JPH0457760B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for electrolytically coloring an anodic oxide film of aluminum or an aluminum alloy, and in particular aims to improve the color uniformity of the colored film and the productivity of the coloring process. be. [Prior Art] Many methods have been proposed and implemented in the past, in which aluminum or aluminum alloys are anodized and then electrolytically colored using various acidic baths as electrolytic baths. For example, Japanese Patent Publication No. 62-61120 discloses that the main component is copper pyrophosphate, contains an additive consisting of metal salts of nickel sulfate, magnesium sulfate, zinc sulfate, or a combination thereof; Inorganic salts such as oxalic acid, tartaric acid,
Contains a PH regulator made of organic acids such as citric acid or a combination thereof;
A coloring method in which the pH is adjusted to 2 or less is disclosed. In addition, in Japanese Patent Publication No. 63-28999, copper pyrophosphate 12 to 15 g/l and nickel sulfate 45 to
50g/l, silver nitrate 0.5~0.75g/l, sulfuric acid 10~15g/l
A coloring method has been disclosed in which a material containing 1 is used, and after applying a DC voltage with the anodized film as positive as a current application method, AC electrolytic coloring is applied. [Problems to be Solved by the Invention] By employing the above coloring method, it is possible to obtain a colored film in the red to reddish-purple range with beautiful color tone and excellent durability. When an aluminum or aluminum alloy profile 20 is arranged on two energized rods 21 and colored, the color tone is not uniform and, as is clear from the measurement results (Fig. 5) described later, it becomes red. It had to be energized for quite a long time to get the purple color. Therefore, as shown in FIG. 6A, the shapes 20 must be arranged in a series and colored, which requires a large number of processing steps and increases costs. Furthermore, the coloring bath employed in the above-mentioned Japanese Patent Publication No. 63-28999 contains silver to improve the freshness of the color tone, and this also increases the cost of the bath. The present invention uses an electrolytic coloring bath using a mixed solution of highly concentrated copper pyrophosphate, nickel sulfate, and sulfuric acid, and then applies a DC voltage using the anodic oxide film as an anode, and then applies an AC voltage to color it. The aim is to solve the above problems. [Means for Solving the Problems] In order to solve the above problems, the present invention provides
A mixed solution of 50 g/l of copper pyrophosphate, 75 to 150 g/l of nickel sulfate, and 20 to 50 g/l of sulfuric acid is used as an electrolytic coloring bath to electrolytically color an anodic oxide film of aluminum or aluminum alloy. It is characterized by applying a direct current voltage to the film as an anode, and then applying an alternating current voltage to color the film. [Example] FIG. 1 is a perspective view showing a state in which an A6063S-T5 extruded section 10 is placed (racked) on a frame 11. The frame 11 includes an aluminum electrolytic frame 12 with a length l of 7000 mm and a height h of 2500 mm, for example, and two pairs of aluminum current-carrying rods 13 extending downward from the lower surface of the aluminum electrolytic frame 12. Each energizing rod 13 faces the electrolytic frame 12 in the longitudinal direction, and seven extruded shapes 10 are fixed in parallel to each energizing rod 13, one pair each. Each energizing rod 1
The interval L between the three is set to 250 mm, for example. In FIG. 1, a to r are the color measurement positions of each section 10 (n, o, q, r are hidden), which will be described later in FIG. 5, and a to j are the surfaces facing the opposite electrode. , j to r are on the back side. As shown in FIG. 2, each section 10 has a rectangular cross section and is formed into a channel shape that opens up and down. Also, the width W is, for example, 150 mm, and the thickness T is, for example,
Each is set to 50mm. FIG. 3 is a sectional view showing a state in which the current-carrying rod 13 of the frame 11 is immersed in a coloring tank 15 to which the present invention can be applied. For example, the coloring tank 15 has a width of 800 mm, a height of 2500 mm,
Each length is set to 6500mm. A counter electrode carbon 16 is fixed to the inner surface of this coloring tank 15. Next, the process will be explained. The profile 10 described in FIGS. 1 and 2 was racked as shown and pretreated in a conventional manner. Thereafter, it was anodized in a 17% H ₂ SO ₄ bath to obtain a film with a thickness of 9 to 13 μm, and then washed with water. Next, the frame 11 is placed in the coloring tank 15 shown in FIG.
The current-carrying rod 13 was immersed. The coloring bath 16 had the composition shown in Table 1. The coloring process was carried out using the voltage waveform shown in FIG. 4 and the conditions of V ⁺ , Vn, t ⁺ and tn shown in Table 1.

[Table] As a result, under all conditions, the color was reddish-purple. In order to examine the uniformity of this color, L, a, and b values were determined using a colorimeter, and measurements were taken at 18 points a to r shown in FIG. The color difference (△E) from other points is calculated by the following formula, assuming the L, a, and b values at each point e as Lo, ao, and bo: △E=[(Lo−L) ² +(ao−a) ² +( bo-b) ² ] ¹
Calculated using ₂ . As a result, the results shown in FIG. 5 were obtained. Note that No. 1 in Table 1 is the conventional composition and AC energization method (Japanese Patent Publication No. 62-61120), No. 2 is the conventional method described above, with only the energization method set to the same method as the present invention. No. 3 is a combination of the coloring bath of the present invention and the above-mentioned conventional AC current supply method, and No. 4 is a method of the present invention. [Measurement Results] When method No. 1 was adopted, the throwing power was the worst, and the color did not turn reddish-purple unless the energization time was set considerably long. When method No. 2 is adopted, the throwing power is improved and the energization time is shorter than that of No. 1, but mass production is still difficult. When method No. 3 is adopted, the color difference is considerably reduced and the energization time is shortened, so production is possible, but it cannot be said that there has been a dramatic improvement. On the other hand, when method No. 4 is adopted, the color difference becomes extremely small and coloring is completed in a short time. From this result, it was confirmed that extremely good productivity could be obtained by employing the present invention. [Effect of the invention] As explained above, according to the present invention, 20 to
A mixed solution of 50 g/l of copper pyrophosphate, 75 to 150 g/l of nickel sulfate, and 20 to 50 g/l of sulfuric acid is used as an electrolytic coloring bath to electrolytically color an anodic oxide film of aluminum or aluminum alloy. We use a method of applying DC voltage to the film as an anode and then applying AC voltage to color it.
As explained in FIG. 1, even if the sections 10 are arranged in two rows and colored, a reddish-purple colored film with excellent throwing power can be obtained, and the current application time can be shortened. be able to. Therefore, by employing the present invention, transparent lacquer-like coatings with excellent durability can be mass-produced in a short time and at low cost. Moreover, by employing the present invention, it is no longer necessary to include silver in the coloring bath, so the cost of the bath can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a frame showing a state in which the extruded profile is racked in the process of the present invention, Fig. 2 is a schematic cross-sectional view of the extruded profile in Fig. 1, and Fig. 3 is a cross-sectional view of the coloring tank of the present invention. 4 is a voltage waveform diagram showing the energization method, FIG. 5 is a distribution diagram showing the measurement results of color difference, and FIG. 6 is a schematic cross-sectional diagram showing the arrangement of extruded shapes.