JPH0421757B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention uniformly colors an anodic oxide film of aluminum or an aluminum alloy to a gray tone overlaid with tones based on various metal salts. It is about the method.

(Prior art) As a method of obtaining a colored film by the so-called current recovery phenomenon, methods described in Japanese Patent Application Laid-Open No. 117844/1984 and the magazine "Metal Surface Technology" 29, No. 7355-360 (1978) are known. ing. In this method, a transparent film is formed by anodizing in an acidic bath such as sulfuric acid or phosphoric acid or an alkaline bath such as sodium hydroxide or sodium phosphate, and then anodization is performed using the method shown in Figure 1. Oxidation treatment voltage V1 is set once to 0~
The voltage is lowered to 3V, and then a voltage V2 lower than the previous voltage is applied again. At that time, as shown in FIG. 2, the current I1 during anodizing treatment is once
After decreasing to around 0, it gradually begins to flow (I
2). Thus, when the current begins to recover, the previously formed transparent coating, ie the coating schematically shown in FIG. 3-1, becomes the coating schematically shown in FIG. 3-2. In Figure 3-1, there is a porous alumite layer 2 on the surface of an aluminum base 1, and the layer 2 has a large number of holes 3 that open on the surface side, and the bottom of the holes 3 and the base 1 are connected to each other. There is a barrier layer 4 between them. In the film shown in Figure 3-2, the hole 3 in the film
Many new pores with smaller diameters are generated at the bottom of the pores 3, and the pores 3 have a so-called branched structure. Therefore, in the film shown in FIG. 3-2, light is diffusely reflected and absorbed, resulting in color development. That is, the film shown in FIG. 3-2 is a colored film having a gray tone.

(Problems to be Solved by the Invention) The colored film obtained by the above method had a drawback of non-uniform color tone. This is due to the following reasons. That is, when the voltage for obtaining the current recovery phenomenon is low and the flat plate material 7 is processed using the electrolytic frame 5 and the electrolytic rod 6 as shown in FIGS. 4-1 and 4-2, the edges This is because there is a difference in the voltages applied between the central portion 7a and the central portion 7b, resulting in different current recovery speeds and different degrees of color development.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrolytic coloring method that can uniformly color an anodic oxide film of aluminum or an aluminum alloy to a gray tone with tones based on various metal salts superimposed. .

(Means for Solving the Problems) The method for electrolytically coloring aluminum and aluminum alloys of the present invention involves performing anodization treatment on aluminum or aluminum alloy materials in an electrolytic bath to form an anodized film, and then The oxide film is subjected to a current recovery treatment in which the voltage of the anodizing treatment is lowered once in the electrolytic bath and then increased to apply a voltage lower than the voltage of the anodizing treatment to give the anodized film a gray color. This coloring film has a color tone of Sn, Ni, Co, Fe, Cu, Se,
metal salts including sulfates, acetates, tartrates or sulfamates of Ag, Au, V, Mn; boric acid;
A direct current or pulse voltage with positive polarity is applied to an electrolytic coloring solution containing a barrier type film forming agent consisting of an acid containing tartaric acid, citric acid, sulfamic acid, sulfosalicylic acid, or cresol sulfonic acid, or an ammonium salt thereof. Then, apply a direct current or pulse voltage, or an alternating current voltage with polar positive as negative, to perform an electrolytic coloring treatment to form the colored film.
It is characterized in that it is uniformly colored to a color tone in which a color tone based on the metal salt is superimposed on the gray color tone.

The most characteristic feature of the method of the present invention is that it obtains a colored film with a gray tone by current recovery treatment, and that it is first coated in an electrolytic coloring solution containing various metal salts and a barrier type film forming agent. Applying a direct current or pulse voltage with positive polarity.

Metal salts are colored by precipitating metals, metal oxides, metal hydrates, or mixtures thereof into the micropores in the oxide film that forms on the surface of the aluminum or aluminum alloy of one electrode during electrolysis. Examples of metal salts include Sn, Ni,
Examples include sulfates, acetates, tartrates, and sulfamates of Co, Fe, Cu, Se, Ag, Au, V, Mn, and the like.

Barrier-type film-forming agents have the role of changing the barrier layer thickness when a direct current or pulsed positive voltage is applied, and include boric acid, tartaric acid, citric acid, sulfamic acid, sulfosalicylic acid, or cresolsulfonic acid. or their ammonium salts.

The voltage is applied in the electrolytic coloring solution by first applying a direct current or pulse voltage with positive polarity, and then applying a direct current or pulse voltage with negative polarity, or an alternating current voltage. . When applying a positive voltage, the voltage is preferably 3V to 30V, the current density is preferably 0.01A/ ^dm2 to 1.0A/ ^dm2 , and the current application time is preferably 2 seconds to 60 seconds. In applying a negative voltage, the voltage is preferably 10V to 30V, the current density is preferably 0.1A/ ^dm2 to 1.0A/ ^dm2 ,
By varying the negative voltage or AC voltage and the current application time while taking into account the positive voltage and current application time, uniformly colored films with various densities can be obtained.

After the electrolytic coloring process, the film is preferably subjected to a sealing treatment using boiled water, steam, etc., or painted as necessary.

(Function) When the anodic oxide film is subjected to current recovery treatment, the anodic oxide film becomes a gray colored film.

Application of a positive voltage makes the coloring uniform, and this is due to the following reasons. Fifth
As schematically shown in the figure, a workpiece 10 made of aluminum or an aluminum alloy is placed in an electrolytic coloring bath 8 facing a counter electrode 9 made of stainless steel or the like.
Suppose that The work 10 has a recess 11. When a voltage is applied between the workpiece 10 and the counter electrode 9 with the workpiece 10 being positive, the barrier layer of the colored film is modified by the barrier type film forming agent contained in the electrolytic coloring liquid. The thickness of this barrier layer increases or decreases depending on the correlation between the applied voltage and the thickness depending on the type of forming agent (for example, 14 angstroms/V in the case of boric acid). , and the bottom 13 of the furthest recess 11, the voltage distribution creates a thicker barrier layer at the end 12 than at the bottom 13.

In this way, the barrier layer thickness is thicker in the portion closer to the counter electrode and thinner in the portion farther away, resulting in a difference in electrical resistance. Therefore, when applying a negative voltage or an alternating current voltage to the workpiece 10 side, the current flowing is controlled, and the current flows more easily in the bottom part 13 far from the counter electrode than in the end part 12 near the counter electrode. As a result, metal deposition becomes uniform.

Therefore, the gray-colored film is uniformly colored based on various precipitated metals, and the anodic oxide film has a uniform color tone in which tones based on various metal salts are superimposed on the gray color. It will be colored.

This is the same even when the workpiece 10 is a flat plate, and between the end portion 7a and the center portion 7b of the processing material 7 in Fig. 4-1, the current tends to concentrate toward the end portion 7a, and As a result, the coloring becomes uniform.

(Example) Next, an example according to the present invention and a comparative example according to a conventional method will be shown.

Comparative Example: Method using so-called current recovery phenomenon A flat plate (2000 mm x 4000 mm) of A1100P-H24 material was hung as shown in Figures 4-1 and 4-2. After normal pretreatment, sulfuric acid 150
g/, anodizing treatment was carried out at 22°C. The voltage at that time was V1=15V according to FIG. 1, and the current was I1=2000A according to FIG. After processing for 30 minutes and setting the voltage to 0 once, V2 in FIG. 1 was set to 5V and electricity was applied for 10 minutes. The current at that time was 300A as I2 in Figure 2. As a result, in FIG. 4-1, the end 7a of the treated material 7
was gray in color, and the center portion 7b of the treated material was a slightly lighter gray color. In other words, an unsuitable colored film was formed on the treated material 7.

Example 1 The same treatment as in Comparative Example was carried out to obtain a non-uniform colored film, which was then washed with water, using 100 g of nickel sulfate and 40 g of boric acid as the electrolytic coloring solution.
In Figure 6, E1=20V, E2=16V, t1=4
As a result of applying electricity for seconds, t2 = 2 seconds, t3 = 10 seconds, and t4 = 60 seconds, the end 7 of the treated material is shown in Figure 4-1.
A and the central portion 7b of the treated material both had a yellowish gray color.

In addition, in FIG. 6, E1 is a positive polarity voltage,
E2 is a voltage of negative polarity, t1 and t3 are boosting times of voltages E1 and E2, respectively, and t2 and t4 are holding times of voltages E1 and E2, respectively.

Example 2 An extruded section of A6063S-T5 (having a concave portion as shown in FIG. 5) was hung as shown in FIG. 7. In Fig. 7, 14 is an electrolytic frame, 14' is an electrolytic rod,
15 is the treated material, 15a is the upper part of the treated material 15, 15
b is the center part, and 15c is the lower part. Note that FIG. 8 is a side view of FIG. 7. After carrying out the usual pretreatment, anodizing treatment was carried out at 20° C. with 100 g of sulfuric acid and 50 g of phosphoric acid, followed by current recovery treatment. The conditions at that time were V1 = 18V (current application time: 30 minutes), V2 = 3V (current application time: 5 minutes), I1 = 3000A, and I2 = 300A, as shown in Figs. 1 and 2. As a result, the color tone at locations 15a to 15c in FIG.
5a=15c had a gray color, and 15b had a light gray color. Furthermore, the concave portion of the profile was entirely light gray in color.

Next, in the same electrolytic coloring solution as in Example 1, the ninth
In the figure, DC voltage E = 15V, AC voltage (effective value) V = 12V, t1 = 10 seconds, t2 = 2 seconds, t3
As a result of energizing with = 10 seconds and t4 = 30 seconds, the color tone of the treated material was a uniform reddish gray in both 15a to 15c and the concave portions of the profile. In addition, in FIG. 9, t1 is the boosting time of the voltage E,
t2 is the holding time of the voltage E, t3 is the boosting time of the voltage V, and t4 is the holding time of the voltage V.

Example 3 A flat plate (3000 mm x 4000 mm) made of A1200P-H24 material was hung as shown in Figure 4-1. After normal pretreatment, trisodium phosphate 50g/,
After anodizing at 20°C, a current recovery process was performed. The conditions at that time are V1 = 20V (energizing time 30 minutes), V2 = 5V according to Figures 1 and 2.
(Electrification time: 7 minutes), I1 = 4000A, I2 = 500A. As a result, the color tone of the treated material was 7a: brownish gray, 7b: yellowish gray. Next, as an electrolytic coloring solution, 30 g of tin acetate/
Boric acid 30g/, triethanolamine 10g/
In Fig. 10, E1=14V, E2=
12V, t1=5 seconds, t2=5 seconds, t3=1 second, t4=5 seconds,
Electricity was applied with t5=1 second and n=60 times. the result,
The color tone of the treated materials became uniform dark gray in both cases 7a and 7b. In addition, in Fig. 10, E
1 is a positive polarity voltage, E2 is a negative polarity voltage, t
1 and t3 are boosting times, t2 and t4 are voltage holding times, t5 is a rest time, and n is the number of repetitions.

(Effects of the Invention) As described above, according to the present invention, it is possible to uniformly color an anodic oxide film of aluminum or an aluminum alloy to a tone in which tones based on various metal salts are superimposed on a gray tone. . Moreover, the electrolytic coloring method according to the present invention is easy to employ industrially and is suitable for producing products with uniform quality.

[Brief explanation of drawings]

Figure 1 is a graph showing the voltage application method in the current recovery process, Figure 2 is a graph showing the change in current over time in the current recovery process, Figure 3-1 is a schematic diagram of a normal anodic oxide film, and Figure 3-2 is a graph showing the voltage application method in the current recovery process. The figure is a schematic diagram of an anodized film during current recovery treatment, Figure 4-1 is a front view schematically showing an example of a method of suspending treated materials in an anodizing treatment factory, and Figure 4-2 is the same as that shown in Figure 4-1. A side view, FIG. 5 is a schematic diagram of an electrolytic coloring device, FIG. 6 is a graph showing an example of a voltage application method in electrolytic coloring, and FIG. 7 is a schematic diagram of another example of a method for suspending treated materials in an anodizing treatment factory. 8 is a side view of FIG. 7, and FIGS. 9 and 10 are graphs showing other examples of voltage application methods in electrolytic coloring.

Claims (1)

[Claims] 1 Aluminum or aluminum alloy material is anodized in an electrolytic bath to form an anodized film, and the voltage of the anodic oxidation is lowered once in the electrolytic bath and then increased. Then, a current recovery treatment is applied to apply a voltage lower than the voltage of the anodic oxidation treatment to make the anodic oxide film a gray colored film. ,Se,Ag,Au,
A barrier consisting of a metal salt containing V, Mn sulfate, acetate, tartrate or sulfamate, and an acid or ammonium salt thereof including boric acid, tartaric acid, citric acid, sulfamic acid, sulfosalicylic acid or cresol sulfonic acid. In an electrolytic coloring solution containing a mold film forming agent, apply a direct current or pulsed voltage with positive polarity, and then apply a direct current or pulsed voltage or alternating current voltage with negative polarity to electrolytically color the liquid. A method for electrolytic coloring of aluminum and aluminum alloys, characterized in that the colored film is uniformly colored in a color tone in which a color tone based on the metal salt is superimposed on the gray color tone.