Preparation method of buried steel pipeline Zn-Mg-Al-Mn sacrificial anode material with improved smelting process

Abstract

The invention discloses a preparation method of a buried steel pipeline Zn-Mg-Al-Mn sacrificial anode material for improving a smelting process in the technical field of metal corrosion protection, and the core of the method is that a brand new prepared nitrogen-sulfur co-doped carbon nanocage loaded nano zinc oxide and magnesium silicate heterojunction composite nanomaterial is used as a modifier; the preparation method comprises the following steps: preheating, mixing and wrapping with magnesium, aluminum and manganese metal raw materials, adding into molten zinc liquid, uniformly dispersing a modifier and alloy elements through multi-stage temperature control smelting, carrying out argon refining, standing, casting, and carrying out surface treatment and low-temperature stabilization heat treatment on a casting to finally prepare the high-performance sacrificial anode material. According to the preparation method, the multifunctional nano modifier is combined with a simplified smelting process, the alloy structure is remarkably refined, and the corrosion process is actively regulated and controlled, so that the sacrificial anode which is excellent in electrochemical performance, uniform in dissolution and long in service life is prepared, and the sacrificial anode is suitable for efficient and long-acting cathode protection of a buried steel pipeline.

Description

Technical Field

[0001] This invention relates to the field of metal corrosion protection technology, specifically to an improved smelting process for preparing Zn-Mg-Al-Mn sacrificial anode materials for buried steel pipelines. Background Technology

[0002] Sacrificial anode cathodic protection technology is one of the key protective measures to ensure the long-term safe operation of buried steel pipelines and prevent corrosion and leakage. This technology electrically connects a more negatively charged metal to the protected steel pipeline, forming a corrosion galvanic cell in the soil electrolyte. This causes the anode material to preferentially corrode and dissolve, thereby continuously providing a protective current to the pipeline, thus cathode-polarizing it to a corrosion-free state. Ideal sacrificial anode materials should possess the following characteristics: a sufficiently negative and stable driving potential, high current efficiency, uniform corrosion dissolution morphology, good casting and processing performance, and long-term stability to adapt to complex soil environments. Currently, the sacrificial anodes widely used in engineering mainly include three major series: magnesium-based, zinc-based, and aluminum-based. Magnesium-based anodes have high driving potentials but suffer from severe self-corrosion, often resulting in low current efficiency. Aluminum-based anodes have large theoretical capacitances but are prone to passivation in soil, leading to unstable performance. Traditional zinc-based anodes, such as high-purity zinc or zinc-aluminum-cadmium alloys, while stable and with high current efficiency, have relatively positive driving potentials, which reduces their protective effect in soil environments with high resistivity, and cadmium-containing formulations pose environmental toxicity issues. Therefore, developing a new type of sacrificial anode material that combines a more negative potential, high efficiency, and excellent environmental adaptability has always been an important research direction in the field of pipeline corrosion protection.

[0003] To improve the performance of zinc-based anodes, researchers have explored modification through multi-element alloying. Adding magnesium and aluminum to zinc is considered an effective strategy. Magnesium shifts the alloy's potential negatively, increasing the driving force, and the resulting intermetallic compounds help refine the grains. Aluminum improves the alloy's fluidity and casting properties, and positively influences the morphology of corrosion products. Furthermore, trace amounts of manganese have been shown to enhance the alloy's corrosion resistance in sulfur-containing media. However, simple compositional adjustments face limitations: alloying elements tend to segregate during solidification, forming coarse second phases. This can lead to uneven dissolution of the anode during service, inducing localized pitting corrosion and premature failure, and may also exacerbate self-corrosion due to micro-galvanic corrosion, reducing current efficiency. While subsequent complex heat treatment processes can improve microstructure uniformity to some extent, this undoubtedly increases production costs and process complexity, making it difficult to meet the cost control requirements of large-scale industrial applications.

[0004] In recent years, the rise of nanomaterials and nanotechnology has provided new ideas for the modification of metallic materials. Introducing nanoparticles as reinforcing phases or modifiers into the metal matrix is ​​expected to significantly refine grains and change phase distribution at the microscale, thereby improving the overall mechanical and electrochemical properties of the material. However, applying this approach to the preparation of sacrificial anode materials still faces significant challenges. On the one hand, nanoparticles have a large specific surface area and high surface energy, making them prone to agglomeration in molten metals, making uniform dispersion difficult. These agglomerates can even become defects and corrosion initiation points. On the other hand, current research mainly focuses on simple physical mixing of single nanoparticles, which has limited regulatory effect on the corrosion process and a single mechanism, failing to achieve multi-dimensional and active regulation of anodic dissolution behavior. Therefore, how to design a novel nanomodifier that is well-compatible with the melt and possesses multiple synergistic mechanisms, and integrate it into zinc-based alloys through a simple, efficient, and easily industrialized smelting process, thereby overcoming the performance limitations of existing sacrificial anode materials, has become a pressing technical problem in this field. This invention is proposed against this background. Summary of the Invention

[0005] The purpose of this invention is to provide an improved smelting process for preparing Zn-Mg-Al-Mn sacrificial anode materials for buried steel pipelines. This method solves the technical problem that existing traditional zinc-based sacrificial anode materials for buried steel pipelines suffer from poor macroscopic electrochemical performance due to the tendency of alloying elements to segregate and poor microstructure uniformity during the smelting process.

[0006] The present invention achieves the above objectives through the following technical solutions: A method for preparing Zn-Mg-Al-Mn sacrificial anode material for buried steel pipelines with an improved smelting process includes the following steps: S1. Zinc ingots are placed in a graphite crucible and then placed in a medium-frequency induction melting furnace. After evacuation, argon gas is introduced. The temperature is raised to 550-600℃ to obtain zinc melt. Nitrogen-sulfur co-doped carbon nanocage-supported nano-zinc oxide and magnesium silicate heterojunction are placed in another crucible and preheated in an oven at 240-260℃. The preheated nitrogen-sulfur co-doped carbon nanocage-supported nano-zinc oxide, magnesium silicate heterojunction, magnesium chips, aluminum chips, and manganese sheets are mixed to obtain a metal mixture. The metal mixture is wrapped with zinc foil to obtain an alloy package. S2, using a preheated graphite bell jar, press the alloying ladle into the bottom of the zinc melt and stir until the contents of the ladle are completely dissolved; then, raise the furnace temperature to 630-650℃ and hold it there. S3. Insert the graphite degassing gun into the bottom of the melt, introduce argon gas for rotary spraying refining, turn off the gas after refining, and remove the gun; let the melt temperature drop to 545-555℃ and stand to obtain a settled melt. S4. Preheat the mold to 145-155℃; pour the settled melt into the preheated mold, cool it to room temperature in air, and then demold to obtain the casting; perform surface sandblasting on the casting to remove oxide scale; obtain the pretreated casting; perform low-temperature stabilization treatment on the pretreated casting in an air-circulating oven at 175-185℃.

[0007] In this invention, the core mechanism for preparing Zn-Mg-Al-Mn sacrificial anode materials for buried steel pipelines with improved smelting process lies in "introducing a multifunctional nano-heterogeneous core through external assistance to drive the ultra-fine solidification structure of the melt and the active regulation of the micro-region electrochemical environment after solidification," thereby achieving a high-performance alloy with an extremely simplified process. First, the pre-synthesized high-stability composite nano-modifier is fully preheated to completely remove the moisture and gas physically adsorbed on its surface, preventing it from splashing in the melt or agglomerating due to gas encapsulation when added to the high-temperature zinc melt. It is then mixed with magnesium shavings, aluminum shavings, and manganese flakes and wrapped with zinc foil to utilize the "explosive effect" of the rapid melting and dispersion of zinc foil in the melt, as well as the local micro-convection generated when the metal shavings melt, to jointly promote the effective carrying of the low-density nano-modifier particles into the depth of the melt and achieve initial physical dispersion. After the alloying ladle is pressed into the melt, the metal components rapidly melt and dissolve under the combined action of electromagnetic stirring and manual agitation. The nano-modifier particles, thanks to their nitrogen-sulfur-doped carbon shells and excellent wettability with the melt, are uniformly suspended and distributed within it. The subsequent multi-stage temperature-controlled holding process is crucial: in the first medium-temperature holding stage, the main purpose is to provide sufficient kinetic conditions for alloying elements such as magnesium, aluminum, and manganese to diffuse and dissolve into the zinc melt, achieving initial homogenization of the composition, while simultaneously allowing the nanoparticles to further fuse with the melt interface. The second, higher-temperature holding stage aims to utilize the higher atomic thermal energy to completely break up any potential nanoparticle agglomerates and promote a highly thermodynamically homogeneous state in the alloy melt, preparing the microstructure for the subsequent solidification process. The subsequent rotary argon refining process works by using the physical action of rising inert bubbles to efficiently adsorb and remove suspended micro-oxide inclusions and dissolved hydrogen from the melt, thereby significantly purifying the melt and reducing impurity phases that become corrosion initiation points after solidification. The settling process allows the purified melt to become calmer and more uniform in temperature, which is beneficial for smooth filling during the final casting. After being poured into the preheated mold, the numerous uniformly distributed nano-modifier particles become an extremely effective heterogeneous nucleation substrate, significantly reducing the nucleation undercooling of the zinc matrix and promoting an ultra-refinement transformation of the solidification structure, resulting in a uniform microstructure with fine grains and a dispersed second phase. The final low-temperature stabilization treatment does not involve a significant phase transition, but rather uses prolonged holding at medium to low temperatures to relax and release the microscopic internal stresses and lattice distortions formed during casting, stabilizing the atomic arrangement at grain boundaries and strengthening the bond between the nano-modifier and the matrix interface. This overall improves the stability and consistency of the electrochemical performance of the anode material, ensuring minimal performance degradation during long-term service.

[0008] According to a preferred embodiment of the present invention, in step S1, the preheating time in the oven at 240-260°C is 1-2 hours.

[0009] According to a preferred embodiment of the present invention, in step S2, the furnace temperature is raised to 630-650°C and held for 15-20 minutes.

[0010] According to a preferred embodiment of the present invention, in step S3, the melt temperature is reduced to 545-555°C and the settling time is 30-40 minutes.

[0011] According to a preferred embodiment of the present invention, in step S4, the low-temperature stabilization treatment time is 4-6 hours.

[0012] According to a preferred embodiment of the present invention, the preparation steps of the nitrogen-sulfur co-doped carbon nanocage-supported nano-zinc oxide and magnesium silicate heterojunction include: A1. In an argon atmosphere glove box, L-phenylalanine and citric acid are added to a polytetrafluoroethylene liner; deionized water is added and stirred to obtain a solution; an ethanol solution of 2,2'-dithiodibenzoic acid is added; stirring is continued to obtain a mixed solution. A2. Place the mixed solution in a reaction vessel; place the reaction vessel in a forced-air drying oven and heat to 195-205℃ and maintain the temperature; after the reaction is completed, allow it to cool naturally to room temperature to obtain a suspension; transfer the suspension to a high-speed centrifuge tube and centrifuge to obtain a solid product; wash the solid product with a mixed solvent of ethanol / acetone to obtain a precipitate; redisperse the precipitate in anhydrous dimethylformamide and sonicate to obtain dispersion A; In step A3, a mixed aqueous solution containing zinc nitrate and magnesium nitrate was added to dispersion A under ice-water bath and continuous stirring to adjust the pH to 9-10. The mixture was stirred at 58-62°C. After centrifugation, the intermediate was washed with water and ethanol to obtain a loaded hydroxide intermediate. The loaded hydroxide intermediate was redispersed in ethanol, and tetraethyl silicate was added dropwise under stirring, followed by deionized water. The reaction was continued at 58-62°C to obtain a reaction mixture. The reaction mixture was centrifuged and washed with ethanol to obtain precipitate B. A4. Place precipitate B in an alumina crucible and put it into a tube furnace; under an argon protective atmosphere, heat to 295-305℃ and hold; heat to 850-950℃ and calcine; after calcine, cool to room temperature with the furnace under an argon atmosphere to obtain powder; grind the powder in a mortar and sieve.

[0013] In this invention, the preparation of the nitrogen-sulfur co-doped carbon nanocage-supported nano-zinc oxide and magnesium silicate heterojunction follows a precise and controllable chemical reaction path of "carrier construction - active component loading - structure crystallization". Its core lies in achieving the composite of each component at the nanoscale and the construction of a specific structure through molecular design and stepwise reaction. The first step involves using L-phenylalanine and citric acid as precursors to undergo complex dehydration, condensation, and carbonization reactions under high-temperature hydrothermal conditions. Phenylalanine provides a nitrogen source and part of the carbon skeleton, and its benzene ring structure helps to form graphitized segments. Citric acid serves as the main carbon source and promotes the formation of hydrophilic oxygen-rich groups. Together, they self-assemble to form the initial carbon nanoparticles. The introduced dithiobenzoic acid decomposes during the reaction, providing a sulfur source and additional aromatic structural segments. Sulfur atoms are doped into the forming carbon skeleton in the form of thiophene, while nitrogen atoms exist in the form of pyridine nitrogen, graphitic nitrogen, etc. This nitrogen-sulfur co-doping significantly alters the electron cloud distribution of the carbon material, enhancing its surface polarity and chemical activity. Finally, under hydrothermal self-assembly and solvothermal effects, nitrogen-sulfur co-doped carbon nanocages with hollow porous structures are formed. The second step involves introducing a mixed solution of zinc and magnesium ions into the aforementioned carbon nanocage dispersion system under low-temperature ice bath conditions. Subsequently, in an alkaline environment, the zinc and magnesium ions undergo simultaneous hydrolysis, uniformly co-precipitating into amorphous composite hydroxides of zinc hydroxide and magnesium hydroxide. These hydroxides then firmly adhere to the inner and outer surfaces of the carbon nanocages through electrostatic adsorption and surface coordination. The third step involves dispersing this intermediate loaded with composite hydroxides in ethanol, adding tetraethyl silicate and introducing a trace amount of water. The tetraethyl silicate undergoes a slow hydrolysis-condensation reaction in the ethanol-water system, generating silica oligomers that chemically react with the magnesium and zinc hydroxides on the surface, gradually encapsulating and depositing to form a composite precursor with zinc-magnesium hydroxide as the core and amorphous zinc-magnesium silicate as the outer shell. The fourth step involves programmed calcination under a protective atmosphere. At lower temperatures, the organic components and water of crystallization in the precursor are completely decomposed and removed. At higher temperatures, profound solid-state chemical reactions and phase transformations occur: zinc hydroxide directly decomposes and crystallizes into zinc oxide, while magnesium hydroxide reacts with amorphous silicates at high temperatures to form crystalline magnesium silicate. Since the reaction begins at the interface of the two phases in close contact, a heterojunction structure is ultimately formed in situ on the surface of the carbon nanocage, where nano-zinc oxide and nano-magnesium silicate particles are intercalated and bonded at the interface. Throughout this process, the carbon nanocage not only acts as a dispersing framework to prevent nanoparticle aggregation, but its doped nitrogen and sulfur atoms also become active sites, strengthening the electronic coupling with the metal oxides. This results in a structurally stable, synergistically composed, multifunctional nanocomposite.

[0014] According to a preferred embodiment of the present invention, in step A1, the stirring time is 1-2 hours.

[0015] According to a preferred embodiment of the present invention, in step A2, the temperature is raised to 195-205°C and held for 12-14 hours.

[0016] According to a preferred embodiment of the present invention, in step A3, the stirring time at 58-62°C is 2-4 hours.

[0017] According to a preferred embodiment of the present invention, in step A4, the temperature is raised to 295-305°C and held for calcination for 1-2 hours.

[0018] The beneficial effects of this invention are as follows: The improved sacrificial anode material preparation method provided by this invention, through the introduction of a newly designed composite nano-modifier and optimization of the preparation process, has produced significant and multifaceted positive technical effects, fundamentally improving the overall performance and application value of the final product.

[0019] First, the most crucial effect of this invention lies in its thorough improvement of the alloy's microstructure and the realization of proactive and intelligent control over the corrosion process. By introducing a composite modifier—a nitrogen-sulfur co-doped carbon nanocage supporting a heterostructure of nano-zinc oxide and magnesium silicate—the common problems of easy agglomeration of alloying elements and coarse second phases in traditional smelting processes are successfully solved. In this modifier, the nitrogen-sulfur co-doped carbon nanocage serves as an ideal carrier, and the heteroatoms on its surface significantly enhance the wettability with the zinc melt, ensuring that nanoparticles can enter the alloy matrix in a highly dispersed state, becoming a large number of uniformly distributed heterogeneous nucleation cores, thereby achieving ultra-fine grains in the final as-cast state. More importantly, the supported nano-zinc oxide and magnesium silicate heterostructure is not an inert additive; it plays the role of a "micro-corrosion regulator" during anodic service. The built-in electric field formed at the heterojunction interface guides the distribution of corrosion current, promoting uniform dissolution; nano-zinc oxide can serve as a slow-release zinc ion source, fine-tuning the local environment; while silicate ions provided by the decomposition of magnesium silicate migrate to the surface of the protected steel pipe, helping to form a denser and more adhesive protective corrosion product film. This multi-synergistic mechanism of "carrier dispersion, heterogeneous nucleation, electric field guidance, and ion slow release" represents a systematic optimization from microscopic physical structure to electrochemical behavior, endowing the material with unprecedented uniform dissolution characteristics and stable protective capabilities.

[0020] Secondly, based on the aforementioned innovations in microstructure and mechanism of action, the sacrificial anode material prepared by this method achieves a breakthrough improvement in macroscopic electrochemical performance and long-term service life. The open-circuit potential of the material is significantly negatively shifted compared to traditional high-purity zinc anodes, providing stronger cathodic protection. Its current efficiency is significantly improved because the uniform and refined microstructure greatly reduces localized micro-cell corrosion caused by compositional inhomogeneity or coarse phases, resulting in a significant reduction in the anode's self-corrosion rate, allowing electrons to be used more effectively for pipeline protection. In long-term electrolysis tests simulating buried soil environments, the anode exhibits an extremely stable dissolution trajectory, forming a uniform layered consumption morphology on the surface, completely avoiding the hidden dangers of localized deep pits or intergranular corrosion that could lead to premature anode fracture and failure. Simultaneously, the active silicon component introduced by the modifier gives the anode system certain environmental adaptability characteristics. Even in complex soils with varying compositions, it can maintain a highly efficient and durable protective effect by promoting the formation of a stable protective film on the pipeline surface, greatly extending the anode's service life and the pipeline's safety protection cycle.

[0021] Finally, the technical advantages of this invention are also prominently reflected in the innovation, economy, and reliability of the preparation process itself, achieving a perfect balance between high performance and industrial-scale production. This invention creatively adopts a strategy of "pre-synthesis of complex modifiers and extreme simplification of the main alloy melting process." The most technically complex tasks of nanocomposite synthesis and structure control are concentrated in the independent chemical preparation stage of the modifier, while the preparation of the main alloy is reduced to four clear and concise steps: pretreatment, melting and alloying, refining and settling, and post-casting treatment. This process eliminates reliance on expensive equipment and eliminates the need for complex multi-stage heat treatments used in traditional processes to improve microstructure, thus significantly reducing production energy consumption, time costs, and stringent requirements for operational skills. It offers a wide process window and high stability in repeated production. This design makes it possible to mass-produce high-performance sacrificial anodes without significantly increasing manufacturing costs, resulting in significant overall economic benefits and strong market competitiveness and promotion potential. Detailed Implementation

[0022] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0023] Example 1: Preparation of the carrier precursor: In an argon-filled glove box, accurately weigh 2.00 g of L-phenylalanine and 1.00 g of citric acid, and add them to a 100 mL polytetrafluoroethylene-lined high-pressure reactor. Add 40 mL of deionized water with a resistivity of 18.2 MΩ·cm, place the entire system on a magnetic stirrer, and stir at 500 rpm for 30 min at room temperature (25°C) until the solid is completely dissolved, forming a clear, transparent, colorless solution.

[0024] Sulfur source introduction and mixing: Using a 100 μL microsyringe, slowly inject 0.15 mL of a 10 mg / mL solution of 2,2'-dithiodibenzoic acid in ethanol (solvent: anhydrous ethanol) into the above clear solution. The solution turns slightly yellow. Continue stirring under the same conditions (25 °C, 500 rpm) for 90 min to ensure thorough mixing and pre-assembly of the precursor, obtaining the final mixed solution.

[0025] Hydrothermal synthesis of carbon nanocages: A polytetrafluoroethylene (PTFE) liner containing a mixed solution was sealed within a stainless steel high-pressure reactor. The reactor was placed in a preheated forced-air drying oven, and the temperature was programmed to rise from room temperature to 200°C at a rate of 3°C / min, and maintained at 200°C for 13 hours for hydrothermal carbonization and doping. After the reaction, the power to the drying oven was turned off, and the reactor was allowed to cool naturally to room temperature (approximately 25°C). The reactor was then opened, yielding a brownish-red colloidal suspension.

[0026] Separation and purification of the product: The entire suspension was transferred to a 50 mL high-speed centrifuge tube and centrifuged at 15,000 rpm for 20 min. The supernatant was carefully decanted and discarded. 30 mL of a pre-prepared ethanol and acetone mixture (volume ratio 1:1) was added to the precipitate, and the precipitate was redispersed using a vortex mixer. The mixture was then centrifuged again at 15,000 rpm for 20 min, and the supernatant was discarded. This washing process was repeated three times. Finally, the washed brownish-black precipitate was redispersed in 30 mL of anhydrous N,N-dimethylformamide (DMF) and ultrasonically treated in a 300 W ultrasonic cleaner for 60 min to obtain a homogeneous and stable black carbon nanocage dispersion A.

[0027] Hydroxide coprecipitation loading: Take a 250 mL three-necked flask, fill it with dispersion A, and place it in an ice-water bath. Attach a mechanical stirrer, a constant-pressure dropping funnel, and a thermometer to the flask. Turn on the stirrer and set the speed to 800 rpm. Slowly add (approximately 1 drop / second) 5.0 mL of a mixed aqueous solution (this solution is composed of equal volumes of 0.1 mol / L zinc nitrate aqueous solution and 0.1 mol / L magnesium nitrate hexahydrate aqueous solution, wherein Zn...) to the vigorously stirred dispersion A through the constant-pressure dropping funnel. 2+ With Mg2+ The molar ratio was 1:1. After the addition was complete, stirring continued in an ice-water bath for 15 minutes. Subsequently, while continuing to stir, a 25% (w / w) ammonia solution was slowly added dropwise using a dropper, and the pH value of the system was monitored in real time using precision pH paper until the pH stabilized at 9.5. The ice-water bath was removed, and the three-necked flask was transferred to an oil bath preheated to 60°C. The reaction was carried out for 90 minutes at 60°C and 800 rpm under a reflux condenser.

[0028] Intermediate separation and silicon source hydrolysis: After the reaction was complete, the mixture in the three-necked flask was transferred to a centrifuge tube and centrifuged at 12,000 rpm for 15 min. The supernatant was discarded. The precipitate was first dispersed with 30 mL of deionized water and washed twice by centrifugation, then washed twice by centrifugation with 30 mL of anhydrous ethanol to obtain a grayish-white intermediate precipitate loaded with zinc-magnesium complex hydroxide. The intermediate was redispersed in 30 mL of anhydrous ethanol and transferred to a clean 100 mL round-bottom flask. The flask was placed in a 60 °C oil bath and equipped with a magnetic stirrer and a condenser. While stirring at 400 rpm, 0.50 mL of tetraethyl orthosilicate (TEOS) was slowly added dropwise (approximately one drop every 30 seconds) using a microsyringe. After the addition was complete, 1.0 mL of deionized water was added to the system to initiate hydrolysis. The oil bath temperature was maintained at 60 °C, and the reaction was continuously stirred for 5 h.

[0029] Precursor collection and high-temperature calcination: After the silicon source hydrolysis reaction, the mixture in the round-bottom flask was transferred to a centrifuge tube and centrifuged at 12000 rpm for 15 min. The supernatant was discarded, and the precipitate was washed three times with 30 mL of anhydrous ethanol by centrifugation to obtain a light gray precipitate B. Precipitate B was transferred to a 50 mL alumina crucible, partially covered with the crucible lid, and placed in the center of the isothermal zone of a horizontal tube furnace. The furnace was closed, the gas line was connected, and high-purity argon gas (purity ≥99.999%) was introduced at a flow rate of 100 sccm for purging for 30 min. Subsequently, under the protection of continuous argon gas at the same flow rate, the tube furnace temperature program was started: In the first stage, the temperature was increased from room temperature to 300℃ at a rate of 5℃ / min and held at 300℃ for 90 min; in the second stage, the temperature was increased from 300℃ to 900℃ at the same rate of 5℃ / min and calcined at 900℃ for 3 h. After calcination, heating was stopped, and the tube furnace was allowed to cool naturally to room temperature (below 50°C) while continuously purging with argon gas. The furnace chamber was opened, the crucible was removed, and a fluffy black powder was obtained.

[0030] Final treatment of the modifier: Transfer the above black powder to an agate mortar and gently grind it manually for 10 minutes. Then, sieve it using a 500-mesh (approximately 25 μm aperture) standard sieve and collect the fine powder that passes through the sieve. This powder is the nitrogen-sulfur co-doped carbon nanocage-supported nano zinc oxide and magnesium silicate heterojunction, which is then placed in a desiccator for later use.

[0031] Preparation of Zn-Mg-Al-Mn sacrificial anode materials.

[0032] Smelting Preparation and Material Pretreatment: High-purity zinc ingots (purity ≥99.995%) were selected. 9827g of zinc ingots were accurately weighed using an electronic balance and placed in a clean graphite crucible. Alloying Additives Preparation: 100.0g of magnesium shavings (purity ≥99.95%), 50.0g of aluminum shavings (purity ≥99.9%), and 8.0g of metallic manganese flakes (purity ≥99.9%) were weighed using an electronic balance. 15.0g of nitrogen-sulfur co-doped carbon nanocage-supported nano-zinc oxide and magnesium silicate heterojunctions were then weighed. The nitrogen-sulfur co-doped carbon nanocage-supported nano-zinc oxide and magnesium silicate heterojunctions were placed in a small corundum crucible and placed in a preheated 250℃ forced-air drying oven for 90 minutes to completely remove adsorbed water. After removal, they were slightly cooled in a desiccator. The baked CNM-01 powder was initially mixed evenly with the weighed magnesium shavings, aluminum shavings, and manganese flakes in a dry environment using a glass rod. Then, it was divided into three equal portions and tightly wrapped with zinc foil of 0.05 mm thickness to form three cylindrical alloying packages.

[0033] Matrix melting and protective atmosphere establishment: Place the graphite crucible containing zinc ingots into the coil of the medium-frequency induction melting furnace and seal the furnace chamber. Start the vacuum pump to evacuate the pressure inside the furnace to below 10 Pa. Close the vacuum valve and open the valve of the high-purity argon gas cylinder (purity ≥99.999%) to fill the furnace chamber with argon gas until the pressure is slightly higher than atmospheric pressure (approximately 0.05 MPa), forming a protective atmosphere. Turn on the medium-frequency induction power supply, set the target temperature to 580℃, and begin heating. Once the temperature reaches 580℃ and stabilizes, the zinc ingots will completely melt, forming a mirror-like, bright zinc melt.

[0034] Multi-stage temperature-controlled alloying: Using a graphite bell jar preheated to 300℃, clamp an alloying ladle, quickly open the charging port on the furnace lid, and rapidly immerse the bell jar and alloying ladle into the bottom of the molten zinc, stirring gently in a circular motion for about 2 minutes, until the zinc foil is completely melted, there is no solid residue inside the ladle, and the surface of the melt does not churn violently. Close the charging port. After the melt temperature stabilizes again at 460℃, add the second and third alloying ladles using the same procedure. After all alloying ladles have been added, set the control temperature of the induction melting furnace to 640℃, with a heating rate of 3℃ / min. After the melt temperature reaches 640℃, hold at this temperature for 17 minutes. The entire alloying process is carried out under argon protection.

[0035] Melt Refining and Settling: After the holding period, insert a preheated (500℃) porous graphite degassing lance into the bottom of the melt through a dedicated hole on the furnace cover. Open the argon valve and introduce high-purity argon into the melt at a constant flow rate of 0.5L / min, while manually rotating the lance slowly to evenly disperse the argon into the melt as small bubbles. This rotary spray refining process lasts for 8 minutes. After refining, first shut off the argon, then slowly remove the lance from the melt. Lower the furnace temperature to 550℃ and allow the melt to cool naturally to this temperature. Once the melt temperature reaches 550℃, allow it to settle at this temperature for 35 minutes to fully homogenize the melt and allow any small inclusions to rise to the surface.

[0036] Casting: During the settling period of the melt, prepare the casting mold. Using a mold with internal dimensions conforming to the standard sacrificial anode specifications, place it in a preheating furnace and heat it to 150°C, holding it at that temperature for at least 1 hour. After settling, open the pouring spout at the bottom of the melting furnace, allowing the 550°C melt to flow smoothly into the preheated 150°C mold. Control the pouring speed to ensure the melt rises smoothly within the mold, avoiding splashing and turbulence.

[0037] Cooling and Post-treatment: After casting, allow the mold containing the casting to cool naturally in room temperature air until fully solidified, then continue cooling to room temperature (approximately 25°C). Demold to obtain a preliminary anodized casting. Use a sandblasting machine to sandblast all surfaces of the casting to thoroughly remove casting oxide scale and any possible surface sand, obtaining a pre-treated casting with a smooth surface and metallic color.

[0038] Low-temperature stabilization heat treatment: Place the sandblasted casting into a preheated forced-air circulation oven at 180℃. Close the oven door and maintain the temperature at 180℃ for 5 hours. After treatment, turn off the oven power and allow the casting to cool to below 80℃ inside the oven before removing it and placing it in a dry environment.

[0039] Example 2 is implemented in the same manner as Example 1, except that 2.00 g of L-phenylalanine and 1.00 g of citric acid are weighed and placed in a polytetrafluoroethylene liner in an argon glove box. 40 mL of deionized water is added, and the mixture is stirred at room temperature for 30 min until clear. 0.15 mL of a 10 mg / mL ethanol solution of 2,2'-dithiodibenzoic acid is added, and stirring continues for 90 min. The mixture is sealed in a high-pressure reactor and placed in a forced-air drying oven, where the temperature is increased to 200°C at 3°C / min and maintained for 12 h. After natural cooling, the resulting suspension is centrifuged at 15000 rpm for 20 min, the supernatant is discarded, and the precipitate is washed three times with 30 mL of a 1:1 v / v ethanol / acetone mixture. The precipitate is redispersed in 30 mL of anhydrous DMF and sonicated for 60 min to obtain dispersion A. 5.0 mL of Zn is added dropwise to dispersion A under an ice-water bath and stirring at 800 rpm.2+ With Mg 2+ A 1:1 molar ratio of mixed nitrate solutions (all concentrations 0.1 mol / L) was prepared, and ammonia was added dropwise to adjust the pH to 10.0. The ice bath was removed, and the mixture was reacted in a 60°C oil bath for 120 min. After centrifugation, the intermediate was washed twice with water and twice with ethanol to obtain the intermediate. This intermediate was redispersed in 30 mL of ethanol, and 0.40 mL of LTEOS was added dropwise with stirring in a 60°C oil bath. Then, 1.0 mL of deionized water was added, and the reaction was continued for 5 h. After centrifugation and washing three times with ethanol, precipitate B was obtained. Precipitate B was placed in an alumina crucible and then placed in a tube furnace under 100 sccm of argon protection. The temperature was increased to 300°C at a rate of 5°C / min and held for 90 min, then increased to 870°C at the same rate and held for 3.5 h. The mixture was cooled in the furnace, ground, and passed through a 500-mesh sieve.

[0040] Weigh 9840g of zinc ingots and place them in a graphite crucible. Evacuate to 10Pa, then purge with argon and heat to 575℃ to melt. Weigh 10.0g of CNM-02 and preheat in a 250℃ oven for 90min. Mix with 80.0g of magnesium shavings, 60.0g of aluminum shavings, and 10.0g of manganese flakes. Divide into three portions and wrap with zinc foil. Use a preheated 300℃ graphite bell jar to press the mixture into the bottom of the melt in batches, stirring to dissolve. Heat the melt to 635℃ and hold for 18min. Insert a preheated graphite spray gun and refine with argon gas at a flow rate of 0.5L / min for 7min. Cool the melt to 548℃ and let it stand for 40min. Place a mold preheated to 148℃ below the pouring gate and pour the settled melt into it. Cool to room temperature in air, then demold and sandblast the surface. The casting was placed in a 178℃ air-circulating oven for 4.5 hours and then cooled in the furnace to obtain the finished anode material.

[0041] Example 3 is implemented in the same manner as Example 1, except that 2.00 g of L-phenylalanine and 1.00 g of citric acid are weighed and placed in a polytetrafluoroethylene liner in an argon glove box. 40 mL of deionized water is added, and the mixture is stirred at room temperature for 30 min until clear. 0.15 mL of a 10 mg / mL ethanol solution of 2,2'-dithiodibenzoic acid is added, and stirring continues for 90 min. The mixture is sealed in a high-pressure reactor and placed in a forced-air drying oven, where the temperature is increased to 205 °C at 3 °C / min and maintained for 12 h. After natural cooling, the resulting suspension is centrifuged at 15000 rpm for 20 min, the supernatant is discarded, and the precipitate is washed three times with 30 mL of a 1:1 v / v ethanol / acetone mixture. The precipitate is redispersed in 30 mL of anhydrous DMF and sonicated for 60 min to obtain dispersion A. 5.0 mL of Zn is added dropwise to dispersion A under an ice-water bath and stirring at 800 rpm. 2+ With Mg 2+A 1:1 molar ratio of mixed nitrate solutions (all concentrations 0.1 mol / L) was prepared, and ammonia was added dropwise to adjust the pH to 9.0. The ice bath was removed, and the mixture was reacted in a 60°C oil bath for 90 min. After centrifugation, the intermediate was washed twice with water and twice with ethanol to obtain the intermediate. This intermediate was redispersed in 30 mL of ethanol, and 0.60 mL of LTEOS was added dropwise with stirring in a 60°C oil bath. Then, 1.0 mL of deionized water was added, and the reaction was continued for 5 h. After centrifugation, the intermediate was washed three times with ethanol to obtain precipitate B. Precipitate B was placed in an alumina crucible and then placed in a tube furnace under 100 sccm of argon protection. The temperature was increased to 300°C at a rate of 5°C / min and held for 90 min, then increased to 930°C at the same rate and held for 2.5 h. The mixture was cooled in the furnace, ground, and passed through a 500-mesh sieve.

[0042] Weigh 9850g of zinc ingots and place them in a graphite crucible. Evacuate to 10Pa, then purge with argon and heat to 585℃ to melt. Weigh 20.0g of CNM-03 and preheat in a 250℃ oven for 90min. Mix with 120.0g of magnesium shavings, 30.0g of aluminum shavings, and 6.0g of manganese flakes. Divide into three portions and wrap with zinc foil. Use a preheated 300℃ graphite bell jar to press the mixture into the bottom of the melt in batches, stirring to dissolve. Heat the melt to 645℃ and hold for 15min. Insert a preheated graphite spray gun and refine with argon gas at a flow rate of 0.5L / min for 10min. Cool the melt to 552℃ and let it stand for 30min. Place a mold preheated to 152℃ below the pouring gate and pour the settled melt into it. Cool to room temperature in air, then demold and sandblast the surface. The casting was placed in a 182℃ air-circulating oven for 5.5 hours and then cooled in the furnace to obtain the finished anode material.

[0043] Comparative Example 1 The specific implementation method is the same as in Example 1, except that no composite nano-modifier is added. 9842g of zinc ingot was weighed and placed in a graphite crucible, evacuated to 10Pa, then filled with argon gas, and heated to 460℃ to melt. 100.0g of magnesium shavings, 50.0g of aluminum shavings, and 8.0g of manganese flakes were weighed, mixed, and divided into three portions wrapped in zinc foil. A graphite bell jar preheated to 300℃ was used to press the mixture into the bottom of the melt in batches, stirring to dissolve it. The melt was heated to 640℃ and held for 17 minutes. A preheated graphite spray gun was inserted, and argon gas was sprayed at a flow rate of 0.5L / min for 8 minutes to refine the melt. The melt was cooled to 550℃ and allowed to stand for 35 minutes. A mold preheated to 150℃ was placed below the pouring gate, and the settled melt was poured in. After cooling to room temperature in air, the casting was demolded and the surface was sandblasted. The casting was placed in a 180℃ air-circulating oven for 5 hours and cooled with the furnace to obtain the comparative anode material.

[0044] Comparative Example 2 The specific implementation method is the same as in Example 1, except that ordinary carbon nanocages are used instead of the composite nanomodifier. Preparation of ordinary carbon nanocages: Except for the absence of 2,2'-dithiodibenzoic acid ethanol solution, the preparation steps (hydrothermal treatment, washing, dispersion) are exactly the same as in Example 1. The resulting product is undoped carbon nanocages. 9827g of zinc ingots were weighed and placed in a graphite crucible, evacuated to 10Pa, then purged with argon gas, and heated to 580℃ to melt. 15.0g of the above ordinary carbon nanocages were weighed and preheated in an oven at 250℃ for 90min, mixed with 100.0g of magnesium shavings, 50.0g of aluminum shavings, and 8.0g of manganese flakes, and divided into three portions wrapped in zinc foil. All subsequent melting, refining, settling, casting, and post-treatment process parameters (temperature, time, flow rate, etc.) were kept consistent with those in Example 1 to obtain the comparative anode material.

[0045] Comparative Example 3 The specific implementation method is the same as in Example 1, except that a simple physically mixed nanopowder is used instead of a composite nanomodifier. Preparation of the simple physically mixed nanopowder: Weigh 10.0g of zinc oxide nanopowder with an average particle size of 50nm and 5.0g of magnesium silicate nanopowder with an average particle size of 100nm, place them in a 500mL zirconia ball mill jar, and add 200g of zirconia grinding balls with a diameter of 10mm. Seal and fix the ball mill jar on a planetary ball mill, and dry ball mill at 300rpm for 6h. After ball milling, remove the mixed powder. Weigh 9827g of zinc ingots and place them in a graphite crucible, evacuate to 10Pa, then purge with argon gas, and heat to 580℃ to melt. Weigh 15.0g of the above physically mixed powder, preheat in a 250℃ oven for 90min, mix with 100.0g of magnesium shavings, 50.0g of aluminum shavings, and 8.0g of manganese flakes, divide into three portions, and wrap with zinc foil. All subsequent smelting, refining, settling, casting, and post-treatment process parameters (temperature, time, flow rate, etc.) were kept consistent with those in Example 1 to obtain the comparative anode material.

[0046] Performance testing The above Examples 1-3 and Comparative Examples 1-3 were subjected to performance testing according to the following method, which included the following steps: The present invention conducted a series of standard electrochemical performance tests and macroscopic corrosion morphology observations on the prepared sacrificial anode material to comprehensively evaluate its overall performance.

[0047] All tests were conducted at room temperature (25±2℃). The test samples were wire-cut from the same part (core) of the castings obtained in Examples 1-3 and Comparative Examples 1-3, with dimensions of 10mm×10mm×5mm. The test surfaces were successively polished to a mirror finish using 400#, 800#, and 1500# sandpaper, ultrasonically cleaned with anhydrous ethanol for 5 minutes, and dried with cold air for later use.

[0048] Electrochemical measurements were performed using a classic three-electrode system: the prepared anode sample was used as the working electrode, with an apparent area of ​​1 cm². 2 The remaining parts were encapsulated with epoxy resin; a saturated calomel electrode (SCE) was used as the reference electrode; and a large-area platinum sheet was used as the auxiliary electrode. The electrolyte was a 3.5 wt.% NaCl solution (prepared from analytical grade NaCl and deionized water) simulating a typical buried soil environment, and high-purity nitrogen was purged for 30 minutes before the test to remove oxygen.

[0049] The open-circuit potential test is performed by immersing the working electrode in the electrolyte and then using a high-impedance electrochemical workstation to monitor the change in its potential over time. Once the potential stabilizes (fluctuation less than ±2mV within 30 minutes), it is recorded and continuously monitored for 24 hours to observe the potential stability.

[0050] Constant current discharge testing is the core of evaluating the performance of sacrificial anodes, with the working electrode subjected to 10 mA / cm² discharge. 2 The sample was continuously discharged for 168 hours (7 days) at a constant current density. During this period, the potential of the working electrode relative to the reference electrode was continuously monitored and recorded using a high-precision zero-resistance galvanometer to evaluate the stability of the working potential. After the discharge, the sample was removed, and the surface corrosion products were carefully removed (chemical cleaning with ammonium chromate solution). After rinsing with distilled water and dehydrating with ethanol, the sample was accurately weighed, and its actual capacitance and current efficiency were calculated according to Faraday's law.

[0051] Dissolution morphology analysis was performed by observing the sample surface after constant current discharge using a scanning electron microscope, focusing on evaluating the depth and uniformity of corrosion pits, as well as the presence of localized rot or intergranular corrosion features.

[0052] The long-term immersion weight loss test involves completely immersing the sample in a 3.5 wt.% NaCl solution for 30 days. After the test, the corrosion products are removed according to standard methods and the sample is weighed. The average corrosion rate is then calculated.

[0053] Test results: Table 1: Test results of each embodiment and comparative example

[0054] As shown in Table 1, compared with Comparative Examples 1-3, Examples 1-3 effectively and comprehensively solved the technical problem of poor macroscopic electrochemical performance caused by the easy segregation of alloying elements and poor microstructure uniformity in traditional zinc-based sacrificial anodes by introducing the nitrogen-sulfur co-doped carbon nanocage-supported nano-zinc oxide and magnesium silicate heterostructure composite modifier designed in this invention and its matching smelting process. The solution to this problem has been directly and strongly confirmed in several key performance indicators.

[0055] First, regarding the potential performance that determines the driving force of cathodic protection, the open-circuit potentials of all three embodiments are significantly negative compared to all comparative examples. Example 1 reaches -1.138V, while Comparative Example 1 is only -1.092V. This is directly due to the fundamental improvement in the ultra-fine alloy structure and micro-electrochemical uniformity after the introduction of the modifier, reducing localized cathode regions formed by component segregation and resulting in a more negative and uniform electrode potential for the overall anode. More importantly, under constant current discharge conditions simulating actual operation, the operating potential fluctuation range of Examples 1-3 (±0.015V to ±0.020V) is much smaller than that of Comparative Examples 1-3 (±0.028V to ±0.035V). This extremely high potential stability is the most direct manifestation of the highly uniform anode structure and the stable and controllable dissolution process, fundamentally overcoming the defects of large potential fluctuations and unstable protection effects caused by the uneven structure of traditional alloys.

[0056] Secondly, regarding the core indicators characterizing anode utilization efficiency and lifespan, the current efficiency (93.8-95.2%) and actual capacitance (768.9-780.5 A·h / kg) of Examples 1-3 significantly surpassed those of Comparative Examples 1-3 (≤87.0% and ≤712.8 A·h / kg). This substantial increase in current efficiency directly confirms that the fine-grained, uniform microstructure promoted by the modifier effectively suppressed harmful micro-cell corrosion (i.e., self-corrosion) caused by coarse second phases or component segregation, allowing the dissolution of the anode metal to be more effectively converted into useful protective current output. This conclusion is strongly supported by corrosion morphology observation: all examples exhibited ideal "layered dissolution" with smooth and uniform surfaces, while Comparative Example 1 showed harmful "honeycomb pitting and deep pits," and Comparative Examples 2 and 3, although showing improvement, still exhibited obvious uneven corrosion characteristics. This fundamental shift from "localized pitting corrosion" to "uniform layered corrosion" is the most direct evidence of suppressed alloy element segregation and a qualitative improvement in microstructure uniformity.

[0057] Furthermore, the lower long-term average corrosion rate of the examples further confirms its resistance to uniform dissolution and its longer expected lifespan. In summary, Comparative Example 1 (unmodified) reveals the inherent defects of traditional alloys; Comparative Example 2 (ordinary carbon cage) shows that physical carriers alone cannot solve the fundamental problem; Comparative Example 3 (physical mixture) indicates that the effect of simple addition without the synergistic effect of nanocomposite structures and interfaces is limited. The excellent and consistent performance of Examples 1-3 collectively proves that the dual mechanism of "heterogeneous nucleation and grain refinement" and "interfacial electric field-guided uniform dissolution" achieved by the present invention through composite nanomodifiers successfully overcomes the problems of alloy element segregation and uneven structure during the melting process. Thus, macroscopically, it simultaneously achieves a more negative and stable potential, higher current efficiency, better dissolution morphology, and longer service life, comprehensively improving the overall electrochemical performance of the sacrificial anode.

[0058] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing Zn-Mg-Al-Mn sacrificial anode material for buried steel pipelines using an improved smelting process, characterized in that, Includes the following steps: S1. Zinc ingots are placed in a graphite crucible and then placed in a medium-frequency induction melting furnace. After evacuation, argon gas is introduced. The temperature is raised to 550-600℃ to obtain zinc melt. Nitrogen-sulfur co-doped carbon nanocage-supported nano-zinc oxide and magnesium silicate heterojunction are placed in another crucible and preheated in an oven at 240-260℃. The preheated nitrogen-sulfur co-doped carbon nanocage-supported nano-zinc oxide, magnesium silicate heterojunction, magnesium chips, aluminum chips, and manganese sheets are mixed to obtain a metal mixture. The metal mixture is wrapped with zinc foil to obtain an alloy package. S2, using a preheated graphite bell jar, press the alloying ladle into the bottom of the zinc melt and stir until the contents of the ladle are completely dissolved; then, raise the furnace temperature to 630-650℃ and hold it there. S3. Insert the graphite degassing gun into the bottom of the melt, introduce argon gas for rotary spraying refining, turn off the gas after refining, and remove the gun; let the melt temperature drop to 545-555℃ and stand to obtain a settled melt. S4. Preheat the mold to 145-155℃; pour the settled melt into the preheated mold, cool it to room temperature in air, and then demold to obtain the casting; perform surface sandblasting on the casting to remove oxide scale; Pre-treated castings; The pretreated castings were subjected to low-temperature stabilization treatment in an air-circulating oven at 175-185℃.

2. The method for preparing Zn-Mg-Al-Mn sacrificial anode material for buried steel pipelines using the improved smelting process according to claim 1, characterized in that, In step S1, the preheating time in the oven at 240-260℃ is 1-2 hours.

3. The method for preparing Zn-Mg-Al-Mn sacrificial anode material for buried steel pipelines using the improved smelting process according to claim 1, characterized in that, In step S2, the furnace temperature is raised to 630-650℃ and held for 15-20 minutes.

4. The method for preparing Zn-Mg-Al-Mn sacrificial anode material for buried steel pipelines using the improved smelting process according to claim 1, characterized in that, In step S3, the melt temperature is lowered to 545-555℃ and left to stand for 30-40 minutes.

5. The method for preparing Zn-Mg-Al-Mn sacrificial anode material for buried steel pipelines using the improved smelting process according to claim 1, characterized in that, In step S4, the low-temperature stabilization treatment takes 4-6 hours.

6. The method for preparing Zn-Mg-Al-Mn sacrificial anode material for buried steel pipelines using an improved smelting process according to any one of claims 1-5, characterized in that, The preparation steps of the nitrogen-sulfur co-doped carbon nanocage-supported nano-zinc oxide and magnesium silicate heterojunction include: Al, in an argon atmosphere glove box, L-phenylalanine and citric acid are added to a polytetrafluoroethylene liner; deionized water is added and stirred to obtain a solution; an ethanol solution of 2,2'-dithiodibenzoic acid is added; stirring is continued to obtain a mixed solution; A2. Place the mixed solution in a reaction vessel; place the reaction vessel in a forced-air drying oven and heat to 195-205℃ and maintain the temperature; after the reaction is completed, allow it to cool naturally to room temperature to obtain a suspension; transfer the suspension to a high-speed centrifuge tube and centrifuge to obtain a solid product; wash the solid product with a mixed solvent of ethanol / acetone to obtain a precipitate; redisperse the precipitate in anhydrous dimethylformamide and sonicate to obtain dispersion A; In step A3, a mixed aqueous solution containing zinc nitrate and magnesium nitrate was added to dispersion A under ice-water bath and continuous stirring to adjust the pH to 9-10. The mixture was stirred at 58-62°C. After centrifugation, the intermediate was washed with water and ethanol to obtain a loaded hydroxide intermediate. The loaded hydroxide intermediate was redispersed in ethanol, and tetraethyl silicate was added dropwise under stirring, followed by deionized water. The reaction was continued at 58-62°C to obtain a reaction mixture. The reaction mixture was centrifuged and washed with ethanol to obtain precipitate B. A4. Place precipitate B in an alumina crucible and put it into a tube furnace; under an argon protective atmosphere, heat to 295-305℃ and hold; heat to 850-950℃ and calcine; after calcine, cool to room temperature with the furnace under an argon atmosphere to obtain powder; grind the powder in a mortar and sieve.

7. The method for preparing Zn-Mg-Al-Mn sacrificial anode material for buried steel pipelines using the improved smelting process according to claim 6, characterized in that, In step A1, stirring should continue for 1-2 hours.

8. The method for preparing Zn-Mg-Al-Mn sacrificial anode material for buried steel pipelines using the improved smelting process according to claim 6, characterized in that, In step A2, the temperature is raised to 195-205℃ and held for 12-14 hours.

9. The method for preparing Zn-Mg-Al-Mn sacrificial anode material for buried steel pipelines using the improved smelting process according to claim 6, characterized in that, In step A3, the stirring time at 58-62℃ is 2-4 hours.

10. The method for preparing Zn-Mg-Al-Mn sacrificial anode material for buried steel pipelines using the improved smelting process according to claim 6, characterized in that, In step A4, the temperature is raised to 295-305℃ and held for calcination for 1-2 hours.

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