Corrosion-resistant aluminum-magnesium alloy material, preparation process and application thereof

Abstract

This invention discloses a corrosion-resistant aluminum-magnesium alloy material, its preparation process, and its applications, belonging to the technical field of metallic materials. The process includes alloy composition design and smelting, homogenization and high-temperature purification treatment, multi-stage temperature deformation processing, and surface densification treatment. The content of heavy metal elements and the Mn / Fe mass ratio are strictly controlled in the alloy composition. A uniform fine-grained structure is obtained through a graded temperature-controlled deformation process. A surface densification technology combining surface mechanical grinding, composite passivation, and organosilicon sealing treatment is employed to form a multi-layer composite protective system consisting of a fine-grained layer, a passivation film, and a sealing film. The aluminum-magnesium alloy prepared by this invention has a tensile strength exceeding 335 MPa, a corrosion rate of less than 0.03 mm / year in a simulated food processing environment, and heavy metal migration levels far below food safety standards. It simultaneously meets the requirements of food machinery for lightweight materials, corrosion resistance, and food safety, demonstrating promising application prospects.

Description

Technical Field

[0001] This invention belongs to the technical field of metallic materials, specifically relating to a corrosion-resistant aluminum-magnesium alloy material, its preparation process, and its application. Background Technology

[0002] Food machinery, as equipment that comes into direct contact with food or food raw materials, has strict requirements for the materials used: First, the materials themselves must have good corrosion resistance and be able to withstand the corrosion of various acids, alkalis, salts and chlorine-containing media during food processing; second, the materials must not cause the migration of harmful substances to food and must meet food safety and hygiene standards; third, the materials must have good processing and forming properties and mechanical strength to meet the manufacturing requirements of complex structural parts.

[0003] Currently, the materials widely used in food processing machinery mainly include stainless steel (304, 316L, etc.) and ordinary aluminum alloys (such as 6061, 6063, etc.). Although stainless steel has excellent corrosion resistance, its high density (about 7.9 g / cm3) results in bulky equipment and high energy consumption. Ordinary aluminum alloys have the advantage of low density (about 2.7 g / cm3), but their corrosion resistance in food processing environments is insufficient, especially in acidic media (such as juice, vinegar, fermented products) and chlorine-containing cleaning agents (such as sodium hypochlorite disinfectant), where ordinary aluminum alloys are prone to pitting corrosion and intergranular corrosion.

[0004] Aluminum-magnesium alloys, as lightweight and high-strength materials, have a density that can be reduced to 2.4~2.6 g / cm3, making them lighter than ordinary aluminum alloys. However, the application of aluminum-magnesium alloys in the food machinery field faces two major technical bottlenecks: first, aluminum-magnesium alloys have poor corrosion resistance, making it difficult to meet the long-term use requirements of food processing environments; second, conventional aluminum-magnesium alloys may contain potentially harmful elements (such as certain heavy metals) that do not meet the safety standards for food contact materials.

[0005] While there are reports in the existing technology of surface coating or anodizing aluminum-magnesium alloys to improve corrosion resistance, the coatings are at risk of wear and peeling during use, and the anodized film has poor stability in alkaline cleaning agent environments, making it difficult to meet the requirements of high-frequency cleaning and disinfection of food machinery. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a corrosion-resistant aluminum-magnesium alloy material, its preparation process and application, so as to solve the problems mentioned in the background art or achieve better technical effects.

[0007] To solve the above-mentioned technical problems, the inventors, through practice and summarization, derived the technical solution of this invention. This invention discloses a corrosion-resistant aluminum-magnesium alloy material, comprising, by mass percentage: 3.2~4.8% Mg, 0.5~1.0% Mn, 0.1~0.25% Zn, 0.05~0.15% Ti, 0.1~0.15% Fe, 0.01~0.03% Cu, 0.01~0.02% Ni, 0.02~0.05% Cr, 0.01% Pb, 0.002% Cd, 0.01% As, other impurity elements ≤0.1%, and the balance being Al; wherein, the Mn / Fe mass ratio is ≥3.0.

[0008] Further, the corrosion-resistant aluminum-magnesium alloy material, by mass percentage, comprises: 3.2~4.2% Mg, 0.5~1.0% Mn, 0.1~0.25% Zn, 0.05~0.15% Ti, 0.1~0.15% Fe, 0.02%~0.03% Cu, 0.01% Ni, 0.02~0.03% Cr, 0.01% Pb, 0.002% Cd, 0.01% As, other impurities ≤0.1%, and the balance being Al; wherein, the Mn / Fe mass ratio is 5~7.

[0009] Further, the corrosion-resistant aluminum-magnesium alloy material, by mass percentage, comprises: 4.2% Mg, 0.65% Mn, 0.12% Zn, 0.08% Ti, 0.12% Fe, 0.02% Cu, 0.01% Ni, 0.03% Cr, 0.01% Pb, 0.002% Cd, 0.01% As, other impurities ≤0.08%, and the balance being Al; wherein, the Mn / Fe mass ratio is 5.42.

[0010] Furthermore, the preparation process of any of the above-mentioned corrosion-resistant aluminum-magnesium alloy materials includes the following steps: S1: Prepare alloy raw materials according to the formula, melt them in an inert gas atmosphere, degas them by rotary blowing, and then keep them at a constant temperature for 10-25 minutes before semi-continuous casting. S2: The ingot obtained in S1 is homogenized and then cooled to room temperature; S3: The alloy material after cooling S2 is subjected to staged deformation processing. The first stage is forged in 3 passes at 400℃; the second stage is rolled in 5 passes at 340℃; and the third stage is finished rolled in 2 passes at 280℃. S4: The alloy material processed by S3 is ball-milled for 15 minutes; then immersed in a composite passivation solution at 50°C, washed with deionized water, and dried with hot air; finally immersed in an organosilicon sealant and baked at 140~150°C for 25~30 minutes to form a sealing film. After natural cooling, the corrosion-resistant aluminum-magnesium alloy material is obtained.

[0011] Furthermore, in step S1, the inert gas is helium, the melting temperature is 720~750℃, and the degassing time is 20~30min.

[0012] Furthermore, in step S2, the homogenization treatment temperature is 480~520℃ and the time is 12~18h; the cooling rate to room temperature is 20℃ / h.

[0013] Furthermore, in S3, the deformation amount per pass in the first forging process does not exceed 20%, and the total deformation amount does not exceed 51%; the deformation amount per pass in the second rolling process does not exceed 15%, and the total deformation amount does not exceed 56%; and the total deformation amount in the third finishing rolling process does not exceed 8%.

[0014] Furthermore, in S4, the grinding balls used in the ball mill are zirconia beads with a diameter of 5 mm; the immersion time in the composite passivation solution is 20-30 min; and the immersion time in the organosilicon sealant is 10-15 min.

[0015] Further, in step S4, the pH of the composite passivation solution is 4.0~4.8; the composite passivation solution is obtained by compounding 2.0~2.5% phytic acid, 1.0~1.5% citric acid, 0.5~0.8% sodium molybdate, 0.1~0.15% cerium nitrate, 0~0.05% sodium dodecyl sulfate, 0.1~0.15% nano silica and the balance deionized water.

[0016] Furthermore, the application of any of the aforementioned corrosion-resistant aluminum-magnesium alloy materials in kitchenware and cookware.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention improves material performance in a coordinated manner from three aspects: composition design, organization control and surface treatment. It strictly controls the content of heavy metal elements. By controlling the Mn / Fe ratio to ≥3.0, manganese and iron form intermetallic compounds, reducing the amount of iron dissolved in the aluminum matrix. This can not only improve the corrosion resistance of the entire alloy material, but also avoid the risk of iron migrating into food, thus greatly improving safety.

[0018] (2) The present invention adopts a three-stage graded temperature control process. By reducing the deformation temperature in stages, the alloy is continuously dynamically recrystallized during the deformation process, avoiding abnormal grain growth, and finally obtaining a uniform fine grain structure of 15~25μm. This grain size can ensure sufficient mechanical strength and toughness, while also reducing the sensitivity to grain boundary corrosion.

[0019] (3) This invention forms a fine-grained layer on the surface of the material through surface mechanical grinding, which not only improves the surface hardness but, more importantly, refines the surface grains and reduces the sites of corrosion initiation. The phytic acid and citric acid in the composite passivation solution are food-grade organic acids that can form a stable complex film with magnesium and aluminum ions. Sodium molybdate, as an oxidizing corrosion inhibitor, can form a molybdate protective film on the surface. Cerium nitrate, as a rare earth salt, can fill the micropores of the film layer and improve the film density. The three-layer protection system (fine-grained layer + passivation film + organosilicon sealing film) works synergistically to significantly improve the corrosion resistance of the material.

[0020] (4) The present invention uses environmentally friendly reagents throughout the preparation process. The surface treatment film is stable and does not fall off after curing. The strict cleaning and drying process ensures that there are no harmful residues on the material surface, which meets the requirements of food machinery that comes into direct contact with food. Detailed Implementation

[0021] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0022] Unless otherwise specified, all raw materials or reagents used in the following examples are commercially available products.

[0023] The composite passivation solution used in this invention is a compound reagent with a pH of 4.0~4.8. The formula by weight percentage is as follows: 2.0~2.5% phytic acid, 1.0~1.5% citric acid, 0.5~0.8% sodium molybdate, 0.1~0.15% cerium nitrate, 0~0.05% sodium dodecyl sulfate, 0.1~0.15% nano silica and the balance deionized water.

[0024] The method for testing the properties of finished aluminum-magnesium alloy materials according to the present invention is as follows: Tensile strength (MPa): Tested according to GB / T 3880.2 standard; Elongation performance (elongation %): tested according to GB / T 3880.2 standard; Corrosion resistance (3.5% NaCl, 168h): The sample was immersed in 3.5% NaCl solution for 168h, and the corrosion rate (mm / year) was measured; the sample was immersed in 5% citric acid solution (pH=2.5) for 72h, and the presence of obvious corrosion spots on the sample surface was observed; a spray cycle test simulating a food processing environment (3% NaCl + 1% lactic acid, 50℃) was conducted for 240h, and the surface rating was 9 (according to GB / T 6461 standard). Food safety testing: Migration tests were conducted according to GB 31604.1-2015. Specifically, 4% acetic acid (60℃, 2h) and 10% ethanol (60℃, 2h) were used as food simulants to test whether the migration of heavy metals was significantly lower than the national standard limits (Pb≤1.0mg / L, Cd≤0.02mg / L, As≤0.04mg / L).

[0025] A corrosion-resistant aluminum-magnesium alloy material, by mass percentage, comprises: 3.2~4.8% Mg, 0.5~1.0% Mn, 0.1~0.25% Zn, 0.05~0.15% Ti, 0.1~0.15% Fe, 0.01~0.03% Cu, 0.01~0.02% Ni, 0.02~0.05% Cr, 0.01% Pb, 0.002% Cd, 0.01% As, other impurity elements ≤0.1%, and the balance being Al; wherein, the Mn / Fe mass ratio is ≥3.0.

[0026] The manufacturing process of the corrosion-resistant aluminum-magnesium alloy thin-walled part includes the following steps: (1) Prepare alloy raw materials according to the above formula, melt them in an inert gas atmosphere at 720~750℃, degas them by rotary blowing (speed 300~400rpm) for 20~30min, and then keep them at the temperature for 10~25min before semi-continuous casting. (2) The ingot obtained in step (1) is homogenized at 480~520℃ for 12~18h and cooled to room temperature at a rate of 20℃ / h; (3) The cooled alloy material is subjected to graded deformation processing. The first stage is forging in 3 passes at 400℃, with the deformation amount per pass not exceeding 20% ​​and the total deformation amount not exceeding 51%. The second stage is rolling in 5 passes at 340℃, with the deformation amount per pass not exceeding 15% and the total deformation amount not exceeding 56%. The third stage is finishing rolling in 2 passes at 280℃, with the total deformation amount not exceeding 8%. (4) Use a zirconia grinding ball with a diameter of 5 mm to grind for 15 min at a vibration frequency of 60 Hz; then immerse in a composite passivation solution at 50 ℃ for 20-30 min, wash with deionized water, and dry with hot air; finally immerse in an organosilicon sealant for 10-15 min and bake at 140-150 ℃ for 25-30 min to form a sealing film with a thickness of 1-3 μm. After natural cooling, the corrosion-resistant aluminum-magnesium alloy material is obtained.

[0027] Example 1 A corrosion-resistant aluminum-magnesium alloy material, by mass percentage, comprises: 4.2% Mg, 0.65% Mn, 0.12% Zn, 0.08% Ti, 0.12% Fe, 0.02% Cu, 0.01% Ni, 0.03% Cr, 0.01% Pb, 0.002% Cd, 0.01% As, other impurities ≤0.08%, and the balance being Al; wherein the Mn / Fe mass ratio is 5.42.

[0028] The manufacturing process of the corrosion-resistant aluminum-magnesium alloy thin-walled part includes the following steps: (1) Prepare alloy raw materials according to the above formula, melt them in an inert gas atmosphere at 740°C, degas them by rotary blowing (300 rpm) for 30 min, and then keep them at the temperature for 25 min before semi-continuous casting. (2) The ingot obtained in step (1) is homogenized at 490°C for 18 hours and then cooled to room temperature at a rate of 20°C / h. (3) The cooled alloy material is subjected to graded deformation processing. The first stage is forged in 3 passes at 400℃, with a single pass deformation of 20% and a total deformation of 51%. The second stage is rolled in 5 passes at 340℃, with a single pass deformation of 15% and a total deformation of 56%. The third stage is finished rolled in 2 passes at 280℃, with a total deformation of 8%. (4) Use a zirconia grinding ball with a diameter of 5 mm to grind for 15 min at a vibration frequency of 60 Hz; then immerse in a composite passivation solution at 50 ℃ (2.0% phytic acid, 1.0% citric acid, 0.5% sodium molybdate, 0.1% cerium nitrate, 0.02% sodium dodecyl sulfate, 0.1% nano silica and the balance deionized water, pH=4.5) for 30 min, wash with deionized water and dry with hot air; finally immerse in an organosilicon sealant for 15 min, bake at 145 ℃ for 30 min, and after natural cooling, obtain corrosion-resistant aluminum-magnesium alloy material.

[0029] Example 2 A corrosion-resistant aluminum-magnesium alloy material, by mass percentage, comprises: 3.2% Mg, 0.7% Mn, 0.15% Zn, 0.1% Ti, 0.1% Fe, 0.01% Cu, 0.02% Ni, 0.02% Cr, 0.01% Pb, 0.002% Cd, 0.01% As, other impurity elements ≤0.06%, and the balance being Al; wherein the Mn / Fe mass ratio is 7.0.

[0030] The manufacturing process of the corrosion-resistant aluminum-magnesium alloy thin-walled part includes the following steps: (1) Prepare alloy raw materials according to the above formula, melt them in an inert gas atmosphere at 750°C, degas them by rotary blowing (400 rpm) for 20 min, and then keep them at the temperature for 25 min before semi-continuous casting. (2) The ingot obtained in step (1) was homogenized at 520°C for 16 hours and then cooled to room temperature at a rate of 20°C / h. (3) The cooled alloy material is subjected to graded deformation processing. The first stage is forging in 3 passes at 400℃, with the deformation amount per pass not exceeding 20% ​​and the total deformation amount not exceeding 51%. The second stage is rolling in 5 passes at 340℃, with the deformation amount per pass not exceeding 15% and the total deformation amount not exceeding 56%. The third stage is finishing rolling in 2 passes at 280℃, with the total deformation amount not exceeding 8%. (4) Use a zirconia grinding ball with a diameter of 5 mm to grind for 15 min at a vibration frequency of 60 Hz; then immerse in a composite passivation solution at 50 ℃ (2.2% phytic acid, 1.3% citric acid, 0.5% sodium molybdate, 0.12% cerium nitrate, 0.01% sodium dodecyl sulfate, 0.12% nano silica and the balance deionized water, pH=4.2) for 30 min, wash with deionized water and dry with hot air; finally immerse in an organosilicon sealant for 10 min and bake at 150 ℃ for 25 min to form a sealing film with a thickness of 1~3 μm. After natural cooling, the corrosion-resistant aluminum-magnesium alloy material is obtained.

[0031] Example 3 A corrosion-resistant aluminum-magnesium alloy material, by mass percentage, comprises: 3.8% Mg, 0.5% Mn, 0.1% Zn, 0.15% Ti, 0.1% Fe, 0.03% Cu, 0.02% Ni, 0.05% Cr, 0.01% Pb, 0.002% Cd, 0.01% As, other impurity elements ≤0.09%, and the balance being Al; wherein the Mn / Fe mass ratio is 5.0.

[0032] The manufacturing process of the corrosion-resistant aluminum-magnesium alloy thin-walled part includes the following steps: (1) Prepare alloy raw materials according to the above formula, melt them in an inert gas atmosphere at 720°C, degas them by rotary blowing (400 rpm) for 30 min, and then keep them at the temperature for 15 min before semi-continuous casting. (2) The ingot obtained in step (1) is homogenized at 480°C for 18 hours and then cooled to room temperature at a rate of 20°C / h. (3) The cooled alloy material is subjected to graded deformation processing. The first stage is forging in 3 passes at 400℃, with the deformation amount per pass not exceeding 20% ​​and the total deformation amount not exceeding 51%. The second stage is rolling in 5 passes at 340℃, with the deformation amount per pass not exceeding 15% and the total deformation amount not exceeding 56%. The third stage is finishing rolling in 2 passes at 280℃, with the total deformation amount not exceeding 8%. (4) Use a zirconia grinding ball with a diameter of 5 mm to grind for 15 min at a vibration frequency of 60 Hz; then immerse in a composite passivation solution (2.5% phytic acid, 1.2% citric acid, 0.6% sodium molybdate, 0.12% cerium nitrate, 0.15% nano silica, pH=4.0) at 50 ℃ for 25 min, wash with deionized water, and dry with hot air; finally immerse in an organosilicon sealant for 15 min and bake at 140 ℃ for 25 min to form a sealing film with a thickness of 1~3 μm. After natural cooling, the corrosion-resistant aluminum-magnesium alloy material is obtained.

[0033] Example 4 A corrosion-resistant aluminum-magnesium alloy material, by mass percentage, comprises: 3.2% Mg, 1.0% Mn, 0.2% Zn, 0.05% Ti, 0.15% Fe, 0.01% Cu, 0.02% Ni, 0.02% Cr, 0.01% Pb, 0.002% Cd, 0.01% As, other impurity elements ≤0.05%, and the balance being Al; wherein the Mn / Fe mass ratio is 6.67.

[0034] The manufacturing process of the corrosion-resistant aluminum-magnesium alloy thin-walled part includes the following steps: (1) Prepare alloy raw materials according to the above formula, melt them in an inert gas atmosphere at 750°C, degas them by rotary blowing (300 rpm) for 30 min, and then keep them at the temperature for 25 min before semi-continuous casting. (2) The ingot obtained in step (1) is homogenized at 520°C for 12 hours and then cooled to room temperature at a rate of 20°C / h. (3) The cooled alloy material is subjected to graded deformation processing. The first stage is forging in 3 passes at 400℃, with the deformation amount per pass not exceeding 20% ​​and the total deformation amount not exceeding 51%. The second stage is rolling in 5 passes at 340℃, with the deformation amount per pass not exceeding 15% and the total deformation amount not exceeding 56%. The third stage is finishing rolling in 2 passes at 280℃, with the total deformation amount not exceeding 8%. (4) Use a zirconia grinding ball with a diameter of 5 mm to grind for 15 min at a vibration frequency of 60 Hz; then immerse in a composite passivation solution at 50 ℃ (2.0% phytic acid, 1.0% citric acid, 0.8% sodium molybdate, 0.12% cerium nitrate, 0.05% sodium dodecyl sulfate, 0.12% nano silica and the balance deionized water, pH=4.8) for 30 min, wash with deionized water and dry with hot air; finally immerse in an organosilicon sealant for 15 min and bake at 140 ℃ for 30 min to form a sealing film with a thickness of 1~3 μm. After natural cooling, the corrosion-resistant aluminum-magnesium alloy material is obtained.

[0035] Example 5 A corrosion-resistant aluminum-magnesium alloy material, by mass percentage, comprises: 4.6% Mg, 0.8% Mn, 0.25% Zn, 0.12% Ti, 0.15% Fe, 0.02% Cu, 0.01% Ni, 0.02% Cr, 0.01% Pb, 0.002% Cd, 0.01% As, other impurity elements ≤0.06%, and the balance being Al; wherein the Mn / Fe mass ratio is 5.33.

[0036] The manufacturing process of the corrosion-resistant aluminum-magnesium alloy thin-walled part includes the following steps: (1) Prepare alloy raw materials according to the above formula, melt them in an inert gas atmosphere at 720°C, degas them by rotary blowing (300 rpm) for 20 min, and then keep them at the temperature for 25 min before semi-continuous casting. (2) The ingot obtained in step (1) is homogenized at 500°C for 12 hours and then cooled to room temperature at a rate of 20°C / h. (3) The cooled alloy material is subjected to graded deformation processing. The first stage is forging in 3 passes at 400℃, with the deformation amount per pass not exceeding 20% ​​and the total deformation amount not exceeding 51%. The second stage is rolling in 5 passes at 340℃, with the deformation amount per pass not exceeding 15% and the total deformation amount not exceeding 56%. The third stage is finishing rolling in 2 passes at 280℃, with the total deformation amount not exceeding 8%. (4) Use a zirconia grinding ball with a diameter of 5 mm to grind for 15 min at a vibration frequency of 60 Hz; then immerse in a composite passivation solution at 50 ℃ (2.3% phytic acid, 1.0% citric acid, 0.8% sodium molybdate, 0.15% cerium nitrate, 0.02% sodium dodecyl sulfate, 0.12% nano silica and the balance deionized water, pH=4.3) for 20 min, wash with deionized water and dry with hot air; finally immerse in an organosilicon sealant for 10 min and bake at 140 ℃ for 30 min to form a sealing film with a thickness of 1~3 μm. After natural cooling, the corrosion-resistant aluminum-magnesium alloy material is obtained.

[0037] Comparative Example 1 The same preparation process as in Example 1 was used, except that the mass ratio of Mn / Fe in the aluminum-magnesium alloy was changed to 2.5, while the trace elements of other components remained unchanged.

[0038] Comparative Example 2 Aluminum-magnesium alloys with the same composition were prepared using conventional hot rolling processes, without surface densification treatment, and only ordinary anodizing treatment was performed.

[0039] The aluminum-magnesium alloy materials prepared in Examples 1-5 and Comparative Examples 1-2 were tested for tensile strength (MPa), elongation (elongation %), corrosion resistance, and food safety. The test and rating results are shown in Table 1 below. Table 1: Performance Comparison of Aluminum-Magnesium Alloy Materials Prepared in Examples 1-5 and Comparative Examples 1-2

[0040] Analysis of Table 1 reveals that the alloy materials prepared in Examples 1-5 show significant differences in both mechanical properties and corrosion resistance compared to Comparative Example 1. This is because when the Mn / Fe mass ratio in the entire alloy system is ≥3, it significantly improves the toughness and plasticity of the aluminum-magnesium alloy material of this invention by altering the phase composition of Fe. Furthermore, Mn enhances the corrosion resistance of the entire alloy material by encapsulating Fe to form a core-shell structure.

[0041] In aluminum-magnesium alloys, Fe is usually an unavoidable or unavoidable impurity element. When the proportion of iron in the alloy is high, it will form coarse and sharp needle-like Al3Fe or Al 13The Fe4 phase, a brittle phase, severely damages the alloy matrix, significantly reducing the alloy's plasticity and toughness. However, the appropriate incorporation of Mn preferentially combines with Fe, transforming the acicular, iron-rich phase into finer, more rounded Al6(Fe,Mn) phases. This reduces the cutting effect on the matrix, and further refinement can be achieved in subsequent casting processes, thereby mitigating or eliminating the harmful effects of Fe in the alloy. Furthermore, in the alloy material of this invention, the Mn / Fe mass ratio is a key factor determining the overall corrosion resistance. By changing the Mn / Fe mass ratio, harmful Fe impurities can be converted into inert, harmless phases, inhibiting microgalvanic corrosion and thus improving the overall corrosion resistance of the material. In aluminum-magnesium alloys, trace amounts of Fe can form microcouples with the magnesium matrix, potentially leading to localized corrosion under certain conditions. The addition of appropriate amounts of Mn can, on the one hand, capture Fe in the material and change its phase morphology, and on the other hand, isolate Fe, inhibiting the formation of microcouples. When the Mn content is appropriately increased, a "core-shell" structure can also be formed—a structure with an iron-rich phase as the core and a manganese-rich phase as the shell. This structure can effectively block the electrical contact between the core and the magnesium matrix, thereby fundamentally cutting off the microcouple corrosion circuit and improving the overall corrosion resistance of the alloy material.

[0042] As can be seen from the comparison between Examples 1-5 and Comparative Example 2, the present invention, in the process of preparing alloy materials, significantly improves the corrosion resistance of the alloy materials by combining chemical conversion films and organic sealing layers through effective synergy among multiple components, enabling the alloy materials to meet the requirements of high corrosion resistance in application scenarios (such as food machinery). The chemical conversion film provides a chemically bonded underlying protection, while also having corrosion inhibition and adhesion promotion functions; while the organosilicon sealing layer provides a physical barrier and hydrophobic function, significantly extending the penetration path of corrosive media.

[0043] In addition, the phytic acid, cerium salt and molybdate in the composite passivation solution of this invention are all environmentally friendly alternative reagents that meet environmental protection requirements. Furthermore, the nano-silica can play an "anchoring" role in the formation of the conversion film, enhancing the mechanical locking and chemical bonding between the organosilicon layer and the conversion film, and effectively preventing interlayer peeling or detachment.

[0044] As can be seen from the comparison of Examples 1 to 5 of the present invention, the aluminum-magnesium alloy material prepared in Example 1 exhibits the best toughness and corrosion resistance. This indicates that although adding an appropriate amount of Mn to the aluminum-magnesium alloy material system of the present invention is beneficial to improving the tensile strength, elongation, and corrosion resistance of the entire alloy material, it is not necessarily true that the higher the Mn / Fe mass ratio, the better. The key is to control the Mn / Fe mass ratio within a critical range through reasonable formulation. Since the alloy material systems formed by different formulations have different "tolerances" for Fe, based on the formulation range and preparation process defined in the present invention, the closer the Mn / Fe mass ratio is to 5.42, the more beneficial it is to improving the tensile strength, elongation, and corrosion resistance of the entire material system.

[0045] This invention utilizes surface mechanical grinding to form a fine-grained layer on the material surface, which not only improves surface hardness but, more importantly, refines the surface grains, reducing the sites of corrosion initiation. The phytic acid and citric acid in the composite passivation solution are food-grade organic acids that can form stable complex films with magnesium and aluminum ions. Sodium molybdate, as an oxidizing corrosion inhibitor, can form a molybdate protective film on the surface. Cerium nitrate, as a rare earth salt, can fill the micropores of the film layer, improving its density. The three-layer protective system (fine-grained layer + passivation film + organosilicon sealing film) works synergistically to significantly improve the material's corrosion resistance. The surface-treated film is stable and does not peel off after curing. A rigorous cleaning and drying process ensures that there are no harmful residues on the material surface, meeting the requirements for food machinery that directly contacts food.

Claims

1. A corrosion-resistant aluminum-magnesium alloy material, characterized in that, By mass percentage, it includes: 3.2~4.8% Mg, 0.5~1.0% Mn, 0.1~0.25% Zn, 0.05~0.15% Ti, 0.1~0.15% Fe, 0.01~0.03% Cu, 0.01~0.02% Ni, 0.02~0.05% Cr, 0.01% Pb, 0.002% Cd, 0.01% As, other impurity elements ≤0.1%, and the balance being Al; wherein, the Mn / Fe mass ratio is ≥3.

0.

2. The corrosion-resistant aluminum-magnesium alloy material according to claim 1, characterized in that, By mass percentage, it includes: 3.2~4.2% Mg, 0.5~1.0% Mn, 0.1~0.25% Zn, 0.05~0.15% Ti, 0.1~0.15% Fe, 0.02%~0.03% Cu, 0.01% Ni, 0.02~0.03% Cr, 0.01% Pb, 0.002% Cd, 0.01% As, other impurities ≤0.1%, and the balance being Al; wherein, the Mn / Fe mass ratio is 5~7.

3. The corrosion-resistant aluminum-magnesium alloy material according to claim 1, characterized in that, By mass percentage, it includes: 4.2% Mg, 0.65% Mn, 0.12% Zn, 0.08% Ti, 0.12% Fe, 0.02% Cu, 0.01% Ni, 0.03% Cr, 0.01% Pb, 0.002% Cd, 0.01% As, other impurities ≤0.08%, and the balance being Al; wherein, the Mn / Fe mass ratio is 5.

42.

4. A preparation process for the corrosion-resistant aluminum-magnesium alloy material as described in any one of claims 1 to 3, characterized in that, The steps are as follows: S1: Prepare alloy raw materials according to the formula, melt them in an inert gas atmosphere, degas them by rotary blowing, and then keep them at a constant temperature for 10-25 minutes before semi-continuous casting. S2: The ingot obtained in S1 is homogenized and then cooled to room temperature; S3: The alloy material after cooling S2 is subjected to staged deformation processing. The first stage is forged in 3 passes at 400℃; the second stage is rolled in 5 passes at 340℃; and the third stage is finished rolled in 2 passes at 280℃. S4: The alloy material processed by S3 is ball-milled for 15 minutes; then immersed in a composite passivation solution at 50°C, washed with deionized water, and dried with hot air; finally immersed in an organosilicon sealant and baked at 140~150°C for 25~30 minutes to form a sealing film. After natural cooling, the corrosion-resistant aluminum-magnesium alloy material is obtained.

5. The preparation process of the corrosion-resistant aluminum-magnesium alloy material according to claim 4, characterized in that, In step S1, the inert gas is helium, the melting temperature is 720~750℃, and the degassing time is 20~30min.

6. The preparation process of the corrosion-resistant aluminum-magnesium alloy material according to claim 4, characterized in that, In step S2, the homogenization process is carried out at a temperature of 480~520℃ for 12~18h; the cooling rate to room temperature is 20℃ / h.

7. The preparation process of the corrosion-resistant aluminum-magnesium alloy material according to claim 4, characterized in that, In S3, the deformation per pass in the first forging process does not exceed 20%, and the total deformation does not exceed 51%; the deformation per pass in the second rolling process does not exceed 15%, and the total deformation does not exceed 56%; and the total deformation in the third finishing rolling process does not exceed 8%.

8. The preparation process of the corrosion-resistant aluminum-magnesium alloy material according to claim 4, characterized in that, In step S4, the grinding balls used in the ball mill are zirconia beads with a diameter of 5 mm; the immersion time in the composite passivation solution is 20-30 min; and the immersion time in the organosilicon sealant is 10-15 min.

9. The preparation process of the corrosion-resistant aluminum-magnesium alloy material according to claim 4, characterized in that, In step S4, the pH of the composite passivation solution is 4.0~4.8; the composite passivation solution is obtained by compounding 2.0~2.5% phytic acid, 1.0~1.5% citric acid, 0.5~0.8% sodium molybdate, 0.1~0.15% cerium nitrate, 0~0.05% sodium dodecyl sulfate, 0.1~0.15% nano silica and the balance deionized water.

10. The application of the corrosion-resistant aluminum-magnesium alloy material according to any one of claims 1 to 3 in kitchenware.

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