Chromium-free passivation solution used in low latitude coastal areas and its preparation method and application

Abstract

The present application relates to passivation liquid technical field, especially IPC C23C22, more particularly to, in the coastal low latitude area uses the chromium-free passivation liquid and its preparation method and application, the present application provides a kind of chromium-free passivation liquid in the coastal low latitude area uses, its preparation raw material includes molybdate, inorganic acid, alcohol amine, nanosol, water-based polyurethane, crosslinking agent, fatty amine soap premix, water-based ultraviolet absorber, water-based wax emulsion, penetration desiccant, water.The chromium-free passivation liquid in the present application can form a layer of superhydrophobic, low water absorption, high density, salt fog corrosion resistance, UV aging resistance, moisture resistance chromium-free passivation film, suitable for being in the galvanized aluminum magnesium steel coiled material in the coastal low latitude area.

Description

Technical Field

[0001] This invention relates to the field of passivation solution technology, particularly to IPC C23C22, and more specifically to a chromium-free passivation solution for use in low-latitude coastal areas, its preparation method, and its application. Background Technology

[0002] Zinc-aluminum-magnesium (ZAM, Zn-Al-Mg) is a new type of steel coil coating technology with better corrosion resistance, processability, edge rust prevention, and low cost. Based on aluminum content, ZAM is classified into low-aluminum (1%–3.5%), medium-aluminum (5%–11%), and high-aluminum (55%). High-aluminum ZAM is commonly used in outdoor construction and engineering, such as building facades, solar panels, greenhouses, prefabricated substation enclosures, and high and low voltage switchgear for power transmission and distribution. High-aluminum ZAM typically requires good outdoor performance, especially in low-latitude coastal areas where the climate is characterized by high humidity, high salt content, and abundant sunlight, placing particularly stringent demands on its resistance to damp heat, salt spray corrosion, and UV aging. Typically, manufacturers of high-aluminum-zinc-aluminum-magnesium steel coils improve their properties by coating the coil surface with an environmentally friendly, chromium-free passivation film.

[0003] Existing patent CN202010649363.3 discloses a chromium-free passivation solution for zinc-aluminum-magnesium steel plates and its preparation method, comprising 0.2-10% zirconium compound; 0.2-25% organic acid and / or organic acid salt; 0.2-80% modified acrylic resin; 0.1-10% functional additives; and deionized water as the balance. The performance of this chromium-free passivation solution is not suitable for coastal areas, and its resistance to damp heat, salt spray corrosion, and ultraviolet aging needs to be improved.

[0004] Therefore, there is a need to develop a chromium-free passivation solution that is suitable for coastal areas, resistant to damp heat, salt spray corrosion, and has excellent UV aging resistance. Summary of the Invention

[0005] To address the problems in the prior art, the first aspect of this invention provides a chromium-free passivation solution with excellent resistance to damp heat, salt spray corrosion, and ultraviolet aging, suitable for use in low-latitude coastal areas. The raw materials for its preparation include molybdate, inorganic acid, alkanolamine, nanosol, waterborne polyurethane, crosslinking agent, fatty amine soap premix, waterborne ultraviolet absorber, waterborne wax emulsion, penetrating desiccant, and water.

[0006] Preferably, the chromium-free passivation solution used in low-latitude coastal areas comprises, by mass percentage, 0.5-5% molybdate, 1-5% inorganic acid, 1-5% alkanolamine, 1-5% nanosol, 20-60% waterborne polyurethane, 0.1-1.0% crosslinking agent, 5-10% fatty amine soap premix, 1-5% waterborne ultraviolet absorber, 1-10% waterborne wax emulsion, 1-5% penetrating desiccant, and the balance being water.

[0007] Preferably, the molybdate includes one or more of sodium molybdate, ammonium molybdate, and potassium molybdate.

[0008] Preferably, the inorganic acid includes one or more of hydrofluoric acid, sulfuric acid, lactic acid, salicylic acid, and oxalic acid.

[0009] Preferably, the hydrofluoric acid has a volume fraction of 40%.

[0010] Preferably, the alkanolamine includes one or more of triethanolamine, monoethanolamine, diethanolamine, diethylene glycolamine, and isopropanolamine.

[0011] Preferably, the nanosol includes one or more of nano-aluminum sol and nano-silica sol.

[0012] Preferably, the average particle size of the nano-aluminum sol is 1-100 nm; more preferably, it is 10 nm.

[0013] Preferably, the nano-aluminum sol is of model JR14W and was purchased from Xuancheng Jingrui New Materials Co., Ltd.

[0014] Preferably, the waterborne polyurethane includes one or both of anionic waterborne polyurethane and nonionic waterborne polyurethane.

[0015] Preferably, the waterborne polyurethane includes one or more of the following: Oubaodi U8001, Oubaodi U9600, Oubaodi U9380, Oubaodi U6150, and Oubaodi U4101, purchased from the Oubaodi brand.

[0016] Preferably, the crosslinking agent includes citric acid or citrate.

[0017] Preferably, the citrate includes aluminum citrate.

[0018] Preferably, the preparation method of the fatty amine soap premix is ​​as follows: short-chain fatty amines and small molecule organic acids are mixed at a molar ratio of (0.8-1.2):1 at 40-50°C, and then water is added to prepare a 0.5-2wt% aqueous dispersion.

[0019] Preferably, the carbon chain in the short-chain fatty amine does not exceed 12; more preferably, the short-chain fatty amine is dodecyl primary amine, CAS number 124-22-1.

[0020] Preferably, the small molecule organic acid includes one of citric acid and oxalic acid.

[0021] Preferably, the aqueous dispersion comprises a fatty amine citric acid soap aqueous dispersion or a fatty amine oxalic acid soap aqueous dispersion.

[0022] In this invention, the addition of nano-aluminum sol, waterborne polyurethane, aluminum citrate, and fatty amine soap premix improves the salt spray corrosion resistance, damp heat resistance, and UV aging resistance of the chromium-free passivation solution applied to galvanized aluminum-magnesium steel coils. The climate characteristics of low-latitude coastal areas—humid air, high salt content, and abundant sunlight—pose particularly stringent requirements for the damp heat resistance, salt spray corrosion resistance, and UV aging resistance of high-aluminum-zinc-aluminum-magnesium steel. The inventors have creatively discovered that the addition of aluminum citrate to the anionic waterborne polyurethane system increases the crosslinking degree of the waterborne polyurethane, forming a denser, less absorbent film on the coating. Simultaneously, during the reaction, the nano-aluminum sol and fatty amine soap premix continuously fill the crosslinked network structure, further enhancing the density and superhydrophobicity of the passivation film, thus providing excellent protection for the coating and effectively preventing the attack of chloride ions and the effects of high UV radiation and high humidity on the passivation film in coastal areas.

[0023] In this invention, by adding molybdate, organic acid, alkanolamine, polyurethane, citrate, and other substances in a compound formulation, both the salt spray resistance and corrosion resistance of the chromium-free passivation solution are improved. The inventors hypothesize that ammonium molybdate, in the acidic environment provided by the organic acid, reacts with metal ions on the metal substrate. Molybdate passivation significantly improves the salt spray resistance of the coating; however, because the passivation film is prone to cracking, its corrosion resistance decreases. This invention uses polyurethane as the main component. Under the action of aluminum citrate, a passivation film is formed on the coating surface. During this process, particles formed by ammonium molybdate and metal ions continuously fill the passivation film formed by the polyurethane, thereby improving the salt spray resistance and corrosion resistance of the passivation film.

[0024] Preferably, the aqueous ultraviolet absorber is a benzotriazole ultraviolet absorber.

[0025] Preferably, the benzotriazole ultraviolet absorber is UV-1130, purchased from the Kemic brand.

[0026] Preferably, the aqueous wax emulsion comprises a polyethylene-type aqueous wax emulsion.

[0027] The chromium-free passivation solution of this invention contains an aqueous wax emulsion, which, when combined with other substances in the system, improves subsequent application performance. The inventors unexpectedly discovered that adding an aqueous wax emulsion to the chromium-free passivation solution allows the wax emulsion to gradually drift upwards to the surface of the passivation film during film formation, improving the passivation film's wear resistance, superhydrophobicity, and scratch resistance, thereby reducing the impact of chloride ions and high humidity / heat.

[0028] Preferably, the polyethylene-type aqueous wax emulsion is BYK 531, purchased from BYK.

[0029] Preferably, the permeation desiccant comprises sodium dioctyl sulfonate.

[0030] Preferably, the CAS number of the sodium dioctyl sulfonate is 577-11-7.

[0031] Preferably, the water is deionized water.

[0032] The second aspect of this invention provides a method for preparing a chromium-free passivation solution for use in low-latitude coastal areas, comprising the following steps: under stirring at room temperature, molybdate, inorganic acid, alkanolamine, nano-sol, waterborne polyurethane, crosslinking agent, fatty amine soap premix, waterborne ultraviolet absorber, waterborne wax emulsion, and penetrating desiccant are added sequentially to water according to the mass percentage of the chromium-free passivation solution. During the addition process, if the added raw material is a solid, it must be allowed to dissolve completely before adding the next raw material.

[0033] A third aspect of the present invention provides an application of a chromium-free passivation solution used in low-latitude coastal areas for the preparation of a chromium-free passivation film on galvanized aluminum-magnesium steel coils.

[0034] Preferably, the galvanized aluminum-magnesium steel coil is a high-aluminum galvanized steel with an aluminum content of 55%.

[0035] Preferably, the preparation method involves coating the surface of the galvanized aluminum-magnesium steel coil with a chromium-free passivation liquid by roller coating, and then drying and curing the wet film of the passivation liquid by a three-stage drying method, thereby forming a dry chromium-free passivation film on the surface of the substrate.

[0036] Preferably, the three-stage drying method includes low-temperature pre-drying (PMT = 60-80°C), medium-temperature drying (PMT = 80-100°C), and high-temperature drying (PMT = 100-120°C).

[0037] Beneficial effects

[0038] 1. In this invention, by adding molybdate, organic acid, alkanolamine, polyurethane, citrate and other substances, the salt spray resistance of the chromium-free passivation solution is improved, as is its corrosion resistance.

[0039] 2. In this invention, by adding nano aluminum sol, waterborne polyurethane, aluminum citrate, and fatty amine soap premix, the salt spray corrosion resistance, damp heat resistance, and UV aging resistance of the chromium-free passivation solution applied to galvanized aluminum-magnesium steel coils are improved.

[0040] 3. In this invention, the UV protection effect of the chromium-free passivation film is further improved by adding benzotriazole UV absorbers.

[0041] 4. The chromium-free passivation solution in this invention contains an aqueous wax emulsion, which, when combined with other substances in the system, improves the subsequent application performance.

[0042] 5. The chromium-free passivation solution in this invention forms a dense metal compound layer on the coating surface by adding suitable metal salts. A suitable polymer resin, combined with a crosslinking agent and coupling agent, forms an excellent organic-inorganic hybrid composite film with superior superhydrophobicity, low water absorption, high density, resistance to salt spray corrosion, UV aging, and damp heat, providing comprehensive protection. Furthermore, various additives, including UV absorbers and penetrating desiccants, further enhance the passivation film's properties. Detailed Implementation

[0043] Example 1

[0044] This embodiment provides a chromium-free passivation solution for use in low-latitude coastal areas. The raw materials and mass percentages for its preparation are shown in Table 1.

[0045] Table 1

[0046] Element raw material Quality percentage (%) molybdate Ammonium molybdate 4 Inorganic acids 40v / v% hydrofluoric acid 3 alcoholamines Diethylene glycolamine 3 Nanosol JR14W 5 Waterborne polyurethane Opel U8001 50 Crosslinking agent Aluminum citrate. 0.8 Fatty amine soap premix Fatty amine citric acid soap aqueous dispersion 5 Water-based UV absorbers UV-1130 2.5 Water-based wax emulsion BYK 531 2 Permeation desiccant Sodium dioctylsulfonate 2 water Deionized water 22.7

[0047] The average particle size of the nano-aluminum sol is 10 nm.

[0048] The nano-aluminum sol was purchased from Xuancheng Jingrui New Materials Co., Ltd.

[0049] The waterborne polyurethane is an anionic waterborne polyurethane.

[0050] The preparation method of the fatty amine soap premix is ​​as follows: short-chain fatty amines and small molecule organic acids are mixed at a molar ratio of 1:1 at 45°C, and then water is added to prepare a 1wt% aqueous dispersion.

[0051] The short-chain fatty amine is dodecyl primary amine, CAS number 124-22-1.

[0052] The small molecule organic acid mentioned is citric acid.

[0053] The aqueous ultraviolet absorber is a benzotriazole-based ultraviolet absorber.

[0054] The UV-1130 was purchased from the Kemick brand.

[0055] The aqueous wax emulsion is a polyethylene-type aqueous wax emulsion.

[0056] The BYK 531 mentioned was purchased from the BYK brand.

[0057] The CAS number of the sodium dioctyl sulfonate is 577-11-7.

[0058] The second aspect of this embodiment provides a method for preparing a chromium-free passivation solution for use in low-latitude coastal areas, comprising the following steps: under stirring at 25°C, molybdate, inorganic acid, alkanolamine, nano-sol, waterborne polyurethane, crosslinking agent, fatty amine soap premix, waterborne ultraviolet absorber, waterborne wax emulsion, and penetrating desiccant are added sequentially to water according to the mass percentage of the chromium-free passivation solution. During the addition process, if the added raw material is a solid, it must be allowed to dissolve completely before adding the next raw material.

[0059] The third aspect of this embodiment provides an application of a chromium-free passivation solution used in low-latitude coastal areas for the preparation of chromium-free passivation films.

[0060] The preparation method involves coating the surface of galvanized aluminum-magnesium steel coil with a chromium-free passivation liquid using a roller coating method, and then drying and curing the wet film of the passivation liquid using a three-stage drying method to form a dry chromium-free passivation film on the surface of the substrate.

[0061] The three-stage drying method includes low-temperature pre-drying (PMT=70℃), medium-temperature drying (PMT=90℃), and high-temperature drying (PMT=110℃).

[0062] Example 2

[0063] This embodiment provides a chromium-free passivation solution for use in low-latitude coastal areas. The raw materials and mass percentages for its preparation are shown in Table 2.

[0064] Table 2

[0065] Element raw material Quality percentage (%) molybdate Ammonium molybdate 5 Inorganic acids 40v / v% hydrofluoric acid 2 alcoholamines Triethanolamine 3 Nanosol JR14W 3 Waterborne polyurethane Opel U9600 45 Crosslinking agent Aluminum citrate 0.8 Fatty amine soap premix Fatty amine oxalic acid soap aqueous dispersion 5 Water-based UV absorbers UV-1130 2.5 Water-based wax emulsion BYK 531 3 Permeation desiccant Sodium dioctylsulfonate 2 water Deionized water 28.7

[0066] The particle size of the nano-aluminum sol is 12±3nm.

[0067] The nano-aluminum sol was purchased from Xuancheng Jingrui New Materials Co., Ltd.

[0068] The waterborne polyurethane is an anionic waterborne polyurethane.

[0069] The preparation method of the fatty amine soap premix is ​​as follows: short-chain fatty amines and small molecule organic acids are mixed at a molar ratio of 1:1 at 45°C, and then water is added to prepare a 1wt% aqueous dispersion.

[0070] The short-chain fatty amine is dodecyl primary amine, CAS number 124-22-1.

[0071] The small molecule organic acids mentioned include oxalic acid.

[0072] The aqueous ultraviolet absorber is a benzotriazole-based ultraviolet absorber.

[0073] The UV-1130 was purchased from the Kemick brand.

[0074] The aqueous wax emulsion is a polyethylene-type aqueous wax emulsion.

[0075] The BYK 531 mentioned was purchased from the BYK brand.

[0076] The CAS number of the sodium dioctyl sulfonate is 577-11-7.

[0077] The second aspect of this embodiment provides a method for preparing a chromium-free passivation solution for use in low-latitude coastal areas, comprising the following steps: under stirring at 25°C, molybdate, inorganic acid, alkanolamine, nano-sol, waterborne polyurethane, crosslinking agent, fatty amine soap premix, waterborne ultraviolet absorber, waterborne wax emulsion, and penetrating desiccant are added sequentially to water according to the mass percentage of the chromium-free passivation solution. During the addition process, if the added raw material is a solid, it must be allowed to dissolve completely before adding the next raw material.

[0078] The third aspect of this embodiment provides an application of a chromium-free passivation solution used in low-latitude coastal areas for the preparation of chromium-free passivation films.

[0079] The preparation method involves coating the surface of galvanized aluminum-magnesium steel coil with a chromium-free passivation liquid using a roller coating method, and then drying and curing the wet film of the passivation liquid using a three-stage drying method to form a dry chromium-free passivation film on the surface of the substrate.

[0080] The three-stage drying method includes low-temperature pre-drying (PMT=70℃), medium-temperature drying (PMT=90℃), and high-temperature drying (PMT=110℃).

[0081] Comparative Example 1

[0082] This comparative example provides a chromium-free passivation solution, the raw materials and mass percentages of which are shown in Table 3.

[0083] Table 3

[0084] Element raw material Quality percentage (%) molybdate Ammonium molybdate 5 Inorganic acids 40v / v% hydrofluoric acid 2 alcoholamines Triethanolamine 3 Waterborne polyurethane Opel U9600 45 Crosslinking agent Aluminum citrate 0.8 Fatty amine soap premix Fatty amine oxalic acid soap aqueous dispersion 5 Water-based UV absorbers UV-1130 2.5 Water-based wax emulsion BYK 531 3 Permeation desiccant Sodium dioctylsulfonate 2 water Deionized water 31.7

[0085] Performance testing

[0086] 1. The 10 g / m³ sample prepared in Examples 1 and 2 was obtained. 2Chromium-free passivation film and 10 g / m prepared using Comparative Example 1 2 The results of the neutral salt spray test on the chromium-free passivation film and the ratio of corrosion area to total area are shown in Table 1. NSS: salt spray rate 1-2 mL / h, sodium chloride brine concentration 5%, pH = 6.8-7.2, temperature 35℃.

[0087] Conclusion: As shown in Table 4, the 10 g / m³ prepared in Examples 1 and 2... 2 The chromium-free passivation film has a smaller corrosion area, and its salt spray performance is significantly better than that of the 10 g / m² film prepared in Comparative Example 1. 2 Chromium-free passivation film.

[0088] Table 4

[0089]

[0090]

[0091] 2. The 10 g / m³ preparations from Examples 1 and 2 were obtained. 2 Chromium-free passivation film and 10 g / m prepared using Comparative Example 1 2 The chromium-free passivation film was subjected to a damp heat test: 40℃, 100% humidity for 8 hours, then 20℃, 70% humidity for 16 hours, and this cycle was repeated. The corrosion status was determined by the percentage of rusted area relative to the total area.

[0092] In conclusion, as shown in Table 5, the rust resistance of the chromium-free passivation films prepared in Examples 1 and 2 is significantly better than that of the 10 g / m² film prepared using Comparative Example 1. 2 Chromium-free passivation film.

[0093] Table 5

[0094]

[0095] 3. The 10g / m² preparation obtained from Examples 1 and 2 was... 2 The chromium-free passivation film underwent a UV resistance test: 8 hours of 340nm UV light at 40℃, followed by 16 hours of condensation at 20℃, repeated cyclically. The color difference ΔE before and after the test was measured using a colorimeter; and the gloss was measured before and after the test using a gloss meter, with the resulting loss calculated.

[0096] Conclusion: Table 6 shows that the chromium-free passivation films prepared in Examples 1 and 2 have excellent UV resistance.

[0097] Table 6

[0098] Example 1 Example 2 Comparative Example 1 1000h - Color difference ΔE 0.5 0.5 3 1000h - Gloss Loss 10％ 10％ 30％ 2000h - Color difference ΔE 1.2 1.1 6 2000h - Gloss Loss 10％ 10％ 50％ 3000h - Color difference ΔE 2.1 1.7 11 3000h - Gloss Loss 30％ 20％ 70％

Claims

1. A chromium-free passivation solution for use in low-latitude coastal areas, characterized in that, The raw materials for its preparation, by mass percentage, include 0.5-5% molybdate, 1-5% inorganic acid, 1-5% alkanolamine, 1-5% nanosol, 20-60% waterborne polyurethane, 0.1-1.0% crosslinking agent, 5-10% fatty amine soap premix, 1-5% waterborne ultraviolet absorber, 1-10% waterborne wax emulsion, 1-5% penetrating desiccant, and the balance being water; The nanosol is a nano-aluminum sol; The preparation method of the fatty amine soap premix is ​​as follows: dodecyl primary amine and small molecule organic acid are mixed at a molar ratio of (0.8-1.2):1 at 40-50°C, and then water is added to prepare a 0.5-2wt% aqueous dispersion. The small molecule organic acids mentioned include one of citric acid and oxalic acid; The crosslinking agent includes aluminum citrate; The described penetrating desiccant includes sodium dioctyl sulfonate.

2. The chromium-free passivation solution for use in low-latitude coastal areas according to claim 1, characterized in that, The molybdate includes one or more of sodium molybdate, ammonium molybdate, and potassium molybdate; the inorganic acid includes one or two of hydrofluoric acid and sulfuric acid.

3. The chromium-free passivation solution for use in low-latitude coastal areas according to claim 1, characterized in that, The alkanolamines include one or more of triethanolamine, monoethanolamine, diethanolamine, diethylene glycolamine, and isopropanolamine.

4. The chromium-free passivation solution for use in low-latitude coastal areas according to claim 1, characterized in that, The aqueous wax emulsion includes a polyethylene-type aqueous wax emulsion.

5. A method for preparing a chromium-free passivation solution for use in low-latitude coastal areas according to any one of claims 1 to 4, characterized in that, The process includes the following steps: under stirring at room temperature, molybdate, inorganic acid, alkanolamine, nano-sol, waterborne polyurethane, crosslinking agent, fatty amine soap premix, waterborne ultraviolet absorber, waterborne wax emulsion, and penetrating desiccant are added to water in sequence according to the mass percentage of the chromium-free passivation solution. If the added raw material is a solid, it must be allowed to dissolve completely before adding the next raw material.

6. The application of a chromium-free passivation solution according to any one of claims 1 to 4 in low-latitude coastal areas, characterized in that, Application in the preparation of chromium-free passivation films on galvanized aluminum-magnesium steel coils.

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