A method for inhibiting the harmful effect of Fe in Al-Si sacrificial anodes by adding Er, Ga

Abstract

This invention belongs to the field of steel corrosion protection surface engineering. Specifically, it discloses a method for suppressing the harmful effects of Fe in Al-Si sacrificial anodes by adding Er and Ga. The alloy composition of the sacrificial anode coating, by element weight percentage, is Si: 10%, Er: 0.5-1.0%, Ga: 0.1-0.2%, with the remainder being Al and other unavoidable elements. When Al-Si sacrificial anodes are used for corrosion protection of steel substrates, the addition of Er forms a new quaternary phase Er₂Al₃Si₂. This phase has low self-corrosion, resulting in more uniform corrosion during operation, which helps improve the overall current efficiency of the alloy. Furthermore, Ga has an activating effect, working with Er to improve the surface activity of the aluminum alloy and mutually promoting the growth of Cl on the alloy surface. ‑ Adsorption accelerates the corrosion of the α-Al matrix in the galvanic cell. Therefore, trace amounts of Ga have a synergistic effect on Er and improve the sacrificial anode performance of aluminum alloys to a certain extent.

Description

Technical Field

[0001] This invention belongs to the field of steel anti-corrosion surface engineering, specifically relating to a method for inhibiting the harmful effects of Fe in Al-Si sacrificial anodes by adding Er and Ga. Background Technology

[0002] Metal corrosion is the most common form of failure in metal equipment and engineering components, causing enormous losses and, in severe cases, catastrophic accidents. Iron and steel corrosion is the most serious, making the search for methods and technologies to prevent steel corrosion of great significance. Sacrificial anode cathodic protection is an important electrochemical corrosion protection method. It connects the metal to be protected to a more reactive metal with a more negative electrode potential, primarily achieving protection of the cathode structure through anodic discharge. Sacrificial anodes not only do not require a continuous external current supply and are easy to install, but they also perform excellently, especially under low resistance conditions. Generally, the sacrificial anode material should possess a sufficiently negative and stable potential, including both open-circuit and closed-circuit potentials, to ensure a sufficient driving potential. However, it should not be too negative to avoid hydrogen evolution in the cathode region, causing hydrogen embrittlement of the protected metal. The difference between the potential of the sacrificial anode material and the protection potential is called the driving potential. Generally, in a good medium, a driving potential of around 0.25V is required; low anodic polarization, low self-corrosion rate, and high current efficiency are also necessary to ensure long-term potential stability and sufficient service life.

[0003] Currently, the main sacrificial anode materials used in industrial corrosion protection are magnesium, aluminum, and zinc. Compared to zinc alloy anodes, aluminum alloy anodes have lower density, higher current efficiency, moderate driving potential, and a large theoretical capacitance (3.6 times that of zinc anodes). They are also inexpensive and readily available, making them particularly suitable for seawater environments. Compared to zinc-based alloys, magnesium alloy anodes have a higher electrode potential and stronger self-corrosion properties. Considering both natural resource reserves, price, and alloy performance, aluminum is the most promising alternative to zinc and magnesium. The development of continuous hot-dip galvanizing aluminum coating alloys is gradually emerging, and many countries have recognized the broad development prospects of aluminum-based alloys and have begun research on aluminum-based sacrificial anodes.

[0004] When steel reacts with aluminum-based anode alloys in the matrix, iron and aluminum readily form Fe-Al intermetallic compounds. These compounds are characterized by high hardness, poor toughness, low compressive strength, and poor plastic deformation ability. Pure aluminum forms a thick alloy layer with poor mechanical properties. Adding silicon to the aluminum alloy molten pool helps suppress the growth of Fe-Al intermetallic compounds and improves the fluidity of the alloy in the molten pool. Furthermore, during the reaction between the sacrificial anode coating alloy and the base steel, iron in the steel inevitably reacts with the sacrificial anode coating alloy and reaches saturation as the production process progresses. Studies have shown that this saturation state is 3.5 wt.% iron by weight. At this point, it readily forms the FeAl3 intermetallic compound phase with aluminum. FeAl3 acts as the cathode phase relative to the aluminum matrix, forming micro-cells with the aluminum matrix. Therefore, in corrosive media, the anodic phase surrounding the cathode phase preferentially corrodes. When there is an excess of FeAl3 phase, it increases the tendency for hydrogen evolution, significantly reduces current efficiency, and easily leads to localized corrosion. Moreover, the FeAl3 phase has a higher electrode potential than steel, making it difficult to achieve effective protection of the steel matrix using sacrificial anodes. Studies have shown that when the silicon content reaches 10 wt.%, the FeAl3 phase almost disappears, forming the τ6(Al9Fe2Si2) phase. This phase reduces the harmful effect of Fe on the sacrificial anode alloy to a certain extent. However, the aluminum base easily forms a dense oxide film with a relatively positive electrode potential, which leads to insufficient driving potential for the sacrificial anode and poor sacrificial anode performance. Therefore, the alloy still needs further optimization. Adding a small amount of rare earth elements is beneficial to the surface activation of the alloy and is expected to improve the sacrificial anode performance. Summary of the Invention

[0005] Given the current situation where sacrificial anodes are insufficient in aluminum alloys and the detrimental effects of Fe in the sacrificial anode process, this invention provides a method to suppress the detrimental effects of Fe in Al-10Si by adding rare earth elements Er and Ga. After adding rare earth Er, a new phase Er2Al3Si2 appears in the alloy. This new phase has less self-corrosion and acts as a "bridging transition," reducing the severe corrosion caused by the large potential difference between the τ6 (Al9Fe2Si2) phase and the matrix α-Al. It also weakens the relatively strong direct corrosion between Fe in the τ6 phase and the matrix Al, thereby increasing the sacrificial anode pathway, homogenizing alloy corrosion, and improving the overall sacrificial anode capability of the alloy.

[0006] The present invention solves the above-mentioned technical problems by adopting the following technical solution:

[0007] This invention specifically provides a method for suppressing the harmful effects of Fe in Al-Si sacrificial anodes by adding rare earth elements Er and Ga. The Al-Si sacrificial anode is composed of the following elements by mass percentage: 10 wt.% silicon, 0.5-1.0 wt.% erbium, 0.1-0.2 wt.% gallium, with the balance being aluminum and other unavoidable impurities. When the above-mentioned Al-Si sacrificial anode is used for corrosion protection of steel substrates, it can suppress the harmful effects of Fe in the Al-Si sacrificial anode.

[0008] The amount of rare earth element Er must be controlled within the range of 0.5wt.%-1.0wt.%. If too little is added, below 0.5wt.%, the effect will be insignificant. If too much is added, above 1.0wt.%, it will lead to an excessive increase in the number of second phases. Excessive galvanic corrosion will cause dissolution to be too fast, which will have an adverse effect on the dissolution morphology and current efficiency of the alloy.

[0009] Further preferred additions include 1.0 wt.% erbium (Er) and 0.2% gallium (Ga).

[0010] The specific harmful effects of inhibition are:

[0011] (1) After adding trace elements Er and Ga, the electrode potential of the alloy with 1.0 Er and 0.2 Ga is about 160 mV lower than that without the two elements, and is more stable. The electrode potential is about 70 mV and 85 mV lower than that with 0.5 and 1.0 Er respectively, thus meeting the requirements of sacrificial anode potential.

[0012] (2) The self-corrosion potential decreases continuously with the addition of Er and Ga. The self-corrosion potential of the alloy with 1.0Er and 0.2Ga is lower than that without the two elements, which means that the current efficiency is improved. Most of the electricity generated by the dissolution of the anode material is used for cathodic protection, and the performance of the alloy sacrificial anode is improved.

[0013] (3) Increased hardness to meet the mechanical performance requirements under certain specific conditions.

[0014] (4) After adding trace elements, the alloy structure is more uniform in microscopic view, which is beneficial to improving corrosion resistance.

[0015] This invention also provides methods for preparing Al-Si coating alloys with different Er and Ga contents, the specific preparation steps of which are as follows:

[0016] (1) Dry and weigh the aluminum granules and Al-Si master alloy, place them in the graphite crucible of the resistance furnace, heat them to 780°C under the protection of argon, and wait for them to melt. Press the Ga and Er granules wrapped in aluminum foil into the bottom of the graphite crucible. You can use a 99 corundum ceramic rod to stir evenly for 1-3 minutes and let it stand for 20-30 minutes.

[0017] The alloy composition should be controlled as follows: Si weight percentage should be 10%, Er weight percentage should be between 0.5% and 1.0%, Gallium weight percentage should be between 0.1% and 0.2%, with the remainder supplemented by aluminum granules. The purity of the aluminum granules and the Al-Si master alloy should both be greater than 99.9%, the purity of Er should be greater than 99.9%, the purity of Ga should be 99.9%, and Fe should be pure iron powder with a purity of 99.99%. During batching, the weight loss of each element should be less than 2% to minimize the impact of burn-off on the overall alloy composition.

[0018] (2) After the alloy is completely melted, remove the slag and surface impurities, add dry aluminum alloy refining agent to degas and remove slag, and keep it warm and stand for 20 minutes.

[0019] (3) Pour the molten alloy into a round cast iron mold preheated to about 400°C, and air cool, refine and cast into a billet.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] The aluminum-based sacrificial anode coating alloy of this invention utilizes widely available raw materials and has low manufacturing costs. The addition of a certain amount of Si allows silicon atoms to fill the atomic vacancies in Fe2Al3, preventing the preferential rapid diffusion of aluminum atoms along the c-axis, thereby inhibiting the growth of Fe-Al intermetallic compounds and improving metal fluidity. Er element possesses excellent properties such as a high melting point, low electrode potential, stronger corrosion resistance, and higher high-temperature resistance. Furthermore, it is cheaper than other rare earth elements and more abundant on Earth, taking into account practical economic factors.

[0022] The addition of Er forms a new quaternary phase, Er₂Al₃Si₂, which exists at grain boundaries and exhibits low self-corrosion, acting as a "bridging transition." This reduces the severe corrosion caused by the large potential difference between the τ₆(Al₉Fe₂Si₂) phase and the α-Al matrix. In severe cases, uneven corrosion can lead to cracking and peeling of the coating alloy, resulting in wasted industrial resources and significantly reduced production efficiency. The presence of the quaternary Er₂Al₃Si₂ phase ensures uniform corrosion of the alloy, significantly reducing the open-circuit potential and resulting in a lower overall anodic polarization, lower self-corrosion rate, and higher current efficiency, thus improving the sacrificial anode performance of the aluminum alloy. This ensures both long-term stable operating potential and sufficient service life. To meet specific mechanical property requirements in certain applications, the new Er₂Al₃Si₂ phase formed by adding rare earth Er improves the hardness of the sacrificial anode alloy. Through structural changes, it alters the alloy's dissolution morphology, which can improve current efficiency to some extent, further enhancing the performance of the alloy sacrificial anode.

[0023] The addition of Er and Ga not only improves the sacrificial anode performance, ensuring a reasonable and sufficient electrode potential, but also enhances the overall properties. Firstly, the addition of Er and Ga results in a more uniform alloy microstructure, which promotes uniform corrosion and facilitates the removal of corrosion products. Secondly, it improves mechanical properties, increasing Vickers hardness by 20 Hv, better meeting the requirements of sacrificial anode performance under special conditions and extending the alloy's service life. Furthermore, testing the effect of continuous Er addition on the solidus and liquidus temperatures of the Al-Si phase revealed that the solidus temperature in the eutectic reaction decreases linearly with Er addition. Adding a certain amount of Er induces solute redistribution in the alloy, refining the dendritic network. Attached Figure Description

[0024] Figure 1 The overall morphology of the Al-10Si(Fe)-0.5Er-0.1Ga alloy in Example 1;

[0025] Figure 2 The overall morphology of the Al-10Si(Fe)-0.5Er-0.2Ga alloy in Example 2;

[0026] Figure 3 The overall morphology of the Al-10Si(Fe)-1.0Er-0.1Ga alloy in Example 3;

[0027] Figure 4 The overall morphology of the Al-10Si(Fe)-1.0Er-0.2Ga alloy in Example 4;

[0028] Figure 5 Overall morphology of Al-10Si(Fe) alloy in Comparative Example 1;

[0029] Figure 6 Overall morphology of the Al-10Si(Fe)-0.5Er alloy in Comparative Example 2;

[0030] Figure 7 Overall morphology of the Al-10Si(Fe)-1.0Er alloy in Comparative Example 3;

[0031] Figure 8 Overall morphology of the Al-10Si(Fe)-0.1Ga alloy in Comparative Example 4;

[0032] Figure 9 Overall morphology of the Al-10Si(Fe)-2Zn-0.1Ga alloy in Comparative Example 5;

[0033] Figure 10 Overall morphology of the Al-10Si(Fe)-1.0Er-0.1Mn alloy in Comparative Example 6;

[0034] Figure 11 Comparison of solidification curves of alloys in Examples 1 and 3 and Comparative Example 4;

[0035] Figure 12 Comparison of open-circuit potentials of Examples 1, 2, 3, and 4 with Comparative Examples 1, 2, and 3;

[0036] Figure 13 Polarization comparison diagram of Example 3 and Comparative Examples 1, 2, and 3;

[0037] Figure 14 Hardness comparison charts of Examples 1 and 3 and Comparative Examples 1, 2, 4, and 5. Detailed Implementation Plan

[0038] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof.

[0039] In sacrificial anode applications for steel corrosion protection, iron in the steel inevitably reacts with the sacrificial anode coating alloy during the production process, reaching its maximum alloy tolerance level, thus affecting the performance of the sacrificial anode. 3.5 wt.% is the maximum alloy tolerance level for iron in aluminum alloys. When the Fe content exceeds 3.5 wt.%, there is a large amount of waste residue on the alloy surface, leading to waste residue accumulation during use and an extremely uneven coating surface, affecting the performance of the coating. In such cases, the plating solution should be replaced immediately. Therefore, this embodiment simulates the application process. The Fe content in the sacrificial anode coating alloy reaches its maximum alloy tolerance level, verifying the effectiveness of sacrificial anode elements in inhibiting the harmful effects of Fe.

[0040] Example 1

[0041] The preparation method of Al-10Si(Fe)-0.5Er-0.1Ga sacrificial anode coating alloy with Fe content of 3.5wt.% specifically includes the following steps: 71g of aluminum granules and 408.5g of Al-12Si master alloy are dried, weighed, and placed in a graphite crucible in a resistance furnace. Under the protection of argon, the crucible is heated to 780℃ and melted. 17.5g of refined Fe powder is then added and stirred. 0.5g of Ga is added, and 2.5g of Er granules wrapped in aluminum foil is pressed into the bottom of the graphite crucible. A 99% corundum ceramic rod can be used for uniform stirring for 1-3 minutes. The mixture is then held at the temperature for 20-30 minutes. After the coating alloy is completely melted, slag is removed to remove surface impurities. Dry aluminum alloy refining agent is added to degas and remove slag. The mixture is held at the temperature for 20 minutes. The molten alloy is then poured into a circular cast iron mold preheated to about 400℃, air-cooled, refined, and cast into a billet.

[0042] Example 2

[0043] The preparation method of Al-10Si(Fe)-0.5Er-0.2Ga sacrificial anode alloy with Fe content of 3.5wt.% specifically includes the following steps: 70.5g of aluminum granules and 408.5g of Al-12Si master alloy are dried, weighed, and placed in a graphite crucible in a resistance furnace. Under the protection of argon, the crucible is heated to 780℃ and melted. 17.5g of refined Fe powder is then added and stirred. 1.0g of Ga is added, and 2.5g of Er granules wrapped in aluminum foil is pressed into the bottom of the graphite crucible. A 99% corundum ceramic rod can be used for uniform stirring for 1-3 minutes. The crucible is then held at the temperature for 20-30 minutes. After the alloy is completely melted, the slag is removed to remove surface impurities. Dry aluminum alloy refining agent is added to degas and remove slag. The crucible is held at the temperature for 20 minutes. The molten alloy is then poured into a circular cast iron mold preheated to about 400℃, air-cooled, refined, and cast into a billet.

[0044] Example 3

[0045] The preparation method of Al-10Si(Fe)-1.0Er-0.1Ga sacrificial anode coating alloy with Fe content of 3.5wt.% specifically includes the following steps: 68.5g of aluminum granules and 408.5g of Al-12Si master alloy are dried, weighed, and placed in a graphite crucible in a resistance furnace. Under the protection of argon, the crucible is heated to 780℃ and melted. 17.5g of refined Fe powder is then added and stirred. 0.5g of Ga is added, and 5g of Er granules wrapped in aluminum foil is pressed into the bottom of the graphite crucible. A 99% corundum ceramic rod can be used for uniform stirring for 1-3 minutes. The crucible is then held at the temperature for 20-30 minutes. After the coating alloy is completely melted, the slag is removed to remove surface impurities. Dry aluminum alloy refining agent is added to degas and remove slag. The crucible is held at the temperature for 20 minutes. The molten alloy is then poured into a circular cast iron mold preheated to about 400℃, air-cooled, refined, and cast into a billet.

[0046] In Al-10Si(Fe)-1.0Er-0.1Ga, Ga mainly exists as a solid solution in the α-Al matrix. With the addition of a small amount of Ga, the Ga phase is difficult to observe in the microstructure. After electrochemical stabilization, the open-circuit potential shifts negatively, primarily due to the activation effect of Ga. Together with Er, Ga enhances the surface activity of the aluminum alloy and mutually promotes the growth of Cl on the alloy surface. - Adsorption accelerates the corrosion of the α-Al matrix in the galvanic cell. Therefore, trace amounts of Ga have a synergistic effect on Er and improve the sacrificial anode capability to a certain extent. In addition, Ga dissolved in the α-Al matrix has a positive effect on improving the overall hardness of the alloy and improving the overall service life of the alloy. This excellent property can be achieved with a Ga content of 0.1 wt.%.

[0047] Example 4

[0048] The preparation method of Al-10Si(Fe)-1.0Er-0.2Ga sacrificial anode alloy with Fe content of 3.5wt.% specifically includes the following steps: 68g of aluminum granules and 408.5g of Al-12Si master alloy are dried, weighed, and placed in a graphite crucible in a resistance furnace. Under the protection of argon, the crucible is heated to 780℃ until it melts. 17.5g of refined Fe powder is then added and stirred. 1.0g of Ga is added, and 5g of Er granules wrapped in aluminum foil is pressed into the bottom of the graphite crucible. A 99% corundum ceramic rod can be used for uniform stirring for 1-3 minutes. The mixture is then held at the temperature for 20-30 minutes. After the alloy is completely melted, slag is removed to remove surface impurities. Dry aluminum alloy refining agent is added to degas and remove slag. The mixture is held at the temperature for 20 minutes. The molten alloy is then poured into a circular cast iron mold preheated to about 400℃, air-cooled, refined, and cast into a billet.

[0049] Comparative Example 1

[0050] The preparation method of Al-10Si(Fe) sacrificial anode coating alloy with Fe content of 3.5wt.% specifically includes the following steps: 74g of aluminum granules and 408.5g of Al-12Si master alloy are dried and weighed, placed in a graphite crucible in a resistance furnace, and heated to 780℃ under argon protection until they melt. 17.5g of refined Fe powder is then added and stirred. A 99% corundum ceramic rod can be used for uniform stirring for 1-3 minutes. The mixture is then held at the temperature for 20-30 minutes. After the coating alloy is completely melted, slag is removed to remove surface impurities. Dry aluminum alloy refining agent is added to degas and remove slag. The mixture is then held at the temperature for 20 minutes. Finally, the molten alloy is poured into a round cast iron mold preheated to about 400℃, air-cooled, refined, and cast into a billet.

[0051] Comparative Example 2

[0052] The preparation method of Al-10Si(Fe)-0.5Er sacrificial anode coating alloy with Fe content of 3.5wt.% specifically includes the following steps: 71.5g of aluminum granules and 408.5g of Al-12Si master alloy are dried and weighed, placed in a graphite crucible in a resistance furnace, and heated to 780℃ under argon protection until they melt. 17.5g of refined Fe powder is then added and stirred. 2.5g of Er granules wrapped in aluminum foil are pressed into the bottom of the graphite crucible. A 99% corundum ceramic rod can be used for uniform stirring for 1-3 minutes. The mixture is then held at the temperature for 20-30 minutes. After the coating alloy is completely melted, slag is removed to remove surface impurities. Dry aluminum alloy refining agent is added to degas and remove slag. The mixture is held at the temperature for 20 minutes. The molten alloy is then poured into a circular cast iron mold preheated to about 400℃, air-cooled, refined, and cast into a billet.

[0053] Comparative Example 3

[0054] The preparation method of Al-10Si(Fe)-1.0Er sacrificial anode coating alloy with Fe content of 3.5wt.% specifically includes the following steps: 69g of aluminum granules and 408.5g of Al-12Si master alloy are dried, weighed, and placed in a graphite crucible in a resistance furnace. Under the protection of argon, the crucible is heated to 780℃ and melted. 17.5g of refined Fe powder is then added and stirred. 5g of Er granules wrapped in aluminum foil are pressed into the bottom of the graphite crucible. A 99% corundum ceramic rod can be used for uniform stirring for 1-3 minutes. The mixture is then held at the temperature for 20-30 minutes. After the coating alloy is completely melted, slag is removed to remove surface impurities. Dry aluminum alloy refining agent is added to degas and remove slag. The mixture is held at the temperature for 20 minutes. The molten alloy is then poured into a circular cast iron mold preheated to about 400℃, air-cooled, refined, and cast into a billet.

[0055] Comparative Example 4

[0056] The preparation method of Al-10Si(Fe)-0.1Ga sacrificial anode coating alloy with Fe content of 3.5wt.% specifically includes the following steps: 73.5g of aluminum granules and 408.5g of Al-12Si master alloy are dried and weighed, placed in a graphite crucible in a resistance furnace, and heated to 780℃ under argon protection until they melt. 17.5g of refined Fe powder is then added and stirred. 0.5g of Ga granules wrapped in aluminum foil is pressed into the bottom of the graphite crucible. A 99% corundum ceramic rod can be used for uniform stirring for 1-3 minutes. The mixture is then held at the temperature for 20-30 minutes. After the coating alloy is completely melted, slag is removed to remove surface impurities. Dry aluminum alloy refining agent is added to degas and remove slag. The mixture is held at the temperature for 20 minutes. The molten alloy is then poured into a circular cast iron mold preheated to about 400℃, air-cooled, refined, and cast into a billet.

[0057] Comparative Example 5

[0058] The preparation method of Al-10Si(Fe)-2Zn-0.1Ga sacrificial anode coating alloy with Fe content of 3.5wt.% specifically includes the following steps: 63.5g of aluminum granules and 408.5g of Al-12Si master alloy are dried, weighed, and placed in a graphite crucible in a resistance furnace. Under the protection of argon, the crucible is heated to 780℃ until it melts. 17.5g of refined Fe powder is then added and stirred. 0.5g of Ga granules wrapped in aluminum foil and 10g of zinc granules are pressed into the bottom of the graphite crucible. A 99% corundum ceramic rod can be used for uniform stirring for 1-3 minutes. The crucible is then held at the temperature for 20-30 minutes. After the coating alloy is completely melted, slag is removed to remove surface impurities. Dry aluminum alloy refining agent is added to degas and remove slag. The crucible is held at the temperature for 20 minutes. The molten alloy is then poured into a circular cast iron mold preheated to about 400℃, air-cooled, refined, and cast into a billet.

[0059] Comparative Example 6

[0060] Comparative Example 6 is an Al-10Si(Fe)-1.0Er-0.1Mn alloy. Compared with Example 1, Comparative Example 6 replaced 0.1Ga with 0.1wt.%Mn. The results showed that Mn was mainly dispersed in the τ6(Al9Fe2Si2) phase and did not form a second phase. Therefore, the addition of the same 0.1wt.%Ga did not have the effect of reducing the potential.

[0061] Experimental results show that the addition of Er manifests as tiny, bright dots in the alloy's microstructure, distributed near the τ6 (Al9Fe2Si2) phase, specifically identified as the Er2Al3Si2 phase by SEM analysis. Furthermore, it was observed that the higher the Er content, the more locally this phase aggregated. These small white dots typically possess high brightness and play a crucial role in aluminum-silicon alloys. Firstly, they significantly reduce the open-circuit potential of the alloy, decreasing the anodic polarization of the sacrificial anode alloy, reducing the self-corrosion rate, and improving efficiency. Moreover, DSC analysis revealed that the solidus temperature decreases with increasing Er content.

[0062] Adding trace amounts of Ga dissolved in the alloy, barely visible to the naked eye, results in a relatively uniform distribution. With the addition of Ga, the open-circuit potential decreases, working synergistically with Er to achieve a lower overall anodic polarization, lower self-corrosion rate, and higher current efficiency in the sacrificial anode alloy, thus improving the sacrificial anode performance of the aluminum alloy. This ensures both long-term stability of the operating potential and sufficient service life.

[0063] In addition, the addition of 0.5 to 1.0 wt.% Er and trace amounts of Ga can improve the hardness of the sacrificial anode alloy, increasing the Vickers hardness by about 20 Hv, which can meet the mechanical property requirements of the alloy in some specific applications.

[0064] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, alterations, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An Al-Si sacrificial anode with added Er and Ga, characterized in that: The Al-Si sacrificial anode is composed of the following weight percentages: 10 wt.% silicon, 0.5-1.0 wt.% erbium, 0.1-0.2 wt.% gallium, with the balance being aluminum and other unavoidable impurities. When the above Al-Si sacrificial anode is used for corrosion protection of a steel substrate with an iron content of 3.5 wt.%, it can suppress the harmful effects of Fe on the Al-Si sacrificial anode. After adding rare earth Er, the Er2Al3Si2 phase appears in the alloy.

2. The method for preparing Al-Si sacrificial anodes with added Er and Ga according to claim 1, characterized in that: The Al-Si sacrificial anode is prepared as follows: (1) Dry and weigh the aluminum granules and Al-Si master alloy, place them in the graphite crucible of the resistance furnace and wait for them to melt. Press the Ga and Er granules wrapped in aluminum foil into the bottom of the graphite crucible, stir evenly, and keep it at a constant temperature. (2) After the alloy is completely melted, remove the slag and surface impurities, add dry aluminum alloy refining agent to degas and remove slag, and keep it warm and stand for a period of time. (3) Pour the molten alloy from step (2) into a preheated circular cast iron mold, air cool, refine and cast into a billet.

3. The method for preparing Al-Si sacrificial anodes with added Er and Ga according to claim 2, characterized in that: The melting temperature is 780℃; the Al-Si master alloy is an Al-Si alloy containing 12.24 wt.% Si.

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