CN111778536B - Aluminum alloy surface compact oxidation process under constant ion gradient - Google Patents
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- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
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Abstract
The invention relates to surface processing of an aluminum alloy device, and belongs to the field of surface treatment of metal materials. The aluminum alloy surface compact oxidation process under the constant ion gradient is characterized in that an aluminum alloy device is placed in an anodic oxidation solution, and oxidation voltage pulses and ultrasonic vibration pulses are alternately applied to carry out anodic oxidation; and ultrasonic vibration pulses are transferred to the aluminum alloy body from solution vibration, and are transmitted to the solution on each part of the alloy surface through the rigid aluminum alloy, so that the difference of ultrasonic pulse density distribution of the solution in the prior art is avoided, and the problem of oxidation imbalance caused by the change of ion concentration difference is difficult to effectively eliminate. The technical scheme can form a compact alumina film with uniform and stable thickness and consistent crystal form on the surface of the aluminum alloy device, and can resist corrosion in an extreme acid-base environment.
Description
Technical Field
The invention relates to processing of aluminum alloy, in particular to a dense oxidation process for the surface of aluminum alloy under a constant ion gradient.
Background
The aluminum alloy has low density, high strength similar to or superior to that of high-quality steel, good plasticity, excellent electric conductivity, heat conductivity and corrosion resistance, is widely used in industry, and is second to steel in use amount. In the existing light industrial products, the components such as aluminum alloy shells, accessories and the like are mostly made of aluminum alloy. However, the aluminum alloy is limited by the chemical activity of aluminum, and after the aluminum alloy material is formed, corresponding surface processing is often required to meet the corrosion resistance and wear resistance of the aluminum alloy device, and the service life is prolonged. In industrial production, an anodic oxidation process is more and more widely adopted to form a compact aluminum oxide film on the surface of an aluminum alloy so as to resist corrosion of external acid-base salts and prolong the service life of an aluminum alloy device.
The existing processes for anodizing aluminum alloys have been developed substantially in the last half century. For example, a high-speed and high-efficiency anodic oxidation process, a normal-temperature anodic oxidation process and a pulse anodic oxidation process are adopted; the latest oxidation solution formula improvement technology can generate a denser anodic oxide film on the surface of the aluminum alloy during the process of aluminum alloy, for example, the corrosion resistance and wear resistance of the anodic oxide film on the surface of the aluminum alloy generated by the anodic oxidation technology can be greatly improved by adding titanium dioxide and other powder in documents. The improvement of the new anodic oxidation technology continuously improves the corrosion resistance of the surface of the aluminum alloy and improves the application range of the aluminum alloy device.
However, the anticorrosion property of the aluminum alloy surface dense alumina film produced by the anodic oxidation processes cannot be fully satisfied for use in extreme environments. For example, under severe environment equipment such as navigation equipment and mining exploration, the corrosion-resistant aluminum alloy surface oxidation film processed by the prior art can only achieve corrosion resistance for more than ten hours, and the application range of the aluminum alloy is still very limited in severe chemical production strong acid environment and high salt content navigation humid environment.
Therefore, in the field of processing and manufacturing of aluminum alloy devices at present, a processing technology capable of effectively improving the surface corrosion resistance of an aluminum alloy material is still a problem to be solved urgently in the field at present.
Disclosure of Invention
The invention aims to solve the technical problem of providing a dense oxidation process for the surface of an aluminum alloy under a constant ion gradient, and solving the problem of low corrosion resistance of an anodic oxide film of the aluminum alloy in the prior art under an extreme environment.
Technical scheme
A dense oxidation process for the surface of an aluminum alloy under a constant ion gradient is characterized by comprising the following steps:
step 1: pretreating the surface of the aluminum alloy;
step 2: placing an aluminum alloy device in an anodic oxidation solution, and alternately applying an oxidation voltage pulse and an ultrasonic vibration pulse to carry out anodic oxidation, wherein the ultrasonic vibration source is the aluminum alloy device;
and step 3: and (3) sealing the oxide film formed by anodic oxidation on the surface of the aluminum alloy by adopting a high-molecular polymer.
Further, the time width of the oxidation voltage pulse in the step 2 is 15-75 ms; the time width of the ultrasonic vibration pulse is not less than 100ms, and preferably 100-1200 ms.
Further, the ultrasonic vibration source in the step 2 is an aluminum alloy device, which means that the ultrasonic vibration patch is fixed on the surface of the aluminum alloy, and the ultrasonic waves are transmitted through the vibration of the aluminum alloy.
Further, in the step 2, the temperature of the anodic oxidation is 30-45 ℃, and the time is 120-300 seconds.
Further, the frequency of the ultrasonic vibration pulse in the step 2 is 100-120 Hz, and the peak intensity of the pulse current is 1A-1.5A/dm2。
Further, the solution of anodic oxidation in step 2 is an acidic mixed solution, and the components comprise 2-8% of sulfate, 5-10% of nitrate and 1-5% of fluoride; among them, the sulfate is preferably sodium sulfate, the nitrate is preferably sodium nitrate, and the fluoride is preferably ammonium bifluoride.
Further, the step 1 of pretreating the surface of the aluminum alloy comprises the following steps: oil removal, alkaline etching, acid washing and surface grinding.
Further, the oil removing process comprises the following steps: degreasing in an alkaline degreasing agent for 180-300 seconds at 40-60 ℃; the alkaline degreasing agent comprises 2-15wt% of sodium carbonate and 3-12wt% of trisodium phosphate.
Further, the alkali etching process comprises the following steps: cleaning for 15-30 seconds in an alkali solution at 25-50 ℃; the alkali solution is preferably sodium hydroxide aqueous solution, and the concentration is 5wt% -8 wt%.
Further, the pickling process comprises the following steps: adding an acid solution, adjusting the aluminum alloy soaking solution to be neutral, and removing a black oxide film on the surface layer; the acid solution is preferably a nitric acid solution, and the concentration is preferably 10-20 wt%.
Further, the surface grinding adopts magnetic steel needle grinding.
Further, in the step 3, the high molecular polymer is selected from polyurethane, and the concentration is 10wt% -50 wt%.
Advantageous effects
According to the technical scheme, an oxidation voltage pulse and an ultrasonic vibration pulse are alternately applied to carry out anodic oxidation, solution ions in the oxidation voltage pulse are transferred to the ultrasonic vibration pulse in the pulse gap of the oxidation voltage to replace the ion solution on the surface of the aluminum alloy when an ion layer on the surface of the aluminum alloy has a higher concentration gradient, the ion concentration gradient difference on the surface of the aluminum alloy is eliminated, then the pulse period of the oxidation voltage is returned again, and the steps are sequentially circulated to form a compact aluminum oxide film with uniform and stable thickness and consistent crystal form on the surface of the aluminum alloy.
In the process, ultrasonic vibration pulses are transferred from solution vibration to aluminum alloy body vibration, and the ultrasonic waves are transmitted to the solution on each part of the surface of the alloy through the rigid aluminum alloy, so that the problems that the ultrasonic pulse density distribution of the solution in the prior art is different, so that the ultrasonic is insufficient on partial areas of the surface of the aluminum alloy, and the ion concentration difference is difficult to uniformly eliminate are solved.
According to the detection results of the samples prepared by the embodiment, the surface of the aluminum alloy device prepared by the technical scheme can be kept from being corroded in an acid mist environment with the humidity of more than 85% and the PH value of 1.5-1.2, and compared with the aluminum alloy device prepared by anodic oxidation in the prior art, the aluminum alloy device prepared by the process has remarkable extreme environment corrosion resistance.
Drawings
FIG. 1 is a test report of a sample prepared according to the embodiment of the present invention.
Detailed Description
The invention will be further elucidated with reference to the specific embodiments and the accompanying drawings.
The invention provides a dense oxidation process for an aluminum alloy surface under a constant ion gradient, which can effectively form a dense and uniform oxidation film on the aluminum alloy surface and effectively improve the corrosion resistance of the aluminum alloy in an extreme acid-base environment.
The aluminum element in the aluminum alloy is taken as a common active metal and is easy to be oxidized by oxygen in the air to generate components such as aluminum oxide and the like, wherein the gamma crystal form aluminum oxide film can effectively protect the aluminum alloy from being further oxidized and damaged. However, when the aluminum alloy is placed in an acidic, alkaline or high-concentration salt environment, electrochemical reaction is easy to occur, components in different areas of the aluminum alloy are inconsistent, microscopic galvanic reaction is formed, aluminum crystal phase in the aluminum alloy is used as a negative electrode to be oxidized, and the oxidized negative electrode is further damaged and expanded. At the moment, if the pH value of the environment is too high, high-concentration acid-base solution invades into the aluminum alloy to corrode the inner layer of the aluminum alloy, so that the aluminum oxide film is damaged and separated. This microscopic galvanic corrosion continues to cause severe corrosion of the surface of the aluminum alloy device, resulting in a change in appearance and a reduction in structural strength.
By its nature, the heterogeneity of the aluminum oxide film on the surface of the aluminum alloy is the root cause of the inability of the aluminum alloy to resist corrosion in extreme environments. In the prior art, an anodic oxidation method is adopted to treat the aluminum alloy, a more compact and higher-thickness aluminum oxide film is formed on the surface of the aluminum alloy, the corrosion resistance of an aluminum alloy device in an extreme acid-base environment can be only slightly prolonged, and once the compact oxide film is gradually damaged, the aluminum alloy device loses the corrosion resistance.
According to the technical scheme, an oxidation voltage pulse and an ultrasonic vibration pulse are alternately applied to carry out anodic oxidation, solution ions in the oxidation voltage pulse are transferred to the ultrasonic vibration pulse in the pulse gap of the oxidation voltage to replace the ion solution on the surface of the aluminum alloy when an ion layer on the surface of the aluminum alloy has a higher concentration gradient, the ion concentration gradient difference on the surface of the aluminum alloy is eliminated, then the pulse period of the oxidation voltage is returned again, and the steps are sequentially circulated to form a compact aluminum oxide film with uniform and stable thickness and consistent crystal form on the surface of the aluminum alloy. In the process, ultrasonic vibration pulses are transferred from solution vibration to aluminum alloy body vibration, and the ultrasonic waves are transmitted to the solution on each part of the surface of the alloy through the rigid aluminum alloy, so that the problems that the ultrasonic pulse density distribution of the solution in the prior art is different, so that the ultrasonic is insufficient on partial areas of the surface of the aluminum alloy, and the ion concentration difference is difficult to uniformly eliminate are solved.
Comparative example 1
Step 1: surface pretreatment of the aluminum alloy: oil removal, alkaline etching, acid washing and surface grinding.
Firstly, degreasing the aluminum alloy device. In this embodiment, the oil removal process includes the steps of: at 40 ℃, the aluminum alloy device is put into an alkaline degreasing agent for degreasing treatment for 180 seconds and taken out, wherein the alkaline degreasing agent is (2-15% of sodium carbonate and 3-12% of trisodium phosphate). And then carrying out alkaline etching treatment on the aluminum alloy device. In this embodiment, the alkaline etching process includes: washing for 15 seconds in an alkali solution at 25 ℃; the alkali solution in this example is preferably an aqueous sodium hydroxide solution with a concentration of 5% by weight. And then carrying out acid cleaning treatment on the aluminum alloy device. In this embodiment, the pickling process includes: adding an acid solution, adjusting the aluminum alloy soaking solution to be neutral, and removing a black oxide film on the surface layer; the acidic solution in this embodiment is preferably a nitric acid solution having a concentration of 10 wt%.
And (3) placing the aluminum alloy device in a grinder, and grinding the surface of the aluminum alloy device by using magnetic steel needle grinding equipment to expose the aluminum alloy metal layer. And (3) placing the aluminum alloy device in an anodic oxidation solution, and continuously applying an oxidation voltage and ultrasonic vibration to carry out anodic oxidation, wherein the ultrasonic vibration is generated by an ultrasonic generator placed in the solution. In this example, the intensity of current at an oxidation voltage was 1A/dm2(ii) a The frequency of the ultrasonic vibration is 100 Hz; the ambient temperature for anodization was 30 deg.f for 120 seconds. In the embodiment, the solution for anodic oxidation is an acidic mixed solution, and the components comprise 2% of sulfate, 5% of nitrate and 1% of fluoride; among them, the sulfate is preferably sodium sulfate, the nitrate is preferably sodium nitrate, and the fluoride is preferably ammonium bifluoride.
And sealing the oxide film formed by anodic oxidation on the surface of the aluminum alloy device after anodic oxidation by adopting the high molecular polymer. The polymer in this example is selected from polyurethanes at a concentration of 10% by weight.
Example 1
Step 1: surface pretreatment of the aluminum alloy: oil removal, alkaline etching, acid washing and surface grinding.
Firstly, degreasing the aluminum alloy device. In this embodiment, the oil removal process includes the steps of: at 40 ℃, the aluminum alloy device is put into an alkaline degreasing agent for degreasing treatment for 180 seconds and taken out, wherein the alkaline degreasing agent is (2-15% of sodium carbonate and 3-12% of trisodium phosphate). And then carrying out alkaline etching treatment on the aluminum alloy device. In this embodiment, the alkaline etching process includes: washing for 15 seconds in an alkali solution at 25 ℃; the alkali solution in this example is preferably an aqueous sodium hydroxide solution with a concentration of 5% by weight. And then carrying out acid cleaning treatment on the aluminum alloy device. In this embodiment, the pickling process includes: adding an acid solution, then adjusting the aluminum alloy soaking solution to be neutral, and removing a black oxide film on the surface layer; the acidic solution in this embodiment is preferably a nitric acid solution having a concentration of 10 wt%.
And (3) placing the aluminum alloy device in a grinder, and grinding the surface of the aluminum alloy device by using magnetic steel needle grinding equipment to expose the aluminum alloy metal layer. Fixing an ultrasonic generator on the surface of the ground aluminum alloy device, placing the aluminum alloy device fixed with the ultrasonic generator in an anodic oxidation solution after protection treatment, and alternately applying an oxidation voltage pulse and an ultrasonic vibration pulse to carry out anodic oxidation. In this example, the pulse time width of the oxidation voltage was 15ms, and the peak intensity of the pulse current was 1A/dm2(ii) a The time width of the ultrasonic vibration pulse is 100ms, and the frequency of the ultrasonic vibration pulse is 100 Hz; the ambient temperature of anodic oxidation is 30-45 ℃, and the time is 120-300 seconds. In the embodiment, the solution for anodic oxidation is an acidic mixed solution, and the components comprise 2% of sulfate, 5% of nitrate and 1% of fluoride; among them, the sulfate is preferably sodium sulfate, the nitrate is preferably sodium nitrate, and the fluoride is preferably ammonium bifluoride.
And sealing the oxide film formed by anodic oxidation on the surface of the aluminum alloy device after anodic oxidation by adopting the high molecular polymer. The polymer in this example is selected from polyurethanes at a concentration of 10% by weight.
Comparative example 2
Step 1: surface pretreatment of the aluminum alloy: oil removal, alkaline etching, acid washing and surface grinding.
Firstly, degreasing the aluminum alloy device. In this embodiment, the degreasing process includes: and (3) at 50 ℃, putting the aluminum alloy device into an alkaline degreasing agent for degreasing treatment for 200 seconds, and taking out. And then carrying out alkali etching treatment on the aluminum alloy device. In this embodiment, the alkaline etching process includes: washing in alkali solution at 40 deg.c for 20 sec; the alkali solution in this example is preferably an aqueous sodium hydroxide solution with a concentration of 7% by weight. And then carrying out acid cleaning treatment on the aluminum alloy device. In this embodiment, the pickling process includes: adding an acid solution, then adjusting the aluminum alloy soaking solution to be neutral, and removing a black oxide film on the surface layer; the acidic solution in this example is preferably a nitric acid solution with a concentration of 15 wt.%.
And (3) placing the aluminum alloy device in a grinder, and grinding the surface of the aluminum alloy device by using magnetic steel needle grinding equipment to expose the aluminum alloy metal layer. And (3) placing the aluminum alloy device in an anodic oxidation solution, and continuously applying an oxidation voltage and ultrasonic vibration to carry out anodic oxidation, wherein the ultrasonic vibration is generated by an ultrasonic generator placed in the solution. In this example, the intensity of current at an oxidation voltage was 1.2A/dm2(ii) a The frequency of the ultrasonic vibration is 120 Hz; the ambient temperature for anodization was 41 ℃ for 200 seconds. In the embodiment, the solution for anodic oxidation is an acidic mixed solution, and the components comprise 6% of sulfate, 7% of nitrate and 3% of fluoride; among them, the sulfate is preferably sodium sulfate, the nitrate is preferably sodium nitrate, and the fluoride is preferably ammonium bifluoride.
And sealing the oxide film formed by anodic oxidation on the surface of the aluminum alloy device after anodic oxidation by adopting the high molecular polymer. The polymer in this example is selected from polyurethanes at a concentration of 40% by weight.
Example 2
Step 1: surface pretreatment of the aluminum alloy: oil removal, alkaline etching, acid washing and surface grinding.
Firstly, degreasing the aluminum alloy device. In this embodiment, the oil removal process includes the steps of: at 50 ℃, the aluminum alloy device is put into an alkaline degreasing agent for degreasing treatment for 200 seconds and taken out, wherein the alkaline degreasing agent is (2-15% of sodium carbonate and 3-12% of trisodium phosphate). And then carrying out alkaline etching treatment on the aluminum alloy device. In this embodiment, the alkaline etching process includes: washing in alkali solution at 10 deg.c for 20 sec; the alkali solution in this example is preferably an aqueous sodium hydroxide solution with a concentration of 7% by weight. And then carrying out acid cleaning treatment on the aluminum alloy device. In this embodiment, the pickling process includes: adding an acid solution, then adjusting the aluminum alloy soaking solution to be neutral, and removing a black oxide film on the surface layer; the acidic solution in this example is preferably a nitric acid solution with a concentration of 15 wt.%.
And (3) placing the aluminum alloy device in a grinder, and grinding the surface of the aluminum alloy device by using magnetic steel needle grinding equipment to expose the aluminum alloy metal layer. Fixing an ultrasonic generator on the surface of the ground aluminum alloy device, after protective treatment,and placing the aluminum alloy device fixed with the ultrasonic generator in an anodic oxidation solution, and alternately applying an oxidation voltage pulse and an ultrasonic vibration pulse to carry out anodic oxidation. In this example, the pulse time width of the oxidation voltage was 50ms, and the peak intensity of the pulse current was 1.2A/dm2(ii) a The time width of the ultrasonic vibration pulse is 600ms, and the frequency of the ultrasonic vibration pulse is 120 Hz; the ambient temperature for anodization was 41 ℃ for 200 seconds. In the embodiment, the solution for anodic oxidation is an acidic mixed solution, and the components comprise 6% of sulfate, 7% of nitrate and 3% of fluoride; among them, the sulfate is preferably sodium sulfate, the nitrate is preferably sodium nitrate, and the fluoride is preferably ammonium bifluoride.
And sealing the oxide film formed by anodic oxidation on the surface of the aluminum alloy device after anodic oxidation by adopting the high molecular polymer. The polymer in this example is selected from polyurethanes at a concentration of 40% by weight.
Comparative example 3
Step 1: surface pretreatment of the aluminum alloy: oil removal, alkaline etching, acid washing and surface grinding.
Firstly, degreasing the aluminum alloy device. In this embodiment, the oil removal process includes the steps of: at 60 ℃, the aluminum alloy device is placed in an alkaline degreasing agent for degreasing treatment for 300 seconds and taken out, wherein the alkaline degreasing agent is (2-15% of sodium carbonate and 3-12% of trisodium phosphate). And then carrying out alkaline etching treatment on the aluminum alloy device. In this embodiment, the alkaline etching process includes: cleaning for 30 seconds in an alkali solution at 50 ℃; the alkali solution in this example is preferably an aqueous sodium hydroxide solution with a concentration of 8% by weight. And then carrying out acid cleaning treatment on the aluminum alloy device. In this embodiment, the pickling process includes: adding an acid solution, then adjusting the aluminum alloy soaking solution to be neutral, and removing a black oxide film on the surface layer; the acidic solution in this example is preferably a nitric acid solution with a concentration of 20 wt.%.
And (3) placing the aluminum alloy device in a grinder, and grinding the surface of the aluminum alloy device by using magnetic steel needle grinding equipment to expose the aluminum alloy metal layer. Placing the aluminum alloy device in an anodic oxidation solution, and continuously applying an oxidation voltage and ultrasonic vibration to carry out anodic oxidation, wherein the ultrasonic vibration is generated by the super-ions placed in the solutionAn acoustic wave generator. In this example, the intensity of current at an oxidation voltage was 1.5A/dm2(ii) a The frequency of the ultrasonic vibration is 110 Hz; the ambient temperature of anodic oxidation is 30-45 ℃, and the time is 120-300 seconds. In the embodiment, the solution for anodic oxidation is an acidic mixed solution, and the components comprise 8% of sulfate, 10% of nitrate and 5% of fluoride; among them, the sulfate is preferably sodium sulfate, the nitrate is preferably sodium nitrate, and the fluoride is preferably ammonium bifluoride.
And sealing the oxide film formed by anodic oxidation on the surface of the aluminum alloy device after anodic oxidation by adopting the high molecular polymer. The polymer in this example is chosen from polyurethanes at a concentration of 50% by weight.
Example 3
Step 1: surface pretreatment of the aluminum alloy: oil removal, alkaline etching, acid washing and surface grinding.
Firstly, degreasing the aluminum alloy device. In this embodiment, the oil removal process includes the steps of: at 60 ℃, the aluminum alloy device is placed in an alkaline degreasing agent for degreasing treatment for 300 seconds and taken out, wherein the alkaline degreasing agent is (2-15% of sodium carbonate and 3-12% of trisodium phosphate). And then carrying out alkaline etching treatment on the aluminum alloy device. In this embodiment, the alkaline etching process includes: cleaning for 30 seconds in an alkali solution at 50 ℃; the alkali solution in this example is preferably an aqueous sodium hydroxide solution with a concentration of 8% by weight. And then carrying out acid cleaning treatment on the aluminum alloy device. In this embodiment, the pickling process includes: adding an acid solution, then adjusting the aluminum alloy soaking solution to be neutral, and removing a black oxide film on the surface layer; the acidic solution in this embodiment is preferably a nitric acid solution having a concentration of 20 wt%.
And (3) placing the aluminum alloy device in a grinder, and grinding the surface of the aluminum alloy device by using magnetic steel needle grinding equipment to expose the aluminum alloy metal layer. Fixing an ultrasonic generator on the surface of the ground aluminum alloy device, placing the aluminum alloy device fixed with the ultrasonic generator in an anodic oxidation solution after protection treatment, and alternately applying an oxidation voltage pulse and an ultrasonic vibration pulse to carry out anodic oxidation. In this example, the pulse time width of the oxidation voltage was 75ms, and the peak intensity of the pulse current was 1.5A/dm2(ii) a The above-mentioned superThe time width of the acoustic vibration pulse is 1200ms, and the frequency of the ultrasonic vibration pulse is 120 Hz; the ambient temperature of anodic oxidation is 30-45 ℃, and the time is 120-300 seconds. In the embodiment, the solution for anodic oxidation is an acidic mixed solution, and the components comprise 8% of sulfate, 10% of nitrate and 5% of fluoride; among them, the sulfate is preferably sodium sulfate, the nitrate is preferably sodium nitrate, and the fluoride is preferably ammonium bifluoride.
And sealing an oxide film formed by anodic oxidation on the surface of the anodized aluminum alloy device by adopting a high-molecular polymer. The polymer in this example is chosen from polyurethanes at a concentration of 50% by weight.
The acid corrosion resistance test was performed on the test samples of comparative examples 1 to 3 prepared according to the prior art and the test samples of examples 1 to 3 prepared according to the present technical scheme. The control sample is tested by hydrochloric acid mist, the surface of the control sample is corroded after 1% hydrochloric acid is sprayed for 30min, the appearance of the aluminum alloy device is changed, and the aluminum alloy device does not have corrosion resistance in a strong acid environment. The test report of the sample prepared in the embodiment 1-3 is shown in the attached figure 1, and the information of the test parameters, the data analysis conclusion and the like is as follows:
test unit: (information hiding)
The name of the client: (information hiding)
The name of the experiment: acid mist test
Test time: 2020.02.20-2020.04.22
The operator: (information hiding)
Purpose of the experiment: the product is subjected to acid mist test to test the corrosion resistance
The experimental method comprises the following steps:
tool: acid mist testing machine
Spraying a 5% hydrogen chloride solution with the humidity of more than 85% and the pH value of 1.5-1.2 in a closed environment at 35 ℃, taking out, washing with clear water, naturally drying at normal temperature for 2 hours, performing a check test, and checking the appearance of the product.
Detection standard: observing whether the plating layer on the surface of the product is corroded, discolored, chapped, peeled and the like.
And (4) experimental conclusion:
after the product is subjected to a salt spray test for 200H, the surface is free from corrosion, discoloration, shedding and peeling, and the test result is qualified.
Claims (8)
1. A dense oxidation process for the surface of an aluminum alloy under a constant ion gradient is characterized by comprising the following steps:
step 1: pretreating the surface of the aluminum alloy;
step 2: placing an aluminum alloy device in an anodic oxidation solution, and alternately applying an oxidation voltage pulse and an ultrasonic vibration pulse to carry out anodic oxidation, wherein the ultrasonic vibration source is the aluminum alloy device;
and step 3: sealing an oxide film formed by anodic oxidation on the surface of the aluminum alloy by adopting a high molecular polymer;
in the step 2, the time width of the oxidation voltage pulse is 15-75 ms; the time width of the ultrasonic vibration pulse is 100-1200 ms; in the step 2, the frequency of the ultrasonic vibration pulse is 100-120 Hz, and the peak intensity of the pulse current is 1A-1.5A/dm2。
2. The process for dense oxidation of the surface of the aluminum alloy under the constant ion gradient as claimed in claim 1, wherein the vibration source of the ultrasonic vibration pulse in the step 2 is the aluminum alloy device, that is, the ultrasonic vibration device and the aluminum alloy device are fixed into a whole, and the ultrasonic wave is transmitted through the vibration of the aluminum alloy device.
3. The aluminum alloy surface dense oxidation process under the constant ion gradient as in claim 1, wherein the solution for anodic oxidation in the step 2 is an acidic mixed solution, and the components comprise 2-8% of sulfate, 5-10% of nitrate and 1-5% of fluoride; wherein the sulfate is selected from sodium sulfate, the nitrate is selected from sodium nitrate, and the fluoride is selected from ammonium bifluoride.
4. The process for densifying the surface of an aluminum alloy under a constant ion gradient as defined in claim 1, wherein the high molecular polymer in step 3 is selected from polyurethane with a concentration of 10-50 wt%.
5. The process for densifying the surface of an aluminum alloy under a constant ion gradient as defined in claim 1, wherein the step of pretreating the surface of the aluminum alloy in step 1 comprises: oil removal, alkaline etching, acid washing and surface grinding.
6. The dense oxidation process for the surface of an aluminum alloy under a constant ion gradient according to claim 5, wherein the degreasing process step comprises: degreasing in an alkaline degreasing agent for 180-300 seconds at 40-60 ℃; the alkaline degreasing agent comprises 2-15wt% of sodium carbonate and 3-12wt% of trisodium phosphate.
7. The process for densifying an aluminum alloy surface with a constant ion gradient according to claim 5, wherein the alkaline etching process step comprises: cleaning for 15-30 seconds in an alkali solution at 25-50 ℃; the alkali solution is sodium hydroxide water solution with the concentration of 5wt% -8 wt%.
8. The process for densifying the surface of an aluminum alloy with a constant ion gradient according to claim 5, wherein the pickling process step comprises: adding an acid solution, adjusting the aluminum alloy soaking solution to be neutral, and removing a black oxide film on the surface layer; the acid solution is a nitric acid solution, and the concentration is 10-20 wt%.
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