Method for applying a colored coating to an alloy

Abstract

In some embodiments, a method for coloring an alloy is provided, comprising anodizing a substrate in an anodizing bath containing phosphoric acid at a constant temperature and voltage for a first period of time to generate an anodized layer including a barrier layer, decreasing the constant voltage applied to the anodizing bath for a second period of time to vary the thickness of the barrier layer and vary the width of pores in the anodized layer, plating the substrate in a plating bath at a first current that is increased over a third period of time according to a current profile of the plating bath, and plating the substrate in the plating bath at a second current for a fourth period of time.

Description

[Technical Field]

[0001] Various methods have been developed for coating light metal alloys with colored anodized films. In many cases, the precise coloring mechanism is not defined. However, the total internal reflection between the clear anodizing treatment, the reflective substrate, and the inorganic deposit is related to the luminance (L). * ) causes changes in chrominance and hue (a * ,b * It is generally understood that these are formed by the destructive interference of incident and reflected light. In the case of organic films, coloration is often a direct result of the selected organic molecules. [Background technology]

[0002] U.S. Patent No. 4,251,330 ('330 patent) discloses a mechanism for imparting strong color to anodized aluminum or aluminum alloys. In this patent, the substrate is anodized with direct current (DC) to a thickness of 15 microns, mostly in a bath of sulfuric acid. Pores are enlarged, mostly in a bath of phosphoric acid, using alternating current (AC) anodizing. Color is achieved by depositing mostly nickel using AC from baths of acidic nickel sulfate, magnesium sulfate, and boric acid. A range of colors from purple to blue and green are produced by destructive interference.

[0003] While AC phosphate anodizing is considered beneficial based on the more uniform widening of the pores, AC deposition resulted in differences in deposition within the modified (widened) pores compared to the original narrow pores. The process disclosed in the '330 patent requires two baths to produce the pore structure necessary for coloring the surface and is therefore not very highly controlled.

[0004] Furthermore, residual acids from the widening and deposition process cause discoloration, which necessitates a further neutralization process.

[0005] European Patent No. 018247981 discloses a direct coloring process using nickel sulfate within a sulfuric acid anodic oxidation structure with AC deposition.

[0006] U.S. Patent No. 5,064,512 discloses a process for staining a sulfate-anodic oxidized substrate using an organotin salt on top of an AC or DC colored substrate. Specifically, this patent discusses the need to stabilize the tin content of the bath and improve the spreadability of the solution. This process requires the complex preparation of a tin-containing colored bath and meticulous monitoring of the tin content to achieve the desired results.

[0007] International Publication No. 01 / 18281 discloses a method for producing primarily black anodized coatings, comprising: producing an oxide layer 8-15 microns thick by anodizing an aluminum or aluminum alloy substrate in a sulfuric acid bath; modifying the pore structure primarily in a phosphoric acid bath using reduced voltage AC or DC anodizing treatment so that most of the pores are unable to participate in the coloring process; and coloring the anodized layer using a bath containing inorganic salts and an AC deposition regime modified with UNICOL®. This process is largely a modification of the process disclosed in the aforementioned '330 patent, but relies on a different pore modification process. In each of the above examples, coloring is derived from modifying the sulfuric acid anodized structure using a phosphoric acid process, and then coloring that portion using an inorganic bath. [Overview of the Initiative] [Means for solving the problem]

[0008] A method for coloring a light metal alloy is provided according to embodiments described herein. One feature disclosed in the embodiments includes generating an anodizing layer including a barrier layer by anodizing a substrate in an anodizing bath containing phosphoric acid over a first period at a constant temperature and constant voltage; changing the thickness of the barrier layer and the width of the pores in the anodizing layer by reducing the constant voltage applied to the anodizing bath over a second period; plating the substrate in a plating bath with a first current that is increased over a third period according to the current profile of the plating bath; and plating the substrate in the plating bath with a second current over a fourth period.

[0009] One feature disclosed in the embodiment is a method comprising: generating an anodic oxide layer including a barrier layer to a thickness of 2 to 10 microns by anodic oxidizing an aluminum alloy substrate in an anodic oxidation bath containing phosphoric acid over a first period at a constant temperature and constant voltage; changing (i) the thickness of the barrier layer positioned between the substrate and the anodic oxide pores, and (ii) the width of the pores in the anodic oxide layer by reducing the constant voltage applied to the anodic oxidation bath over a second period; plating the aluminum alloy substrate in a plating bath with a first current that is increased over a third period according to the direct current (DC) plating current profile of the plating bath; partially filling the pores in the anodic oxide layer with metal nanorods by plating the aluminum alloy substrate in the plating bath with a second current over a fourth period; and forming a sealing layer by sealing the pores in the anodic oxide layer. In one embodiment, the step of sealing the pores leaves a gap between the metal nanorods and the sealing layer.

[0010] One disclosed feature of the embodiment is to pretreat an aluminum alloy substrate, activate the aluminum alloy substrate, anodize the aluminum alloy substrate in an anodic oxidation bath containing phosphoric acid over a first period at a constant temperature and a constant voltage to generate an anodic oxidation layer, reduce the constant voltage applied to the anodic oxidation bath over a second period to change the thickness of the barrier layer and change the width of the pores in the anodic oxidation layer, rinse the aluminum alloy substrate to further reduce the thickness of the barrier layer, electroplate the aluminum alloy substrate in an electroplating bath through a plurality of electroplating stages to deposit coloring metal nanorods into the pores of the anodic oxidation layer, and seal the pores of the anodic oxidation layer while leaving voids above the metal nanorods.

Brief Description of the Drawings

[0011] [Figure 1] Figure 1 is a flowchart showing an example of a method for manufacturing a thin colored film. [Figure 2] Figure 2 is a diagram showing an example of a sulfuric acid anodized substrate. [Figure 3] Figure 3 is a diagram showing an example of a phosphoric acid anodized substrate of the present disclosure. [Figure 4] Figure 4 is a surface electron microscope (SEM) image showing an example of a phosphoric acid anodized structure of the present disclosure. [Figure 5] Figure 5 is a SEM image showing an example of a cross-section of an anodized colored substrate of the present disclosure. [Figure 6] Figure 6 is a SEM image showing an example of a close-up image of a cross-section. [Figure 7] Figure 7 is a diagram showing an example of an ultraviolet imaging spectrometer (UVIS) spectrum corresponding to a colored hybrid film on 6061 aluminum of the present disclosure. [Figure 8] Figure 8 is an example of a graph showing the relationship between the anodic oxidation charge passed, the electroplating ampere-minutes, and the color in the process of the present disclosure. [Figure 9]FIG. 9 is an example diagram showing the color generation mechanism of the present disclosure. [Figure 10] FIG. 10 is an example graph showing the relationship between the average roughness of the substrate of the present disclosure and the gloss of the film. [Figure 11] FIG. 11 is an example graph showing the maximum achievable anodic oxidation layer thickness for several phosphoric acid concentrations of the present disclosure. [Figure 12] FIG. 12 is a set of example images and a table showing the effects of barrier layer thinning and temperature on the film color of the present disclosure. [Figure 13] FIG. 13 is a cross-sectional view of a film based on one aspect of the present invention showing voids for maintaining surface color.

Mode for Carrying Out the Invention

[0012] The examples described in this specification provide a process for generating a thin colored film on aluminum or a light metal alloy. As described above, various methods for coating alloys have been developed. Anodic oxide films on aluminum (including aluminum alloys) can be colored using both organic and inorganic colorants. Coloring is generally performed by immersing the anodized surface and the counter electrode in a bath containing an appropriate inorganic salt or a combination of an inorganic salt and an organic molecule, and applying an alternating current between the anodized surface and the counter electrode to deposit an organic or inorganic material into the pores.

[0013] Conventional methods can have numerous drawbacks or be inefficient. The present disclosure provides a method for anodizing and coloring the surfaces of aluminum and other light metals using a two-step process involving phosphoric acid anodizing and direct metal deposition. Therefore, the process of the present disclosure can be said to be more efficient and environmentally friendly based on less energy usage, less volatile organic compounds, and less waste.

[0014] In one embodiment, the process may incorporate one or more of the following steps: degreasing the alloy substrate; electropolishing the substrate; activating the surface; anodizing a 2-10 micron film on the substrate in an anodic oxidation bath substantially containing phosphoric acid at a predetermined temperature and voltage-current profile, electrodepositing metal into the anodic oxidation pores at a predetermined temperature and current profile; and sealing the pores with a transparent medium. The total average thickness of the hybrid film may be approximately 2-15 microns.

[0015] Figure 1 shows an example method 100 for producing a colored coating with a thin film according to the present disclosure. In one embodiment, this method 100 can be carried out by various equipment or tools in a processing facility under the control of a processor or controller.

[0016] In block 102, method 100 begins. In block 104, method 100 can pre-treat a substrate. In one embodiment, the substrate may include aluminum or any aluminum alloy.

[0017] The pretreatment may include degreasing the substrate in an alkaline bath, roughening the substrate in polyethylene glycol, sulfuric acid, hydrofluoric acid, or other similar solutions, and etching the substrate in a nitric acid solution. An example of such pretreatment may be a commercial aluminum surface pretreatment called Probright AL. The solution used to roughen the substrate can also clean the substrate surface as etching is performed.

[0018] One example of pretreatment may involve first degreasing the substrate in a commercial solution, such as Activax, commercially available from MacDermid, Inc. Rinsing may follow the degreasing step. The effect of rinsing the substrate before anodizing may be to remove surface impurities, which can lead to defects in the thin anodized layer.

[0019] In one embodiment, the pretreatment may include electropolishing the substrate in a bath selected from the following ranges, namely 70-85% H3PO4, 2-4% HF, 6-9% H2SO4, and 5-20% glycerol. The electropolishing bath may be maintained at a temperature of 70-80 degrees Celsius (°C) at a voltage (V) of approximately 12 V. The electropolishing bath may contain a lead-counter electrode. The electropolishing process forms a uniform substrate surface with a low mean roughness (Ra). This contributes to achieving a glossy colored film. The electropolished substrate may then be rinsed in deionized (DI) water before the activation and anodic oxidation processes described below.

[0020] The average surface roughness Ra of the aluminum alloy substrate is directly related to the apparent gloss of the colored coating. In one embodiment, the Ra of the substrate before anodizing may be 1.8 to 4 in order to obtain a matte surface. In one embodiment, Ra may be approximately 2.

[0021] In one embodiment, the Ra of the substrate before anodizing may be 0.4 to 1.8 in order to obtain a semi-gloss surface. In one embodiment, Ra may be approximately 0.8 to 1.2.

[0022] In one embodiment, the Ra of the substrate before anodizing may be 0 to 0.4 in order to achieve a glossy finish. In one embodiment, Ra may be less than approximately 0.2.

[0023] In block 106, method 100 can activate the substrate. The substrate can be activated before anodizing. The activation step offers several advantages to certain alloys. An example of the activation step may involve activating the surface in a bath containing 40 vol% HNO3 and 1 to 10 ml (ML / L) of HF per liter. In one embodiment, 20 to 50 vol% HNO3 may be used. The bath may be maintained at a temperature of 20°C to 25°C with the substrate immersed and stirred about once per second for 20 to 40 seconds.

[0024] In block 108, method 100 places a substrate in an anodic oxidation bath containing phosphoric acid and an additive or solvent. The additive or solvent supports the desired anodic oxidation voltage and thus determines the pore structure, which in turn determines the resulting film color. The bath can produce a thin anodic oxidation layer by containing at least phosphoric acid and sulfuric acid over an initial period. In one embodiment, the temperature, electrical parameters, and bath composition are shown in Figure 5 and include a uniform high-density distribution of thin-walled pores with a diameter of 50 to 160 nanometers (nm), as described further below.

[0025] The anodic oxidation bath mainly contains phosphoric acid along with small amounts of sulfuric acid and oxalic acid. The bath composition is selected from the range of H3PO4 (40-600 ml / l per liter), H2SO4 (0-15 ml / l), and HOOCCOOH (1-10 g / L per liter). In one embodiment, the concentration of H3PO4 may be about 150 ml / l, the concentration of H2SO4 may be about 0.6 ml / l, the concentration of HOOCCOOH may be about 1 g / l, and the solvent is DI water.

[0026] In some embodiments, other additives may be added to obtain the desired pore structure in the anodized layer. Examples of other additives, as will be further detailed below, may include small amounts of copper sulfate, chelating agents, and similar substances.

[0027] For any given phosphoric acid concentration in the anodic oxidation bath, there may be a maximum anodic oxidation thickness that can be achieved based on the pore-expanding effect of phosphoric acid. In one embodiment, the maximum anodic oxidation thickness may be about 6 microns. Increasing the phosphoric acid concentration increases the conductivity of the anodic oxidation bath and, consequently, the current density for a fixed anodic oxidation voltage. Increasing the phosphoric acid concentration also increases pore-expanding properties and film solubility, thus creating the aforementioned limit on the anodic oxidation film thickness. It has been shown that adding 0-15 wt% or about 10 wt% of short-chain alcohol cools the growing pore structure and reduces the surface solubility of the porous anodic oxidation structure by the anodic oxidation bath. Adding 0-80 wt% or about 50 wt% of ethylene glycol increases the viscosity of the electrolyte, thereby reducing the pore-expanding rate at the cost of reducing the growth rate of the porous anodic oxidation film. A smaller volume of phosphoric acid allows for a thicker anodic oxidation layer. This improves the mechanical performance of the coating, but it requires a longer anodizing time because the film growth becomes slower.

[0028] The thickness of the barrier layer and pore structure is known to be a determining factor in the film color described in the examples below. The thickness of the barrier layer is proportional to the anodic oxidation voltage. However, the pore width is also proportional to the anodic oxidation voltage. In many cases, the requirement for a thicker barrier layer with narrower pores can play an important role in forming functional colored films. It has been found that adding polyethylene glycol, or similar organic substances that increase the viscosity of the anodic oxidation solution, in the range of 10-50 wt%, enables a higher anodic oxidation voltage. A higher anodic oxidation voltage generates a thicker barrier layer while maintaining a lower or smaller pore diameter than conventional methods. Using NAH2PO4 or LiH2PO4 instead of up to 50% H3PO4 reduces acidity, and consequently the solubility of the pore walls and barrier layer, enabling a higher voltage, a thicker barrier layer, and narrower pores. The thus generated thicker barrier layer can be altered by thinning as described below to produce the correct or desired color for the film.

[0029] In block 110, method 100 anodizes a substrate at a predetermined voltage and temperature for a time required to generate a pore structure. For example, the substrate may be placed in an anodizing bath. The anodizing bath may be operated at a constant temperature of 5°C to 40°C, or 27°C to 31°C. The bath temperature can be adjusted to generate an optimal pore structure. In one embodiment, the temperature can be maintained within ±2°C. In one embodiment, the temperature can be maintained within ±1°C. In one embodiment, the temperature can be maintained within ±0.5°C.

[0030] In one embodiment, a constant voltage may be applied to the anodic oxidation bath. In one embodiment, the voltage is 60V to 280V, and the current is 2 amperes per square decimeter (A / dm²). 2 By having the maximum current density of ), it is possible to provide an optimal pore distribution, density, and structure, as will be described later.

[0031] In one embodiment, the initial voltage may be 60 to 80 volts, and the anodizing period may be 10 to 40 minutes. In another embodiment, the voltage may be approximately 65V, and the period may be approximately 20 minutes.

[0032] The thickness of the anodized film / layer in this disclosure may be generated or grown to be 2 to 10 microns. However, the thickness may be 2 to 8 microns. In one embodiment, the thickness may be 4 to 5 microns. Anodizing under the above conditions for 20 minutes results in an anodized film with a thickness of approximately 6 microns. In one embodiment, pulsed DC anodizing may be employed. In one embodiment, the hue of the film may depend on the thickness of the anodized layer (also referred to herein as the barrier layer), as described below. In the case of an anodizing bath consisting of an acid or a mixture of acids, the anodized layer may be generally defined as including a compact barrier layer immediately adjacent to the alloy substrate and a porous layer above the barrier, the pores of which extend substantially perpendicularly from the barrier layer to the surface. In block 112, method 100 can optionally generate microstructures by changing the voltage and temperature of the anodized layer over an additional period of time. For example, the thickness of the barrier layer and the width of the pores can be varied (for instance, by decreasing the thickness of the barrier layer while increasing the width of the pores, or by increasing the thickness of the barrier layer while decreasing the width of the pores).

[0033] In one embodiment, by reducing the anodizing voltage according to the voltage profile, the barrier layer can be thinned, light absorption increased, and consequently the color darkened, as shown in Figure 5. As described below, the width of the anodized pores and the thickness of the barrier layer are formed as a function of the anodizing voltage and the dissolution output of the anodizing electrolyte. In one embodiment, the anodizing voltage is reduced by only 50%, and the anodizing process is continued for 2 to 10 minutes, or for about 5 minutes in one embodiment.

[0034] In one embodiment, the anodic oxidation voltage is similarly reduced by 50% over a period of 2 to 10 minutes, or in one embodiment, over a period of approximately 5 minutes. The anodic oxidation voltage is then reduced again by 50% over a further period of 2 to 10 minutes, or in one embodiment, over a period of approximately 5 minutes.

[0035] In one embodiment, the anodizing voltage is gradually reduced from an initial voltage to 15% of the initial voltage over periods of 2 to 20 minutes, 5 to 15 minutes, or 8 to 12 minutes. Further reductions using different voltages and periods are possible to form various pore structures.

[0036] In block 114, method 100 optionally involves chemically rinsing the substrate. For example, rinsing the substrate in a solution can further thin the barrier layer and prepare the substrate for plating with a coloring metal. In one embodiment, rinsing can thin the barrier layer by partially dissolving the anodic oxidation end cap. In one embodiment, the solution may be a bath containing 0.5 to 5 mL / L of HF.

[0037] The anodized substrate to be treated can be immersed in a rinse bath for about 30 seconds while being stirred about once per second. It will be apparent to those skilled in the art that the barrier layer can be chemically thinned using other chemical baths and methods.

[0038] In block 116, method 100 involves plating a substrate according to a current profile by placing the substrate in a bath containing a metal sulfate or metal cyanide, thereby generating metal nanorods at the base of the pores. In one embodiment, nickel sulfate may be, for example, a metal source for generating a colored film, hereafter referred to as the coloring metal. The coloring metal can be plated into the pores of the anodized layer of the substrate in the electrodeposition bath according to a plating current profile over a predetermined period of time. For example, the colored electrodeposited film can be deposited onto an anodized film from a bath selected from a variety of possible baths. The electrical parameters relating to the metallic color deposition are controlled by a first plating stage and a second plating stage. The first plating stage may include a first plating current that can be applied over a first plating period. The second plating stage may include a second plating current that can be applied over a second plating period.

[0039] In another embodiment, the coloring metal may be any pure metal, including but not limited to silver, gold, copper, cobalt, and tin, or a metal alloy, including but not limited to zinc-nickel, nickel-phosphorus, cobalt-phosphorus, or similar materials.

[0040] In one embodiment, the substrate may optionally be immersed in a metal coloring solution for 0 to 6 minutes before plating. In one embodiment, the substrate may be immersed for about 3 minutes. Immersing the substrate in the metal coloring solution allows metal ions to completely diffuse into the pores and allows any residual anodic oxidation solution to be rinsed out of the pores.

[0041] In one embodiment, the plating process for generating metal nanorods at the base of the pores and coloring the substrate can be carried out in multiple stages. The first color deposition stage can proceed over a first plating period. During the first plating period, the first DC plating current profile is set to a predetermined percentage of the second plating current. The second plating current is set to a predetermined percentage of the nominal plating current corresponding to the selected bath composition. The first plating current may be selected to be 10% to 50% of the second plating current. In one embodiment, the first plating current may be selected to be approximately 33% of the second plating current.

[0042] The second plating current may be selected to be 1% to 20% of the nominal plating current corresponding to the selected bath composition. In one embodiment, the second plating current may be selected to be approximately 10% of the nominal plating current corresponding to the selected bath composition. The first plating current profile can ensure nucleation of the coloring metal at the bottom of the anodized porous structure. The nominal plating current can be defined by a Technical Data Sheet (TDS) provided by the plating bath preparer.

[0043] For example, the DC plating current for the semi-bright nickel baths mentioned herein is 2-4 A / dm 2It may be so. In one embodiment, the nominal plating current is 3 A / dm for the bath described herein. 2 This may be the case. The first current profile may be set such that the plating current changes gradually from 0 to a selected current over a period of 2 to 8 minutes. In one embodiment, the current may be increased gradually over a period of 3 minutes.

[0044] The second plating period may be sufficient to grow metal nanorods to partially fill the anodic oxide pores without reaching the top of any of the pores. In one embodiment, the second plating period depends on the thickness of the anodized film and the desired brightness, as will be described later.

[0045] A sufficient time can be defined by the following function. In one embodiment, 2 to 10 minutes is sufficient time to generate a black surface within a 6-micron anodic oxide layer in a semi-bright nickel bath with a second plating current of 10% of the nominal plating current. The plating rate corresponding to this reduced current has been found to be 0.05 to 0.5 times the plating rate corresponding to the bath under nominal operating conditions. Therefore, the plating period for which the plating current is applied is given by the following equation (1):

number

[0046] In one embodiment, pulsed DC or pulsed / pulsed inversion plating can be employed. Pulsed plating can result in uniform nanorod length by both limiting hydrogen generation and altering metal nucleation at the base of the anodic oxidation pores.

[0047] In one embodiment, the first electrodeposited layer can be deposited from a semi-bright nickel bath, for example, Chemipure / Niflow, commercially available from CMP India. In another embodiment, the first electrodeposited layer may be deposited from a copper bath. In yet another embodiment, the electrodeposited layer may be deposited from a simple nickel sulfate bath. In yet another embodiment, the first electrodeposited layer may be deposited from a zinc-nickel bath available from Atotech Corporation. Here, the availability of zinc in the first electrodeposited layer may be useful for generating a transparent seal layer, as will be further described later. Other suitable metal layers can be selected by those skilled in the art.

[0048] In block 118, method 100 seals the substrate according to one of several methods. For example, a coating (e.g., a colored coating via the above-mentioned metal plating) may be sealed. Sealing the coating ensures that the coating provides corrosion resistance while retaining its color. A 6-micron coating has sufficient scratch resistance for most applications, but without the sealing process, its corrosion resistance is insufficient.

[0049] In one embodiment, the sealing process can completely close the pores, making the substrate surface water-impermeable and providing high corrosion resistance. Traditionally, anodized substrates are sealed by immersion in a bath of boiling water or nickel acetate. Such a process only minimizes corrosion of the film, including large pores formed primarily in the phosphoric acid anodizing bath. To ensure that the sealing does not interfere with the appearance of the film, the sealing layer may be transparent and may provide low refractive index spaces (voids) above the metal nanorods. Unlike traditional sealing techniques, two sealing approaches produce acceptable results.

[0050] In one embodiment, the required voids are maintained by blocking the anodic oxidation pores with transparent nanoparticles. The transparent nanoparticles are sized to match the width of the pore openings. In one embodiment, the transparent nanoparticles are polymethyl methacrylate (pMMA) nanoparticles, and an emulsion of pMMA in water is deposited on the colored surface. The inventors have found that by depositing a diluted solution on the surface, the pores are effectively blocked as the transparent nanoparticles are drawn into the pores by capillary action as the solvent (water, ethanol, or other suitable solvent) dries. In one embodiment, the color is maintained by blocking 60% to 100% of the pores. In a preferred embodiment, >90% of the pores are blocked. Figure 13 shows a cross-section of a film according to one embodiment of the present invention. Here, transparent pMMA nanoparticles 1301 block the anodic oxidation tube pore 1302, allowing the transparent pDUDMA seal (or similar transparent seal) 1303 to cover and completely protect the film surface while maintaining the void within the pore 1302. This void is essential for maintaining the refractive index between the air and the pore wall 1305. The refractive index is the cause of the surface color, as shown below.

[0051] In one embodiment, transparent pMMA nanoparticles of appropriate size were generated from a bath containing 20-100 mL / L of methyl methacrylate (MMA) along with 0.001-1 wt% sodium dodecyl sulfate (SDS) relative to the MMA to control the number and size of micelles. The inventors found that controlling the size of the micelles into which the MMA migrates controls the particle size. Transparency is ensured by controlling the initiator dynamics and lowering the polydispersity index of pMMA by adding sodium bicarbonate or another alkali metal bicarbonate as a buffer at 0.5-2 wt% relative to the MMA. Ammonium persulfate (APS) is the initiator, and the MMA is polymerized by adding it at 0.4-2.5 wt% of the monomer. Sodium bisulfite or a similar alkali metal bisulfite is added as a reducing agent.

[0052] In another embodiment, any transparent nanoparticles may be used to block the pores.

[0053] In one embodiment, the sealing approach uses a SOL / GEL process. In the SOL / GEL process, alumina SOL is formed and deposited on the surface. In one embodiment, such alumina SOL is prepared with 0.025 M aluminum tri-sec-butoxide (ATSB) and the remainder of a solution formed with 1.5 mL of anhydrous ethanol per gram of ATSB, hydrochloric acid to adjust the pH, and water of appropriate purity. The process of combining these reagents in the correct order and in the correct manner will be apparent to those skilled in the art. SOL can be deposited by immersing the article in SOL, spraying the surface with 1 to 5 light coats (3 light coats in some cases), or using electrophoretic deposition to fill the pores. In one embodiment, SOL can fill the pores with little or no effect on the colored surface. After filling the pores, the substrate is baked at 100°C to 300°C (approximately 120°C in one embodiment) for 10 minutes to 480 minutes (approximately 30 minutes in one embodiment) to change the SOL so that the SOL seals the surface and provides a transparent appearance.

[0054] In one embodiment, the sealing approach may use a surface polymerization film. Here, the surface can be activated by heating to 100-300°C (less than approximately 200°C in one embodiment) for 0-180 minutes (30 minutes in one embodiment). Alternatively, the surface can be activated by immersion in a diluted solution of ZnO nanoparticles and drying before monomer application. Monomers are selected from precursors including, as an example, polyurethane dimethacrylate (PUDMA), methyl methacrylate (MMA), methyl acrylate (MA), butyl acrylate (BA), and butyl methacrylate (BMA). In one embodiment, PUDMA may be selected as the monomer. The monomer is applied to the surface by spin coating, spray coating, or other methods. The surface is exposed to 500 microwatts (μW / cm²) per square centimeter at wavelengths of 200 nanometers (nm) to 400 nm (approximately 254 nm in one embodiment). 2 ) ~2000 μW / cm²2 (In one embodiment, it is irradiated with ultraviolet (UV) light at an intensity of about 1000 μW / cm 2 ) for 2 to 60 minutes (about 10 minutes in one embodiment). The polymer is then cured at a temperature of 30 to 120 °C (80 °C in one embodiment) for 1 to 12 hours (about 2 hours in one embodiment). The result is an optically clear and tough film that is well-bonded to the surface.

[0055] In another embodiment, the sealing layer may be an automotive clear coat or an electrophoretic clear coat. As will be apparent to those skilled in the art, numerous sealing approaches can be employed as long as the sealing material is optically transparent. In step 120, method 100 ends.

[0056] FIG. 2 shows an example of an anodized layer / film 204. The anodized layer 204 is produced from a sulfuric acid bath and can include a barrier layer 203. The pore width 201 may depend on the temperature, composition of the bath, and anodizing voltage. The pore depth 202 may depend on the anodizing voltage and time. The thickness indicated by the dimension 205 of the barrier layer 203 may depend on the bath composition and anodizing voltage. Direct coloring of such surfaces can be difficult based on the relatively narrow pores and (for example, 7 to 15 nm in diameter) inter-pore distances.

[0057] Several methods have been developed to reduce the problem of direct coloring with different degrees of success. Briefly as described above, one such method described in U.S. Patent No. 4,251,330 and subsequent patent specifications is widely known as the Anolok II interference coloring process.

[0058] Here, a low-voltage secondary phosphoric acid anodizing process is used to expand the lower end of the anodizing pores and effectively block certain pores from the electroplating process. Metal is deposited within a subset of the pores, and color is generated by the weakening interference between the incident light rays and the reflected light rays. The light incident on the empty pores is scattered by the metal filling the adjacent pores, darkening the surface.

[0059] Another example briefly mentioned above is disclosed in International Publication No. 01 / 18281 ('181 Patent). The '181 Patent describes the formation of branched nanoporous structures after a sulfuric acid bath by using a combination of low-voltage DC and AC pore expansion, primarily in a phosphoric acid bath. These pore structures are filled from a bath containing a metal salt, typically nickel, using modified AC electrodeposition. Incident light is scattered from the metal, and the film has a dark or black appearance.

[0060] Figure 3 is a cross-sectional view showing an example of a phosphoric acid-anodized substrate 301 of the present disclosure. In one embodiment, the substrate 301 may be anodized primarily in a phosphoric acid anodizing bath, as described above. Unlike a sulfuric acid bath, anodizing in a phosphoric acid bath forms significantly wider pores. A magnified view of a single anodized pore 302 allows for a more easily understood particular appearance of the present invention. The base diameter (dp.base) 305 of the pore opening 303 may be 50 to 150 nm, depending on the anodizing voltage (VA) and bath temperature. Phosphoric acid attacks Al2O3 more aggressively than sulfuric acid, resulting in wider pores. The diameter at the surface (dp.surf) 304 is primarily a function of the bath temperature and phosphoric acid concentration. In one embodiment, the following relationship holds for nominal bath operating temperatures of 18°C ​​to 30°C and phosphoric acid concentrations: (2) to (5):

number

[0061] Widening the pores is a major advantage of using a phosphoric acid anodic oxidation bath, because color is generated by the interference between the incident light 311 and the reflected light 312. Widening the pores 302 provides a wider viewing angle in which the color appears uniform. This is known as "flop" in commercial standards for colored coatings with pigments.

[0062] It has been found that thinning the barrier layer 203 shown in Figure 2 yields improved results. The thickness of the barrier layer 203 is determined by the pore width (d p.baseThe pore width is proportional to the anodizing voltage (VA). Therefore, a lower anodizing voltage can be used to thin the barrier layer 203. Thus, halving the voltage halves the width, allowing, for example, four pores 307 to be generated at the base of a single pore 302, and the thickness of the barrier layer 203 to be halved. Subpores (e.g., pores 307) can be generated in a short time, typically less than 10 minutes, or in some embodiments less than 5 minutes. Halving the anodizing voltage a second time results in a total of 16 subpores 308 and an extremely thin barrier of less than 25 nm. Thinning the barrier layer 203 facilitates the deposition of the coloring metal 309.

[0063] Figure 9 is an example diagram illustrating the color generation mechanism of the present disclosure. Figure 9 illustrates the main processes by which an anodized and plated film based on the present disclosure affects both hue and brightness.

[0064] In one embodiment, the film includes a nanostructured substrate 901, a barrier layer 902, a pore 903, and a lateral pore 904 within the pore wall 905. Two optical paths are shown. Optical path 920 corresponds to light entering the pore 903. Optical path 920 may be directly absorbed by the nanostructured metal film or reflected by the nanostructured metal film. The reflected light may exit the pore 903 as shown by line 922, or be absorbed by the lateral pore 904 as shown by line 923. The absorption is understood to be a combination of total internal reflection and surface plasmon effect. Optical path 940 represents light that enters the pore wall 905 directly, or enters the lateral pore 904 and is refracted by the pore wall 905. The metal film on the pore wall 905 acts as an optical guide, channeling the light to the substrate 901. Light is reflected / refracted by the film / substrate boundary and the film / nanostructure metal boundary 942. The channel of the barrier layer 902 between the nanostructure metal film and the substrate 901 acts as a bandpass filter for light. The peak admittance frequency depends on the thickness of the barrier layer 902. Light exiting the filter, as shown by line 944, is transported to the surface through the pore wall 905. The relative refractive indices of the alumina film (905), aluminum substrate (901), metal nanorods (942), and air within the pores (903) are the cause of the color. The inventors have determined that the voids are important for minimizing light absorption (and thus the black or dark-colored film). A further cause of color is the dimensions of the photonic crystal formed by the spacing of the lateral pores (904), which is related to the thickness of the barrier layer.

[0065] While I don't want to be bound by theory, it can be understood that two distinct mechanisms influence the perceived color of the film. Brightness may depend on pore size and light absorption within the pores. Hue may depend on the thickness and uniformity of the barrier layer.

[0066] Referring again to Figure 3, several publications suggest that the horizontal pores 306 shown in Figure 3 are due to copper in the aluminum alloy. However, when filled with nickel, the horizontal pores 306 act as nanoparticles and can absorb light 313 by surface plasmon absorption.

[0067] Many aluminum alloys naturally contain copper; for example, 6061 aluminum contains 0.15-0.4% copper, while 6022 aluminum contains 0.01-0.11% copper. Variations in the amount of copper affect the number of horizontal pores 306 and, consequently, the darkness of the coating. Adding 0%-0.5% (or about 1% in one embodiment) of copper sulfate to the anodic oxidation bath makes it possible to overcome copper deficiency in some alloys. Chelating agents, such as ethylenediaminetetraacetic acid (EDTA) or similar chemicals, can prevent copper deposition on the cathode plate.

[0068] Therefore, this disclosure clarifies the fundamental differences between colored surfaces produced using sulfuric acid anodized surfaces and colored surfaces produced by this disclosure.

[0069] Figure 7 shows an example of an ultraviolet imaging spectrometer (UVIS) spectrum corresponding to the colored hybrid coating on 6061 aluminum of this disclosure. The UVIS spectrum was measured on a UV2550 spectrophotometer, commercially available from Labomed Inc., against a barium chloride reference. The key cause of the virtually flat absorption spectrum, as expected from the black coloration, is thought to be plasmon absorption by horizontal nanopores. The slightly higher absorption at 200 nm is a result of destructive interference formed by pore widths of approximately 100 nm. Reflections from the pore walls are significantly attenuated at this wavelength. [Examples]

[0070] The following embodiments illustrate specific operating conditions and demonstrate the implementation of the disclosure. However, these embodiments should not be considered limiting to the scope of the disclosure. The embodiments are selected to specifically illustrate the manner of coloring of thin anodized alloy surfaces.

[0071] Example 1 - Effect of Ra (average roughness) reduction pretreatment on hybrid anodized 6061Al with electrodeposited SB-Ni Eleven examples of colored coatings comprising a thin anodized layer in combination with a semi-gloss nickel layer provide dark black surfaces with varying degrees of gloss.

[0072] Each sample was a 2 cm x 2 cm 6061 aluminum specimen, which was mechanically polished using wet emery paper in several steps ranging from 400 grit to 1200 grit. The mechanical polishing process varied for each sample.

[0073] Next, surface contaminants were removed by immersing each sample in a 70°C commercial alkaline Prelude AC-100 bath with gentle aeration for 8 minutes. The samples were then rinsed with DI water.

[0074] Samples requiring a surface finish with extremely low average roughness (Ra) were then electropolished for 0 to 4 minutes in a bath containing H3PO4, HF, H2SO4, and glycerol in a volume ratio of 70:2:8:20. The electropolishing bath was maintained at a temperature of 80°C with a voltage of 12V applied between the test specimen and the Pb cathode to produce surfaces with an average roughness (Ra) of 0.1 to 0.5. The average roughness (Ra) of each sample was measured.

[0075] Next, the electropolished substrate was rinsed in DI water before activation, and the surface was conditioned by immersion in 50% by volume nitric acid at room temperature for 1 minute.

[0076] The test specimens were uniformly anodized in an anodic oxidation bath at 27°C for 10 minutes. The anodic oxidation bath composition was H3PO4 205 mL / L, H2SO4 0.6 mL / L, and HOOCCOOH 1 g / L. 2 A / dm 2 Constant current anodizing treatment was performed. It is believed that constant current anodizing treatment is used when coloring a thin film to create a more uniform anodic oxide pore structure. Under these conditions, the voltage rapidly increased to 58V and then slowly decreased to approximately 45V. The anodic oxide layer was approximately 2.5 microns thick.

[0077] On the electrodeposition stage, semi-bright nickel was electroplated into the anodic oxidation pores. The bath was a commercial CheMiPure SB bath, commercially available from CMT Pvt. Ltd of India. The plating time was 90 minutes, and the temperature was 60°C. Initially, the current was 0 A / dm 2 From 0.10 A / dm 2 The current is then changed with a gradient over 2 minutes, and then 0.1 A / dm over 80 minutes. 2 This was maintained at a constant level. This was the nominal plating current of the selected bath, 2-4 A / dm 2 Compared to the above, the semi-gloss nickel filling thickness was 2.5 microns, and the anodized layer was approximately 1 micron thick.

[0078] The resulting film was a uniform glossy black. Figure 10 is an example graph showing the relationship between the average surface roughness of the substrate and the gloss of the film of this disclosure. Graph 1001 shows a fit curve demonstrating the relationship between the initial average surface roughness of the substrate and the measured gloss in gloss units (GU) of the colored film. GU 100 represents a highly polished reference black sample, while GU 0 represents a completely matte sample.

[0079] Example 2 - Effect of Ra-enhancing pretreatment on hybrid anodized 6061Al with electrodeposited SB-Ni A colored coating containing a thin anodized layer in combination with a semi-gloss nickel layer provides a matte dark black surface.

[0080] A 2 cm x 2 cm 6061 aluminum test specimen was mechanically polished using 400 grit wet emery abrasive paper to achieve an average surface roughness of Ra 2.5.

[0081] Next, surface contaminants were removed by immersing the sample in a 70°C commercial alkaline Prelude AC-100 bath with gentle aerating for 8 minutes. The sample was then rinsed with DI water.

[0082] Next, the substrate was rinsed in DI water before activation, and the surface was conditioned by immersion in 50% by volume nitric acid at room temperature for 1 minute.

[0083] The test specimens were uniformly anodized in an anodic oxidation bath at 27°C for 10 minutes. The anodic oxidation bath composition was H3PO4 205 mL / L, H2SO4 0.6 mL / L, and HOOCCOOH 1 g / L. 2 A / dm 2 Constant current anodizing treatment was applied. It is believed that applying constant current anodizing treatment when coloring a thin film results in the creation of a more uniform anodic oxidation pore structure.

[0084] Under these conditions, the voltage rapidly increased to 58V and then slowly decreased to approximately 45V. The anodic oxide layer was approximately 2.5 microns thick. On the electrodeposition stage, semi-bright nickel was electroplated into the anodic oxide pores. The bath was a commercial CheMiPure SB bath, commercially available from CMT Pvt. Ltd of India. The plating time was 90 minutes, and the temperature was 60°C. Initially, the current was 0 A / dm 2 From 0.10 A / dm 2 The current is then changed with a gradient over 2 minutes, and then 0.1 A / dm over 80 minutes. 2 This was maintained at a constant level. This was the nominal plating current of the selected bath, 2-4 A / dm 2 Compared to that, the thickness was approximately 1 micron.

[0085] The resulting film was dull black. Figure 4 is a scanning electron microscope (SEM) image 401 showing an example of a phosphorylated structure of the present disclosure. SEM image 401 shows an unsealed colored film on a 6061 aluminum substrate based on one embodiment of the present disclosure. Here, the anodizing voltage was approximately 58V, and the anodic oxidation rate was calculated from 1 square micron 402 to be 60 / μm 2 The pore density was given, and the average pore width was 80 nm (invisible). The effect of pore widening on the surface can be clearly seen from 100 square nm 403 with a pore width of approximately 105 nm.

[0086] Figure 5 is an SEM image showing an example of a cross-section of the anodized colored substrate of this disclosure. Figure 6 is an SEM image showing an example of a close-up image of the cross-section of the anodized colored substrate of this disclosure. In Figures 5 and 6, the anodized colored substrate is 6061 aluminum.

[0087] Figure 5 shows the aluminum substrate 501. Figure 5 shows how horizontal pores connect to the main pores within box 502 at a density of approximately one pore every 100 nm in the case of a 4% copper content. Horizontal pores are not present closest to the surface. Here, pore widening occurs due to dissolution in the anodic oxidation bath. The resulting film is shown in insert image 503. This image shows the following properties (L * ,a * ,b * It has the characteristic (CIELAB) (7.1, -1.0, 0.5).

[0088] Figure 6 shows the aluminum substrate 601. In Figure 6, the periodic filling of pores by nickel can be clearly seen in box 602.

[0089] Example 3 - Relationship between anodic oxidation time and plating metal deposition time in surface color generation Approximately 32 6061-T6 aluminum substrates were prepared for this example. Each sample was 3 cm × 5 cm and prepared equally.

[0090] Next, surface contaminants were removed by immersing each sample in a 70°C commercial alkaline Prelude AC-100 bath with gentle aeration for 10 minutes. Smut was removed from the surface by immersing the samples in 50% nitric acid. The samples were rinsed with DI water between each step.

[0091] The main anodic oxidation bath compositions were H3PO4 205 mL / L, H2SO4 0.6 mL / L, and HOOCCOOH 1 g / L. A titanium mesh was used as the counter electrode, and the anodic oxidation bath electrolyte on the surface of the example was restored using strong air agitation. The anodic oxidation bath was placed in a water bath, and the solution temperature was maintained at 24±1°C to 36±1°C depending on the bath composition and the desired color.

[0092] By varying the bath composition, higher anodic oxidation voltages were supported. For voltages of 90–120V, H3PO4 was excluded, and a 75–80% ethanol solution was used instead of DI water. From 120–150V onwards, ethylene glycol was used as the solvent instead of DI water. At >150V, 50% H3PO4 and 50% NaH2PO4 were used instead of H3PO4.

[0093] Constant voltage DC anodizing was employed, with the voltage limited to the range of 60-280V. In addition, the maximum current was limited to 2.0 A / dm2. Eight samples were anodized under each voltage condition. The anodizing process was carried out for various periods of approximately 15 to 25 minutes. The duration was determined by the total charge passed. The total charge was calculated for each treated sample from the voltage and current records measured over the anodizing period. For each voltage, the charge passed was kept constant for the eight samples. After anodizing, the samples were immediately rinsed in DI water and then immersed in a metal deposition solution.

[0094] In the electrodeposition stage, semi-gloss Ni was electroplated into the anodic oxidation pores. The bath used was CheMiPure SB, a commercially available bath from CMT Pvt. Ltd of India. The bath was maintained at a temperature of 60°C, and air agitation was used to ensure uniformity of the deposit. Initially, the current was 0 A / dm 2 From 0.1 A / dm 2 Next, the gradient was applied and changed over 2 minutes, and then, as shown in Figure 8 and described in more detail below, 0.1 A / dm over various periods. 2 It was kept constant.

[0095] After rinsing the plated samples in DI water and carefully drying them, the samples were imaged against a white background, and color measurements were performed by calculating the L, a, b color coordinates of the samples using ImageJ 1.52 software.

[0096] Sample data was analyzed to create a model of the color generation mechanism. Figure 8 is an example graph showing the relationship between voltage (60-280V), plating amperage (2-10 amperage), and color in the process of this disclosure. The graph in Figure 8 shows representative sample colors as spectra corresponding to each anodizing voltage and nickel electrodeposition time. In each case, the color corresponding to a given anodizing voltage follows a spectrum from silver / gray, through a specific color corresponding to the anodizing voltage, to the metallic color corresponding to the plated metal.

[0097] It is understood that several processes may be involved in the film color. Figure 6 above shows a cross-section of a row of partially filled anodic oxidation pores. Low deposition ampere-min / dm 2 (<2 amperes-min / dm 2 ) deposits little to no metal (i.e., extremely short metal nanorods) (e.g., bar 802 in Figure 8), regardless of the anodic oxidation charge that passes through. Here, light is almost entirely reflected by the substrate, resulting in transparency of the barrier layer color through the silver-gray appearance of the aluminum alloy of the underlying substrate (as determined by substrate 901 in Figure 9, for example).

[0098] For narrow anodized pores (e.g., low anodizing voltage), as more metal deposition amperes-minutes are applied, the substrate is rapidly shielded by the nanostructured metal 942 shown in Figure 9. The resulting color is primarily a function of light absorption by the glossy metal deposition (e.g., the lateral pores 923 shown in Figure 9). Both light entering the pore (e.g., optical path 920) and light reflected from the substrate and entering the anodized layer (e.g., optical path 940) are involved in light absorption. This produces a black or gray band, as indicated by bar 803 in Figure 8. However, as the anodizing voltage increases, wider pores can be formed, and metal deposition becomes easier accordingly. This results in a compact metal layer at the base of the pore. Here, the film color is dominated by a combination of light absorption within the pore and the blue spectrum of color produced by the selective absorption of light across barrier layers of these thicknesses (e.g., barrier layer 902 shown in Figure 9). As the anodic oxidation voltage increases, the pores widen, and for each anodic oxidation voltage, a dominant color is generated from violet-purple (bar 803 in Figure 8), shades of blue (bars 804-806 in Figure 8), green (bars 807-808 in Figure 8), yellow (bar 809 in Figure 8), orange (bars 811-812 in Figure 8), and red (bar 813 in Figure 8). As the pores widen, the range of metal deposition amperes-minutes over which the color is perceptible increases.

[0099] As the ampere-min of metal deposition increases, the average pore filling also increases. At high ampere-mins, metallic color is dominant (as indicated by bar 801 in Figure 8). However, periodic filling ranges occur based on variations in the nucleation process (e.g., shown in the image in Figure 5). Three color generation mechanisms compete to produce the perceived film color. Firstly, the depth of deposited metal controls the amount of light absorption. Here, lateral pore filling provides excess absorption due to the plasmon effect, as shown in the image in Figure 5.

[0100] Secondly, the light refracted and reflected between the barrier layer and the lower aluminum substrate is then filtered in a form determined by the geometry and length of the light pipe (e.g., the optical path shown by line 940 in Figure 9). The frequency selectivity of this light pipe is proportional to its length. This length depends on the depth of the metal in the hole, the hole diameter, and the thickness of the anodized film barrier layer. As will be apparent to those skilled in the art, there are multiple effective lengths of the light pipe, depending on the angle of incidence and associated reflection. Thus, there are transmission and absorption spectra.

[0101] Finally, light is directly reflected from the metal surface. Here, the distance between the metal surface and the top of the hole results in destructive or constructive interference depending on the optical path length and wavelength, as shown by the optical paths indicated by lines 920 and 922 in Figure 9.

[0102] The distribution of wavelengths emanating from the film generates the perceived film color, and the total amount of incident light absorbed within the structure causes the resulting color to be darker or the brightness to decrease. Here, the film tends to move towards black. The narrower the pores, and consequently the narrower the lateral walls, the more constrained the light path becomes. This leads to greater control over the film color. This allows for a broader metallic deposition zone where a single color is perceived.

[0103] Table 1 shows the resulting color (RGB) and color variation (ΔE) across the entire surface for several anodizing voltages and temperatures. Higher temperatures in any given bath formulation increase the porosity of the anodized surface and darken the color. [Table 1]

[0104] Example 4 - Relationship between phosphoric acid concentration and maximum anodic oxidation thickness Fifteen 6061-T6 aluminum substrates were prepared equally.

[0105] Next, surface contaminants were removed by immersing each sample in a 70°C commercial alkaline Prelude AC-100 bath with gentle aeration for 10 minutes. Smut was removed from the surface by immersing the samples in 50% nitric acid. The samples were rinsed with DI water between each step.

[0106] The anodic oxidation bath composition in each case was H3PO4 (100 ml / l to 210 ml / l depending on the sample), H2SO4 (0.6 mL / L), and HOOCCOOH (1 g / L). The counter electrode was a titanium mesh, and the anodic oxidation bath electrolyte on the surface of the example was restored using strong air agitation. The anodic oxidation bath was placed in a water bath, and the solution temperature was maintained at 25 ± 1°C.

[0107] Constant voltage DC anodizing was employed with the voltage limited to 60V. In addition, the maximum current was limited to 2.0A / dm2. Anodizing was performed for various periods ranging from approximately 20 minutes to 120 minutes. The duration was determined by the total charge passed through. The total charge was calculated for each sample treatment from the voltage and current records measured over the anodizing period.

[0108] The sample was rinsed in DI water and allowed to change sufficiently. The sample was sectioned, mounted as a metallographic specimen, and the thickness of the anodized film was measured.

[0109] Figure 11 is an example of a graph showing the maximum achievable anodic oxide layer thickness for several phosphoric acid concentrations in this disclosure. Graph 1101 shows the relationship between the phosphoric acid concentration in the bath and the maximum achievable anodic oxide film thickness. As previously mentioned, thicker films improve the mechanical properties of the film at the expense of the time required to produce the film and the transparency of the colored coating.

[0110] Example 5 - Effects of barrier layer thinning and anodic oxidation bath temperature on a dark gray coating Five 6022-T4 aluminum substrates were prepared equally.

[0111] Next, surface contaminants were removed by immersing each sample in a 70°C commercial alkaline Prelude AC-100 bath for 10 minutes with gentle aerating. The sample was immersed in Probright AL® alkaline cleaner at room temperature for 2 minutes. The sample was smut-removed in 50% nitric acid at room temperature for 90 seconds. The sample was electropolished in a bath containing H3PO4, HF, H2SO4, and glycerol in a volume ratio selected from the following range: 70-85:2-4:6-9:5-20. The electropolishing bath was maintained at a temperature of 65 degrees Celsius (°C), a voltage of 12V, and with a Pb counter electrode for 0-8 minutes. The sample was rinsed with DI water between each step.

[0112] The anodic oxidation bath composition in each case was H3PO4 (150 ml / l to 250 ml / l depending on the sample), H2SO4 (0.6 mL / L), and HOOCCOOH (1 g / L). A titanium mesh was used as the counter electrode, and the anodic oxidation bath electrolyte on the surface of the example was restored using strong air agitation. The anodic oxidation bath was placed in a water bath, and the temperature of the anodic oxidation bath was maintained using ice, so the temperature varied between 27 and 33 ± 3°C depending on the sample.

[0113] Constant voltage DC anodizing was employed with the voltage limited to 60V. In addition, the maximum current was limited to 2.0A / dm2. Anodizing was performed for 20 minutes, and various barrier layer thinning periods were applied to each sample for a total of 10-12 minutes at a reduced anodizing voltage of 30V and / or 15V. The samples were rinsed in DI water and immediately placed in the electroplating bath.

[0114] The sample was placed in a Chemipure / Niflow semi-bright nickel plating bath, commercially available from CMP India. The bath was maintained at 60°C, and the anode was a nickel chip in a bagged titanium mesh basket. Nickel ions were initially allowed to penetrate the pores by immersing the sample for 3 minutes. The plating current was set to 0 A / dm². 2 From 0.1 A / dm 2The current was then changed with a gradient over a period of 2 minutes. After that, the current was changed to 0.1 A / dm² over a further 2 minutes. 2 The current was then maintained at 0.3 A / dm² for an additional 10 minutes. 2 It increased to [a certain value]. The sample was then rinsed and dried.

[0115] Figure 12 is a set of image examples and a table illustrating the effects of barrier layer thinning and temperature on the film color of the present disclosure. Figure 12 shows the resulting samples 1201-1205, their color profiles, and anodizing temperatures. The anodizing bath temperature has only a slight effect on pore size and barrier layer thickness, but significantly affects the total dissolution rate of the anodized layer in the phosphoric acid bath. The level and scale of barrier layer thinning also control how much of the visible spectrum of light is filtered out from the light reflected from the film. This causes a change in color. In Figure 12, all five samples 1201-1205 exhibit a dark gray color, but samples 1201, 1202, and 1205 contain a blue hue, sample 1203 contains a red hue, and sample 1204 exhibits an orange-yellow hue. Table 1206 shows various processing parameters for each of the samples 1201-1205.

[0116] Example 6 - Effect of copper on color Three 6061-T6 aluminum substrates and three 6022-T4 aluminum substrates were prepared equally.

[0117] Surface contaminants were removed by immersing each sample in a 70°C commercial alkaline Prelude AC-100 bath with gentle aeration for 10 minutes. Smut was removed from the surface by immersing the samples in 50% nitric acid. The samples were rinsed with DI water between each step.

[0118] The anodic oxidation bath composition in each case was H3PO4 (30 ml / l to 300 ml / l depending on the sample), H2SO4 (0.6 mL / L), and HOOCCOOH (1 g / L). The counter electrode was a titanium mesh, and the anodic oxidation bath electrolyte on the surface of the example was restored using strong air agitation. The anodic oxidation bath was placed in a water bath, and the solution temperature was maintained at 25 ± 1°C.

[0119] Constant voltage DC anodizing was employed, with the voltage limited to 60-100V, depending on the 6061 / 6022 sample comparison pair. In addition, the maximum current was limited to 2.0 A / dm2. Anodizing was performed for various periods ranging from approximately 20 minutes to 120 minutes. The duration was determined by the total charge passed through. The total charge was calculated for each sample treatment from the voltage and current records measured over the anodizing period.

[0120] Each sample was rinsed in DI water and allowed to change sufficiently. The samples were sectioned and mounted in resin via metallographic preparation. The anodized films were investigated for pore size, as well as the occurrence rate, size, and frequency of lateral pores (1204 in Figure 12) that form interporosity.

[0121] As shown in Table 1 below, for the same anodizing voltage and charge passed, the 6061 sample had larger and more numerous lateral pores compared to the 6022 sample, although the 6022 aluminum alloy had wider pore diameters. Roughly speaking, the volume of lateral pores generated is proportional to the copper content of the alloy, while the change in main pore volume is related to the volume of lateral pores.

[0122] The measured luminances for the 6022 and 6061 aluminum alloy samples were 45.5 and 25.8, respectively. The change in luminance corresponds directly to the change in lateral hole diameter, the assumed light absorption by lateral hole 923, and the optical path described above, represented by line 920 in Figure 12. [Table 2]

[0123] Example 7 - Effect of hole plugging and sealing Ten 100 x 25 mm 6061 aluminum substrates were anodized and colored to produce the dark gray surface described above. The samples were either left unsealed, sealed only with DUDMA, or the nanopores were blocked with pMMA (to maintain voids) followed by sealing with DUDMA.

[0124] Regarding the DUDMA seal, a solution of ZnO nanoparticles in DI water acted as a surface initiator by adhering to the surface and drying, maintaining the transparency of the pDUDMA coating. The surface was then immersed three times in pure DUDMA diluted to 80 vol% with tetrahydrofuran (THF) or an organic substance to control evaporation, such as acetone or ethyl acetate. The sample was exposed to strong UV light with a dominant wavelength of 365 nm while simultaneously being heated to 75 ± 5°C. After 30 minutes, the DUDMA polymerized to form a transparent film.

[0125] MMA nanoparticles were pre-prepared to seal the openings in a porous, anodized film. 180 mL of deionized water was added to a 300 mL Erlenmeyer flask along with 0.070 g of potassium bicarbonate (KHCO3), 0.024 g of ammonium persulfate (APS), and 0.029 g of sodium dodecyl sulfate (SDS), and the mixture was stirred at 600 rpm by magnetic stirring. The solution was heated to 75°C. 5 mL of methyl methacrylate (MMA) monomer was added to the flask, followed by 0.0070 g of sodium bisulfite (NaHSO3). The flask was loosely sealed with a stopper, and the temperature was monitored for 3 hours. The solution was then removed and rapidly cooled to room temperature by immersion in an ice bath.

[0126] Thermogravimetric analysis showed a 90% conversion yield from MMA monomer to PMMA nanoparticles. Dynamic light scattering indicated an average particle size of 110 nm with a polydispersity index of 0.02.

[0127] By photographing a sample in an optical cabinet with an image processed using ImageJ software, color changes are measured, thereby determining the color in RGB terms and the variance ΔE between average colors of samples.

number

[0128] The sealed samples showed an 8-fold improvement in corrosion resistance, as shown in Table 2, but the apparent color was noticeably different. This difference was more pronounced with lighter samples, with a ΔE of >20. Samples with pores blocked with nanoparticles and sealed with pDUDMA showed a 20-fold improvement in corrosion resistance and imperceptible color change.

[0129] Corrosion performance was measured by a neutral salt spray test according to standard B117. Samples were rinsed, washed, and analyzed daily for corrosion. The time to the first corrosion was recorded. [Table 3]

[0130] Needless to say, variations and other features and functions of those disclosed above, or combinations thereof, can be used to create a number of other different systems or applications. Various alternatives, modifications, changes, or improvements thereafter can be made by those skilled in the art that are not currently foreseeable or anticipated. These are also included in the claims below. Some embodiments of the present invention are described in the following sections [1]-

[37] . [1] (a) An anodic oxidation layer including a barrier layer is generated by anodic oxidation of the substrate in an anodic oxidation bath containing phosphoric acid over a first period at a constant temperature and constant voltage. (b) By reducing the constant voltage applied to the anodic oxidation bath over a second period, the thickness of the barrier layer is changed and the width of the pores in the anodic oxidation layer is changed. (c) Plating the substrate in a plating bath with a first current that is increased over a third period according to the current profile of the plating bath, and (d) Plating the substrate in the plating bath with a second current over a fourth period, A method that includes the following steps. [2] The method according to item 1, wherein the substrate comprises an aluminum alloy. [3] The method according to item 1, wherein in step (a), the anodic oxidation bath further comprises copper sulfate and a chelating agent. [4] The method according to item 1, wherein in step (a), the constant temperature is a temperature of 20°C to 40°C. [5] The method according to item 1, wherein in step (a), the maximum current density is 2 amperes per square decimeter, and the constant voltage is a voltage of 60 volts to 280 volts. [6] The method according to item 1, wherein in step (b), the constant voltage is reduced by 50%, and the second period includes 2 to 10 minutes. [7] The method according to item 1, further comprising reducing the constant voltage applied to the anodic oxidation bath again before the plating in step (b). [8] The method according to item 1, wherein in step (b), the voltage applied to the anodic oxidation bath is reduced to (i) reduce the thickness of the barrier layer and (ii) increase the width of the pores in the anodic oxidation layer. [9] The method according to item 1, wherein the barrier layer is positioned between the substrate and the anodic oxidation pore.

[10] The method according to item 1, wherein in step (d), the plating of the substrate partially fills the pores in the anodic oxide layer with metal nanorods.

[11] The method according to item 10, further comprising the step of covering the resulting pores in the anodized layer with a sealing layer.

[12] The method according to item 10 or 11, wherein the step of covering the hole with a sealing layer forms a gap between the hole and the sealing layer.

[13] (a) An anodic oxidation of an aluminum alloy substrate in an anodic oxidation bath containing phosphoric acid over a first period at a constant temperature and constant voltage to generate an anodic oxidation layer with a thickness of 2 to 10 microns, wherein the anodic oxidation layer includes a barrier layer. (b) By reducing the constant voltage applied to the anodic oxidation bath over a second period, the thickness of the barrier layer is changed and the width of the pores in the anodic oxidation layer is changed. (c) Plating the aluminum alloy substrate in a plating bath with a first current that is increased over a third period according to the direct current (DC) plating current profile of the plating bath. (d) Plating the aluminum alloy substrate in the plating bath with a second current over a fourth period to partially fill the pores in the anodized layer, and (e) sealing the holes in the anodized layer, A method that includes the following steps.

[14] The method according to item 13, wherein in step (a), the anodic oxidation bath contains 50 to 600 milliliters (ml / L) of phosphoric acid, 1 to 15 ml / L of sulfuric acid, and 1 to 10 grams (g / L) of HOOCCOOH per liter.

[15] The method according to item 13, wherein in step (a), the anodic oxidation bath comprises 0 to 5 weight percent copper sulfate and ethylenediaminetetraacetic acid (EDTA).

[16] The method according to item 13, wherein in step (a), a pulsed DC current is applied to the anodic oxidation bath.

[17] In step (c), the plating bath has a nominal plating current of 2 amperes per square decimeter (A / dm 2 )~4A / dm 2 The method according to item 13, comprising a semi-bright nickel bath.

[18] The method according to item 17, wherein in step (d), the second current is 1% to 20% of the nominal plating current of the plating bath.

[19] The method according to item 17 or 18, wherein the first current is 10% to 50% of the second current.

[20] The method according to item 13, wherein the barrier layer is positioned between the substrate and the anodic oxidation pore.

[21] The method according to item 13, wherein in step (d), the plating of the substrate partially fills the pores in the anodic oxide layer with metal nanorods.

[22] The method according to item 13, wherein in step (e) of sealing the pores in the anodized layer, a void is formed between the pores and the sealing layer.

[23] (a) Optionally, pre-treat the aluminum alloy substrate. (b) Activating the aluminum alloy substrate, (c) An anodic oxidation of the aluminum alloy substrate in an anodic oxidation bath containing phosphoric acid over a first period at a constant temperature and constant voltage, thereby generating an anodic oxidation layer including a barrier layer. (d) By reducing the constant voltage applied to the anodic oxidation bath over a second period, the thickness of the barrier layer is changed and the width of the pores in the anodic oxidation layer is changed. (e) Further reducing the thickness of the barrier layer by rinsing the aluminum alloy substrate, (f) Plating the aluminum alloy substrate in a plating bath through multiple plating stages to deposit a coloring metal into the pores of the anodized layer, and (g) sealing the holes in the anodized layer, A method that includes the following steps.

[24] The aforementioned pretreatment step (a) is Degreasing the aluminum alloy substrate in an alkaline bath, Roughening the aluminum alloy substrate in a solution of phosphoric acid, polyethylene glycol, sulfuric acid, and hydrofluoric acid, and Etching the aluminum alloy substrate in a nitric acid solution. The method described in item 23, including the method described in item 23.

[25] The method according to item 24, wherein the average roughness (Ra) of the aluminum alloy substrate is 0.4 to 1.8.

[26] In step (f), the plurality of plating stages, A first plating stage that applies a first current which is increased over a third period according to the current profile of the plating bath, A second plating stage that applies a constant second current over a fourth period, The method described in item 23, including the method described in item 23.

[27] The method according to item 23, wherein the barrier layer is positioned between the substrate and the anodic oxidation pore.

[28] The method according to item 23, wherein in the step (g) of sealing the pores in the anodized layer, a void is formed between the pores and the sealing layer.

[29] A coated structure manufactured according to any of the methods described in items 1 through 12.

[30] A coated structure manufactured according to any of the methods described in items 13 to 22.

[31] A coated structure manufactured in accordance with any of the methods described in items 23 to 29.

[32] A coated structure, ·Metal base layer, A barrier layer located between the substrate layer and the anodized pores. An anodized layer having a plurality of spaced-apart pores that extend through the anodized layer toward the barrier layer, Includes, Each of the holes, spaced apart from each other, has a variable width along its length. A structure with a coating.

[33] The coated structure according to item 33, wherein the width of each spaced-apart pore is narrower at the pore end closer to the base layer and wider at the other end of the pore.

[34] The coated structure according to item 33 or 34, wherein at least some of the spaced holes are partially filled with metal.

[35] A coated structure according to any of items 33 to 35, wherein a coating layer exists so as to cover the aforementioned anodic-oxidized layer.

[36] The coated structure according to item 36, wherein the coating layer seals the holes through the anodized layer.

[37] The coated structure according to item 36 or 37, wherein voids exist at midpoints along the length between at least some of the spaced-apart pores and the coating layer.

Claims

1. (a) An anodic oxidation layer having main pores is generated by anodic oxidation of a substrate in an anodic oxidation bath containing phosphoric acid over a first period at a constant temperature and constant voltage, where each main pore includes a lateral pore, and the anodic oxidation layer includes a barrier layer. (b) By reducing the constant voltage applied to the anodic oxidation bath over a second period, the thickness of the barrier layer is changed and the width of the main pores in the anodic oxidation layer is changed. (c) Plating the substrate in a plating bath with a first current that is increased over a third period according to the current profile of the plating bath, thereby partially filling the main holes and lateral holes and generating a plasmon surface, and (d) Plating the substrate in the plating bath with a second current over a fourth period, and partially filling the main pores and lateral pores with metal nanorods. (e) Covering the main pores of the anodic oxide layer with a sealing layer, and forming a void between the metal nanorod and the sealing layer, A method for forming a colored film on an alloy, including the following steps.

2. The method according to claim 1, wherein the substrate comprises an aluminum alloy.

3. The method according to claim 1, wherein in step (a), the anodic oxidation bath further comprises copper sulfate and a chelating agent.

4. The method according to claim 1, wherein in step (a), the constant temperature is a temperature of 20°C to 40°C.

5. The method according to claim 1, wherein in step (a), the constant voltage is a voltage of 60 volts to 280 volts, with a maximum current density of 2 amperes per square decimeter.

6. The method according to claim 1, wherein in step (b), the constant voltage is reduced by 50%, and the second period includes 2 to 10 minutes.

7. The method according to claim 1, wherein in step (b), reducing the voltage applied to the anodic oxidation bath reduces (i) the thickness of the barrier layer and (ii) the width of the main pores in the anodic oxidation layer.

8. The method according to claim 1, wherein the barrier layer is positioned midway between the substrate and the main hole.

9. (a) An anodic oxidation of an aluminum alloy substrate in an anodic oxidation bath containing phosphoric acid over a first period under constant temperature and constant DC or pulsed current and / or constant DC or pulsed voltage, thereby generating an anodic oxidation layer with a thickness of 2 to 10 microns, wherein the anodic oxidation layer includes main pores, each main pore includes lateral pores, and the anodic oxidation layer includes a barrier layer. (b) By reducing the constant DC or pulsed current and / or constant DC or pulsed voltage applied to the anodic oxidation bath over a second period, the thickness of the barrier layer is changed and the width of the main holes in the anodic oxidation layer is changed. (c) Plating the aluminum alloy substrate in a plating bath with a first current that is increased over a third period according to the direct current (DC) plating current profile of the plating bath. (d) Plating the aluminum alloy substrate in the plating bath with a second current over a fourth period to partially fill the main pores and lateral pores in the anodic oxide layer and to generate a plasmon surface, and (e) sealing the main pores of the anodic oxide layer to form a sealing layer, and creating a void between the main pores and the sealing layer. A method for forming a plasmon-colored film, including the following steps.

10. The method according to claim 9, wherein in step (a), the anodic oxidation bath contains 50 to 600 milliliters (ml / L) of phosphoric acid, 1 to 15 ml / L of sulfuric acid, and 1 to 10 grams (g / L) of oxalic acid per liter.

11. The method according to claim 9, wherein in step (a), the anodic oxidation bath comprises 1 to 5 weight percent of copper sulfate and ethylenediaminetetraacetic acid (EDTA).

12. In step (c), the plating bath has a nominal plating current of 2 amperes per square decimeter (A / dm ２ ) ~4 A / dm ２ The method according to claim 9, comprising a semi-bright nickel bath.

13. The method according to claim 12, wherein in step (d), the second current is 1% to 20% of the nominal plating current of the plating bath.

14. The method according to claim 12, wherein the first current is 10% to 50% of the second current.

15. The method according to claim 9, wherein the barrier layer is positioned midway between the substrate and the main hole.

16. (a) Optionally, pre-treat the aluminum alloy substrate. (b) Activating the aluminum alloy substrate, (c) Anodizing the aluminum alloy substrate in an anodizing bath containing phosphoric acid over a first period at a constant temperature and constant voltage to generate an anodized layer having main pores, where each main pore includes a lateral pore, and the anodized layer includes a barrier layer. (d) By reducing the constant voltage applied to the anodic oxidation bath over a second period, the thickness of the barrier layer is changed and the width of the main pores in the anodic oxidation layer is changed. (e) Plating the aluminum alloy substrate in a plating bath through multiple plating stages to deposit metal nanorods in the main pores and lateral pores of the anodic oxide layer, and (f) Sealing the main pores of the anodic oxide layer and forming a void between the metal nanorod and the sealing layer, A method for forming a colored film on an alloy, including the following steps.

17. The aforementioned pretreatment step (a) is Degreasing the aluminum alloy substrate in an alkaline bath, Roughening the aluminum alloy substrate in a solution of phosphoric acid, polyethylene glycol, sulfuric acid, and hydrofluoric acid, and Etching the aluminum alloy substrate in a nitric acid solution. The method according to claim 16, including the method described in claim 16.

18. The method according to claim 16, wherein the average roughness (Ra) of the aluminum alloy substrate is 0.4 to 1.

8.

19. In step (e), the plurality of plating stages, A first plating stage that applies a first current which is increased over a third period according to the current profile of the plating bath, A second plating stage that applies a constant second current over a fourth period, The method according to claim 16, including the method described in claim 16.

20. The method according to claim 16, wherein the barrier layer is positioned midway between the substrate and the main hole.

21. The method according to claim 16, wherein in step (f) of sealing the main pores of the anodic oxide layer, the void between the main pores and the sealing layer is maintained by nanoparticles adapted to block the main pores.

22. A coated structure manufactured according to the method of any one of claims 1 to 21, ・Metal base layer, - A barrier layer located between the substrate layer and the main pore, - An anodized layer having a plurality of spaced main pores that extend through the anodized layer toward the barrier layer, Includes, Each of the main holes, which are spaced apart from each other, has a variable width along the length of the hole. A structure with a coating.

23. The coated structure according to claim 22, wherein the width of each of the spaced main holes is narrower at the hole end closer to the base layer and wider at the other end of the hole.

24. The coated structure according to claim 22 or 23, wherein at least some of the spaced main holes are partially filled with metal.

25. The coated structure according to any one of claims 22 to 24, wherein a coating layer is present so as to cover the anodized layer.

26. The coated structure according to claim 25, wherein the coating layer seals the main pores through which the anodized layer passes.

27. The coated structure according to claim 25 or 26, wherein voids exist at midpoints along the length between at least some of the main holes which are spaced apart from each other and the coating layer.

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