Anticorrosive coating for stainless steel tube heat exchanger plate and preparation method of anticorrosive coating

Abstract

The invention belongs to the field of power plant stainless steel tube heat exchanger tube plate anticorrosive coatings, and relates to a stainless steel tube heat exchanger plate anticorrosive coating and a preparation method thereof. Comprising prime paint, middle-layer paint and surface-layer paint, the prime paint comprises a component A, a component B and a component C; the middle layer coating comprises a component A, a component B, a component C and glass flakes; the surface layer coating comprises a component A, a component B and iron oxide red; wherein the component A comprises bisphenol A epoxy resin, xylene and ethanol; the component B comprises m-phenylenediamine and ethanol; the component C is prepared from dibutyl phthalate and xylene; the anticorrosive paint disclosed by the invention has good flexibility, adhesive force, permeability resistance and wear resistance, circulating water can be prevented from slightly permeating into condensed water after paint anticorrosive treatment is carried out on the pipe orifice of the heat exchange pipe and the expanded opening of the pipe plate, and the problems of equipment corrosion and unit shutdown caused by water quality problems of a thermal power plant unit are avoided.

Description

Technical Field

[0001] The invention belongs to the field of anti-corrosion coatings for tube plates of stainless steel tube heat exchangers in power plants, and relates to an anti-corrosion coating for stainless steel tube heat exchanger plates and a preparation method thereof. Background Art

[0002] During the operation of thermal power plants in my country, condensers and oil coolers, as important heat exchange equipment, play a key role in cooling high-temperature steam into water and cooling oil to an appropriate temperature. These devices usually use copper tubes and carbon steel tube sheets to connect through expansion processes. However, as time goes by, especially in the long-term high-temperature and high-pressure working environment of the unit, copper tubes often suffer from pitting corrosion and leakage. The occurrence of pitting corrosion leads to a decrease in the corrosion resistance of copper tubes, which not only affects the feed water and steam quality of the unit, but also may cause hidden dangers to the normal operation of the generator unit. In particular, the leakage caused by the corrosion of copper tubes will pollute the water quality of circulating cooling water and condensate, thereby affecting the safe and stable operation of the unit. Therefore, the corrosion problem of copper tubes has always been a technical problem that needs to be solved urgently during the operation of thermal power plants.

[0003] With the advancement of science and technology and the continuous development of materials, the use of stainless steel pipes to replace copper pipes has become an important direction for the transformation of condensers and oil coolers in thermal power plants. Compared with copper pipes, stainless steel pipes have better corrosion resistance, high temperature resistance and mechanical strength, which can effectively solve the problem of easy corrosion of copper pipes, extend the service life of equipment, and reduce the frequency of maintenance and replacement. However, despite the many advantages of stainless steel pipes, there is still a problem that cannot be ignored in the process of connecting with carbon steel tube sheets.

[0004] Due to the difference in expansion coefficients between stainless steel and carbon steel, these two metals will expand or contract to different degrees when the temperature changes. This thermal expansion and contraction phenomenon causes stress on the connection surface between the stainless steel tube and the carbon steel tube sheet, forming tiny gaps or cracks. These cracks will cause the circulating cooling water to leak into the condensate system through the pipe opening, which will in turn affect the water quality of the generator set and may cause a certain proportion of pollutants in the condensate, affecting the steam quality and increasing the corrosion risk of the system, thereby affecting the safe and economic operation of the unit.

[0005] In order to solve this problem, it has become a feasible technical means to use anti-corrosion coatings to seal and anti-corrosion the connection between stainless steel pipes and carbon steel tube sheets. At present, some anti-corrosion coatings have been applied in this field, mainly used to protect the expansion joints between stainless steel pipe mouths and carbon steel tube sheets. However, current anti-corrosion coatings face some challenges. First, the adhesion of anti-corrosion coatings is insufficient, and it is difficult to form a strong adhesion layer between stainless steel and carbon steel, and it is easy to fall off due to temperature fluctuations and stress. Secondly, the flexibility of anti-corrosion coatings is poor, and it cannot effectively adapt to the thermal expansion and contraction stresses generated by the two metals under temperature changes, resulting in cracks or peeling of the coating, and it is impossible to maintain a good anti-corrosion effect for a long time. Therefore, the existing anti-corrosion coatings cannot meet the high requirements for temperature resistance, corrosion resistance and mechanical properties in actual operation. Summary of the invention

[0006] The object of the present invention is to provide an anti-corrosion coating for a stainless steel tube heat exchanger plate and a preparation method thereof, so as to solve the problem of micro-leakage at the expansion joint between the stainless steel tube and the carbon steel tube plate of the heat exchanger in the prior art.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention provides an anti-corrosion coating for a stainless steel tube heat exchanger plate, comprising a primer, an intermediate layer and a surface layer; the primer comprises component A, component B and component C; the intermediate layer comprises component A, component B, component C and glass flakes; the surface layer comprises component A, component B and red iron oxide; wherein component A comprises bisphenol A epoxy resin, xylene and ethanol; component B comprises metaphenylenediamine and ethanol; component C comprises dibutyl phthalate and xylene.

[0008] Preferably, the mass ratio of component A, component B and component C in the primer is (45-50): (4-5): (9-10).

[0009] Preferably, the mass ratio of component A, component B, component C and glass flakes in the intermediate layer coating is (90-100): (18-20): (8-10): (25-30).

[0010] Preferably, the mass ratio of component A, component B and red iron oxide in the surface coating is (45-50): (9-10): (4-5).

[0011] Preferably, the mass ratio of bisphenol A epoxy resin, xylene and ethanol in component A is (9-10): (1-2): (1-2).

[0012] Preferably, the mass ratio of the intermediate phenylenediamine and ethanol in the B component is (4-5): (4-5).

[0013] Preferably, the mass ratio of dibutyl phthalate to xylene in the component C is (18-20):(9-10).

[0014] Preferably, the size of the glass flakes is 80-100 mesh.

[0015] Preferably, the size of the red iron oxide is 80-100 mesh.

[0016] In a second aspect, the present invention provides a method for preparing an anticorrosive coating for a stainless steel tube heat exchanger plate, comprising: Mix bisphenol A epoxy resin, xylene and ethanol, stir and heat in a water bath to obtain component A; Mix m-phenylenediamine and ethanol, and heat in a water bath to obtain component B; Dibutyl phthalate and xylene are mixed and stirred to obtain component C; Mixing and stirring component A, component B and component C to obtain a base coating; Mixing and stirring component A, component B, component C and glass flakes to obtain an intermediate layer coating; The component A, the component B and red iron oxide are mixed and stirred to obtain a surface coating.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The anti-corrosion coating for the stainless steel tube heat exchanger plate of the present invention has good flexibility and good adhesion to both stainless steel and carbon steel; glass flakes are added to the middle layer of the anti-corrosion coating, which has good permeability resistance and greatly improves the anti-corrosion life of the coating; red iron oxide is added to the surface layer of the anti-corrosion coating, and the coating has wear resistance and sealing properties. The anti-corrosion coating of the present invention has good flexibility, adhesion, permeability resistance and wear resistance. After the coating anti-corrosion treatment is applied to the tube mouth of the heat exchange tube and the expansion mouth of the tube plate, the circulating water can be prevented from micro-infiltrating into condensed water, and the equipment corrosion and unit tripping problems of the thermal power plant units due to water quality problems can be avoided, thereby ensuring the safe operation of the thermal power generating units. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0019] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0020] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0021] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0022] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0023] The first object of the present invention is to provide an anti-corrosion coating for a stainless steel tube heat exchanger plate, comprising a primer, an intermediate layer and a surface layer; the primer comprises component A, component B and component C; the intermediate layer comprises component A, component B, component C and glass flakes; the surface layer comprises component A, component B and red iron oxide; wherein component A comprises bisphenol A type epoxy resin, xylene and ethanol; component B comprises metaphenylenediamine and ethanol; component C comprises dibutyl phthalate and xylene.

[0024] The coating system of the present invention enhances the mechanical strength of the overall coating through compounding at different levels. Heat exchangers usually work in high temperature and high pressure environments, and the chemical components contained in the anti-corrosion coating of the present invention, such as epoxy resin and xylene, can maintain good stability and durability under high temperature conditions, thereby extending the service life of the equipment. The bisphenol A epoxy resin of the base coating has good adhesion and chemical corrosion resistance; the glass flakes of the middle layer not only provide mechanical protection, but also enhance the coating's anti-permeability. In addition, the glass flakes, as reinforcing materials, provide additional support during thermal expansion and thermal contraction, further improving the high temperature resistance; the red iron oxide added to the surface coating not only improves the wear resistance of the coating, but also enhances its resistance to acidic, alkaline and oxidizing substances in the environment, and is particularly suitable for use in highly corrosive environments such as heat exchangers.

[0025] The mass ratio of component A, component B and component C in the primer is (45-50): (4-5): (9-10), and the ratio helps the coating to obtain good adhesion, corrosion resistance, high temperature resistance and flexibility, while having good workability and curing properties.

[0026] The mass ratio of component A, component B, component C and glass flakes in the intermediate layer coating is (90-100): (18-20): (8-10): (25-30). Glass flakes are the key to the intermediate layer coating. Glass flakes have excellent permeability resistance and mechanical strength, can effectively block the penetration of corrosive media, enhance the impact resistance and scratch resistance of the coating, and prevent the damage of the coating and water penetration.

[0027] The mass ratio of component A, component B and red iron oxide in the surface coating is (45-50): (9-10): (4-5). As a pigment in the surface coating, red iron oxide not only provides excellent antioxidant ability, but also has strong heat resistance and chemical resistance, and can effectively improve the coating's resistance to acidic and alkaline substances in the environment, preventing the coating from failing due to changes in the external environment. Red iron oxide can also enhance the coating's sun protection ability and avoid aging caused by ultraviolet rays.

[0028] In addition, the size of glass flakes and red iron oxide is 80~100 mesh, which helps to ensure the uniformity, density and long-term weather resistance of the coating, so that the coating can resist chemical corrosion and cope with the pressure and wear caused by environmental changes.

[0029] The mass ratio of bisphenol A epoxy resin, xylene and ethanol in the component A is (9~10): (1~2): (1~2). Bisphenol A epoxy resin is the main component of the primer, has excellent chemical corrosion resistance, good adhesion and heat resistance, and can provide strong substrate protection. Epoxy resin has a strong cross-linking structure, which makes the coating strong and durable. Xylene, as a solvent, has good solubility and low volatility, which can effectively adjust the viscosity of the coating and help the coating to be evenly distributed on the surface of the stainless steel tube heat exchanger tube sheet. Ethanol, as an auxiliary solvent, can not only adjust the fluidity of the coating, but also reduce the bubbles generated during the curing process and improve the flatness of the coating.

[0030] The mass ratio of m-phenylenediamine and ethanol in the B component is (4-5): (4-5). m-phenylenediamine is a curing agent that can promote the chemical reaction between the epoxy resin and the surface of the tube sheet of the stainless steel tube heat exchanger, thereby improving the hardness, adhesion and chemical corrosion resistance of the coating. Ethanol acts as a solvent in the B component and participates in the curing reaction of the coating together with the epoxy resin, and helps adjust the curing speed and fluidity.

[0031] The mass ratio of dibutyl phthalate to xylene in the component C is (18-20): (9-10). Dibutyl phthalate is a plasticizer that can improve the flexibility and crack resistance of the coating, reduce the brittleness of the coating, and make the coating less likely to crack or fall off during use. Xylene, as a solvent, helps adjust the viscosity of the coating, making it easier to apply, and has good volatility, which helps the coating dry quickly.

[0032] The present invention forms a multiple protection system through a three-layer coating structure of a base coating, an intermediate coating and a surface coating. Each layer of coating has different functional characteristics. The base coating provides good basic protection, the intermediate coating improves corrosion resistance, and the surface coating plays a role in surface protection and weather resistance. The present invention can provide a comprehensive anti-corrosion effect, extend the service life of the tube sheet, and effectively resist erosion in various corrosive environments.

[0033] The second object of the present invention is to provide a method for preparing an anticorrosive coating for a stainless steel tube heat exchanger plate, comprising: Mix bisphenol A epoxy resin, xylene and ethanol in a mass ratio of (9-10):(1-2):(1-2), stir for 10-30 minutes, heat in a water bath at 50-60°C for 8-12 hours, and obtain component A after being uniformly dissolved; Mix m-phenylenediamine and ethanol in a mass ratio of (4-5):(4-5), and heat in a water bath at 30-40°C for 4-6 hours to obtain component B; Dibutyl phthalate and xylene are mixed in a mass ratio of (18-20):(9-10), and stirred for 5-10 minutes to obtain component C; Component A, component B and component C are mixed in a mass ratio of (45-50): (4-5): (9-10), and stirred at 2000-4000 r / min for 10-30 min to obtain a base coating; Mix component A, component B, component C and glass flakes in a mass ratio of (90-100): (18-20): (8-10): (25-30), and stir at 2000-4000 r / min for 10-30 min to obtain an intermediate layer coating; Mix component A, component B and red iron oxide in a mass ratio of (45-50):(9-10):(4-5), and stir at 2000-4000 r / min for 10-30 min to obtain a surface coating.

[0034] The method of the present invention is relatively simple to operate, and can complete the mixing and reaction of the components at a relatively low temperature and under appropriate stirring conditions, does not require complicated equipment and technical requirements, is suitable for large-scale production, and has a high prospect for industrial application.

[0035] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0036] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0037] Example 1 Bisphenol A epoxy resin, xylene and ethanol were mixed in a mass ratio of 9:1:1, stirred for 10 minutes, heated in a water bath at 50°C for 8 hours, and dissolved uniformly to obtain component A; Mix m-phenylenediamine and ethanol in a mass ratio of 1:1, and heat in a water bath at 30°C for 4 hours to obtain component B; Dibutyl phthalate and xylene were mixed in a mass ratio of 2:1 and stirred for 5 minutes to obtain component C; Component A, component B and component C were mixed in a mass ratio of 45:4:9, and stirred at 2000 r / min for 10 min to obtain a base coating; Component A, component B, component C and 80-mesh glass flakes were mixed in a mass ratio of 90:18:8:25, and stirred at 2000 r / min for 10 min to obtain an intermediate layer coating; Component A, component B and 80-mesh red iron oxide were mixed in a mass ratio of 45:9:4, and stirred at 2000 r / min for 10 minutes to obtain a surface coating.

[0038] Example 2 Bisphenol A epoxy resin, xylene and ethanol were mixed in a mass ratio of 10:1:1, stirred for 15 minutes, heated in a water bath at 50°C for 9 hours, and dissolved uniformly to obtain component A; Mix m-phenylenediamine and ethanol in a mass ratio of 4:5, and heat in a water bath at 30°C for 4 hours to obtain component B; Dibutyl phthalate and xylene were mixed in a mass ratio of 9:5 and stirred for 6 minutes to obtain component C; Component A, component B and component C were mixed in a mass ratio of 50:4:9, and stirred at 2500 r / min for 15 min to obtain a base coating; Component A, component B, component C and 80-mesh glass flakes were mixed in a mass ratio of 100:18:8:25, and stirred at 2500 r / min for 15 min to obtain an intermediate layer coating; Component A, component B and 100-mesh red iron oxide were mixed in a mass ratio of 50:9:4, and stirred at 2500 r / min for 15 minutes to obtain a surface coating.

[0039] Example 3 Bisphenol A epoxy resin, xylene and ethanol were mixed in a mass ratio of 9:2:1, stirred for 20 minutes, heated in a water bath at 55°C for 10 hours, and dissolved uniformly to obtain component A; Mix m-phenylenediamine and ethanol in a mass ratio of 4:5, and heat in a water bath at 35°C for 5 hours to obtain component B; Dibutyl phthalate and xylene were mixed in a mass ratio of 20:9 and stirred for 8 minutes to obtain component C; Component A, component B and component C were mixed in a mass ratio of 45:5:9, and stirred at 3000 r / min for 20 min to obtain a base coating; Component A, component B, component C and 100-mesh glass flakes were mixed in a mass ratio of 18:4:2:5, and stirred at 3000 r / min for 20 min to obtain an intermediate layer coating; Component A, component B and 80-mesh red iron oxide were mixed in a mass ratio of 45:10:4, and stirred at 3000 r / min for 20 minutes to obtain a surface coating.

[0040] Example 4 Bisphenol A epoxy resin, xylene and ethanol were mixed in a mass ratio of 9:1:2, stirred for 25 minutes, heated in a water bath at 55°C for 11 hours, and dissolved uniformly to obtain component A; Mix m-phenylenediamine and ethanol in a mass ratio of 5:4, and heat in a water bath at 40°C for 6 hours to obtain component B; Dibutyl phthalate and xylene were mixed in a mass ratio of 19:9 and stirred for 8 minutes to obtain component C; Component A, component B and component C were mixed in a mass ratio of 45:4:10, and stirred at 3500 r / min for 25 min to obtain a base coating; Component A, component B, component C and 90-mesh glass flakes were mixed in a mass ratio of 45:9:4:15, and stirred at 3500 r / min for 25 min to obtain an intermediate layer coating; Component A, component B and 90-mesh red iron oxide were mixed in a mass ratio of 45:9:5, and stirred at 3500 r / min for 25 minutes to obtain a surface coating.

[0041] Example 5 Bisphenol A epoxy resin, xylene and ethanol were mixed in a mass ratio of 5:1:1, stirred for 30 minutes, heated in a water bath at 60°C for 12 hours, and dissolved uniformly to obtain component A; Mix m-phenylenediamine and ethanol in a mass ratio of 5:4, and heat in a water bath at 40°C for 6 hours to obtain component B; Dibutyl phthalate and xylene were mixed in a mass ratio of 2:1 and stirred for 10 minutes to obtain component C; Component A, component B and component C were mixed in a mass ratio of 10:1:2, and stirred at 4000 r / min for 30 min to obtain a base coating; Component A, component B, component C and 100-mesh glass flakes were mixed in a mass ratio of 10:2:1:3, and stirred at 4000 r / min for 30 min to obtain an intermediate layer coating; Component A, component B and 100-mesh red iron oxide were mixed in a mass ratio of 10:2:1, and stirred at 4000 r / min for 30 minutes to obtain a surface coating.

[0042] Performance test results The coating test pieces made from the coatings of Examples 1 to 5 and the coating test pieces made from other coatings were subjected to coating detection tests, and the test performances were as follows: (1) Acid resistance and salt resistance test The coating test pieces prepared from the coatings of Examples 1 to 5 and other coatings were immersed in 10% sulfuric acid solution prepared in distilled water, 3% sodium chloride solution, and a constant temperature water bath at 80° C. The test results are shown in Table 1.

[0043] Table 1 Test data of coating acid resistance and salt resistance

[0044] (2) Temperature change resistance test The coating test pieces prepared from the coatings of Examples 1 to 5 and other coatings were placed in a refrigerator freezer at -14°C for 2 hours; the test pieces were taken out and quickly placed in an oven at 160°C and maintained at 160°C for 2 hours; this cycle was repeated 3 times. The test results are shown in Table 2.

[0045] Table 2 Coating temperature resistance test data

[0046] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An anticorrosive coating for stainless steel tube heat exchanger plates, characterized in that: It comprises a base coating, an intermediate coating and a surface coating; the base coating comprises component A, component B and component C; the intermediate coating comprises component A, component B, component C and glass flakes; the surface coating comprises component A, component B and red iron oxide; wherein component A comprises bisphenol A epoxy resin, xylene and ethanol; component B comprises metaphenylenediamine and ethanol; component C comprises dibutyl phthalate and xylene.

2. The anti-corrosion coating for stainless steel tube heat exchanger plate according to claim 1, characterized in that: The mass ratio of component A, component B and component C in the primer is (45-50): (4-5): (9-10).

3. The anti-corrosion coating for stainless steel tube heat exchanger plate according to claim 1, characterized in that: The mass ratio of component A, component B, component C and glass flakes in the intermediate layer coating is (90-100): (18-20): (8-10): (25-30).

4. The anti-corrosion coating for stainless steel tube heat exchanger plate according to claim 1, characterized in that: The mass ratio of component A, component B and red iron oxide in the surface coating is (45-50): (9-10): (4-5).

5. The anti-corrosion coating for stainless steel tube heat exchanger plate according to claim 1, characterized in that: The mass ratio of bisphenol A epoxy resin, xylene and ethanol in the component A is (9-10): (1-2): (1-2).

6. The anti-corrosion coating for stainless steel tube heat exchanger plate according to claim 1, characterized in that: The mass ratio of the intermediate phenylenediamine and ethanol in the B component is (4-5): (4-5).

7. The anti-corrosion coating for stainless steel tube heat exchanger plate according to claim 1, characterized in that: The mass ratio of dibutyl phthalate to xylene in the component C is (18-20): (9-10).

8. The anti-corrosion coating for stainless steel tube heat exchanger plate according to claim 1, characterized in that: The size of the glass flakes is 80 to 100 meshes.

9. The anti-corrosion coating for stainless steel tube heat exchanger plate according to claim 1, characterized in that: The size of the red iron oxide is 80-100 meshes.

10. The method for preparing an anticorrosive coating for a stainless steel tube heat exchanger plate according to claims 1 to 9, characterized in that: include: Mix bisphenol A epoxy resin, xylene and ethanol, stir and heat in a water bath to obtain component A; Mix m-phenylenediamine and ethanol, and heat in a water bath to obtain component B; Mix dibutyl phthalate and xylene, and stir to obtain component C; Mixing and stirring component A, component B and component C to obtain a base coating; Mixing and stirring component A, component B, component C and glass flakes to obtain an intermediate layer coating; The A component, the B component and the red iron oxide are mixed and stirred to obtain the surface coating.

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