Powder coating for anticorrosion steel pipe for conveying seawater and preparation method and application thereof

Abstract

The present application relates to the technical field of paint, in particular to a powder coating for anticorrosion steel pipe for conveying seawater and a preparation method and application thereof. The powder coating for anticorrosion steel pipe provided by the present application adopts an epoxy powder coating layer with excellent electric conductivity and corrosion resistance as a bottom layer, a zinc-rich powder coating layer containing zinc powder as an intermediate layer, and an antifouling powder coating layer as a surface layer. The zinc-rich coating layer of the intermediate layer can be connected to the base material of the anticorrosion steel pipe through the electrically conductive coating layer of the bottom layer to form an electrically conductive path, thereby playing a cathodic protection role of a sacrificial anode. The antifouling coating layer of the surface layer can effectively prevent the adhesion of microorganisms and reduce the risk of microbial corrosion. Meanwhile, the problem of poor interlayer adhesion is solved through a special formula and process.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a powder coating for anti-corrosion steel pipes used for transporting seawater, its preparation method and application. Background Technology

[0002] In seawater transportation projects, anti-corrosion steel pipes are used in C5-M grade highly corrosive environments, and are continuously subjected to the combined erosion of multiple media such as seawater infiltration and marine microbial attachment. This places stringent requirements on the overall performance of anti-corrosion coatings. Existing coating technologies for anti-corrosion of steel pipes in marine environments still have long-standing unresolved technical problems.

[0003] Existing technologies directly use zinc-rich epoxy powder. The high zinc content results in extremely poor adhesion between the coating and the metal substrate, leading to blistering and peeling during service. Insufficient bonding with the surface layer prevents the sustained cathodic protection of the zinc powder sacrificial anode. Furthermore, when the zinc-rich layer directly contacts the substrate, the zinc powder is prone to localized agglomeration, resulting in island-like conductive pathways and significant fluctuations in cathodic protection efficiency. When using ordinary hot-melt epoxy powder for corrosion protection, it relies solely on the physical shielding effect of the coating, making it highly susceptible to pitting and perforation in high-chloride marine environments. Summary of the Invention

[0004] In view of this, the present invention provides a powder coating for anti-corrosion steel pipes used for seawater transportation, its preparation method, and its application. The present invention achieves efficient corrosion protection through a three-layer coating structure. The bottom layer is an epoxy powder coating with excellent conductivity and corrosion resistance; the middle layer is a zinc-rich powder coating containing zinc powder; and the top layer is an antifouling powder coating. The zinc-rich coating in the middle layer can form a conductive path with the substrate of the anti-corrosion steel pipe through the conductive coating in the bottom layer, thus playing a cathodic protection role as a sacrificial anode. The antifouling coating in the top layer can effectively prevent microbial adhesion, reducing the risk of microbial corrosion. Simultaneously, the problem of poor interlayer adhesion is solved through a special formula and process.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a powder coating for anti-corrosion steel pipes used for transporting seawater, comprising base powder, intermediate powder and flour; The base powder, by weight, comprises 20-30 parts of bisphenol A epoxy resin, 20-30 parts of phenolic epoxy resin, 15-25 parts of phenolic curing agent, 0.5-2 parts of accelerator, 0.5-2 parts of coupling agent, 0.5-2 parts of nano silica, 5-10 parts of glass flakes, 10-15 parts of silica powder, 10-15 parts of wollastonite powder, 0.5-1 part of leveling agent, 0.5-1 part of defoamer, 1-5 parts of conductive carbon black, and 1-5 parts of carbon nanotubes. The intermediate powder, by weight, comprises 30-50 parts of bisphenol A epoxy resin, 10-25 parts of phenolic curing agent, 0.5-2 parts of accelerator, 0.5-2 parts of coupling agent, 5-10 parts of mica powder, 30-40 parts of spherical zinc powder, 5-15 parts of flake zinc powder, 5-10 parts of ferrophosphorus powder, 0.5-1 part of leveling agent, 0.5-1 part of defoamer, and 1-5 parts of carbon nanotubes. The flour, by weight, comprises 20-30 parts of bisphenol A epoxy resin, 10-30 parts of phenolic epoxy resin, 15-25 parts of phenolic curing agent, 0.5-2 parts of accelerator, 0.5-2 parts of coupling agent, 0.5-2 parts of nano silica, 5-10 parts of silica powder, 5-10 parts of wollastonite powder, 0.5-1 part of leveling agent, 0.5-1 part of defoamer, 1-5 parts of polytetrafluoroethylene wax, 5-10 parts of modified solid organosilicon resin, 5-10 parts of fluorinated acrylic resin, 1-5 parts of zinc oxide, 1-2 parts of titanium dioxide, and 1-2 parts of pigment.

[0006] In a second aspect, the present invention provides a method for preparing the powder coating described in the first aspect, comprising the following steps: Bisphenol A type epoxy resin, phenolic epoxy resin, coupling agent, nano silica, glass flakes, silica powder, wollastonite powder, and leveling agent are mixed evenly in a mixer, then extruded using a twin-screw extruder, and then pressed and crushed using a water-cooled tablet press. The crushed raw materials are then mixed evenly again in a mixer with phenolic curing agent, accelerator, defoamer, conductive carbon black, and carbon nanotubes, and then extruded using a twin-screw extruder, pressed and crushed using a water-cooled tablet press, and then ground into powder. The powder is then sieved through an 80-120 mesh sieve to prepare the base powder. Bisphenol A type epoxy resin, phenolic curing agent, accelerator, coupling agent, mica powder, spherical zinc powder, flake zinc powder, ferrophosphorus powder, leveling agent, defoamer, and carbon nanotubes are mixed evenly in a mixer, then extruded using a twin-screw extruder, then compressed and crushed using a water-cooled tablet press, and then ground into powder. The powder is then sieved through a 60-120 mesh screen to prepare intermediate powder. Bisphenol A type epoxy resin, phenolic epoxy resin, phenolic curing agent, accelerator, coupling agent, nano silica, silica powder, wollastonite powder, leveling agent, defoamer, polytetrafluoroethylene wax, modified solid organosilicon resin, fluorinated acrylic resin, zinc oxide, titanium dioxide, and pigment are mixed evenly in a mixer, then extruded using a twin-screw extruder, then pressed and crushed using a water-cooled tablet press, and finally ground into powder. The powder is then sieved through a 60-120 mesh screen to prepare flour.

[0007] Thirdly, the present invention provides the application of the powder coating described in the first aspect in the corrosion protection of steel pipes.

[0008] Fourthly, the present invention provides a corrosion-resistant steel pipe for transporting seawater, comprising a steel pipe, wherein a paint film is attached to the inner and outer wall surfaces of the steel pipe, and the paint film is formed by the powder coating described in the first aspect.

[0009] Fifthly, the present invention provides a coating process for a corrosion-resistant steel pipe for transporting seawater. The steel pipe is preheated and derusted, then heated, and rotated by a mechanical device. The powder base powder, intermediate powder and flour described in the first aspect are sprayed sequentially on the inner and outer walls of the steel pipe. The residual heat of the steel pipe is used to melt and solidify the powder, and then the pipe is allowed to cool naturally.

[0010] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) This invention provides a three-layer coating structure for anti-corrosion steel pipes used for transporting seawater. The zinc-rich coating in the middle layer can form a conductive path with the substrate of the anti-corrosion steel pipe through the conductive coating at the bottom layer, thus playing the role of a cathodic protection structure of sacrificial anode; the antifouling coating at the top layer can effectively prevent the adhesion of microorganisms and reduce the risk of microbial corrosion. It innovatively solves the problems of poor adhesion of the zinc-rich coating at the bottom layer of traditional anti-corrosion steel pipes and the problems of microbial adhesion and seawater corrosion resistance of steel pipes during seawater transportation.

[0011] (2) The addition of phenolic modified epoxy resin to the base powder of this invention greatly enhances the adhesion between the powder coating and the steel pipe. The nano-silica added to the base powder can fill the pores of the powder coating, reducing the porosity of the coating. The glass flake material has a sheet-like structure, which further enhances the cathodic disbondment resistance and corrosion resistance of the base powder. The added conductive carbon black and carbon nanotube materials can play a synergistic role, giving the entire coating system an extremely low resistivity, thus better ensuring electron flow.

[0012] (3) The intermediate powder of the present invention is a zinc-rich powder that acts as a sacrificial anode. The main film-forming substance of the intermediate powder is epoxy resin, which has a similar structure to the film-forming substances of the base powder and flour, and has good compatibility and interlayer bonding. The added spherical zinc powder and flake zinc powder are the main anode materials, which work together to reduce the amount of zinc powder used. The added ferrophosphorus powder and carbon nanotubes have good conductivity and can connect with the substrate through the conductive structure of the bottom layer to form a conductive path, thereby enabling the zinc powder in the intermediate layer to act as a sacrificial anode and improve the service life of the anti-corrosion steel pipe.

[0013] (4) The flour of the present invention contains polytetrafluoroethylene wax, modified solid organosilicon resin, fluorinated acrylic resin and other materials, which play a synergistic role in reducing the surface energy of the coating and preventing the adhesion of microorganisms. The addition of zinc oxide can slowly dissolve zinc ions, which have an inhibitory effect on bacteria, diatoms and barnacle larvae. Detailed Implementation

[0014] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0015] In seawater transportation projects, anti-corrosion steel pipes operate in C5-M grade highly corrosive environments, continuously subjected to the combined erosion of multiple media such as seawater infiltration and marine microbial adhesion. This places stringent demands on the overall performance of anti-corrosion coatings. Existing coating technologies for anti-corrosion of steel pipes in marine environments still have long-standing industry pain points and technical defects that remain unresolved. Existing technologies directly use epoxy zinc-rich powder, but the high zinc content results in extremely poor adhesion between the coating and the metal substrate. During service, it is prone to blistering and peeling, and the bonding with the surface layer is poor, rendering the cathodic protection effect of the zinc powder sacrificial anode ineffective. Simultaneously, when the zinc-rich layer directly contacts the substrate, the zinc powder is prone to localized agglomeration, resulting in an island-like distribution of conductive pathways and significant fluctuations in cathodic protection efficiency. When using ordinary hot-melt epoxy powder for corrosion protection, it relies solely on the physical shielding effect of the coating, making it highly susceptible to pitting and perforation in high-chloride marine environments. Traditional liquid anti-corrosion coatings employ an epoxy zinc-rich primer + epoxy micaceous iron oxide intermediate coat + acrylic polyurethane topcoat. On one hand, the interlayer bonding between the three coatings is poor. In marine environments, where diurnal temperature variations can exceed 40°C, frequent temperature cycles lead to continuous stress concentration between layers, easily causing interlayer delamination, coating cracking, and failure of the physical shielding barrier, significantly shortening the anti-corrosion lifespan. On the other hand, liquid coatings have high VOC emissions, long construction cycles, and high coating porosity, failing to meet environmental protection requirements and hindering continuous industrial-scale coating of steel pipes. Currently, there is no existing powder coating system that simultaneously solves the core challenges of long-term cathodic protection and multi-factor synergistic corrosion protection for anti-corrosion steel pipes used for seawater transportation. Therefore, developing a powder coating material with high adhesion, high conductivity stability, high cathodic protection efficiency, long-term corrosion resistance, and high-efficiency antifouling is of great engineering significance for the long-term safe service of anti-corrosion steel pipes used for seawater transportation.

[0016] Based on this, the present invention provides a powder coating for anti-corrosion steel pipes used for transporting seawater, comprising base powder, intermediate powder and flour; The base powder, by weight, comprises 20-30 parts of bisphenol A epoxy resin, 20-30 parts of phenolic epoxy resin, 15-25 parts of phenolic curing agent, 0.5-2 parts of accelerator, 0.5-2 parts of coupling agent, 0.5-2 parts of nano silica, 5-10 parts of glass flakes, 10-15 parts of silica powder, 10-15 parts of wollastonite powder, 0.5-1 part of leveling agent, 0.5-1 part of defoamer, 1-5 parts of conductive carbon black, and 1-5 parts of carbon nanotubes. The intermediate powder, by weight, comprises 30-50 parts of bisphenol A epoxy resin, 10-25 parts of phenolic curing agent, 0.5-2 parts of accelerator, 0.5-2 parts of coupling agent, 5-10 parts of mica powder, 30-40 parts of spherical zinc powder, 5-15 parts of flake zinc powder, 5-10 parts of ferrophosphorus powder, 0.5-1 part of leveling agent, 0.5-1 part of defoamer, and 1-5 parts of carbon nanotubes. The flour, by weight, comprises 20-30 parts of bisphenol A epoxy resin, 10-30 parts of phenolic epoxy resin, 15-25 parts of phenolic curing agent, 0.5-2 parts of accelerator, 0.5-2 parts of coupling agent, 0.5-2 parts of nano silica, 5-10 parts of silica powder, 5-10 parts of wollastonite powder, 0.5-1 part of leveling agent, 0.5-1 part of defoamer, 1-5 parts of polytetrafluoroethylene wax, 5-10 parts of modified solid organosilicon resin, 5-10 parts of fluorinated acrylic resin, 1-5 parts of zinc oxide, 1-2 parts of titanium dioxide, and 1-2 parts of pigment.

[0017] This invention employs a three-layer structure: an epoxy powder coating with excellent conductivity and corrosion resistance, prepared from conductive carbon black and conductive carbon nanotubes as the bottom layer; a zinc-rich powder coating with spherical and flake zinc powder as the main components in the middle layer; and an antifouling coating with polytetrafluoroethylene wax, modified solid silicone resin, fluorinated acrylic resin, zinc oxide, and titanium dioxide as the main components. The zinc-rich coating in the middle layer connects with the substrate of the anti-corrosion steel pipe through the conductive coating at the bottom layer, forming a conductive path and acting as a sacrificial anode cathodic protection structure. The antifouling coating at the top layer effectively prevents microbial adhesion and reduces the risk of microbial corrosion. This innovatively solves the problems of poor adhesion of traditional zinc-rich coatings used in anti-corrosion steel pipes and the issues of microbial adhesion and seawater corrosion during seawater transportation.

[0018] Furthermore, the bisphenol A type epoxy resin in the base powder has a softening point of 85℃-130℃, including at least one of one-step epoxy resin and two-step epoxy resin.

[0019] Furthermore, the phenolic epoxy resin in the base powder includes at least one of Amanda 1168, Amanda 1177HTM, Amanda 1178HT, ES503, ES3065, NPCN-702, and 704 resins. Specifically, Amanda 1168, Amanda 1177HTM, and Amanda 1178HT were purchased from Daqing Qinglu Langrun Technology Co., Ltd.; ES503 and ES3065 were purchased from Shaanxi Jinchen; NPCN-702 was purchased from Nanya Electronics; and 704 resin was purchased from Baling Petrochemical.

[0020] Furthermore, the phenolic curing agent in the base powder includes at least one of KD404, KD405, KD406, V-2083, V-2081, V-2059, 969 series, and 979 series curing agents. Specifically, KD404, KD405, and KD406 were purchased from Gukdu, South Korea; V-2083, V-2081, and V-2059 were purchased from Shaanxi Jinchen; and the 969 series and 979 series curing agents from Daqing Qinglu were purchased from Daqing Qinglu.

[0021] Furthermore, the coupling agent in the base powder is a powder coupling agent containing epoxy groups; preferably, the coupling agent is at least one of PCA-302A and PCA-302E. PCA-302A and PCA-302E are purchased from Nanjing Nengde Company.

[0022] Furthermore, the nano-silica in the base powder is a hydrophobic fumed silica product; preferably, the nano-silica is at least one of R-972 and R-974. Specifically, the nano-silica is commercially available Evonik R-972 or R-974.

[0023] Furthermore, the glass flakes in the base powder are materials modified with coupling agents, including commercially available 100-400 mesh glass flake products.

[0024] Furthermore, the silica powder in the base powder has a mesh size of 800-1500 mesh.

[0025] Furthermore, the wollastonite powder in the base powder has a mesh size of 800-1500, which is commercially available.

[0026] Furthermore, the leveling agent in the base powder is an acrylic ester product. Leveling aids include at least one of Ningbo Nanhai's PV88, Wuhan Yincai's L88, and Ningbo Weikai Chemical's WK538.

[0027] Furthermore, the defoamer mentioned in the base powder is a benzoin-based product, including at least one of pure benzoin and anti-yellowing benzoin. Examples include commercially available products such as Wuhan Yincai's L307, Nanhai Chemical's benzoin, and Ningbo Weikai's WK307.

[0028] Furthermore, the conductive carbon black mentioned in the base powder is Noryon EC600JD, EC300J, Cabot BP2000, or Orion Special Black series.

[0029] Furthermore, the carbon nanotubes in the base powder are at least one of Cabot ATHLOS 200, Tiannai Technology TN-SW100, and Shandong Dazhan DT-300.

[0030] The addition of phenolic epoxy resin to the base powder of this invention significantly enhances the adhesion between the powder coating and the steel pipe. The nano-silica added to the base powder fills the pores of the powder coating, reducing its porosity. The glass flake material, with its sheet-like structure, further enhances the base powder's resistance to cathodic disbondment and its corrosion resistance. The added conductive carbon black and carbon nanotube materials work synergistically, resulting in an extremely low resistivity for the entire coating system, better ensuring electron flow. The base powder employs a two-stage extrusion process: first, the resin and fillers are extruded and dispersed, then a second extrusion is performed with the curing agent and conductive agent. This avoids the performance degradation of the conductive agent during high-temperature extrusion and improves the uniformity of filler dispersion, further enhancing the coating's density and adhesion.

[0031] Furthermore, the bisphenol A type epoxy resin in the intermediate powder has a softening point of 85℃-130℃, including at least one of one-step epoxy resin and two-step epoxy resin.

[0032] Furthermore, the phenolic curing agent in the intermediate powder includes at least one of KD404, KD405, KD406, V-2083, V-2081, V-2059, 969 series, and 979 series curing agents. Specifically, KD404, KD405, and KD406 were purchased from Gukdu, South Korea; V-2083, V-2081, and V-2059 were purchased from Shaanxi Jinchen; and the 969 series and 979 series curing agents from Daqing Qinglu were purchased from Daqing Qinglu.

[0033] Furthermore, the accelerator in the intermediate powder is an imidazole or cycloamidinium compound, including at least one of 2-methylimidazole and 2-isopropylimidazole.

[0034] Furthermore, the coupling agent in the intermediate powder is a powder coupling agent containing epoxy groups. The coupling agent includes at least one of PCA-302A and PCA-302E from Nanjing Nengde Company.

[0035] Furthermore, the mica powder mentioned in the intermediate powder is 200-600 mesh white mica powder.

[0036] Furthermore, the spherical zinc powder in the intermediate powder is spherical zinc powder with a particle size D50 of 20-50 μm.

[0037] Furthermore, the flaky zinc powder in the intermediate powder is flaky zinc powder with a particle size D50 of 10-20 μm.

[0038] Furthermore, the phosphorus iron powder mentioned in the intermediate powder is a product with a mesh size of 600-1000.

[0039] Furthermore, the leveling agent in the intermediate powder is an acrylate product. Leveling aids include at least one of the following: PV88 from Ningbo Nanhai, L88 from Wuhan Yincai, and WK538 from Ningbo Weikai Chemical.

[0040] Furthermore, the defoamer mentioned in the intermediate powder is a benzoin-based product, including at least one of pure benzoin and anti-yellowing benzoin. Examples include commercially available products such as Wuhan Yincai's L307, Nanhai Chemical's benzoin, and Ningbo Weikai's WK307.

[0041] Furthermore, the carbon nanotubes in the intermediate powder are at least one of Cabot ATHLOS 200, Tiannai Technology TN-SW100, and Shandong Dazhan DT-300.

[0042] The intermediate powder of this invention is a zinc-rich powder that acts as a sacrificial anode. The main film-forming substance of the intermediate powder is epoxy resin, which has a similar structure to the film-forming substances of the base powder and flour, exhibiting excellent compatibility and interlayer bonding. The added spherical and flake zinc powders serve as the main anode materials, synergistically reducing the amount of zinc powder required. The added iron phosphate powder and carbon nanotubes have excellent electrical conductivity, enabling them to connect with the substrate through the underlying conductive structure to form a conductive path. This allows the zinc powder in the intermediate layer to act as a sacrificial anode, improving the service life of the anti-corrosion steel pipe.

[0043] Furthermore, the modified solid organosilicon resin in the flour includes at least one of commercially available hydroxyl-modified solid organosilicon resin and epoxy-modified solid organosilicon resin.

[0044] Furthermore, the bisphenol A type epoxy resin in the flour has a softening point of 85℃-130℃, including at least one of one-step epoxy resin and two-step epoxy resin.

[0045] Furthermore, the phenolic epoxy resin in the flour includes at least one of Amanda 1168, Amanda 1177HTM, Amanda 1178HT, ES503, ES3065, NPCN-702, and 704 resins. Specifically, Amanda 1168, Amanda 1177HTM, and Amanda 1178HT were purchased from Daqing Qinglu Langrun Technology Co., Ltd.; ES503 and ES3065 were purchased from Shaanxi Jinchen; NPCN-702 was purchased from Nanya Electronics; and 704 resin was purchased from Baling Petrochemical.

[0046] Furthermore, the phenolic curing agent in the flour includes at least one of KD404, KD405, KD406, V-2083, V-2081, V-2059, 969 series, and 979 series curing agents. Specifically, KD404, KD405, and KD406 were purchased from Gukdu, South Korea; V-2083, V-2081, and V-2059 were purchased from Shaanxi Jinchen; and the 969 series and 979 series were purchased from Daqing Qinglu.

[0047] Furthermore, the accelerator in the flour is an imidazole or cycloamidinium compound, including at least one of 2-methylimidazole and 2-isopropylimidazole.

[0048] Furthermore, the coupling agent in the flour is a powder coupling agent containing epoxy groups. The coupling agent includes at least one of PCA-302A and PCA-302E from Nanjing Nengde Company.

[0049] Furthermore, the nano-silica mentioned in the flour is a hydrophobic fumed silica product, commonly including commercially available Evonik R-972 and R-974.

[0050] Furthermore, the silica powder mentioned in the flour is a silica powder product with a mesh size of 800-1500.

[0051] Furthermore, the wollastonite powder mentioned in the flour is an 800-1500 mesh wollastonite powder product.

[0052] Furthermore, the leveling agent in the flour is an acrylic ester product. Leveling aids include at least one of Ningbo Nanhai's PV88, Wuhan Yincai's L88, and Ningbo Weikai Chemical's WK538.

[0053] Furthermore, the defoamer mentioned in the flour is a benzoin-based product, including at least one of pure benzoin and anti-yellowing benzoin. Examples include commercially available products such as Wuhan Yincai's L307, Nanhai Chemical's benzoin, and Ningbo Weikai's WK307.

[0054] Furthermore, the polytetrafluoroethylene wax in the flour is a product with a particle size D50 of 2-5 μm.

[0055] Furthermore, the fluorinated acrylic resin mentioned in the flour is a commercially available solid fluorinated acrylic resin product with a softening point of 80-100℃.

[0056] Furthermore, the zinc oxide in the flour is at least one of commercially available direct zinc oxide, active zinc oxide, and nano zinc oxide.

[0057] Furthermore, the titanium dioxide mentioned in the flour is rutile titanium dioxide.

[0058] Furthermore, the pigment in the flour is at least one of phthalocyanine blue, phthalocyanine green, medium chrome yellow, 254 red, permanent violet, and ultramarine.

[0059] The flour of this invention incorporates polytetrafluoroethylene wax, modified solid organosilicon resin, fluorinated acrylic resin, and other materials, which work synergistically to reduce the surface energy of the coating and prevent the adhesion of microorganisms. The addition of zinc oxide allows for the slow release of zinc ions, which inhibit the growth of bacteria, diatoms, and barnacle larvae.

[0060] This invention provides a method for preparing the powder coating described above, comprising the following steps: Bisphenol A type epoxy resin, phenolic epoxy resin, coupling agent, nano silica, glass flakes, silica powder, wollastonite powder, and leveling agent are mixed evenly in a mixer, then extruded using a twin-screw extruder, and then pressed and crushed using a water-cooled tablet press. The crushed raw materials are then mixed evenly again in a mixer with phenolic curing agent, accelerator, defoamer, conductive carbon black, and carbon nanotubes, and then extruded using a twin-screw extruder, pressed and crushed using a water-cooled tablet press, and then ground into powder. The powder is then sieved through an 80-120 mesh sieve to prepare the base powder. Bisphenol A type epoxy resin, phenolic curing agent, accelerator, coupling agent, mica powder, spherical zinc powder, flake zinc powder, ferrophosphorus powder, leveling agent, defoamer, and carbon nanotubes are mixed evenly in a mixer, then extruded using a twin-screw extruder, then compressed and crushed using a water-cooled tablet press, and then ground into powder. The powder is then sieved through a 60-120 mesh screen to prepare intermediate powder. Bisphenol A type epoxy resin, phenolic epoxy resin, phenolic curing agent, accelerator, coupling agent, nano silica, silica powder, wollastonite powder, leveling agent, defoamer, polytetrafluoroethylene wax, modified solid organosilicon resin, fluorinated acrylic resin, zinc oxide, titanium dioxide, and pigment are mixed evenly in a mixer, then extruded using a twin-screw extruder, then pressed and crushed using a water-cooled tablet press, and finally ground into powder. The powder is then sieved through a 60-120 mesh screen to prepare flour.

[0061] This invention provides the application of the powder coating described above in the corrosion protection of steel pipes.

[0062] The present invention also provides a corrosion-resistant steel pipe for transporting seawater, comprising a steel pipe, wherein the inner and outer surfaces of the steel pipe are coated with a paint film, the paint film being formed from the aforementioned corrosion-resistant powder material.

[0063] The present invention also provides a coating process for anti-corrosion steel pipes for transporting seawater. The steel pipe is preheated and derusted, then heated. The steel pipe is rotated by a mechanical device, and the above-mentioned powder coating base powder, intermediate powder and flour are sprayed sequentially on the inner and outer walls of the steel pipe. The residual heat of the steel pipe is used to melt and solidify the coating, and then the pipe is allowed to cool down naturally.

[0064] This invention employs a one-time continuous spraying process, utilizing the residual heat of the steel pipe for curing, eliminating the need for secondary heating, thereby improving construction efficiency and reducing energy consumption.

[0065] Furthermore, after preheating and rust removal, the anchor pattern depth on the surface of the steel pipe reaches 40-100 μm; the surface rust removal grade reaches Sa2.5.

[0066] Furthermore, the steel pipe is preheated and derusted before being heated to 180 ℃-210 ℃.

[0067] Furthermore, a base powder of 300-400 μm, an intermediate powder of 300-400 μm, and a flour of 200-400 μm are sequentially sprayed onto the inner and outer walls of the steel pipe.

[0068] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0069] Example 1 Preparation of foundation powder: 20 parts of bisphenol A type epoxy resin HY905 (softening point 100 ℃) from Anhui Hengyuan, 20 parts of phenolic epoxy resin Amanda 1168 from Daqing Qinglu Langrun Co., Ltd., 0.5 parts of coupling agent PCA-302A from Anhui Nengde, 0.5 parts of nano silica R972 from Evonik, 5 parts of 100-mesh silane coupling agent modified glass flakes from Nuocheng Chemical, 15 parts of 1200-mesh silica powder from Anhui Gerui, 15 parts of 800-mesh wollastonite powder from Jiangxi Aote, and 1 part of leveling agent L88 from Wuhan Yincai were sequentially added to a tumbling mixer and stirred for 10 minutes to ensure uniform mixing. The mixture was then extruded through a twin-screw extruder set at 105 ℃ with a length-to-diameter ratio of 14:1. The extruded material was then compressed and crushed into flake fragments using a water-cooled tablet press.

[0070] The crushed raw materials were mixed with 18.5 parts of Shaanxi Jinchen's phenolic curing agent V2083, 0.5 parts of accelerator 2-methylimidazole, 1 part of Wuhan Yincai's L307 defoamer, 2 parts of Cabot's BP2000 conductive carbon black, and 1 part of Shandong Dazhan's DT300 carbon nanotubes. The above raw materials were added to a tumbling mixer and stirred for 10 minutes to ensure uniform mixing. Then, the mixture was extruded through a twin-screw extruder with a set temperature of 105 ℃ and a length-to-diameter ratio of 14:1. The extruded material was pressed and crushed into flakes by a water-cooled tablet press, and then ground into powder by a grinding mill. The powder was then sieved through a 100-mesh sieve to prepare the base powder.

[0071] Preparation of intermediate flour: The following ingredients were prepared: 40 parts of bisphenol A type epoxy resin HY904 (softening point 90 ℃) from Anhui Hengyuan, 10 parts of phenolic curing agent V2083 from Shaanxi Jinchen, 0.5 parts of accelerator 2-methylimidazole, 1 part of coupling agent PCA-302A from Anhui Nengde, 5 parts of mica powder GA-1 from Anhui Gerui, 30 parts of spherical zinc powder WL-10 from Hunan Xinweiling, 5 parts of flake zinc powder WL-P6 from Hunan Xinweiling, 5.5 parts of phosphorus iron powder PF906 from Henan Huijin, 1 part of leveling agent L88 from Wuhan Yincai, 1 part of defoamer L307 from Wuhan Yincai, and 1 part of carbon nanotubes DT300 from Shandong Dazhan.

[0072] The above raw materials are sequentially added to a rotary mixer and stirred for 10 minutes to ensure uniform mixing. Then, the mixture is extruded through a twin-screw extruder with a set temperature of 105 ℃ and a length-to-diameter ratio of 14:1. The extruded material is then compressed and crushed into flakes by a water-cooled tablet press, and then ground into powder by an ACM mill. The powder is then sieved through an 80-mesh screen to prepare intermediate powder.

[0073] Flour preparation: 30 parts of bisphenol A type epoxy resin HY905 (softening point 100 ℃) from Anhui Hengyuan and phenolic epoxy resin Amanda from Daqing Qinglu Langrun Co., Ltd. 10 parts of 1168 resin, 15 parts of Shaanxi Jinchen's phenolic curing agent V2083, 0.8 parts of accelerator 2-methylimidazole, 1.7 parts of Anhui Nengde's coupling agent PCA-302A, 0.5 parts of Evonik's nano silica R972, 10 parts of Anhui Gree's 1200-mesh silica powder, 10 parts of Jiangxi Aote's 800-mesh wollastonite powder, 1 part of Wuhan Yincai's leveling agent L88, 1 part of Wuhan Yincai's L307 defoamer, 1 part of Nanjing Tianshi's polytetrafluoroethylene wax PTEF0107, 10 parts of Wacker's epoxy-modified solid silicone resin HP1250, 5 parts of Shandong Huaxia Shenzhou's fluorinated acrylic resin FS701, 1 part of Jiangsu Hehai Nano's zinc oxide Nano-ZnO 30S, 2 parts of Sichuan Longmang's titanium dioxide R219, and 1 part of phthalocyanine blue.

[0074] The above raw materials are sequentially added to a rotary mixer and stirred for 10 minutes to ensure uniform mixing. Then, the mixture is extruded through a twin-screw extruder with a set temperature of 105 ℃ and a length-to-diameter ratio of 14:1. The extruded material is then pressed and crushed into flakes by a water-cooled tablet press, and then ground into powder by an ACM mill. The powder is then sieved through a 100-mesh screen to produce flour.

[0075] Preparation of anti-corrosion steel pipes: The steel pipe is preheated at 40 ℃ using medium-frequency induction heating to remove surface moisture, and then subjected to shot blasting to achieve an anchor pattern depth of 40-100 μm and a surface rust removal grade of Sa2.5. The rust-removed steel pipe is then heated to 210 ℃, and rotated using a mechanical device. A 300 μm thick base powder, a 300 μm thick intermediate powder, and a 200 μm thick flour layer are sprayed onto the inner and outer walls of the pipe, respectively. The residual heat of the steel pipe is used to melt and solidify the coating, thus producing the anti-corrosion steel pipe product.

[0076] Comparative Example 1: Use only the foundation powder from Example 1.

[0077] Preparation of anti-corrosion steel pipes: The steel pipe is preheated at 40 ℃ using medium-frequency induction heating to remove surface moisture, and then subjected to shot blasting to achieve an anchor pattern depth of 40-100 μm and a surface rust removal grade of Sa2.5. The rust-removed steel pipe is then heated to 210 ℃, and a mechanical device is used to rotate the pipe, spraying an 800 μm thick base powder onto both the inner and outer walls. The residual heat of the pipe is then used to melt and solidify the powder, producing the anti-corrosion steel pipe product.

[0078] Comparative Example 2: Only the intermediate powder from Example 1 was used.

[0079] Preparation of anti-corrosion steel pipes: The steel pipe is preheated at 40 ℃ using medium-frequency induction heating to remove surface moisture, and then subjected to shot blasting to achieve an anchor pattern depth of 40-100 μm and a surface rust removal grade of Sa2.5. The rust-removed steel pipe is then heated to 210 ℃, and a mechanical device is used to rotate the pipe, spraying an 800 μm thick intermediate powder coating onto both the inner and outer walls. The coating is then melted and solidified using the residual heat of the pipe, resulting in the anti-corrosion steel pipe product.

[0080] Comparative Example 3: Use only the flour from Example 1.

[0081] Preparation of anti-corrosion steel pipes: The steel pipe is preheated at 40 ℃ using medium-frequency induction heating to remove surface moisture, and then subjected to shot blasting to remove rust, achieving an anchor pattern depth of 40-100 μm and a surface rust removal grade of Sa2.5. The rust-removed steel pipe is then heated to 210 ℃, and a mechanical device is used to rotate the pipe, spraying an 800 μm thick layer of flour onto both the inner and outer walls. The residual heat of the steel pipe is then used to melt and solidify the powder, producing the anti-corrosion steel pipe product.

[0082] Comparative Example 4: Use only the base powder and intermediate powder from Example 1.

[0083] Preparation of anti-corrosion steel pipes: The steel pipe is preheated at 40 ℃ using medium-frequency induction heating to remove surface moisture, and then subjected to shot blasting to achieve an anchor pattern depth of 40-100 μm and a surface rust removal grade of Sa2.5. The rust-removed steel pipe is then heated to 210 ℃, and rotated using a mechanical device. A 400 μm thick base powder and a 400 μm thick intermediate powder are sprayed onto the inner and outer walls of the pipe, respectively. The residual heat of the steel pipe is used for melting and solidification, thus producing the anti-corrosion steel pipe product.

[0084] Comparative Example 5: Use only the base powder and flour from Example 1.

[0085] Preparation of anti-corrosion steel pipes: The steel pipe is preheated at 40 ℃ using medium-frequency induction heating to remove surface moisture, and then subjected to shot blasting to achieve an anchor pattern depth of 40-100 μm and a surface rust removal grade of Sa2.5. The rust-removed steel pipe is then heated to 210 ℃, and rotated using a mechanical device. A 400 μm thick base powder coating and a 400 μm thick flour coating are then sprayed onto the inner and outer walls of the pipe, respectively. The residual heat of the steel pipe is used to melt and solidify the coating, thus producing the anti-corrosion steel pipe product.

[0086] Example 2: The base powder and intermediate powder are the same as those in Example 1.

[0087] Flour preparation: 30 parts of bisphenol A type epoxy resin HY905 (softening point 100 ℃) from Anhui Hengyuan and phenolic epoxy resin Amanda from Daqing Qinglu Langrun Co., Ltd. 10 parts of 1168 resin, 15 parts of Shaanxi Jinchen's phenolic curing agent V2083, 0.8 parts of accelerator 2-methylimidazole, 1.7 parts of Anhui Nengde's coupling agent PCA-302A, 0.5 parts of Evonik's nano silica R972, 10 parts of Anhui Gree's 1200-mesh silica powder, 10 parts of Jiangxi Aote's 800-mesh wollastonite powder, 1 part of Wuhan Yincai's leveling agent L88, 1 part of Wuhan Yincai's L307 defoamer, 1 part of Nanjing Tianshi's polytetrafluoroethylene wax PTEF0107, 5 parts of Wacker's epoxy-modified solid silicone resin HP1250, 10 parts of Shandong Huaxia Shenzhou's fluorinated acrylic resin FS701, 1 part of Jiangsu Hehai Nano's zinc oxide Nano-ZnO 30S, 2 parts of Sichuan Longmang's titanium dioxide R219, and 1 part of phthalocyanine blue.

[0088] The above raw materials are sequentially added to a rotary mixer and stirred for 10 minutes to ensure uniform mixing. Then, the mixture is extruded through a twin-screw extruder with a set temperature of 105 ℃ and a length-to-diameter ratio of 14:1. The extruded material is then pressed and crushed into flakes by a water-cooled tablet press, and then ground into powder by an ACM mill. The powder is then sieved through a 100-mesh screen to produce flour.

[0089] Preparation of anti-corrosion steel pipes: The preparation process of the anti-corrosion steel pipe in Example 2 is the same as that in Example 1.

[0090] Comparative Example 6: Preparation of foundation powder: 40 parts of bisphenol A type epoxy resin HY905 (softening point 100℃) from Anhui Hengyuan, 0.5 parts of coupling agent PCA-302A from Anhui Nengde, 0.5 parts of nano silica R972 from Evonik, 5 parts of 100-mesh glass flakes from Nuocheng Chemical, 15 parts of 1200-mesh silica powder from Anhui Gerui, 15 parts of 800-mesh wollastonite powder from Jiangxi Aote, and 1 part of leveling agent L88 from Wuhan Yincai were sequentially added to a tumbling mixer and stirred for 10 minutes to ensure uniform mixing. The mixture was then extruded through a twin-screw extruder set at 105℃ with a length-to-diameter ratio of 14:1. The extruded material was then compressed and crushed into flake fragments using a water-cooled tablet press.

[0091] The crushed raw materials were mixed with 18.5 parts of Shaanxi Jinchen's phenolic curing agent V2083, 0.5 parts of accelerator 2-methylimidazole, 1 part of Wuhan Yincai's L307 defoamer, 2 parts of Cabot's BP2000 conductive carbon black, and 1 part of Shandong Dazhan's DT300 carbon nanotubes. The above raw materials were added to a tumbling mixer and stirred for 10 minutes to ensure uniform mixing. Then, the mixture was extruded through a twin-screw extruder with a set temperature of 105 ℃ and a length-to-diameter ratio of 14:1. The extruded material was pressed and crushed into flakes by a water-cooled tablet press, and then ground into powder by a grinding mill. The powder was then sieved through a 100-mesh sieve to prepare the base powder.

[0092] The intermediate flour and wheat flour in Comparative Example 6 are the same as those in Example 2.

[0093] The processing technology of the anti-corrosion steel pipe in Comparative Example 6 is the same as that in Example 2.

[0094] Comparative Example 7: The base powder and flour in Comparative Example 7 are the same as those in Example 2.

[0095] Preparation of intermediate flour: The following ingredients were prepared: 40 parts of bisphenol A type epoxy resin HY904 (softening point 90 ℃) from Anhui Hengyuan, 10 parts of phenolic curing agent V2083 from Shaanxi Jinchen, 0.5 parts of accelerator 2-methylimidazole, 1 part of coupling agent PCA-302A from Anhui Nengde, 5 parts of mica powder GA-1 from Anhui Gerui, 35 parts of spherical zinc powder WL-10 from Hunan Xinweiling, 5.5 parts of phosphorus iron powder PF906 from Henan Huijin, 1 part of leveling agent L88 from Wuhan Yincai, 1 part of defoamer L307 from Wuhan Yincai, and 1 part of carbon nanotubes DT300 from Shandong Dazhan.

[0096] The above raw materials are sequentially added to a rotary mixer and stirred for 10 minutes to ensure uniform mixing. Then, the mixture is extruded through a twin-screw extruder with a set temperature of 105 ℃ and a length-to-diameter ratio of 14:1. The extruded material is then compressed and crushed into flakes by a water-cooled tablet press, and then ground into powder by an ACM mill. The powder is then sieved through an 80-mesh screen to prepare intermediate powder.

[0097] The processing technology of the anti-corrosion steel pipe in Comparative Example 7 is the same as that in Example 2.

[0098] Comparative Example 8: The base powder and intermediate powder in Comparative Example 8 are the same as those in Example 2.

[0099] Flour preparation: The following products were prepared: 30 parts of bisphenol A type epoxy resin HY905 (softening point 100 ℃) from Anhui Hengyuan; 10 parts of phenolic epoxy resin Amanda 1168 from Daqing Qinglu Langrun Co., Ltd.; 15 parts of phenolic curing agent V2083 from Shaanxi Jinchen; 0.8 parts of accelerator 2-methylimidazole; 1.7 parts of coupling agent PCA-302A from Anhui Nengde; 0.5 parts of nano silica R972 from Evonik; 10 parts of 1200-mesh silica powder from Anhui Grei; 10 parts of 800-mesh wollastonite powder from Jiangxi Aote; 1 part of leveling agent L88 from Wuhan Yincai; 1 part of defoamer L307 from Wuhan Yincai; 1 part of polytetrafluoroethylene wax PTEF0107 from Nanjing Tianshi; 15 parts of fluorinated acrylic resin FS701 from Shandong Huaxia Shenzhou; and 1 part of zinc oxide Nano-ZnO from Jiangsu Hehai Nano. One part of 30S product, two parts of Sichuan Longmang titanium dioxide R219 product, and one part of phthalocyanine blue.

[0100] The above raw materials are sequentially added to a rotary mixer and stirred for 10 minutes to ensure uniform mixing. Then, the mixture is extruded through a twin-screw extruder with a set temperature of 105 ℃ and a length-to-diameter ratio of 14:1. The extruded material is then pressed and crushed into flakes by a water-cooled tablet press, and then ground into powder by an ACM mill. The powder is then sieved through a 100-mesh screen to produce flour.

[0101] The anti-corrosion steel pipe processing technology in Comparative Example 8 is the same as that in Example 2.

[0102] Comparative Example 9: Preparation of foundation powder: 20 parts of bisphenol A type epoxy resin HY905 (softening point 100 ℃) from Anhui Hengyuan, 20 parts of phenolic epoxy resin Amanda 1168 from Daqing Qinglu Langrun Co., Ltd., 0.5 parts of coupling agent PCA-302A from Anhui Nengde, 0.5 parts of nano silica R972 from Evonik, 5 parts of 100-mesh glass flakes from Nuocheng Chemical, 15 parts of 1200-mesh silica powder from Anhui Gerui, 15 parts of 800-mesh wollastonite powder from Jiangxi Aote, and 1 part of leveling agent L88 from Wuhan Yincai were sequentially added to a rotary mixer and stirred for 10 minutes to ensure uniform mixing. The mixture was then extruded through a twin-screw extruder set at 105 ℃ with a length-to-diameter ratio of 14:1. The extruded material was then compressed and crushed into flake fragments using a water-cooled tablet press.

[0103] The crushed raw materials were mixed with 18.5 parts of Shaanxi Jinchen's phenolic curing agent V2083, 0.5 parts of accelerator 2-methylimidazole, 1 part of Wuhan Yincai's L307 defoamer, and 3 parts of Cabot's BP2000 conductive carbon black. The raw materials were then added to a tumbling mixer and stirred for 10 minutes to ensure uniform mixing. The mixture was then extruded through a twin-screw extruder with a set temperature of 105℃ and a length-to-diameter ratio of 14:1. The extruded material was then pressed and crushed into flakes by a water-cooled tablet press, and then ground into powder by a grinding mill. The powder was then sieved through a 100-mesh screen to prepare the base powder.

[0104] The intermediate flour and wheat flour in Comparative Example 9 are the same as those in Example 2.

[0105] The processing technology of the anti-corrosion steel pipe in Comparative Example 9 is the same as that in Example 2.

[0106] Comparative Example 10 Preparation of foundation powder: Weigh out the following components separately: 30 parts of Anhui Hengyuan bisphenol A type epoxy resin HY905, 20 parts of Daqing Qinglu Langrun Technology Co., Ltd. phenolic epoxy resin Amanda1177HTM, 5 parts of Asahi Kasei isocyanate modified epoxy resin AER4004, 15 parts of Shaanxi Jinchen phenolic curing agent Shaanxi Jinchen V-2083, 4 parts of Tianjin Guangda Bingfeng New Material Technology Co., Ltd. polyvinyl butyral SD-2, 0.5 parts of accelerator 2-methylimidazole, 2 parts of Nanjing Nengde Co., Ltd. coupling agent PCA-302A, 2 parts of Evonik nano silica R-972, 20 parts of pigments and fillers (titanium dioxide: phthalocyanine blue: barium sulfate = 2:1:12), 1 part of Wuhan Yincai leveling agent L88, and 0.5 parts of Wuhan Yincai defoamer L307. The above raw materials are sequentially added to a rotary mixer and stirred for 10 minutes to ensure uniform mixing. Then, the mixture is extruded through a twin-screw extruder with a set temperature of 105℃ and a length-to-diameter ratio of 16:1. The extruded material is then compressed and crushed into flakes by a water-cooled tablet press, and then ground into powder by an ACM mill. The powder is then sieved through a 100-mesh screen to prepare the base powder.

[0107] Preparation of intermediate flour: Component A is the base powder from Example 1; Preparation of component B: Weigh out 70 parts of maleic anhydride-grafted polyethylene F-1 (melt index of 15g / 10min at 2.16kg, 190℃) produced by Donghong Pipe Industry, 15 parts of maleic anhydride-grafted polyethylene wax PEMA4351 from Klein, 14 parts of polyvinyl butyral SD-2 from Tianjin Guangda Bingfeng New Material Technology Co., Ltd., and 1 part of defoamer L307 from Wuhan Yincai. Mix these raw materials evenly in a high-speed mixer at room temperature. Then, extrude the mixture through a twin-screw extruder at 140-200℃, followed by melting, extrusion, cooling, and pelletizing processes to produce granular material. Cool the granular material in a cooling tank containing liquid nitrogen. Grind the liquid nitrogen-cooled granules into powder using an ultra-low temperature grinding process. Sieve the powder through an 80-mesh sieve to obtain component B. Add component A and component B to a double cone mixer at a 1:1 mass ratio and mix for 15 minutes. The intermediate powder is then discharged from the double cone mixer.

[0108] Flour preparation: Weigh out the following raw materials: 50 parts of maleic anhydride-grafted polyethylene F-1 (melt index of 15g / 10min at 2.16kg, 190℃), 5 parts of ultra-high molecular weight polyethylene VH245 from Daehan Oil & Chemical, 5 parts of maleic anhydride-grafted polyethylene wax PEMA4351 from Klein, 10 parts of compatibilizer ACX-41 from Daikin Industries, 10 parts of polytetrafluoroethylene PTEF-0141 from Nanjing Tianshi, 14.5 parts of fused silica powder, 5 parts of pigment (titanium dioxide: phthalocyanine blue), and 0.5 parts of antioxidant 215. Mix the above raw materials evenly in a high-speed mixer at room temperature, and then process them into granular material using a twin-screw extruder at 140-200℃ through melting, extrusion, cooling, and pelletizing processes. The granular material is placed in a cooling tank containing liquid nitrogen to cool it down. The liquid nitrogen-cooled granules are then ground into powder using an ultra-low temperature grinding process. The powder is then sieved through a 100-mesh sieve to obtain flour.

[0109] Preparation of anti-corrosion steel pipes: The steel pipe is preheated at 40℃ using medium-frequency induction heating to remove surface moisture, followed by shot blasting to achieve an anchor pattern depth of 40-100μm and a surface rust removal grade of Sa2.5. The rust-removed steel pipe is then heated to 180℃ and rotated using a mechanical device. A 200μm thick base powder and a 200μm thick intermediate powder are sprayed onto the inner and outer walls of the pipe, respectively. The pipe is then placed in a 230℃ heating furnace for melting, solidification, and leveling for 15 minutes. After removal from the furnace, the surface of the anti-corrosion layer on both the inner and outer walls is roughened. While still rotating and hot, a 300μm thick layer of flour is sprayed onto the pipe. While still rotating, the pipe is placed back into the 230℃ heating furnace for melting and leveling for another 15 minutes. The pipe is then removed and allowed to cool naturally.

[0110] Comparative Example 11 Preparation of foundation powder: Weigh out the following components: 50 parts of bisphenol A type epoxy resin (604 resin from Anhui Meijia), 10 parts of phenolic epoxy resin (Amanda1177HTM resin from Daqing Qinglu), 15 parts of phenolic curing agent (969A-2 product from Daqing Qinglu), 0.5 parts of accelerator (2-methylimidazole), 5 parts of polyvinylidene chloride resin (PVDC) (SLV20 type resin from Zhejiang Juhua), 2 parts of coupling agent (PCA-302A coupling agent from Nanjing Nengde Company), 15 parts of pigment and filler (titanium dioxide: phthalocyanine blue: barium sulfate = 2:1:12), 0.5 parts of heat stabilizer (calcium zinc stabilizer), 1 part of leveling agent (L88 product from Wuhan Yincai), and 1 part of defoamer (anti-yellowing benzoin). The above raw materials are sequentially added to a rotary mixer and stirred for 10 minutes to ensure uniform mixing. Then, the mixture is extruded through a twin-screw extruder with a set temperature of 95°C and a length-to-diameter ratio of 16:1. The extruded material is then compressed and crushed into flakes by a water-cooled tablet press, and then ground into powder by an ACM mill. The powder is then sieved through a 120-mesh screen to prepare the base powder.

[0111] Preparation of intermediate flour: 80 parts of SLV20 polyvinylidene chloride (PVDC) resin from Zhejiang Juhua, 9 parts of tributyl acetylacetic acid plasticizer, 3 parts of calcium-zinc stabilizer heat stabilizer, 7 parts of light calcium carbonate, and 1 part of anti-yellowing benzoin defoamer were weighed out. The above raw materials were added to a high-speed mixer at a set temperature of 80℃ and mixed evenly. The mixture was then processed into granules using a twin-screw extruder at 140-170℃ through melting, extrusion, cooling, and pelletizing processes. The granules were then placed in a cooling tank containing liquid nitrogen for cryogenic cooling, and the liquid nitrogen-cooled granules were ground into powder using an ultra-low temperature grinding process. The powder was then sieved through a 100-mesh sieve to obtain intermediate powder.

[0112] Flour preparation: Ten parts of polyvinylidene chloride (PVDC) resin (Zhejiang Juhua SLV20 type), 0.5 parts of calcium-zinc stabilizer, 69 parts of low-density polyethylene resin (Yanshan Petrochemical LD615), 10 parts of maleic anhydride-grafted low-density polyethylene resin (DuPont 4206), 10 parts of pigments and fillers (titanium dioxide: phthalocyanine blue: barium sulfate = 2:1:7), and 0.5 parts of antioxidants (hindered phenolic antioxidant 1010: phosphite antioxidant 168 = 1:2) were weighed out. The above raw materials were mixed evenly in a high-speed mixer at room temperature, and then processed into granules through a twin-screw extruder at 140-180℃ via melting, extrusion, cooling, and pelletizing. The granules were then placed in a cooling tank containing liquid nitrogen for cryogenic cooling, and the liquid nitrogen-cooled granules were ground into powder using an ultra-low temperature grinding process. The powder was then sieved through a 100-mesh sieve to obtain flour.

[0113] Preparation of coated steel pipes: The steel pipe is preheated at 40℃ using medium-frequency induction heating to remove surface moisture, and then undergoes shot blasting to remove rust, achieving an anchor pattern depth of 40-100μm and a rust removal grade of Sa2.5. The rust-removed steel pipe is then heated to 180℃ and rotated using a mechanical device. A 200μm thick base powder, a 100μm thick intermediate powder, and a 300μm thick flour layer are sprayed onto the inner and outer walls of the pipe, respectively. While maintaining rotation, the steel pipe is placed in a 160℃ heating furnace for melting and leveling for 10 minutes. The pipe is then removed and allowed to cool naturally.

[0114] Detection method: 1. Adhesion test: The pull-out method in GB / T 5210-2006 was used to test the adhesion between the base powder and the steel pipe, the adhesion between the base powder and the intermediate powder, the adhesion between the intermediate powder and the flour, the adhesion between the intermediate powder and the steel pipe, and the adhesion between the flour and the steel pipe.

[0115] 2. Resistance to cathodic disbondment: The resistance to cathodic disbondment of the coating was tested using the test method in SY / T4113.3-2019 with parameters of 65℃, -1.5V and 28d.

[0116] 3. Salt spray resistance: The test method in GB / T1771-2007 is adopted to conduct a 5000-hour neutral salt spray test and test the width of the corrosion spread by the scribing.

[0117] 4. Resistance to microbial adhesion: The test was conducted for 8 cycles using the dynamic simulation experiment method in GB / T7789-2007, and the resistance to microbial adhesion was scored using the scoring method in GB / T5370-2007.

[0118] 5. Substrate Resistivity Test: The following method was used to test the substrate resistivity in the examples and comparative examples: DN100 steel pipes are preheated at 40℃ using medium-frequency induction heating to remove surface moisture, followed by shot blasting to achieve an anchor pattern depth of 40-100 μm and a surface rust removal grade of Sa2.5. The rust-removed pipes are then heated to 210℃ and rotated using a mechanical device. A 300 μm layer of primer powder is sprayed onto both the inner and outer walls of the pipe, and the residue heat is used to melt and solidify the powder, producing the anti-corrosion steel pipe product. The resistivity is tested using a high-resistivity meter according to the MT181-88 standard.

[0119] The test results are shown in Tables 1 and 2.

[0120] Table 1. Detection data results of the examples and comparative examples.

[0121] Table 2. Detection data results of the examples and comparative examples.

[0122] As shown in Table 1 above, the test data reveals the following: Compared to Comparative Example 1, Example 1, using only base powder as the anti-corrosion coating, exhibits poor salt spray resistance, cathodic disbondment resistance, and resistance to microbial adhesion. Comparing Example 1 with Comparative Example 2, Comparative Example 2 uses only intermediate powder as the anti-corrosion coating. Due to the high zinc content in the intermediate powder, adhesion to the metal is poor, resulting in poor cathodic disbondment resistance and resistance to microbial adhesion. Comparing Example 1 with Comparative Example 3, Comparative Example 3 uses only flour as the anti-corrosion layer. Because it contains low surface energy substances such as solid silicone resin, fluorinated acrylic resin, and polytetrafluoroethylene wax, adhesion between the surface layer and the metal is poor, and cathodic disbondment resistance and salt spray resistance also deteriorate. Comparing Example 1 with Comparative Example 4, Comparative Example 4 uses a combination of base powder and flour as the anti-corrosion layer, resulting in significantly poorer resistance to microbial corrosion. Comparing Example 1 with Comparative Example 5, Comparative Example 5 used base powder and flour as the anti-corrosion layer. Due to the lack of the sacrificial anode effect of the zinc-rich coating in the intermediate layer, the coating's resistance to cathodic disbondment and salt spray performance deteriorated. Comparing Example 1 with Example 2, the proportions of solid silicone resin and fluorinated acrylic resin in the flour were adjusted, revealing different effects of different proportions of solid silicone resin and fluorinated acrylic resin on resistance to microbial adhesion. Comparing Example 2 with Comparative Example 6, the removal of phenolic epoxy resin from the base powder in Comparative Example 6 reduced the density of the underlying layer, resulting in decreased adhesion, resistance to cathodic disbondment, and salt spray performance, as well as a decrease in the underlying resistivity. Comparing Example 2 with Comparative Example 7, the replacement of flake zinc powder with spherical zinc powder in the intermediate powder in Comparative Example 7 prevented the synergistic effect of the flake and spherical zinc powders from being utilized, leading to poorer corrosion resistance, decreased resistance to cathodic disbondment, and salt spray performance. Comparing Example 2 with Comparative Example 8, the removal of solid silicone resin from the flour in Comparative Example 8 prevented the synergistic effect of the solid silicone resin and fluorinated acrylic resin from being utilized, resulting in reduced resistance to microbial corrosion. Comparing Example 2 with Comparative Example 9, the removal of carbon nanotubes from the base powder in Comparative Example 9 prevented the synergistic effect of conductive carbon black and carbon nanotubes from being utilized, increasing the resistivity of the coating. The underlying layer could not form a conductive pathway connecting the intermediate zinc-rich coating and the metal tube, thus preventing the sacrificial anode from functioning and deteriorating the coating's resistance to cathodic disbondment and salt spray.

[0123] Comparative Example 10 is a solution from our company's previous patent (publication number CN119799129A). Through comparative analysis between Example 2 and Comparative Example 10, although the bonding strength between the bottom layer and the middle layer, and between the middle layer and the top layer in Comparative Example 10 is relatively high, the bottom layer of Comparative Example 10 has a high resistivity and poor resistance to cathodic disbondment, salt spray, and antimicrobial adhesion because the bottom powder does not contain conductive carbon black, carbon nanotubes, zinc powder, and the flour does not contain solid organosilicon resin, fluorinated acrylic resin, polytetrafluoroethylene wax, or other low surface energy substances. Comparative Example 11 is a solution from our company's previous patent (publication number CN116716020A). Through comparative analysis between Example 2 and Comparative Example 11, it was found that the bottom powder of Comparative Example 11 did not contain conductive carbon black, carbon nanotubes, or other substances, the intermediate powder did not contain zinc powder, and the flour did not contain solid organosilicon resin, fluorinated acrylic resin, polytetrafluoroethylene wax, or other low surface energy substances. Therefore, the resistivity of the bottom layer of Comparative Example 11 was relatively high, and its resistance to cathodic disbondment, salt spray, and antimicrobial adhesion was poor.

[0124] Data from Examples 1 and 2 show that the anti-corrosion powder material of this invention exhibits excellent adhesion and resistance to cathodic disbondment between the powder and the steel pipe. The bottom layer powder, through the addition of conductive carbon black and carbon nanotubes, forms a conductive pathway, connecting the metal pipe with the intermediate zinc-rich coating, thus acting as a sacrificial anode and enhancing the overall corrosion resistance of the coating. The anti-corrosion powder material also possesses excellent resistance to microbial adhesion, reducing corrosion caused by microbial adhesion during seawater transportation and further extending the service life of the steel pipe.

[0125] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A powder coating for anti-corrosion steel pipes used for transporting seawater, characterized in that, Includes base flour, intermediate flour, and wheat flour; The base powder, by weight, comprises 20-30 parts of bisphenol A epoxy resin, 20-30 parts of phenolic epoxy resin, 15-25 parts of phenolic curing agent, 0.5-2 parts of accelerator, 0.5-2 parts of coupling agent, 0.5-2 parts of nano silica, 5-10 parts of glass flakes, 10-15 parts of silica powder, 10-15 parts of wollastonite powder, 0.5-1 part of leveling agent, 0.5-1 part of defoamer, 1-5 parts of conductive carbon black, and 1-5 parts of carbon nanotubes. The intermediate powder, by weight, comprises 30-50 parts of bisphenol A epoxy resin, 10-25 parts of phenolic curing agent, 0.5-2 parts of accelerator, 0.5-2 parts of coupling agent, 5-10 parts of mica powder, 30-40 parts of spherical zinc powder, 5-15 parts of flake zinc powder, 5-10 parts of ferrophosphorus powder, 0.5-1 part of leveling agent, 0.5-1 part of defoamer, and 1-5 parts of carbon nanotubes. The flour, by weight, comprises 20-30 parts of bisphenol A epoxy resin, 10-30 parts of phenolic epoxy resin, 15-25 parts of phenolic curing agent, 0.5-2 parts of accelerator, 0.5-2 parts of coupling agent, 0.5-2 parts of nano silica, 5-10 parts of silica powder, 5-10 parts of wollastonite powder, 0.5-1 part of leveling agent, 0.5-1 part of defoamer, 1-5 parts of polytetrafluoroethylene wax, 5-10 parts of modified solid organosilicon resin, 5-10 parts of fluorinated acrylic resin, 1-5 parts of zinc oxide, 1-2 parts of titanium dioxide, and 1-2 parts of pigment.

2. The powder coating as described in claim 1, characterized in that, The bisphenol A type epoxy resin in the base powder has a softening point of 85℃-130℃, including at least one of one-step epoxy resin and two-step epoxy resin; and / or, the phenolic epoxy resin in the base powder includes at least one of Amanda1168, Amanda1177HTM, Amanda1178HT, ES503, ES3065, NPCN-702, and 704 resin; and / or, the phenolic curing agent in the base powder includes at least one of KD404, KD405, KD406, V-2083, V-2081, V-2059, 969 series, and 979 series curing agents; and / or, the coupling agent in the base powder is a powder coupling agent containing epoxy groups.

3. The powder coating as described in claim 1, characterized in that, The nano-silica in the base powder is a hydrophobic fumed silica product; preferably, the nano-silica is at least one of R-972 and R-974; and / or, the silica powder in the base powder has a mesh size of 800-1500 mesh; and / or, the wollastonite powder in the base powder has a mesh size of 800-1500 mesh commercially available; and / or, the leveling agent in the base powder is an acrylate product; and / or, the defoamer in the base powder is a benzoin product, including at least one of pure benzoin and anti-yellowing benzoin.

4. The powder coating as described in claim 1, characterized in that, The bisphenol A type epoxy resin in the intermediate powder has a softening point of 85℃-130℃, including at least one of one-step epoxy resin and two-step epoxy resin; and / or, the phenolic curing agent in the intermediate powder includes at least one of KD404, KD405, KD406, V-2083, V-2081, V-2059, 969 series, and 979 series curing agents; and / or, the accelerator in the intermediate powder is an imidazole or cycloamidinium compound, including at least one of 2-methylimidazole and 2-isopropylimidazole; and / or, the coupling agent in the intermediate powder is a powder coupling agent containing epoxy groups; and / or, the intermediate powder contains... The mica powder in the intermediate powder is 200-600 mesh white mica powder; and / or, the spherical zinc powder in the intermediate powder is spherical zinc powder with a particle size D50 of 20-50 μm; and / or, the flake zinc powder in the intermediate powder is flake zinc powder with a particle size D50 of 10-20 μm; and / or, the ferrophosphorus powder in the intermediate powder is a 600-1000 mesh product; and / or, the leveling agent in the intermediate powder is an acrylate product; and / or, the defoamer in the intermediate powder is a benzoin product, including at least one of pure benzoin and anti-yellowing benzoin.

5. The powder coating as described in claim 1, characterized in that, The modified solid organosilicon resin in the flour includes at least one of hydroxyl-modified solid organosilicon resin and epoxy-modified solid organosilicon resin; and / or, the softening point of the bisphenol A type epoxy resin in the flour is 85℃-130℃. The flour contains at least one of a one-step epoxy resin and a two-step epoxy resin; and / or, the phenolic epoxy resin in the flour contains at least one of Amanda1168, Amanda1177HTM, Amanda1178HT, ES503, ES3065, NPCN-702, and 704 resins; and / or, the phenolic curing agent in the flour contains at least one of KD404, KD405, KD406, V-2083, V-2081, V-2059, 969 series, and 979 series curing agents; and / or, the accelerator in the flour is an imidazole or cycloamidinium compound, including at least one of 2-methylimidazole and 2-isopropylimidazole; and / or, the coupling agent in the flour is a powder coupling agent containing epoxy groups; and / or, the nano silica in the flour is a hydrophobic fumed silica product; and / or, the flour... The silica powder in the flour is an 800-1500 mesh silica powder product; and / or, the wollastonite powder in the flour is an 800-1500 mesh wollastonite powder product; and / or, the leveling agent in the flour is an acrylic ester product; and / or, the defoamer in the flour is a benzoin-based product, including at least one of pure benzoin and anti-yellowing benzoin; and / or, the polytetrafluoroethylene wax in the flour is a product with a particle size D50 of 2-5 μm; and / or, the fluorinated acrylic resin in the flour is a commercially available solid fluorinated acrylic resin product with a softening point of 80-100℃; and / or, the zinc oxide in the flour is at least one of commercially available direct zinc oxide, active zinc oxide, and nano zinc oxide; and / or, the titanium dioxide in the flour is rutile titanium dioxide; and / or, the pigment in the flour is at least one of phthalocyanine blue, phthalocyanine green, medium chrome yellow, 254 red, permanent violet, and ultramarine.

6. The method for preparing powder coating as described in claim 1, characterized in that, Includes the following steps: Bisphenol A type epoxy resin, phenolic epoxy resin, coupling agent, nano silica, glass flakes, silica powder, wollastonite powder, and leveling agent are mixed evenly in a mixer, then extruded using a twin-screw extruder, and then pressed and crushed using a water-cooled tablet press. The crushed raw materials are then mixed evenly again in a mixer with phenolic curing agent, accelerator, defoamer, conductive carbon black, and carbon nanotubes, and then extruded using a twin-screw extruder, pressed and crushed using a water-cooled tablet press, and then ground into powder. The powder is then sieved through an 80-120 mesh sieve to prepare the base powder. Bisphenol A type epoxy resin, phenolic curing agent, accelerator, coupling agent, mica powder, spherical zinc powder, flake zinc powder, ferrophosphorus powder, leveling agent, defoamer, and carbon nanotubes are mixed evenly in a mixer, then extruded using a twin-screw extruder, then compressed and crushed using a water-cooled tablet press, and then ground into powder. The powder is then sieved through a 60-120 mesh screen to prepare intermediate powder. Bisphenol A type epoxy resin, phenolic epoxy resin, phenolic curing agent, accelerator, coupling agent, nano silica, silica powder, wollastonite powder, leveling agent, defoamer, polytetrafluoroethylene wax, modified solid organosilicon resin, fluorinated acrylic resin, zinc oxide, titanium dioxide, and pigment are mixed evenly in a mixer, then extruded using a twin-screw extruder, then pressed and crushed using a water-cooled tablet press, and finally ground into powder. The powder is then sieved through a 60-120 mesh screen to prepare flour.

7. The application of the powder coating as described in claim 1 in the corrosion protection of steel pipes.

8. A corrosion-resistant steel pipe for transporting seawater, characterized in that, It includes a steel pipe; the inner and outer surfaces of the steel pipe are coated with a paint film; the paint film is formed by the powder coating as described in claim 1.

9. A coating process for a corrosion-resistant steel pipe used for transporting seawater, characterized in that, After the steel pipe is preheated and derusted, it is heated and rotated by a mechanical device. The aforementioned powder coating base powder, intermediate powder and flour are sprayed sequentially on the inner and outer walls of the steel pipe. The residual heat of the steel pipe is used to melt and solidify the coating, and then it is allowed to cool down naturally.

10. The coating process as described in claim 9, characterized in that, After preheating and rust removal, the anchor pattern depth on the surface of the steel pipe reaches 40-100 μm; And / or, the steel pipe is heated to 180 ℃-210 ℃ after preheating and rust removal; And / or, spray 300-400 μm of base powder, 300-400 μm of intermediate powder, and 200-400 μm of flour successively onto the inner and outer walls of the steel pipe.

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