A stainless steel passivation solution and preparation method thereof

Abstract

The present invention belongs to the technical field of stainless steel surface treatment, and specifically relates to a stainless steel passivation solution and a preparation method thereof. The composition includes the following raw materials: cerium salt, copper sulfate, citric acid, sodium dihydrogen phosphate, ammonium molybdate, sodium tungstate, amino-silane-modified SiO2 nanoparticles, polyethylene glycol, L-ascorbic acid, polyaspartic acid, an anti-settling agent and a surfactant, and the balance is deionized water. The present invention solves the problem of weak interfacial bonding force of the traditional passivation layer by using amino-epoxy silane-modified SiO2 nanoparticles to construct a three-dimensional network skeleton; in the formula of the present invention, biodegradable components such as citric acid and polyaspartic acid account for a very high proportion, and the cerium salt adopts a low-toxic rare earth compound, and the molybdenum / tungsten elements are fixed in the form of stable oxides. The EDTA dosage is significantly reduced through compounding technology, and the three-dimensional network is combined with the adsorption of residual ions to achieve a balance between environmental friendliness and long-term anti-corrosion performance.

Description

Technical Field

[0001] The invention belongs to the technical field of stainless steel surface treatment, and particularly relates to a stainless steel passivation solution and a preparation method thereof. Background Art

[0002] Stainless steel has become a core material in aerospace, biomedicine, food processing, chemical equipment and other fields due to its excellent corrosion resistance, mechanical strength and surface finish. However, its corrosion resistance is essentially dependent on the nano-scale chromium oxide (Cr2O3) passivation film naturally formed on the surface. During mechanical processing (such as cutting, welding, polishing) or service, this passivation film is easily damaged and causes multiple risks: the residual free iron (Fe) and carbon (C) particles form a micro-battery effect, inducing local electrochemical corrosion; high temperature processing leads to the formation of chromium carbide (Cr X C) precipitation, resulting in chromium-poor areas and weakening the continuity of the passivation film; while pollutants such as grease and oxides attached to the surface will accelerate the chloride ion (Cl ⁻ ) penetration, exacerbating pitting corrosion and stress corrosion cracking (SCC). Although traditional physical rust prevention technologies (such as coating rust-proof oil and spray painting) can block corrosive media in the short term, they have defects such as volatile organic compound (VOCs) pollution, easy peeling of the film layer and affecting the conductivity of the material. For this reason, chemical passivation treatment uses acidic media (such as nitric acid and citric acid) to dissolve surface pollutants and activate the matrix, and promotes the selective oxidation of chromium with the help of oxidants (molybdates and persulfates), and generates a dense Cr2O3 / Fe3O4 composite oxide film in situ on the metal surface. At the same time, silica sol or rare earth salts (such as Ce 3+ ) Close the micropores and block the corrosive media (O2, H2O, Cl ⁻ ) diffusion path, thereby achieving long-term corrosion protection, zero substrate size loss and food-grade cleanliness requirements. However, traditional passivation solutions represented by the nitric acid-hydrofluoric acid (HNO3-HF) system still have significant technical bottlenecks. For example, the severe toxicity of hydrofluoric acid and the NOx gas volatilized by nitric acid will endanger operational safety, and the cost of treating fluorine-containing wastewater is relatively high. In addition, it is easy to cause over-corrosion to materials such as duplex steel, resulting in increased surface roughness, and the passivation film's resistance to marine environment corrosion is also extremely poor. Therefore, based on the above problems, it is extremely necessary to develop a safe, environmentally friendly and corrosion-resistant stainless steel passivation solution. Summary of the Invention

[0003] In view of the defects of the prior art, the present invention aims to provide a stainless steel passivation solution and its preparation method. The present invention adopts amino-epoxy silane to modify SiO2 nanoparticles to construct a three-dimensional network skeleton, and the surface amino groups of the nanoparticles react with Ce in the cerium salt to form a three-dimensional network skeleton. 3+The coordination anchoring metal active sites form a passivation core, while the epoxy group forms a covalent bond with the substrate hydroxyl group through a ring-opening reaction, solving the problem of weak interfacial bonding in the traditional passivation layer. Then, sodium carboxymethyl cellulose is used to construct a hydrogen bond cross-linked network to strengthen adhesion. Combined with the aminated SiO2 network, the physical-chemical dual-mode adsorption of iron ions is achieved, and polyaspartic acid is used to achieve efficient capture of metal ions, solving the contradiction between heavy metal leakage and environmental protection in traditional passivation solutions. In the formula of the present invention, biodegradable components such as citric acid and polyaspartic acid account for a very high proportion, and cerium salts use low-toxic rare earth compounds, and molybdenum / tungsten elements are fixed in the form of stable oxides. The EDTA dosage is significantly reduced through compounding technology, and the three-dimensional network is combined to adsorb residual ions, achieving a balance between environmental friendliness and long-term anti-corrosion performance.

[0004] The technical effect of the present invention is achieved through the following technical scheme: a stainless steel passivation solution, which comprises the following raw materials in percentage by mass: 0.2-0.5% of cerium salt, 0.1-0.3% of copper sulfate, 2-3% of citric acid, 0.4-0.6% of sodium dihydrogen phosphate, 0.3-0.6% of ammonium molybdate, 0.2-0.5% of sodium tungstate, 1.2-2% of amino-silane modified SiO2 nanoparticles, 0.5-1% of polyethylene glycol, 0.8-1.5% of L-ascorbic acid, 0.8-1.2% of polyaspartic acid, 1.2-1.5% of anti-settling agent and 0.1-0.3% of surfactant, and the balance is deionized water.

[0005] Preferably, the cerium salt is any one of cerium nitrate, cerium sulfate and cerium chloride, and further preferably is cerium nitrate;

[0006] Preferably, the anti-settling agent is sodium carboxymethyl cellulose;

[0007] Preferably, the surfactant is disodium edetate;

[0008] Preferably, the specific preparation steps of the amino-silane modified SiO2 nanoparticles are as follows:

[0009] S1: Add SiO2 nanoparticles to anhydrous ethanol, disperse them evenly with ultrasonic treatment, centrifuge, filter, and vacuum dry at 120℃ for 2-3h to obtain activated SiO2;

[0010] S2: Add the activated SiO2 prepared in step S1 to a 95wt% ethanol solution, disperse it evenly by ultrasonic treatment, then slowly add γ-aminopropyltriethoxysilane dropwise at a rate of 0.5-1mL / min, adjust the pH to 4.8-5.5 with glacial acetic acid, heat to 60-65°C for 3-4h, centrifuge, filter, wash repeatedly with 75wt% ethanol 3 times, and dry in a vacuum at 60°C for 6-12h to obtain amino SiO2;

[0011] S3: adding the amino SiO2 prepared in step S2 to a 90 wt% ethanol solution, dispersing it evenly through ultrasonic treatment, adding triethylamine, and then slowly adding γ-glycidyloxypropyltrimethoxysilane dropwise at a rate of 0.1-0.2 mL / min, stirring and reacting at 45-50°C for 5-6 hours, centrifuging, repeatedly washing with acetone and ethanol three times, and vacuum drying at 40°C for 12-16 hours to obtain amino-silane-modified SiO2 nanoparticles;

[0012] Preferably, in step S1, the ratio of the amount of the SiO2 nanoparticles to anhydrous ethanol is 1 g:50 mL;

[0013] Preferably, in step S2, the ratio of the activated SiO2, ethanol solution and γ-aminopropyltriethoxysilane is 1 g:200 mL:0.3-0.5 mL;

[0014] Preferably, in step S3, the ratio of the amount of the amino SiO2, the ethanol solution and the γ-glycidyloxypropyltrimethoxysilane is 1 g:100-150 mL:0.8-1 mL; the amount of triethylamine added is 2-4% by volume of the amount of γ-glycidyloxypropyltrimethoxysilane added;

[0015] Preferably, another aspect of the present invention is to provide a preparation process of a stainless steel passivation solution, wherein the specific preparation process is as follows:

[0016] S101: Add citric acid, sodium dihydrogen phosphate, and an anti-settling agent to 50% of the total water volume of deionized water, heat to 50-60°C, and stir until completely dissolved. Then, add copper sulfate, ammonium molybdate, and sodium tungstate in sequence, maintaining a stirring speed of 200-300 rpm, until a uniform and transparent solution is formed to obtain a mixed solution.

[0017] S102: slowly adding the amino-silane-modified SiO2 nanoparticles to the mixed solution prepared in step S101, ultrasonically treating it, adding cerium salt, heating it to 55-60°C, and stirring it at 300-500 rpm for 1-2 hours to obtain an activated solution;

[0018] S103: Cooling the activation solution prepared in step S102 to 40-45° C., adding L-ascorbic acid, and stirring at 200-300 rpm for 2-3 hours, then sequentially adding polyaspartic acid and a surfactant, and adjusting the pH to 3.5-4.5 with dilute sulfuric acid and ammonia water, and stirring at 300-500 rpm for 1-2 hours to obtain a complex system;

[0019] S104: adding polyethylene glycol to the complexing system prepared in step S103, heating to 45-55° C. and stirring for 30-50 minutes, adding the remaining deionized water, and ultrasonically degassing to obtain a passivation solution;

[0020] Preferably, in step S102, the ultrasonic treatment parameters are 30-40 kHz, 100-120 W, and time 20-30 min;

[0021] Preferably, in step S104, the ultrasonic degassing treatment parameters are 40 kHz, 100-150 W, and time 15-20 min.

[0022] The beneficial effects of the present invention are as follows:

[0023] The present invention uses amino-epoxy silane modified silicon dioxide (SiO2) nanoparticles to construct a three-dimensional network skeleton, and the surface amino groups of the SiO2 nanoparticles interact with the Ce in the cerium salt. 3+ The silane reacts with the metal active site to form a passivation core, and the epoxy group at the end of the silane forms a covalent bond with the hydroxyl group on the surface of the metal substrate through a ring-opening reaction, which significantly enhances the chemical bonding between the nanoparticles and the matrix. 2+ ), iron ions (Fe 3+ ) forms a soluble complex, which cooperates with the carboxylic acid groups of polyaspartic acid to accelerate the spread of the passivation film. At the same time, the branched molecular chains of polyaspartic acid can selectively chelate free Fe 3+ , synergistically chelate metal ions and inhibit Fe(OH)3 precipitation, inhibiting rust deposition. Ammonium molybdate and sodium tungstate are reduced by L-ascorbic acid to form a molybdenum-tungsten composite oxide film, where L-ascorbic acid has both reducing and environmental friendliness, and can reduce Fe 3+ Reduced to easily complexed Fe 2+ , and the strong chelating ability of disodium ethylenediaminetetraacetic acid (EDTA) synergistically removes iron ions in the system and blocks the chain corrosion reaction caused by iron ions.

[0024] In the formula used in the present invention, sodium carboxymethyl cellulose is a natural polysaccharide derivative. Its hydroxyl groups form a hydrogen bond cross-linking network with the epoxy groups on the surface of silicon dioxide, which enhances the adhesion of the passivation film while dispersing the iron oxide particles through the steric hindrance of the molecular chain to avoid local corrosion. The water-soluble ether chain of polyethylene glycol and the carboxylic acid group of disodium ethylenediaminetetraacetic acid form a hydrophobic-hydrophilic dynamic protective layer through molecular self-assembly. Disodium ethylenediaminetetraacetic acid can not only stabilize heavy metal ions and reduce environmental release, but also bind to free Fe 2+ / Fe 3+ It forms a stable chelate and improves the recycling efficiency of the passivation liquid. The three-dimensional network of amino silica captures iron ions through the dual effects of physical adsorption and amino coordination, and cooperates with the chelating function of polyaspartic acid to form a graded iron ion removal mechanism.

[0025] In the formula used by the passivation solution of the present invention, citric acid, polyaspartic acid, sodium carboxymethyl cellulose and L-ascorbic acid are all biodegradable components, cerium salt selects low-toxic rare earth compounds, and molybdenum / tungstate is fixed in the passivation film in the form of stable oxides, significantly reducing the risk of heavy metal ion leakage. Although disodium ethylenediaminetetraacetic acid has strong chelating properties, its dosage is effectively reduced by compounding polyaspartic acid and sodium carboxymethyl cellulose, and residual metal ions are adsorbed in combination with the silica network to achieve a balance between environmental friendliness and efficient removal of iron ions. In summary, the final system constructed by the synergistic effect of multiple substances of the present invention is coordinated by biodegradable components, stabilized heavy metal fixation and multi-stage iron ion chelation-adsorption, achieving the unity of green environmental protection and long-term anti-corrosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 1 is a graph showing the adhesion test results of the passivation solutions prepared in Example 2 of the present invention and Comparative Examples 1 to 4;

[0028] Figure 2 This is a SEM scanning electron microscope image of the passivation solution prepared in Example 2 of the present invention after being subjected to a salt spray corrosion resistance test;

[0029] Figure 3 This is the FTIR infrared spectrum of the amino-epoxysilane modified SiO2 nanoparticles prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. It should be noted that unless otherwise specified, the raw materials involved in the present invention were purchased through conventional commercial channels.

[0031] Example 1: A stainless steel passivation solution, comprising the following raw materials in percentage by mass: 0.2% cerium salt, 0.1% copper sulfate, 2% citric acid, 0.4% sodium dihydrogen phosphate, 0.3% ammonium molybdate, 0.2% sodium tungstate, 1.2% amino-silane modified SiO2 nanoparticles, 0.5% polyethylene glycol, 0.8% L-ascorbic acid, 0.8% polyaspartic acid, 1.2% anti-settling agent and 0.1% surfactant, the balance being deionized water.

[0032] The specific preparation steps of the amino-silane modified SiO2 nanoparticles are as follows:

[0033] S1: 1 g of SiO2 nanoparticles were added to 50 mL of anhydrous ethanol, dispersed evenly by ultrasonic treatment, centrifuged, filtered, and dried in vacuum at 120 °C for 2 h to obtain activated SiO2;

[0034] S2: 1 g of activated SiO2 prepared in step S1 was added to 200 mL of 95 wt% ethanol solution and dispersed evenly by ultrasonic treatment. Then, 0.3 mL of γ-aminopropyltriethoxysilane was slowly added dropwise at a rate of 0.5 mL / min. The pH was adjusted to 5.5 with glacial acetic acid. The mixture was heated to 60°C for 3 h, centrifuged, filtered, and washed repeatedly with 75 wt% ethanol for 3 times. The mixture was vacuum dried at 60°C for 6 h to obtain amino-SiO2.

[0035] S3: 1 g of the amino-modified SiO2 prepared in step S2 was added to 100 mL of 90 wt% ethanol solution, and the mixture was dispersed evenly by ultrasonic treatment. 0.016 mL of triethylamine was added, and then 0.8 mL of γ-glycidyloxypropyltrimethoxysilane was slowly added dropwise at a rate of 0.1 mL / min. The mixture was stirred at 45°C for 5 h, centrifuged, and washed with acetone and ethanol three times. The mixture was vacuum-dried at 40°C for 12 h to obtain amino-silane-modified SiO2 nanoparticles.

[0036] The specific preparation steps of the stainless steel passivation solution are as follows:

[0037] S101: Add citric acid, sodium dihydrogen phosphate, and sodium carboxymethyl cellulose to 50% of the total water volume of deionized water, heat to 50°C, and stir until completely dissolved. Then, add copper sulfate, ammonium molybdate, and sodium tungstate in sequence, maintaining the stirring speed at 200 rpm, until a homogeneous transparent solution is formed to obtain a mixed solution.

[0038] S102: Slowly add the amino-silane-modified SiO2 nanoparticles to the mixed solution prepared in step S101, with ultrasonic treatment parameters of 30 kHz, 100 W, and time of 20 min, add cerium sulfate, heat to 55°C, and stir at 300 rpm for 1 hour to obtain an activated solution;

[0039] S103: Cool the activation solution prepared in step S102 to 40° C., add L-ascorbic acid, and stir at 200 rpm for 2 h. Then, add sodium dihydrogen phosphate, polyaspartic acid, and disodium ethylenediaminetetraacetic acid in sequence, adjust the pH to 3.5 with dilute sulfuric acid and ammonia water, and stir at 300 rpm for 1 h to obtain a complex system.

[0040] S104: adding polyethylene glycol to the complexing system prepared in step S103, heating to 45° C. and stirring for 30 minutes, adding the remaining deionized water, and ultrasonically degassing at parameters of 40 kHz, 100 W, and time for 15 minutes to obtain a passivation solution.

[0041] Example 2: A stainless steel passivation solution, comprising the following raw materials in percentage by mass: 0.5% cerium salt, 0.3% copper sulfate, 3% citric acid, 0.6% sodium dihydrogen phosphate, 0.6% ammonium molybdate, 0.5% sodium tungstate, 2% amino-silane modified SiO2 nanoparticles, 1% polyethylene glycol, 1.5% L-ascorbic acid, 1.2% polyaspartic acid, 1.5% anti-settling agent and 0.2% surfactant, the balance being deionized water.

[0042] The specific preparation steps of the amino-silane modified SiO2 nanoparticles are as follows:

[0043] S1: 1 g of SiO2 nanoparticles were added to 50 mL of anhydrous ethanol, dispersed evenly by ultrasonic treatment, centrifuged, filtered, and dried in vacuum at 120 °C for 3 h to obtain activated SiO2;

[0044] S2: 1 g of activated SiO2 prepared in step S1 was added to 200 mL of 95 wt% ethanol solution and dispersed evenly by ultrasonic treatment. Then, 0.5 mL of γ-aminopropyltriethoxysilane was slowly added dropwise at a rate of 1 mL / min. The pH was adjusted to 5.2 with glacial acetic acid. The mixture was heated to 65°C for 3.5 h, centrifuged, filtered, and washed repeatedly with 75 wt% ethanol for 3 times. The mixture was vacuum dried at 60°C for 12 h to obtain amino-SiO2.

[0045] S3: 1 g of the amino-modified SiO2 prepared in step S2 was added to 150 mL of 90 wt% ethanol solution, and the mixture was dispersed evenly by ultrasonic treatment. 0.04 mL of triethylamine was added, and then 1 mL of γ-glycidyloxypropyltrimethoxysilane was slowly added dropwise at a rate of 0.15 mL / min. The mixture was stirred at 50°C for 5.5 h, centrifuged, and washed with acetone and ethanol three times. The mixture was vacuum-dried at 40°C for 16 h to obtain amino-silane-modified SiO2 nanoparticles.

[0046] The specific preparation steps of the stainless steel passivation solution are as follows:

[0047] S101: Add citric acid, sodium dihydrogen phosphate, and sodium carboxymethyl cellulose to 50% of the total water volume of deionized water, heat to 60°C, and stir until completely dissolved. Then, add copper sulfate, ammonium molybdate, and sodium tungstate in sequence, maintaining the stirring speed at 300 rpm, until a homogeneous transparent solution is formed to obtain a mixed solution.

[0048] S102: Slowly add the amino-silane-modified SiO2 nanoparticles to the mixed solution prepared in step S101, and ultrasonically treat the mixture at 40 kHz, 120 W, and for 25 min. Then, add cerium nitrate, heat to 60°C, and stir at 500 rpm for 1.5 h to obtain an activated solution.

[0049] S103: Cool the activation solution prepared in step S102 to 45° C., add L-ascorbic acid, and stir at 300 rpm for 2.5 hours. Then, add polyaspartic acid and disodium edetate in sequence, adjust the pH to 4 with dilute sulfuric acid and ammonia water, and stir at 500 rpm for 1.5 hours to obtain a complex system.

[0050] S104: adding polyethylene glycol to the complexing system prepared in step S103, heating to 55° C. and stirring for 40 min, adding the remaining deionized water, and ultrasonically degassing at 40 kHz, 150 W, for 18 min to obtain a passivation solution.

[0051] Example 3: A stainless steel passivation solution, comprising the following raw materials in percentage by mass: 0.4% cerium salt, 0.2% copper sulfate, 2.5% citric acid, 0.5% sodium dihydrogen phosphate, 0.5% ammonium molybdate, 0.4% sodium tungstate, 1.6% amino-silane modified SiO2 nanoparticles, 0.8% polyethylene glycol, 1.3% L-ascorbic acid, 1% polyaspartic acid, 1.4% anti-settling agent and 0.3% surfactant, the balance being deionized water.

[0052] The specific preparation steps of the amino-silane modified SiO2 nanoparticles are as follows:

[0053] S1: 1 g of SiO2 nanoparticles were added to 50 mL of anhydrous ethanol, dispersed evenly by ultrasonic treatment, centrifuged, filtered, and dried in vacuum at 120 °C for 2.5 h to obtain activated SiO2;

[0054] S2: 1 g of activated SiO2 prepared in step S1 was added to 200 mL of 95 wt% ethanol solution and dispersed evenly by ultrasonic treatment. Then, 0.4 mL of γ-aminopropyltriethoxysilane was slowly added dropwise at a rate of 0.8 mL / min. The pH was adjusted to 4.8 with glacial acetic acid. The mixture was heated to 62°C for 4 h, centrifuged, filtered, and washed repeatedly with 75 wt% ethanol for 3 times. The mixture was vacuum dried at 60°C for 10 h to obtain amino-SiO2.

[0055] S3: 1 g of the amino-modified SiO2 prepared in step S2 was added to 130 mL of a 90 wt% ethanol solution, and the mixture was dispersed evenly by ultrasonic treatment. 0.035 mL of triethylamine was added, and then 0.9 mL of γ-glycidyloxypropyltrimethoxysilane was slowly added dropwise at a rate of 0.2 mL / min. The mixture was stirred at 48°C for 6 h, centrifuged, and washed with acetone and ethanol three times. The mixture was vacuum-dried at 40°C for 15 h to obtain amino-silane-modified SiO2 nanoparticles.

[0056] The specific preparation steps of the stainless steel passivation solution are as follows:

[0057] S101: Add citric acid, sodium dihydrogen phosphate, and sodium carboxymethyl cellulose to 50% of the total water volume in deionized water, heat to 55°C, and stir until completely dissolved. Then, add copper sulfate, ammonium molybdate, and sodium tungstate in sequence, maintaining the stirring speed at 250 rpm, until a homogeneous transparent solution is formed to obtain a mixed solution.

[0058] S102: Slowly add the amino-silane-modified SiO2 nanoparticles to the mixed solution prepared in step S101, with ultrasonic treatment parameters of 35 kHz, 110 W, and time of 30 min, add cerium chloride, heat to 58°C, and stir at 400 rpm for 2 h to obtain an activated solution;

[0059] S103: Cool the activation solution prepared in step S102 to 42° C., add L-ascorbic acid, and stir at 260 rpm for 3 h. Then, add polyaspartic acid and disodium edetate in sequence, adjust the pH to 4.5 with dilute sulfuric acid and ammonia water, and stir at 400 rpm for 2 h to obtain a complex system.

[0060] S104: adding polyethylene glycol to the complexing system prepared in step S103, heating to 50° C. and stirring for 50 min, adding the remaining deionized water, and performing ultrasonic degassing at parameters of 40 kHz, 140 W, and time of 20 min to obtain a passivation solution.

[0061] Comparative Example 1: The operation of Comparative Example 1 is basically the same as that of Example 2, except that unmodified SiO2 nanoparticles are used in Comparative Example 1 to replace amino-silane-modified SiO2 nanoparticles.

[0062] Comparative Example 2: The operation of Comparative Example 2 is basically the same as that of Example 2, except that the cerium salt is removed in Comparative Example 2.

[0063] Comparative Example 3: The operation of Comparative Example 3 is substantially the same as that of Example 2, except that L-ascorbic acid is removed in Comparative Example 3.

[0064] Comparative Example 4: The operation of Comparative Example 4 is basically the same as that of Example 2, except that polyaspartic acid is removed in Comparative Example 4.

[0065] Performance testing:

[0066] Adhesion test: The passivation solutions prepared in Example 2 and Comparative Examples 1 to 4 were passivated using conventional techniques to treat 304 stainless steel samples. Then, a universal material testing machine was used to gradually apply tension at a constant rate (10 mm / min) to test the adhesion (N / mm) when the coating began to fall off. 2 ), the result is as follows Figure 1 shown.

[0067] Depend on Figure 1 The results show that the passivation solution prepared by the present invention has excellent adhesion and can effectively adhere to stainless steel for long-term use. From the results of Comparative Example 1 and Example 2, it can be seen that the SiO2 network is missing and only physical adsorption is relied upon, the epoxy covalent bond and amino coordination are missing, and the adhesion is significantly reduced. From the results of Comparative Example 2 and Example 2, it can be seen that the cerium salt forms a passivation core through amino coordination, selectively anchored at the metal active site, and enhances the local bonding strength. When the cerium salt is missing, the SiO2 network is only bonded to the substrate through hydrogen bonds and van der Waals forces, and the adhesion is significantly affected. From the results of Comparative Example 3 and Example 2, it can be seen that the lack of L-ascorbic acid leads to the partial Fe 3+ It was not effectively reduced, and the deposition of Fe(OH)3 destroyed the continuity of the passivation film. Local stress concentration caused interface peeling, which affected the adhesion to a certain extent. From the results of Comparative Example 4 and Example 2, it can be seen that the absence of polyaspartic acid and the increase in the proportion of EDTA may have led to a loose chelating network, and the hydrogen bond crosslinking between the SiO2 network and the substrate was also affected to a certain extent, thereby affecting the adhesion.

[0068] Contact angle test: The passivation solutions prepared in Examples 1 to 3 above were passivated with 304 stainless steel samples using conventional techniques, and then the contact angle test was performed. All samples were tested at room temperature and 50% humidity. A 5 μL water droplet was used for each test. The test results are shown in Table 1.

[0069] Table 1. Contact angle test results of stainless steel treated with passivation solution

[0070]

[0071] As can be seen from the results in Table 1, the passivation solution prepared by the present invention has excellent hydrophobicity after passivation treatment, which can effectively support the feasibility of the hydrophobic-hydrophilic dynamic protective layer in the design of the passivation solution and can inhibit electrochemical corrosion by reducing the penetration of water molecules.

[0072] Corrosion resistance test: The passivation solutions prepared in Example 2 and Comparative Examples 1 to 4 were passivated using conventional technical means to treat 304 stainless steel samples. Then, a salt spray test was performed at 50°C using a 5% NaCl solution for 300 h. The appearance changes were recorded at 36 h, 96 h, 168 h, and 300 h, respectively. The results are shown in Table 2. The passivation solutions prepared in Example 2 and Comparative Examples 1 to 3 were passivated using conventional technical means to treat 304 stainless steel samples. The samples were immersed in a 6% FeCl3 solution, the temperature was set at 50°C, the test time was 24 h, and the pitting density (individuals / cm2) was recorded at 4 h, 12 h, and 24 h. 2 ), the results were recorded as average values, and the results are shown in Table 3.

[0073] Table 2. Salt spray corrosion resistance test results of stainless steel treated with passivation solution

[0074]

[0075] Table 3. Pitting corrosion resistance test results of stainless steel treated with passivation solution

[0076]

[0077] From the results of Table 2 and Table 3, it can be seen that the passivation solution prepared by the present invention has excellent corrosion resistance. The multi-layer network structure can effectively block the penetration of chloride ions and achieve long-term use. From the results of Comparative Example 1 and Example 2, it can be seen that the lack of a three-dimensional network leads to accelerated penetration of chloride ions and a significant decrease in corrosion resistance. However, cerium salts and chelating agents (EDTA + polyaspartic acid) still effectively delay the appearance of red rust. From the results of Comparative Example 2 and Example 2, it can be seen that the lack of cerium ions prevents the formation of passivation cores, and the metal active sites lose selective protection, which leads to local pitting in weak areas. It germinates preferentially and expands rapidly; from the results of Comparative Example 3 and Example 2, it can be seen that the lack of L-ascorbic acid leads to the lack of Mo-W film, which in turn leads to an increase in the chloride ion penetration path, an accelerated corrosion rate, and the deposition of Fe(OH)3 destroys the continuity of the film, resulting in an expansion of the white rust area in the salt spray test; from the results of Comparative Example 4 and Example 2, it can be seen that the lack of polyaspartic acid leads to an incomplete chelating network, the excessive proportion of EDTA affects the density of the film layer, and chloride ions penetrate rapidly in the loose area of the film layer, thereby causing the white rust to spread; and from the results of Comparative Example 3, it can be seen that

[0078] Spectrum test: The stainless steel passivation film of Example 2 after the salt spray corrosion resistance test was subjected to SEM scanning spectrum test. The test results are as follows: Figure 2 As shown; the spectrum of the amino-epoxysilane modified SiO2 nanoparticles prepared in Example 2 was measured using an FTIR spectrometer, and the results were as follows Figure 3 shown.

[0079] Depend on Figure 2 The results show that the passivation solution prepared by the present invention can maintain good protection and corrosion resistance of stainless steel after passivation treatment after 240 hours of salt spray corrosion, with no obvious accumulation of corrosion products on the surface and no obvious depressions or pits.

[0080] Depend on Figure 3 The results show that in the spectrum between 3200 and 3500 cm -1 There is an obvious broad absorption valley near 800-1200 cm -1 A typical Si–O–Si vibration peak can be seen in the region, and it is between 2800 and 3000 cm -1 The obvious shoulder peaks showed that the alkyl chains were successfully introduced on the surface.

[0081] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A stainless steel passivation solution, characterized in that: The composition includes the following raw materials in percentage by mass: 0.2-0.5% of cerium salt, 0.1-0.3% of copper sulfate, 2-3% of citric acid, 0.4-0.6% of sodium dihydrogen phosphate, 0.3-0.6% of ammonium molybdate, 0.2-0.5% of sodium tungstate, 1.2-2% of amino-epoxy silane-modified SiO2 nanoparticles, 0.5-1% of polyethylene glycol, 0.8-1.5% of L-ascorbic acid, 0.8-1.2% of polyaspartic acid, 1.2-1.5% of anti-settling agent and 0.1-0.3% of surfactant, and the balance is deionized water; The anti-settling agent is sodium carboxymethyl cellulose; The cerium salt is any one of cerium nitrate, cerium sulfate and cerium chloride; The surfactant is disodium edetate; The specific preparation steps of the amino-epoxy silane-modified SiO2 nanoparticles are as follows: S1: Add SiO2 nanoparticles to anhydrous ethanol, disperse them evenly with ultrasonic treatment, centrifuge, filter, and vacuum dry to obtain activated SiO2; S2: Add the activated SiO2 prepared in step S1 to the ethanol solution, disperse it evenly by ultrasonic treatment, then slowly add γ-aminopropyltriethoxysilane dropwise, adjust the pH with glacial acetic acid, heat to react, centrifuge, filter, repeatedly wash with ethanol, and vacuum dry to obtain amino SiO2; S3: Add the amino SiO2 prepared in step S2 to the ethanol solution, disperse it evenly through ultrasonic treatment, add triethylamine, and then slowly add γ-glycidyloxypropyltrimethoxysilane dropwise, stir to react, centrifuge, repeatedly wash with acetone and ethanol, and vacuum dry to obtain amino-epoxy silane-modified SiO2 nanoparticles.

2. A stainless steel passivation solution according to claim 1, characterized in that: In step S2, the ratio of the activated SiO2, ethanol solution and γ-aminopropyltriethoxysilane is 1 g:200 mL:0.3-0.5 mL.

3. A stainless steel passivation solution according to claim 2, characterized in that, In step S3, the ratio of the amount of the amino SiO2, the ethanol solution and the γ-glycidyloxypropyltrimethoxysilane is 1g:100-150mL:0.8-1mL; the amount of triethylamine added is 2-4% of the volume of the γ-glycidyloxypropyltrimethoxysilane added.

4. A method for preparing a stainless steel passivation solution according to any one of claims 1 to 3, characterized in that: The specific preparation steps are as follows: S101: Add citric acid, sodium dihydrogen phosphate, and an anti-precipitation agent to deionized water, heat, and stir until completely dissolved. Then, add copper sulfate, ammonium molybdate, and sodium tungstate in sequence while maintaining the stirring speed until a uniform and transparent solution is formed to obtain a mixed solution. S102: slowly adding the amino-epoxy silane-modified SiO2 nanoparticles to the mixed solution prepared in step S101, ultrasonically treating it, adding cerium salt, heating it, and stirring it to obtain an activated solution; S103: Cooling the activated solution prepared in step S102, adding L-ascorbic acid, stirring, then sequentially adding polyaspartic acid and a surfactant, adjusting the pH with dilute sulfuric acid and ammonia water, stirring, and obtaining a complexing system; S104: adding polyethylene glycol to the complexing system prepared in step S103, heating and stirring, adding the remaining deionized water, and ultrasonically degassing to obtain a passivation solution.

5. A method for preparing a stainless steel passivation solution according to claim 4, characterized in that: In step S102, the ultrasonic treatment parameters are 30-40 kHz, 100-120 W, and time 20-30 min.

6. A method for preparing a stainless steel passivation solution according to claim 5, characterized in that: In step S104, the ultrasonic degassing treatment parameters are 40 kHz, 100-150 W, and time 15-20 min.

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