Bathroom steel with nano-antibacterial function and preparation method thereof

Abstract

The invention relates to bathroom steel with a nano-antibacterial function and a preparation method of the bathroom steel. The bathroom steel comprises a steel substrate, a Ni-P-Ag electroplated layer and a nano-antibacterial coating, the thickness of the Ni-P-Ag electroplated layer ranges from 8 micrometers to 12 micrometers, the Ni-P-Ag electroplated layer comprises, by mass, 86.5%-90.9% of Ni, 9%-13% of P and 0.1%-0.5% of Ag, and the surface porosity of the electroplated layer ranges from 2% to 5%. The nano antibacterial coating covers the surface of the electroplated layer, the thickness of the nano antibacterial coating is 3-6 microns, and the nano antibacterial coating comprises the following components: 0.5-2wt% of nano Ag particles and the balance of nano TiO2; a Ti-O-P chemical bond is formed on the interface of the coating and the electroplated layer. The steel for the bathroom has excellent salt spray corrosion resistance, coating adhesive force and antibacterial performance, the coating adhesive force is larger than or equal to 18 MPa, the antibacterial rate of the steel for the bathroom reaches 99% or above, and after the coating is abraded by 50%, the antibacterial rate of the steel for the bathroom is still larger than or equal to 90%.

Description

Technical Field

[0001] This invention belongs to the technical field of special metal materials for sanitary ware, specifically relating to a sanitary ware steel with nano-antibacterial function and its preparation method. Background Technology

[0002] Bathroom environments are constantly exposed to high temperatures and humidity, and are prone to water stains and dirt buildup, providing ideal conditions for the growth of pathogenic bacteria such as Escherichia coli and Staphylococcus aureus. This not only affects the appearance and lifespan of bathroom products but may also pose a health hazard through contact transmission. Currently, the most commonly used metal material in the bathroom industry is 304 stainless steel. While it has some corrosion resistance, it lacks inherent antibacterial properties and requires surface treatment to achieve an antibacterial effect. However, this process suffers from the following technical drawbacks: its antibacterial properties are limited and lack durability. Existing antibacterial treatments often rely on single Ag ions or TiO2 coatings. Ag ions are easily released during washing, causing the antibacterial effect to diminish over time. Pure TiO2 coatings require ultraviolet light to activate their antibacterial activity, resulting in significantly reduced antibacterial efficiency in low-light indoor environments, failing to meet the need for all-weather antibacterial protection. Insufficient coating adhesion: The stainless steel substrate and the surface antibacterial coating lack effective chemical bonding, relying only on physical adsorption or mechanical interlocking. Under long-term thermal cycling and frictional impact, the coating is prone to peeling and blistering, not only losing its antibacterial function but also exposing the substrate and causing corrosion. Difficulty in achieving both corrosion resistance and antibacterial properties: Adding high Ag content to improve antibacterial properties can easily lead to a loose coating structure and reduced corrosion resistance; while traditional Ni-P electroplating layers have excellent corrosion resistance, they themselves have no antibacterial ability, and high-temperature sintering of the antibacterial coating can easily lead to crystallization and embrittlement of the Ni-P layer, destroying the corrosion-resistant structure.

[0003] To address the aforementioned issues, there is an urgent need to develop a bathroom steel that achieves long-lasting antibacterial properties, high corrosion resistance, and strong coating adhesion through component optimization and synergistic process design, in order to resolve the pain points of existing technologies such as single function, conflicting performance, and short service life. Summary of the Invention

[0004] This invention provides a bathroom steel with nano-antibacterial function and its preparation method, addressing the problems of current bathroom steel having only a single antibacterial function, conflicting antibacterial and corrosion resistance properties, and short service life. The bathroom steel prepared by this invention exhibits excellent salt spray corrosion resistance, coating adhesion, and antibacterial properties. The coating adhesion is ≥18MPa, and the antibacterial rate of the bathroom steel reaches over 99%. Even after 50% coating wear, the antibacterial rate of the bathroom steel remains ≥90%.

[0005] In a first aspect, the present invention relates to a bathroom steel with nano-antibacterial function, comprising a steel substrate, a Ni-P-Ag electroplating layer and a nano-antibacterial coating; The steel matrix comprises, by weight percentage: C 0.03-0.08%, Si 0.15-0.35%, Mn 0.4-0.8%, Cr 11-13%, Ni 0.8-1.2%, Cu 0.02-0.06%, Ti 0.03-0.05%, with the balance being Fe and unavoidable impurities; The Ni-P-Ag electroplating layer has a thickness of 8-12 μm and its composition by mass fraction is: Ni 86.5-90.9%, P 9-13%, Ag 0.1-0.5%, and the surface porosity of the electroplating layer is 2-5%. The nano antibacterial coating covers the surface of the electroplating layer and has a thickness of 3-6 μm. Its composition includes: 0.5-2 wt% nano Ag particles, with the remainder being nano TiO2. The interface between the coating and the electroplating layer forms Ti-OP chemical bonds.

[0006] Preferably, the particle size of the nano-TiO2 is 10-30 nm, and the particle size of the nano-Ag particles is 15-40 nm.

[0007] Preferably, the electroplated layer forms a surface pore diameter of 0.5-2μm and a pore depth of 2-5μm.

[0008] Secondly, the present invention relates to a method for preparing sanitary ware steel with nano-antibacterial function, comprising the following steps: (1) Steel matrix preparation: The steel matrix is ​​prepared by distributing the materials according to the steel matrix composition, melting in a medium frequency induction furnace, casting under argon protection, and continuous casting to obtain a billet; the billet is heated to 1100-1180℃ for hot rolling, the final rolling temperature is 850-920℃, air-cooled to room temperature, and then machined to obtain the steel matrix; (2) Steel substrate pretreatment: The steel substrate is mechanically ground, alkaline washed to remove oil, acid washed to remove rust, rinsed with deionized water and then dried. (3) Ni-P-Ag alloy electroplating: The pretreated steel substrate is used as the cathode and graphite as the anode, and is placed in the electroplating solution for electroplating; the components of the electroplating solution are: NiSO4・6H2O 190-260g / L, NaH2PO2・H2O 30-50g / L, Na3C6H5O7・2H2O 18-35g / L, NH4Cl 12-22g / L, AgNO3 0.5-2g / L, and the pH is adjusted to 4.2-5.8; the electroplating temperature is 45-65℃, and the current density is 1.2-3.5A / dm³. 2 The electroplating time is 25-45 minutes, forming a Ni-P-Ag electroplated layer with a surface porosity of 2-5%. (4) Plasma activation of electroplated layer: The electroplated steel substrate is placed in a plasma treatment instrument, and Ar / O2 mixed gas is introduced. The activation treatment is carried out for 3-8 minutes under the conditions of power 150-250W and pressure 5-10Pa. (5) Preparation of nano antibacterial coating: Tetrabutyl titanate, anhydrous ethanol and glacial acetic acid are mixed at a volume ratio of 1:(3-5):(0.5-1.2). After stirring for 30-60 min, 0.8-2.5 wt% nano Ag particles relative to the mass of tetrabutyl titanate are added and stirring is continued for 25-45 min. The viscosity is adjusted to 25-35 mPa·s to obtain an antibacterial coating solution. The coating solution is coated onto the surface of the activated electroplated layer by dip coating at a speed of 6-12 mm / s. Then, it is dried at 80-120℃ for 1.5-2.5 h and then placed in a muffle furnace and heated to 420-520℃ at 5-10℃ / min for 2-3.5 h. After cooling to room temperature, a nano antibacterial coating is formed that is bonded to the electroplated layer through Ti-OP bonds.

[0009] Preferably, in step (3), the pore diameter of the electroplated layer is 0.5-2μm and the pore depth is 2-5μm.

[0010] Preferably, the volume ratio of the Ar / O2 mixed gas in step (4) is 8:2-6:4.

[0011] Preferably, in step (5), the sintering temperature is increased to 420-520℃ at 5-10℃ / min and sintered for 2-3.5h.

[0012] The beneficial effects of this invention are as follows: Co-deposition is achieved by adding Ag ions to the Ni-P electroplating solution, forming Ag nanocrystal nuclei. This enhances coating adhesion and serves as an Ag ion reservoir, extending antibacterial durability. By controlling the P content in the electroplated layer, Ti-OP covalent bonds are formed during sintering, improving coating adhesion while preventing high-temperature damage to the Ni-P layer. This ensures the corrosion resistance of the electroplated layer while improving its adhesion and high-temperature stability.

[0013] By precisely controlling the porosity, pore size, and pore depth of the electroplated layer, a "physical anchoring" structure is formed, reducing the coating peeling rate from the current 15% to below 0.5%. Achieving synergistic performance between the steel substrate, electroplated layer, and antibacterial coating, the prepared bathroom steel exhibits excellent salt spray corrosion resistance, coating adhesion, and antibacterial properties. The coating adhesion is ≥18MPa, and the antibacterial rate of the bathroom steel reaches over 99%. Even after 50% coating wear, the antibacterial rate of the bathroom steel remains ≥90%. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the preparation process of a sanitary ware steel with nano-antibacterial function disclosed in an embodiment of the present invention. Detailed Implementation

[0016] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Existing bathroom steels suffer from problems such as limited antibacterial properties, conflicting antibacterial and corrosion-resistant properties, and short service life. To address these technical issues, this invention provides a bathroom steel with nano-antibacterial properties, comprising a steel substrate, a Ni-P-Ag electroplating layer, and a nano-antibacterial coating. The steel matrix comprises, by weight percentage: C 0.03-0.08%, Si 0.15-0.35%, Mn 0.4-0.8%, Cr 11-13%, Ni 0.8-1.2%, Cu 0.02-0.06%, Ti 0.03-0.05%, with the balance being Fe and unavoidable impurities; The Ni-P-Ag electroplating layer has a thickness of 8-12 μm and its composition by mass fraction is: Ni 86.5-90.9%, P 9-13%, Ag 0.1-0.5%, and the surface porosity of the electroplating layer is 2-5%. The nano antibacterial coating covers the surface of the electroplating layer and has a thickness of 3-6 μm. Its composition includes: 0.5-2 wt% nano Ag particles, with the remainder being nano TiO2. The interface between the coating and the electroplating layer forms Ti-OP chemical bonds.

[0018] In one embodiment, the particle size of the nano-TiO2 is 10-30 nm, and the particle size of the nano-Ag particles is 15-40 nm.

[0019] In one embodiment, the electroplated layer forms a surface pore diameter of 0.5-2 μm and a pore depth of 2-5 μm.

[0020] In steel matrix composition design, carbon (C) is a major strengthening element in steel, but excessive amounts can lead to a decrease in steel toughness and it easily combines with chromium (Cr) to form Cr₂. 23C6 carbides deplete Cr at grain boundaries, reducing corrosion resistance. Controlling the content to 0.03-0.08% ensures the yield strength of the steel substrate while avoiding intergranular corrosion risk, meeting the machining and load-bearing requirements of bathroom components. Cr content 11-13%: Cr is the core element for steel's corrosion resistance, forming a continuous and dense Cr2O3 passivation film on the surface, preventing the intrusion of corrosive media. A content of 11-13% ensures basic corrosion resistance of the steel substrate in humid bathroom environments while controlling costs, providing a stable base for subsequent coatings. Ni content 0.8-1.2%: Ni promotes austenite formation in steel, improving its toughness and low-temperature impact resistance. It also works synergistically with Cr to enhance the stability of the passivation film. Cu content 0.02-0.06%: Cu can form Cu ions on the steel surface, which have certain antibacterial properties and can refine the grains and improve the strength of the steel; however, excessive amount will lead to a decrease in the hot working performance of the steel and hot cracking. The addition of trace amounts of 0.02-0.06% can give the steel substrate auxiliary antibacterial ability without affecting the processing performance, forming a "dual antibacterial" synergy with the subsequent coating.

[0021] The Ni-P-Ag electroplating layer is designed with a thickness of 8-12μm and a composition of Ni 86.5-90.9%, P 9-13%, and Ag 0.1-0.5%. The surface porosity is 2-5%, the pore size is 0.5-2μm, and the pore depth is 2-5μm.

[0022] The thickness of the electroplating layer needs to balance corrosion resistance and coating adhesion. When it is less than 8μm, it cannot completely cover the surface defects of the steel substrate (such as scratches and micro-pits), and local corrosion is likely to occur. When it is greater than 12μm, the internal stress of the electroplating layer increases, and cracking is likely to occur after cooling, which also increases the electroplating time and cost. A thickness of 8-12μm can ensure effective protection of the steel substrate while avoiding the risk of internal stress cracking.

[0023] Electroplating layer P content 9-13%: P is the key element for achieving amorphization of the electroplating layer. The amorphous structure has no grain boundary defects, which can significantly improve corrosion resistance. At the same time, P can diffuse to the coating interface during the subsequent sintering process and form Ti-OP chemical bonds with TiO2, achieving the dual function of "corrosion resistance-interfacial bonding". When it is below 9%, the electroplating layer is prone to crystallization, the corrosion resistance decreases, and there is not enough P atoms to form interfacial bonds. When it is above 13%, the electroplating layer has excessive hardness and increased brittleness, and is easy to peel off under mechanical impact.

[0024] Ag content 0.1-0.5%: Ag is the core antibacterial element, which is co-deposited in the Ni-P layer to form uniformly distributed Ag nanocrystal nuclei. On the one hand, Ag nanocrystal nuclei can serve as "active sites" to enhance the physical bonding between the subsequent nano-antibacterial coating and the electroplated layer, thereby improving the adhesion. On the other hand, Ag nuclei can serve as a reservoir of Ag ions. When the Ag particles in the surface nano-antibacterial coating are depleted due to water washing, Ag ions are slowly released through the potential difference between Ni-P and Ag via electrochemical action, replenishing the antibacterial activity and prolonging the antibacterial durability. When the content is below 0.1%, the reservoir effect is not obvious, and the antibacterial durability is insufficient. When the content is above 0.5%, Ag particles are prone to agglomeration, resulting in a loose structure of the electroplated layer and reduced corrosion resistance. The trace addition of 0.1-0.5% achieves a balance between long-lasting antibacterial effect and corrosion resistance.

[0025] Electroplated layer surface porosity 2-5%, pore diameter 0.5-2μm, pore depth 2-5μm: The pore structure is the key design for achieving the "physical anchoring" of the coating. The pores can serve as penetration channels for the nano-antibacterial coating liquid. After coating, the coating liquid fills the pores, forming an "anchor" structure, which greatly increases the coating contact area. When the pore diameter is less than 0.5μm, the coating liquid is difficult to penetrate, resulting in poor anchoring effect. When it is greater than 2μm, the pores are insufficient to guarantee the corrosion resistance of the coating. When the pore depth is less than 2μm, the anchoring depth is insufficient, and the coating is easy to peel off. When it is greater than 5μm, the effective protective thickness of the electroplated layer decreases, and the corrosion resistance decreases. A porosity of 2-5% can maximize the coating adhesion while ensuring the overall corrosion resistance of the electroplated layer, avoiding the defect of "easy peeling off" of existing smooth electroplated layers.

[0026] The nano antibacterial coating has a thickness of 3-6 μm and consists of 0.5-2 wt% nano Ag particles and the remainder is nano TiO2. The TiO2 particle size is 10-30 nm and the Ag particle size is 15-40 nm.

[0027] The coating thickness of 3-6μm needs to balance antibacterial activity and coating strength. Nano-Ag particles are the core of room-temperature dark-state antibacterial activity. When the particle size is 15-40nm, the specific surface area is the largest and the Ag ion release efficiency is the highest. When the particle size is below 15nm, the particles are prone to agglomeration, and the antibacterial activity decreases. When the content of nano-Ag particles is less than 0.5%, the dark-state antibacterial efficiency is insufficient (antibacterial rate <90%). When it is higher than 2wt%, the cost increases and the coating color is prone to yellowing, affecting the appearance. This design forms a "double-layer antibacterial" structure with the Ag crystal nucleus of the electroplated layer. The Ag particles in the surface coating achieve immediate antibacterial effect, while the Ag crystal nucleus in the electroplated layer provides long-term replenishment. TiO2 is a photocatalytic antibacterial element. When the particle size is 10-30nm, it has excellent ultraviolet light absorption capacity, which destroys the bacterial cell membrane. At the same time, TiO2, as a coating matrix, can fix Ag particles and prevent them from being lost quickly. When the particle size is greater than 30nm, the photocatalytic activity decreases. When the particle size is less than 10nm, the particles are prone to agglomeration, resulting in poor coating uniformity. This design forms a "dark-light state" synergistic antibacterial effect with Ag particles, which solves the defect of poor antibacterial effect of pure TiO2 in a weak light environment.

[0028] Ti-OP interface bond: The coating and the electroplated layer are bonded through Ti-OP bonds. During the sintering process, P atoms in the electroplated layer diffuse to the interface and form covalent bonds (Ti-OP) with Ti atoms in TiO2. The bonding strength of this chemical bond is much higher than that of physical adsorption, which can prevent the coating and the electroplated layer from separating during high-temperature sintering and improve the bonding strength between the coating and the electroplated layer. At the same time, the formation of Ti-OP bonds can reduce the sintering temperature of TiO2 (densification can be achieved without high temperature), avoid the crystallization and embrittlement of Ni-P electroplated layer caused by high temperature (>550℃), and protect the amorphous corrosion-resistant structure of the electroplated layer.

[0029] like Figure 1 As shown, a method for preparing sanitary ware steel with nano-antibacterial function according to an embodiment of the present invention includes the following steps: (1) Steel matrix preparation: The steel matrix is ​​prepared by distributing the materials according to the steel matrix composition, melting in a medium frequency induction furnace, casting under argon protection, and continuous casting to obtain a billet; the billet is heated to 1100-1180℃ for hot rolling, the final rolling temperature is 850-920℃, air-cooled to room temperature, and then machined to obtain the steel matrix; (2) Steel substrate pretreatment: The steel substrate is mechanically ground, alkaline washed to remove oil, acid washed to remove rust, rinsed with deionized water and then dried. (3) Ni-P-Ag alloy electroplating: The pretreated steel substrate is used as the cathode and graphite as the anode, and is placed in the electroplating solution for electroplating; the components of the electroplating solution are: NiSO4・6H2O 190-260g / L, NaH2PO2・H2O 30-50g / L, Na3C6H5O7・2H2O 18-35g / L, NH4Cl 12-22g / L, AgNO3 0.5-2g / L, and the pH is adjusted to 4.2-5.8; the electroplating temperature is 45-65℃, and the current density is 1.2-3.5A / dm³. 2 The electroplating time is 25-45 minutes, forming a Ni-P-Ag electroplated layer with a surface porosity of 2-5%. (4) Plasma activation of electroplated layer: The electroplated steel substrate is placed in a plasma treatment instrument, and Ar / O2 mixed gas is introduced. The activation treatment is carried out for 3-8 minutes under the conditions of power 150-250W and pressure 5-10Pa. (5) Preparation of nano antibacterial coating: Tetrabutyl titanate, anhydrous ethanol and glacial acetic acid are mixed at a volume ratio of 1:(3-5):(0.5-1.2). After stirring for 30-60 min, 0.8-2.5 wt% nano Ag particles relative to the mass of tetrabutyl titanate are added and stirring is continued for 25-45 min. The viscosity is adjusted to 25-35 mPa·s to obtain an antibacterial coating solution. The coating solution is coated onto the surface of the activated electroplated layer by dip coating at a speed of 6-12 mm / s. Then, it is dried at 80-120℃ for 1.5-2.5 h and then placed in a muffle furnace and heated to 420-520℃ at 5-10℃ / min for 2-3.5 h. After cooling to room temperature, a nano antibacterial coating is formed that is bonded to the electroplated layer through Ti-OP bonds.

[0030] In one embodiment, the pore diameter of the electroplated layer in step (3) is 0.5-2 μm and the pore depth is 2-5 μm.

[0031] In one embodiment, the volume ratio of the Ar / O2 mixed gas in step (4) is 8:2-6:4.

[0032] In one embodiment, in step (5), the sintering temperature is increased to 420-520℃ at 5-10℃ / min and sintered for 2-3.5h.

[0033] Electroplating parameter design: A temperature of 45-65℃ ensures a stable deposition rate and a smooth electroplated layer surface (Ra≤0.2μm). Time and current density are used in synergistic control of the plating thickness to ensure an 8-12μm thickness and 2-5% porosity.

[0034] By treating the coating with Ar / O2 plasma, tiny pits (50-100 nm in diameter) are etched into the coating surface, and these pits provide "physical anchor points".

[0035] Sintering heating rate: 5-10℃ / min, holding at 420-520℃ for 2-3.5h: Slow heating avoids cracking of the coating due to thermal expansion differences, ensuring no cracking in coatings of different thicknesses. Sintering temperature: 420-520℃ is the optimal temperature for TiO2 anatase phase formation, while also promoting P diffusion to form Ti-OP bonds. Below 420℃, tetrabutyl titanate is not completely converted to TiO2, resulting in insufficient antibacterial activity; above 520℃, TiO2 transforms to the rutile phase, reducing photocatalytic activity, and the Ni-P layer easily crystallizes. Holding time: 2-3.5h. Less than 2h results in incomplete reaction, low TiO2 conversion, and insufficient Ti-OP bond quantity; more than 3.5h increases energy consumption and the coating is prone to over-densification, affecting Ag ion release. 2-3.5h ensures complete reaction, complete TiO2 conversion, and a sufficient number of Ti-OP bonds. The sanitary steel prepared by this invention has excellent salt spray corrosion resistance, coating adhesion and antibacterial properties. The coating adhesion is ≥18MPa, the antibacterial rate of the sanitary steel reaches more than 99%, and even after the coating is worn by 50%, the antibacterial rate of the sanitary steel is still ≥90%.

[0036] The embodiments of the present invention are described in detail below. The composition of the sanitary ware steel of Embodiments 1-4 and Comparative Examples 1-3 is shown in Table 1.

[0037] Table 1: Composition of bathroom steel in Examples 1-4 and Comparative Examples 1-3:

[0038] The process parameters used in the preparation methods of Examples 1-4 and Comparative Examples 1-4 of this invention are shown in Table 2.

[0039] Table 2: Process parameters used in the preparation methods of Examples 1-4 and Comparative Examples 1-4:

[0040] The steel substrate composition, electroplating layer and coating composition of Comparative Example 4 are the same as those of Example 2. The only difference between Comparative Example 4 and Example 2 is the sintering temperature. See Table 2 for details.

[0041] Performance tests were conducted on the sanitary ware steels of the above-mentioned comparative examples and examples. According to GB / T10125-2021, the neutral salt spray (NSS) test was performed, and the time to the first appearance of red rust was recorded to determine the salt spray corrosion resistance. According to GB / T5210-2006, the coating adhesion was determined using the pull-off method, and the average of three measurements was taken. According to JISZ2801-2000 "Antibacterial Processed Products – Test Methods for Antibacterial Properties and Antibacterial Effects", the antibacterial rate after action against common bacteria (Escherichia coli and Staphylococcus aureus) was determined, and the antibacterial rate was calculated. The results are shown in Table 3.

[0042] Table 3: Performance data of the examples and comparative examples:

[0043] As can be seen from Table 3, the sanitary steel prepared by the present invention has excellent salt spray corrosion resistance, coating adhesion and antibacterial properties. The coating adhesion is ≥18MPa, the antibacterial rate of the sanitary steel reaches more than 99%, and even after the coating is worn by 50%, the antibacterial rate of the sanitary steel is still ≥90%.

[0044] Compared with Examples 1-4, Comparative Examples 1-4, after adjusting the process parameters of the Ni-P-Ag electroplating layer, the thickness of the coating, and the sintering temperature, could not guarantee the number of Ti-OP bonds and the full formation of TiO2 antibacterial components. The adhesion of the coating decreased, resulting in a significant decrease in salt spray corrosion resistance, coating adhesion, and antibacterial performance.

[0045] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A type of bathroom steel with nano-antibacterial function, characterized in that, Includes a steel substrate, a Ni-P-Ag electroplating layer, and a nano-antibacterial coating; The steel matrix comprises, by weight percentage: C 0.03-0.08%, Si 0.15-0.35%, Mn 0.4-0.8%, Cr 11-13%, Ni 0.8-1.2%, Cu 0.02-0.06%, Ti 0.03-0.05%, with the balance being Fe and unavoidable impurities; The Ni-P-Ag electroplating layer has a thickness of 8-12 μm and its composition by mass fraction is: Ni 86.5-90.9%, P 9-13%, Ag 0.1-0.5%, and the surface porosity of the electroplating layer is 2-5%. The nano antibacterial coating covers the surface of the electroplating layer and has a thickness of 3-6 μm. Its composition includes: 0.5-2 wt% nano Ag particles, with the remainder being nano TiO2. The interface between the coating and the electroplating layer forms Ti-OP chemical bonds.

2. The bathroom steel with nano-antibacterial function according to claim 1, characterized in that, The nano-TiO2 particles have a diameter of 10-30 nm, and the nano-Ag particles have a diameter of 15-40 nm.

3. The bathroom steel with nano-antibacterial function according to claim 1, characterized in that, The electroplated layer forms a surface pore diameter of 0.5-2μm and a pore depth of 2-5μm.

4. A method for preparing sanitary ware steel with nano-antibacterial function as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Steel matrix preparation: The steel matrix is ​​prepared by distributing the materials according to the steel matrix composition, melting in a medium frequency induction furnace, casting under argon protection, and continuous casting to obtain a billet; the billet is heated to 1100-1180℃ for hot rolling, the final rolling temperature is 850-920℃, air-cooled to room temperature, and then machined to obtain the steel matrix; (2) Steel substrate pretreatment: The steel substrate is mechanically ground, alkaline washed to remove oil, acid washed to remove rust, rinsed with deionized water and then dried. (3) Ni-P-Ag alloy electroplating: The pretreated steel substrate is used as the cathode and graphite as the anode, and is placed in the electroplating solution for electroplating; the components of the electroplating solution are: NiSO4・6H2O 190-260g / L, NaH2PO2・H2O 30-50g / L, Na3C6H5O7・2H2O 18-35g / L, NH4Cl 12-22g / L, AgNO3 0.5-2g / L, and the pH is adjusted to 4.2-5.8; the electroplating temperature is 45-65℃, and the current density is 1.2-3.5A / dm³. 2 The electroplating time is 25-45 minutes, forming a Ni-P-Ag electroplated layer with a surface porosity of 2-5%. (4) Plasma activation of electroplated layer: The electroplated steel substrate is placed in a plasma treatment instrument, and Ar / O2 mixed gas is introduced. The activation treatment is carried out for 3-8 minutes under the conditions of power 150-250W and pressure 5-10Pa. (5) Preparation of nano antibacterial coating: Tetrabutyl titanate, anhydrous ethanol and glacial acetic acid are mixed at a volume ratio of 1:(3-5):(0.5-1.2). After stirring for 30-60 min, 0.8-2.5 wt% nano Ag particles relative to the mass of tetrabutyl titanate are added and stirring is continued for 25-45 min. The viscosity is adjusted to 25-35 mPa·s to obtain an antibacterial coating solution. The coating solution is coated onto the surface of the activated electroplated layer by dip coating at a speed of 6-12 mm / s. Then, it is dried at 80-120℃ for 1.5-2.5 h and then placed in a muffle furnace and heated to 420-520℃ at 5-10℃ / min for 2-3.5 h. After cooling to room temperature, a nano antibacterial coating is formed that is bonded to the electroplated layer through Ti-OP bonds.

5. The method for preparing sanitary ware steel with nano-antibacterial function according to claim 4, characterized in that, In step (3), the surface pore diameter of the electroplated layer is 0.5-2μm and the pore depth is 2-5μm.

6. The method for preparing sanitary ware steel with nano-antibacterial function according to claim 4, characterized in that, In step (4), the volume ratio of the Ar / O2 mixed gas is 8:2-6:

4.

7. The method for preparing sanitary ware steel with nano-antibacterial function according to claim 4, characterized in that, In step (5), the sintering temperature is increased to 420-520℃ at a rate of 5-10℃ / min and sintered for 2-3.5 hours.

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