Epoxy metal primer as well as preparation method and application thereof

Abstract

The invention discloses an epoxy metal primer as well as a preparation method and application thereof, the epoxy metal primer is applied to a rust removal and rust prevention coating and coating system, the epoxy metal primer has remarkable salt fog resistance, adhesive force and weather resistance, a zinc phosphate and aluminum triphosphate composite rust prevention pigment, a modified epoxy emulsion and a high-density barium sulfate filler are adopted, the coating has excellent shielding performance, and the service life of the coating is prolonged. Corrosive media can be effectively blocked, and the salt spray resistance time is remarkably prolonged; meanwhile, the modified polysiloxane defoaming agent, the wetting leveling agent, the optimized curing agent and the optimized flash-rust inhibitor are adopted, so that the binding force between the coating and various metal substrates is enhanced, and the integrity of the coating is kept under the conditions of long-term mechanical shock, thermal cycle and damp heat. The coating is suitable for various construction conditions, simple and convenient to operate, compact and flat in coating film and capable of being widely applied to the fields of bridges, ships, petrochemical equipment and the like, the service life of a metal structure is remarkably prolonged, and maintenance and replacement cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of water-based coatings, and in particular relates to an epoxy metal primer and a preparation method and application thereof. Background Art

[0002] The wide application of metal materials in the fields of industry, construction, shipbuilding, automobiles, etc. has greatly promoted the development of modern industry. However, due to the long-term exposure of metal materials to the environment, they are corroded by oxygen, moisture, salt and other corrosive media, which makes them very susceptible to rust, resulting in the degradation of structural performance and shortened service life. Therefore, the development and application of anti-rust primers are crucial in the protection of metal materials.

[0003] Epoxy emulsion is widely used in metal anticorrosion primers because of its excellent adhesion, mechanical properties, chemical corrosion resistance and film-forming properties. By reacting with a suitable curing agent to form a dense cross-linked structure, it can effectively block the penetration of corrosive media and improve the protective performance of the coating. However, the existing anti-rust epoxy primers still have deficiencies in salt spray resistance, adhesion, weather resistance and long-term anti-rust performance. The development of a new anti-rust metal epoxy primer with excellent salt spray resistance, excellent adhesion, good weather resistance and long-term anti-rust performance is an urgent need in the current technical field.

[0004] At the same time, the current methods for dealing with rust on metal surfaces are either simple rust removal or spraying anti-rust paint after rust removal, but the paint does not have good adhesion, salt spray resistance, and cannot be well colored. Therefore, a paint product with rust removal, rust prevention and good coloring ability is needed to form a good anti-rust structure on the metal surface and extend the service life of the metal structure. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide an epoxy metal primer and a preparation method and application thereof.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: an epoxy metal primer, comprising component A and component B, wherein the mass ratio of component A to component B is 3-5:1; Calculated by weight of the epoxy metal primer raw material, the component A comprises: 170-200 parts of deionized water, 1-3 parts of preservative, 10-15 parts of dispersant, 1-3 parts of defoamer, 50-150 parts of titanium dioxide, 50-100 parts of anti-rust pigment, 100-250 parts of barium sulfate, 250-450 parts of epoxy emulsion, 2-5 parts of wetting and leveling agent, 7-13 parts of thickener; The B component includes 200-300 parts of a curing agent, 500-1000 parts of deionized water and 50-100 parts of an anti-flash rust agent.

[0009] As a preferred embodiment of the epoxy metal primer of the present invention, the dispersant includes one or more of modified styrene maleic anhydride copolymer solution, modified polyether, and acrylic copolymer polymer dispersant.

[0010] As a preferred embodiment of the epoxy metal primer of the present invention, the defoaming agent is one or more of polyether polysiloxane copolymer and modified silicone emulsion.

[0011] As a preferred embodiment of the epoxy metal primer of the present invention, the anti-rust pigment is composed of anti-rust pigment 1 and anti-rust pigment 2, wherein the anti-rust pigment 1 is a zinc phosphate anti-rust pigment, and the anti-rust pigment 2 is an aluminum tripolyphosphate anti-rust pigment.

[0012] As a preferred embodiment of the epoxy metal primer of the present invention, the anti-rust pigment comprises 40-60 parts of anti-rust pigment 1 and 10-40 parts of anti-rust pigment 2.

[0013] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing an epoxy metal primer.

[0014] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing an epoxy metal primer, comprising: Component A: add deionized water, preservative, defoamer, dispersant, titanium dioxide, and barium sulfate in sequence at a speed of 200-500 r / min, increase the speed to 1000-1200 r / min, and disperse for 8-15 minutes to obtain the first part of slurry; put the first part of slurry into a horizontal sand mill for grinding; add epoxy emulsion and wetting and leveling agent to the ground first part of slurry, and evenly disperse at 500-700 r / min for 10-15 minutes, then add thickener at a stirring speed of 1000-1200 r / min, and continue stirring for 10-20 minutes to obtain component A; Component B: add deionized water and anti-flash rust agent to the curing agent, mix well, and obtain component B.

[0015] As a preferred embodiment of the epoxy metal primer of the present invention, the epoxy metal primer is used in the preparation of rust-removing and rust-preventing coatings.

[0016] In order to solve the above technical problems, the present invention also provides the following technical solutions: a rust-removing and rust-preventing coating, comprising an epoxy metal primer, a rust conversion agent and a two-component polyurethane topcoat.

[0017] In order to solve the above technical problems, the present invention also provides the following technical solutions: a rust-removing and rust-proofing coating, which is obtained by coating the rust-removing and rust-proofing coating, wherein, from the inside to the outside, it includes a rust conversion layer coated on the rusty metal surface, an epoxy primer layer coated on the rust conversion layer, and a topcoat layer coated on the epoxy primer layer.

[0018] As a preferred embodiment of the rust removing and anti-rust coating of the present invention, the topcoat layer material is a two-component polyurethane topcoat; the rust conversion liquid layer has a thickness of 20-30 μm, the epoxy anti-rust primer has a thickness of 40-50 μm, and the two-component polyurethane topcoat layer has a thickness of 30-40 μm.

[0019] Beneficial effects of the invention: The invention provides an epoxy metal primer and a preparation method thereof, and applies the epoxy metal primer to rust removal and rust prevention coatings and coating systems, which have significant salt spray resistance, adhesion, and weather resistance. The coating adopts zinc phosphate and aluminum tripolyphosphate composite rust prevention pigments, modified epoxy emulsions, and high-density barium sulfate fillers, and has excellent shielding properties, can effectively block corrosive media, and significantly improve the salt spray resistance time; at the same time, the modified polysiloxane defoamer, wetting and leveling agent, and optimized curing agent and anti-flash rust agent formula are adopted to enhance the bonding force between the coating and various metal substrates, and maintain the integrity of the coating under long-term mechanical shock, thermal cycle, and wet and hot conditions; in addition, by introducing a rust conversion agent, efficient conversion of metal surface rust is achieved, and a three-layer structure is formed with the epoxy primer and the two-component polyurethane topcoat, further improving the mechanical strength, wear resistance, and corrosion resistance of the coating system; finally, the invention has a variety of construction conditions, is easy to operate, and has a dense and smooth coating film, and can be widely used in bridges, ships, petrochemical equipment, automobile chassis, and other fields, significantly extending the service life of metal structures and reducing maintenance and replacement costs. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0023] The following examples of the present invention use raw materials as follows: The preservative used is Pengtu's BM-6; The dispersant used is BYK 2080; The defoaming agent used is Digo 902W; Titanium dioxide uses Dongjia 2377; Anti-rust pigment 1 uses zinc phosphate from Sanjing; Anti-rust pigment 2 uses APW-Ⅱ from Sanjing; Barium sulfate adopts Guangyuan GS5000; The epoxy emulsion adopts 0254 from Yuanbang Chemical; The wetting and leveling agent is Digo 4100; The thickener is Wanhua U905; The curing agent is 702 from Yuanbang Chemical; The anti-flash rust agent used is Enze's HY-78.

[0024] Example 1

[0025] This embodiment provides a method for preparing an epoxy metal primer, specifically: Weigh the raw materials according to the following formula: Component A: 191 parts of deionized water, 2 parts of preservative (2-methyl-4-isothiazoline-3-one), 12 parts of dispersant (modified styrene maleic anhydride copolymer), 2 parts of defoamer (polyether modified silicone copolymer emulsion), 100 parts of titanium dioxide (rutile titanium dioxide), 50 parts of anti-rust pigment 1 (zinc phosphate), 30 parts of anti-rust pigment 2 (aluminum tripolyphosphate), 200 parts of barium sulfate (1250 mesh), 400 parts of epoxy emulsion (water-based macromolecular epoxy emulsion), 3 parts of wetting and leveling agent (polyether modified polysiloxane), 10 parts of thickener (polyurethane thickener); Component B: 200 parts of curing agent (modified polyamine), 725 parts of deionized water and 75 parts of anti-flash rust agent (water-based anti-flash rust agent).

[0026] Preparation of component A: Deionized water, preservative, defoamer, dispersant, titanium dioxide, and barium sulfate were added in sequence at a speed of 300 r / min, and the speed was increased to 1200 r / min, and the mixture was dispersed for 15 minutes to obtain the first part of slurry; the first part of slurry was put into a horizontal sand mill for grinding; epoxy emulsion and wetting and leveling agent were added to the ground first part of slurry, and the mixture was uniformly dispersed at 700 r / min for 15 minutes, and then a thickener was added at a stirring speed of 1200 r / min, and the mixture was stirred for 10 minutes to obtain component A; Preparation of component B: Add deionized water and anti-flash rust agent to the curing agent, stir and mix evenly to obtain component B.

[0027] Example 2

[0028] The coating formula of the present embodiment is as follows: Component A: 191 parts of deionized water, 2 parts of preservative (2-methyl-4-isothiazoline-3-one), 12 parts of dispersant (modified styrene maleic anhydride copolymer), 2 parts of defoamer (polyether modified silicone copolymer emulsion), 100 parts of titanium dioxide (rutile titanium dioxide), 50 parts of anti-rust pigment 1 (zinc phosphate), 30 parts of anti-rust pigment 2 (aluminum tripolyphosphate), 200 parts of barium sulfate (1250 mesh), 450 parts of epoxy emulsion (water-based macromolecular epoxy emulsion), 3 parts of wetting and leveling agent (polyether modified polysiloxane), 10 parts of thickener (polyurethane thickener); Component B: 250 parts of curing agent (modified polyamine), 725 parts of deionized water and 75 parts of anti-flash rust agent (water-based anti-flash rust agent).

[0029] Preparation of component A: Deionized water, preservative, defoamer, dispersant, titanium dioxide, and barium sulfate were added in sequence at a speed of 300 r / min, the speed was increased to 1200 r / min, and the mixture was dispersed for 15 minutes to obtain the first part of slurry; The first part of the slurry is fed into a horizontal sand mill for grinding; Add epoxy emulsion and wetting and leveling agent to the first part of the slurry after grinding, and evenly disperse them at 700 r / min for 15 minutes, then add thickener at a stirring speed of 1200 r / min, and continue stirring for 10 minutes to obtain component A; Preparation of component B: Add deionized water and anti-flash rust agent to the curing agent, stir and mix evenly to obtain component B.

[0030] Example 3

[0031] The coating formula of the present embodiment is as follows: Component A: 191 parts of deionized water, 2 parts of preservative (2-methyl-4-isothiazoline-3-one), 12 parts of dispersant (modified styrene maleic anhydride copolymer), 2 parts of defoamer (polyether modified silicone copolymer emulsion), 100 parts of titanium dioxide (rutile titanium dioxide), 40 parts of anti-rust pigment 1 (zinc phosphate), 40 parts of anti-rust pigment 2 (aluminum tripolyphosphate), 200 parts of barium sulfate (1250 mesh), 400 parts of epoxy emulsion (water-based macromolecular epoxy emulsion), 3 parts of wetting and leveling agent (polyether modified polysiloxane), 10 parts of thickener (polyurethane thickener); Component B: 200 parts of curing agent (modified polyamine), 725 parts of deionized water and 75 parts of anti-flash rust agent (water-based anti-flash rust agent).

[0032] Preparation of component A: Deionized water, preservative, defoamer, dispersant, titanium dioxide, and barium sulfate were added in sequence at a speed of 300 r / min, the speed was increased to 1200 r / min, and the mixture was dispersed for 15 minutes to obtain the first part of slurry; The first part of the slurry is fed into a horizontal sand mill for grinding; Add epoxy emulsion and wetting and leveling agent to the first part of the slurry after grinding, and evenly disperse them at 700 r / min for 15 minutes, then add thickener at a stirring speed of 1200 r / min, and continue stirring for 10 minutes to obtain component A; Preparation of component B: Add deionized water and anti-flash rust agent to the curing agent, stir and mix evenly to obtain component B.

[0033] Table 1 is a comparison of the performance test results of epoxy metal primers applied on metal surfaces in different embodiments: Table 1 Performance test of epoxy metal primers prepared in Examples 1 to 3 applied on metal surfaces project index Example 1 Example 2 Example 3 Adhesion (cross-cut test / grade) ≤1 0 0 0 Pencil hardness Agreed 2H 2H 2H Flash rust inhibition normal normal normal normal Water resistance / h Agreed 500h 600h 520h Salt spray resistance / h Agreed 960h 1150h 1030h It can be seen from the data in Table 1 that the epoxy metal primers prepared in Examples 1 to 3 of the present invention all have good adhesion, salt spray resistance and other properties.

[0034] Among them, in Example 2, the ratio of "epoxy-curing agent" is adjusted by a standard algorithm formula, specifically: the amount of curing agent = (emulsion amount * curing agent active hydrogen equivalent) / (epoxy equivalent * excess ratio). In Example 2, compared with Examples 1 and 3, the amount of curing agent added is increased, and the amount of epoxy emulsion added is increased according to a reasonable ratio. From the performance test results, it can be seen that after the curing agent and epoxy emulsion are increased, the water resistance and salt spray resistance time are increased. It can be seen that a reasonable curing agent and epoxy emulsion are combined to effectively improve the water resistance and salt spray resistance of the metal primer.

[0035] Comparative Example 1 The difference between this comparative example and Example 2 is that the dispersant is adjusted to the sodium salt dispersant product of "Nopco 5040", and the remaining steps and processes are referred to Example 1, to obtain the epoxy metal primer prepared under the conditions of different types of dispersants in this comparative example, and the relevant properties are measured and compared with Example 1. The results are shown in Table 2.

[0036] Table 2 Composition obtained in Comparative Example 1 project index Example 1 Comparative Example 1 Adhesion (cross-cut test / grade) ≤1 0 0 Pencil hardness Agreed 2H H Flash rust inhibition normal normal normal Water resistance / h Agreed 500h 355h Salt spray resistance / h Agreed 960h 460h Storage stability (50℃ 7 days) No precipitation, flocculation, or severe stratification normal precipitation

[0037] Comparative Example 2 The difference between this comparative example and Example 1 is that the dispersant is adjusted to an amine salt dispersant, and an amine salt dispersant product is selected. The remaining steps and processes are all referred to Example 1. The epoxy metal primer prepared under the conditions of different types of dispersants in this comparative example is obtained, and the relevant properties are measured and compared with Example 1. The results are shown in Table 3.

[0038] Table 3 Epoxy metal primer obtained in Comparative Example 2 project index Example 1 Comparative Example 1 Adhesion (cross-cut test / grade) ≤1 0 1 Pencil hardness Agreed 2H H Flash rust inhibition normal normal normal Water resistance / h Agreed 500h 300h Salt spray resistance / h Agreed 960h 550h Storage stability (50℃ 7 days) No precipitation, flocculation, or severe stratification normal Anti-coarsening, flocculation Combining Tables 2 and 3, it can be seen that the type of dispersant has a significant effect on the performance of the composition. It can be seen from the test indicators that after the dispersant in the formula of Example 1 was replaced by sodium salt and amine salt dispersants, respectively, unsatisfactory conditions were found in the test indicators such as adhesion, water resistance, and salt spray resistance. This is because ordinary sodium salts and amine salts cannot be used for epoxy anti-rust primers. Sodium salts are not suitable because they will cause the water resistance and salt spray resistance of the metal primer to be insufficient; amine salt dispersants are not suitable because epoxy emulsions themselves are very easy to react with amines, so amine substances cannot be contained in the A component system. At the same time, the two comparative examples after adjusting the type of dispersant were unqualified in the storage stability test. After replacing with sodium salt dispersants, the metal primer of comparative example 1 showed precipitation in the storage stability test at 50°C for 7 days, and after replacing with amine salt dispersants, the metal primer of comparative example 2 showed anti-coarsening and flocculation in the storage stability test at 50°C for 7 days, both of which did not meet the performance indicators of the metal primer.

[0039] In summary, the choice of dispersant type has a great influence on the performance indicators of epoxy metal primer. Choosing a suitable dispersant can effectively improve the water resistance, salt spray resistance, and especially the storage stability of epoxy metal primer.

[0040] Comparative Example 3

[0041] The difference between this comparative example and Example 1 is that the amount of curing agent added is increased to 350 parts, and the remaining steps and processes are all referred to Example 1.

[0042] The epoxy metal primer prepared in Comparative Example 3 was tested, and the comparison results with Examples 1 and 2 are shown in Table 4.

[0043] Table 4 Epoxy Metal Primer Obtained in Comparative Example 3 project index Example 1 Example 2 Comparative Example 3 Adhesion (cross-cut test / grade) ≤1 0 0 0 Pencil hardness Agreed 2H 2H H Flash rust inhibition normal normal normal normal Water resistance / h Agreed 500h 600h 430h Salt spray resistance / h Agreed 960h 1150h 800h It can be seen from Table 3 that after increasing the amount of curing agent added in component B, the mechanical properties of the epoxy metal primer all showed different degrees of decline. Compared with Example 1 and Example 2, it can be found that when the epoxy emulsion and curing agent are gradually added according to the standard formula in Example 2, the overall performance of the epoxy metal primer is in an improved state, while when the curing agent is added alone in Comparative Example 3, the performance has declined. This is because when the amount of curing agent added gradually increases, excess curing agent will remain in the coating, causing the paint film to dry slowly and become sticky, thereby affecting the pencil hardness, water resistance and salt spray resistance of the metal primer.

[0044] Therefore, the addition of curing agent should be controlled within a certain range. At this time, the reaction between epoxy emulsion and curing agent reaches a balance, the cross-linking density of the coating is moderate, and it exhibits the best adhesion, salt spray resistance, water resistance and hardness, and has excellent construction performance, moderate drying time, and a dense and smooth coating.

[0045] Comparative Example 4

[0046] The difference between this comparative example and Example 1 is that the addition amount of the anti-rust pigment 1 is reduced to 0, and the addition amount of the anti-rust pigment 2 is increased to 80 parts. The rest of the formula and preparation process are the same as those of Example 1.

[0047] Comparative Example 5

[0048] The difference between this comparative example and Example 1 is that the addition amount of the anti-rust pigment 2 is reduced to 0, and the addition amount of the anti-rust pigment 1 is increased to 80 parts, and the rest of the formula and preparation process are the same as those of Example 1.

[0049] The epoxy metal primers prepared in Comparative Examples 4 and 5 were tested, and the comparison results with those in Example 1 are shown in Table 5.

[0050] Table 5 Epoxy metal primers obtained in Comparative Examples 4 and 5 project index Example 1 Comparative Example 4 Comparative Example 5 Adhesion (cross-cut test / grade) ≤1 0 1 1 Pencil hardness Agreed 2H 2H 2H Flash rust inhibition normal normal normal normal Water resistance / h Agreed 500h 480h 460h Salt spray resistance / h Agreed 960h 510h 570h It can be concluded from Table 5 that when the addition amount of the anti-rust pigment 1 and the anti-rust pigment 2 is reduced to 0 parts respectively, and compared with the anti-rust pigment 1 and the anti-rust pigment 2 of Example 1, it is found that when the anti-rust pigment 1 or the anti-rust pigment 2 is used alone, the salt spray resistance of the epoxy metal primer is not good. This is because zinc phosphate mainly provides initial corrosion protection by generating a zinc phosphate passivation layer, that is, a shielding film, and aluminum tripolyphosphate forms a chelate with the metal surface through tripolyphosphate ions, thereby enhancing the compactness of the passive film, delaying the penetration of corrosive ions, and improving the long-term salt spray resistance. Therefore, the anti-rust pigment 1 (zinc phosphate) provides initial salt spray resistance, and the anti-rust pigment 2 (aluminum tripolyphosphate) provides later salt spray resistance. The salt spray resistance time of the two can reach 1000-1200 hours when used in combination, which is extended by more than 50%, providing full-effect salt spray resistance. At the same time, the adhesion of the combination of the anti-rust pigment 1 and the anti-rust pigment 2 can be improved to level 0, which is better than level 1 when used alone.

[0051] Comparative Example 6

[0052] The difference between this comparative example and Example 1 is that the type of anti-rust pigment 1 is replaced with a borate anti-rust pigment, the added amount remains unchanged, and the rest of the formula and preparation process are the same as those of Example 1.

[0053] The epoxy metal primer prepared in Comparative Example 6 was tested, and the comparison results with those in Example 1 are shown in Table 6.

[0054] Table 6 Epoxy Metal Primer Obtained in Comparative Example 6 project index Example 1 Comparative Example 6 Adhesion (cross-cut test / grade) ≤1 0 1 Pencil hardness Agreed 2H H Flash rust inhibition normal normal normal Water resistance / h Agreed 500h Coating blistering and peeling Salt spray resistance / h Agreed 960h 450h As shown in Table 6, when the zinc phosphate antirust pigment 1 is replaced with a borate antirust pigment, the epoxy metal primer has a significant decline in various properties, mainly in the reduction of pencil hardness to H. In the water resistance test, the coating bubbling and shedding occurred, and the salt spray resistance was only 450h. This is a decrease of more than 50%, which is because: 1. Borate anti-rust pigments have relatively high solubility in aqueous environments and are prone to forming borate ions. These ions have poor stability under neutral or weakly alkaline conditions and are difficult to form a dense passivation film, which makes it impossible to effectively prevent the penetration of corrosive ions, resulting in a weak initial shielding effect; 2. Compared with zinc phosphate, borate pigments have weaker chelating ability for metal ions, especially they cannot form a high-density, stable passivation layer on the metal surface, making their initial anti-corrosion effect and long-term salt spray resistance inferior to zinc phosphate, and they cannot provide continuous and effective protection; 3. Borate anti-rust pigments are more likely to hydrolyze or precipitate in the coating system, especially in high humidity and high salt spray environments, which will lead to decreased adhesion and loose structure of the coating, reducing the mechanical strength and durability of the coating, affecting its long-term application.

[0055] At the same time, the synergistic effect with aluminum tripolyphosphate is poor. Specifically, the protection mechanism of aluminum tripolyphosphate relies on its strong chelating ability with metal ions to form a dense passivation layer. When zinc phosphate is replaced by borate, the density of the passivation layer is greatly reduced.

[0056] Furthermore, the combination of zinc phosphate and aluminum tripolyphosphate can form a double-layer shielding structure - initial rapid protection (zinc phosphate) + long-term deep protection (aluminum tripolyphosphate). However, the combination of borate + aluminum tripolyphosphate lacks this synergistic effect, and both initial and long-term corrosion resistance are poor.

[0057] Comparative Example 7

[0058] The difference between this comparative example and Example 1 is that the epoxy emulsion is replaced with "128 epoxy resin", and the rest of the formula and preparation process are the same as those of Example 1.

[0059] The epoxy metal primer prepared in Comparative Example 7 was tested, and the comparison results with those in Example 1 are shown in Table 6.

[0060] Table 7 Epoxy metal primer obtained in Comparative Example 7 project index Example 1 Comparative Example 7 Adhesion (cross-cut test / grade) ≤1 0 2 Pencil hardness Agreed 2H 2H Flash rust inhibition normal normal normal Water resistance / h Agreed 500h 450h Salt spray resistance / h Agreed 960h 500h It can be seen from Table 7 that when the epoxy emulsion is replaced with "128 epoxy resin", the performance of the epoxy metal primer has declined significantly, as shown in the following: 1. The adhesion of 128 epoxy resin on metal substrate is significantly reduced. The adhesion of 128 epoxy resin on metal substrate is much lower than that of water-based macromolecular epoxy emulsion. The cross-cut test is reduced from level 0 to level 2. This is because the 128 epoxy resin coating has high rigidity and cannot adapt to the subtle changes on the surface of rusty metal. The bonding force between the rust conversion film and the metal substrate is weak, and local peeling or delamination may occur, which will lead to weakened adhesion; 2. The fogging and water resistance performance is poor. After replacing 128 epoxy resin to prepare the metal primer, the salt spray resistance of the primer dropped to 500 hours, which is nearly 50% lower than the salt spray resistance of 960 hours after using the corresponding water-based macromolecular epoxy emulsion.

[0061] This is because 128 epoxy resin is difficult to emulsify, resulting in the inability to form a dense shielding layer when it is used to prepare metal primer, which makes it easy for corrosive ions to penetrate, thereby accelerating the failure of the coating's protective function; at the same time, the water resistance of the primer is also reduced from 500 hours to 4500 hours, and the surface coating is prone to problems such as film seepage, bubbling, and rust expansion in high humidity and salt spray environments.

[0062] Furthermore, the experimental data of Comparative Example 7 show that 128 epoxy resin cannot provide the same performance as the water-based macromolecular epoxy emulsion in the formulation of the epoxy metal primer prepared in the present invention. Although it has certain cost advantages, it performs poorly in terms of adhesion, salt spray resistance and water resistance. The water-based macromolecular epoxy emulsion selected in the present invention can provide a higher cross-linking density and a better shielding effect, and performs better in high-performance anti-rust coatings.

[0063] This shows that not all epoxy emulsions are suitable for the high-performance anti-rust formulation of the present invention. The material combination selected by the present invention is the best solution after repeated tests and optimization verification, and has significant technical advantages and practical application value.

[0064] Example 4

[0065] This embodiment provides a rust-removing and rust-preventing coating, including a rust conversion agent, an epoxy metal primer and a two-component polyurethane topcoat, which are reasonably used in combination according to specific rust-removing and rust-preventing parts.

[0066] Specifically, the active ingredients in rust converters are usually organic carboxylic acids, phosphoric acid and their salts. Its working principle is to use the active ingredients to contact the metal surface with ferric oxide (Fe2O3 red rust) and ferric oxide (Fe3O4 blue oxide). Through the chemical conversion phase film corrosion inhibition mechanism, after 0.5-1 hour at room temperature, the rust and oxide scale are naturally converted to form a tight bright gray-black anti-rust film layer, which blocks the contact between the metal and oxygen and water vapor in the atmosphere, and slows down the oxidation process of the metal.

[0067] The main function of the rust converter is to react chemically with the iron oxide (rust) on the metal surface to form a dense, indestructible protective layer (passivation film). This protective layer can isolate air and moisture, thereby preventing the iron from oxidizing when it comes into contact with air and moisture and generating new rust.

[0068] Furthermore, the key ingredients in epoxy metal primer include epoxy emulsion (modified macromolecular epoxy resin), composite anti-rust pigment (zinc phosphate and aluminum tripolyphosphate), dispersant (modified styrene maleic anhydride copolymer), anti-flash rust agent (water-based anti-flash rust agent), etc., which provide strong water resistance, salt spray resistance, etc.

[0069] Specifically, during construction, there are micron-scale concave-convex structures on the surface of the rust conversion layer after curing. These microstructures provide more interlocking sites for the epoxy primer coating. When coating, the epoxy primer can partially penetrate into the pores of the rust conversion layer. After the metal primer is cured, a physical interlocking is formed, which enhances the mechanical adhesion of the coating. In addition, the high cross-linking density polymer network formed after the epoxy metal primer is cured can provide effective mechanical support for the rust conversion layer and prevent the coating from cracking or peeling.

[0070] Furthermore, after the epoxy metal primer is cured, the two-component polyurethane topcoat sprayed has excellent weather resistance and chemical stability. Its dense coating film further enhances the barrier effect against ultraviolet rays, moisture and corrosive substances, providing better protection for the metal surface and making it more rust-resistant.

[0071] The coating system of the present invention adopts a multi-layer structure combination design of a rust converter, an epoxy metal primer, and a two-component polyurethane topcoat. Through the scientifically optimized multi-layer synergistic effect, the rust converter converts the loose rust on the metal surface into a dense passivation film, fills the microscopic pores and forms a rough surface, reduces the occurrence of subsequent corrosion, and enhances the adhesion of the subsequent coating; the epoxy metal primer penetrates and embeds the microporous structure of the passivation layer, mechanically locks with its surface, forms a stable base coating, provides excellent adhesion and corrosion resistance, and finally the two-component polyurethane topcoat and the microporous structure on the surface of the epoxy primer are interlocked, so that it is more closely combined with the epoxy metal primer, improves the stability, mechanical strength and aesthetics of the overall coating, and finally forms a multi-layer protection system from the inside to the outside. Multi-layer shielding superposition makes it difficult for corrosive media to penetrate the entire coating system, thereby significantly extending the anti-rust life of the metal, and has excellent resistance to high salt spray and high humidity environments. The overall system achieves high bonding between the layers of the coating through physical locking, and enhances the anti-peeling performance.

[0072] It should be noted that in the prior art, separate rust converters or anti-rust primers are mostly used for short-term protection, while the present invention achieves a balance between long-term corrosion resistance and mechanical strength through scientific combination. It not only has the functions of rust removal, rust prevention, and long-term protection, but also has excellent adhesion and mechanical properties, which significantly improves the overall performance of the coating, breaks through the limitations of the prior art, and provides a new solution for metal surface protection.

[0073] Comparative Example 8

[0074] In this comparative example, the epoxy metal primer obtained in comparative example 7 (epoxy emulsion is replaced by 128 epoxy resin) is applied to the rust removing and anti-rust coating given in Example 4, and the epoxy metal primer obtained in combination with Example 1 applied to the rust removing and anti-rust coating is compared with the epoxy metal primer obtained in comparative example 7 applied to the rust removing and anti-rust coating, and the key properties such as adhesion, water resistance and salt spray resistance are tested on rusty metal, as shown in Table 8 below.

[0075] Table 8 Rust-removing and anti-rust coating obtained in Comparative Example 8 project index Example 4 (Epoxy Emulsion) Comparative Example 8 (Epoxy Resin) Adhesion (cross-cut test / grade) ≤1 0 1 Pencil hardness Agreed 2H 2H Flash rust inhibition normal normal normal Water resistance / h Agreed 600h 500h Salt spray resistance / h Agreed 1100h 600h As shown in Table 8, the rust-removing and rust-proofing coating obtained by using the epoxy metal primer prepared by the formula of the present invention, when applied on rusty metal, has good adhesion (grade 0), good water resistance (no change after 600 hours) and excellent salt spray resistance (no obvious corrosion after 1100 hours). However, the epoxy metal primer after replacing the epoxy resin has changed in performance test when the rust converter and the two-component polyurethane topcoat remain unchanged. Specifically:

[0076] 1. Adhesion decreases. The epoxy emulsion of the present invention forms a strong cross-linked structure through physical intercalation with the rust conversion film and the metal surface, achieving excellent adhesion. The 128 epoxy resin in Comparative Example 8 has poor adhesion itself, resulting in the overall primer being unable to form a stable bond with the rust conversion film or the metal surface, causing the coating to be easily peeled off. Despite the reinforcement of the two-component polyurethane topcoat, the overall adhesion still drops to level 1.

[0077] 2. The salt spray resistance is significantly reduced. When the epoxy primer of the present invention is applied, it can partially penetrate into the pores of the rust conversion layer. After the metal primer is cured, a physical fit is formed, thereby enhancing the mechanical adhesion of the coating. Moreover, the high cross-linking density polymer network formed after the epoxy metal primer is cured can provide effective mechanical support for the rust conversion layer, prevent cracking or peeling of the coating, and effectively block the penetration of corrosive ions. The salt spray resistance time is as long as more than 1,000 hours. Combined with the mechanical strength such as weather resistance provided by the two-component polyurethane topcoat, the coating system formed by the overall rust removal and rust prevention coating has better performance.

[0078] However, the 128 epoxy resin in Comparative Example 8 is not easily emulsified, resulting in partial flocculation and failure of the system, which results in the metal primer prepared using it being unable to form a dense shielding layer, so that corrosive ions are easy to penetrate, thereby accelerating the failure of the protective function of the coating. The surface coating is prone to problems such as film seepage, bubbling, and rust expansion in high humidity and salt spray environments. After it is cured and coated with a two-component polyurethane topcoat, it still cannot achieve good salt spray resistance.

[0079] It can be seen that not all epoxy metal primer formulations can be combined with rust converters and two-component polyurethane topcoats to form a three-layer protective structure with excellent performance.

[0080] Alternative materials in the prior art cannot provide the same performance in practical applications. This is not only due to the limitations of the materials themselves, but also because the coordinated optimization of the multi-layer structure and materials of the present invention is the result of scientific design and repeated verification. The present invention significantly improves the anti-rust, mechanical and weather resistance of the coating through specific material selection and interlayer interaction.

[0081] Example 5

[0082] This embodiment provides a rust-removing and rust-preventing coating, which includes, from the inside to the outside, a rust conversion liquid layer coated on the rusty metal surface, an epoxy primer layer coated on the rust conversion layer, and a topcoat layer coated on the epoxy primer layer, wherein the topcoat layer material is a two-component polyurethane topcoat.

[0083] Furthermore, in a specific construction, the thickness of the rust conversion liquid layer is 30 μm, the thickness of the epoxy primer layer can be applied to 50 μm, and the thickness of the two-component polyurethane topcoat layer is 40 μm.

[0084] It should be noted that the two-component polyurethane topcoat layer can provide better coloration as well as excellent weather resistance, fullness and gloss for the overall protective coating.

[0085] Preferably, the rust conversion agent is applied to the rusty metal surface by roller coating or brush coating, so that the rust conversion liquid can better penetrate into the pores of the rust, react deeply, and react better with the epoxy metal primer to form a protective layer; Preferably, the epoxy primer layer is sprayed so that it can better combine with the rust conversion liquid layer; Preferably, the two-component polyurethane topcoat layer is sprayed to make the metal surface more uniform and beautiful.

[0086] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An epoxy metal primer, characterized in that: include, Component A and component B, wherein the mass ratio of component A to component B is 3-5:1; Calculated by weight of the epoxy metal primer raw material, the component A comprises: 170-200 parts of deionized water, 1-3 parts of preservative, 10-15 parts of dispersant, 1-3 parts of defoamer, 50-150 parts of titanium dioxide, 50-100 parts of anti-rust pigment, 100-250 parts of barium sulfate, 250-450 parts of epoxy emulsion, 2-5 parts of wetting and leveling agent, 7-13 parts of thickener; The B component includes, 200-300 parts of curing agent, 500-1000 parts of deionized water and 50-100 parts of anti-flash rust agent.

2. The epoxy metal primer according to claim 1, characterized in that: The dispersant includes one or more of modified styrene maleic anhydride copolymer solution, modified polyether, and acrylic copolymer polymer dispersant.

3. The epoxy metal primer as claimed in claim 2, characterized in that: The defoaming agent is one or more of polyether polysiloxane copolymer and modified silicone emulsion.

4. The epoxy metal primer according to claim 1, characterized in that: The anti-rust pigment is composed of an anti-rust pigment 1 and an anti-rust pigment 2, wherein the anti-rust pigment 1 is a zinc phosphate anti-rust pigment, and the anti-rust pigment 2 is an aluminum tripolyphosphate anti-rust pigment.

5. The epoxy metal primer as claimed in claim 4, characterized in that: The anti-rust pigment comprises 40-60 parts of the anti-rust pigment 1 and 10-40 parts of the anti-rust pigment 2.

6. The method for preparing the epoxy metal primer according to any one of claims 1 to 5, characterized in that: include, Component A: add deionized water, preservative, defoamer, dispersant, titanium dioxide, and barium sulfate in sequence at a speed of 200-500 r / min, increase the speed to 1000-1200 r / min, and disperse for 8-15 minutes to obtain the first part of slurry; The first part of the slurry is fed into a horizontal sand mill for grinding; Add epoxy emulsion and wetting and leveling agent to the first part of the slurry after grinding, and evenly disperse them at 500-700 r / min for 10-15 minutes, then add thickener at a stirring speed of 1000-1200 r / min, and continue stirring for 10-20 minutes to obtain component A; Component B: Add deionized water and anti-flash rust agent to the curing agent, stir and mix evenly to obtain component B.

7. Use of any one of claims 1 to 5 epoxy metal primers in the preparation of rust-removing and rust-preventing coatings.

8. A rust-removing and rust-preventing coating, characterized in that: The epoxy metal primer according to claim 1 to claim 5 further comprises: Rust converter, two-component polyurethane topcoat.

9. A rust-removing and rust-preventing coating, characterized in that: Obtained by coating the rust-removing and rust-preventing coating as claimed in claim 8, wherein, from the inside to the outside, it includes a rust conversion liquid layer coated on the rusty metal surface, an epoxy primer layer coated on the rust conversion layer, and a topcoat layer coated on the epoxy primer layer.

10. The rust-removing and rust-preventing coating according to claim 9, characterized in that: The topcoat layer material is a two-component polyurethane topcoat.