Environment-friendly aluminum alloy zinc stripping agent and use method thereof

Abstract

The invention provides an environment-friendly aluminum alloy zinc stripping agent and a using method thereof, and belongs to the technical field of chemical stripping, and the environment-friendly aluminum alloy zinc stripping agent comprises the following raw materials in percentage by weight: 30-50% of an oxidizing agent, 10-15% of sodium sulfate, 1-10% of a stabilizer, 0.5-5% of a surfactant, 3-5% of modified carbon black and the balance of water. The zinc stripping agent is good in zinc stripping effect, free of damage to a base material, high in zinc stripping speed and suitable for industrial large-scale application.

Description

Technical Field

[0001] The invention relates to a stripping agent, in particular to an aluminum alloy zinc stripping agent, and belongs to the technical field of chemical stripping. Background Art

[0002] At present, most aluminum alloy electroplating plants use a two-step zinc immersion process. The first zinc immersion removes the oxide film and replaces it with a zinc layer. After the first zinc immersion, a nitric acid solution or a mixed solution of nitric acid and ammonium bifluoride is used to strip the zinc to remove the poor zinc layer and activate the substrate for the second zinc immersion.

[0003] Nitric acid stripping is a mature process with good results. However, its use easily produces toxic gases such as nitrogen oxides, which pollute the environment and harm human health. It does not meet environmental and safety requirements and is gradually being phased out. The stripping solution contains high levels of total nitrogen, requiring treatment before discharge, increasing disposal costs. Summary of the Invention

[0004] In view of the above problems, the present invention provides an environmentally friendly aluminum alloy zinc stripping agent and a method of using the same, which are used to improve the aluminum alloy zinc stripping effect and increase the zinc stripping speed.

[0005] To achieve the above objectives, the technical solution of the present invention is: an environmentally friendly aluminum alloy zinc stripping agent, which includes the following types of raw materials in weight percentage: 30-50% oxidant, 10-15% sodium sulfate, 1-10% stabilizer, 0.5-5% surfactant, 3-5% modified carbon black, and the balance is water.

[0006] Furthermore, the oxidant is persulfate or percarbonate.

[0007] Furthermore, the stabilizer is at least one of water-soluble organic phosphonic acid and its salts, hexametaphosphoric acid and its salts, ethylenediaminetetraacetic acid and its salts, polyacrylic acid, and sodium silicate.

[0008] Furthermore, the surfactant is any one of OP-10, X-100, H95, and sodium lauryl sulfate.

[0009] Furthermore, the modified carbon black is persulfate-modified carbon black.

[0010] Furthermore, the preparation steps of the modified carbon black include: mixing carbon black with a persulfate aqueous solution, ultrasonically dispersing, stirring and reacting at a predetermined temperature, centrifuging and washing with water, and vacuum drying.

[0011] Furthermore, the carbon black is N110 carbon black, and the persulfate aqueous solution is ammonium persulfate aqueous solution.

[0012] Furthermore, the mass fraction of the persulfate aqueous solution is 0.016-0.020%, the ultrasonic dispersion time is 1-1.5 hours, the predetermined temperature is 30° C., the stirring reaction is 20-25 hours, and the vacuum drying temperature is 80° C.

[0013] A method for using an environmentally friendly aluminum alloy zinc stripping agent comprises the following steps: taking a predetermined amount of zinc stripping agent and acid, adding them to water to prepare a zinc stripping solution, placing an aluminum alloy workpiece to be zinc stripped into the zinc stripping solution, treating the workpiece for a period of time, and then taking the workpiece out.

[0014] Furthermore, the concentration of the zinc stripping agent in the zinc stripping solution is 20-80 g / L, and at least one of 10-30 g / L sulfuric acid or 1-5 g / L citric acid is added. The aluminum alloy workpiece to be stripped is placed in the zinc stripping solution and treated for 5-60 seconds at room temperature to achieve zinc stripping.

[0015] The beneficial effects of the environmentally friendly aluminum alloy zinc stripping agent and the use method thereof of the present invention are: The zinc stripping agent of the present invention has good zinc stripping effect, does not damage the substrate, has a fast zinc stripping speed, and is suitable for industrial large-scale application.

[0016] The oxidant in the zinc stripping agent of the present invention is the main component of the corrosive coating, and the higher the content, the faster the stripping speed. The surfactant increases the corrosion inhibition effect and stabilizes the solution. The stabilizer stabilizes the zinc stripping solution by complexing metal ions or reducing the diffusion of ions in the solution, not only increasing the stripping speed to a certain extent but also improving the utilization rate of the oxidant. The presence of citric acid inhibits corrosion of the substrate, protecting the substrate from damage during the stripping process.

[0017] The addition of sodium sulfate in the present invention increases the conductivity of the solution, promotes the corrosion of the zinc layer by the oxidant, and promotes the complexation of zinc ions and the stabilizer. The present invention also adds a modified carbon black component. The addition of the modified carbon black further increases the conductivity of the zinc stripping solution, further promotes the corrosion of the zinc layer by the oxidant, and accelerates the zinc stripping speed. Moreover, due to its large surface area, the modified carbon black can interconnect the macromolecular organic matter in the stabilizer to form more complexation sites, complex and stably bind the zinc ions more quickly, promote the forward progress of the oxidation reaction, and shorten the zinc stripping time. In addition, the surface of the modified carbon black carries a certain amount of hydrogen ions, provides a certain acidic environment, and maintains the stability of the reaction environment. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention are described clearly and completely below. Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0019] An environmentally friendly aluminum alloy zinc stripping agent comprises the following raw materials in weight percentage: 30-50% of an oxidant, 10-15% of sodium sulfate, 1-10% of a stabilizer, 0.5-5% of a surfactant, 3-5% of modified carbon black, and the balance being water.

[0020] Furthermore, the oxidant is persulfate or percarbonate; the stabilizer is at least one of water-soluble organic phosphonic acid and its salts, hexametaphosphoric acid and its salts, ethylenediaminetetraacetic acid and its salts, polyacrylic acid, and sodium silicate; the surfactant is any one of OP-10, X-100, H95, and sodium lauryl sulfate; and the modified carbon black is persulfate-modified carbon black.

[0021] Furthermore, the preparation steps of the modified carbon black include: mixing carbon black with a persulfate aqueous solution, ultrasonically dispersing, stirring and reacting at a predetermined temperature, centrifuging and washing with water, and vacuum drying; Further preferably, the carbon black is N110 carbon black, the persulfate aqueous solution is an ammonium persulfate aqueous solution; the mass fraction of the persulfate aqueous solution is 0.016-0.020%, the ultrasonic dispersion time is 1-1.5h, the predetermined temperature is 30°C, the stirring reaction is 20-25h, and the vacuum drying temperature is 80°C.

[0022] A method for using an environmentally friendly aluminum alloy zinc stripping agent, comprising the steps of: adding a predetermined amount of zinc stripping agent and acid to water to prepare a zinc stripping solution, placing an aluminum alloy workpiece to be stripped of zinc in the zinc stripping solution, treating for a period of time, and then removing the workpiece. Preferably, the concentration of the zinc stripping agent in the zinc stripping solution is 20-80 g / L, the acid added is at least one of 10-30 g / L of sulfuric acid or 1-5 g / L of citric acid, and the aluminum alloy workpiece to be stripped of zinc is placed in the zinc stripping solution and treated at room temperature for 5-60 seconds to achieve zinc stripping.

[0023] The zinc stripping agent and the use method thereof of the present invention are applicable to all types of aluminum alloy workpieces to be stripped of zinc. Example 1

[0024] An environmentally friendly aluminum alloy dezincification agent comprises the following raw materials, by weight percentage: 30% sodium persulfate, 15% sodium sulfate, 1% diphosphonic acid, 2% hexametaphosphoric acid, 5% OP-10, 3% modified carbon black, and the balance water. The modified carbon black is ammonium persulfate-modified N110 carbon black, prepared according to the above method.

[0025] When stripping zinc from an aluminum alloy workpiece, first take 20g of the above-mentioned stripping agent, add 10g of sulfuric acid, add water and stir to prepare 1L of stripping solution, place the workpiece in it, and treat at room temperature.

[0026] The stripping method of this embodiment is: hang the parts to be stripped on a hanger, immerse them in the prepared stripping solution until the parts meet the stripping standards, remove them, clean them and proceed to the next process. The following embodiments are the same.

[0027] The zinc removal effect and detection method (the following examples use the same detection method) are as follows: 1) The zinc stripping speed is based on the time required to achieve the desired zinc stripping speed. In this embodiment, the zinc stripping speed is 35s.

[0028] 2) Zinc Stripping Amount: The total amount of zinc stripped from the stripped part by continuously processing it until it fails to meet the stripping standards. In this example, the stripping amount was 6g, and the time taken was 15 seconds, with 0.4g stripped per second.

[0029] 3) Method for detecting the content of zinc ions in zinc stripping solution: In an acetic acid-sodium acetate buffer solution with a pH of 5.4-5.9, sodium thiosulfate and potassium fluoride are used to mask copper ions, and complexometric titration is performed using xylenol orange as an indicator. The details are as follows: The sample volume (V1) should be 15-20 ml, and the EDTA concentration should be 0.05 mol / L. Add one drop of 1 g / L methyl orange indicator and neutralize with hydrochloric acid (1+1) until the methyl orange turns red. Then, add one drop of ammonia (1+1) until it turns yellow. Add 15 mL of acetic acid-sodium acetate buffer solution and 2-3 mL of 100 g / L sodium thiosulfate solution, and mix thoroughly. Add 2-3 drops of 5 g / L xylenol orange indicator and titrate with EDTA standard solution until the solution turns from wine red to yellow. This is the endpoint.

[0030] Sample zinc ion content C zinc = CV 65.38 / V1 g / L In the formula: C--EDTA concentration, mol / L; V--EDTA standard solution volume used for titration, ml; 65.38--zinc ion molecular weight; V1--sample volume, ml.

[0031] After the zinc removal in this embodiment was completed, the zinc ion content detected in the zinc removal solution was 5.98 g / L, which was basically consistent with the above zinc removal amount.

[0032] 4) Appearance inspection: mainly through visual observation. After the stripping of zinc, the aluminum alloy workpiece is uniformly white with no residue.

[0033] 5) Conductivity test, use a conductivity meter to test, specifically: a. Press and hold the "open / off" button to put the instrument into measurement mode; b. Press the "Temperature" key to display the solution temperature value.

[0034] c. Insert the conductivity meter, which has been cleaned with distilled water, into the solution to be measured. Read and record the data after it stabilizes.

[0035] The conductivity of the zinc stripping solution prepared in this embodiment is: 26000±100 μs / cm.

[0036] The pH value of the solution (prepared zinc stripping solution) should be tested frequently during use and controlled between 1.5 and 2.5. If it exceeds 2.5, 3-8 kg of zinc stripping agent should be added. In addition, if the area of ​​the aluminum plate is used as the measurement standard, the pH value of the solution should be tested every 125 m 2 -150m 2 Supplement 1kg. Example 2

[0037] An environmentally friendly aluminum alloy stripping agent comprises the following raw materials, by weight percentage: 50% ammonium persulfate, 10% sodium sulfate, 5% ethylenediaminetetraacetic acid, 3% sodium lauryl sulfate, 5% modified carbon black, and the balance water. The modified carbon black is ammonium persulfate-modified N110 carbon black, prepared according to the above method.

[0038] When stripping zinc from an aluminum alloy workpiece, first take 80g of the above-mentioned stripping agent, add 3g of citric acid, add water and stir to prepare 1L of stripping solution, place the workpiece in it, and treat at room temperature.

[0039] Zinc removal effect: In this embodiment, the zinc stripping speed is 10 seconds; the zinc stripping amount is 7g, and 0.7g is stripped per second; after the zinc stripping is completed, the zinc ion content detected in the zinc stripping solution is 0.69g / L; after the zinc stripping is completed, the surface of the aluminum alloy workpiece is uniformly white, and no zinc residue is left; the conductivity of the configured zinc stripping solution is: 29000±100μs / cm.

[0040] Comparison of Example 2 and Example 1 shows that although the total amount of sodium sulfate and carbon black added in Example 2 is lower than that in Example 1, the amount of modified carbon black added is higher than that in Example 1, the conductivity is slightly higher, and the amount of persulfate added is larger, thereby comprehensively improving the speed of zinc removal and the complexation rate of the stabilizer to zinc ions. Example 3

[0041] An environmentally friendly aluminum alloy dezincification agent comprises the following raw materials, by weight: 40% ammonium percarbonate, 12% sodium sulfate, 3% polyacrylic acid, 5% sodium silicate, 0.5% X-100, 4% modified carbon black, and the balance water. The modified carbon black is ammonium persulfate-modified N110 carbon black, prepared according to the above method.

[0042] When stripping zinc from an aluminum alloy workpiece, first take 50 g of the above-mentioned stripping agent, add 15 g of sulfuric acid and 3 g of citric acid, add water and stir to prepare 1 L of stripping solution, place the workpiece in it, and treat at room temperature.

[0043] Zinc removal effect: In this embodiment, the zinc stripping speed is 20 seconds; the zinc stripping amount is 6 grams, and 0.3 grams of zinc are stripped per second; after the zinc stripping is completed, the zinc ion content detected in the zinc stripping solution is 0.58 g / L; after the zinc stripping is completed, the surface of the aluminum alloy workpiece is uniformly white, and no zinc residue is left; the conductivity of the configured zinc stripping solution is: 28000±100 μs / cm.

[0044] Comparative Examples 1-3 Comparative Examples 1-3 are comparative experiments of Example 2, except that sodium sulfate is not added to the zinc stripping agent in Comparative Example 1, 8% sodium sulfate is added in Comparative Example 2, and 17% sodium sulfate is added in Comparative Example 3. The rest is the same as Example 2.

[0045] Zinc removal effect: In Comparative Example 1, the stripping speed was 45 seconds; the stripping amount was 7 grams, with a stripping rate of 0.16 grams per second. After stripping, the zinc ion content detected in the stripping solution was 0.68 g / L. After stripping, the aluminum alloy workpiece's surface was uniformly white, with virtually no zinc residue. The conductivity of the prepared stripping solution was 15,000 ± 100 μs / cm. This indicates that omitting sodium sulfate would reduce the stripping solution's conductivity, which would slow the stripping speed. However, since the addition of modified carbon black did not significantly reduce the conductivity, the stripping speed remained within 60 seconds, demonstrating a relatively good stripping effect.

[0046] In Comparative Example 2, the stripping speed was 35 seconds; the stripping amount was 7g, or 0.2g per second. After stripping, the zinc ion content detected in the stripping solution was 0.69g / L. The surface of the aluminum alloy workpiece was uniformly white after stripping, with virtually no zinc residue. The conductivity of the prepared stripping solution was 23000±100μs / cm. This also indicates that reducing the amount of sodium sulfate added reduces the conductivity of the stripping solution, resulting in a longer stripping time.

[0047] In Comparative Example 3, the stripping speed was 15 seconds, the stripping amount was 7g, and 0.47g of zinc was stripped per second. After stripping, the zinc ion content in the stripping solution was 0.69g / L. The surface of the aluminum alloy workpiece was uniformly white after stripping, with virtually no zinc residue. The conductivity of the prepared stripping solution was 34000±100μs / cm. This indicates that increasing the amount of sodium sulfate added increases the conductivity to a certain extent, but does not accelerate the stripping speed.

[0048] Comparison of Comparative Examples 1-3 with Example 2 shows that the amount of sodium sulfate added has a significant effect on the conductivity, and the conductivity directly affects the speed of zinc removal. The optimal zinc removal effect can be achieved within the limited range of sodium sulfate addition in the present invention. Too low or too high an amount of sodium sulfate addition is not conducive to zinc removal.

[0049] Comparative Examples 4-8 Comparative Examples 4-8 are comparative experiments of Example 2, except that no modified carbon black is added in Comparative Example 4, 2% of modified carbon black is added in Comparative Example 5, 6% of modified carbon black is added in Comparative Example 6, an equal amount of sodium sulfate is used instead of modified carbon black in Comparative Example 7, and modified carbon black is replaced with unmodified carbon black in Comparative Example 8. The rest is the same as in Example 2.

[0050] Zinc removal effect: In Comparative Example 4, the stripping speed was 55 seconds, the stripping amount was 7 grams, and 0.13 grams of zinc was stripped per second. After stripping, the zinc ion content detected in the stripping solution was 0.68 g / L. After stripping, the aluminum alloy workpiece was uniformly whitened, with virtually no zinc residue. The conductivity of the prepared stripping solution was 14500 ± 100 μs / cm. Comparison with Example 2 shows that omitting the modified carbon black results in reduced conductivity and impaired zinc ion complexation, resulting in poor stripping results and prolonged processing time.

[0051] In comparative example 5, the zinc stripping speed is 30s; the zinc stripping amount is 7g, and the zinc stripping is 0.23g per second; the zinc ion content detected in the zinc stripping solution after the zinc stripping is completed is 0.69g / L; the surface of the aluminum alloy workpiece is also uniformly white after the zinc stripping, and there is basically no zinc residue; the conductivity of the configured zinc stripping solution is: 21500±100μs / cm. In comparative example 6, the zinc stripping speed is 12s; the zinc stripping amount is 7g, and the zinc stripping is 0.58g per second; the zinc ion content detected in the zinc stripping solution after the zinc stripping is completed is 0.70g / L; the surface of the aluminum alloy workpiece is also uniformly white after the zinc stripping, and there is basically no zinc residue; the conductivity of the configured zinc stripping solution is: 33500±100μs / cm. Comparison of comparative examples 5 and 6 with example 2 shows that the amount of modified carbon black added will affect the conductivity of the zinc stripping solution, and that too high or too low conductivity will have a certain effect on the zinc stripping efficiency; and the amount of modified carbon black added will directly affect the effect of the stabilizer complexing zinc ions.

[0052] The zinc stripping speed of Comparative Example 7 is 25s; the zinc stripping amount is 7g, and the zinc stripping is 0.28g per second; the zinc ion content detected in the zinc stripping solution after the zinc stripping is 0.69g / L; the surface of the aluminum alloy workpiece is also uniformly white after zinc stripping, and there is basically no zinc residue; the conductivity of the configured zinc stripping solution is: 21300±100μs / cm. Compared with Example 2, although the conductivity has not changed significantly, the zinc ion content in the solution is high after the zinc stripping is completed, indicating that the lack of modified carbon black affects the effect of the stabilizer on the complexing of zinc ions, so that the reaction of the oxidant oxidizing the zinc coating is suppressed to a certain extent, thereby slowing down the zinc stripping speed; Compared with Comparative Example 5, Comparative Example 7 has basically the same conductivity, but the zinc stripping speed of Comparative Example 7 is slower, which also indirectly illustrates that the lack of modified carbon black affects the complexing effect of the stabilizer on zinc ions, resulting in a certain resistance to the forward reaction of the oxidant oxidation reaction.

[0053] In Comparative Example 8, the stripping speed was 23 seconds; the stripping amount was 7g, or 0.30g per second. After stripping, the zinc ion content detected in the stripping solution was 0.69g / L. The surface of the aluminum alloy workpiece was uniformly white after stripping, with virtually no zinc residue. The conductivity of the prepared stripping solution was 23500±100μs / cm. A comparison with Example 2 shows that the replacement of modified carbon black with carbon black, due to its poor dispersibility in the stripping solution, does not contribute significantly to conductivity, and has little effect on the complexation of the stabilizer with zinc ions. This is comparable to the effect of Comparative Example 7, which did not include modified carbon black.

[0054] Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

Claims

1. An environmentally friendly aluminum alloy zinc stripping agent, characterized in that: The invention comprises the following raw materials in weight percentage: 30-50% of an oxidant, 10-15% of sodium sulfate, 1-10% of a stabilizer, 0.5-5% of a surfactant, 3-5% of modified carbon black, and the balance is water.

2. The environmentally friendly aluminum alloy zinc stripping agent according to claim 1, characterized in that: The oxidant is persulfate or percarbonate.

3. The environmentally friendly aluminum alloy zinc stripping agent according to claim 1, characterized in that: The stabilizer is at least one of water-soluble organic phosphonic acid and its salts, hexametaphosphoric acid and its salts, ethylenediaminetetraacetic acid and its salts, polyacrylic acid, and sodium silicate.

4. The environmentally friendly aluminum alloy zinc stripping agent according to claim 1, characterized in that: The surfactant is any one of OP-10, X-100, H95, and sodium lauryl sulfate.

5. The environmentally friendly aluminum alloy zinc stripping agent according to claim 1, characterized in that: The modified carbon black is persulfate-modified carbon black.

6. The environmentally friendly aluminum alloy zinc stripping agent according to claim 5, characterized in that: The preparation steps of the modified carbon black include: mixing carbon black with a persulfate aqueous solution, ultrasonically dispersing, stirring and reacting at a predetermined temperature, centrifuging and washing with water, and vacuum drying.

7. The environmentally friendly aluminum alloy zinc stripping agent according to claim 6, characterized in that: The carbon black is N110 carbon black, and the persulfate aqueous solution is an ammonium persulfate aqueous solution.

8. The environmentally friendly aluminum alloy zinc stripping agent according to claim 6, characterized in that: The mass fraction of the persulfate aqueous solution is 0.016-0.020%, the ultrasonic dispersion time is 1-1.5 hours, the predetermined temperature is 30° C., the stirring reaction is 20-25 hours, and the vacuum drying temperature is 80° C.

9. A method for using the environmentally friendly aluminum alloy zinc stripping agent according to claims 1-8, characterized in that: The method of use comprises the following steps: adding a predetermined amount of zinc stripping agent and acid into water to prepare a zinc stripping solution, placing the aluminum alloy workpiece to be zinc stripped into the zinc stripping solution, treating the workpiece for a period of time, and then taking the workpiece out.

10. The method of use according to claim 9, characterized in that: The concentration of the zinc stripping agent in the zinc stripping solution is 20-80g / L, and the added acid is at least one of 10-30g / L sulfuric acid or 1-5g / L citric acid. The aluminum alloy workpiece to be stripped is placed in the zinc stripping solution and treated for 5-60s at room temperature for zinc stripping.