Coating for preventing oxidation and passivation of steel surface as well as preparation method and application of coating

Abstract

The invention relates to the technical field of coatings, in particular to a coating for preventing oxidation and passivation of a steel surface as well as a preparation method and application of the coating. The invention discloses a coating for preventing oxidation and passivation of a steel surface. The coating comprises a component A and a component B, the component A comprises the following raw materials in parts by weight: 20-25 parts of polyvinyl alcohol, 10-15 parts of amphoteric polyurethane, 10-12 parts of a rust conversion agent, 1-2 parts of an accelerant, 3-4 parts of a corrosion inhibitor, 2-3 parts of a stabilizer and 10-15 parts of a solvent A; the component B comprises the following raw materials in parts by weight: 2-4 parts of a curing agent and 10-15 parts of a solvent A; the rust conversion agent is prepared from phosphoric acid and tannic acid according to the weight ratio of 1: 1; the coating can penetrate into micropores in the surface of steel, the protection effect is enhanced, and the problems that a traditional coating is insufficient in adhesive force on low-surface-treatment steel and poor in weather resistance and flexibility are solved.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, and in particular to a coating for preventing oxidation and passivation of steel surfaces, and a preparation method and application thereof. Background Art

[0002] With the development of industry, steel materials are increasingly used in the fields of construction, bridges, ships, etc. However, the corrosion problem of steel has always been a major challenge that needs to be solved. In order to extend the service life of steel products and reduce maintenance costs, the research and development and application of anti-oxidation passivation (i.e. anti-corrosion) coatings on the steel surface are particularly important.

[0003] At present, there are many types of anti-corrosion coatings on the market, including but not limited to oil-based paints, alkyd paints, epoxy resin paints, and polyurethane paints. These coatings achieve the purpose of anti-corrosion by forming a physical barrier to isolate oxygen and moisture. In recent years, water-based coatings have received increasing attention due to their environmentally friendly characteristics. They use water as a solvent, reduce the emission of volatile organic compounds (VOCs), and meet the requirements of modern society for environmental protection.

[0004] Nevertheless, existing anti-corrosion coatings still face some difficult to overcome problems:

[0005] 1. Insufficient adhesion

[0006] Many coatings have poor adhesion to hot-dip galvanized steel or rusted surfaces, resulting in ineffective protection.

[0007] 2. Poor weather resistance and flexibility

[0008] Some coatings are prone to aging, cracking and losing their protective functions after long-term exposure to the natural environment.

[0009] 3. Environmental pollution

[0010] Traditional solvent-based coatings contain a large amount of organic solvents, which can pollute the environment and pose a threat to human health during production and use.

[0011] 4. Harsh construction conditions

[0012] Some high-performance anti-corrosion coatings require strict surface pretreatment, which increases the difficulty and cost of construction.

[0013] To this end, the present invention discloses a coating for preventing oxidation and passivation of steel surface, and a preparation method and application thereof. Summary of the invention

[0014] In order to overcome the shortcomings of the prior art, the present invention provides a coating for preventing oxidation passivation of steel surface and its preparation method and application. The amphoteric polyurethane contains rich polyhydroxy functional groups, which can form a tight chemical bond with the metal surface, providing an immediate anti-corrosion barrier, and due to the presence of its hydrophilic chain extender, it can penetrate into the micropores on the steel surface, thereby enhancing the protective effect and solving the problems of insufficient adhesion of traditional coatings on low-surface-treated steel, and poor weather resistance and flexibility.

[0015] In a first aspect of the present application, there is provided a coating for preventing oxidation and passivation of steel surface, comprising component A and component B;

[0016] The component A comprises the following raw materials in parts by weight:

[0017] 20-25 parts of polyvinyl alcohol, 10-15 parts of amphoteric polyurethane, 10-12 parts of rust remover, 1-2 parts of accelerator, 3-4 parts of corrosion inhibitor, 2-3 parts of stabilizer, 10-15 parts of solvent A;

[0018] The component B comprises the following raw materials in parts by weight:

[0019] 2-4 parts of curing agent, 10-15 parts of solvent A;

[0020] The rust-removing agent is composed of phosphoric acid and tannic acid in a weight ratio of 1:1;

[0021] The method for preparing the amphoteric polyurethane comprises the following steps: using isophorone diisocyanate, polytetramethylene glycol, N-methyldiethanolamine and 2,2-dimethylolpropionic acid as raw materials, and preparing a waterborne polyurethane prepolymer by a prepolymerization method;

[0022] Then, polyhydroxy D-xylose is introduced as a cross-linking modifier to react with the isocyanate groups in the waterborne polyurethane prepolymer for graft polymerization to form amphoteric polyurethane.

[0023] In some embodiments, the accelerator is citric acid.

[0024] In some specific embodiments, the corrosion inhibitor is polyaniline, and the molecular weight of the polyaniline is 5000-15000.

[0025] In some embodiments, the stabilizer is hydroxycellulose.

[0026] In some specific embodiments, the curing agent is any one of 3-methyl-1-aziridine and 1-aziridine ethanol.

[0027] In some specific embodiments, a pigment is further included, and the pigment includes any one or both of red iron oxide and titanium dioxide.

[0028] In some specific embodiments, the solvent A consists of water and ethanol in a weight ratio of 3:1.

[0029] In some specific embodiments, the molecular weight of the polyvinyl alcohol is 70,000-100,000.

[0030] The second aspect of the present application provides a method for preparing the coating according to the first aspect, comprising the following steps:

[0031] (1) Preparation of component A

[0032] According to the composition of each raw material of component A, materials are taken; polyvinyl alcohol, amphoteric polyurethane, rust-removing agent, accelerator, corrosion inhibitor, stabilizer, and solvent A are fully mixed at room temperature, and then mixed at 50-60° C. for 2 hours, and cooled to room temperature to obtain component A;

[0033] (2) Preparation of component B

[0034] According to the composition of each raw material of component B, materials are taken and then fully mixed to obtain component B;

[0035] When in use, component A and component B are mixed and applied in a weight ratio of 50:2-3.

[0036] The third aspect of the present application provides an application of a coating, wherein the coating described in the first aspect or the coating prepared by the preparation method described in the second aspect is applied to rust prevention or corrosion prevention of steel products.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The coating formed by the coating described in the present application can not only effectively prevent oxidation and passivation of the steel surface in the short term, but also maintain effective protection for a long time due to the long-term existence of chemical bonding.

[0039] The coating described in the present application reduces the use of harmful solvents, meets the requirements of modern green chemical industry, and is beneficial to environmental protection and human health. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0041] Figure 1 This is a process flow chart of a method for preparing a coating for preventing oxidation and passivation of steel surfaces as described in this application. DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments, and the contents mentioned in the implementation modes are not intended to limit the present invention.

[0043] As used herein, "and / or" includes the term of all combinations of any one or more associated listed items. The terms used herein are only used to describe specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "a", "an", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It is further understood that "including", when used in this specification, specifies the stated features, integers, steps, operations, elements and / or compositions, but does not exclude the existence or addition of one or more other features, integers, steps, operations, elements, compositions and / or combinations thereof.

[0044] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. It is further understood that terms, such as defined in commonly used dictionaries, are interpreted in accordance with their meanings in the context of the relevant art and are not in an idealized or overly formal sense unless explicitly so defined herein.

[0045] The exemplary invention described herein may appropriately lack any one or more element limitations that are not specifically disclosed herein. Therefore, the terms "comprise", "include", "contain", etc. should be understood broadly and non-restrictively. In addition, the terminology used herein is used as a description, not a limitation, and it is unintentional to use these terminology expressions that do not include any equivalent characteristics, but only describe some of their characteristics, but various modifications are possible within the scope of the present invention according to the rights. Therefore, although the present invention has been specifically disclosed by preferred embodiments and optional features, the modifications disclosed herein to embody the changes of the present invention may be recorded by those skilled in the art, and such modifications and changes will be considered to be within the scope of the present invention.

[0046] A coating for preventing oxidation and passivation of steel surface comprises component A and component B. Component A comprises the following raw materials in parts by weight:

[0047] 20-25 parts of polyvinyl alcohol, 10-15 parts of amphoteric polyurethane, 10-12 parts of rust remover, 1-2 parts of accelerator, 3-4 parts of corrosion inhibitor, 2-3 parts of stabilizer, 10-15 parts of solvent A;

[0048] The component B comprises the following raw materials in parts by weight:

[0049] 2-4 parts of curing agent, 10-15 parts of solvent A;

[0050] The rust-removing agent is composed of phosphoric acid and tannic acid in a weight ratio of 1:1;

[0051] The method for preparing the amphoteric polyurethane comprises the following steps: using isophorone diisocyanate (IPDI), polytetramethylene ether glycol (PTMG), N-methyldiethanolamine (N-MDEA) and 2,2-dimethylolpropionic acid (DMPA, a hydrophilic chain extender) as raw materials, and preparing a waterborne polyurethane prepolymer by a prepolymerization method;

[0052] Then, polyhydroxy D-xylose is introduced as a cross-linking modifier to react with the isocyanate groups in the waterborne polyurethane prepolymer for graft polymerization to form amphoteric polyurethane.

[0053] In the present application, the rust remover is composed of phosphoric acid (using concentrated phosphoric acid) and tannic acid in a weight ratio of 1:1. The rust remover converts rust into a stable non-toxic filler to achieve rust-free painting, thereby preventing the development of corrosion; the amphoteric polyurethane forms a star-shaped structure by introducing a polyhydroxy structure, thereby improving adhesion and water resistance, and can be adsorbed on the metal surface to form a protective film to prevent oxygen and moisture from contacting the steel substrate; polyvinyl alcohol, as part of the film-forming substance, provides flexibility and strength to the coating.

[0054] Therefore, the coating prepared by the above technical scheme uses a rust-removing agent (such as phosphoric acid and tannic acid) to react chemically with rust to generate a stable compound, which prevents the rust from continuing to expand and achieves the purpose of rust-resistant coating; the amphoteric polyurethane can form a tightly fitting protective layer on the metal surface, physically isolate oxygen and moisture in the external environment, and delay the corrosion process; the corrosion inhibitor (such as polyaniline) can form a dense film on the metal surface, increase its oxidation and reduction properties, and reduce the possibility of corrosion. In addition, it can also establish multiple connection points with the metal surface to enhance adhesion.

[0055] At the same time, in the above technical solution, renewable raw materials are used instead of traditional fossil resources, which reduces environmental pollution; and through modification and optimization of the formula, the use of harmful solvents (such as xylene) is reduced, thereby improving the environmental performance of the product.

[0056] Specifically, the accelerator is citric acid, which can accelerate chemical reactions and help the coating to cure faster. The weight of the accelerator is 1-2 parts. If the amount of the accelerator is too small, it will not have the desired accelerator effect and extend the construction period; if the amount of the accelerator is too large, it may cause the curing to be too fast and difficult to operate.

[0057] Specifically, the corrosion inhibitor is polyaniline, and the molecular weight of polyaniline is 5000-15000. Polyaniline hinders electron transfer through electric field effect, shielding effect, and passivation effect to prevent further corrosion of the metal. The weight of the corrosion inhibitor is selected to be 3-4 parts. When the amount of the corrosion inhibitor is insufficient, the protective effect is poor and local corrosion is prone to occur; when the amount of the corrosion inhibitor is too much, the material cost is increased and it may also cause a burden on the environment.

[0058] Specifically, the stabilizer is hydroxycellulose (CAS: 9004-62-0), which ensures the stability of the coating system and avoids separation or precipitation of components; the stabilizer is selected in an amount of 2-3 parts by weight, and insufficient amount of the stabilizer will cause the coating to be unstable and stratification may occur during the storage period; excessive amount of the stabilizer may change the rheological properties of the coating and affect its use.

[0059] In component A, 10-15 parts by weight of solvent A is selected. Solvent A is used as a dispersion medium to help mix and adjust viscosity. Too little solvent A will make the coating too thick and difficult to apply; too much solvent A will take longer to evaporate the solvent, increasing drying time and cost.

[0060] Specifically, the curing agent is any one of 3-methyl-1-aziridine and 1-aziridine ethanol. The curing agent reacts with the active functional groups in component A to promote the cross-linking and curing of the coating to form a solid coating. The curing agent is selected in an amount of 2-4 parts by weight. When the amount of the curing agent added is insufficient, the curing is incomplete and the coating hardness is insufficient. Excessive amount of the curing agent added may lead to excessive cross-linking, making the coating brittle and fragile.

[0061] Specifically, the pigment includes any one or two of red iron oxide and titanium dioxide, which gives the paint color and also can play a certain physical barrier role to enhance the anti-corrosion effect. The pigment weight is selected to be 3-5 parts. If the amount of pigment is too little, the color is light and the covering power is poor; if the amount of pigment is too much, it will not only waste resources, but also may interfere with the functions of other ingredients.

[0062] Specifically, the solvent A is composed of water and ethanol in a weight ratio of 3:1.

[0063] Specifically, the molecular weight of the polyvinyl alcohol is 70,000-100,000, which provides flexibility and strength to the coating; the weight of the polyvinyl alcohol is 20-25 parts. If it is lower than this range, the coating may be too fragile and unable to effectively protect the substrate; if it exceeds this range, the coating may be too soft, affecting its mechanical properties.

[0064] Specifically, the weight proportion of the amphoteric polyurethane is 10-15 parts. The amphoteric polyurethane can form a tightly fitting protective film and increase adhesion. When the amount of the amphoteric polyurethane added is insufficient, the protective layer formed is not dense enough and cannot fully prevent moisture and oxygen from contacting the metal. Too much amphoteric polyurethane added will increase costs and may not necessarily bring additional benefits.

[0065] The weight of the rust-removing agent is 10-12 parts. The rust-removing agent can transform rust into stable compounds to achieve rust-free coating. When the amount of the rust-removing agent is small, it is not enough to completely transform all the rust, leaving potential corrosion points; when the amount of the rust-removing agent is large, it may cause unnecessary chemical reactions and even produce side effects.

[0066] like Figure 1 The method for preparing the above-mentioned coating comprises the following steps:

[0067] (1) Preparation of component A

[0068] According to the composition of each raw material of component A, materials are taken; polyvinyl alcohol, amphoteric polyurethane, rust-removing agent, accelerator, corrosion inhibitor, stabilizer, and solvent A are fully mixed at room temperature (e.g., at room temperature, mixing at a stirring speed of 200 r / min for 1 hour), mixed at 50-60° C. for 2 hours, and cooled to room temperature to obtain component A;

[0069] (2) Preparation of component B

[0070] According to the composition of each raw material of component B, take the materials, and then mix them thoroughly (such as mixing for 1 hour at room temperature and a stirring speed of 200 r / min) to obtain component B;

[0071] When in use, the components A and B are mixed and applied in a weight ratio of 50:2-3 (eg, applied at room temperature, at a stirring speed of 200 r / min, after mixing for 1 minute).

[0072] The present application provides an application of a coating, wherein the coating described above is applied to the rust prevention or corrosion prevention of steel products, and can be applied to large steel structures, buildings, bridges, offshore drilling platforms, and cultural relics corrosion prevention projects and restoration work.

[0073] The specific process can be carried out as follows:

[0074] (1) Metal surface treatment: Treat severe rust on the metal surface. Thin rust spots can be ignored; (2) Coating method: Brushing, spraying or other coating methods. For example, the thickness of each layer of spray paint film is 20-30μm. If the corrosion is serious, spray 3 times more. The coating curing time is 5-6h at room temperature;

[0075] The coating for preventing oxidation and passivation of the steel surface described in the present application is further described through the following preparation examples, embodiments, comparative examples, and experimental examples;

[0076] Preparation Example 1

[0077] The preparation method of amphoteric polyurethane comprises the following steps:

[0078] 1. Prepare the ingredients

[0079] Raw material and chemical name:

[0080] Isophorone diisocyanate (IPDI);

[0081] Polytetramethylene glycol (PTMG), molecular weight 1000;

[0082] N-Methyldiethanolamine (N-MDEA);

[0083] 2,2-dimethylolpropionic acid (DMPA), as a hydrophilic chain extender;

[0084] D-Xylose;

[0085] Dibutyltin dilaurate (DBTDL) as catalyst;

[0086] Triethylamine (TEA);

[0087] acetone;

[0088] Deionized water;

[0089] 2. Feeding amount and feeding ratio:

[0090] The -NCO / OH molar ratio of IPDI to PTMG was set to 3.2.

[0091] N-MDEA accounted for 4% of the total raw material.

[0092] DMPA accounted for 7% of the total raw material.

[0093] The amount of D-xylose used was 0.003 mol relative to the total amount of IPDI and PTMG.

[0094] 3. Preparation process:

[0095] (1) Prepolymer synthesis: 1 mol of IPDI and vacuum-dehydrated PTMG were added to a reaction vessel equipped with a stirrer and a reflux device, the temperature was raised to 70°C, stirred in an oil bath, and DBTDL catalyst was added to react for 2 hours to form a polyurethane prepolymer.

[0096] (2) Chain extension reaction: The temperature was then raised to 80°C, and N-MDEA and DMPA were added in sequence to carry out a chain extension reaction for 2 hours to obtain an amphoteric polyurethane prepolymer.

[0097] (3) Modification reaction: Keep the temperature constant and continue to add a predetermined amount of D-xylose for an additional 2 hours of reaction to allow the D-xylose to react with the isocyanate groups in the prepolymer, thereby introducing a polyhydroxy structure to form a star-shaped amphoteric polyurethane.

[0098] (4) Neutralization and emulsification: After cooling to 40°C, TEA was added dropwise for complete neutralization. At the same time, an appropriate amount of acetone was added according to the viscosity of the system. The temperature was then cooled to room temperature. Deionized water was added under rapid stirring to complete the emulsification process and obtain an emulsion.

[0099] (5) Purification: The emulsion is finally passed through a dialysis bag to remove unreacted small molecular monomers to obtain pure amphoteric polyurethane. The obtained pure amphoteric polyurethane is in the form of an emulsion.

[0100] The prepared amphoteric polyurethane was tested by Fourier infrared spectroscopy, and it was found that in the infrared spectrum of amphoteric polyurethane, 2262 cm^ -1 The strong absorption peak originally belonging to NCO in IPDI monomer disappears, and at 3320 cm^ -1 A weak peak appeared near 3225-3410cm^ -1 The polyhydroxyl association peak at did not appear, indicating that the polyhydroxyl groups in D-xylose had completely reacted with NCO to form the expected star-shaped structure.

[0101] Dynamic light scattering was used to detect the amphoteric polyurethane, and the average particle size was 81.47nm. The low viscosity and appropriate particle size of the amphoteric polyurethane make it easy to coat and form a continuous and uniform film during the drying process; its good thermal stability and high mechanical strength ensure that the formed protective layer is not easy to crack or fall off.

[0102] The amphoteric polyurethane with amphoteric characteristics can adsorb and form a tightly fitting protective film on the metal surface, preventing oxygen and moisture from contacting the steel substrate, thereby delaying the corrosion process. In addition, its hydrophobicity also helps to reduce the possibility of water vapor penetration.

[0103] The small particle size of the amphoteric polyurethane and the presence of a hydrophilic chain extender (2,2-dimethylolpropionic acid) increase its permeability, allowing it to penetrate deep into the micropores on the steel surface, providing better protection. Moreover, its multifunctional structure is able to establish multiple connection points in the internal space, further strengthening the adhesion.

[0104] Amphoteric polyurethanes not only provide an immediate anti-corrosion barrier by increasing the binding sites with the metal surface, but also maintain effective protection for a longer period of time due to long-term chemical bonding.

[0105] The preparation method of amphoteric polyurethane involves the following chemical reaction process:

[0106]

[0107] Example 1

[0108] A coating for preventing oxidation and passivation of steel surface comprises component A and component B. Component A comprises the following raw materials in parts by weight:

[0109] 20 parts of polyvinyl alcohol, 10 parts of amphoteric polyurethane, 10 parts of rust remover, 1 part of accelerator, 3 parts of corrosion inhibitor, 2 parts of stabilizer, 10 parts of solvent A;

[0110] The component B comprises the following raw materials in parts by weight:

[0111] 2 parts of curing agent, 10 parts of solvent A;

[0112] Wherein: the rust removal agent is composed of phosphoric acid and tannic acid in a weight ratio of 1:1;

[0113] The preparation method of the amphoteric polyurethane is carried out according to Preparation Example 1.

[0114] The accelerator is citric acid;

[0115] The corrosion inhibitor is polyaniline, and the molecular weight of polyaniline is 5000;

[0116] The stabilizer is hydroxycellulose;

[0117] The curing agent is 3-methyl-1-aziridine.

[0118] The solvent A is composed of water and ethanol in a weight ratio of 3:1.

[0119] The molecular weight of the polyvinyl alcohol is 70,000.

[0120] The method for preparing the coating for preventing oxidation and passivation of the steel surface comprises the following steps:

[0121] (1) Preparation of component A

[0122] According to the composition of each raw material of component A, materials are taken; polyvinyl alcohol, amphoteric polyurethane, rust-removing agent, accelerator, corrosion inhibitor, stabilizer, and solvent A are fully mixed at room temperature, and then mixed at 50° C. for 2 hours, and cooled to room temperature to obtain component A;

[0123] (2) Preparation of component B

[0124] According to the composition of each raw material of component B, materials are taken and then fully mixed to obtain component B;

[0125] When in use, component A and component B are mixed and applied in a weight ratio of 50:2.

[0126] Example 2

[0127] A coating for preventing oxidation and passivation of steel surface comprises component A and component B. Component A comprises the following raw materials in parts by weight:

[0128] 25 parts of polyvinyl alcohol, 15 parts of amphoteric polyurethane, 12 parts of rust remover, 2 parts of accelerator, 4 parts of corrosion inhibitor, 3 parts of stabilizer, 15 parts of solvent A;

[0129] The component B comprises the following raw materials in parts by weight:

[0130] 4 parts of curing agent, 15 parts of solvent A;

[0131] Wherein: the rust removal agent is composed of phosphoric acid and tannic acid in a weight ratio of 1:1;

[0132] The preparation method of the amphoteric polyurethane is carried out according to Preparation Example 1.

[0133] The accelerator is citric acid;

[0134] The corrosion inhibitor is polyaniline, and the molecular weight of polyaniline is 15000;

[0135] The stabilizer is hydroxycellulose;

[0136] The curing agent is 1-aziridine ethanol.

[0137] The solvent A is composed of water and ethanol in a weight ratio of 3:1.

[0138] The molecular weight of the polyvinyl alcohol is 100,000.

[0139] The method for preparing the coating for preventing oxidation and passivation of the steel surface comprises the following steps:

[0140] (1) Preparation of component A

[0141] According to the composition of each raw material of component A, materials are taken; polyvinyl alcohol, amphoteric polyurethane, rust-removing agent, accelerator, corrosion inhibitor, stabilizer, and solvent A are fully mixed at room temperature, and then mixed at 60° C. for 2 hours, and cooled to room temperature to obtain component A;

[0142] (2) Preparation of component B

[0143] According to the composition of each raw material of component B, materials are taken and then fully mixed to obtain component B;

[0144] When in use, component A and component B are mixed and applied in a weight ratio of 50:3.

[0145] Example 3

[0146] A coating for preventing oxidation and passivation of steel surface comprises component A and component B. Component A comprises the following raw materials in parts by weight:

[0147] 22 parts of polyvinyl alcohol, 13 parts of amphoteric polyurethane, 11 parts of rust remover, 1.5 parts of accelerator, 3.5 parts of corrosion inhibitor, 2.5 parts of stabilizer, 13 parts of solvent A;

[0148] The component B comprises the following raw materials in parts by weight:

[0149] 3 parts of curing agent, 13 parts of solvent A;

[0150] Wherein: the rust removal agent is composed of phosphoric acid and tannic acid in a weight ratio of 1:1;

[0151] The preparation method of the amphoteric polyurethane is carried out according to Preparation Example 1.

[0152] The accelerator is citric acid;

[0153] The corrosion inhibitor is polyaniline, and the molecular weight of polyaniline is 9000;

[0154] The stabilizer is hydroxycellulose;

[0155] The curing agent is 3-methyl-1-aziridine.

[0156] The solvent A is composed of water and ethanol in a weight ratio of 3:1.

[0157] The molecular weight of the polyvinyl alcohol is 80,000.

[0158] The method for preparing the coating for preventing oxidation and passivation of the steel surface comprises the following steps:

[0159] (1) Preparation of component A

[0160] According to the composition of each raw material of component A, materials are taken; polyvinyl alcohol, amphoteric polyurethane, rust-removing agent, accelerator, corrosion inhibitor, stabilizer, and solvent A are fully mixed at room temperature, and then mixed at 55° C. for 2 hours, and cooled to room temperature to obtain component A;

[0161] (2) Preparation of component B

[0162] According to the composition of each raw material of component B, materials are taken and then fully mixed to obtain component B;

[0163] When in use, component A and component B are mixed and applied in a weight ratio of 50:2.5.

[0164] Example 4

[0165] A coating for preventing oxidation and passivation of steel surface, comprising component A and component B.

[0166] The component A comprises the following raw materials in parts by weight:

[0167] 21 parts of polyvinyl alcohol, 11 parts of amphoteric polyurethane, 11 parts of rust remover, 1 part of accelerator, 3 parts of corrosion inhibitor, 2 parts of stabilizer, 11 parts of solvent A;

[0168] The component B comprises the following raw materials in parts by weight:

[0169] 2 parts of curing agent, 11 parts of solvent A;

[0170] Wherein: the rust removal agent is composed of phosphoric acid and tannic acid in a weight ratio of 1:1;

[0171] The preparation method of the amphoteric polyurethane is carried out according to Preparation Example 1.

[0172] The accelerator is citric acid;

[0173] The corrosion inhibitor is polyaniline, and the molecular weight of polyaniline is 7000;

[0174] The stabilizer is hydroxycellulose;

[0175] The curing agent is any one of 3-methyl-1-aziridine and 1-aziridine ethanol.

[0176] The solvent A is composed of water and ethanol in a weight ratio of 3:1.

[0177] The molecular weight of the polyvinyl alcohol is 80,000.

[0178] The method for preparing the coating for preventing oxidation and passivation of the steel surface comprises the following steps:

[0179] (1) Preparation of component A

[0180] According to the composition of each raw material of component A, materials are taken; polyvinyl alcohol, amphoteric polyurethane, rust-removing agent, accelerator, corrosion inhibitor, stabilizer, and solvent A are fully mixed at room temperature, and then mixed at 50° C. for 2 hours, and cooled to room temperature to obtain component A;

[0181] (2) Preparation of component B

[0182] According to the composition of each raw material of component B, materials are taken and then fully mixed to obtain component B;

[0183] When in use, component A and component B are mixed and applied in a weight ratio of 50:2.

[0184] Example 5

[0185] A coating for preventing oxidation and passivation of steel surface comprises component A and component B. Component A comprises the following raw materials in parts by weight:

[0186] 24 parts of polyvinyl alcohol, 14 parts of amphoteric polyurethane, 12 parts of rust remover, 1.5 parts of accelerator, 3 parts of corrosion inhibitor, 3 parts of stabilizer, 14 parts of solvent A;

[0187] The component B comprises the following raw materials in parts by weight:

[0188] 3 parts of curing agent, 14 parts of solvent A;

[0189] Wherein: the rust removal agent is composed of phosphoric acid and tannic acid in a weight ratio of 1:1;

[0190] The preparation method of the amphoteric polyurethane is carried out according to Preparation Example 1.

[0191] The accelerator is citric acid;

[0192] The corrosion inhibitor is polyaniline, and the molecular weight of polyaniline is 14000;

[0193] The stabilizer is hydroxycellulose;

[0194] The curing agent is composed of 3-methyl-1-aziridine and 1-aziridine ethanol in a weight ratio of 1:1.

[0195] The solvent A is composed of water and ethanol in a weight ratio of 3:1.

[0196] The molecular weight of the polyvinyl alcohol is 90,000.

[0197] The method for preparing the coating for preventing oxidation and passivation of the steel surface comprises the following steps:

[0198] (1) Preparation of component A

[0199] According to the composition of each raw material of component A, materials are taken; polyvinyl alcohol, amphoteric polyurethane, rust-removing agent, accelerator, corrosion inhibitor, stabilizer, and solvent A are fully mixed at room temperature, and then mixed at 60° C. for 2 hours, and cooled to room temperature to obtain component A;

[0200] (2) Preparation of component B

[0201] According to the composition of each raw material of component B, materials are taken and then fully mixed to obtain component B;

[0202] When in use, component A and component B are mixed and applied in a weight ratio of 50:2.5.

[0203] Comparative Example 1

[0204] A coating for preventing oxidation passivation of steel surface, without adding amphoteric polyurethane, and 30 parts of polyvinyl alcohol, and other conditions are consistent with those of Example 1.

[0205] Comparative Example 2

[0206] A coating for preventing oxidation and passivation of steel surface, wherein no rust-removing agent is added to component A, and other conditions are consistent with those in Example 1.

[0207] Comparative Example 3

[0208] A coating for preventing oxidation passivation of steel surface, wherein no stabilizer is added to component A, and other conditions are consistent with those in Example 1.

[0209] Comparative Example 4

[0210] A coating for preventing oxidation passivation of steel surface; the amphoteric polyurethane is the amphoteric polyurethane prepolymer in Preparation Example 1; and other conditions are consistent with those in Example 1.

[0211] Comparative Example 5

[0212] A coating for preventing oxidation passivation of steel surface, without adding polyvinyl alcohol, but with 30 parts of amphoteric polyurethane, and other conditions are consistent with those of Example 1.

[0213] The coatings prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to the following performance tests:

[0214] Experimental example

[0215] The coatings prepared by Examples 1 to 5 and Comparative Examples 1 to 5 were applied to the surface of the steel structure by brushing to form a coating, and the dry film thickness of the coating was 40-45 μm. The hardness, water resistance, impact resistance and adhesion of the coating were tested. At the same time, the salt spray resistance of the coating was tested. Each experiment was conducted at least 3 times in parallel, and the average value was taken. The results are shown in Table 1.

[0216] The test standards in the experimental examples are as follows:

[0217] Paint and varnish pencil method for determination of paint film hardness "GB / T 6739-2022"

[0218] Determination of water resistance of paint film "GB / T 1733-1993"

[0219] Determination of impact resistance of paint film "GB / T 1732-2020";

[0220] Determination of neutral salt spray resistance of paints and varnishes GB / T 1771-2007.

[0221] Paint and varnish cross-cut test GB / T 9286-2021

[0222] Table 1

[0223]

[0224] As can be seen from Table 1, the coatings of Examples 1 to 5 performed well in terms of hardness, water resistance, impact strength, adhesion and salt spray resistance. The specific results are as follows:

[0225] Hardness: The hardness of all examples is 3H, indicating that the coating has good hardness.

[0226] Water resistance (h): ranges from 371 hours to 395 hours, indicating that these coatings are able to resist the effects of moisture for a long time without losing their properties.

[0227] Impact strength (J / m): The value is between 156 and 167, indicating that the coating has sufficient toughness and impact resistance.

[0228] Adhesion: All examples achieved Grade 1, which is the best grade and means that there is very strong adhesion between the coating and the substrate.

[0229] Salt spray resistance (h): Test results show that the salt spray resistance time is as long as 1057 hours to 1124 hours, which means that the coating can provide long-term protection in corrosive environments.

[0230] It can also be seen from Table 1 that the coating properties of Comparative Example 1 are hardness: 2H, water resistance (h): 185 hours, impact strength (J / m): 112, adhesion: 4 levels, and salt spray resistance (h): 586 hours; Comparative Example 1 does not add amphoteric polyurethane, but increases the amount of polyvinyl alcohol. Due to the lack of chemical bonding and close-fitting protective layer provided by amphoteric polyurethane, the overall protective performance of the coating is reduced. Specifically, the water resistance and salt spray resistance are significantly reduced, and the adhesion is also reduced from level 1 in Example 1 to level 4, which indicates that the bonding force between the coating and the substrate is greatly weakened.

[0231] The coating properties of Comparative Example 2 are hardness: 1H, water resistance (h): 287 hours, impact strength (J / m): 48, adhesion: Level 2, and salt spray resistance (h): 247 hours; in Comparative Example 2, component A does not contain a rust remover. The function of a rust remover is to convert rust into stable compounds, thereby preventing the development of corrosion. Therefore, without a rust remover, the coating cannot effectively treat existing rust, resulting in a significant decrease in water resistance and salt spray resistance, and a significant deterioration in adhesion and impact strength.

[0232] The coating properties of Comparative Example 3 are hardness: 3H, water resistance (h): 350 hours, impact strength (J / m): 85, adhesion: Level 2, and salt spray resistance (h): 908 hours; there is no stabilizer in component A of Comparative Example 3. Stabilizers (such as hydroxycellulose) ensure the stability of the coating system and prevent component separation or precipitation. Although the hardness remains at 3H, the impact strength and adhesion are reduced. This may be due to the lack of stabilizers, which may cause the coating to delaminate during the storage period, affecting the quality and performance of the final coating.

[0233] The coating properties of Comparative Example 4 are hardness: 2H, water resistance (h): 330 hours, impact strength (J / m): 75, adhesion: level 3, and salt spray resistance (h): 810 hours; Comparative Example 4 uses an unmodified amphoteric polyurethane prepolymer instead of the modified amphoteric polyurethane in Preparation Example 1. The modification process introduces a polyhydroxy structure, which enhances the crosslinking density of the polyurethane and its ability to bind to the metal surface. Therefore, the unmodified version is inferior to Example 1 in all properties, especially in adhesion and impact strength.

[0234] The coating properties of Comparative Example 5 are hardness: 1H, water resistance (h): 310 hours, impact resistance (J / m): 92, adhesion: level 1, and salt spray resistance (h): 954 hours; Comparative Example 5 does not contain polyvinyl alcohol, but increases the amount of amphoteric polyurethane. Polyvinyl alcohol provides the flexibility and strength of the coating film, and its absence leads to a decrease in hardness. Although the adhesion is still level 1, the overall mechanical properties (such as impact resistance) are affected. In addition, water resistance and salt spray resistance are also reduced, indicating that polyvinyl alcohol is very important for improving the comprehensive performance of the coating.

[0235] In summary, in the coating described in the present application, the amphoteric polyurethane contains abundant polyhydroxyl functional groups, which can form a tight chemical bond with the metal surface, and due to the presence of its hydrophilic chain extender, it can penetrate into the micropores on the steel surface, thereby enhancing the protective effect; the amphoteric polyurethane not only provides an immediate anti-corrosion barrier, but also maintains effective protection for a longer period of time through long-term chemical bonding.

[0236] Rust-transforming agents (phosphoric acid and tannic acid) convert rust into stable, non-toxic fillers, enabling rust-free painting, thus preventing the development of corrosion. This feature makes it possible to use the coating directly even on surfaces that already have slight rust without additional rust removal.

[0237] As an efficient corrosion inhibitor, polyaniline forms a dense film on the metal surface, increasing its oxidation and reduction properties and reducing the possibility of corrosion. At the same time, it can also establish multiple connection points with the metal surface to enhance adhesion.

[0238] Hydroxycellulose as a stabilizer ensures the stability of the coating system, avoids separation or precipitation of components, and ensures the quality stability of the coating and its long-lasting performance after construction.

[0239] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A coating for preventing oxidation and passivation of steel surface, characterized in that: The invention comprises component A and component B, wherein component A comprises the following raw materials in parts by weight: 20-25 parts of polyvinyl alcohol, 10-15 parts of amphoteric polyurethane, 10-12 parts of rust remover, 1-2 parts of accelerator, 3-4 parts of corrosion inhibitor, 2-3 parts of stabilizer, 10-15 parts of solvent A; The component B comprises the following raw materials in parts by weight: 2-4 parts of curing agent, 10-15 parts of solvent A; The rust-removing agent is composed of phosphoric acid and tannic acid in a weight ratio of 1:1; The method for preparing the amphoteric polyurethane comprises the following steps: using isophorone diisocyanate, polytetramethylene glycol, N-methyldiethanolamine and 2,2-dimethylolpropionic acid as raw materials, and preparing a waterborne polyurethane prepolymer by a prepolymerization method; Then, polyhydroxy D-xylose is introduced as a cross-linking modifier to react with the isocyanate groups in the waterborne polyurethane prepolymer for graft polymerization to form amphoteric polyurethane.

2. The coating according to claim 1, characterized in that The accelerator is citric acid.

3. The coating according to claim 1, characterized in that The corrosion inhibitor is polyaniline.

4. The coating according to claim 1, characterized in that The stabilizer is hydroxycellulose.

5. The coating according to claim 1, characterized in that The curing agent is any one of 3-methyl-1-aziridine and 1-aziridine ethanol.

6. The coating according to claim 1, characterized in that Also included is a pigment, which includes any one or both of red iron oxide and titanium dioxide.

7. The coating according to claim 1, characterized in that The solvent A is composed of water and ethanol in a weight ratio of 3:

1.

8. The coating according to claim 1, characterized in that The molecular weight of the polyvinyl alcohol is 70,000-100,000.

9. The method for preparing the coating according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Preparation of component A According to the composition of each raw material of component A, materials are taken; polyvinyl alcohol, amphoteric polyurethane, rust-removing agent, accelerator, corrosion inhibitor, stabilizer, and solvent A are fully mixed at room temperature, and then mixed at 50-60° C. for 2 hours, and cooled to room temperature to obtain component A; (2) Preparation of component B According to the composition of each raw material of component B, take the materials and then fully mix them to obtain component B; When in use, component A and component B are mixed and applied in a weight ratio of 50:2-3.

10. Application of coating, characterized in that, The coating according to any one of claims 1 to 8 or the coating prepared by the preparation method according to claim 9 is applied to the corrosion protection of steel products.

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