A method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy

Abstract

The present invention belongs to the technical field of magnesium alloy surface treatment, and specifically relates to a method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy. The method comprises the following steps: placing the pretreated soluble magnesium alloy in a chemical plating solution, performing chemical plating treatment, placing the soluble magnesium alloy in a TiO2-SiO2 epoxy organic film layer solution after the chemical plating treatment, and performing organic film layer uniform plating treatment at room temperature to obtain a corrosion-resistant composite film layer; wherein the TiO2-SiO2 epoxy organic film layer solution is composed of a solute and a solvent. The present invention solves the problem that a single chemical plating or organic plating has poor bonding with a soluble magnesium alloy, and has poor acid and alkali resistance and temperature resistance. By preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy, the corrosion resistance of the magnesium alloy is improved; at the same time, the chemical plating solution and the organic plating solution used have stable ingredients, are pollution-free, do not produce precipitation and other precipitates, are suitable for the surface treatment of magnesium alloy products, and are convenient and practical.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium alloy surface treatment, and in particular relates to a method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy. Background Art

[0002] With the rapid development of society and technology, the world has attached great importance to the development of basic metal materials. Among them, lightweighting has become an important focus of the development of basic metal materials. Therefore, the development of lightweight alloys represented by magnesium, titanium and aluminum has attracted great attention.

[0003] As a typical lightweight alloy, magnesium alloy has advantages such as low density, high specific strength, good thermal conductivity, and excellent electromagnetic shielding performance. It is widely used in aerospace and other fields. However, magnesium and magnesium alloys have high chemical and electrochemical activity, poor stability, and very low electrode potential. The electrode potential of magnesium is -2.34 V, and its corrosion resistance is poor. It is easily corroded in actual application environments, which greatly shortens the service life of magnesium alloys and limits their application. Among them, Mg-Zn-Cu magnesium alloy is a typical soluble magnesium alloy with a fast dissolution rate and very easy to corrode. It has high requirements for the coating process and corrosion resistance of the film layer.

[0004] Currently, the primary method for improving the corrosion resistance of magnesium alloys is surface treatment, which can significantly enhance their corrosion resistance. Current surface treatment methods for magnesium alloys include electroless plating, electroplating, chemical conversion, anodizing, and organic coating. Electroless plating offers advantages such as wide substrate compatibility, uniform coating thickness, excellent coating performance, environmental friendliness, and high efficiency and convenience. Organic coating, with its significant advantages of simple preparation, high production efficiency, and excellent corrosion resistance, has gradually become one of the primary surface treatment methods for magnesium alloys in engineering applications. Electroless plating, also known as electroless plating, involves the reduction of metal ions on the surface of a base metal in the presence of a reducing agent in a solution, resulting in metal deposition. Organic coatings are formed using organic materials. Epoxy organic coatings are organic coatings primarily based on epoxy resins. They offer advantages such as flexibility, strong corrosion resistance, and low cost. However, single electroless or organic plating methods exhibit poor adhesion to Mg-Zn-Cu soluble magnesium alloys and exhibit poor acid, alkali, and temperature resistance. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems in the prior art of poor bonding between single chemical plating or organic plating and Mg-Zn-Cu soluble magnesium alloys, and poor acid and alkali resistance and temperature resistance, and provide a method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy. By using chemical plating and TiO2-SiO2 epoxy organic film layer treatment on the surface of the Mg-Zn-Cu soluble magnesium alloy, a corrosion-resistant composite film layer is prepared, thereby improving the corrosion resistance of the magnesium alloy, having good bonding with the substrate, and having good high-temperature resistance. At the same time, the chemical plating solution and organic plating solution used have stable formula components, are pollution-free, do not produce precipitation and other precipitates, are suitable for surface treatment of magnesium alloy products, and are convenient and practical.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] The present invention provides a method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy, comprising the following steps:

[0008] The soluble magnesium alloy samples were pretreated.

[0009] The pretreated soluble magnesium alloy is placed in a chemical plating solution and subjected to chemical plating treatment to reduce metal ions in the plating solution into metal deposits, thereby obtaining a Ni-P alloy film layer on the surface of the soluble magnesium alloy sample; wherein the chemical plating solution is made of a Ni-P chemical plating solution system.

[0010] After the chemical plating treatment, the soluble magnesium alloy is placed in a TiO2-SiO2 epoxy organic film layer solution, and the organic film layer is plated at room temperature to obtain a TiO2-SiO2 epoxy organic film layer on the surface of the soluble magnesium alloy sample, thereby obtaining a corrosion-resistant composite film layer on the surface of the soluble magnesium alloy; wherein the TiO2-SiO2 epoxy organic film layer solution is composed of a solute and a solvent, the solute includes epoxy resin, nano-TiO2 particles, SiO2 particles, oleic acid and polyamide resin, and the mass ratio of epoxy resin, nano-TiO2 particles, SiO2 particles, oleic acid and polyamide resin is 1~100:0.1~10:0.1~10:0.1~10:1~100.

[0011] In the present invention, as a preferred embodiment of the present invention, the mass ratio of epoxy resin, nano-TiO2 particles, SiO2 particles, oleic acid and polyamide resin can be any ratio between 1~100:0.1~10:0.1~10:0.1~10:1~100. It should be noted that the present invention does not specifically limit the particle size of TiO2 particles, as long as it is nanometer level, there is no particle size requirement for SiO2 particles, the epoxy resin is E44 type epoxy resin, and the polyamide resin is 650 type polyamide resin. Nano-TiO2 particles, SiO2 particles and oleic acid are added to the epoxy organic film layer to prepare a TiO2-SiO2 composite organic film layer. The nano-TiO2 particles improve the thermal stability and impact resistance of the organic film layer due to their stable chemical properties and excellent thermal stability; the SiO2 particles are white amorphous flocs with significant anti-aging and chemical resistance, which improves the corrosion resistance of the organic film layer; oleic acid is an unsaturated fatty acid and one of the most common fatty acids in nature. It can improve the plating ability of the organic film solution and make the thickness of the organic film layer uniform.

[0012] The present invention adopts a chemical plating method to generate a uniform chemical plating layer on the surface of a soluble magnesium alloy sample. On the basis of the chemical plating layer, a composite organic plating layer is formed to effectively solve the problems of weak bonding strength, poor temperature resistance and poor acid and alkali resistance of the epoxy organic film layer. The chemical plating adopts Ni-P chemical plating, and the surface of the obtained chemical plating film layer is uniform and well bonded; however, the chemical plating film layer has reduced bonding ability in a solution environment and at higher temperatures, is easily fallen off, and has poor corrosion resistance; the epoxy organic film layer has good corrosion resistance in a solution environment, but has poor bonding with the magnesium alloy sample, so the respective advantages of the two are combined to adopt the first step of chemical plating and the second step of TiO2-SiO2 composite organic film layer to obtain a composite film layer with strong corrosion resistance and good heat resistance, thereby improving the corrosion resistance of the magnesium alloy, having good bonding with the substrate, and having good high temperature resistance.

[0013] In a preferred embodiment, the chemical plating solution comprises the following components: 5 g / L~30 g / L NiSO4·6H2O, 5 g / L~30 g / L Na3C6H5O7·2H2O, 5 g / L~30 g / L Na2CO3, 5 g / L~20 g / L NH3HF2, 5 g / L~30 g / L NaH2PO2 and 20 mL~100 mL NH3·H2O, and the solvent of the chemical plating solution is water. In the present invention, the chemical plating solution contains metal ions such as Ni 2+ , reducing agent NaH2PO2, complexing agent Na3C6H5O7·2H2O, plating solution stabilizer, etc. In the electroless nickel-phosphorus plating reaction of magnesium alloy, the metal ion Ni in the electroless plating solution 2+The nickel is reduced to metal by the reducing agent NaH2PO2 and deposited on the surface of the magnesium alloy substrate. The reducing agent NaH2PO2 is an electron donor. The complexing agent Na3C6H5O7·2H2O not only has a complexing effect, but also plays an important catalytic role in the precipitation of P in the plating solution. NH3HF2 can accelerate the deposition rate of nickel. Na2CO3 can ensure that the solution is alkaline. NH3·H2O is responsible for regulating the overall pH value of the solution. The composition of the formed chemical plating solution is stable and no precipitation or other precipitates are produced. The experimental process is simple to operate and is suitable for large-scale operation and application. It is suitable for the surface treatment of magnesium alloy products and is convenient and practical.

[0014] As a preferred embodiment of the present invention, in the chemical plating solution, the component concentration of NiSO4·6H2O can be any value between 5 g / L and 30 g / L, such as 5 g / L, 10 g / L, 15 g / L or 30 g / L, the component concentration of Na3C6H5O7·2H2O can be any value between 5 g / L and 30 g / L, such as 5 g / L, 10 g / L, 20 g / L or 30 g / L, the component concentration of Na2CO3 can be any value between 5 g / L and 30 g / L, such as 5 g / L, 10 g / L, 20 g / L or 30 g / L, the component concentration of NH3HF2 can be any value between 5 g / L and 20 g / L, such as 5 g / L, 10 g / L, 15 g / L or 20 g / L, and the component concentration of NaH2PO2 can be any value between 5 g / L and 30 g / L, such as 5 g / L, 10 g / L, 20 g / L or 30 g / L. g / L, 20 g / L or 30 g / L, etc. The content of NH3·H2O can be any value between 20 mL and 100 mL, such as 20 mL, 40 mL, 80 mL or 100 mL.

[0015] In a preferred embodiment, the temperature during the electroless plating process is 70°C to 100°C, the pH of the electroless plating solution is 7 to 15, and the electroless plating treatment time is 10 min to 15 min. As a preferred embodiment of the present invention, the heating temperature for the electroless plating process can be any value between 70°C and 100°C, such as 70°C, 80°C, 90°C, or 100°C. In the present invention, the purpose of water bath heating is to ensure the deposition rate. The more important reason is that when the temperature is lower than 70°C, the oxidation reaction of the hypophosphite in the electroless nickel plating cannot proceed, so it cannot provide atomic hydrogen, resulting in the inability of nickel ions to be reduced to nickel, and the electroless nickel plating production stops.

[0016] In a preferred embodiment, after the electroless plating treatment, after the magnesium alloy sample is dried after the electroless plating is completed, a TiO2-SiO2 epoxy organic film layer is plated. The solvent of the TiO2-SiO2 epoxy organic film layer solution is N-methylpyrrolidone, and the mass volume ratio of the epoxy resin to N-methylpyrrolidone is 1 g to 100 g: 20 mL to 100 mL. In the present invention, the epoxy resin is E44 epoxy resin, the polyamide resin is 650 polyamide resin, and TiO2-SiO2 acts as an organic coating additive in the entire organic solution. Nano-TiO2 particles and SiO2 particles are added to the epoxy organic film layer. The nano-TiO2 particles improve the thermal stability and impact resistance of the organic film layer due to their stable chemical properties and excellent thermal stability. The SiO2 particles are white amorphous flocs with significant aging resistance and chemical resistance, thereby improving the corrosion resistance of the organic film layer.

[0017] In a preferred embodiment, during the blanket plating process of the organic film layer, stirring is performed at room temperature for 1 to 12 hours, and the blanket plating process is in a stirring state. As a preferred embodiment of the present invention, the stirring time can be any value between 1 hour and 12 hours, such as 1 hour, 2 hours, 4 hours, 6 hours, or 12 hours. In the present invention, the blanket plating process is in a stirring state in order to improve the uniformity of the organic solution, because the presence of the epoxy resin and polyamide resin in the organic solution makes the solution as a whole more viscous, and it is necessary to ensure the uniformity of the solution.

[0018] In a preferred embodiment, the soluble magnesium alloy is a Mg-Zn-Cu soluble magnesium alloy, comprising, by weight percentage, 5 wt.% to 7 wt.% zinc, 1 wt.% to 3 wt.% copper, 0.4 wt.% to 0.9 wt.% zirconium, 0.5 wt.% to 2 wt.% rare earth elements, and the balance being magnesium and unavoidable impurities, totaling 100%. The rare earth elements are gadolinium, yttrium, cerium, neodymium, and lanthanum. In the present invention, Mg-Zn-Cu magnesium alloy is a typical soluble magnesium alloy with a fast dissolution rate and is very easy to corrode, and has high requirements for the coating process and the corrosion resistance of the film layer. However, the single chemical plating or organic plating in the existing technology has poor bonding with the Mg-Zn-Cu soluble magnesium alloy, and has poor acid and alkali resistance and temperature resistance. Based on this, the present invention adopts a chemical plating method to generate a uniform chemical plating layer on the surface of the sample. On the basis of the chemical plating layer, a composite organic plating layer is used to effectively solve the problems of weak bonding, poor temperature resistance and poor acid and alkali resistance of the epoxy organic film layer. The preparation of a composite film layer on the Mg-Zn-Cu soluble magnesium alloy can effectively expand the anti-corrosion application field of the magnesium alloy.

[0019] In a preferred embodiment, a method for pretreating a soluble magnesium alloy comprises the following steps: sanding a soluble magnesium alloy sample with sandpaper to remove surface oxides, then ultrasonically cleaning the sample with acetone; alkali-washing the ultrasonically cleaned soluble magnesium alloy sample, and then ultrasonically cleaning the sample again in acetone. The sandpaper is water-treated sandpaper with a mesh size of 600-800 mesh, and the alkaline wash solution comprises the following components: 50-100 g / L NaOH and 5-20 g / L Na₃PO₄.

[0020] In a preferred embodiment, the ultrasonic cleaning time is 5 min to 20 min, the alkali cleaning time is 5 min to 20 min, the ultrasonic cleaning temperature is 25°C to 50°C, and the alkali cleaning temperature is 25°C to 100°C. Grinding to remove surface oxides, ultrasonic cleaning and alkali cleaning are to remove impurities on the surface of the soluble magnesium alloy to promote the bonding between the chemical plating layer and the soluble magnesium alloy matrix; the time of ultrasonic cleaning can be any value between 5 min and 20 min, such as 5 min, 10 min or 20 min, and the temperature can be any value between 25 ℃ and 50 ℃, such as 25 ℃, 30 ℃ or 50 ℃; the time of alkali cleaning can be any value between 5 min and 20 min, such as 5 min, 10 min or 20 min, the solute of the alkali cleaning solution is NaOH and Na3PO4, the solvent is deionized water, the mass ratio of the solute NaOH and Na3PO4 in the alkali cleaning solution is 3:1, and the alkali cleaning solution has the following component composition: 50 g / L~100 g / L of NaOH, 5 g / L~20 g / L of Na3PO4, and the temperature of alkali cleaning can be any value between 25 ℃ and 100 ℃, such as 25 ℃, 30 ℃, 60 ℃, 90 ℃ or 100 ℃, etc.

[0021] In a preferred embodiment, after the blanketing treatment of the organic film layer is completed, the organic film layer is dried at 60°C to 180°C for 6 to 24 hours to obtain a corrosion-resistant composite film layer on the surface of the soluble magnesium alloy. As a preferred embodiment of the present invention, the drying temperature can be any value between 60°C and 180°C, such as 60°C, 120°C, or 180°C, and the drying time can be any value between 6 hours and 24 hours, such as 6 hours, 12 hours, or 24 hours.

[0022] The present invention also provides a corrosion-resistant composite film on the surface of a soluble magnesium alloy prepared by the aforementioned preparation method. The present invention utilizes chemical plating and TiO2-SiO2 epoxy organic film treatment technology to produce a composite film with excellent corrosion resistance, good bonding, and good acid, alkali, and high-temperature resistance. Furthermore, the composite film exhibits transparency, clarity, and impact resistance.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention adopts a chemical plating method to generate a uniform chemical plating layer on the surface of the sample. On the basis of the chemical plating layer, a composite organic plating layer is formed to effectively solve the problems of weak bonding, poor temperature resistance and poor acid and alkali resistance of the epoxy organic film layer. Among them, the chemical plating adopts Ni-P chemical plating, and the surface of the obtained chemical plating film layer is uniform and well bonded; however, the chemical plating film layer has a reduced bonding ability in a solution environment and at a high temperature, is easy to fall off, and has poor corrosion resistance; the epoxy organic film layer has good corrosion resistance in a solution environment, but has poor bonding with the magnesium alloy sample, so the advantages of the two are combined to adopt the first step of chemical plating and the second step of TiO2-SiO2 composite organic film layer to obtain a composite film layer with strong corrosion resistance and good heat resistance, thereby improving the corrosion resistance of the magnesium alloy, having good bonding with the substrate, and having good high temperature resistance.

[0025] (2) The present invention adds nano-TiO2 particles, SiO2 particles and oleic acid to the epoxy organic film layer to prepare a TiO2-SiO2 composite organic film layer, wherein the nano-TiO2 particles improve the thermal stability and impact resistance of the organic film layer due to their stable chemical properties and excellent thermal stability; the SiO2 particles are white amorphous flocs with significant anti-aging and chemical resistance, thereby improving the corrosion resistance of the organic film layer; oleic acid is an unsaturated fatty acid and one of the most common fatty acids in nature, which can improve the plating ability of the organic film solution and make the thickness of the organic film layer uniform.

[0026] (3) The chemical plating solution and TiO2-SiO2 epoxy organic film solution used in the present invention are simple and easy to implement, low in cost and high in production efficiency; the chemical plating solution has stable composition and does not produce precipitation or other precipitates; the experimental process is simple to operate and is suitable for large-scale operation and application, and is suitable for the surface treatment of magnesium alloy products, which is convenient and practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a rectangular sample diagram of the Mg-Zn-Cu soluble magnesium alloy of the present invention, wherein: Figure 1 Figure a is a plane diagram, and figure b is a three-dimensional diagram.

[0028] Figure 2 This is the hydrogen evolution experimental device of the present invention.

[0029] Figure 3 The hydrogen evolution content of the Mg-Zn-Cu soluble magnesium alloy of Comparative Example 1 of the present invention at different times.

[0030] Figure 4 This is a surface morphology of the Mg-Zn-Cu soluble magnesium alloy of Comparative Example 1 of the present invention after hydrogen evolution.

[0031] Figure 5 This is a graph showing the change in hydrogen evolution content and surface morphology of the Mg-Zn-Cu soluble magnesium alloy after hydrogen evolution according to Example 1 of the present invention, wherein: Figure 5 Figure a is a line graph showing the change in hydrogen evolution content, and figure b is a surface morphology graph.

[0032] Figure 6 This is a graph showing the change in hydrogen evolution content and surface morphology of the Mg-Zn-Cu soluble magnesium alloy after hydrogen evolution according to Example 2 of the present invention, wherein: Figure 6 Figure a is a line graph showing the change in hydrogen evolution content, and figure b is a surface morphology graph.

[0033] Figure 7 This is a graph showing the change in hydrogen evolution content and surface morphology of the Mg-Zn-Cu soluble magnesium alloy after hydrogen evolution according to Example 3 of the present invention, wherein: Figure 7 Figure a is a line graph showing the change in hydrogen evolution content, and figure b is a surface morphology graph.

[0034] Figure 8 This is a graph showing the change in hydrogen evolution content and surface morphology of the Mg-Zn-Cu soluble magnesium alloy after hydrogen evolution in Comparative Example 2 of the present invention, wherein: Figure 8 Figure a is a line graph showing the change in hydrogen evolution content, and figure b is a surface morphology graph.

[0035] Figure 9 This is a graph showing the change in hydrogen evolution content and surface morphology of the Mg-Zn-Cu soluble magnesium alloy after hydrogen evolution in Comparative Example 3 of the present invention, wherein: Figure 9 Figure a is a line graph showing the change in hydrogen evolution content, and figure b is a surface morphology graph. DETAILED DESCRIPTION

[0036] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0038] The following is further described through specific examples.

[0039] Example 1

[0040] A method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy comprises the following steps:

[0041] S1. Pretreatment of soluble magnesium alloy samples:

[0042] A Mg-Zn-Cu soluble magnesium alloy comprising, by weight percentage, 6 wt.% zinc, 2 wt.% copper, 0.6 wt.% zirconium, 0.7 wt.% rare earth gadolinium, 0.4 wt.% rare earth yttrium, 0.4 wt.% rare earth cerium, 0.3 wt.% rare earth neodymium, 0.2 wt.% rare earth lanthanum, and the balance being magnesium and unavoidable impurities, the total amount being 100%.

[0043] The soluble magnesium alloy sample was polished with 600-mesh water-treated sandpaper to remove surface oxides, and then ultrasonically cleaned with acetone at 30°C for 10 min. The soluble magnesium alloy sample after ultrasonic cleaning was alkaline washed. The solutes of the alkaline washing solution were NaOH and Na3PO4, and the solvent was deionized water. The mass ratio of the solutes NaOH and Na3PO4 in the alkaline washing solution was 3:1. The alkaline washing solution had the following component concentrations: 60 g / L NaOH and 20 g / L Na3PO4. The alkaline washing was carried out at 30°C for 10 min. The sample after alkaline washing was again placed in acetone and ultrasonically cleaned at 30°C for 10 min.

[0044] S2. Place the pretreated soluble magnesium alloy in an electroless plating solution, wherein the electroless plating solution has the following components: 30 g / L NiSO4·6H2O, 20 g / L Na3C6H5O7·2H2O, 20 g / L Na2CO3, 10 g / L NH3HF2, 25 g / L NaH2PO2 and 50 mL NH3·H2O, and the solvent is deionized water; perform electroless plating at 70°C to reduce the metal ions in the plating solution to metal deposits, and obtain a Ni-P alloy film on the surface of the soluble magnesium alloy sample.

[0045] S3. After the chemical plating treatment, the sample is dried and the soluble magnesium alloy is placed in a TiO2-SiO2 epoxy organic film solution. The TiO2-SiO2 epoxy organic film solution has the following component ratio: 0.4 g nano-TiO2 particles, 0.4 g SiO2 particles, 0.1 g oleic acid, 20 g E44 epoxy resin, 12 g 650 polyamide resin and 15 mL N-methylpyrrolidone; the organic film layer is plated at room temperature with electromagnetic stirring at room temperature. After plating for 4 hours, the sample is taken out and vacuum dried at 120°C for 24 hours to obtain a TiO2-SiO2 epoxy organic film layer; that is, a corrosion-resistant composite film layer on the surface of the soluble magnesium alloy is obtained.

[0046] Example 2

[0047] A method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy comprises the following steps:

[0048] S1. Pretreatment of soluble magnesium alloy samples:

[0049] A Mg-Zn-Cu soluble magnesium alloy comprising, by weight percentage, 6 wt.% zinc, 2 wt.% copper, 0.6 wt.% zirconium, 0.7 wt.% rare earth gadolinium, 0.4 wt.% rare earth yttrium, 0.4 wt.% rare earth cerium, 0.3 wt.% rare earth neodymium, 0.2 wt.% rare earth lanthanum, and the balance being magnesium and unavoidable impurities, the total amount being 100%.

[0050] The soluble magnesium alloy sample was polished with 600-mesh water-treated sandpaper to remove surface oxides, and then ultrasonically cleaned with acetone at 30°C for 10 min. The soluble magnesium alloy sample after ultrasonic cleaning was alkaline washed. The solutes of the alkaline washing solution were NaOH and Na3PO4, and the solvent was deionized water. The mass ratio of the solutes NaOH and Na3PO4 in the alkaline washing solution was 3:1. The alkaline washing solution had the following component concentrations: 60 g / L NaOH and 20 g / L Na3PO4. The alkaline washing was carried out at 30°C for 10 min. The sample after alkaline washing was again placed in acetone and ultrasonically cleaned at 30°C for 10 min.

[0051] S2. Place the pretreated soluble magnesium alloy in an electroless plating solution, wherein the electroless plating solution has the following components: 30 g / L NiSO4·6H2O, 20 g / L Na3C6H5O7·2H2O, 20 g / L Na2CO3, 10 g / L NH3HF2, 25 g / L NaH2PO2 and 50 mL NH3·H2O, and the solvent is deionized water; perform electroless plating at 70°C to reduce the metal ions in the plating solution to metal deposits, and obtain a Ni-P alloy film on the surface of the soluble magnesium alloy sample.

[0052] S3. After the chemical plating treatment, the sample is dried and the soluble magnesium alloy is placed in a TiO2-SiO2 epoxy organic film solution. The TiO2-SiO2 epoxy organic film solution has the following component ratio: 0.2 g nano-TiO2 particles, 0.4 g SiO2 particles, 0.1 g oleic acid, 20 g E44 epoxy resin, 12 g 650 polyamide resin and 15 mL N-methylpyrrolidone; the organic film layer is plated at room temperature with electromagnetic stirring at room temperature. After plating for 4 hours, the sample is taken out and vacuum dried at 120°C for 24 hours to obtain a TiO2-SiO2 epoxy organic film layer; that is, a corrosion-resistant composite film layer on the surface of the soluble magnesium alloy is obtained.

[0053] Example 3

[0054] A method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy comprises the following steps:

[0055] S1. Pretreatment of soluble magnesium alloy samples:

[0056] A Mg-Zn-Cu soluble magnesium alloy comprising, by weight percentage, 6 wt.% zinc, 2 wt.% copper, 0.6 wt.% zirconium, 0.7 wt.% rare earth gadolinium, 0.4 wt.% rare earth yttrium, 0.4 wt.% rare earth cerium, 0.3 wt.% rare earth neodymium, 0.2 wt.% rare earth lanthanum, and the balance being magnesium and unavoidable impurities, the total amount being 100%.

[0057] The soluble magnesium alloy sample was polished with 600-mesh sandpaper to remove surface oxides, and then ultrasonically cleaned with acetone at 30°C for 10 min. The soluble magnesium alloy sample after ultrasonic cleaning was alkaline washed. The solutes of the alkaline washing solution were NaOH and Na3PO4, and the solvent was deionized water. The mass ratio of the solutes NaOH and Na3PO4 in the alkaline washing solution was 3:1. The alkaline washing solution had the following component concentrations: 60 g / L NaOH and 20 g / L Na3PO4. The alkaline washing was carried out at 30°C for 10 min. The sample after alkaline washing was again placed in acetone and ultrasonically cleaned at 30°C for 10 min.

[0058] S2. Place the pretreated soluble magnesium alloy in an electroless plating solution, wherein the electroless plating solution has the following components: 30 g / L NiSO4·6H2O, 20 g / L Na3C6H5O7·2H2O, 20 g / L Na2CO3, 10 g / L NH3HF2, 25 g / L NaH2PO2 and 50 mL NH3·H2O, and the solvent is deionized water; perform electroless plating at 70°C to reduce the metal ions in the plating solution to metal deposits, and obtain a Ni-P alloy film on the surface of the soluble magnesium alloy sample.

[0059] S3. After the chemical plating treatment, the sample is dried and the soluble magnesium alloy is placed in a TiO2-SiO2 epoxy organic film solution. The TiO2-SiO2 epoxy organic film solution has the following component ratio: 0.6 g nano-TiO2 particles, 0.4 g SiO2 particles, 0.1 g oleic acid, 20 g E44 epoxy resin, 12 g 650 polyamide resin and 15 mL N-methylpyrrolidone; the organic film layer is plated at room temperature with electromagnetic stirring at room temperature. After plating for 4 hours, the sample is taken out and vacuum dried at 120°C for 24 hours to obtain a TiO2-SiO2 epoxy organic film layer; that is, a corrosion-resistant composite film layer on the surface of the soluble magnesium alloy is obtained.

[0060] Comparative Example 1

[0061] A method for preparing a soluble magnesium alloy surface with corrosion resistance comprises the following steps:

[0062] Pretreatment of soluble magnesium alloy samples:

[0063] A Mg-Zn-Cu soluble magnesium alloy comprising, by weight percentage, 6 wt.% zinc, 2 wt.% copper, 0.6 wt.% zirconium, 0.7 wt.% rare earth gadolinium, 0.4 wt.% rare earth yttrium, 0.4 wt.% rare earth cerium, 0.3 wt.% rare earth neodymium, 0.2 wt.% rare earth lanthanum, and the balance being magnesium and unavoidable impurities, the total amount being 100%.

[0064] The soluble magnesium alloy sample was polished with 600-mesh wet sandpaper to remove surface oxides, and then ultrasonically cleaned with acetone at 30°C for 10 min. The soluble magnesium alloy sample after ultrasonic cleaning was alkali-washed, and the solutes of the alkali washing solution were NaOH and Na3PO4, and the solvent was deionized water. The mass ratio of the solutes NaOH and Na3PO4 in the alkali washing solution was 3:1. The alkali washing solution had the following component concentrations: 60 g / L NaOH, 20 g / L Na3PO4. The alkali washing was carried out at 30°C for 10 min. The sample after alkali washing was again placed in acetone and ultrasonically cleaned at 30°C for 10 min to obtain a soluble magnesium alloy with surface corrosion resistance.

[0065] Comparative Example 2

[0066] A method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy comprises the following steps:

[0067] S1. Pretreatment of soluble magnesium alloy samples:

[0068] A Mg-Zn-Cu soluble magnesium alloy comprising, by weight percentage, 6 wt.% zinc, 2 wt.% copper, 0.6 wt.% zirconium, 0.7 wt.% rare earth gadolinium, 0.4 wt.% rare earth yttrium, 0.4 wt.% rare earth cerium, 0.3 wt.% rare earth neodymium, 0.2 wt.% rare earth lanthanum, and the balance being magnesium and unavoidable impurities, the total amount being 100%.

[0069] The soluble magnesium alloy sample was polished with 600-mesh water-treated sandpaper to remove surface oxides, and then ultrasonically cleaned with acetone at 30°C for 10 min. The soluble magnesium alloy sample after ultrasonic cleaning was alkaline washed. The solutes of the alkaline washing solution were NaOH and Na3PO4, and the solvent was deionized water. The mass ratio of the solutes NaOH and Na3PO4 in the alkaline washing solution was 3:1. The alkaline washing solution had the following component concentrations: 60 g / L NaOH and 20 g / L Na3PO4. The alkaline washing was carried out at 30°C for 10 min. The sample after alkaline washing was again placed in acetone and ultrasonically cleaned at 30°C for 10 min.

[0070] S2. Place the pretreated soluble magnesium alloy in an electroless plating solution, wherein the electroless plating solution has the following components: 30 g / L NiSO4·6H2O, 20 g / L Na3C6H5O7·2H2O, 20 g / L Na2CO3, 10 g / L NH3HF2, 25 g / L NaH2PO2 and 50 mL NH3·H2O, and the solvent is deionized water; perform electroless plating at 70°C to reduce the metal ions in the plating solution to metal deposits, and obtain a Ni-P alloy film on the surface of the soluble magnesium alloy sample.

[0071] S3. After the chemical plating treatment, the sample is dried and the soluble magnesium alloy is placed in an epoxy organic film solution. The epoxy organic film solution has the following component ratio: 20 g E44 epoxy resin, 12 g 650 polyamide resin and 15 mL N-methylpyrrolidone; the organic film layer is plated at room temperature with electromagnetic stirring at room temperature. After plating for 4 hours, the sample is taken out and vacuum dried at 120°C for 24 hours to obtain the epoxy organic film layer; that is, a corrosion-resistant composite film layer on the surface of the soluble magnesium alloy is obtained.

[0072] Comparative Example 3

[0073] A method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy comprises the following steps:

[0074] S1. Pretreatment of soluble magnesium alloy samples:

[0075] A Mg-Zn-Cu soluble magnesium alloy comprising, by weight percentage, 6 wt.% zinc, 2 wt.% copper, 0.6 wt.% zirconium, 0.7 wt.% rare earth gadolinium, 0.4 wt.% rare earth yttrium, 0.4 wt.% rare earth cerium, 0.3 wt.% rare earth neodymium, 0.2 wt.% rare earth lanthanum, and the balance being magnesium and unavoidable impurities, the total amount being 100%.

[0076] The soluble magnesium alloy sample was polished with 600-mesh water-treated sandpaper to remove surface oxides, and then ultrasonically cleaned with acetone at 30°C for 10 min. The soluble magnesium alloy sample after ultrasonic cleaning was alkaline washed. The solutes of the alkaline washing solution were NaOH and Na3PO4, and the solvent was deionized water. The mass ratio of the solutes NaOH and Na3PO4 in the alkaline washing solution was 3:1. The alkaline washing solution had the following component concentrations: 60 g / L NaOH and 20 g / L Na3PO4. The alkaline washing was carried out at 30°C for 10 min. The sample after alkaline washing was again placed in acetone and ultrasonically cleaned at 30°C for 10 min.

[0077] S2. Place the pretreated soluble magnesium alloy in an electroless plating solution, wherein the electroless plating solution has the following components: 30 g / L NiSO4·6H2O, 20 g / L Na3C6H5O7·2H2O, 20 g / L Na2CO3, 10 g / L NH3HF2, 25 g / L NaH2PO2 and 50 mL NH3·H2O, and the solvent is deionized water; perform electroless plating at 30°C to reduce the metal ions in the plating solution to metal deposits, and obtain a Ni-P alloy film on the surface of the soluble magnesium alloy sample.

[0078] S3. After the chemical plating treatment, the sample is dried and the soluble magnesium alloy is placed in a SiO2 epoxy organic film solution. The SiO2 epoxy organic film solution has the following component ratio: 0.4 g SiO2 particles, 0.1 g oleic acid, 20 g E44 epoxy resin, 12 g 650 polyamide resin and 15 mL N-methylpyrrolidone; the organic film layer is plated at room temperature with electromagnetic stirring at room temperature. After plating for 4 hours, the sample is taken out and vacuum dried at 120°C for 24 hours to obtain a SiO2 epoxy organic film layer; that is, a corrosion-resistant composite film layer on the surface of the soluble magnesium alloy is obtained.

[0079] The hydrogen evolution rate, weight loss rate and macroscopic morphology of the Mg-Zn-Cu soluble magnesium alloys of Examples 1 to 3 and Comparative Examples 1 to 3 were tested:

[0080] The Mg-Zn-Cu soluble magnesium alloys of Examples 1 to 3 and Comparative Examples 1 and 2 were prepared using rectangular specimens of 40 mm × 20 mm × 5 mm. Figure 1 This is a rectangular sample diagram of the Mg-Zn-Cu soluble magnesium alloy of the present invention, wherein: Figure 1 Figure a is a plane diagram, and figure b is a three-dimensional diagram. Figure 1 As shown, the present invention uses a rectangular sample of 40 mm×20 mm×5 mm to test the hydrogen evolution rate, weight loss rate and macroscopic morphology.

[0081] Figure 2This is the hydrogen evolution experimental device of the present invention. Figure 2 As shown, the sample rack 1 includes a support base 101, a support rod 102 and a cross bar 103. The support rod 102 is arranged on the support base 101, and the cross bar 103 is arranged on the support rod 102. A culture dish 2 is placed on the support base 101, and a support 201 is arranged in the culture dish 2. A long-necked funnel 3 is placed on the support 201. The long-necked funnel 3 is inverted on the support 201. An inverted measuring cylinder 4 is sleeved on the neck of the long-necked funnel 3. The measuring cylinder 4 is clamped on the cross bar 103. 3.5% NaCl solution is provided in the culture dish 2, the long-necked funnel 3 and the measuring cylinder 4. The soluble magnesium alloy rectangular sample is placed in the funnel of the long-necked funnel 3.

[0082] The Mg-Zn-Cu soluble magnesium alloy of Comparative Example 1 was placed in a hydrogen evolution device. After a certain period of hydrogen evolution, all the solution in the graduated cylinder was discharged, the hydrogen evolution experiment was completed, and the corresponding hydrogen evolution data graph was obtained.

[0083] Figure 3 The hydrogen evolution content of the Mg-Zn-Cu soluble magnesium alloy of Comparative Example 1 of the present invention at different times. Figure 3 As shown, it is found that the uncoated Mg-Zn-Cu soluble magnesium alloy undergoes hydrogen evolution reaction with a large amount of hydrogen evolution and a fast hydrogen evolution rate. Therefore, the uncoated Mg-Zn-Cu soluble magnesium alloy has extremely poor corrosion resistance.

[0084] The weight loss rate of the Mg-Zn-Cu soluble magnesium alloy of Comparative Example 1 was calculated after being treated according to the national standard. The size and weight changes of the sample of Comparative Example 1 after the 2-h hydrogen evolution test are shown in Table 1.

[0085] Table 1 shows the size and weight changes of the sample of Comparative Example 1 of the present invention after 2h hydrogen evolution experiment

[0086]

[0087] The weight loss rate is calculated using the corrosion rate formula, which is shown in formula (1):

[0088] Formula (1).

[0089] In formula (1): R-weight loss rate, mm / a; M-mass of sample before test, g; M1-mass of sample after test, g; S-total area of sample, cm 2 ; T-experimental time h; D-material density kg / m 3 .

[0090] From the data in Table 1, it can be calculated that the weight loss rate R of the sample is 1.59 10 3mm / a, indicating that the uncoated Mg-Zn-Cu soluble magnesium alloy sample is prone to hydrogen evolution reaction in 3.5% NaCl solution. The hydrogen evolution rate is very fast, the weight loss rate is very high, and it is very easy to corrode. Therefore, it is particularly important to use an economical and effective coating method.

[0091] Figure 4 This is the surface morphology of the Mg-Zn-Cu soluble magnesium alloy of Comparative Example 1 of the present invention after hydrogen evolution. Figure 4 As shown in FIG, by observing the macroscopic morphology of the uncoated Mg-Zn-Cu soluble magnesium alloy sample after hydrogen evolution, it can be found that the surface is corroded and the sample that originally had a metallic luster has become a rough and uneven surface.

[0092] The Mg-Zn-Cu soluble magnesium alloys of Examples 1 to 3 and Comparative Examples 2 to 3 were placed in a hydrogen evolution device. After a certain period of hydrogen evolution, all the solution in the graduated cylinder was discharged, and the hydrogen evolution experiment was completed. The corresponding hydrogen evolution data graph and macroscopic sample graph after corrosion were obtained.

[0093] Figure 5 This is a graph showing the change in hydrogen evolution content and surface morphology of the Mg-Zn-Cu soluble magnesium alloy after hydrogen evolution according to Example 1 of the present invention, wherein: Figure 5 Figure a is a line graph showing the change of hydrogen evolution content, and Figure b is a surface morphology graph. Figure 5 As shown in Figure a, the sample of Example 1 does not undergo hydrogen evolution reaction within 12 hours, and the film layer does not break after the hydrogen evolution experiment, indicating that the film layer has good corrosion resistance, good bonding between the film layer and the substrate, and excellent corrosion resistance of the film layer itself, and will not cause corrosion problems caused by poor bonding and insufficient corrosion resistance. Figure 5 As shown in Figure b, the TiO2-SiO2 epoxy organic film exhibited no cracking after the hydrogen evolution experiment, demonstrating its strong corrosion resistance and excellent bonding strength, preventing film failure over extended periods. Compared to epoxy and SiO2 epoxy organic films, the TiO2-SiO2 epoxy organic film exhibits significantly improved corrosion resistance, high-temperature resistance, and chemical resistance, demonstrating superior corrosion protection.

[0094] Figure 6 This is a graph showing the change in hydrogen evolution content and surface morphology of the Mg-Zn-Cu soluble magnesium alloy after hydrogen evolution according to Example 2 of the present invention, wherein: Figure 6 Figure a is a line graph showing the change of hydrogen evolution content, and Figure b is a surface morphology graph. Figure 6 As shown in Figure a, the sample of Example 2 does not undergo hydrogen evolution reaction within 9 hours, but undergoes hydrogen evolution reaction after 9 hours; Figure 6As shown in Figure b, after the hydrogen evolution experiment, no large-scale cracking occurred on the surface of the TiO2-SiO2 epoxy organic film layer, indicating that the film layer has good corrosion resistance, but the corrosion resistance is worse than that of Example 1.

[0095] Figure 7 This is a graph showing the change in hydrogen evolution content and surface morphology of the Mg-Zn-Cu soluble magnesium alloy after hydrogen evolution according to Example 3 of the present invention, wherein: Figure 7 Figure a is a line graph showing the change of hydrogen evolution content, and Figure b is a surface morphology graph. Figure 7 As shown in Figure a, the sample of Example 3 does not undergo hydrogen evolution reaction within 10 hours, but undergoes hydrogen evolution reaction after 10 hours; Figure 7 As shown in Figure b, after the hydrogen evolution experiment, no large-scale cracking occurred on the surface of the TiO2-SiO2 epoxy organic film layer, indicating that the film layer has good corrosion resistance, but the corrosion resistance is worse than that of Example 1.

[0096] Figure 8 The figure shows the change in hydrogen evolution content and surface morphology of the Mg-Zn-Cu soluble magnesium alloy after hydrogen evolution in Comparative Example 2 of the present invention. Figure 8 Figure a is a line graph showing the change of hydrogen evolution content, and Figure b is a surface morphology graph. Figure 8 As shown in Figure a, the sample of Comparative Example 2 does not undergo hydrogen evolution reaction within 3 hours, indicating that the epoxy organic film layer has a certain corrosion resistance. After more than 3 hours, hydrogen evolution reaction will occur immediately, and the hydrogen evolution rate is relatively fast, but the hydrogen evolution rate is much lower than that of the sample without film coating, indicating that the film layer has a large range of corrosion but not all corroded away, only local corrosion occurs. As the corrosion continues, the amount of hydrogen evolution becomes larger and larger, and the hydrogen evolution rate becomes faster and faster. Figure 8 As shown in Figure b, after the hydrogen evolution test, the sample clearly separated from the substrate, indicating poor adhesion between the epoxy organic film and the substrate. After the film ruptures, the corrosion of the NaCl solution causes other unruptured film locations on the sample to fall off from the substrate, exposing a larger area of the sample to the NaCl solution. This results in a faster hydrogen evolution rate and makes it more susceptible to corrosion. This shows that the main problem with the epoxy organic coating layer is poor adhesion, which causes other locations to fall off when ruptures occur, resulting in poor corrosion resistance of the epoxy organic film.

[0097] Figure 9 The figure shows the change in hydrogen evolution content and surface morphology of the Mg-Zn-Cu soluble magnesium alloy after hydrogen evolution in Comparative Example 3 of the present invention. Figure 9 Figure a is a line graph showing the change of hydrogen evolution content, and Figure b is a surface morphology graph. Figure 9As shown in Figure a, the sample of Comparative Example 3 does not undergo hydrogen evolution reaction within 8 hours, indicating that the corrosion resistance of the SiO2 epoxy organic film layer is better than that of the epoxy organic film layer; however, at a longer time, that is, more than 8 hours, hydrogen evolution corrosion will also occur, indicating that the SiO2 epoxy organic film layer will still be broken due to the corrosion resistance of the film layer itself or the poor bonding strength between the film layer and the substrate; Figure 9 As shown in Figure b, after the hydrogen evolution experiment, the film layer will rupture. However, when observing the sample after rupture, it will be found that after the film layer ruptures, the phenomenon of complete detachment from the sample due to the rupture of the film layer does not occur as with the epoxy organic film layer; This shows that the SiO2 epoxy organic film layer has a strong bonding force with the substrate and will not detach from the substrate. Therefore, the hydrogen evolution rate is also lower than that of Comparative Example 1. However, due to its own insufficient corrosion resistance, the SiO2 epoxy organic coating will also rupture, causing the substrate to be corroded. It can be seen that the SiO2 epoxy organic film layer has insufficient corrosion resistance and will still be corroded over a long period of time. Therefore, it is very necessary to improve the corrosion resistance of the SiO2 epoxy organic film layer itself.

[0098] In summary, the present invention adopts the chemical plating method to generate a uniform chemical plating layer on the surface of the sample, and then uses a composite organic plating layer on the basis of the chemical plating layer to effectively solve the problems of weak bonding strength, poor temperature resistance and poor acid and alkali resistance of the epoxy organic film layer. Among them, the chemical plating adopts Ni-P chemical plating, and the surface of the obtained chemical plating film layer is uniform and well bonded; but the chemical plating film layer has a decreased bonding ability in a solution environment and at higher temperatures, is easy to fall off, and has poor corrosion resistance; the epoxy organic film layer has good corrosion resistance in a solution environment, but has poor bonding with the magnesium alloy sample, so combining the respective advantages of the two, the first step of chemical plating and the second step of TiO2-SiO2 composite organic film layer are adopted to obtain a composite film layer with strong corrosion resistance and good heat resistance, thereby improving the corrosion resistance of the magnesium alloy, having good bonding with the substrate, and having good high temperature resistance.

[0099] It should be noted that when numerical ranges are mentioned in the present invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints may be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes preferred embodiments. Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they understand the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0100] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy, characterized in that: The following steps are involved: The pretreated soluble magnesium alloy is placed in an electroless plating solution for electroless plating, so that the metal ions in the plating solution are reduced to metal deposits, and a Ni-P alloy film layer is obtained on the surface of the soluble magnesium alloy sample; The chemical plating solution comprises the following components in concentrations: 5 g / L to 30 g / L NiSO4·6H2O, 5 g / L to 30 g / L Na3C6H5O7·2H2O, 5 g / L to 30 g / L Na2CO3, 5 g / L to 20 g / L NH3HF2, 5 g / L to 30 g / L NaH2PO2, and 20 mL to 100 mL NH3·H2O, and the solvent of the chemical plating solution is water; After the chemical plating treatment, the soluble magnesium alloy is placed in a TiO2-SiO2 epoxy organic film solution, and the organic film is plated at room temperature to obtain a TiO2-SiO2 epoxy organic film on the surface of the soluble magnesium alloy sample, thereby obtaining a corrosion-resistant composite film on the surface of the soluble magnesium alloy. The TiO2-SiO2 epoxy organic film solution is composed of a solute and a solvent, wherein the solute includes epoxy resin, nano-TiO2 particles, SiO2 particles, oleic acid and polyamide resin, and the mass ratio of epoxy resin, nano-TiO2 particles, SiO2 particles, oleic acid and polyamide resin is 1~100:0.1~10:0.1~10:0.1~10:1~100.

2. The method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy according to claim 1, characterized in that: The temperature during the chemical plating process is 70°C to 100°C, the pH of the chemical plating solution is 7 to 15, and the chemical plating time is 10 min to 15 min.

3. The method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy according to claim 1, characterized in that: The solvent of the TiO2-SiO2 epoxy organic film solution is N-methylpyrrolidone, and the mass volume ratio of the epoxy resin and N-methylpyrrolidone is 1 g~100 g:20 mL~100 mL; the epoxy resin is E44 type epoxy resin, and the polyamide resin is 650 type polyamide resin.

4. The method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy according to claim 1, characterized in that: During the blanket plating process of the organic film layer, the stirring time is 1 h to 12 h, and the blanket plating process is in a stirring state.

5. The method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy according to claim 1, characterized in that: The soluble magnesium alloy is a Mg-Zn-Cu series soluble magnesium alloy, which includes, by weight percentage, 5 wt.% to 7 wt.% of zinc, 1 wt.% to 3 wt.% of copper, 0.4 wt.% to 0.9 wt.% of zirconium, 0.5 wt.% to 2 wt.% of rare earth elements, and the balance being magnesium and unavoidable impurities, which totals 100%.

6. The method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy according to claim 1, characterized in that: The pretreatment method of a soluble magnesium alloy comprises the following steps: grinding a soluble magnesium alloy sample with sandpaper to remove surface oxides, and then ultrasonically cleaning the soluble magnesium alloy sample with acetone; alkali-washing the ultrasonically cleaned soluble magnesium alloy sample, and placing the alkali-washed sample in acetone for ultrasonic cleaning again.

7. The method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy according to claim 6, characterized in that: The ultrasonic cleaning time is 5 min~20 min, the alkaline cleaning time is 5 min~20 min, the ultrasonic cleaning temperature is 25 ℃~50 ℃, and the alkaline cleaning temperature is 25 ℃~100 ℃.

8. The method for preparing a corrosion-resistant composite film layer on the surface of a soluble magnesium alloy according to claim 1, characterized in that: After the organic film layer is subjected to the blanket coating treatment, it is dried at 60°C to 180°C for 6 h to 24 h to obtain a corrosion-resistant composite film layer on the surface of the soluble magnesium alloy.

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