A full deep sea eight-element aluminum alloy sacrificial anode and a preparation method thereof

Abstract

This invention belongs to the field of metal material corrosion protection technology, specifically relating to a highly active aluminum alloy sacrificial anode for full ocean depth and its preparation method. The sacrificial anode uses Al as the main raw material, with added alloying elements: Zn, In, Ga, Mg, Ti, Ca, and Mn. The preparation method involves first heating Al and Zn to 750–1000℃, then adding In, Ga, Mg, Ti, Ca, and Mn, and finally casting at a temperature of 700–750℃. By adding Ca, an octet aluminum alloy sacrificial anode for full ocean depth is formed. The activation ability is improved by the dissolution and redeposition of In and Ga, the disruption of the continuity and density of the oxide layer by Zn and Mg, and the activation of the Al matrix surface by micron-level dot pairs. At the same time, Ti refines the grain size, resulting in a uniform and segregated distribution of alloying elements, avoiding internal self-corrosion, and improving current efficiency. It can be applied to full ocean depth environments from 0 to 10000 meters, with a current efficiency of 90–95%.

Description

Technical fields:

[0001] This invention belongs to the field of metal material corrosion protection technology, specifically relating to a highly active aluminum alloy sacrificial anode for full ocean depth and its preparation method, which can maintain high activity and high current efficiency in the extreme environment of the deep sea at a depth of 10,000 meters, and avoid the phenomenon of self-passivation of the anode. Background technology:

[0002] The development of deep-sea engineering towards environments exceeding 10,000 meters in depth is unstoppable. However, severe deep-sea corrosion has consistently hampered the rapid development of deep-sea engineering equipment. Sacrificial anode protection is the most effective method for corrosion protection of marine engineering equipment. Current aluminum alloy anodes used in shallow waters encounter problems in the high-pressure, low-temperature, and low-oxygen environments of the deep sea due to the difficulty of "dissolution-redeposition" by active alloying elements such as In and Zn. These problems lead to surface crusting, decreased current efficiency, and severe self-corrosion, failing to meet the protection requirements of metal equipment in deep-sea environments, let alone the protection needs of metal equipment in extremely deep-sea areas exceeding 10,000 meters in depth, such as the Mariana Trench. Therefore, developing sacrificial anode materials with high activity, synergistic effects of multiple alloying elements, uniform microstructure, and high current efficiency, suitable for deep-sea environments, has become an urgent problem to be solved.

[0003] Commercially available sacrificial anodes for deep-sea applications are primarily aluminum alloy sacrificial anodes. For example, Chinese Patent 201610211695.7 discloses a method for preparing a high-performance aluminum alloy sacrificial anode for deep-sea environments. The resulting aluminum alloy sacrificial anode is suitable for high-pressure, low-temperature, and low-oxygen deep-sea environments and features stable working potential, easy detachment of corrosion products, uniform corrosion morphology, environmentally friendly formulation, high capacitance and current efficiency, and good casting performance. It uses aluminum as the matrix, adding zinc, indium, tin, and gallium elements, and is prepared by a casting method. The resulting aluminum alloy sacrificial anode performs well in simulated deep-sea environments (static water pressure 30 MPa, temperature 4℃, dissolved oxygen content 2.5–3 mg / L). The current efficiency of L) is higher than 90%, the working potential is 1.10 to -1.06V (Ag / AgCl), and the capacity is greater than 2600Ah / kg; Chinese Patent 202310318260.2 discloses an aluminum alloy sacrificial anode for deep-sea environments, the chemical composition of which includes aluminum, zinc, indium and silicon, the mass fraction of zinc is 4.95 to 5.35%, the mass fraction of indium is 0.017 to 0.018%, the mass fraction of silicon is 0.08 to 0.09%, and the balance is aluminum; its working potential is ≤ -1.05V and the electrochemical capacity is ≥ 2500Ah / kg in a simulated deep-sea environment with a temperature of 4℃ and a dissolved oxygen content of 2.7mg / L. Chinese Patent 201810529402.9 discloses a seven-element aluminum alloy sacrificial anode material for deep-sea environments, which, by mass percentage, contains the following components: zinc 5-6%, indium 0.02-0.08%, silicon 0.05-0.2%, cerium 0.1-0.6%, titanium 0.01-0.07%, magnesium 0.5-2.0%, with the balance being aluminum and iron impurities <0.1%. Its operating potential in a simulated deep-sea environment (temperature 10±1℃, hydrostatic pressure 10MPa, dissolved oxygen content 2mg / L) is -0.94 to -1.09V, its capacitance is 2365.3-2500.3Ah / kg, and its current efficiency is 83.4-88.1%. Chinese Patent 201110085962.8 discloses a sacrificial anode for deep-sea environments, using aluminum as raw material and adding zinc, indium, and silicon. The weight percentages of each component are as follows: zinc 3.0-5.0%, indium 0.01-0.02%, silicon 0.10-0.20%; total impurities ≤0.16%, of which iron impurities ≤0.13% and copper impurities ≤0.006%; the balance is aluminum; its working potential in a simulated deep-sea low-temperature environment (temperature 10℃, deoxygenated) is -1.12 to -1.05V, current efficiency >93%, and capacitance >2600Ah / kg.Chinese Patent 201510418356.1 discloses a high-efficiency aluminum alloy sacrificial anode for deep-sea applications, using electrolytic primary aluminum liquid as raw material. The alloy composition is as follows: zinc 5-6 wt%, indium 0.02-0.025 wt%, magnesium 1.5-2.0 wt%, titanium 0.05-0.06 wt%, iron 0.08-0.15 wt%, and aluminum as the balance. Under simulated deep-sea low-temperature conditions (temperature 4℃, dissolved oxygen content 4 mg / L), its working potential is -1.069 to -1.092 V, its current efficiency is 93.1-93.7%, and its capacitance is 2662-2675 Ah / kg. Chinese Patent 200810249621.8 discloses an aluminum alloy sacrificial anode suitable for deep-sea environments. It uses A00 aluminum as the main raw material, with added elements zinc, indium, magnesium, titanium, gallium, and manganese. The weight percentages of each component are as follows: zinc 2.0–5.5%, indium 0.03–0.08%, magnesium 0.5–2.0%, titanium 0.05–0.2%, gallium 0.05–0.55%, manganese 0.02–1.2%, and the total impurity content is ≤0.30%, of which impurities iron + copper + nickel ≤0.15%, silicon + calcium ≤0.15%, and the balance is aluminum. Its operating potential in a simulated 800-meter deep-sea low-temperature environment (temperature 4℃, dissolved oxygen content 4mg / L, hydrostatic pressure 8MPa) is -1.05 to -1.10V, and its current efficiency is 90.2–91.8%. Chinese Patent 201410311844.8 discloses an aluminum alloy sacrificial anode with high current efficiency suitable for deep-sea environments. It uses aluminum as the base material and adds zinc, indium, tin, magnesium, and titanium alloying elements. The specific component ratio (wt%) is: zinc 4.0–6.0%, indium 0.020–0.030%, tin 0.05–0.10%, magnesium 0.5–1.0%, and titanium 0.05–0.10%, with impurities of iron <0.050%, copper <0.010%, and the balance being aluminum. Its current efficiency in a simulated deep-sea environment (temperature 4℃, hydrostatic pressure 8MPa) is greater than 92%, and its open-circuit potential is -1.05 to -1.20. Chinese Patent 201110142890.6 discloses an aluminum alloy sacrificial anode for deep-sea environments, composed of aluminum, zinc, indium, and cadmium, with the following weight percentages: aluminum 94-98 parts, zinc 3-5 parts, indium 0.04-0.06 parts, and cadmium 0.01-0.03 parts. Its operating potential in a simulated deep-sea environment (temperature 4℃, hydrostatic pressure 8MPa) is -1.07 to -1.10V, its current efficiency is 86-90%, and its capacitance is 2500-2700 Ah / kg. The sacrificial anode in the aforementioned patent exhibits good activation performance in deep-sea environments, dissolves uniformly, and its corrosion products are easily detached.

[0004] Although existing deep-sea anodes have current efficiencies exceeding 90%, their testing hydrostatic pressures are all less than 30 MPa, making them only suitable for cathodic protection of metallic structural materials in deep-sea environments ranging from 0 to 3000 meters. In deep-sea environments exceeding 10,000 meters, where hydrostatic pressures exceed 100 MPa, sacrificial anodes may malfunction due to Cl... - Accelerated ion diffusion rates exacerbate self-corrosion, severely impacting anodic current efficiency. Therefore, such anodes cannot operate long-term in deep-sea environments ranging from 3000 to 10000 meters. Currently, there are no reports on sacrificial anode materials suitable for cathodic protection of metallic structural materials in these environments, nor on related research. Therefore, this study aims to develop and design a highly active, high-current-efficiency aluminum alloy anode suitable for deep-sea environments at depths of 10,000 meters, and its preparation method. Summary of the Invention:

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and to develop and design an aluminum alloy sacrificial anode with high activity, synergistic effect of multiple alloying elements, uniform microstructure, and high current efficiency for cathodic protection of metal structural materials in the full deep-sea environment from 0 to 10,000 meters.

[0006] To achieve the above objectives, the present invention relates to a deep-sea octet aluminum alloy sacrificial anode using Al as the main raw material, with added alloying elements: Zn, In, Ga, Mg, Ti, Ca, and Mn. The weight percentages of each component are as follows: Zn 2.5–3.5 wt%, In 0.01–0.03 wt%, Ga 0.01–0.03 wt%, Mg 0.5–2.0 wt%, Ti 0.005–0.02 wt%, Ca 0.02–0.1 wt%, Mn 0.05–0.2 wt%, impurity Fe content <0.1%, impurity Cu content <0.01%, impurity Si content <0.01%, and the balance being Al. The total amount of alloying elements does not exceed 6%.

[0007] The alloying elements Zn, In, Ga and Mg in this invention are activation elements that are dissolved in Al matrix. Low contents of In and Ga activate the Al matrix surface by dissolving and redepositing. The oxides formed by Zn and Mg destroy the continuity and compactness of the oxide layer on the Al matrix surface through volume effect, thus inhibiting the formation of a crust on the Al matrix surface.

[0008] Ti and Ca exist in the Al matrix as uniformly distributed micron-sized precipitates (AlTi3, Al4Ca), forming uniformly distributed micron-sized corrosion couples with the Al matrix, which can activate the surface of the Al matrix.

[0009] Mn can balance the impurity Fe, stabilize the activity of the sacrificial anode in the full deep-sea octet aluminum alloy, and reduce the self-corrosion rate.

[0010] The process of preparing a deep-sea octagonal aluminum alloy sacrificial anode according to the present invention is as follows:

[0011] First, Al and Zn are heated to 750–1000°C according to the set ratio to bring them to a molten state;

[0012] Then, add In, Ga, Mg, Ti, Ca and Mn according to the set ratio, stir and mix thoroughly, keep warm, and let stand for 2 to 5 minutes;

[0013] Finally, the anode was cast at a temperature of 700–750℃ and quenched in water at room temperature to obtain a sacrificial anode of octagonal aluminum alloy with an average grain size of less than 500 μm. The micron-sized precipitates formed by the alloying elements are uniformly distributed in the grains, and the precipitate size is less than 10 μm.

[0014] The present invention relates to a method for preparing a full-deep-sea octagonal aluminum alloy sacrificial anode. The prepared full-deep-sea octagonal aluminum alloy sacrificial anode is suitable for cathodic protection of high-strength steel structures in deep-sea environments of 0 to 10,000 meters. Its working potential in deep-sea seawater of 0 to 10,000 meters is -1.053V to -1.140V, its current efficiency is 90 to 95%, its surface dissolution is uniform, its corrosion products are easy to detach, and its activation performance is good.

[0015] The octet aluminum alloy sacrificial anode of the present invention can also be prepared by other metallurgical methods such as powder metallurgy.

[0016] Compared with existing technologies, this invention forms a full-deep-sea octet aluminum alloy sacrificial anode by adding Ca. It enhances activation capability through the dissolution and redeposition of In and Ga, the disruption of oxide layer continuity and density by Zn and Mg, and the activation of the Al matrix surface by micron-level dot pairs. Simultaneously, Ti refines the grain size, resulting in a uniform and segregated distribution of alloying elements, preventing internal self-corrosion and improving current efficiency. This invention can be applied to full-depth seawater environments from 0 to 10,000 meters, achieving a current efficiency of 90-95%, significantly exceeding the applicable range of 0-3,000 meters, demonstrating significant practicality. Attached image description:

[0017] Figure 1 Metallographic image of the grain structure of the full deep-sea octagonal aluminum alloy sacrificial anode prepared in Example 1 of the present invention.

[0018] Figure 2 Scanning electron microscope (SEM) image of the micron-scale precipitates of the full-deep-sea octagonal aluminum alloy sacrificial anode prepared in Example 1 of this invention.

[0019] Figure 3The image shows the corroded surface of the octagonal aluminum alloy sacrificial anode prepared in Example 4 of this invention after electrochemical performance testing. Detailed implementation method:

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Example 1:

[0022] This embodiment relates to a full deep-sea octet aluminum alloy sacrificial anode, with Al as the main raw material and alloying elements added: Zn, In, Ga, Mg, Ti, Ca, and Mn. The weight percentages of each component are as follows: Zn 3.5wt%, In 0.03wt%, Ga 0.01wt%, Mg 2.0wt%, Ti 0.02wt%, Ca 0.1wt%, Mn 0.2wt%, impurity Fe content <0.1%, impurity Cu content <0.01%, impurity Si content <0.01%, and the balance being Al.

[0023] The specific process of its preparation is as follows:

[0024] First, heat Al and Zn to 750–1000°C to bring them to a molten state;

[0025] Then, add In, Ga, Mg, Ti, Ca and Mn, stir and mix thoroughly, keep warm, and let stand for 2 to 5 minutes;

[0026] Finally, it is cast at a temperature of 700-750℃ and then quenched in water at room temperature.

[0027] Metallographic images of the microstructure of the obtained deep-sea octagonal aluminum alloy sacrificial anode are as follows: Figure 1 As shown, the average grain size of the alloy is 480 μm;

[0028] Scanning electron microscope (SEM) images of the precipitated phase obtained from the fully deep-sea octagonal aluminum alloy sacrificial anode are as follows: Figure 2 As shown, the micron-sized precipitates rich in alloying elements mainly precipitate within the grains, and their size is less than 10 μm.

[0029] Example 2:

[0030] The weight percentages of the components of the full deep-sea octet aluminum alloy sacrificial anode involved in this embodiment are as follows: Zn 3.0wt%, In 0.02wt%, Ga 0.02wt%, Mg 1.5wt%, Ti 0.01wt%, Ca 0.1wt%, Mn 0.1wt%, Fe impurity content <0.1%, Cu impurity content <0.01%, Si impurity content <0.01%, and the balance is Al;

[0031] The specific process of its preparation is the same as in Example 1.

[0032] Example 3:

[0033] The octet aluminum alloy sacrificial anode involved in this embodiment has the following weight percentages of Al components: Zn 2.5wt%, In 0.01wt%, Ga 0.03wt%, Mg 1.0wt%, Ti 0.005wt%, Ca 0.05wt%, Mn 0.05wt%, Fe impurity content <0.1%, Cu impurity content <0.01%, Si impurity content <0.01%, and the balance is Al;

[0034] The specific process of its preparation is the same as in Example 1.

[0035] Example 4:

[0036] The weight percentages of the components of the full deep-sea octet aluminum alloy sacrificial anode involved in this embodiment are as follows: Zn 3.0wt%, In 0.02wt%, Ga 0.02wt%, Mg 0.5wt%, Ti 0.005wt%, Ca 0.05wt%, Mn 0.05wt%, Fe impurity content <0.1%, Cu impurity content <0.01%, Si impurity content <0.01%, and the balance is Al;

[0037] The specific process of its preparation is the same as in Example 1.

[0038] Example 5:

[0039] This embodiment relates to accelerated testing of the electrochemical performance of the full deep-sea octagonal aluminum alloy sacrificial anodes prepared in Examples 1-4;

[0040] Accelerated electrochemical performance tests were conducted on the octagonal aluminum alloy sacrificial anodes prepared in Examples 1-4 according to the national standard GB / T17848-1999.

[0041] The test results of the full-deep-sea octagonal aluminum alloy sacrificial anode prepared in Example 1 in shallow seawater at room temperature showed that: the working potential was -1.053 to -1.124V, the current efficiency was 95%, the dissolution was uniform with no obvious local corrosion, the corrosion products had no obvious adhesion, and the activation was good.

[0042] The test results of the full-deep-sea octagonal aluminum alloy sacrificial anode prepared in Example 2 in a simulated 2000-meter deep-sea environment (hydrostatic pressure of 20 MPa, dissolved oxygen content of 0.5 mg / L, and temperature of 5℃) showed that: the working potential was -1.059 to -1.128 V, the current efficiency was 94.3%, the dissolution was uniform with no obvious local corrosion, the corrosion products had no obvious adhesion, and the activation was good;

[0043] The test results of the full-deep-sea octagonal aluminum alloy sacrificial anode prepared in Example 3 in a simulated 5000-meter deep-sea environment (hydrostatic pressure of 50 MPa, dissolved oxygen content of 3 mg / L, and temperature of 2℃) showed that: the working potential was -1.062 to -1.137 V, the current efficiency was 92.7%, the dissolution was uniform with no obvious local corrosion, the corrosion products had no obvious adhesion, and the activation was good.

[0044] The test results of the fully deep-sea octagonal aluminum alloy sacrificial anode prepared in Example 4 in a simulated 10,000-meter deep-sea environment (hydrostatic pressure of 100 MPa, dissolved oxygen content of 2 mg / L, and temperature of 2 °C) showed that the working potential was -1.056 to -1.117 V, the current efficiency was 90.7%, and the corrosion surface was as shown in the figure. Figure 3 As shown, the dissolution was uniform with no obvious localized corrosion, the corrosion products showed no obvious adhesion, and the activation was good.

Claims

1. An eight-element aluminum alloy sacrificial anode characterized by, Al is used as the main raw material, and alloying elements are added: Zn, In, Ga, Mg, Ti, Ca and Mn; Ti and Ca exist in the Al matrix as micron-sized precipitates, forming micron-sized corrosion couples with the Al matrix and activating the Al matrix surface; The weight percentages of each component are as follows: Zn 2.5~3.5wt%, In 0.01~0.03wt%, Ga 0.01~0.03wt%, Mg 0.5~2.0wt%, Ti 0.005~0.02wt%, Ca 0.02~0.1wt%, Mn 0.05~0.2wt%, Fe impurity content <0.1%, Cu impurity content <0.01%, Si impurity content <0.01%, and the balance is Al.

2. An eight-element aluminum alloy sacrificial anode according to claim 1, wherein The total amount of alloying elements shall not exceed 6%.

3. The octet aluminum alloy sacrificial anode according to claim 2, characterized in that, Zn, In, Ga, and Mg are the activating elements dissolved in the Al matrix. In and Ga activate the Al matrix surface through dissolution and redeposition. The oxides formed by Zn and Mg disrupt the continuity and compactness of the oxide layer on the Al matrix surface through volume effect, thus inhibiting the formation of a crust on the Al matrix surface. Mn balances the impurity Fe.

4. The method for preparing an octagonal aluminum alloy sacrificial anode according to any one of claims 1 to 3, characterized in that, The process is as follows: First, Al and Zn are melted; Then, add In, Ga, Mg, Ti, Ca and Mn, stir to mix, keep warm, and let stand; Finally, cast and quench in water at room temperature; In this process, Al and Zn are heated to 750~1000℃ to melt them; The settling time is 2-5 minutes; The casting temperature is 700~750℃.

5. The method for preparing an octet aluminum alloy sacrificial anode according to claim 4, characterized in that, The average grain size of the prepared octagonal aluminum alloy sacrificial anode is less than 500 μm, and the micron-sized precipitates formed by the alloying elements are uniformly distributed in the grains with a precipitate size of less than 10 μm.

6. The method for preparing an octet aluminum alloy sacrificial anode according to claim 4, characterized in that, The prepared octagonal aluminum alloy sacrificial anode has an operating potential of -1.053V to -1.140V and a current efficiency of 90% to 95% in seawater at depths of 0 to 10,000 meters. It is suitable for cathodic protection of high-strength steel structures in environments ranging from 0 to 10,000 meters.

7. The method for preparing an octet aluminum alloy sacrificial anode according to claim 4, characterized in that, It is prepared using metallurgical methods, including powder metallurgy.

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