WO2024106824A1 - Coated aluminum substrate and method for manufacturing same - Google Patents

Abstract

Provided are a coated aluminum substrate and a method for manufacturing same, the aluminum substrate comprising: an aluminum substrate; a passivation film formed on at least one surface of the aluminum substrate; and a resin film formed on the passivation film, wherein multiple polygonal fine irregularities are formed on the surface of the aluminum substrate, the average major diameter of the polygonal fine irregularities being 0.1 to 5 μm, and the area fraction occupied by the multiple polygonal fine irregularities is 10% or less.

Description

Coated aluminum substrate and manufacturing method thereof

This specification relates to a coated aluminum substrate and a method of manufacturing the same.

Aluminum (Al) material has high dimensional precision and can be mass-produced in a shorter time than iron in the production of lightweight castings. Additionally, it is widely used in various industrial fields due to its high castability, low density, high productivity, low shrinkage, and relatively high strength characteristics. Despite these advantages and various applicability, aluminum has the problem of deteriorating mechanical properties due to corrosion occurring even in a not very harsh environment.

To solve this problem, a method of adding elements such as Mn, Mg, Si and Cr to aluminum and using it as an alloy, an anodizing method of creating an artificial anodic oxide film on the surface of the aluminum material, and electrical conduction. There are chromate coating methods and phosphate coating methods that create a possible chemical conversion film. Among these, the anodizing method can provide excellent corrosion resistance in forming a protective film of aluminum alloy material. However, the anodizing method is advantageous in terms of corrosion resistance, but not only does the anodizing process take an excessive amount of time, but the surface hardness increases excessively during anodizing, making subsequent processing difficult. Therefore, anodizing is used for aluminum materials in a state in which processing has been completed. There are many process limitations as processing must be performed.

Accordingly, there is a need to develop a new surface treatment technology that provides excellent corrosion resistance to aluminum materials and has excellent processability.

One aspect is to provide a coated aluminum substrate with excellent corrosion resistance and processability through surface treatment and a method of manufacturing the same.

According to one aspect of the present invention, it includes an aluminum-based substrate, a passive film formed on at least one surface of the aluminum-based substrate, and a resin film formed on the passive film, and a plurality of polygons are formed on the surface of the aluminum-based substrate. A coated aluminum-based substrate is provided in which fine irregularities are formed, the average long diameter of the polygonal fine irregularities is 0.1 to 5 μm, and the area fraction occupied by the plurality of polygonal fine irregularities is 10% or more.

In one embodiment, the glossiness of the aluminum-based substrate on which the polygonal fine irregularities are formed may be 20 to 60 GU.

In one embodiment, the arithmetic mean roughness (Ra) of the aluminum-based substrate on which the polygonal fine irregularities are formed may be 0.45 to 0.7 μm.

In one embodiment, the passivation film may include at least one selected from the group consisting of a titanium-based compound, a fluorine-based compound, and a fluorine-based compound.

In one embodiment, the resin film may include urethane resin and acrylic resin.

In one embodiment, the thickness of the resin film may be 1 to 15 μm.

According to another aspect of the present invention, (a) preparing an aluminum-based substrate; (b) immersing the aluminum-based substrate in a first etching solution to remove a surface oxide layer on the aluminum-based substrate and forming coarse irregularities on at least one surface of the aluminum-based substrate; (c) immersing the aluminum-based substrate on which the coarse irregularities are formed in a second etching solution to form a plurality of polygonal fine irregularities on at least one surface of the aluminum-based substrate on which the coarse irregularities are formed; (d) forming a passive film on at least one surface of the aluminum-based substrate on which the polygonal fine irregularities are formed; and (e) forming a resin film on the passive film, wherein the average major diameter of the polygonal fine irregularities is 0.1 to 5 μm, and the area fraction occupied by the plurality of polygonal fine irregularities is 10% or more. A method for manufacturing an aluminum-based substrate is provided.

In one embodiment, the ratio of the glossiness of the aluminum-based substrate after forming the polygonal fine irregularities to the glossiness of the aluminum-based substrate before forming the coarse irregularities may be 0.15 to 0.55.

In one embodiment, the ratio of the arithmetic average roughness of the aluminum-based substrate after forming the polygonal fine irregularities to the arithmetic average roughness of the aluminum-based substrate before forming the coarse irregularities may be 1.2 to 2.0.

In one embodiment, the first etching solution may include a hydroxide of an alkali metal or an alkaline earth metal.

In one embodiment, the hydroxide of an alkali metal or alkaline earth metal may be at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, magnesium hydroxide, aluminum hydroxide, lithium hydroxide, and ammonium hydroxide.

In one embodiment, the second etching solution may include an organic acid and a fluorine compound having at least one hydroxy group in the molecule.

In one embodiment, the organic acid having at least one hydroxy group in the molecule may be at least one selected from the group consisting of gluconic acid, citric acid, tartaric acid, and malic acid.

In one embodiment, the fluorine compound is ammonium fluoride, acidic ammonium fluoride, potassium fluoride, ammonium borofluoride, potassium bifluoride, potassium borofluoride, sodium fluoride, sodium bifluoride, aluminum fluoride, boronic acid fluoride, lithium fluoride, It may be at least one selected from the group consisting of calcium fluoride and copper fluoride.

In one embodiment, the second etching solution may not contain hydrogen peroxide and persulfate.

In one embodiment, the temperature for performing steps (b) and (c) may be 40 to 80°C.

In one embodiment, the performance time of step (c) may be 1 second to 5 minutes.

According to one embodiment of the present invention, a plurality of polygonal fine irregularities are formed on an aluminum-based substrate, thereby improving adhesion with a film coated on the substrate, and excellent physical properties such as corrosion resistance and processability can be realized.

The effect of one aspect of the present specification is not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration described in the detailed description or claims of the present specification.

Figure 1 is an image of the corrosion resistance evaluation of the machined part according to an embodiment of the present specification, Figure 1(a) is an image of the corrosion resistance evaluation of the machined part on the substrate before bending processing in Example 1, and Figure 1(b) is an image of the corrosion resistance of the machined part according to the embodiment of the present specification. This is an image of the corrosion resistance evaluation of the processed part of the substrate after bending in Example 1, and Figure 1(c) is an image of the corrosion resistance of the processed part of the substrate before and after bending of Comparative Example 1.

Figure 2 is an image of adhesion evaluation according to an embodiment of the present specification.

Figure 3 is an image of machinability evaluation according to an embodiment of the present specification.

Figure 4 shows the results of SEM image analysis before surface treatment, after first etching, and after second etching of Example 1 of the present specification.

Figure 5 shows the results of SEM image analysis of the change in secondary etching performance time according to an embodiment of the present specification.

Figure 6 shows the results of analysis of the average major axis of Example 1 of the present specification.

Figure 7 shows the results of surface roughness analysis according to an embodiment of the present specification.

Figure 8 shows the results of gloss analysis according to an embodiment of the present specification.

Below, one aspect of the present specification will be described. However, the description in this specification may be implemented in various different forms, and therefore is not limited to the embodiments described herein. In order to clearly explain one aspect of the present specification, parts unrelated to the description have been omitted.

Throughout the specification, when a part is said to be “connected” to another part, this includes not only cases where it is “directly connected,” but also cases where it is “indirectly connected” with another member in between. . Additionally, when a part is said to “include” a certain component, this does not mean that other components are excluded, but that other components can be added, unless specifically stated to the contrary.

When a range of numerical values is described herein, unless the specific range is stated otherwise, the value has the precision of significant figures given in accordance with the standard rules in chemistry for significant figures. For example, the number 10 includes the range 5.0 to 14.9, and the number 10.0 includes the range 9.50 to 10.49.

Hereinafter, an embodiment of the present specification will be described in detail with reference to the attached drawings.

Coated aluminum base

A coated aluminum substrate according to one aspect may include an aluminum-based substrate, a passive film formed on at least one side of the aluminum-based substrate, and a resin film formed on the passive film.

The aluminum-based substrate may be a commonly used aluminum or aluminum alloy without particular limitation, and may be, for example, pure aluminum, aluminum alloy for casting, or aluminum alloy for whole body, and more specifically, Al 1000 series, Al 3000 series. , it may be one or more selected from Al 4000 series, Al 5000 series, Al 6000 series, and Al 7000 series, and preferably Al 1000 series, but is not limited thereto.

The surface of the aluminum-based substrate is characterized in that a plurality of polygonal fine irregularities are formed. The polygonal fine irregularities can improve the bonding strength between the aluminum-based substrate and the passive film, and enhance adhesion with the resin film, which is the final coating layer.

The average major diameter of the fine irregularities of the polygon may be 0.1 to 5 μm. For example, 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm μm, 1.7μm, 1.8μm, 1.9μm, 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3.0μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4.0μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm , 5.0 μm, or a value between these two values. If the average length of the polygonal fine irregularities is outside the above range, corrosion resistance or processability may be reduced.

The term “average major axis” used in this specification refers to the long side of a rectangle with the smallest area among the rectangles circumscribed by polygonal fine irregularities measured as the major axis by image analysis of scanning electron microscope (SEM) observation, respectively. It means the diameter of 50% of the cumulative area obtained from the area distribution of .

The area fraction occupied by the plurality of polygonal fine irregularities may be 10% or more. For example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25. %, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58% , 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75 %, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, It may be 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a value between any two of these values. If the area fraction occupied by the plurality of polygonal fine irregularities is less than 10%, the bonding force and adhesion due to the fine irregularities may be reduced, thereby reducing the corrosion resistance and processability of the coated aluminum-based substrate. Meanwhile, as the area fraction occupied by the fine irregularities of the plurality of polygons increases, it is advantageous for bonding force and adhesion, so the present invention does not specifically limit the upper limit. However, if the area fraction occupied by the fine irregularities of the plurality of polygons is above a certain level, the upper limit is not particularly limited. The average major diameter may become excessively large due to excessive overlap between adjacent fine irregularities, so taking this into account, the upper limit can be limited to about 85%.

As an example, the glossiness of the aluminum-based substrate on which polygonal fine irregularities are formed may be 20 to 60 GU. For example, 20GU, 21GU, 22GU, 23GU, 24GU, 25GU, 26GU, 27GU, 28GU, 29GU, 30GU, 31GU, 32GU, 33GU, 34GU, 35GU, 36GU, 37GU, 38GU, 39GU, 40GU, 41GU, 42GU, It may be 43GU, 44GU, 45GU, 46GU, 47GU, 48GU, 49GU, 50GU, 51GU, 52GU, 53GU, 54GU, 55GU, 56GU, 57GU, 58GU, 59GU, 60GU, or a value between these two values. As long as the glossiness of the aluminum-based substrate satisfies the above range, polygonal fine irregularities can be uniformly formed on the surface of the substrate.

As an example, the arithmetic mean roughness (Ra) of the aluminum-based substrate on which the polygonal fine irregularities are formed may be 0.45 to 0.7 μm. For example, 0.45μm, 0.46μm, 0.47μm, 0.48μm, 0.49μm, 0.50μm, 0.51μm, 0.52μm, 0.53μm, 0.54μm, 0.55μm, 0.56μm, 0.57μm, 0.58μm, , 0.60 It may be μm, 0.61μm, 0.62μm, 0.63μm, 0.64μm, 0.65μm, 0.66μm, 0.67μm, 0.68μm, 0.69μm, 0.70μm or a value between any two of these values. If the arithmetic mean roughness (Ra) is outside the above range, fine irregularities may be formed poorly or excessively, resulting in reduced bonding force and adhesion with the dynamic coating and the resin coating.

The term “arithmetic average roughness (Ra)” used in this specification is the average value for the center line of the height of the surface of the substrate due to the fine irregularities, and is the average value of the sum of the absolute values of the deviations from the center line to the measured length. The arithmetic mean roughness (Ra) is the most widely used roughness parameter as it is suitable for evaluating gloss, surface strength, surface treatment, friction, and electrical contact resistance, but exceptional peaks and/or valleys are Ra. does not affect

In the present invention, there is no particular limitation on the method of forming the plurality of polygonal fine irregularities on the surface of the aluminum-based substrate, but according to a non-limiting example, the plurality of polygonal fine irregularities are formed on the surface of the aluminum-based substrate, which will be described later. It can be formed by primary and secondary etching processes. A plurality of polygonal fine irregularities are formed on the surface of the substrate that has been subjected to the primary and secondary etching, and the surface area of the substrate is maximized by the fine irregularities, thereby improving the bonding force and adhesion with the passive film and resin film that are subsequently laminated. there is.

As an example, the passive film may be formed on at least one surface of the aluminum-based substrate, and the substrate is immersed in a chemical treatment solution to form a thin inert chemical film, that is, a passive film, on the surface of the aluminum-based substrate. Oxidation of the surface can be prevented, and the corrosion resistance and processability of the coated aluminum-based substrate can be improved through excellent adhesion with the resin film to be coated afterwards.

As an example, the passivation film may include at least one selected from the group consisting of titanium-based compounds and fluorine-based compounds. For example, the titanium-based compound may be one selected from the group consisting of titanium phosphate, titanium nitrate, titanium hydroxide, titanium dioxide, and mixtures of two or more thereof, but is not limited thereto. Additionally, for example, the fluorine-based compound may be one selected from the group consisting of titanium fluoride, manganese fluoride, titanium fluoride oxide, manganese fluoride oxide, and mixtures of two or more of these, but is not limited thereto. Since the passive film does not contain a chromium compound, it can prevent environmental pollution and human health problems caused by the emission of hexavalent chromium and can be excellent in eco-friendliness.

The resin film may be formed on the passive film, and may be coated in combination with the passive film.

As an example, the resin film may include a urethane resin and an acrylic resin, for example, a urethane-acrylic hybrid resin. The urethane-acrylic hybrid resin may be manufactured by adding an acrylic monomer to a polyurethane prepolymer obtained by reacting polyol and isocyanate and copolymerizing it, but is not limited thereto.

The urethane-acrylic hybrid resin can compensate for insufficient physical properties by combining urethane resin and acrylic resin with each other, rather than simply blending them. Specifically, it is possible to simultaneously realize the excellent corrosion resistance, abrasion resistance, chemical resistance, processability, weather resistance, and low-temperature properties of urethane resin and the excellent corrosion resistance, solvent resistance, durability, and weather resistance of acrylic resin. In addition, urethane-acrylic hybrid resin is a water-based resin and can improve eco-friendliness.

As an example, the thickness of the resin film may be 1 to 15 μm. For example, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2.0μm, 2.5μm, 3.0μm, 3.5μm, 4.0μm, 4.5μm. μm, 5.0μm, 5.5μm, 6.0μm, 6.5μm, 7.0μm, 7.5μm, 8.0μm, 8.5μm, 9.0μm, 9.5μm, 10.0μm, 10.5μm, 11.0μm, 11.5μm, 12.0μm, 12.5μm, It may be 13.0μm, 13.5μm, 14.0μm, 14.1μm, 14.2μm, 14.3μm, 14.4μm, 14.5μm, 14.6μm, 14.7μm, 14.8μm, 14.9μm, 15.0μm, or a value between any two of these values. If the thickness of the resin film is less than the above range, the corrosion resistance of the coated aluminum base may decrease, and if it exceeds the above range, peeling may occur and durability and processability may be reduced.

Manufacturing method of coated aluminum substrate

According to another aspect, a method of manufacturing a coated aluminum substrate includes the steps of a) preparing an aluminum-based substrate; (b) immersing the aluminum-based substrate in a first etching solution to remove a surface oxide layer on the aluminum-based substrate and forming coarse irregularities on at least one surface of the aluminum-based substrate; (c) immersing the aluminum-based substrate on which the coarse irregularities are formed in a second etching solution to form a plurality of polygonal fine irregularities on at least one surface of the aluminum-based substrate on which the coarse irregularities are formed; (d) forming a passive film on at least one surface of the aluminum-based substrate on which the polygonal fine irregularities are formed; and (e) forming a resin film on the passive film, wherein the average major diameter of the polygonal fine irregularities is 0.1 to 5 μm, and the area fraction occupied by the plurality of polygonal fine irregularities may be 10% or more. there is.

As an example, in step (a), an aluminum-based substrate can be prepared, and a degreasing process can be performed. In the degreasing process, oil and foreign substances on the surface of the aluminum-based substrate can be primarily removed by immersing the aluminum-based substrate in a degreasing liquid. By performing the degreasing process, the efficiency of the subsequent process can be improved and a high-quality coated aluminum-based substrate can be manufactured.

Depending on the type, the degreasing may include solvent degreasing, emulsion cleaning using a liquid emulsifying a surfactant in solvent and water, ultrasonic degreasing, electro cleaning, and alkaline cleaning. etc. can be mentioned. There is no particular limitation in the degreasing step, and degreasing liquid commonly used for degreasing can be used.

As an example, a rinsing process may be additionally performed after completing the degreasing process, but is not limited to this. A water washing process may be performed to prevent contamination by degreasing liquid remaining after the degreasing process.

As an example, in step (b), the aluminum-based substrate may be immersed in a first etching solution to remove the surface oxide layer on the aluminum-based substrate and form coarse irregularities on at least one surface of the aluminum-based substrate. Specifically, step (b) is a primary etching process that secondarily removes oil and foreign substances on the surface of the substrate that were not removed in the degreasing process of step (a), removes the surface oxidation layer, and removes aluminum. This may be a step of forming coarse irregularities on the surface of the base material.

As an example, the first etching solution may include a hydroxide of an alkali metal or an alkaline earth metal.

As an example, the hydroxide of the alkali metal or alkaline earth metal may be at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, magnesium hydroxide, aluminum hydroxide, lithium hydroxide, and ammonium hydroxide. When the first etching solution contains a hydroxide of an alkali metal or an alkaline earth metal, coarse irregularities can be formed more easily than when the first etching solution does not contain the hydroxide.

As an example, the first etching solution may further include a surfactant. The surfactant may be at least one nonionic surfactant selected from the group consisting of polyethylene glycol, polypropylene glycol, polyether polyol, polyglycol oleic acid, gelatin, and ethylene oxide (EO)-propylene oxide (PO) copolymer. However, it is not limited to this. When the first etching solution contains a nonionic surfactant, the linearity of the coarse irregularities is improved, and coarse irregularities at a level suitable for forming polygonal fine irregularities can be formed.

As an example, the first etching solution may further include at least one dispersant selected from the group consisting of acrylic acid maleic acid copolymer and its metal salt, polycarboxylic acid, and polyethylene glycol. In this case, coarse irregularities can be easily formed even under mild conditions (e.g., low temperature, short time).

As an example, a rinsing process may be additionally performed after completing the first etching process, but is not limited to this. A water washing process may be performed to prevent contamination by the first etching solution remaining after the first process. In particular, the first etching process is an etching using a base, and a hydrogen radical reaction may occur due to residual ions on the surface of the substrate, which may cause corrosion, so it is preferable to remove the remaining ions through a water washing process.

As an example, the aluminum-based substrate on which the coarse irregularities are formed in step (c) may be immersed in a second etching solution to form a plurality of polygonal fine irregularities on at least one side of the substrate.

As an example, the second etching solution may include an organic acid and a fluorine compound having at least one hydroxy group in the molecule. The organic acid having at least one hydroxy group in the molecule and the fluorine compound interact to form polygonal fine irregularities on the surface of the aluminum-based substrate on which coarse irregularities have been formed.

As an example, the organic acid having at least one hydroxy group in the molecule may be at least one selected from the group consisting of gluconic acid, citric acid, tartaric acid, and malic acid, but is not limited thereto.

As an example, the fluorine compound includes ammonium fluoride, acidic ammonium fluoride, potassium fluoride, ammonium borofluoride, potassium bifluoride, potassium borofluoride, sodium fluoride, sodium bifluoride, aluminum fluoride, boronic acid, lithium fluoride, calcium fluoride, and It may be at least one selected from the group consisting of copper fluoride, but is not limited thereto.

As an example, the second etching solution may not contain hydrogen peroxide and persulfate. If the second etching liquid contains hydrogen peroxide or persulfate, productivity may decrease due to changes over time due to the instability of the liquid, the amount of waste liquid may increase, and stability may be reduced due to heat and gas generation due to rapid decomposition. . In addition, it may be difficult to secure the desired level of adhesion and processability by hindering the formation of homogeneous fine irregularities.

As an example, the average long diameter of the fine irregularities of the polygon may be 0.1 to 5 μm. For example, 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm μm, 1.7μm, 1.8μm, 1.9μm, 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3.0μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4.0μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm , 5.0 μm, or a value between these two values. If the average length of the polygonal fine irregularities is outside the above range, corrosion resistance or processability may be reduced.

As an example, the area fraction occupied by the fine irregularities of the plurality of polygons may be 10% or more. For example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25. %, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58% , 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75 %, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, It may be 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a value between any two of these values. If the area fraction occupied by the plurality of polygonal fine irregularities is less than 10%, the bonding force and adhesion due to the fine irregularities may be reduced, thereby reducing the corrosion resistance and processability of the coated aluminum-based substrate.

As an example, the aluminum-based substrate may be subjected to primary etching and secondary etching processes in steps (b) and (c), respectively, and specifically, etching using a base and etching using an acid may be performed alternately. there is. Etching using a base and etching using an acid are different in their surface treatment effect and activity of the surface of the substrate after etching, and thus can effectively improve the bonding force and adhesion with the subsequent passive film and resin film. In addition, the first etching solution in step (b) consists of sodium hydroxide, potassium hydroxide, etc., so even if a rinsing process is performed after the etching treatment, there is a high probability that Na ⁺ ions and OH ^- ions remain on the surface of the substrate. The remaining Na ⁺ ions and OH ^- ions can be removed by the second etching solution in step (c), and oxides generated by the residual ions can be removed, so the dismut process can be omitted.

As an example, the performance temperature of steps (b) and (c) may be 40 to 80°C. For example, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C, 55 ℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, It may be 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, or a value between two of these values. If the operating temperature is outside the above range, the removal of the oxide layer and the formation of fine irregularities on the surface of the substrate may be poor, which may reduce the bonding force and adhesion with the passive film and resin film, and the corrosion resistance and processability of the coated aluminum-based substrate may decrease. You can.

As an example, the execution time of step (c) may be 1 second to 5 minutes. For example, 1 second, 2 seconds, 3 seconds, 4 seconds, 5 seconds, 6 seconds, 7 seconds, 8 seconds, 9 seconds, 10 seconds, 11 seconds, 12 seconds, 13 seconds, 14 seconds, 15 seconds, 16. seconds, 17 seconds, 18 seconds, 19 seconds, 20 seconds, 21 seconds, 22 seconds, 23 seconds, 24 seconds, 25 seconds, 26 seconds, 27 seconds, 28 seconds, 29 seconds, 30 seconds, 31 seconds, 32 seconds, 33 seconds, 34 seconds, 35 seconds, 36 seconds, 37 seconds, 38 seconds, 39 seconds, 40 seconds, 41 seconds, 42 seconds, 43 seconds, 44 seconds, 45 seconds, 46 seconds, 47 seconds, 48 seconds, 49 seconds , 50 seconds, 51 seconds, 52 seconds, 53 seconds, 54 seconds, 55 seconds, 56 seconds, 57 seconds, 58 seconds, 59 seconds, 1 minute, 1.5 minutes, 2 minutes, 2.5 minutes, 3 minutes, 3.5 minutes, 4 It can be minutes, 4.5 minutes, 5 minutes, or any value between the two. If the execution time is too short, it may be difficult to sufficiently form a plurality of polygonal fine irregularities on the surface of the aluminum-based substrate, and conversely, if the execution time is too long, the average length of the fine irregularities may become excessively large.

As an example, the ratio of the glossiness of the aluminum-based substrate after steps (b) and (c) to the glossiness of the aluminum-based substrate in step (a) may be 0.15 to 0.55. For example, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, , 0.35, 0.36, 0.37, It may be 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, or a value between these two values. If the gloss ratio is outside the above range, the formation of fine irregularities may be poor, which may reduce the bonding force and adhesion with the passive film and the resin film, and the corrosion resistance and processability of the coated aluminum-based substrate may decrease.

As an example, the ratio of the arithmetic average roughness of the aluminum-based substrate after steps (b) and (c) to the arithmetic average roughness of the aluminum-based substrate in step (a) may be 1.2 to 2.0. For example, it may be 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, 2.00, or a value between two of these values. If the arithmetic mean roughness ratio is outside the above range, the formation of fine irregularities may be poor, which may result in reduced bonding and adhesion with the passive film and resin film, and the corrosion resistance and processability of the coated aluminum-based substrate may be reduced.

As an example, a rinsing process may be additionally performed after completing the secondary etching process, but is not limited to this. In order to prevent contamination by the second etchant remaining after the secondary process, a water washing process may be performed to improve bonding strength with the subsequent passivation film.

As an example, in step (d), a passive film may be formed on one surface of the aluminum-based substrate on which the polygonal fine irregularities are formed.

The passive film is a thin inert chemical film, that is, a passive film, obtained by immersing an aluminum-based substrate in a chemical treatment solution. It can prevent oxidation of the surface of the aluminum-based substrate, and is coated with excellent adhesion to the resin film to be coated afterwards. The corrosion resistance and processability of aluminum-based substrates can be improved.

As an example, the passivation film may include at least one selected from the group consisting of titanium-based compounds and fluorine-based compounds. For example, the titanium-based compound may be one selected from the group consisting of titanium phosphate, titanium nitrate, titanium hydroxide, titanium dioxide, and mixtures of two or more thereof, but is not limited thereto. Additionally, for example, the fluorine-based compound may be one selected from the group consisting of titanium fluoride, manganese fluoride, titanium fluoride oxide, manganese fluoride oxide, and mixtures of two or more of these, but is not limited thereto. Since the passive film does not contain a chromium compound, it can prevent environmental pollution and human health problems caused by the emission of hexavalent chromium and can be excellent in eco-friendliness.

As an example, in step (e), a resin film may be formed on the passive film.

The resin film may include a urethane resin and an acrylic resin, for example, a urethane-acrylic hybrid resin. The urethane-acrylic hybrid resin may be manufactured by adding an acrylic monomer to a polyurethane prepolymer obtained by reacting polyol and isocyanate and copolymerizing it, but is not limited to this, and the physical properties and effects of the urethane-acrylic hybrid resin are not limited thereto. is the same as described above.

As an example, the thickness of the resin film may be 1 to 15 μm. For example, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2.0μm, 2.5μm, 3.0μm, 3.5μm, 4.0μm, 4.5μm. μm, 5.0μm, 5.5μm, 6.0μm, 6.5μm, 7.0μm, 7.5μm, 8.0μm, 8.5μm, 9.0μm, 9.5μm, 10.0μm, 10.5μm, 11.0μm, 11.5μm, 12.0μm, 12.5μm, It may be 13.0μm, 13.5μm, 14.0μm, 14.1μm, 14.2μm, 14.3μm, 14.4μm, 14.5μm, 14.6μm, 14.7μm, 14.8μm, 14.9μm, 15.0μm, or a value between any two of these values. If the thickness of the resin film is less than the above range, the corrosion resistance of the coated aluminum base may decrease, and if it exceeds the above range, peeling may occur and durability and processability may be reduced.

Hereinafter, embodiments of the present specification will be described in more detail. However, the following experimental results describe only representative experimental results among the above examples, and the scope and content of the present specification cannot be interpreted as being reduced or limited by the examples. Each effect of various implementations of the present specification that are not explicitly presented below will be described in detail in the corresponding section.

Example 1

A specimen of 10 cm wide, 5 cm long, and 2 cm thick was prepared from an aluminum 1000 series substrate, then immersed in a degreasing solution to perform a degreasing process, and then washed with distilled water.

Next, the substrate was immersed in a first etching solution containing sodium hydroxide and potassium hydroxide at 60°C to perform a primary etching treatment, and then washed with distilled water.

Next, the substrate was immersed in a second etching solution at 60°C containing tartaric acid and sodium fluoride to perform a secondary etching treatment for 20 seconds, and then washed with distilled water.

A passivation film and a urethane-acrylic hybrid resin film were sequentially formed on the first and second etching-treated substrates to prepare a coated aluminum-based substrate.

Example 2

A coated aluminum-based substrate was manufactured in the same manner as Example 1, except that the secondary etching was performed for 8 seconds.

Example 3

A coated aluminum-based substrate was manufactured in the same manner as in Example 1, except that the secondary etching was performed for 12 seconds.

Comparative Example 1

A coated aluminum-based substrate was manufactured in the same manner as in Example 1, except that the first and second etching processes were omitted.

Comparative Example 2

A coated aluminum-based substrate was manufactured in the same manner as in Example 1, except that the step of forming a passive film was omitted.

Experimental Example 1: Evaluation of corrosion resistance of machined parts

In order to evaluate the corrosion resistance of the machined part with or without surface treatment, the aluminum-based substrates of Examples and Comparative Examples were bent at 180° (0T bending), and then the aluminum-based substrates before and after processing were placed in a salt spray tester. The occurrence times of blackening and white rust were measured according to the standard (ASTM B117-11), and the results are shown in Table 1 and Figure 1. At this time, 5% salt water (temperature 35°C, pH 6.8) was used, and 2 ml/80 cm ² of salt water was sprayed per hour. The surface-treated substrate of Example 1 was maintained at SST for 240 hours, and the surface-treated substrate of Comparative Example 1 was maintained at SST for 120 hours to measure the time for occurrence of blackening and white rust. The test results of the substrate before bending (straight) of Example 1 are shown in FIG. 1(a), and the test results of the substrate after bending (bent) are shown in FIG. 1(b). The test results of the substrate of Comparative Example 1 before and after bending are shown. The test results are shown in Figure 1(c).

If the red rust occurrence time was less than 120 hours, it was evaluated as “

division	Comparative Example 1	Example 1
Before bending processing (straight)	X	◎
After bending (bent)	X	◎

Referring to Table 1 and Figure 1, Example 1 showed excellent corrosion resistance of the machined part both before and after processing due to surface treatment. On the other hand, in Comparative Example 1 in which surface treatment was omitted, it can be confirmed that the corrosion resistance of the machined part is poor. In particular, in Comparative Example 1 in which 180° bending processing was performed, a large amount of corrosion can be confirmed with the naked eye, showing that the corrosion resistance of the machined part is poor. You can check the worst ones.

Experimental Example 2: Adhesion evaluation

To evaluate adhesion according to the presence or absence of surface treatment, 100 lattice shapes with a pitch of 1 mm were formed by making cuts on the surface of the aluminum-based substrate of Examples and Comparative Examples with a cutter reaching to the interface between the aluminum-based substrate and the passive film layer, and using an Ericksen extruder. It was extruded to 6 mm.

The Eriksen extrusion conditions were based on JIS-Z-2247-2006 (Eriksen value symbol: IE): punch diameter: 20 mm, die diameter: 27 mm, and drawing width: 27 mm.

After Ericksen extrusion, a tape peeling test was performed, and adhesion was evaluated three times in total by determining the remaining state of the resin film, and the results are shown in Table 2 and Figure 2. The judgment criteria are as follows.

◎: Peeling area less than 5% and no peeling

O: Peeling area less than 30% 5% or more

△: Peeling area less than 50% but more than 30%

X: Peeling area 50% or more

pH ranges from 3 to 8

division	Comparative Example 1	Comparative Example 2	Example 1
1 time	X	O	◎
Episode 2	X	O	◎
3rd time	△	O	◎

Referring to Table 2 and Figure 2, the substrate of Example 1 showed excellent adhesion as no peeling occurred in all three evaluations. It can be confirmed that the adhesion between the surface-treated aluminum substrate and the passive film and resin film is improved. On the other hand, Comparative Example 1, in which surface treatment was omitted, showed a peeling area of more than 50% in multiple evaluations, confirming that adhesion was poor, and Comparative Example 2, which was surface treated but did not form a passivation film, showed a peeling area of more than 50% in all evaluations. It can be seen that the adhesion is somewhat reduced due to the omission of the passive film as the peeling area is less than 100%.

Experimental Example 3: Machinability evaluation

To evaluate processability according to surface treatment, the aluminum substrate of Example 1 was flattened until just before fracture and the degree of peeling was visually evaluated, and the image is shown in Figure 3.

Referring to Figure 3, it can be seen that the aluminum substrate of Example 1 has no cracks or peeling at all, showing excellent adhesion to the resin film, which is the final coating layer, through surface treatment, and aluminum products using this have excellent corrosion resistance and processability. We can confirm that it can be implemented.

Experimental Example 4: SEM analysis according to surface treatment

In order to examine the surface changes of the aluminum substrate according to surface treatment, the surface of the aluminum substrate before surface treatment, after primary etching, and after secondary etching during the manufacturing process of Example 1 was analyzed by SEM at magnifications of 1000x and 3000x, respectively. , the resulting image is shown in Figure 4.

Referring to Figure 4, by comparing the images before surface treatment and after the first etching, it can be confirmed that oil such as foreign substances were removed and the oxide layer was removed after the first etching. Looking at the image of the surface of the substrate after secondary etching, it can be seen that a plurality of polygonal fine irregularities were formed on the surface of the substrate.

Experimental Example 5: SEM analysis according to secondary etching performance time

SEM analysis of the aluminum substrate according to the secondary etching time was performed at 1000x and 3000x magnification, respectively, and the resulting images are shown in Figure 5.

Looking at Figure 5, it can be seen that in Examples 1 to 3, a plurality of polygonal fine irregularities were formed on the surfaces of all substrates, and in particular, it can be confirmed that the most fine irregularities were formed on the substrate of Example 1.

Experimental Example 6: Analysis of average major axis of fine irregularities

In the manufacturing process of Example 1, after the secondary etching process, the surface of the aluminum substrate was analyzed by SEM to measure the minimum and maximum lengths, and the results are shown in FIG. 6.

Referring to Figure 6(a), the minimum major diameter was measured to be 164㎚, and referring to Figure 6(b), the maximum major diameter was measured to be 2.24㎛, so the average major diameter of fine irregularities formed by secondary etching is 0.1 ~ It can be confirmed that it was formed in the 3㎛ range.

Experimental Example 7: Surface roughness analysis according to surface treatment

In order to analyze the surface roughness of the aluminum substrate according to surface treatment, the arithmetic mean roughness (Ra) value was measured on the surface of the substrate immediately after the secondary etching process in the manufacturing process of Examples 1 and 2 and Comparative Example 1 using a non-contact roughness meter. , the results are shown in Figure 7.

Referring to Figure 7, Examples 1 and 2 surface treated by a secondary etching process had Ra values measured at 0.59 μm and 0.565 μm, respectively, and Comparative Example 1 where surface treatment was omitted had an Ra value measured at 0.379 μm. It has been done. It can be confirmed that the Ra value changes as fine irregularities are formed on the surface of the substrate of Examples 1 and 2 through surface treatment, and in Examples 1 and 2, the surface area is improved by the fine irregularities, resulting in the passive film and resin film. It can be confirmed that adhesion can be improved.

Experimental Example 8: Analysis of glossiness according to surface treatment

In order to analyze the gloss of the aluminum substrate according to surface treatment, the surface of the substrate immediately after the secondary etching process in the manufacturing process of Examples 1 and 2 and Comparative Example 1 was measured at a glossiness of 3 at a measuring angle of 60° using a BYK gloss meter. Measurements were made several times, and the results are shown in Table 3 and Figure 8.

division	Example 1	Example 2	Comparative Example 1
1 time	24.6	46.3	113.0
Episode 2	32.5	40.3	124.0
3rd time	31.0	54.9	147.0
average value	29.4	48.2	128.0

(Unit: GU) Referring to Table 3 and Figure 8, it can be seen that the gloss of surface treated Examples 1 and 2 was significantly reduced due to the formation of fine irregularities compared to Comparative Example 1.

The description of the present specification described above is for illustrative purposes, and a person skilled in the art to which an aspect of the present specification pertains can easily transform it into another specific form without changing the technical idea or essential features described in the present specification. You will be able to understand it. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. For example, each component described as single may be implemented in a distributed manner, and similarly, components described as distributed may also be implemented in a combined form.

The scope of the present specification is indicated by the claims described below, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present specification.

Claims (17)

1. An aluminum base material,

   A passive film formed on at least one surface of the aluminum-based substrate,

   It includes a resin film formed on the passive film,

   A plurality of polygonal fine irregularities are formed on the surface of the aluminum-based substrate,

   The average major diameter of the fine irregularities of the polygon is 0.1 to 5 μm,

   A coated aluminum-based substrate, wherein the area fraction occupied by the plurality of polygonal fine irregularities is 10% or more.
2. According to paragraph 1,

   A coated aluminum-based substrate having a glossiness of 20 to 60 GU.
3. According to paragraph 1,

   A coated aluminum-based substrate wherein the arithmetic average roughness (Ra) of the aluminum-based substrate on which polygonal fine irregularities are formed is 0.45 to 0.7 μm.
4. According to paragraph 1,

   A coated aluminum-based substrate, wherein the passive film includes at least one selected from the group consisting of titanium-based compounds and fluorine-based compounds.
5. According to paragraph 1,

   A coated aluminum-based substrate, wherein the resin film includes a urethane resin and an acrylic resin.
6. According to paragraph 1,

   A coated aluminum-based substrate wherein the resin film has a thickness of 1 to 15 μm.
7. (a) preparing an aluminum-based substrate;

   (b) immersing the aluminum-based substrate in a first etching solution to remove a surface oxide layer on the aluminum-based substrate and forming coarse irregularities on at least one surface of the aluminum-based substrate;

   (c) immersing the aluminum-based substrate on which the coarse irregularities are formed in a second etching solution to form a plurality of polygonal fine irregularities on at least one surface of the aluminum-based substrate on which the coarse irregularities are formed;

   (d) forming a passive film on at least one surface of the aluminum-based substrate on which the polygonal fine irregularities are formed; and

   (e) forming a resin film on the passive film,

   The average major diameter of the fine irregularities of the polygon is 0.1 to 5 μm,

   A method of manufacturing a coated aluminum-based substrate, wherein the area fraction occupied by the plurality of polygonal fine irregularities is 10% or more.
8. In clause 7,

   A method for producing a coated aluminum-based substrate, wherein the ratio of the glossiness of the aluminum-based substrate after forming the polygonal fine irregularities to the glossiness of the aluminum-based substrate before forming the coarse irregularities is 0.15 to 0.55.
9. In clause 7,

   A method for producing a coated aluminum-based substrate, wherein the ratio of the arithmetic average roughness of the aluminum-based substrate after forming the polygonal fine irregularities to the arithmetic average roughness of the aluminum-based substrate before forming the coarse irregularities is 1.2 to 2.0.
10. In clause 7,

    A method of producing a coated aluminum-based substrate, wherein the first etching solution includes a hydroxide of an alkali metal or an alkaline earth metal and a surfactant.
11. According to clause 10,

    The hydroxide of the alkali metal or alkaline earth metal is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, magnesium hydroxide, aluminum hydroxide, lithium hydroxide, and ammonium hydroxide.
12. In clause 7,

    A method of producing a coated aluminum-based substrate, wherein the second etching solution includes an organic acid and a fluorine compound having at least one hydroxy group in the molecule.
13. According to clause 12,

    The organic acid having at least one hydroxy group in the molecule is at least one selected from the group consisting of gluconic acid, citric acid, tartaric acid, and malic acid.
14. According to clause 12,

    The fluorine compounds include ammonium fluoride, acidic ammonium fluoride, potassium fluoride, ammonium borofluoride, potassium bifluoride, potassium borofluoride, sodium fluoride, sodium bifluoride, aluminum fluoride, boronic acid, lithium fluoride, calcium fluoride, and copper fluoride. A method of producing a coated aluminum-based substrate, which is at least one selected from the group consisting of.
15. In clause 7,

    A method of producing a coated aluminum-based substrate, wherein the second etchant does not contain hydrogen peroxide and persulfate.
16. In clause 7,

    A method for producing a coated aluminum-based substrate, wherein steps (b) and (c) are performed at a temperature of 40 to 80°C.
17. In clause 7,

    A method for producing a coated aluminum-based substrate, wherein the performance time of step (c) is 1 second to 5 minutes.

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