JPH0472089A - Aluminum plating bath - Google Patents

Abstract

PURPOSE:To obtain a safe Al electroplating bath capable of forming a lustrous, smooth and dense plating film by adding an anhydrous metal halide to a molten aluminum halide-pyridinium salt mixture. CONSTITUTION:An aluminum halide is mixed with at least one kind of compd. selected among monoalkylpyridinium halides, dialkylpyridinium halides, 1- alkylimidazolium halides and 1,3-dialkylimidazolium halides in (1:1)-(3:1) molar ratio, the mixture is melted to prepare a plating bath and at least one of anhydrous metal halides of Mn, Zn, Ni, Cu, Fe, Pb and Co is added to the plating bath by 0.5-20g/l. A brightener such as a carbonyl compd. is further added by 0.1-15g/l as required. The resulting Al electroplating bath does not invite the danger of explosion even by contact with the air or water and can form a plating film having superior quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrolytic aluminum plating bath that can be used at room temperature, and in particular to a bright aluminum plating bath that can be used as a general surface treatment for decoration or corrosion protection. The present invention relates to an electric aluminum plating bath for forming a certain aluminum plating layer.

[Prior Art] It is well known that aluminum metal materials have excellent corrosion resistance.However, aluminum has a large affinity for oxygen and its potential is less noble than hydrogen, so
Electrodeposition from aqueous solutions is difficult. Therefore, aluminum electroplating has conventionally been carried out in an organic solvent-based plating bath or a molten salt bath.

Here, as organic solvent-based plating baths, AlICl3 and LiA I! , 84 or LiH dissolved in ether, tetrahydrofuran, Na
Toluene solutions of F.2A 1 (CJs) 3 are typical, but these baths are difficult to handle and pose an explosion risk if they come into contact with air or water.

Therefore, a mixed molten salt bath of aluminum halide and alkylpyridinium halide has been proposed as a bath without the risk of explosion (Japanese Patent Application Laid-Open No. 70592/1983).
62-70593).

However, the plating from this plating bath lacks luster, making it difficult to obtain a smooth and dense plating film.

[Problems to be Solved by the Invention] The present invention provides an electrolytic aluminum plating bath that is free from the danger of explosion even when it comes into contact with air or water, and can provide a glossy, smooth, and dense plating film. The purpose is to

[Means for Solving the Problems] The present invention is based on the knowledge that the above problems can be effectively achieved by adding one or more types of anhydrous metal halides to a molten mixture of an aluminum halide compound, a pyridinium salt, etc. It was done.

That is, the present invention provides aluminum halides from the group consisting of (A) aluminum halides, and (B) monoalkylpyridinium halides, dialkylpyridinium halides, 1-alkylimidazolium halides, and 1,3-dialkylimidazolium halides. Mn, Zn, Ni, C
Provided is an electrolytic aluminum plating bath characterized in that it contains 0.5 to 20 g/l of at least one of inorganic metal halides such as u, Fe, Pb, and Co.

The aluminum halide of the present invention is represented by ARXs, where X is a halogen such as chlorine.

Furthermore, the monoalkylpyridinium halide used in the present invention is represented by the following formula (1).

(In the formula, R1 is an alkyl group having 1 to 12 carbon atoms, and X is a halogen.) Furthermore, the dialkylpyridinium halogen compound of the present invention is represented by the following formula (n).

It is a p-halogen. ) Furthermore, the 1,3-dialkylimidazolium halide of the present invention is represented by formula (IV).

(In the formula, R+ is an alkyl group having 1 to 12 carbon atoms, 1 is
An alkyl group having 1 to 6 carbon atoms, and X: halogen. ) Further used in the present invention. The l-alkylimidazolium halogen compound is represented by formula (III).

(In the formula, R3 is an alkyl group having 1 to 12 carbon atoms, X is (in the formula, R3 is an alkyl group having 1 to 12 carbon atoms, R4 is an alkyl group having 1 to 6 carbon atoms, and X is a halogen.) The molten bath for obtaining a good plating film of the present invention uses components (A) and (B) at a molar ratio of 1:1 to 3:1, preferably 2:I to form a molten salt. do.

This is because when the aluminum halide content is less than 1:1, a reaction that appears to decompose pyridinium and imidazolium cations occurs, and when it is more than 3:1, the viscosity of the plating bath increases, resulting in bath deterioration and This is because it causes poor plating, which is not preferable.

In the present invention, the molten salt contains an anhydrous metal halide, for example, metal chlorides MnC1z, ZnC1z,
NiC1t, CuCl, CuCj! z, FeCf!
= ,PbCj! By adding one type or a mixture of two or more of CoCl 2 and the like, it is possible to densify the crystals and obtain a glossy effect during electrodeposition.

The concentration of this anhydrous metal halide added is 0.5 to 2
0 g/l, preferably 2-10 g/l. Note that particularly excellent effects were obtained when Mn (Ilz 4 to 10 g/j!) was added.

Also, the additive concentration is 0.5 to 20 g/I! , the effect is small below 0.5 g/1, while 20
g/! This is because if it exceeds this amount, black smut-like precipitation will occur, making it impossible to obtain a good aluminum coating.

In the present invention, electrodeposition is achieved by adding at least one of a carbonyl compound, an amide compound, a hydrazide compound, an acetylene alcohol compound, and a nitrogen heterocyclic compound as a brightening agent to the molten salt to which the anhydrous metal halide has been added. In this case, the crystals can be further densified and an excellent gloss effect can be obtained.

The concentration of this brightening agent is 0.1 to 15 g/j! , preferably 1 to 5 g/Il. This means that the additive concentration is 0.
．． If it is less than 1 g, the effect will be small, while if it exceeds 15 g/l, black smut will precipitate when plating is carried out at a high current density, making it impossible to obtain a good aluminum plating film.

Next, each gloss imparting agent will be explained in detail.

As carbonyl compounds according to the invention, mention may be made of aldehydes, ketones and lactones. Here, the aldehyde is an aliphatic aldehyde having 2 to 12 carbon atoms, such as tribromoacetaldehyde, n-butyraldehyde, metaldehyde, 2-ethylhexylaldehyde,
Lauryl aldehyde, etc. can be used, and aromatic aldehydes such as benzaldehyde, 0-chlorobenzaldehyde, P-)raldehyde, anisaldehyde, 0-benzaldehyde sulfonic acid, P-dimethylaminobenzaldehyde, terephthalaldehyde, etc. can be used. Further, as the ketone, for example, benzalacetone, acetophenone, benzylacetone can be used, and as the lactone, coumarin, 7-diethylamino-4-methylcoumarin, etc. can be used.

Examples of the amide compound include aromatic sulfonamides and sulfonimides, such as 0-sulfobenzimide, dibenzenesulfonimide, N-benzoylbenzenesulfamide, thiosaccharin, diallylsulfamide, and the like.

Further, examples of the hydrazide compound include maleic acid hydrazide, isonicotinic acid hydrazidophthalic acid hydrazide, etc., and examples of the acetylene alcohol compound include propargyl alcohol, 2-butyl-1,4-diol, 2-butyl-1,4-diol, and the like.
-Methyl-3-butynediol and the like.

Examples of the acetylene alcohol compound include propargyl alcohol and 1,4-butynediol.

Examples of the nitrogen heterocyclic compound include compounds selected from pyridine, pyrimidine, and imidazole derivatives, such as pyridine sulfonic acid, nicotinic acid, nicotinic acid amide, uracil, thiouracil, N-methylimidazole, and thionicotinic acid amide.

Electroplating is performed using direct current or pulsed current at a bath temperature of 2.
5-80°C, preferably 40-60°C, current density 0
．． 1 to 108/d, preferably 0.5 to 2.0 ^
It is preferable to carry out the electrolysis under the electrolytic conditions of /dlI2.

Although the plating bath of the present invention is safe even when exposed to oxygen or moisture, it is recommended to perform the plating in a dry oxygen-free atmosphere (in dry N2 or Ar) from the viewpoint of maintaining the stability of the plating bath and the plating properties. desirable.

Furthermore, when performing plating, it is necessary to stir the liquid or shake the object to be plated. The current density can be further increased by using a jet stream, ultrasonic stirring, or the like.

However, when plating a shaped part, it is desirable to weaken the agitation and process at a low current density over a long period of time in order to improve the throwing power.

As the anode, an Al plate is preferred, but an insoluble anode may also be used. However, in this case, it is necessary to maintain the bath composition constant by replenishing Af salt.

[Effects of the Invention] The plating bath of the present invention has no danger of explosion or ignition (because it can produce an aluminum coating with a smooth, dense, and glossy surface at room temperature or low temperature (40 to 60°C),
It has good workability and is advantageous for industrialization.

Therefore, by using the plating bath of the present invention, aluminum plating can be easily applied to electrical parts, automobiles, aircraft, ship parts, etc. that require decorative properties and corrosion resistance.

Next, the present invention will be explained in more detail by way of examples.

[Example I AJQCI! MnCj! A plating bath was prepared by adding t7g/I-. Next, a copper plate (3 mm thick) used as a cathode was pretreated with alkaline degreasing, electrolytic cleaning, and pickling, followed by water washing, alcohol washing, and drying.

In electrolytic plating, the copper plate is used as a cathode and the aluminum plate (purity 99.99% by weight) is used as an anode, and the plate is immersed in the plating bath kept at 40°C, and a DC current of 2^/da is applied in a nitrogen gas (dry) atmosphere. The plating bath was stirred for 20 minutes using a Starcy device.

The resulting aluminum plating film is dense and has a metallic luster, and the plating weight is 190cm/dIII.
! The gloss level was 400 gloss.

The glossiness was measured using a digital glossmeter (Model GM-26) manufactured by Murakami Color Research Institute (Co., Ltd.) at an angle of 20°.

In addition, the plating weight in the examples is (mold weight after plating of the object to be plated - weight before plating of the object to be plated) ÷ surface area (ds
It was converted by

Example 2 AjICj! ZnCj! z 6 g / j! Add IA
Plating was carried out in the same manner as in Example 1, except that the plating was carried out using the same method as in Example 1.

As a result, a dense and glossy aluminum plating film was obtained. Plating weight is 100■/dI11! The gloss level was 295 gloss.

Example 3 A (MnCL
Plating was performed in the same manner as in Example 1, except that 5 g/L PbCfg 2 g/i was added and the current density was set to I A/da+''.

As a result, a dense and glossy aluminum plating film was obtained. Plating weight is 90■/dm", gloss level is 49
It was 0 gross.

Example 4 A1. MnCj! and 1-butylimidazolium bromide are mixed and melted in a 2:1 molar ratio in a bath.
z 5 g/l=,0-sulfobenzimide-1
,6g/i, current density 0.5.1.0.2
．． Plating was performed in the same manner as in Example 1, except that 0 and 3, OA/do+'' were used.

As a result, a dense and glossy aluminum plating film was obtained at any current density. Plating Irl is 45.
90.180.270 K/da+” T: Ant, glossiness was 265.420.350 and 220 gloss.

Example 5 28 g/l of MnCl was added to a bath prepared by mixing and melting AICls and butylpyridinium chloride at a molar ratio of 2:1.
Plating was carried out in the same manner as in Example 1, except that the current density was set to IA/d+'' by adding .

As a result, a dense and glossy aluminum plating film was obtained. The plating weight was 95 cm/dffl'' and the gloss was 350 gloss.

Example 6 AffiCI! , 3 and N-butylimidazolium bromide at a molar ratio of 2:1.
Plating was carried out in the same manner as in Example 1, except that 1 g/l was added and the current density was set to I A/da''.

As a result, a dense and glossy aluminum plating film was obtained. The plating weight was 100 .mu./da" and the gloss was 370 gloss.

Example 7 1/IC/! MnCl z2 and N-butylimidazolium bromide were mixed in a molar ratio of 2=1.
Plating was carried out in the same manner as in Example 1, except that 2 g/l of maleic acid hydrazide was added and the current density was set to IA/ds''.

As a result, a dense and glossy aluminum plating film was obtained. The plating weight was 90 .mu./da+" and the gloss was 130 gloss.

Comparative Example 1 AlC1z and butylpyridinium chloride at 2:1
Plating was carried out in the same manner as in Example 1, except that a plating bath formed by mixing and melting at a molar ratio of was used.

The aluminum plating film thus obtained was white and matte, and the crystals were coarse. The plating weight at this time is 2
00■/dm'', and the gloss level was 2 gloss.

Comparative Example 2 A1. Plating was carried out in the same manner as in Example 1, except that a bath was prepared by mixing and melting C1x and 1-methyl-3-butylimidazolium bromide at a molar ratio of 2=1.

The aluminum plating film thus obtained was white and matte, and the crystals were coarse. At this time, the plating weight is 2
00■/d-2, and the gloss level was 3 gloss.

The compositions and results obtained for Examples and Comparative Examples are summarized in Table 1.

Part 1 table

[Brief explanation of drawings]

Figure 1 is an electron micrograph (1,000x magnification) showing the metal structure of the surface of the plating (Example 1) obtained using the aluminum plating bath of the present invention, and Figure 2 is an electron micrograph (1,000x magnification) showing the metal structure of the surface of the plating obtained using the aluminum plating bath of the present invention. This is an electron micrograph (1,000x magnification) showing the metal structure of the surface of the plating (Comparative Example 2) obtained using the bath. The molar ratio of mixing with each other is 2:I.

Claims (2)

[Claims] (1) At least one selected from the group consisting of (A) aluminum halide, and (B) monoalkylpyridinium halide, dialkylpyridinium halide, 1-alkylimidazolium halide, and 1,3-dialkylimidazolium halide. Mn, Zn, Ni, Cu, Fe, Pb
, at least one anhydrous metal halide of Co.
An electrolytic aluminum plating bath characterized in that it contains 5 to 20 g/l. (2) 0.1 to 15 g of at least one of a carbonyl compound, an amide compound, a hydrazide compound, an acetylene alcohol compound, and a nitrogen heterocyclic compound as a brightening agent;
The electrolytic aluminum plating bath according to claim 1, wherein the electrolytic aluminum plating bath contains: /l.