭素原子数１〜３の直鎖又は分岐鎖状のアルキル基であり、Ｘはハロゲン原子であり、ハロゲン原子としては反応性を考慮すると臭素原子が最も好ましい。）
具体的なＮ−アルキルピラゾリウムハライド類及びＮ，Ｎ’−アルキルピラゾリウムハライド類としては、例えば１−メチルピラゾリウムクロライド、１−メチルピラゾリウムブロマイド、１−プロピルピラゾリウムクロライド、１−プロピルピラゾリウムブロマイド、１−ブチルピラゾリウムクロライド、１−ブチルピラゾリウムブロマイド、１−ヘキシルピラゾリウムクロライド、１−ヘキシルピラゾリウムブロマイド、１−メチル−２−エチルピラゾリウムクロライド、１−メチル−２−エチルピラゾリウムブロマイド、１−メチル−２−プロピルピラゾリウムクロライド、１−メチル−２−プロピルピラゾリウムブロマイド、１−プロピル−２−メチルピラゾリウムクロライド、１−プロピル−２−メチルピラゾリウムブロマイド、１−ブチル−２−メチルピラゾリウムクロライド、１−ブチル−２−メチルピラゾリウムブロマイド、１−へキシル−２−メチルピラゾリウムクロライド、１−へキシル−２−メチルピラゾリウムブロマイド、１，２−ジメチルピラゾリウムクロライド、１，２−ジメチルピラゾリウムブロマイド、１，２−ジエチルピラゾリウムクロライド、１，２−ジエチルピラゾリウムブロマイドなどが挙げられる。 The N-alkylpyrazolium halides and N, N′-alkylpyrazolium halides used as the compound (B) in the present invention are represented by, for example, the following general formula (III).

(Wherein R ₅ is a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, preferably a linear or branched alkyl group having 1 to 5 carbon atoms, R ⁶ is a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, preferably a hydrogen atom or a linear or branched alkyl group having 1 to 3 carbon atoms. X is a halogen atom, and a bromine atom is most preferable as the halogen atom in consideration of reactivity.)
Specific examples of N-alkylpyrazolium halides and N, N′-alkylpyrazolium halides include 1-methylpyrazolium chloride, 1-methylpyrazolium bromide, and 1-propylpyrazolium chloride. 1-propylpyrazolium bromide, 1-butylpyrazolium chloride, 1-butylpyrazolium bromide, 1-hexylpyrazolium chloride, 1-hexylpyrazolium bromide, 1-methyl-2-ethylpyrazo Rium chloride, 1-methyl-2-ethylpyrazolium bromide, 1-methyl-2-propylpyrazolium chloride, 1-methyl-2-propylpyrazolium bromide, 1-propyl-2-methylpyrazolium chloride 1-propyl-2-methylpyrazolium bromide, 1 -Butyl-2-methylpyrazolium chloride, 1-butyl-2-methylpyrazolium bromide, 1-hexyl-2-methylpyrazolium chloride, 1-hexyl-2-methylpyrazolium bromide, 1 1,2-dimethylpyrazolium chloride, 1,2-dimethylpyrazolium bromide, 1,2-diethylpyrazolium chloride, 1,2-diethylpyrazolium bromide and the like.

（式中、Ｒ₇は水素原子又は炭素原子数１〜１２の直鎖状、分岐鎖状又は環状のアルキル基であり、好ましくは炭素原子数１〜５の直鎖又は分岐鎖状のアルキル基であり、Ｒ₈は水素原子又は炭素原子数１〜６の直鎖状、分岐鎖状又は環状のアルキル基であり、好ましくは水素原子又は炭素原子数１〜３の直鎖状又は分岐鎖状のアルキル基であるが、但しＲ₇及びＲ₈はともに水素原子であることはなく、Ｘはハロゲン原子であり、ハロゲン原子としては反応性を考慮すると臭素原子が最も好ましい。）
具体的なＮ−アルキルピロリジニウムハライド類及びＮ，Ｎ−アルキルピロリジニウムハライド類としては、例えば１−メチルピロリジニウムクロライド、１−メチルピロリジニウムブロマイド、１，１−ジメチルピロリジニウムクロライド、１−エチル−１−メチルピロリジニウムクロライド、１−エチルピロリジニウムクロライド、１−プロピルピリジニウムクロライド、１−メチル−１−プロピルピリジニウムクロライド、１−ブチル−１−メチルピロリジニウムクロライド、１−エチル−１−プロピルピリジニウムクロライド、１−メチル−１−ヘキシルピリジニウムクロライド、１−ブチルピロリジニウムクロライド、１−エチル−１−メチルピリジニウムクロライドなどが挙げられる。 Examples of the N-alkylpyrrolidinium halides and N, N-alkylpyrrolidinium halides used as the compound (B) in the present invention are represented by the following general formula (IV).

(In the formula, R ₇ is a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, preferably a linear or branched alkyl group having 1 to 5 carbon atoms. And R ₈ is a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, preferably a hydrogen atom or a linear or branched chain having 1 to 3 carbon atoms. However, R ₇ and R ₈ are not both hydrogen atoms, X is a halogen atom, and the halogen atom is most preferably a bromine atom in consideration of reactivity.)
Specific N-alkylpyrrolidinium halides and N, N-alkylpyrrolidinium halides include, for example, 1-methylpyrrolidinium chloride, 1-methylpyrrolidinium bromide, 1,1-dimethylpyrrolidinium. Chloride, 1-ethyl-1-methylpyrrolidinium chloride, 1-ethylpyrrolidinium chloride, 1-propylpyridinium chloride, 1-methyl-1-propylpyridinium chloride, 1-butyl-1-methylpyrrolidinium chloride, Examples include 1-ethyl-1-propylpyridinium chloride, 1-methyl-1-hexylpyridinium chloride, 1-butylpyrrolidinium chloride, 1-ethyl-1-methylpyridinium chloride, and the like.

  In addition, the compound (B) includes the above-mentioned N-alkylpyridinium halides, N-alkylimidazolium halides, N, N′-alkylimidazolium halides, N-alkylpyrazolium halides, N, N′— It may be a mixture of two or more of alkyl pyrazolium halides, N-alkyl pyrrolidinium halides and N, N-alkyl pyrrolidinium halides, and also a mixture of two or more of different halogen atoms. May be.

  In the present invention, the ratio of the number of moles of (A) aluminum halide to the number of moles of (B) compound is preferably in the range of 1: 1 to 3: 1, more preferably 2: 1. By setting the molar ratio in such a range, the reaction that seems to be decomposed of pyridinium, imidazolium, pyrazolium or pyrrolidinium cation is prevented, the viscosity of the plating bath is increased, the bath is deteriorated and the plating is poor. Can be prevented.

  The (C) high boiling point aromatic hydrocarbon solvent used in the present invention is not limited as long as it is soluble in the molten salt and does not decrease the electric conductivity of the molten salt, but preferably has a boiling point of 160 ° C. The aromatic hydrocarbon solvent described above (when measured under atmospheric pressure), preferably an alkyl-substituted and / or hydroxy-substituted aromatic hydrocarbon solvent. Examples of the alkyl substituent include a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms. Examples of the aromatic nucleus include benzene, indene, indane, tetralin, naphthalene, and fluorene. Specifically, for example, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,2,3,4-tetramethylbenzene, 1,2,3,5-tetramethylbenzene, 1, 2,4,5-tetramethylbenzene, 1,3-diethylbenzene, P-cymene, 4-propyltoluene, n-butylbenzene, 3-butyltoluene, 1-ethyl-4-isopropylbenzene, 3,5-diethyltoluene 1,3,5-triethylbenzene, 1,3-dipropylbenzene, 5-tert-butyl-1,3-dimethylbenzene, n-pentylbenzene, n-octylbenzene, cyclohexylbenzene, hydroindane, methylindane, Dimethylindane, ethylindane, methylnaphthalene, dimethylnaphthalene, 1,2,3,4-tetrahydride Such as naphthalene, and the like. These can be used alone or in combination of two or more. Of these, alkyl-substituted and / or hydroxy-substituted benzene or naphthalene is preferable, and alkyl-substituted benzene or hydroxy-substituted naphthalene is most preferable. The concentration of such a high-boiling aromatic hydrocarbon solvent in the bath is preferably in the range not exceeding 50% by volume, more preferably in the range of 1 to 50% by volume, and further preferably in the range of 5 to 25% by volume. The range is most preferably 10 to 20% by volume. (C) When the high-boiling aromatic hydrocarbon solvent is used in such a range, the electric Al or Al alloy plating bath of the present invention has a flash point of 50 ° C, preferably 55 ° C, more preferably 61 ° C (atmospheric pressure). In the case of measurement below), and the contactability of the plating bath is improved, uniform plating is obtained, and the corrosion resistance is improved. In addition, there is no increase in electrical conductivity and risk of flammability.

The electric Al or Al alloy plating bath of the present invention may contain (D) one or more organic polymers selected from the group consisting of a styrene polymer and an aliphatic diene polymer. Specific examples of the styrene polymer used as the organic polymer (D) in the present invention include, for example, styrene homopolymers such as styrene, α-methylstyrene, vinyltoluene, and m-methylstyrene, copolymers of these, or Copolymers of styrene monomers and other polymerizable vinyl monomers can be mentioned. Examples of the vinyl monomers include maleic anhydride, maleic acid, acrylic acid, methacrylic acid, methyl methacrylate, glycidyl methacrylate, itaconic acid, acrylamide, acrylonitrile, maleimide, vinyl pyridine, vinyl carbazole, acrylic ester, methacrylic acid. Examples include esters, fumaric acid esters, vinyl ethyl ether, and vinyl chloride. Of these, α, β-unsaturated carboxylic acids having 3 to 10 carbon atoms or alkyl (C1 to 3) esters thereof are preferable.
Examples of the aliphatic diene polymer used as the organic polymer (D) in the present invention include polymers such as butadiene, isoprene and pentadiene. Preferably, it is a polymer having a branched chain of 1, 2, or 3, 4 structure, or a copolymer of these with other polymerizable vinyl monomers. Examples of the vinyl monomer include those described for the styrene polymer.
(D) The weight average molecular weight of the organic polymer is preferably in the range of 200 to 80,000. In particular, low-medium molecular weight polystyrene having a weight average molecular weight of about 300 to 5,000 and poly-α-methylstyrene are most preferable because of good molten salt solubility. The concentration in the bath is preferably in the range of 0.1 to 50 g / l, more preferably in the range of 1 to 10 g / l. (D) When an organic polymer is used in such a range, dendrid precipitation can be prevented, a surface smoothing effect can be exhibited, and plating and injury can be prevented from occurring.

The electric Al or Al alloy plating bath of the present invention may contain (E) a brightener. (E) Brighteners include aliphatic aldehydes, aromatic aldehydes, aromatic ketones, nitrogen-containing unsaturated heterocyclic compounds, hydrazide compounds, S-containing heterocyclic compounds, aromatic hydrocarbons having an S-containing substituent, aromatic Examples thereof include one or more compounds selected from carboxylic acids and derivatives thereof, aliphatic carboxylic acids having a double bond and derivatives thereof, acetylene alcohol compounds, and trifluoroethylene chloride resins.
The aliphatic aldehyde is, for example, an aliphatic aldehyde having 2 to 12 carbon atoms, and specific examples include tribromoacetaldehyde, metaaldehyde, 2-ethylhexyl aldehyde, lauryl aldehyde, and the like.
The aromatic aldehyde is, for example, an aromatic aldehyde having 7 to 10 carbon atoms. Specifically, 0-carboxybenzaldehyde, benzaldehyde, 0-chlorobenzaldehyde, p-tolualdehyde, anisaldehyde, p-dimethylaminobenzaldehyde, terephthalaldehyde Etc.
The aromatic ketone is, for example, an aromatic ketone having 8 to 14 carbon atoms, and specific examples include benzalacetone, benzophenone, acetophenone, terephthaloyl benzyl chloride and the like.
The nitrogen-containing unsaturated heterocyclic compound is, for example, a nitrogen heterocyclic compound having 3 to 14 carbon atoms. Specifically, pyrimidine, pyrazine, pyridazine, s-triazine, quinoxaline, phthalazine, 1,10-phenanthroline, 1,2 , 3-benzotriazole, acetoguanamine, cyanuric chloride, imidazole-4-acrylic acid and the like.

Examples of the hydrazide compound include maleic acid hydrazide, isonicotinic acid hydrazide, phthalic acid hydrazide, and the like.
The S-containing heterocyclic compound is, for example, an S-containing heterocyclic compound having 3 to 14 carbon atoms, and specific examples include thiouracil, thionicotinic acid amide, s-trithiane, 2-mercapto-4,6-dimethylpyrimidine and the like. .
The aromatic hydrocarbon having an S-containing substituent is, for example, an aromatic hydrocarbon having an S-containing substituent having 7 to 20 carbon atoms, specifically, thiobenzoic acid, thioindigo, thioindoxyl, thioxanthene, thioxanthone. 2-thiocoumarin, thiocresol, thiodiphenylamine, thionaphthol, thiophenol, thiobenzamide, thiobenzanilide, thiobenzaldehyde, thionaphthenequinone, thionaphthene, thioacetanilide and the like.
Aromatic carboxylic acids and derivatives thereof are, for example, aromatic carboxylic acids having 7 to 15 carbon atoms and derivatives thereof, and specific examples include benzoic acid, terephthalic acid, and ethyl benzoate.
The aliphatic carboxylic acid having a double bond and a derivative thereof are, for example, an aliphatic carboxylic acid having a double bond having 3 to 12 carbon atoms and a derivative thereof. Specifically, acrylic acid, crotonic acid, methacrylic acid, acrylic Acid-2-ethylhexyl, 2-ethylhexyl methacrylate and the like.
Examples of the acetylene alcohol compound include propargyl alcohol.
Examples of the fluororesin include a trifluorochloroethylene resin having an average molecular weight of 500 to 1300.
(E) The concentration of the brightener in the bath is preferably in the range of 0.001 to 0.1 mol / l, more preferably in the range of 0.002 to 0.02 mol / l. In the electric Al or Al alloy plating bath of the present invention, when the brightening agent (E) is used in such a range, a smoothing effect is obtained, and even when plating is performed at a high current density, black smut-like precipitation is obtained. It does not occur.
In the electric Al or Al alloy plating bath of the present invention, (D) an organic polymer or (E) a brightener may be used in combination, or these two types may be used in combination.

The electric Al or Al alloy plating bath of the present invention is (F) a salt of one or more metals selected from the group consisting of Zr, Ti, Mo, W, Mn, Ni, Co, Sn, Cu and Zn. And / or Si compounds may be contained. When the metal salt or Si compound is added to the electric Al or Al alloy plating bath of the present invention, alloy plating with the added metal or Si is obtained. For example, an Al plating film obtained using ZrCl ₄ becomes Al—Zr alloy plating, and the corrosion resistance is improved. As the metal salt, a halide is preferable, and a chloride is particularly preferable from the viewpoint of easy handling. Examples of such metal salts include titanium chloride, molybdenum bromide, manganese iodide, nickel bromide, cobalt chloride, and tungsten fluoride. Examples of the Si compound include SiO ₂ fine powder and colloidal silica.
The concentration of the metal salt in the bath is preferably 0.5 to 100 g / l, more preferably 1 to 50 g / l, and still more preferably 5 to 20 g / l. In the electric Al or Al alloy plating bath of the present invention, when the metal salt is used in such a range, alloy plating with excellent corrosion resistance is obtained, and no black powder is precipitated.

Electroplating is used as a plating method using the electric Al or Al alloy plating bath of the present invention. Electroplating can be performed by direct current or pulse current, and pulse current is particularly preferable. When using a pulse current with a duty ratio (ON / OFF ratio) of preferably 1: 2 to 2: 1, most preferably 1: 1, an ON time of 5 to 20 ms, and an OFF time of 5 to 20 ms. It is preferable because the particles to be electrodeposited become dense and smooth. The bath temperature is usually in the range of 25 to 120 ° C, preferably in the range of 50 to 80 ° C. Current density is usually in the range of 0.1~15A / dm ^2, preferably in the range of 0.5~5A / dm ^2. The electric Al or Al alloy plating bath of the present invention is safe even when exposed to oxygen and moisture, but is in a dry oxygen-free atmosphere (dry nitrogen or dry argon from the standpoint of maintaining the stability of the plating bath and plating properties). Middle). Further, when electroplating is performed, it is desirable to stir the liquid or / and swing the object to be plated. For example, if a jet jet or ultrasonic stirring is used, the current density can be further increased.
However, when plating complex shaped parts, it is desirable to perform plating for a long time at a cathode current density as low as 0.5 to 1 A / dm ² without stirring or weakening in order to improve wearability. The anode may be an insoluble anode. However, when an insoluble anode is used, it is necessary to replenish aluminum halide or the like to keep the bath composition constant.

Using the electric Al or Al alloy plating bath of the present invention, a smooth and dense Al or Al alloy plating film can be coated on various metals such as iron, zinc, and ceramics or ceramic substrates.
The Zr eutectoid rate in the Al—Zr alloy plating film obtained by using, for example, an electric Al—Zr alloy plating bath containing ZrCl ₄ in the electric Al alloy plating bath of the present invention is preferably 1 to 40% by weight. More preferably, it is 3 to 35% by weight, and most preferably 10 to 30% by weight. By setting it as such Zr eutectoid rate, the corrosion resistance of an Al-Zr alloy plating film becomes favorable.
The thickness of the Al or Al alloy plating film obtained using the electric Al or Al alloy plating bath of the present invention is usually 1 to 50 μm, preferably 5 to 20 μm.

(Examples 1 to 10)
In a bath formed by mixing and melting AlCl ₃ (481 g / l) and 1-methyl-3-propylimidazolium bromide (64.7 g / l) (2: 1 molar ratio), a high-boiling aromatic hydrocarbon solvent 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,2,3,4-tetrahydronaphthalene are mixed as shown in Table 1 below, and zirconium chloride is added as shown in Table 1 below. -Zr alloy plating bath was prepared. Next, as a pretreatment, the iron plate (plate thickness 0.5 mm) used as the cathode was subjected to alkali degreasing, alkaline electrolytic washing and pickling, water washing, ethyl alcohol washing and drying. The iron plate is used as a cathode, the aluminum plate (purity 99.9%) as an anode, and immersed in the electric Al—Zr alloy plating bath maintained at 50 ° C. in a dry nitrogen gas atmosphere for 5 minutes. Al—Zr alloy plating was performed with a pulse current (duty ratio: 1/1, ON time: 10 ms, OFF time: 10 ms). The plating bath was stirred with a stirrer. Table 1 shows 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,2,3,4-tetrahydronaphthalene bath concentration, plating bath flash point, zirconium chloride bath concentration and Table 2 shows the electrolytic conditions, and the evaluation results of the Zr eutectoid rate (%), smoothness, adhesion and corrosion resistance of the obtained Al—Zr alloy plating film.

(Examples 11 to 16)
In a bath formed by mixing and melting AlCl ₃ (481 g / l) and 1-methyl-3-propylimidazolium bromide (64.7 g / l) (2: 1 molar ratio), a high-boiling aromatic hydrocarbon solvent 20% by volume of 1,2,4-trimethylbenzene and 5 g / l of zirconium chloride were added. Furthermore, as shown in Table 2 below, (D) an organic polymer and (E) a brightener were added to prepare an electric Al—Zr alloy plating bath. Next, as a pretreatment, the iron plate (plate thickness 0.5 mm) used as the cathode was subjected to alkali degreasing, alkaline electrolytic washing and pickling, water washing, ethyl alcohol washing and drying. The iron plate is used as a cathode, the aluminum plate (purity 99.9%) as an anode, and immersed in the electric Al—Zr alloy plating bath maintained at 50 ° C. for 5 minutes in a dry nitrogen gas atmosphere. Then, Al—Zr alloy plating was performed. The plating bath was stirred with a stirrer. Table 3 shows the types and concentrations of additives in the bath, the flash point of the plating bath, and the electrolysis conditions. Table 4 shows the eutectoid rate (%), smoothness, and adhesion of the obtained Al-Zr alloy plating film. The evaluation result of property and corrosion resistance is shown.

(Comparative Examples 1-3)
In a bath formed by mixing and melting AlCl ₃ (481 g / l) and 1-methyl-3-propylimidazolium bromide (64.7 g / l) (2: 1 molar ratio) as shown in Table 5 below (D) An organic polymer and (E) brightener were added to prepare an electric Al plating bath. Next, as a pretreatment, the iron plate (plate thickness 0.5 mm) used as the cathode was subjected to alkali degreasing, alkaline electrolytic washing and pickling, water washing, ethyl alcohol washing and drying. The iron plate is used as a cathode, the aluminum plate (purity 99.9%) as an anode, and immersed in the electric Al plating bath maintained at 50 ° C. in a dry nitrogen gas atmosphere for 5 minutes, and Al plating is performed in a direct current in the same plating bath. Went. The plating bath was stirred with a stirrer. Table 5 shows the types of additives, the concentration in the bath, the flash point of the plating bath, and the electrolysis conditions, and Table 6 shows the evaluation results of the smoothness, adhesion and corrosion resistance of the obtained Al plating film.

(Comparative Examples 4 and 5)
Zirconium chloride (5 g / l) was added to a bath obtained by mixing and melting AlCl ₃ (481 g / l) and 1-methyl-3-propylimidazolium bromide (64.7 g / l) (2: 1 molar ratio). In addition, an electric Al—Zr alloy plating bath was prepared without adding a high-boiling aromatic hydrocarbon solvent. Next, as a pretreatment, the iron plate (plate thickness 0.5 mm) used as the cathode was subjected to alkali degreasing, alkaline electrolytic washing and pickling, water washing, ethyl alcohol washing and drying. The iron plate is used as a cathode, the aluminum plate (purity 99.9%) as an anode, and immersed in the electric Al—Mn alloy plating bath maintained at 50 ° C. in a dry nitrogen gas atmosphere for 5 minutes. Then, Al—Zr alloy plating was performed. The plating bath was stirred with a stirrer. Table 7 shows the types and concentrations of additives in the bath, the flash point of the plating bath, and the electrolysis conditions. Table 8 shows the eutectoid rate (%), smoothness and adhesion of the obtained Al—Zr alloy plating film. The evaluation result of property and corrosion resistance is shown.

(Comparative Example 6)
An electric Al—Zr alloy plating bath was prepared in the same manner as in Example 1 except that the same amount of toluene was added in place of 1,2,3-trimethylbenzene as the high boiling point solvent in Example 1. Next, as a pretreatment, the iron plate (plate thickness 0.5 mm) used as the cathode was subjected to alkali degreasing, alkaline electrolytic washing and pickling, water washing, ethyl alcohol washing and drying. The iron plate is used as a cathode, the aluminum plate (purity 99.9%) as an anode, and immersed in the electric Al—Mn alloy plating bath maintained at 50 ° C. in a dry nitrogen gas atmosphere for 5 minutes. Then, Al—Zr alloy plating was performed. The plating bath was stirred with a stirrer. Table 9 shows the flash point and electrolysis conditions of the plating bath, and Table 10 shows the evaluation results of the eutectoid rate (%), smoothness, adhesion and corrosion resistance of the obtained Al-Zr alloy plating film.

(Measurement method of Zr eutectoid rate (%) and thickness)
The Zr eutectoid rate (%) and thickness of the Al—Zr alloy plating film were measured using a fluorescent X-ray analyzer (manufactured by SII Nanotechnology, Inc., Micro Element Monitor SEA5120).

(Measurement method of red rust occurrence time in SST)
The red rust generation time in SST was measured according to the salt spray test method (JIS Z2371).

(Measurement method of smoothness)
The smoothness of the film was measured using a surface roughness measuring machine (manufactured by Kosaka Laboratory, Surfcoder SE-30H).

(Measurement method of adhesion)
The adhesion of the film was determined by a tape peeling test. In the tape peeling test, the substrate is bent 180 ° with the surface of the alloy plating film facing inward, then returned to its original position, and the cellophane adhesive tape (with a width of 18 mm as defined in JIS Z1522) is erased (as defined in JIS S6050). Within 90 seconds, the tape was held at a right angle to the attached surface, and one end of the tape was peeled off instantaneously, and the presence or absence of film peeling was visually determined.

(Measurement method of flash point of plating bath)
The flash point of the plating bath was measured by the dangerous substance class 4 flash point test method according to the manual for conducting dangerous goods confirmation test of the Fire Service Act.

Claims (8)

  (A) Aluminum halide, (B) N-alkylpyridinium halides, N-alkylimidazolium halides, N, N′-alkylimidazolium halides, N-alkylpyrazolium halides, N, N′— One or more compounds selected from the group consisting of alkyl pyrazolium halides, N-alkylpyrrolidinium halides and N, N-alkylpyrrolidinium halides, (C) high-boiling aromatic hydrocarbons An electric Al or Al alloy plating bath containing a solvent, wherein the molar ratio of (A) aluminum halide to (B) compound is 1: 1 to 3: 1 and the flash point is 50 ° C. or higher. Al or Al alloy plating bath.   The electric Al or Al alloy plating bath according to claim 1, having a flash point of 61 ° C or higher.   (C) The electric Al or Al alloy plating bath according to claim 1 or 2, wherein the high-boiling aromatic hydrocarbon solvent is contained in a range not exceeding 50% by volume.   (D) The content of any one of Claims 1-3 which contains 0.1-50 g / l of 1 type, or 2 or more types of organic polymers chosen from the group which consists of a styrene-type polymer and an aliphatic diene-type polymer. Electric Al or Al alloy plating bath.   (E) The electric Al or Al alloy plating bath according to any one of claims 1 to 4, comprising a brightener in an amount of 0.001 to 0.1 mol / l.   (F) 0.5 to 100 g / s of one or more metal salts and / or Si compounds selected from the group consisting of Zr, Ti, Mo, W, Mn, Ni, Co, Sn, Cu and Zn. The electric Al or Al alloy plating bath according to any one of claims 1 to 5, which contains l.   An electroplating method using the electric Al or Al alloy plating bath according to any one of claims 1 to 6.   The plating method according to claim 7, wherein the electroplating is performed with a pulse current.