Metal anticorrosive coating for offshore platform and construction method thereof

Abstract

The application discloses a kind of metal anticorrosive coating for offshore platform and construction method, belong to anticorrosive coating material technical field, the coating is three-layer system: primer layer is formed by zinc powder, aluminum magnesium alloy powder and conductive pigment and filler continuous conductive / sacrificial micro-network, intermediate coating layer is formed by basalt flake micro-inclination arrangement and interface coupling agent dense anti-permeation barrier, finish coating layer adopts two-stage erosion-resistant particles and combines epoxy-polysiloxane-fluorosilicon resin system, provides high toughness and erosion resistance, the construction method includes surface pretreatment, primer two-stage directional curing, intermediate coating wet-on-wet overcoating and heat cycle curing, finish coating segmented crosslinking curing and local rapid repair, can be constructed in humid or local water environment, guarantee coating density and interlaminar adhesion.The coating of the application has the advantages of corrosion resistance, sea wave erosion resistance, high adhesion, strong construction operability, etc., can significantly prolong the service life of offshore platform steel structure.

Description

Technical Field

[0001] This invention relates to the field of anti-corrosion coating materials technology, and in particular to an anti-corrosion coating for marine platforms and its application method. Background Technology

[0002] Offshore platform structures are exposed to seawater for extended periods, with the surface area being particularly vulnerable to both moisture and oxygen, making it the region most severely affected by steel corrosion. Traditional anti-corrosion coatings primarily employ high-zinc primers and epoxy or polyurethane topcoats, but these methods present the following problems in practical applications:

[0003] The primer has a high zinc powder content, but it suffers from severe sedimentation and agglomeration. High zinc powder content can easily lead to increased internal stress in the coating, uneven coating thickness, and affect the continuity of the conductive network in the primer and the sacrificial anode protection effect.

[0004] The interfacial bonding between the intermediate coat and the primer and topcoat is insufficient. Existing epoxy-polysiloxane or epoxy-fluorosilicone resin systems have weak adhesion between the intermediate coat and the primer, which easily leads to peeling in humid environments, affecting the overall anti-corrosion life of the coating.

[0005] The topcoat is not resistant to erosion and wave impact. In water areas with high tidal ranges, the topcoat is frequently eroded by waves. Under long-term erosion, traditional topcoats are prone to micropores, cracks, and decreased hydrophobicity, which reduces the overall durability of the coating.

[0006] Therefore, there is an urgent need to develop a new type of anti-corrosion coating and application method suitable for the surface area of ​​offshore platforms, which can be applied in humid environments, with a primer forming a continuous conductive / sacrificial micronetwork, a middle coat forming a dense barrier, and a top coat with erosion resistance and hydrophobic properties, in order to extend the service life of offshore platform structures. Summary of the Invention

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A metal anti-corrosion coating for marine platforms includes a primer layer, a middle coat layer, and a topcoat layer. The primer layer comprises (by weight) 10-29 parts zinc powder, 5-19 parts aluminum-magnesium alloy powder, 1-4 parts corrosion inhibitor microcapsules, and 3-14 parts flake alumina. The middle coat layer comprises 1-7 parts conductive pigments and fillers and 10-24 parts basalt flakes. The topcoat layer comprises 2-9 parts erosion-resistant reinforcing particles. The primer layer is disposed on the innermost side, the topcoat layer is disposed on the outermost side, and the middle coat layer is disposed between the primer layer and the topcoat layer.

[0009] The mass ratio of zinc powder to aluminum-magnesium alloy powder in the primer layer is 2~5:1, the particle size of the zinc powder is 3~10μm, and the particle size of the aluminum-magnesium alloy powder is 2~20μm.

[0010] The corrosion inhibitor microcapsule shell material in the primer layer is urea-formaldehyde resin or polyurea, the core material contains molybdate, zinc phosphate or benzotriazole, and the shell wall thickness accounts for 10-25% of the diameter.

[0011] The conductive pigments and fillers in the intermediate coating layer are selected from one or more of graphene, conductive carbon black, conductive mica, or metal oxides, and the average particle size of the conductive pigments and fillers is 50~500nm.

[0012] The intermediate paint layer also contains an interface coupling agent, and the basalt flakes have an average thickness of 2~6μm and an aspect ratio of 50~400. The basalt flakes are arranged at a slight tilt angle during spraying and thermal cycling.

[0013] The erosion-resistant reinforcing particles in the topcoat layer are divided into two grades according to particle size: 200~1000nm and 1~5μm. The large particles form an erosion-resistant skeleton, and the small particles fill the gaps in the skeleton.

[0014] The topcoat layer includes fluorosilicone resin, which is compositely bonded with the erosion-resistant reinforcing particles.

[0015] The thicknesses of the primer layer, the intermediate coat layer, and the topcoat layer are 80~150μm, 150~250μm, and 60~120μm, respectively.

[0016] A method for applying an anti-corrosion coating to a marine platform includes the following steps:

[0017] a. Surface pretreatment: Sandblast or wet spray the steel structure surface to a cleanliness level of Sa2.5~Sa3.0, and activate it with 3~7 parts (by weight) of sodium chloride solution for 10~60 seconds and then blow dry;

[0018] b. The primer layer undergoes two-stage directional curing: after high-pressure spraying of the primer layer, it is first naturally cured for 10-20 minutes, and then heated at 35-50 degrees Celsius for 15-40 minutes to form a directional three-dimensional conductive network of zinc powder and aluminum-magnesium alloy powder;

[0019] c. Wet-on-wet overcoating of the intermediate paint layer: when the primer layer is surface dry but the degree of curing is 20~40%, the intermediate paint layer is sprayed to form a continuous resin chain segment interlocking structure between the primer layer and the intermediate paint layer;

[0020] d. The intermediate paint layer is densified by thermal cycling: after spraying, it is naturally cooled by air for 5 to 20 minutes, and then heat-cured at 45 to 60 degrees Celsius for 20 to 40 minutes, so that the basalt flakes are arranged in parallel at a slight inclination.

[0021] e. Segmented cross-linking and curing of the topcoat layer: After spraying the topcoat layer, it is first allowed to cure naturally for 2-3 hours, and then heated to 50-60 degrees Celsius to improve the cross-linking degree and erosion resistance of the topcoat layer;

[0022] The second stage of the dual-stage directional curing of the primer layer is heated using infrared or hot air circulation, with the surface temperature rise rate controlled at 0.5–2.0 degrees Celsius per minute.

[0023] Compared with existing technologies, the present invention has the following significant advantages:

[0024] 1. Formation of a continuous conductive / sacrificial micronetwork in the primer. Zinc powder and aluminum-magnesium alloy powder in the primer undergo two-stage directional curing to form a continuous three-dimensional conductive network, achieving uniform sacrificial anodic protection and effectively delaying corrosion of steel structures in water-surface areas.

[0025] 2. Enhanced density and cross-layer adhesion of the intermediate coat. The basalt flakes in the intermediate coat are arranged at a slight inclination and an interfacial coupling agent is added to form a "labyrinthine water barrier," which improves the density of the coating and forms a stable interpenetrating network structure with the primer and topcoat, significantly enhancing cross-layer adhesion.

[0026] 3. The topcoat layer exhibits excellent erosion resistance and hydrophobicity. The topcoat employs a two-stage erosion-resistant particle system (large particle skeleton and small particle filler), combined with epoxy-polysiloxane-fluorosilicone resin co-curing, providing a high-toughness, multi-scale composite structure that significantly improves resistance to wave erosion and hydrophobicity.

[0027] 4. Improved overall coating performance and extended service life. Through the synergistic effect of each layer, the coating achieves long-term corrosion resistance, moisture resistance, erosion resistance, and improved adhesion in the water surface area, significantly extending the service life of the coating and structure, while maintaining high operability and controllable costs. Detailed Implementation

[0028] The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0029] According to the present invention, a metal anti-corrosion coating for marine platforms includes a primer layer, a middle layer, and a topcoat layer. The primer layer includes (by weight) 11-29 parts zinc powder, 6-19 parts aluminum-magnesium alloy powder, 2-4 parts corrosion inhibitor microcapsules, and 4-14 parts flake alumina. The middle layer includes (by weight) 2-7 parts conductive pigments and fillers and 11-24 parts basalt flakes. The topcoat layer includes (by weight) 3-9 parts erosion-resistant particles. The primer layer is disposed on the innermost side, the topcoat layer is disposed on the outermost side, and the middle layer is disposed between the primer layer and the topcoat layer.

[0030] effect:

[0031] The zinc powder is a sacrificial anode metal that preferentially corrodes at points of coating damage or microcracks, protecting the offshore platform steel substrate (anode sacrificial protection). It also participates in forming local electron transport paths. When the zinc powder content is less than 10 parts, the coverage of the sacrificial anode and the total metal content are insufficient to provide effective cathodic protection in tidal zones, and red rust will quickly appear under alternating salt spray and wave conditions. When the zinc powder content is greater than 30 parts, it will lead to an increase in the overall powder load of the coating, resulting in increased coating viscosity, poor flow during construction, film shrinkage and chalking, as well as increased costs and potentially reduced coating adhesion (excessive zinc powder damages the continuous resin phase).

[0032] The aluminum-magnesium alloy powder is used to supplement and stabilize the protective performance of the zinc powder: on the one hand, it forms a micro-couple / conductive micro-network between metals, enhancing the continuity of cathodic protection in a low zinc background; on the other hand, its alloy composition (containing Mg) can form a dense corrosion product layer (partial passivation) during corrosion, reducing the excessive consumption of zinc. When the aluminum-magnesium alloy powder is less than 5 parts, it cannot construct an effective auxiliary conductive network and buffering effect, and the primer loses its design purpose. When the aluminum-magnesium alloy powder is greater than 20 parts, it will cause the total amount of metal powder in the coating to be too high, resulting in increased brittleness, decreased coating toughness and possible particle agglomeration, reducing impact resistance and adhesion.

[0033] The corrosion inhibitor microcapsules, acting as self-healing reservoirs, allow for the formation of an adsorption-inhibiting film or complex on the metal surface when microcracks or mechanical damage occur in the coating. This is achieved through localized shearing, friction, and electrochemical changes that break down the microcapsule shell. Consequently, the corrosion inhibitor microcapsules (such as imidazoline, molybdate, etc.) inhibit localized corrosion. When the amount of corrosion inhibitor microcapsules is less than 1 part, the release amount is insufficient to form an effective inhibitory film. When the amount of corrosion inhibitor microcapsules is greater than 5 parts, it can affect the density and leveling properties of the primer and generate porosity or impact on mechanical properties during the curing process.

[0034] The lamellar alumina forms a parallel lamellar barrier structure in the coating, increasing the diffusion path of water, oxygen, and salt ions to the metal surface ("maze effect"), thereby improving the barrier performance and erosion resistance of the coating film. Less than 3 parts of lamellar alumina cannot form an effective continuous lamellar shielding layer in the coating film, while more than 15 parts of lamellar alumina will cause a significant increase in the formulation viscosity, affecting spray leveling and potentially causing particle accumulation / stress concentration.

[0035] The conductive pigments and fillers, together with the zinc powder and aluminum-magnesium alloy powder in the primer, form a cross-layer conductive pathway, ensuring the electrical connectivity for electrochemical protection even if the surface is damaged. The average particle size of the conductive pigments and fillers is 50~500nm. When the conductive pigments and fillers are less than 1 part, the pathways are discontinuous; when the conductive pigments and fillers are more than 8 parts, the flowability is poor, which may lead to conductive short circuits and localized over-corrosion.

[0036] The basalt flakes form a large aspect ratio layered barrier, improving shielding and corrosion resistance, and can form a slightly tilted arrangement during thermal cycling. When the basalt flakes are less than 10 parts, the pathways are discontinuous; when the basalt flakes are more than 25 parts, the fluidity is poor, which may lead to conductive short circuits and localized over-corrosion.

[0037] The erosion-resistant particles are silicon carbide (SiC) particles, which are graded to form a skeleton-filler structure, improving resistance to wave erosion and abrasion. Hydrophobic components (such as fluorosilicone or hydrophobic agents) reduce the surface contact angle, reduce water retention / adhesion, and lower the probability of biofouling. Less than 2 parts of the erosion-resistant particles have no effect, while more than 10 parts affect flowability.

[0038] Experimental details:

[0039] To ensure comparability for single-variable comparisons, all samples were prepared and tested under the following baseline conditions, with all formulations, application, and curing conditions being identical except for the tested variable:

[0040] Reference formulation for base resin (using a uniform base for comparison): 100 parts epoxy resin, 15 parts curing agent (used as the base for the primer and intermediate coat; the topcoat is treated separately according to the topcoat system).

[0041] Spraying curing conditions (baseline): After spraying, cure at room temperature of 22 degrees Celsius for 15 minutes, then cure the primer in the second stage at 40 degrees Celsius for 30 minutes. At the corresponding wet-on-wet window, spray the intermediate coat when the primer is 30% cured (controlled by Shore hardness measurement), and cure the intermediate coat by thermal cycling at 50 degrees Celsius for 30 minutes. Then, cure the topcoat naturally for 2.5 hours, and then cure it at 55 degrees Celsius for 90 minutes.

[0042] Substrate: Q235 / Q345 steel specimen (size 150 × 100 × 3 mm), surface sandblasted to Sa2.5, salt washed and air-dried;

[0043] Test replication: n = 3 for each sample group, and the results are taken as mean ± standard deviation. Statistical analysis is performed using a two-sided test.

[0044] The zinc powder test groups were set up as follows: control group (baseline formula containing 20 parts zinc); group 1 (low zinc: 10 parts); group 2 (very low zinc: 8 parts); group 3 (high zinc: 30 parts), and the values ​​of other components remained the same as in this embodiment.

[0045] Test methods and metrics:

[0046] Neutral salt spray test (ASTM B117 / GB / T 2423.17): Record the time (h) for the appearance of red rust and the rust area (mm). 2 );

[0047] Adhesion (ASTM D4541 or pull-out tester, unit MPa);

[0048] Macroscopic pulverization of the surface and surface roughness (Ra, μm);

[0049] Results (mean, n=3):

[0050] Table 1: Results of Rust Prevention Experiments with Coatings of Different Zinc Powder Contents

[0051]

[0052] Conclusion: Reducing the amount of zinc powder leads to the earlier appearance and increased area of ​​red rust, while increasing the amount of zinc powder can slightly prolong the rust-free time but will significantly affect adhesion and workability (decreased adhesion and poor leveling). Therefore, 20 parts is the preferred compromise.

[0053] The magnesium alloy powder test groups were: control (10 parts); group 1 (aluminum-free magnesium powder); group 2 (low-aluminum magnesium powder, 5 parts); and group 3 (high-aluminum magnesium powder, 20 parts).

[0054] Test methods and metrics: Lateral / through resistance test (four-probe / two-electrode method or surface resistance) to evaluate the continuity of the conductive network;

[0055] Salt spray test (record the time to red rust);

[0056] Impact / bending tests are used to assess toughness and adhesion damage (ASTM D2794 / ISO 1519).

[0057] Result (n=3):

[0058] Table 2: Experimental Results of Coating Performance with Different Aluminum-Magnesium Alloy Powder Content

[0059]

[0060] Conclusion: Without aluminum magnesium powder, conductivity is poor and corrosion resistance is reduced; although a high content can slightly improve conductivity and rust-free time, it will make the coating brittle (increase peeling after bending). Therefore, 10 parts is the preferred compromise.

[0061] The corrosion inhibitor microcapsule test groups were set up as follows: control (3 parts); group 1 (no corrosion inhibitor microcapsules); group 2 (low amount 1 part of corrosion inhibitor microcapsules); group 3 (high amount 5 parts of corrosion inhibitor microcapsules).

[0062] Test methods and metrics:

[0063] Scratches (artificial) + 48h brine immersion for observation of corrosion points and products (SEM / EDS observation of adsorption film);

[0064] Electrochemical local measurements (local open circuit potential / local polarization curve) were used to determine the suppression effect at the scratch point;

[0065] Leveling / porosity measurement (microscopy, bubble counting).

[0066] Result (n=3):

[0067] Table 3: Experimental results of self-healing effects with different microcapsule contents of corrosion inhibitors

[0068]

[0069] Conclusion: Without the aforementioned corrosion inhibitor microcapsules, the scratches corroded rapidly; an appropriate amount of 3 parts of the aforementioned corrosion inhibitor microcapsules significantly delayed corrosion at the scratches and reduced local current density. While excessive amounts of the aforementioned corrosion inhibitor microcapsules slightly prolonged the protection period, they introduced porosity, affecting overall performance. Therefore, 3 parts is the preferred amount.

[0070] The alumina flakes were set up as follows: control (5 samples); group 1 (lower 3 samples); group 2 (higher 15 samples); group 3 (no alumina flakes).

[0071] Test methods and metrics:

[0072] A higher EIS (electrochemical impedance spectroscopy) indicates better barrier properties.

[0073] Seawater scouring test (simulated scouring rate 0.5 m / s, thickness loss recorded in μm);

[0074] Evaluation of leveling and sprayability.

[0075] Result (n=3)

[0076] Table 4: Barrier performance test results for different alumina contents

[0077]

[0078] Conclusion: The above-mentioned flake alumina significantly improves impedance and erosion resistance, but exceeding the upper limit affects construction. 5 parts is the preferred option that balances both effect and construction.

[0079] The conductive pigment and filler test groups were set up as follows: control (5 samples), no conductive pigment and filler, 1 sample with low conductivity, and 8 samples with high conductivity. Indicators: interlayer resistance and salt spray corrosion resistance time. Conclusion: No conductive pigment and filler → significantly increased interlayer resistance and decreased salt spray corrosion resistance time by 30–40%.

[0080] The basalt flake test groups were set up as follows: control (20 samples), no flakes, 10 samples with low resistance, and 25 samples with high resistance. Indicators: impedance, permeation rate, and interfacial peeling strength. Conclusion: The impedance and water immersion resistance of the no-flake samples decreased by 30%, and the interfacial bonding was weakened.

[0081] The erosion-resistant particle test groups were set up as follows: control (5 graded samples), 5 ungraded samples (all small particles or all large particles), and no particles. Indicators included: thickness loss due to seawater erosion, surface micro-cracks, and contact angle. Conclusions: The graded scheme resulted in the least thickness loss, while the ungraded scheme resulted in losses of approximately 25-30 μm for both large and small particles. Contact angle: approximately 110° for the group with hydrophobic agent and approximately 80° for the group without.

[0082] (1) The primer layer undertakes the functions of "electrochemical function" and "original adhesion". The primer layer adopts the combination of zinc powder, aluminum-magnesium alloy powder, corrosion inhibitor microcapsules and flake alumina to achieve the following functions:

[0083] ① Provide cathodic protection (sacrificial anode protection) to the steel substrate.

[0084] ② Initial adhesion and interface stability are formed. The zinc powder and the aluminum-magnesium alloy powder match the surface roughness of the steel substrate to form "mechanical locking". The flake alumina improves the water resistance of the primer.

[0085] ③ It provides a self-healing corrosion inhibition function, and the corrosion inhibitor microcapsules are only released when the local corrosion current decreases or mechanical shearing occurs.

[0086] (2) The intermediate paint layer performs the functions of "cross-layer conductivity, overall coating barrier and gradient buffer". The intermediate paint layer uses the conductive pigments and fillers and the basalt flakes (which can be arranged at an angle) to achieve the following functions:

[0087] ① Construct a functional transition zone between the primer and the topcoat to avoid the adhesion effect caused by the different stiffness of the two layers.

[0088] ② A cross-layer conductive network is formed. The primer provides cathodic protection, but if the topcoat and intermediate coat are completely insulated, the ability of current to pass through the damaged area will be limited. Therefore, the conductive filler is added to the intermediate coat to form a conductive gradient, so that the local damage points can still receive electron flow from the primer.

[0089] ③ The basalt flakes can self-organize to form an inclined-parallel structure (especially naturally arranged in wet-on-wet conditions), providing a long diffusion path and increasing the resistance to diffusion of water and chloride ions.

[0090] (3) The topcoat layer provides "erosion resistance and hydrophobic anti-adhesion" functions. The topcoat uses graded erosion-resistant particles, which can effectively form a defense against external physical impacts and water contact, achieving the following functions:

[0091] ① Improve surface hydrophobicity and reduce water film retention.

[0092] ② Reduce surface contaminants, biofouling, and erosion from mud and sand.

[0093] The mass ratio of zinc powder to aluminum-magnesium alloy powder in the primer layer is 2~5:1, the particle size of the zinc powder is 3~10μm, and the particle size of the aluminum-magnesium alloy powder is 2~20μm.

[0094] The primer layer provides electrochemical protection, and its 2-5:1 mass ratio effectively ensures sufficient sacrificial anolyte phase (zinc powder) and auxiliary anolyte phase (aluminum-magnesium alloy powder). Their roles in the system differ as follows: the zinc powder has a more negative potential (approximately -1.0 V), preferentially sacrificing and dissolving to provide primary cathodic protection, forming the dominant conductive network at the bottom layer. The aluminum-magnesium alloy powder has a slightly higher potential than zinc (-0.9 ~ -0.95 V), forming a synergistic sacrificial system with zinc. Its function is to improve the continuity of the conductive path and increase electron migration efficiency. The aluminum-magnesium alloy powder dissolves more slowly than zinc, providing a "delayed protection" effect and extending the overall protection life. When the zinc powder ratio is too low (less than 2:1), the sacrificial current is insufficient, failing to provide effective cathodic protection in the tidal zone. The potential is biased towards the positive, making it impossible to keep the steel substrate within the protection potential window. In actual tests, the self-corrosion potential in a system where the zinc powder to aluminum-magnesium alloy powder ratio is 1:1 increased from -1.01V to -0.92V, significantly reducing the protective capability. Therefore, 2:1 is the minimum functional limit. Excessive zinc powder (greater than 5:1) produces significant side effects: an "overly dense metallic phase" appears in the conductive network, reducing the mechanical strength of the coating. The high oil absorption of the zinc powder leads to a sharp increase in primer viscosity, making application difficult. The sacrificial anode dissolves too quickly, resulting in strong initial protection but rapid decay. In actual observations, when the zinc powder to aluminum-magnesium alloy powder ratio is 7:1, the water absorption rate increases by approximately 30% after 24 hours, and zinc bubbles appear after 240 hours of salt spray testing. Therefore, 5:1 is the upper limit for ensuring workability, mechanical properties, and cathodic protection life.

[0095] The particle size of the zinc powder determines the effective surface area of ​​the sacrificial anode and the continuity of the electron conduction path. When the particle size is greater than 10 μm, the number of conductive contact points decreases and the protection efficiency drops. When the particle size is less than 3 μm, the surface area is too large, making it prone to agglomeration, oxidation, and rapid consumption.

[0096] The particle size of the aluminum-magnesium alloy powder determines the conductive path for long-term sacrificial anode function and auxiliary methods. When the particle size is less than 2 μm, it is easily oxidized into aluminum oxide and magnesium oxide, significantly reducing the sacrificial capacity. At the same time, it increases oil absorption, causing a sharp increase in viscosity. Fine particles have strong migration in the system and unstable distribution. When the particle size is greater than 20 μm, "local voids" will form inside the coating, the electron conduction path becomes sparse, and it is impossible to form a continuous network with zinc powder.

[0097] The microcapsule shell of the corrosion inhibitor in the primer layer is made of urea-formaldehyde resin or polyurea, and the core material contains molybdate, zinc phosphate, or benzotriazole. The shell wall thickness accounts for 10-25% of the diameter. The molybdate is a typical oxidizing corrosion inhibitor; after the microcapsules rupture, it can promote the formation of a stable oxide film on the newly exposed iron / steel surface, accelerate the formation of a "passivation film," increase the local corrosion potential, slow down the oxygen reduction reaction rate, and reduce the corrosion current. The released zinc phosphate can form a dense iron phosphate / zinc phosphate conversion film on the steel surface. The benzotriazole has good organic adsorption film forming ability.

[0098] The conductive pigments and fillers in the intermediate coating are selected from one or more of graphene, conductive carbon black, conductive mica, or metal oxides, with an average particle size limited to 50-500 nm. Graphene possesses ultra-high conductivity, enabling the formation of an efficient electron migration network in the intermediate coating. Its two-dimensional layered structure enhances the shielding properties of the intermediate coating, reduces microcrack propagation, and provides microcurrent bypass channels, allowing the electrochemical protection of the primer's sacrificial anode system to be conducted to more distant locations. Conductive carbon black primarily provides a low-cost conductive path; when used in conjunction with graphene, it forms a multi-scale conductive network, improving wet conductivity. Conductive mica significantly extends the penetration path of corrosive media, improving the mechanical strength and impact resistance of the intermediate coating, making it suitable for areas subjected to repeated seawater impacts. Metal oxides provide stable semiconductor conductivity, reducing the impact of environmental temperature and humidity changes on conductivity, and contributing to improved weather resistance and photo-aging stability of the intermediate coating. When the average particle size is less than 50 nm, the conductive pigments and fillers may excessively aggregate with the intermediate coating resin system. Aggregation reduces the integrity of the conductive network, leading to a decrease in conductivity. When the wavelength exceeds 500 nm, the interfacial bonding force decreases, resulting in microvoids inside the coating, increasing the "node spacing" of the conductive network, and significantly reducing the electron migration capability.

[0099] The intermediate coating layer also includes an interfacial coupling agent, and the basalt flakes have an average thickness of 2-6 μm and an aspect ratio of 50-400. The basalt flakes are arranged at a slight angle during spraying and thermal cycling. The interfacial coupling agent is a silane-based agent, which effectively enhances the interfacial bonding between the basalt flakes and the resin matrix. The 2-6 μm thickness of the basalt flakes ensures sufficient rigidity, preventing cracking during spraying or thermal cycling; however, excessive thickness would reduce coating smoothness. The 50-400 aspect ratio of the basalt flakes ensures the formation of a continuous "labyrinthine water barrier" within the coating, extending the penetration path of water and corrosive ions. During spraying and thermal cycling, the basalt flakes are arranged at a slight angle (approximately 5-15°), forming an overlapping shielding structure that significantly reduces water penetration while also ensuring good leveling and adhesion during coating application.

[0100] The erosion-resistant reinforcing particles in the topcoat layer are divided into two sizes: 200-1000 nm and 1-5 μm. Larger particles form an erosion-resistant skeleton, while smaller particles fill the gaps in the skeleton. The larger particles bear the main stress from water flow and wave erosion, improving the overall hardness and resistance to mechanical peeling of the coating, and preventing coating thickness loss caused by long-term wave erosion in tidal zones. The smaller particles increase coating density, reduce micropore formation, enhance resistance to moisture and ion penetration, and block the penetration pathways of corrosive media.

[0101] The topcoat layer includes fluorosilicone resin, which is hydrophobically modified and combined with the erosion-resistant reinforcing particles to maintain low surface energy under long-term seawater impact and ultraviolet environment, thereby reducing seawater adhesion and the adhesion of corrosive microorganisms.

[0102] The thicknesses of the primer layer, the intermediate coat layer, and the topcoat layer are 80~150μm, 150~250μm, and 60~120μm, respectively. The primer layer, with a thickness of 80~150μm, provides basic corrosion protection and acts as a sacrificial anode, forming a preliminary conductive / sacrificial micronetwork. This ensures that corrosion initiation is delayed in humid environments near water surfaces. Adjusting the primer thickness ensures that the zinc powder and aluminum-magnesium powder are evenly distributed in the coating, preventing sedimentation or agglomeration. When the thickness is less than 80μm, the zinc / aluminum-magnesium micronetwork is discontinuous, resulting in poor corrosion protection. When the thickness is greater than 150μm, internal stress is easily generated, affecting adhesion and increasing curing time. The intermediate coat layer, 150-250 μm thick, establishes a continuous impermeable barrier, preventing water and corrosive ions from further penetrating to the primer. A thicker intermediate coat layer provides ample embedding space for the basalt flakes and conductive pigments and fillers, forming a composite conductive network and a "maze-like water-blocking pathway." This ensures a fully interpenetrating network at the interlayer interface, improving the adhesion between the primer and topcoat. A thickness less than 150 μm results in an insufficient impermeable barrier and limited conductive / maze structure; a thickness greater than 250 μm leads to construction difficulties, flakes easily lifting, and poor leveling. The topcoat layer, 60-120 μm thick, provides final water erosion resistance and a hydrophobic surface, maintaining a smooth coating surface and preventing micropores and cracks. A moderate thickness ensures uniform distribution of the dual-stage erosion-resistant particles and hydrophobic modifier, while also guaranteeing workability. A thickness less than 60 μm results in insufficient hydrophobicity and erosion resistance; a thickness greater than 120 μm leads to easy cracking of the coating and long construction and drying cycles.

[0103] A method for applying an anti-corrosion coating to a marine platform according to the present invention includes the following steps:

[0104] a. Surface pretreatment: The steel structure surface is sandblasted or wet-sprayed to a cleanliness level of Sa2.5~Sa3.0, and then activated with 3~7 parts (by weight) of sodium chloride solution for 10~60 seconds and then dried; Sandblasting or wet spraying to a cleanliness level of Sa2.5~Sa3.0 can remove rust and oil stains, and provide roughness to enhance adhesion. Spraying with sodium chloride solution for 10~60 seconds can slightly activate the steel surface, increase the surface micro-charge, and facilitate the formation of a uniform directional conductive / sacrificial micro-network of zinc powder and aluminum-magnesium alloy powder in the primer;

[0105] b. The primer layer undergoes a two-stage directional curing process: After high-pressure spraying of the primer layer, it is first naturally cured for 10-20 minutes, and then heated at 35-50 degrees Celsius for 15-40 minutes to allow the zinc powder and aluminum-magnesium alloy powder to form a directional three-dimensional conductive network. The 10-20 minute natural curing after spraying eliminates surface textures and bubbles generated during spraying, ensuring a smooth primer. Heating at 35-50 degrees Celsius for 15-40 minutes promotes the directional alignment of the zinc powder and aluminum-magnesium alloy powder, forming a continuous three-dimensional conductive network, providing a foundation for the sacrificial anode protection and conductivity of the primer.

[0106] c. Wet-on-wet overcoating of the intermediate paint layer: When the primer layer is surface dry but the degree of curing is 20~40%, the intermediate paint layer is sprayed to form a continuous resin chain segment interlocking structure between the primer layer and the intermediate paint layer; ensuring cross-layer adhesion and a continuous anti-seepage barrier, while not damaging the conductive network of the primer.

[0107] d. The intermediate paint layer is densified by thermal cycling: After spraying, it is naturally cooled by air for 5 to 20 minutes, and then heat-cured at 45 to 60 degrees Celsius for 20 to 40 minutes, so that the basalt flakes are arranged in parallel at a slight inclination angle; this avoids cracking of the coating surface and promotes the arrangement of the basalt flakes at a slight inclination angle, forming a labyrinthine water-blocking path, improving density and corrosion resistance;

[0108] e. Segmented cross-linking and curing of the topcoat layer: After spraying the topcoat layer, it is first naturally cured for 2-3 hours, and then heated to 50-60 degrees Celsius to improve the cross-linking degree and scour resistance of the topcoat layer; ensuring the smoothness of the coating surface and improving scour resistance and hydrophobicity.

[0109] According to the present invention, a method for applying a metal anti-corrosion coating to a marine platform is provided. In the second stage of the two-stage directional curing of the primer layer, heating is achieved using infrared or hot air circulation, with the surface temperature rise rate controlled between 0.5 and 2.0 degrees Celsius per minute. The infrared or hot air circulation heating method is selected based on the scale of the application, ensuring uniformity in large-area or localized applications and guaranteeing the directional migration of conductive pigments and fillers in the primer layer along its thickness direction, forming a continuous conductive network.

[0110] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A metal anticorrosive coating for offshore platforms, characterized by, The coating includes a primer layer, a midcoat layer and a topcoat layer, the primer layer includes zinc powder 11-29 parts by mass, aluminum-magnesium alloy powder 6-29 parts by mass, corrosion inhibitor microcapsules 2-4 parts by mass, and flaky alumina 4-14 parts by mass, the midcoat layer includes conductive pigment 2-7 parts by mass, and basalt flakes 11-24 parts by mass, and the topcoat layer includes erosion-resistant reinforcing particles 2-9 parts by mass, the primer layer is arranged at the innermost side, the topcoat layer is arranged at the outermost side, the midcoat layer is arranged between the primer layer and the topcoat layer, the shell material of the corrosion inhibitor microcapsules in the primer layer is urea-formaldehyde resin or polyurea, and the core material contains molybdate, zinc phosphate or benzotriazole.

2. The anticorrosive coating for offshore platform according to claim 1, characterized in that, The mass ratio of the zinc powder to the aluminum-magnesium alloy powder in the primer layer is 2-5:1, the particle size of the zinc powder is 3-10 μm, and the particle size of the aluminum-magnesium alloy powder is 2-20 μm.

3. The anticorrosive coating for offshore platform according to claim 1, characterized in that, The thickness of the shell material of the corrosion inhibitor microcapsules in the primer layer accounts for 10-25% of the diameter.

4. The anticorrosive coating for offshore platform according to claim 1, wherein The conductive pigment in the midcoat layer includes one or more of graphene, conductive carbon black, conductive mica or metal oxide, and the average particle size of the conductive pigment is 50-500 nm.

5. The anticorrosive coating for offshore platform according to claim 1, wherein The midcoat layer further contains an interfacial coupling agent, and the average thickness of the basalt flakes is 2-6 μm, and the aspect ratio is 50-400, and the basalt flakes are arranged at a micro-inclination angle during spraying and heat cycling.

6. The anticorrosive coating for offshore platform according to claim 1, wherein The erosion-resistant reinforcing particles in the topcoat layer are divided into two levels according to particle size, i.e. 200-1000 nm and 1-5 μm, the large particles form an anti-erosion skeleton, and the small particles fill the gaps in the skeleton.

7. The anticorrosive coating for offshore platform according to claim 1, wherein The topcoat layer includes fluorosilicon resin, and the fluorosilicon resin is connected with the erosion-resistant reinforcing particles in a composite manner.

8. The anticorrosive coating for offshore platform according to claim 1, wherein The thicknesses of the primer layer, the midcoat layer and the topcoat layer are respectively 80-150 μm, 150-250 μm and 60-120 μm.

9. A method for applying a metal anticorrosive coating to an offshore platform, characterized by, The method includes the following steps: applying the metal anticorrosive coating for offshore platforms according to any one of claims 1-8, a. surface pretreatment: sandblasting or wet blasting the surface of the steel structure to a cleanliness level of Sa2.5-Sa3.0, and then spraying 3-7 parts by mass of sodium chloride solution for 10-60 seconds and blowing dry; b. two-stage directional curing of the primer layer: after high-pressure spraying of the primer layer, first natural curing for 10-20 minutes, and then heating at 35-50 degrees Celsius for 15-40 minutes, so that the zinc powder and the aluminum-magnesium alloy powder form a directional three-dimensional conductive network; c. wet-on-wet coating of the midcoat layer: when the primer layer is surface dry but the curing degree is 20-40%, the midcoat layer is sprayed, so that the primer layer and the midcoat layer form a continuous resin segment mosaic structure; d. heat cycle densification of the midcoat layer: after spraying, natural cold air for 5-20 minutes, and then heat curing at 45-60 degrees Celsius for 20-40 minutes, so that the basalt flakes are arranged in parallel at a micro-inclination angle; e. segmented crosslinking curing of the topcoat layer: after spraying the topcoat layer, first natural curing for 2-3 hours, and then heating at 50-60 degrees Celsius.

10. The method of claim 9, wherein the method is characterized by: The second stage of the two-stage directional curing of the primer layer uses infrared or hot air circulation heating, and the surface temperature rise rate is controlled at 0.5-2.0 degrees Celsius per minute.

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