Surface conditioning agent used before natural color passivation of die-casting aluminum and preparation method of surface conditioning agent

Abstract

The invention discloses a surface conditioning agent used before natural color passivation of die-casting aluminum and a preparation method thereof, and relates to the technical field of die-casting aluminum. The surface conditioning agent comprises the following components in parts by weight: 50-80% of water, 1-6% of polyethylene glycol-600, 1-6% of formic acid, 2-8% of potassium nitrate, 5-20% of oxalic acid, 2-15% of tartaric acid and 1-5% of glycolic acid. The preparation method of the surface conditioning agent for the die-casting aluminum before natural color passivation comprises the following steps: step 1, adding polyethylene glycol-600, potassium nitrate, oxalic acid, formic acid, glycolic acid and tartaric acid into water, and uniformly dispersing; and stirring for 30 minutes. And 2, measuring the density of the mixed solution, supplementing the residual water, continuously stirring for 10 minutes until the mixed solution is completely and uniformly mixed, standing for 10 minutes, and cooling to room temperature. And step 3, after the detection is qualified, sub-packaging into buckets. The use amount of nitric acid is reduced, the aluminum alloy pickling activation process is milder and more environmentally friendly, a passivation film uniform in color can be obtained through subsequent aluminum alloy passivation, and meanwhile corrosion resistance is improved.

Description

Technical Field

[0001] This invention belongs to the field of die-cast aluminum technology, specifically, it relates to a surface conditioning agent for die-cast aluminum before passivation and its preparation method. Background Technology

[0002] Die-cast aluminum is widely used in many fields such as automotive manufacturing, aerospace, and electronics due to its good casting properties, machinability, and relatively light weight. However, die-cast aluminum is susceptible to corrosion in natural environments, which affects its appearance and performance, and reduces its service life. The main forms of corrosion include oxidation corrosion and pitting corrosion.

[0003] To improve the corrosion resistance of die-cast aluminum, it is typically subjected to passivation treatment. Passivation treatment forms a dense protective film on the surface of the die-cast aluminum. This film prevents oxygen, moisture, and other corrosive media from contacting the die-cast aluminum, thereby effectively improving its corrosion resistance while ensuring a consistent appearance.

[0004] Pickling and activation of aluminum alloys is an essential step in the passivation process. The quality of activation determines the corrosion resistance and appearance of the passivation film. The pickling and activation methods vary for different trivalent chromium passivation systems. For trivalent chromium passivation systems rich in sulfate, nitric acid activation has a significant impact on passivation, while oxalic acid activation has a very important effect on trivalent chromium passivation systems rich in nitrate.

[0005] In existing technologies, the pickling and activation before trivalent chromium passivation involves activating with 100-500 mL / L nitric acid solution for 1-2 seconds. This process is not suitable for large-scale production. Furthermore, the high concentration of the first nitric acid will generate a large amount of yellow fumes during the activation process, which is highly corrosive to equipment and personnel. In addition, the operation time is very short, making it unsuitable for automated production requirements.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a surface conditioning agent for die-cast aluminum before passivation and its preparation method, thereby solving the problems mentioned in the background art.

[0008] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows: A surface conditioning agent for die-cast aluminum before passivation, comprising the following components in parts by weight: Water 50-80%, polyethylene glycol-600 1-6%, formic acid 1-6%, potassium nitrate 2-8%, oxalic acid 5-20%, tartaric acid 2-15%, glycolic acid 1-5%.

[0009] Optionally, a surface conditioner for die-cast aluminum before passivation comprises the following components in parts by weight: Water 73%, polyethylene glycol-600 2%, formic acid 2%, potassium nitrate 5%, oxalic acid 10%, tartaric acid 5%, glycolic acid 3%.

[0010] Optionally, a surface conditioner for die-cast aluminum before passivation comprises the following components in parts by weight: Water 60%, polyethylene glycol-600 5%, formic acid 5%, potassium nitrate 3%, oxalic acid 15%, tartaric acid 10%, glycolic acid 2%.

[0011] A method for preparing a surface conditioning agent for die-cast aluminum before passivation includes the following steps: Step 1: Add polyethylene glycol-600, potassium nitrate, oxalic acid, formic acid, glycolic acid and tartaric acid to water and disperse evenly, then stir for 30 minutes.

[0012] Step 2: Measure the density of the mixed solution, add the remaining water, continue stirring for 10 minutes until completely mixed, let stand for 10 minutes, and let it cool to room temperature.

[0013] Step 3: After passing the inspection, the products are packaged into barrels.

[0014] Optionally, in step three, a corrosion resistance test needs to be performed during the inspection. The specific test steps include: S10: 6061-T6 aluminum alloy is cleaned by alkaline ultrasonic degreasing and then rinsed with water three times. S11: Remove oxide scale by alkaline etching, rinse three times with water, and then soak in an aqueous solution of surface conditioner. S12: After rinsing three times with pure water, soak in a trivalent chromium passivation solution containing sulfate. S13: After rinsing with pure water three times, and then drying with hot air and blowing water, a light yellow uniform passivation film is obtained. S14: After aging, apply copper sulfate droplets and perform a neutral salt spray test; The surface conditioner content in the aqueous solution is 5-15%, the immersion time in the aqueous solution is 1-3 min, the immersion temperature of the trivalent chromium passivation solution is 25-35 ℃, the immersion time is 4-6 min, the aging time is 20-30 h, the copper sulfate drop time is 1.5-2.5 min, and the neutral salt spray test time is 440-500 h.

[0015] Optionally, in step three, a corrosion resistance test needs to be performed during the inspection. The specific test steps include: S20: Use an acidic degreasing cleaner, ultrasonically clean the die-cast aluminum ADC-12, and then rinse with water three times. S21: Soak in an aqueous solution of surface conditioner; S22: After washing three times with water, soak in a trivalent chromium passivation solution containing a certain proportion of sulfate and nitrate ions. S23: After washing three times with water, compressed air blows away excess moisture, and blow-drying is performed to obtain a uniform blue passivation film. S24: After aging at room temperature, apply copper sulfate droplets and perform a neutral salt spray test; The process includes: surface conditioner content in aqueous solution of 5-15%, immersion time of 1-3 min, sulfate to nitrate ratio of 4:1, trivalent chromium passivation solution content of 5-15%, immersion temperature of 30-40℃ for 4-6 min, forced-air drying temperature of 70-90℃ for 15-25 min, aging at room temperature for 20-30 h, copper sulfate drop time of 40-60 s, and neutral salt spray test duration of 200-300 h.

[0016] Optionally, in step three, a corrosion resistance test needs to be performed during the inspection. The specific test steps include: S30: For die-cast aluminum A380, use an acidic degreasing cleaner, ultrasonic cleaning, and water rinsing three times; S31: Soak in an aqueous solution of surface conditioner; S32: After washing three times with water, soak in a trivalent chromium passivation solution containing a certain proportion of sulfate and nitrate ions. S33: After washing three times with water, excess moisture is blown away with compressed air, and then the film is dried by forced air to obtain a uniform colored passivation film. S34: After aging at room temperature, apply copper sulfate droplets and perform a neutral salt spray test for 300 hours; The process includes: surface conditioner content of 5-15% in aqueous solution, soaking time of 1-3 min, sulfate to nitrate ratio of 3:1, trivalent chromium passivation solution content of 5-15%, soaking temperature of 30-40℃ for 4-6 min, forced air drying temperature of 70-90℃ for 15-25 min, aging at room temperature for 20-30 h, copper sulfate drop time of 40-60 s, and neutral salt spray test duration of 200-300 h.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art. Of course, any product implementing the present invention does not necessarily need to achieve all of the following advantages at the same time: This invention reduces the amount of nitric acid used, making the pickling and activation process of aluminum alloys gentler and more environmentally friendly. It also results in a uniformly colored passivation film for subsequent aluminum alloy passivation and improves corrosion resistance.

[0018] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0019] The accompanying drawings described below are merely some embodiments. Those skilled in the art can obtain other drawings based on these drawings without any creative effort. In the drawings: Figure 1 Flowchart of the preparation method for surface conditioning agent before passivation of die-cast aluminum.

[0020] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0021] The invention will now be described in further detail with reference to the accompanying drawings.

[0022] Example 1: This example provides a surface conditioning agent for die-cast aluminum before passivation, comprising the following components in parts by weight: Water 50-80%, polyethylene glycol-600 1-6%, formic acid 1-6%, potassium nitrate 2-8%, oxalic acid 5-20%, tartaric acid 2-15%, glycolic acid 1-5%. Example 2: A surface conditioner for die-cast aluminum before passivation, comprising the following components in parts by weight: Water 73%, polyethylene glycol-600 2%, formic acid 2%, potassium nitrate 5%, oxalic acid 10%, tartaric acid 5%, glycolic acid 3%. Example 3: A surface conditioner for die-cast aluminum before passivation, comprising the following components in parts by weight: Water 60%, polyethylene glycol-600 5%, formic acid 5%, potassium nitrate 3%, oxalic acid 15%, tartaric acid 10%, glycolic acid 2%. Example 4: Corrosion resistance test: After alkaline ultrasonic degreasing and cleaning, 6061-T6 aluminum alloy was washed three times with water, alkali-etched to remove oxide scale, and rinsed three times with clean water. It was then immersed in a 10% aqueous solution as described in Example 2 for 2 minutes, rinsed three times with pure water, and then immersed in a trivalent chromium passivation solution containing sulfate at 30°C for 5 minutes. After rinsing three times with pure water and drying with hot air and blowing water, a light yellow, uniform passivation film was obtained. After aging for 24 hours, copper sulfate was applied for 2 minutes and 10 seconds, and a neutral salt spray test was conducted for 480 hours.

[0023] The die-cast aluminum ADC-12 was ultrasonically cleaned at 65°C for 5 minutes with an acidic degreasing cleaner, then rinsed with water three times, and then soaked in a 10% aqueous solution of Example 2 for 2 minutes. After rinsing with water three times, it was soaked in a 10% trivalent chromium passivation solution with a sulfate to nitrate ratio of 4:1 at 35°C for 5 minutes and 30 seconds. After rinsing with water three times, excess water was blown away with compressed air, and the film was dried in a forced-air dryer at 80°C for 20 minutes to obtain a uniform blue passivation film. After aging at room temperature for 24 hours, the copper sulfate drop time was 45 seconds, and the film was tested with neutral salt spray for 240 hours. Example 5: Corrosion resistance test: After alkaline ultrasonic degreasing and cleaning, 6061-T6 aluminum alloy was washed three times with water, alkali-etched to remove oxide scale, and rinsed three times with clean water. It was then immersed in a 10% aqueous solution (as described in Example 3) for 2 minutes, rinsed three times with pure water, and then immersed in a trivalent chromium passivation solution containing sulfate at 30°C for 5 minutes and 30 seconds. After rinsing three times with pure water and drying with hot air and blowing water, a uniform yellow passivation film was obtained. After aging for 24 hours, copper sulfate was applied for 2 minutes, and a neutral salt spray test was conducted for 450 hours.

[0024] For die-cast aluminum A380, an acidic degreasing cleaner was used. After ultrasonic cleaning at 65°C for 5 minutes, it was washed three times with water. Then, it was soaked in a 10% aqueous solution of Example 3 for 2 minutes and washed three times with water. After that, it was soaked in a 10% trivalent chromium passivation solution with a sulfate to nitrate ratio of 3:1 at 35°C for 4 minutes and 30 seconds. After washing three times with water, excess water was blown away with compressed air, and the film was dried at 80°C for 20 minutes to obtain a uniform colored passivation film. After aging at room temperature for 24 hours, the copper sulfate drop time was 50 seconds, and the film was tested with neutral salt spray for 300 hours.

[0025] The key focus of this patent is solving the challenge of pickling and activation before trivalent chromium passivation. Most papers and patents use 100-500 mL / L nitric acid solution for 1-2 seconds of activation. This process is unsuitable for large-scale production because the high nitric acid concentration generates excessive yellow fumes during activation, which are highly corrosive to equipment and personnel. Furthermore, the short operation time makes it unsuitable for automated production. Therefore, this patent reduces the amount of nitric acid used, making the pickling and activation process for aluminum alloys gentler and more environmentally friendly. This results in a uniformly colored passivation film for subsequent aluminum alloy passivation, while also improving corrosion resistance.

[0026] This invention is not limited to the embodiments described above. Anyone should understand that structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention. Technical aspects, shapes, and structures not described in detail in this invention are all publicly known technologies.

Claims

1. An adjustment agent for die cast aluminum uncoated pre- passivated front surface, characterized by, The following components are included by weight parts: Water 50-80%, polyethylene glycol-600 1-6%, formic acid 1-6%, potassium nitrate 2-8%, oxalic acid 5-20%, tartaric acid 2-15%, glycolic acid 1-5%.

2. A die cast aluminum natural passivation front surface conditioner according to claim 1, characterized in that, The following components are included by weight parts: Water 73%, polyethylene glycol-600 2%, formic acid 2%, potassium nitrate 5%, oxalic acid 10%, tartaric acid 5%, glycolic acid 3%.

3. A die cast aluminum mill finish front surface conditioner according to claim 1, wherein, The following components are included by weight parts: Water 60%, polyethylene glycol-600 5%, formic acid 5%, potassium nitrate 3%, oxalic acid 15%, tartaric acid 10%, glycolic acid 2%.

4. A method for producing a die-cast aluminum natural passivation front surface conditioner, characterized by, The following steps are included: Step one: add polyethylene glycol-600, potassium nitrate, oxalic acid, formic acid, glycolic acid and tartaric acid into water and disperse uniformly, stir for 30 min; Step two: measure the density of the mixed solution, add the remaining water, continue to stir for 10 min until completely mixed, stand for 10 min, and cool to room temperature; Step three: after detection, pack into barrels.

5. A method of preparing a surface conditioner for die cast aluminum prior to natural passivation according to claim 4, characterized in that, In step three, corrosion resistance testing is required during detection, and the specific testing steps include: S10: after alkaline ultrasonic oil removal cleaning of 6061-T6 aluminum alloy, water washing three times; S11: after removing the oxide scale by alkali etching, cleaning with water three times, and then soaking with an aqueous solution of surface conditioner; S12: after cleaning with pure water three times, soaking with trivalent chromium passivation solution containing sulfate; S13: after cleaning with pure water three times, blowing water and hot air drying to obtain a light yellow and uniform passivation film; S14: after aging, copper sulfate is dropped, and neutral salt spray testing is performed.

6. A method of preparing a surface conditioner for die cast aluminum prior to natural passivation according to claim 5, characterized in that, The content of the surface conditioner in the aqueous solution is 5-15%, the soaking time of the aqueous solution is 1-3 min, the soaking temperature of the trivalent chromium passivation solution is 25-35 ℃, the soaking time is 4-6 min, the aging time is 20-30 h, the copper sulfate dropping time is 1.5-2.5 min, and the neutral salt spray testing time is 440-500 h.

7. A method of preparing a pre-finish surface conditioner for die cast aluminum according to claim 4, characterized in that, In step three, corrosion resistance testing is required during detection, and the specific testing steps include: S20: after ultrasonic cleaning with acidic oil removal cleaner for die-cast aluminum ADC-12, water washing three times; S21: soaking with an aqueous solution of surface conditioner; S22: after water washing three times, soaking with trivalent chromium passivation solution containing a certain proportion of sulfate and nitrate; S23: after water washing three times, blowing off excess water with compressed air, and blowing dry to obtain a uniform blue passivation film; S24: after aging at room temperature, copper sulfate is dropped, and neutral salt spray testing is performed.

8. A method of preparing a surface conditioner for die cast aluminum prior to natural passivation according to claim 7, characterized in that, The content of the surface conditioner in the aqueous solution is 5-15%, the soaking time of the aqueous solution is 1-3 min, the ratio of sulfate to nitrate is 4:1, the content of the trivalent chromium passivation solution is 5-15%, the soaking temperature of the trivalent chromium passivation solution is 30-40 ℃, the time is 4-6 min, the blowing dry temperature is 70-90 ℃, the blowing dry time is 15-25 min, the room temperature aging time is 20-30 h, the copper sulfate dropping time is 40-60 s, and the neutral salt spray testing time is 200-300 h.

9. A method of preparing a surface conditioner for die cast aluminum prior to natural passivation according to claim 4, characterized in that, In step three, corrosion resistance test is needed during detection, and the specific test steps include: S30: ultrasonic cleaning with acid degreasing cleaning agent for die-casting aluminum A380, water washing three times; S31: soaking with water solution of surface conditioner; S32: after water washing three times, soaking with trivalent chromium passivation solution containing a certain proportion of sulfate and nitrate; S33: after water washing three times, blowing off the excess water by compressed air, and blowing drying to obtain uniform color passivation film; S34: after normal temperature aging, copper sulfate dripping, and neutral salt spray test for 300 h.

10. A method of preparing a pre-finish surface conditioner for die cast aluminum according to claim 9, characterized in that, The content of surface conditioner in water solution is 5-15%, the soaking time in water solution is 1-3 min, the ratio of sulfate and nitrate is 3:1, the content of trivalent chromium passivation solution is 5-15%, the soaking temperature of trivalent chromium passivation solution is 30-40℃, the soaking time is 4-6 min, the blowing drying temperature is 70-90℃, the blowing drying time is 15-25 min, the normal temperature aging time is 20-30 h, the copper sulfate dripping time is 40-60 s, and the neutral salt spray test time is 200-300 h.

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