Preparation method of novel passivator

Abstract

The invention relates to the technical field of passivators, and discloses a preparation method of a novel passivator, 4-chloromethyl benzoyl hydrazine is prepared from methyl 4-chloromethyl benzoate and hydrazine hydrate, 4-bromomethyl benzoyl hydrazine is prepared through a bromination reaction, and 4-bromomethyl benzoyl hydrazine and acrylamide are subjected to a bromination reaction in cuprous bromide and 2, 2, 6-trimethyl-1, 3-pentanediol monoisobutyrate to prepare the novel passivator. Generating polyacrylamide grafted benzoyl hydrazine under the action of 2, 2 '-dipyridyl; the dialdehyde nano-cellulose is prepared according to the bamboo pulp board raw material, and finally the polyacrylamide grafted benzoyl hydrazine and the dialdehyde nano-cellulose are cross-linked to obtain the passivator with excellent corrosion resistance. According to the novel passivator prepared in the invention, the corrosion resistance can be improved, and the adsorption capacity and the heavy metal ion fixing capacity of the novel passivator are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of passivators, and specifically to a preparation method of a novel passivator. Background Art

[0002] With the development of modern industry, stainless steel has become the preferred material in many high-end fields due to its excellent corrosion resistance, good mechanical strength, and beautiful surface quality. However, during the processing, the surface of stainless steel is easily affected by oil stains, high-temperature oxides, welding scars, and micromolecular impurities, resulting in a decrease in its corrosion resistance and affecting the service life and appearance quality of the product. To improve the corrosion resistance of the stainless steel surface, a series of pretreatment and post-treatment processes are usually required, including chemical treatment processes such as degreasing, pickling, and passivation. These processes can not only remove surface contaminants but also enhance the corrosion resistance of the metal by forming a dense protective film.

[0003] In recent years, with the increasingly strict environmental protection regulations and the continuous improvement of the product quality requirements in the manufacturing industry, the traditional passivation process mainly based on chromates has been gradually phased out due to its high toxicity and large pollution. Instead, the research and development of more environmentally friendly, efficient, and stable novel passivators and supporting treatment processes have been carried out. Currently, the common passivation methods mainly include inorganic salts (such as phosphates, silicates) and organic corrosion inhibitors (such as benzotriazole, imidazoline). However, these methods generally have problems such as non-dense film formation, poor adhesion, and insufficient durability. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a preparation method of a novel passivator, which improves the corrosion resistance and also enhances its adsorption capacity and the ability to fix heavy metal ions.

[0005] A preparation method of a novel passivator, the preparation method comprising: Step S1: Methyl 4-chloromethylbenzoate and hydrazine hydrate with a mass ratio of (2.4 - 2.6):1 are added to a reaction vessel, and then 20 - 25 mL of ethanol is added. The mixture is heated under reflux for 6 - 8 h, cooled, and then filtered, washed, and dried with ethanol to obtain 4-chloromethylbenzohydrazide; Step S2: 4-chloromethylbenzohydrazide is added to a reaction vessel, and then N-bromosuccinimide and benzoyl peroxide are added. Then 50 - 55 mL of ethyl acetate is added, and the mixture is refluxed at 60 - 70 °C for 4 - 6 hours, and then filtered and purified to obtain 4-bromomethylbenzohydrazide; Step S3: Add 4-bromomethylbenzohydrazide and acrylamide into a reaction vessel, add 50 - 55 mL of N,N-dimethylformamide, purge with nitrogen to remove oxygen, then add cuprous bromide and 2,2'-bipyridine. Under nitrogen protection, react for 8 - 10 h. After the reaction, filter, and dry at 55 - 65 °C for 3 - 5 h to obtain benzohydrazide grafted with polyacrylamide; Step S4: Dissolve benzohydrazide grafted with polyacrylamide in an N,N-dimethylformamide solution, add it into a reaction vessel, then add dialdehyde nanocellulose, install a condenser, place it in a dark place, stir and react under light protection at 75 - 80 °C for 3 - 5 h, wash with an N,N-dimethylformamide solution, and then centrifugally displace with deionized water to obtain a novel passivator.

[0006] Preferably, the mass ratio of 4-chloromethylbenzohydrazide, N-bromosuccinimide, and benzoyl peroxide is (11.6 - 12.4):(5.8 - 6.4):1.

[0007] Preferably, the mass ratio of 4-bromomethylbenzohydrazide, acrylamide, cuprous bromide, and 2,2'-bipyridine is (9 - 11):(60 - 80):1:(2.1 - 2.3).

[0008] Preferably, the mass ratio of benzohydrazide grafted with polyacrylamide and dialdehyde nanocellulose is (1.5 - 2):1.

[0009] Preferably, the preparation method of dialdehyde nanocellulose is as follows: Add 20 g to 25 g of bamboo pulp board raw material into 1200 mL of sulfuric acid solution with a mass fraction of 50%, perform ultrasonic treatment at 60 - 70 °C for 4 - 6 h, dialyze to neutrality, then add 5 g to 6 g of sodium periodate, place it in a dark place and stir and react under light protection at 40 - 45 °C for 4 - 6 h, and then dialyze for 2 - 3 d to remove the sodium periodate therein to obtain oxidized dialdehyde nanocellulose.

[0010] Preferably, the pH of sodium periodate is 3.5 - 4.

[0011] Beneficial technical effects: In the present invention, methyl 4-chloromethylbenzoate reacts with hydrazine hydrate to prepare 4-chloromethylbenzohydrazide, and 4-bromomethylbenzohydrazide is prepared through a bromination reaction. 4-Bromomethylbenzohydrazide and acrylamide react under the action of cuprous bromide and 2,2'-bipyridine to form benzohydrazide grafted with polyacrylamide; dialdehyde nanocellulose is prepared from bamboo pulp board raw material. Finally, benzohydrazide grafted with polyacrylamide and dialdehyde nanocellulose are crosslinked to obtain a passivator with excellent corrosion prevention performance.

[0012] The passivation agent generated by the present invention, in terms of corrosion resistance, due to the synergistic effect of hydrazide and hydrazone bonds and the comprehensive coverage protection provided by the three-dimensional network structure, effectively prevents the intrusion of corrosive media, and also has a very strong adsorption capacity. A large number of hydrazide groups can form stable complexes with heavy metal ions, thereby realizing the effective adsorption and fixation of harmful metal ions; in terms of mechanical stability, due to the use of nanocellulose as the skeleton and the construction of a three-dimensional crosslinked network through hydrazone bonds, the passivation agent has excellent anti-shear and anti-scouring capabilities, ensuring its long-term stability and reliability in complex environments. In addition, the presence of polyacrylamide hydrophilic segments makes the material also perform excellently in terms of dispersibility, being able to be uniformly dispersed in the aqueous phase system, further enhancing its effect in practical applications; from an environmental protection perspective, the passivation agent uses natural bamboo pulp as a raw material, which is not only widely sourced and renewable, but also has good biodegradability, reducing the risk of environmental pollution and reflecting a high degree of environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is the preparation process of benzoylhydrazide grafted with polyacrylamide.

[0014] Figure 2 is the preparation process of the novel passivation agent. SPECIFIC EMBODIMENTS

[0015] Example 1 A preparation method of a novel passivation agent, the preparation method comprising: Step S1: Add 1.85 g of methyl 4-chloromethylbenzoate and 0.75 g of hydrazine hydrate to a reaction vessel, then add 25 mL of ethanol, heat under reflux for 8 h, cool, and perform suction filtration, washing, and drying with ethanol to obtain 4-chloromethylbenzoylhydrazide; Step S2: Add 5 g of 4-chloromethylbenzoylhydrazide to a reaction vessel, then add 3 g of N-bromosuccinimide and 0.5 g of benzoyl peroxide, then add 50 mL of ethyl acetate, reflux at 60 °C for 6 hours, and then perform filtration and purification to obtain 4-bromomethylbenzoylhydrazide; Step S3: Add 10 g of 4-bromomethylbenzoylhydrazide and 70 g of acrylamide to a reaction vessel, add 50 mL of N,N-dimethylformamide, purge with nitrogen to remove oxygen, then add 1.0 g of cuprous bromide and 2.2 g of 2,2'-bipyridine, and react under nitrogen protection for 9 h. After the reaction, filter and dry at 60 °C for 5 h to obtain benzoylhydrazide grafted with polyacrylamide; Step S4: Add 20 g of bamboo pulp board raw material into 1200 mL of sulfuric acid solution with a mass fraction of 50%, perform ultrasonic treatment at 70 °C for 6 h, dialyze until neutral, then add 6 g of sodium periodate with a pH of 3.5, place it in the dark and stir to react for 6 h at 40 °C, and then dialyze for 2 d to remove the sodium periodate therein to obtain oxidized dialdehyde nanocellulose; Step S5: Dissolve 3 g of polyacrylamide-grafted benzohydrazide in N,N-dimethylformamide solution, add it to the reaction vessel, then add 2 g of dialdehyde nanocellulose, install a condenser, place it in the dark, and stir to react for 5 h at 80 °C in the dark. Wash with N,N-dimethylformamide solution, and then centrifuge and replace with deionized water to obtain a novel passivator.

[0016] Example 2 A preparation method of a novel passivator, the preparation method comprising: Step S1: Add 1.8 g of methyl 4-chloromethylbenzoate and 0.75 g of hydrazine hydrate into the reaction vessel, then add 20 mL of ethanol, heat under reflux for 6 h, cool and then perform suction filtration, washing, and drying with ethanol to obtain 4-chloromethylbenzohydrazide; Step S2: Add 5.8 g of 4-chloromethylbenzohydrazide into the reaction vessel, then add 2.8 g of N-bromosuccinimide and 0.5 g of benzoyl peroxide, then add 50 mL of ethyl acetate, reflux at 70 °C for 6 hours, and then perform filtration and purification to obtain 4-bromomethylbenzohydrazide; Step S3: Add 9 g of 4-bromomethylbenzohydrazide and 60 g of acrylamide into the reaction vessel, add 50 mL of N,N-dimethylformamide, purge with nitrogen to remove oxygen, then add 1.0 g of cuprous bromide and 2.1 g of 2,2'-bipyridine, and react for 8 h under nitrogen protection. After the reaction, filter and dry at 55 °C for 3 h to obtain polyacrylamide-grafted benzohydrazide; Step S4: Add 25 g of bamboo pulp board raw material into 1200 mL of sulfuric acid solution with a mass fraction of 50%, perform ultrasonic treatment at 60 °C for 4 h, dialyze until neutral, then add 5 g of sodium periodate with a pH of 4, place it in the dark and stir to react for 4 h at 45 °C, and then dialyze for 3 d to remove the sodium periodate therein to obtain oxidized dialdehyde nanocellulose; Step S5: Dissolve 4 g of polyacrylamide-grafted benzohydrazide in N,N-dimethylformamide solution, add it to the reaction vessel, then add 2 g of dialdehyde nanocellulose, install a condenser, place it in the dark, and stir to react for 3 h at 75 °C in the dark. Wash with N,N-dimethylformamide solution, and then centrifuge and replace with deionized water to obtain a novel passivator.

[0017] Example 3 A preparation method of a novel passivator, the preparation method comprising: Step S1: Add 1.95 g of methyl 4-chloromethylbenzoate and 0.75 g of hydrazine hydrate into a reaction vessel, then add 25 mL of ethanol, reflux under heating for 7 h, after cooling, perform suction filtration, washing and drying with ethanol to obtain 4-chloromethylbenzohydrazide; Step S2: Add 6.2 g of 4-chloromethylbenzohydrazide into a reaction vessel, then add 3.2 g of N-bromosuccinimide and 0.5 g of benzoyl peroxide, then add 55 mL of ethyl acetate, reflux at 65 °C for 4 hours, then perform filtration and purification to obtain 4-bromomethylbenzohydrazide; Step S3: Add 11 g of 4-bromomethylbenzohydrazide and 80 g of acrylamide into a reaction vessel, add 55 mL of N,N-dimethylformamide, purge with nitrogen to remove oxygen, then add 1.0 g of cuprous bromide and 2.3 g of 2,2'-bipyridine, under nitrogen protection, react for 10 h, after the reaction, filter, and dry at 65 °C for 4 h to obtain benzohydrazide grafted with polyacrylamide; Step S4: Add 23 g of bamboo pulp board raw material into 1200 mL of sulfuric acid solution with a mass fraction of 50%, perform ultrasonic treatment at 65 °C for 5 h, dialyze until neutral, then add 5.5 g of sodium periodate with a pH of 4, place in the dark and stir for 4 h while avoiding light, then dialyze for 2 d to remove the sodium periodate therein to obtain oxidized dialdehyde nanocellulose; Step S5: Dissolve 3.5 g of benzohydrazide grafted with polyacrylamide in an N,N-dimethylformamide solution, add it into a reaction vessel, then add 2 g of dialdehyde nanocellulose, install a condenser, place in the dark, react with stirring at 75 °C for 4 h while avoiding light, wash with an N,N-dimethylformamide solution, and then perform centrifugal replacement with deionized water to obtain the novel passivator.

[0018] Example 4 A preparation method of a novel passivator, the preparation method comprising: Step S1: Add 1.9 g of methyl 4-chloromethylbenzoate and 0.75 g of hydrazine hydrate into a reaction vessel, then add 20 mL of ethanol, reflux under heating for 8 h, after cooling, perform suction filtration, washing and drying with ethanol to obtain 4-chloromethylbenzohydrazide; Step S2: Add 6.2 g of 4-chloromethylbenzohydrazide into a reaction vessel, then add 3.2 g of N-bromosuccinimide and 0.5 g of benzoyl peroxide, then add 55 mL of ethyl acetate, reflux at 60 °C for 4 hours, then perform filtration and purification to obtain 4-bromomethylbenzohydrazide; Step S3: Add 9 g of 4-bromomethylbenzohydrazide and 80 g of acrylamide into a reaction vessel, add 50 mL of N,N-dimethylformamide, purge with nitrogen to remove oxygen, then add 1.0 g of cuprous bromide and 2.2 g of 2,2'-bipyridine. Under nitrogen protection, react for 10 h. After the reaction, filter and dry at 55 °C for 5 h to obtain polyacrylamide-grafted benzohydrazide; Step S4: Add 25 g of bamboo pulp board raw material into 1200 mL of sulfuric acid solution with a mass fraction of 50%, perform ultrasonic treatment at 60 °C for 5 h, dialyze to neutrality, then add 6 g of sodium periodate with a pH of 4, place in the dark and stir to react for 4 h at 40 °C, and then dialyze for 2 d to remove the sodium periodate therein to obtain oxidized dialdehyde nanocellulose; Step S5: Dissolve 4 g of polyacrylamide-grafted benzohydrazide in N,N-dimethylformamide solution, add it into a reaction vessel, then add 2 g of dialdehyde nanocellulose, install a condenser, place in the dark, stir and react at 80 °C for 5 h, wash with N,N-dimethylformamide solution, and then centrifuge and displace with deionized water to obtain a novel passivator.

[0019] Comparative Example 1 The preparation method of traditional passivator, the preparation method includes: Step S1: Add 1.48 g of methyl benzoate and 0.75 g of hydrazine hydrate into a reaction vessel, then add 25 mL of ethanol, heat under reflux for 8 h, cool and perform suction filtration with ethanol, wash, and dry to obtain benzohydrazide.

[0020] Comparative Example 2 The preparation method of traditional passivator, the preparation method includes: Step S1: Add 1.85 g of methyl 4-chloromethylbenzoate and 0.75 g of hydrazine hydrate into a reaction vessel, then add 25 mL of ethanol, heat under reflux for 8 h, cool and perform suction filtration with ethanol, wash, and dry to obtain 4-chloromethylbenzohydrazide; Step S2: Add 5 g of 4-chloromethylbenzohydrazide into a reaction vessel, then add 3 g of N-bromosuccinimide and 0.5 g of benzoyl peroxide, add 50 mL of ethyl acetate, reflux at 60 °C for 6 h, and then perform filtration and purification to obtain 4-bromomethylbenzohydrazide; Step S3: Add 10 g of 4-bromomethylbenzohydrazide and 70 g of acrylamide into a reaction vessel, add 50 mL of N,N-dimethylformamide, purge with nitrogen to remove oxygen, then add 1.0 g of cuprous bromide and 2.2 g of 2,2'-bipyridine. Under nitrogen protection, react for 9 h. After the reaction, filter and dry at 60 °C for 5 h to obtain polyacrylamide-grafted benzohydrazide.

[0021] Comparative Example 3 Preparation method of oxidized cellulose, comprising: adding 23 g of bamboo pulp board raw material to 1200 mL of sulfuric acid solution with a mass fraction of 50%, performing ultrasonic treatment at a temperature of 65 °C for 5 h, dialyzing until neutral, then adding 5.5 g of sodium periodate with a pH of 4, placing it in the dark and stirring for light-free reaction at 45 °C for 4 h, and then dialyzing for 2 d to remove the sodium periodate therein to obtain oxidized dialdehyde nanocellulose. Stirring the dialdehyde nanocellulose for light-free reaction at 80 °C for 5 hours, washing with N,N-dimethylformamide solution, and then centrifugally replacing with deionized water to obtain oxidized cellulose.

[0022] Comparative Example 4 Preparation method of hydrazide-grafted cellulose, comprising: Step S1: Adding 20 g of bamboo pulp board raw material to 1200 mL of sulfuric acid solution with a mass fraction of 50%, performing ultrasonic treatment at a temperature of 70 °C for 6 h, dialyzing until neutral, then adding 6 g of sodium periodate with a pH of 3.5, placing it in the dark and stirring for light-free reaction at 40 °C for 6 h, and then dialyzing for 2 d to remove the sodium periodate therein to obtain oxidized dialdehyde nanocellulose; Step S2: Weighing 10 g of dialdehyde nanocellulose and adding it to 200 mL of N,N-dimethylformamide, adding 5 g of hydrazine hydrate, adding 1 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 0.5 g of N-hydroxysuccinimide. Under nitrogen protection, stirring the mixture at room temperature for 24 hours. After the reaction is completed, filtering and washing with N,N-dimethylformamide, dialyzing with deionized water until neutral, and freeze-drying to obtain hydrazide-grafted cellulose.

[0023] Using the FeCl3 immersion test, the pitting corrosion resistance of the passivation film obtained by the stainless steel under the acidic passivation process. The corrosion weight loss test refers to GB / T 17897-2016 "Corrosion of Metals and Alloys - Pitting Corrosion Test Method for Stainless Steel by Ferric Chloride". The specimen size is 40 mm × 50 mm × 1.5 mm. The process flow is grinding → water washing → pickling → film removal → passivation → neutralization and water washing → dehydration → drying. Calculating the corrosion rate at 50 °C, and the unit is g / m 2 , and the corrosion rate is calculated by the formula V = (W0 - W1) / (S × T), where W0 is the mass of the specimen before the test, W1 is the mass of the specimen after the test, S is the surface area of the specimen, and T is the test time of 1 d.

[0024] As can be seen from the tables of Examples 1-4 and Comparative Examples 1-4, the corrosion rates of Examples 1-4 are significantly lower than those of Comparative Examples 1-4. This is because benzoylhydrazide has a hydrazide group, which can form a stable complex with the metal surface. Polyacrylamide-grafted benzoylhydrazide grafts polyacrylamide onto benzoylhydrazide through ATRP reaction, increasing the molecular chain length and the number of active sites. Dialdehyde nanocellulose contains abundant aldehyde groups after oxidation treatment and can crosslink with hydrazide groups through hydrazone bonds to form a three-dimensional network structure. It has a high specific surface area and porous structure, which is beneficial to the adsorption and fixation of heavy metal ions. The presence of hydrazone bonds improves the stability and durability of the material, while enhancing its resistance to acidic environments. The three-dimensional network structure prevents the occurrence of agglomeration phenomena.

[0025] The hydrazide groups on benzoylhydrazide and polyacrylamide can form a stable complex with the metal surface, preventing the further diffusion of corrosive media. The three-dimensional network structure provided by dialdehyde nanocellulose not only increases the number of active sites but also enhances the overall stability, effectively covering the metal surface and providing a long-lasting protection effect.

[0026] In Comparative Example 1, only benzoylhydrazide is contained. Although a single hydrazide group can form a complex with the metal surface, it is easily washed away by corrosive media due to the lack of support from a carrier, resulting in limited protection effect. Compared with the composite material, single benzoylhydrazide can only provide local protection and is difficult to form a continuous protective film, so the anti-corrosion performance is poor.

[0027] In Comparative Example 2, polyacryloylhydrazide passivator grafts polyacrylamide through ATRP reaction but does not crosslink with cellulose. The polyacrylamide chain segments increase the number of active sites, but due to the lack of a three-dimensional network structure, the interaction between polymer chains is weak and agglomeration is likely to occur. Although the hydrazide groups provide a certain protection effect, due to the lack of support from a carrier, the protection effect is not as good as that of the composite material in the examples, so the anti-corrosion performance is poor.

[0028] In Comparative Example 3, dialdehyde nanocellulose obtained by oxidation treatment contains abundant aldehyde groups but does not graft hydrazide groups or other functional groups. Cellulose itself has good mechanical strength and dispersibility, but due to the lack of active groups, its adsorption ability is limited. Although aldehyde groups can react with certain substances, in anti-corrosion applications, single aldehyde groups are not sufficient to provide effective protection. Due to the lack of active groups such as hydrazide groups, the anti-corrosion effect of cellulose passivator is poor and it cannot effectively prevent the diffusion of corrosive media.

[0029] In Comparative Example 4, hydrazide groups were grafted onto cellulose to form a relatively complex structure. Through carboxymethylation and hydrazide grafting treatment, the number of active groups on the cellulose surface was increased, enhancing its adsorption capacity. Although the hydrazide-grafted cellulose passivator has a certain protective effect, due to the lack of support from polymer segments such as polyacrylamide, the protective effect is inferior to that of the examples, so the anti-corrosion performance is lower than that of the examples.

Claims

1. A preparation method of a novel passivator, characterized in that The preparation method includes the following steps: Step S1: Add methyl 4-(chloromethyl)benzoate and hydrazine hydrate into a reaction vessel, then add 20 - 25 mL of ethanol, heat under reflux for 6 - 8 h, cool, and then perform suction filtration, washing, and drying with ethanol to obtain 4-(chloromethyl)benzohydrazide; Step S2: Add 4-(chloromethyl)benzohydrazide into a reaction vessel, then add N-bromosuccinimide and benzoyl peroxide, then add 50 - 55 mL of ethyl acetate, reflux at 60 - 70 °C for 4 - 6 hours, and then perform filtration and purification to obtain 4-(bromomethyl)benzohydrazide; Step S3: Add 4-(bromomethyl)benzohydrazide and acrylamide into a reaction vessel, add 50 - 55 mL of N,N-dimethylformamide, purge with nitrogen to remove oxygen, then add copper(I) bromide and 2,2'-bipyridine, and react under nitrogen protection for 8 - 10 h. After the reaction, filter, and dry at 55 - 65 °C for 3 - 5 h to obtain benzohydrazide grafted with polyacrylamide; Step S4: Dissolve benzohydrazide grafted with polyacrylamide in an N,N-dimethylformamide solution, add it to a reaction vessel, then add dialdehyde nanocellulose, install a condenser, place it in a dark place, stir and react under light protection at a certain temperature for 3 - 5 h, wash with an N,N-dimethylformamide solution, and then perform centrifugal replacement with deionized water to obtain a novel passivator.

2. The preparation method of the novel passivator according to claim 1, characterized in that, In step S1, the mass ratio of methyl 4-(chloromethyl)benzoate to hydrazine hydrate is (2.4 - 2.6):

1.

3. The preparation method of the novel passivator according to claim 1, characterized in that, In step S2, the mass ratio of 4-(chloromethyl)benzohydrazide, N-bromosuccinimide, and benzoyl peroxide is (11.6 - 12.4):(5.8 - 6.4):

1.

4. The preparation method of the novel passivator according to claim 1, characterized in that, In step S3, the mass ratio of 4-(bromomethyl)benzohydrazide, acrylamide, copper(I) bromide, and 2,2'-bipyridine is (9 - 11):(60 - 80):1:(2.1 - 2.3).

5. The preparation method of the novel passivator according to claim 1, characterized in that, In step S4, the mass ratio of benzohydrazide grafted with polyacrylamide to dialdehyde nanocellulose is (1.5 - 2):

1.

6. The preparation method of the novel passivator according to claim 1, characterized in that, In step S4, the reaction temperature is 75 - 80 °C.

7. The preparation method of the novel passivator according to claim 1, characterized in that, The preparation method of the dialdehyde nanocellulose is as follows: Add 20 g to 25 g of bamboo pulp board raw material into 1200 mL of sulfuric acid solution, perform ultrasonic treatment at 60 - 70 °C for 4 - 6 h, dialyze until neutral, then add 5 g to 6 g of sodium periodate, place it in a dark place and stir and react under light protection at 40 - 45 °C for 4 - 6 h, and then dialyze for 2 - 3 d to remove the sodium periodate therein to obtain oxidized dialdehyde nanocellulose.

8. The preparation method of the novel passivator according to claim 7, characterized in that, The mass fraction of the sulfuric acid solution is 50%.

9. The preparation method of the novel passivator according to claim 7, wherein, The pH of the sodium periodate is 3.5 - 4.

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