JPS6360290A - Blackening solution for aluminum or its alloy - Google Patents

Abstract

PURPOSE:To obtain a blackening soln. forming a uniform black film on Al at a low temp. by preparing a soln. contg. specified amounts of Zn ions and Sb ions and adjusted to a specified pH. CONSTITUTION:Zinc oxide and diantimony trioxide are dissolved in water so that the resulting aq. soln. contains >=1g/l, preferably 4-20g/l Zn ions and 0.05-5g/l, preferably 0.2-2g/l Sb ions and the soln. is adjusted to >=12pH with NaOH or the like to prepare a blackening soln. for Al or Al alloys. The weight ratio of Zn ions/Sb ions in the soln. is 1/2-300/1. Al or an Al alloy pretreated by cleaning or other method is immersed in the blackening soln. at 20-45 deg.C for about 1-3min. By this one-stage treatment, a stable black film having a uniform color tone is formed with tight adhesion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a treatment solution for forming a black colored film on aluminum or an aluminum alloy. product parts, optical equipment parts,
The present invention relates to a treatment liquid used to form a black film on aluminum or aluminum alloys used as electronic device parts by chemical substitution.

[Conventional technology]

Japanese Patent Publication No. 44-8338 describes a method of forming a blackened galvanized film on the surface of aluminum (including aluminum alloys, the same shall apply hereinafter) using a chemical displacement galvanizing method.
The publication discloses a method in which chemical displacement zinc plating is performed as a first stage treatment, followed by immersion in a weakly acidic heated aqueous solution containing a molybdate and a fluoride as a second stage treatment.

Furthermore, as a method for improving the appearance of the blackened coating obtained by the method of Japanese Patent Publication No. 44-8338 and facilitating wastewater treatment, the method of Japanese Patent Publication No. 55-51030 discloses calcium ions, zinc ions, nitrite ion,
All methods are proposed in which aluminum is immersed in a -9 to 12 treatment solution containing silicate ions. The temperature of the treatment liquid in this method is 80℃ or boiling point, and the immersion time is 1
It is explained that the duration is 0 to 40 minutes. In this method, the processing temperature is set at 80°C or higher, in order to prevent the rate of coloring from decreasing if the temperature of the processing liquid is lower than 80°C.

As a blackening method that does not rely on the zinc substitution method, there is a method in which aluminum to be treated is immersed in an aqueous solution containing sulfuric acid, sodium chromate, hydrochloric acid, potassium permanganate, and a surfactant by heating.

[Problem that the invention seeks to solve]

As mentioned above, conventional aluminum blackening treatments require high temperatures and long periods of time to achieve the desired coloring effect. Therefore, there were problems such as a large consumption of heating energy and an increased risk of the processing liquid coming into contact with the operator.

Furthermore, conventional aluminum blackening treatment is a two-stage treatment.

Therefore, there has been a strong desire for a low-temperature aluminum blackening treatment solution that can form a film having a finished appearance equal to or better than that of conventional treatment solutions in a single step at a film formation rate equal to or higher than that of conventional treatment solutions.

(c) Means and operation for solving the problems] The present invention has been made to solve the above problems, and is made by immersing aluminum in an alkaline aqueous solution containing zinc and antimony. It is an object of the present invention to provide a substitution type blackening treatment liquid for aluminum that can form a black film on the surface.

Therefore, the treatment liquid according to the present invention has zinc ion 111/
1 or more and antimony ion 0.05 to 5 g/no, and has a pH of 12 or more. On the surface of aluminum immersed in the treatment solution according to the present invention, dissolution of aluminum in the alkaline aqueous solution first begins, and then Zn and sb ions dissolved in the treatment solution are reduced and co-exist on the surface of aluminum. analyze. As a result, a coating having a black appearance is formed. Such film formation proceeds at low temperatures (20 to 45°C).

Hereinafter, the entire composition of the treatment liquid according to the present invention will be explained in detail.

In order to include zinc in the treatment solution, zinc oxide, zinc carbonate, zinc hydroxide, zinc nitrate, etc. are added to the solution.

Dissolve. In addition to these, zinc sulfate, zinc chloride, etc. can also be used. In short, a method may be adopted in which zinc ions are present in an aqueous solution. The concentration of zinc in the treatment solution is 1
1/1 or more, especially 4-20I/! A range of is preferred. When the zinc concentration is lower than 1 g/l, no galvanized film is formed. There is no particular upper limit to the zinc concentration, and zinc may be added to the aqueous solution up to the solubility limit. This limit makes it difficult to dissolve more than 309/l of zinc valve even if the voice adjustment described below is performed. That is, 30E/1 is generally the solubility limit for zinc.

Preferred methods for incorporating antimony include adding and dissolving compounds such as antimony triate, antimonyl potassium tartrate, and antimonyl sodium tartrate, but are not limited to these methods. All methods of making it exist should be adopted. The concentration of antimony in the treatment solution ranges from 0.05 to 5 g/l. If the antimony concentration is as low as 0.051/l, the plated branch film will have almost the same color as the galvanized film, and no black film will be formed. On the other hand, if the antimony concentration exceeds 5 Ells, the adhesion of the coating decreases, which is not preferable.

A more preferable concentration of antimony is 0.2 to 2 E/1.

The following table shows the results of an experiment in which film formation and properties were investigated by varying the concentrations of zinc and antimony, and the preferred ratio of these concentrations will be explained. In this experiment, aluminum (
Standard 52S) is degreased and washed with water.

After pickling and water washing, immerse in a -14 aqueous solution at 25°C for 2 minutes,
It was then washed with water and dried. Zinc and antimony were added as zinc oxide and antimony trioxide, respectively.

The rest B below Table 1 Note: The meanings of the symbols in Table 2 are as follows.

Q Strong blackness
t ratio f) E 1/2 (Zn i, tyai=1.P
/l: Sb ion concentration = 21713) or the zinc ion/antimony ion weight ratio is 3.
It can be seen that when the ratio exceeds 00/1 (Zn ion concentration = 15.9/): Sb ion concentration = 0.05 g/l), the blackness of the coating decreases. When the weight ratio of zinc ions/antimony ions is in the range of 2/1 to 100/1, the degree of blackness is further increased.

- of the treatment liquid of the present invention is 12 or more. If the pH is less than 12, the etching of aluminum becomes weak, resulting in insufficient formation of a black film. When the pH of the treatment liquid is 13 or more,
Furthermore, since the etching power is increased, a black film can be formed in a short time.

Since the zinc-added dissolving compound is acidic, neutral or weakly alkaline, it is necessary to add an alkaline compound to adjust the pH and dissolve the zinc compound.

As such an alkali compound, sodium hydroxide or potassium hydroxide is preferred because it is easily available, and in addition to these, sodium carbonate, trisodium phosphate, etc. can also be used.

To perform blackening treatment with the above-mentioned treatment liquid,
After sufficiently cleaning the aluminum and removing the oxide film by a known method described in Japanese Patent Publication No. 8338 or Japanese Patent Publication No. 55-51030, the aluminum is immersed in the above treatment liquid.

If the dipping temperature is too low, it will take a long time to form a black film, while if the dipping temperature is too high, the resulting film will have poor adhesion, which can be dangerous for work.
It is appropriate to carry out the reaction at 45°C. The immersion time varies depending on the temperature and composition of the treatment liquid and the material of the object to be treated, but is generally 1 to 3 minutes.

After immersion in the treatment solution, a blackened aluminum article is obtained by washing with water and drying.

In order to further improve the blackening treatment of the present invention and make it an industrially desirable surface treatment method, the following treatment liquid components can be adjusted.

In order to moderately suppress the rate of reduction and precipitation of zinc from the plating solution and improve the adhesion of the film, the plating solution should preferably contain 5 to 15%! Add //l nitrate. As the nitrate, sodium nitrate, potassium nitrate, or zinc nitrate may be used within a range that maintains the zinc content of the plating solution at the above concentration. For the same purpose as nitrates, nitrites such as sodium nitrite, preferably 0.5 to 5j! /1. You can also add

If the same processing solution is not replenished with the 'liT solution and the number of processing increases, the aging of the processing solution will be accelerated. In order to suppress aging of the processing solution, a chelating agent such as an oxycargenate salt such as sodium citrate or sodium tartrate or a sodium salt or potassium salt of EDTA is added to the processing solution.
/l can also be added.

Furthermore, in order to improve the adhesion of the film formed on aluminum with the plating solution of the present invention, a surfactant of, for example, 0.0
It is also possible to add 5 to 11/l.

Although the surfactant is not limited to a particular type, nonionic surfactants are preferred from the viewpoint of low foaming properties.

〔Effect of the invention〕

According to the present invention, it is possible to form a uniform black wave gX with sufficiently strong adhesion and a uniform black color that can compete with conventional coatings in terms of color tone at a low temperature. This saves energy, reduces the risk of work, and makes it possible to industrially mass-produce products with stable color tones.

Furthermore, since the treatment liquid is a one-component type, the process can be shortened compared to a two-stage treatment.

Hereinafter, the present invention will be further explained with reference to Examples.

Treatment material Nialuminum plate Material 2S aluminum alloy plate Material 528 Treatment process 1) Alkaline cleaning Perco Cleaner N372 (Nippon Parkerizing ■'B) IU/1.60℃, 1 minute spray 2) Water washing 3) Pickling 10% HC1, room temperature , 15 seconds immersion 4)
Washing with water 5) Displacement plating treatment Immersion at 25°C for 2 minutes in the case of Example 1 and 3 minutes in the case of Example 2 Table 2 Plating treatment solution 6) Washing with water 7) Drying Approximately 80°C, 5 minutes As a comparative example, Blackening treatment described in No. 8338 (however, the temperature of the treatment liquid contained in the Mo fit machine is 4
0°C).

Comparative example treated material Same treatment steps as the example 1) Alkaline cleaning Same as the example 2) Water washing Same as the example 3) Pickling Same as the example 4) Water washing Same as the example 5) ZnIt replacement plating 3 Aluminum plate (Material) 28) i An aluminum alloy plate (material 52S) was immersed in the treatment solution of Comparative Example 1 and the treatment solution of Comparative Example 2 at 35° C. for 25 seconds.

6) Washing with water 7) Black treatment (NH4) 6MO, 024-4H20151/13NH
4F 49/1 Wednesday
The remainder was immersed in the above treatment solution (40° C.) for 8 minutes (see Example 1 of tVj Publication No. 44-8338).

8) Washing with water Same as the example 9) Drying Same test method as the example 1) Appearance 0... Uniform and calm black Δ... Black color unevenness 2) Adhesive coating with a dry cloth The removability of the film when rubbed strongly was investigated.

○...The film is not removed at all. Δ... Some coating is removed Table 4

Claims (1)

[Claims] 1. Zinc ion 1 g/l or more and antimony ion 0.0
5 to 5 g/l and a pH of 12 or more. 2. The blackening treatment solution for aluminum or aluminum alloy according to claim 1, wherein the weight ratio of zinc ions/antimony ions in the aqueous solution is in the range of 1/2 to 300/1.