Multi-responsive self-healing long-acting coating on magnesium alloy surface and preparation method and application thereof

Abstract

This invention discloses a multi-responsive self-healing long-lasting coating for magnesium alloy surfaces, its preparation method, and its application, relating to the field of surface modification technology. The method includes a hydrothermal reaction on a magnesium alloy surface to obtain in-situ grown Mg(OH)₂; electrophoretic deposition of polydopamine on the in-situ grown Mg(OH)₂; preparation of silica-encapsulated silver nanorods loaded with dopamine nanoparticles; uniform dispersion of the nanoparticles in a polycaprolactone solution to obtain a polycaprolactone solution containing nanoparticles; and coating the polydopamine with the polycaprolactone solution containing nanoparticles, thus forming a multi-responsive self-healing long-lasting coating on the magnesium alloy surface. This invention constructs an early warning system based on Mg(OH)₂ on the magnesium alloy surface, responding to Mg… 2+ A composite coating with good inorganic-organic bonding achieves durable and stable multi-layer protection through pH and near-infrared light (NIR). This coating not only provides long-lasting corrosion protection but also has de-icing and marine antifouling functions.

Description

Technical Field

[0001] This invention relates to the field of surface modification technology, specifically to a multi-response self-healing long-lasting coating for magnesium alloy surfaces, its preparation method, and its application. Background Technology

[0002] Magnesium alloys possess high strength and toughness, and their relatively low density makes them the lightest and strongest structural alloys. This allows for the design of lighter engineering systems and reduced energy consumption. Magnesium alloys are also used for lightweighting in the transportation and electronics industries due to their electromagnetic shielding properties, heat dissipation capabilities, and machinability. In recent years, magnesium alloys have also shown great potential in various new applications, from batteries to biomedical products. However, their high electronegativity and corrosion susceptibility have remained obstacles to their further application in various fields.

[0003] Two feasible approaches to controlling the corrosion sensitivity of magnesium alloys are: developing novel corrosion-resistant magnesium alloys and surface modification of magnesium alloys. Coating preparation is one of the most effective means of metal corrosion protection. For magnesium alloys, metal coatings are prone to galvanic corrosion. Individual inorganic coatings have limited corrosion resistance, while purely organic coatings have poor adhesion to the substrate. Therefore, inorganic and organic coatings are usually combined. However, coatings inevitably suffer damage and cracking during the corrosion protection process, leading to a decrease in corrosion resistance. Therefore, it is necessary to develop long-lasting coatings with damage repair capabilities. These damage-repairing coatings are divided into functional repair coatings and shape repair coatings. Functional repair coatings restore the protective ability of the coating by loading corrosion inhibitors; shape repair coatings repair the morphology and structure of the coating through reversible polymer reactions, chemical bond rearrangement, and shape memory effects. Long-lasting coatings with damage repair capabilities can promptly repair surface damage to the coating when it is damaged, restoring the long-term protective effect of the coating. This has significant research value and economic benefits in magnesium alloy protection. Summary of the Invention

[0004] To address the shortcomings of the aforementioned background technology, this invention primarily solves the problem that existing coatings inevitably suffer damage and cracking during the corrosion protection process, leading to a decline in corrosion resistance. This invention provides a multi-response self-healing long-lasting coating for magnesium alloy surfaces, its preparation method, and its application. The method first involves a hydrothermal reaction of the magnesium alloy to obtain in-situ grown Mg(OH)₂. This Mg(OH)₂ coating, being obtained in situ, possesses excellent adhesion and releases a warning signal Mg before the magnesium alloy substrate is about to corrode. 2+ and OH - This process stimulates the repair of corrosion cracks; then, a layer of PDA is electrophoretically deposited on the Mg(OH)2 surface. The PDA in the middle can adhere to and connect the upper and lower layers, enhancing the adhesion between the coatings. The PDA can also interact with Mg...2+ Chelating enhances the corrosion resistance of the coating; finally, a layer of PCL containing core-shell structured nanoparticles AgNR@MSN@DA is spin-coated onto the PDA surface. When the coating is damaged or the magnesium alloy is corroded, OH groups are released. - Enhancing the alkalinity of the environment allows PCL to decompose and release DA from the nanoparticles AgNR@MSN@DA. DA then polymerizes into PDA in response to the alkaline environment, which re-forms strong hydrogen with PCL or re-polymerizes with the electrophoretically deposited intermediate PDA layer to repair cracks. Simultaneously, NIR irradiation is applied, utilizing the synergistic photothermal effect of AgNR and PDA to raise the temperature of the PCL coating and induce melting and flow to repair cracks. This creates an early warning system based on Mg(OH)2 on the magnesium alloy surface, responding to Mg... 2+ A composite coating with good inorganic-organic bonding, which achieves durable and stable multi-layer protection through pH and NIR, not only provides long-lasting corrosion protection but also has de-icing and marine antifouling functions.

[0005] The first objective of this invention is to provide a method for preparing a multi-response self-healing long-lasting coating on a magnesium alloy surface, comprising the following steps:

[0006] A hydrothermal reaction was carried out on the surface of a magnesium alloy to obtain in-situ grown Mg(OH)2;

[0007] Polydopamine was electrophoretically deposited on in-situ grown Mg(OH)2.

[0008] Prepare silica-coated silver nanorods loaded with dopamine nanoparticles; uniformly disperse the nanoparticles in a polycaprolactone solution to obtain a polycaprolactone solution containing nanoparticles.

[0009] A polycaprolactone solution containing nanoparticles is coated onto polydopamine to create a multi-response, self-healing, long-lasting coating on a magnesium alloy surface.

[0010] Preferably, when carrying out the hydrothermal reaction on the magnesium alloy surface, the hydrothermal solution concentration is 0.001~0.1 g / mL NaOH solution, the temperature is 80~160 ℃, and the reaction time is 1~12 h.

[0011] Preferably, when electrophoretically depositing polydopamine on in-situ grown Mg(OH)2, the electrophoretic solution is a DA solution of 1~10 mg / mL, and the solvent of the DA solution is deionized water;

[0012] During electrophoretic deposition, the distance between the anode and cathode is 8–15 mm, and the applied current is 2–6 mA / cm². 2 The electrophoretic deposition time is 1~10 min; among them, a magnesium alloy containing in-situ grown Mg(OH)2 is used as the cathode.

[0013] Preferably, in the polycaprolactone solution containing nanoparticles, the concentration of polycaprolactone is 1-20 wt%; and the concentration of nanoparticles is 1-30 mg / mL.

[0014] Polycaprolactone solution is prepared by dissolving polycaprolactone in one or more of dichloromethane, chloroform, and acetone.

[0015] Preferably, when coating polycaprolactone solution containing nanoparticles onto polydopamine, the coating is performed by spin coating, wherein during spin coating, the spin is held for 10 to 90 seconds at both the low-speed stage (200-800 rpm) and the high-speed stage (1000-3000 rpm).

[0016] Preferably, the silica-encapsulated silver nanorods and dopamine-loaded nanoparticles comprise nanoparticles with silica as the shell, silver nanorods as the core, and dopamine as the pore loading medium; wherein the silver nanorods have a length of 100~120 nm and an aspect ratio of 4.16±0.13.

[0017] The thickness of the silica shell is 10~80 nm;

[0018] The dopamine loading rate is 5-95% by mass.

[0019] Preferably, before the magnesium alloy surface undergoes a hydrothermal reaction, the magnesium alloy surface is further subjected to pretreatment, including: polishing the magnesium alloy surface with sandpaper, and then ultrasonically treating the magnesium alloy with acetone and anhydrous ethanol for 5-15 minutes respectively.

[0020] Preferably, the magnesium alloy includes AZ series, ZK series, WE series or JDBM magnesium alloy.

[0021] The second objective of this invention is to provide a self-healing, long-lasting coating with multiple responses on magnesium alloy surfaces.

[0022] A third objective of this invention is to provide an application of a coating in the modification of metal surfaces.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] This invention provides a multi-response self-healing long-lasting coating for magnesium alloy surfaces, its preparation method, and its application. The invention constructs a composite coating with good inorganic-organic bonding on the magnesium alloy surface. The in-situ formed Mg(OH)2 is tightly bonded to the magnesium alloy matrix. Dopamine molecules, rich in phenolic hydroxyl and amine groups, self-polymerize in situ under the dual effects of the slightly alkaline environment and electric field on the Mg(OH)2 surface, forming a highly adhesive PDA coating. PDA forms strong hydrogen bonds with Mg(OH)2 and the outer PCL layer, thus forming a three-layer tightly connected composite coating that effectively isolates the magnesium alloy from direct contact with the environment, improving the corrosion resistance of the magnesium alloy.

[0025] This invention constructs a long-lasting composite coating on the surface of magnesium alloys that provides early warning of corrosion initiation and prevents further corrosion. Just before corrosion reaches the magnesium alloy substrate, the Mg(OH)₂ coating is disrupted, releasing magnesium. 2+ and OH - This causes the intermediate PDA layer and the outer PCL layer to respond to Mg, respectively. 2+ and OH - By activating corrosion inhibition, this composite coating achieves highly efficient protection functions, including early warning of corrosion and prevention of corrosion.

[0026] This invention constructs a Mg-responsive structure on the surface of a magnesium alloy. 2+ The self-healing, long-lasting coating releases Mg when the coating is damaged or the magnesium alloy corrodes. 2+ The intermediate PDA layer contains many phenolic hydroxyl groups (-OH), which can react with Mg. 2+ Coordination is used to generate a polymer-metal complex (PDA-Mg), which can fill cracks and protect the coating.

[0027] This invention constructs a pH-responsive, self-healing, long-lasting coating on the surface of a magnesium alloy. When the coating is damaged or the magnesium alloy corrodes and cracks, OH groups are released. - By enhancing the alkalinity of the environment, PCL decomposes under alkaline conditions to release DA from the nanoparticles AgNR@MSN@DA. DA polymerizes into PDA in response to pH, which then re-forms strong hydrogen with PCL or re-polymerizes with the electrophoretically deposited intermediate PDA layer to repair cracks, thereby preventing further corrosion.

[0028] This invention constructs a self-healing, long-lasting coating on the surface of a magnesium alloy that responds to NIR. When irradiated with NIR, the photosensitizers PDA and AgNR@MSN@DA exert a photothermal response, causing the coating temperature to rise rapidly. The higher temperature causes PCL to melt and flow to repair cracks, thereby delaying the corrosion of the magnesium alloy and extending the protective effect of the coating.

[0029] This invention constructs a coating containing AgNR@MSN@DA nanoparticles on the surface of a magnesium alloy. MSN can control the Ag content. +The slow release of DA makes the pH-NIR responsive coating's protective effect longer-lasting; AgNR can synergistically act as a photothermal responder with PDA, increasing the coating temperature during NIR irradiation, thus achieving photothermal corrosion protection and photothermal de-icing of the coating; AgNR releases Ag + It can effectively kill bacteria and prevent biological fouling from colonizing and accumulating on the hull, opening up a new way for marine pollution prevention. Attached Figure Description

[0030] Figure 1 A schematic diagram of the preparation process of a multi-response self-healing long-lasting coating on a magnesium alloy surface.

[0031] Figure 2 SEM images of (a) AgNR and (b) AgNR@MSN prepared in Example 1.

[0032] Figure 3 SEM images of (a) magnesium alloy ZK61, (b) ZK61 / Mg(OH)2, (c) ZK61 / Mg(OH)2 / PDA and (d) ZK61 / Mg(OH)2 / PDA / PCL.

[0033] Figure 4 The polarization curves are for magnesium alloy ZK61 and various coated samples.

[0034] Figure 5 The photothermal properties of coatings (a) Mg(OH)2 / PDA / pure PCL and (b) Mg(OH)2 / PDA / PCL are compared.

[0035] Figure 6 The image shows a thermal image of the Mg(OH)2 / PDA / PCL coating.

[0036] Figure 7 The photothermal stability of the Mg(OH)2 / PDA / PCL coating.

[0037] Figure 8 Optical images of (a) Mg(OH)2 / PDA / PCL, (b) Mg(OH)2 / PDA / pure PCL and (c) pure PCL containing scratches before and after NIR irradiation.

[0038] Figure 9 The experimental phenomena of galvanic cells before (a) and after (b) irradiation of the scratched Mg(OH)2 / PDA / PCL coating with NIR. Detailed Implementation

[0039] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0040] This invention addresses the issue of coatings designed to repair damage, categorizing them into functional repair coatings and shape repair coatings. Functional repair coatings restore the coating's protective capabilities by loading corrosion inhibitors; shape repair coatings repair the coating's morphology and structure through reversible polymer reactions, chemical bond rearrangement, and shape memory effects. These long-lasting coatings with damage-repairing capabilities can promptly repair surface damage when the coating is compromised, restoring its long-term protective effect. This has significant research value and economic benefits in the protection of magnesium alloys.

[0041] The purpose of this invention is to provide a multi-responsive, self-healing, long-lasting coating for magnesium alloy surfaces, its preparation method, and its application. The method includes: performing a hydrothermal reaction on a magnesium alloy to obtain in-situ grown Mg(OH)₂; electrophoretically depositing a layer of polydopamine (PDA) on the Mg(OH)₂ surface; spin-coating a layer of polycaprolactone (PCL) containing nanoparticles onto the PDA surface; the nanoparticles are AgNR@MSN@DA nanoparticles composed of silica (MSN)-encapsulated silver nanorods (AgNR) and loaded with dopamine (DA). This invention constructs an early warning system based on Mg(OH)₂ on the magnesium alloy surface, responding to Mg… 2+ A composite coating with good inorganic-organic bonding achieves durable and stable multi-layer protection through pH and near-infrared light (NIR). This coating not only provides long-lasting corrosion protection but also has de-icing and marine antifouling functions.

[0042] To achieve the above objectives, the first aspect of this invention provides a method for preparing a multi-response self-healing long-lasting coating on a magnesium alloy surface, comprising the following steps:

[0043] A hydrothermal reaction was carried out on the surface of a magnesium alloy to obtain in-situ grown Mg(OH)2;

[0044] Polydopamine was electrophoretically deposited on in-situ grown Mg(OH)2.

[0045] Prepare silica-coated silver nanorods loaded with dopamine nanoparticles; uniformly disperse the nanoparticles in a polycaprolactone solution to obtain a polycaprolactone solution containing nanoparticles.

[0046] A polycaprolactone solution containing nanoparticles is coated onto polydopamine to create a multi-response, self-healing, long-lasting coating on a magnesium alloy surface.

[0047] This invention constructs a composite coating with good inorganic-organic bonding on the surface of magnesium alloy. The in-situ formed Mg(OH)2 is tightly bonded to the magnesium alloy matrix. Dopamine molecules, which contain abundant phenolic hydroxyl and amine groups, self-polymerize in situ under the dual action of the slightly alkaline environment and electric field on the Mg(OH)2 surface, forming a PDA coating with high adhesion. PDA forms strong hydrogen bonds with Mg(OH)2 and the outer PCL layer, thereby forming a three-layer tightly connected composite coating, which effectively isolates the magnesium alloy from direct contact with the environment and improves the corrosion resistance of the magnesium alloy.

[0048] This invention constructs a coating containing AgNR@MSN@DA nanoparticles on the surface of a magnesium alloy. MSN can control the Ag content. + The slow release of DA makes the pH-NIR responsive coating's protective effect longer-lasting; AgNR can synergistically act as a photothermal responder with PDA, increasing the coating temperature during NIR irradiation, thus achieving photothermal corrosion protection and photothermal de-icing of the coating; AgNR releases Ag + It can effectively kill bacteria and prevent biological fouling from colonizing and accumulating on the hull, opening up a new way for marine pollution prevention.

[0049] In the hydrothermal reaction on the magnesium alloy surface, the hydrothermal solution concentration is 0.001~0.1 g / mL NaOH solution, the temperature is 80~160 ℃, and the reaction time is 1~12 h.

[0050] When electrophoretically depositing polydopamine on in-situ grown Mg(OH)2, the electrophoretic solution is a DA solution of 1~10 mg / mL, and the solvent of the DA solution is deionized water.

[0051] During electrophoretic deposition, the distance between the anode and cathode is 8–15 mm, and the applied current is 2–6 mA / cm². 2 The electrophoretic deposition time is 1~10 min; among them, a magnesium alloy containing in-situ grown Mg(OH)2 is used as the cathode.

[0052] In the polycaprolactone solution containing nanoparticles, the polycaprolactone concentration is 1~20 wt%; the nanoparticle concentration is 1~30 mg / mL.

[0053] Polycaprolactone solution is prepared by dissolving polycaprolactone in one or more of dichloromethane, chloroform, and acetone.

[0054] When coating polycaprolactone solution containing nanoparticles onto polydopamine, a spin coating method is used. During spin coating, the coating is carried out at both the low-speed stage (200-800 rpm) and the high-speed stage (1000-3000 rpm) for 10-90 seconds.

[0055] The silica-encapsulated silver nanorods and dopamine-loaded nanoparticles include nanoparticles formed with silica as the shell, silver nanorods as the core, and dopamine as the pore loading material; wherein the silver nanorods have a length of 100~120 nm and an aspect ratio of 4.16±0.13.

[0056] The thickness of the silica shell is 10~80 nm;

[0057] The dopamine loading rate is 5-95% by mass.

[0058] Before the magnesium alloy surface undergoes a hydrothermal reaction, a pretreatment of the magnesium alloy surface is also included, which includes: polishing the magnesium alloy surface with sandpaper, and then ultrasonically treating the magnesium alloy with acetone and anhydrous ethanol for 5-15 minutes respectively.

[0059] The magnesium alloys include AZ series, ZK series, WE series or JDBM magnesium alloys.

[0060] In one embodiment, a method for preparing a multi-response self-healing long-lasting coating on a magnesium alloy surface includes the following steps:

[0061] Step 1: Pre-treat the magnesium alloy by sanding the surface with sandpaper, and then ultrasonically treat the magnesium alloy with acetone and anhydrous ethanol respectively.

[0062] Step 2: The magnesium alloy is subjected to a hydrothermal reaction to obtain in-situ grown Mg(OH)2. A NaOH solution is prepared, and the treated magnesium alloy is placed in a reaction vessel containing the NaOH solution. The reaction vessel is then placed in an oven for reaction. After the reaction is complete, the sample is removed, rinsed with deionized water, and air-dried.

[0063] Step 3: Electrophoretically deposit a layer of PDA on the Mg(OH)2 surface. Prepare the DA solution and stir it evenly to obtain the electrophoretic solution; deposit the coating on the magnesium alloy surface containing the Mg(OH)2 coating using a constant current mode, and then remove the sample and let it air dry in a cool place.

[0064] Step 4: Synthesize silica-encapsulated silver nanorods (AgNR@MSN) nanoparticles. This includes the following steps:

[0065] ① Preparation of AgNR using the gold seed method;

[0066] ② Preparation of core-shell structured nanoparticles AgNR@MSN by sol-gel method;

[0067] For example, the specific preparation method for AgNR by the gold seed method is as follows:

[0068] 1.1) At room temperature, CTAC (50 mM, 8.95 mL), citric acid (5 mM, 1 mL), and HAuCl4 (50 mM, 0.05 mL) were added to the solution in sequence. Then, HAuCl4 was rapidly reduced with sodium borohydride (25 mM, 0.25 mL). After 2 min, the bottle was capped and the seed solution was heated at 80 °C for 90 min to obtain the gold seed solution.

[0069] 1.2) Under vigorous stirring, the gold seed solution (1 mL) was added to a growth aqueous solution containing CTAB (20 mL, 100 mM), HAuCl4 (0.2 mL, 50 mM), AgNO3 (0.2 mL, 10 mM), HCl (0.4 mL, 1 M), and ascorbic acid (AA) (0.16 mL, 100 mM). The mixture was allowed to stand at 30 °C for 4 h to obtain gold bipyramids. After reacting for 4 h, the solution was centrifuged (10000 rpm, 30 min) to remove excess reagents and redispersed in CTAC (10 mM, 1 mL).

[0070] 1.3) Under vigorous stirring, a solution of AgNO3 (10 mM) and AA (100 mM) was added to a solution of gold bipyramidal powder (10 mL) containing CTAC (10 mM) at room temperature. Throughout the addition process, the molar ratio of [AA]:[AgNO3] was maintained. + The concentration of 4 was kept constant. After the addition was complete, the mixture was stirred vigorously at 60 °C for 2 h. Finally, the resulting solution was centrifuged (10000 rpm, 30 min) and redispersed in water to obtain AgNR.

[0071] An exemplary method for preparing core-shell structured nanoparticles AgNR@MSN using the sol-gel method is as follows:

[0072] 2.1) Add CHCl3 solution to the prepared AgNR solution to prepare a mixed solution with a concentration of 5 mg / mL. Add CTAB solution (5 mM, 2 mL) to the solution under vigorous stirring and mix thoroughly. Then, heat the mixture at 65°C for 20 min to remove CHCl3, and add it to 86 mL of an aqueous solution containing CTAB (1.5 mM) and NaOH (16 mM, 0.7 mL) at room temperature, and mix thoroughly.

[0073] 2.2) The above solution was transferred to 80 °C, and 1 mL of TEOS was slowly added dropwise under vigorous stirring and reacted for 2 h. After the reaction was completed, the product was centrifuged (10000 rpm, 10 min) to remove excess reagents and collected. The sample was added to an ethanol solution (6 g / L) containing NH4NO3 and extracted for 24 h to remove the remaining template agent in the product. After extraction, the product was washed 6 times alternately with deionized water and anhydrous ethanol, and then the product was collected and dried to obtain AgNR@MSN mesoporous nanoparticles with a core-shell structure.

[0074] Step 5: Loading DA onto core-shell mesoporous AgNR@MSN nanoparticles. A DA solution of a certain concentration was prepared, and 10 mg of core-shell structured AgNR@MSN nanoparticles were incorporated into the DA solution. After gently stirring the solution for 24 h, the DA-loaded solution was centrifuged (10000 rpm, 10 min) to remove the supernatant. The product was collected and dried to obtain silica-coated silver nanorods loaded with dopamine nanoparticles (AgNR@MSN@DA).

[0075] Step 6: Spin-coat a layer of PCL containing AgNR@MSN@DA nanoparticles onto the PDA surface. Prepare a PCL solution using acetone as the solvent; add AgNR@MSN@DA nanoparticles with a core-shell mesoporous structure to the PCL solution, and sonicate to disperse the nanoparticles evenly in the solution; drop the PCL solution containing nanoparticles onto the sample surface, and then hold it for a certain time at both the low-speed and high-speed stages. After spin-coating, remove the sample and allow it to air dry naturally.

[0076] A second aspect of the present invention provides a self-healing, long-lasting coating with multiple responses on the surface of magnesium alloys.

[0077] A third aspect of the present invention provides an application of a coating in the modification of metal surfaces.

[0078] It should be noted that, unless otherwise specified, the experimental methods used in this invention are all conventional methods; and the reagents and materials used, unless otherwise specified, are all commercially available.

[0079] Example 1

[0080] For the preparation method of the multi-response long-lasting coating on the surface of magnesium alloy ZK61, please refer to [link to documentation]. Figure 1 As shown, it includes the following steps:

[0081] Step 1: Pre-treat the ZK61 magnesium alloy. Polish the surface of the magnesium alloy with 600#, 1000#, 1500# and 2000# sandpaper respectively, and then use acetone and anhydrous ethanol to ultrasonically treat the magnesium alloy for 10 min each.

[0082] Step 2: Magnesium alloy ZK61 is subjected to a hydrothermal reaction to obtain in-situ grown Mg(OH)2. First, a NaOH solution with a concentration of 0.1 g / mL is prepared; the treated ZK61 is placed in a reaction vessel containing 50 mL of NaOH solution; the reaction vessel is placed in an oven at 80 ℃ for 3 h; after the reaction is completed, the ZK61 is removed, rinsed with deionized water and air-dried naturally.

[0083] Step 3: Electrophoretically deposit a PDA layer on the Mg(OH)₂ surface. Prepare a 2 mg / mL DA solution and stir for 10 min; deposit the coating on the ZK61 surface containing the Mg(OH)₂ coating using a constant current mode. The distance between the 316L stainless steel anode and the ZK61 cathode is 10 mm, the deposition time is 3 min, and the deposition current is 4 mA / cm². 2 Then, take out ZK61 and let it air dry in a cool place.

[0084] Step 4: Prepare core-shell structured mesoporous nanoparticles AgNR@MSN.

[0085] Step 5: Loading DA onto core-shell mesoporous AgNR@MSN nanoparticles, including: preparing a DA solution with a concentration of 10 mg / mL, incorporating 10 mg of core-shell structured nanoparticles AgNR@MSN into the DA solution, gently stirring the solution for 24 h; centrifuging the solution (10000 rpm, 10 min) and drying to collect the product.

[0086] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 10 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 10 mg / mL, and sonicate for 5 min to disperse the solution evenly; thus obtaining a PCL solution containing nanoparticles.

[0087] 500 µL of PCL solution containing nanoparticles was dropped onto the sample surface. The sample was then spin-coated at 500 rpm for 10 s at a low speed and at 2000 rpm for 10 s at a high speed. After spin-coating, the sample was removed and allowed to air dry.

[0088] Example 1 investigates the effects of hydrothermal solvent concentration, hydrothermal temperature, and hydrothermal time on the corrosion resistance of a multi-response self-healing long-lasting coating on the surface of magnesium alloy ZK61 using a single variable method.

[0089] Example 1-1

[0090] Same as Example 1, except that,

[0091] Step 2: Magnesium alloy ZK61 was subjected to a hydrothermal reaction to obtain in-situ grown Mg(OH)2. First, a NaOH solution with a concentration of 0.05 g / mL was prepared; the treated ZK61 was placed in a reaction vessel containing 50 mL of NaOH solution; the reaction vessel was placed in an oven at 120 ℃ for 7 h; after the reaction was completed, the ZK61 was removed, rinsed with deionized water, and air-dried.

[0092] Examples 1-2

[0093] Same as Example 1, except that,

[0094] Step 2: Magnesium alloy ZK61 was subjected to a hydrothermal reaction to obtain in-situ grown Mg(OH)2. First, a NaOH solution with a concentration of 0.001 g / mL was prepared; the treated ZK61 was placed in a reaction vessel containing 50 mL of NaOH solution; the reaction vessel was placed in an oven at 160 ℃ for 12 h; after the reaction was completed, the ZK61 was removed, rinsed with deionized water, and air-dried.

[0095] Example 2

[0096] A method for preparing a multi-response long-lasting coating on the surface of magnesium alloy ZK61 includes the following steps:

[0097] Step 1: Pre-treat the ZK61 magnesium alloy. Polish the surface of the magnesium alloy with 600#, 1000#, 1500# and 2000# sandpaper respectively, and then ultrasonically treat the magnesium alloy with acetone and anhydrous ethanol for 10 min each.

[0098] Step 2: Magnesium alloy ZK61 was subjected to a hydrothermal reaction to obtain in-situ grown Mg(OH)2. First, a NaOH solution with a concentration of 0.1 g / mL was prepared; the treated ZK61 was placed in a reaction vessel containing 50 mL of NaOH solution; the reaction vessel was placed in an oven at 120 ℃ for 3 h; after the reaction was completed, the ZK61 was removed, rinsed with deionized water, and air-dried naturally.

[0099] Step 3: Electrophoretically deposit a PDA layer on the Mg(OH)₂ surface. Prepare a 2 mg / mL DA solution and stir for 10 min; deposit the coating on the ZK61 surface containing the Mg(OH)₂ coating using a constant current mode. The distance between the 316L stainless steel anode and the ZK61 cathode is 10 mm, the deposition time is 1 min, and the deposition current is 2 mA / cm². 2 Then, the sample was removed and placed in a cool place to air dry naturally.

[0100] Step 4: Prepare core-shell structured mesoporous nanoparticles AgNR@MSN.

[0101] Step 5: Loading DA onto core-shell mesoporous AgNR@MSN nanoparticles, including: preparing a DA solution with a concentration of 10 mg / mL, incorporating 10 mg of core-shell structured nanoparticles AgNR@MSN into the DA solution, gently stirring the solution for 24 h; centrifuging the solution (10000 rpm, 10 min) and drying to collect the product.

[0102] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 10 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 10 mg / mL, and sonicate for 5 min to disperse the solution evenly; thus obtaining a PCL solution containing nanoparticles.

[0103] 500 µL of PCL solution containing nanoparticles was dropped onto the sample surface. The sample was then spin-coated at 500 rpm for 10 s at a low speed and at 2000 rpm for 10 s at a high speed. After spin-coating, the sample was removed and allowed to air dry.

[0104] Example 2 investigates the effects of electrophoretic solution concentration, electrophoretic deposition time, and electrophoretic deposition current on the corrosion resistance of a multi-response self-healing long-lasting coating on the surface of magnesium alloy ZK61 using a single variable method.

[0105] Example 2-1

[0106] Same as Example 2, except that,

[0107] Step 3: Electrophoretically deposit a PDA layer on the Mg(OH)₂ surface. Prepare a 5 mg / mL DA solution and stir for 10 min; deposit the coating on the ZK61 surface containing the Mg(OH)₂ coating using a constant current mode. The distance between the 316L stainless steel anode and the ZK61 cathode is 10 mm, the deposition time is 3 min, and the deposition current is 4 mA / cm². 2 Then, the sample was removed and placed in a cool place to air dry naturally.

[0108] Example 2-2

[0109] Same as Example 2, except that,

[0110] Step 3: Electrophoretically deposit a PDA layer on the Mg(OH)₂ surface. Prepare a 10 mg / mL DA solution and stir for 10 min; deposit the coating on the ZK61 surface containing the Mg(OH)₂ coating using a constant current mode. The distance between the 316L stainless steel anode and the ZK61 cathode is 10 mm, the deposition time is 5 min, and the deposition current is 6 mA / cm². 2 Then, the sample was removed and placed in a cool place to air dry naturally.

[0111] Example 3

[0112] A method for preparing a multi-response long-lasting coating on the surface of magnesium alloy ZK61 includes the following steps:

[0113] Step 1: Pre-treat the ZK61 magnesium alloy. Polish the surface of the magnesium alloy with 600#, 1000#, 1500# and 2000# sandpaper respectively, and then ultrasonically treat the magnesium alloy with acetone and anhydrous ethanol for 10 min each.

[0114] Step 2: Magnesium alloy ZK61 was subjected to a hydrothermal reaction to obtain in-situ grown Mg(OH)2. First, a NaOH solution with a concentration of 0.1 g / mL was prepared; the treated ZK61 was placed in a reaction vessel containing 50 mL of NaOH solution; the reaction vessel was placed in an oven at 120 ℃ for 3 h; after the reaction was completed, the ZK61 was removed, rinsed with deionized water, and air-dried naturally.

[0115] Step 3: Electrophoretically deposit a PDA layer on the Mg(OH)₂ surface. Prepare a 2 mg / mL DA solution and stir for 10 min; deposit the coating on the ZK61 surface containing the Mg(OH)₂ coating using a constant current mode. The distance between the 316L stainless steel anode and the ZK61 cathode is 10 mm, the deposition time is 3 min, and the deposition current is 4 mA / cm². 2 Then, the sample was removed and placed in a cool place to air dry naturally.

[0116] Step 4: Prepare core-shell structured mesoporous nanoparticles AgNR@MSN.

[0117] Step 5: Load DA onto core-shell mesoporous AgNR@MSN nanoparticles. Prepare a DA solution with a concentration of 10 mg / mL. Add 10 mg of core-shell nanoparticles AgNR@MSN to the DA solution and stir gently for 24 h. Centrifuge the solution (10000 rpm, 10 min) and dry to collect the product.

[0118] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 5 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 10 mg / mL, and sonicate for 5 min to disperse the solution evenly; thus obtaining a PCL solution containing nanoparticles.

[0119] 500 µL of PCL solution containing nanoparticles was dropped onto the sample surface. The sample was then spin-coated at 500 rpm for 10 s at a low speed and at 2000 rpm for 10 s at a high speed. After spin-coating, the sample was removed and allowed to air dry.

[0120] Example 3 investigates the effect of PCL solution concentration on the corrosion resistance of a multi-response self-healing long-lasting coating on the surface of magnesium alloy ZK61 using a single variable method.

[0121] Example 3-1

[0122] Same as Example 3, except that,

[0123] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 10 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 10 mg / mL, and sonicate for 5 min to ensure uniform dispersion; thus obtaining a PCL solution containing nanoparticles.

[0124] Example 3-2

[0125] Same as Example 3, except that,

[0126] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 20 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 10 mg / mL, and sonicate for 5 min to ensure uniform dispersion; thus obtaining a PCL solution containing nanoparticles.

[0127] Example 4

[0128] A method for preparing a multi-response long-lasting coating on the surface of magnesium alloy ZK61 includes the following steps:

[0129] Step 1: Pre-treat the ZK61 magnesium alloy. Polish the surface of the magnesium alloy with 600#, 1000#, 1500# and 2000# sandpaper respectively, and then ultrasonically treat the magnesium alloy with acetone and anhydrous ethanol for 10 min each.

[0130] Step 2: Magnesium alloy ZK61 was subjected to a hydrothermal reaction to obtain in-situ grown Mg(OH)2. First, a NaOH solution with a concentration of 0.1 g / mL was prepared; the treated ZK61 was placed in a reaction vessel containing 50 mL of NaOH solution; the reaction vessel was placed in an oven at 120 ℃ for 3 h; after the reaction was completed, the ZK61 was removed, rinsed with deionized water, and air-dried naturally.

[0131] Step 3: Electrophoretically deposit a PDA layer on the Mg(OH)₂ surface. Prepare a 2 mg / mL DA solution and stir for 10 min; deposit the coating on the ZK61 surface containing the Mg(OH)₂ coating using a constant current mode. The distance between the 316L stainless steel anode and the ZK61 cathode is 10 mm, the deposition time is 3 min, and the deposition current is 4 mA / cm². 2 Then, the sample was removed and placed in a cool place to air dry naturally.

[0132] Step 4: Prepare core-shell structured mesoporous nanoparticles AgNR@MSN.

[0133] Step 5: Load DA onto core-shell mesoporous AgNR@MSN nanoparticles. Prepare a DA solution with a concentration of 10 mg / mL. Add 10 mg of core-shell nanoparticles AgNR@MSN to the DA solution and stir gently for 24 h. Centrifuge the solution (10000 rpm, 10 min) and dry to collect the product.

[0134] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 10 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 10 mg / mL, and sonicate for 5 min to ensure uniform dispersion; drop 500 µL of the PCL solution containing nanoparticles onto the sample surface, and then spin-coat at 800 rpm for 10 s at both the low-speed stage and the high-speed stage at 3000 rpm. After spin-coating, remove the sample and allow it to air dry naturally.

[0135] Example 4 investigates the effects of spin coating speed and spin coating time on the uniformity of a multi-response self-healing long-lasting coating on the surface of magnesium alloy ZK61 using a single variable method.

[0136] Example 4-1

[0137] Same as Example 4, except that,

[0138] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 10 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 10 mg / mL, and sonicate for 5 min to ensure uniform dispersion; drop 500 µL of the PCL solution containing nanoparticles onto the sample surface, and then hold the spin-coating at 200 rpm for 30 s at a low speed and 1000 rpm for 30 s respectively. After spin-coating, remove the sample and allow it to air dry.

[0139] Example 4-2

[0140] Same as Example 4, except that,

[0141] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 10 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 10 mg / mL, and sonicate for 5 min to ensure uniform dispersion; drop 500 µL of the PCL solution containing nanoparticles onto the sample surface, and then spin-coat at 500 rpm for 60 s at a low speed and 2000 rpm for 60 s respectively. After spin-coating, remove the sample and allow it to air dry.

[0142] Example 4-3

[0143] Same as Example 4, except that,

[0144] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 10 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 10 mg / mL, and sonicate for 5 min to ensure uniform dispersion; drop 500 µL of the PCL solution containing nanoparticles onto the sample surface, and then spin-coat at 800 rpm for 90 s at both the low-speed stage and the high-speed stage at 3000 rpm. After spin-coating, remove the sample and allow it to air dry.

[0145] Example 5

[0146] A method for preparing a multi-response long-lasting coating on the surface of magnesium alloy ZK61 includes the following steps:

[0147] Step 1: Pre-treat the ZK61 magnesium alloy. Polish the surface of the magnesium alloy with 600#, 1000#, 1500# and 2000# sandpaper respectively, and then ultrasonically treat the magnesium alloy with acetone and anhydrous ethanol for 10 min each.

[0148] Step 2: Magnesium alloy ZK61 was subjected to a hydrothermal reaction to obtain in-situ grown Mg(OH)2. First, a NaOH solution with a concentration of 0.1 g / mL was prepared; the treated ZK61 was placed in a reaction vessel containing 50 mL of NaOH solution; the reaction vessel was placed in an oven at 120 ℃ for 3 h; after the reaction was completed, the ZK61 was removed, rinsed with deionized water, and air-dried naturally.

[0149] Step 3: Electrophoretically deposit a PDA layer on the Mg(OH)₂ surface. Prepare a 2 mg / mL DA solution and stir for 10 min; deposit the coating on the ZK61 surface containing the Mg(OH)₂ coating using a constant current mode. The distance between the 316L stainless steel anode and the ZK61 cathode is 10 mm, the deposition time is 3 min, and the deposition current is 4 mA / cm². 2 Then, the sample was removed and placed in a cool place to air dry naturally.

[0150] Step 4: Prepare core-shell structured mesoporous nanoparticles AgNR@MSN.

[0151] Step 5: Load DA onto core-shell mesoporous AgNR@MSN nanoparticles, prepare a DA solution with a concentration of 2 mg / mL, incorporate 10 mg of core-shell nanoparticles AgNR@MSN into the DA solution, and gently stir the solution for 6 h; centrifuge the solution (10000 rpm, 10 min) and dry to collect the product.

[0152] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 10 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 10 mg / mL, and sonicate for 5 min to ensure uniform dispersion; drop 500 µL of the PCL solution containing nanoparticles onto the sample surface, and then spin-coat at 500 rpm for 10 s at both the low-speed stage and the high-speed stage at 2000 rpm. After spin-coating, remove the sample and allow it to air dry.

[0153] Example 5 investigates the effect of the amount of DA loaded on the AgNR@MSN nanoparticles on the corrosion resistance of a multi-response self-healing long-lasting coating on the surface of magnesium alloy ZK61 using a single variable method.

[0154] Example 5-1

[0155] Same as Example 5, except that,

[0156] Step 5: Load DA onto core-shell mesoporous AgNR@MSN nanoparticles. Prepare a DA solution with a concentration of 10 mg / mL. Add 10 mg of core-shell nanoparticles AgNR@MSN to the DA solution and stir gently for 12 h. Centrifuge the solution (10000 rpm, 10 min) and dry to collect the product.

[0157] Example 5-2

[0158] Same as Example 5, except that,

[0159] Step 5: Load DA onto core-shell mesoporous AgNR@MSN nanoparticles. Prepare a DA solution with a concentration of 20 mg / mL. Add 10 mg of core-shell nanoparticles AgNR@MSN to the DA solution and stir gently for 24 h. Centrifuge the solution (10000 rpm, 10 min) and dry to collect the product.

[0160] Example 6

[0161] A method for preparing a multi-response long-lasting coating on the surface of magnesium alloy ZK61 includes the following steps:

[0162] Step 1: Pre-treat the ZK61 magnesium alloy. Polish the surface of the magnesium alloy with 600#, 1000#, 1500# and 2000# sandpaper respectively, and then ultrasonically treat the magnesium alloy with acetone and anhydrous ethanol for 10 min each.

[0163] Step 2: Magnesium alloy ZK61 was subjected to a hydrothermal reaction to obtain in-situ grown Mg(OH)2. First, a NaOH solution with a concentration of 0.1 g / mL was prepared; the treated ZK61 was placed in a reaction vessel containing 50 mL of NaOH solution; the reaction vessel was placed in an oven at 120 ℃ for 3 h; after the reaction was completed, the ZK61 was removed, rinsed with deionized water, and air-dried naturally.

[0164] Step 3: Electrophoretically deposit a PDA layer on the Mg(OH)₂ surface. Prepare a 2 mg / mL DA solution and stir for 10 min; deposit the coating on the ZK61 surface containing the Mg(OH)₂ coating using a constant current mode. The distance between the 316L stainless steel anode and the ZK61 cathode is 10 mm, the deposition time is 3 min, and the deposition current is 4 mA / cm². 2 Then, the sample was removed and placed in a cool place to air dry naturally.

[0165] Step 4: Prepare core-shell structured mesoporous nanoparticles AgNR@MSN.

[0166] Step 5: Load DA onto core-shell mesoporous AgNR@MSN nanoparticles. Prepare a DA solution with a concentration of 10 mg / mL. Add 10 mg of core-shell nanoparticles AgNR@MSN to the DA solution and stir gently for 24 h. Centrifuge the solution (10000 rpm, 10 min) and dry to collect the product.

[0167] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 10 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 0 mg / mL, and sonicate for 5 min to ensure uniform dispersion; drop 500 µL of the PCL solution containing nanoparticles onto the sample surface, and then hold the solution at 500 rpm for 10 s at both the low-speed stage and the high-speed stage at 2000 rpm. After spin-coating, remove the sample and allow it to air dry naturally to obtain the multi-response long-lasting coating (Mg(OH)2 / PDA / pure PCL) on the surface of magnesium alloy ZK61.

[0168] Example 6 investigates the effect of the concentration of core-shell structured nanoparticles AgNR@MSN@DA added to the PCL coating on the corrosion resistance of a multi-response self-healing long-lasting coating on the surface of magnesium alloy ZK61 using a single variable method.

[0169] Example 6-1

[0170] Same as Example 6, except that,

[0171] The concentration of nanoparticles was 5 mg / mL.

[0172] Example 6-2

[0173] Same as Example 6, except that,

[0174] The concentration of nanoparticles was 10 mg / mL.

[0175] Example 6-3

[0176] Same as Example 6, except that,

[0177] The concentration of nanoparticles was 20 mg / mL.

[0178] Example 7

[0179] A method for preparing a multi-response long-lasting coating on the surface of magnesium alloy ZK61 includes the following steps:

[0180] Step 1: Pre-treat the ZK61 magnesium alloy. Polish the surface of the magnesium alloy with 600#, 1000#, 1500# and 2000# sandpaper respectively, and then ultrasonically treat the magnesium alloy with acetone and anhydrous ethanol for 10 min each.

[0181] Step 2: Magnesium alloy ZK61 was subjected to a hydrothermal reaction to obtain in-situ grown Mg(OH)2 (ZK61 / Mg(OH)2). First, a NaOH solution with a concentration of 0.1 g / mL was prepared; the treated ZK61 was placed in a reaction vessel containing 50 mL of NaOH solution; the reaction vessel was placed in an oven at 120 ℃ for 3 h; after the reaction was completed, the ZK61 was removed, rinsed with deionized water, and air-dried naturally.

[0182] Step 3: Electrophoretically deposit a PDA layer (ZK61 / Mg(OH)2 / PDA) on the Mg(OH)2 surface. Prepare a 2 mg / mL DA solution and stir for 10 min; deposit the coating on the ZK61 surface containing the Mg(OH)2 coating using a constant current mode. The distance between the 316L stainless steel anode and the ZK61 cathode is 10 mm, the deposition time is 3 min, and the deposition current is 4 mA / cm². 2 Then, the sample was removed and placed in a cool place to air dry naturally.

[0183] Step 4: Prepare core-shell structured mesoporous nanoparticles Ag@MSN.

[0184] Step 5: Load DA onto core-shell mesoporous AgNR@MSN nanoparticles. Prepare a DA solution with a concentration of 10 mg / mL. Add 10 mg of core-shell nanoparticles AgNR@MSN to the DA solution and stir gently for 24 h. Centrifuge the solution (10000 rpm, 10 min) and dry to collect the product.

[0185] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 10 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 10 mg / mL, and sonicate for 5 min to ensure uniform dispersion; drop 500 µL of the PCL solution containing nanoparticles onto the sample surface, and then hold the spin-coating at 500 rpm (low speed) and 2000 rpm (high speed) for 10 s respectively. After spin-coating, remove the sample and allow it to air dry naturally to obtain a multi-response long-lasting coating (Mg(OH)2 / PDA / PCL) on the surface of magnesium alloy ZK61.

[0186] Example 7 provides a ZK61 magnesium alloy (ZK61 / Mg(OH)2 / PDA / PCL) with a multi-response self-healing long-lasting coating protection obtained by the above preparation method.

[0187] Example 8

[0188] A method for preparing a multi-response long-lasting coating on the surface of magnesium alloy AZ31 includes the following steps:

[0189] Step 1: Pre-treat the magnesium alloy AZ31. Use 600#, 1000#, 1500#, and 2000# sandpaper to polish the surface of the magnesium alloy, and then use acetone and anhydrous ethanol to ultrasonically treat the magnesium alloy for 10 minutes each.

[0190] Step 2: Magnesium alloy AZ31 was subjected to a hydrothermal reaction to obtain in-situ grown Mg(OH)2. First, a NaOH solution with a concentration of 0.1 g / mL was prepared; the treated AZ31 was placed in a reactor containing 50 mL of NaOH solution; the reactor was placed in an oven at 120 ℃ for 3 h; after the reaction was completed, the AZ31 was removed, rinsed with deionized water, and air-dried naturally.

[0191] Step 3: Electrophoretically deposit a layer of PDA on the Mg(OH)₂ surface. Prepare a 2 mg / mL DA solution and stir for 10 min; deposit the coating on the AZ31 surface containing the Mg(OH)₂ coating using a constant current mode. The distance between the 316L stainless steel anode and the AZ31 cathode is 10 mm, the deposition time is 3 min, and the deposition current is 4 mA / cm². 2 Then, take AZ31 out and let it air dry in a cool place.

[0192] Step 4: Prepare core-shell structured mesoporous nanoparticles Ag@MSN.

[0193] Step 5: Loading DA onto core-shell mesoporous AgNR@MSN nanoparticles, including: preparing a DA solution with a concentration of 10 mg / mL, incorporating 10 mg of core-shell structured nanoparticles AgNR@MSN into the DA solution, gently stirring the solution for 24 h; centrifuging the solution (10000 rpm, 10 min) and drying to collect the product.

[0194] Step 6: Spin-coat a layer of PCL containing nanoparticles onto the PDA surface. Prepare a 10 wt% PCL solution using acetone as the solvent; add core-shell structured AgNR@MSN@DA nanoparticles to the PCL solution at a concentration of 10 mg / mL, and sonicate for 5 min to ensure uniform dispersion; drop 500 µL of the PCL solution containing nanoparticles onto the sample surface, and then spin-coat at 500 rpm for 10 s at both the low-speed stage and the high-speed stage at 2000 rpm. After spin-coating, remove the sample and allow it to air dry.

[0195] Example 8 differs from Example 7 only in the type of magnesium alloy.

[0196] To illustrate the performance of the multi-response self-healing long-lasting coating on magnesium alloy surfaces provided by this invention, see [link to relevant documentation]. Figures 2-9 As shown, an explanation will be provided.

[0197] Figure 2 SEM images of (a) AgNR and (b) AgNR@MSN prepared in Example 1.

[0198] Figure 2 Image (a) shows that the length of AgNR is 100-120 nm. Figure 2 In (b), we can see that AgNR is a core-shell structured nanoparticle with an MSN shell surrounding it.

[0199] Figure 3 SEM images of (a) ZK61, (b) ZK61 / Mg(OH)2, (c) ZK61 / Mg(OH)2 / PDA and (d) ZK61 / Mg(OH)2 / PDA / PCL samples prepared in Example 7.

[0200] Figure 3 (b) shows the Mg(OH)2 coating along... Figure 3 In-situ growth of sandpaper scratches on the surface of ZK61 magnesium alloy (a) Figure 3 In (c), it can be seen that the PDA adheres tightly to the Mg(OH)2 coating, covering the scratches. Figure 3 In the middle (d) layer, the PCL containing nanoparticles completely covers the scratches, and the entire coating is smooth and uniform.

[0201] Figure 4 The figures show the potentiodynamic polarization curves of the coating samples in Example 7. The corrosion current densities of the prepared coatings Z-Mg(OH)2, ZH-PDA, and ZHP-PCL gradually decrease, and are all lower than the corrosion current density of magnesium alloy ZK61, indicating that the ZHP-PCL composite coating of this invention greatly improves the corrosion resistance of the magnesium alloy. Z-Mg(OH)2, ZH-PDA, and ZHP-PCL are abbreviations for ZK61 / Mg(OH)2, ZK61 / Mg(OH)2 / PDA, and ZK61 / Mg(OH)2 / PDA / PCL, respectively.

[0202] Figure 5 The photothermal properties of the Mg(OH)2 / PDA / PCL coating in Example 7 and the Mg(OH)2 / PDA / pure PCL coating in Example 6 are compared.

[0203] Figure 5 In the middle (a), the coatings Mg(OH)2 / PDA / pure PCL are shown at different power densities of 0.5 W / cm². 2 1.0 W / cm 2 2.0W / cm 2 The temperature change after 5 minutes of NIR irradiation showed that NIR with different power densities caused the coating temperature to rise within 5 minutes. Figure 5(b) shows the Mg(OH)₂ / PDA / PCL coating at different power densities of 0.5 W / cm². 2 1.0 W / cm 2 2.0 W / cm 2 The temperature change after 5 minutes of NIR irradiation was observed. The addition of AgNR further increased the coating temperature after NIR irradiation.

[0204] Figure 6 The thermal imaging image of the Mg(OH)2 / PDA / PCL coating in Example 7, at a power density of 1.0 W / cm². 2 Under NIR irradiation, the Mg(OH)2 / PDA / PCL coating can be heated to the melting point of PCL, 60 °C, within 2 min.

[0205] Figure 7 The photothermal stability of the Mg(OH)2 / PDA / PCL coating in Example 7 is shown. The Mg(OH)2 / PDA / PCL coating is compared at different power densities of 0.5 W / cm². 2 1.0 W / cm 2 2.0 W / cm 2 When irradiated with NIR, the coating temperature changes stably, indicating that the Mg(OH)2 / PDA / PCL coating has stable photothermal properties.

[0206] Figure 8 Optical images of the scratched Mg(OH)2 / PDA / PCL (a), Mg(OH)2 / PDA / pure PCL (b), and scratched pure PCL (c) of Examples 7 and 6 before and after NIR irradiation.

[0207] Figure 8 In Figure (a), the Mg(OH)₂ / PDA / PCL coating with scratches is at a power density of 1.0 W / cm². 2 After 10 minutes of NIR irradiation, the scratches were repaired. This was due to the photothermal effect of PDA and AgNR, which raised the coating temperature to the melting point of PCL, causing the PCL to melt and repair the cracks. Figure 8 In (b), the scratched Mg(OH)2 / PDA / pure PCL coating was repaired due to the photothermal effect of PDA. Figure 8 (c) is a scratched coated pure PCL at a power density of 1.0 W / cm². 2 The scratches were not repaired after 10 minutes of NIR irradiation. Pure PCL does not have a photothermal effect when irradiated with NIR, and the coating temperature did not reach the melting point of PCL, so the scratches could not be repaired.

[0208] It should be noted that polydopamine (PDA) is a polymer material polymerized from dopamine (DA) monomers. It has abundant functional groups, such as phenolic hydroxyl groups and amino groups. This chemical structure endows polydopamine with the property of absorbing near-infrared light and converting light energy into heat energy under near-infrared light irradiation, thereby producing a photothermal effect.

[0209] Silver nanorods (AgNRs) exhibit strong surface plasmon resonance (SPR) absorption characteristics in the near-infrared region. This characteristic enables AgNRs to achieve high photothermal conversion efficiency under laser irradiation at specific near-infrared wavelengths. By adjusting the size and shape of the silver nanorods, their SPR absorption peaks can be matched with the laser wavelength to optimize the photothermal effect.

[0210] The coating provided by this invention contains electrophoretically deposited PDA and AgNR@MSN@DA dispersed in PCL. The photothermal effect of PDA and AgNR (the SPR of this AgNR matches 808 nm) causes the composite coating to rapidly heat up to the melting point of PCL (60°C) under irradiation with 808 nm near-infrared light (NIR), and the melting flow of PCL is used to repair coating cracks.

[0211] Figure 9 The galvanic cell experiment results for the scratched Mg(OH)2 / PDA / PCL coating in Example 7 before and after NIR irradiation are shown.

[0212] Figure 9 In the middle (a), a primary battery device is designed with magnesium alloy ZK61 containing scratch-coated Mg(OH)2 / PDA / PCL as the negative electrode and a copper rod as the positive electrode. As the coating is scratched, magnesium alloy ZK61 is corroded and undergoes a redox reaction, converting chemical energy into electrical energy to make the diode light up. Figure 9 (b) shows the ZK61 magnesium alloy containing a scratch-resistant coating Mg(OH)2 / PDA / PCL, processed at 1.0 W / cm². 2 After being repaired by NIR irradiation and used as the negative electrode, and with the copper rod as the positive electrode, it was found that the galvanic cell device was insufficient to make the diode light up. This was because there was not enough chemical energy to be converted into electrical energy. The damaged coating was repaired, protecting the magnesium alloy ZK61.

[0213] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a multi-responsive self-healing long- lasting coating on the surface of a magnesium alloy, characterized in that, The method comprises the following steps: performing a hydrothermal reaction on the surface of the magnesium alloy to obtain in-situ grown Mg(OH)2; electrophoretically depositing polydopamine on the in-situ grown Mg(OH)2; preparing nanoparticles of silica-coated silver nanorods and loaded with dopamine; uniformly dispersing the nanoparticles in a polycaprolactone solution to obtain a polycaprolactone solution containing the nanoparticles; coating the polycaprolactone solution containing the nanoparticles on the polydopamine to obtain a multi-responsive self-repairing long-acting coating layer on the surface of the magnesium alloy; when performing the hydrothermal reaction on the surface of the magnesium alloy, the concentration of the hydrothermal solution is 0.001-0.1 g / mL of NaOH solution, the temperature is 80-160 ℃, and the reaction time is 1-12 h; when electrophoretically depositing the polydopamine on the in-situ grown Mg(OH)2, the electrophoretic solution is 1-10 mg / mL of DA solution, and the solvent of the DA solution is deionized water; In the electrophoretic deposition, the distance between the anode and the cathode is 8-15 mm, the applied current is 2-6 mA / cm 2 , and the time of electrophoretic deposition is 1-10 min; wherein the magnesium alloy containing in-situ grown Mg(OH)2 is used as the cathode; in the polycaprolactone solution containing the nanoparticles, the concentration of the polycaprolactone is 1-20 wt%, and the concentration of the nanoparticles is 1-30 mg / mL; the polycaprolactone solution is prepared by dissolving polycaprolactone in one or more of dichloromethane, trichloromethane and acetone; when coating the polycaprolactone solution containing the nanoparticles on the polydopamine, a spin coating method is used for coating, wherein, during the spin coating, the low-speed stage is 200-800 rpm and the high-speed stage is 1000-3000 rpm, and each stage stays for 10-90 s; the nanoparticles of the silica-coated silver nanorods and loaded with dopamine comprise a silica shell, a silver nanorod core and dopamine as a channel load, and are formed; the thickness of the silica shell layer is 10-80 nm; the dopamine loading rate is 5-95% by mass percentage.

2. The method for preparing a multi-response self-healing long-lasting coating on a magnesium alloy surface according to claim 1, characterized in that, Before the hydrothermal reaction on the surface of the magnesium alloy, the method further comprises pretreating the surface of the magnesium alloy, including: using sandpaper to polish the surface of the magnesium alloy, and then using acetone and anhydrous ethanol to ultrasonically treat the magnesium alloy for 5-15 min.

3. The method for preparing a multi-response self-healing long-lasting coating on a magnesium alloy surface according to claim 1, characterized in that, The magnesium alloy comprises an AZ series, a ZK series, a WE series or a JDBM magnesium alloy. 4.A multi-responsive self-repairing long-acting coating layer on the surface of a magnesium alloy prepared by the method of any one of claims 1-3. 5.Use of the coating layer of claim 4 in the modification of a metal surface.

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