Corrosion prevention method for low-pressure steel pipe pole in coastal area

Abstract

The invention discloses an anti-corrosion method for a low-pressure steel pipe pole in a coastal area, which comprises the following steps: arranging a spiral grain pavement on the outer wall of the steel pipe pole, and sequentially arranging an outer anti-corrosion layer I, an outer anti-corrosion layer II and an outer anti-corrosion layer III from inside to outside after a micron-sized honeycomb porous structure is formed on the spiral grain pavement; the inner wall of the steel pipe pole is provided with a net-shaped grain surface, and after a micron-sized honeycomb porous structure is formed on the net-shaped grain surface, an inner anti-corrosion layer I, an inner anti-corrosion layer II and an inner anti-corrosion layer III are sequentially arranged from inside to outside; wherein flow guide grooves are formed in the spiral grain surface and the net-shaped grain surface and are used for discharging penetrating fluid; according to the anti-corrosion method provided by the invention, the anti-corrosion performance is synergistically enhanced through multiple mechanisms, and the overall corrosion resistance is remarkably improved by combining the design of the composite coating with layered inner and outer walls with multiple mechanisms such as chemical passivation, sacrificial anodes and physical shielding.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of corrosion protection, and particularly relates to a corrosion protection method for low-voltage steel pipe poles in coastal areas. BACKGROUND

[0002] A low-voltage steel pipe pole is a support structure specially used for low-voltage distribution lines (usually referring to 400V and below voltage levels), and is made of a single round cone or multi-prism steel pipe, and belongs to a component of power transmission infrastructure. In order to improve the service life of the steel pipe pole, a corrosion protection material is sprayed to improve the service life of the steel pipe pole. For example, a zinc grease corrosion protection steel pipe pole and a coating method thereof are disclosed in Chinese patent CN201610156497.5. The zinc grease corrosion protection steel pipe pole comprises a steel pipe body, a zinc layer, a corrosion-resistant layer and a cover layer. The zinc layer, the corrosion-resistant layer and the cover layer are sequentially coated on the steel pipe body. The coating preparation method comprises the following steps: pretreatment, part processing, secondary treatment, spraying of the zinc layer, spraying of the corrosion-resistant layer and spraying of the cover layer.

[0003] Although the corrosion protection coating of the steel pipe pole in the prior art can achieve the purpose of corrosion protection, the traditional zinc layer, the corrosion-resistant layer and the cover layer lack chemical bonding and electrochemical synergistic mechanism, and the corrosion protection layer lacks synergistic effect, so it is difficult to resist the penetration corrosion of the high-salt mist environment in the coastal area, and the layered protection system is not designed for the different corrosion environments of the inner and outer walls of the steel pipe pole, and the inner and outer wall protection is single. In addition, the steel pipe pole coating in the prior art cannot be repaired locally through microcapsule slow release or pH response mechanism after damage, and lacks self-repairing function, which leads to rapid expansion of pitting corrosion and insufficient long-acting corrosion inhibition. Therefore, it is urgent to design a composite corrosion protection coating for low-voltage steel pipe poles in coastal areas and a preparation method thereof to solve the above problems of the steel pipe pole coating. SUMMARY

[0004] This section aims to summarize some aspects of the embodiments of the application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, abstract and title, and such simplifications or omissions cannot be used to limit the scope of the application.

[0005] In view of the above and / or problems existing in the prior art, the present application is proposed.

[0006] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art and provide a corrosion protection method for low-voltage steel pipe poles in coastal areas.

[0007] To solve the above technical problems, the present application provides the following technical solutions: comprising,

[0008] The outer wall of the steel pipe pole 1 is provided with a spiral texture surface 2, a micron-sized honeycomb porous structure is formed on the spiral texture surface 2, and then an outer corrosion-resistant layer I 3, an outer corrosion-resistant layer II 4, and an outer corrosion-resistant layer III 5 are sequentially arranged from the inside to the outside;

[0009] The inner wall of the steel pipe pole 1 is provided with a net texture surface 6, a micron-sized honeycomb porous structure is formed on the net texture surface 6, and then an inner corrosion-resistant layer I 7, an inner corrosion-resistant layer II 8, and an inner corrosion-resistant layer III 9 are sequentially arranged from the inside to the outside;

[0010] The spiral texture surface 2 and the net texture surface 6 are provided with flow guide grooves for discharging the permeate;

[0011] The flow guide grooves are filled with polyaniline microcapsule corrosion inhibitors.

[0012] As a preferred scheme of the anti-corrosion method, the depth of the flow guide groove is 1-2 mm, the shell porosity of the polyaniline microcapsule corrosion inhibitor is 4.5-10%, the polyaniline microcapsule corrosion inhibitor is composed of a core and a shell, the material of the core is benzotriazole, the material of the shell is a polyaniline / silicon dioxide hybrid material, and the polyaniline microcapsule corrosion inhibitor releases benzotriazole repair agent when pH≤4.

[0013] As a preferred scheme of the anti-corrosion method, the depth of the spiral texture surface 2 is 0.2-0.5 mm, and the pitch is 3-5 mm; the depth of the net texture surface 6 is 0.1-0.3 mm, and the grid size is 2x2-5x5 mm; the pore size of the micron-sized honeycomb porous structure is 5-10 μm, the pore depth is 10-20 μm, and the porosity is 30-40%.

[0014] As a preferred scheme of the anti-corrosion method, the material of the outer corrosion-resistant layer I 3 is a composite material of doped polyaniline dodecylbenzenesulfonic acid and epoxy resin, and the doping amount of polyaniline relative to dodecylbenzenesulfonic acid is 8-12 wt%.

[0015] As a preferred scheme of the anti-corrosion method, the material of the outer corrosion-resistant layer II 4 is a composite material of inorganic zinc-rich paint and polyaniline microcapsule corrosion inhibitor, and the doping amount of polyaniline microcapsule corrosion inhibitor relative to inorganic zinc-rich paint is 0.8-1.2 wt%.

[0016] As a preferred scheme of the anti-corrosion method, the material of the outer corrosion-resistant layer III 5 is a composite material of doped acidized carbon nanotube fluorocarbon resin and silane coupling agent modified nanosilica, and the addition amount of silane coupling agent modified nanosilica relative to doped acidized carbon nanotube fluorocarbon resin is 3-7 wt%.

[0017] As a preferred scheme of the anti-corrosion method, the material of the inner anti-corrosion layer I 7 is a composite material of tar epoxy resin and lithium molybdate corrosion inhibitor, and the doping amount of the lithium molybdate corrosion inhibitor is 3-5 wt% compared with the tar epoxy resin.

[0018] As a preferred scheme of the anti-corrosion method, the material of the inner anti-corrosion layer II 8 is a composite material of polyurethane and graphene oxide modified by a silane coupling agent, and the addition amount of the silane coupling agent is 20-30 wt% compared with the graphene oxide, and the material of the inner anti-corrosion layer III 9 is a super-hydrophobic silicone-acrylate emulsion.

[0019] As a preferred scheme of the anti-corrosion method, the outer wall of the steel pipe pole 1 is processed into a spiral pattern surface 2 by a numerical control rolling machine after sand blasting rust removal, the inner wall of the steel pipe pole 1 is processed into a net pattern surface 6 by fiber laser etching after sand blasting rust removal, and the spiral pattern surface 2 and the net pattern surface 6 are both obtained by electrolytic activation to have a micron-level honeycomb porous structure.

[0020] The outer anti-corrosion layer I 3 is obtained by coating and curing through an electrophoretic deposition process, the outer anti-corrosion layer II 4 is obtained by coating and then heat treatment through a supersonic flame spraying process, and the outer anti-corrosion layer III 5 is obtained by coating and curing through a spin coating process.

[0021] The inner anti-corrosion layer I 7 is obtained by coating and curing through a centrifugal spin coating process, the inner anti-corrosion layer II 8 is obtained by coating and curing through a high-pressure airless spraying device, and the inner anti-corrosion layer III 9 is obtained by spraying and curing through an aerosol-assisted deposition process.

[0022] As a preferred scheme of the anti-corrosion method, the outer anti-corrosion layer II 4 is obtained by coating and then heat treatment through a supersonic flame spraying process, wherein in the supersonic flame spraying process, the particle size of zinc powder is 5-8 μm, the gas pressure is 0.5-1 MPa, and the powder feeding rate is 30-38 g / min.

[0023] The present application has the following advantages:

[0024] (1) The anti-corrosion method for low-pressure steel pipe poles in coastal areas provided by the present application enhances the anti-corrosion performance through multiple mechanisms, and significantly improves the overall corrosion resistance through the design of the layered composite coating on the inner and outer walls, combined with multiple mechanisms such as chemical passivation, sacrificial anode and physical shielding.

[0025] (2) The outer wall spiral pattern can enhance the adhesion of the coating, combined with the high weather resistance of the fluorocarbon surface layer, resist salt spray erosion, and the inner wall grid pattern improves the coating coverage, cooperates with the super-hydrophobic layer to reduce the condensate water adhesion, at the same time, the flow guide groove and the pH response microcapsule realize the directional discharge of the permeate and the acid environment triggers self-repair, forming a dynamic protection system, so that the steel pipe pole has the differentiation of the inner and outer walls, and can be applied to complex environments;

[0026] (3) The core-shell structure microcapsule realizes accurate repair of the damaged area, the benzotriazole slow-release mechanism prolongs the corrosion inhibition period, the graphene and carbon nanotube enhance the conductivity and mechanical strength of the coating, inhibit galvanic corrosion and crack propagation, ensure the long-term stability of the coating in a strong corrosive environment, and realize the breakthrough of self-repair and long-term corrosion inhibition technology; The outer coating polyaniline / epoxy resin and the inorganic zinc-rich layer form an electrochemical synergy, and the inner coating graphene and lithium molybdate construct a three-dimensional protection network, effectively resisting coastal high-salt mist and condensate water corrosion, and prolonging the service life of the steel pipe pole;

[0027] (4) Electrolytic activation and laser etching process reduce energy consumption and material loss, and through supersonic flame spraying of the coating containing microcapsules, on the one hand, the utilization rate of zinc powder is improved, and on the other hand, the integrity of the microcapsule shell is ensured, avoiding the incompatibility of microcapsules with traditional coating processes; Aerosol deposition realizes uniform nanoscale film formation, and the whole process has strong compatibility and is suitable for large-scale production, taking into account environmental protection and economy. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0029] Figure 1 The structure diagram of the low-pressure steel pipe pole in the coastal area prepared in the embodiment 1 of the present application.

[0030] Figure 2 The flowchart of the anti-corrosion method of the low-pressure steel pipe pole in the coastal area in the embodiment 1 of the present application. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation manner of the present application will be described in detail in the following with reference to the embodiment of the specification.

[0032] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced without the specific details. In other instances, well-known methods have not been described in detail in order not to unnecessarily obscure aspects of the present application. The present application is not limited to the embodiments described herein.

[0033] It is also noted that, as used herein, "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the present application. The appearances of the phrase "in one embodiment" or "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are the various embodiments necessarily mutually exclusive, with reference to each other.

[0034] The preparation method of the KH-550 modified graphene oxide in the present application is as follows: graphene oxide and γ-aminopropyl triethoxysilane (KH-550) are ultrasonically dispersed at 50 DEG C for 2 hours to obtain modified graphene oxide with a sheet spacing expanded to 0.8-1.2 nm, wherein the addition amount of KH-550 is 20-30 wt% compared with graphene oxide.

[0035] The preparation method of the polyaniline microcapsule corrosion inhibitor in the present application is as follows: benzotriazole and polyaniline prepolymer are mixed at a mass ratio of 1:3 to form an inner core emulsion at 60 DEG C under stirring; TEOS and ethanol are mixed at a volume ratio of 1:4, and a silica shell layer is coated on the surface of the inner core through ammonia catalysis, wherein the shell layer thickness of the outer shell is 200-300 nm; aniline monomer and ammonium persulfate are in-situ polymerized at 0-5 DEG C to wrap a polyaniline conductive layer outside the shell layer, wherein the aniline monomer concentration is 0.2 mol / L.

[0036] In the fluorocarbon resin coating in the present application, 0.1-0.3 wt% carbon nanotubes are added as a conductive reinforcing phase, wherein the carbon nanotubes are subjected to mixed acid acidification treatment, the mixed acid is obtained by mixing concentrated sulfuric acid and concentrated nitric acid at a mass ratio of 3:1, the length is 10-20 μm, the diameter is 20-30 nm, and the volume resistivity of the dispersed FEVE type fluorocarbon resin coating is ≤1*10 6 Ω·cm.

[0037] In the present application, the adhesion test refers to the grid method detection according to GB / T5210 standard.

[0038] In the present application, the salt spray resistance experiment refers to 2000 hours of neutral salt spray test according to ASTM B117 salt spray test standard.

[0039] In the present application, the electrochemical impedance spectrum refers to ASTM G106 standard test.

[0040] In the present application, the self-repairing verification method is as follows: drop pH=3 HCl solution at the flow guide groove, and observe the release and repair of the microcapsule within 24 hours.

[0041] Embodiment 1

[0042] The embodiment provides a corrosion prevention method for a low-pressure steel pipe pole in a coastal area, and particularly relates to the following technical scheme.

[0043] (1) Pipe body pretreatment: Q345B steel pipe is selected, with an outer diameter of 200 mm and a wall thickness of 8 mm;

[0044] The inner and outer walls of the steel pipe pole 1 are subjected to sand blasting rust removal treatment, wherein the particle size of the steel sand is 1.0 mm, and the pressure is 0.7 MPa, so that the surface cleanliness reaches the Sa2.5 level; the outer surface is machined by a numerical control rolling machine to obtain a helical groove surface 2 with a pitch of 4 mm and a depth of 0.3 mm, wherein the roller pressure is 12 MPa; the inner surface is machined by a fiber laser etching machine to obtain a mesh groove surface 6 with a depth of 0.2 mm and a size of 3*3 mm, wherein the etching power is 250 W, and the scanning speed is 1000 mm / s;

[0045] The pipe body is immersed in a mixed solution of dilute sulfuric acid and sodium dodecyl sulfate (SDS), a direct current voltage of 4 V is applied, and electrolysis is performed for 12 min to obtain an activated surface with a micron-level honeycomb porous structure, wherein the concentration of dilute sulfuric acid is 5 wt%, and the concentration of SDS is 0.8 wt%.

[0046] The helical groove surface 2 and the mesh groove surface 6 are provided with annular flow guide grooves at both ends of the steel pipe, with a groove depth of 1.5 mm, and the annular flow guide grooves are filled with polyaniline microcapsule corrosion inhibitors with a particle size of 80 μm, and the shell porosity of the polyaniline microcapsule corrosion inhibitors is 5%;

[0047] (2) Preparation of the outer corrosion prevention layer:

[0048] Through an electrophoretic deposition process, doped polyaniline dodecylbenzenesulfonic acid (DBSA) and an epoxy resin mixed solution are deposited on the helical groove surface 2 after electrolytic activation at a voltage of 40 V for 6 min to obtain an outer corrosion prevention layer I 3 with a thickness of 40 μm, and the outer corrosion prevention layer I 3 is cured at room temperature for 24 h, with a curing humidity of ≤65%, to obtain a corrosion prevention layer, wherein the doping amount of polyaniline relative to dodecylbenzenesulfonic acid is 10 wt%;

[0049] An inorganic zinc-rich coating and a polyaniline microcapsule corrosion inhibitor mixture are sprayed by a supersonic flame spraying process to obtain an outer corrosion prevention coating II 4 with a thickness of 80 μm, and the outer corrosion prevention coating II 4 is heat treated at 150°C for 1 h, wherein the particle size of zinc powder is 6 μm, the gas pressure is 0.7 MPa, the powder feeding rate is 35 g / min, and the addition amount of polyaniline microcapsule corrosion inhibitor relative to the inorganic zinc-rich coating is 1 wt%, wherein the shell porosity of the polyaniline microcapsule corrosion inhibitor is 5%;

[0050] The mixture of the acidized carbon nanotube-doped FEVE type fluorocarbon resin and the KH-550 modified SiO2 is coated on the outer anticorrosion layer II 4 by a spin coating method at a speed of 1000 r / min to obtain an outer anticorrosion layer III 5 with a thickness of 60 μm, and baking at 140 ℃ for 2.5 h, the surface contact angle of the anticorrosion layer is ≥110°, wherein the doping amount of the silane-modified SiO2 relative to the fluorocarbon resin is 5 wt%, and the doping amount of the acidized carbon nanotube relative to the FEVE type fluorocarbon resin is 0.1 wt%.

[0051] (3) Inner anticorrosion layer preparation:

[0052] The mixture of the tar epoxy resin and the lithium molybdate corrosion inhibitor is coated on the reticular surface 6 by a centrifugal spin coating process at a speed of 1800 r / min, and the inner anticorrosion layer I 7 with a total thickness of 30 μm is obtained after coating 3 times and baking at 80 ℃ for 1 h, and then curing at room temperature for 24 h, wherein the doping amount of the lithium molybdate corrosion inhibitor relative to the tar epoxy resin is 4 wt%;

[0053] The mixture of the polyurethane and the KH-550 modified graphene oxide is sprayed by a high-pressure airless spraying device at a pressure of 13 MPa to obtain the inner anticorrosion layer II 8 with a thickness of 50 μm, and then pre-curing at 60 ℃ for 30 min, and then curing at 120 ℃ for 2 h, wherein the doping amount of the KH-550 modified graphene oxide relative to the polyurethane is 0.3 wt%, and the addition amount of the KH-550 relative to the graphene oxide is 20 wt%;

[0054] Then, the super-hydrophobic silicone-acrylate emulsion is sprayed by an aerosol-assisted deposition process at an atomization pressure of 0.4 MPa and a spraying distance of 200 mm to obtain the inner anticorrosion layer III 9 with a thickness of 20 μm, and then baking at 80 ℃ for 40 min to obtain the anticorrosion layer with a contact angle of 152°;

[0055] The structure of the composite anticorrosion coating prepared in Example 1 is shown in Figure 1 , and the flow of the anticorrosion method is shown in Figure 2 . Figure 1 (a) is a side view, Figure 1 (b) is a cross-sectional view. Wherein, 1 is a pipe body, 2 is a spiral surface, 3 is an outer anticorrosion layer I, 4 is an outer anticorrosion layer II, 5 is an outer anticorrosion layer III, 6 is a reticular surface, 7 is an inner anticorrosion layer I, 8 is an inner anticorrosion layer II, and 9 is an inner anticorrosion layer III.

[0056] The inner and outer coatings prepared in Example 1 are subjected to salt spray testing, and the results show that the outer coating has no blistering, and the rust area of the inner coating is only 3%≤5%, and since the graphene and lithium molybdate in the inner coating construct a three-dimensional protective network, they effectively resist high salt mist in the coastal area.

[0057] The impedance value of the inner and outer coating prepared in Example 1 is obtained, and the impedance value of the inner coating is 1.2 x 10 8 Ω·cm 2 ≥1 x 10 8 Ω·cm 2 The impedance value of the outer coating is 6 x 10 7 Ω·cm 2 ≥5 x 10 7 Ω·cm 2 It shows that the coating can effectively prevent the corrosion medium from contacting the metal substrate, thereby delaying or preventing the corrosion of the metal.

[0058] The pencil hardness of the inner and outer coating prepared in Example 1 is obtained, and the outer coating is 2H and the inner coating is H, which shows that the inner and outer coating both have high hardness, high scratch resistance and wear resistance.

[0059] The pH = 3 HCl solution is added dropwise at the flow guide groove prepared in Example 1, and the repair effect is observed for 24 h and the electrochemical impedance values before and after repair are compared. The results show that the repair film coverage rate reaches 92% ≥ 90%, the film thickness is 3 μm in the range of 2-5 μm, the impedance value after repair is restored to 85% of the original value, that is, the electrochemical impedance value decay rate is ≤ 20%, and the permeate discharge rate is 0.6 mL / min. It can be seen that the flow guide groove filled with polyaniline microcapsule corrosion inhibitor realizes the directional discharge of permeate and the self-repair triggered by acidic environment, forming a dynamic protection system.

[0060] Example 2

[0061] The difference between this example and Example 1 is that the addition amount of KH-550 compared with graphene oxide in the preparation process of anticorrosion layer II in step (3) is adjusted to 25 wt%, and the rest of the preparation process is the same as Example 1, and the composite coating of this example is prepared.

[0062] Comparative Example 1

[0063] The difference between this comparative example and Example 1 is that the graphene oxide is not modified in the preparation process of anticorrosion layer II in step (3), and the rest of the preparation process is the same as Example 1, and the composite coating of this comparative example is prepared.

[0064] The tensile strength, condensate contact angle and coating pitting depth of the coating prepared in Example 2 and Comparative Example 1 are tested, and the results are shown in Table 1. As can be seen from Table 1, the tensile strength of the modified coating is improved by 18%, and the mechanical properties of the coating are significantly improved. The superhydrophobicity of the modified coating is improved, and the corrosion of the coating by condensate is reduced.

[0065] The pitting depth of the coating prepared by unmodified graphene oxide in Comparative Example 1 is 60 μm. Since the unmodified graphene oxide layers are prone to agglomeration, the interlayer spacing is <0.8 nm, and the graphene oxide layers are not uniformly dispersed in the polyurethane, forming local defect channels. The condensed water penetrates into the substrate through the defects, accelerating the expansion of the pitting, and thus the pitting depth is large. The pitting depth of Example 3 is only 35 μm, which is reduced by 41.7% compared with the unmodified graphene oxide. This is because the silane coupling agent KH-550 expands the interlayer spacing, forms a dense three-dimensional physical barrier, and the amino group (—NH2) forms a hydrogen bond with the polyurethane matrix, improving the interfacial bonding force. The graphene oxide and the corrosion inhibitor such as lithium molybdate work together to build a three-dimensional protective network inside the coating. The three-dimensional barrier network and the passivation effect of lithium molybdate synergistically inhibit the penetration of Cl - and corrosion of corrosive media, and thus the pitting depth is reduced to 35 μm.

[0066] Table 1 Influence of modified graphene oxide on the performance of the coating

[0067]

[0068]

[0069] Example 3

[0070] The difference between this example and Example 1 is that the shell porosity of the polyaniline microcapsule corrosion inhibitor in the flow channel in step (1) is adjusted to 4.5%, and the rest of the preparation process is the same as that of Example 1, and the composite coating of this example is prepared.

[0071] Comparative Example 2

[0072] The difference between this comparative example and Example 3 is that only inorganic zinc-rich paint is sprayed to prepare the outer corrosion protection coating II in step (2), and no polyaniline microcapsule corrosion inhibitor is added, and the rest of the preparation process is the same as that of Example 3, and the composite coating of the comparative example is prepared.

[0073] The zinc powder consumption rate is tested when the outer corrosion protection coating II of Example 3 and Comparative Example 2 is prepared. It is found that since the zinc-rich layer of the present application not only acts as a sacrificial anode, but also forms an electrochemical-chemical double protection with the polyaniline microcapsule, the zinc powder consumption rate in Example 3 is reduced from 30% of the zinc powder consumption rate of the coating in Comparative Example 2 to 12%.

[0074] The inner and outer coatings prepared in Example 3 are subjected to salt spray testing, and it is found that the rust area of the outer coating is 0.5%, and the rust area of the inner coating is 1.8%, which has a more excellent corrosion protection effect than the coating of Example 1.

[0075] Comparative Example 3

[0076] The difference between the present comparative example and Example 1 is that the shell porosity of the polyaniline microcapsule corrosion inhibitor in the flow channel in step (1) is adjusted to 11% and 12%, and the rest of the preparation process is the same as that of Example 1, thereby preparing the composite coating of the present comparative example.

[0077] The coatings prepared in Examples 1, 3 and Comparative Example 3 are subjected to accelerated aging test in a 85°C humid heat environment for 6 months to simulate 5 years of service.

[0078] It is found that when the shell porosity is 4.5% and 5%, the polyaniline / silica hybrid shell slowly hydrolyzes in the humid heat environment, and the benzotriazole core is released on demand, the microcapsule release rate is 0.08 mg / (cm2·year), and the single release amount is ≤0.1 mg / cm2. 2 The repair film thickness is 3 μm, the repair coverage can reach more than 90%, the release period is ≥5 years, the corrosion inhibitor is zero released when pH>4, and the invalid loss is avoided. When the shell porosity reaches 11% and 12%, the corrosion inhibitor is released in advance, the repair coverage is less than 70%, the release period is <3 years, and the release requirement cannot be met.

[0079] Comparative Example 4

[0080] The difference between the present comparative example and Example 3 is that the polyaniline / silica hybrid shell of the polyaniline microcapsule corrosion inhibitor in the preparation process of the outer corrosion protection coating II in step (2) is adjusted to only polyaniline as the shell, and the rest of the preparation process is the same as that of Example 3, thereby preparing the composite coating of the present comparative example.

[0081] The release rate of the polyaniline microcapsule of Comparative Example 4 is tested, and it is found that the release rate of the microcapsule is as low as 40%, which cannot realize the repair of the coating.

[0082] Example 4

[0083] The difference between the present example and Example 1 is that the addition amount of acidified carbon nanotubes in the preparation process of the outer corrosion protection coating III in step (2) is adjusted to 0.2 wt% compared with the FEVE type fluorocarbon resin, and the rest of the preparation process is the same as that of Example 1, thereby preparing the composite coating of the present example.

[0084] Comparative Example 5

[0085] The difference between the present comparative example and Example 1 is that the acidified carbon nanotubes are not added to the FEVE type fluorocarbon resin in the preparation process of the outer corrosion protection coating III in step (2), and the rest of the preparation process is the same as that of Example 1, thereby preparing the composite coating of the present comparative example.

[0086] The impact resistance of the coating prepared in Example 4 and Comparative Example 5 and the surface contact angle after 3 months were tested, and the results are shown in Table 2. It can be seen that the surface of the coating prepared by adding acidified carbon nanotubes has no cracks, while the coating without the addition has a network of cracks. The surface contact angle of the coating with the addition of acidified carbon nanotubes remains at about 110° after 3 months, while the surface contact angle of the coating without the addition of acidified carbon nanotubes decreases to 95°.

[0087] Table 2 Effect of the addition of acidified carbon nanotubes on the performance of the coating

[0088]

[0089] Comparative Example 6

[0090] The difference between this comparative example and Example 1 is that no flow guide groove is provided in step (1), and the microcapsules are directly incorporated into the coating. The rest of the preparation process is the same as that of Example 1, and the composite coating of this comparative example is prepared.

[0091] The performance of the coating prepared in Example 1 and Comparative Example 6 was tested, and the results are shown in Table 3. As can be seen from Table 3, the absence of a flow guide groove results in the inability of the microcapsules to be directionally enriched in the corrosion area. After the release triggered by the HCl solution with pH = 3, the coverage rate of the repair film is only 1 / 2 of that with the flow guide groove. The rust area is as high as 12% after 2000h of salt spray testing.

[0092] Table 3 Effect of the flow guide groove on the performance of the coating

[0093]

[0094]

[0095] Comparative Example 7

[0096] The difference between this comparative example and Example 1 is that no pattern is provided on the inner and outer walls in step (1), and the coating is prepared on a smooth substrate without the pattern. The rest of the preparation process is the same as that of Example 1, and the composite coating of this comparative example is prepared.

[0097] The performance of the coating of Example 1 and Comparative Example 7 was tested. It was found that the adhesion of the coating prepared on the smooth surface of the substrate after sandblasting was reduced to 4B without laser etching and rolling process on the surface of the substrate, while the adhesion of the coating with the pattern on the surface reached 6B. The outer coating blistered after salt spray, and the amount of condensed water adhered to the inner coating increased by 50%. The spiral pattern (pitch 3-5mm) increased the salt spray resistance by 40%, and the contact angle of the fluorocarbon resin was ≥110°. The grid pattern (2x2-5x5mm) reduced the amount of condensed water adhered by 70%, and the contact angle of the super-hydrophobic layer was ≥150°.

[0098] Comparative Example 8

[0099] The difference between the present comparative example and example 1 is that the surface is not subjected to the electro-activation treatment in step (1) and the coating is prepared directly, and the rest of the preparation process is the same as that of example 1, and the composite coating of the present comparative example is prepared.

[0100] The coating prepared in example 1 and comparative example 8 is tested for performance, and it is found that the coating prepared by omitting the electrolytic activation step is subject to interfacial peeling after wet heat aging, and the coating bonding strength is only 4.5 MPa, while the coating bonding strength after activation reaches 15 MPa. This is because the polarity of the multiple coating materials used in the present application is greatly different, and the prepared coating reduces the condensate water attachment while facing the risk of interlayer peeling, and through the combination of electrolytic activation and laser etching, a honeycomb structure with a pore size of 5-10 μm and a porosity of 30-40% is formed on the surface of the steel pipe, thereby improving the anchoring force of the coating and overcoming the risk of interlayer peeling.

[0101] In summary, the present application provides a composite corrosion-resistant coating for low-pressure steel pipe poles in coastal areas and a preparation method thereof, which is prepared based on the difference in corrosion mechanism between the inner wall and the outer wall, i.e., the electrochemical corrosion of condensate water on the inner wall and the salt spray erosion on the outer wall.

[0102] The outer wall spiral texture can enhance the adhesion of the coating, and in combination with the high weather resistance of the fluorocarbon surface layer, it can resist salt spray erosion, and the inner wall grid texture can improve the coverage of the coating, cooperate with the super-hydrophobic layer to reduce the condensate water attachment, and at the same time, the flow guide groove and the pH-responsive microcapsule realize the directional discharge of the permeate and the triggering of self-repair in acidic environment, forming a dynamic protection system, so that the steel pipe pole has the ability of differentiation between the inner wall and the outer wall, and is suitable for complex environments.

[0103] The core-shell structure microcapsule realizes precise repair of damaged areas, the benzotriazole slow-release mechanism prolongs the corrosion inhibition period, and the graphene and carbon nanotube enhance the electrical conductivity and mechanical strength of the coating, inhibit galvanic corrosion and crack propagation, and ensure the long-term stability of the coating in a strong corrosive environment, realizing the breakthrough of self-repair and long-term corrosion inhibition technology. The outer coating polyaniline / epoxy resin and the inorganic zinc-rich layer form an electrochemical synergy, and the inner coating graphene and lithium molybdate construct a three-dimensional protection network, effectively resisting high salt spray and condensate water corrosion in coastal areas, and prolonging the service life of the steel pipe pole, realizing long-term synergistic protection of the low-pressure steel pipe pole in coastal areas.

[0104] The electrolytic activation and laser etching process reduces energy consumption and material loss, and through the supersonic flame spraying of the coating containing microcapsules, on the one hand, the utilization rate of zinc powder is improved, and on the other hand, the integrity of the microcapsule shell is ensured, avoiding the incompatibility of microcapsules with traditional coating processes, the aerosol deposition realizes uniform film formation at the nanoscale, and the whole process has strong compatibility and is suitable for large-scale production, taking into account environmental protection and economy.

[0105] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced, without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A method of protecting a low pressure steel pipe pole in a coastal area, characterized by: Comprising, The outer wall of the steel pipe pole (1) is provided with a spiral pattern surface (2), a micron-level honeycomb porous structure is formed on the spiral pattern surface (2), and then an outer corrosion-resistant layer I (3), an outer corrosion-resistant layer II (4), and an outer corrosion-resistant layer III (5) are sequentially arranged from inside to outside; The inner wall of the steel pipe pole (1) is provided with a mesh pattern surface (6), a micron-level honeycomb porous structure is formed on the mesh pattern surface (6), and then an inner corrosion-resistant layer I (7), an inner corrosion-resistant layer II (8), and an inner corrosion-resistant layer III (9) are sequentially arranged from inside to outside; The spiral pattern surface (2) and the mesh pattern surface (6) are provided with flow guide grooves for discharging the permeate; The flow guide grooves are filled with polyaniline microcapsule corrosion inhibitors.

2. The corrosion protection method of claim 1, wherein: The depth of the flow guide grooves is 1-2 mm, the porosity of the polyaniline microcapsule corrosion inhibitor is 4.5-10%, the polyaniline microcapsule corrosion inhibitor is composed of an inner core and an outer shell, the material of the inner core is benzotriazole, the material of the outer shell is polyaniline / silicon dioxide hybrid material, and the polyaniline microcapsule corrosion inhibitor releases benzotriazole repair agent when pH≤4.

3. The corrosion protection method of claim 1, wherein: The depth of the spiral pattern surface (2) is 0.2-0.5 mm, and the pitch is 3-5 mm; the depth of the mesh pattern surface (6) is 0.1-0.3 mm, and the grid size is 2x2-5x5 mm; the pore size of the micron-level honeycomb porous structure is 5-10 μm, the pore depth is 10-20 μm, and the porosity is 30-40%.

4. The corrosion protection method of claim 1, wherein: The material of the outer corrosion-resistant layer I (3) is a composite material of doped polyaniline dodecylbenzenesulfonic acid and epoxy resin, and the doping amount of polyaniline relative to dodecylbenzenesulfonic acid is 8-12 wt%.

5. The corrosion protection method of claim 1, wherein: The material of the outer corrosion-resistant layer II (4) is a composite material of inorganic zinc-rich paint and polyaniline microcapsule corrosion inhibitor, and the doping amount of polyaniline microcapsule corrosion inhibitor relative to inorganic zinc-rich paint is 0.8-1.2 wt%.

6. The corrosion protection method of claim 1, wherein: The material of the outer corrosion-resistant layer III (5) is a composite material of doped acidized carbon nanotube fluorocarbon resin and silane coupling agent modified nano silicon dioxide, and the addition amount of silane coupling agent modified nano silicon dioxide relative to doped acidized carbon nanotube fluorocarbon resin is 3-7 wt%.

7. The corrosion protection method of claim 1, wherein: The material of the inner corrosion-resistant layer I (7) is a composite material of tar epoxy resin and lithium molybdate corrosion inhibitor, and the doping amount of lithium molybdate corrosion inhibitor relative to tar epoxy resin is 3-5 wt%.

8. The corrosion protection method of claim 1, wherein: The material of the inner corrosion-resistant layer II (8) is a composite material of polyurethane and silane coupling agent modified graphene oxide, and the addition amount of silane coupling agent relative to graphene oxide is 20-30 wt%, and the material of the inner corrosion-resistant layer III (9) is super-hydrophobic silicone-acrylate emulsion.

9. The corrosion protection method of claim 1, wherein: The outer wall of the steel pipe pole (1) is processed by sand blasting and then by numerical control rolling to obtain the spiral pattern surface (2), the inner wall of the steel pipe pole (1) is processed by sand blasting and then by fiber laser etching to obtain the mesh pattern surface (6), and the spiral pattern surface (2) and the mesh pattern surface (6) are both provided with micron-level honeycomb porous structures by electrolytic activation; The outer anticorrosive layer I (3) is obtained by coating and curing through an electrophoretic deposition process, the outer anticorrosive layer II (4) is obtained by coating through a supersonic flame spraying process and then heat treatment, and the outer anticorrosive layer III (5) is obtained by coating and curing through a spin coating process; The inner anticorrosive layer I (7) is obtained by coating and curing through a centrifugal spin coating process, the inner anticorrosive layer II (8) is obtained by coating and curing through a high-pressure airless spraying device, and the inner anticorrosive layer III (9) is obtained by spraying and curing through an aerosol-assisted deposition process.

10. The method of preserving according to claim 9, wherein: The outer anticorrosive layer II (4) is obtained by coating through a supersonic flame spraying process and then heat treatment, wherein in the supersonic flame spraying process, the particle size of zinc powder is 5-8 μm, the gas pressure is 0.5-1 MPa, and the powder feeding rate is 30-38 g / min.

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