High hemispherical emissivity surface treatment method

Abstract

The invention relates to the technical field of aluminum alloy sulfuric acid anodic oxidation surface treatment. The invention discloses a high hemispherical emissivity surface treatment method which comprises the following steps: S1, pretreatment: after oil is removed by adopting an alkaline composite oil removal agent, acid pickling is performed by using mixed acid liquor to remove an oxide layer and coarsen the surface at the same time; s2, anodic oxidation with sulfuric acid: placing in a composite system of HSO and citric acid for electrolytic oxidation; s3, coloring: dyeing with a mixed solution of anthraquinone dye and a surfactant; and S4, hole sealing: immersing into a hole sealing solution composed of deionized water and nickel acetate for hole sealing treatment. High emissivity is achieved only through regulation and control of technological parameters, the production process is simplified, and the cost is reduced; the emissivity is improved by more than 20% compared with that of a conventional process, and the performance is stable in a wide temperature range; based on transformation of traditional sulfuric acid anodic oxidation equipment, industrial mass production is easy to realize; while the emissivity is improved, the corrosion resistance and wear resistance of the oxidation film are maintained.

Description

Technical Field

[0001] This invention relates to the field of sulfuric acid anodizing surface treatment technology for aluminum alloys. Background Technology

[0002] Generally, the black surface of aluminum alloy frames is colored using the conventional sulfuric acid anodizing process. While sulfuric acid anodizing is the mainstream treatment for aluminum alloys, the conventional selection of process parameters (electrolyte composition, oxidation conditions, and coloring parameters) is not optimized for hemispherical emissivity, resulting in low hemispherical emissivity (only 0.6~0.7) and poor stability. Specifically: 1. Under conventional process parameters, the oxide film structure is dense but the radiation capacity is weak, which cannot meet the equipment's high-efficiency heat dissipation requirements. There are electrolyte defects, namely, the oxide film formed by a single sulfuric acid system has low porosity (15~20%) and small radiation area. 2. It relies on additional coatings / doping, resulting in high process complexity and limited oxidation conditions. Specifically, under conventional current density / temperature parameters, the growth rate of the oxide film does not match the pore structure, leading to poor radiation characteristics. 3. The emissivity of the black oxide surface fluctuates significantly with increasing temperature (>150℃), indicating insufficient thermal stability and defects in the coloring process, namely uneven dye adsorption, poor surface radiation consistency, and limited room for improvement in emissivity. Summary of the Invention

[0003] The purpose of this invention is to provide a surface treatment method for high hemispherical emissivity, which can significantly improve the emissivity of black hemispherical surfaces without introducing additional materials.

[0004] To address the aforementioned technical problems, this invention provides a method for treating a surface with high hemispherical emissivity, comprising the following steps: S1. Pretreatment: After degreasing with an alkaline composite degreasing agent, pickling with mixed acid solution removes the oxide layer and roughens the surface at the same time. S2, Sulfuric acid anodizing: electrolytic oxidation in a composite system of H2SO4 and citric acid; S3. Coloring: Dyeing with a mixture of anthraquinone dyes and surfactants; S4. Sealing: Immerse the pores in a sealing solution composed of deionized water and nickel acetate for sealing treatment.

[0005] In step S1, the alkaline composite degreasing agent is a mixed solution of NaOH and Na2CO3, wherein the concentration of NaOH is 30 g / L and the concentration of Na2CO3 is 20 g / L; the mixed acid solution is a mixed solution of HNO3 and HF, wherein the concentration of HNO3 is 5% and the concentration of HF is 0.5%.

[0006] In step S1, degreasing is performed at 65°C for 4 minutes, and the residual oil on the surface after degreasing is less than 0.1 mg / cm². Pickling is performed at room temperature for 1.5 minutes, and the surface roughness after pickling is 0.8~1.2 μm.

[0007] In step S2, the concentration of H2SO4 in the H2SO4 and citric acid composite system is 180 g / L, and the concentration of citric acid is 15 g / L.

[0008] In step S2, the operating parameters for electrolytic oxidation are: current density 2.0 A / dm², temperature 16±1℃, and oxidation time 25 min.

[0009] In step S3, the concentration of the anthraquinone dye in the mixture of anthraquinone dye and surfactant is 8 g / L, and the concentration of the surfactant is 0.5 g / L.

[0010] In step S3, the anthraquinone dye is an anthraquinone-type black dye, and the surfactant is sodium dodecyl sulfate.

[0011] In step S3, the staining operation parameters are: temperature 55℃, pH=5.0±0.2, staining time 12min.

[0012] In step S4, the sealing solution composed of deionized water and nickel acetate has a nickel acetate concentration of 8 g / L, with the remainder being deionized water.

[0013] In step S4, the sealing parameters are: temperature 92℃, pH=6.0±0.2, and time 12min.

[0014] Compared with existing technologies, this invention achieves high emissivity simply by adjusting process parameters, simplifying the production process and reducing costs; the emissivity is increased by more than 20% compared with conventional processes, and the performance is stable over a wide temperature range; it is based on the modification of traditional sulfuric acid anodizing equipment, making it easy to achieve industrial mass production; while improving the emissivity, it maintains the corrosion resistance and wear resistance of the oxide film.

[0015] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0016] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0017] Figure 1 This is a flowchart illustrating at least one embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the embodiments of this invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the embodiments of this invention to facilitate a better understanding of this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments. The division of the following embodiments is for ease of description and should not constitute any limitation on the specific implementation of this invention. The embodiments can be combined with and referenced by each other without contradiction.

[0019] Example 1 like Figure 1 The high hemispherical emissivity surface treatment method shown includes the following steps: S1. Pretreatment: After degreasing with an alkaline composite degreasing agent, pickling with mixed acid solution removes the oxide layer and roughens the surface at the same time. S2, Sulfuric acid anodizing: electrolytic oxidation in a composite system of H2SO4 and citric acid; S3. Coloring: Dyeing with a mixture of anthraquinone dyes and surfactants; S4. Sealing: Immerse the pores in a sealing solution composed of deionized water and nickel acetate for sealing treatment.

[0020] Example 2 Based on Example 1, in step S1, the alkaline composite degreasing agent is a mixed solution of NaOH and Na2CO3, wherein the concentration of NaOH is 30 g / L and the concentration of Na2CO3 is 20 g / L; the mixed acid solution is a mixed solution of HNO3 and HF, wherein the concentration of HNO3 is 5% and the concentration of HF is 0.5%.

[0021] Furthermore, in step S1, the degreasing is carried out at a temperature of 65°C for 4 minutes, and the residual oil on the surface after degreasing is less than 0.1 mg / cm². The pickling is carried out at room temperature for 1.5 minutes, and the surface roughness after pickling is 0.8~1.2 μm.

[0022] Example 3 Based on Example 1, in step S2, the concentration of H2SO4 in the composite system of H2SO4 and citric acid is 180 g / L, and the concentration of citric acid is 15 g / L.

[0023] Furthermore, in step S2, the operating parameters for electrolytic oxidation are: current density 2.0 A / dm², temperature 16±1℃, and oxidation time 25 min.

[0024] Example 4 Based on Example 1, in step S3, the concentration of anthraquinone dye in the mixture of anthraquinone dye and surfactant is 8 g / L, and the concentration of surfactant is 0.5 g / L.

[0025] Preferably, in step S3, the anthraquinone dye is an anthraquinone-type black dye, and the surfactant is sodium dodecyl sulfate.

[0026] Furthermore, in step S3, the staining operation parameters are: temperature 55℃, pH=5.0±0.2, staining time 12min.

[0027] Example 5 Based on Example 1, in step S4, the sealing solution composed of deionized water and nickel acetate has a nickel acetate concentration of 8 g / L, and the remainder is deionized water.

[0028] Furthermore, in step S4, the operating parameters for the sealing treatment are: temperature 92℃, pH=6.0±0.2, and time 12min.

[0029] Example 6 Based on the above embodiments, the following steps are adopted: S1. Preprocessing Degreasing: Use an alkaline composite degreasing agent (NaOH 30g / L + Na2CO3 20g / L), temperature 65℃, time 4min, to ensure that the surface oil residue is <0.1mg / cm²; Pickling: Use a mixed acid solution of 5% HNO3 + 0.5% HF at room temperature for 1.5 min to remove the oxide layer and slightly roughen the surface (roughness Ra = 0.8~1.2 μm).

[0030] S2. Sulfuric acid anodizing parameters (core control step) Electrolyte composition: H2SO4 (180g / L) + citric acid (15g / L) composite system; Oxidation conditions: current density 2.0 A / dm², temperature 16±1℃, oxidation time 25 min; Effect: Formation of porous Al2O3 films with a porosity of 28-32% and a pore diameter of 60-90nm (film thickness 18-22μm), increasing the surface radiation area.

[0031] S3. Black coloring Dye system: An anthraquinone black dye (concentration 8 g / L) + surfactant (sodium dodecyl sulfate 0.5 g / L) mixture was used; Coloring conditions: temperature 55℃, pH=5.0±0.2, coloring time 12min; Effect: The dye uniformly fills the pores of the oxide film and forms a micro-agglomerate structure within the pores, enhancing the infrared radiation capability.

[0032] S4. Sealing parameters Sealing solution: Deionized water + nickel acetate (8 g / L) system; Sealing conditions: temperature 92℃, pH=6.0±0.2, time 12min; Effect: Low-temperature hydration sealing ensures that the dye does not leak out of the pores, while maintaining the porous radiation structure of the oxide film.

[0033] Emissivity effect: Through the above parameter adjustment, the hemispherical emissivity of the black aluminum alloy surface is stably 0.85~0.90 (fluctuation ≤±2% within the range of room temperature to 200℃), and the neutral salt spray test is ≥500h (maintaining corrosion resistance).

[0034] Based on this embodiment, three batches of aluminum alloy frames with the same structure (parts shown in the figure) were selected. The black surface was treated using both conventional and the process described in this embodiment. The hemispherical emissivity (using an infrared emissivity meter, test wavelength 8~14μm) and corrosion resistance were tested. The results are as follows:

[0035] As can be seen, the hemispherical emissivity of the process in this embodiment is more than 25% higher than that of the conventional process, and the emissivity fluctuation at high temperature is only 1 / 8 of that of the conventional process, while the corrosion resistance is also enhanced.

[0036] Therefore, this invention, based on the combination of "composite electrolyte (H2SO4 + citric acid) + precise oxidation parameters (current density / temperature / time)" in the sulfuric acid anodizing of aluminum alloys, can be used to improve the emissivity of black hemispherical surfaces; based on the "dye + surfactant" system and parameters in the black coloring process, it effectively achieves uniform dye adsorption and radiation structure optimization; at the same time, the whole-process parameter synergistic control scheme from pretreatment to sealing can improve emissivity without introducing additional materials.

[0037] Those skilled in the art will understand that the above embodiments can be modified in form and detail in practical applications without departing from the spirit and scope of the invention.

Claims

1. A method for treating a surface with high hemispherical emissivity, characterized in that: Includes the following steps: S1. Pretreatment: After degreasing with an alkaline composite degreasing agent, pickling with mixed acid solution removes the oxide layer and roughens the surface at the same time. S2, Sulfuric acid anodizing: electrolytic oxidation in a composite system of H2SO4 and citric acid; S3. Coloring: Dyeing with a mixture of anthraquinone dyes and surfactants; S4. Sealing: Immerse the pores in a sealing solution composed of deionized water and nickel acetate for sealing treatment.

2. The high hemispherical emissivity surface treatment method as described in claim 1, characterized in that, In step S1, the alkaline composite degreasing agent is a mixed solution of NaOH and Na2CO3, wherein the concentration of NaOH is 30 g / L and the concentration of Na2CO3 is 20 g / L; the mixed acid solution is a mixed solution of HNO3 and HF, wherein the concentration of HNO3 is 5% and the concentration of HF is 0.5%.

3. The high hemispherical emissivity surface treatment method as described in claim 1, characterized in that, In step S1, degreasing is performed at 65°C for 4 minutes, and the residual oil on the surface after degreasing is less than 0.1 mg / cm². Pickling is performed at room temperature for 1.5 minutes, and the surface roughness after pickling is 0.8~1.2 μm.

4. The high hemispherical emissivity surface treatment method as described in claim 1, characterized in that, In step S2, the concentration of H2SO4 in the H2SO4 and citric acid composite system is 180 g / L, and the concentration of citric acid is 15 g / L.

5. The high hemispherical emissivity surface treatment method as described in claim 1, characterized in that, In step S2, the operating parameters for electrolytic oxidation are: current density 2.0 A / dm², temperature 16±1℃, and oxidation time 25 min.

6. The high hemispherical emissivity surface treatment method as described in claim 1, characterized in that, In step S3, the concentration of the anthraquinone dye in the mixture of anthraquinone dye and surfactant is 8 g / L, and the concentration of the surfactant is 0.5 g / L.

7. The high hemispherical emissivity surface treatment method as described in claim 1, characterized in that, In step S3, the anthraquinone dye is an anthraquinone-type black dye, and the surfactant is sodium dodecyl sulfate.

8. The high hemispherical emissivity surface treatment method as described in claim 1, characterized in that, In step S3, the staining operation parameters are: temperature 55℃, pH=5.0±0.2, staining time 12min.

9. The high hemispherical emissivity surface treatment method as described in claim 1, characterized in that, In step S4, the sealing solution composed of deionized water and nickel acetate has a nickel acetate concentration of 8 g / L, with the remainder being deionized water.

10. The high hemispherical emissivity surface treatment method as described in claim 1, characterized in that, In step S4, the sealing parameters are: temperature 92℃, pH=6.0±0.2, and time 12min.

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