Preparation method of plush-shaped anti-corrosion coating strongly attached to aluminum alloy surface

Abstract

The invention discloses a preparation method of a plush strong-fitting aluminum alloy surface anti-corrosion coating, which comprises the following steps: cleaning an aluminum alloy matrix, putting the aluminum alloy matrix into an electrolyte for anodic oxidation treatment, and constructing a porous surface on the surface of the aluminum alloy matrix; placing the aluminum alloy matrix with the porous surface in a silane coupling agent solution, taking out the aluminum alloy matrix, drying the aluminum alloy matrix, and repeatedly dipping and drying the aluminum alloy matrix for multiple times; then placing the surface in a silver nitrate solution, taking out the surface, drying the surface, and repeatedly dipping and drying the surface for multiple times to obtain a primary modified surface; placing the matrix in a sodium alginate aqueous solution, taking out the matrix, drying the matrix, and repeatedly dipping and drying the matrix for multiple times to obtain a secondary high-flatness surface; and placing the modified substrate in a hydrothermal solution for reaction to obtain the plush corrosion-resistant surface. The method solves the problems that in the prior art, in the service process of the aluminum alloy, a surface coating is prone to falling off and corrosion is prone to occurring.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation methods of protective materials, and particularly relates to a preparation method of a fluffy and strongly adherent anti-corrosion coating on the surface of aluminum alloy. Background Art

[0002] Aluminum is one of the most abundant metallic elements in the earth's crust. Aluminum and its alloys are typical light metal materials and have great application value in the fields of aerospace, transportation, construction, etc. Aluminum is a very active metallic element. Under natural conditions, it can form a dense aluminum oxide film with certain corrosion resistance on its surface. However, in more demanding actual application environments, the oxide film is easily damaged by cracks that expand after being stressed. At the same time, under the action of moisture in nature and chloride ions in the air, due to the destruction of the surface passivation layer of aluminum, galvanic corrosion will be accelerated, resulting in rapid corrosion of aluminum and its alloys, and further leading to inevitable safety hazards. In the actual service of aluminum alloy, especially when aluminum alloy is used in load-bearing structures, stress concentration is likely to form on its surface, leading to pitting corrosion, and further irreversible general corrosion under the influence of environmental factors. To ensure the safe use of aluminum alloy, a corrosion-resistant coating is usually grown in-situ or applied externally on its surface. However, most of the existing coatings have the problem of poor adhesion, resulting in insufficient bonding force with aluminum alloy and causing peeling, and thus it is difficult to ensure sufficient anti-corrosion efficacy and cannot meet the actual use requirements.

[0003] Chinese Patent "A Corrosion-Resistant Coating on the Surface of Aluminum Alloy and Its Preparation Method" (Application No. CN202411164526.3, Publication No.: CN118909537A, Publication Date: November 8, 2024) discloses a corrosion-resistant coating on the surface of aluminum alloy and its preparation method, which is a coating for the surface of aluminum alloy that is resistant to electrochemical and microbial corrosion, scale prevention, and superhydrophobic in a highly corrosive seawater environment. However, it directly coats the modified coating on the surface of aluminum alloy, and the bonding strength between the coating and the substrate is insufficient. Therefore, constructing a corrosion-resistant coating on the surface of aluminum alloy that highly adheres to the substrate, effectively improves the corrosion resistance, and is green and environmentally friendly is an urgent problem to be solved in the field of aluminum alloy protective materials. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of a fluffy and strongly adherent anti-corrosion coating on the surface of aluminum alloy, which solves the problems that the surface coating of aluminum alloy is prone to peeling and corrosion during service in the prior art.

[0005] The technical solution adopted by the present invention is that the preparation method of the fluffy and strongly adherent anti-corrosion coating on the surface of aluminum alloy is specifically implemented according to the following steps: Step 1: After cleaning the aluminum alloy substrate, put it into an electrolyte for anodic oxidation treatment to construct a porous surface on its surface; Step 2: Place the aluminum alloy substrate with a porous surface obtained in Step 1 in a silane coupling agent solution, take it out and dry it, and repeat the impregnation and drying process multiple times; then place it in a silver nitrate solution, take it out and dry it, and repeat the impregnation and drying multiple times to obtain a primary modified surface; Step 3: Place the substrate obtained in Step 2 in an aqueous sodium alginate solution, take it out and dry it, and repeat the impregnation and drying process multiple times to obtain a secondary highly flat surface; Step 4: React the substrate modified in Step 3 in a hydrothermal solution to obtain a furry corrosion-resistant surface.

[0006] The features of the present invention also lie in: In Step 1, the specific cleaning process of the aluminum alloy substrate is as follows: Place the aluminum alloy substrate successively in a 5-10% sodium hydroxide solution, a 5-10% nitric acid, and deionized water for three-step cleaning, with each cleaning for 5-10 minutes. After taking out the aluminum alloy, blow it dry with cold air.

[0007] In Step 1, the electrolyte consists of 15-35 g / L boric acid, 15-35 g / L sulfuric acid, and 10-20 g / L oxalic acid; the current density of anodic oxidation increases by 0.5 A / dm every 5 min 2 , the oxidation time is 30-60 min, and the oxidation temperature is 5-25 °C.

[0008] In Step 2, place the aluminum alloy substrate with a porous surface obtained in Step 1 in a 2-4% silane coupling agent solution for 10-30 min, take it out and dry it with cold air for 10-15 min, and repeat the impregnation and drying process 3-5 times.

[0009] In Step 2, place the aluminum alloy impregnated with the silane coupling agent in a 2-4% silver nitrate solution for 10-30 min, take it out and dry it in the air for 10-15 min, and repeat the impregnation and drying 2-3 times to obtain a primary modified surface.

[0010] In Step 2, the silane coupling agent is a thiosilane coupling agent or an amino silane coupling agent.

[0011] Step 3 is specifically as follows: Place the substrate obtained in Step 2 in a 2-4% aqueous sodium alginate solution for 10-30 min, take it out and dry it with cold air for 10-15 min, and repeat the impregnation and drying process 3-5 times to obtain a secondary highly flat surface.

[0012] In Step 4, the specific preparation process of the hydrothermal solution is as follows: Add zinc chloride to water, stir for 3 - 5 h at a rotation speed of 250 - 400 r / min, and then ultrasonically disperse for 15 - 30 min to prepare a zinc chloride solution with a mass concentration of 0.2 - 0.4 wt%. Adjust the pH to 10 - 12 with 5 - 25% ammonia water to obtain a hydrothermal solution.

[0013] In step 4, the hydrothermal reaction temperature is 100 - 150 °C and the time is 8 - 12 h.

[0014] The beneficial effects of the present invention are: The method of the present invention first constructs a porous structure with a high specific surface area on the surface of the aluminum alloy matrix by anodic oxidation, providing more reaction sites for the subsequent modified coating; secondly, a simple and efficient multi-layer impregnation method is adopted, and the precipitant silver nitrate is fixed on the surface by a silane coupling agent to form a primary transition coating, and the strong adhesion of itself provides adhesion for the subsequent secondary coating; finally, the surface is leveled with the gelling agent sodium alginate and a zinc oxide fluffy surface is formed by a hydrothermal reaction.

[0015] The silane coupling agent can undergo a hydrolysis reaction in the presence of moisture to generate silanol groups, which undergo a condensation reaction with active groups such as hydroxyl groups in subsequent modification, isolating moisture from the matrix and further improving the adhesion ability. The gelling agent forms internal micro-prestresses by the contraction force formed by the cross-linking of internal molecular chains. When an external force acts, it is dispersed in time to avoid stress concentration, effectively inhibiting the initiation of cracks and hindering the further propagation of cracks. When an external force acts, it attracts and "captures" chloride ions in the actual application environment through its own force-electricity conversion, making them form precipitate particles with the precipitant, further strengthening the coating by particles. The three-dimensional network structure formed by the further cross-linking of metal ions just provides sufficient space for the precipitation of the precipitant, while ensuring that the coating has a certain flexibility and better conforms to the use of the matrix, further improving the local strength of the coating.

[0016] In addition, the finally prepared fluffy surface has a high specific surface area, and at the same time, external metal elements are introduced to form a primary battery with chloride ions, protecting the matrix aluminum alloy from participating in the corrosion reaction and further improving the safety of aluminum alloy applications. Description of the Drawings

[0017] Figure 1 It is a structural diagram of the anti-corrosion coating prepared by the method of the present invention. Detailed Embodiments

[0018] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0019] The preparation method of the fluffy and strongly adherent aluminum alloy surface anti-corrosion coating of the present invention is specifically implemented according to the following steps: Step 1, constructing a porous surface: First, the aluminum alloy is successively placed in a 5 - 10% sodium hydroxide solution, a 5 - 10% nitric acid, and deionized water for three - step primary cleaning. Each step is washed for 5 - 10 minutes. After taking out the aluminum alloy and drying it with cold air, it is placed in an electrolyte composed of 15 - 35 g / L boric acid, 15 - 35 g / L sulfuric acid, and 10 - 20 g / L oxalic acid. The current density is adjusted to increase by 0.5 A / dm every 5 min 2 、the anodizing time is 30 - 60 min, and the oxidation temperature is 5 - 25 °C to obtain a porous surface.

[0020] Step 2, preparing a primary transition surface: The aluminum alloy substrate with a porous surface obtained in Step 1 is placed as a whole in a 2 - 4% silane coupling agent solution for 10 - 30 min, taken out and dried with cold air for 10 - 15 min, and the impregnation - drying treatment is repeated 3 - 5 times; then it is placed in a 2 - 4% silver nitrate solution for 10 - 30 min, taken out and dried in the air for 10 - 15 min, and after repeating the impregnation - drying 2 - 3 times, a primary modified surface is obtained.

[0021] Step 3, constructing a secondary highly flat surface: The substrate obtained in Step 2 is placed as a whole in a 2 - 4% sodium alginate aqueous solution for 10 - 30 min, taken out and dried with cold air for 10 - 15 min, and the impregnation - drying treatment is repeated 3 - 5 times to obtain a secondary highly flat surface.

[0022] Step 4, preparing a fluffy corrosion - resistant surface: Zinc chloride is added to water and stirred at a rotation speed of 250 - 400 r / min for 3 - 5 h, and then ultrasonically dispersed for 15 - 30 min to prepare a zinc chloride solution with a mass concentration of 0.2 - 0.4 wt%; the pH is adjusted to 10 - 12 with 5 - 25% medium - concentration ammonia water to obtain a hydrothermal solution; the substrate modified in Step 3 is placed in this hydrothermal solution, the hydrothermal temperature is adjusted to 100 - 150 °C, and the hydrothermal time is 8 - 12 h to obtain a fluffy corrosion - resistant surface.

[0023] Example 1: Step 1, the aluminum alloy is successively placed in a 5% sodium hydroxide solution, a 5% nitric acid, and deionized water for three - step primary cleaning. Each step is washed for 5 minutes. After taking out the aluminum alloy and drying it with cold air, it is placed in an electrolyte composed of 15 g / L boric acid, 15 g / L sulfuric acid, and 10 g / L oxalic acid. The current density is adjusted to increase by 0.5 A / dm every 5 min 2 、the anodizing time is 30 min, and the oxidation temperature is 5 °C to obtain a porous surface.

[0024] Step 2: Place the modified substrate in a 2% silane coupling agent solution for 10 minutes, take it out and dry it with cold air for 10 minutes, and repeat the treatment 3 times; then place it in a 2% silver nitrate solution for 10 minutes and dry it in air for 10 minutes. After repeating 2 times, a first-level modified surface is obtained.

[0025] Step 3: Place the substrate obtained in Step 2 as a whole in a 2% sodium alginate aqueous solution for 10 minutes, take it out and dry it with cold air for 10 minutes, and repeat the treatment 3 times to obtain a second-level highly flat surface.

[0026] Step 4: Add 0.4 g of zinc chloride to 200 ml of water, adjust the magnetic stirring speed to 250 r / min, stir for 3 h, then ultrasonically disperse for 15 minutes, and adjust the pH to 10 with 5% medium-concentration ammonia water to obtain a hydrothermal solution. Place the substrate modified in Step 3 in the hydrothermal solution, adjust the hydrothermal temperature to 100 °C, and the hydrothermal time to 8 h to obtain a fluffy corrosion-resistant surface.

[0027] Example 2: Step 1: Place the aluminum alloy in 6% sodium hydroxide solution, 6% nitric acid, and deionized water in turn for three-step primary cleaning, with each step lasting for 7 minutes. After taking out the aluminum alloy and drying it with cold air, place it in an electrolyte composed of 20 g / L boric acid, 20 g / L sulfuric acid, and 15 g / L oxalic acid, and adjust the current density to increase by 0.5 A / dm every 5 minutes 2 and an anodizing time of 40 minutes, and an oxidation temperature of 10 °C to obtain a porous surface.

[0028] Step 2: Place the modified substrate in a 2.5% silane coupling agent solution for 15 minutes, take it out and dry it with cold air for 11 minutes, and repeat the treatment 4 times; then place it in a 2.5% silver nitrate solution for 11 minutes and dry it in air for 10 minutes. After repeating 2 times, a first-level modified surface is obtained.

[0029] Step 3: Place the substrate obtained in Step 2 as a whole in a 3% sodium alginate aqueous solution for 20 minutes, take it out and dry it with cold air for 12 minutes, and repeat the treatment 4 times to obtain a second-level highly flat surface.

[0030] Step 4: Add 0.5 g of zinc chloride to 200 mL of water, adjust the magnetic stirring speed to 300 r / min, stir for 3.5 h, then ultrasonically disperse for 20 minutes, and adjust the pH to 10 with 10% medium-concentration ammonia water to obtain a hydrothermal solution. Place the substrate modified in Step 3 in the hydrothermal solution, adjust the hydrothermal temperature to 120 °C, and the hydrothermal time to 9 h to obtain a fluffy corrosion-resistant surface.

[0031] Example 3: Step 1: Place the aluminum alloy in an 8% sodium hydroxide solution, 8% nitric acid, and deionized water in sequence for three-step primary cleaning. Clean each step for 8 minutes. After taking out the aluminum alloy and drying it with cold air, place it in an electrolyte composed of 25 g / L boric acid, 25 g / L sulfuric acid, and 15 g / L oxalic acid, and adjust the current density to increase by 0.5 A / dm every 5 min 2 、anodic oxidation time of 50 min, and oxidation temperature of 20 °C to obtain a porous surface.

[0032] Step 2: Place the modified substrate in a 3% amino-functional silane coupling agent solution for 25 min, take it out and dry it with cold air for 13 min, and repeat the treatment 4 times; then place it in a 3% silver nitrate solution for 25 min and dry it in air for 13 min. After repeating 3 times, obtain a first-level modified surface.

[0033] Step 3: Place the substrate obtained in Step 2 as a whole in a 3% sodium alginate aqueous solution for 25 min, take it out and dry it with cold air for 13 min, and repeat the treatment 4 times to obtain a second-level highly flat surface.

[0034] Step 4: Add 0.6 g of zinc chloride to 200 ml of water, adjust the magnetic stirring speed to 350 r / min, stir for 4 h, then ultrasonically disperse for 25 min, and adjust the pH to 11 with 20% medium-concentration ammonia water to obtain a hydrothermal solution. Place the substrate modified in Step 3 in the hydrothermal solution, adjust the hydrothermal temperature to 140 °C, and the hydrothermal time to 9 h to obtain a fluffy corrosion-resistant surface.

[0035] Example 4: Step 1: Place the aluminum alloy in a 10% sodium hydroxide solution, 10% nitric acid, and deionized water in sequence for three-step primary cleaning. Clean each step for 10 minutes. After taking out the aluminum alloy and drying it with cold air, place it in an electrolyte composed of 35 g / L boric acid, 35 g / L sulfuric acid, and 20 g / L oxalic acid, and adjust the current density to increase by 0.5 A / dm every 5 min 2 、anodic oxidation time of 60 min, and oxidation temperature of 25 °C to obtain a porous surface.

[0036] Step 2: Place the modified substrate in a 4% amino-functional silane coupling agent solution for 30 min, take it out and dry it with cold air for 15 min, and repeat the treatment 5 times; then place it in a 4% silver nitrate solution for 30 min and dry it in air for 15 min. After repeating 3 times, obtain a first-level modified surface.

[0037] Step 3: Place the substrate obtained in Step 2 as a whole in a 4% sodium alginate aqueous solution for 30 min, take it out and dry it with cold air for 15 min, and repeat the treatment 5 times to obtain a second-level highly flat surface.

[0038] Step 4: Add 0.8 g of zinc chloride into 200 ml of water, adjust the magnetic stirring speed to 400 r / min, stir for 5 h, then ultrasonically disperse for 30 min, adjust the pH to 12 with 25% medium-concentration ammonia water to obtain a hydrothermal solution. Place the matrix modified in Step 3 in the hydrothermal solution, adjust the hydrothermal temperature to 150 °C, and the hydrothermal time to 12 h to obtain a fluffy corrosion-resistant surface.

[0039] Example 5: Step 1: Place the aluminum alloy in 10% sodium hydroxide solution, 5% nitric acid, and deionized water in sequence for three-step primary cleaning, with each step lasting for 8 minutes. After taking out the aluminum alloy and drying it with cold air, place it in an electrolyte composed of 15 g / L boric acid, 35 g / L sulfuric acid, and 15 g / L oxalic acid, and adjust the current density to increase by 0.5 A / dm every 5 min 2 , with an anodic oxidation time of 50 min and an oxidation temperature of 15 °C to obtain a porous surface.

[0040] Step 2: Place the modified matrix in a 4% amino silane coupling agent solution for 20 min, take it out and dry it with cold air for 15 min, and repeat the treatment 5 times; then place it in a 3% silver nitrate solution for 10 min and dry it in air for 15 min, and repeat 3 times to obtain a first-level modified surface.

[0041] Step 3: Place the matrix obtained in Step 2 as a whole in a 2% sodium alginate aqueous solution for 30 min, take it out and dry it with cold air for 15 min, and repeat the treatment 4 times to obtain a second-level highly flat surface.

[0042] Step 4: Add 0.7 g of zinc chloride into 200 ml of water, adjust the magnetic stirring speed to 400 r / min, stir for 3 h, then ultrasonically disperse for 30 min, adjust the pH to 12 with 25% medium-concentration ammonia water to obtain a hydrothermal solution. Place the matrix modified in Step 3 in the hydrothermal solution, adjust the hydrothermal temperature to 130 °C, and the hydrothermal time to 12 h to obtain a fluffy corrosion-resistant surface.

[0043] Example 6: Step 1: Place the aluminum alloy in 8% sodium hydroxide solution, 8% nitric acid, and deionized water in sequence for three-step primary cleaning, with each step lasting for 5 minutes. After taking out the aluminum alloy and drying it with cold air, place it in an electrolyte composed of 15 g / L boric acid, 35 g / L sulfuric acid, and 10 g / L oxalic acid, and adjust the current density to increase by 0.5 A / dm every 5 min 2 , with an anodic oxidation time of 45 min and an oxidation temperature of 15 °C to obtain a porous surface.

[0044] Step 2: Place the modified substrate in an amino-functional silane coupling agent solution with a concentration of 3% for 30 min. After taking it out, dry it with cold air for 15 min and repeat the treatment 4 times. Subsequently, place it in a silver nitrate solution with a concentration of 4% for 15 min and dry it in air for 15 min. Repeat this 3 times to obtain a first-level modified surface.

[0045] Step 3: Place the entire substrate obtained in Step 2 in an aqueous sodium alginate solution with a concentration of 4% for 30 min. After taking it out, dry it with cold air for 10 min and repeat the treatment 3 times to obtain a second-level highly flat surface.

[0046] Step 4: Add 0.5 g of zinc chloride to 200 ml of water, adjust the magnetic stirring speed to 250 r / min, stir for 3 h, then ultrasonically disperse for 30 min. Adjust the pH to 11 with 10% medium-concentration ammonia water to obtain a hydrothermal solution. Place the substrate modified in Step 3 in the hydrothermal solution, adjust the hydrothermal temperature to 130 °C, and the hydrothermal time to 10 h to obtain a plush corrosion-resistant surface.

[0047] Comparative Example 1: This comparative example is basically the same as Example 4, except that in this comparative example, the preparation of the second-level highly flat surface is not carried out, that is, Step 3 in Example 4 is not carried out. The specific steps are as follows: Step 1: Place the aluminum alloy in 10% sodium hydroxide solution, 10% nitric acid, and deionized water for three-step initial cleaning, with each step being cleaned for 10 minutes. After taking out the aluminum alloy and drying it with cold air, place it in an electrolyte composed of 35 g / L boric acid, 35 g / L sulfuric acid, and 20 g / L oxalic acid. Adjust the current density to increase by 0.5 A / dm every 5 min 2 , the anodization time is 60 min, and the oxidation temperature is 25 °C to obtain a porous surface.

[0048] Step 2: Place the modified substrate in an amino-functional silane coupling agent solution with a concentration of 4% for 30 min. After taking it out, dry it with cold air for 15 min and repeat the treatment 5 times. Subsequently, place it in a silver nitrate solution with a concentration of 4% for 30 min and dry it in air for 15 min. Repeat this 3 times to obtain a first-level modified surface.

[0049] Step 3: Add 0.8 g of zinc chloride to 200 ml of water, adjust the magnetic stirring speed to 400 r / min, stir for 5 h, then ultrasonically disperse for 30 min. Adjust the pH to 12 with 25% medium-concentration ammonia water to obtain a hydrothermal solution. Place the substrate modified in Step 2 in the hydrothermal solution, adjust the hydrothermal temperature to 150 °C, and the hydrothermal time to 12 h to obtain a plush corrosion-resistant surface.

[0050] Comparative Example 2: This comparative example is basically the same as Example 4, except that in this comparative example, the preparation of the plush corrosion-resistant surface is not carried out, that is, step 4 in Example 4 is not carried out. The specific steps are as follows: Step 1, place the aluminum alloy in 10% sodium hydroxide solution, 10% nitric acid, and deionized water in turn for three-step primary cleaning. Each step is washed for 10 minutes. After taking out the aluminum alloy and drying it with cold air, place it in an electrolyte composed of 35 g / L boric acid, 35 g / L sulfuric acid, and 20 g / L oxalic acid. Adjust the current density to increase by 0.5 A / dm every 5 minutes 2 , anodic oxidation time of 60 minutes, and oxidation temperature of 25 °C to obtain a porous surface.

[0051] Step 2, place the modified substrate in a 4% amino silane coupling agent solution for 30 minutes, take it out and dry it with cold air for 15 minutes, and repeat the treatment 5 times; then place it in a 4% silver nitrate solution for 30 minutes and dry it in the air for 15 minutes. After repeating 3 times, a first-level modified surface is obtained.

[0052] Step 3, place the substrate obtained in Step 2 as a whole in a 4% sodium alginate aqueous solution for 30 minutes, take it out and dry it with cold air for 15 minutes, and repeat the treatment 5 times to obtain a second-level highly flat surface.

[0053] Carry out a corrosion resistance experiment on the aluminum alloys prepared in Examples 1-4 and Comparative Examples 1-2 and the unmodified aluminum alloy substrate. The specific operation is to vertically place and fix the aluminum alloy substrate before and after modification to be characterized in the corrosion solution, control the temperature at 25 °C, the corrosion time at 90 h, the corrosion solution is 5% sodium chloride solution, and use dilute sulfuric acid to adjust the pH value of the solution to 4. The measured corrosion resistance performance results are shown in Table 1.

[0054] Table 1 Comparison of Corrosion Resistance of Examples 1-4, Comparative Examples 1-2 and Unmodified Aluminum Alloy

[0055] As can be seen from Table 1, the method of the present invention prepares a plush corrosion-resistant coating on the surface of aluminum alloy through anodic oxidation, multi-layer impregnation method and hydrothermal reaction method. The coating has a high bonding strength with the substrate, and at the same time has high corrosion resistance after modification, further improving the safety of practical applications. At the same time, in Comparative Example 1, the secondary high-flat surface was not prepared in the original operation process. It can be seen that its bonding strength decreased. Due to the absence of the secondary high-flat surface, the reaction sites of the precipitant and chloride ions were missing. At the same time, the uneven surface would have an adverse effect on the preparation of the next coating, resulting in a decrease in the overall bonding strength and impedance value. In Comparative Example 2, the plush corrosion-resistant surface was not prepared in the original operation process, making the coating unable to form a primary battery with chloride ions under the use conditions and unable to capture the precipitation of chloride ions inside it. Instead, chloride ions are more likely to react with the substrate aluminum alloy. Although the bonding strength did not decrease much, the impedance value was low.

Claims

1. A method for preparing a plush, strong-bonding anti-corrosion coating on an aluminum alloy surface, characterized in that: Follow the steps below to implement it: Step 1, after cleaning the aluminum alloy substrate, placing it in an electrolyte for anodizing treatment to construct a porous surface on the surface; Step 2, placing the aluminum alloy substrate with a porous surface obtained in step 1 in a silane coupling agent solution, taking it out and drying it, repeating the immersion and drying treatment for multiple times; then placing it in a silver nitrate solution, taking it out and drying it, repeating the immersion and drying treatment for multiple times, to obtain a primary modified surface; Step 3, placing the substrate obtained in step 2 in a sodium alginate aqueous solution, taking it out and drying it, repeating the immersion and drying process for multiple times to obtain a secondary high-flat surface; Step 4: Place the modified substrate in step 3 in a hydrothermal solution to react and obtain a plush corrosion-resistant surface.

2. The method for preparing a plush, strong bonding aluminum alloy surface anti-corrosion coating according to claim 1, characterized in that: In step 1, the specific cleaning process of the aluminum alloy substrate is: The aluminum alloy substrate is placed in 5-10% sodium hydroxide solution, 5-10% nitric acid, and deionized water in turn for three-step cleaning, with each step taking 5-10 minutes. After taking out the aluminum alloy, blow dry it with cold air.

3. The method for preparing a plush, strong bonding aluminum alloy surface anti-corrosion coating according to claim 1, characterized in that: In step 1, the electrolyte is composed of 15-35 g / L boric acid, 15-35 g / L sulfuric acid, and 10-20 g / L oxalic acid; the current density of the anodic oxidation increases by 0.5 A / dm every 5 min. 2 , oxidation time 30-60min, oxidation temperature 5-25℃.

4. The method for preparing a plush, strong bonding aluminum alloy surface anti-corrosion coating according to claim 1, characterized in that: In step 2, the aluminum alloy substrate with a porous surface obtained in step 1 is placed in a silane coupling agent solution with a concentration of 2-4% for 10-30 minutes, taken out and dried with cold air for 10-15 minutes, and the immersion drying process is repeated 3-5 times.

5. The method for preparing a plush strong bonding aluminum alloy surface anti-corrosion coating according to claim 1, characterized in that: In step 2, the aluminum alloy impregnated with the silane coupling agent is placed in a 2-4% silver nitrate solution for 10-30 minutes, taken out and dried in air for 10-15 minutes, and the impregnation and drying are repeated 2-3 times to obtain a primary modified surface.

6. The method for preparing a plush strong bonding aluminum alloy surface anti-corrosion coating according to claim 1, characterized in that: In step 2, the silane coupling agent is a sulfur silane coupling agent or an amino silane coupling agent.

7. The method for preparing a plush, strong bonding aluminum alloy surface anti-corrosion coating according to claim 1, characterized in that: Step 3 is as follows: The substrate obtained in step 2 is placed in a sodium alginate aqueous solution with a concentration of 2-4% for 10-30 minutes, taken out and dried with cold air for 10-15 minutes, and the immersion and drying process is repeated 3-5 times to obtain a secondary high-flat surface.

8. The method for preparing the plush strong bonding aluminum alloy surface anti-corrosion coating according to claim 1, characterized in that: In step 4, the specific configuration process of the hydrothermal solution is: Zinc chloride is added into water, stirred at a speed of 250-400 r / min for 3-5 hours, and then ultrasonically dispersed for 15-30 minutes to prepare a zinc chloride solution with a mass concentration of 0.2-0.4wt%; 5-25% ammonia water is used to adjust the pH to 10-12 to obtain a hydrothermal solution.

9. The method for preparing a plush strong bonding aluminum alloy surface anti-corrosion coating according to claim 1, characterized in that: In step 4, the hydrothermal reaction temperature is 100-150° C. and the reaction time is 8-12 h.

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