High-strength corrosion-resistant aluminum profile machining process

Abstract

The invention discloses a high-strength corrosion-resistant aluminum profile machining process, and belongs to the technical field of metal material surface treatment. According to the aluminum profile machining process, stepped current arcing oxidation and double hole sealing treatment are adopted, and the two innovative points of process steps are connected with each other and have a synergistic effect. The stepped current composite anodic oxidation provides a substrate with an optimized structure and rich active points for double hole sealing, and the double hole sealing furthest consolidates and exerts the corrosion resistance of the composite oxide film. The process conditions are mild, used chemicals are environment-friendly, the addition amount of rare earth elements is small, but the effect is remarkable, and the method is particularly suitable for the 6-series aluminum alloy profile with strict requirements for strength and corrosion resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal material surface treatment, and particularly relates to a high-strength corrosion-resistant aluminum profile processing technology. BACKGROUND

[0002] Aluminum alloy profiles are widely used in fields such as building doors and windows, curtain walls, rail transit, aerospace and automobile manufacturing due to their small density, high specific strength and easy processing. However, aluminum alloy is prone to pitting corrosion, intergranular corrosion and the like in some harsh environments such as marine atmosphere and industrial acid rain, and the surface hardness and wear resistance thereof need to be improved.

[0003] At present, the mainstream method for improving the performance of aluminum profiles is anodic oxidation treatment. Traditional anodic oxidation processes such as sulfuric acid anodic oxidation can generate a porous oxide film on the surface of aluminum material, and the corrosion resistance is improved through sealing treatment. However, the process has the following disadvantages: the inner layer of the oxide film has insufficient strength: the inner layer structure of the oxide film generated by conventional anodic oxidation is often not dense enough, and there are micro defects, which leads to general overall adhesion and peeling resistance of the film layer, and cracks are easily generated when mechanical stress is borne. The corrosion resistance has a bottleneck: the corrosion resistance of a single anodic oxidation film, especially the ability to resist Cl - ion erosion, is limited. The subsequent conventional hot sealing or cold sealing process mainly blocks the porous layer, and the long-term barrier effect on the corrosion medium is limited, and the surface hardness of the film layer may be reduced. Strength and corrosion resistance are difficult to balance: in order to obtain high strength, alloy composition optimization and heat treatment are often required, but this sometimes has an adverse effect on corrosion resistance. The existing surface treatment process is difficult to significantly and synergistically improve the corrosion resistance of the substrate while maintaining high strength.

[0004] Therefore, it is a technical problem to be solved in the art to develop a composite treatment process that can simultaneously obtain high hardness and excellent corrosion resistance on the surface of an aluminum profile. SUMMARY

[0005] The application aims to provide an aluminum profile processing and treatment process to obtain an aluminum profile with high strength and excellent corrosion resistance.

[0006] To achieve the above technical purpose, the technical solution adopted by the application is as follows: A high-strength corrosion-resistant aluminum profile processing technology, comprising the following processes: Step (1) Pretreatment: sequentially performing degreasing, alkali etching, neutralization and water washing on the aluminum profile substrate; Step (2) Composite anodic oxidation: placing the pretreated aluminum profile in a composite electrolyte, applying a step current to perform arc oxidation at a temperature of 15-20℃; Step (3) Double sealing treatment: First-stage inorganic sealing: Immerse the oxidized aluminum profile of the prototype in a nickel-cerium composite sealing agent at 98℃ for 15-25 minutes; Second-stage organic-inorganic hybrid sealing: Immerse the aluminum profile after the first-stage sealing in a silane-fluorocarbon hybrid solution at 70-80℃ for 30-60 minutes, and then remove it and cure it at 180-200℃ for 20-30 minutes. Step (4) Cooling, cleaning, and drying.

[0007] Furthermore, in step (2), the step current is: with a current density of 1-2 A / dm 2 Starting from this point, the step height increases by 0.5A / dm every 60 seconds. 2 When the current density reaches 5A / dm 2 When the voltage is high, switch to DC regulated mode and oxidize for 20-40 minutes at 15-25V.

[0008] Furthermore, the composite electrolyte in step (2) consists of: sulfuric acid 150-180 g / L, oxalic acid 15-25 g / L, citric acid 5-10 g / L, nano silica sol 10-20 g / L, cerium nitrate 1-3 g / L, and the remainder is deionized water.

[0009] Furthermore, the solid content of the nano-silica sol is 30%.

[0010] Furthermore, in step (3), the nickel-cerium composite sealing agent is: nickel sulfate 5-8 g / L, cerium chloride 1-2 g / L, and the remainder is deionized water, with the pH adjusted to 5.5-6.5.

[0011] Furthermore, in step (3), the silane-fluorocarbon hybrid solution contains 5-10% by mass of silane coupling agent KH-560 and 3-5% by mass of fluorocarbon resin emulsion, and the solvent is deionized water.

[0012] Furthermore, in step (1), degreasing involves immersing the aluminum profile in an alkaline degreasing solution at 50°C for 5-10 minutes.

[0013] Furthermore, the alkaline degreasing solution comprises 10-20 g / L sodium hydroxide, 20-30 g / L sodium carbonate, and 10-20 g / L sodium phosphate.

[0014] Furthermore, in step (1), alkaline etching involves immersing the aluminum profile in a 1 mol / L sodium hydroxide solution at 50°C for 3-8 minutes.

[0015] Furthermore, in step (1), the neutralization is performed with a 20% nitric acid solution at room temperature for 1-3 minutes; the water wash is performed with running clean water.

[0016] The first innovation of this invention is the stepped current oxidation process.

[0017] A composite electrolyte containing nano-silica sol and rare earth cerium salts is used, combined with a stepped-wave arc initiation power control mode. In the early stage of oxidation, a stepped voltage boost is used to make the arc discharge more uniform and gentle, promoting the interaction between nano-SiO2 particles and Ce. 3+ The ions work synergistically to embed themselves into the micropores and defects of the growing alumina film. This not only refines the grain size of the oxide film, making its inner structure more compact and enhancing the film-substrate bonding, but also the introduction of rare earth cerium alters the electrochemical properties of the film, increasing its breakdown potential, thereby fundamentally improving the compactness, hardness, and pitting resistance of the oxide film.

[0018] Innovation point two of this invention: Dual sealing process A dual-sealing strategy, first inorganic and then organic, was employed to achieve hierarchical and deep sealing of the porous layer of the anodic oxide film. The first-stage inorganic sealing utilizes Ni... 2+ and Ce 3+ At high temperatures, it reacts with alumina to form composite ceramic phases such as NiAl2O4 and CeO2, firmly sealing the bottom and middle of the pores. Secondary sealing utilizes the synergistic film-forming effect of the Si-O-Si network formed after silane hydrolysis and fluorocarbon resin to create a continuous protective film with strong hydrophobicity and high chemical inertness on the outermost layer of the oxide film. This not only further blocks the intrusion of corrosive media but also endows the surface with excellent wear resistance and self-cleaning properties. The two-stage sealing functions complement each other, achieving comprehensive protection from the depths of the pores to the surface.

[0019] Beneficial effects The two innovative aspects of this invention are that the process steps are interconnected and synergistically enhanced. Composite anodizing provides a substrate with optimized structure and abundant active sites for double sealing, while double sealing maximizes and enhances the corrosion resistance of the composite oxide film.

[0020] The process conditions of this invention are mild, and all the chemicals used are environmentally friendly. The amount of rare earth elements added is small but the effect is significant. It is particularly suitable for 6-series aluminum alloy profiles with stringent requirements for strength and corrosion resistance. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0022] Example 1 A high-strength, corrosion-resistant aluminum profile processing technology includes the following steps: Step (1) Pretreatment: The aluminum profile substrate is subjected to degreasing, alkaline etching, neutralization and water washing in sequence; Step (2) Composite anodizing: The pretreated aluminum profile is placed in a composite electrolyte, and an arc-starting oxidation is performed by applying a stepped current at a temperature of 15°C. Step (3) Double sealing treatment: First-stage inorganic sealing: Immerse the oxidized aluminum profile of the prototype in a nickel-cerium composite sealing agent at 98℃ for 15 minutes; Second-stage organic-inorganic hybrid sealing: Immerse the aluminum profile after the first-stage sealing in a silane-fluorocarbon hybrid solution at 70℃ for 30 minutes, and then take it out and cure it at 180℃ for 30 minutes. Step (4) Cooling, cleaning, and drying.

[0023] The step current in step (2) is: with a current density of 1 A / dm 2 Starting from this point, the step height increases by 0.5A / dm every 60 seconds. 2 When the current density reaches 5A / dm 2 Then, switch to DC regulated mode and oxidize for 20 minutes at 15V.

[0024] The composite electrolyte in step (2) consists of: 150 g / L sulfuric acid, 25 g / L oxalic acid, 10 g / L citric acid, 20 g / L nano silica sol, 1 g / L cerium nitrate, and the remainder is deionized water.

[0025] In step (3), the nickel-cerium composite sealing agent is: 5 g / L nickel sulfate, 1 g / L cerium chloride, and the remainder is deionized water, with the pH adjusted to 6.5.

[0026] In step (3), the silane-fluorocarbon hybrid solution contains 5% by mass of silane coupling agent KH-560 and 3% by mass of fluorocarbon resin emulsion, and the solvent is deionized water.

[0027] In step (1), degreasing involves immersing the aluminum profile in an alkaline degreasing solution at 50°C for 10 minutes.

[0028] The alkaline degreasing solution comprises 20 g / L sodium hydroxide, 30 g / L sodium carbonate, and 20 g / L sodium phosphate.

[0029] In step (1), alkaline etching involves immersing the aluminum profile in a 1 mol / L sodium hydroxide solution at 50°C for 3 minutes.

[0030] In step (1), the neutralization is performed with a 20% nitric acid solution at room temperature for 1 minute; the water wash is performed with running clean water.

[0031] Example 2 A high-strength, corrosion-resistant aluminum profile processing technology includes the following steps: Step (1) Pretreatment: The aluminum profile substrate is subjected to degreasing, alkaline etching, neutralization and water washing in sequence; Step (2) Composite anodizing: The pretreated aluminum profile is placed in a composite electrolyte, and an arc-starting oxidation is performed by applying a stepped current at a temperature of 20°C; Step (3) Double sealing treatment: First-stage inorganic sealing: Immerse the oxidized aluminum profile of the prototype in a nickel-cerium composite sealing agent at 98℃ for 20 minutes; Second-stage organic-inorganic hybrid sealing: Immerse the aluminum profile after the first-stage sealing in a silane-fluorocarbon hybrid solution at 75℃ for 45 minutes, and then take it out and cure it at 190℃ for 25 minutes. Step (4) Cooling, cleaning, and drying.

[0032] The step current in step (2) is: with a current density of 2A / dm 2 Starting from this point, the step height increases by 0.5A / dm every 60 seconds. 2 When the current density reaches 5A / dm 2 At that time, switch to DC regulated mode and oxidize for 30 minutes at 20V.

[0033] The composite electrolyte in step (2) consists of: 160 g / L sulfuric acid, 20 g / L oxalic acid, 8 g / L citric acid, 10 g / L nano silica sol, 2 g / L cerium nitrate, and the remainder is deionized water.

[0034] In step (3), the nickel-cerium composite sealing agent is: 6 g / L nickel sulfate, 2 g / L cerium chloride, and the remainder is deionized water, with the pH adjusted to 5.5.

[0035] In step (3), the silane-fluorocarbon hybrid solution contains 8% by mass of silane coupling agent KH-560 and 4% by mass of fluorocarbon resin emulsion, and the solvent is deionized water.

[0036] In step (1), degreasing involves immersing the aluminum profile in an alkaline degreasing solution at 50°C for 5 minutes.

[0037] The alkaline degreasing solution comprises 10 g / L sodium hydroxide, 20 g / L sodium carbonate, and 10 g / L sodium phosphate.

[0038] In step (1), alkaline etching involves immersing the aluminum profile in a 1 mol / L sodium hydroxide solution at 50°C for 8 minutes.

[0039] In step (1), the neutralization is performed with a 20% nitric acid solution at room temperature for 3 minutes; the water wash is performed with running clean water.

[0040] Example 3 A high-strength, corrosion-resistant aluminum profile processing technology includes the following steps: Step (1) Pretreatment: The aluminum profile substrate is subjected to degreasing, alkaline etching, neutralization and water washing in sequence; Step (2) Composite anodizing: The pretreated aluminum profile is placed in a composite electrolyte, and an arc-starting oxidation is performed by applying a stepped current at a temperature of 20°C; Step (3) Double sealing treatment: First-stage inorganic sealing: Immerse the oxidized aluminum profile of the prototype in a nickel-cerium composite sealing agent at 98℃ for 25 minutes; Second-stage organic-inorganic hybrid sealing: Immerse the aluminum profile after the first-stage sealing in a silane-fluorocarbon hybrid solution at 80℃ for 60 minutes, and then take it out and cure it at 200℃ for 20 minutes. Step (4) Cooling, cleaning, and drying.

[0041] The step current in step (2) is: with a current density of 1 A / dm 2 Starting from this point, the step height increases by 0.5A / dm every 60 seconds. 2 When the current density reaches 5A / dm 2 At that time, switch to DC regulated mode and oxidize for 40 minutes at 25V.

[0042] The composite electrolyte in step (2) consists of: 180 g / L sulfuric acid, 15 g / L oxalic acid, 5 g / L citric acid, 15 g / L nano silica sol, 3 g / L cerium nitrate, and the remainder is deionized water.

[0043] In step (3), the nickel-cerium composite sealing agent is: 8 g / L nickel sulfate, 2 g / L cerium chloride, and the remainder is deionized water, with the pH adjusted to 6.

[0044] In step (3), the silane-fluorocarbon hybrid solution contains 10% by mass of silane coupling agent KH-560 and 5% by mass of fluorocarbon resin emulsion, and the solvent is deionized water.

[0045] In step (1), degreasing involves immersing the aluminum profile in an alkaline degreasing solution at 50°C for 8 minutes.

[0046] The alkaline degreasing solution comprises 15 g / L sodium hydroxide, 25 g / L sodium carbonate, and 15 g / L sodium phosphate.

[0047] In step (1), alkaline etching involves immersing the aluminum profile in a 1 mol / L sodium hydroxide solution at 50°C for 5 minutes.

[0048] In step (1), the neutralization is performed with a 20% nitric acid solution at room temperature for 2 minutes; the water wash is performed with running clean water.

[0049] Comparative Example 1 Compared with Example 3, this comparative example does not use a stepped current in step (2), but only a DC current of 5A / dm. 2 Except for the steps in Example 3, the rest of the steps are the same.

[0050] Comparative Example 2 Compared with Example 3, this comparative example is the same as Example 3 except that step (3) only uses a first-level inorganic pore sealing.

[0051] Comparative Example 3 Compared with Example 3, this comparative example is the same as Example 3 except that step (3) only uses a two-stage organic-inorganic hybrid sealing method.

[0052] Performance testing Using commercially available 6063 aluminum alloy produced by a certain company as the material, the alloy composition of the tested aluminum profiles was: Mg 0.5%, Si 0.5%, Fe 0.15%, Mn 0.01%, Cu 0.01%, Ti 0.02%, with the balance being Al. The aluminum profiles prepared according to the processing techniques of Examples 1-3 and Comparative Examples 1-4 were subjected to relevant performance tests. The specific test methods and results are as follows: Corrosion resistance test: The neutral salt spray test is conducted according to GB / T10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test": using a 5% sodium chloride solution, a temperature of 35±2℃, and a pH value of 6.5-7.2. After observation for 7 days, the average corrosion rate is calculated. Average corrosion rate (mm / a) = (K×W) / (A×T×D), where: K = 3.65×10 3 W represents the corrosion weight loss of the sample (g), and A represents the sample area (cm²). 2 T represents the test time (d), and D represents the material density (g / cm³). 3 ); Contact angle test: The static water contact angle of each sample was measured using a contact angle measuring instrument; Mechanical property testing: Tensile strength was tested in accordance with GB / T228.1-2010 "Metallic materials - Tensile testing - Part 1 - Room temperature test method", and the data are shown in Table 1.

[0053] Table 1. Performance test results of aluminum profiles in each treatment group

[0054] As shown in Table 1, the embodiments of the processing technology of the present invention exhibit the lowest corrosion rate. Comparative Example 1, due to the lack of a stepped current, suffers from increased oxide film defects and a significant decrease in corrosion resistance. Comparative Example 2 also shows a decrease in corrosion resistance due to only having a primary sealing stage, which lacks secondary sealing for surface protection. Furthermore, Comparative Example 3, without a primary sealing stage to plug the holes and the middle section, results in incomplete hole sealing, allowing corrosive media to easily penetrate. In addition, Table 1 shows that the aluminum profiles prepared by the processing technology of the present invention have high strength and good corrosion resistance, making them suitable for complex climates and working environments. Comparative Examples 1-3 verify the key corrosion resistance aspects of "stepped current" and "double sealing" in the processing technology.

[0055] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A high strength corrosion resistant aluminum mill process, characterized by, The process comprises the following steps: Step (1) pretreatment: sequentially performing degreasing, alkali etching, neutralization and water washing on the aluminum profile base; Step (2) composite anodic oxidation: placing the pretreated aluminum profile in a composite electrolyte, applying a step current to perform arc oxidation at a temperature of 15-20℃; Step (3) double sealing treatment: first-stage inorganic sealing: immersing the aluminum profile after oxidation in a 98℃ nickel-cerium composite sealing agent for 15-25 minutes; second-stage organic-inorganic hybrid sealing: immersing the aluminum profile after the first-stage sealing in a silane-fluorocarbon hybrid solution, immersing at 70-80℃ for 30-60 minutes, and taking out and solidifying at 180-200℃ for 20-30 minutes; Step (4) cooling, cleaning and drying.

2. The high strength corrosion resistant aluminum mill process of claim 1, wherein, The step (2) is a ladder current of 1-2 A / dm 2 As a start, every 60 seconds the ladder is raised by 0.5 A / dm 2 When the current density reaches 5 A / dm 2 The current is then changed to a steady direct current mode, and oxidation is carried out for 20-40 minutes at a voltage of 15-25 V.

3. The high strength corrosion resistant aluminum mill process of claim 1, wherein, The composite electrolyte in step (2) is: sulfuric acid 150-180g / L, oxalic acid 15-25g / L, citric acid 5-10g / L, nano-silica sol 10-20g / L, cerium nitrate 1-3g / L, and the rest is deionized water.

4. The high strength corrosion resistant aluminum mill process of claim 1, wherein, The nickel-cerium composite sealing agent in step (3) is: nickel sulfate 5-8g / L, cerium chloride 1-2g / L, and the rest is deionized water, and the pH is adjusted to 5.5-6.

5.

5. The high strength corrosion resistant aluminum mill process of claim 1, wherein, The silane-fluorocarbon hybrid solution in step (3) contains 5-10% silane coupling agent KH-560 and 3-5% fluorocarbon resin emulsion by mass fraction, and the solvent is deionized water.

6. The high strength corrosion resistant aluminum mill process of claim 1, wherein, The degreasing in step (1) is immersing the aluminum profile in an alkaline degreasing solution at 50℃ for 5-10 minutes.

7. The high strength corrosion resistant aluminum mill process of claim 6, wherein, The alkaline degreasing solution comprises 10-20g / L sodium hydroxide, 20-30g / L sodium carbonate and 10-20g / L sodium phosphate.

8. The high strength corrosion resistant aluminum mill process of claim 1, wherein, The alkali etching in step (1) is placing the aluminum profile in a 1mol / L sodium hydroxide solution at 50℃ for 3-8 minutes.

9. The high strength corrosion resistant aluminum mill process of claim 1, wherein, The neutralization in step (1) is a 20% nitric acid solution at room temperature for 1-3 minutes; and the water washing is flowing clean water.

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