Substituted phosphate crystalline oxalate film passivator, preparation method and application

Abstract

This invention discloses a crystalline oxalate film passivating agent as an alternative to phosphates, comprising, by weight percentage: 15.0%–30.0% sodium oxalate, 10.0%–20.0% potassium titanium oxalate, 5.0%–9.0% nitric acid, 10.0%–15.0% sodium dodecyl sulfate, 3.0%–5.0% complexing agent, 1.0%–4.0% corrosion inhibitor, and the balance being water. This crystalline oxalate passivation film forms a more uniform and dense film compared to phosphate passivation, and is more environmentally friendly.

Description

Technical Field

[0001] This invention relates to metal surface passivation technology, specifically to the preparation technology and application of a crystalline oxalate film passivating agent that can replace phosphate. Background Technology

[0002] Metal surface passivation is a common method of metal corrosion protection. It primarily utilizes the chemical reaction between the metal and substances in the environment such as oxygen, water, and acids to form a passivation film, thereby improving the metal's corrosion resistance. While traditional phosphate conversion membrane systems have undergone technological improvements and optimizations, they cannot fundamentally solve the problem of large amounts of phosphate generated during the phosphating process. This leads to the discharge of large quantities of phosphorus-containing wastewater during production, causing eutrophication of water bodies and deteriorating water quality, posing significant harm to aquatic life and human health. Typically, 1-3g of phosphating slag (mainly composed of zinc phosphate, iron phosphate, and nickel phosphate) is generated per square meter after phosphating. Direct discharge of this waste into the environment not only occupies land and wastes land resources, but its storage also harms the soil and the environment. According to the "National Hazardous Waste List" promulgated in November 2020, phosphating slag belongs to HW17 category hazardous waste and must be recycled and treated by specialized institutions, further increasing treatment costs.

[0003] Chinese Patent 202110743160.5 discloses a chromium-free and fluorine-free passivating agent for aluminum materials, applied in the field of passivation and corrosion protection. The raw materials for preparation, by weight, include: 5-15 parts phosphate ester, 0.5-1.2 parts chelating agent, 0-0.1 parts penetrant, 0.8-2 parts corrosion inhibitor, and the balance being water. This patent breaks away from the traditional synthesis route of passivating agents containing harmful ions such as chromium and fluorine; however, the phosphate ester raw material introduced phosphorus, causing environmental pollution. This invention uses oxalate instead of phosphate, resulting in a denser and more uniform film, meeting process requirements while protecting the environment.

[0004] Chinese Patent 200910187641.1 discloses a room-temperature passivating agent for steel workpieces before spray coating. The raw materials and their mass percentages are: phytic acid 2-8%, tartaric acid 0.1-3%, citric acid 0.3-2%, sodium benzoate 2-6%, triethanolamine 4-8%, and tap water as the balance. The preparation method is as follows: Add measured tap water to a reaction vessel, start the stirrer at room temperature and pressure, and stir at a speed of 450-550 rpm. Add tartaric acid, sodium benzoate, triethanolamine, citric acid, and phytic acid sequentially, stirring continuously for 20-40 minutes after each addition. After all materials are added, continue stirring for 0.5-1.5 hours until the solution in the reaction vessel is a light purple, transparent, uniform, water-soluble liquid. Sampling and packaging are then possible. The raw material provided in this invention, phytic acid, also known as inositol hexaphosphate, is a major source of phosphorus and causes environmental pollution. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of traditional phosphating technologies and provide a crystalline oxalate film passivating agent that can replace phosphates, its preparation method, and its application.

[0006] The crystalline oxalate film passivating agent that replaces phosphates according to the present invention is made from the following components by weight percentage:

[0007]

[0008] Preferably, the crystalline oxalate film passivating agent that replaces phosphate is made from the following components by weight percentage:

[0009]

[0010] The water mentioned is purified water.

[0011] The nitric acid can maintain the pH value of the solution, ensuring the passivation reaction proceeds.

[0012] The sodium dodecyl sulfate described herein makes the passivation film layer uniform and fine.

[0013] The complexing agent is one or more of oxalate, acetate, and carboxylate.

[0014] The corrosion inhibitor is one of sodium silicate or borate, which mainly forms an oxide film on the metal surface to prevent corrosion reaction.

[0015] The method for preparing the crystalline oxalate film passivating agent that replaces phosphate is characterized by comprising the following steps in sequence:

[0016] (1) According to the above-mentioned proportions, first dissolve sodium oxalate, potassium titanium oxalate and nitric acid in 1 / 3-1 / 2 of the total water, stir evenly until the solution is completely dissolved and clear.

[0017] (2) Add sodium dodecyl sulfate, complexing agent and corrosion inhibitor to the solution in step (1) in sequence, stir for 1-2 hours until the solution is uniform and transparent;

[0018] (3) Add the remaining water to the solution in step (2) while stirring to make it completely dissolved and uniform, which is the crystalline oxalate film passivating agent.

[0019] The reaction principle of this invention is as follows:

[0020] During passivation, oxalic acid reacts with metal ions to form oxalate, which then forms a dense oxalate film on the metal surface. Simultaneously, the addition of sodium oxalate and potassium titanium oxalate effectively improves the metal surface condition, resulting in a more uniform and fine passivation film. The combination of sodium dodecyl sulfate and a complexing agent further accelerates the formation of the oxalate passivation film, leading to higher passivation efficiency. Finally, the addition of a certain amount of corrosion inhibitor and nitric acid effectively prevents blackening caused by over-corrosion of the metal, ensuring that the passivation solution acts uniformly and stably on the metal surface.

[0021] Moreover, in the aforementioned crystalline oxalate film passivating agent that replaces phosphate, sodium oxalate and potassium titanium oxalate are inorganic salts and are the main substances for film formation.

[0022] The present invention also includes the application of the crystalline oxalate film passivating agent in metal passivation.

[0023] The beneficial effects of this invention are as follows:

[0024] 1) This crystalline oxalate film passivating agent does not contain phosphorus and will not cause phosphorus pollution during use. Compared with traditional phosphorus-containing chemical agents, the crystalline oxalate passivation film is more uniform and dense than phosphate passivation, which is more in line with environmental protection requirements and helps to reduce the phosphorus content in water bodies, thereby mitigating environmental problems such as eutrophication. (2) Compared with the traditional physical sealing method, the passivation treatment will not increase the thickness of the workpiece, will not change the color, and will improve the precision and added value of the product, and the operation is more convenient. (3) Passivation promotes the formation of an oxygen molecular structure passivation film on the metal surface. The film layer is dense and stable, and has a self-repairing effect in the air. Therefore, compared with the traditional method of applying anti-rust oil, the passivation film formed by this invention is more stable and more corrosion resistant. Detailed Implementation

[0025] Further explanation of the technical solution of the present invention:

[0026] The complexing agent described in the examples is sodium methacrylate, and the corrosion inhibitor described in the examples is sodium silicate.

[0027] Example 1

[0028] A technical solution for a crystalline oxalate film passivating agent that replaces phosphates, comprising the following components by weight percentage:

[0029]

[0030] The preparation method of the above-mentioned crystalline oxalate film passivating agent as an alternative to phosphate is as follows:

[0031] Step 1: According to the above formula, first dissolve 25.0% sodium oxalate, 14.0% potassium titanium oxalate, and 5.0% nitric acid in 1 / 3 of the total water, stir until completely dissolved and the solution is clear.

[0032] Step 2: Add 12.0% sodium dodecyl sulfate, 4.0% complexing agent, and 1.0% corrosion inhibitor to the beaker or reaction vessel from Step 1, and stir for about 1 hour until the solution is uniform and transparent.

[0033] Step 3: Add the remaining water to the beaker or reaction vessel from Step 2 while stirring until it is completely dissolved and homogeneous. This is the finished crystalline oxalate film passivating agent.

[0034] The physicochemical properties of the finished product are as follows:

[0035] Colorless and transparent liquid

[0036] pH value 7.8

[0037] Specific gravity 1.15

[0038] Example 2

[0039] A technical solution for a crystalline oxalate film passivating agent that replaces phosphates, comprising the following components by weight percentage:

[0040]

[0041] The preparation method of the above-mentioned crystalline oxalate film passivating agent as an alternative to phosphate is as follows:

[0042] Step 1: According to the above formula, first dissolve 20.0% sodium oxalate, 16.0% potassium titanium oxalate, and 7.0% nitric acid in 1 / 3 of the total water, stir well until the solution is completely dissolved and clear.

[0043] Step 2: Add 10.0% sodium dodecyl sulfate, 5.0% complexing agent, and 2.0% corrosion inhibitor to the beaker or reactor from Step 1, and stir for about 1.2 hours until the solution is uniform and transparent.

[0044] Step 3: Add the remaining water to the beaker or reaction vessel from Step 2 while stirring until it is completely dissolved and homogeneous. This is the finished crystalline oxalate film passivating agent.

[0045] The physicochemical properties of the finished product are as follows:

[0046] Colorless and transparent liquid

[0047] pH value 7.4

[0048] Specific gravity 1.18

[0049] Example 3

[0050] A technical solution for a crystalline oxalate film passivating agent that replaces phosphates, comprising the following components by weight percentage:

[0051]

[0052] The preparation method of the above-mentioned crystalline oxalate film passivating agent as an alternative to phosphate is as follows:

[0053] Step 1: According to the above formula, first dissolve 28.0% sodium oxalate, 15.0% potassium titanium oxalate, and 8.0% nitric acid in 1 / 3 of the total water, stir well until the solution is completely dissolved and clear.

[0054] Step 2: Add 15.0% sodium dodecyl sulfate, 3.0% complexing agent, and 1.2% corrosion inhibitor to the beaker or reactor from Step 1, and stir for about 1.5 hours until the solution is uniform and transparent.

[0055] Step 3: Add the remaining water to the beaker or reaction vessel from Step 2 while stirring until it is completely dissolved and homogeneous. This is the finished crystalline oxalate film passivating agent.

[0056] The physicochemical properties of the finished product are as follows:

[0057] Colorless and transparent liquid

[0058] pH value 7.5

[0059] Specific gravity 1.16

[0060] All raw materials in the technical solution of this invention can be purchased on the market.

[0061] The passivation method implemented in this invention is as follows: A cold-rolled galvanized sheet with dimensions of 80mm×50mm×2mm is used. After degreasing and washing, it is placed in the above-mentioned film passivating agent finished solution prepared at 3% and passivated at room temperature for about 10 minutes. Then it is dried and ready for testing.

[0062] The passivation film test data of this invention embodiment are shown in Table 1.

[0063] Table 1

[0064]

[0065] As can be seen from Table 1, the crystalline oxalate film passivator prepared in Example 3 has the best salt spray resistance and meets the corrosion resistance requirements.

[0066] The technical specifications of the crystalline oxalate film passivating agent that replaces phosphate according to the present invention are shown in Table 2.

[0067] Table 2

[0068] Serial Number project index Test methods 1 Salt spray resistance 1000h Salt spray test chamber 2 Moist heat resistance 1800h GB / T1740 3 Color difference 0.6 GB / T11186.3-1989 4 Impact resistance No cracks or peeling were found. GB / T1732-1993 5 Cupping test No shedding was observed. GB / T9753-2007

[0069] As can be seen from Table 2, the crystalline oxalate film passivating agent of the present invention has better performance indicators than existing passivating agents in all aspects. It can replace phosphate passivation, reduce water treatment costs, and the process is simple and easy to operate.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A crystalline oxalate film passivator as a substitute for phosphate, characterized by comprising: It is made of the following components by weight percentage: sodium oxalate 15.0%–30.0%, potassium titanium oxalate 10.0%–20.0%, nitric acid 5.0%–9.0%, sodium dodecyl sulfate 10.0%–15.0%, complexing agent 3.0%–5.0%, corrosion inhibitor 1.0%–4.0%, and the balance being water.

2. The alternative phosphate-replacing crystalline oxalate-based skin passivator according to claim 1, characterized in that, It is made of the following components by weight percentage: sodium oxalate 20.0%–30.0%, potassium titanium oxalate 12.0%–16.0%, nitric acid 5.0%–9.0%, sodium dodecyl sulfate 10.0%–15.0%, complexing agent 3.0%–5.0%, corrosion inhibitor 1.0%–4.0%, and the balance being water.

3. The alternative phosphate-replacing crystalline oxalate-based skin passivator according to claim 1, characterized in that, It is made of the following components by weight percentage: sodium oxalate 28.0%, potassium titanium oxalate 15.0%, nitric acid 8.0%, sodium dodecyl sulfate 15.0%, complexing agent 3.0%, corrosion inhibitor 1.20%, and the balance being water.

4. The alternative phosphate-replacing crystalline oxalate-based skin passivator according to claim 1, characterized in that, The complexing agent is one or more of oxalate, acetate, and carboxylate.

5. The alternative phosphate-replacing crystalline oxalate-based skin passivator according to claim 1, characterized in that, The corrosion inhibitor is one or more of sodium silicate and borate.

6. The method of producing a crystalline oxalate film passivant for replacing phosphate according to any one of claims 1 to 5, characterized by, Includes the following steps: (1) First, dissolve sodium oxalate, potassium titanium oxalate and nitric acid in 1 / 3 to 1 / 2 of the total water, stir until completely dissolved and the solution is clear; (2) Add sodium dodecyl sulfate, complexing agent and corrosion inhibitor to the solution in step (1) in sequence, stir for 1-2 hours until the solution is uniform and transparent; (3) Add the remaining water to the solution in step (2) while stirring to make it completely dissolved and uniform, which is the crystalline oxalate film passivating agent.

7. The use of the crystalline oxalate film passivating agent that replaces phosphate according to any one of claims 1-5 in metal passivation.

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