A sacrificial anode for use in alternating wet and dry environments on beaches, seas, and land, and a preparation method thereof

Abstract

The present invention provides a sacrificial anode for use in alternating wet-dry environments on beaches, seas, and land, and a preparation method thereof. The sacrificial anode is based on Al and further comprises Zn, In, Mg, Ga, Bi, and optionally Sn and Pb metal elements, wherein the mass percentages of each metal element are as follows: Zn: 3.00-4.00%; In: 0.017-0.02%; Mg: 1.00-1.50%; Ga: 0.10-0.15%; Sn: 0-0.12%; Bi: 0.40-0.50%; Pb: 0-0.03%; and the balance is Al. The sacrificial anode has the characteristics of stable working potential (continuously stable at -1.0V) in alternating wet-dry environments, easy shedding of corrosion products, uniform corrosion morphology, high current efficiency, large actual capacitance, and good casting performance.

Description

Technical Field

[0001] The invention belongs to the technical field of metal anti-corrosion, and particularly relates to a sacrificial anode used in a dry-wet alternating environment of a beach, sea, and land bank, and a preparation method thereof. Background Art

[0002] Sacrificial anode cathodic protection is a method to prevent metal corrosion. Its basic principle is to use the characteristic that the potential of the sacrificial anode material is lower than that of the protected metal to cause the sacrificial anode to be continuously oxidized and consumed, thereby protecting the cathode metal from corrosion.

[0003] Aluminum-based sacrificial anodes have been gradually used in the past decade due to their advantages such as negative potential, large capacitance and light weight, especially in cathodic protection of marine engineering.

[0004] Patent CN112481617A discloses a zinc alloy sacrificial anode suitable for corrosion protection and polarity reversal resistance of special steel materials in marine environments. The zinc alloy sacrificial anode comprises the following chemical compositions by weight: Al: 0.1-0.5%, Mg: 0.05-0.5%, Ce: 0.5-2%, Fe ≤ 0.005%, Cu ≤ 0.005%, Pb ≤ 0.006%, Si ≤ 0.1%, with the balance being zinc. The zinc alloy sacrificial anode has an open circuit potential of -1.0 to -0.9V and an actual capacitance of ≥800A·h / kg.

[0005] Patent CN102492949B discloses a low-drive potential aluminum alloy sacrificial anode for use in oily seawater environments. The sacrificial anode is made from high-purity aluminum as its primary raw material, with zinc, bismuth, and silicon added. The weight percentages of each component are: zinc 0.5-2.0%, bismuth 1.0-3.0%, silicon 0.10-0.50%, and other impurities: magnesium, indium, and titanium ≤ 0.15%, iron ≤ 0.15%, with the balance being aluminum. The sacrificial anode is manufactured using a casting process. Its operating potential in oily seawater is between -0.75 and -0.85V, its current efficiency is no less than 75%, and it dissolves evenly, with the product easily falling off. The present invention can be used to protect materials such as high-strength steel, stainless steel, and titanium alloys in oily seawater environments.

[0006] While existing aluminum-based sacrificial anodes exhibit stable activation performance in marine environments, they are unsuitable for alternating soil wet-dry conditions due to several drawbacks: Corrosion products are difficult to shed in these conditions, hindering aluminum anode activation, reducing activation performance, and lowering actual capacitance and current efficiency. Furthermore, these impeded corrosion products accumulate on the anode surface, solidifying into a shell in a dry state and ultimately causing anode failure. The chloride ion content in alternating soil wet-dry conditions is far lower than that in seawater, making it difficult for these ions to penetrate the passivation film on the aluminum anode surface, inhibiting anode activation and dissolution.

[0007] Therefore, it is an urgent problem to develop a new sacrificial anode that is suitable for the alternating dry and wet environment of beaches, seas and land, with a relatively negative potential, large capacitance, high efficiency, and easy shedding of corrosion products. Summary of the Invention

[0008] In order to solve the above problems, the present invention provides a sacrificial anode for use in alternating dry-wet environments on beaches, seas and land. The system is improved based on the Al-Zn-In sacrificial anode system. Appropriate amounts of metal elements, such as Mg, Ga, Sn and Bi, are added to the anode through a casting method. As a result, the sacrificial anode has the characteristics of stable working potential (continuously stable at -1.0V), easy shedding of corrosion products, uniform corrosion morphology, high current efficiency, large actual capacitance and good casting performance in the alternating dry-wet environment.

[0009] The technical solutions of the present invention are as follows:

[0010] The present invention provides a sacrificial anode for use in alternating wet and dry environments on beaches, seas, and land. The sacrificial anode is based on Al and further comprises Zn, In, Mg, Ga, Bi, and optionally Sn and Pb metal elements, wherein the mass percentage of each metal element is:

[0011] Zn: 3.00-4.00%;

[0012] In: 0.017-0.02%;

[0013] Mg: 1.00-1.50%;

[0014] Ga: 0.10-0.15%;

[0015] Sn: 0-0.12%;

[0016] Bi: 0.40-0.50%;

[0017] Pb: 0-0.03%;

[0018] The balance is Al.

[0019] Furthermore, the mass percentage of each metal element in the sacrificial anode is:

[0020] Zn: 4.00%;

[0021] In: 0.02%;

[0022] Mg: 1.00%;

[0023] Ga: 0.10%;

[0024] Sn: 0.10%;

[0025] Bi: 0.50%;

[0026] The balance is Al.

[0027] Furthermore, the mass percentage of each metal element in the sacrificial anode is:

[0028] Zn: 4.00%;

[0029] In: 0.02%;

[0030] Mg: 1.00%;

[0031] Ga: 0.10%;

[0032] Bi: 0.40%;

[0033] Pb: 0.03%

[0034] The balance is Al.

[0035] Furthermore, the mass percentage of each metal element in the sacrificial anode is:

[0036] Zn: 4.00%;

[0037] In: 0.02%;

[0038] Mg: 1.50%;

[0039] Ga: 0.10%;

[0040] Sn: 0.10%

[0041] Bi: 0.50%;

[0042] The balance is Al.

[0043] In the present invention, the corrosion potential is the potential of the sacrificial anode itself in the medium, and the working potential is the potential when the sacrificial anode protects other materials.

[0044] Furthermore, in a simulated dry-wet alternating environment of the beach, sea and land, the corrosion rates of the sacrificial anode after 5 days of dry-wet alternation and 10 days of dry-wet alternation were 0.201-0.239 mg / cm 2 ·Day, 0.629~0.849mg / cm 2 ·sky.

[0045] Furthermore, in a simulated wet-dry alternating environment of the beach, sea and land, the corrosion potential of the sacrificial anode after 5 days of wet-dry alternation and 10 days of wet-dry alternation was -1.06V~-1.02V and -1.06V~-1.04V, and the corrosion current density was 3.5×10 -6 ~6.2×10 - 6 A / cm2 and 5.6×10 -6 ~7.2×10 -6 A / cm 2 .

[0046] Furthermore, in a simulated beach, sea, and shore dry-wet alternating environment, the current efficiency of the sacrificial anode after 5 days of dry-wet alternation and 10 days of dry-wet alternation was 53.59-54.13% and 52.03-52.55%, respectively.

[0047] Furthermore, in a simulated wet-dry alternating environment of a beach, sea, and land, the open circuit potential of the sacrificial anode remains at a negative level, and remains at -1.06V to -1.05V as the wet-dry alternating time increases.

[0048] Furthermore, in a simulated wet-dry alternating environment of a beach, sea, and land, the working potential of the sacrificial anode remains at a negative level, and remains at -0.98V to -1.03V as the wet-dry alternating time increases.

[0049] Furthermore, the simulated alternating wet-dry environment of the beach and seashore is a simulated alternating wet-dry environment of coastal soil, wherein the alternating wet-dry time ratio of the soil environment is 6h:6h, that is, the soil dry-wet environment is switched every 6 hours, the soil moisture content of the dry environment is 15%, and the soil wet environment is completely submerged in seawater. The soil is clay, to which a certain amount of NaCl, Na2CO3, NaHCO3, and Na2SO4 are added to make the concentration of each ion in the soil reach Na + =0.551%, Cl - =0.372%, CO3 2- =0.0192%, HCO3 - =0.0293%, SO4 2- =0.0557%.

[0050] Furthermore, the actual capacitance of the sacrificial anode in a fully immersed seawater environment reaches 2679A·h·kg -1 , the current efficiency reaches 93.46%.

[0051] Furthermore, the current efficiency of the sacrificial anode in a dry-wet alternating environment can reach 52.14%, the open circuit potential is maintained at -1.05V, and the operating potential is stabilized at about -1.03V.

[0052] In the sacrificial anode of the present invention, Al is used as the matrix and other metal elements are added to form an Al alloy, wherein:

[0053] Zn: Adding more alloying elements to the aluminum anode can make the anode easier to alloy, have a uniform composition, and easily shed corrosion products, and the anode potential shifts negatively by 100 to 300 mV. In addition, Zn will accelerate the nucleation of ZnAl2O4 spinel. Because the molar volume of ZnAlO4 is greater than that of Al2O3, it can increase the defects of the passivation film on the surface of the aluminum anode and destroy the integrity of the passivation film. The solubility of Zn in Al is about 2%. When the Zn content is high (4% to 5%), it is easy to aggravate the segregation phenomenon in the anode. Therefore, the Zn content should not be greater than 4%.

[0054] In: Adding In to aluminum alloy anode materials can have a strong activation effect. Studies have found that the synergistic effect of Zn and In can enhance the adsorption of chloride ions by the anode material, thereby activating the anode material. Excessive In elements will exist in the form of segregation or metal compounds, reducing the overall performance of the anode material. Therefore, the content of In elements in aluminum alloy anodes is strictly controlled. The solid solubility of In elements in aluminum is relatively low, less than 0.01% at 20°C. Excessive In elements will exist in the form of segregation or metal compounds, reducing the overall performance of the anode material. Some standards point out that the most appropriate In element addition amount for Al-Zn-In based anode materials is 0.02%.

[0055] Mg: Adding a small amount of Mg to aluminum alloy anode materials can improve the current efficiency of the anode material. Mg can reduce the impurity content by changing the impurity state in the aluminum alloy, thereby improving anode performance. Mg can change the microstructure of the aluminum alloy anode, promoting its uniform dissolution and polarization properties, thereby improving cathodic protection performance. At room temperature, the solubility of Mg in aluminum is approximately 1.5%. When other alloying elements are added at the same time, the solid solubility of Mg in Al decreases to approximately 1%. When the Mg content in the aluminum alloy is too high, it reacts with Al to form Mg2Al3, which aggravates intergranular corrosion of the anode and reduces the anode current efficiency.

[0056] Ga is the main activating element. 0.01% Ga can play an activating role. When the Ga content reaches 0.1%, the aluminum anode potential shifts significantly negatively. It can be evenly dissolved in the aluminum alloy, changing the alloy grain size and second phase properties, promoting the uniform dissolution of the anode alloy, and improving its overall electrochemical performance.

[0057] Sn, when added in an amount of 0.09% or more, significantly inhibits the growth of aluminum anodic oxide film. It can significantly reduce the alloy's anodic potential and improve current efficiency. However, due to its low solid solubility, a large amount of Sn will form precipitates. The increase in precipitates will accelerate the self-corrosion of the alloy.

[0058] Bi acts as an activator, expanding the aluminum alloy lattice and weakening the passivation of the surface oxide film. It can also increase the solid solubility of other activating elements and improve anode performance. Adding a small amount of Bi to Al-Zn-Sn can increase the solubility of Sn in Al, thereby reducing the need for subsequent heat treatment of the anode material and improving anode performance. Considering the alloy's activity, electrochemical performance, and cost, a Bi addition of 0.4% to 0.5% is more appropriate.

[0059] Pb can form a low-melt mixture with Bi and Ga with good flow properties, which can destroy the oxide film on the surface of the aluminum anode, continuously activate the anode, and improve the electrochemical performance. However, the content should not be too high, otherwise it will easily accumulate at the grain boundaries.

[0060] The present invention also provides a method for preparing the aforementioned sacrificial anode, the method comprising:

[0061] Step 1: Material processing: Dry the raw materials, aluminum ingots, zinc particles, aluminum-magnesium alloy, indium, bismuth, optional tin and lead, as well as crucibles and molds in a drying oven in advance.

[0062] Step 2: Prepare the sacrificial anode by melt casting method:

[0063] Add the preheated aluminum ingot into the crucible and melt it in a melting furnace heated to 710°C. After the material is completely melted, stir for 40-60 seconds to obtain molten aluminum liquid.

[0064] Lower the melting furnace temperature to 690°C, add the preheated aluminum-magnesium alloy into the aluminum liquid, stir for 40s-60s after the material is completely melted, then add the preheated zinc particles and stir until completely melted to obtain melt A;

[0065] Raise the melting furnace temperature to 710°C, add gallium and preheated indium, bismuth, and optional tin and lead into melt A respectively until they are completely melted to obtain melt B;

[0066] The temperature of the melting furnace is maintained at 710° C., and the melt B is allowed to stand for 10 to 12 minutes. After the melt B is fully stirred and impurities are removed, the melt B is poured and cooled.

[0067] Furthermore, the smelting furnace can produce, for example, 360g of sacrificial anode aluminum alloy at a time. The specific raw material mass is: 14.4g zinc, 0.072g indium, 36g aluminum-magnesium alloy (magnesium mass fraction 10%), 0.36g gallium, 0.36g tin, 1.8g bismuth, and the rest is aluminum.

[0068] Furthermore, in step 1, the weighed aluminum ingot, zinc particles, and aluminum-magnesium alloy are placed in a drying oven at a temperature of 200° C. and dried for 40-50 minutes for later use;

[0069] Wrap the indium, bismuth, and optional tin and lead metals to be added with aluminum foil to form a metal sheet, place it in a drying oven at a temperature of 200° C. and dry it for 40 to 50 minutes, and then dry it for later use;

[0070] Place the crucible and graphite oil tank mold in a drying oven at 200°C for later use.

[0071] Furthermore, the inner dimensions of the graphite oil tank mold are 80×80×40 (mm).

[0072] Furthermore, if the gallium is not preheated, the preheating temperature is too high to find a suitable container, and the gallium is easily adhered to the surface of the container, and there will be residue when it is added to the melting furnace, resulting in deviation of the alloy composition.

[0073] Furthermore, in step 2, after the melt B is fully stirred, impurities floating on the surface are removed with a carbon rod, the graphite oil tank mold is taken out from the drying oven, and the melt B after impurities are removed is poured into the graphite oil tank mold by holding the crucible with a crucible clamp. The mold is placed on a high-temperature resistant quartz plate and cooled to room temperature of 20°C in a ventilated place.

[0074] Furthermore, the indium, tin and bismuth are made of metal powder, which is convenient for accurate weighing and conducive to smelting.

[0075] The beneficial effects of the present invention are as follows:

[0076] The novel sacrificial anode of the present invention has the advantages of low corrosion resistance, high corrosion tendency, strong anode dissolution ability and continuous dissolution by adding appropriate amounts of Zn, In, Mg, Ga, Bi, and optional Sn and Pb metal elements. When tested in a simulated dry-wet alternating environment, the duration of the dry-wet alternation has little effect on the corrosion potential of the sacrificial anode, and the corrosion potential throughout the dry-wet alternation process does not differ much, remains at a relatively negative level, and is stable at -1.06V to -1.02V.

[0077] The open circuit potential of the sacrificial anode remained at a relatively negative level under the alternating dry-wet environment. As the experiment progressed, the open circuit potential did not show an obvious positive shift, but instead showed a small negative shift. The open circuit potential was relatively stable, remaining at -1.06V to -1.05V.

[0078] The sacrificial anode has a strong surface corrosion activity, is less affected by the passivation film on the surface, has good continuous activation discharge characteristics, and maintains a high activation energy.

[0079] In summary, the sacrificial anode has excellent comprehensive properties such as stable working potential, easy shedding of corrosion products, uniform corrosion morphology, high current efficiency, large actual capacitance, good casting performance, and relatively negative corrosion potential. In addition, the formula is environmentally friendly, the raw materials are low-cost and easy to obtain, the preparation process is simple, and it is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 These are SEM images of the sacrificial anode of Example 1 of the present invention after undergoing different cycles in a simulated coastal soil dry-wet alternating environment.

[0081] Figure 2 These are SEM images of the sacrificial anode of Example 2 of the present invention after undergoing different cycles in a simulated coastal soil dry-wet alternating environment.

[0082] Figure 3 The SEM images of the comparative national standard type II aluminum-based anode after different cycles in a simulated coastal soil dry-wet alternating environment.

[0083] Figure 4 This is the working potential change curve of the sacrificial anode in Example 1 of the present invention.

[0084] Figure 5 This is the working potential change curve of the sacrificial anode in Example 2 of the present invention.

[0085] Figure 6 This is the working potential change curve of the national standard II type aluminum-based anode for comparison.

[0086] Figure 7 This is the open circuit potential change curve of the sacrificial anode in Example 1 of the present invention.

[0087] Figure 8 This is the open circuit potential change curve of the sacrificial anode in Example 2 of the present invention.

[0088] Figure 9 This is the open circuit potential change curve of the national standard II type aluminum-based anode for comparison. DETAILED DESCRIPTION

[0089] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0090] Example 1

[0091] The present invention provides a sacrificial anode for use in alternating wet and dry environments on beaches, seas, and land. The sacrificial anode is based on Al and further comprises metal elements such as Zn, In, Mg, Ga, Sn, and Bi. The mass percentages of the metal elements are shown in Table 1.

[0092] Table 1: Content of sacrificial anode components in Example 1

[0093]

[0094] The preparation method is as follows:

[0095] Step 1: Material preparation and processing: Prepare aluminum ingots, aluminum-magnesium alloy, zinc particles, gallium liquid, and metal powders of indium, tin, and bismuth. The purity of each metal is above 99.9%. The aluminum ingot uses 3g / aluminum particles, and the magnesium content of the aluminum-magnesium alloy is 10%. To facilitate weighing and smelting, the metal powders of indium, tin, bismuth and zinc particles are wrapped with aluminum foil with a purity of 99.99%.

[0096] The melting and casting process is carried out in a medium frequency induction furnace. The specific operation steps are as follows:

[0097] 1) Place the weighed aluminum ingot, zinc particles, and aluminum-magnesium alloy in a drying oven at 200°C and dry for 40-50 minutes.

[0098] Wrap the indium, tin, and bismuth metal powders to be added with aluminum foil to form metal sheets, place them in a drying oven at 200° C. and dry them for 40 to 50 minutes.

[0099] 2) Place the crucible and a graphite oil tank mold with inner dimensions of 80×80×40 (mm) in a drying oven at 200°C for drying;

[0100] Step 2: Prepare the sacrificial anode by melt casting method:

[0101] Add the preheated aluminum ingot to the crucible and melt it in a melting furnace at 710°C for 10-15 minutes. After the material is completely melted, stir it for one minute to obtain molten aluminum liquid.

[0102] Lower the melting furnace temperature to 690°C and add the preheated aluminum-magnesium alloy into the aluminum liquid. After the material is completely melted, stir for one minute and then add the preheated zinc particles. Stir until completely melted to obtain melt A.

[0103] The melting furnace temperature was raised to 710°C, and liquid gallium and preheated metal flakes made of indium, tin, and bismuth metal powders wrapped in aluminum foil were added to melt A until completely melted, thereby obtaining melt B.

[0104] After the melt B is fully stirred, impurities floating on the surface are removed with a carbon rod, the graphite oil tank mold is taken out from the drying oven, and the melt B after impurities are removed is poured into the graphite oil tank mold by holding the crucible with a crucible clamp. The mold is placed on a high-temperature resistant quartz plate and cooled to room temperature of 20° C. in a ventilated place to obtain the sacrificial anode.

[0105] Example 2

[0106] The present invention provides a sacrificial anode for use in alternating wet and dry environments on beaches, seas, and land. The sacrificial anode is based on Al and further comprises metal elements such as Zn, In, Mg, Ga, Bi, and Pb. The mass percentages of the metal elements are shown in Table 2.

[0107] Table 2: Content of sacrificial anode components in Example 2

[0108]

[0109] The preparation method is as follows:

[0110] Step 1: Material preparation and processing: Prepare aluminum ingots, aluminum-magnesium alloy, zinc particles, gallium liquid, and metal powders of indium, bismuth, and lead. The purity of each metal is above 99.9%. The aluminum ingots use 3g / aluminum particles, and the magnesium content of the aluminum-magnesium alloy is 10%. To facilitate weighing and smelting, the metal powders of indium, tin, bismuth, and zinc particles are wrapped in aluminum foil with a purity of 99.99%.

[0111] The melting and casting process is carried out in a medium frequency induction furnace. The specific operation steps are as follows:

[0112] 1) Place the weighed aluminum ingot, zinc particles, and aluminum-magnesium alloy in a drying oven at 200°C and dry for 40-50 minutes.

[0113] Wrap the indium, bismuth, and lead metal powders to be added with aluminum foil to form metal sheets, place them in a drying oven at 200° C. and dry them for 40 to 50 minutes, and then dry them for later use;

[0114] 2) Place the crucible and a graphite oil tank mold with inner dimensions of 80×80×40 (mm) in a drying oven at 200°C for drying;

[0115] Step 2: Prepare the sacrificial anode by melt casting method:

[0116] Add the preheated aluminum ingot to the crucible and melt it in a melting furnace at 710°C for 10-15 minutes. After the material is completely melted, stir it for one minute to obtain molten aluminum liquid.

[0117] Lower the melting furnace temperature to 690°C and add the preheated aluminum-magnesium alloy into the aluminum liquid. After the material is completely melted, stir for one minute and then add the preheated zinc particles. Stir until completely melted to obtain melt A.

[0118] The melting furnace temperature was raised to 710°C, and liquid gallium and preheated metal flakes made of indium, bismuth, and lead metal powders wrapped in aluminum foil were added to melt A until completely melted, thereby obtaining melt B.

[0119] After the melt B is fully stirred, impurities floating on the surface are removed with a carbon rod, the graphite oil tank mold is taken out from the drying oven, and the melt B after impurities are removed is poured into the graphite oil tank mold by holding the crucible with a crucible clamp. The mold is placed on a high-temperature resistant quartz plate and cooled to room temperature of 20° C. in a ventilated place to obtain the sacrificial anode.

[0120] Example 3

[0121] The present invention provides a sacrificial anode for use in alternating wet and dry environments on beaches, seas, and land. The sacrificial anode is based on Al and further comprises metal elements such as Zn, In, Mg, Ga, Sn, and Bi. The mass percentages of the metal elements are shown in Table 1.

[0122] Table 3 Table of composition and content of sacrificial anode in the embodiment

[0123]

[0124] The preparation method is as follows:

[0125] Step 1: Material preparation and processing: Prepare aluminum ingots, aluminum-magnesium alloy, zinc particles, gallium liquid, and metal powders of indium, tin, and bismuth. The purity of each metal is above 99.9%. The aluminum ingot uses 3g / aluminum particles, and the magnesium content of the aluminum-magnesium alloy is 10%. To facilitate weighing and smelting, the metal powders of indium, tin, bismuth and zinc particles are wrapped with aluminum foil with a purity of 99.99%.

[0126] The melting and casting process is carried out in a medium frequency induction furnace. The specific operation steps are as follows:

[0127] 1) Place the weighed aluminum ingot, zinc particles, and aluminum-magnesium alloy in a drying oven at 200°C and dry for 40-50 minutes.

[0128] Wrap the indium, tin, and bismuth metal powders to be added with aluminum foil to form metal sheets, place them in a drying oven at 200° C. and dry them for 40 to 50 minutes.

[0129] 2) Place the crucible and a graphite oil tank mold with inner dimensions of 80×80×40 (mm) in a drying oven at 200°C for drying;

[0130] Step 2: Prepare the sacrificial anode by melt casting method:

[0131] Add the preheated aluminum ingot to the crucible and melt it in a melting furnace at 710°C for 10-15 minutes. After the material is completely melted, stir it for one minute to obtain molten aluminum liquid.

[0132] Lower the melting furnace temperature to 690°C and add the preheated aluminum-magnesium alloy into the aluminum liquid. After the material is completely melted, stir for one minute and then add the preheated zinc particles. Stir until completely melted to obtain melt A.

[0133] The melting furnace temperature was raised to 710°C, and liquid gallium and preheated metal flakes made of indium, tin, and bismuth metal powders wrapped in aluminum foil were added to melt A until completely melted, thereby obtaining melt B.

[0134] After the melt B is fully stirred, impurities floating on the surface are removed with a carbon rod, the graphite oil tank mold is taken out from the drying oven, and the melt B after impurities are removed is poured into the graphite oil tank mold by holding the crucible with a crucible clamp. The mold is placed on a high-temperature resistant quartz plate and cooled to room temperature of 20° C. in a ventilated place to obtain the sacrificial anode.

[0135] Comparative Example

[0136] The mass percentages of the various elements in the national standard II type aluminum-based anode of the comparative example are shown in Table 3:

[0137] Table 3 National Standard Type II Sacrificial Anode Composition Content

[0138]

[0139] Test Case

[0140] 1. Full Seawater Immersion Current Efficiency Test According to the requirements of GB-T 17848-1999 Test Method for Electrochemical Performance of Sacrificial Anodes, the anode samples of the examples and comparative examples were processed and artificial seawater was prepared. Then, the conventional test method was used with a test time of 240 hours and a current density of 1 mA / cm 2 ;

[0141] Corrosion products are removed by preparing rust removal liquid in accordance with the requirements of GBT 16545-2015 Corrosion of Metals and Alloys - Removal of Corrosion Products on Corrosion Test Specimens.

[0142] Under full seawater immersion, the sacrificial anode of Example 1 has an average current efficiency of 93.46%, an average actual capacitance of 2679.353 A·h·kg-1, and corrosion products easily fall off with no obvious adhesion traces. The test shows high effectiveness in conventional seawater environments.

[0143] Under full seawater immersion, the average current efficiency of the sacrificial anode of Example 2 was 54.78%, and the average actual capacitance was 1572.653 A·h·kg-1. A large amount of white flocs adhered to the surface of the anode, which had a certain impact on the continuous activation of the anode.

[0144] 2. The simulated coastal soil dry-wet alternating environment test was conducted under the conditions of a soil dry-wet ratio of 6h:6h and a test period of 10 days. The test was conducted in a self-designed test chamber. The soil used in the test was clay, with a soil moisture content of 15% in the dry environment and a soil wet environment where the seawater completely submerged the soil. A certain amount of NaCl, Na2CO3, NaHCO3, Na2SO4 and other reagents were added to make the concentration of each ion in the soil reach Na + =0.551%, Cl - =0.372%, CO3 2- =0.0192%, HCO3 - =0.0293%, SO4 2- = 0.0557%, simulating a coastal soil corrosion environment, using deionized water. Three parallel specimens—a sealed rod anode—were buried vertically in the self-corrosion test apparatus, and a sealed block anode specimen was also buried in the soil. The center of the sacrificial anode was 10 cm from the soil surface, and the distance between each specimen was at least 3 cm. Three parallel specimens were set up for each test set and compared with each other. After the test cycle, the corresponding anode specimens were removed, the corrosion products and corrosion morphology were observed, and the anode specimens were weighed.

[0145] like Figure 1 , which are SEM images of the sacrificial anode of Example 1 of the present invention after undergoing different cycles in a simulated coastal soil dry-wet alternating environment. Figure 1 (a) and Figure 1 (b) Corrosion SEM images after 5 and 10 days of cycling under alternating dry-wet conditions, respectively. The SEM images show that the corrosion pits on the sacrificial anode surface have deepened, corrosion has further developed, and the anode surface remains activated. Overall, the sacrificial anode exhibits good activated corrosion characteristics, with minimal surface corrosion products. The anode maintains sustained activation and excellent electrochemical performance.

[0146] like Figure 2 , which are SEM images of the sacrificial anode of Example 2 of the present invention after different cycles in a simulated coastal soil dry-wet alternating environment. Figure 2 (a) is the corrosion SEM image of the sample after 5 days of cycling under dry-wet alternating conditions. Figure 2 (b) is an SEM image of corrosion after 10 days of alternating dry-wet cycles. The image shows a layer of corrosion products attached to the surface of Example 2. This layer of corrosion products begins to appear around the corrosion pits after 5 days of alternating dry-wet cycles. At this point, the corrosion pits are relatively small and have not yet developed into larger pits. After 10 days of alternating dry-wet cycles, the corrosion pits expand in size, with increased adhesion of corrosion products and visible cracks within the pits.

[0147] The average corrosion rates of three parallel samples after 5 and 10 days of cycling in a dry-wet alternating environment in Example 1 were calculated by weighing the anode samples before and after corrosion, and the average corrosion rates were 0.216 mg / cm 2 Day, 0.629 mg / cm 2 The higher the corrosion rate, the stronger the surface activity is, the smaller the passive film is, and the more soluble the metal is, the higher the activation energy is.

[0148] The average corrosion rates of the three parallel samples in Example 2 after 5 and 10 days of cycling in a dry-wet alternating environment were 0.101 mg / cm 2 Day, 0.157 mg / cm 2 ·sky.

[0149] On the contrary Figure 3 Shown are SEM images of the comparative national standard type II aluminum-based anode after different cycles in a simulated coastal soil dry-wet alternating environment.

[0150] Figure 3 (a) and Figure 3 (b) Corrosion SEM images of the national standard II type aluminum-based anode of the comparative example after 5 days and 10 days in a dry-wet alternating environment. From the SEM images, it can be observed that after 5 days of dry-wet alternation in the soil, the aluminum anode has obvious corrosion pits on the surface, and there are corrosion products adhering around them. After 10 days of dry-wet alternation, the corrosion pits on the surface of the aluminum anode deepened. Some corrosion products around the corrosion pits adhered to the surface of the aluminum anode with soil, preventing the corrosion pits from spreading to the surrounding area. Corrosion can only continue in the vertical direction, causing the corrosion pits to deepen. As the dry-wet alternation time increases, corrosion pits appear on the surface of the aluminum anode and deepen into the interior of the aluminum anode over time. Corrosion products gradually accumulate on the surface of the aluminum anode over time, causing the aluminum anode to have a reduced solubility, weakened discharge capacity, and reduced electrochemical performance.

[0151] The average corrosion rates after 5 and 10 days of cycling under dry-wet alternating conditions were 0.0351 mg / cm 2 Day, 0.0311 mg / cm 2 It is obvious that the corrosion rate of aluminum anode decreases with the extension of the cycle period.

[0152] like Figure 4 As shown, the sacrificial anode in Example 1 has a relatively negative operating potential. The duration of the dry-wet cycle has little effect on the operating potential, with the operating potential remaining relatively negative throughout the dry-wet cycle. In Example 1, the operating potential is relatively positive when the soil is dry, but shifts negatively when the soil is wet. The operating potential fluctuates slightly and remains relatively stable, stabilizing at -1.03 V in the later stages.

[0153] The working potential of Example 2 is as follows Figure 5 As shown, the open circuit potential of Example 2 is -1.0 V in the early stage of the dry-wet alternation, and stabilizes at around -1.04 V after 10 days of dry-wet alternation.

[0154] On the contrary Figure 6 As shown, the working potential of the comparative aluminum anode changes over the course of a day. Its working potential is related to the wet / dry state of the corrosive environment. During the 0-6h and 12-18h periods of the day, when the soil is wet, the working potential of the aluminum anode is relatively negative. During these periods, the anode performs well, enabling sustained dissolution and providing sufficient current. During the 6-12h and 18-24h periods, when the soil is dry, the working potential shifts positively by approximately 0.2V. This is primarily due to surface corrosion products in the dry state, which prevent the aluminum anode from dissolving, causing its performance to decline. Over the entire cycle, the working potential of the aluminum anode fluctuates from -0.9V at the beginning of the test to -0.8V.

[0155] like Figure 7 As shown in the figure, it can be seen that the open circuit potential of the sacrificial anode of Example 1 remains at a relatively negative level under the dry-wet alternating environment, and as the dry-wet alternating time increases, the open circuit potential does not show an obvious positive shift, but instead shows a small negative shift. The open circuit potential is relatively stable and remains at around -1.05V.

[0156] The open circuit potential of the sacrificial anode of Example 2 is as follows: Figure 8 As shown, the working potential fluctuates around -1.04 V. In Example 2, when the soil is dry, the working potential is relatively positive. When the soil is wet, the working potential shifts negatively to varying degrees. The working potential of Example 2 is slightly lower than that of Example 1, but tends to increase over time.

[0157] On the contrary Figure 9 As shown, from Figure 9 It can be seen that the open circuit potential of the aluminum anode in the comparative example gradually shifts positively with the extension of the dry-wet alternation time, rising from -1.12V in the early stage of the experiment to -0.97V in the later stage. The open circuit potential shifts positively significantly, the electrochemical properties decrease, the corrosion tendency of the anode decreases, and the activated corrosion characteristics decrease.

[0158] In addition, the sacrificial anode of Example 1 has undergone multiple dry-wet cycles in the soil, and its average current efficiency is more than 50%, and is relatively stable. After 5 days of dry-wet cycles, the average current efficiency is 52.39%, and after 10 days of dry-wet cycles, the average current efficiency is 52.23%. As the dry-wet cycles proceed, the current efficiency does not fluctuate significantly, and has good continuous activation discharge performance, and the current efficiency is relatively ideal. The sacrificial anode of Example 2 has undergone multiple dry-wet cycles in the soil, and its average current efficiency is more than 50%, and is relatively stable. After 5 days of dry-wet cycles, the average current efficiency is 57.61%, and after 10 days of dry-wet cycles, the average current efficiency is 57.01%. As the dry-wet cycles proceed, the current efficiency does not fluctuate significantly, and has good continuous activation discharge performance, and the current efficiency is relatively ideal.

[0159] On the contrary, the current efficiency of the aluminum anode of the comparative example in the soil dry-wet alternating environment is 27.62% and 41.19% when the cycle period is 5 days and 10 days, respectively, which is relatively low.

[0160] In summary, the sacrificial anode of the present invention has the advantages of low corrosion resistance, high corrosion tendency, strong anode dissolution ability and continuous dissolution, relatively negative corrosion potential, strong surface activity, small surface passivation film, and high activation energy. Its open circuit potential remains at a relatively negative level under the dry-wet alternating environment. As the experiment progresses, the open circuit potential does not show a significant positive shift, but instead shows a small negative shift. The open circuit potential is relatively stable, remaining at around -1.05 V. The dry-wet alternation duration has little effect on the corrosion potential. The corrosion potential during the entire dry-wet alternation process does not differ much and remains at a relatively negative level.

[0161] However, in a soil-wet-dry alternating corrosive environment, the corrosion rate of a national standard II aluminum anode decreases with increasing wet-dry alternating cycles. The self-corrosion products of the anode in this soil-wet-dry alternating environment are primarily aluminum oxides, with a relatively uniform corrosion morphology that is not easily detached. The open-circuit potential, working potential, and corrosion potential of the aluminum anode shift positively with increasing wet-dry alternating cycles, resulting in decreased reactivation performance and hindering the aluminum anode's ability to maintain and maintain its protective function in this environment. The working potential of the aluminum anode is related to the wet-dry state of the corrosive environment. When the soil is wet, the working potential of the aluminum anode is more negative, resulting in better performance and enabling sustained dissolution and sufficient current. When the soil is dry, the working potential shifts positively, primarily because surface corrosion products in the dry state prevent dissolution, leading to decreased performance. The wet-dry alternating soil corrosive environment causes corrosion products to accumulate on the surface of the aluminum anode, causing corrosion pits to spread into the interior of the anode. This increases electrochemical impedance, hinders anode activation, weakens ion diffusion, and reduces surface charge transfer, slowing the charge transfer rate.

[0162] Compared with the national standard II type aluminum anode, the present invention increases the Mg content, improves the anode dissolution ability and polarization performance, and makes the corrosion potential more negative; the addition of the metal element Ga plays an activation role, causes the aluminum anode potential to shift negatively, strengthens the surface activity, and promotes the uniform dissolution of the anode alloy; in addition, the present invention adds the metal element Bi, which can serve as an activator to weaken the passivation performance of the oxide film on the anode surface, so that the passivation film on the anode surface is smaller; the metal element Sn can inhibit the growth of the aluminum anode oxide film, reduce the anode potential of the aluminum anode, and improve the current efficiency; the metal element Pb can form a low-melt mixture with Bi and Ga with good flow properties, which can destroy the oxide film on the surface of the aluminum anode, continuously activate the anode, and improve the electrochemical performance.

[0163] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent variation based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A sacrificial anode for use in alternating wet and dry environments on beaches, seas, and land, characterized in that: The sacrificial anode is based on Al and further comprises Zn, In, Mg, Ga, Bi, and optionally Sn and Pb metal elements, wherein the mass percentage of each metal element is: Zn: 3.00-4.00%; In: 0.017-0.02%; Mg: 1.00-1.50%; Ga: 0.10-0.15%; Sn: 0-0.12%; Bi: 0.40-0.50%; Pb: 0-0.03%; The remainder is Al; In the simulated dry-wet alternating environment of the beach and land, the corrosion rates of the sacrificial anode after 5 days of dry-wet alternation and 10 days of dry-wet alternation were 0.201~0.239mg / cm 2 ·Day, 0.629~0.849 mg / cm 2 ·sky; In the simulated wet-dry alternating environment of the beach, sea and land, the open circuit potential of the sacrificial anode remained at a negative level, and remained at -1.06V~-1.05V as the wet-dry alternating time prolonged; In a simulated wet-dry alternating environment, the working potential of the sacrificial anode remained negative, ranging from -1.03V to -0.98V as the wet-dry alternating time increased. In a simulated beach and shore dry-wet alternating environment, the current efficiency of the sacrificial anode after 5 days of dry-wet alternation and 10 days of dry-wet alternation was 53.59-54.13% and 52.03-52.55%, respectively.

2. The sacrificial anode according to claim 1, characterized in that The mass percentage of each metal element in the sacrificial anode is: Zn: 4.00%; In: 0.02%; Mg: 1.00%; Ga: 0.10%; Sn: 0.10%; Bi: 0.50%; The balance is Al.

3. The sacrificial anode according to claim 1, characterized in that The mass percentage of each metal element in the sacrificial anode is: Zn: 4.00%; In: 0.02%; Mg: 1.00%; Ga: 0.10%; Bi: 0.50%; Pb: 0.03% The balance is Al.

4. The sacrificial anode according to claim 1, characterized in that The mass percentage of each metal element in the sacrificial anode is: Zn: 4.00%; In: 0.02%; Mg: 1.50%; Ga: 0.10%; Sn:0.10% Bi: 0.50%; The balance is Al.

5. The sacrificial anode according to claim 1, 2, 3 or 4, characterized in that: In the simulated wet-dry alternating environment of the beach, sea and land, the corrosion potential of the sacrificial anode after 5 days of wet-dry alternation and 10 days of wet-dry alternation was -1.06V~-1.02V and -1.06V~-1.04V, respectively, and the corrosion current density was 3.5×10 -6 ~6.2×10 -6 A / cm 2 and 5.6×10 -6 ~7.2×10 -6 A / cm 2 .

6. A method for preparing a sacrificial anode for use in alternating wet and dry environments on beaches, seas, and land as claimed in any one of claims 1 to 5, characterized in that: The method comprises: Step 1: Material processing: Dry the raw materials, aluminum ingots, zinc particles, aluminum-magnesium alloy, indium, optional tin and lead, bismuth, as well as crucibles and molds in a drying oven in advance; Step 2: Prepare the sacrificial anode by melt casting method: Add the preheated aluminum ingot into the crucible and melt it in a melting furnace heated to 710°C. After the material is completely melted, stir for 40-60 seconds to obtain molten aluminum liquid. Lower the melting furnace temperature to 690°C, add the preheated aluminum-magnesium alloy into the aluminum liquid, stir for 40s-60s after the material is completely melted, then add the preheated zinc particles and stir until completely melted to obtain melt A; Raise the melting furnace temperature to 710°C, add gallium, preheated indium, optional tin and lead, and bismuth into melt A respectively, until they are completely melted to obtain melt B; The melting furnace temperature is maintained at 710° C., and the melt B is allowed to stand for 10 to 12 minutes. After the melt B is fully stirred and impurities are removed, the melt B is poured and cooled.

7. The preparation method according to claim 6, characterized in that In step 1, the weighed aluminum ingot, zinc particles, and aluminum-magnesium alloy are placed in a drying oven at a temperature of 200° C. and dried for 40-50 minutes for later use; Wrap the indium, optional tin, lead, and bismuth metals to be added with aluminum foil to form a metal sheet, place it in a drying oven at a temperature of 200° C. and dry it for 40 to 50 minutes, and then dry it for later use; Place the crucible and graphite oil tank mold in a drying oven at a temperature of 190~210℃ for later use.

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