CN103215630B - The method in aluminium alloy anode oxide film hole is closed with inorganic-organic composite silicon colloidal sol - Google Patents

Abstract

The method of sealing the pores of aluminum alloy anodized film with organic-inorganic composite silica sol is to coat or deposit an organic-inorganic composite silica sol layer on the surface of the aluminum or aluminum alloy anode after pretreatment, and then dry, Made by sintering. The organic-inorganic composite silica sol is composed of 0.5-30ml silane reagent or ethyl orthosilicate, 0.5-30ml inorganic silicon solution, 1-40ml water, 1-90ml organic solvent, 0.05-100g filler powder and 0.01-10g Made with surfactants. The present invention uses organic-inorganic composite silica sol to close the pores of aluminum and aluminum alloy anodic oxidation films by coating, brushing, dipping, high-pressure spraying, electrostatic spraying, cathode or anode electrophoresis, and reduces environmental pollution. Organic-inorganic composite silicon Sol is an environmentally friendly surface coating method that can avoid phase change and brittle cracks caused by high temperature processes; the process is easy to implement, the equipment is relatively simple, and the coating, brushing, dipping, spraying and electrophoresis processes are easy to control, and industrial production can be realized. Low, even coating film. <b />

Description

Method for closing pores of aluminum alloy anodized film with organic-inorganic composite silica sol

technical field

The present invention relates to a method for sealing the micropores of aluminum or aluminum alloy and parts containing aluminum after anodic oxidation, in particular to a method for sealing the pores of aluminum alloy anodized film with organic-inorganic composite silica sol, especially through coating, Brushing, dipping, high-pressure air spraying, electrostatic spraying, electrophoretic coating and other technologies are used to seal the aluminum and aluminum alloy anodic oxide films to achieve a better sealing effect.

Background technique

Due to the advantages of high specific strength, good thermal and electrical conductivity, and light weight, aluminum and its aluminum alloys have broad application prospects in modern industries such as aerospace, construction, and automobiles. However, aluminum alloys are soft, have poor wear resistance, and are easily corroded. The nature of aluminum is relatively active, and the oxide film formed on the surface in the air has certain corrosion resistance, but the thickness of this oxide film is only a few nanometers to tens of nanometers, the hardness is also very low, and the ability to resist environmental erosion is poor. Therefore, the necessary surface strengthening treatment is often carried out before use. Aluminum and its alloys are placed in an appropriate electrolyte as the anode for electrification treatment. Under the action of an external electric field, an oxide film can be formed on the surface of the aluminum product. The thickness is between 5-20um, its corrosion resistance, wear resistance, and electrical insulation are greatly improved, which greatly broadens the application range of aluminum and its alloy materials, but the porous film obtained by anodic oxidation of aluminum alloys is produced by the oxidation process. The oxide film has high porosity and adsorption capacity, and is easily corroded by pollution and corrosive media, especially aggressive anions (such as Clˉ, S ^2ˉ , containing cations, etc.) and water molecules can still pass through the oxide film, resulting in Corrosion (especially small hole corrosion) and wear resistance become worse, so sealing treatment must be carried out to improve its corrosion resistance, anti-pollution ability and ability to fix pigment bodies.

Contents of the invention

The object of the present invention is to provide a method for sealing the pores of aluminum alloy anodized film with organic-inorganic composite silica sol, so as to improve the corrosion resistance and pollution resistance of the film.

The technical solutions adopted are:

The method for sealing the pores of aluminum alloy anodized film with organic-inorganic composite silica sol comprises the following process steps:

1. Pretreatment: It is a known technology to loosen scale, degrease, descale and polish aluminum or aluminum alloy anodes.

2. Oxidation of aluminum or aluminum alloy anode. The pretreated aluminum or aluminum alloy anode is anodized, and the anodic oxidation adopts a DC power supply. The power supply voltage is 8~22V, the current density is 1.0~2.2A/dm ² , and the anodic oxidation time is 5~60min, and the film thickness is obtained. 1~20μm anodic oxidation film, the anodic oxidation is preferably incomplete oxidation, so that the surface of the aluminum or aluminum alloy electrode is rough.

3. Coating or depositing one or more organic-inorganic composite silica sol layers on the surface of the anodized film of aluminum or aluminum alloy.

4. Drying: Dry at 50~120°C for 10 minutes to 24 hours to obtain a dry film;

5. Sintering: Sinter in a muffle furnace at 50-1200°C for 2min-5h to obtain a film with good adhesion and a film thickness of 0.5-25μm.

Coating or depositing the organic-inorganic composite silica sol layer can be prepared by known coating, brushing, dipping, high-pressure air spraying, electrostatic spraying or electrophoretic deposition.

The preparation method of organic-inorganic composite silica sol is: take 0.5~30ml silane reagent or ethyl orthosilicate, 0.5~30ml inorganic silica sol, 1~40ml water, 1~90ml organic solvent, 0.05~100g filler powder, 0.01 ~10g of surfactant was stirred evenly to obtain organic-inorganic composite silica sol.

The above-mentioned organic substance silane reagent or ethyl orthosilicate is a variety of commercially available silane reagents, silane coupling agents or ethyl orthosilicate. During experimentation or production, the silane or ethyl orthosilicate is first compounded , and then stir the solution to fully hydrolyze the silane or ethyl orthosilicate.

Inorganic silica sol is prepared by ion exchange method, dispersion method, electrolytic electrodialysis method, peptization method, elemental silicon dissolution method, etc. Composite silica sol can also contain uniformly dispersed nano-silicon oxide dissolved in water, and dispersed nano-silicon oxide Silica dispersant.

The above organosilane coupling agents are: chloropropyltrimethoxysilane (WD-30), vinyltrichlorosilane, vinyltriethoxysilane (WD-20), vinyltris(β-methoxyethyl) Oxy)silane (A-172), γ-methacryloxypropyltrimethoxysilane (KH570), vinyltrimethoxysilane, γ-glycidyl ether propyltrimethoxysilane (KH- 560), vinyltriacetoxysilane, β-(3,4 epoxycyclohexane)ethyldimethoxysilane, γ-mercaptopropyldimethoxysilane (KH-590), γ-mercapto Propyltriethoxysilane (KH-845-4), γ-Aminopropyltriethoxysilane (KH-550, WD-50), N-β-(Aminoethyl)-γ-Aziryl Trimethoxysilane (KH-792, WD-51), γ-ureidopropyltriethoxysilane, anilinomethyltriethoxysilane (ND-42), anilinomethyldimethoxysilane (ND -73), ɑ-methacryloxymethyltriethoxysilane (ND-NS), hexylaminomethyltriethoxysilane (ND-24), dimethyldiethoxysilane (DDS) , KH-567 silane coupling agent, KH-460 silane coupling agent, KH-450 silane coupling agent, KH-578 silane coupling agent, KH-470 silane coupling agent, KH-5501 silane coupling agent, KH792 , DL602, DL171 and other silane coupling agents.

The above filler powders are: glass fiber, silica, alumina, titanium oxide, zirconia, magnesium oxide, calcium oxide, zinc oxide, iron oxide, white carbon black, silicate, talcum powder, mica, clay, hydrogen Aluminum oxide, iron powder, aluminum powder, silicon powder, Fe ₃ Al powder, asbestos, magnesium hydroxide, graphite, boron nitride, carbon black, calcium carbonate, calcium sulfate, barium sulfate, carboxymethyl cellulose, epoxy Powders of nanometer (0.1~100nm) or micrometer (0.1~100μm) substances such as resin, polyurethane, phenolic resin and melamine resin.

The above surfactants are organic surfactants (dispersants) and inorganic dispersants. Organic dispersants include acrylic acid (ester), polymethacrylic acid amine, polymethacrylic acid, polyethylene ethylenediamine, N-N-dimethylformamide, triethanolamine, citric acid diamine, polyvinyl alcohol, polyvinyl acetal Butyraldehyde, Sodium Dodecylbenzene Sulfonate, Sodium Lauryl Sulfate, Sodium Laurosilicate, Polyethylene Glycol, Polyoxyethylene Ether, Polyoxypropylene Ether, Polyvinylpyrrolidone, Oleic Acid, Citric Acid, Maleic acid (ester) and their derivatives, the hydrophobic terminal monomers are mostly unsaturated hydrocarbons, such as styrene, ethylene, butadiene, diisobutylene, methyl vinyl ether, vinyl acetate, a-methylbenzene Ethylene, etc., polyphosphate (such as sodium hexametaphosphate), silicate, etc. Inorganic dispersants include: sodium carbonate, sodium borate, sodium hexametaphosphate, sodium polyphosphate, potassium tripolyphosphate (KTPP) and tetrapotassium pyrophosphate (TKPP), etc.

The above-mentioned organic solvents are organic solvents such as ethanol, ethylene glycol, methanol, butanol, benzene, toluene, xylene, and chloroform.

The molecular formula of the silane coupling agent is Y(CH ₂ )nSiX ₃ . Here, n=0-3; X—hydrolyzable group; Y—organic functional group, capable of reacting with the resin. X is usually chloro, methoxy, ethoxy, methoxyethoxy, acetoxy, etc. When these groups are hydrolyzed, they will generate silanol, which will combine with inorganic substances to form siloxane. Y is vinyl, amino, epoxy, methacryloxy, mercapto or ureido. These reactive groups can react with organic substances to combine. Therefore, by using silane coupling agent, a "molecular bridge" can be built between the interface of inorganic substances and organic substances, and the two materials with different properties can be connected together to improve the performance of composite materials and increase the bonding strength.

The above-mentioned organic-inorganic composite silica sol can also be replaced by a single mixed solution of silane, alcohol and water or a single inorganic silica sol solution.

The advantages of the present invention are:

The present invention uses organic-inorganic composite silica sol to close the pores of aluminum and aluminum alloy anodic oxidation films by coating, brushing, dipping, high-pressure spraying, electrostatic spraying, cathode or anode electrophoresis, and replaces the dichromate of aluminum alloy anodic oxide films. Closed technology to reduce environmental pollution. Organic-inorganic composite silica sol is an environmentally friendly surface coating method that can avoid phase change and brittle cracks caused by high temperature processes; the process is easy to implement and the equipment is relatively simple. Coating, brushing, and dipping , Spraying and electrophoresis processes are easy to control, can realize industrial production, low cost, uniform coating film.

detailed description

The method for sealing the pores of aluminum alloy anodized film with organic-inorganic composite silica sol comprises the following process steps:

(1) Pre-treatment: Loosen the scale on the surface of the aluminum or aluminum alloy anode plate, and use sandpaper for polishing from coarse to fine, and finally select the type of sandpaper to be 2000 ^# ; nitric acid solution used for descaling: deionized water = 0.5~ 2:1; the alkali concentration used for alkali etching is 30g/L; after alkali etching, a layer of hanging ash is often attached to the surface of the workpiece, and the anodic oxidation treatment can be performed after removing the hanging ash with a light-emitting solution. The polishing solution uses nitric acid solution, nitric acid: water = 0.5 ~2:1, for use;

(2) Anodizing: Anodizing the aluminum or aluminum alloy anode after pretreatment, using a DC power supply for anodizing, setting the power supply voltage to 12V, current density to 1.5A/dm ² , and anodizing time to 30min to obtain a film thickness of 15μm anodized film, the anodic oxidation can be incomplete, and the surface is rough, which is used to improve the bonding force between aluminum alloy and organic-inorganic silicon coating;

(3) The organic-inorganic composite silica sol is prepared by coating, brushing, dipping, high-pressure air spraying, electrostatic spraying, and electrophoresis on the oxide film of the aluminum or aluminum alloy positive plate.

Using high-pressure air spraying: With the extension of spraying time and the increase of spraying pressure, the thickness of the coating will increase.

Electrophoretic deposition ^: with a current density of 10A/dm2 and a voltage of 50V, the electrophoretic silica sol is deposited in the pores of the aluminum or aluminum alloy anodized film, washed with deionized water, and repeated 5 times;

(4) Drying: Dry at 50°C for 24 hours to obtain a dry film;

(5) Sintering: Sinter in a muffle furnace at 800°C for 2 hours to obtain a film with good adhesion.

The above-mentioned organic substances are silane reagents or ethyl orthosilicate, which are commercially available various silane reagents, silane coupling agents or ethyl orthosilicate. Mix, then stir the solution to fully hydrolyze the silane or ethyl orthosilicate.

Claims (1)

1. A method for sealing aluminum alloy anodized film holes with organic-inorganic composite silica sol, is characterized in that: comprise following processing step: ① Pre-treatment: loosen scale, degrease, descale and polish aluminum or aluminum alloy anodes; ②Oxidation of aluminum or aluminum alloy anodes: anodize the pretreated aluminum or aluminum alloy anodes, use DC power supply for anodic oxidation, set power supply voltage 8~22V, current density 1.0~2.2A/dm ² , anodic oxidation The time is 5~60min, and an anodic oxide film with a film thickness of 1~20μm is obtained; ③ Prepare one or more layers of organic-inorganic composite silica sol coating on the surface of the anodized film of aluminum or aluminum alloy by coating, brushing, dipping, high-pressure air spraying, or electrostatic spraying; ④Drying: Dry at 50~120℃ for 10 minutes~24 hours to obtain a dry film layer; ⑤Sintering: sintering in a muffle furnace at 50~1200°C for 2min~5h to obtain a film layer with good adhesion and a film thickness of 0.5~25μm; ⑥The preparation method of the organic-inorganic composite silica sol is: take 0.5~30ml silane reagent or ethyl orthosilicate, 0.5~30ml inorganic silica sol, 1~40ml water, 1~90ml organic solvent, 0.05~100g filler powder, 0.01~10g surfactant and stir evenly to obtain organic-inorganic composite silica sol.