Magnesium alloy sacrificial anode and production method thereof

Abstract

The invention relates to the technical field of magnesium alloy sacrificial anodes, in particular to a magnesium alloy sacrificial anode and a production method thereof, and the production method comprises composite electromagnetic field continuous casting and femtosecond laser gradient activation treatment. A matrix structure is optimized by applying an alternating magnetic field and an electrostatic field, a Ca / Mn enrichment layer is formed, and nanopores and a Sn (at) Ag conductive network are introduced by femtosecond laser processing, so that the surface activity and the corrosion resistance are remarkably improved. The grain of the prepared anode is refined to 15-20 [mu] m, the segregation index is lower than 0.15, and the surface sheet resistance is 0.8-1.2 ohm. According to the method, the problems of grain boundary corrosion sensitivity and surface modification limitation in a traditional process are solved, synergistic matching of the matrix and the surface is achieved, and the service performance of the anode in extreme environments such as deep sea and polar regions is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sacrificial anodes, and in particular relates to a magnesium alloy sacrificial anode and a production method thereof. Background Art

[0002] At present, magnesium alloy sacrificial anodes generally adopt gravity casting or continuous casting processes (such as CN112695282A). Although they can meet the basic performance requirements in practical applications, they still show certain limitations under complex working conditions. During the solidification process, alloying elements such as Mn and Ca tend to form coarse intermetallic compounds (such as Al8Mn5) at the grain boundaries, resulting in the preferential initiation of intergranular corrosion, which affects the service life of the anode. In addition, although conventional electromagnetic stirring (CN113843394A) can refine the grains, elements such as Zn and Ag produce radial segregation (segregation index > 0.35) under the action of centrifugal force in the melt, further limiting performance improvement. At the same time, a thick oxide layer (> 5μm) is easily formed on the surface of the ingot, which requires additional machining to remove, increasing material loss by 10-15%.

[0003] The surface treatment methods commonly used in the industry also have significant limitations. Although chemical activation methods (such as HNO3+H3PO4 pickling, CN110616394A) can obtain an activated surface, the porosity of the porous layer formed (pore size 1-3μm) decreases by more than 60% after immersion in seawater for 48 hours, affecting long-term stability. Although the ceramic layer generated by micro-arc oxidation technology (CN112941516A) has good corrosion resistance, it shifts the anode working potential positively by 0.1-0.2V, reducing the driving force of cathodic protection. Thermal sprayed metal coatings (such as Al-Zn coatings, CN113293325A) are prone to peeling under surge impact due to low interfacial bonding strength (<15MPa), making it difficult to meet harsh environmental requirements.

[0004] In special scenarios such as deep sea and polar regions, the combined application of existing technologies may cause synergistic failure problems. For example, when a fine-grained anode (grain size < 20 μm) with optimized casting process is combined with a surface nano-processing (such as CN114107969A), the corrosion channel penetration rate is accelerated due to the excessive density of grain boundaries. The difference in thermal expansion coefficient between the conductive enhancement layer (such as graphene coating, CN113817999A) and the substrate (Δα = 8.7×10 -6 Furthermore, anode performance indicators specified in the international standard ISO15589-1 (such as current efficiency > 85%) generally drop to 70%-75% in high-pressure environments above 10 MPa, indicating that existing technologies are insufficient under extreme conditions.

[0005] Although CN114107969A proposed laser cladding to improve anode surface activity, it did not solve the problem of substrate sensitivity to grain boundary corrosion; and the rotating magnetic field casting device developed by CN113843394A, while capable of refining the microstructure, exacerbated the depletion of surface elements. This field has long been plagued by the dilemma of a split in the "matrix optimization-surface modification" technical route, resulting in performance degradation of the anode under complex service conditions. These situations indicate that existing technologies need to be further optimized to cope with complex working conditions in order to improve the overall performance and adaptability of the anode. Summary of the Invention

[0006] The present invention aims to overcome the shortcomings of the existing technology and address or at least mitigate the performance degradation of magnesium alloy sacrificial anodes under complex service conditions due to issues such as sensitivity to grain boundary corrosion, limitations in surface modification, and matrix-surface synergistic failure. The present invention provides a magnesium alloy sacrificial anode and a production method thereof. This method combines composite electromagnetic field continuous casting with femtosecond laser gradient activation treatment to achieve a synergistic match between anode matrix microstructure optimization and surface activity enhancement, thereby improving the anode's service performance under extreme environments.

[0007] To achieve the above object, the present invention provides the following technical solution: a magnesium alloy sacrificial anode and a production method thereof, comprising the following steps:

[0008] S1. Composite electromagnetic field continuous casting

[0009] S1a, raw material pretreatment, using high-purity magnesium ingot as the base material, adding Ca, Mn and Ag, smelting under argon protection, and refining and degassing the melt with hexachloroethane;

[0010] S1 b, electromagnetic field application, during the casting process, an alternating magnetic field and an electrostatic field are applied, the frequency of the alternating magnetic field is 50-100Hz, the magnetic induction intensity is 0.3-0.5T, the field strength of the electrostatic field is 15-20kV / m, and the direction is parallel to the ingot axis; under the action of the magnetic field, the melt generates vortex stirring 120-150 times per minute, and the electric field drives Ca 2 +、Mn 2 + Directed migration towards the mold end, forming a Ca / Mn enriched layer with a thickness of 200-300nm on the ingot surface;

[0011] S2, Femtosecond Laser Gradient Activation Treatment

[0012] S2a, surface pretreatment, the ingot is CNC turned to a surface roughness of Ra ≤ 0.8 μm, ultrasonically cleaned with acetone and then dried with nitrogen purge;

[0013] S2b, laser activation, using a femtosecond laser with a wavelength of 1030 nm for gradient activation treatment, with a pulse width of 350 fs, a repetition rate of 100 kHz, a spot diameter of 30 μm, a scanning speed of 2000 mm / s, and an overlap rate of 40%; layered processing to produce a pyramidal base and nanopores, wherein the pyramidal base has a height of 20-30 μm, and the nanopore is located at the top of the pyramidal base and has an aperture of 50-100 nm;

[0014] S2c, in-situ conductive layer generation: spray an ethanol suspension containing Sn@Ag core-shell particles on the laser processing area, use the laser thermal effect to make the local temperature reach 800-1000℃, and the Sn@Ag core-shell particles are melted and embedded in the root of the cone to form a three-dimensional conductive network, and the surface resistance is reduced to 0.8-1.2Ω.

[0015] In order to further realize the present invention, the following technical solutions may be preferably used:

[0016] Preferably, in step S1a, 0.5-1.2 wt% Ca, 0.3-0.6 wt% Mn and 0.1-0.3 wt% Ag are added to a high-purity magnesium ingot, which is then heated to 720-750° C. under argon protection to form a melt.

[0017] Preferably, forming control is performed during the execution of step S1, and the forming control is specifically configured as follows:

[0018] The casting speed was controlled at 0.8-1.2 m / min, the cooling water flow was adjusted to 80-120 L / min, the temperature gradient was maintained at 15-20° C. / cm, and an ingot with a diameter of 150 mm was obtained.

[0019] Preferably, in step S1 b, when the frequency of the alternating magnetic field is set to 80-100 Hz, the grain size inside the ingot is refined to 15-20 μm, and the segregation index is reduced to below 0.15;

[0020] When the direction of the electrostatic field is 10°-30° with the ingot axis, Ca 2 +、Mn 2 + migration path is regulated, and the uniformity of the surface Ca / Mn enriched layer is improved.

[0021] Preferably, in step S2b, the layered processing is divided into two steps. The power of the first layer is 8W, forming a cone base with a height of 20-30 μm, and the power of the second layer is increased to 12W, generating nanopores with an aperture of 50-100 nm at the top of the cone.

[0022] Preferably, when the power of the second layer is increased to 15W, nanopores with higher porosity are generated at the top of the cone.

[0023] Preferably, step S3 is performed after step S1 is performed;

[0024] S3, performance testing

[0025] S3a, applying a pressure of more than 10 MPa in a closed chamber to record the changes in anode current efficiency;

[0026] S3b, setting a low temperature environment of -40°C to -60°C in a thermostat to evaluate the stability of the anode surface activity;

[0027] S3c, simulate extreme wave conditions through a dynamic surge impact device to detect the peeling tendency of the surface coating.

[0028] A magnesium alloy sacrificial anode is prepared using the above-mentioned production method. The internal structure of the anode is composed of fine and uniform grains with a grain size of 15-20 μm and a segregation index of less than 0.15. The surface is covered with a Ca / Mn enriched layer with a thickness of 200-300 nm. The enriched layer is tightly bonded to the substrate and has no cracks or defects at the interface. After femtosecond laser treatment, the surface forms a gradient structure, including a pyramidal base with a height of 20-30 μm and nanopores with an aperture of 50-100 nm. Sn@Ag core-shell particles are embedded at the base of the pyramid to form a three-dimensional conductive network. The surface resistance is 0.8-1.2 Ω.

[0029] Preferably, the particle size of the Sn@Ag core-shell particles is 200-500 nm, and the conductive network formed after being embedded in the root of the cone has a close bonding relationship with the cone base and the nanopores.

[0030] The magnesium alloy sacrificial anode according to claim 8 is characterized in that the transition area between the cone base and the nanopores presents a gradient change feature, which alleviates the thermal stress concentration problem caused by the difference in thermal expansion coefficient.

[0031] The beneficial effects of the present invention are:

[0032] The present invention achieves uniform refinement of the anode matrix structure through composite electromagnetic field continuous casting, solves the problem of intergranular corrosion caused by coarse intermetallic compounds at the grain boundaries in traditional casting processes, and at the same time reduces the segregation index and improves the uniformity of alloy element distribution. Femtosecond laser gradient activation treatment significantly enhances the electrochemical activity and corrosion resistance of the anode surface by introducing nanopores and conductive networks, avoiding the problems of decreased porosity and insufficient interface bonding strength in traditional surface treatment methods. In addition, the present invention achieves a coordinated match between the matrix and surface modification by optimizing the composite electromagnetic field parameters and the laser processing technology, solving the dilemma of the separation of the "matrix optimization-surface modification" technical route, and significantly improving the service performance of the anode in extreme environments such as the deep sea and the polar regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a flow chart of the steps of the production method of the present invention.

[0034] Figure 2 This is a structural diagram of the magnesium alloy sacrificial anode of the present invention. DETAILED DESCRIPTION

[0035] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0036] The following will clearly and completely describe 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 the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

[0037] Reference Figure 1 and Figure 2 The present invention provides a magnesium alloy sacrificial anode and a production method thereof, which realizes the synergistic matching of anode matrix structure optimization and surface activity enhancement through the technical means of combining composite electromagnetic field continuous casting with femtosecond laser gradient activation treatment. The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0038] The composite electromagnetic field continuous casting process includes the synergistic effect of alternating magnetic field and electrostatic field. The melt is affected by the alternating magnetic field during the casting process. The frequency is set to 50-100 Hz and the magnetic induction intensity is 0.3-0.5 T. The circumferential Lorentz force generated by the alternating magnetic field causes a vortex stirring of 120-150 times per minute to form inside the melt. This stirring action can promote the uniform distribution of alloy elements in the melt. At the same time, the strength of the electrostatic field is set to 15-20 kV / m and the direction is parallel to the ingot axis. The electrostatic field drives the Ca 2 +、Mn 2+Directional migration toward the mold end forms a Ca / Mn enriched layer with a thickness of 200-300nm on the surface of the ingot. This enriched layer is tightly bonded to the ingot matrix and there are no obvious cracks or defects at the interface. The casting speed is controlled at 0.8-1.2m / min, the cooling water flow is adjusted to 80-120L / min to achieve directional solidification, and the temperature gradient is maintained at 15-20℃ / cm. Finally, an ingot with a diameter of 150mm is obtained, the grain size inside the ingot is refined to 15-20μm, and the segregation index is reduced to below 0.15. This structural feature provides excellent base conditions for subsequent processes.

[0039] The femtosecond laser gradient activation treatment is carried out in two steps. First, the ingot obtained by composite electromagnetic field continuous casting is CNC turned to make its surface roughness reach Ra≤0.8μm, and the surface pretreatment is completed by acetone ultrasonic cleaning and nitrogen purging and drying. Then, a femtosecond laser with a wavelength of 1030nm is used for processing, with a pulse width of 350fs, a repetition frequency of 100kHz, a spot diameter of 30μm, a scanning speed of 2000mm / s, and an overlap rate of 40%. When the first layer power is set to 8W, a cone base with a height of 20-30μm is generated on the surface of the ingot. When the second layer power is increased to 12W, nanopores with an aperture of 50-100nm are generated on the top of the cone base. An ethanol suspension containing Sn@Ag core-shell particles with a particle size of 200-500nm is sprayed into the laser processing area. The laser thermal effect is used to raise the local temperature to 800-1000°C. The Sn@Ag core-shell particles completely melt at this temperature and embed into the root of the pyramidal base, forming a three-dimensional conductive network. The surface resistance is reduced to 0.8-1.2Ω. The transition region between the pyramidal base and the nanopores exhibits a gradient change feature, effectively alleviating the thermal stress concentration problem caused by the difference in thermal expansion coefficient. The conductive network formed after the Sn@Ag core-shell particles are embedded in the root of the pyramidal base has a close bonding relationship with the pyramidal base and the nanopores, and the interface bonding strength exceeds 20MPa.

[0040] The synergistic relationship between composite electromagnetic field continuous casting and femtosecond laser gradient activation treatment is reflected in many aspects. The Ca / Mn enriched layer formed in the composite electromagnetic field continuous casting process provides a stable substrate for the femtosecond laser gradient activation treatment, avoiding the surface cracking problem caused by uneven matrix structure. The nanopores introduced by femtosecond laser processing and the three-dimensional conductive network formed by Sn@Ag core-shell particles significantly improve the electrochemical activity and corrosion resistance of the anode surface. When the laser power is set to 12W, the bonding strength between the cone base and the nanopores reaches the highest value. At this time, the interface bonding strength exceeds 20MPa. The internal structure of the ingot can be further optimized by adjusting the composite electromagnetic field parameters. For example, increasing the alternating magnetic field frequency to 80-100Hz can significantly refine the grain size to 15-20μm, while reducing the segregation index to below 0.15. Changing the direction of the electrostatic field so that it is at a certain angle to the ingot axis, such as 10°-30°, can adjust the Ca 2 +、Mn 2 + migration path, improving the uniformity of the surface Ca / Mn enriched layer, and the femtosecond laser processing parameters can be flexibly adjusted according to actual needs. For example, by increasing the second layer power to 15W, nanopores with higher porosity can be generated at the top of the cone, thereby enhancing the surface activity.

[0041] The performance test is used to verify the service performance of the anode under different working conditions. The test modules include a closed cabin, a constant temperature chamber and a dynamic surge impact device. The closed cabin applies a pressure of more than 10MPa to simulate the high-pressure environment of the deep sea and records the changes in the anode current efficiency. The constant temperature chamber is set to a low temperature environment of -40℃ to -60℃ to evaluate the stability of the anode surface activity. The dynamic surge impact device simulates extreme wave conditions to detect the peeling tendency of the surface coating. The layout of these test modules and their functional diagrams clearly demonstrate the performance of the anode under complex service conditions. The closed cabin, constant temperature chamber and dynamic surge impact device are independently tested for different environmental factors to ensure that the anode can maintain excellent service performance under various extreme conditions.

[0042] The present invention achieves uniform refinement of the anode matrix structure through composite electromagnetic field continuous casting, solving the intergranular corrosion problem caused by coarse intermetallic compounds at grain boundaries in traditional casting processes. Femtosecond laser gradient activation treatment significantly enhances the electrochemical activity and corrosion resistance of the anode surface by introducing a three-dimensional conductive network formed by nanopores and Sn@Ag core-shell particles. Optimization of composite electromagnetic field parameters and laser processing technology achieves a coordinated match between matrix and surface modification, solving the dilemma of the separation of matrix optimization and surface modification technology routes, and significantly improving the service performance of the anode in extreme environments such as deep sea polar regions.

[0043] In order to better enable relevant personnel in this technical field to fully understand and implement the present invention, the specific implementation principle of the present invention is supplemented below with reference to a specific application scenario.

[0044] In the composite electromagnetic field continuous casting process, the melt is first placed under the synergistic effect of an alternating magnetic field and an electrostatic field. The alternating magnetic field generates a circumferential Lorentz force with a frequency of 50-100 Hz and a magnetic induction intensity of 0.3-0.5 T, which causes the melt to form a vortex stirring at 120-150 times per minute. This stirring action effectively promotes the uniform distribution of alloy elements in the melt, avoiding the radial segregation problem of elements such as Zn and Ag caused by centrifugal force in traditional processes. At the same time, the electrostatic field is applied parallel to the axial direction of the ingot with a field strength of 15-20 kV / m, driving the Ca 2 + and Mn 2 +Directional migration toward the mold end. This process forms a Ca / Mn-rich layer with a thickness of 200-300nm on the surface of the ingot. This enriched layer is tightly bonded to the matrix and has no obvious cracks or defects. By controlling the casting speed to 0.8-1.2m / min and adjusting the cooling water flow to 80-120L / min, ensuring that the temperature gradient is maintained at 15-20℃ / cm, directional solidification is achieved. Finally, an ingot with a diameter of 150mm is obtained, the internal grain size of which is refined to 15-20μm and the segregation index is reduced to below 0.15, providing excellent substrate conditions for subsequent femtosecond laser gradient activation treatment.

[0045] During the femtosecond laser gradient activation (FLLA) treatment, the ingot was first CNC-machined to a surface roughness of Ra ≤ 0.8 μm. Surface pretreatment was completed by ultrasonic cleaning with acetone and drying with nitrogen purge. Subsequently, processing was performed using a femtosecond laser with a wavelength of 1030 nm, a pulse width of 350 fs, a repetition rate of 100 kHz, a spot diameter of 30 μm, a scanning speed of 2000 mm / s, and an overlap ratio of 40%. The first processing power was set at 8 W, creating a pyramidal base with a height of 20-30 μm on the ingot surface. The second processing power was increased to 12 W, creating nanopores with a diameter of 50-100 nm at the top of the pyramidal base. An ethanol suspension containing Sn@Ag core-shell particles was sprayed onto the laser processing area. The laser thermal effect generated a local temperature of 800-1000°C, at which the Sn@Ag core-shell particles completely melted and embedded themselves at the base of the pyramidal base, forming a three-dimensional conductive network. The transition region between the pyramidal base and the nanopore exhibits a gradient, effectively alleviating thermal stress concentration caused by differences in thermal expansion coefficients. The conductive network formed by the embedded Sn@Ag core-shell particles is tightly bonded to the pyramidal base and the nanopore, with an interfacial bonding strength exceeding 20 MPa.

[0046] The synergistic relationship between composite electromagnetic field continuous casting and femtosecond laser gradient activation treatment is further reflected in many aspects. The Ca / Mn enriched layer formed during the composite electromagnetic field continuous casting process provides a stable substrate for the femtosecond laser gradient activation treatment, avoiding the problem of surface cracking caused by uneven matrix structure. The three-dimensional conductive network formed by the nanopores introduced by femtosecond laser processing and the Sn@Ag core-shell particles significantly improves the electrochemical activity and corrosion resistance of the anode surface. When the laser power is set to 12W, the bonding strength between the cone base and the nanopores reaches the highest value, and the interface bonding strength exceeds 20MPa. In addition, by adjusting the composite electromagnetic field parameters, such as increasing the alternating magnetic field frequency to 80-100Hz, the grain size can be further refined to 15-20μm, while reducing the segregation index to below 0.15; changing the direction of the electrostatic field so that it is at a certain angle to the ingot axis (such as 10°-30°), the Ca 2 +、Mn 2 + migration path, improving the uniformity of the surface Ca / Mn enriched layer.

[0047] Performance testing verifies the anode's service performance under various operating conditions. A sealed chamber applies pressure exceeding 10 MPa, simulating high-pressure deep-sea environments, and records changes in anode current efficiency. A thermostat maintains low temperatures of -40°C to -60°C to assess the stability of anode surface activity. A dynamic surge impact device simulates extreme wave conditions to detect the tendency of surface coatings to peel. These test modules independently test different environmental factors to ensure the anode maintains excellent service performance under various extreme conditions.

[0048] Through the above steps, composite electromagnetic field continuous casting achieves uniform refinement of the anode matrix structure, solving the problem of intergranular corrosion caused by coarse intermetallic compounds at the grain boundaries in traditional casting processes. Femtosecond laser gradient activation treatment significantly enhances the electrochemical activity and corrosion resistance of the anode surface by introducing a three-dimensional conductive network formed by nanopores and Sn@Ag core-shell particles. Optimizing composite electromagnetic field parameters and laser processing technology achieves a coordinated match between matrix and surface modification, solving the dilemma of the "matrix optimization-surface modification" technical route being separated, and significantly improving the service performance of the anode in extreme environments such as the deep sea and polar regions.

[0049] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A magnesium alloy sacrificial anode and a production method thereof, characterized in that: The following steps are involved: S1. Composite electromagnetic field continuous casting S1a, raw material pretreatment, using high-purity magnesium ingot as the base material, adding Ca, Mn and Ag, smelting under argon protection, and refining and degassing the melt with hexachloroethane; S1b, electromagnetic field application, during the casting process, an alternating magnetic field and an electrostatic field are applied, the frequency of the alternating magnetic field is 50-100Hz, the magnetic induction intensity is 0.3-0.5T, the field strength of the electrostatic field is 15-20kV / m, and the direction is parallel to the ingot axis; under the action of the magnetic field, the melt generates vortex stirring 120-150 times per minute, and the electric field drives Ca 2 +、Mn 2 + Directed migration towards the mold end, forming a Ca / Mn enriched layer with a thickness of 200-300nm on the ingot surface; S2, Femtosecond Laser Gradient Activation Treatment S2a, surface pretreatment, the ingot is CNC turned to a surface roughness of Ra ≤ 0.8 μm, ultrasonically cleaned with acetone and then dried with nitrogen purge; S2b, laser activation, using a femtosecond laser with a wavelength of 1030 nm for gradient activation treatment, with a pulse width of 350 fs, a repetition rate of 100 kHz, a spot diameter of 30 μm, a scanning speed of 2000 mm / s, and an overlap rate of 40%; layered processing to produce a pyramidal base and nanopores, wherein the pyramidal base has a height of 20-30 μm, and the nanopore is located at the top of the pyramidal base and has an aperture of 50-100 nm; S2c, in-situ conductive layer generation: spray an ethanol suspension containing Sn@Ag core-shell particles on the laser processing area, use the laser thermal effect to make the local temperature reach 800-1000℃, and the Sn@Ag core-shell particles are melted and embedded in the root of the cone to form a three-dimensional conductive network, and the surface resistance is reduced to 0.8-1.2Ω.

2. The production method according to claim 1, characterized in that In the step S1a, 0.5-1.2 wt% Ca, 0.3-0.6 wt% Mn and 0.1-0.3 wt% Ag are added to a high-purity magnesium ingot, and the ingot is heated to 720-750° C. under argon protection to form a melt.

3. The production method according to claim 1, characterized in that During the execution of step S1, forming control is performed, and the forming control is specifically configured as follows: The casting speed was controlled at 0.8-1.2 m / min, the cooling water flow was adjusted to 80-120 L / min, the temperature gradient was maintained at 15-20° C. / cm, and an ingot with a diameter of 150 mm was obtained.

4. The production method according to claim 1, characterized in that In step S1b, when the frequency of the alternating magnetic field is set to 80-100 Hz, the grain size inside the ingot is refined to 15-20 μm, and the segregation index is reduced to below 0.15; When the direction of the electrostatic field is 10°-30° to the ingot axis, Ca 2 +、Mn 2 + migration path is regulated, and the uniformity of the surface Ca / Mn enriched layer is improved.

5. The production method according to claim 1, characterized in that In step S2b, the layered processing is divided into two steps. The power of the first layer is 8W, forming a cone base with a height of 20-30 μm. The power of the second layer is increased to 12W, generating nanopores with an aperture of 50-100 nm at the top of the cone.

6. The production method according to claim 5, characterized in that When the power of the second layer is increased to 15W, nanopores with higher porosity are generated at the top of the cone.

7. The production method according to claim 1, characterized in that After executing step S1, execute step S3; S3, performance testing S3a, applying a pressure of more than 10 MPa in a closed chamber to record the changes in anode current efficiency; S3b, setting a low temperature environment of -40°C to -60°C in a thermostat to evaluate the stability of the anode surface activity; S3c, simulate extreme wave conditions through a dynamic surge impact device to detect the peeling tendency of the surface coating.

8. A magnesium alloy sacrificial anode, characterized in that: The anode is prepared by the production method according to any one of claims 1 to 7, and the internal structure is composed of fine and uniform grains with a grain size of 15-20μm and a segregation index of less than 0.15; the surface is covered with a Ca / Mn enriched layer with a thickness of 200-300nm, which is tightly bonded to the substrate and has no cracks or defects at the interface; the surface is treated with a femtosecond laser to form a gradient structure, including a cone base with a height of 20-30μm and nanopores with a pore size of 50-100nm, and Sn@Ag core-shell particles are embedded in the root of the cone to form a three-dimensional conductive network with a surface resistance of 0.8-1.2Ω.

9. The magnesium alloy sacrificial anode according to claim 8, characterized in that: The particle size of Sn@Ag core-shell particles is 200-500nm. After being embedded in the root of the cone, the conductive network formed has a close bonding relationship with the cone base and the nanopores.

10. The magnesium alloy sacrificial anode according to claim 8, characterized in that: The transition area between the cone base and the nanopores exhibits a gradient change feature, which alleviates the thermal stress concentration problem caused by the difference in thermal expansion coefficient.

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