CN110983411A - Preparation method of natural color conversion film on surface of aluminum alloy - Google Patents
Preparation method of natural color conversion film on surface of aluminum alloy Download PDFInfo
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- 229910000838 Al alloy Inorganic materials 0.000 title claims abstract description 99
- 238000006243 chemical reaction Methods 0.000 title claims abstract description 22
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 230000003647 oxidation Effects 0.000 claims abstract description 31
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 31
- 238000000034 method Methods 0.000 claims abstract description 30
- 238000007739 conversion coating Methods 0.000 claims abstract 5
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 45
- 238000005406 washing Methods 0.000 claims description 29
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 29
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 27
- 229910017604 nitric acid Inorganic materials 0.000 claims description 27
- 238000004040 coloring Methods 0.000 claims description 23
- 239000007788 liquid Substances 0.000 claims description 23
- 230000032683 aging Effects 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 17
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 claims description 16
- 239000000126 substance Substances 0.000 claims description 12
- 238000004140 cleaning Methods 0.000 claims description 10
- 238000005530 etching Methods 0.000 claims description 10
- 239000011609 ammonium molybdate Substances 0.000 claims description 9
- APUPEJJSWDHEBO-UHFFFAOYSA-P ammonium molybdate Chemical compound [NH4+].[NH4+].[O-][Mo]([O-])(=O)=O APUPEJJSWDHEBO-UHFFFAOYSA-P 0.000 claims description 9
- 235000018660 ammonium molybdate Nutrition 0.000 claims description 9
- 229940010552 ammonium molybdate Drugs 0.000 claims description 9
- RSYUFYQTACJFML-DZGCQCFKSA-N afzelechin Chemical compound C1([C@H]2OC3=CC(O)=CC(O)=C3C[C@@H]2O)=CC=C(O)C=C1 RSYUFYQTACJFML-DZGCQCFKSA-N 0.000 claims description 8
- 239000003513 alkali Substances 0.000 claims description 8
- 238000002791 soaking Methods 0.000 claims description 8
- 239000011775 sodium fluoride Substances 0.000 claims description 8
- 235000013024 sodium fluoride Nutrition 0.000 claims description 8
- 150000003754 zirconium Chemical class 0.000 claims description 8
- 238000005237 degreasing agent Methods 0.000 claims description 7
- 239000013527 degreasing agent Substances 0.000 claims description 7
- 238000007598 dipping method Methods 0.000 claims description 7
- 230000003746 surface roughness Effects 0.000 claims description 7
- 238000000605 extraction Methods 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 239000000956 alloy Substances 0.000 abstract description 6
- 230000007797 corrosion Effects 0.000 abstract description 6
- 238000005260 corrosion Methods 0.000 abstract description 6
- 229910045601 alloy Inorganic materials 0.000 abstract description 5
- 230000007935 neutral effect Effects 0.000 abstract description 5
- 150000003839 salts Chemical class 0.000 abstract description 5
- 239000007921 spray Substances 0.000 abstract description 5
- 238000004381 surface treatment Methods 0.000 abstract description 5
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 238000009776 industrial production Methods 0.000 abstract description 2
- 231100000331 toxic Toxicity 0.000 abstract description 2
- 230000002588 toxic effect Effects 0.000 abstract description 2
- 238000002161 passivation Methods 0.000 description 11
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 10
- 229910052782 aluminium Inorganic materials 0.000 description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 8
- 238000005238 degreasing Methods 0.000 description 6
- 239000000843 powder Substances 0.000 description 6
- 230000002431 foraging effect Effects 0.000 description 5
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 239000011651 chromium Substances 0.000 description 4
- 238000003754 machining Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000003801 milling Methods 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 238000005488 sandblasting Methods 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 239000012378 ammonium molybdate tetrahydrate Substances 0.000 description 1
- FIXLYHHVMHXSCP-UHFFFAOYSA-H azane;dihydroxy(dioxo)molybdenum;trioxomolybdenum;tetrahydrate Chemical compound N.N.N.N.N.N.O.O.O.O.O=[Mo](=O)=O.O=[Mo](=O)=O.O=[Mo](=O)=O.O=[Mo](=O)=O.O[Mo](O)(=O)=O.O[Mo](O)(=O)=O.O[Mo](O)(=O)=O FIXLYHHVMHXSCP-UHFFFAOYSA-H 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 238000005282 brightening Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000012994 industrial processing Methods 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 229910001234 light alloy Inorganic materials 0.000 description 1
- 239000002932 luster Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000007745 plasma electrolytic oxidation reaction Methods 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
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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
- C25D11/14—Producing integrally coloured layers
-
- 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
- C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
- C25D11/08—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids
-
- 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
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- Chemical Kinetics & Catalysis (AREA)
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Abstract
The invention discloses a preparation method of an aluminum alloy surface natural color conversion film, and belongs to the technical field of alloy surface treatment. The method of the invention adopts the method of generating the conversion coating on the surface of the aluminum alloy, so that the electronic product taking the aluminum alloy as the structural member effectively meets the electromagnetic shielding performance requirement, has certain corrosion resistance, and is widely applied to the fields of electronic products, aerospace, marine traffic and the like. The method has stable technological parameters and formula, the toxic harmfulness of the method is far less than that of the traditional manufacturing method, and the aluminum alloy surface conversion film manufactured by the method has better conductivity, better neutral salt spray resistance and uniform film color; the invention has high production efficiency, the once qualified rate of conductive oxidation of the obtained aluminum alloy product can reach 91 percent, and the invention is beneficial to large-scale industrial production.
Description
Technical Field
The invention relates to a preparation method of an aluminum alloy surface natural color conversion film, and belongs to the technical field of alloy surface treatment.
Background
The aluminum and the alloy thereof have the advantages of high specific strength, good heat conductivity and electrical conductivity, beautiful color, easy forming and processing, excellent physical and chemical properties, low price and the like, are widely applied to departments of aerospace, transportation, building and the like, and are the most widely applied and used alloys in light alloys. Although the surface of aluminum and its alloy is easy to form a thin and dense oxide film in the atmosphere medium, which has a certain corrosion resistance, its thickness is limited, about 5-200nm, and the film is amorphous, and is easy to be damaged during processing and transportation, and is easy to be contaminated. Meanwhile, the aluminum alloy material has low hardness and poor wear resistance, so that the aluminum alloy is often worn, corroded and damaged, and the aluminum alloy product can be a finished product only after being subjected to surface treatment.
Common aluminum surface treatment methods include anodic oxidation, chemical oxidation, micro-arc oxidation and the like. The chemical oxidation method has the advantages of small influence on the fatigue property of the aluminum workpiece, simple equipment, no need of electric energy, low cost, short treatment time, high production efficiency, low requirement on a base material, suitability for surface treatment of complex parts and the like, and is widely applied. Hexavalent chromium passivation films have been used to date because of their excellent properties. However, hexavalent chromium is a highly toxic material ranked at the 17 th position in the most dangerous material table of the united states Environmental Protection Agency (EPA), and the electric and electronic products released to the european union market after 7/1 2006 are required by the european union RoHS directive and must not contain harmful substances such as hexavalent chromium. The harm of hexavalent chromium compounds to the environment has prompted active research on effective replacement techniques for hexavalent chromium passivation. The replacement research work of aluminum alloy hexavalent chromium passivation mainly adopts trivalent chromium passivation and chromium-free passivation. At present, the research time of the chromium-free passivation process is short, the passivation mechanism is not clear, the corrosion resistance and the appearance are inferior to those of hexavalent chromium passivation, and the requirement of high corrosion resistance cannot be met, so the application in industry is limited. The passivation film obtained by trivalent chromium passivation has white and bright color, high hardness and excellent mechanical property, the dispersion performance and the covering capacity of the passivation film are far higher than those of hexavalent chromium, more importantly, the toxicity of the trivalent chromium is only l% of that of the hexavalent chromium, the trivalent chromium conversion film accords with RoHS regulations, and the wastewater is easy to treat, thereby being the most promising conversion film for replacing the hexavalent chromium conversion film. The method has the advantages of high film density, uniform film, high production efficiency, low production cost and contribution to large-scale industrial processing, and the neutral salt spray resistance test can reach more than 220 h.
Disclosure of Invention
The invention aims to provide a preparation method of an aluminum alloy surface natural color conversion film aiming at the defects of the prior art, wherein an aluminum alloy product has metallic appearance and meets the requirement of electromagnetic shielding performance, and the neutral salt spray resistant time reaches 220 hours which is far beyond the military standard, and the preparation method specifically comprises the following steps:
(1) and (3) carrying out oil removal, alkaline etching and nitric acid polishing treatment on the aluminum alloy with the surface roughness Ra of 4 grade or above for later use.
(2) Conductive oxidation coloring: putting the aluminum alloy after the light extraction into a prepared conductive oxidation liquid at the temperature of 25-35 ℃ for coloring treatment for 3-5 min, and washing the aluminum alloy with cold water at normal temperature for 3-5 s; the content and the proportion of the conductive oxidation liquid are as follows: 2-3 g/L of chromium potassium sulfate, 0.5-1 g/L of zirconium salt, 0.3-0.8 g/L of ammonium molybdate, 2.5-5 g/L of sodium fluoride, 3-20 ml/L of nitric acid with the mass percentage concentration of 30% and 5-10 ml/L of sodium hydroxide with the mass percentage concentration of 40%.
(3) And (5) drying the aluminum alloy subjected to coloring cleaning, and carrying out aging treatment to obtain a finished product.
Preferably, the specific process of degreasing in the invention is as follows: soaking the aluminum alloy in a chemical degreasing agent at the temperature of 50-65 ℃ for 1-3 min, and cleaning the aluminum alloy with cold water at normal temperature for 1-3 min, wherein the degreasing agent is prepared from 50-70 g/L of chemical degreasing powder (industrial grade); the oil removal aims at thoroughly removing oil stains on the surface of the material and cleaning the surface, and the specific oil removal time can be adjusted according to the amount of the oil stains on the surface.
Preferably, the specific process of the alkaline etching of the invention is as follows: and (3) placing the aluminum alloy subjected to oil removal treatment into a sodium hydroxide solution with the mass percent concentration of 60% and the temperature of 40-60 ℃ to soak for 50-60 s, and washing with cold water at normal temperature for 3-5 min.
Preferably, the nitric acid light extraction process of the invention comprises the following steps: and (3) placing the aluminum alloy subjected to alkali washing treatment into normal-temperature nitric acid brightening liquid for treatment for 3-5 min, washing the aluminum alloy for 1-2 min at normal temperature by cold water, wherein the mass percentage concentration of the nitric acid is 45% -60%, and the nitric acid is favorable for removing the black film on the surface after alkali etching and enables the surface to have luster.
Preferably, the aging condition is aging in an oven at 55-65 ℃ for 6-10 min, and the aging treatment can effectively improve the adhesive force of the natural-color oxide film on the aluminum alloy.
All percentages in the present invention are mass percentages unless otherwise specified.
Ammonium molybdate according to the present invention is preferably ammonium molybdate tetrahydrate.
The invention has the beneficial effects that:
according to the invention, ammonium molybdate is added as a reasonable corrosion inhibitor of the conductive oxidation liquid, so that the film growth is uniform in the film forming process, the film is found to be compact and the corrosion resistance is obviously improved by observing under a scanning electron microscope, nitric acid is used as a film forming promoter, the film generation time is short, the production efficiency is greatly improved, and the reasonable aging process is added, and important process parameters in each process step are adjusted simultaneously, so that the film has firmer adhesive force, the treated aluminum alloy product has metal texture in appearance, meets the requirement of electromagnetic shielding performance, the formed aluminum alloy natural color oxidation film has excellent performance, the neutral salt spray resistance time reaches 220h and far exceeds the military standard; the method has high production efficiency, the color of the obtained aluminum alloy surface conversion film is the natural color of the aluminum alloy, the primary qualified rate of conductive oxidation can reach 91 percent, and the method is favorable for large-scale industrial production.
Drawings
FIG. 1 is a scanning electron micrograph of a natural-color conversion film on the surface of an aluminum alloy prepared in comparative example 1;
FIG. 2 is a scanning electron micrograph of a natural color conversion film of the aluminum alloy prepared in example 3.
Detailed Description
The invention will be described in more detail with reference to the following figures and examples, but the scope of the invention is not limited thereto.
Example 1
A preparation method of an aluminum alloy surface natural color conversion film comprises the following process steps:
(1) sand blasting: the surface of the aluminum alloy was subjected to sand blasting with 140 mesh glass beads under a pressure of 500KPa to control the surface roughness Ra to 4 levels.
(2) Oil removal: the aluminum alloy after sand blasting is put into a degreasing agent (prepared by industrial grade chemical degreasing powder) with the temperature of 50 ℃ and the concentration of 50g/L for soaking for 1min, and then is cleaned for 3min at normal temperature by cold water.
(3) Alkaline etching: and (3) soaking the aluminum alloy subjected to the oil removal treatment in a sodium hydroxide solution at the temperature of 40 ℃ for 50s, and washing the aluminum alloy with cold water at normal temperature for 3 min.
(4) Nitric acid light emission: and (3) putting the aluminum alloy subjected to alkali washing treatment into nitric acid bright dipping liquid with the mass percentage concentration of 45% for treatment for 3min, and washing with cold water at normal temperature for 1 min.
(5) Conductive oxidation coloring: putting the bright aluminum alloy into a conductive oxidation liquid at the temperature of 25 ℃ for coloring treatment for 3min, and washing the aluminum alloy for 3s at normal temperature by cold water; the conductive oxidation liquid comprises the following components in percentage by weight: 2g/L of chromium potassium sulfate, 0.5g/L of zirconium salt, 0.3g/L of ammonium molybdate, 2.5g/L of sodium fluoride, 3ml/L of 30% nitric acid and 5ml/L of 40% sodium hydroxide.
(6) Drying: and drying the aluminum alloy subjected to coloring cleaning by using a compressed air gun.
(7) Aging: and (4) putting the dried aluminum alloy into a drying oven with the temperature of 55 ℃ for aging, and aging for 10min to obtain a finished product.
Example 2
A preparation method of an aluminum alloy surface natural color conversion film comprises the following process steps:
(1) and (3) machining: the surface of the aluminum block is milled by a milling machine for 2cm in thickness, so that the surface roughness Ra is controlled to be 4 levels.
(2) Oil removal: the aluminum alloy with the milled surface is placed into an oil removing agent (prepared by industrial grade chemical oil removing powder) with the temperature of 50 ℃ and the concentration of 55g/L to be soaked for 1.5min, and then the aluminum alloy is cleaned for 1min at normal temperature by cold water.
(3) Alkaline etching: and (3) soaking the aluminum alloy subjected to the oil removal treatment in a sodium hydroxide solution at the temperature of 45 ℃ for 50s, and washing the aluminum alloy with cold water at normal temperature for 5 min.
(4) Nitric acid light emission: and (3) putting the aluminum alloy subjected to alkali washing treatment into nitric acid bright dipping liquid with the mass percentage concentration of 45% for treatment for 5min, and washing with cold water at normal temperature for 2 min.
(5) Conductive oxidation coloring: putting the bright aluminum alloy into a conductive oxidation liquid at the temperature of 30 ℃ for coloring treatment for 4min, and washing the aluminum alloy with cold water at normal temperature for 5 s; the conductive oxidation liquid comprises the following components in percentage by weight: 2.5g/L of chromium potassium sulfate, 0.5g/L of zirconium salt, 0.5g/L of ammonium molybdate, 3g/L of sodium fluoride, 6ml/L of 30% nitric acid and 6ml/L of 40% sodium hydroxide.
(6) Drying: and drying the aluminum alloy subjected to coloring cleaning by using a compressed air gun.
(7) Aging: and (3) putting the dried aluminum alloy into a drying oven with the temperature of 60 ℃ for aging, and aging for 10min to obtain a finished product.
Example 3
A preparation method of an aluminum alloy surface natural color conversion film comprises the following process steps:
(1) and (3) machining: the surface of the aluminum block is milled by a milling machine for 3cm in thickness, so that the surface roughness Ra is controlled to be 5 level.
(2) Oil removal: the aluminum alloy with the milled surface is placed into a degreasing agent (prepared by industrial grade chemical degreasing powder) with the temperature of 55 ℃ and the concentration of 60g/L to be soaked for 2min, and then the aluminum alloy is cleaned with cold water at normal temperature for 2 min.
(3) Alkaline etching: and (3) putting the aluminum alloy subjected to the oil removal treatment into a sodium hydroxide solution at the temperature of 50 ℃ for soaking for 55s, and washing with cold water at normal temperature for 3 min.
(4) Nitric acid light emission: and (3) putting the aluminum alloy subjected to alkali washing treatment into nitric acid bright dipping liquid with the mass percentage concentration of 50% for treatment for 3min, and washing the aluminum alloy for 1min at normal temperature by cold water.
(5) Conductive oxidation coloring: putting the bright aluminum alloy into a conductive oxidation liquid at the temperature of 35 ℃ for coloring treatment for 5min, and washing the aluminum alloy for 5s at normal temperature by cold water; the conductive oxidation liquid comprises the following components in percentage by weight: 3g/L of chromium potassium sulfate, 1g/L of zirconium salt, 0.6g/L of ammonium molybdate, 3g/L of sodium fluoride, 8ml/L of 30% nitric acid and 8ml/L of 40% sodium hydroxide.
(6) Drying: and drying the aluminum alloy subjected to coloring cleaning by using a compressed air gun.
(7) Aging: and (3) putting the dried aluminum alloy into a drying oven with the temperature of 65 ℃ for aging, and aging for 8min to obtain a finished product.
Example 4
A preparation method of an aluminum alloy surface natural color conversion film comprises the following process steps:
(1) and (3) machining: the surface of the aluminum block is milled by a milling machine to a thickness of 5cm, so that the surface roughness Ra is controlled to be 6 grades.
(2) Oil removal: the aluminum alloy with the milled surface is placed into a 60g/L degreasing agent (prepared by industrial grade chemical degreasing powder) with the temperature of 60 ℃ to be soaked for 3min, and then is cleaned with cold water at normal temperature for 2 min.
(3) Alkaline etching: and (3) soaking the aluminum alloy subjected to the oil removal treatment in a sodium hydroxide solution at the temperature of 50 ℃ for 60s, and washing the aluminum alloy with cold water at normal temperature for 3 min.
(4) Nitric acid light emission: and (3) putting the aluminum alloy subjected to alkali washing treatment into nitric acid bright dipping liquid with the mass percentage concentration of 55% for treatment for 4min, and washing with cold water at normal temperature for 1 min.
(5) Conductive oxidation coloring: putting the bright aluminum alloy into a conductive oxidation liquid at the temperature of 35 ℃ for coloring treatment for 5min, and washing the aluminum alloy for 5s at normal temperature by cold water; the conductive oxidation liquid comprises the following components in percentage by weight: 3g/L of chromium potassium sulfate, 1g/L of zirconium salt, 0.7g/L of ammonium molybdate, 4g/L of sodium fluoride, 12ml/L of 30% nitric acid and 10ml/L of 40% sodium hydroxide.
(6) Drying: and drying the aluminum alloy subjected to coloring cleaning by using a compressed air gun.
(7) Aging: and (3) putting the dried aluminum alloy into a drying oven with the temperature of 60 ℃ for aging, and aging for 9min to obtain a finished product.
Example 5
A preparation method of an aluminum alloy surface natural color conversion film comprises the following process steps:
(1) and (3) machining: the surface of the aluminum block is milled by a milling machine to a thickness of 7cm, so that the surface roughness Ra is controlled to be 5 level.
(2) Oil removal: the aluminum alloy with the milled surface is placed into a 60g/L degreasing agent (prepared by industrial grade chemical degreasing powder) with the temperature of 65 ℃ to be soaked for 3min, and then is cleaned for 2min at normal temperature by cold water.
(3) Alkaline etching: and (3) soaking the aluminum alloy subjected to the oil removal treatment in a sodium hydroxide solution at the temperature of 60 ℃ for 60s, and washing the aluminum alloy with cold water at normal temperature for 4 min.
(4) Nitric acid light emission: and (3) putting the aluminum alloy subjected to alkali washing treatment into nitric acid bright dipping liquid with the mass percentage concentration of 60% for treatment for 4min, and washing the aluminum alloy for 1min at normal temperature by cold water.
(5) Conductive oxidation coloring: putting the bright aluminum alloy into a conductive oxidation liquid at the temperature of 25 ℃ for coloring treatment for 5min, and washing the aluminum alloy for 5s at normal temperature by cold water; the conductive oxidation liquid comprises the following components in percentage by weight: 3g/L of chromium potassium sulfate, 0.7g/L of zirconium salt, 0.5g/L of ammonium molybdate, 5g/L of sodium fluoride, 20ml/L of 30% nitric acid and 10ml/L of 40% sodium hydroxide.
(6) Drying: and drying the aluminum alloy subjected to coloring cleaning by using a compressed air gun.
(7) Aging: and (3) putting the dried aluminum alloy into a drying oven with the temperature of 60 ℃ for aging, and aging for 10min to obtain a finished product.
The finished products prepared in the above examples 1-5 are subjected to performance detection, and the detection results show that the finished products have excellent electromagnetic shielding performance, all mechanical properties meet the national standard requirements, wherein the neutral salt spray resistance time reaches over 220h and far exceeds the military standard requirements, the color of the obtained aluminum alloy surface conversion film is the natural color of the aluminum alloy, the formula is stable, and the aluminum alloy surface conversion film has good practicability and is suitable for large-scale production and application of enterprises.
Comparative example 1
The remaining steps are the same as in example 3, except that: the conductive oxidation coloring step comprises: putting the bright aluminum alloy into a conductive oxidation liquid at the temperature of 25 ℃ for coloring treatment for 3min, and washing the aluminum alloy for 3s at normal temperature by cold water; the conductive oxidation liquid comprises the following components in percentage by weight: 3g/L of chromium potassium sulfate, 0.5g/L of zirconium salt, 2.5g/L of sodium fluoride and 5ml/L of 40% sodium hydroxide.
The scanning electron microscope image of the aluminum alloy surface natural color conversion film prepared in comparative example 1 is shown in fig. 1, and fig. 2 is the scanning electron microscope image of the aluminum alloy natural color conversion film prepared in example 3, and it can be seen from the images that the film layer prepared in example 3 has better compactness, the porosity is obviously reduced, the microcracks are obviously reduced, and the film layer quality is greatly improved.
The above embodiments are preferred embodiments of the present invention, and all similar processes and equivalent variations to those of the present invention should fall within the scope of the present invention.
Claims (5)
1. The preparation method of the natural color conversion film on the surface of the aluminum alloy is characterized by comprising the following steps:
(1) carrying out oil removal, alkaline etching and nitric acid bright dipping treatment on the aluminum alloy with the surface roughness Ra of 4 grade or above for later use;
(2) conductive oxidation coloring: putting the aluminum alloy after the light extraction into a prepared conductive oxidation liquid at the temperature of 25-35 ℃ for coloring treatment for 3-5 min, and washing the aluminum alloy with cold water at normal temperature for 3-5 s; the content and the proportion of the conductive oxidation liquid are as follows: 2-3 g/L of chromium potassium sulfate, 0.5-1 g/L of zirconium salt, 0.3-0.8 g/L of ammonium molybdate, 2.5-5 g/L of sodium fluoride, 3-20 ml/L of nitric acid with the mass percentage concentration of 30% and 5-10 ml/L of sodium hydroxide with the mass percentage concentration of 40%;
(3) and (5) drying the aluminum alloy subjected to coloring cleaning, and carrying out aging treatment to obtain a finished product.
2. The method for preparing the natural color conversion coating on the surface of the aluminum alloy according to claim 1, which is characterized in that: the specific process of deoiling is: and (3) putting the aluminum alloy into a chemical degreasing agent at the temperature of 50-65 ℃, soaking for 1-3 min, and cleaning for 1-3 min at normal temperature by using cold water.
3. The method for preparing the natural color conversion coating on the surface of the aluminum alloy according to claim 1, which is characterized in that: the specific process of the alkaline etching is as follows: and (3) placing the aluminum alloy subjected to oil removal treatment into a sodium hydroxide solution with the mass percent concentration of 60% and the temperature of 40-60 ℃ to soak for 50-60 s, and washing with cold water at normal temperature for 3-5 min.
4. The method for preparing the natural color conversion coating on the surface of the aluminum alloy according to claim 1, which is characterized in that: the specific process of the nitric acid light emission is as follows: and (3) putting the aluminum alloy subjected to alkali washing treatment into a normal-temperature nitric acid bright dipping solution for treatment for 3-5 min, and washing the aluminum alloy with cold water at normal temperature for 1-2 min, wherein the mass percentage concentration of the nitric acid is 45-60%.
5. The method for preparing the natural color conversion coating on the surface of the aluminum alloy according to claim 1, which is characterized in that: the aging condition is aging in an oven at 50-65 ℃ for 6-10 min.
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| CN202010012681.9A CN110983411A (en) | 2020-01-07 | 2020-01-07 | Preparation method of natural color conversion film on surface of aluminum alloy |
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