CN114481147A - Environment-friendly aviation aluminum alloy anodic oxidation pretreatment deoxidizing solution and deoxidizing method - Google Patents
Environment-friendly aviation aluminum alloy anodic oxidation pretreatment deoxidizing solution and deoxidizing method Download PDFInfo
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- CN114481147A CN114481147A CN202210354404.5A CN202210354404A CN114481147A CN 114481147 A CN114481147 A CN 114481147A CN 202210354404 A CN202210354404 A CN 202210354404A CN 114481147 A CN114481147 A CN 114481147A
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- aluminum alloy
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
- C23G1/16—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions using inhibitors
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
- C23G1/22—Light metals
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/04—Anodisation of aluminium or alloys based thereon
- C25D11/16—Pretreatment, e.g. desmutting
Abstract
The environment-friendly aviation aluminum alloy anodic oxidation pretreatment deoxidizing solution consists of sodium carbonate, sodium hydroxide, a corrosion inhibitor, a leveling agent and a surfactant, and the mass concentration of the deoxidizing solution is as follows in sequence: 70-90 g/L, 7-10 g/L, 10-20 g/L, 15-20 g/L and 0.5-1 g/L. The deoxidation method comprises the steps of putting the deoiled aluminum alloy into a deoxidation solution for deoxidation treatment for 3-9 min, controlling the pH of the deoxidation solution to be 12.5-13.5 and the temperature to be 50-60 ℃; and then, washing with deionized water, and performing light extraction treatment in 30wt% nitric acid at room temperature for 30-70 s. The deoxidizing solution does not contain hexavalent chromium and fluoride ions, is beneficial to the health and environment of operators, and has a deoxidizing effect capable of meeting the deoxidizing requirement of aluminum alloy anodic oxidation pretreatment.
Description
Technical Field
The invention relates to a deoxidizing solution for pretreatment of anodic oxidation of an environment-friendly aviation aluminum alloy and a deoxidizing method, and particularly belongs to the technical field of aluminum alloy surface treatment.
Background
The aviation aluminum material is an ultrahigh-strength wrought aluminum alloy and has a severe service environment. For example, the commonly used 2024 aluminum alloy on an airplane contains 4% of copper and less than 93% of aluminum, alloy elements such as copper and the like for improving the mechanical property of the aluminum alloy are added, the microstructure of the aluminum alloy is not uniform due to heat treatment, the corrosion resistance of the aluminum alloy is reduced, and anodic oxidation is the most commonly used surface treatment means for improving the corrosion resistance of the aviation aluminum alloy material. The aluminum alloy can generate a layer of oxide film in natural environment, and the existence of the oxide film can influence the growth process of the aluminum alloy anode oxide film, thereby influencing the performance of the anode oxide film. Therefore, it is necessary to perform deoxidation treatment to remove a natural oxide film on the surface of the aluminum alloy, that is, deoxidation treatment before anodic oxidation of the aluminum alloy.
The aluminium alloy deoxidation solution adopted by the aviation industry of China is HNO3Chromic anhydride and HF are prepared according to a certain proportion (short for three-acid deoxidation). Tri-acid deoxidation etches the oxide, Cr, on the substrate surface by HF6+Can effectively inhibit the corrosion rate of HF on a substrate, HNO3The main function of the cleaning agent is to remove hanging ash. The aviation aluminum alloy after the three-acid deoxidation treatment has uniform and smooth surface and few defects, and provides favorable conditions for subsequent surface treatment such as anodic oxidation and the like. CN202110386092.1 proposes a chemical oxidation method of aluminum alloy, and the pretreatment deoxidation treatment adopts triacid to carry out deoxidation. The deoxidation treatment before the chemical milling processing of CN201811582641.7 and CN201410009213.0 aviation aluminum alloy also adopts the three-acid deoxidation treatment, but Cr in the three-acid deoxidation liquid6+Toxic and carcinogenic. The improved three-acid deoxidation process of magantin, etc. can retain nitric acid and hydrofluoric acid, and at the same time can use ferric sulfate and additive to substitute chromic anhydride. The hydrofluoric acid contained in the process is toxic and strong in irritation, so that certain potential safety production hazards are caused. Obviously, the deoxidation process of the chromium/fluorine-containing aluminum alloy is replaced by a more environment-friendly process, so that a safe and environment-friendly deoxidation solution and a deoxidation method for aviation aluminum alloy anodic oxidation pretreatment are urgently needed at present.
Disclosure of Invention
On the premise of meeting the requirement of deoxidation of aviation aluminum alloy, the invention provides an environment-friendly deoxidation solution and a deoxidation method for pretreatment of anodic oxidation of aviation aluminum alloy in order to solve the problem of high pollution of the existing deoxidation solution for aviation aluminum alloy.
The environment-friendly aviation aluminum alloy anodic oxidation pretreatment deoxidizing solution consists of sodium carbonate, sodium hydroxide, a corrosion inhibitor, a leveling agent and a surfactant, and the mass concentration of the deoxidizing solution is as follows in sequence: 70-90 g/L, 7-10 g/L, 10-20 g/L, 15-20 g/L and 0.5-1 g/L.
The deoxidation method of the deoxidation solution comprises the following two steps:
step 1: putting the deoiled aluminum alloy into a deoxidizing solution for deoxidizing for 3-9 min, and controlling the pH of the deoxidizing solution to be 12.5-13.5 and the temperature to be 50-60 ℃;
step 2: and (3) cleaning the aluminum alloy treated in the step (1) by using deionized water, and then carrying out light extraction treatment in 30wt% of nitric acid for 30-70 s at room temperature.
The corrosion inhibitor is one or the combination of two of sodium molybdate and sodium nitrate.
The leveling agent is thiourea.
The surfactant is sodium dodecyl sulfate.
The aluminum alloy is 2000 series aluminum alloy, 7000 series aluminum alloy or 6000 series aluminum alloy.
Aluminum alloys are amphoteric metals that react with alkali. The reaction speed of the strong alkali and the aluminum alloy is high, which easily causes the over corrosion of the aluminum alloy to cause the surface roughness (see figure 3 of example 6), so the invention adopts the sodium carbonate with higher concentration and alkalescence. Sodium carbonate hydrolysis in aqueous solution, CO ionization3 2-With H in water+Combined into HCO3 -So that the aqueous solution of sodium carbonate is alkaline. In addition, sodium carbonate also serves as a buffer. Due to sodium carbonate solution OH-The concentration is low, the reaction of the aluminum alloy is slow, and the reaction speed can be accelerated after a small amount of sodium hydroxide is added.
Sodium molybdate can form a neutral aluminum molybdate compound with aluminum to cover the surface of the aluminum to form a protective corrosion inhibition film, so that corrosion is reduced. Sodium nitrate is an oxidizing corrosion inhibitor that forms a passive film on the metal surface, thereby producing a corrosion inhibiting effect. In the deoxidizing solution, sodium molybdate and sodium nitrate are added to stabilize the corrosion reaction speed of the aluminum alloy.
Thiourea can form a layer of thick mucosa or passive film on the surface of the aluminum alloy to protect the concave part and avoid over-high dissolution, and the dissolution speed of the microcosmic convex part of the surface is obviously higher than that of the concave part, so that the roughness of the surface is reduced, and the surface of the aluminum alloy tends to be flat in the corrosion process.
Sodium dodecyl sulfate is an anionic surfactant, and can reduce the interfacial tension of the solution, so that hydrogen bubbles generated by corrosion reaction are difficult to stay on the surface of the aluminum alloy. Therefore, the sodium dodecyl sulfate can reduce the defects of the aluminum alloy surface caused by hydrogen bubbles in the deoxidation process.
The surface of the aluminum alloy after the deoxidation treatment has black hanging ash which is caused by precipitation of alloy elements such as copper and the like in the aluminum alloy, and the hanging ash can be removed by adopting 30wt% of nitric acid to obtain a bright aluminum alloy surface.
The invention has the beneficial effects that:
1. the deoxidizing solution disclosed by the invention does not contain hexavalent chromium and fluoride ions, is beneficial to the health and environment of operators, can meet the deoxidizing requirement of aluminum alloy pretreatment before anodic oxidation, and can effectively overcome the problems of toxic carcinogenesis, no environmental pollution and the like of the traditional triacid deoxidizing solution process.
2. Compared with the three-acid deoxidation, the deoxidation effect of the deoxidation liquid has no obvious difference on the metallographic morphology of the surface of the aluminum alloy (see the figure 1 and the figure 2 in particular), and after sulfuric acid anodic oxidation and sealing are carried out subsequently, no corrosion is caused after a neutral salt spray test is carried out for 800 h.
Drawings
FIG. 1 shows the metallographic morphology of a sample of a 2024-T3 aluminum alloy treated by deoxidation with a conventional triacid deoxidation solution according to example 1 of the present invention;
FIG. 2 is a metallographic structure of a sample of 2024-T3 aluminum alloy subjected to deoxidation treatment by using a deoxidation solution in example 2 of the present invention;
FIG. 3 is the metallographic morphology of a sample of 2024-T3 aluminum alloy treated by NaOH alone as a deoxidizing solution in example 6 of the present invention;
FIG. 4 is a macroscopic view of a sample of 2024-T3 aluminum alloy treated by deoxidation with a deoxidation solution according to example 2 of the present invention;
FIG. 5 shows the results of the 800-hour neutral salt spray test performed on the aluminum alloy test piece subjected to deoxidation treatment with the deoxidation solution and 2024-T3 in example 2 of the present invention after sulfuric acid anodizing and sealing treatment.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Example 1
The traditional formula of the triacid deoxygenation solution is as follows: HNO3The aluminum alloy with the model number of 2024-T3 was deoxidized with the concentration of 100ml/L, the concentration of chromic anhydride of 50g/L and the concentration of HF of 10 ml/L.
The traditional triacid deoxygenation liquid is prepared by controlling the deoxygenation treatment temperature to be 20 ℃ and the deoxygenation time to be 3 min.
Example 2
The formula of the deoxidation solution is as follows: the sodium carbonate concentration is 80g/L, the sodium hydroxide concentration is 8g/L, the sodium molybdate concentration is 2g/L, the sodium nitrate concentration is 10g/L, the thiourea concentration is 20g/L, the sodium dodecyl sulfate concentration is 0.6g/L, and the aluminum alloy with the model number of 2024-T3 is subjected to deoxidation treatment.
The pH value of the deoxygenation liquid is 13.5, the deoxygenation treatment temperature is controlled to be 55 ℃, and the deoxygenation time is 3 min; then at 30wt% HNO3The solution was subjected to a light extraction treatment for 50 s.
Example 3
The formula of the deoxidation solution is as follows: the concentration of sodium carbonate is 70g/L, the concentration of sodium hydroxide is 7g/L, the concentration of sodium molybdate is 1g/L, the concentration of sodium nitrate is 12g/L, the concentration of thiourea is 15g/L, the concentration of sodium dodecyl sulfate is 0.7g/L, and the aluminum alloy with the model number of 6061 is deoxidized.
The pH of the deoxygenation liquid is 12.5, the temperature is controlled to be 60 ℃, and the deoxygenation time is 6 min; then the light extraction treatment is carried out for 30 s in a 30wt% HNO3 solution.
Example 4
The formula of the deoxidation solution is as follows: the concentration of sodium carbonate is 70g/L, the concentration of sodium hydroxide is 7g/L, the concentration of sodium molybdate is 3g/L, the concentration of sodium nitrate is 15g/L, the concentration of thiourea is 20g/L, the concentration of sodium dodecyl sulfate is 0.5g/L, and the aluminum alloy with the model number of 6063 is deoxidized.
The pH of the deoxygenation liquid is 12.8, the temperature is controlled to be 60 ℃, and the deoxygenation time is 8 min; then, the solution of 30wt% HNO3 was treated for 40 s to give a gloss.
Example 5
The formula of the deoxidation solution is as follows: the concentration of sodium carbonate is 90g/L, the concentration of sodium hydroxide is 8g/L, the concentration of sodium molybdate is 3g/L, the concentration of sodium nitrate is 17g/L, the concentration of thiourea is 20g/L, the concentration of sodium dodecyl sulfate is 0.9g/L, and the aluminum alloy with the model number of 7075 is deoxidized.
The pH of the deoxygenation liquid is 13.1, the temperature is controlled to be 57 ℃, and the deoxygenation time is 9 min; then the light extraction treatment is carried out for 60 s in a 30wt% HNO3 solution.
Example 6
The NaOH deoxidation solution comprises the following components: the NaOH concentration was 50g/L, and the aluminum alloy model 2024-T3 was subjected to deoxidation treatment.
And controlling the temperature of NaOH deoxygenation liquid at 45 ℃ and the deoxygenation time at 3 min.
The implementation effect of the invention is shown in figures 1-5.
FIGS. 1 and 2 are metallographic photographs of the aluminum alloy 2024-T3 that was deoxidized using examples 1 and 2, respectively. As can be seen from the figures 1 and 2, the shape after deoxidation of the embodiment 2 is very similar to the shape of deoxidation of the traditional triacid deoxidation liquid, and the surface of the aluminum alloy is relatively flat. FIG. 3 is a metallographic photograph of 2024-T3 deoxidized with sodium hydroxide. As can be seen from FIG. 3, the surface of the aluminum alloy after deoxidation by sodium hydroxide has a large number of defects, and the deoxidation effect is far inferior to that of the example 2 and the three-acid deoxidation. As can be seen from FIG. 4, the surface of the 2024-T3 aluminum alloy treated by the method of the embodiment 2 is flat and bright, and can meet the requirements of anodic oxidation production of aviation aluminum alloy.
As can be seen in FIG. 5, the samples of the 2024-T3 aluminum alloy treated in example 2 were sulfuric acid anodized and blocked, and tested by the neutral salt spray test to achieve 800 hours before corrosion, which is 336 hours far beyond the standard, indicating that the deoxidation of embodiment 2 can be used for the pretreatment of the anodic oxidation of the 2024-T3 aluminum alloy.
The above examples only express embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (6)
1. The environment-friendly aviation aluminum alloy anodic oxidation pretreatment deoxidizing solution is characterized in that: the deoxidizing solution consists of sodium carbonate, sodium hydroxide, a corrosion inhibitor, a leveling agent and a surfactant, and the mass concentration of the deoxidizing solution is as follows in sequence: 70-90 g/L, 7-10 g/L, 10-20 g/L, 15-20 g/L and 0.5-1 g/L.
2. The environment-friendly aviation aluminum alloy anodic oxidation pretreatment deoxidizing solution as claimed in claim 1, wherein the deoxidizing solution comprises: the deoxidation method of the deoxidation solution comprises the following two steps:
step 1: putting the aluminum alloy subjected to oil removal and cleaning into a deoxidizing solution for deoxidizing for 3-9 min, and controlling the pH of the deoxidizing solution to be 12.5-13.5 and the temperature to be 50-60 ℃;
step 2: and (2) cleaning the aluminum alloy treated in the step (1) by using deionized water, and then performing bright dipping treatment in 30wt% of nitric acid for 30-70 s at room temperature.
3. The environment-friendly aviation aluminum alloy anodic oxidation pretreatment deoxidizing solution as claimed in claim 1, wherein the deoxidizing solution comprises: the corrosion inhibitor is one or the combination of two of sodium molybdate and sodium nitrate.
4. The environmental-friendly aviation aluminum alloy anodic oxidation pretreatment deoxidizing solution as claimed in claim 1, wherein the deoxidizing solution comprises: the leveling agent is thiourea.
5. The environment-friendly aviation aluminum alloy anodic oxidation pretreatment deoxidizing solution as claimed in claim 1, wherein the deoxidizing solution comprises: the surfactant is sodium dodecyl sulfate.
6. The environment-friendly aviation aluminum alloy anodic oxidation pretreatment deoxidizing solution as claimed in claim 1, wherein the deoxidizing solution comprises: the aluminum alloy is 2000 series aluminum alloy, 7000 series aluminum alloy or 6000 series aluminum alloy.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3728188A (en) * | 1971-07-29 | 1973-04-17 | Amchem Prod | Chrome-free deoxidizing and desmutting composition and method |
| CN102965709A (en) * | 2012-10-18 | 2013-03-13 | 北京航空航天大学 | Environmental long-term pre-treatment process for surface anodization of aluminum alloy |
| US20130270120A1 (en) * | 2011-06-24 | 2013-10-17 | Apple Inc. | Cosmetic defect reduction in anodized parts |
| CN103498180A (en) * | 2013-08-23 | 2014-01-08 | 北京星航机电装备有限公司 | Environment-friendly anodic oxidation pretreatment process |
| CN110373699A (en) * | 2019-08-22 | 2019-10-25 | 南昌航空大学 | A kind of ZL105 aluminium alloy sand casting hard anodizing electrolyte and method for oxidation |
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2022
- 2022-04-06 CN CN202210354404.5A patent/CN114481147A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3728188A (en) * | 1971-07-29 | 1973-04-17 | Amchem Prod | Chrome-free deoxidizing and desmutting composition and method |
| US20130270120A1 (en) * | 2011-06-24 | 2013-10-17 | Apple Inc. | Cosmetic defect reduction in anodized parts |
| CN102965709A (en) * | 2012-10-18 | 2013-03-13 | 北京航空航天大学 | Environmental long-term pre-treatment process for surface anodization of aluminum alloy |
| CN103498180A (en) * | 2013-08-23 | 2014-01-08 | 北京星航机电装备有限公司 | Environment-friendly anodic oxidation pretreatment process |
| CN110373699A (en) * | 2019-08-22 | 2019-10-25 | 南昌航空大学 | A kind of ZL105 aluminium alloy sand casting hard anodizing electrolyte and method for oxidation |
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