Environment-friendly aluminum material surface treatment liquid and treatment method thereof

Abstract

The invention discloses environment-friendly aluminum material surface treatment fluid and a treatment method thereof.The preparation method of the treatment fluid comprises the steps that phytic acid, sodium nitrate and ammonium fluoride are sequentially added into deionized water and stirred until the phytic acid, the sodium nitrate and the ammonium fluoride are completely dissolved; adding sodium silicate and stirring to obtain a homogeneous solution; adjusting the pH value of the mixed solution to 2.5-4.5 by using citric acid or ammonia water; and finally, deionized water is added, the concentration of all components in a mixed solution is made to meet 50-150 g / L, the concentration of sodium nitrate is made to meet 10-50 g / L, the concentration of ammonium fluoride is made to meet 5-20 g / L, the concentration of sodium silicate is made to meet 10-30 g / L, and standing is conducted for 5 h or above at the normal temperature to obtain the environment-friendly The treatment method comprises the following steps: firstly, pretreating the surface of an aluminum workpiece, soaking the aluminum workpiece in the surface treatment liquid, and treating for 5-20 minutes under the condition of 20-50 DEG C; and finally, washing with deionized water, sealing in hot water at the temperature of 80-100 DEG C for 10-20 minutes, and drying at the temperature of 80-95 DEG C for 15-30 minutes. The surface treatment liquid is excellent in environmental protection property and oxidation effect.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment, and particularly relates to an environmentally friendly aluminum surface treatment liquid and a treatment method thereof. Background Art

[0002] Aluminum and aluminum alloys are widely used in aerospace, automotive, electronics, and other fields due to their excellent electrical and thermal conductivity, corrosion resistance, and machinability. However, they are susceptible to corrosion in the natural environment and typically require surface treatment to improve their corrosion resistance, such as anodizing and chemical oxidation. Chemical oxidation has attracted widespread attention due to its simplicity and low cost. Currently, common chemical oxidation methods for aluminum and aluminum alloys include chromate, phosphate, and zirconate. However, chromate chemical oxidation solutions contain hexavalent chromium, which is highly toxic and carcinogenic, posing significant risks to the environment and human health, and their use has been gradually restricted. While phosphate and zirconate chemical oxidation solutions are relatively environmentally friendly, their corrosion resistance still needs to be improved. Phytic acid, a natural organophosphorus compound extracted from plants, exhibits excellent chelating and sustained-release properties and can form a dense composite film with aluminum ions. Applying phytic acid to the chemical oxidation treatment of aluminum and aluminum alloys holds promise for developing an environmentally friendly and efficient chemical oxidation method. Summary of the Invention

[0003] The purpose of the present invention is to provide an environmentally friendly aluminum surface treatment liquid and a treatment method thereof, so as to solve the problems of poor environmental protection and poor oxidation effect of existing aluminum and aluminum alloy chemical oxidation liquids.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] The present invention provides an environmentally friendly aluminum surface treatment liquid, and the preparation method of the treatment liquid is as follows:

[0006] 1) Add phytic acid, sodium nitrate, and ammonium fluoride to deionized water in sequence and stir at 200-300 rpm until completely dissolved;

[0007] 2) adding sodium silicate to the mixed solution obtained in step 1) and continuing to stir at a speed of 200-300 r / min until a homogeneous solution is obtained;

[0008] 3) adjusting the pH of the mixed solution obtained in step 2) to 2.5-4.5 using citric acid or ammonia water;

[0009] 4) Deionized water is added to the pH-adjusted mixed solution to make the concentrations of the components in the mixed solution meet 50-150 g / L, sodium nitrate 10-50 g / L, ammonium fluoride 5-20 g / L, and sodium silicate 10-30 g / L, and the mixture is allowed to stand at room temperature for more than 5 hours to obtain an environmentally friendly aluminum surface treatment solution.

[0010] The present invention provides an environmentally friendly aluminum surface treatment method, comprising the following steps:

[0011] 1) Pretreatment: Degreasing, water washing, and nitric acid pickling are performed on the surface of the aluminum workpiece to remove oil stains, oxide film and impurities on the surface of the aluminum workpiece;

[0012] 2) Oxidation treatment: Immerse the pretreated aluminum workpiece in the above-mentioned surface treatment solution at 20-50°C for 5-20 minutes;

[0013] 3) Post-treatment: Rinse the oxidized aluminum workpiece with deionized water, seal it in hot water at 80-100°C for 10-20 minutes, and then dry it at 80-95°C for 15-30 minutes.

[0014] Beneficial effects

[0015] 1) The surface treatment liquid of the present invention does not contain toxic and harmful substances such as chromate and heavy metals. In addition, phytic acid is biodegradable, which greatly reduces the cost of wastewater treatment and is environmentally friendly.

[0016] 2) The surface treatment solution of the present invention has a simple composition, low cost, and is easy to prepare;

[0017] 3) Sodium silicate is hydrolyzed to form SiO2 gel during the high-temperature sealing stage, which fills the pores of the film layer and increases the corrosion resistance time of the salt spray test to 150h without substrate corrosion. DETAILED DESCRIPTION

[0018] The present invention is described in detail below through examples.

[0019] Example 1

[0020] The specific steps for preparing the environmentally friendly aluminum surface treatment liquid are as follows: first, add 60L of deionized water to a container; weigh 8000g of phytic acid, 4000g of sodium nitrate, and 1200g of ammonium fluoride, respectively, add them to the above container in turn, and stir at 250r / min until completely dissolved; weigh 1500g of sodium silicate, add it to the above solution in three equal parts, and continue stirring at 250r / min until a homogeneous solution is obtained; adjust the pH to 3.0 with citric acid; add deionized water to 100L, and let it stand at room temperature for 5 hours before use.

[0021] The environmentally friendly aluminum surface treatment method includes the following steps: first, the aluminum workpiece is degreased (at room temperature, until all the oil is removed), washed with water, pickled with nitric acid (at room temperature, 2 minutes), and pre-treated with water washing, then the prepared oxidation liquid is heated to 30°C, the pre-treated workpiece is immersed in the chemical oxidation liquid for 10 minutes, rinsed with deionized water, sealed in deionized water at 85°C for 20 minutes, and dried at 90°C for 25 minutes.

[0022] Example 2

[0023] The specific steps for preparing the environmentally friendly aluminum surface treatment liquid are as follows: first, add 60L of deionized water into a container; weigh 10,000g of phytic acid, 3,000g of sodium nitrate, and 1,300g of ammonium fluoride, respectively, add them into the above container in turn, and stir at 300r / min until completely dissolved; weigh 2,000g of sodium silicate, add it into the above solution in three equal parts, and continue stirring at 300r / min until a homogeneous solution is obtained; adjust the pH to 3.5 with citric acid; add deionized water to 100L, and let it stand at room temperature for 5 hours before use.

[0024] The environmentally friendly aluminum surface treatment method includes the following steps: first, the aluminum workpiece is degreased (at room temperature, until all the oil is removed), washed with water, pickled with nitric acid (at room temperature, 2 minutes), and pre-treated with water, then the prepared treatment liquid is heated to 40°C, the pre-treated workpiece is immersed in the treatment liquid for 15 minutes, rinsed with deionized water, sealed in deionized water at 95°C for 15 minutes, and dried at 90°C for 25 minutes.

[0025] Example 3

[0026] The specific steps for preparing the environmentally friendly aluminum surface treatment liquid are as follows: first, add 60L of deionized water into a container; weigh 12,000g of phytic acid, 4,000g of sodium nitrate, and 1,300g of ammonium fluoride, respectively, add them into the above container in turn, and stir at 300r / min until completely dissolved; weigh 2,500g of sodium silicate, add it into the above solution in three equal parts, and continue stirring at 300r / min until a homogeneous solution is obtained; adjust the pH to 3.5 with citric acid; add deionized water to 100L, and let it stand at room temperature for 5 hours before use.

[0027] The environmentally friendly aluminum surface treatment method includes the following steps: first, the aluminum workpiece is degreased (at room temperature, until all the oil is removed), washed with water, pickled with nitric acid (at room temperature, 2 minutes), and pre-treated with water, then the prepared treatment liquid is heated to 35°C, the pre-treated workpiece is immersed in the treatment liquid for 15 minutes, rinsed with deionized water, sealed in deionized water at 85°C for 15 minutes, and dried at 95°C for 20 minutes.

[0028] Comparative Example

[0029] The steps for preparing the oxidizing solution are as follows: first, add 60L of deionized water to a container; weigh 2500g of chromic anhydride and add it to the deionized water in five times, stirring until completely dissolved; weigh 5000g of phosphoric acid, 400g of ammonium bifluoride, and 300g of diammonium hydrogen phosphate respectively, and add them to the above solution in sequence (each component is added at an interval of 5 minutes), and stir until completely dissolved; weigh 100g of boric acid and add it to the above solution, stirring until completely dissolved; add deionized water to 100L, and let it stand at room temperature for 24 hours before use.

[0030] The surface treatment steps of aluminum materials are as follows: first, the aluminum workpiece is degreased (at room temperature, until all the oil is removed), washed with water, pickled with nitric acid (at room temperature, 2 minutes), and pre-treated with water washing; then the prepared oxidizing solution is heated to 40°C, and the pre-treated workpiece is immersed in the oxidizing solution for 6 minutes; after water washing, it is dried at 90°C for 25 minutes.

[0031] The aluminum workpieces treated according to Examples 1-3 and the comparative example were tested for corrosion resistance, film thickness, adhesion, and environmental friendliness according to the following standards. The test results are shown in Table 1.

[0032] 1. Corrosion resistance

[0033] In accordance with the requirements of GJB150.11A-2009 "Military Equipment Laboratory Environmental Test Methods Part 11 Salt Spray Test", the corrosion resistance test is carried out using a test procedure of alternating 24-hour salt spray and 24-hour drying. The results are calculated based on the time when the parts begin to corrode.

[0034] 2. Film thickness

[0035] Use eddy current thickness gauge to test the coating thickness (standard: ISO 2360).

[0036] 3. Adhesion

[0037] Cross-hatch test (ISO 2409): the passivation film must reach level 0 (no peeling).

[0038] 4. Environmental protection

[0039] Detection of hexavalent chromium (Cr6+) content in wastewater must comply with the "Electroplating Pollutant Emission Standards"

[0040] GB21900-2008 limit, Cr6+<0.2mg / L, total chromium<1mg / L.

[0041] Table 1

[0042]

[0043]

Claims

1. An environmentally friendly aluminum surface treatment liquid, characterized in that: The preparation method of the treatment solution is as follows: 1) Add phytic acid, sodium nitrate, and ammonium fluoride to deionized water in sequence and stir at 200-300 rpm until completely dissolved; 2) adding sodium silicate to the mixed solution obtained in step 1) and continuing to stir at a speed of 200-300 r / min until a homogeneous solution is obtained; 3) adjusting the pH of the mixed solution obtained in step 2) to 2.5-4.5 using citric acid or ammonia water; 4) Deionized water is added to the pH-adjusted mixed solution to make the concentrations of the components in the mixed solution meet 50-150 g / L, sodium nitrate 10-50 g / L, ammonium fluoride 5-20 g / L, and sodium silicate 10-30 g / L, and the mixture is allowed to stand at room temperature for more than 5 hours to obtain an environmentally friendly aluminum surface treatment solution.

2. An environmentally friendly aluminum surface treatment method, characterized in that: The following steps are involved: 1) Pretreatment: Degreasing, water washing, and nitric acid pickling are performed on the surface of the aluminum workpiece to remove oil stains, oxide film and impurities on the surface of the aluminum workpiece; 2) Oxidation treatment: immersing the pretreated aluminum workpiece in the surface treatment solution as claimed in claim 1 at a temperature of 20 to 50° C. for 5 to 20 minutes; 3) Post-treatment: Rinse the oxidized aluminum workpiece with deionized water, seal it in hot water at 80-100°C for 10-20 minutes, and then dry it at 80-95°C for 15-30 minutes.

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