Multi-principal-element alloy coating for relieving formation of marine biofouling and preparation method of multi-principal-element alloy coating

Abstract

The invention discloses a multi-principal-element alloy coating for relieving formation of marine biofouling and a preparation method of the multi-principal-element alloy coating, and belongs to the technical field of thermal spraying coatings and preparation methods of the thermal spraying coatings. Powder used for preparing the coating is pre-alloyed powder prepared by adopting an inert gas atomization method; the steel comprises the following chemical components in percentage by weight: 10-30% of Cr, 8-22% of Ni, 1-10% of Mo, 5-30% of Cu, 0.1-0.7% of Nb, less than or equal to 0.3% of C, less than or equal to 1.0% of Si, less than or equal to 2.0% of Mn, less than or equal to 0.05% of P, less than or equal to 0.03% of S and the balance of Fe. The adding weight ratio of Cu to Nb ranges from 10 to 290. The antibacterial rate of the multi-principal element alloy coating on pseudomonas aeruginosa and bacillus Vietnam within 6 hours reaches 99.9%; an inhibition effect is formed on the attachment behavior of marine algae fouling organisms within 7 days, and the fouling coverage ratio is lower than 5%.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal spray coatings and their preparation methods, and particularly relates to a multi-principal element alloy coating with the function of alleviating the formation of marine biofouling. This coating is prepared by supersonic flame spraying technology and is applied to the surface of marine engineering equipment in full contact with the marine environment. Background Art

[0002] In the field of marine engineering, the problem of marine biofouling caused by unnecessary biological attachment on the surface of equipment not only causes serious harm to the marine economy and ecosystem, but also significantly reduces the performance and safety of marine engineering equipment. Currently, the main methods for marine fouling control include mechanical cleaning, electrolyzed seawater, chemical agents, and antifouling coatings. Among them, antifouling coatings have become the preferred means to solve the problem of marine biofouling due to their economy and high efficiency. However, existing industrial antifouling coatings mainly rely on organic copolymers, which show problems of insufficient mechanical properties during service, and the excessive release of antifouling agents causes potential pollution to the marine environment, which urgently needs to be solved.

[0003] To overcome the limitations of organic-based antifouling coatings in terms of environmental friendliness, bonding strength, and service life, researchers have developed metal-based antifouling coatings containing antifouling agents. Metal coatings not only significantly improve the bonding strength, mechanical properties, and service life of the coatings, but also reduce the toxicity of the coatings. Currently, the more widely studied metal-based antifouling coatings mainly include Cu-Ag, Cu-Ti, Cu-Ni, and Cu-stainless steel composite coatings. However, the existing Cu / X antifouling system coatings still face the problem of uncontrollable release of antifouling factors. This is because traditional metal coating preparation usually adopts a powder mixing process, and the physical combination between different metals easily leads to obvious division of anodes and cathodes, thus accelerating the corrosion performance of the coatings and making them less stable than single metals during service. Therefore, the design of metal antifouling composition systems and the innovation of powder preparation methods have become the key directions for the development of new antifouling coatings. In addition, there are a wide range of choices for metal coating preparation technologies, mainly including cold spraying, thermal spraying, and electroplating. Among them, thermal spraying technology has become the preferred option due to its wide material adaptability, high efficiency, and small thermal impact on the substrate.

[0004] Based on the above background, innovations in the three aspects of metal coating powder preparation method, composition design, and coating preparation process are expected to provide new ideas for the development of antifouling coatings and propose practical solutions for improving the environmental friendliness of coatings. Summary of the Invention

[0005] The object of the present invention is to provide a multi-principal element alloy coating capable of alleviating the formation of marine biofouling and a preparation method thereof. The main technical feature of the present invention is to use a pre-alloyed powder of a multi-principal element alloy as the powder for spraying. By adding copper (Cu) and niobium (Nb) to the powder, while the multi-principal element alloy coating has strong corrosion resistance, it can alleviate the formation of biofouling on the surface of marine engineering equipment. The multi-principal element alloy coating can achieve an antibacterial rate of 99.9% against typical marine fouling symbiotic bacteria (such as Pseudomonas aeruginosa and Bacillus vietnamensis) within 6 hours. Within 7 days, it can inhibit the attachment behavior of marine algal fouling organisms, and the fouling coverage ratio is less than 5%. The corrosion current density of the multi-principal element alloy coating in the service environment is 50 nA / cm 2 -300 nA / cm 2 . The multi-principal element alloy coating can be widely applied to the surface of marine engineering metal equipment, such as the legs of jacket platforms in offshore platforms, the propeller blades of ships, the impellers and pump casings of seawater pumps, etc.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A multi-principal element alloy coating for alleviating the formation of marine biofouling in the present invention, the powder used for preparing the coating is a pre-alloyed powder prepared by an inert gas atomization method; the chemical composition of the pre-alloyed powder, by weight percentage, is: Cr: 10% - 30%, Ni: 8% - 22%, Mo: 1% - 10%, Cu: 5% - 30%, Nb: 0.1% - 0.7%, C: ≤0.3%, Si: ≤1.0%, Mn: ≤2.0%, P: ≤0.05%, S: ≤0.03%, and the balance is Fe.

[0007] Further, the chemical composition of the pre-alloyed powder is: Cr: 18% - 25%, Ni: 10% - 20%, Mo: 3% - 8%, Cu: 10% - 25%, Nb: 0.2% - 0.5%, C: ≤0.3%, Si: ≤1.0%, Mn: ≤2.0%, P: ≤0.05%, S: ≤0.03%, and the balance is Fe.

[0008] Further, in the chemical composition of the pre-alloyed powder, the addition weight ratio range of Cu and Nb is between 10 - 290. Further still, the addition weight ratio range of Cu and Nb is between 22 - 120.

[0009] Further, the D50 value of the particle size distribution of the pre-alloyed powder is 10.0 μm - 75.0 μm. Further still, the D50 value of the particle size distribution of the pre-alloyed powder is 25.0 μm - 53.0 μm.

[0010] The preparation method of a multi-principal element alloy coating with the function of alleviating marine biofouling according to the present invention includes pre-treating the surface of the substrate before spraying, including sandblasting the surface of the substrate. After the pre-treatment is completed, the multi-principal element alloy coating is prepared by using the high-velocity oxy-fuel spraying technology to spray on the surface of the substrate.

[0011] Further, the surface of the substrate is sandblasted. The abrasive for sandblasting is white fused alumina sand. The pressure of the sandblasting compressed air is 0.5 MPa - 0.6 MPa, the sandblasting distance is 100 mm - 150 mm, the surface roughness of the substrate after sandblasting is Ra 3.0 μm - 3.5 μm, and the surface of the substrate is cleaned with acetone.

[0012] Further, a high-velocity oxy-fuel spraying device is used to spray the working layer. The process parameters are as follows: the kerosene flow rate is 5.0 GPH - 7.0 GPH, the oxygen flow rate is 1600 SCFH - 2200 SCFH, the flow rate of the powder-feeding gas nitrogen is 20 SCFH - 30 SCFH, the powder-feeding rate is 20 g / min - 60 g / min, the spraying distance is 300 mm - 500 mm, the number of coating layers is 15 - 25 layers, and the obtained coating thickness is 350 μm - 500 μm. Furthermore, the high-velocity oxy-fuel spraying process parameters are as follows: the kerosene flow rate is 6.0 GPH - 6.8 GPH, the oxygen flow rate is 1850 SCFH - 2100 SCFH, the flow rate of the powder-feeding gas nitrogen is 22 SCFH - 26 SCFH, the powder-feeding rate is 30 g / min - 50 g / min, the spraying distance is 350 mm - 400 mm, the number of coating layers is 18 - 22 layers, and the obtained coating thickness is 400 μm - 450 μm.

[0013] In the multi-principal element alloy coating system involved in the present invention, Cu and Nb are crucial alloy elements, and they are the necessary prerequisites to ensure the inhibitory effect of the coating on marine biofouling. Regarding the Cu element, in the present invention, by delicately designing its addition amount, it exceeds the solid solubility limit of Cu in the multi-principal element alloy. In this way, supersaturated Cu will exist in the form of a precipitated phase in the coating matrix. This special form of existence creates conditions for the release of copper ions, thereby achieving the purpose of antifouling. The addition of the Nb element is also of great significance. Nb acts as a coating layer for the copper-rich precipitated phase in the coating. By precisely controlling its addition amount, the release rate of copper ions can be effectively regulated. The schematic diagram of the action process and effect of Cu and Nb in the multi-principal element alloy coating is shown in Figure 1 . This measure is of great significance, and it can significantly reduce the potential harm that the antifouling coating may cause to the marine environment. Exploring deeply from the microscopic level, the release process of copper ions actually involves the dynamic conversion between monovalent copper ions and divalent copper ions. At the same time, the metabolic process of microorganisms in the marine environment will produce reactive oxygen species (ROS) with weak oxidizing properties, such as superoxide anion radicals (O2- ), and hydrogen peroxide (H2O2). At this time, cuprous ions will undergo a classic Fenton reaction with H2O2 to generate highly oxidizing ROS, such as hydroxyl radicals (•OH). These highly oxidizing ROS can effectively inhibit the formation of biofilms and thus prevent the occurrence of biofouling. The remarkable feature of the present invention is that the antifouling coating does not solely rely on the toxicity of cuprous ions to achieve the dominant antifouling effect. Instead, by cleverly adding Nb elements, the conversion process of different valence states of cuprous ions is precisely regulated. Specifically, the addition of Nb effectively slows down the conversion rate of cuprous ions to cupric ions. During the release process of cuprous ions, more cuprous ions can be retained to participate in the formation process of highly oxidizing ROS. These highly oxidizing ROS can damage biological cells and thus fundamentally inhibit the generation of biofouling. This unique antifouling mechanism has dual advantages. On the one hand, it effectively reduces the excessive release of cuprous ions and reduces the risk of damage to the marine ecological environment; on the other hand, it fully exerts the catalytic role of cuprous ions and, through the ROS-mediated pathway, achieves efficient control of microbial biofilms and biofouling, providing a more environmentally friendly and efficient solution to the antifouling problem in the field of ocean engineering.

[0014] Advantages of the present invention: 1. By using pre-alloyed powder to prepare the coating, the present invention realizes the control of the coating microstructure, avoids the occurrence of galvanic corrosion between different mixed metals, and improves the corrosion resistance of the coating.

[0015] 2. By adding Cu and Nb elements, the coating of the present invention has the function of effectively alleviating the formation of marine biofouling. By controlling the conversion process of different valence states of cuprous ions, accelerating the catalytic process of ROS, and increasing the expression level of ROS, while reducing the release rate of cuprous ions, it effectively inhibits marine biofouling. Description of the drawings

[0016] Figure 1 It is a schematic diagram of the action process and effect of Cu and Nb in the multi-principal element alloy coating in the present invention. Detailed implementation manners

[0017] According to the content of the present invention, the technical solution of the present invention is further illustrated by specific examples. The following examples are only for helping to understand the present invention and are not regarded as specific limitations of the present invention. The powder information used in the examples and comparative examples is shown in Table 1, and the process parameters of supersonic flame spraying are shown in Table 2. In the implementation process of the present invention, 316L stainless steel for ocean engineering is selected.

[0018] A preparation method of a multi-principal element alloy coating for alleviating the formation of marine biofouling is as follows: (1) Substrate material pretreatment: The stainless-steel surface was subjected to sandblasting. The abrasive used for sandblasting was white fused alumina. The pressure of the sandblasting compressed air was set at 0.55 MPa, and the sandblasting distance was set at 135 mm. After sandblasting, the surface roughness of the specimen was Ra 3.3 μm. After sandblasting, the substrate surface was cleaned with acetone and dried for standby.

[0019] (2) Preparation of the supersonic flame spraying coating: First, pre-alloyed powder was prepared by the inert gas atomization method. The powder information is shown in Table 1. Then, the pre-alloyed powder was put into the powder feeder. During spraying, the spray gun was kept perpendicular to the specimen, and the coating was prepared according to the spraying process parameters in Table 2.

[0020] Table 1 Basic information of the powders for preparing the multi-principal element alloy coatings in the examples and comparative examples:

[0021] Table 2 Setting of the spraying process parameters for the multi-principal element alloy coatings in the examples and comparative examples:

[0022] 1. Antibacterial performance test: According to the standard of GB / T 2591-2003 "Test Methods and Antibacterial Effects for Antibacterial Plastics", the antibacterial performance of the multi-principal element alloy coatings shown in Table 1 and Table 2 was quantitatively tested. Two typical biofouling bacteria in the ocean were selected for the test, namely Pseudomonas aeruginosa ( Pseudomonas aeruginosa , Gram-negative bacterium) and Bacillus vietnamensis ( Bacillus vietnamensis , Gram-positive bacterium). The coating and the bacteria were co-cultured for 6 hours, and the concentration of the co-cultured bacteria was set at (1 - 2)×10 8 CFU / mL. The test results of the antibacterial performance are shown in Table 3. Among them, the control material selected for the antibacterial performance test was 316L stainless steel without coating. The calculation formula for the antibacterial rate was: Antibacterial rate (%) = [(Number of viable bacteria on the 316L stainless-steel surface - Number of viable bacteria on the multi-principal element alloy coating surface) / Number of viable bacteria on the 316L stainless-steel surface]×100%.

[0023] 2. Biofouling inhibition performance test: The anti-fouling performance of the multi-principal element alloy coating was evaluated using a self-developed dynamic anti-fouling performance evaluation system for simulating the marine environment in the laboratory. The dynamic anti-fouling evaluation system strictly controlled the light intensity, light cycle, water temperature, water quality, and room temperature. By adjusting the parameters of the downlights, the sunlight intensity in the actual sea area was simulated, and the parameters were set as follows: 7:00 - 10:00, pure white, 20w; 10:00 - 13:00, pure white, 40w; 13:00 - 16:00, pure white, 50w; 16:00 - 19:00, pure white, 30w; 19:00 - 22:00, pure white, 10w; Turned off from 22:00 to 7:00.

[0024] In terms of water temperature, based on the annual average water temperature in the South China Sea area, the water temperature is set at 27°C and the room temperature is set at 27°C. The water quality is controlled by adopting a multi-stage filtration system. The substrate sample sprayed with the multi-principal element alloy coating is embedded in a mold filled with epoxy resin, ensuring that the coating surface is exposed. The exposed coating is completely immersed in the dynamic anti-fouling evaluation system, and the immersion time is set at 7 days. The coating is photographed and observed under a fluorescence microscope to analyze the fouling attachment on the coating surface after the co-culture is completed. The ImageJ software is used to quantitatively analyze the fouling coverage on the sample surface and calculate the biofouling coverage rate. The test results are shown in Table 3.

[0025] 3. Corrosion resistance test: The coating is immersed in an artificial seawater solution, and the potentiodynamic polarization curves of the coatings in the examples and comparative examples of the present invention are measured to obtain the corrosion current density of the coating i corr , and the test results are shown in Table 3.

[0026] Table 3 Setting of process parameters for preparing multi-principal element alloy coatings in examples and comparative examples:

[0027] It can be seen from the results in Table 3 that the multi-principal element alloy coatings in Examples 1 - 8 of the present invention exhibit effective antibacterial properties. Moreover, it can effectively inhibit the attachment of biofouling, making its coverage rate during the cultivation period not higher than 5%. In addition, the corrosion resistance of the coating is an important indicator for its service life in engineering applications. The i corr value is in the range of 50 nA / cm 2 -300 nA / cm 2 which meets the requirements of the present invention. Therefore, the appropriate powder particle size distribution, powder composition, and setting of the supersonic flame spraying process parameters are the key factors for the present invention to obtain an effective multi-principal element alloy coating.

[0028] Supersonic flame spraying has size requirements for the powder particle size distribution selected, which can affect the corrosion resistance of the coating. An overly small D50 value means that the powder particles are finer and the specific surface area increases significantly. During supersonic flame spraying, fine particles are prone to agglomeration. During the flight and deposition of the agglomerated particles, there will be more voids and defects inside the coating, making it difficult to form a dense coating structure. This loose structure provides channels for corrosive media, which can penetrate along these voids into the interior of the coating and then come into contact with the substrate, leading to a reduction in the corrosion resistance of the coating (Comparative Example 1), and reducing the service life of the coating. An overly large D50 value, in addition to causing an increase in the porosity of the coating, will also result in non-uniform composition and structure of the coating. The particle sizes at different positions vary significantly, resulting in inconsistent coating properties, and further leading to a reduction in the corrosion resistance of the coating (Comparative Example 2).

[0029] The addition amount of Cu element in the multi-principal element alloy coating with the function of alleviating marine biofouling has an important impact on its antibacterial and antifouling effects. If the added Cu content is too low, effective antibacterial and antifouling effects cannot be achieved (Comparative Example 3). If the added amount of Cu is too high, due to the increase in the content of the precipitated phase, the corrosion resistance of the coating is reduced, thus affecting the service life of the coating (Comparative Example 4).

[0030] The addition of Nb element can effectively control the copper ion release rate, improve its corrosion resistance, avoid the environmental impact and the influence on the coating service life caused by the release of Cu, and effectively slow down the conversion rate of monovalent copper ions to divalent copper ions, retaining more monovalent copper ions to participate in the formation process of strongly oxidizing ROS. If the added amount of Nb is too low, the improvement effect on the corrosion resistance of the coating will not be significant. Even if copper within the scope defined in the present invention is added, it is impossible to ensure that the antibacterial and antifouling properties reach the effectiveness required by the present invention (Comparative Example 5). If the added amount of Nb is too high, the corrosion resistance of the coating is significantly improved, but at the same time, the release and valence conversion of copper ions are inhibited, thus reducing the antibacterial and antifouling properties of the coating (Comparative Example 6).

[0031] In addition, in the pre-alloyed powder, Nb is in the core-shell structure of the copper-rich precipitated phase, which restricts its release process. Therefore, there are certain proportional restrictions on the addition amounts of Cu and Nb. Even if the addition amounts of Cu and Nb are both within the defined ranges, it is impossible to ensure that the coating exhibits excellent antibacterial and antifouling properties while having good corrosion resistance. When the Cu / Nb ratio is too low, it indicates that the degree of encapsulation of the copper-rich phase by Nb increases, restricting the release process of copper ions, and the coating shows poor antibacterial and antifouling properties (Comparative Example 7). However, when the Cu / Nb ratio is too high, it indicates that the degree of encapsulation of the copper-rich phase by Nb in the coating weakens, reducing the corrosion resistance of the coating and shortening the service life of the coating (Comparative Example 8).

[0032] For the preparation of the multi-principal element alloy coating, the composition and particle size of the pre-alloyed powder are one of the factors affecting the coating properties. On the other hand, the process parameters of the high-velocity oxy-fuel spraying also affect the antibacterial, antifouling, and corrosion resistance of the coating. When the kerosene flow rate is too low during the high-velocity oxy-fuel spraying process, it will lead to a loose coating microstructure and reduced corrosion resistance (Comparative Example 9). When the kerosene flow rate during the high-velocity oxy-fuel spraying process is too high, it can cause incomplete combustion, resulting in defects such as pores and inclusions in the coating, reducing the coating density and corrosion resistance (Comparative Example 10).

[0033] When the oxygen flow rate is too low in the high-velocity oxy-fuel spraying, it can lead to incomplete combustion of the pre-alloyed powder, a decrease in the coating density, an increase in the porosity, and an impact on the corrosion resistance of the coating (Comparative Example 11). While when the oxygen flow rate is too high, the excessive oxygen flow rate will cause excessive oxidation of the metal powder, resulting in the consumption of Cu in the coating, thereby reducing the antibacterial and antifouling properties of the coating (Comparative Example 12).

[0034] In the high-velocity oxy-fuel spraying process, the nitrogen flow rate plays a key role. When the nitrogen flow rate is too low, the deposition rate of the powder ejected from the nozzle reaching the substrate surface decreases significantly. This change directly leads to a poor coating density, and more pores and defects will be formed inside. Such deterioration of the coating structure greatly reduces its corrosion resistance, and further seriously affects the service life of the coating (Comparative Example 13). On the contrary, if the nitrogen flow rate is too high, the high-speed nitrogen gas flow will cause the spraying particles to violently impact the substrate surface at a higher speed. This high-speed impact will generate large residual stresses inside the coating. The existence of the residual stresses greatly reduces the stability of the coating. During actual use, the coating is more likely to have problems such as cracks and deformations, and it is difficult to effectively resist the external corrosion (Comparative Example 14).

[0035] If the powder feeding rate in supersonic flame spraying is too low, the coating will be discontinuous due to insufficient powder supply, resulting in a decrease in the bonding strength between the powders in the coating, and then gaps will appear, affecting the corrosion resistance of the coating (Comparative Example 15). When the powder feeding rate is too high, the powder cannot be fully heated and accelerated, and some powders are deposited on the substrate without being completely melted, increasing the porosity of the coating and reducing the corrosion resistance of the coating (Comparative Example 16).

[0036] In addition, the distance between the spray gun and the substrate during spraying will also affect the quality of the coating. If the spraying distance is too short, the kinetic energy of the particles when they reach the substrate is too large, which may cause impact damage to the substrate. At the same time, since the distance between the spray gun and the substrate is close, the heat on the substrate is concentrated and deformation is likely to occur. The surface roughness of the coating increases, the internal stress of the coating increases, and defects such as cracks appear, thus reducing the corrosion resistance of the coating (Comparative Example 17). If the spraying distance is too far, the heat exchange time between the powder particles and the surrounding gas during flight is long, the temperature and speed decrease, and the kinetic energy and heat energy when reaching the substrate are insufficient, resulting in a decrease in the denseness of the coating and the corrosion resistance being affected (Comparative Example 18).

[0037] The preparation of the final coating also needs to consider the limitation of the number of spray layers. If the number of spray layers is too low, the coating is thin and is easily damaged under harsh working conditions, and the thin coating cannot effectively protect the substrate, resulting in a decrease in corrosion resistance (Comparative Example 19). If the number of coating layers is too high, problems such as cracking and peeling of the coating will occur due to the generation of internal stress, resulting in a decrease in the corrosion resistance of the coating (Comparative Example 20).

[0038] From the results of the above examples and comparative examples, it can be seen that only when the addition amounts of Cu and Nb, the D50 size of the pre-alloyed powder, and the supersonic flame spraying process parameters are within a certain appropriate range and cooperate with each other can the multi-principal element alloy coating have the effect of alleviating marine biofouling and have a good service life cycle.

[0039] The above examples are only used to illustrate the technical concept and characteristics of the present invention, and their purpose is to enable those skilled in the art who are familiar with this technology to understand the content of the present invention and implement it accordingly, and cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A multi-principal element alloy coating for alleviating the formation of marine biofouling, characterized in that, The powder used for preparing the coating is a pre-alloyed powder prepared by an inert gas atomization method; the chemical composition of the pre-alloyed powder, by weight percentage, is: Cr: 10% - 30%, Ni: 8% - 22%, Mo: 1% - 10%, Cu: 5% - 30%, Nb: 0.1% - 0.7%, C: ≤0.3%, Si: ≤1.0%, Mn: ≤2.0%, P: ≤0.05%, S: ≤0.03%, and the balance is Fe; the weight ratio range of the added Cu and Nb is between 10 and 290.

2. The multi-principal element alloy coating for alleviating the formation of marine biofouling according to claim 1, wherein The chemical composition of the pre-alloyed powder is: Cr: 18% - 25%, Ni: 10% - 20%, Mo: 3% - 8%, Cu: 10% - 25%, Nb: 0.2% - 0.5%, C: ≤0.3%, Si: ≤1.0%, Mn: ≤2.0%, P: ≤0.05%, S: ≤0.03%, and the balance is Fe; the weight ratio range of the added Cu and Nb is between 22 and 120.

3. The multi-principal element alloy coating for alleviating the formation of marine biofouling according to claim 1, characterized in that, The D50 value of the particle size distribution of the pre-alloyed powder is 10.0 μm - 75.0 μm.

4. A multi-principal element alloy coating for mitigating the formation of marine biofouling, according to claim 3, wherein The D50 value of the particle size distribution of the pre-alloyed powder is 25.0 μm - 53.0 μm.

5. A multi-principal element alloy coating for alleviating the formation of marine biofouling according to claim 1, characterized in that, The multi-principal element alloy coating for mitigating the formation of marine biofouling has an antibacterial rate of 99.9% against Pseudomonas aeruginosa and Bacillus vietnamensis within 6 hours; within 7 days, it inhibits the attachment behavior of marine algal fouling organisms, and the fouling coverage ratio is less than 5%; the corrosion current density of the multi-principal element alloy coating for mitigating the formation of marine biofouling in the service environment is 50 nA / cm 2 - 300 nA / cm 2 .

6. A method for preparing a multi-principal element alloy coating for alleviating the formation of marine biofouling according to any one of claims 1-5, characterized in that, It includes pre-treating the surface of the substrate before spraying, including sandblasting the surface of the substrate; after completing the pre-treatment, a multi-principal element alloy coating is prepared by spraying on the surface of the substrate using the high-velocity oxy-fuel spraying technology.

7. The preparation method of a multi-principal element alloy coating for alleviating the formation of marine biofouling according to claim 6, characterized in that, The surface of the substrate is sandblasted. The abrasive for sandblasting is white fused alumina. The pressure of the sandblasting compressed air is 0.5 MPa - 0.6 MPa, the sandblasting distance is 100 mm - 150 mm, the surface roughness of the substrate after sandblasting is Ra 3.0 μm - 3.5 μm, and the surface of the substrate is cleaned with acetone.

8. The preparation method of a multi-principal element alloy coating for alleviating the formation of marine biofouling according to claim 6, characterized in that, The working layer is sprayed using a high-velocity oxy-fuel spraying device. The process parameters are: the kerosene flow rate is 5.0 GPH - 7.0 GPH, the oxygen flow rate is 1600 SCFH - 2200 SCFH, the flow rate of the powder-feeding gas nitrogen is 20 SCFH - 30 SCFH, the powder-feeding rate is 20 g / min - 60 g / min, the spraying distance is 300 mm - 500 mm, the number of coating layers is 15 - 25 layers, and the obtained coating thickness is 350 μm - 500 μm.

9. The preparation method of a multi-principal element alloy coating for alleviating the formation of marine biofouling according to claim 8, characterized in that, The high-velocity oxy-fuel spraying process parameters are: the kerosene flow rate is 6.0 GPH - 6.8 GPH, the oxygen flow rate is 1850 SCFH - 2100 SCFH, the flow rate of the powder-feeding gas nitrogen is 22 SCFH - 26 SCFH, the powder-feeding rate is 30 g / min - 50 g / min, the spraying distance is 350 mm - 400 mm, the number of coating layers is 18 - 22 layers, and the obtained coating thickness is 400 μm - 450 μm.

Images