A non-phosphorus, high-efficiency, biodegradable neutral rust remover and a preparation method thereof
By combining phosphorus-free complexing agents and organic acids, sodium isoascorbate is used to reduce Fe3+, along with surfactants and corrosion inhibitors, a highly efficient and environmentally friendly neutral rust removal effect is achieved. This solves the environmental and efficiency problems of traditional rust removers, ensuring that the metal substrate is bright and corrosion-free.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI THRIVING SPECIAL OIL SCI & TECH
- Filing Date
- 2026-03-30
- Publication Date
- 2026-06-09
AI Technical Summary
Existing neutral rust removers mostly contain phosphates, which can cause parts to corrode and discolor, have poor biodegradability, and fail to meet environmental protection requirements. Furthermore, traditional rust removal methods are inefficient and dangerous.
A combination of phosphorus-free complexing agents, organic acids, flash rust inhibitors, surfactants, and corrosion inhibitors is used. Through a reduction-complexing-stripping mechanism, sodium isoascorbate is used to reduce Fe3+ to Fe2+, forming a stable coordination geometry. This is combined with nonionic surfactants to penetrate the rust layer, and a special corrosion inhibitor is used to protect the metal substrate, forming a double protection.
It achieves a 2-3 times increase in rust removal efficiency, completely removes rust without discoloration, leaves the metal substrate bright, is environmentally friendly, meets green chemistry requirements, and reduces waste liquid treatment costs.
Smart Images
Figure CN122169100A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of metal surface treatment technology, and more specifically, to a phosphorus-free, efficient, biodegradable neutral rust remover and its preparation method. Background Technology
[0002] In the field of metal processing and protection, rust removal is a crucial pretreatment step to ensure coating adhesion, electroplating quality, and rust prevention effects. Traditional rust removal methods mainly include strong acid (such as hydrochloric acid, sulfuric acid, and phosphoric acid) rust removal, strong alkali rust removal, and mechanical grinding rust removal. However, these methods have many inherent drawbacks: strong acid rust removal is fast, but it easily causes "hydrogen embrittlement" and over-corrosion of the metal substrate, the operation process is dangerous, and the generated acid mist and waste liquid have a large environmental impact; strong alkali rust removal has limited ability to dissolve certain rust products; mechanical rust removal is difficult to handle complex workpieces, and is labor-intensive and inefficient.
[0003] With increasingly stringent environmental regulations and the development of chelating chemistry and corrosion inhibition technologies, neutral rust removers have emerged and become a research hotspot. Common neutral rust removers often contain phosphoric acid and its salts, such as trisodium phosphate and organophosphonic acid, as complexing agents. While they possess good rust removal effects, they also present problems such as easy corrosion and discoloration of parts, poor biodegradability, and inability to meet production safety and environmental emission requirements.
[0004] Therefore, developing a truly phosphorus-free, highly efficient, and environmentally friendly neutral rust remover that provides good protection for a variety of metal substrates remains a pressing technical challenge in this field. Summary of the Invention
[0005] In order to ensure high rust removal efficiency without using phosphorus complexing agents, this application provides a phosphorus-free, high-efficiency, biodegradable neutral rust remover and its preparation method.
[0006] In a first aspect, this application provides a phosphorus-free, highly efficient, and biodegradable neutral rust remover, employing the following technical solution: A phosphorus-free, highly efficient, biodegradable neutral rust remover, composed of the following components by weight percentage: 15-30% phosphorus-free complexing agent; Organic acids 1-3%; Sodium isoascorbate 3-5%; Anti-flash rust agent 5-10%; Corrosion inhibitor 2-5%; Surfactant 1-3%; Water balance.
[0007] By adopting the above-mentioned technical solution: It was previously widely believed in the field that achieving efficient rust removal and excellent corrosion inhibition required reliance on phosphates or highly toxic components. This application, through the synergistic effect of a multi-mechanism "reduction-complexation-stripping" process, increases the overall rust removal rate by 2-3 times, and achieves or even surpasses the comprehensive performance of existing technologies without using phosphorus / fluorine-containing substances, thus overcoming this technical bias.
[0008] Among them, the "peeling an onion" rust removal method is used, firstly using sodium isoascorbate to remove the insoluble Fe. 3+ Reduced to readily soluble Fe 2+ This created dissolution channels, after which these Fe 2+ It will be rapidly complexed and dissolved by the phosphorus-free complexing agent present in the solution. Once one layer of rust is dissolved, the next layer of rust is exposed, and sodium isoascorbate continues to reduce the newly exposed Fe. 3+ This process is repeated, peeling away the rust layer by layer, much like peeling an onion. This process greatly accelerates the overall rust removal rate.
[0009] Optionally, the phosphorus-free complexing agent is one or more of the following: tetrasodium glutamate diacetate, trisodium ethylenediamine disuccinate, trisodium hydroxyethylenediamine triacetate, trisodium methylglycine diacetate, tetrasodium iminodisuccinate, tetrasodium aspartate diacetate, and tetrasodium hydroxyiminodisuccinate.
[0010] By adopting the above technical solutions, these phosphorus-free complexing agents are all recognized biodegradable and environmentally friendly amino-polycarboxylic acid phosphorus-free complexing agents. They have high selectivity for heavy metal ions such as copper and iron. They have strong active attack capabilities and can powerfully "grab" iron ions in rust to form a stable and soluble coordination geometry, thereby dissolving and peeling off the rust layer and achieving chemical dissolution.
[0011] Optionally, the organic acid may be one or more of citric acid, gluconic acid, and glycolic acid.
[0012] By adopting the above technical solution, an organic acid is added. This acid is mild, non-toxic, harmless, and easily biodegradable. Adding a small amount can adjust the pH value to the neutral range, allowing the phosphorus-free complexing agent to be in its most active state, resulting in a synergistic effect between the two.
[0013] Optionally, the anti-flash rust agent is one or more of sodium citrate, sodium gluconate, sodium glycolate, and sodium formate.
[0014] By adopting the above technical solution, the anti-flash rust agent has excellent water solubility, and after cleaning, it is not easy to form insoluble deposits on the surface of parts, thus avoiding secondary pollution. It is easy to rinse and perfectly balances cleaning efficiency and environmental friendliness.
[0015] Optionally, the surfactant is a nonionic surfactant.
[0016] Optionally, the nonionic surfactant is one of fatty alcohol polyoxyethylene ether, isotridecyl alcohol polyoxyethylene ether, fatty acid methyl ester ethoxylate, or alkyl glycoside.
[0017] By adopting the above technical solution, the rust remover can effectively wet the surface of the rust layer and penetrate into the interior of the rust layer, breaking down the rust layer from the inside. This improves the rust removal speed.
[0018] Optionally, the corrosion inhibitor is: Aluminum corrosion inhibitors DX521 and DX5869; Copper corrosion inhibitors DX509 and DX1662; Multifunctional corrosion inhibitors DX506, DX5810, and DX5819; One or more of the ferrous metal corrosion inhibitors DX319 and DX635.
[0019] By adopting the above technical solution: using environmentally friendly corrosion inhibitors, and using specific corrosion inhibitors for different metal substrates: For aluminum and aluminum alloys, DX521 or DX5869 are recommended. For copper and copper alloys, select DX509 or DX1662; For ferrous metals, choose DX319 or DX635; For multi-metal mixed systems, multifunctional corrosion inhibitors DX506, DX5810 or DX5819 can be selected.
[0020] Optionally, the corrosion inhibitor includes a copper corrosion inhibitor, and the amount of the copper corrosion inhibitor is 0.25-0.5% of the total amount of the neutral rust remover.
[0021] By adopting the above technical solution, if the amount of copper corrosion inhibitor exceeds the above range, it will significantly reduce or even completely stop the rust removal speed of the metal. The fundamental reason is that the original intention and excellent effect of this type of corrosion inhibitor is to form an extremely strong and dense protective film with the metal surface (especially copper and its alloys, including steel). This film is exceptionally stable.
[0022] Therefore, the concentration of rust remover needs to be precisely controlled during formulation to achieve a balance between "protecting the substrate" and "allowing a reasonable rust removal rate". In the neutral rust remover of this application, the optimal addition range is 0.25-0.50%.
[0023] Secondly, this application provides a method for preparing a phosphorus-free, highly efficient, and biodegradable neutral rust remover, which adopts the following technical solution and includes the following steps: Add the anti-flash rust agent to hot water at 60-80℃ and stir until completely dissolved. Then, while stirring, add the phosphorus-free complexing agent, organic acid, sodium isoascorbate, surfactant, and corrosion inhibitor in sequence, and stir to mix.
[0024] By adopting the above technical solution, a specific feeding sequence is used to first rapidly dissolve the poorly soluble anti-flash rust agent under hot water conditions, and then other components are added in sequence, ensuring that each component can be fully dissolved and dispersed, and finally forming a stable and uniform liquid product. The process is simple and easy to industrialize.
[0025] In summary, this application has the following beneficial effects: 1. The neutral rust remover of this application uses biodegradable amino polycarboxylate as the main complexing agent, which completely replaces the traditional phosphorus / fluorine-containing components, eliminates phosphorus emissions from the source, solves the problem of eutrophication of water bodies, and has low wastewater treatment costs, meeting the requirements of green chemistry. Through the synergistic effect of multiple mechanisms of "reduction-complexation-stripping", especially the introduction of sodium isoascorbate, it breaks through the kinetic bottleneck of single complexation rust removal, increases the rust removal rate by 2-3 times, and greatly improves production efficiency. 2. Through optimization, this application uses specialized corrosion inhibitors for different metals, which solves the problem of simultaneously protecting multiple metals such as steel, iron, aluminum, and copper under neutral conditions. After rust removal, the metal substrate is bright and corrosion-free, with a high pitting corrosion inhibition rate. The anti-flash rust agent and the corrosion inhibitor work together to form a double protection on the clean metal surface, ensuring that the workpiece does not rust again at room temperature for a long time after rust removal, providing a sufficient time window for subsequent processes. Attached Figure Description
[0026] Figure 1 This is a diagram showing the effect of no discoloration on the metal parts after corrosion testing using the neutral rust remover of Example 2 in this application; Figure 2 This is a diagram showing the discoloration of metal parts after corrosion testing using the phosphorus-containing neutral commercially available rust remover (Comparative Example 4) as described in this application. Figure 3 This is a drawing of a metal part that has not undergone rust removal in this application; Figure 4 This is a diagram of a metal part after a rust removal experiment using the neutral rust remover of Example 2. Detailed Implementation
[0027] The present application will be further described in detail below with reference to the embodiments. All components are commercially available.
[0028] Examples 1-6
[0029] A phosphorus-free, highly efficient, and biodegradable neutral rust remover, the components of which and their corresponding weights are shown in Table 1, is prepared by the following steps: Add the anti-flash rust agent to hot water at 70°C, with the hot water accounting for 30% of the total water mass. Stir at 500 rpm for 10 minutes until completely dissolved. Then, while stirring, add the phosphorus-free complexing agent, organic acid, sodium isoascorbate, surfactant, corrosion inhibitor, and the remaining water in sequence. Stir and mix for 10 minutes to obtain the final product.
[0030] It should be noted that in this embodiment, the temperature of the hot water can be selected within the range of 60-80℃ to dissolve the anti-flash rust agent. This application only uses one temperature as an example for brief introduction, but it does not affect the application of other temperatures in this application.
[0031] Table 1. Components and their weights (kg) in Examples 1-6
[0032] It should be noted that in the embodiments of this application, each component can be selected from the following ranges. This selection does not have a significant impact on the detection data of this application. This application only briefly introduces one or more of them as examples, but it does not affect the application of other selections in this application: The phosphorus-free complexing agent can be selected from one or more of the following: tetrasodium glutamate diacetate, trisodium ethylenediamine disuccinate, trisodium hydroxyethylenediamine triacetate, trisodium methylglycine diacetate, tetrasodium iminodisuccinate, tetrasodium aspartic acid diacetate, and tetrasodium hydroxyiminodisuccinate; the nonionic surfactant can be selected from one of the following: fatty alcohol polyoxyethylene ether, isomeric tridecyl alcohol polyoxyethylene ether, fatty acid methyl ester ethoxylate, and alkyl glycoside; the corrosion inhibitor is a metal corrosion inhibitor from Dexu New Materials (Guangzhou) Co., Ltd., selected according to the metal substrate, such as DX521 and DX5869 for aluminum corrosion inhibitors, DX509 and DX1662 for copper corrosion inhibitors, DX506, DX5810, and DX5819 for multifunctional corrosion inhibitors, and DX319 and DX635 for ferrous metal corrosion inhibitors.
[0033] Comparative Example 1
[0034] A neutral rust remover, which differs from Example 2 in that it does not contain sodium isoascorbate.
[0035] Comparative Example 2
[0036] A neutral rust remover, differing from Example 2 in that the amount of tetrasodium diacetate of glutamic acid is reduced to 10 kg.
[0037] Comparative Example 3
[0038] A neutral rust remover, differing from Example 2 in that it uses ferrous ammonium sulfate hexahydrate instead of sodium isoascorbate.
[0039] Comparative Example 4
[0040] A commercially available neutral phosphorus-containing rust remover is prepared by conventionally mixing 10 kg of hydroxyethylidene diphosphate, 20 kg of trisodium phosphate, 2 kg of isotridecyl alcohol polyoxyethylene ether, 1 kg of ferrous metal corrosion inhibitor DX-635, 1 kg of aluminum corrosion inhibitor DX5869, 0.5 kg of copper corrosion inhibitor DX1662 and 65.5 kg of water.
[0041] Comparative Example 5
[0042] A neutral rust remover, differing from Example 2 in that the amount of tetrasodium diacetate of glutamic acid is increased to 35 kg.
[0043] Performance testing
[0044] The neutral rust removers prepared in the examples and comparative examples were subjected to the following performance tests, and the test results are recorded in Table 2.
[0045] Detection methods
[0046] 1. pH value: Use precision test paper with pH 6.4-8.0 to directly measure the pH value of the rust remover stock solution.
[0047] 2. Rust removal inspection: Test specimens: Rusty metal parts were selected for rust removal testing. Test conditions: Ultrasonic rust removal, temperature 50℃, observe and record the treatment time for the metal parts to become rust-free.
[0048] 3. Rust Return Effect Inspection: After removing rust, the metal parts are placed directly on the laboratory bench at room temperature for 30 minutes without rinsing with water, and the surface of the parts is observed to see if rust returns or discoloration occurs.
[0049] 4. Corrosion test: The corrosion test was conducted according to JB / T 4323-2019 Water-based Metal Cleaning Agents - 5.7. Main test parameters: Test temperature: 70±2℃, Test time: 2 hours for non-ferrous metals, 4 hours for ferrous metals.
[0050] Table 2 Performance Test Results
[0051] Referring to Table 2, the pH value of all embodiments remained stable between 6.5 and 7.5, which meets the standard for neutral rust removers.
[0052] The experimental results from Examples 1-3 and Comparative Example 1 show that the addition of sodium isoascorbate breaks through the kinetic bottleneck of single complexation rust removal, and can increase the rust removal rate by 2-3 times. Figure 1 No discoloration or rust was observed after rust removal. Figure 3 and Figure 4 The images show the rust removal process before and after, demonstrating that the proposed solution has a superior rust removal effect. The experimental results of Examples 2 and 6 and Comparative Examples 2 and 5 show that the optimal amount of phosphorus-free complexing agent is around 20%. Although the rust removal effect was not significantly improved after increasing the amount of phosphorus-free complexing agent in Comparative Example 5, considering factors such as overall cost, the amount of phosphorus-free complexing agent should not exceed the range of the examples.
[0053] The test results of Example 2 and Comparative Example 3 show that ferrous ammonium sulfate hexahydrate cannot replace sodium isoascorbate, and the rust remover itself has an odor after the addition of ferrous ammonium sulfate hexahydrate.
[0054] The rust phenomenon in Comparative Example 4 is shown below. Figure 2 ; Further adjustments to the dosage of copper corrosion inhibitor revealed that the amount of copper corrosion inhibitor added has a certain impact on the rust removal time of the parts.
[0055] This is because adding too much copper corrosion inhibitor can significantly reduce or even completely stop the rust removal speed of metal. The fundamental reason is that the original design intent and superior effect of these corrosion inhibitors are achieved by forming an extremely strong and dense protective film with the metal surface (especially copper and its alloys, including steel). This film is exceptionally stable. When this protective film covers the metal or rust surface, it severely hinders the rust removal process in several ways: Preferential Adsorption and Site Occupation: Copper-based corrosion inhibitor molecules preferentially adsorb onto the most active sites on the metal surface, including defects and pores in rust and fresh metal surfaces. These sites are normally the "breakthrough points" and "fast lanes" for complexation reactions. By occupying these sites, the corrosion inhibitor effectively blocks these rapid pathways for complexation reactions. The protective film exhibits high stability: this complexed film remains stable over a wide pH range (including weakly acidic). It directly blocks the contact between the rust-removing solution and the underlying rust (Fe2O3, FeOOH) or the metal substrate, forming a physical barrier that becomes the primary kinetic obstacle.
[0056] Altering surface potential: The formation of the adsorption film alters the electrical double layer structure and electrode potential at the metal / solution interface, potentially causing passivation of the metal surface and thus inhibiting the electrochemical reaction. Therefore, the concentration of rust remover needs to be precisely controlled during the formulation process to achieve a balance between "protecting the substrate" and "allowing a reasonable rust removal rate". In the neutral rust remover of this application, the optimal addition range is 0.25-0.50%.
[0057] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.
Claims
1. A phosphorus-free, highly efficient, biodegradable neutral rust remover, characterized in that, It consists of the following components by weight percentage: 15-30% phosphorus-free complexing agent; Organic acids 1-3%; Sodium isoascorbate 3-5%; Anti-flash rust agent 5-10%; Corrosion inhibitor 2-5%; Surfactant 1-3%; Water balance.
2. The phosphorus-free, high-efficiency, biodegradable neutral rust remover according to claim 1, characterized in that: The phosphorus-free complexing agent is one or more of the following: tetrasodium glutamate diacetate, trisodium ethylenediaminedisuccinate, trisodium hydroxyethylenediaminetriacetate, trisodium methylglycine diacetate, tetrasodium iminodisuccinate, tetrasodium aspartate diacetate, and tetrasodium hydroxyiminodisuccinate.
3. The phosphorus-free, high-efficiency, biodegradable neutral rust remover according to claim 1, characterized in that: One or more of the organic acids citric acid, gluconic acid, and glycolic acid.
4. The phosphorus-free, high-efficiency, biodegradable neutral rust remover according to claim 1, characterized in that: The flash rust inhibitor is one or more of sodium citrate, sodium gluconate, sodium glycolate, and sodium formate.
5. The phosphorus-free, high-efficiency, biodegradable neutral rust remover according to claim 1, characterized in that: The surfactant is a nonionic surfactant.
6. The phosphorus-free, high-efficiency, biodegradable neutral rust remover according to claim 5, characterized in that: The nonionic surfactant is one of fatty alcohol polyoxyethylene ether, isotridecyl alcohol polyoxyethylene ether, fatty acid methyl ester ethoxylate, and alkyl glycoside.
7. The phosphorus-free, high-efficiency, biodegradable neutral rust remover according to claim 1, characterized in that, The corrosion inhibitor is: Aluminum corrosion inhibitors DX521 and DX5869; Copper corrosion inhibitors DX509 and DX1662; Multifunctional corrosion inhibitors DX506, DX5810, and DX5819; One or more of the ferrous metal corrosion inhibitors DX319 and DX635.
8. The phosphorus-free, high-efficiency, biodegradable neutral rust remover according to claim 1, characterized in that: The corrosion inhibitor includes a copper corrosion inhibitor, and the amount of the copper corrosion inhibitor is 0.25-0.5% of the total amount of the neutral rust remover.
9. A method for preparing the phosphorus-free, highly efficient, biodegradable neutral rust remover according to any one of claims 1-8, characterized in that, Includes the following steps: Add the anti-flash rust agent to hot water at 60-80℃ and stir until completely dissolved. Then, while stirring, add the phosphorus-free complexing agent, organic acid, sodium isoascorbate, surfactant, and corrosion inhibitor in sequence, and stir to mix.