Cold plate pre-spraying degreaser without phosphorization and vitrification and preparation method of cold plate pre-spraying degreaser

Abstract

The invention relates to the field of metal surface treatment, and mainly relates to a cold plate pre-spraying degreaser free of phosphorization and vitrification and a preparation method of the cold plate pre-spraying degreaser. The invention relates to a degreaser before spraying a cold plate without phosphorization and vitrification. The degreaser comprises the following components by mass concentration: 2-8 g / L of alkali, 2-7 g / L of sodium salt, 4-12 g / L of surfactant, 1-3 g / L of complexing agent, 1-4 g / L of antirust additive and water. The degreasing agent has the effects of efficient degreasing, short-term rust prevention and coating adhesive force increase, and is convenient to use.

Description

Technical Field

[0001] This application relates to the field of metal surface treatment, and mainly to a degreasing agent for cold plates before spraying that does not require phosphating or ceramic coating, and its preparation method. Background Technology

[0002] Every minute, a large amount of steel worldwide undergoes chemical or electrochemical corrosion, turning into rust. Each year, a quarter of the annual steel production is lost due to rust and corrosion, resulting in enormous losses. To reduce these losses and extend the lifespan of steel products, anti-corrosion treatments are typically applied, such as galvanizing, Dacromet coating, painting, and powder coating. The ultimate goal is to isolate steel products from the external environment, preventing rust and corrosion.

[0003] After spraying, steel parts not only avoid corrosion but also become more aesthetically pleasing and durable. The prerequisite for spraying is ensuring the steel surface is clean and oil-free, and a film is applied to enhance adhesion. Spraying plants typically use phosphate coatings and ceramic coatings to improve adhesion.

[0004] Because phosphating has a wider range of applications and can treat rusty products, resulting in better adhesion and rust prevention, many painting plants still use phosphating. However, phosphating has a significant drawback: environmental issues. Sludge continuously forms in the phosphating bath during use, requiring daily removal and thus increasing solid waste and disposal costs.

[0005] In the ceramic coating process, the coating tank does not require slag removal, which greatly improves environmental friendliness. However, it also has significant limitations, namely, some rusty products cannot be used with this process. This is because rusty products must first undergo cleaning and rust removal treatment, and are prone to rusting again after ceramic coating.

[0006] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this application is to provide a degreasing agent for cold-rolled steel plates that does not require phosphating or ceramic coating before spraying, and its preparation method, aiming to solve the above-mentioned process defects or limitations. The degreasing agent of this application has the effects of high efficiency in degreasing, short-term rust prevention, and increased coating adhesion, and is easy to use.

[0008] The technical solution of this application is as follows: A degreasing agent for cold-rolled steel plates that does not require phosphating or ceramic coating before spraying, comprising the following raw materials by mass concentration: alkali 2-8 g / L, sodium salt 2-7 g / L, surfactant 4-12 g / L, complexing agent 1-3 g / L, rust inhibitor 1-4 g / L, and water as the balance. For ease of distinction, the water here is referred to as Water A.

[0009] Furthermore, the rust-inhibiting additive includes one or more of 1,2-propanediamine, quaternary aminopolyvinylimidazole, triethanolamine, diethylenetriamine, diisopropylamine, triethanolamine borate, and triethanolamine p-aminobenzoate.

[0010] Furthermore, the rust-inhibiting additive is triethanolamine-p-aminobenzoate; The triethanolamine-p-aminobenzoic acid ester comprises, by mass parts, the following raw materials: 40-45 parts p-aminobenzoic acid, 75-85 parts triethanolamine, and 110-130 parts water. For ease of distinction, the water here is referred to as water B.

[0011] Furthermore, the preparation method of the triethanolamine-p-aminobenzoate includes the following steps: The p-aminobenzoic acid and the triethanolamine are mixed; the mixture is stirred at 45-55°C until the solution turns yellow. Continue adding water B, and keep warm at 45-55℃ for 20-30 minutes to obtain the triethanolamine-p-aminobenzoate.

[0012] The carboxyl group of p-aminobenzoic acid and the amino group of triethanolamine undergo esterification under heating conditions to generate an ester compound with dual active groups—the amino group provides strong adsorption capacity, while the ester group imparts hydrophobic properties. Water acts as a solvent to promote molecular diffusion during the reaction and also regulates the reaction process through hydrolysis equilibrium during the heat treatment stage, ensuring that the degree of esterification is controlled within the optimal range for rust prevention and degreasing performance.

[0013] The synthesized triethanolamine-p-aminobenzoate possesses dual "adsorption-hydrophobicity" properties. Specifically, the amino group forms a physical adsorption layer on the metal surface through hydrogen bonds and coordination bonds, preventing the penetration of corrosive media; the hydrophobic segments of the ester group repel water molecules, reduce interfacial free energy, and inhibit rust recurrence.

[0014] Compared to traditional rust inhibitors, its advantage lies in the balance of "rust prevention and degreasing" functions. When the addition amount is 1-4g / L, it can form a dense protective film through physical adsorption, but it will not cause the film layer to become loose due to excessive adsorption. At the same time, it avoids competing with surfactants for adsorption sites and maintains degreasing efficiency.

[0015] Furthermore, the alkali includes one or more of sodium hydroxide and potassium hydroxide; The sodium salt includes one or more of sodium carbonate, sodium metasilicate pentahydrate, sodium bicarbonate, sodium citrate, sodium tripolyphosphate, sodium pyrophosphate, and sodium acetate; The surfactant includes one or more of FMEE and polyvinyl alcohol ether; The complexing agent includes one or more of the following: ethylenediaminetetraacetic acid, sodium tripolyphosphate, sodium gluconate, sodium aminotriacetate, sodium citrate, sodium polyacrylate, and hydrolyzed polymaleic anhydride.

[0016] Furthermore, the alkali is potassium hydroxide; The sodium salt is sodium carbonate; The surfactant is a mixture of FMEE and polyvinyl alcohol ether; The complexing agent is sodium gluconate.

[0017] Furthermore, the triethanolamine-p-aminobenzoic acid ester comprises, by mass parts, the following raw materials: 41 parts p-aminobenzoic acid, 79 parts triethanolamine, and 120 parts water B.

[0018] Furthermore, the rust-inhibiting additive is 3-4 g / L in terms of mass concentration.

[0019] This application develops a novel degreasing agent system by selecting specific substances and defining unique proportions. Through multi-component synergy, it achieves degreasing, rust prevention, and environmental protection. Surfactants, at room temperature, rapidly emulsify and dissolve oil stains on the surface of cold-rolled steel plates through the directional arrangement of their hydrophilic and lipophilic groups, forming micelles dispersed in the aqueous phase for highly efficient degreasing. Alkali decomposes fatty acids in the oil stains through saponification, while simultaneously neutralizing acidic substances on the metal surface, creating a suitable alkaline environment for the surfactants and accelerating their penetration and dissolution of the oil stains. Sodium salts, such as sodium carbonate, can remove impurities from the metal surface through ion exchange and also accelerate degreasing by saponifying vegetable oils. Sodium metasilicate pentahydrate forms a protective film to inhibit rust recurrence. Complexing agents, such as gluconic acid, form stable complexes with metal ions, blocking electrochemical corrosion pathways. Rust-inhibiting additives can be adsorbed onto the metal surface to form a hydrophobic film, preventing oxygen and water molecules from contacting the substrate.

[0020] Each component forms a closed loop in the "degreasing-rust prevention" functional chain: surfactants, alkalis, and sodium salts complete the removal of oil stains, complexing agents and rust-preventing additives block the corrosion reaction, and water serves as a medium to achieve uniform dispersion of the overall system.

[0021] The degreasing agent provided in this application can avoid the generation of sludge and solid waste in traditional phosphating processes, complies with EU RoHS environmental standards, and is suitable for multi-metal products such as cold-rolled steel and stainless steel. Under the premise of ensuring environmental protection, it has good degreasing, rust prevention and adhesion improvement effects.

[0022] This application also provides a method for preparing a degreasing agent for cold-rolled steel plates that does not require phosphating or ceramic coating before spraying, comprising the following steps: mixing all raw materials to obtain the degreasing agent for cold-rolled steel plates that does not require phosphating or ceramic coating before spraying.

[0023] Furthermore, if the surfactant contains two or more, the method includes the following steps: The raw materials, excluding the surfactant, are mixed evenly to obtain a clear solution; The surfactants are mixed to obtain a mixed solution; The mixed solution and the clarified solution are mixed to obtain the degreasing agent for cold plate that does not require phosphating or ceramic coating before spraying.

[0024] Compared with the prior art, this application has the following beneficial effects: 1. Environmental advantages: The degreasing agent of this application is free of phosphates, safe and environmentally friendly, and fully complies with the EU RoHS standard. It can be widely used for cleaning cold-rolled steel plates, stainless steel and other products.

[0025] 2. Economic and Practical Advantages: The degreasing agent of this application contains unique degreasing surfactants and rust-inhibiting additives. It can quickly emulsify and degrease at room temperature, resulting in not only fast degreasing speed but also eliminating the need for a phosphating or ceramic coating process. Furthermore, it provides some inter-process rust prevention, prevents rust recurrence, and does not affect adhesion. Eliminating the phosphating or ceramic coating process not only saves on process costs but also simplifies operation, as it does not have the strict process parameter requirements of phosphating and ceramic coating. It boasts advantages such as high efficiency, environmental friendliness, and economy. Detailed Implementation

[0026] This application provides a degreasing agent for cold-rolled steel plates that does not require phosphating or ceramic coating before spraying, and a method for preparing the same. To make the objectives, technical solutions, and effects of this application clearer and more explicit, the following provides a more detailed description. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0027] This application provides a degreasing agent for cold-rolled steel plates that does not require phosphating or ceramic coating before spraying. By mass concentration, it includes the following raw materials: alkali 2-8g / L, sodium salt 2-7g / L, surfactant 4-12g / L, complexing agent 1-3g / L, rust inhibitor 1-4g / L, and water balance (water A).

[0028] Alkali: The alkali is sodium hydroxide or potassium hydroxide; preferably, the alkali is potassium hydroxide. Potassium hydroxide, with the molecular formula KOH, is a strong alkali with high corrosiveness. It is generally in flake or granular form, readily soluble in water (releasing heat upon dissolution) to form an alkaline solution, and also hygroscopic, readily absorbing water vapor (hygroscopicity) and carbon dioxide (deterioration) from the air. Potassium hydroxide is a strong alkaline, has strong penetrating power, and good emulsification properties for vegetable oils. At the same concentration as sodium hydroxide, potassium hydroxide has better water solubility and better compatibility with surfactants, synergistically accelerating the degreasing process.

[0029] Sodium salt: The sodium salt is selected from one or more of sodium carbonate, sodium metasilicate pentahydrate, sodium bicarbonate, sodium citrate, sodium tripolyphosphate, sodium pyrophosphate, and sodium acetate. Preferably, the sodium salt is sodium carbonate; sodium carbonate has good emulsifying properties for vegetable oils and is inexpensive.

[0030] Surfactants: The degreasing agent of this application is mainly used to clean a mixture of palm oil and mineral oil, which is difficult to clean. Therefore, it is necessary to select a surfactant with good degreasing properties, such as one or more of FMEE and polyvinyl alcohol ether, to ensure both good degreasing performance and a certain degree of low foaming performance.

[0031] When the surfactant is a mixture of FMEE and polyvinyl alcohol ether, the mass ratio of FMEE to polyvinyl alcohol ether is 2:1.

[0032] Complexing agent: The complexing agent is one or a mixture of two or more of the following: ethylenediaminetetraacetic acid (EDTA disodium or tetrasodium), sodium tripolyphosphate, sodium gluconate, sodium aminotriacetate (NTA), sodium citrate, sodium polyacrylate, and hydrolyzed polymaleic anhydride (HPMA). Preferably, the complexing agent is sodium gluconate; sodium gluconate has both complexing properties and a certain degree of rust prevention.

[0033] Rust-inhibiting additives: Since the object being cleaned is cold-rolled steel products, rust is very likely to reappear on the surface after the surface oil is washed away and rinsed with water. Therefore, rust-inhibiting additives are needed. The rust-inhibiting additives are selected from one or more of 1,2-propanediamine, quaternary aminopolyvinylimidazole, triethanolamine, diethylenetriamine, diisopropylamine, triethanolamine borate, and triethanolamine p-aminobenzoate. Preferably, the rust-inhibiting additive is triethanolamine p-aminobenzoate.

[0034] Triethanolamine p-aminobenzoate, by mass parts, comprises the following raw materials: 40-45 parts p-aminobenzoic acid, 75-85 parts triethanolamine, and 110-130 parts water (water B).

[0035] The preparation method of triethanolamine p-aminobenzoate includes the following steps: Weigh out p-aminobenzoic acid and place it in a beaker. Separately weigh out triethanolamine and mix it thoroughly with p-aminobenzoic acid.

[0036] While heating to 45-55℃ and stirring, the solution slowly turns yellow.

[0037] Add water (water B) after 5-15 minutes, heat to 45-55℃ and keep warm for 20-30 minutes. The synthesis of triethanolamine p-aminobenzoate is complete.

[0038] This application also provides a method for preparing a degreasing agent for cold-rolled steel plates that does not require phosphating or ceramic coating before spraying, comprising the following steps.

[0039] Step 1: Add the alkali, sodium salt, complexing agent, and rust inhibitor to tap water (water A) in sequence and stir until a clear solution is obtained.

[0040] Step 2: Stir the surfactant (FMEE, polyvinyl alcohol ether) until a mixed solution is obtained.

[0041] Step 3: Add the mixed solution to the clear solution and stir for 5-15 minutes to obtain a degreasing agent for cold plates that do not require phosphating or ceramic coating before spraying.

[0042] This application also provides a method for using a degreasing agent before spraying cold-rolled steel plates that does not require phosphating or ceramic coating, including the following process: Room temperature degreasing agent sprayed onto cold plate for 2 minutes — 50℃ degreasing agent soaked into cold plate for 3 minutes — rinsed with tap water — rinsed with tap water — dried — sprayed with epoxy resin powder — cured — packaged.

[0043] The present application will be further described below through specific embodiments.

[0044] Example 1 A degreasing agent for cold-rolled steel plates that does not require phosphating or ceramic coating before spraying, comprising the following components by mass concentration: 6.6 g / L potassium hydroxide, 2 g / L sodium gluconate, 3.3 g / L sodium carbonate, 6 g / L FMEE, 3 g / L polyvinyl alcohol ether, 2 g / L triethanolamine para-aminobenzoate, and the remainder being tap water (Water A).

[0045] The preparation of triethanolamine p-aminobenzoate includes the following steps: Weigh 41 g of p-aminobenzoic acid into a beaker, and separately weigh 79 g of triethanolamine, mixing them thoroughly with the p-aminobenzoic acid. Heat to 50°C while stirring; the solution slowly turns yellow. After 10 minutes, add 120 g of water (water B), heat to 50°C and maintain this temperature for half an hour. The synthesis of triethanolamine p-aminobenzoic acid ester is complete.

[0046] A method for preparing a degreasing agent for cold-rolled steel plates that does not require phosphating or ceramic coating before spraying includes the following steps.

[0047] Step 1: Add potassium hydroxide, sodium carbonate, sodium gluconate, and triethanolamine para-aminobenzoate to tap water (water A) in sequence and stir until a clear solution is obtained.

[0048] Step 2: Mix FMEE and polyvinyl alcohol ether, stir well to obtain a mixed solution.

[0049] Step 3: Add the mixed solution to the clear solution and stir for 10 minutes to obtain a degreasing agent for cold plates that do not require phosphating or ceramic coating before spraying.

[0050] Example 2 A degreasing agent for cold-rolled steel plates that does not require phosphating or ceramic coating before spraying, differing from Example 1 in that the triethanolamine para-aminobenzoate content is 3 g / L.

[0051] Example 3 A degreasing agent for cold-rolled steel plates that does not require phosphating or ceramic coating before spraying, differing from Example 1 in that the triethanolamine para-aminobenzoate content is 4 g / L.

[0052] Comparative Example 1 A degreasing agent for cold-rolled steel plates before spraying, which differs from Example 1 in that the triethanolamine para-aminobenzoate content is 5 g / L.

[0053] Comparative Example 2 A degreasing agent for cold-rolled steel plates before spraying, which differs from Example 1 in that the triethanolamine para-aminobenzoate content is 6 g / L.

[0054] Performance Evaluation 1. Degreasing effect The degreasing effect of the degreasing agents prepared in Examples 1-3 and Comparative Examples 1-2 was tested by gravimetric method.

[0055] The experimental method involved testing two cold-plate specimens (100*50*0.5mm) for each example / comparative example at room temperature. The specimens were first weighed and recorded as weight A. The weighed specimens were then immersed in a 1:1 mixture of palm oil and mineral oil for 1 minute, removed, and allowed to air dry for 24 hours. The weights were then recorded as weight B. The soaked and dried specimens were then treated as follows: sprayed with a degreasing agent at room temperature for 30 seconds, immersed in the degreasing agent at 50°C for 1 minute, sprayed with tap water for 2 minutes, and dried at 110°C for 3 minutes (all tap water was at room temperature). The treated specimens were then weighed and recorded as weight C.

[0056] Oil removal rate = (BC / BA)%, the average oil removal rate of each example / comparative example is taken as the final oil removal rate. The test results are shown in Table 1.

[0057] 2. Rust prevention test The test piece was made of cold-rolled steel plate, with dimensions of 100*50*0.5mm. The test piece was sprayed and cleaned with a degreasing agent for 2 minutes, then immersed in the degreasing agent for 2 minutes, rinsed with tap water (both the degreasing agent and tap water were at room temperature), and allowed to air dry. The test piece was visually inspected for rust. The time it took for rust to form was recorded.

[0058] 3. Adhesion test (1) The test piece is a cold plate with a size of 100*50*0.5mm. First, spray it in degreasing agent for 2 minutes, soak it in degreasing agent for 2 minutes, rinse it with tap water (the degreasing agent and tap water are at room temperature), then dry it at 110℃ for 3 minutes, spray it with epoxy resin powder, cure it at 210℃ for 10 minutes, and cool it. The test piece is tested 24 hours after cooling.

[0059] The adhesion effect is evaluated according to the following methods and indicators: a. Cross-cut test: Draw a 100-grid pattern on the test piece with a blade, spaced 1 mm apart. The evaluation criterion is to apply 3M tape to the 100-grid area, press it flat, and then quickly and forcefully peel the tape vertically from one side at a certain speed. Calculate the number of coating squares that are torn off. Record the results in Table 1 according to the ASTM rating.

[0060] b. Boiling Method: Boil the test piece in a pressure cooker for 2 hours, then remove and let cool. Use a blade to draw a grid of 100 lines on the test piece, spaced 1 mm apart. The evaluation criterion is to apply 3M tape to the grid lines, press it flat, and then quickly and forcefully peel the tape vertically from one side at a certain speed. Calculate the number of coating lines that are torn off. Record the results in Table 1 according to the ASTM rating.

[0061] The test results are shown in Table 1.

[0062] Table 1

[0063] As shown in Table 1 above, the higher the content of the rust inhibitor triethanolamine p-aminobenzoate, the greater the impact on adhesion. This rust inhibitor is a physical adsorbent; the higher the content, the more rust inhibitor is adsorbed onto the iron product, resulting in a thicker film layer. However, the outer layer's adsorption force on the iron product is weaker, and the adsorbed film layer is more porous, reducing the electrostatic adsorption between the coating and the iron product, ultimately leading to reduced adhesion. At the same time, because more rust inhibitor is adsorbed onto the iron product (Comparative Examples 1-2), the degreasing agent's ability to penetrate, emulsify, and dissolve oil is reduced, also resulting in decreased cleaning power.

[0064] Regarding rust prevention testing, cold-rolled steel sheets rust easily when exposed to water. Therefore, after cleaning with degreasing agents, the rust can be observed with the naked eye. However, in industrial production, cold-rolled steel sheets are usually moved to the next step very quickly after cleaning, so the rust prevention time does not need to be too long.

[0065] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of this application.

Claims

1. A cold plate spraying pre-degreasing agent without phosphating and vitrification, characterized in that, By mass concentration, base 2-8 g / L, sodium salt 2-7 g / L, surfactant 4-12 g / L, complexing agent 1-3 g / L, anti-rust additive 1-4 g / L, water.

2. The non-phosphorized, non-boronized, cold plate pre-spraying degreasing agent according to claim 1, characterized in that, The anti-rust additive comprises one or more than two of 1,2-propylenediamine, quaternary amino polyethylene imidazole, triethanolamine, diethylenetriamine, diisopropylamine, triethanolamine borate, and triethanolamine p-aminobenzoate.

3. The non-phosphorized, non-boronized, cold plate prespraying degreasing agent according to claim 1, characterized in that, The anti-rust additive is triethanolamine p-aminobenzoate. The triethanolamine p-aminobenzoate comprises, by mass fraction, the following preparation raw materials: 40-45 parts of p-aminobenzoic acid, 75-85 parts of triethanolamine, and 110-130 parts of water.

4. The non-phosphorized, non-boronized, cold plate prespraying degreasing agent according to claim 3, characterized in that, The preparation method of the triethanolamine p-aminobenzoate comprises the following steps: The p-aminobenzoic acid and the triethanolamine are mixed and stirred at 45-55°C until the solution turns yellow; The water is continuously added, heated to 45-55°C for 20-30 min, and the triethanolamine p-aminobenzoate is obtained.

5. The non-phosphorized, non-boronized, cold plate prespraying degreasing agent according to claim 1, characterized in that, The base comprises one or more than two of sodium hydroxide and potassium hydroxide; The sodium salt comprises one or more than two of sodium carbonate, sodium metasilicate pentahydrate, sodium bicarbonate, sodium citrate, sodium tripolyphosphate, sodium pyrophosphate, and sodium acetate; The surfactant comprises one or more than two of FMEE and polyvinyl alcohol ether; The complexing agent comprises one or more than two of ethylenediaminetetraacetate, sodium tripolyphosphate, sodium gluconate, sodium nitrilotriacetate, sodium citrate, sodium polyacrylate, and hydrolyzed polymaleic anhydride.

6. The non-phosphorized, non-boronized, cold plate prespraying degreasing agent according to claim 1, characterized in that, The base is potassium hydroxide; The sodium salt is sodium carbonate; The surfactant is a mixture of FMEE and polyvinyl alcohol ether; The complexing agent is sodium gluconate.

7. The non-phosphorized, non-boronized, cold plate prespraying degreasing agent according to claim 2, characterized in that, The triethanolamine p-aminobenzoate comprises, by mass fraction, the following preparation raw materials: 41 parts of p-aminobenzoic acid, 79 parts of triethanolamine, and 120 parts of water.

8. The non-phosphorized, non-boronized, cold plate prespraying degreasing agent according to claim 1, characterized in that, By mass concentration, the anti-rust additive is 3-4 g / L.

9. A method for preparing a cold plate spraying pre-degreasing agent without phosphating and vitrification according to any one of claims 1-8, characterized in that, The method comprises the following steps: mixing all the raw materials to obtain the phosphating and ceramizing-free cold plate pre-spraying oil removal agent.

10. The method for preparing the degreasing agent for cold-rolled steel plates before spraying that does not require phosphating or ceramic coating according to claim 9, characterized in that, If the surfactant comprises two or more than two, the method comprises the following steps: Mixing the raw materials except the surfactant uniformly to obtain a clear solution; Mixing the surfactants to obtain a mixed solution; Mixing the mixed solution and the clear solution to obtain the phosphating and ceramizing-free cold plate pre-spraying oil removal agent.

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