A corrosion-proof coating for stainless steel tube heat exchanger plates and a method for producing the same

Abstract

The present application belongs to the field of anti-corrosion coating of stainless steel tube heat exchanger tube plate in power plant, and relates to a kind of stainless steel tube heat exchanger plate anticorrosive paint and preparation method;Including bottom coating, intermediate layer coating and surface coating;The bottom coating includes A component, B component and C component;The intermediate layer coating includes A component, B component, C component and glass flake;The surface coating includes A component, B component and red iron oxide;Among them, the A component includes bisphenol A type epoxy resin, dimethylbenzene and ethanol;The B component includes m-phenylenediamine and ethanol;The C component includes dibutyl phthalate and dimethylbenzene;The anti-corrosion coating of the present application has good flexibility, adhesion, penetration resistance and wear resistance, and after implementing coating anti-corrosion treatment on the heat exchange tube nozzle and tube plate expansion opening, it can avoid the slight penetration of circulating water into the condensate water, and avoid the problem of equipment corrosion and unit tripping due to water quality problems in thermal power plant unit.

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] In the operation of my country's thermal power plants, condensers and oil coolers are crucial heat exchange equipment, playing a crucial role in cooling high-temperature steam into water and oil to an appropriate temperature. These devices typically utilize copper tubes and carbon steel tube sheets connected through expansion joints. However, over time, especially under the long-term high-temperature and high-pressure operating environments of the units, copper tubes often develop pitting corrosion and leakage. This pitting corrosion reduces the corrosion resistance of the copper tubes, affecting not only the feedwater and steam quality of the units but also potentially jeopardizing the normal operation of the generator sets. In particular, leakage caused by copper tube corrosion can contaminate the circulating cooling water and condensate, further impacting the safe and stable operation of the units. Therefore, copper tube corrosion remains a pressing technical challenge in the operation of thermal power plants.

[0003] With technological advancements and the continuous development of materials, replacing copper tubes with stainless steel has become a key trend in the renovation of condensers and oil coolers in thermal power plants. Compared to copper tubes, stainless steel tubes offer superior corrosion resistance, high-temperature resistance, and mechanical strength, effectively addressing the corrosion issues associated with copper tubes, extending equipment life, and reducing the frequency of repairs and replacements. However, despite these numerous advantages, stainless steel tubes still face a significant challenge when connecting to carbon steel tube sheets.

[0004] Due to the different expansion coefficients of stainless steel and carbon steel, these two metals expand or contract to varying degrees with temperature fluctuations. This thermal expansion and contraction stresses the joints between the stainless steel tubes and the carbon steel tube sheets, forming tiny gaps or cracks. These cracks can cause circulating cooling water to leak through the pipe openings and into the condensate system, impacting the generator set's water quality. This can cause the condensate to contain a certain proportion of contaminants, affecting steam quality and increasing the risk of system corrosion, thus affecting the safe and economical 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 parts between stainless steel pipes and carbon steel tube sheets. At present, some anti-corrosion coatings have been applied in this field, mainly for protecting the expansion joints between stainless steel pipe ends 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 they cannot effectively adapt to the thermal expansion and contraction stresses generated by the two metals under temperature changes, resulting in cracks or peeling in 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 purpose 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:

[0008] 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 coating and a surface layer coating; the primer comprises component A, component B and component C; the intermediate layer coating comprises component A, component B, component C and glass flakes; the surface layer coating comprises component A, component B and red iron oxide; wherein, component A comprises bisphenol A epoxy resin, xylene and ethanol; component B comprises m-phenylenediamine and ethanol; and component C comprises dibutyl phthalate and xylene.

[0009] Preferably, the mass ratio of component A, component B and component C in the primer is (45-50): (4-5): (9-10).

[0010] 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).

[0011] Preferably, the mass ratio of component A, component B and red iron oxide in the surface coating is (45-50): (9-10): (4-5).

[0012] Preferably, the mass ratio of bisphenol A epoxy resin, xylene and ethanol in component A is (9-10): (1-2): (1-2).

[0013] Preferably, the mass ratio of the intermediate phenylenediamine and ethanol in the B component is (4-5): (4-5).

[0014] Preferably, the mass ratio of dibutyl phthalate to xylene in the component C is (18-20): (9-10).

[0015] Preferably, the size of the glass flakes is 80-100 mesh.

[0016] Preferably, the size of the red iron oxide is 80-100 mesh.

[0017] In a second aspect, the present invention provides a method for preparing an anti-corrosion coating for a stainless steel tube heat exchanger plate, comprising:

[0018] Mixing bisphenol A epoxy resin, xylene and ethanol, stirring and heating in a water bath to obtain component A;

[0019] Mix m-phenylenediamine and ethanol, and heat in a water bath to obtain component B;

[0020] Dibutyl phthalate and xylene are mixed and stirred to obtain component C;

[0021] Mixing and stirring component A, component B and component C to obtain a primer;

[0022] Mixing and stirring component A, component B, component C and glass flakes to obtain an intermediate layer coating;

[0023] Component A, component B and red iron oxide are mixed and stirred to obtain a surface coating.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The anti-corrosion coating for stainless steel tube heat exchanger plates described in the present invention has excellent flexibility and good adhesion to both stainless steel and carbon steel. Glass flakes are added to the middle layer of the anti-corrosion coating, providing excellent permeability resistance and significantly increasing the coating's corrosion resistance life. Red iron oxide is added to the surface layer of the anti-corrosion coating, providing the coating with wear resistance and sealing properties. The anti-corrosion coating of the present invention has excellent flexibility, adhesion, permeability resistance, and wear resistance. After applying the coating anti-corrosion treatment to the heat exchange tube orifices and tube sheet expansion joints, it can prevent micro-infiltration of condensate from circulating water, avoid equipment corrosion and unit tripping due to water quality problems in thermal power plant units, and ensure the safe operation of thermal power generating units. DETAILED DESCRIPTION

[0026] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0027] 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.

[0028] All features, such as values, amounts, contents, and concentrations, described herein as numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0029] In this document, unless otherwise specified, “include,” “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.”

[0030] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0031] 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 coating and a surface layer coating; the primer comprises component A, component B and component C; the intermediate layer coating comprises component A, component B, component C and glass flakes; the surface layer coating comprises component A, component B and red iron oxide; wherein, component A comprises bisphenol A epoxy resin, xylene and ethanol; component B comprises m-phenylenediamine and ethanol; and component C comprises dibutyl phthalate and xylene.

[0032] 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, 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 impermeability. In addition, the glass flakes, as reinforcing materials, provide additional support during thermal expansion and thermal contraction, further improving 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, making it particularly suitable for use in highly corrosive environments such as heat exchangers.

[0033] The mass ratio of component A, component B, and component C in the primer is (45-50): (4-5): (9-10), which helps the coating obtain good adhesion, corrosion resistance, high temperature resistance, and flexibility, while also having good workability and curing properties.

[0034] 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 key to the intermediate layer coating. They possess excellent permeability resistance and mechanical strength, effectively blocking the penetration of corrosive media, enhancing the coating's impact and scratch resistance, and preventing damage and moisture penetration.

[0035] The mass ratio of component A, component B, and red iron oxide in the topcoat is (45-50):(9-10):(4-5). As a pigment in the topcoat, red iron oxide not only provides excellent antioxidant properties but also possesses strong heat and chemical resistance. This effectively improves the coating's resistance to acidic and alkaline substances in the environment, preventing coating failure due to environmental changes. Red iron oxide also enhances the coating's sun protection, preventing UV-induced aging.

[0036] 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.

[0037] The mass ratio of bisphenol A epoxy resin, xylene, and ethanol in component A is (9-10): (1-2): (1-2). Bisphenol A epoxy resin is the main component of the primer, exhibiting excellent chemical corrosion resistance, good adhesion, and heat resistance, providing strong substrate protection. The epoxy resin has a strong cross-linking structure, making the coating durable. Xylene, as a solvent, has good solubility and low volatility, effectively regulating the viscosity of the coating and helping the coating to be evenly distributed on the surface of the stainless steel tube heat exchanger tube sheet. Ethanol, as an auxiliary solvent, not only regulates the fluidity of the coating but also reduces bubbles generated during the curing process, improving the smoothness of the coating.

[0038] The mass ratio of m-phenylenediamine to ethanol in component B is (4-5):(4-5). m-phenylenediamine is a curing agent that promotes the chemical reaction between the epoxy resin and the surface of the stainless steel tube heat exchanger tube sheet, thereby improving the coating's hardness, adhesion, and chemical resistance. Ethanol acts as a solvent in component B, participating in the coating's curing reaction along with the epoxy resin and helping to adjust the curing speed and fluidity.

[0039] The mass ratio of dibutyl phthalate to xylene in component C is (18-20):(9-10). Dibutyl phthalate, a plasticizer, improves the coating's flexibility and crack resistance, reduces its brittleness, and makes it less susceptible to cracking or shedding during use. Xylene, a solvent, helps adjust the coating's viscosity, making it easier to apply. Its high volatility also helps the coating dry quickly.

[0040] This invention utilizes a three-layer coating structure consisting of a primer, an intermediate layer, and a topcoat to create a multi-layered protection system. Each layer has distinct functional characteristics: the primer provides excellent basic protection, the intermediate layer enhances corrosion resistance, and the topcoat provides surface protection and weather resistance. This invention provides comprehensive corrosion protection, extending the service life of the tubesheet and effectively resisting corrosion in various corrosive environments.

[0041] A second object of the present invention is to provide a method for preparing an anti-corrosion coating for a stainless steel tube heat exchanger plate, comprising:

[0042] 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 dissolve evenly to obtain component A;

[0043] 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;

[0044] Dibutyl phthalate and xylene were mixed in a mass ratio of (18-20):(9-10), and stirred for 5-10 minutes to obtain component C;

[0045] 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 primer;

[0046] Component A, component B, component C and glass flakes are mixed in a mass ratio of (90-100): (18-20): (8-10): (25-30), and stirred at 2000-4000 r / min for 10-30 min to obtain an intermediate layer coating;

[0047] Component A, component B and red iron oxide are mixed in a mass ratio of (45-50): (9-10): (4-5), and stirred at 2000-4000 r / min for 10-30 min to obtain a surface coating.

[0048] 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 complex equipment and technical requirements, is suitable for large-scale production, and has high industrial application prospects.

[0049] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, 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 equally within the scope limited by the appended claims of the application.

[0050] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0051] Example 1

[0052] 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;

[0053] 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;

[0054] Dibutyl phthalate and xylene were mixed in a mass ratio of 2:1 and stirred for 5 minutes to obtain component C;

[0055] 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 primer;

[0056] 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;

[0057] 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.

[0058] Example 2

[0059] Mix bisphenol A type epoxy resin, xylene and ethanol according to the mass ratio of 10:1:1, stir for 15 min, heat in water bath at 50℃ for 9h, and then get A component after dissolved uniformly;

[0060] Mix m-phenylenediamine and ethanol according to the mass ratio of 4:5, and then get B component after heated in water bath at 30℃ for 4h;

[0061] Mix dibutyl phthalate and xylene according to the mass ratio of 9:5, and then get C component after stirred for 6 min;

[0062] Mix A component, B component and C component according to the mass ratio of 50:4:9, and then get bottom coating after stirred at 2500r / min for 15 min;

[0063] Mix A component, B component, C component and 80 mesh glass flake according to the mass ratio of 100:18:8:25, and then get middle coating after stirred at 2500r / min for 15 min;

[0064] Mix A component, B component and 100 mesh iron oxide red according to the mass ratio of 50:9:4, and then get top coating after stirred at 2500r / min for 15 min.

[0065] Example 3

[0066] Mix bisphenol A type epoxy resin, xylene and ethanol according to the mass ratio of 9:2:1, stir for 20 min, heat in water bath at 55℃ for 10h, and then get A component after dissolved uniformly;

[0067] Mix m-phenylenediamine and ethanol according to the mass ratio of 4:5, and then get B component after heated in water bath at 35℃ for 5h;

[0068] Mix dibutyl phthalate and xylene according to the mass ratio of 20:9, and then get C component after stirred for 8 min;

[0069] Mix A component, B component and C component according to the mass ratio of 45:5:9, and then get bottom coating after stirred at 3000r / min for 20 min;

[0070] Mix A component, B component, C component and 100 mesh glass flake according to the mass ratio of 18:4:2:5, and then get middle coating after stirred at 3000r / min for 20 min;

[0071] Mix A component, B component and 80 mesh iron oxide red according to the mass ratio of 45:10:4, and then get top coating after stirred at 3000r / min for 20 min.

[0072] Example 4

[0073] 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;

[0074] 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;

[0075] Dibutyl phthalate and xylene were mixed in a mass ratio of 19:9 and stirred for 8 minutes to obtain component C;

[0076] 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 primer;

[0077] 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;

[0078] 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.

[0079] Example 5

[0080] 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;

[0081] 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;

[0082] Dibutyl phthalate and xylene were mixed in a mass ratio of 2:1 and stirred for 10 minutes to obtain component C;

[0083] 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 primer;

[0084] 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;

[0085] 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.

[0086] Performance test results

[0087] The coating test pieces prepared from the coatings of Examples 1 to 5 and the coating test pieces prepared from other coatings were subjected to coating detection tests. The test performance is as follows:

[0088] (1) Acid resistance and salt resistance test

[0089] Coating test pieces prepared from the coatings of Examples 1 to 5 and other coatings were immersed in 10% sulfuric acid solution and 3% sodium chloride solution prepared in distilled water, respectively, in a constant temperature water bath at 80°C. The test results are shown in Table 1.

[0090] Table 1 Test data of coating acid resistance and salt resistance

[0091]

[0092] (2) Temperature change resistance test

[0093] The coating test pieces prepared from the coatings of Examples 1 to 5 and other coatings were placed in a 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 three times. The test results are shown in Table 2.

[0094] Table 2 Coating temperature change resistance test data

[0095]

[0096] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An anti-corrosion coating for tube sheets of stainless steel tube heat exchangers, characterized in that: The invention comprises a primer, an intermediate layer and a top 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 top layer comprises component A, component B and red iron oxide; wherein component A comprises bisphenol A epoxy resin, xylene and ethanol; component B comprises m-phenylenediamine and ethanol; and component C comprises dibutyl phthalate and xylene. The mass ratio of component A, component B and component C in the primer is (45-50): (4-5): (9-10); 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); The mass ratio of component A, component B and red iron oxide in the surface coating is (45-50): (9-10): (4-5); The mass ratio of bisphenol A epoxy resin, xylene and ethanol in component A is (9-10): (1-2): (1-2); The mass ratio of the intermediate phenylenediamine and ethanol in the B component is (4-5): (4-5); The mass ratio of dibutyl phthalate to xylene in the component C is (18-20): (9-10); The size of the glass flakes is 80-100 mesh; The size of the red iron oxide is 80-100 meshes.

2. The method for preparing an anti-corrosion coating for a stainless steel tube heat exchanger tube sheet according to claim 1, characterized in that: include: Mixing bisphenol A epoxy resin, xylene and ethanol, stirring and heating 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 primer; Mixing and stirring component A, component B, component C and glass flakes to obtain an intermediate layer coating; Component A, component B and red iron oxide are mixed and stirred to obtain a surface coating.

Images