Light alloy composite film layer and method for producing the same

Abstract

This invention discloses a light alloy composite film and its preparation method. The light alloy composite film includes a light alloy, a micro-arc oxidation layer on the surface of the light alloy, a fluorescent corrosion inhibitor layer on the surface of the micro-arc oxidation layer, and a sol-gel layer on the surface of the fluorescent corrosion inhibitor layer. The sol-gel layer includes a corrosion inhibitor; the fluorescent corrosion inhibitor layer includes a fluorescent corrosion inhibitor. This invention, by adding two corrosion inhibitors to the light alloy composite film, utilizes the corrosion inhibition effects of the fluorescent corrosion inhibitor and the fluorescence effect of the fluorescent corrosion inhibitor to enhance the corrosion protection performance and corrosion stability of the light alloy composite film. Simultaneously, it serves as an early warning system for the corrosion degree of the light alloy composite film, significantly improving the long-term corrosion resistance of the light alloy and enabling its long-term service life.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of light alloy material, more particularly, to a light alloy composite film layer and a preparation method thereof. BACKGROUND

[0002] With the introduction of relevant policies such as energy saving and emission reduction, light alloys (such as aluminum alloys, magnesium alloys or titanium alloys, etc.) have been widely used and advocated in the aviation, aerospace, weapons and civil industries as substitutes for metal materials such as steel to reduce the weight of parts, but the light alloys have defects such as low hardness and easy oxidation at high temperature, which seriously limit the application range of light alloys.

[0003] In order to overcome the above-mentioned defects of light alloy materials, there are currently protective coatings of light alloy materials prepared by micro-arc oxidation technology. Micro-arc oxidation technology is a new type of surface treatment technology with simple process, high efficiency and green environmental protection. This treatment can in-situ grow a micro-arc oxidation film layer mainly composed of base metal oxides on the surface of non-ferrous metals such as magnesium, aluminum, titanium and their alloys. The micro-arc oxidation film layer has the characteristics of high corrosion resistance, good wear resistance and good combination with the substrate. However, the traditional micro-arc oxidation film layer has unevenly distributed loose pores, and the corrosion medium can easily pass through these pores to corrode the light alloy, resulting in pitting corrosion and inducing large-area corrosion, which weakens the protection of the film layer to the substrate. Therefore, it is generally necessary to use a sealing post-treatment to further improve the corrosion resistance of the micro-arc oxidation film layer. Sol-gel method is a promising coating preparation technology with simple process equipment and low price, and can effectively improve the defects of the micro-arc oxidation film.

[0004] However, the sol-gel film layer prepared by the existing sol-gel method only ensures the corrosion resistance of the micro-arc oxidation film layer by sealing the pores on the surface of the micro-arc oxidation film layer. Once the sol-gel film layer is damaged, the corrosion protection function is affected. SUMMARY

[0005] The purpose of the present application is to overcome the above-mentioned defects of the prior art, and to provide a light alloy composite film layer and a preparation method thereof, which can improve the corrosion resistance and stability and have the function of warning the degree of corrosion.

[0006] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows:

[0007] A light alloy composite film layer, comprising a light alloy, a micro-arc oxidation layer located on the surface of the light alloy, a fluorescent corrosion inhibitor layer located on the surface of the micro-arc oxidation layer, and a sol-gel layer located on the surface of the fluorescent corrosion inhibitor layer; the sol-gel layer comprises a corrosion inhibitor; the fluorescent corrosion inhibitor layer comprises a fluorescent corrosion inhibitor.

[0008] The application further provides a preparation method of the light alloy composite film layer.

[0009] The light alloy is placed in an electrolyte for micro-arc oxidation treatment, so as to form a micro-arc oxidation layer on the surface of the light alloy, thereby obtaining the light alloy with the micro-arc oxidation layer;

[0010] The light alloy with the micro-arc oxidation layer is added into a fluorescent corrosion inhibitor for loading, so as to form a fluorescent corrosion inhibitor layer on the surface of the micro-arc oxidation layer, thereby obtaining the light alloy with the fluorescent corrosion inhibitor layer and the micro-arc oxidation layer;

[0011] The light alloy with the fluorescent corrosion inhibitor layer and the micro-arc oxidation layer is placed in a sol-gel solution containing a corrosion inhibitor for dip-coating, so as to form a sol-gel layer on the surface of the fluorescent corrosion inhibitor layer, thereby obtaining the light alloy composite film layer.

[0012] The application has the following beneficial effects:

[0013] The fluorescent corrosion inhibitor layer and the sol-gel layer perform sealing treatment on the micro-arc oxidation layer, and part of the fluorescent corrosion inhibitor is filled in the pores in the micro-arc oxidation layer, thereby further performing sealing treatment and effectively preventing the environmental corrosion medium from directly entering the surface of the light alloy through the micropores, so as to improve the corrosion resistance of the light alloy composite film layer. When the light alloy composite film layer is corroded, the corrosion inhibitor in the sol-gel layer and the fluorescent corrosion inhibitor in the fluorescent corrosion inhibitor layer can penetrate to the surface of the light alloy along with the environmental corrosion medium (such as water molecules), so as to form a corrosion-resistant protective film on the surface of the light alloy, thereby ensuring the corrosion resistance of the light alloy, and the double-layer corrosion-resistant protective film improves the corrosion resistance stability of the light alloy composite film layer. The fluorescent corrosion inhibitor in the fluorescent corrosion inhibitor layer has a fluorescence effect, and the fluorescent corrosion inhibitor presents fluorescence under the irradiation of ultraviolet light. Therefore, the distribution and consumption of the fluorescent corrosion inhibitor can be reflected by the distribution and brightness of the fluorescence of the fluorescent corrosion inhibitor, thereby playing a warning role for the corrosion degree of the light alloy composite film layer.

[0014] Compared with the traditional sol-gel post-treatment method, the application adds double corrosion inhibitors into the light alloy composite film layer, utilizes the corrosion inhibition effect of the fluorescent corrosion inhibitor and the corrosion inhibitor and the fluorescence effect of the fluorescent corrosion inhibitor, thereby improving the corrosion resistance and the corrosion resistance stability of the light alloy composite film layer, playing a warning role for the corrosion degree of the light alloy composite film layer, greatly improving the long-term corrosion resistance of the light alloy, and realizing the long-term service of the light alloy. BRIEF DESCRIPTION OF DRAWINGS

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] in:

[0017] Figure 1 The images show the XRD patterns of the micro-arc oxidation layer without 2-mercaptobenzothiazole and the micro-arc oxidation layer with 2-mercaptobenzothiazole loaded in Example 1.

[0018] Figure 2 These are the Nyquist plots of Example 1 and Comparative Examples 1-4.

[0019] Figure 3 These are Bode plots for Example 1 and Comparative Examples 1-4.

[0020] Figure 4 These are the Nyquist plots of Example 2 and Comparative Examples 5-8.

[0021] Figure 5 These are Bode plots for Example 2 and Comparative Examples 5-8.

[0022] Figure 6 This is a fluorescence image of the sample after immersion and lifting in Example 1 before immersion.

[0023] Figure 7 This is a fluorescence image of the sample after immersion and lifting in Example 1.

[0024] Figure 8 This is a fluorescence image of the unimpregnated sample from Example 1. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention discloses a light alloy composite film layer, which includes a light alloy, a micro-arc oxidation layer on the surface of the light alloy, a fluorescent corrosion inhibitor layer on the surface of the micro-arc oxidation layer, and a sol-gel layer on the surface of the fluorescent corrosion inhibitor layer; the sol-gel layer includes a corrosion inhibitor; and the fluorescent corrosion inhibitor layer includes a fluorescent corrosion inhibitor.

[0027] Specifically, this invention involves applying a fluorescent corrosion inhibitor layer and a sol-gel layer to the surface of the micro-arc oxidation layer. These layers seal the pores within the micro-arc oxidation layer, and further fill the pores with fluorescent corrosion inhibitor, effectively preventing corrosive media from directly entering and corroding the light alloy surface through the micropores, thus improving the corrosion resistance of the light alloy composite film. When the light alloy composite film is corroded, the corrosion inhibitors in both the sol-gel layer and the fluorescent corrosion inhibitor layer can penetrate the light alloy surface along with the corrosive media (such as water molecules), forming a corrosion-resistant protective film. This double-layered corrosion-resistant protective film enhances the corrosion stability of the light alloy composite film, significantly improving the long-term corrosion resistance of the light alloy. The fluorescent corrosion inhibitor in the fluorescent corrosion inhibitor layer also has a fluorescent effect. Under ultraviolet light, the fluorescent corrosion inhibitor will fluoresce. Therefore, by observing the distribution and brightness of the fluorescence of the fluorescent corrosion inhibitor, the distribution and consumption of the fluorescent corrosion inhibitor can be reflected, thus playing an early warning role in the corrosion degree of the light alloy.

[0028] In one specific embodiment, the corrosion inhibitor accounts for 0.08% to 3.00% of the mass percentage of the sol-gel layer.

[0029] Specifically, by adjusting the mass percentage of corrosion inhibitor in the sol-gel layer to a suitable range, the light alloy composite film layer can exhibit excellent corrosion inhibition and early warning of corrosion levels.

[0030] In one specific embodiment, the fluorescent corrosion inhibitor includes one or more of 2-mercaptobenzothiazole, 2-mercaptobenzoimidazolium, and coumarin.

[0031] Preferably, the fluorescent corrosion inhibitor is 2-mercaptobenzothiazole. The N and S heteroatoms in the thiazole ring can provide lone pairs of electrons, which can adsorb and form a corrosion-resistant protective film on the surface of the light alloy. Under ultraviolet light, the fluorescent corrosion inhibitor will exhibit blue fluorescence. The distribution and brightness of the blue fluorescence of 2-mercaptobenzothiazole can reflect the distribution and consumption of 2-mercaptobenzothiazole in the light alloy composite film, thereby playing an early warning role in the corrosion degree of the light alloy.

[0032] In one specific embodiment, the corrosion inhibitor includes one or more of phenolphthalein and its derivatives, benzotriazole and its derivatives, and fumaric acid and its derivatives.

[0033] Preferably, the corrosion inhibitor is phenolphthalein. By introducing phenolphthalein into the sol-gel layer, the phenolphthalein will undergo a color reaction once the sol-gel layer is eroded. Combined with the luminescence warning of the fluorescent corrosion inhibitor layer, the light alloy composite film layer has dual warning functions of color change and luminescence, which can provide timely warning of corrosion and also has excellent anti-corrosion performance.

[0034] In one specific embodiment, the thickness of the sol-gel layer is 0.70 μm to 1.70 μm.

[0035] In one specific embodiment, the thickness of the sol-gel layer includes, but is not limited to, 0.70 μm, 1.00 μm, 1.20 μm, 1.50 μm, 1.70 μm, etc.

[0036] In one specific embodiment, the light alloy includes one or more of aluminum alloys, magnesium alloys, copper alloys, and titanium alloys.

[0037] In one specific embodiment, the sol-gel layer further comprises the following components by weight percentage: 30.00% to 35.00% of a silane coupling agent, 7.00% to 10.00% of a complexing agent, 0.40% to 1.00% of an acid catalyst, and 4.00% to 6.00% of tetraethyl orthosilicate.

[0038] Specifically, tetraethyl orthosilicate and silane coupling agent are used as precursors to form a stable transparent sol system through hydrolysis and condensation reactions in the liquid phase. The colloidal particles in the sol slowly polymerize to form a sol-gel layer with a three-dimensional spatial network structure.

[0039] In one specific embodiment, the silane coupling agent includes one or more of γ-glycidyl etheroxypropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, and trimethoxy(3-methoxypropyl)silane.

[0040] In one specific embodiment, the complexing agent includes one or more of ethyl acetoacetate, ethylenediaminetetraacetic acid, citric acid, and polyethylene glycol.

[0041] In one specific embodiment, the acid catalyst includes one or more of acetic acid, nitric acid, and hydrochloric acid.

[0042] This invention also discloses a method for preparing a light alloy composite film, comprising the following steps:

[0043] 1) Light alloys are placed in an electrolyte for micro-arc oxidation treatment to form a micro-arc oxidation layer on the surface of the light alloy, thus obtaining a light alloy with a micro-arc oxidation layer.

[0044] In one specific embodiment, step 1) specifically includes the following steps:

[0045] 1.1) Prepare the electrolyte.

[0046] In one specific embodiment, the electrolyte includes one or both of an alkaline silicate system and a neutral silicate system. Preferably, the electrolyte is an alkaline silicate system.

[0047] Because the required electrolyte composition must be compatible with the light alloy material, in one specific embodiment, when the light alloy is an aluminum alloy, the electrolyte comprises the following components at concentrations of: 4 g / L to 12 g / L sodium silicate, 5 g / L to 8 g / L potassium hydroxide, and 2 ml / L to 5 ml / L glycerol. In one specific embodiment, when the light alloy is a magnesium alloy, the electrolyte comprises the following components by mass percentage: 10 g / L to 15 g / L sodium silicate, 4 g / L to 12 g / L potassium hydroxide, and 1 ml / L to 5 ml / L glycerol.

[0048] Specifically, sodium silicate is the main film-forming agent for preparing the film layer, which easily passivates the base metal, thereby causing breakdown and triggering discharge. Glycerol is a conductive agent that can improve the conductivity of the solution, and at the same time, glycerol can improve the dispersibility of the micro-arc oxidation solution. Potassium hydroxide is a pH adjuster that ensures that the pH of the solution is between 2 and 3, providing a stable electrolyte environment for the preparation of micro-arc oxidation films.

[0049] In one specific embodiment, when the light alloy is a magnesium alloy, the electrolyte also contains 0.8 g / L to 4 g / L of sodium fluoride to accelerate the film growth rate and 1 g / L to 4 g / L of sodium hexametaphosphate to complex metal ions in the electrolyte.

[0050] 1.2) The light alloy is placed in the electrolyte of step 1.1). The electrolyte is placed in a stainless steel electrolytic cell. The light alloy is used as the anode and the stainless steel plate of the electrolytic cell is used as the cathode. Micro-arc oxidation treatment is performed to form a micro-arc oxidation layer on the surface of the light alloy, thus obtaining a light alloy with a micro-arc oxidation layer.

[0051] In one specific embodiment, the micro-arc oxidation process employs a constant current method, with the current for micro-arc oxidation being 1.00A~2.40A.

[0052] In one specific embodiment, the forward current density of the micro-arc oxidation treatment is 50 mA / cm². 2 ~200mA / cm 2 .

[0053] In one specific embodiment, the negative current density of the micro-arc oxidation treatment is 40.00 mA / cm². 2 ~100.00mA / cm 2 .

[0054] In one specific embodiment, the forward duty cycle of the micro-arc oxidation process is 20% to 40%.

[0055] In one specific embodiment, the negative duty cycle of the micro-arc oxidation treatment is 20% to 50%.

[0056] In one specific embodiment, the pulse frequency of the micro-arc oxidation treatment is 400Hz~500Hz.

[0057] In one specific embodiment, the micro-arc oxidation treatment time is 5 min to 10 min.

[0058] Specifically, the parameters affecting micro-arc oxidation mainly include electrolyte composition, electrical parameters of micro-arc oxidation, and processing time. This invention, through selecting a suitable electrolyte and adjusting corresponding process parameters, controls the morphology of the micro-arc oxidation layer, thereby obtaining a micro-arc oxidation layer with excellent corrosion resistance, wear resistance, and good adhesion.

[0059] 2) A fluorescent corrosion inhibitor is added to a light alloy with a micro-arc oxide layer for loading, and a fluorescent corrosion inhibitor layer is formed on the surface of the micro-arc oxide layer, resulting in a light alloy with a fluorescent corrosion inhibitor layer and a micro-arc oxide layer.

[0060] In one specific embodiment, step 2) specifically includes: adding a fluorescent corrosion inhibitor to a solvent to obtain a mixture, placing a light alloy with a micro-arc oxidation layer in a pressure vessel, evacuating the pressure vessel and injecting the obtained mixture until the micro-arc oxidation layer on the surface of the light alloy is completely submerged, and after vacuum treatment for 1 to 2 hours, a light alloy with a fluorescent corrosion inhibitor layer and a micro-arc oxidation layer is obtained. During this process, the fluorescent corrosion inhibitor enters the micropores of the micro-arc oxidation layer to achieve filling.

[0061] 3) The light alloy with a fluorescent corrosion inhibitor layer and a micro-arc oxidation layer is immersed and pulled in a sol-gel solution containing corrosion inhibitor to form a sol-gel layer on the surface of the fluorescent corrosion inhibitor layer, thus obtaining a light alloy composite film.

[0062] In one specific embodiment, step 3) specifically includes:

[0063] 3.1) Mix the silane coupling agent of any embodiment of the present invention with a solvent to obtain component A.

[0064] 3.2) The complexing agent, tetraethyl orthosilicate and acid catalyst of any embodiment of the present invention are mixed with a solvent to obtain component B of the adhesive.

[0065] 3.3) Add component B dropwise to component A. After the addition is complete, add the corrosion inhibitor and stir for 30 min to 1 h. Then, age the mixture for 12 h to 24 h to obtain a sol-gel solution containing the corrosion inhibitor.

[0066] 3.4) The light alloy with a fluorescent corrosion inhibitor layer and a micro-arc oxidation layer is immersed in a sol-gel solution containing corrosion inhibitor for impregnation and pulling, and a sol-gel layer is formed on the surface of the fluorescent corrosion inhibitor layer to obtain a light alloy composite film.

[0067] In one specific embodiment, the immersion and lifting speed is 80 mm / min to 100 mm / min; the immersion and lifting time is 5 min to 10 min; and the number of immersion and lifting cycles is 1 to 2.

[0068] In one specific embodiment, the solvent includes one or both of anhydrous ethanol and water.

[0069] In one specific embodiment, the process further includes drying the sol-gel layer to remove the solvent. Specifically, this includes: first drying the sol-gel layer at 60°C to 65°C for 2 to 3 hours; second drying the sol-gel layer after the first drying at 90°C to 95°C for 1 to 2 hours; and third drying the sol-gel layer after the second drying at 120°C to 125°C for 0.5 to 1 hour, to obtain a light alloy composite film. In this embodiment, the use of staged gradient drying results in a film with good adhesion and a dense structure.

[0070] In one specific embodiment, prior to the micro-arc oxidation process in step 1), a pretreatment of the light alloy is further included to ensure more uniform film growth in subsequent processes, specifically including:

[0071] The light alloy was polished sequentially using sandpaper with a grit of 400 to 1200 grit. The surface of the polished light alloy was then polished until it became mirror-like and free of scratches. After that, the polished light alloy was ultrasonically cleaned with pure water and anhydrous ethanol for 5 to 15 minutes and dried at 20°C to 60°C for 5 minutes to 1 hour to obtain the pretreated light alloy.

[0072] The method for preparing the light alloy composite film of the present invention has the advantages of low cost, simple process and environmental protection. After micro-arc oxidation treatment on the surface of light alloy, fluorescent corrosion inhibitor is loaded to prepare micro-arc oxidation layer and fluorescent corrosion inhibitor layer. Then, sol-gel sealing treatment is performed. The corrosion resistance of the light alloy composite film is significantly higher than that of the single micro-arc oxidation layer.

[0073] The following are specific examples.

[0074] Example 1

[0075] The aluminum alloy composite film layer in this embodiment includes an aluminum alloy, a micro-arc oxidation layer on the surface of the aluminum alloy, a fluorescent corrosion inhibitor layer on the surface of the micro-arc oxidation layer, and a bilayer sol-gel layer on the surface of the fluorescent corrosion inhibitor layer. The fluorescent corrosion inhibitor in the fluorescent corrosion inhibitor layer is 2-mercaptobenzothiazole. The corrosion inhibitor in the sol-gel layer is phenolphthalein.

[0076] The method for preparing the light alloy composite film in this embodiment includes the following steps:

[0077] 1) The aluminum alloy (3cm in length, 3cm in width and 0.5cm in thickness) was polished sequentially with 400 grit, 600 grit, 800 grit and 1200 grit sandpaper. The surface of the polished light alloy was then polished until it was mirror-like and free of scratches. After that, the polished light alloy was ultrasonically cleaned with deionized water and anhydrous ethanol for 10 minutes and dried at 60℃ for 10 minutes to obtain the pretreated light alloy.

[0078] 2) Prepare the electrolyte. In this embodiment, the electrolyte is an aqueous solvent and adopts an alkaline silicate system, which consists of the following components at the following concentrations: 4 g / L sodium silicate, 5 g / L potassium hydroxide and 2 ml / L glycerol.

[0079] 3) Place the pretreated aluminum alloy in the electrolyte from step 2). The electrolyte is placed in a stainless steel electrolytic cell. Use the aluminum alloy as the anode and the stainless steel plate of the electrolytic cell as the cathode. Perform micro-arc oxidation treatment for 10 minutes to form a micro-arc oxidation layer on the surface of the light alloy, thus obtaining an aluminum alloy with a micro-arc oxidation layer. The micro-arc oxidation treatment parameters are: constant current method, micro-arc oxidation current of 1A, and forward current density of 50mA / cm². 2 The negative current density is 40 mA / cm². 2 The positive duty cycle is 40%, the negative duty cycle is 20%, and the pulse frequency is 500Hz.

[0080] 4) Mix 0.4g of 2-mercaptobenzothiazole with 60ml of anhydrous ethanol to obtain a mixture. Place the aluminum alloy with the micro-arc oxide layer in a pressure vessel. After evacuating the pressure vessel, inject 35ml of the mixture until the micro-arc oxide layer on the surface of the light alloy is completely submerged. After vacuum treatment for 1h, a fluorescent corrosion inhibitor layer is formed on the surface of the micro-arc oxide layer, thus obtaining an aluminum alloy with a fluorescent corrosion inhibitor micro-arc oxide layer.

[0081] 5) Prepare a 34 ml solution of anhydrous ethanol, deionized water, and γ-glycidyl etheroxypropylmethyldiethoxysilane in a mass ratio of 15:7:12, and stir for 1 h to obtain component A. Prepare a 15.6 ml solution of anhydrous ethanol, ethyl acetoacetate, tetraethyl orthosilicate, and acetic acid in a mass ratio of 6:3:6:0.6, and stir for 1 h to obtain component B. Add component B dropwise to component A. After complete addition, add 0.2 mmol of phenolphthalein, stir for 30 min, and then age for 12 h to obtain a sol-gel solution containing phenolphthalein.

[0082] 6) Immerse the aluminum alloy with the fluorescent corrosion inhibitor layer and the micro-arc oxidation layer into a sol-gel solution containing phenolphthalein at a speed of 100 mm / min for 5 min. After drying at 60℃ for 3 h, 90℃ for 1 h and 120℃ for 0.5 h respectively, a sol-gel layer with a thickness of 0.70 μm is formed on the surface of the fluorescent corrosion inhibitor layer. Repeat this step once more to obtain the aluminum alloy composite film.

[0083] Example 2

[0084] The lightweight alloy composite film in this embodiment includes a magnesium alloy, a micro-arc oxidation layer on the surface of the magnesium alloy, a fluorescent corrosion inhibitor layer on the surface of the micro-arc oxidation layer, and a bilayer sol-gel layer on the surface of the fluorescent corrosion inhibitor layer. The fluorescent corrosion inhibitor in the fluorescent corrosion inhibitor layer is 2-mercaptobenzothiazole. The corrosion inhibitor in the sol-gel layer is phenolphthalein.

[0085] The electrolyte in this embodiment is an aqueous solvent and adopts an alkaline silicate system, consisting of the following components at the following concentrations: 10 g / L sodium silicate, 5 g / L potassium hydroxide, 1.25 g / L sodium hexametaphosphate, 0.8 g / L sodium fluoride, and 4 ml / L glycerol.

[0086] The preparation method of the light alloy composite film in this embodiment is the same as that in Example 1. The magnesium alloy composite film of this application is obtained according to the preparation method of Example 1.

[0087] Comparative Example 1

[0088] This comparative example uses untreated aluminum alloy.

[0089] Comparative Example 2

[0090] The aluminum alloy composite film in this comparative example consists only of aluminum alloy and a micro-arc oxidation film layer located on the surface of the aluminum alloy. The preparation method of the aluminum alloy composite film in this comparative example is the same as that in Example 1.

[0091] Comparative Example 3

[0092] The aluminum alloy composite film in this comparative example includes an aluminum alloy, a micro-arc oxidation layer on the surface of the aluminum alloy, and a fluorescent corrosion inhibitor layer on the surface of the micro-arc oxidation layer. The fluorescent corrosion inhibitor in the fluorescent corrosion inhibitor layer is 2-mercaptobenzothiazole. The preparation method of the aluminum alloy composite film in this comparative example is the same as that in Example 1.

[0093] Comparative Example 4

[0094] The only difference between the aluminum alloy composite film layer in this comparative example and that in Example 1 is that the double-layer sol-gel layer in this comparative example does not contain phenolphthalein.

[0095] Comparative Example 5

[0096] This comparative example uses an untreated magnesium alloy.

[0097] Comparative Example 6

[0098] The magnesium alloy composite film in this comparative example consists only of magnesium alloy and a micro-arc oxidation film layer located on the surface of magnesium alloy. The preparation method of the magnesium alloy composite film in this comparative example is the same as that in Example 1.

[0099] Comparative Example 7

[0100] The magnesium alloy composite film in this comparative example includes a magnesium alloy, a micro-arc oxidation layer on the surface of the magnesium alloy, and a fluorescent corrosion inhibitor layer on the surface of the micro-arc oxidation layer. The fluorescent corrosion inhibitor layer is made of 2-mercaptobenzothiazole. The preparation method of the magnesium alloy composite film in this comparative example is the same as that in Example 1.

[0101] Comparative Example 8

[0102] The only difference between the magnesium alloy composite film layer of this comparative example and Example 1 is that the bilayer sol-gel layer of this comparative example does not contain phenolphthalein.

[0103] Test case

[0104] 1. XRD phase analysis was performed on the micro-arc oxidation layer without 2-mercaptobenzothiazole and the micro-arc oxidation layer with 2-mercaptobenzothiazole in Example 1. The results are as follows: Figure 1 As shown, Figure 1 The XRD patterns of the micro-arc oxide layer without and with 2-mercaptobenzothiazole in Example 1 are shown (MAO represents the micro-arc oxide layer without 2-mercaptobenzothiazole; MBT+MAO represents the micro-arc oxide layer with 2-mercaptobenzothiazole). The results show that the main component of the micro-arc oxide layer formed on the aluminum alloy surface is aluminum oxide. By comparing the characteristic peaks of the micro-arc oxide layer with 2-mercaptobenzothiazole, it was found that the peak positions of the micro-arc oxide layer with 2-mercaptobenzothiazole in the range of 11° to 33° basically correspond to the peak positions of MBT, indicating that 2-mercaptobenzothiazole was successfully loaded onto the micro-arc oxide layer.

[0105] 2. Electrochemical impedance spectroscopy (EIS) tests were performed on the samples of Examples 1-2 and Comparative Examples 1-8 using a Wuhan Corrtest CS350 electrochemical workstation to analyze the corrosion resistance of the light alloy composite film. The specific test method is as follows: A three-electrode system was used, with the samples of Examples 1-2 and Comparative Examples 1-8 serving as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum mesh as the auxiliary electrode. A 3.5 wt.% NaCl solution was used as the corrosion medium, and the test area was 1 cm². 2 The test temperature was 25℃, and the test results were as follows: Figures 2-5 As shown, Figure 2The Nyquist plots are for Example 1 and Comparative Examples 1-4. Figure 3 The Bode plots are for Example 1 and Comparative Examples 1-4. Figure 4 The Nyquist plots for Example 2 and Comparative Examples 5-8 are shown. Figure 5 The Bode plots are for Example 2 and Comparative Examples 5-8.

[0106] according to Figure 2 and Figure 4 The test results show that the diameter of the fitted curve in Example 1 is larger than that in Comparative Examples 1-4, and the diameter of the fitted curve in Example 2 is larger than that in Comparative Examples 5-8. A larger fitted curve diameter indicates better corrosion resistance; therefore, Examples 1 and 2 exhibit superior corrosion resistance compared to the comparative examples.

[0107] according to Figure 3 The test results show that the low-frequency impedance modulus value of Example 1 is greater than that of Comparative Examples 1-4, and the low-frequency impedance modulus of Example 1 reaches 2.09 × 10⁻⁶. 8 Ωcm 2 .according to Figure 5 The test results show that the low-frequency impedance modulus values ​​in Example 2 are all greater than those in Comparative Examples 5-8, with the low-frequency impedance modulus value in Example 2 reaching 5.29 × 10⁻⁶. 6 Ωcm 2 In particular, a larger impedance modulus value in the low-frequency region indicates better corrosion resistance. Therefore, Examples 1 and 2 have superior corrosion resistance compared to the comparative example.

[0108] This invention demonstrates that by adding dual corrosion inhibitors to the light alloy composite film layer, utilizing the corrosion inhibition effects of fluorescent corrosion inhibitors and other corrosion inhibitors, the corrosion protection performance and corrosion stability of the light alloy composite film layer are enhanced, while the corrosion resistance of the light alloy is greatly improved.

[0109] And according to Figures 2-5 The test results also show that the corrosion resistance of the samples improved with each additional treatment.

[0110] 3. After analyzing the luminescence of the film layer of the unimpregnated and impregnated samples from Example 1 using fluorescence microscopy, the impregnated samples were immersed in 3.5 wt.% NaCl for 25 days. The luminescence of the film layer of the immersed samples was then analyzed using fluorescence microscopy. The test results are as follows: Figures 6-8 , Figures 6-7 The images shown are fluorescence images of the sample after immersion and extraction in Example 1, before and after immersion. Figure 8 The image shows a fluorescence image of the unimpregnated sample from Example 1.

[0111] according to Figure 6 The test results show that the loading of 2-mercaptobenzothiazole in the samples after soaking and subsequent extraction can be observed using a fluorescence microscope. Figure 6 The blue spots in the image are the fluorescence emitted by 2-mercaptobenzothiazole.

[0112] according to Figure 7 The test results show that after immersion, the number of light spots in the image decreased significantly, and the brightness of the light spots also decreased significantly. This indicates that during the immersion process, 2-mercaptobenzothiazole was partially consumed as it adsorbed onto the surface of the light alloy to form a corrosion-resistant protective film. Therefore, the distribution and brightness of the fluorescence of 2-mercaptobenzothiazole can reflect the distribution and consumption of 2-mercaptobenzothiazole in the composite film layer of the light alloy, thus serving as an early warning system for the degree of corrosion of the light alloy.

[0113] according to Figure 6 and Figure 8 The test results show that Figure 6 The number of light spots in the middle is less than Figure 8 The number of light spots indicates that even if the sol-gel layer formed on the surface of the fluorescent corrosion inhibitor layer is a transparent film, it will still affect the transmittance of the fluorescent corrosion inhibitor layer as the inner layer. This application, by adjusting the micro-arc oxidation process and the dip-coating process, enables the prepared light alloy composite film to avoid this defect. Figure 6 As shown, fluorescent corrosion inhibitors in the light alloy composite film can be successfully identified. Therefore, the light alloy composite film has both excellent early warning function for corrosion degree and excellent corrosion resistance and protection performance.

[0114] Example 3

[0115] The lightweight alloy composite film in this embodiment includes an aluminum alloy, a micro-arc oxidation layer on the surface of the aluminum alloy, a fluorescent corrosion inhibitor layer on the surface of the micro-arc oxidation layer, and a bilayer sol-gel layer on the surface of the fluorescent corrosion inhibitor layer. The fluorescent corrosion inhibitor in the fluorescent corrosion inhibitor layer is 2-mercaptobenzothiazole. The corrosion inhibitor in the sol-gel layer is 2.04% phenolphthalein.

[0116] The electrolyte in this embodiment is an aqueous solvent and adopts an alkaline silicate system, consisting of the following components at the following concentrations: 6 g / L sodium silicate, 6 g / L potassium hydroxide, and 3 ml / L glycerol.

[0117] The preparation method of the light alloy composite film in this embodiment is the same as that in Example 1. The aluminum alloy composite film of this application is obtained according to the preparation method of Example 1.

[0118] The light alloy composite film obtained in this embodiment achieves the same effect as in Example 1.

[0119] Example 4

[0120] The lightweight alloy composite film in this embodiment includes a magnesium alloy, a micro-arc oxidation layer on the surface of the magnesium alloy, a fluorescent corrosion inhibitor layer on the surface of the micro-arc oxidation layer, and a bilayer sol-gel layer on the surface of the fluorescent corrosion inhibitor layer. The fluorescent corrosion inhibitor in the fluorescent corrosion inhibitor layer is 2-mercaptobenzothiazole. The corrosion inhibitor in the sol-gel layer is phenolphthalein.

[0121] The electrolyte in this embodiment is an aqueous solvent and adopts an alkaline silicate system, consisting of the following components at the following concentrations: 12 g / L sodium silicate, 6 g / L potassium hydroxide, 1.5 g / L sodium hexametaphosphate, 1 g / L sodium fluoride, and 5 ml / L glycerol.

[0122] The preparation method of the light alloy composite film in this embodiment is the same as that in Example 1. The magnesium alloy composite film of this application is obtained according to the preparation method of Example 1.

[0123] The light alloy composite film obtained in this embodiment achieves the same effect as in Example 2.

[0124] In summary, compared with the traditional sol-gel post-treatment method, this invention, by adding dual corrosion inhibitors to the light alloy composite film layer, utilizes the corrosion inhibition effects of fluorescent corrosion inhibitors and the fluorescence effect of fluorescent corrosion inhibitors to enhance the corrosion protection performance and corrosion stability of the light alloy composite film layer, while also serving as an early warning function for the corrosion degree of the light alloy composite film layer. This can greatly improve the long-term corrosion resistance of light alloys and achieve long-term service of light alloys.

[0125] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A lightweight alloy composite film, characterized in that, The light alloy composite film layer includes a light alloy, a micro-arc oxidation layer on the surface of the light alloy, a fluorescent corrosion inhibitor layer on the surface of the micro-arc oxidation layer, and a sol-gel layer on the surface of the fluorescent corrosion inhibitor layer. In this process, the light alloy with the micro-arc oxide layer is loaded with a fluorescent corrosion inhibitor, and the fluorescent corrosion inhibitor layer is formed on the surface of the micro-arc oxide layer. The sol-gel layer includes a corrosion inhibitor; The fluorescent corrosion inhibitor layer is 2-mercaptobenzothiazole, and the corrosion inhibitor in the sol-gel layer is phenolphthalein. The sol-gel layer is prepared from a sol-gel solution comprising the following components by mass percentage: 30.00% to 35.00% silane coupling agent, 7.00% to 10.00% complexing agent, 0.40% to 1.00% acid catalyst, and 4.00% to 6.00% tetraethyl orthosilicate.

2. The lightweight alloy composite film layer according to claim 1, characterized in that, The corrosion inhibitor in the sol-gel layer accounts for 0.08% to 3.00% of the mass of the sol-gel layer.

3. The lightweight alloy composite film layer according to claim 1, characterized in that, The thickness of the sol-gel layer is 0.70 μm to 1.70 μm; The light alloy includes one or more of aluminum alloys, magnesium alloys, copper alloys, and titanium alloys.

4. The lightweight alloy composite film layer according to claim 1, characterized in that, The silane coupling agent includes one or more of γ-glycidyl oxypropyl methyl diethoxysilane, 3-aminopropyltrimethoxysilane, and trimethoxy(3-methoxypropyl)silane; The complexing agent includes one or more of ethyl acetoacetate, ethylenediaminetetraacetic acid, citric acid, and polyethylene glycol; The acid catalyst includes one or more of acetic acid, nitric acid, and hydrochloric acid.

5. A method for preparing a light alloy composite film according to any one of claims 1 to 4, characterized in that, Includes the following steps: A light alloy is placed in an electrolyte for micro-arc oxidation treatment to form a micro-arc oxidation layer on the surface of the light alloy, thereby obtaining a light alloy with a micro-arc oxidation layer. The light alloy with the micro-arc oxide layer is loaded with a fluorescent corrosion inhibitor to form a fluorescent corrosion inhibitor layer on the surface of the micro-arc oxide layer, thus obtaining a light alloy with a fluorescent corrosion inhibitor layer and a micro-arc oxide layer. The light alloy having a fluorescent corrosion inhibitor layer and a micro-arc oxidation layer is immersed and pulled in a sol-gel solution containing a corrosion inhibitor to form a sol-gel layer on the surface of the fluorescent corrosion inhibitor layer, thus obtaining the light alloy composite film.

6. The method for preparing the light alloy composite film according to claim 5, characterized in that, The current for the micro-arc oxidation treatment is 1.00A~2.40A; The forward current density of the micro-arc oxidation treatment is 50.00 mA / cm². 2 ~200.00mA / cm 2 ; The negative current density of the micro-arc oxidation treatment is 40.00 mA / cm². 2 ~100.00mA / cm 2 ; The forward duty cycle of the micro-arc oxidation treatment is 20.00%~40.00%; The negative duty cycle of the micro-arc oxidation treatment is 20.00%~50.00%; The micro-arc oxidation treatment time is 5 min to 10 min; The electrolyte includes an alkaline silicate system or a neutral silicate system; The immersion lifting speed is 80 mm / min to 100 mm / min; The immersion and lifting time is 5 to 10 minutes; The immersion and lifting process is repeated 1 to 2 times.

7. The method for preparing the light alloy composite film according to claim 6, characterized in that, When the light alloy is an aluminum alloy, the electrolyte comprises components with the following concentrations: Sodium silicate at concentrations of 4 g / L to 12 g / L, potassium hydroxide at concentrations of 5 g / L to 8 g / L, and glycerol at concentrations of 2 ml / L to 5 ml / L.

8. The method for preparing the light alloy composite film according to claim 6, characterized in that, When the light alloy is a magnesium alloy, the electrolyte comprises the following components: Sodium silicate at 10 g / L to 15 g / L, potassium hydroxide at 4 g / L to 12 g / L, sodium hexametaphosphate at 1 g / L to 4 g / L, sodium fluoride at 0.8 g / L to 4 g / L, and glycerol at 1 ml / L to 5 ml / L.

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