Manufacturing method of corrosion-resistant pre-coated steel strip and pre-coated hot-dip coating steel strip resistant to corrosion of CX-grade extreme environment

Abstract

The invention relates to the technical field of continuous coating of steel strips, and particularly discloses a manufacturing method of a corrosion-resistant pre-coating film steel strip and a pre-coating film hot-dip coating layer steel strip resistant to CX-grade extreme environment corrosion. According to the invention, the preparation method of the pre-coating hot-dip coating steel strip is optimized, and the pre-coating hot-dip coating steel strip prepared according to the method disclosed by the invention can sufficiently resist corrosion even in a CX-grade corrosion environment due to the synergistic cooperation of the alloy coating primer layer, the alloy coating finish paint layer and the passivation layer generated in passivation treatment; and the service life is longer and the replacement frequency is lower, so that the defects in the related technology are overcome.

Description

Technical Field

[0001] The present application relates to the technical field of continuous coating of steel strips, and more specifically, to a method for manufacturing a corrosion-resistant pre-coated steel strip and a pre-coated hot-dip coated steel strip resistant to CX-level extreme environmental corrosion. Background Art

[0002] Corrosion-resistant pre-coated steel strip, commonly known as color-coated steel strip, is a composite material obtained by processing a layer of hot-dip coating on a steel substrate and then undergoing pre-coating treatment. It can usually increase the life of the steel strip from 3-5 years to 25-30 years, and can reduce the frequency of replacement of the steel strip. It is a typical low-carbon, energy-saving advanced steel material.

[0003] According to the ISO9223 standard, the corrosion environment is divided into five basic levels: C1-C5, of which C3 is a medium corrosion environment, C1 and C2 are very low and low-level corrosion environments, and C4 and C5 are high and very high-level corrosion environments. With the serious environmental pollution, the extremely harsh CX level has been added, for a total of six levels. In recent years, with the development of my country's large-scale animal husbandry, modern assembly construction industry and modern science and technology represented by 5G, the demand for steel strips used in CX extreme environments has increased.

[0004] With respect to the above-mentioned related technologies, the inventor believes that the corrosion resistance principle of pre-coated steel strips is mainly to shield and isolate metal materials from corrosive media, so that corrosive media cannot directly corrode metal materials, thereby increasing service life. However, due to the low bonding rate between the alloy coating and the primer, the low bonding rate between the primer and the topcoat, the high porosity inside the primer and the topcoat, and the large maximum gap inside the primer and the topcoat, the shielding and isolation performance of the pre-coated steel strips currently on the market is poor, so it is difficult to serve for a long time in a CX-level corrosion environment, resulting in the need for frequent replacement. Summary of the invention

[0005] At present, the isolation performance of pre-coated steel strips on the market is poor, and it is difficult to serve for a long time in a CX-level corrosion environment, and it needs to be replaced frequently. In order to improve this defect, the present application provides a method for manufacturing a corrosion-resistant pre-coated steel strip and a pre-coated hot-dip coated steel strip resistant to CX-level extreme environment corrosion.

[0006] In a first aspect, the present application provides a method for manufacturing a corrosion-resistant pre-coated steel strip, which adopts the following technical solution: A method for manufacturing a corrosion-resistant pre-coated steel strip, comprising the following steps: (1) hot-dip plating a steel substrate in a continuous hot-dip plating production line, and then pre-passivating the formed alloy coating so that the contact angle between the alloy coating and the passivation solution is ≤15°, and then passivating the alloy coating with the passivation solution; (2) pre-treatment of the passivated alloy coating before chemical coating in a continuous pre-coating film production line, so that the contact angle between the passivated alloy coating and the chemical coating liquid is ≤15°, and then chemical coating treatment of the passivated alloy coating is performed using the chemical coating liquid; (3) applying a primer to the surface of the alloy coating after chemical coating in a continuous pre-coating film production line to form a primer layer; the bonding rate between the primer and the alloy coating is ≥99.999%, the porosity of the primer layer is ≤0.001%, and the maximum gap of the primer layer is ≤600nm; (4) The surface of the primer layer is alkaline-washed in a continuous pre-coating production line, and then a topcoat is applied to form a topcoat layer, thereby completing the preparation of the steel strip; the bonding rate between the topcoat and the primer layer is ≥99.999%, the porosity of the topcoat layer is ≤0.001%, and the maximum gap between the primer layer and the topcoat layer is ≤600nm.

[0007] By adopting the above technical scheme, the present application optimizes the preparation method of pre-coated hot-dip coated steel strip. First, a pre-passivation pretreatment is performed to control the contact angle between the alloy coating and the passivation solution; then the alloy coating is passivated so that a dense passivation layer can be formed on the surface of the alloy coating. Then, by performing a pre-chemical coating pretreatment, the contact angle between the passivated alloy coating and the chemical coating solution is controlled, and then the passivated alloy coating is subjected to a chemical coating treatment, so that a dense chemical coating is further formed on the surface of the passivation layer. On the basis of forming the above-mentioned passivation layer and chemical coating, the present application realizes the control of performance parameters such as the bonding rate between the alloy coating and the primer, the bonding rate between the primer and the topcoat, the porosity inside the primer and the topcoat, and the maximum gap inside the primer and the topcoat, and increases the barrier shielding effect of the primer layer and the topcoat layer, so that the corrosive medium is not easy to pass through the primer layer and the topcoat layer, and limits the contact between the corrosive medium and the alloy coating. Thanks to the coordinated cooperation of the alloy coating, primer layer and topcoat layer, the pre-coated hot-dip coated steel strip prepared according to the method of the present application can fully resist corrosion even in a CX-level corrosion environment, has a longer service life and a lower replacement frequency, thus overcoming the defects in the related technology.

[0008] Preferably, the passivation treatment is performed by spraying or immersion.

[0009] By adopting the above technical solution, the efficiency and uniformity of the passivation treatment can be improved, which helps to ensure the quality of the passivation layer.

[0010] Preferably, in step (1) and step (2) of the method, the pretreatment is carried out in the following manner: alkaline washing is performed using a 1-2wt% sodium hydroxide solution, followed by rinsing with water, then acid washing is performed using a 1-2wt% hydrochloric acid solution, followed by rinsing again, and finally drying to complete the pretreatment steps.

[0011] By adopting the above technical solution, the cleanliness of the alloy coating surface can be fully improved, providing good conditions for subsequent passivation and coating processes.

[0012] Preferably, both the primer and the topcoat contain resin materials, and the resin materials include a first resin and a second resin. The curing temperature of the first resin is 220-260°C, and the curing temperature of the second resin is 160-200°C.

[0013] By adopting the above technical solution, the present application limits the resin material contained in the primer and topcoat, and limits the curing temperature of the resin material to two ranges. When the coating is cured on the coating production line, the temperature changes from high to low, and the first resin with a high curing temperature is cured first, which will form many microscopic holes due to its transition from liquid to solid. At this time, the second resin with a low curing temperature is still in liquid state and can flow into these holes, so that the holes can be filled completely, which is conducive to reducing the porosity and reducing the maximum gap. When the temperature drops further, the second resin will also be cured.

[0014] Preferably, the weight of the second resin accounts for 20-50% of the total weight of the resin material.

[0015] By adopting the above technical solution, the present application optimizes the proportion of the second resin in the resin material, ensuring that there is a sufficient amount of resin with a low curing temperature to fill the microscopic pores generated by the resin with a high curing temperature during the curing process, which is beneficial to reducing the porosity and reducing the maximum gap.

[0016] Preferably, the primer and topcoat contain solid powder material, wherein D 90 The particle size is 100-300nm.

[0017] By adopting the above technical solution, the particle size of the solid powder material is controlled, thereby preventing the microscopic pores inside the coating from being too large due to the large particle size of the powder material, which is beneficial to reducing the porosity and the maximum gap.

[0018] Preferably, in the primer and topcoat, the proportion of the solid powder material existing in the resin in the form of a single particle is ≥ 90%, and the proportion of the solid powder material existing in the resin in the form of two or less particles is 100%.

[0019] By adopting the above technical solution, the solid powder material can be evenly distributed in the coating, thereby reducing the aggregation of particles, which is beneficial to reducing the holes caused by agglomeration between solid powders, and is beneficial to reducing the porosity and the maximum gap.

[0020] In summary, by taking the above measures, the porosity of the primer and topcoat layers can be guaranteed to be ≤0.001% and the maximum voids ≤600nm.

[0021] In a second aspect, the present application provides a pre-coated hot-dip coated steel strip resistant to CX-level extreme environment corrosion, adopting the following technical solution.

[0022] A pre-coated hot-dip coated steel strip resistant to CX-level extreme environmental corrosion comprises a steel substrate, an alloy coating, a primer layer and a topcoat layer, wherein the alloy coating is coated on the surface of the steel substrate, the primer layer is coated on the surface of the alloy coating, and the topcoat layer is coated on the surface of the primer layer.

[0023] By adopting the above-mentioned technical scheme, the pre-coated hot-dip coated steel strip resistant to CX-level extreme environment corrosion of the present application is coated with an alloy coating, a primer layer and a topcoat layer in sequence on the surface of the steel substrate, which can fully overcome the defects in the relevant technology, and can fully resist corrosion even in a CX-level corrosion environment, and has a longer service life and a lower replacement frequency.

[0024] Preferably, the alloy coating is an Al-Zn-Mg alloy coating, and the adhesion amount of the alloy coating is 500-550 g / m 2 .

[0025] By adopting the above technical scheme, the present application optimizes the type, thickness range and adhesion amount of the alloy coating, which helps to fully protect the steel substrate, so that the pre-coated hot-dip coated steel strip resistant to CX-level extreme environment corrosion can serve for a long time in a CX-level corrosion environment.

[0026] Preferably, the thickness of the primer layer is 8-10 μm, and the thickness of the topcoat layer is 50-60 μm.

[0027] By adopting the above technical solution, the present application optimizes the thickness range of the primer layer and the topcoat layer to help fully protect the steel substrate, so that the pre-coated hot-dip coated steel strip resistant to CX-level extreme environment corrosion can serve for a long time in a CX-level corrosion environment.

[0028] In summary, this application has the following beneficial effects: 1. The present application optimizes the preparation method of pre-coated hot-dip coated steel strip. Thanks to the coordinated cooperation of the alloy coating, primer layer and topcoat layer, the pre-coated hot-dip coated steel strip prepared according to the method of the present application can fully resist corrosion even in a CX-level corrosion environment, and has a longer service life and a lower replacement frequency, thereby overcoming the defects in the relevant technology.

[0029] 2. The present application performs pretreatment on the alloy coating before passivation in a continuous hot-dip plating production line, which can improve the efficiency and uniformity of the passivation treatment and help ensure the quality of the passivation layer.

[0030] 3. The present application performs pretreatment on the passivated alloy coating before chemical coating in a continuous pre-coating film production line, which provides good conditions for subsequent chemical coating, thereby improving the bonding rate between the primer and the alloy coating.

[0031] 4. The present application performs a pre-treatment of the primer surface after the primer is applied in a continuous pre-coating film production line before applying the topcoat, thereby improving the bonding rate between the topcoat and the primer.

[0032] 5. The present application limits the curing temperature of the resin material to two ranges. When the coating is cured on the coating production line, the temperature changes from high to low. The first resin with a high curing temperature is cured first, and many microscopic holes are formed due to its transition from liquid to solid. At this time, the second resin with a low curing temperature is still in liquid and can flow into these holes. When the temperature drops further, it will also solidify and fill the holes completely, which is beneficial to reduce the porosity and reduce the maximum gap.

[0033] 6. The present application optimizes the proportion of the second resin in the resin material to ensure that the resin with a low curing temperature has a sufficient amount to fill the microscopic holes generated by the resin with a high curing temperature during the curing process, which is beneficial to reducing the porosity and the maximum gap.

[0034] 7. The present application controls the particle size of the solid powder material, thereby preventing the microscopic pores inside the coating from being too large due to the large particle size of the powder material, which is beneficial to reducing the porosity and the maximum void. DETAILED DESCRIPTION

[0035] The present application is further described in detail below in conjunction with embodiments, preparation examples and comparative examples. The raw materials involved in the present application can all be obtained commercially. Example

[0036] Examples 1-5 The following description is given by taking Example 1 as an example.

[0037] Example 1 The primer used in this embodiment is composed of a resin material, a solid powder material and a diluent liquid material. The resin material is composed of 50wt% of a first resin and 50wt% of a second resin (referred to as the resin ratio in Table 1). The weight ratio of the solid powder material to the resin material and the diluent liquid material is 55:40:50. 90The particle size is 300nm (referred to as solid particle size in Table 1), the proportion of solid powder material in the primer resin in the form of a single particle is 90% (referred to as dispersion ratio in Table 1), the proportion of solid powder material in the form of two or less particles in the resin is 100%, and the solid powder material is polyaniline particles. The first resin is a fluorocarbon resin, the second resin is an epoxy resin, the curing temperature of the first resin is 220°C (referred to as the first curing temperature in Table 1), and the curing temperature of the second resin is 160°C (referred to as the second curing temperature in Table 1).

[0038] The topcoat used in this embodiment is formulated with a resin having the same curing temperature range as the primer.

[0039] The passivation liquid used in this embodiment is a chromium-free passivation liquid. Since the components of the chemical coating liquid and passivation liquid of various manufacturers on the market are not disclosed, as long as the chemical coating liquid and passivation liquid of the same system from the same manufacturer are used, there will be no incompatibility problem. Therefore, this application uses the chemical coating liquid and passivation liquid of the same system from the same manufacturer.

[0040] This embodiment provides a method for manufacturing a corrosion-resistant pre-coated steel strip, comprising the following steps: (1) Hot dip coating of steel substrates in a continuous hot dip coating line to obtain a coating weight of 500 g / m 2 The alloy coating is pre-treated before passivation so that the contact angle between the alloy coating and the passivation solution is 15° (referred to as the first contact angle in Table 1), and then the alloy coating is passivated using the passivation solution by spraying; in this step, the composition of the plating bath used for hot-dip plating is 55wt% Al+2.0wt% Mg+Zn; (2) pre-treatment of the passivated alloy coating before chemical coating in a continuous pre-coating film production line, so that the contact angle between the passivated alloy coating and the chemical coating liquid is 15° (referred to as the second contact angle in Table 1), and then chemical coating treatment of the passivated alloy coating is performed using the chemical coating liquid; (3) coating the surface of the alloy coating after chemical coating to form a primer layer; the bonding rate between the primer and the alloy coating is 99.9992% (referred to as the first bonding rate in Table 1), the porosity inside the primer layer is 0.0008% (referred to as the first porosity in Table 1), and the maximum void of the primer layer is 600 nm (referred to as the first void size in Table 1); (4) The surface of the primer layer is alkaline washed and then a topcoat is applied to form a topcoat layer, thereby completing the preparation of the steel strip; the bonding ratio between the topcoat and the primer layer is 99.9995% (referred to as the second bonding ratio in Table 1), the porosity inside the topcoat layer is 0.0008% (referred to as the second porosity in Table 1), and the maximum void inside the topcoat layer is 600nm (referred to as the second void size in Table 1).

[0041] In the above steps (1) and (2), the specific steps of pretreatment are: using 1wt% (referred to as alkali solution concentration in Table 1) sodium hydroxide solution for alkali washing, then rinsing with water, then using 1wt% (referred to as acid solution concentration in Table 1) hydrochloric acid solution for acid washing, then rinsing again, and finally drying to complete the pretreatment steps.

[0042] This embodiment also provides a pre-coated hot-dip coated steel strip resistant to CX-level extreme environmental corrosion, which is prepared according to the above method. The pre-coated hot-dip coated steel strip resistant to CX-level extreme environmental corrosion includes a steel substrate, an alloy coating, a primer layer and a topcoat layer, wherein the alloy coating is coated on the surface of the steel substrate, the primer layer is coated on the surface of the alloy coating, and the topcoat layer is coated on the surface of the primer layer. The alloy coating is an Al-Zn-Mg alloy coating, the thickness of the primer layer is 8 μm (abbreviated as H1 in Table 1), and the thickness of the topcoat layer is 50 μm (abbreviated as H2 in Table 1).

[0043] As shown in Table 1, the main difference between Examples 1-5 is that the production and processing parameters of the pre-coated hot-dip coated steel strip resistant to CX-level extreme environment corrosion are different.

[0044] Table 1 sample Example 1 Example 2 Example 3 Example 4 Example 5 Resin ratio 50:50 55:45 60:40 70:30 80:20 Solid particle size / nm 300 250 200 150 100 Dispersion ratio / % 90 92 93 94 95 First curing temperature / ℃ 220 230 240 250 260 Second curing temperature / ℃ 160 170 180 190 200 Passivation method Spray Spray soak soak soak First contact angle / ° 15 14 11 10 7 Second contact angle / ° 15 14 13 12 10 First binding rate / % 99.992 99.993 99.995 99.994 99.997 First porosity / % 0.0008 0.0003 0.001 0.0006 0.0004 Second binding rate / % 99.9995 99.9993 99.9996 99.9998 99.9994 Second porosity / % 0.0008 0.0006 0.0009 0.0007 0.001 The first gap size / nm 600 570 440 320 200 Second gap size / nm 600 585 477 289 193 Alkali concentration / wt% 1 1.2 1.5 1.8 2 Acid concentration / wt% 1 1.1 1.3 1.7 2 <![CDATA[H1 / μm]]> 8 8.5 9 9.5 10 <![CDATA[H2 / μm]]> 50 52 55 58 60 Example 6 The difference between this embodiment and embodiment 1 is that D of the solid powder material 90 The particle size is 350nm.

[0045] Example 7 The difference between this embodiment and embodiment 1 is that the proportion of the solid powder material in the primer and the topcoat in the state of single particles is 86%.

[0046] Example 8 The difference between this embodiment and embodiment 1 is that the curing temperature of the first resin is 200°C.

[0047] Example 9 The difference between this embodiment and embodiment 1 is that the curing temperature of the second resin is 140°C.

[0048] Example 10 The difference between this embodiment and embodiment 1 is that the thickness of the alloy plating layer is 35 μm.

[0049] Embodiment 11 The difference between this embodiment and embodiment 1 is that the thickness of the primer layer is 5 μm.

[0050] Example 12 The difference between this embodiment and embodiment 1 is that the thickness of the topcoat layer is 45 μm.

[0051] Comparative Example Comparative Example 1 The difference between this comparative example and Example 1 is that in step (1) of the method for manufacturing a corrosion-resistant pre-coated steel strip, the contact angle between the alloy coating and the passivation solution is controlled to be 17°.

[0052] Comparative Example 2 The difference between this comparative example and Example 1 is that in step (2) of the method for manufacturing a corrosion-resistant pre-coated steel strip, the contact angle between the passivated alloy coating and the coating liquid is controlled to be 18°.

[0053] Comparative Example 3 The difference between this comparative example and Example 1 is that the bonding rate between the primer and the alloy coating is 99.8922% Comparative Example 4 The difference between this comparative example and Example 1 is that the bonding rate between the topcoat and the primer layer is 99.8856%.

[0054] Comparative Example 5 The difference between this comparative example and Example 1 is that the porosity of the primer layer is 0.0014%.

[0055] Comparative Example 6 The difference between this comparative example and Example 1 is that the porosity of the topcoat layer is 0.0016%.

[0056] Comparative Example 7 The difference between this comparative example and Example 1 is that the maximum gap between the primer layer and the topcoat layer is 650 nm.

[0057] Comparative Example 8 The difference between this comparative example and Example 1 is that after the formation of the primer layer is completed, the topcoat layer is not processed, and finally a pre-coated hot-dip coated steel strip consisting only of a steel substrate, an alloy coating layer and a primer layer is obtained.

[0058] Comparative Example 9 The difference between this comparative example and Example 1 is that after the alloy coating is formed, the primer layer is not processed and the topcoat layer is directly processed, and finally a pre-coated hot-dip coated steel strip consisting only of a steel substrate, an alloy coating and a topcoat layer is obtained.

[0059] Performance testing methods 1. Coating adhesion The weighing method is used to detect the coating adhesion on the surface of the hot-dip coated steel strip. The steps are as follows: (1) After hot-dip coating, take a sample and use an electronic balance to measure and record the total weight of the hot-dip coated steel strip substrate and coating; (2) The surface coating is removed by pickling, leaving the steel substrate, and the weight of the substrate is measured using a balance.

[0060] (3) The coating adhesion amount was calculated based on the difference between the two measurement results and the substrate area. The results are shown in Table 2.

[0061] 2. Use a coating thickness gauge to measure the thickness of the primer coating and the topcoat coating. The results are shown in Table 2.

[0062] 3. Corrosion resistance Referring to the requirements of GB / T 10125-2012 Artificial atmosphere corrosion test salt spray test, the hot-dip coated steel strip was subjected to a copper accelerated acetate salt spray test, and the time for the appearance of red rust in each group of tests (referred to as corrosion time) was recorded. The results are shown in Table 2.

[0063] Table 2 Combining Examples 1-12 and Comparative Examples 1-9 and Table 2, it can be seen that when the coating adhesion, primer thickness, and topcoat thickness are similar, the corrosion time of each embodiment and comparative example is quite different. There are three main reasons why the pre-coated steel strips of Comparative Examples 1-9 are difficult to serve for a long time in a CX-level corrosion environment. First, the adhesion between the alloy coating and the steel substrate is poor. There are microcracks between the alloy coating and the steel substrate. The corrosive medium in the environment can enter the microcracks and cause galvanic corrosion between the steel substrate and the coating. Second, due to the coarse coating structure, there is relatively serious galvanic corrosion between different structures inside the coating. Third, due to the high impurity content inside the coating, there is relatively serious galvanic corrosion between the coating structure and the impurities. It is precisely because of the above three reasons that the corrosion resistance of the entire coating and coating is affected.

[0064] Embodiments 1-12 optimize the preparation method of the pre-coated hot-dip coated steel strip, and specifically achieve the following points: (1) The present application performs pretreatment of the alloy coating before passivation in a continuous hot-dip plating production line, which can improve the efficiency and uniformity of the passivation treatment and help ensure the quality of the passivation layer. The present application performs pretreatment of the passivated alloy coating before chemical coating in a continuous pre-coating film production line, which provides good conditions for subsequent chemical coating, thereby improving the bonding rate between the primer and the alloy coating.

[0065] (2) The bonding rate between the topcoat and the primer is improved by treating the primer surface before applying the topcoat in a continuous pre-coating film production line.

[0066] (3) The present application limits the curing temperature of the resin material to two ranges. When the coating is cured on the coating production line, the temperature changes from high to low. The first resin with a high curing temperature is cured first, and many microscopic holes are formed due to its transition from liquid to solid. At this time, the second resin with a low curing temperature is still in liquid state and can flow into these holes. When the temperature drops further, it will also solidify and fill the holes completely, which is beneficial to reduce the porosity and reduce the maximum gap.

[0067] (4) The present application optimizes the proportion of the second resin in the resin material to ensure that the resin with a low curing temperature has a sufficient amount to fill the microscopic pores generated by the resin with a high curing temperature during the curing process, which is beneficial to reducing the porosity and the maximum gap.

[0068] (5) The present application controls the particle size of the solid powder material, thereby preventing the microscopic pores inside the coating from being too large due to the large particle size of the powder material, which is beneficial to reducing the porosity and the maximum void.

[0069] In summary, in Examples 1-12, thanks to the coordinated cooperation of the alloy coating, the primer layer and the topcoat layer, the pre-coated hot-dip coated steel strip prepared according to the method of the present application can fully resist corrosion even in a CX-level corrosion environment, and has a longer service life and a lower replacement frequency, thereby overcoming the defects in the related art.

[0070] Combining Examples 1-5 and Comparative Examples 2-9 and Table 2, it can be seen that the corrosion time measured in Examples 1-5 is relatively long, indicating that the synergistic cooperation of the alloy coating, the primer layer and the topcoat layer, and the passivation layer produced in the passivation treatment makes the pre-coated film hot-dip coated steel strip prepared according to the method of the present application fully resistant to corrosion even in a CX-level corrosion environment, and has a longer service life and a lower replacement frequency. When the contact angle between the alloy coating and the passivation solution, the contact angle between the passivated alloy coating and the chemical coating solution, the bonding rate between the primer and the alloy coating, the bonding rate between the topcoat and the primer layer, the porosity of the primer layer, the porosity of the topcoat layer, and the maximum gap between the primer layer and the topcoat layer exceed the range specified in the present application, or when any one of the primer layer and the topcoat layer is missing, the corrosion resistance of the pre-coated film hot-dip coated steel strip is poor.

[0071] Combining Examples 1-5 and Examples 6-12 and Table 2, it can be seen that when the D of the solid powder material 90 When parameters such as particle size, the proportion of solid powder material in the state of single particles, the curing temperature of the first resin, the curing temperature of the second resin, the thickness of the alloy coating, the thickness of the primer layer, and the thickness of the topcoat layer are beyond the range specified in this application, the corrosion resistance of the pre-coated hot-dip coated steel strip is relatively poor, but is still better than the results of the comparative examples.

[0072] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for manufacturing a corrosion-resistant pre-coated steel strip, characterized in that: The following steps are involved: (1) Hot-dip plating is performed on a steel substrate in a continuous hot-dip plating production line, and then the formed alloy coating is pre-treated before passivation so that the contact angle between the alloy coating and the passivation solution is ≤15°, and then the alloy coating is passivated using the passivation solution; (2) Pre-treatment of the passivated alloy coating before chemical coating in a continuous pre-coating film production line so that the contact angle between the passivated alloy coating and the chemical coating liquid is ≤15°, and then chemical coating treatment of the passivated alloy coating is performed using the chemical coating liquid; (3) Applying a primer to the surface of the alloy coating after chemical coating in a continuous pre-coating production line to form a primer layer; the bonding rate between the primer and the alloy coating is ≥99.999%, the porosity of the primer layer is ≤0.001%, and the maximum gap of the primer layer is ≤600nm; (4) The surface of the primer layer is alkaline-washed in a continuous pre-coating production line, and then a topcoat is applied to form a topcoat layer, thereby completing the preparation of the steel strip; the bonding rate between the topcoat and the primer layer is ≥99.999%, the porosity of the topcoat layer is ≤0.001%, and the maximum gap between the primer layer and the topcoat layer is ≤600nm.

2. The method for manufacturing a corrosion-resistant pre-coated steel strip according to claim 1, characterized in that: The passivation treatment is performed by spraying or immersing.

3. The method for manufacturing a corrosion-resistant pre-coated steel strip according to claim 1, characterized in that: In step (1) and step (2) of the method, the pretreatment is carried out as follows: alkaline washing is performed using a 1-2 wt% sodium hydroxide solution, followed by rinsing with water, acid washing is performed using a 1-2 wt% hydrochloric acid solution, followed by rinsing again, and finally drying to complete the pretreatment steps.

4. The method for manufacturing a corrosion-resistant pre-coated steel strip according to claim 1, characterized in that: The primer and the topcoat both contain resin materials, and the resin materials include a first resin and a second resin. The curing temperature of the first resin is 220-260°C, and the curing temperature of the second resin is 160-200°C.

5. The method for manufacturing a corrosion-resistant pre-coated steel strip according to claim 4, characterized in that: The weight of the second resin accounts for 20-50% of the total weight of the resin material.

6. The method for manufacturing a corrosion-resistant pre-coated steel strip according to claim 4, characterized in that: The primer and topcoat contain solid powder material, the D 90 The particle size is 100-300nm.

7. The method for manufacturing a corrosion-resistant pre-coated steel strip according to claim 6, characterized in that: In the primer and topcoat, the proportion of the solid powder material existing in the resin in the form of a single particle is ≥90%, and the proportion of the solid powder material existing in the resin in the form of two or less particles is 100%.

8. The pre-coated hot-dip coated steel strip resistant to CX-level extreme environment corrosion according to any one of claims 1 to 7, characterized in that: The invention comprises a steel substrate, an alloy coating, a primer layer and a topcoat layer. The alloy coating is coated on the surface of the steel substrate, the primer layer is coated on the surface of the alloy coating, and the topcoat layer is coated on the surface of the primer layer.

9. The pre-coated hot-dip coated steel strip resistant to CX-level extreme environment corrosion according to claim 8, characterized in that: The alloy coating is an Al-Zn-Mg alloy coating, and the adhesion amount of the alloy coating is 500-550g / m 2 .

10. The pre-coated hot-dip coated steel strip resistant to CX-level extreme environment corrosion according to claim 8, characterized in that: The thickness of the primer layer is 8-10 μm, and the thickness of the topcoat layer is 50-60 μm.

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