Rare earth modified microbe-resistant corrosion resistant coating steel and method for preparing the same

Abstract

The present application relates to the field of metal materials, and proposes a rare earth modified microbial corrosion resistant coating steel and a preparation method thereof.The rare earth modified microbial corrosion resistant coating steel comprises a steel base and a double-layer protective coating arranged on the surface of the steel base; the double-layer protective coating comprises a cerium dioxide rare earth modified bottom layer and an Sb-Mn functional surface layer from inside to outside. Through the above technical scheme, the problem of insufficient microbial corrosion resistance of the coating steel used at sea in the related art during long-term use is solved.

Description

Technical Field

[0001] This invention relates to the field of metallic materials technology, specifically to a rare earth-modified microbial corrosion-resistant coated steel and its preparation method. Background Technology

[0002] Marine engineering equipment, especially key components such as offshore wind power foundations, towers, and transition sections, are exposed to a complex corrosive environment rich in chloride ions, dissolved oxygen, and sulfate-reducing bacteria (SRB). The presence of SRB accelerates pitting corrosion, crevice corrosion, and stress corrosion cracking in steel, and its metabolite, hydrogen sulfide, is extremely corrosive to steel, seriously threatening the long-term safe service life of the equipment.

[0003] Currently, protection against microbial corrosion mainly relies on surface coating technology. Existing technologies commonly use organic coatings containing a single antibacterial agent (such as silver or copper ions). However, single antibacterial components are easily lost, have poor antibacterial durability, and are difficult to effectively inhibit the adhesion and reproduction of SRB (sulfuric acid bacteria) for a long period. Many antibacterial components are unevenly dispersed in the coating or easily migrate and are lost, failing to exert a continuous and stable effect at the corrosion interface. Furthermore, once the coating is damaged, it lacks self-repairing capabilities, and corrosion will rapidly spread at the damaged site.

[0004] Therefore, developing a microbial corrosion resistant coating with long-lasting antibacterial properties is of great significance for improving the reliability and service life of equipment such as offshore wind power. Summary of the Invention

[0005] This invention proposes a rare earth-modified microbial corrosion-resistant coated steel and its preparation method to solve or alleviate the above-mentioned problems.

[0006] The technical solution of the present invention is as follows: This invention proposes a rare earth-modified microbial corrosion-resistant coated steel, comprising a steel substrate and a double-layer protective coating disposed on the surface of the steel substrate; The dual-layer protective coating consists of a cerium dioxide rare earth modified base layer and an Sb-Mn functional surface layer, from the inside out.

[0007] Preferably, the cerium dioxide rare earth modified base layer is obtained by curing a rare earth modified coating; the rare earth modified coating comprises the following components in parts by weight: 100 parts epoxy resin, 7.6-14.5 parts cerium dioxide, 30-40 parts curing agent, and 15.3-27.3 parts diluent.

[0008] Preferably, the Sb-Mn functional surface layer is obtained by curing an Sb-Mn functional coating, which comprises the following components in parts by weight: 100 parts epoxy resin, 1.9 to 3.8 parts filler, 30 to 40 parts curing agent, and 16 to 26 parts diluent.

[0009] Preferably, the filler comprises antimony dioxide and manganese dioxide.

[0010] Preferably, the filler is prepared by pretreatment with a silane coupling agent.

[0011] Preferably, the mass ratio of antimony dioxide to manganese dioxide is 0.5~1:0.8~1.2.

[0012] Preferably, the amount of the silane coupling agent added is 1.5% to 2.0% of the total mass of antimony dioxide and manganese dioxide.

[0013] Preferably, in rare earth modified coatings, the curing agent includes a polyurethane curing agent.

[0014] Preferably, in the rare earth modified coating, the diluent is xylene and cyclohexanone in a volume ratio of 0.8 to 1.2:1.

[0015] Preferably, in the Sb-Mn functional coating, the curing agent includes a polyurethane curing agent.

[0016] Preferably, in the Sb-Mn functional coating, the diluent is xylene and cyclohexanone in a volume ratio of 0.8 to 1.2:1.

[0017] This invention also proposes a method for preparing rare earth-modified microbial corrosion-resistant coated steel, comprising the following steps: S1. Treat the surface of the steel substrate to obtain pretreated steel; coat the pretreated steel with rare earth modified coating, let it stand, and obtain steel containing cerium dioxide rare earth modified underlayer. S2. Apply Sb-Mn functional coating to the cerium dioxide rare earth modified base layer of the steel and cure it to obtain the rare earth modified microbial corrosion resistant coating steel.

[0018] Preferably, the curing process is divided into a first curing and a second curing; the temperatures and times of the first curing and the second curing are different; the temperature of the second curing is higher than that of the first curing.

[0019] Preferably, the first curing temperature is 85°C and the time is 1 hour; the second curing temperature is 100°C and the time is 2 hours.

[0020] The beneficial effects of this invention are as follows: Currently, organic coatings with added single antibacterial agents (such as silver or copper ions) often exhibit insufficient adhesion to the steel substrate, making them prone to peeling failure under alternating loads such as ocean tides and wave impacts. Single antibacterial components are also susceptible to leakage and loss, making it difficult to maintain antibacterial activity for long periods. Furthermore, most antibacterial substances exhibit poor dispersion within the coating and are highly prone to migration and loss, hindering stable and continuous release at corrosion interfaces. Simultaneously, damaged coatings lack self-repair capabilities, and corrosion can rapidly spread to the damaged areas.

[0021] In this invention, a cerium dioxide rare earth modified underlayer and an Sb-Mn functional surface layer are applied to the surface of steel, improving the long-term resistance to microbial corrosion. The cerium dioxide rare earth modified underlayer first enhances the bonding strength and density with the steel. The Sb-Mn functional surface layer further enhances the resistance of Sb to microbial corrosion by releasing it in a slow-release form, thereby disrupting the cell membrane structure of microorganisms such as SRB and inhibiting their activity. Meanwhile, Mn optimizes the structure of the corrosion product film, making it more dense and stable. Sb and Mn produce a synergistic effect in the corrosive microenvironment, jointly resisting microbial and electrochemical corrosion. When the coating is damaged, the cerium dioxide in the underlayer and the Sb and Mn elements in the surface layer can work synergistically in the corrosive medium to promote the formation of a protective repair product film at the damaged site, delaying further corrosion and extending the overall protection period. After the coating is damaged, the marine corrosive medium (containing Cl) can further enhance its resistance to microbial corrosion. - H2O, O2, and SRB metabolites can penetrate to the damaged area and react synergistically with exposed cerium dioxide, antimony dioxide, and manganese dioxide. Cerium dioxide can undergo redox reactions in the corrosive microenvironment, catalyzing the formation of a dense transition layer containing Fe3O4 on the steel surface, initially blocking further penetration of the corrosive medium. Antimony dioxide reacts with H2S produced by SRB metabolism to generate Sb2S3, while slowly releasing Sb. 3+ Sb 3+ Not only can it disrupt the integrity of SRB cell membranes and inhibit SRB proliferation, but it can also combine with Fe ions produced by corrosion to form antimony-containing ferrite compounds, filling the tiny gaps at the damaged sites; manganese dioxide is reduced to Mn during the corrosion process. 2+ Mn 2+ Doping is introduced into the Fe3O4 lattice, partially replacing Fe. 2+ Optimizing the crystal structure of the passivation film makes the repair product film denser and more stable, while Mn 2+ It has a certain inhibitory effect on the metabolic enzyme activity of SRB, further enhancing the antibacterial effect; the three work synergistically to ultimately form a continuous and dense repair product film at the damaged site, realizing the self-repair function of the coating. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a scanning electron microscope (SEM) image of cerium dioxide used in this invention. Detailed Implementation

[0024] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will be described through embodiments.

[0026] A specific embodiment of the first aspect of the present invention provides a rare earth modified microbial corrosion resistant coated steel, comprising a steel substrate and a double-layer protective coating disposed on the surface of the steel substrate; The double-layer protective coating consists of a cerium dioxide rare earth modified base layer and an Sb-Mn functional surface layer, from the inside out.

[0027] In one embodiment of the present invention, the thickness of the double-layer protective coating is 50~80μm and the porosity is ≤0.8%.

[0028] In one embodiment of the present invention, the cerium dioxide rare earth modified base layer is obtained by curing a rare earth modified coating; the rare earth modified coating comprises the following components in parts by weight: 100 parts epoxy resin, 7.6 to 14.5 parts cerium dioxide, 30 to 40 parts curing agent, and 15.3 to 27.3 parts diluent.

[0029] In this invention, cerium dioxide exhibits irregular blocky and spherical morphologies, with a primary particle size distribution between 40 and 70 nm and an average particle size of approximately 50 nm. A certain degree of soft agglomeration exists between the particles, with aggregate sizes ranging from approximately 150 to 500 nm. This is due to the high surface energy of the nanoparticles and does not affect their dispersion and functionality in the coating system. This microstructure indicates that the cerium dioxide used in this invention possesses nanoscale size and a high specific surface area, which is beneficial for uniform dispersion in epoxy resin coatings, providing abundant active sites, thereby enhancing the adhesion between the coating and the steel substrate, reducing coating porosity, and catalyzing the formation of a dense Fe3O4 repair film after coating damage, achieving long-term resistance to microbial corrosion and self-repair function.

[0030] In one embodiment of the present invention, the curing agent in the rare earth modified coating includes a polyurethane curing agent.

[0031] In one embodiment of the present invention, the diluent in the rare earth modified coating is xylene and cyclohexanone in a volume ratio of 0.8 to 1.2:1.

[0032] In one embodiment of the present invention, the Sb-Mn functional surface layer is obtained by curing an Sb-Mn functional coating, which comprises the following components in parts by weight: 100 parts epoxy resin, 1.9 to 3.8 parts filler, 30 to 40 parts curing agent, and 16 to 26 parts diluent; the filler comprises silane coupling agent modified antimony dioxide and manganese dioxide.

[0033] In one embodiment of the present invention, the curing agent in the Sb-Mn functional coating includes a polyurethane curing agent.

[0034] In one embodiment of the present invention, the diluent in the Sb-Mn functional coating is xylene and cyclohexanone in a volume ratio of 0.8 to 1.2:1.

[0035] In this invention, the curing agent in the rare earth modified coating and Sb-Mn functional coating serves to promote the cross-linking and curing of the epoxy resin, forming a dense paint film and improving the coating's hardness, adhesion, and weather resistance. The diluent in the rare earth modified coating and Sb-Mn functional coating serves to reduce the coating's viscosity and improve its flowability and workability; the volume ratio of xylene to cyclohexanone in the diluent is 0.8~1.2:1, for example, it can be any value from 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, or any range between any two values, preferably 1:1.

[0036] In one embodiment of the present invention, the method for preparing the filler includes the following steps: Antimony dioxide and manganese dioxide were added to ethanol to obtain a suspension; silane coupling agent was added to the suspension, followed by water, and the mixture was stirred, centrifuged, dried, and ground to obtain the filler.

[0037] In one embodiment of the present invention, the mass ratio of antimony dioxide to manganese dioxide is 0.5~1:0.8~1.2; the mass concentration of the suspension is 20%; the amount of silane coupling agent added is 1.5%~2.0% of the total mass of antimony dioxide and manganese dioxide; the mass ratio of silane coupling agent to water is 0.3~0.4:0.1~0.15; the stirring temperature is 55~65℃, the stirring speed is 250~350 r / min, and the stirring time is 1.5~2.5 h; the centrifugation speed is 2500~3500 r / min, and the centrifugation time is 8~12 min.

[0038] In this invention, the amount of silane coupling agent added is 1.5% to 2.0% of the total mass of antimony dioxide and manganese dioxide, for example, it can be any point value among 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, and 2.0%, or any range between any two point values.

[0039] A specific embodiment of the second aspect of the present invention provides a method for preparing rare earth-modified microbial corrosion-resistant coated steel, used to prepare the rare earth-modified microbial corrosion-resistant coated steel provided in the specific embodiment of the first aspect of the present invention, comprising the following steps: S1. Surface treatment of steel to obtain pretreated steel; coating the pretreated steel with rare earth modified coating, and allowing it to stand to obtain steel containing cerium dioxide rare earth modified base layer; S2. Apply Sb-Mn functional coating to steel containing cerium dioxide rare earth modified bottom wet film to obtain steel with double protective coating wet film, cure to obtain rare earth modified microbial corrosion resistant coating steel.

[0040] In one embodiment of the present invention, the steel surface treatment includes the following steps: cleaning the steel substrate surface by degreasing and rust removal, and then treating it with a laser roughening process.

[0041] In one embodiment of the present invention, the laser roughening process has a power of 150W, a scanning speed of 500mm / s, a spot overlap rate of 50%, a scanning spacing of 100μm, and a surface roughness of 1.5~2.5μm for the pretreated steel. During the laser roughening process, the steel is roughened by scanning in a grid pattern, forming a composite structure of 10~50μm micro-pits and 1~5μm nano-waves. The surface roughness (Ra) after roughening is 2.0μm.

[0042] In this invention, laser roughening of the steel surface can increase the contact area and mechanical interlocking force between the coating and the substrate.

[0043] In one embodiment of the present invention, a method for preparing rare earth modified coatings includes the following steps: mixing epoxy resin, diluent and cerium dioxide evenly, and finally adding curing agent to obtain rare earth modified coatings.

[0044] In one embodiment of the present invention, the settling time is 15-20 minutes.

[0045] In one embodiment of the present invention, the preparation method of Sb-Mn functional coating includes the following steps: mixing epoxy resin, diluent and filler evenly, and finally adding curing agent to obtain rare earth modified coating.

[0046] In this invention, both rare earth modified coatings and Sb-Mn functional coatings are prepared on-site to prevent premature curing.

[0047] In one embodiment of the present invention, the curing process is divided into a first curing and a second curing; the temperature of the first curing is 85°C and the time is 1 hour; the temperature of the second curing is 100°C and the time is 2 hours; after curing, the temperature is reduced to below 80°C at a rate of 5°C / min, and then the product is taken out and allowed to cool naturally.

[0048] In this invention, the coating is applied by electrostatic spraying and the curing is done by low-temperature curing. Both of these processes are mature and therefore easier to industrialize, making them suitable for on-site or factory coating of large steel structural components for offshore wind power.

[0049] The present invention will now be described in detail with reference to preferred embodiments and comparative examples. The preferred embodiments of the invention described below can be modified in various ways, and therefore the scope of the invention should not be construed as limited to the preferred embodiments described in detail below. Preferred embodiments are provided to help those skilled in the art to more readily understand the invention.

[0050] In the following examples and comparative examples, the epoxy resin is bisphenol A type epoxy resin E-44 with an epoxy equivalent of 210-240 g / Eq; the average particle size of cerium dioxide is 50 nm; the curing agent is type 650; the average particle size of antimony dioxide is 50 nm; the manganese dioxide is electrolytic manganese dioxide with an average particle size of 300 nm; and the average particle size of silicon dioxide is 50 nm.

[0051] Example 1 A method for preparing rare earth-modified microbial corrosion-resistant coated steel includes the following steps: S1. The surface of Q355NF steel plate is degreased and rusted, and the rust removal reaches Sa2.5 level. Then, a pulsed fiber laser (power 150W, scanning speed 500mm / s, spot overlap rate 50%, scanning spacing 100μm) is used to perform grid scanning roughening on the surface, forming a composite structure of 30μm micro-pits and 2.5μm nano-ripples. After roughening, the surface roughness Ra=2.0μm, and the pretreated steel is obtained. Rare earth modified coating is electrostatically sprayed on the pretreated steel (electrostatic spraying voltage is 60kV, flow rate is 200mL / min, spray gun distance is 30cm, pressure is 0.3MPa), forming a cerium dioxide rare earth modified bottom layer wet film with a thickness of 30μm. After standing at room temperature for 15min, the steel with surface-dried cerium dioxide rare earth modified bottom layer wet film is obtained. S2. Electrostatically spray Sb-Mn functional coating onto the steel with a surface-dried cerium dioxide rare earth modified bottom wet film (electrostatic spraying voltage: 60kV, flow rate: 200mL / min, spray gun distance: 30cm, pressure: 0.3MPa) to obtain steel with a double-layer protective coating wet film (the thickness of the Sb-Mn functional surface wet film is 45μm). Place the sprayed test plate in an oven, first keep it at 85℃ for 1 hour, then raise the temperature to 100℃ and keep it at 100℃ for 2 hours, and then cool it down to below 80℃ at a rate of 5℃ / min. Remove it and let it cool naturally to obtain rare earth modified microbial corrosion resistant coated steel (total coating thickness is 75μm). The porosity was determined to be 0.65% by mercury intrusion porosimetry, and there were no defects such as bubbles or pinholes in the appearance. The preparation method of rare earth modified coatings includes the following steps: 11.5g of cerium dioxide was uniformly dispersed in 100g of epoxy resin under the action of a high shear disperser (3500r / min). Then, 17.4g of diluent (xylene and cyclohexanone in a volume ratio of 1:1) was added, and finally 35g of curing agent was added and mixed evenly to obtain rare earth modified coating. The preparation method of Sb-Mn functional coatings includes the following steps: Take 20g of a mixture of antimony dioxide and manganese dioxide powder and add it to 100mL of anhydrous ethanol (the mass ratio of antimony dioxide to manganese dioxide is 0.8:1) to obtain a suspension with a mass concentration of 20%. Add 0.35g of silane coupling agent KH550 and 0.1g of deionized water, stir at 60℃ and 300r / min for 2h, then centrifuge at 3000r / min for 10min, dry at 80℃ for 2h, and finally grind and pass through a 200-mesh sieve to obtain the filler; disperse 2.8g of filler in 100g of epoxy resin, add 17.4g of diluent (xylene and cyclohexanone in a 1:1 volume ratio), and finally add 35g of curing agent and mix evenly to obtain Sb-Mn functional coating.

[0052] Example 2 A method for preparing rare earth-modified microbial corrosion-resistant coated steel includes the following steps: S1. The surface of Q355NF steel plate is degreased and rust-removed to Sa2.5 grade. Then, a pulsed fiber laser (power 150W, scanning speed 500mm / s, spot overlap rate 50%, scanning spacing 100μm) is used to perform grid-like scanning roughening on the surface, forming a composite structure of 20μm micropits and 4.5μm nano-ripples. After roughening, the surface roughness Ra=2.0μm, and the pretreated steel is obtained. Rare earth modified coating is electrostatically sprayed onto the pretreated steel (electrostatic spraying voltage is 60kV, flow rate is 200mL / min, spray gun distance is 30cm, pressure is 0.3MPa), forming a cerium dioxide rare earth modified bottom layer wet film with a thickness of 22μm. After standing at room temperature for 20min, the steel with a cerium dioxide rare earth modified bottom layer wet film containing surface dryness is obtained. S2. Electrostatically spray Sb-Mn functional coating onto the steel with a surface-dried cerium dioxide rare earth modified bottom wet film (electrostatic spraying voltage: 60kV, flow rate: 200ml / min, spray gun distance: 30cm, pressure: 0.3MPa) to obtain steel with a double-layer protective coating wet film (the thickness of the Sb-Mn functional surface wet film is 28μm). Place the sprayed test plate in an oven, first keep it at 85℃ for 1 hour, then raise the temperature to 100℃ and keep it at 100℃ for 2 hours, and then cool it down to below 80℃ at a rate of 5℃ / min. Remove it and let it cool naturally to obtain rare earth modified microbial corrosion resistant coated steel (total coating thickness is 50μm). The porosity was determined to be 0.7% by mercury intrusion porosimetry, and there were no defects such as bubbles or pinholes in the appearance. The preparation method of rare earth modified coatings includes the following steps: 7.6g of cerium dioxide was uniformly dispersed in 100g of epoxy resin under the action of a high shear disperser (3500r / min). Then, 15.3g of diluent (xylene and cyclohexanone in a volume ratio of 1:1) was added, and finally 30g of curing agent was added and mixed evenly to obtain rare earth modified coating. The preparation method of Sb-Mn functional coatings includes the following steps: Take 20g of a mixture of antimony dioxide and manganese dioxide powder and add it to 100mL of anhydrous ethanol (the mass ratio of antimony dioxide to manganese dioxide is 0.5:0.8) to obtain a suspension with a mass concentration of 20%. Add 0.3g of silane coupling agent KH550 and 0.1g of deionized water, stir at 60℃ and 300r / min for 2h, then centrifuge at 3000r / min for 10min, dry at 80℃ for 2h, and finally grind and pass through a 200-mesh sieve to obtain the filler; disperse 1.9g of filler in 100g of epoxy resin, add 16g of diluent (xylene and cyclohexanone in a volume ratio of 0.8:1), and finally add 30g of curing agent and mix evenly to obtain Sb-Mn functional coating.

[0053] Example 3 A method for preparing rare earth-modified microbial corrosion-resistant coated steel includes the following steps: S1. The surface of Q355NF steel plate is degreased and rust-removed, achieving a rust removal grade of Sa2.5. Then, a pulsed fiber laser (power 150W, scanning speed 500mm / s, spot overlap rate 50%, scanning spacing 100μm) is used to perform grid-like scanning roughening on the surface, forming a composite structure of 45μm micro-pits and 1.5μm nano-ripples. After roughening, the surface roughness Ra=2.0μm, resulting in pretreated steel. Rare earth modified coating is electrostatically sprayed onto the pretreated steel (electrostatic spraying voltage 60kV, flow rate 200mL / min, spray gun distance 30cm, pressure 0.3MPa), forming a cerium dioxide rare earth modified bottom layer wet film with a thickness of 35μm. After standing at room temperature for 20min, steel with a cerium dioxide rare earth modified bottom layer wet film containing surface dryness is obtained. S2. Electrostatically spray Sb-Mn functional coating onto the steel with a surface-dried cerium dioxide rare earth modified bottom wet film (electrostatic spraying voltage: 60kV, flow rate: 200ml / min, spray gun distance: 30cm, pressure: 0.3MPa) to obtain steel with a double-layer protective coating wet film (the thickness of the Sb-Mn functional surface wet film is 45μm). Place the sprayed test plate in an oven, first keep it at 85℃ for 1 hour, then raise the temperature to 100℃ and keep it at 100℃ for 2 hours, and then cool it down to below 80℃ at a rate of 5℃ / min. Remove it and let it cool naturally to obtain rare earth modified microbial corrosion resistant coated steel (total coating thickness is 80μm). The porosity was determined to be 0.75% by mercury intrusion porosimetry, and there were no defects such as bubbles or pinholes in the appearance. The preparation method of rare earth modified coatings includes the following steps: 14.5g of cerium dioxide was uniformly dispersed in 100g of epoxy resin under the action of a high shear disperser (3500r / min). Then, 27.3g of diluent (xylene and cyclohexanone in a volume ratio of 1:1) was added, and finally 40g of curing agent was added and mixed evenly to obtain rare earth modified coating. The preparation method of Sb-Mn functional coatings includes the following steps: Take 20g of a mixture of antimony dioxide and manganese dioxide powder and add it to 100mL of anhydrous ethanol (the mass ratio of antimony dioxide to manganese dioxide is 0.5:0.8) to obtain a suspension with a mass concentration of 20%. Add 0.4g of silane coupling agent KH550 and 0.15g of deionized water, stir at 60℃ and 300r / min for 2h, then centrifuge at 3000r / min for 10min, dry at 80℃ for 2h, and finally grind and pass through a 200-mesh sieve to obtain the filler; disperse 3.8g of filler in 100g of epoxy resin, add 26g of diluent (xylene and cyclohexanone in a volume ratio of 1.2:1), and finally add 40g of curing agent and mix evenly to obtain Sb-Mn functional coating.

[0054] Example 4 Except for replacing antimony dioxide with antimony powder in the preparation method of Sb-Mn functional coating, the rest is the same as in Example 1.

[0055] Comparative Example 1 A method for preparing a microbial corrosion-resistant coated steel includes the following steps: S1. The surface of Q355NF steel plate is degreased and rusted, and the rust removal reaches Sa2.5 level. Then, a pulsed fiber laser (power 150W, scanning speed 500mm / s, spot overlap rate 50%, scanning spacing 100μm) is used to perform grid-like scanning roughening on the surface, forming a composite structure of 30μm micro-pits and 2.5μm nano-ripples. After roughening, the surface roughness Ra=2.0μm, and the pretreated steel is obtained. Epoxy zinc-rich primer is electrostatically sprayed onto the pretreated steel (electrostatic spraying voltage is 60kV, flow rate is 200mL / min, spray gun distance is 30cm, pressure is 0.3MPa), forming an epoxy zinc-rich primer wet film with a thickness of 30μm. After standing at room temperature for 15min, the steel with a surface-dried epoxy zinc-rich primer wet film is obtained. S2. Epoxy asphalt topcoat was electrostatically sprayed onto the steel with a surface-dried epoxy zinc-rich primer wet film (electrostatic spraying voltage: 60kV, flow rate: 200mL / min, spray gun distance: 30cm, pressure: 0.3MPa) to obtain steel with a double-layer protective coating wet film (epoxy asphalt topcoat wet film thickness: 45μm). The sprayed test plate was placed in an oven and first kept at 85℃ for 1 hour, then heated to 100℃ and kept at 100℃ for 2 hours, and then cooled to below 80℃ at a rate of 5℃ / min. After being removed and allowed to cool naturally, a microbial corrosion-resistant coated steel was obtained (total coating thickness: 75μm). The porosity was determined to be 1.4% by mercury intrusion porosimetry, and there were no defects such as bubbles or pinholes in the appearance.

[0056] Comparative Example 2 Except for removing the cerium dioxide rare earth modified bottom layer, the rest is the same as in Example 1.

[0057] Comparative Example 3 Except for removing the Sb-Mn functional surface layer, everything else is the same as in Example 1.

[0058] Comparative Example 4 Except for replacing antimony dioxide with manganese dioxide in the preparation method of Sb-Mn functional coating, the rest is the same as in Example 1.

[0059] Comparative Example 5 Except for replacing manganese dioxide with antimony dioxide in the preparation method of Sb-Mn functional coating, the rest is the same as in Example 1.

[0060] Comparative Example 6 Except for replacing cerium dioxide with silicon dioxide in the preparation method of rare earth modified coatings, the rest is the same as in Example 1.

[0061] The following performance tests were conducted on the rare earth-modified microbial corrosion-resistant coated steels prepared in Examples 1-4 and Comparative Examples 1-6: (1) Destructive strength: The test method is specified in GB / T 5210-2006 "Paints and Varnishes - Pull-off Adhesion Test". (2) Microbial corrosion resistance test: According to ASTM G1, the sample was immersed in Postgate C medium (30℃) inoculated with SRB for 30 days. The electrochemical impedance modulus |Z| at 0.01Hz was tested using an electrochemical workstation. The impedance drop was statistically analyzed. The smaller the impedance drop, the better the microbial corrosion resistance. (3) Cyclic corrosion test: According to GB / T 10125-2021 "Artificial atmosphere corrosion test - salt spray test", the acetic acid salt spray test is adopted, the test cycle is 1008h, and the rust width at the coating scribing is measured. (4) Sb 3+ Release amount: determined by inductively coupled plasma mass spectrometry (ICP-MS) (immersion in 3.5wt% NaCl solution); (5) Repair film thickness: Observed and measured using scanning electron microscopy (SEM).

[0062] The test results are shown in Tables 1 and 2 below.

[0063] Table 1. Performance test results of rare earth modified microbial corrosion resistant coated steels prepared in Examples 1-4 and Comparative Examples 1-6

[0064] (1) Compared with Example 1, after removing the cerium dioxide rare earth modified bottom layer, the coating damage strength decreased from 17.0 MPa to 7.0 MPa, and the bonding strength decreased significantly. After SRB immersion, the impedance decreased significantly and the salt spray corrosion width increased significantly. The repair film thickness was only 1.1 μm. The resistance to microbial corrosion, resistance to cyclic corrosion and self-healing performance were completely deteriorated, proving that the cerium dioxide rare earth modified bottom layer is the key to improving the coating-substrate bonding strength and strengthening the overall protective performance.

[0065] (2) Comparing Comparative Examples 4 and 5 with Example 1, when Mn is missing, Sb 3+ Increased release indicates that Sb is easily lost and its antibacterial durability is reduced. When antimony dioxide or manganese dioxide is used alone, the resistance to microbial corrosion and cyclic corrosion decreases, and the repair film thickness becomes thinner. This indicates that the synergistic effect of Sb and Mn can effectively optimize the corrosion product film structure, slow down the loss of Sb, and improve long-term protection and self-repair capabilities.

[0066] (3) Compared with Example 1, Comparative Example 6 showed that after replacing cerium dioxide with silicon dioxide, the coating adhesion, resistance to microbial corrosion and self-healing ability all decreased significantly, proving that the catalytic passivation effect of nano cerium dioxide is far superior to that of silicon dioxide, and it is the core filler for high-performance coating.

[0067] (4) Comparing Example 4 and Example 1, after replacing antimony dioxide with metallic antimony powder, Sb 3+ The cumulative release was only 0.1%, which was insufficient to exert a sustained antibacterial effect. After 30 days of SRB immersion, the impedance decreased by 2.5%, and the resistance to microbial corrosion was significantly reduced.

[0068] To verify the self-healing effect of the coating after damage, damage tests were conducted on Examples 1, 4, and Comparative Examples 2, 4, and 6: a 0.5 mm wide scratch with a depth penetrating the coating to the substrate was made on the coating surface using a blade. The samples were then immersed in a 3.5 wt% NaCl solution (simulating a marine environment), and samples were taken at 1, 3, and 7 days. The formation of the repair film at the scratch was observed using SEM, and the electrochemical impedance modulus (|Z| 0.01 Hz) at the scratch was also measured. The test results are shown in Table 2.

[0069] Table 2. Performance test results of rare earth modified microbial corrosion resistant coated steels prepared in Examples 1, 4, and Comparative Examples 2, 4, and 6.

[0070] In Example 1, after immersion for 7 days, the |Z| at the scratched area continuously increased by 0.01 Hz, indicating that the repair film was intact and dense, demonstrating a significant self-healing effect. In contrast, the impedance values ​​of Comparative Examples 2, 6, and Example 4 decreased with increasing time, while the impedance of Comparative Example 4 increased slowly with increasing time. Furthermore, the integrity and density of the repair films in Comparative Examples 2, 4, 6, and Example 4 were all poor. This further illustrates that after the coating is damaged, the underlying cerium dioxide and the surface antimony and manganese elements can synergistically form a film, effectively inhibiting the spread of corrosion and enhancing long-term protection capabilities.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A rare earth-modified microbial corrosion-resistant coated steel, characterized in that, It includes a steel substrate and a double-layer protective coating disposed on the surface of the steel substrate; The dual-layer protective coating consists of a cerium dioxide rare earth modified base layer and an Sb-Mn functional surface layer, from the inside out.

2. The rare earth-modified microbial corrosion-resistant coated steel according to claim 1, characterized in that, The cerium dioxide rare earth modified base layer is obtained by curing a rare earth modified coating; the rare earth modified coating comprises the following components in parts by weight: 100 parts epoxy resin, 7.6~14.5 parts cerium dioxide, 30~40 parts curing agent, and 15.3~27.3 parts diluent.

3. The rare earth-modified microbial corrosion-resistant coated steel according to claim 1, characterized in that, The Sb-Mn functional surface layer is obtained by curing Sb-Mn functional coating, which comprises the following components in parts by weight: 100 parts epoxy resin, 1.9-3.8 parts filler, 30-40 parts curing agent, and 16-26 parts diluent. The filler includes antimony dioxide and manganese dioxide.

4. The rare earth-modified microbial corrosion-resistant coated steel according to claim 3, characterized in that, The filler was prepared by pretreatment with a silane coupling agent.

5. The rare earth-modified microbial corrosion-resistant coated steel according to claim 4, characterized in that, The mass ratio of antimony dioxide to manganese dioxide is 0.5~1:0.8~1.2; The amount of the silane coupling agent added is 1.5% to 2.0% of the total mass of antimony dioxide and manganese dioxide.

6. The rare earth-modified microbial corrosion-resistant coated steel according to claim 2, characterized in that, The curing agent includes a polyurethane curing agent; The diluent is xylene and cyclohexanone in a volume ratio of 0.8 to 1.2:

1.

7. The rare earth-modified microbial corrosion-resistant coated steel according to claim 3, characterized in that, The curing agent includes a polyurethane curing agent; The diluent is xylene and cyclohexanone in a volume ratio of 0.8 to 1.2:

1.

8. A method for preparing rare earth-modified microbial corrosion-resistant coated steel, used to prepare the rare earth-modified microbial corrosion-resistant coated steel according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Surface treatment of the steel substrate to obtain pretreated steel; A rare earth modified coating is applied to the pretreated steel and left to stand to obtain steel with a rare earth modified underlayer containing cerium dioxide. S2. Apply Sb-Mn functional coating to the cerium dioxide rare earth modified base layer of the steel and cure it to obtain the rare earth modified microbial corrosion resistant coating steel.

9. The method for preparing a rare earth-modified microbial corrosion-resistant coated steel according to claim 8, characterized in that, The curing process is divided into a first curing and a second curing; the temperatures and times for the first curing and the second curing are different; the temperature for the second curing is higher than the temperature for the first curing.

10. The method for preparing a rare earth-modified microbial corrosion-resistant coated steel according to claim 9, characterized in that, The first curing temperature is 85℃ and the time is 1 hour; the second curing temperature is 100℃ and the time is 2 hours.

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