JPS6238440B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for coloring and adding a striped pattern to an aluminum extrusion, and its purpose is to apply a desired color to the surface of the aluminum extrusion by electrolytic treatment, and to create a straight-grain pattern. The present invention provides a method for forming a striped pattern. That is, the method of coloring and streaking aluminum extrusions according to the present invention uses copper of 0.05 to
The first step is to anodize an extruded material made of aluminum-based alloy containing 4.0% in an oxalic acid electrolyte to form an oxide film, and the voltage is suddenly increased from the value in the first step to 5 to 35 V in the same electrolyte. The process consists of a second step in which the product treated in the first step is subjected to a constant voltage electrolytic treatment after being lowered to a temperature of 100.degree. In the first step of anodizing an extruded material made of a copper-containing aluminum-based alloy in an oxalic acid electrolyte,
If the copper content of the aluminum-based alloy is less than 0.05%, the desired coloration cannot be obtained, and if it exceeds 4.0%, the formed film will be soft and have poor corrosion resistance, so it should be limited to a range of 0.05 to 4.0%. be done. Also,
The concentration of oxalic acid is preferably 1 to 5% by weight, particularly preferably 2 to 3% by weight. Electrolysis is performed using alternating current, direct current, or a superimposed flow of alternating current and direct current, and may be constant current electrolysis or constant voltage electrolysis. In the second step of performing constant-voltage electrolysis after a sudden voltage drop, the electrolytic current does not flow immediately after the voltage drop, but begins to flow gradually after several seconds to several minutes, and after a while it returns to a steady state. reach. This phenomenon is called a recovery phenomenon. Due to this phenomenon, an anodic oxide film is formed and the base aluminum surface is uniformly roughened.As a result, the anodic oxide film formed in the first step becomes opaque due to diffuse reflection on this rough surface. Become something. here,
It is preferable that the voltage drop from the voltage in the first step to the voltage in the second step be performed rapidly.In actual operation, the energization in the first step is temporarily stopped, and then the voltage is reduced to the predetermined voltage again at the beginning of the second step. The method of applying it is often used. If the voltage in the second step is less than 5V, the above-mentioned current recovery effect will be small and the roughening of the underlying surface will not progress, and if it exceeds 35V, a film will rapidly form and the roughening of the underlying surface will disappear. 5 to 35V
limited to the range of Particularly preferred voltage is 20~
It is 25V. Further, the current in this step may be either an alternating current, a direct current, or a superimposed flow of alternating current and direct current. The processing time of the second step is not particularly limited, but
If the time is less than 5 minutes, the roughening of the underlying surface will not progress;
If the time exceeds 5 minutes, the rough surface of the base will disappear, so the time is preferably 5 to 25 minutes. Particularly preferably, the time is 10 to 20 minutes. The third step is to perform AC electrolytic treatment in an electrolytic solution containing metal salts.
In the process, the surface of the aluminum extrusion is colored and a straight-grained striped pattern is formed. The reason why this phenomenon occurs is not clear, but it is thought to be as follows. In extruded aluminum materials, a texture that is oriented in the extrusion direction always appears on the surface, but in normal anodizing or coloring treatments, patterns due to such orientation hardly appear. However, in the case of the present invention, as described above, as a result of the first and second steps, an opaque milky white color appears due to the roughening of the underlying aluminum surface. In this state, no pattern is formed at all, but due to the constant voltage electrolytic treatment in the second step, the underlying aluminum surface is roughened and a very thin film layer is formed on the underlying surface. This film layer has a structure and thickness that are significantly influenced by the orientation and crystalline direction of the underlying aluminum surface. Therefore, when such an aluminum extruded material is subjected to the third electrolytic treatment for the purpose of coloring, due to the structure and thickness of the above-mentioned film layer, the form of the metal or metal oxide deposited in the film changes. A difference occurs in the amount of deposited wood, and this difference causes the appearance of straight-grained streaks in the wood. Metal salts in the electrolyte in the third step include nitric acid, sulfuric acid, hydrochloric acid of metals such as nickel, copper, silver, cobalt, chromium, cadmium, titanium, manganese, molybdenum, calcium, magnesium, vanadium, gold, lead, and zinc. , oxalic acid, acetic acid, tartaric acid, chromic acid, phosphoric acid, etc., and representative examples thereof include nickel sulfate, copper sulfate, and silver sulfate. Further, the alternating current in the third step may have a waveform whose polarity changes alternately, and is not limited to a so-called sine wave alternating current. The voltage and energization time in the third step are 5V and less than 5 minutes, coloring and streak pattern formation will not progress, and 35V and less than 5 minutes.
Even if the heating time exceeds 25 minutes, no significant improvement in the effect is observed. Therefore, the heating time is preferably 5 to 35 V and 5 to 25 minutes. As described above, according to the present invention, it is possible to apply desired coloring to the surface of an aluminum material and to form a straight-grained striped pattern. Examples of this invention will be described below. Example 1 First step: As a test sample, a plate-shaped extruded material (75 mm
× 100 mm × 6 mm) was prepared, one side of this was medium polished and finished with a cloth. Then add this to 5
% NaOH aqueous solution at a temperature of 70° C. for 30 seconds, and then degreased with a 50% HNO ₃ aqueous solution at room temperature. The thus pretreated aluminum extruded material was mixed with 71.0 g of total acid, 19.3 g of free acid, and 10.3 g of dissolved aluminum.
In 14 oxalic acid electrolytes containing
Anodization treatment was performed using direct current at a current density of 1.5 A/dm ² for 20 minutes. Second step: After the electricity supply was once stopped, the product treated in the first step was subjected to direct current electrolysis treatment in the same electrolytic solution at a temperature of 35° C. and a voltage of 25 V for 15 minutes. Third step: Of the electrolyte solution with the composition shown in Table 2 below.
The product treated in the second step was subjected to AC electrolysis treatment using a Ni-containing solution at a voltage of 15 V for 3 minutes. Finally, the electrolytically treated product was immersed in boiling pure water for 20 minutes to seal the pores. Table 3 summarizes the processing conditions for the above 1st to 3rd steps.
The color tone and appearance thus obtained are also shown in Table 3. Examples 2 to 13 The voltage and energization time in the second step were varied, and the electrolyte in the third step was a Cu-containing solution and an Ag-containing solution in addition to the Ni-containing solution (shown in Table 2). The operation of Example 1 was repeated by changing the current application time. The processing conditions, color tone and appearance are also shown in Table 3. Comparative Example The operations of the first step and second step of Example 1 were repeated, but the third step was omitted. Table 3 also shows the treatment conditions, color tone, and appearance of this treated product.

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[Table] As can be seen from Table 3, in the case of Ni-containing liquids and Cu-containing liquids, the treated products exhibit a pale silver gray to dark gray color tone, and in the case of Ag-containing liquids,
It had a beige to dark gray-yellow color tone. In addition, a straight grain pattern appeared in each of the examples.

Claims (1)

[Claims] 1. A first step in which an extruded material made of aluminum-based alloy containing 0.05 to 4.0% copper is anodized in an oxalic acid electrolyte to form an oxide film, and a voltage is changed from the value in the first step in the same electrolyte. A second step in which the product treated in the first step is subjected to constant voltage electrolysis after the voltage is suddenly lowered to 5 to 35V, and a third step in which the product treated in the second step is subjected to AC electrolysis in an electrolytic solution containing a metal salt. A method for coloring and adding streaks to aluminum extrusions.