JP2024065796A - Aqueous anti-rust surface treatment composition, surface-coated aluminum member using same, and method for producing surface-coated aluminum member - Google Patents

Abstract

[Problem] To provide an aqueous anti-rust surface treatment composition with excellent corrosion resistance. [Solution] The aqueous anti-rust surface treatment composition of the present invention is an aqueous anti-rust surface treatment composition for aluminum-based substrates, which is used to form a silicon film on an anodic oxide film or a chemical conversion film formed on the surface of the aluminum-based substrate, and contains a silane coupling agent, inorganic colloid particles, and a solvent containing water. [Selected Figure] Figure 1

Description

The present invention relates to an aqueous anticorrosive surface treatment composition, a surface-coated aluminum member using the same, and a method for producing a surface-coated aluminum member.

Various developments have been made in aqueous surface treatment agents for treating the surfaces of metal components. For example, the technology described in Patent Document 1 is known as a technology of this type. Patent Document 1 describes a technology for treating the zinc-plated surface of hot-dip galvanized steel and the like using an aqueous metal surface treatment agent (Claim 1, paragraph 0068, etc.)

JP 2014-237880 A

The aqueous metal surface treatment agent described in the above Patent Document 1 has been studied for use on zinc-plated surfaces, but has not yet been fully studied for use in the surface treatment of aluminum-based substrates.
As a result of investigations by the present inventors, it was found that there is room for improvement in terms of corrosion resistance in surface treatment techniques for aluminum-based substrates.

Currently, aluminum-based substrates have a smaller specific gravity than zinc-plated steel-based substrates, and research and development is being conducted into various applications that take advantage of this advantage.
However, aluminum-based substrates are often anodized and coated when used for exterior parts, and anodized when used for automobile parts and electrical appliance parts. In addition, they are generally used as interior materials and are rarely used in environments exposed to water, so they have been used without taking any corrosion prevention measures.

Anodizing (alumite) is a well-known surface treatment technique for aluminum-based substrates.
However, the inventors of the present invention have found that an anodized coating film formed on an aluminum-based substrate may have reduced corrosion resistance. The anodized coating film is susceptible to thermal degradation, and may crack due to heat.

Based on this knowledge, further intensive research led to the discovery that by forming a silicon film on the anodized film formed on the surface of an aluminum-based substrate using an aqueous anti-rust surface treatment composition containing a silane coupling agent and aqueous colloidal silica, the aluminum-based substrate, in particular an aluminum die-cast substrate, can be made to have excellent corrosion resistance against water and salt, which led to the completion of the present invention.

Furthermore, as a result of the inventors' investigations, it was found that by forming a silicon film on a chemical conversion film formed on the surface of an aluminum-based substrate using the above-mentioned aqueous rust-preventive surface treatment composition, in the same manner as in the case of an anodized film, it is possible to achieve excellent corrosion resistance against water and salt in an aluminum-based substrate, in particular an aluminum die-cast substrate, and this has led to the completion of the present invention.
Furthermore, it has been found that aluminum-based substrates coated with a chemical conversion coating and a silicon coating can maintain electrical conductivity at the substrate surface even after a salt fountain test.

According to one aspect of the present invention, the following aqueous anticorrosive surface treatment composition, surface-coated aluminum member, and surface-coated aluminum member are provided.

1. An aqueous rust-preventive surface treatment composition for an aluminum-based substrate, which is used to form a silicon film on an anodic oxide film or a chemical conversion film formed on the surface of the aluminum-based substrate, comprising:
A silane coupling agent;
Inorganic colloid particles;
A solvent comprising water;
1. An aqueous anti-rust surface treatment composition comprising:
2. The aqueous rust-preventive surface treatment composition according to 1.,
1. An aqueous anti-rust surface treatment composition, wherein the solvent comprises an alcohol.
3. The aqueous rust-preventive surface treatment composition according to 2.,
The content of the alcohol in the aqueous rust-preventive surface treatment composition is 0.1 mass % or more and 20 mass % or less.
4. The aqueous rust-preventive surface treatment composition according to 2. or 3.,
The aqueous rust-preventive surface treatment composition has an alcohol content of 1 mass % or more and 20 mass % or less, based on a total content of the water and the alcohol of 100 mass %.
5. The aqueous rust-preventive surface treatment composition according to any one of 1. to 4.,
An aqueous rust-preventive surface treatment composition comprising a water-dispersible resin.
6. The aqueous rust-preventive surface treatment composition according to 5.,
The aqueous rust-preventive surface treatment composition comprises at least one water-dispersible resin selected from the group consisting of polyacrylic resins, silicone resins, phenolic resins, epoxy resins, polyurethane resins, polyester resins, polyvinyl butyral resins, phenolic resins, and modified versions thereof.
7. The aqueous rust-preventive surface treatment composition according to any one of 1. to 6.,
The aqueous anti-rust surface treatment composition comprises a rust inhibitor.
8. The aqueous rust-preventive surface treatment composition according to any one of 1. to 6.,
An aqueous anticorrosive surface treatment composition comprising a water-soluble transition metal compound.
9. The aqueous rust-preventive surface treatment composition according to any one of 1. to 8.,
An aqueous anti-rust surface treatment composition that is substantially free of chromium components.
10. A surface preparation step including an anodizing treatment step of forming an anodized film by performing an anodizing treatment on the surface of an aluminum-based substrate, or a chemical conversion treatment step of forming a chemical conversion film by performing a chemical conversion treatment;
and a surface treatment step of applying an aqueous rust-preventive surface treatment composition containing a silane coupling agent, inorganic colloid particles, and a solvent containing water onto the surface of the anodized film or the chemical conversion film, and drying the composition to form a silicon film.
A method for producing a surface-coated aluminum member.
11. An aluminum-based substrate;
An anodized film or a chemical conversion film formed on the surface of the aluminum-based base material;
a silicon coating formed on the surface of the anodized coating or the chemical conversion coating, the silicon coating being a dried film of an aqueous antirust surface treatment composition containing a silane coupling agent and aqueous colloidal silica;
A surface-coated aluminum member comprising:

The present invention provides an aqueous anticorrosive surface treatment composition with excellent corrosion resistance, a surface-coated aluminum member using the same, and a method for producing a surface-coated aluminum member.

FIG. 1 is a cross-sectional view showing a schematic example of the configuration of a surface-coated aluminum member according to an embodiment of the present invention. FIG. 1 is a cross-sectional view showing a schematic example of the configuration of a surface-coated aluminum member according to an embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings. Note that in all drawings, similar components are given similar reference symbols and descriptions are omitted where appropriate. Also, the drawings are schematic and do not correspond to the actual dimensional ratios.

An overview of the manufacturing method for the surface-coated aluminum member of this embodiment is described below.

The manufacturing method of the surface-coated aluminum member of this embodiment includes a base treatment step in which anodizing is performed on the surface of the aluminum-based substrate to form an anodized film, or a chemical conversion treatment is performed to form a chemical conversion film, and a surface treatment step in which an aqueous rust-preventive surface treatment composition is applied to the surface of the anodized film or chemical conversion film, and then dried to form a silicon film.

The aqueous anti-rust surface treatment composition includes a silane coupling agent, aqueous colloidal silica, and a solvent containing water. The aqueous anti-rust surface treatment composition is an aqueous anti-rust treatment agent for aluminum-based substrates, and is used to form a silicon film on the aluminum-based substrate.

In recent years, the production of aluminum die castings as aluminum-based substrates has increased.
The aluminum die casting has a rough surface composition and may contain silicon as a compositional component, so it is generally known that it is difficult to subject the aluminum die casting to anodizing treatment.
Although the detailed mechanism is unclear, it is believed that this is because, due to the characteristics of the anodizing treatment, it is difficult to form a uniform anodic oxide film on a relatively rough surface or a surface containing Si elements.
Therefore, when anodizing is performed on aluminum die casting, there is room for improvement in terms of stable corrosion resistance.
Furthermore, when only anodizing is performed, the oxide film formed on the surface of the aluminum-based base material may be unevenly distributed (varied), and the corrosion resistance may not be fully exhibited.

According to this embodiment, by forming a silicon film using an aqueous rust-preventive surface treatment composition on an anodized film or a chemical conversion film formed on the surface of an aluminum-based substrate, it is possible to stably improve corrosion resistance against water and salt. In addition, corrosion resistance against heat can also be improved. Even when the aluminum-based substrate is made of aluminum die casting, such improved corrosion resistance can be achieved.

In the first embodiment, the anodizing treatment (priming treatment) and the surface treatment process are used in combination, that is, a laminate of an anodized film and a silicon film is formed on the surface of an aluminum-based base material, which makes it possible to improve not only excellent corrosion resistance but also thermal corrosion resistance and stable corrosion resistance.
Although the detailed mechanism is unclear, it is thought that because anodized films and silicon films have different anti-rust mechanisms, which cause corrosion to progress quickly from the starting point and are easily affected by variations in the composition of the surface material, the silicon film reinforces the corrosion resistance of the anodized film, resulting in a synergistic effect on corrosion resistance.

In the second embodiment, a chemical conversion treatment (substrate treatment) and a surface treatment process are used in combination, that is, a laminate of a chemical conversion coating and a silicon coating is formed on the surface of an aluminum-based substrate. This provides excellent corrosion resistance. Also, it is possible to improve thermal corrosion resistance and stable corrosion resistance.
Although the detailed mechanism is unclear, it is believed that the Zr and the like contained in the chemical conversion coating and the Si contained in the silicon coating can each appropriately control the corrosion potential (corrosion resistance potential), thereby improving the above-mentioned corrosion resistance.

Furthermore, the surface of the aluminum-based substrate underlying the chemical conversion coating maintains electrical conductivity before and after the salt water fountain test, i.e., an excessive increase in surface resistance can be suppressed. Therefore, by covering the surface of the low-resistance aluminum-based substrate with the chemical conversion coating and the silicon coating, the low resistance can be maintained even after exposure to the external environment.
Therefore, the manufacturing method and surface-coated aluminum member of the second embodiment can be suitably used for aluminum products that require low resistance.
Examples of such aluminum products include electrical signal transmitting/receiving components, connectors, electromagnetic wave covers, and the like.

From the viewpoint of corrosion resistance, such a method of performing chemical conversion treatment on the surface of an aluminum-based substrate can be used as an alternative to the above-mentioned anodizing treatment method. However, since anodizing treatment forms an oxide film on the surface of the aluminum-based substrate, the chemical conversion treatment method of the second embodiment is preferred from the viewpoint of maintaining the conductivity of the aluminum-based substrate.

Anodizing requires large amounts of water and electricity, as well as specialized equipment, and in some regions it is difficult to set up anodizing equipment that meets these requirements.
In contrast, the surface treatment process of this embodiment does not require the conditions required for anodizing, and can be carried out relatively easily in any region. Furthermore, the facility for carrying out the surface treatment process can be easily constructed, and can be installed alongside an existing facility.

In addition, the anodized film may be painted, but this must usually be done within about 24 hours after the anodizing treatment, because paint becomes difficult to adhere to the surface of the anodized film after a certain amount of time has passed since the treatment.
Therefore, one conventional supply chain using anodizing is as follows:
First, the substrate material (such as aluminum material) is supplied from the material manufacturer to the processing manufacturer, which then anodizes the material (and shapes it if necessary) and supplies it to the manufacturing manufacturer. If anodizing is used as a prerequisite, it depends on the processing manufacturer, so customizing the supply chain is not easy.

In contrast, the surface of a silicon film made of the aqueous rust-preventive surface treatment composition of this embodiment can be painted with paint.

In addition, by using the surface treatment process of this embodiment, it is possible to easily customize the conventional supply chain since it is not necessary to go through a supplier (a processing manufacturer that provides anodizing treatment or shape processing), which was previously necessary. In an environment where competition is becoming more intense, it is possible to strategically strengthen and optimize relationships with suppliers and efficiently achieve cost reduction. For example, a manufacturer can directly purchase substrate materials from a material manufacturer and in-house the coating treatment of the paint composition, thereby strengthening purchasing power with respect to the material manufacturer and reducing manufacturing costs. In addition, a manufacturer can increase the amount of purchase from the material manufacturer and outsource the coating treatment, thereby improving manufacturing efficiency and reducing manufacturing costs. In addition, by decentralizing the processing process, i.e., by arranging separate suppliers for the coating treatment and the shape processing treatment and optimizing the channel, it is possible to further increase the design freedom of the supply chain.
In addition, the surface treatment process using the aqueous rust-preventive surface treatment composition of the present embodiment can be a simpler process than anodizing (alumite), which allows for greater design freedom in the supply chain.

Furthermore, depending on the surface shape and surface composition of the aluminum-based substrate, it may be difficult to form a silicon film on such a surface.
In such a case, if the aqueous rust-preventive surface treatment composition contains an alcohol as a solvent, it is possible to increase the wettability of the surface and improve the film-forming properties.
However, depending on the usage environment, it may be required to keep the alcohol content low. In this case, the alcohol content in the aqueous rust-preventive surface treatment composition can be reduced to improve ease of handling. Even when using an aqueous rust-preventive surface treatment composition with a reduced alcohol content, the adhesion of the silicon film to the aluminum substrate, particularly the surface of aluminum die casting, can be improved by applying it on the above-mentioned chemical conversion film or an anodized film, thereby achieving high corrosion resistance overall.

The manufacturing method for surface-coated aluminum components is described in detail below.

An example of a manufacturing method for the surface-coated aluminum member of this embodiment may include a base treatment step including a chemical conversion treatment step of applying a chemical conversion treatment to the surface of an aluminum-based substrate to form a chemical conversion coating, or an anodizing treatment step of applying an anodizing treatment to form an anodized coating, and a surface treatment step of applying an aqueous rust-preventive surface treatment composition containing a silane coupling agent, aqueous colloidal silica, and a solvent containing water, onto the chemical conversion coating or the anodized coating, and drying to form a silicon coating.
This aqueous anticorrosive surface treatment composition (hereinafter sometimes simply referred to as "the composition") contains a silane coupling agent, aqueous colloidal silica, a water-dispersible resin, and a solvent containing water.

The aluminum-based substrate is not particularly limited as long as it is a metal material containing aluminum element as a main component, but may be composed of aluminum alone or an aluminum alloy. The content of the aluminum element as the main component is, for example, 50 mass% or more, preferably 60 mass% or more, more preferably 70 mass% or more, and even more preferably 80 mass% or more in terms of mass, relative to 100 mass% of the aluminum-based substrate.
The aluminum alloy may contain, as a metal element, Si, Mg, Mn, Cu, etc. in addition to Al, and may further contain Zn, Fe, Ni, Sn, Pb, Ti, etc.
Examples of aluminum alloys include Al-Si based, Al-Si-Mg based, Al-Mg based, Al-Mg-Mn based, Al-Si-Cu based, and Al-Si-Cu-Mg based alloys.

The aluminum-based substrate may be aluminum die-cast.
Aluminum die casting is a metal component made by forcing molten aluminum alloy metal into a mold and mass-producing highly accurate castings in a short period of time.

Examples of aluminum die castings include ADC1, ADC3, ADC5, ADC6, ADC10, ADC12, ADC14, etc.

The shape of the surface-coated aluminum member is not particularly limited, and it may be plate-shaped, ring-shaped, rod-shaped, or have the shape of various products or parts.

As the above-mentioned chemical conversion treatment, known treatment methods can be adopted, and examples thereof include phosphate treatment containing zinc, manganese, iron, calcium, etc.; zirconium-based treatment containing zirconium, titanium, hafnium, etc.; chromium salt treatment (chromate treatment) containing zinc, aluminum, copper, etc. and trivalent chromium, etc.; fermite treatment (black dyeing treatment); chemical conversion treatment containing cerium, vanadium, tungsten, etc.; and the like.
Among these, from the viewpoint of reducing the environmental load, non-chromium-based chemical conversion treatments such as phosphate treatment and zirconium-based treatment can be used. As the phosphate treatment, a treatment liquid containing zinc phosphate can be used. As the zirconium-based treatment, a treatment liquid containing zirconium can be used.

By carrying out a chemical conversion treatment, a chemical conversion coating such as a zinc phosphate coating or a zirconium coating can be formed on at least a portion or the entire surface of the aluminum-based substrate.

Furthermore, phosphate treatment and zirconium-based treatment are superior in aesthetics and scratch resistance compared to fermite treatment. Among these, zirconium-based treatment allows the color of the underlying plating film to be visually observed through the zirconium conversion coating compared to phosphate treatment, achieving a more aesthetically pleasing appearance. Zirconium-based treatment also prevents discoloration of the plating film, making it useful for a variety of applications.

In addition, phosphate treatment and zirconium-based treatment can reduce variation in corrosion resistance compared to cerium (Ce)-based chemical conversion treatment and chromate treatment.

In the above-mentioned anodizing treatment, an electric current is passed through the aluminum-based substrate as the anode in an electrolyte solution containing, for example, sulfuric acid, oxalic acid, or other organic acids, and an oxide film is formed on the surface of the aluminum-based substrate by electrolysis.

By performing anodizing, an anodized film can be formed on at least a portion or the entire surface of the aluminum-based substrate.

In the above surface treatment process, for example, an aqueous anti-rust surface treatment composition is applied to at least a part or the entire surface of the chemical conversion coating or anodized coating, and then a drying treatment is performed to form a silicon coating.

Methods for applying the composition include immersing the aluminum-based substrate in the composition, using a spin coater, and spraying the composition.

The drying process may be performed at room temperature, 20 to 25°C, or by heating to an appropriate temperature. For example, the drying process may be performed at a temperature of 80°C to 200°C for 5 to 240 minutes.

The above manufacturing method results in a surface-coated aluminum component.

Surface treatment equipment for carrying out such surface treatment steps can be installed alongside existing metal processing equipment.
The metal processing facility prepares an aluminum-based substrate prior to the surface treatment process. This aluminum-based substrate may or may not have a chemical conversion coating or an anodized coating formed on its surface.
The surface treatment facility applies the aqueous rust-preventive surface treatment composition to the aluminum-based substrate transported from the metal processing facility and then performs a drying treatment on the aluminum-based substrate. An example of the surface treatment facility may include a container for holding the aqueous rust-preventive surface treatment composition and a heating device for drying the aluminum-based substrate immersed in the composition in the container.

Here, we will explain each component of the aqueous anti-rust surface treatment composition in detail.

The method for producing the aqueous anti-rust surface treatment composition is not particularly limited, but it can be obtained by mixing the following components. The order in which the components are mixed is not limited, and they can be mixed in any order.

The aqueous anti-rust surface treatment composition contains at least a silane coupling agent, aqueous colloidal silica, and a solvent containing water.

The aqueous anti-rust surface treatment composition can be used to form a silicon film on a chemical conversion film or anodized film formed on the surface of an aluminum-based substrate.

<Silane coupling agent>
The aqueous anticorrosive surface treatment composition contains a silane coupling agent.
By using the silane coupling agent, the composition containing the water-dispersible resin or the aqueous colloidal silica can be stabilized as an aqueous solution. In addition, the silane coupling agent can improve the affinity between the aqueous colloidal silica or the water-dispersible resin, so that a stable aqueous solution (composition) can be formed.
As the silane coupling agent, a water-soluble silane coupling agent having an alkoxy group that can be dissolved in water is used.

The silane coupling agent may be, for example, an alkoxysilane represented by the general formula ( ^R1 ) _mSi ( ^OR2 ) _4-m (wherein ^R1 is a functional group having 1 to 20 carbon atoms, ^R2 is a lower alkyl group, and m is an integer of 0 to 3), or a compound obtained by hydrolyzing and condensing this. The silane coupling agent may be partially hydrolyzed in the composition.

Specific examples of the silane coupling agent represented by the above general formula _include , for example, Si( _OCH3 ) ₄ , Si( _{OC2H5 ) 4} , _{CH3Si ( OCH3 ) 3} , CH3Si( _OC2H5 ) ₃ , _C2H5Si ( _OCH3 ) ₃ , C2H5Si(OC2H5) ₃ , _CH2 (O) _CHCH2O ( _CH2 ) _3Si ( _{OCH3 ) 3} , _{CH2 =} C( _CH3 ) _COO ( _CH2 ) _3Si ( _OCH3 ) ₃ , _CH2 =CHCOO( _CH2 ) _3Si ( _OCH3 ) ₃ , _H2N ( _CH2 ) _3Si ( _OCH3 ) ₃ , HS( _{CH 2} ) _3Si ( _OCH3 ) ₃ , OCN( _CH2 ) _3Si ( _OC2H5 ) _{3 ,} etc.

In addition, in the above chemical formula, examples of the functional group in R ¹ include vinyl, 3-glycidoxypropyl, 3-glycidoxypropylmethyl, 2-(3,4-epoxycyclohexyl)ethyl, p-styryl, 3-methacryloxypropyl, 3-methacryloxypropylmethyl, 3-acryloxypropyl, 3-aminopropyl, N-2-(aminoethyl)-3-aminopropyl, N-2-(aminoethyl)-3-aminopropylmethyl, N-phenyl-3-aminopropyl, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyl, 3-ureidopropyl, 3-mercaptopropyl, and 3-isocyanatopropyl groups.

In the above chemical formula, specific examples of lower alkyl groups include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, 1-ethylpropyl, isopentyl, and neopentyl.

The water-soluble silane coupling agent may include, for example, a silane coupling agent having an epoxy group as a functional group (epoxy silane) or a silane coupling agent having an amino group as a functional group (amino silane). Among these, it is more preferable to use epoxy silane from the viewpoint of corrosion resistance.

Examples of the epoxy silanes include glycidyl or epoxy group-containing trialkoxysilane compounds such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexylethyl)trimethoxysilane.

The content of the silane coupling agent in the aqueous anticorrosive surface treatment composition is, for example, 0.5% by mass to 12% by mass, preferably 1% by mass to 11% by mass, and more preferably 1.5% by mass to 10% by mass, calculated as solid content.

In this specification, the range "to" indicates that the upper and lower limits are included, unless otherwise specified.
The solid content refers to the remainder after removing volatile components such as water, alcohol solvent, etc. This solid content may be the residue remaining after the reaction of each component after the aqueous rust-preventive surface treatment composition is heat-treated.

<Inorganic colloid particles>
The aqueous anticorrosive surface treatment composition contains inorganic colloidal particles, and it is preferable that the inorganic colloidal particles contain, for example, aqueous colloidal silica.

The water-soluble colloidal silica is dispersed in a water solvent or a mixed solvent containing water, and contains inorganic particles composed of SiO _2. The average particle size of the inorganic particles may be, for example, 1 to 200 nm.

The aqueous anticorrosive surface treatment composition may contain inorganic colloidal particles composed of inorganic oxides such as Al ₂ O ₃ , TiO ₂ , ZrO ₂ , Fe ₂ O _3, etc., other than the aqueous colloidal silica. The inorganic colloidal particles are composed of inorganic particles dispersed in water.

By using aqueous colloidal silica, the strength of the film obtained from the aqueous anticorrosive surface treatment composition can be further improved. In addition, the dispersibility in the composition can be increased, so that a silicon film can be formed in which the silica particles are uniformly dispersed throughout the film.

The stable pH range of the aqueous colloidal silica is on the acidic, neutral, or alkaline side. Among these, from the viewpoint of the solution stability of the composition, aqueous colloidal silica that is stable at an acidic pH can be used.

The inorganic particles have an average particle size of, for example, 1 to 200 nm, preferably 3 to 100 nm. By using nano-sized inorganic particles, aggregation and precipitation can be suppressed when using an aqueous mixed solvent of water and alcohol, and a composition with excellent liquid stability can be prepared. In addition, the rust prevention performance of products surface-treated with the composition can be improved.

By using inorganic colloidal particles such as aqueous colloidal silica, an even stronger coating structure can be achieved.

The content of the aqueous colloidal silica or inorganic colloidal particles in the aqueous anticorrosive surface treatment composition is, for example, 0.5% by mass to 12% by mass, preferably 0.6% by mass to 10% by mass, and more preferably 0.8% by mass to 8% by mass, calculated as solid content. By making the content equal to or greater than the lower limit, it is possible to impart an appropriate strength to the film. By making the content equal to or less than the upper limit, it is possible to achieve a balance in the physical properties of the film.

The content of the aqueous colloidal silica or inorganic colloidal particles is, for example, 10 to 300 parts by mass, preferably 15 to 200 parts by mass, and more preferably 20 to 150 parts by mass, calculated as solid content, per 100 parts by mass of the silane coupling agent.

<Water-dispersible resin>
The aqueous rust-preventive surface treatment composition may contain at least one of a water-dispersible resin and/or a water-soluble resin.
Among these, it is preferable to contain a water-dispersible resin.

Water-dispersible resins are made up of resins that disperse in water. Water-soluble resins are made up of resins that dissolve in water.

The resin constituting the water-dispersible resin or water-soluble resin may be appropriately selected from resins that can be dispersed in water, and examples of such resins include polyacrylic acid resins, silicone resins, phenolic resins, epoxy resins, polyurethane resins, polyester resins, polyvinyl butyral resins, phenolic resins, and modified products thereof. These may be used alone or in combination of two or more.
Among these, from the viewpoint of corrosion resistance and durability of the film, polyacrylic resin, epoxy resin, polyurethane resin, silicone resin, etc. may be used as the water-dispersible resin.

By using a water-dispersible resin, the corrosion resistance of the film can be improved even more than with a water-soluble resin. Although the detailed mechanism is unclear, it is thought that this is because the resin can be prevented from dissolving in water and other components.
In addition, by using a water-dispersible resin, the resin is prevented from being dissolved by H groups or OH groups that remain due to incomplete reaction in the silicon film during film formation, or by moisture, which is believed to improve corrosion resistance.

The content of the water-dispersible resin in the aqueous rust-preventive surface treatment composition is, for example, 1% by mass to 12% by mass, preferably 1.5% by mass to 11% by mass, and more preferably 2% by mass to 10% by mass, calculated as the solid content. By making the content equal to or greater than the lower limit, the heat resistance and corrosion resistance of the film can be improved. By making the content equal to or less than the upper limit, the physical properties of the film can be balanced.
The content of the water-dispersible resin is, in terms of solid content, for example, 5 parts by mass to 300 parts by mass, preferably 10 parts by mass to 250 parts by mass, and more preferably 20 parts by mass to 200 parts by mass, relative to 100 parts by mass of the silane coupling agent.
The content of the water-soluble resin may be in the same range as the content of the water-dispersible resin.

<Solvent>
The aqueous rust-preventive surface treatment composition includes a solvent containing water. This solvent may be composed of an aqueous solvent containing only water, or may be composed of an aqueous mixed solvent containing water and a hydrophilic solvent other than water.

Examples of the water include city water, distilled water, ion-exchanged water, etc.

The hydrophilic solvent may be a polar organic solvent such as alcohol. From the viewpoint of solution stability, the aqueous mixed solvent may be composed of a mixed solvent of water and alcohol. The content ratio of water in the aqueous mixed solvent can be determined in consideration of the chemical properties and blending amounts of each component in the aqueous rust-preventive surface treatment composition.

Examples of the alcohol that can be used include low-boiling alcohols with a boiling point of less than 100°C, such as methanol, ethanol, n-propyl alcohol, and isopropyl alcohol, and high-boiling alcohols with a boiling point of 100°C or higher, such as isobutanol, methyl cellosolve, ethyl cellosolve, propylene glycol monomethyl ether (PGME), butyl cellosolve, ethylene glycol monotertiary butyl ether (ETB), and diformaldehyde methoxyethanol. These may be used alone or in combination of two or more.

Among these, one or more alcohols selected from the group consisting of methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, s-butyl alcohol, and t-butyl alcohol may be included due to their high availability and high solubility in each component. In addition, by using low-boiling point alcohols such as methyl alcohol (boiling point: 64.7°C), ethyl alcohol (boiling point: 78.37°C), and iso-propyl alcohol (boiling point: 82.4°C), it becomes possible to form a coating film in a lower temperature environment or a drier environment.

In this embodiment, the use of alcohol improves the solubility of each component, and improves the storage stability of the resulting aqueous anti-rust surface treatment composition. Although the reason is not clear, the use of a mixed solvent containing water and alcohol can improve the anti-rust performance of the film formed on the surface of an aluminum-based substrate having a zinc surface. In addition, alcohol can suppress foaming of the aqueous anti-rust surface treatment composition, thereby suppressing bubbles from entering the coating and causing the siliceous film to become uneven.

The content of the alcohol in the aqueous anticorrosive surface treatment composition is, for example, 0.1% by mass to 20% by mass, preferably 0.2% by mass to 12% by mass, and more preferably 0.3% by mass to 10% by mass. By keeping the content within the above range, the long-term storage stability of the composition can be improved. In addition, by keeping the content below the above upper limit, the adhesion can be improved.

The content of the alcohol is, for example, 0.1% by mass to 20% by mass, preferably 0.2% by mass to 15% by mass, and more preferably 0.3% by mass to 14% by mass, based on the total content of the water and alcohol (100% by mass). By keeping the content within such a range, the long-term storage stability of the aqueous rust-preventive surface treatment composition can be improved.

The content of the alcohol is, for example, 1 to 300 parts by mass, preferably 2 to 200 parts by mass, and more preferably 3 to 170 parts by mass, relative to 100 parts by mass of the total content of the silane coupling agent and the water-dispersible resin. By making the content equal to or greater than the lower limit, a composition in which the silane coupling agent is stably dissolved can be realized. By making the content equal to or less than the upper limit, the dispersibility of the water-dispersible resin can be increased. By making the content within the above range, the long-term storage stability of the composition can be increased.

The pH of the aqueous anti-rust surface treatment composition can be appropriately selected depending on the components contained therein, but if it contains a phosphoric acid-based rust inhibitor, it may be on the acidic side, for example, 4.0 to 6.9, but if it does not contain a phosphoric acid-based rust inhibitor, it may be on the alkaline side. An alkaline aqueous anti-rust surface treatment composition may not contain a water-soluble transition metal compound.

The pH of the alkaline aqueous anticorrosive surface treatment composition is, for example, 7.0 to 13.0, preferably 7.2 to 12.0.

In this embodiment, the pH can be measured using a pH meter at a liquid temperature of the aqueous rust-preventive surface treatment composition of 25°C ± 1°C. A liquid temperature of 25°C is usually used, but a variation of about +1°C or -1°C can be tolerated.

<Water-soluble transition metal compound>
The aqueous anticorrosive surface treatment composition may or may not contain a water-soluble transition metal compound.
The water-soluble transition metal compound includes a water-soluble titanium compound or a water-soluble zirconium compound. The water-soluble transition metal compound is capable of dissolving in water.

The water-soluble titanium compound may include one or more selected from the group consisting of inorganic titanium compounds, peroxotitanates, amine-based water-soluble titanates, and chelate-based titanates (water-soluble titanium chelating agents).Specific examples of the water-soluble titanium compound include inorganic titanium compounds such as titanium trichloride, titanium tetrachloride, titanium sulfate, and titanium oxychloride, inorganic or chelate-based peroxotitanates, amine-based water-soluble titanates obtained by reacting titanium alkoxide with water in the presence of amines, and chelate-based titanates (water-soluble titanium chelating agents) such as oxycarboxylic acid chelate titanium in which oxycarboxylic acids such as lactic acid, malic acid, citric acid, tartaric acid, gluconic acid, and glycol are coordinated, and alkanolamine chelate titanium in which alkanols such as monoethanolamine, diethanolamine, and triethanolamine are coordinated.
In addition, the water-soluble zirconium compound may have a structure similar to that of the water-soluble titanium compound, and may include, for example, one or more selected from the group consisting of inorganic zirconium compounds, peroxozirconates, amine-based water-soluble zirconates, and chelate-based zirconates.

The aqueous anticorrosive surface treatment composition may contain, as a curing component, an organic transition metal compound such as an organic titanium compound, such as an organic titanium alkoxide, an organic titanium chelate, or an organic titanium acylate, or an organic zirconium compound, such as an organic zirconium alkoxide, an organic zirconium chelate, or an organic zirconium acylate. By including this curing component, a structure in which the component in the film structure and the curing component are crosslinked, or a self-crosslinking structure can be obtained.

The titanium chelating agent may be, for example, an organic compound or an oligomer thereof represented by the general formula Ti(X) ₄ . In the general formula, X is selected from a hydroxyl group, a lower alkoxy group, and a chelating substituent, and the four Xs may be the same or different.

Examples of the lower alkoxy group include alkoxy groups having 6 or less carbon atoms, preferably 4 or less carbon atoms, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, and tert-butoxy.
The chelating substituent is, for example, a group derived from an organic compound capable of forming a chelating agent, such as β-diketones such as acetylacetone, alkylcarbonylcarboxylic acids and their esters such as acetoacetic acid, and alkanolamines such as triethanolamine.
Specific examples of the chelating substituent include lactate, ammonium lactate, triethanolamine, acetylacetonate, acetoacetate, and ethyl acetoacetate.

The water-soluble transition metal compound is, for example, 0.01% to 7% by mass, preferably 0.015% to 5% by mass, and more preferably 0.02% to 3% by mass, calculated as solid content in the entire aqueous rust-preventive surface treatment composition.

The content of the water-soluble transition metal compound is, for example, 0.1 to 50 parts by mass, preferably 0.5 to 150 parts by mass, and more preferably 1 to 20 parts by mass, calculated as solid content, relative to 100 parts by mass of the silane coupling agent.

<Rust inhibitor>
The aqueous anti-rust surface treatment composition may or may not contain a rust inhibitor.

As the rust inhibitor, a phosphoric acid-based rust inhibitor or the like is used.
As the phosphoric acid-based rust inhibitor, at least one of a highly condensed phosphate and a polyvalent phosphoric acid ester may be used.

The highly condensed phosphate may be a salt of a highly condensed product obtained by dehydration condensation of four or more phosphoric acids.
The degree of condensation of phosphoric acid in the highly condensed phosphate (the number of structural units derived from phosphoric acid in a molecule) is, for example, 4 or more, preferably 5 or more, and more preferably 6 or more. This can improve corrosion resistance. On the other hand, the upper limit of the degree of condensation is not particularly limited, but may be, for example, 50 or less, 40 or less, or 30 or less.

The highly condensed phosphate may have, for example, a linear structure, a cyclic structure, or a network structure in which linear structures and cyclic structures are mutually bonded. Among these, it is preferable that the highly condensed phosphate has a cyclic structure or a network structure.

The polyvalent phosphate ester is a compound having a plurality of phosphate ester residues. The phosphate ester residues have a monophosphate structure or a diphosphate structure. The alcohol moiety forming the phosphate ester residue may be any of a primary alcohol, a secondary alcohol, and a tertiary alcohol.
A specific example of the polyvalent phosphate ester is phytic acid.

The content of either the highly condensed phosphate or the polyvalent phosphate ester, or the total content of these, is, in terms of solids content, for example, 0.1% by mass to 1.0% by mass, preferably 0.15% by mass to 0.9% by mass, and more preferably 0.3% by mass to 0.75% by mass in the entire aqueous rust-preventive surface treatment composition. By making the content equal to or greater than the lower limit, corrosion resistance can be improved. By making the content equal to or less than the upper limit, the physical properties of the film can be balanced.

(Other ingredients)
The aqueous rust-preventive surface treatment composition may contain other additives in addition to the above components.
As the other additives, various additives usually contained in the primer material can be used, such as pH adjusters, lubricants, preservatives, fillers, colorants, surfactants, defoamers, leveling agents, antibacterial agents, etc. These may be used alone or in combination of two or more. The amount of the additives added can be appropriately set depending on the application.

Examples of the preservatives include isothiazolinone compounds.

As an example of an aqueous anti-rust surface treatment composition (aqueous anti-rust treatment agent), all of the components contained in the composition may be composed of water-soluble components or water-dispersible components. In other words, the aqueous anti-rust surface treatment composition may be composed of an aqueous solution containing only water-soluble components or water-dispersible components.

In the technical field of aqueous rust prevention treatment agents, the amount of chromium contained in aqueous rust prevention treatment agents is limited from the perspective of environmental considerations, but some aqueous rust prevention treatment agents contain trivalent chromium or hexavalent chromium.

In contrast, the aqueous anti-rust surface treatment composition of the present embodiment is substantially free of chromium components such as hexavalent chromium and trivalent chromium, and can therefore be used as a chromium-free anti-rust treatment agent. This makes it possible to realize an aqueous anti-rust surface treatment composition with reduced environmental impact.

From the viewpoint of further improving the rust prevention properties, it is possible to include a necessary amount of trivalent chromium; however, for example, the amount of this trivalent chromium is preferably limited to 1 mass % or less, more preferably limited to 0.5 mass % or less, even more preferably limited to 0.1 mass % or less, based on the entire aqueous rust prevention surface treatment composition, and it is particularly preferable that the amount of trivalent chromium is substantially not included.
In this specification, the amounts of hexavalent chromium and trivalent chromium refer to the contents of chromium salts having these specific valences.

An example of a surface-coated aluminum member of this embodiment includes an aluminum-based substrate and a silicon coating formed on the surface of the aluminum-based substrate, the silicon coating being made of an aqueous anticorrosive surface treatment composition that contains a silane coupling agent and aqueous colloidal silica.

An example of the surface-coated aluminum member of this embodiment may include an aluminum-based base material, a chemical conversion coating or an anodized coating formed on the surface of the aluminum-based base material, and the silicon coating formed on the surface of the chemical conversion coating or the anodized coating.

Figures 1 and 2 are cross-sectional views showing an example of the configuration of a surface-coated aluminum component 100.

1 and 2, the silicon film 40 in the surface-coated aluminum member 100 may be used as a topcoat layer. That is, the aqueous rust-preventive surface treatment composition of the present embodiment can be used to form a topcoat layer of an aluminum-based substrate.
The silicon film of the top coat layer of the surface-coated aluminum member may be coated with a paint.

The surface-coated aluminum component 100 in FIG. 1 has a layered structure of an aluminum-based substrate 10, a chemical conversion coating 20, and a silicon coating 40.

The surface-coated aluminum member 100 in FIG. 2 has a layered structure of an aluminum-based substrate 10, an anodized film 22, and a silicon film 40.

The silicon film 40 is formed by drying the aqueous rust-preventive surface treatment composition described above.
In the silicon film 40, each component contained in the aqueous rust-preventive surface treatment composition is in a state of undergoing various crosslinking reactions, spatial arrangements, and/or dispersion, as described below. In the silicon film 40, the solvent including water is in a state of being removed by drying, but it is acceptable that some of it inevitably remains.

Although the detailed mechanism is unclear, the structure of the silicon film 40 is presumed to be as follows.
Silane coupling agents can form silicon coatings having two-dimensional and/or three-dimensional crosslinked structures by crosslinking reactions such as hydrolysis and condensation of silyl groups contained in the molecules. The silicon coatings may have alkoxy groups derived from the silane coupling agents. Inorganic particles such as silica having an appropriate particle size are appropriately arranged in the void spaces in the silicon coatings, so that a highly dense silicon coating can be obtained. The surfaces of the inorganic particles such as silica can form chemical bonds with the silicon atoms of the silane coupling agents in the crosslinked structures via oxygen atoms.
Furthermore, silicon atoms derived from the silane coupling agent and transition metal atoms derived from the water-soluble transition metal compound chemically bond to the base film of the chemical conversion film 20 or the anodized film 22 via oxygen atoms, and the silicon film 40 physically bonds to the base film, thereby improving adhesion between the silicon film 40 and the chemical conversion film 20 or the anodized film 22.
In addition, when the aqueous rust-preventive surface treatment composition contains a water-dispersible resin and/or a water-dispersible resin, it softens when heated and almost all of it is incorporated into the silicon film, but on the other hand, the water-soluble resin disappears in part when heated, and not all of it is included in the silicon film.
In addition, when the aqueous rust-preventive surface treatment composition contains a water-soluble transition metal compound, a film having a crosslinked structure is formed by the dehydration condensation reaction between the hydrolysis condensate of the silane coupling agent and the water-soluble transition metal compound.For example, a crosslinked structure is formed in the film between the silicon atom derived from the silane coupling agent and the transition metal atom derived from the water-soluble transition metal compound via an oxygen atom.In addition, the water-soluble transition metal compound can promote the chemical bond with the silane coupling agent or other components contained therein, and form a film with high strength.
In addition, when the aqueous rust-preventive surface treatment composition contains a highly condensed phosphate, the highly condensed phosphate can be appropriately positioned in the film, and the phosphate ions derived from the highly condensed phosphate can be appropriately coordinated to the transition metal atoms derived from the water-soluble transition metal compound, thereby increasing the density of the film and realizing a silicon film with excellent corrosion resistance.

The chemical conversion coating 20 may contain one or more metals contained in the treatment liquid used for the chemical conversion treatment. For example, the chemical conversion coating 30 may contain one or more elements selected from the group consisting of zinc element and zirconium element.

The anodized film 22 is porous, is made of aluminum oxide, and may contain alumina as its main component.

For painting, known paints can be used, such as colored paints, metallic paints, clear paints, colored clear paints, epoxy paints, etc.

Depending on the purpose, the surface-coated aluminum component 100 may be provided with films other than these, and each coating may have a single layer or multiple layers.

The surface-coated aluminum component 100 can provide excellent rust resistance to aluminum-based substrates, making it suitable for a wide range of applications. For example, it can be used for components that are exposed to sunlight or water.

The surface-coated aluminum member 100 can be used for aluminum parts and can be incorporated into aluminum products.
The surface-coated aluminum member 100 can be used, for example, as parts or parts constituting parts of vehicle parts such as automobiles, machine parts, electronic parts, building materials, factory equipment parts, commercial equipment parts, and home equipment parts.

The structure of this embodiment includes a surface-coated aluminum member 100. Examples of this structure include any structure that includes the above-mentioned components, such as vehicles such as automobiles, mechanical devices, electronic devices, buildings, factory equipment, commercial equipment, and household equipment.

The above describes the embodiments of the present invention, but these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of the present invention are included in the present invention.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the description of these examples.

<Preparation of aqueous antirust surface treatment composition>
Each component was weighed according to the blending ratio (mass %) of the raw material components shown in Table 1, and mixed using a stirrer to obtain aqueous rust-preventive surface treatment compositions of Samples 1 to 6.

The information for each component shown in Table 1 is as follows:
(Silane coupling agent)
Epoxy silane 1: 3-glycidoxypropyltriethoxysilane (manufactured by Wacker Asahi Kasei Silicone Co., Ltd., GF-82, solid content: 67% by mass)
(Water-dispersible resin)
Modified epoxy resin 1: Water-based modified epoxy resin having a water-dispersible acrylic polymer (Arakawa Chemical Industries, Ltd., Modelix 305, solid content: 40% by mass)
Polyurethane resin 1: Water-dispersible polyurethane resin (manufactured by Lubrizol, solid content: 60% by mass)
Polyurethane resin 2: Water-dispersible polyurethane resin (Stahl Polymers, solid content: 60% by mass)
(Water-soluble transition metal compounds)
Titanium chelating agent 1: Titanium triethanolamine (manufactured by Matsumoto Fine Chemical Co., Ltd., TC-400, solid content: 20% by mass)
(Inorganic colloidal particles)
Aqueous colloidal silica 1: (Nissan Chemical Industries, Ltd., Snowtex ST-O, acidic sol, particle size: 20 nm, solid content: 40% by mass)
Aqueous colloidal silica 2: (Nissan Chemical Industries, Ltd., Snowtex ST-N, neutral sol, particle size: 10 to 15 nm, solid content: 20% by mass)
(Preservative)
Isothiazolinone compound 1: isothiazolinone compound (manufactured by San-ai Oil Co., Ltd., IT-25XA, solid content: 100% by mass)
(solvent)
・Water 1: Ion-exchanged water ・Alcohol 1: Isopropyl alcohol

Aluminum-based substrate: Aluminum die-cast ADC12

In Table 1, the contents of non-solvent components (silane coupling agent, water-dispersible resin, water-soluble transition metal compound, inorganic colloid particles, and preservative) represent the amounts used.

<Production of surface-coated metal components>

(Chemical conversion treatment)
The aluminum-based substrate was immersed in the zirconium treatment solution (zirconium treatment), taken out, and then dried to obtain an aluminum-based substrate having a chemical conversion coating on its surface.

(Anodizing)
An electric current was passed through the aluminum-based substrate as the anode in an electrolyte solution containing sulfuric acid (anodizing treatment), and the substrate was removed, washed, and dried to obtain an aluminum-based substrate having an anodized film on its surface.

(surface treatment)
An aluminum-based substrate having a chemical conversion coating or an anodized coating on its surface was immersed in the aqueous rust-preventive surface treatment composition of Samples 1 to 6 shown in Table 1, and then heated at 120°C for 15 minutes and dried to form a silicon coating having a thickness of about 1 µm on the chemical conversion coating or anodized coating.

In Examples 1 to 6, the aluminum-based substrate was subjected to the above chemical conversion treatment and the above surface treatment in this order to prepare a test specimen.
In Examples 7 to 12, the aluminum-based substrate was subjected to the above-mentioned anodizing treatment and the above-mentioned surface treatment in this order to prepare a test specimen.
In Comparative Example 1, an aluminum-based substrate was subjected to only the chemical conversion treatment described above, and used as a test piece. In Comparative Example 2, an aluminum-based substrate was subjected to only the anodizing treatment described above, and in Comparative Example 3, the aluminum-based substrate was used as the test piece as it was.

The following evaluation items were evaluated using each test piece obtained.

<Continuous salt spray test: SST test>
For the test pieces of each Example and Comparative Example, a salt spray test (SST, test temperature: 35°C) was carried out for 72 to 240 hours in accordance with JIS Z2371. At the test times of 72, 168, and 240 hours, the state of rust on the surface of each test piece was observed and evaluated based on the following criteria. The results are shown in Table 2.
⊚: No corrosion or discoloration, in good condition.
○: No corrosion, but slight discoloration was observed.
△: Discoloration or slight corrosion is observed, but at a level that does not pose a problem for practical use.
×: The corroded area is 1% or more, and there is a problem in practical use.
XX: Corrosion has occurred over the entire surface, and there is a problem in practical use.

<Combined Cycle Test: CCT Test>
For the test pieces of each Example and Comparative Example, a combined cycle test (2 hours of salt spray at 35°C, → 4 hours of drying at 60°C, → 2 hours of wetting at 50°C, for a total of 8 hours, was carried out in accordance with JASO M 609 for 72 to 240 hours. At the test times of 72, 168, and 240 hours, the state of rust on the surface of each test piece was observed and evaluated based on the following criteria. The results are shown in Table 2.
⊚: No corrosion or discoloration, in good condition.
○: No corrosion, but slight discoloration was observed.
△: Discoloration or slight corrosion is observed, but at a level that does not pose a problem for practical use.
×: The corroded area is 1% or more, and there is a problem in practical use.
XX: Corrosion has occurred over the entire surface, and there is a problem in practical use.

Examples 1 to 12 showed results in which superior corrosion resistance was obtained compared to Comparative Examples 1 to 3.
Furthermore, for the test pieces of Examples 1 to 6 and Comparative Examples 1 to 3, the resistance values of the surface of the aluminum-based substrate were measured at 0 hours and 240 hours of the SST test using an electric resistance meter, penetrating from the silicon film to the chemical conversion film or anodized film. As a result, when the resistance values at 0 hours and 240 hours of the SST test were compared, it was found that in Comparative Examples 1 to 3, the resistance value tended to increase from 10 to 10, whereas in Examples 1 to 6, the resistance value tended to remain at 10 or less with almost no increase.

10 Aluminum-based substrate 20 Chemical conversion film 22 Anodized film 30 Silicon film

Claims (11)

An aqueous rust-preventive surface treatment composition for an aluminum-based substrate, which is used to form a silicon film on an anodic oxide film or a chemical conversion film formed on the surface of the aluminum-based substrate, comprising:
A silane coupling agent;
Inorganic colloid particles;
A solvent comprising water;
1. An aqueous anti-rust surface treatment composition comprising: The aqueous anticorrosive surface treatment composition according to claim 1,
1. An aqueous anti-rust surface treatment composition, wherein the solvent comprises an alcohol. The aqueous anticorrosive surface treatment composition according to claim 2,
The content of the alcohol in the aqueous rust-preventive surface treatment composition is 0.1 mass % or more and 20 mass % or less. The aqueous anticorrosive surface treatment composition according to claim 2,
The aqueous rust-preventive surface treatment composition has an alcohol content of 1 mass % or more and 20 mass % or less, based on a total content of the water and the alcohol of 100 mass %. The aqueous rust-preventive surface treatment composition according to claim 1 or 2,
An aqueous rust-preventive surface treatment composition comprising a water-dispersible resin. The aqueous rust-preventive surface treatment composition according to claim 5,
The aqueous rust-preventive surface treatment composition comprises at least one water-dispersible resin selected from the group consisting of polyacrylic resins, silicone resins, phenolic resins, epoxy resins, polyurethane resins, polyester resins, polyvinyl butyral resins, phenolic resins, and modified versions thereof. The aqueous rust-preventive surface treatment composition according to claim 1 or 2,
The aqueous anti-rust surface treatment composition comprises a rust inhibitor. The aqueous rust-preventive surface treatment composition according to claim 1 or 2,
An aqueous anticorrosive surface treatment composition comprising a water-soluble transition metal compound. The aqueous rust-preventive surface treatment composition according to claim 1 or 2,
An aqueous anti-rust surface treatment composition that is substantially free of chromium components. a surface preparation step including an anodizing step of performing an anodizing treatment on the surface of an aluminum-based substrate to form an anodized film, or a chemical conversion treatment step of performing a chemical conversion treatment to form a chemical conversion film;
and a surface treatment step of applying an aqueous anticorrosive surface treatment composition containing a silane coupling agent, inorganic colloid particles, and a solvent containing water onto the surface of the anodized film or the chemical conversion film, and drying the composition to form a silicon film.
A method for producing a surface-coated aluminum member. An aluminum-based base material;
An anodized film or a chemical conversion film formed on the surface of the aluminum-based base material;
a silicon coating formed on the surface of the anodized coating or the chemical conversion coating, the silicon coating being a dried film of an aqueous antirust surface treatment composition containing a silane coupling agent and aqueous colloidal silica;
A surface-coated aluminum member comprising:

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