A corrosion protection system for container plates and its preparation process

Abstract

This invention discloses a container plate anti-corrosion system and its preparation process. The container plate anti-corrosion system includes a substrate, a pre-base coating on the surface of the substrate, and an electrostatic anti-corrosion coating on the surface of the pre-base coating. The thickness of the pre-base coating is 5-10 μm. The VOC content of the pre-base coating is less than 50 g / L. The container plate anti-corrosion system of this invention significantly improves the anti-corrosion performance, forming a triple synergistic anti-corrosion closed loop. The alloy coating of the zinc-aluminum-magnesium coated steel plate, through the dual effects of sacrificial anode protection and barrier protection, combined with the passivation enhancement effect of the pre-base integrated reagent and the dense shielding function of the electrostatic powder coating, forms a triple synergistic anti-corrosion system of "sacrificial anode protection → interface passivation enhancement → external medium shielding", rather than a simple superposition of the properties of each coating.

Description

Technical Field

[0001] This invention relates to the field of container corrosion protection technology, and more specifically to a container plate corrosion protection system and its preparation process. Background Technology

[0002] As a core carrier of global logistics and transportation, dry cargo containers are constantly exposed to complex corrosive environments such as marine atmospheres, industrial dust, and alternating high and low temperatures. Their corrosion resistance directly determines their service life and transportation safety, and the efficiency and long-term effectiveness of container coating processes are core technical pain points in the industry. Currently, the mainstream dry cargo container corrosion protection system in the industry adopts a multi-layer coating structure of "weathering steel plate + zinc powder primer + intermediate paint + topcoat". Although this system can meet basic corrosion protection requirements, it has many technical defects and limitations.

[0003] First, the construction process is cumbersome and complex, requiring multiple steps such as primer spraying, curing, intermediate coat spraying, curing, topcoat spraying, and curing. Strict control of intervals and ambient temperature and humidity between each step is necessary, making the construction difficult and demanding on the skills of operators. Second, production efficiency is low. The multiple coating and curing processes result in a lengthy production cycle, and manual coating is prone to problems such as missed areas, runs, and uneven coating thickness, leading to a high rework rate. Third, cost control is difficult. The procurement cost of multi-layer paint materials is high, and the multiple processes significantly increase labor and energy costs. Furthermore, the material utilization rate of traditional paint systems is only 60-70%, resulting in significant material waste. Finally, environmental performance is poor. Traditional paint systems contain large amounts of volatile organic compounds (VOCs), resulting in high VOC emissions during construction and curing, polluting the atmosphere. Moreover, paint waste disposal is difficult, which does not align with current green production principles.

[0004] Furthermore, the corrosion resistance of traditional systems is limited by the physical adhesion and bonding of each coating. After long-term service, problems such as coating peeling and rust spread easily occur, making it difficult to meet the long-term use requirements of containers in extreme corrosive environments. Existing technologies have disclosed the basic corrosion resistance performance of zinc-aluminum-magnesium coated steel plates, as well as composite corrosion protection systems combining zinc-aluminum-magnesium plates with traditional multi-layer paints. However, composite systems combining zinc-aluminum-magnesium plates with water-based pre-priming coatings and electrostatic powder coatings have not yet been disclosed, and the chemical bonding between the pre-priming and electrostatic powder coatings has not been achieved. Therefore, developing a container corrosion protection system that is easy to construct, has excellent corrosion resistance, is cost-effective, and is environmentally friendly and low-carbon has become an urgent technical problem to be solved by the industry. Summary of the Invention

[0005] The purpose of this invention is to provide a container plate anti-corrosion system and its preparation process. The container plate anti-corrosion system of this invention is simple to construct, has excellent anti-corrosion performance, and has outstanding advantages in environmental protection and low carbon emissions.

[0006] Therefore, the present invention provides a container plate anti-corrosion system, the container plate anti-corrosion system including a substrate, the surface of the substrate being provided with a pre-base coating, and the surface of the pre-base coating being provided with an electrostatic anti-corrosion coating.

[0007] In some embodiments of the present invention, the thickness of the pre-base coating is 5-10 μm.

[0008] In some embodiments of the present invention, the VOC content of the pre-base coating is less than 50 g / L.

[0009] In some embodiments of the present invention, the pre-base coating comprises the following components in parts by weight: 1-3 parts silane, 15-25 parts water-based resin, 3-5 parts inorganic zirconium-titanium-molybdenum composite chromium-free corrosion inhibitor, 2-4 parts adhesion promoter, and 2-4 parts film-forming aid.

[0010] In some embodiments of the present invention, the silane includes aminosilane and / or epoxysilane, and the aqueous resin includes aqueous polyester resin and / or aqueous epoxy resin.

[0011] In some embodiments of the present invention, the thickness of the electrostatic anti-corrosion coating is 50-70 μm.

[0012] In some embodiments of the present invention, the electrostatic anti-corrosion coating comprises the following components in parts by weight: 55%-65% carboxylated polyester resin, 4%-6% curing agent, 10%-20% filler, 20%-30% pigment, 0.8%-1.5% leveling agent, 0.3%-0.6% defoamer, 0.5%-1.0% light stabilizer, 0.2%-0.5% nonionic / anionic surfactant, and 0.1%-0.3% imidazole curing accelerator.

[0013] In some embodiments of the present invention, the acid value of the carboxylated polyester resin is 30-45 mg KOH / g, the curing agent includes triglycidyl isocyanurate, the filler includes barium sulfate, the pigment includes rutile titanium dioxide and color paste, the leveling agent includes polyacrylates, the defoamer includes benzoin, and the light stabilizer includes UV-531 / 770.

[0014] This invention also provides a preparation process for the aforementioned container plate anti-corrosion system, comprising: (1) Substrate pretreatment: The substrate is cut into continuous plates that meet the size of a container, and then subjected to weak alkali degreasing, multi-stage pure water rinsing, and zirconium titanium silane composite passivation treatment in sequence. (2) Cold working and welding assembly: The pre-treated substrate is cold working, arc welding / gas shielded welding and overall assembly are carried out according to the container manufacturing process. The welded parts are ground until there is no welding slag or oxide scale on the surface and the cleanliness reaches Sa2.0 level or above. (3) Pre-base coating: The pre-base coating is uniformly coated onto the surface of the assembled container substrate using a roller coater, and the coating thickness is controlled to be 5-10 μm; then it is sent into a hot air circulating drying oven, dried and cooled to room temperature to form a dense pre-base coating. (4) Electrostatic powder coating: The container substrate coated with the pre-base coating is sent into the electrostatic powder coating chamber and coated with polyester resin electrostatic powder. The dry film thickness is controlled to be 50-70μm, and the uniformity of electrostatic powder adhesion on the substrate surface after spraying is ≥95%. (5) Curing and molding: The coated container substrate is sent into the drying room and baked at a constant temperature to ensure that the coating curing degree is ≥95% and to avoid the coating from bubbling due to excessive heating. After baking, it is naturally cooled to room temperature to prevent the coating from cracking and bulging due to sudden cooling.

[0015] In some embodiments of the present invention, step (1), the weak alkaline degreasing treatment uses a sodium carbonate / trisodium phosphate composite degreasing agent with a mass concentration of 3-5%, a treatment temperature of 40-60℃, and a treatment time of 3-8 seconds, requiring that it does not corrode the ZAM coating, does not turn black, and does not lose its gloss; the conductivity of the outlet water of the multi-stage pure water rinsing is <50μS / cm to prevent residue from being carried into the passivation solution; the chromium-free passivation uses zirconium titanium silane composite passivation by spraying to form a uniform and dense inorganic conversion film on the substrate surface, with a film weight of 20-60mg / m², and the plate temperature after treatment is 60-80℃ to avoid passivation film failure.

[0016] Compared with the prior art, the advantages and positive effects of the present invention are: The corrosion resistance is significantly improved, forming a triple synergistic anti-corrosion closed loop: the alloy coating of the zinc-aluminum-magnesium coated steel plate, through the dual effects of sacrificial anode protection and barrier protection, combined with the passivation enhancement effect of the pre-base integrated reagent and the dense shielding function of the electrostatic powder coating, forms a triple synergistic anti-corrosion system of "sacrificial anode protection → interface passivation enhancement → external medium shielding", rather than a simple superposition of the performance of each coating. According to GB / T 10125-2021 testing, the salt spray corrosion resistance time of this system is ≥2000 hours (without red rust), which is more than 67% higher than the traditional system, far exceeding the 1200-hour standard of the traditional weathering steel plate + multi-layer paint system. It can extend the service life of containers to more than 12 years and perform better in extreme corrosive environments such as marine atmospheres; moreover, the system of this invention has an artificial accelerated aging resistance of ≥4000 hours, which is far better than the 2000 hours of the traditional system.

[0017] The construction process is extremely simple and efficient, resulting in a leap in production efficiency: It abandons the cumbersome process of traditional multi-layer paint spraying and multiple curing, and only retains the core coating process of one pre-primer combined with reagent coating and drying + one electrostatic powder spraying and curing. The production process is simplified by more than 60%, eliminating the need to repeatedly adjust construction parameters and wait for the coating to dry and cure for a long time. This greatly reduces the difficulty of construction and reliance on manual labor, resulting in a very low rework rate and an increase in production efficiency of more than 40%. It is perfectly adapted to the large-scale container production and assembly line production.

[0018] Production costs are significantly reduced and material utilization is greatly improved: there is no need to purchase multiple paint materials such as zinc powder primer, intermediate paint, and topcoat. The utilization rate of electrostatic powder materials reaches 80-90% (compared to only 60-70% for traditional paints). The recycled powder can be reused, and there is no waste of paint liquid or paint mist. At the same time, the labor input and energy consumption of multiple painting processes are reduced, and the overall production cost is reduced by 20-25% compared with the traditional system. The production cost of a single 20-foot dry cargo container is reduced by about 22% compared with the traditional system.

[0019] Its environmental and low-carbon advantages are prominent, aligning with dual carbon goals: the electrostatic powder coating has no VOC emissions, and the pre-base integration reagent is an aqueous system with a VOC content of less than 50g / L (tested according to GB / T 23985-2009), reducing pollutant emissions by more than 80% compared to traditional paint systems; simplified processes and improved material utilization can reduce carbon emissions during production, reducing carbon emissions by 25-35kg per container and 30kg per 20-foot dry cargo container (calculated according to GB / T 32151.24-2022), which meets green production goals.

[0020] The coating exhibits strong bonding stability and significantly improved durability: the silane coupling agent in the pre-base bonding agent can form chemical bonds between the zinc-aluminum-magnesium coating and the electrostatic powder coating, achieving an adhesion level of ISO 2409:2007 (National Standard GB / T 9286-1998) Grade 1, effectively preventing problems such as coating peeling and blistering during long-term service; moreover, the mechanical strength of the electrostatic powder coating reaches GB / T 6739-2006 pencil hardness ≥2H and impact resistance ≥50kg·cm, which is 30% higher than traditional paint coatings, making it suitable for collision and friction scenarios in container logistics transportation.

[0021] This technology represents a differentiated upgrade from existing zinc-aluminum-magnesium (ZAM) related systems. Compared to a single ZAM board, it adds a double-layer protection of pre-primer and electrostatic powder coating, solving the problems of easy scratching and insufficient weather resistance of pure ZAM boards, and meeting the needs of long-term outdoor transportation of containers. Compared to the ZAM + traditional paint system, it abandons multi-layer paint spraying, replacing paint with electrostatic powder coating and replacing traditional passivation + primer with pre-primer coating, achieving triple optimization in process, environmental protection, and cost. Moreover, the coating bonding method has been upgraded from physical adhesion to chemical bonding, significantly improving durability.

[0022] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0023] Figure 1 This is a schematic cross-sectional view of a structural section of an embodiment of the container plate anti-corrosion system of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0025] like Figure 1 As shown, the container plate anti-corrosion system of the present invention includes a substrate 10, a pre-base coating 11 on the surface of the substrate 10, and an electrostatic anti-corrosion coating 12 on the surface of the pre-base coating 11.

[0026] The thickness of the substrate 10 is selected from 1.2-6.0mm according to the container design requirements. The substrate 10 is made of hot-dip galvanized aluminum-magnesium coated steel plate, which is a weather-resistant steel plate. The zinc-aluminum-magnesium alloy coating on the surface is formed by hot-dip galvanizing process, forming a dense multiphase structure, which has excellent sacrificial anode protection performance and barrier protection capability.

[0027] The weight percentages of each component in the zinc-aluminum-magnesium alloy coating are: Al 5-11%, Mg 0.5-1.5%, and Zn 87.5-94.5%. Among them, Al 5-11% ensures the density of the alloy coating, Mg 0.5-1.5% can improve the sacrificial anode protection performance and avoid excessive coating brittleness, and Zn 87.5-94.5% forms the main zinc-based anti-corrosion system. This proportion range achieves the optimal synergy between sacrificial anode and barrier protection.

[0028] The surface density of zinc-aluminum-magnesium alloy coating is 80-120 g / m³. 2 When applied to extreme corrosive marine atmospheric environments, a concentration of 100-120 g / m is preferred. 2 If the zinc-aluminum-magnesium alloy coating is too thin, it is prone to breakage and exposure of the substrate during processing, leading to rapid corrosion; if the zinc-aluminum-magnesium alloy coating is too thick, it will become brittle and easily powder.

[0029] The alloy coating surface of hot-dip galvanized aluminum-magnesium coated steel sheet undergoes chromium-free passivation treatment, resulting in a tight bond with the pre-base coating. The passivation film weight is 20-60 mg / m³. 2 Below 20 mg / m³ 2 If the membrane is discontinuous and porous, chloride ions can penetrate directly, causing corrosion protection failure; if the membrane is too thick, the surface roughness and density of the membrane will be unbalanced, and it will be prone to pinholes and poor adhesion when the pre-base coating is applied by roller.

[0030] The pre-base coating 11 is applied to the passivation film surface of the hot-dip galvanized aluminum-magnesium coated steel sheet by roller coating. The coating thickness is 5-10μm. It has the functions of both bottom passivation and base coating adhesion, which can enhance the chemical bond connection between the substrate and the subsequent powder coating and further improve the anti-corrosion performance.

[0031] The coating of the pre-base layer 11 is a water-based system with a VOC content of less than 50 g / L (tested according to GB / T 23985-2009).

[0032] The pre-base coating 11 comprises the following components in parts by weight: 1-3 parts silane, 15-25 parts water-based resin, 3-5 parts inorganic zirconium-titanium-molybdenum composite chromium-free corrosion inhibitor, 2-4 parts adhesion promoter, and 2-4 parts film-forming aid.

[0033] Silanes act as chemical bond bridges, which can improve interlayer adhesion and corrosion resistance.

[0034] Water-based resins are the main film-forming agents, which can provide coating strength and density.

[0035] Inorganic zirconium-titanium-molybdenum composite chromium-free corrosion inhibitor: Chromium-free passivation provides long-lasting corrosion protection and rust inhibition.

[0036] Adhesion promoters can improve wetting and strengthen interlayer bonding.

[0037] Film-forming aids can assist in film formation and ensure drying and appearance quality.

[0038] Silanes include aminosilanes and / or epoxysilanes, and waterborne resins include waterborne polyester resins and / or waterborne epoxy resins.

[0039] Adhesion promoters include one or more of the following: phosphate esters, silane coupling agents, and titanate / zirconate esters.

[0040] After mixing all components of the pre-base coating 11, stir at 300-500 r / min for 20-30 min, let stand for 10-15 min at room temperature in a sealed environment to defoam, and then use.

[0041] Electrostatic anti-corrosion powder is sprayed onto the surface of the pre-base coating 11 using an automated fluidized bed electrostatic spray gun. The dry film thickness of the electrostatic anti-corrosion coating 12 is 50-70μm, and 60-70μm is selected when applied to extreme marine atmospheric corrosion environments. It has excellent weather resistance, corrosion resistance and mechanical strength, and its salt spray corrosion resistance time is ≥2000 hours. It forms a chemical bond with the pre-base coating 11.

[0042] The electrostatic anti-corrosion coating 12 comprises the following components in parts by weight: 55%-65% carboxylated polyester resin, 4%-6% curing agent, 10%-20% filler, 20%-30% pigment, 0.8%-1.5% leveling agent, 0.3%-0.6% defoamer, 0.5%-1.0% light stabilizer, 0.2%-0.5% nonionic / anionic surfactant, and 0.1%-0.3% imidazole curing accelerator.

[0043] The weight percentage of carboxylated polyester resin is 55%–65%. If it is less than 55%, it will result in insufficient film formation, a brittle coating, poor impact resistance, and weak corrosion protection. If it is more than 65%, it will result in insufficient other components such as fillers and pigments, leading to poor hiding power of the coating, soaring costs, and insufficient hardness.

[0044] The curing agent (TGIC) should be 4%–6% by weight. Less than 4% will result in insufficient cross-linking, soft coating, poor solvent resistance, and incomplete curing; more than 6% will result in excessive cross-linking, brittle coating, easy cracking upon impact, and wasted costs.

[0045] The filler (barium sulfate) should be 10%–20% by weight. If it is less than 10%, the coating will be too soft, easily scratched, and costly. If it is more than 20%, the coating will become brittle, have reduced impact resistance, poor powder application rate, and rough surface.

[0046] The weight percentage of pigments (titanium dioxide + color paste) is 20%–30%. If it is less than 20%, the coating will not cover properly, resulting in obvious color difference and reduced weather resistance. If it is more than 30%, the resin will not be able to encapsulate the pigments, resulting in poor dispersion, rough surface, and reduced adhesion.

[0047] The leveling agent should be 0.8%–1.5% by weight. If it is less than 0.8%, the coating surface will be uneven and have many pinholes; if it is more than 1.5%, the coating surface will be too slippery, affecting interlayer adhesion and making it easy to form pinholes.

[0048] The defoamer (benzoin) should be 0.3%–0.6% by weight. A content below 0.3% will result in a large number of pinholes and bubbles on the coating surface; a content above 0.6% will result in a sticky coating surface, affect gloss, and leave excessive residue.

[0049] The light stabilizer (UV-531 / 770) has a weight ratio of 0.5%–1.0%. A weight ratio below 0.5% will result in insufficient aging resistance of the coating, which will fail after 2000 hours; a weight ratio above 1.0% will result in high cost, easy precipitation, and affect the adhesion of the coating.

[0050] The surfactant content is 0.2%–0.5% by weight. Below 0.2% will result in poor dispersion, low coating gloss, and a dirty surface; above 0.5% will affect static electricity and reduce powder application rate.

[0051] The weight percentage of imidazole curing accelerators is 0.1%–0.3%. A percentage below 0.1% will result in slow or incomplete curing, while a percentage above 0.3% will result in excessively rapid reaction, blistering, pinholes, and high internal stress in the coating.

[0052] Carboxylated polyester resin serves as the film-forming matrix, providing weather resistance, mechanical strength, and adhesion. The acid value of the carboxylated polyester resin is 30-45 mg KOH / g, designed to achieve a sufficient and appropriate crosslinking density with the TGIC curing agent. This ensures the coating possesses high hardness, good toughness, excellent adhesion, water resistance, and salt spray resistance, while also meeting the requirements for rapid curing in automated production lines at 170–180℃.

[0053] The curing agent is triglycidyl isocyanurate. The epoxy groups of triglycidyl isocyanurate react with the carboxyl groups of the carboxyl polyester resin at 170-180℃ to form a three-dimensional network structure, which determines the curing temperature and speed.

[0054] The filler is barium sulfate, which can reduce costs, improve hardness, coverage, and chemical resistance.

[0055] The pigment is a mixture of rutile titanium dioxide and color paste, providing color, hiding power and lightfastness, with rutile titanium dioxide accounting for 85-95% of the total weight of the pigment.

[0056] The leveling agent is a polyacrylate, which can improve the surface smoothness of the electrostatic anti-corrosion coating and eliminate pinholes.

[0057] The defoamer is benzoin, which can degas and eliminate pinholes and bubbles.

[0058] The light stabilizer is UV-531 / 770 or a mixture thereof, which can resist ultraviolet rays and improve the outdoor weather resistance life of the electrostatic anti-corrosion coating.

[0059] Nonionic / anionic surfactants can improve the dispersibility of pigments / fillers.

[0060] Imidazole curing accelerators can reduce the activation energy of crosslinking reactions, enabling efficient curing at medium temperatures.

[0061] The preparation process of the container plate anti-corrosion system of the present invention includes the following steps: (1) Substrate pretreatment: hot-dip galvanized aluminum-magnesium coated steel plates are cut into continuous plates that meet the dimensions of containers, and then subjected to weak alkali degreasing, multi-stage pure water rinsing, and zirconium-titanium-silane composite passivation treatment in sequence.

[0062] Weak alkaline degreasing uses a sodium carbonate / trisodium phosphate composite degreasing agent with a mass concentration of 3-5%, at a temperature of 40-60℃ for 3-8 seconds, requiring no corrosion of the ZAM coating, no blackening, and no loss of gloss.

[0063] The conductivity of the outlet water from the multi-stage pure water rinsing is <50μS / cm to prevent residue from being carried into the passivation solution.

[0064] Chromium-free passivation employs a spray-based zirconium-titanium-silane composite passivation method, forming a uniform and dense inorganic conversion film on the zinc-aluminum-magnesium surface, with a film weight of 20-60 mg / m³. 2 After treatment, the plate temperature should be 60-80℃ to avoid passivation film failure.

[0065] (2) Cold working and welding assembly: The pre-treated plates are cold working, electric arc welding / gas shielded welding and overall assembly are carried out according to the container manufacturing process. The welded parts are ground until there is no welding slag or oxide scale on the surface and the cleanliness reaches Sa2.0 level or above.

[0066] (3) Pre-base coating: Under an environment of 20-30℃ and relative humidity ≤65%, a roller coater (roller speed 10-20r / min, roller gap pressure 0.1-0.3MPa) is used to uniformly coat the pre-base agent onto the surface of the assembled container substrate, and the coating thickness is controlled to be 5-10μm; then it is sent into a hot air circulating drying oven (wind speed 1-2m / s) and dried at 80-100℃ for 5-10 minutes. After drying, it is cooled to room temperature to form a dense pre-base coating.

[0067] (4) Electrostatic powder coating: The container coated with the pre-primer is sent into the electrostatic spraying chamber (ambient temperature 20-28℃, relative humidity 40-60%). An automatic fluidization electrostatic spray gun is used (fluidization pressure 0.05-0.1MPa, fluidization rate 50-100g / min). Under the conditions of spraying voltage 50-80kV, spraying distance 20-30cm, and compressed air pressure 0.3-0.5MPa, polyester resin electrostatic powder is sprayed. The dry film thickness is controlled to be 50-70μm. The uniformity of electrostatic powder adhesion on the surface of the board after spraying is ≥95%, and there is no obvious missed spraying or accumulation. The actual utilization rate of electrostatic powder material is 80-90%. The recovered powder can be reused after sieving.

[0068] (5) Curing and molding: The coated container is sent into the drying room and heated to 170-180℃ (workpiece temperature) at a heating rate of 5-10℃ / min. It is then baked at a constant temperature for 25-30 minutes to ensure that the coating curing degree is ≥95% and to avoid the coating from bubbling due to excessive heating. After baking, it is naturally cooled to room temperature to prevent the coating from cracking and bulging due to sudden cooling, and to form an electrostatic anti-corrosion coating that is tightly bonded to the pre-base coating.

[0069] The anti-corrosion system for container plates of this invention significantly improves corrosion resistance, forming a triple synergistic anti-corrosion closed loop: the alloy coating of the zinc-aluminum-magnesium coated steel plate, through the dual effects of sacrificial anode protection and barrier protection, combined with the passivation enhancement effect of the pre-base integrated reagent and the dense shielding function of the electrostatic powder coating, forms a triple synergistic anti-corrosion system of "sacrificial anode protection → interface passivation enhancement → external medium shielding," rather than a simple superposition of the performance of each coating. According to GB / T 10125-2021 testing, the salt spray corrosion resistance time of this system is ≥2000 hours (without red rust), which is more than 67% higher than the traditional system, far exceeding the 1200-hour standard of the traditional weathering steel plate + multi-layer paint system. This can extend the service life of containers to more than 12 years, and it performs better in extreme corrosive environments such as the marine atmosphere. Furthermore, the system of this invention has an accelerated aging resistance of ≥4000 hours, far superior to the 2000 hours of the traditional system.

[0070] The construction process of this invention is extremely simple and efficient, resulting in a leapfrog improvement in production efficiency: It abandons the cumbersome process of traditional multi-layer paint spraying and multiple curing, retaining only one pre-primer combined with reagent coating and drying + one electrostatic powder spraying and curing core coating process, simplifying the production process by more than 60%, eliminating the need for repeated adjustment of construction parameters and long waiting time for the coating surface to dry and cure, greatly reducing construction difficulty and reliance on manual labor, with an extremely low rework rate and an increase in production efficiency of more than 40%, perfectly adapting to containerized large-scale and assembly line production.

[0071] The present invention significantly reduces production costs and greatly improves material utilization: there is no need to purchase multiple paint materials such as zinc powder primer, intermediate paint, and topcoat; the utilization rate of electrostatic powder material reaches 80-90% (compared to only 60-70% for traditional paint); the recycled powder can be reused; and there is no waste of paint liquid or paint mist. At the same time, it reduces the labor input and energy consumption of multiple painting processes, and the overall production cost is reduced by 20-25% compared with the traditional system. The production cost of a single 20-foot dry cargo container is reduced by about 22% compared with the traditional system.

[0072] The environmental and low-carbon advantages are prominent: the electrostatic powder coating has no VOC emissions, and the pre-base integration reagent is an aqueous system with a VOC content of less than 50g / L (tested according to GB / T 23985-2009), which reduces pollutant emissions by more than 80% compared to traditional paint systems; simplifying processes and improving material utilization can reduce carbon emissions during production, reducing carbon emissions by 25-35kg per container and 30kg per 20-foot dry cargo container (calculated according to GB / T 32151.24-2022), which meets the goals of green production.

[0073] The coating exhibits strong bonding stability and significantly improved durability: the silane coupling agent in the pre-base bonding agent can form chemical bonds between the zinc-aluminum-magnesium coating and the electrostatic powder coating, achieving an adhesion level of ISO 2409:2007 (National Standard GB / T 9286-1998) Grade 1, effectively preventing problems such as coating peeling and blistering during long-term service; moreover, the mechanical strength of the electrostatic powder coating reaches GB / T 6739-2006 pencil hardness ≥2H and impact resistance ≥50kg·cm, which is 30% higher than traditional paint coatings, making it suitable for collision and friction scenarios in container logistics transportation.

[0074] Compared to a single zinc-aluminum-magnesium sheet, this invention adds a double layer of protection with pre-primer and electrostatic powder coating, solving the problems of easy scratching and insufficient weather resistance of pure zinc-aluminum-magnesium sheet surface, and is suitable for the needs of long-term outdoor transportation of containers. Compared to the zinc-aluminum-magnesium + traditional paint system, it abandons multi-layer paint spraying, replaces paint with electrostatic powder coating, and replaces traditional passivation + primer with pre-primer coating, achieving triple optimization of process, environmental protection and cost. Moreover, the coating bonding method is upgraded from physical adhesion to chemical bonding, which greatly improves durability. Example

[0075] The preparation process of the container plate anti-corrosion system in this embodiment includes the following steps: Substrate selection: Hot-dip galvanized aluminum-magnesium coated steel sheet is used as the substrate. The substrate is 2.5mm thick SPA-H weathering steel sheet, suitable for 20-foot containers. The surface density of the zinc-aluminum-magnesium alloy coating on the substrate surface is 120g / m³. 2 (Adapted to marine atmospheric environment, corresponding to a physical thickness of approximately 18.5μm, with a zinc-aluminum-magnesium alloy density of 6.4g / cm³) 3 (Calculated), the zinc-aluminum-magnesium alloy coating composition includes: Al 7%, Mg 1.5%, Zn 89.5%.

[0076] Preparation of pre-base coating: 2 parts epoxy silane (KH560), 18 parts waterborne polyester resin, 3 parts inorganic zirconium-titanium-molybdenum composite chromium-free corrosion inhibitor, 2 parts adhesion promoter, and 2 parts film-forming aid propylene glycol methyl ether acetate; after mixing all components, stir at 350 r / min for 25 min, let stand for 12 min at room temperature in a sealed environment to defoam, and then set aside.

[0077] Substrate pretreatment: Hot-dip galvanized aluminum-magnesium coated steel sheets are cut into continuous sheets that conform to the dimensions of containers, and then subjected to weak alkali degreasing, multi-stage pure water rinsing, and zirconium-titanium-silane composite passivation treatment in sequence.

[0078] Weak-alkali degreasing is performed using a 4% (w / w) sodium carbonate / trisodium phosphate composite degreasing agent at 50°C for 5 seconds. Multi-stage pure water rinsing results in an outlet water conductivity of 40 μS / cm. Zirconium-titanium silane composite passivation is then applied (spray method, membrane weight 40 mg / m², post-treatment plate temperature 70°C).

[0079] Cold working welding assembly: After the pre-treated plates are cold-worked, they are then welded and assembled using gas shielded welding. The welded areas are sanded to Sa2.0 grade, with no weld slag or oxide scale.

[0080] Pre-primer coating: At 25℃ and 60% relative humidity, the roller coater is used to roll the coating at a speed of 15r / min and a roller gap pressure of 0.2MPa to a thickness of 8μm; then it is sent to a hot air circulating drying oven (wind speed 1.5m / s) and dried at 90℃ for 8 minutes, and then cooled to room temperature to form a pre-primer integrated coating.

[0081] Electrostatic powder coating: In an electrostatic spraying chamber at 25℃ and 50% relative humidity, an automatic fluidized electrostatic spray gun (fluidization pressure 0.08MPa, fluidization rate 70g / min) is used. Under the conditions of spraying voltage 50-80kV, spraying distance 25cm, and compressed air pressure 0.4MPa, polyester resin electrostatic powder is sprayed, and the dry film thickness is controlled at 60μm (suitable for marine atmospheric environments). The uniformity of electrostatic powder adhesion on the board surface is 96%. The components of the polyester resin electrostatic powder, by weight percentage, are: 60% high weather-resistant carboxylated polyester resin, 5% triglycidyl isocyanurate, 15% barite powder, 18% mixture of rutile titanium dioxide and pigment (rutile titanium dioxide accounts for 90% of the pigment), and 2% total of additives such as leveling agent, benzoin, light stabilizer (UV-531), dispersant / wetting agent (non-ionic), and curing accelerator.

[0082] Curing and molding: The temperature is increased to 175℃ (workpiece temperature) at a heating rate of 8℃ / min, and then baked at a constant temperature for 28 minutes. The coating curing degree is ≥95%. After baking, the coating is naturally cooled to room temperature to obtain the finished container panel.

[0083] Performance Testing: Test samples were 100mm×50mm container plates for salt spray testing and 200mm×100mm container plates for cross-cut corrosion testing; neutral salt spray testing was conducted according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test", achieving a salt spray corrosion resistance time of 2000 hours (no red rust); adhesion was tested according to GB / T 9286-1998 "Cross-cut Test of Paints and Varnishes", reaching ISO 2409:2007 Level 1; the pre-base reagent was tested according to GB / T 23985-2009 "Determination of Volatile Organic Compounds (VOC) Content in Paints and Varnishes", with a VOC content of 42g / L; according to GB / T According to 32151.24-2022 "Greenhouse Gas Emissions Accounting and Reporting Requirements Part 24: Container Manufacturing", the production cost of a single 20-foot dry cargo container is reduced by 22% compared to the traditional system, and carbon emissions are reduced by 30 kg; according to GB / T 6739-2006 testing, the pencil hardness is 2H, the impact resistance is 50 kg·cm; and the utilization rate of electrostatic powder materials is 88%.

[0084] Comparative Example 1 The specific steps for manufacturing dry cargo containers using existing mainstream anti-corrosion systems are as follows: Substrate selection: SPA-H weathering steel plates with technical requirements are selected as the substrate and cut into plates that conform to the dimensions of a 20-foot container.

[0085] Substrate pretreatment: Mechanical sandblasting removes surface oxide scale and oil stains, and compressed air blows away dust, achieving a surface cleanliness level of Sa2.5.

[0086] Primer spraying: Spray zinc-rich primer onto the substrate surface at a rate of 0.06 L / m², and bake in an oven at 40°C for 5-8 minutes to form a primer layer with a dry film thickness of 30 μm.

[0087] Assembly and forming: Welding and assembling the coated panels.

[0088] Intermediate coat spraying: After the primer dries, spray the polyester intermediate coat at a rate of 0.13 L / m², and place it in an oven at 50-65℃ for 6-10 minutes to form an intermediate coat with a dry film thickness of 50 μm.

[0089] Topcoat spraying: After the intermediate coat is surface dry, spray the acrylic topcoat at a rate of 0.11 L / m², and place it in an oven at 55-75℃ for 12 minutes to form a topcoat layer with a dry film thickness of 40 μm.

[0090] The construction environment for the traditional anti-corrosion system is the same as in Example 1. Performance tests (same standards and sample specifications as above): Salt spray corrosion resistance for 1200 hours (red rust appears); adhesion reaches ISO 2409:2007 level 2; VOC emissions are 380g / L (overall system); the production cost of a single 20-foot dry cargo container is 1.28 times that of Example 1, and the carbon emissions are 1.45 times that of Example 1; pencil hardness is 1H, impact resistance is 38kg·cm; resistance to accelerated aging for 2000 hours; overall material utilization rate is 65%.

[0091] The test results show that the anti-corrosion system of container plates in Example 1 of the present invention far surpasses the existing traditional container plate system in Comparative Example 1 in terms of anti-corrosion performance, construction efficiency, material utilization, environmental protection, cost control and low carbon emissions.

[0092] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A corrosion protection system for container plates, characterized in that, The container plate anti-corrosion system includes a substrate, the surface of which is provided with a pre-base coating, and the surface of the pre-base coating is provided with an electrostatic anti-corrosion coating.

2. The container plate anti-corrosion system as described in claim 1, characterized in that, The thickness of the pre-base coating is 5-10 μm.

3. The container plate anti-corrosion system as described in claim 1, characterized in that, The VOC content of the pre-coating layer is less than 50 g / L.

4. The container plate anti-corrosion system as described in claim 1, characterized in that, The pre-base coating comprises the following components in parts by weight: 1-3 parts silane, 15-25 parts water-based resin, 3-5 parts inorganic zirconium-titanium-molybdenum composite chromium-free corrosion inhibitor, 2-4 parts adhesion promoter, and 2-4 parts film-forming aid.

5. The container plate anti-corrosion system as described in claim 4, characterized in that, Silanes include aminosilanes and / or epoxysilanes, and waterborne resins include waterborne polyester resins and / or waterborne epoxy resins.

6. The container plate anti-corrosion system as described in claim 1, characterized in that, The thickness of the electrostatic anti-corrosion coating is 50-70 μm.

7. The container plate anti-corrosion system as described in claim 1, characterized in that, The electrostatic anti-corrosion coating comprises the following components in parts by weight: 55%-65% carboxylated polyester resin, 4%-6% curing agent, 10%-20% filler, 20%-30% pigment, 0.8%-1.5% leveling agent, 0.3%-0.6% defoamer, 0.5%-1.0% light stabilizer, 0.2%-0.5% nonionic / anionic surfactant, and 0.1%-0.3% imidazole curing accelerator.

8. The container plate anti-corrosion system as described in claim 7, characterized in that, The acid value of the carboxylated polyester resin is 30-45 mg KOH / g. The curing agent includes triglycidyl isocyanurate, the filler includes barium sulfate, the pigments include rutile titanium dioxide and color paste, the leveling agent includes polyacrylates, the defoamer includes benzoin, and the light stabilizer includes UV-531 / 770.

9. A process for the preparation of a container plate anticorrosion system according to any one of claims 1-8, characterized by, include: (1) Substrate pretreatment: The substrate is cut into continuous plates that meet the size of a container, and then subjected to weak alkali degreasing, multi-stage pure water rinsing, and zirconium titanium silane composite passivation treatment in sequence. (2) Cold working and welding assembly: The pre-treated substrate is cold working, arc welding / gas shielded welding and overall assembly are carried out according to the container manufacturing process. The welded parts are ground until there is no welding slag or oxide scale on the surface and the cleanliness reaches Sa2.0 level or above. (3) Pre-base coating: The pre-base coating is uniformly coated onto the surface of the assembled container substrate using a roller coater, and the coating thickness is controlled to be 5-10 μm; then it is sent into a hot air circulating drying oven, dried and cooled to room temperature to form a dense pre-base coating. (4) Electrostatic powder coating: The container substrate coated with the pre-base coating is sent into the electrostatic powder coating chamber and coated with polyester resin electrostatic powder. The dry film thickness is controlled to be 50-70μm, and the uniformity of electrostatic powder adhesion on the substrate surface after spraying is ≥95%. (5) Curing and molding: The coated container substrate is sent into the drying room and baked at a constant temperature to ensure that the coating curing degree is ≥95% and to avoid the coating from bubbling due to excessive heating. After baking, it is naturally cooled to room temperature to prevent the coating from cracking and bulging due to sudden cooling.

10. The preparation process of the container plate anti-corrosion system as described in claim 9, characterized in that, In step (1), the weak alkaline degreasing treatment uses a sodium carbonate / trisodium phosphate composite degreasing agent with a mass concentration of 3-5%, a treatment temperature of 40-60℃, and a treatment time of 3-8 seconds. It is required that the ZAM coating is not corroded, does not turn black, and does not lose its gloss. The conductivity of the outlet water from the multi-stage pure water rinsing is <50μS / cm to prevent residue from being carried into the passivation solution; Chromium-free passivation employs a spray-type zirconium-titanium-silane composite passivation method, forming a uniform and dense inorganic conversion film on the substrate surface. The film weight is 20-60 mg / m², and the board temperature after treatment is 60-80℃ to avoid passivation film failure.

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