JPH0244915B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a method for electrolytically coloring aluminum materials to provide colored aluminum materials used for construction materials such as housing sashes and exteriors, that is, after anodizing aluminum materials, metal salts are applied to the aluminum materials. This invention relates to an electrolytic coloring method in which a secondary electrolytic treatment is performed in an electrolytic solution containing aluminum to produce a unique color tone on the surface of an aluminum material. In this specification, the term aluminum is used to include its alloys. Conventional Techniques Conventionally, methods for electrolytically coloring aluminum materials include the alternating current electrolytic coloring method (Asada method) in which alternating current electrolysis is carried out in an electrolytic solution containing metal salts, boric acid, and ammonium salts, and the electrolytic coloring method containing metal salts and boric acid. Direct current electrolytic coloring method (Sumika method), which performs direct current electrolysis in a liquid using an aluminum material as a cathode, or, more recently, the Asada method, which uses alternating positive and negative electrolytes in an electrolytic solution containing metal salts, boric acid, and ammonium salts. A so-called rectangular wave inverter method is known in which electrolytic treatment is performed by repeatedly applying a rectangular wave voltage. Problems to be Solved by the Invention However, with the AC electrolytic coloring method, coloring takes a long time, and when the aluminum material is an extruded shape with a complicated shape, the coloring of the convex parts of the material is dark and the coloring of the concave parts is dark. The disadvantages were that the coloring became lighter, and in the case of long aluminum materials, the coloring became darker at the ends. On the other hand, in the case of the direct current electrolytic coloring method, although coloring can be achieved in a relatively short time, it is sensitive to alkali metal ions in the electrolyte, making solution management troublesome. There was a drawback that spalling due to destruction was likely to occur. On the other hand, with the square wave inverter method, although relatively good throwing power can be obtained, there are limitations in further improving the throwing power, it takes time to color the film, and it is also sensitive to alkali metal ions. The problem was that spalling was more likely to occur. This invention solves the above-mentioned drawbacks of the conventional technology, and enables electrolytic coloring of aluminum materials that further improves uniform coloring (throwing ability), achieves deep coloring in a short time, and prevents spalling. The purpose is to provide a method. Means for Solving the Problems In order to achieve the above object, the present invention basically adopts a square wave inverter method, and also solves the problem that the limit of improving the throwing power in the conventional square wave inverter method is Considering that this is due to the fact that it contains ammonium salt as a PH regulator, the basic premise is to use a square wave inverter method using an electrolyte that does not contain ammonium salt. . And under this premise,
In order to further improve the throwing power and prevent spalling, the inventor repeatedly conducted various experiments and research, and as a result, determined the absolute values of the positive and negative peak voltages, the energization time of the positive and negative voltages, and the peak voltage and rectangular wave frequency. It was discovered that good results could be obtained by establishing a certain relationship, and this led to the completion of this invention. That is, this invention is an aluminum material subjected to a secondary electrolytic treatment by applying a rectangular wave voltage that alternates between positive and negative in an electrolytic bath consisting essentially of an aqueous solution of a metal salt and boric acid to an aluminum material that has been subjected to an anodizing treatment. In the electrolytic coloring method for materials, the absolute values of the positive and negative peak voltages of the rectangular wave and the energization times of the positive and negative voltages are respectively set equal, and the absolute values of the positive and negative peak voltages and the rectangular wave frequency are set as shown in the attached drawing. , point A (1Hz, 15V), point B (5Hz, 17V), point C (10Hz,
19V), point D (50Hz, 27V), point E (60Hz, 29V), point F (60Hz, 33V), point G (50Hz, 31V), point H (10Hz,
The gist of this paper is a method for electrolytically coloring aluminum material, which is characterized in that the electrolytic treatment is performed by setting the value within the range surrounded by point I (5 Hz, 21 V), point I (5 Hz, 21 V), and point J (1 Hz, 19 V). The treatment solution, electrolytic conditions, etc. for the anodizing treatment applied to the aluminum material before the electrolytic treatment are not particularly limited, but
Generally, treatment is performed using a sulfuric acid method. The electrolytic solution used in the secondary electrolytic coloring treatment is essentially made of Ni, Cu, or
It is a solution consisting of metal salts such as Se and Sn and boric acid, and does not contain ammonium salts such as ammonium sulfate as a PH regulator. This is because there is a limit to the improvement in throwing power with an electrolytic solution containing ammonium salt. In the above, "substantially"
and other ingredients that do not affect the coloring performance, e.g.
The purpose is to allow the inclusion of Na ⁺ , K ⁺ , etc. To give an example of an electrolytic solution, for example, when using Ni salt, 20 to 150 g of nickel sulfate and 10 to 150 g of boric acid are used.
An electrolytic solution consisting of 50 g/aqueous solution can be suitably used. When such Ni salt is used, the aluminum material has a bronze color tone. The voltage applied in the secondary electrolytic treatment is a rectangular wave voltage that alternates between positive and negative, as shown in FIG. In addition, in this invention, in order to achieve the intended purpose, the absolute value Va of the positive peak voltage of the rectangular wave and the absolute value Vc of the negative peak voltage (hereinafter, the absolute value of the peak voltage is simply referred to as the peak voltage value). ) must be equal, and the positive voltage conduction time ta and the negative voltage conduction time tc must be equal.
Furthermore, in order to obtain good uniform electrodeposition through short-time processing, the positive and negative peak voltages Va and Vc and the square wave frequency are plotted in the graph of Fig. 2 under the conditions of Va = Vc and ta = tc. It is required to set the value within the shaded area. In other words, the graph shown in Figure 2 is a semi-logarithmic graph in which the horizontal axis represents the frequency of the rectangular wave on a logarithmic scale, while the vertical axis represents the peak voltage value on a normal linear scale. , 1 Hz, 5 Hz, 10 Hz, 50 Hz, and 60 Hz. Here, the coordinates of each point are shown as point A (1Hz,
15V), point B (5Hz, 17V), point C (10Hz, 19V), point D (50Hz, 27V), point E (60Hz, 29V), point F (60Hz,
33V), point G (50Hz, 31V), point H (10Hz, 23V), point I (5Hz, 21V), and point J (1Hz, 19V). As is clear from Figure 2, the range of peak voltage values appropriate for uniform coloring and short-time processing changes depending on the frequency of the rectangular wave voltage that is the electrolytic treatment voltage, and as the frequency increases, the necessary peak voltage value also increases. Become. The reason why the appropriate peak voltage value changes depending on the frequency is considered as follows. That is, in the secondary electrolytic coloring treatment according to the present invention, the cathode plays the role of reducing and precipitating the metal, and the anode plays the role of repairing and forming the barrier layer in the anodized film on the surface of the aluminum material that has been destroyed on the cathode side. However, it is thought that the density and layer thickness of this repaired and regenerated barrier layer are responsible for the uniform coloring properties. The density of the regenerated barrier layer depends on the current application time ta and tc of positive and negative voltages, and the layer becomes denser when the current application time is long, that is, when the frequency is low. On the other hand, the layer thickness of the barrier layer is the peak voltage value Va,
Depending on Vc, the higher the peak voltage value, the thicker the layer thickness. Therefore, when the frequency is low, the barrier layer becomes dense and stable even if the layer thickness is thin.
In other words, good uniform coloring and coloring speed can be obtained even if the peak voltage is small. Conversely, as the frequency increases, the current application time becomes shorter, resulting in a barrier layer that lacks density. This is compensated for by increasing the peak voltage value and increasing the layer thickness to stabilize the barrier layer and ensure uniform coloration. In other words, the peak voltage values Va, Vc are the frequency
If the voltage is less than 29 V at 60 Hz, less than 27 at 50 Hz, less than 19 V at 10 Hz, and less than 17 V at 5 Hz, the barrier layer will be thin and non-uniform, resulting in poor uniform coloring and slow coloring speed. Also, below 15V at 1Hz, Ni
Coloring becomes impossible due to the deposition voltage. on the other hand,
Va, Vc exceeds 19V at frequency 1Hz, 21V at 5Hz
exceeds 23V at 10Hz, exceeds 31V at 50Hz,
When the voltage exceeds 33 V at 60 Hz, the barrier layer is too dense or too thick, so that it becomes difficult to color, and the coloring speed becomes slow and spalling occurs. Note that the peak voltage value and rectangular wave frequency can be set to arbitrary values as long as the values are within the area of the present invention indicated by diagonal lines in FIG. I'm becoming more sensitive. Therefore, bath management becomes troublesome, but on the other hand, since the peak voltage value is small, the power cost becomes low. On the other hand, the higher the frequency, the less sensitive it is to alkali metals, making bath management easier, but the higher the frequency, the higher the electricity cost because it requires a larger peak voltage. Therefore, when implementing the present invention industrially, the peak voltage value and frequency may be appropriately set in consideration of ease of bath management and power cost. Effects of the Invention As described above, the present invention performs a secondary electrolytic treatment for electrolytic coloring on an anodized aluminum material in an electrolytic bath consisting essentially of an aqueous solution of metal salts and boric acid, with positive and negative peak voltage values. Since the application is performed by applying a rectangular wave voltage in which the energization time of the positive and negative voltages are set equal, and the peak voltage value and frequency are set in a certain relationship, it is possible to achieve even better uniform coloring without shading in a short time. At the same time,
It is also possible to prevent the occurrence of spalling and to provide aluminum materials with a beautiful external color tone with high efficiency. As a result, the commercial value of aluminum materials used as building materials can be improved. Example Aluminum plate made of A1100 alloy (thermal treatment)
H24) were prepared. First, as a pretreatment, the aluminum plate was sequentially subjected to nitric acid degreasing, caustic etching, and nitric acid neutralization, and then subjected to a liquid temperature of 20±
Current 1.1A/d in 15% sulfuric acid solution at 1℃
The anodic oxidation treatment was carried out under conditions of m ² and electrolysis time of 35 minutes. The thickness of the anodic oxide film formed on the surface of the aluminum plate as described above was about 9 μm. Next, the above aluminum plate was subjected to a secondary electrolytic coloring treatment using a square wave inverter method. In the secondary electrolytic treatment, as shown in Fig. 3, a carbon counter electrode 2 is installed at one end of a frame 1 made of vinyl chloride resin, and the three aluminum test plates A, B, Using a test cell in which C was placed facing a carbon counter electrode, this cell was heated with _NiSO4 .
After being immersed in an electrolytic solution consisting of an aqueous solution of 6H ₂ O: 50 g/, H ₃ BO ₃ : 30 g/ and containing Na ⁺ and K ⁺ ions, the three test plates and carbon were electrically short-circuited. A square wave voltage was applied between the electrode and the counter electrode. The square wave voltage was calculated by changing the peak voltage value and frequency to various values as shown in Table 1, under the conditions that the positive and negative peak voltage values and the energization times of the positive and negative voltages were set equal, respectively, and the processing time shown in the table. I went. In addition, in the test cell, the distance l between the carbon counter electrode and the opposing surface of aluminum sample plate A is
200 mm, and the interval between each test plate was 10 mm. Three test plates A, which have undergone metal coloring treatment,
For B and C, the L value (lightness) of both sides of each test plate was measured using a color difference meter. The results are shown in Table 1. On the other hand, using the same test cell and electrolytic solution of the same composition as above, the conventional AC electrolytic coloring treatment (No. 22) was performed under the conditions of 15 V AC and 6 minutes of treatment time, and the voltage of 15 V DC was applied using the test plate as the cathode. Direct current electrolytic coloring treatment (No. 23) was carried out by applying voltage for 3 minutes. Also,
Add (NH ₄ ) ₂ SO ₄ to the above electrolyte as an electrolyte: 30
Using an aqueous solution to which g/ is added, the voltage ±
Coloring treatment was carried out using a rectangular wave inverter method by applying a rectangular wave voltage of 20 V and a frequency of 5 Hz (No. 24). The results are also shown in Table 1.

【table】

[Table] Shows the opposite side.
(Note 2) △L is the difference between the maximum and minimum L value.
From the above results, it was confirmed that the product of the present invention has a small value of △L, therefore it is possible to uniformly color the aluminum material without shading in a short time, and it also does not cause spalling. I got it.

[Brief explanation of drawings]

Fig. 1 is a waveform diagram of the rectangular wave voltage applied in the electrolytic treatment according to the present invention, Fig. 2 is a graph showing the relationship between the peak voltage value of the rectangular wave voltage and frequency, and Fig. 3 is a test used in the example. FIG. Va...Positive peak voltage value, Vc...Negative peak voltage value, ta...Positive voltage energization time, tc...Negative voltage energization time.

Claims (1)

[Claims] 1 Electrolytic coloring of aluminum materials that undergoes secondary electrolytic treatment by applying a rectangular wave voltage that alternates between positive and negative in an electrolytic bath consisting essentially of an aqueous solution of metal salts and boric acid to anodized aluminum materials. In the method, the absolute values of the positive and negative peak voltages of the rectangular wave and the energization times of the positive and negative voltages are respectively set equal, and the absolute values of the positive and negative peak voltages and the rectangular wave frequency are set at point A (as shown in the attached drawing). 1Hz,
15V), point B (5Hz, 17V), point C (10Hz, 19V), point D (50Hz, 27V), point E (60Hz, 29V), point F (60Hz,
33V), point G (50Hz, 31V), point H (10Hz, 23V), point I (5Hz, 21V), and point J (1Hz, 19V) to perform electrolytic treatment. A method for electrolytically coloring aluminum materials.