Phosphate inorganic anticorrosive coating and its spraying construction method

Abstract

The application discloses a phosphate inorganic anticorrosive coating and a spraying construction method thereof. The coating comprises A component and B component which are stored independently. The A component is an acidic base slurry, comprising potassium dihydrogen phosphate, acidic silica sol, a composite corrosion inhibitor, superfine silica powder, metakaolin and deionized water. The B component is an alkaline solidified powder, comprising heavy-burning magnesium oxide, mica powder, alumina refractory filler, borax, sodium fluorosilicate and silicon-aluminum adjusting powder. During construction, the A component is pumped through a first feeding channel, and the B component is pneumatically transported through a second feeding channel. The two components are combined at the outlet end of a nozzle and immediately sprayed onto the surface of a metal base material. The heavy-burning magnesium oxide is graded by double particle sizes, and the mica powder is compounded with alumina refractory fillers of different particle sizes. The method can reduce early solidification and nozzle clogging, improve spraying continuity, coating uniformity, adhesion, salt mist resistance, high-temperature resistance and corrosion medium barrier performance, and is suitable for ships, marine equipment, rail transit and tunnel steel structures.

Description

Technical Field

[0001] This invention belongs to the field of inorganic coatings, specifically relating to a phosphate inorganic anti-corrosion coating and its spraying method. Background Technology

[0002] Metal structures are commonly used in shipbuilding, marine engineering equipment, rail transportation, tunnel engineering, and high-temperature industrial facilities. During long-term service, they are susceptible to corrosion from water vapor, salt spray, chloride ions, and high temperatures. While existing organic anti-corrosion coatings are easy to apply, they are prone to softening, decomposition, and powdering under continuous high temperatures or flame exposure, resulting in a decrease in adhesion and barrier properties. They cannot simultaneously provide both corrosion resistance and high-temperature resistance. Phosphate inorganic coatings offer advantages such as high-temperature resistance, non-flammability, and inorganic curing. However, because the acidic phosphate component reacts gradually with the alkaline curing component such as magnesium oxide, if the two components are mixed before transportation or spraying, the slurry will remain in the pipeline for a longer time, leading to a rapid increase in viscosity, partial thickening, and even caking in the pipes or nozzles. This not only reduces the stability of continuous spraying but may also cause inconsistencies in the actual mixing ratio in different areas, resulting in coating thickness fluctuations, pinholes, bubbles, or cracks.

[0003] Furthermore, when using magnesium oxide of a single particle size as the curing component, it is difficult to simultaneously control the pneumatic conveying state of the powder and the curing process after spraying. Ordinary inorganic filler systems mostly focus on single filling or heat resistance functions, and are insufficient in comprehensively regulating the diffusion path of corrosive media and the stability of the coating skeleton under high-temperature conditions. Therefore, how to ensure that the acidic base material and the alkaline curing powder can be stored separately, while enabling them to quickly and uniformly merge together near spraying, thereby improving the particle size distribution of the cured powder and the inorganic filler system, in order to improve the application stability, anti-corrosion performance, and high-temperature resistance of phosphate anti-corrosion coatings, remains a problem that needs to be solved. Summary of the Invention

[0004] To address the aforementioned deficiencies, this invention provides a phosphate inorganic anti-corrosion coating comprising independently stored component A and component B, wherein component A and component B are separately supplied to a spraying device during application and mixed at the nozzle outlet of the spraying device. The A component is an acidic slurry, comprising, by weight: 20-45 parts potassium dihydrogen phosphate, 25-55 parts acidic silica sol, 1-8 parts composite corrosion inhibitor, 3-15 parts ultrafine silica powder, 2-12 parts metakaolin, and 5-20 parts deionized water. Component B is an alkaline curing powder, comprising by weight: 35-70 parts of calcined magnesium oxide, 10-30 parts of mica powder, 10-35 parts of alumina refractory filler, 0.5-6 parts of borax, 0.3-4 parts of sodium fluorosilicate, and 2-15 parts of silica-alumina conditioning powder.

[0005] Further, the mixing mass ratio of component A to component B is 100:(70-150); the pH of component A at 25°C is 2.0-4.5, and the apparent viscosity at 25°C is 800 mPa·s-3500 mPa·s.

[0006] Furthermore, the silica solid content of the acidic silica sol is 20wt% to 40wt%, and the average particle size is 8nm to 30nm; the mass ratio of potassium dihydrogen phosphate to the acidic silica sol is 1:(0.8 to 2.2).

[0007] Furthermore, the composite corrosion inhibitor is a chromium-free corrosion inhibitor, and the composite corrosion inhibitor includes at least two of molybdate, tungstate, phytate, zinc phosphate and rare earth salt; The molybdates include one or at least two of sodium molybdate, potassium molybdate, ammonium molybdate, ammonium heptamolybdate, zinc molybdate, calcium molybdate, or magnesium molybdate; the tungstates include one or at least two of sodium tungstate, potassium tungstate, ammonium tungstate, ammonium metatungstate, zinc tungstate, calcium tungstate, or magnesium tungstate; the phytates include one or at least two of sodium phytate, potassium phytate, ammonium phytate, zinc phytate, calcium phytate, magnesium phytate, aluminum phytate, cerium phytate, or lanthanum phytate; the zinc phosphates include one or at least two of zinc phosphate, basic zinc phosphate, zinc aluminum phosphate, zinc calcium phosphate, zinc molybdenum phosphate, zinc iron phosphate, or zinc phosphomolybdate; the rare earth salts include one or at least two of cerium nitrate, lanthanum nitrate, yttrium nitrate, cerium chloride, lanthanum chloride, cerium sulfate, lanthanum sulfate, cerium acetate, lanthanum acetate, cerium carbonate, or lanthanum carbonate.

[0008] Further, the recalcined magnesium oxide includes a first recalcined magnesium oxide and a second recalcined magnesium oxide, wherein the D50 particle size of the first recalcined magnesium oxide is 8μm to 15μm, the D50 particle size of the second recalcined magnesium oxide is 20μm to 35μm, the mass ratio of the first recalcined magnesium oxide to the second recalcined magnesium oxide is 1:(0.3 to 1.0), and the MgO content of both the first recalcined magnesium oxide and the second recalcined magnesium oxide is not less than 90wt%.

[0009] Further, the mica powder is flaky mica powder with a D50 particle size of 20μm to 80μm; the alumina refractory filler includes first alumina powder and second alumina powder, the first alumina powder has a D50 particle size of 3μm to 15μm, the second alumina powder has a D50 particle size of 20μm to 60μm, and the mass ratio of the mica powder to the alumina refractory filler is 1:(0.8 to 2.5).

[0010] Furthermore, the silicon-aluminum conditioning powder includes one or at least two of metakaolin, ultrafine silica powder, silica fume, or calcined kaolin; the moisture content of the mixed component B is not higher than 1.0 wt%, and the D90 particle size is not greater than 100 μm.

[0011] This application also provides a spraying method for the phosphate inorganic anti-corrosion coating as described above, comprising the following steps: S1: Add potassium dihydrogen phosphate to acidic silica sol and deionized water and stir to dissolve. Then add composite corrosion inhibitor, ultrafine silica powder and metakaolin. After shearing and dispersion, obtain component A. Store component A in a sealed container. S2: Mix calcined magnesium oxide, mica powder, alumina refractory filler, borax, sodium fluorosilicate and silica-alumina conditioning powder evenly to obtain component B, and store component B in a moisture-proof and sealed manner. S3: The A component is fed to the nozzle of the spraying equipment through the first feeding channel, and the B component is fed to the nozzle through the second feeding channel which is independent of the first feeding channel, so that the A component and the B component merge at the nozzle outlet. S4: Immediately spray the combined components A and B onto the surface of the metal substrate to form a phosphate inorganic anti-corrosion coating.

[0012] Furthermore, the first feeding channel uses a pumping method to transport component A, and the second feeding channel uses compressed air pneumatic conveying to transport component B; the nozzle includes a central channel for transporting component A and a channel for transporting component B located on the outer periphery of the central channel, and the confluence of component A and component B is located at the nozzle outlet or 5mm to 30mm from the nozzle outlet tip; the conveying pressure of component A is 0.3MPa to 0.8MPa, and the compressed air pressure for transporting component B is 0.3MPa to 0.7MPa.

[0013] Furthermore, during spraying, the distance between the nozzle outlet and the surface of the metal substrate is 200mm to 600mm, and the thickness of the wet coating formed by a single spray is 0.5mm to 3.0mm; the metal substrate includes carbon steel, low alloy steel, stainless steel or aluminum alloy.

[0014] Compared with the prior art, the technical solution of this application has the following beneficial effects: 1. This application stores the acidic component A and the alkaline component B separately and transports them through independent feeding channels. This keeps the two components separate until they reach the nozzle outlet, and then they converge at or near the nozzle outlet before being sprayed onto the metal substrate surface. This reduces viscosity increases, agglomeration, and pipeline blockage caused by premature reaction of the acid and alkali components during storage and transportation. It allows the spraying equipment to maintain a more stable and continuous feeding state and improves the uniformity of the sprayed material ratio and coating thickness.

[0015] 2. This application uses a dual-particle-size curing powder composed of first-burned magnesium oxide and second-burned magnesium oxide. The different particle sizes of magnesium oxide cooperate within component B, ensuring pneumatic conveying of the powder while facilitating full contact with component A after spraying, forming a continuous inorganic curing structure. Compared to using single-particle-size reburned magnesium oxide, this reduces pinholes, bubbles, and cracks caused by asynchronous local curing, improving the film integrity of the coating and the interfacial stability of the metal substrate.

[0016] 3. In this application, flake mica powder is compounded with alumina refractory fillers of different particle sizes in component B. The flake mica powder can form a relatively tortuous path for the migration of corrosive media inside the coating, while the alumina fillers of different particle sizes can fill the gaps of different sizes in the inorganic curing structure and form a heat-resistant support skeleton, so that the resulting coating has good density, salt spray barrier performance and high temperature structural stability.

[0017] 4. In this application, component A consists of potassium dihydrogen phosphate, acidic silica sol, ultrafine silica powder, metakaolin, and a composite corrosion inhibitor to form an acidic base material system. After it is combined with component B at the nozzle end and sprayed onto the metal substrate, the phosphate curing system and the silica component together form a continuous inorganic coating. At the same time, the composite corrosion inhibitor participates in the protection of the metal / coating interface, thereby improving the adhesion of the coating and reducing the degree of salt spray and chloride ion migration into the interior of the metal substrate along the coating.

[0018] 5. This application utilizes dual-channel instant mixing spraying, dual-particle size distribution of reburned magnesium oxide, and compounding of sheet-like shielding filler and refractory filler to coordinate the coating application process with the curing film formation process. This allows for simultaneous consideration of continuous spraying, coating uniformity, corrosion protection, and high-temperature resistance, making it suitable for ships, marine engineering equipment, rail transportation, tunnel steel structures, and other metal components requiring corrosion and high-temperature protection. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1

[0021] This embodiment provides a phosphate inorganic anti-corrosion coating, comprising component A and component B stored independently of each other.

[0022] Component A, by weight, comprises 45 parts potassium dihydrogen phosphate, 36 parts acidic silica sol, 1 part composite corrosion inhibitor, 15 parts ultrafine silica powder, 7 parts metakaolin, and 5 parts deionized water. The composite corrosion inhibitor consists of 0.4 parts sodium molybdate and 0.6 parts zinc phosphate. The acidic silica sol has a silica solid content of 20 wt%, an average particle size of 30 nm, and a potassium dihydrogen phosphate to acidic silica sol mass ratio of 1:0.8. The resulting component A has a pH of 2.0 at 25°C and an apparent viscosity of 3500 mPa·s.

[0023] Component B, by weight, comprises 35 parts of reburned magnesia, 30 parts of flake mica powder, 24 parts of alumina refractory filler, 6 parts of anhydrous borax, 0.3 parts of sodium fluorosilicate, and 8 parts of metakaolin. The reburned magnesia consists of 17.5 parts of first-burned magnesia and 17.5 parts of second-burned magnesia, with a mass ratio of 1:1.0. The first-burned magnesia has an MgO content of 90 wt% and a D50 particle size of 8 μm, while the second-burned magnesia has an MgO content of 95 wt% and a D50 particle size of 35 μm. The flake mica powder has a D50 particle size of 80 μm. The alumina refractory filler consists of 8 parts of first-burned alumina powder and 16 parts of second-burned alumina powder. The first-burned alumina powder has a D50 particle size of 3 μm, and the second-burned alumina powder has a D50 particle size of 60 μm. The mass ratio of mica powder to alumina refractory filler is 1:0.8. The water content of the mixed component B is 0.4 wt%, and the D90 particle size is 100 μm.

[0024] In the preparation and spraying process, this embodiment also provides a spraying method for the phosphate inorganic anticorrosive coating as described above, including the following steps S1-S4: S1: Add potassium dihydrogen phosphate to acidic silica sol and deionized water, stir at 400 r / min for 5 min, then add composite corrosion inhibitor, ultrafine silica powder and metakaolin, and shear and disperse at 1200 r / min for 10 min to obtain component A and store it in a sealed container.

[0025] S2: Add each powder in component B to a dry powder mixer and mix at 300 r / min for 8 min to obtain component B. Store the mixture in a moisture-proof, sealed container.

[0026] S3: During construction, component A is pumped to the nozzle through the first feeding channel at a mass flow rate of 1.00 kg / min, and component B is pneumatically conveyed to the nozzle through the second feeding channel at a mass flow rate of 0.70 kg / min, ensuring a mass ratio of component A to component B of 100:70. The conveying pressure for component A is 0.8 MPa, and the pneumatic conveying pressure for component B is 0.3 MPa. The nozzle employs a structure where component A is conveyed through a central channel and component B is conveyed through an outer peripheral channel, with the two components converging at the nozzle outlet.

[0027] S4: Immediately spray the combined components A and B onto the surface of the metal substrate to form a phosphate inorganic anti-corrosion coating.

[0028] In this embodiment, Q235 carbon steel plate was used as the main coating substrate, and the distance between the nozzle outlet and the substrate surface was 400 mm. A single spray coating formed a 3.0 mm thick wet coating. The same method was also used to verify the film formation on the surface of Q355 low alloy steel plate.

[0029] Example 2

[0030] This embodiment provides a phosphate inorganic anti-corrosion coating, comprising component A and component B stored independently of each other.

[0031] Component A, by weight, comprises 25 parts potassium dihydrogen phosphate, 55 parts acidic silica sol, 4.5 parts composite corrosion inhibitor, 3 parts ultrafine silica powder, 12 parts metakaolin, and 12 parts deionized water. The composite corrosion inhibitor consists of 2 parts sodium tungstate and 2.5 parts sodium phytate. The acidic silica sol has a silica solid content of 40 wt% and an average particle size of 8 nm. The mass ratio of potassium dihydrogen phosphate to acidic silica sol is 1:2.2. The resulting component A has a pH of 4.5 at 25°C and an apparent viscosity of 2100 mPa·s.

[0032] Component B, by weight, comprises 52 parts of reburned magnesia, 14 parts of flake mica powder, 35 parts of alumina refractory filler, 0.5 parts of anhydrous borax, 2 parts of sodium fluorosilicate, and 15 parts of calcined kaolin. The reburned magnesia consists of 40 parts of first-burned magnesia and 12 parts of second-burned magnesia, with a mass ratio of 1:0.3. The first-burned magnesia has an MgO content of 96 wt% and a D50 particle size of 12 μm, while the second-burned magnesia has an MgO content of 90 wt% and a D50 particle size of 20 μm. The flake mica powder has a D50 particle size of 50 μm. The alumina refractory filler consists of 20 parts of first-burned alumina powder and 15 parts of second-burned alumina powder, with the first-burned alumina powder having a D50 particle size of 15 μm and the second-burned alumina powder having a D50 particle size of 20 μm. The mass ratio of mica powder to alumina refractory filler is 1:2.5. The water content of the mixed component B is 1.0 wt%, and the D90 particle size is 90 μm.

[0033] In the preparation and spraying process, this embodiment also provides a spraying method for the phosphate inorganic anticorrosive coating as described above, including the following steps S1-S4: In the preparation and spraying process, this embodiment also provides a spraying method for the phosphate inorganic anticorrosive coating as described above, including the following steps S1-S4: S1: Add 25 parts of potassium dihydrogen phosphate to 55 parts of acidic silica sol and 12 parts of deionized water, stir at 400 r / min for 5 min, then add 2 parts of sodium tungstate, 2.5 parts of sodium phytate, 3 parts of ultrafine silica powder and 12 parts of metakaolin, and shear and disperse at 1200 r / min for 10 min to obtain component A and store it in a sealed container.

[0034] S2: Add 40 parts of first-burned magnesium oxide, 12 parts of second-burned magnesium oxide, 14 parts of flake mica powder, 20 parts of first alumina powder, 15 parts of second alumina powder, 0.5 parts of anhydrous borax, 2 parts of sodium fluorosilicate, and 15 parts of calcined kaolin to a dry powder mixer and mix at 300 r / min for 8 min to obtain component B, which should be stored in a moisture-proof and sealed container.

[0035] S3: During construction, component A is pumped to the nozzle through the first feeding channel at a mass flow rate of 1.00 kg / min, and component B is pneumatically conveyed to the nozzle through the second feeding channel at a mass flow rate of 1.50 kg / min, ensuring a mass ratio of component A to component B of 100:150. The conveying pressure for component A is 0.3 MPa, and the pneumatic conveying pressure for component B is 0.5 MPa. The nozzle employs a structure where component A is conveyed through a central channel and component B is conveyed through an outer peripheral channel. The two components converge inside the nozzle, 5 mm from the nozzle outlet.

[0036] S4: Immediately spray the combined components A and B through the nozzle onto the surface of the metal substrate to form a phosphate inorganic anti-corrosion coating.

[0037] In this embodiment, Q235 carbon steel plate was used as the main coating substrate, and the distance between the nozzle outlet and the substrate surface was 600mm. A single spray coating formed a 0.5mm thick wet coating. The same method was also used to verify the film formation on the surface of 304 stainless steel plate.

[0038] Example 3

[0039] This embodiment provides a phosphate inorganic anti-corrosion coating, comprising component A and component B stored independently of each other.

[0040] Component A, by weight, comprises 20 parts potassium dihydrogen phosphate, 25 parts acidic silica sol, 8 parts composite corrosion inhibitor, 9 parts ultrafine silica powder, 2 parts metakaolin, and 20 parts deionized water. The composite corrosion inhibitor consists of 3 parts cerium nitrate, 2 parts lanthanum acetate, and 3 parts zinc phosphate. The acidic silica sol has a silica solid content of 30 wt%, an average particle size of 18 nm, and a potassium dihydrogen phosphate to acidic silica sol mass ratio of 1:1.25. The resulting component A has a pH of 3.2 at 25°C and an apparent viscosity of 800 mPa·s.

[0041] Component B, by weight, comprises 70 parts of reburned magnesia, 10 parts of flake mica powder, 10 parts of alumina refractory filler, 3 parts of anhydrous borax, 4 parts of sodium fluorosilicate, and 2 parts of silica-alumina conditioning powder, wherein the silica-alumina conditioning powder consists of 1 part of ultrafine silica powder and 1 part of silica fume. The reburned magnesia consists of 43.75 parts of first-burned magnesia and 26.25 parts of second-burned magnesia, with a mass ratio of 1:0.6; the first-burned magnesia has an MgO content of 93wt% and a D50 particle size of 15μm, while the second-burned magnesia has an MgO content of 94wt% and a D50 particle size of 28μm. The flake mica powder has a D50 particle size of 20μm. The alumina refractory filler consists of 5 parts of first-burned alumina powder and 5 parts of second-burned alumina powder; the first-burned alumina powder has a D50 particle size of 9μm, and the second-burned alumina powder has a D50 particle size of 40μm, with a mass ratio of mica powder to alumina refractory filler of 1:1. The water content of the mixed component B is 0.7wt%, and the D90 particle size is 80μm.

[0042] In the preparation and spraying process, this embodiment also provides a spraying method for the phosphate inorganic anticorrosive coating as described above, including the following steps S1-S4: S1: Add 20 parts of potassium dihydrogen phosphate to 25 parts of acidic silica sol and 20 parts of deionized water, stir at 400 r / min for 5 min, then add 3 parts of cerium nitrate, 2 parts of lanthanum acetate, 3 parts of zinc phosphate, 9 parts of ultrafine silica powder and 2 parts of metakaolin, and shear and disperse at 1200 r / min for 10 min to obtain component A and store it in a sealed container.

[0043] S2: Add 43.75 parts of first-burned magnesium oxide, 26.25 parts of second-burned magnesium oxide, 10 parts of flake mica powder, 5 parts of first alumina powder, 5 parts of second alumina powder, 3 parts of anhydrous borax, 4 parts of sodium fluorosilicate, 1 part of ultrafine silica powder as a silica-alumina conditioning powder, and 1 part of silica fume to a dry powder mixer and mix at 300 r / min for 8 min to obtain component B, and store it in a moisture-proof and sealed container.

[0044] S3: During construction, component A is pumped to the nozzle through the first feeding channel at a mass flow rate of 1.00 kg / min, and component B is pneumatically conveyed to the nozzle through the second feeding channel at a mass flow rate of 1.10 kg / min, ensuring a mass ratio of component A to component B of 100:110. The conveying pressure for component A is 0.55 MPa, and the pneumatic conveying pressure for component B is 0.7 MPa. The nozzle employs a structure where component A is conveyed through a central channel and component B is conveyed through an outer peripheral channel. The two components converge inside the nozzle, 30 mm from the nozzle outlet.

[0045] S4: Immediately spray the combined components A and B through the nozzle onto the surface of the metal substrate to form a phosphate inorganic anti-corrosion coating.

[0046] In this embodiment, Q235 carbon steel plate was used as the main coating substrate, and the distance between the nozzle outlet and the substrate surface was 200mm. A single spray coating formed a 1.8mm thick wet coating. The same method was also used to verify the film formation on the surface of 6061 aluminum alloy plate.

[0047] Comparative Example 1 This comparative example is based on Example 1. The difference between Example 1 and Example 2 is that the independent dual-channel conveying of component A and component B and the nozzle outlet merging method are cancelled. Component A and component B are pre-mixed in a mixing container outside the spraying equipment and stirred at 600 r / min for 2 min. Then, they are sent to ordinary nozzles for spraying through the same conveying pipeline. The other raw material composition, the distribution ratio of component A and component B and the spraying substrate are the same as in Example 1.

[0048] This comparative example changes the merging position of component A and component B and the delivery method after mixing, and is used to compare it with the instantaneous merging spraying method at the nozzle outlet.

[0049] Comparative Example 2 This comparative example is based on Example 2, but differs from Example 2 in that: the dual particle size distribution of the first and second reburned magnesium oxides is removed, and they are replaced with a single reburned magnesium oxide of equal total weight, wherein the MgO content of the single reburned magnesium oxide is 96wt% and the D50 particle size is 18μm; during spraying, components A and B are still transported independently and then merged 5mm before the nozzle outlet, and all other conditions are the same as in Example 2.

[0050] The difference in this comparative example is the particle size distribution of the recalcined magnesium oxide in component B. It does not change the dual-channel spraying and nozzle end convergence method, which is different from the technical means of comparative example 1.

[0051] Comparative Example 3 This comparative example is based on Example 3, but differs from Example 3 in that: the flaky mica powder and the alumina refractory filler composed of the first alumina powder and the second alumina powder are removed, and the above filler is replaced with ordinary calcined alumina powder of equal total weight, wherein the D50 particle size of the ordinary calcined alumina powder is 25μm; the composition of the remaining components A and B and the dual-channel confluence construction method at the nozzle end are the same as in Example 3.

[0052] The modified comparative example differs in the sheet-like shielding filler and the dual-particle-size refractory filler system in component B, but does not change the dual-particle-size composition of reburned magnesia or the spraying and merging method. It represents a different technical variable from Comparative Example 1 and Comparative Example 2.

[0053] Test Example 1: Stability and Early Film Formation Performance of Spray Coating Components A and B obtained from Examples 1-3 and Comparative Examples 1-3 were tested separately. Three batches of samples were prepared independently for each group. Sampling was carried out in accordance with GB / T 3186-2006 "Sampling of Paints, Varnishes and Raw Materials for Paints and Varnishes". Each group was continuously sprayed for 30 minutes according to the conveying and spraying method specified in the corresponding examples or comparative examples. The number of abnormal spraying stops caused by material agglomeration and discontinuous material supply during the spraying process was recorded. After the test, the cured material adhering to the nozzle and near the outlet was collected and weighed. The sprayed material was continuously collected and weighed at the nozzle outlet for 30 seconds every 5 minutes. The coefficient of variation of the mass flow rate of the output material was calculated based on the results of 6 samplings. In addition, a coating was prepared on the surface of Q235 carbon steel plate. Three parallel test plates were set up in each group. The surface drying time was measured according to GB / T 1728-2020 "Determination of Drying Time of Paint Film and Putty Film". After curing for 7 days, the dry film thickness was measured at 5 evenly selected points on each test plate according to GB / T 13452.2-2008 "Determination of Film Thickness of Paints and Varnishes". The difference between the maximum and minimum values ​​was taken as the thickness range. Simultaneously, a 100cm... 2 The number of pinholes, bubbles, and visible cracks within the area is counted.

[0054] Table 1. Test results of spray coating stability and early film formation performance

[0055] Note: Surface drying time is calculated from the time of spraying.

[0056] As shown in Table 1, Examples 1-3 did not experience any abnormal spraying interruptions during 30 minutes of continuous spraying, with nozzle caking mass ranging from only 1.8g to 2.4g and output mass flow rate variation coefficients ranging from 2.6% to 3.5%. In contrast, Comparative Example 1, where components A and B were pre-mixed and transported through the same pipeline, experienced five abnormal spraying interruptions within 30 minutes, with nozzle caking mass increasing to 38.6g and output mass flow rate variation coefficients reaching 18.7%. Furthermore, Comparative Example 1 showed a reduced surface drying time of 12 minutes, a cured dry film thickness variation of 268μm, and 15 pinholes / bubbles and 15 cracks / 100cm². 2 and 8 strips / 100cm 2 This indicates that keeping components A and B separate within independent feeding channels and only merging at the nozzle outlet prevents phosphate and magnesium oxide from prematurely reacting during transport, ensuring that the reaction mainly occurs during the spraying and deposition stages. This balances continuous feeding, immediate curing, and film uniformity.

[0057] Although Comparative Example 2 still used a dual-channel nozzle confluence method, after replacing the dual-particle-size recalcined magnesia with a single-particle-size recalcined magnesia, the mass of the nozzle agglomerate increased to 7.9 g; the coefficient of variation of the discharge mass flow rate also increased to 7.8%; the surface drying time increased to 37 min; and the number of pinholes, bubbles, and cracks were 7 per 100 cm. 2 and 5 strips / 100cm 2 It is evident that the combination of different particle sizes of recalcined magnesium oxide is beneficial for balancing the powder delivery state and the curing and film formation process after spraying. Comparative Example 3 mainly changed the functional filler system, which had a relatively small impact on the stability of continuous spraying, but the coating thickness uniformity and the number of defects were still lower than those of the example. In summary, the dual-channel nozzle end instant mixing and the particle size distribution of recalcined magnesium oxide in this application are not simply parallel relationships, but rather form a combination in the two continuous stages of construction delivery and post-spray curing, resulting in better spraying continuity, curing controllability, and thick film quality for the phosphate inorganic anti-corrosion coating.

[0058] Test Example 2: Coating Interface Bonding, Corrosion Barrier, and High Temperature Resistance Test Test coatings were prepared on the surface of Q235 carbon steel plates using the spraying methods of Examples 1-3 and Comparative Examples 1-3, with three parallel samples in each group. To reduce the interference of coating thickness on the protective results, the dry film thickness after 7 days of curing was uniformly controlled to 1.00 mm ± 0.05 mm by single or multiple spraying, and verified according to GB / T 13452.2-2008. The pull-off adhesion test was conducted according to GB / T 5210-2006 "Paints and Varnishes - Pull-off Adhesion Test". The salt spray test was conducted according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test", using a 5 wt% NaCl solution at a test temperature of 35℃ ± 2℃. The time when the coating first blistered or the substrate corroded was recorded. In addition, a 50 mm long artificial scratch was prepared in the center of the test plate, and the average corrosion expansion width on one side of the scratch was measured after 1000 h of salt spray. During the electrochemical impedance spectroscopy test, the test plate was immersed in a 3.5 wt% NaCl solution for 30 days, with a depth of 10 cm. 2 The coating area is used as the working area, in 10 5 Hz~10 -2 Electrochemical impedance spectroscopy was performed within the Hz range, and the impedance modulus at 0.01 Hz was recorded. For heat resistance testing, in accordance with GB / T 1735-2009 "Determination of Heat Resistance of Paints and Varnishes", the test panel was kept at 500℃ for 2 hours, and after cooling, the adhesion was measured again using the pull-off method. Additionally, the front of the test panel was subjected to an 800℃ heat source for 30 minutes, and the temperature rise at the center of the back was recorded using thermocouples. This process was repeated 10 times under the condition of heating at 500℃ for 30 minutes and cooling to 25℃ as one thermal cycle, and the results were statistically analyzed over a 100cm section. 2 The number of visible cracks generated within the region.

[0059] Table 2. Test results of coating interface bonding, corrosion protection and high temperature resistance.

[0060] Table 2 shows that the pull-off adhesion of Examples 1-3 after 7 days of room temperature curing reached 7.0 MPa to 7.5 MPa, the time without blistering or rusting in neutral salt spray reached 1680 h to 1920 h, the unilateral corrosion expansion width of scratches after 1000 h of salt spray was only 0.4 mm to 0.6 mm, and the low-frequency impedance after 30 days of immersion in 3.5 wt% NaCl reached 8.8 × 10⁻⁶. 8 Ω·cm 2 ~1.2×10 9 Ω·cm 2 In contrast, Comparative Example 1, due to the mixing of components A and B before transportation, resulted in more coating defects, with an adhesion of only 4.2 MPa. Its salt spray non-foaming and non-rusting time was shortened to 720 hours, and its low-frequency impedance decreased to 1.8 × 10⁻⁶. 7 Ω·cm 2This indicates that instant mixing at the nozzle outlet not only improves the continuity of construction but also reduces non-uniform gelation caused by premature reaction during the conveying stage, allowing the material sprayed onto the substrate surface to maintain good reactivity and interfacial bonding, thereby improving the density of the coating and the performance of the anti-corrosion barrier.

[0061] Comparative Example 2, using magnesium oxide re-calcined with a single particle size, exhibited a salt spray non-foaming and non-rusting time of 1200 hours and a low-frequency impedance of 2.9 × 10⁻⁶. 8 Ω·cm 2 The adhesion decreased to 4.3 MPa after treatment at 500℃, indicating that the dual-particle-size recalcined magnesium oxide, in addition to improving the feeding and film uniformity during the spraying stage, also facilitates the formation of a continuous and stable inorganic curing structure. In Comparative Example 3, after removing the flake mica powder and dual-particle-size alumina refractory filler, the time without blistering or rusting under neutral salt spray was only 960 hours, the width of the unilateral corrosion spread of scratches increased to 1.9 mm, the temperature rise at the back center after 30 minutes at 800℃ reached 221℃, and 8 scratches / 100cm were produced after 10 thermal cycles. 2 The cracks indicate that the combination of flaky mica powder and alumina refractory fillers of different particle sizes can simultaneously improve the barrier path of corrosive media and the stability of the coating skeleton under high temperature conditions.

[0062] Based on the above test results, this application avoids uncontrolled premature curing during construction and transportation by independently storing and transporting the acidic A component and the alkaline B component, and by immediately merging them at the nozzle outlet. The particle size distribution of the first and second calcined magnesium oxides improves the uniformity of curing and the continuity of the coating after spraying. Furthermore, a stable inorganic filler system is constructed using flake mica powder and dual-particle-size alumina refractory filler. These combined techniques result in a phosphate inorganic anti-corrosion coating that simultaneously possesses good spraying stability, metal-substrate adhesion, salt spray and chloride ion barrier properties, and high-temperature integrity, meeting the protection requirements of metal components in marine engineering, rail transportation, tunnels, and high-temperature corrosive environments.

[0063] 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 phosphate inorganic anti-corrosion coating, characterized in that, It includes components A and B, which are stored independently. Components A and B are separately delivered to the spraying equipment during construction and mixed at the nozzle outlet of the spraying equipment. The A component is an acidic slurry, comprising, by weight: 20-45 parts potassium dihydrogen phosphate, 25-55 parts acidic silica sol, 1-8 parts composite corrosion inhibitor, 3-15 parts ultrafine silica powder, 2-12 parts metakaolin, and 5-20 parts deionized water. Component B is an alkaline curing powder, comprising by weight: 35-70 parts of calcined magnesium oxide, 10-30 parts of mica powder, 10-35 parts of alumina refractory filler, 0.5-6 parts of borax, 0.3-4 parts of sodium fluorosilicate, and 2-15 parts of silica-alumina conditioning powder.

2. The phosphate inorganic anti-corrosion coating according to claim 1, characterized in that, The mixing mass ratio of component A to component B is 100:(70-150); the pH of component A at 25°C is 2.0-4.5, and the apparent viscosity at 25°C is 800 mPa·s-3500 mPa·s.

3. The phosphate inorganic anti-corrosion coating according to claim 1, characterized in that, The acidic silica sol has a silica solid content of 20wt% to 40wt% and an average particle size of 8nm to 30nm; the mass ratio of potassium dihydrogen phosphate to the acidic silica sol is 1:(0.8 to 2.2).

4. The phosphate inorganic anti-corrosion coating according to claim 1, characterized in that, The composite corrosion inhibitor is a chromium-free corrosion inhibitor, and the composite corrosion inhibitor includes at least two of molybdate, tungstate, phytate, zinc phosphate and rare earth salt; The molybdates include one or at least two of sodium molybdate, potassium molybdate, ammonium molybdate, ammonium heptamolybdate, zinc molybdate, calcium molybdate, or magnesium molybdate; the tungstates include one or at least two of sodium tungstate, potassium tungstate, ammonium tungstate, ammonium metatungstate, zinc tungstate, calcium tungstate, or magnesium tungstate; the phytates include one or at least two of sodium phytate, potassium phytate, ammonium phytate, zinc phytate, calcium phytate, magnesium phytate, aluminum phytate, cerium phytate, or lanthanum phytate; the zinc phosphates include one or at least two of zinc phosphate, basic zinc phosphate, zinc aluminum phosphate, zinc calcium phosphate, zinc molybdenum phosphate, zinc iron phosphate, or zinc phosphomolybdate; the rare earth salts include one or at least two of cerium nitrate, lanthanum nitrate, yttrium nitrate, cerium chloride, lanthanum chloride, cerium sulfate, lanthanum sulfate, cerium acetate, lanthanum acetate, cerium carbonate, or lanthanum carbonate.

5. The phosphate inorganic anti-corrosion coating according to claim 1, characterized in that, The recalcined magnesium oxide includes a first recalcined magnesium oxide and a second recalcined magnesium oxide. The first recalcined magnesium oxide has a D50 particle size of 8 μm to 15 μm, and the second recalcined magnesium oxide has a D50 particle size of 20 μm to 35 μm. The mass ratio of the first recalcined magnesium oxide to the second recalcined magnesium oxide is 1:(0.3 to 1.0), and the MgO content of both the first recalcined magnesium oxide and the second recalcined magnesium oxide is not less than 90 wt%.

6. The phosphate inorganic anti-corrosion coating according to claim 1, characterized in that, The mica powder is flaky mica powder with a D50 particle size of 20μm to 80μm; the alumina refractory filler includes first alumina powder and second alumina powder, the first alumina powder has a D50 particle size of 3μm to 15μm, the second alumina powder has a D50 particle size of 20μm to 60μm, and the mass ratio of the mica powder to the alumina refractory filler is 1:(0.8 to 2.5).

7. The phosphate inorganic anti-corrosion coating according to claim 1, characterized in that, The silicon-aluminum conditioning powder includes one or at least two of metakaolin, ultrafine silica powder, silica fume, or calcined kaolin; the moisture content of the mixed component B is not higher than 1.0 wt%, and the D90 particle size is not greater than 100 μm.

8. A method for spraying an inorganic phosphate anticorrosive coating as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Add potassium dihydrogen phosphate to acidic silica sol and deionized water and stir to dissolve. Then add composite corrosion inhibitor, ultrafine silica powder and metakaolin. After shearing and dispersion, obtain component A. Store component A in a sealed container. S2: Mix calcined magnesium oxide, mica powder, alumina refractory filler, borax, sodium fluorosilicate and silica-alumina conditioning powder evenly to obtain component B, and store component B in a moisture-proof and sealed manner. S3: The A component is fed to the nozzle of the spraying equipment through the first feeding channel, and the B component is fed to the nozzle through the second feeding channel which is independent of the first feeding channel, so that the A component and the B component merge at the nozzle outlet. S4: Immediately spray the combined components A and B onto the surface of the metal substrate to form a phosphate inorganic anti-corrosion coating.

9. The spraying method according to claim 8, characterized in that, The first feeding channel uses a pump to transport component A, and the second feeding channel uses compressed air to transport component B. The nozzle includes a central channel for transporting component A and a channel for transporting component B located on the outer periphery of the central channel. The confluence of component A and component B is located at the nozzle outlet or 5mm to 30mm from the nozzle outlet tip. The conveying pressure of component A is 0.3MPa to 0.8MPa, and the compressed air pressure for transporting component B is 0.3MPa to 0.7MPa.

10. The spraying application method according to claim 8, characterized in that, During spraying, the distance between the nozzle outlet and the surface of the metal substrate is 200mm to 600mm, and the thickness of the wet coating formed by a single spray is 0.5mm to 3.0mm; the metal substrate includes carbon steel, low alloy steel, stainless steel or aluminum alloy.

Images