WO2015011778A1 - Anti-corrosion coating film structure, metallic member equipped with same, anti-corrosion treatment method, and surface-treating agent - Google Patents

Abstract

An anti-corrosion coating film structure having such a structure that an intermediate layer and a silane coupling layer are laminated in this order on the surface of a metal base material is formed. The intermediate layer is formed of an oxide or hydroxide of at least one metal selected from the group consisting of Ce, La and Y. It is desirable that the intermediate layer contains at least one element selected from the group consisting of Mo, W and V. Thus, it becomes possible to provide a surface having high corrosion resistance and excellent heat resistance, solvent resistance and sliding properties.

Description

Anticorrosive film structure, metal member having the same, anticorrosive treatment method and surface treatment agent

The present invention relates to surface treatment that prevents corrosion on the surface of a metal member.

As a surface treatment of corrosion resistance which has been conventionally carried out, there is a chromate treatment using hexavalent chromium such as chromic acid and dichromic acid. However, from the viewpoint of environmental problems in recent years, surface treatment containing hexavalent chromium is regulated, and development of non-chromium surface treatment is vigorously promoted.

As an example of the non-chromium surface treatment, there is one using a silane coupling agent.

Patent Document 1 discloses a silane coupling agent and at least one selected from the group consisting of vanadium, tungsten, cobalt, aluminum, manganese, cerium, niobium, tin, magnesium, yttrium, calcium, zinc, bismuth, nickel, chromium and molybdenum. An aqueous surface treatment agent containing a compound containing one element is described.

JP, 2009-280889, A

In the case of using a trivalent chromium chelate complex, a vanadium compound or the like, there is a problem that a thick film of about several micrometers is formed.

Moreover, in the anticorrosion method using a silane coupling agent, the thing which satisfies sufficient corrosion resistance is not obtained. In addition, the organofunctional silane has a problem that it is easily removed by rinsing or the like because the bond with the metal surface is not sufficient.

Furthermore, in order to use a silane coupling agent to enhance anticorrosion performance, treatment is often performed stepwise with a plurality of silane coupling agents, and more steps are required. Because of this, it is energy inefficient and has time. Therefore, there are many problems in practical use.

An object of the present invention is to form a coating excellent in heat resistance, solvent resistance and slidability as well as improving corrosion resistance on the surface of a metal.

The anticorrosive film structure of the present invention has a structure in which an intermediate layer and a silane coupling layer are laminated in this order on the surface of a metal substrate, and the intermediate layer is one type selected from the group consisting of Ce, La and Y. It is characterized in that it is formed of an oxide or hydroxide of any of the above metals.

According to the present invention, the surface of the metal can be made high in corrosion resistance and excellent in heat resistance, solvent resistance and sliding property.

It is a schematic cross section which shows the typical film | membrane structure of this invention.

The present invention relates to a surface treatment method for preventing corrosion of metal surfaces. In this method, a rare earth oxide or hydroxide represented by cerium is deposited on a metal, and an organic coating layer with a silane coupling agent is further formed on the metal surface. In other words, the inorganic-organic composite laminated film is formed on the metal surface. This not only improves the corrosion resistance, but also provides a surface excellent in heat resistance, solvent resistance, slidability and smoothness.

The metal surface targeted in the present invention exhibits very smooth and functional characteristics as represented by the surface of a magnetic disk, and is directed to thin films, but with regard to corrosion protection of a thick bulking agent. Is also valid.

The present invention is excellent in corrosion resistance, particularly pitting resistance, by forming a rare earth hydroxide or oxide on metal and forming a stable silane coupling layer thereon, and the function of the metal surface is maintained as it is. It relates to realizing providing a surface having.

The metal anticorrosion method targeted by the present invention is not only to improve the corrosion resistance but also to provide a surface excellent in heat resistance, solvent resistance and slidability, and is further represented by the surface of a magnetic disk. To provide a surface that remains very smooth and functional. Therefore, the properties required as a substance for coating a metal surface are as follows.

(1) To show the corrosion inhibiting action (inhibition of general corrosion) of the target metal or their alloys. Not only overall corrosion but also high pitting resistance in a chloride environment is also required to ensure reliability.

(2) To form a smooth and dense film with as few defects as possible.

(3) Having the function of the metal surface as it is. For example, in the case of a hard disk, it should have a structure that does not cause deterioration of the magnetic recording characteristics due to the increase of the magnetic distance between the magnetic head and the magnetic recording medium. In the case of a sensor, it may be mentioned that it has a sensing function as it is.

The corrosive environment is basically the air or water system, but there are factors such as acidification or alkalization due to decomposition and dissolution of surrounding materials and air pollutants, and contamination with chloride, etc. And corrosion resistance in salt water environment is required.

With regard to the above (1), as a result of various investigations, in order to form a surface excellent not only in corrosion resistance but also in heat resistance, solvent resistance, slidability and smoothness, hydroxides of rare earths on metals or It has been found that this can be achieved by forming an intermediate layer with an oxide and further forming a silane coupling layer thereon. The hydroxide or oxide of the rare earth itself has high corrosion resistance, but it is possible to further improve the corrosion resistance by forming a silane coupling layer having high corrosion resistance and high water repellency thereon.

With regard to the above (2), it is important to form the silane coupling layers in parallel and firmly. The silane coupling agent reacts with hydroxyl groups on the surface to form a chemical bond with the surface through dehydration reaction, so the more the hydroxyl groups are on the surface, the more closely they can be arranged. This results in the formation of a film with few defects at the molecular order level. For example, when bistriethoxysilylpropyl tetrasulfide is used, bistriethoxysilylpropyl tetrasulfide forms a strong coordination bond with aluminum or an aluminum alloy and is thermally treated to share bistriethoxysilylpropyl tetrasulfide molecules. In order to form a bond and form a strong bistriethoxysilylpropyl tetrasulfide molecular film on the metal surface, a film which is extremely dense without defects and excellent in adhesion is formed.

With regard to the above (3), for example, since silane coupling agents such as bistriethoxysilylpropyl tetrasulfide are arranged in molecular order, they form thin oxides or hydroxides of rare earths and form such a silane cup By using the ring agent, it is possible to highly suppress corrosion on the surface which maintains the very smooth and high functional properties.

The present invention is characterized in that an intermediate layer formed of a rare earth (rare earth element) oxide or hydroxide is disposed between the surface of the metal substrate and the silane coupling layer. Here, the rare earth elements mean lanthanoids of Sc and Y and La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu (total 17 types) .

FIG. 1 schematically shows a typical anticorrosive film structure of the present invention.

In the figure, on the surface of the metal base 1, an intermediate layer 2 and a silane coupling layer 3 are laminated in this order. The intermediate layer 2 is formed of an oxide or hydroxide of one or more metals selected from the group consisting of Ce, La and Y. The intermediate layer 2 preferably contains one or more elements selected from the group consisting of Mo, W and V. Further, since the intermediate layer 2 and the silane coupling layer 3 are very thin films, the gloss of the metal substrate 1 is visually observed as it is on the surface.

The metal member having the anticorrosion coating structure shown in this figure has high corrosion resistance and is excellent in heat resistance, solvent resistance and sliding property.

The metal substrate is preferably formed of a transition metal or a plated steel of cobalt or zinc. Here, the transition metal means an element from Group 3 to Group 11 in the periodic table.

Also, the metal substrate may be formed of aluminum, cobalt, nickel or iron or an alloy thereof.

The details of the invention are described below.

As a manufacturing method, a one-step treatment method (forming a rare earth layer and a silane coupling layer simultaneously; hereinafter, also referred to as a "one-step method") and a two-step treatment method (forming a rare earth layer) followed by forming a silane coupling layer There are two types of “two-step method” below. Describe each case.

<One-step method>
A compound containing rare earth, a silane coupling agent, a hydrolyzing agent, a reaction accelerator, and a pH adjuster are added to the solvent 1 to prepare a treatment liquid. The metal substrate is immersed in this treatment liquid for a fixed time. This forms a rare earth oxide or hydroxide on the metal surface and simultaneously forms a silane coupling layer thereon.

In addition, since a silane coupling agent is easy to react with water and to polymerize, when storing, it is desirable to be in a state of being dissolved in an organic solvent. In addition, storage is desirable in a place with low humidity. From such a point, it is desirable to store the compound containing the rare earth in the state of an aqueous solution and store separately from the silane coupling agent. The aqueous solution may be mixed with hydrogen peroxide and molybdate, tungstate or vanadate.

[Solvent 1]
Basically, in order to improve the solubility of the silane coupling agent, a solvent such as one or more alcohols is used as a solvent. The alcohol further improves the stability of the treatment solution as well as the wettability of the metal substrate.

Since the silane coupling agent basically needs to be hydrolyzed, a solvent having a high affinity to water is preferable. Specifically, methanol, ethanol, propanol, butanol and their isomers, ketones such as acetone, methyl ethyl ketone and diethyl ketone, ethers such as dimethyl ether, ethyl methyl ether, diethyl ether and tetrahydrofuran, ethylene glycol and propylene glycol And glycols such as diethylene glycol are used. Besides the alcohol, for example, an organic solvent such as hexane, tetrahydrofuran or xylene may be used.

〔rare earth〕
The rare earths used to form the oxide or hydroxide as an intermediate layer include cerium, lanthanum and yttrium. They can be used in the form of nitrates, sulfates, chlorides, oxalates, acetates or phosphates. In particular, nitrate is desirable among them. The concentration is preferably 1 × 10 −4 to 1 × 10 ⁻¹ M, and more preferably 1 × 10 −3 to 1 × 10 ⁻² M.

〔Silane coupling agent〕
Those used as silane coupling agents are roughly classified into the following two types.

One is represented by the chemical formula X _{3 -n} SiR'SiX _3-n . Here, n is 0 or 1, and X is from a hydrolyzable group (methoxy group, ethoxy group, methoxyethoxy group, propyl group, butyl group, isobutyl group, s-butyl group, t-butyl group and acetyl group) And X may be the same or different. R 'is also selected from the group consisting of an alkyl group, an alkenyl group, and an alkenyl group substituted with at least one amino group or an S group. For example, bis triethoxysilyl ethane _{(BTSE) (H 5 C 2} O) 3 Si-CH 2 CH 2 -Si (OC 2 H 5) 3, bis-triethoxysilylpropyl amine _{(BTSPA) (H 5 C 2} O) 3 Si -(CH ₂ ) ₃ -NH- (CH ₂ ) _3- (OC ₂ H ₅ ) ₃ , bistriethoxysilylpropyl tetrasulfide (BTSPS) (H ₂ C ₂ O) ₃ Si- (CH ₂ ) ₃ -S ₄ And-(CH ₂ ) ₃ -Si (OC ₂ H ₅ ) _{3 and the} like.

Another type is an organofunctional silane represented by the formula X _3-n R _n Si-Y. Here, n is 0 or 1, and X is a hydrolyzable group such as methoxy, ethoxy, methoxyethoxy, propyl, butyl, isobutyl, s-butyl, t-butyl and acetyl. And X may be the same or different, and Y is represented by amino group, mercapto group, phenyl group, vinyl group, epoxy group, methacryl group, isocyanate group, ureido group, mercapto group Are selected from the group consisting of organic functional groups and aryl groups.

For example, vinylsilane CH ₂ CHCHSi (OCH ₂ CH ₃ ) ₃ , 3-glycidoxypropyltrimethoxysilane CH _2- (O) -CHCH ₂ OCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ , 3-mercaptopropyl Triethoxysilane HSCH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ , 3-aminopropyltriethoxysilane H ₂ NCH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ , phenyltriethoxysilane (C ₂ H) ₅ O) ₃ Si-C ₆ H ₅ , 3-methacryloxypropyl triethoxysilane CH ₂ CC (CH ₃ ) COOCH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ , 3-isocyanatopropyltrimethoxysilane O _{= C = NCH 2 CH 2 CH} 2 Si (OCH 2 CH 3) 3 Decyltrimethoxysilane _{CH 3 (CH 2) 9 Si} (OCH 3) 3, 3- ureidopropyltriethoxysilane _{(C 2} H ₅₎ etc. _{3 SiC 3 H 6 NHC (O} ) NH 2 and the like.

Besides, octadecyltriethoxysilane, bistriethoxysilylethane, bistriethoxysilylhexane, bistriethoxysilylethylene, bistrimethoxysilylethylbenzene and the like are also effective. The aforementioned silane coupling agents are at least partially, preferably completely hydrolyzed. The concentration of these silane coupling agents is about 0.05 to 10% by weight, more preferably 0.2 to 2% by weight.

[Hydrolyzing agent]
Water needs to be added in order to hydrolyze the silane coupling agent. The amount of water used is suitably in the range of about 2% to 20% with respect to the entire treatment solution. In order to enhance hydrolysis and solution stability, 0.2 to 1.0% of acetic acid may be added as appropriate. The optimum value of the addition amount of acetic acid is 0.5%.

[Reaction accelerator]
A reaction promoter such as hydrogen peroxide may be added to promote the formation reaction of the rare earth oxide or hydroxide as well as the silane coupling layer formation reaction. When hydrogen peroxide is used, several percent is suitable.

[PH adjuster]
In order to promote the hydrolysis reaction of the silane coupling agent and the formation reaction of the oxide or hydroxide, it is preferable to maintain the pH at 7 or less, preferably to 2 to 6 if possible. . As the pH adjuster, hydroxides such as potassium hydroxide, ammonia, acetic acid, formic acid, sulfuric acid, hydrochloric acid, nitric acid and the like are suitable.

〔Additive〕
The corrosion resistance can be further improved by including an element having a plurality of valences in the rare earth oxide layer or hydroxide layer. In order for this multivalent number of anions to have this effect, it is effective to add the corresponding oxo acid as an additive in the form of a salt. The oxo acid salts include molybdate, tungstate and vanadate. Besides these, salts containing phosphate and zirconium are also effective as additives. The concentration of the additive is suitably about 0.2 to 1.0%.

[Post-processing]
After the immersion treatment, it is dried by blowing air or spin-out with a spinner. It may be dried by maintaining the temperature range from room temperature to 50 ° C.

Furthermore, after the treatment, a heat treatment may be performed for the purpose of performing a crosslinking reaction of the silane coupling layer. This can improve the corrosion resistance. The heat treatment is preferably performed at a temperature of 100 to 200 ° C. for 30 minutes to 2 hours in the air, and more preferably at a temperature of 100 to 150 ° C. for 30 minutes to 1 hour.

As a method of adjusting the solution, for example, it can be adjusted by the following method.

The silane coupling agent is added to the solvent 1 and acetic acid is further added to adjust to a predetermined pH. Furthermore, water for hydrolysis is added and stirred vigorously for several hours in that state. Thereafter, the compound of the rare earth, the reaction accelerator and the additive are dissolved to a predetermined concentration after standing for one day. The processing time is suitably from several tens minutes to several hours. The following examples and comparative examples all show the case of immersion for 2 hours (however, only comparative example 8 is the case of immersion for 100 h).

Two-stage method
The metal base is immersed in a solution (aqueous solution) in which the compound containing the rare earth in the solvent 2 and the reaction accelerator are added to form an oxide or hydroxide of the rare earth on the metal base. Next, the metal base on which the oxide or hydroxide film of rare earth is formed is dipped in a solution in which a silane coupling agent, a hydrolyzing agent, a reaction accelerator and a pH adjuster are added to solvent 3 (organic solvent). , Form a silane coupling layer.

It is preferable that the solution containing the solvent 2 (aqueous solution) and the solution containing the solvent 3 (organic solvent) be separately stored. The aqueous solution may be mixed with hydrogen peroxide and molybdate, tungstate or vanadate.

(first stage)
Form oxides or hydroxides of the rare earths.

[Solvent 2]
Basically use water.

〔rare earth〕
Rare earths used for oxide or hydroxide formation include cerium, lanthanum and yttrium. They can be used in the form of nitrates, sulfates, chlorides, oxalates, acetates or phosphates. In particular, nitrate is desirable among them.

[Reaction accelerator]
A reaction promoter such as hydrogen peroxide may be added to promote the formation reaction of rare earth oxides or hydroxides.

〔Additive〕
The corrosion resistance can be further improved by including an element having a plurality of valences in the rare earth oxide layer or hydroxide layer. In order for this multivalent number of anions to have this effect, it is effective to add the corresponding oxo acid as an additive in the form of a salt. The oxo acid salts include molybdate, tungstate and vanadate. Besides them, salts containing phosphate or zirconium as an additive are also effective.

[Post-processing]
After the immersion treatment, it is dried by blowing air or spin-out with a spinner. Alternatively, it may be dried by maintaining the temperature range from room temperature to 50 ° C.

(Second stage)
Form a silane coupling layer.

[Solvent 3]
Since the solubility of some silane coupling agents in water is limited, basically, in order to improve the solubility of the silane coupling agent, one or more alcohols, etc. (organic ) Is used. The alcohol further improves the stability of the treatment solution as well as the wettability of the metal substrate. The silane coupling agent is preferably a solvent having a high affinity for water since it basically needs to be hydrolyzed. Specifically, methanol, ethanol, propanol, butanol and their isomers, ketones such as acetone, methyl ethyl ketone and diethyl ketone, ethers such as dimethyl ether, ethyl methyl ether, diethyl ether and tetrahydrofuran, ethylene glycol and propylene glycol And glycols such as diethylene glycol are used. The organic solvent other than alcohol may be, for example, hexane, tetrahydrofuran, xylene or the like.

〔Silane coupling agent〕
Those used as silane coupling agents are roughly classified into the following two types. One of them is represented by the structure of X _3-n SiR'SiX _3-n , n is 0 or 1, and X is a hydrolyzable group such as methoxy, ethoxy, methoxyethoxy, propyl, butyl It is selected from the group consisting of a group, isobutyl group, s-butyl group, t-butyl group and acetyl group, and X's may be the same or different. R 'is also selected from the group consisting of an alkyl group, an alkenyl group, an alkenyl group substituted with at least one amino group or an S group. For example, bis triethoxysilyl ethane _{(BTSE) (H 5 C 2} O) 3 Si-CH 2 CH 2 -Si (OC 2 H 5) 3, bis-triethoxysilylpropyl amine _{(BTSPA) (H 5 C 2} O) 3 Si -(CH ₂ ) ₃ -NH- (CH ₂ ) _3- (OC ₂ H ₅ ) ₃ , bistriethoxysilylpropyl tetrasulfide (BTSPS) (H ₂ C ₂ O) ₃ Si- (CH ₂ ) ₃ -S ₄ And-(CH ₂ ) ₃ -Si (OC ₂ H ₅ ) _{3 and the} like. Another type is the organofunctional silane represented by the structure X _{3 -n} R _n Si-Y, n is 0 or 1, and X is a hydrolyzable methoxy group, ethoxy group, methoxyethoxy Group selected from the group consisting of a propyl group, a butyl group, an isobutyl group, an s-butyl group, a t-butyl group and an acetyl group, and X may be the same or different, and Y is an amino group, a mercapto group It is selected from the group consisting of an organic functional group represented by a group, a vinyl group, an epoxy group, a methacryl group, an isocyanate group, a ureido group, a mercapto group and an alkyl group. For example, vinylsilane CH ₂ CHCHSi (OCH ₂ CH ₃ ) ₃ , 3-glycidoxypropyltrimethoxysilane CH _2- (O) -CHCH ₂ OCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ , 3-mercaptopropyl Triethoxysilane HSCH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ , 3-aminopropyltriethoxysilane H ₂ NCH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ , phenyltriethoxysilane (C ₂ H) ₅ O) ₃ Si-C ₆ H ₅ , 3-methacryloxypropyl triethoxysilane CH ₂ CC (CH ₃ ) COOCH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ , 3-isocyanatopropyltrimethoxysilane O = C = NCH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ And decyltrimethoxysilane CH ₃ (CH ₂ ) ₉ Si (OCH ₃ ) ₃ , 3-ureidopropyltriethoxysilane (C ₂ H ₅ ) ₃ SiC ₃ H ₆ NHC (O) NH _{2 and the} like.

Besides, octadecyltriethoxysilane, bistriethoxysilylethane, bistriethoxysilylhexane, bistriethoxysilylethylene, bistrimethoxysilylethylbenzene and the like are also effective. The aforementioned silane coupling agents are at least partially, preferably completely hydrolyzed. The concentration of these silane coupling agents is about 0.05 to 10% by weight, more preferably 0.2 to 1% by weight.

[Hydrolyzing agent]
Water needs to be added because it is necessary to hydrolyze the silane coupling agent. The amount of water to be used is suitably in the range of about 2 to 20% with respect to the entire treatment solution. In order to enhance hydrolysis and solution stability, 0.2 to 1.0% of acetic acid may be added as appropriate. The addition amount of acetic acid is optimally 0.5%.

[PH adjuster]
In order to accelerate the hydrolysis reaction of the silane coupling agent and the formation reaction of the oxide or hydroxide, the pH is preferably maintained at 7 or less, and more preferably 2 to 6 . As the pH adjuster, hydroxides such as potassium hydroxide, ammonia, acetic acid, formic acid, sulfuric acid, hydrochloric acid, nitric acid and the like are suitable. After the immersion treatment, it is dried by blowing air or spin-out with a spinner. It may be dried by maintaining the temperature range from room temperature to 50 ° C. Furthermore, corrosion resistance can be improved by heat-processing for the purpose of performing the crosslinking reaction of a silane coupling layer after a process. As the heat treatment, the temperature is preferably 100 to 200 ° C., and the time is preferably 30 minutes to 2 hours, and more preferably 100 to 150 ° C. for 30 minutes to 1 hour.

[Post-processing]
After the immersion treatment, it is dried by blowing air or spin-out with a spinner. It may be dried by maintaining the temperature range from room temperature to 50 ° C. Furthermore, corrosion resistance can be improved by heat-processing for the purpose of performing the crosslinking reaction of a silane coupling layer after a process. As the heat treatment, it is preferable to set the temperature to 100 to 200 ° C. and the time to 30 minutes to 2 hours in an air atmosphere, and more preferably 100 to 150 ° C. for 30 minutes to 1 hour.

The solution can be prepared, for example, by the following method.

In the preparation of the first-stage solution, the rare earth compound, the reaction accelerator and the additive are dissolved in the solvent 2. The processing time of the first stage is suitably from several tens minutes to several hours. The following examples all show the case of immersion for 2 hours.

In the preparation of the second-stage solution, a silane coupling agent, a hydrolyzing agent, and a pH adjuster are added to the solvent 3, and the solution is vigorously stirred for 1 hour. The processing time for the second stage is suitably several minutes to several hours. The following examples all show the case where each treatment was immersed for 30 minutes.

The following was carried out as a corrosion evaluation.

Samples of cobalt and aluminum and alloys thereof were prepared by sputtering titanium oxide as an adhesion layer on a silicon wafer, and then sputtering and depositing the target aluminum or aluminum alloy thereon. In addition, as a bulking agent, galvanized steel sheet, carbon steel, and nickel were also used. Various materials were heat-treated, that is, heat-treated at 100 ° C. in air for 1 h in air after forming a film by the above-described one-step method or two-step method.

The following two methods were evaluated for corrosion resistance evaluation.

(1) Electrochemical test: 1 cm ^{2 of} the sample subjected to rare earth-silane coupling treatment and heat treatment was left, and the other part was sealed. It was immersed in a 3.5 wt% NaCl aqueous solution. After immersion for 10 minutes, when the potential was stabilized, the potential was scanned at a scanning speed of 30 mV / min in the anode direction based on a potential as low as −100 mV from the immersion potential, and the current was measured. After measurement, the corrosion current density was determined using the Tafel equation. Further, the potential at which the current rises sharply was taken as a pitting potential, and when the potential was 500 mV or more, the pitting resistance was considered to be good. The more noble this potential, the better the pitting resistance.

(2) Immersion test: The sample subjected to the rare earth-silane coupling treatment and the heat treatment was immersed in a 3.5% NaCl solution. The occurrence of pitting was observed by an optical microscope. Those with no change were represented by ○, those with no occurrence of pitting but with a discoloration area were represented by Δ, and those with occurrence of pitting were indicated by x.

Hereinafter, specific embodiments to which the present invention is applied will be described with reference to a table. Although not described in particular, all test temperatures are 25 ° C.

Table 1 shows an example and a comparative example (electrochemical evaluation) in the case of one-step treatment.

　〔一段処理のＡｌに関して〕
　（比較例１）
　未処理のＡｌの腐食電流密度は０．０５２μＡ／ｃｍ^２、孔食電位は－６５０ｍＶである。

[Regarding Al in One-Step Process]
(Comparative example 1)
The corrosion current density of untreated Al is 0.052 μA / cm ² and the pitting potential is -650 mV.

The comparative example 1 is a numerical value which becomes a standard in considering improvement of the corrosion resistance of Al. Compared to this, the lower the corrosion current density, the better the shift of the pitting potential to the noble side (the larger the value to +), the better the corrosion resistance.

(Comparative example 5)
The corrosion current density in a 3.5 wt% NaCl solution of Al treated with a 0.02 M aqueous solution of cerium nitrate is 0.033 μA / cm ² , and the pitting potential is −520 mV.

(Comparative example 6)
The corrosion current density in a 3.5 wt% NaCl solution of Al in an aqueous ethanol solution containing 1 wt% BTSE, 10% H ₂ O and 1 wt% hydrogen peroxide is 0.038 μA / cm ² and the pitting potential is -615 mV. The sample is heat-treated at 100 ° C. for 1 h.

(Comparative example 7)
The corrosion current density in a 3.5 wt% NaCl solution of Al in an aqueous ethanol solution containing 1 wt% BTSE and 10% H ₂ O is 0.048 μA / cm ² , and the pitting potential is -648 mV. The sample is heat-treated at 100 ° C. for 1 h.

(Comparative example 8)
The corrosion current density in a 3.5 wt% NaCl solution of Al in an aqueous ethanol solution containing 1 wt% BTSE and 10% H ₂ O is less than 0.001 μA / cm ² (below detection limit), and the pitting potential is −320 mV. The immersion time is 100 h only in this example. The sample is heat-treated at 100 ° C. for 1 h.

The Al was treated with an aqueous ethanol solution containing 0.02 M cerium nitrate, 1 wt% BTSE and 10% H ₂ O. The corrosion current density of the treated material in a 3.5 wt% NaCl solution is less than 0.001 μA / cm ² (below the detection limit), and the pitting potential is -180 mV. Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment. The sample is heat-treated at 100 ° C. for 1 h. By means of photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), and Auger electron spectroscopy (AES), cerium hydroxide and oxide are formed on Al, and a BTSE layer is formed thereon. (The structure is as shown in FIG. 1).

Comparative Example 5 is a case where only cerium nitrate is treated, but although the corrosion current density is slightly lower than Comparative Example 1 and the pitting potential is also slightly shifted to the noble side, the extent thereof is small, this example There is no significant improvement in corrosion resistance. In this case, it was confirmed that cerium hydroxide and oxide were formed on Al.

Comparative Example 7 is the case of treatment with BTSE, but although the corrosion current density is slightly lower than Comparative Example 1, the pitting potential is hardly changed, and the corrosion resistance improvement as in this Example is not seen. In this case, it was confirmed that a BTSE layer was formed on Al.

Comparative Example 6 is the case of treatment with BTSE, but although the corrosion current density is slightly lower than Comparative Example 1, the pitting potential hardly changes, and the corrosion resistance improvement as seen in this example is not seen. In this case, it was confirmed that the BTSE layer was formed on the aluminum oxide layer thicker than the natural oxide film on Al.

When the present example and comparative examples 5 to 7 are compared, it is insufficient with cerium oxide or cerium hydroxide, BTSE layer or base metal oxide or base metal hydroxide layer + BTSE layer to significantly improve the corrosion resistance. It can be said that the structure of the cerium oxide layer or the cerium hydroxide layer + the BTSE layer is essential. Comparative Example 8 has the same composition as Comparative Example 7, but the immersion time is as long as 100 h (the immersion time is not written in Table 1. In other cases, the immersion time is 2.0 h as described above) Is). If it is immersed for a long time, the same corrosion resistance as in the case of this example can be obtained, but in order to obtain high corrosion resistance in a short time, the configuration of the cerium oxide layer or the cerium hydroxide layer + the BTSE layer is essential.

It was treated with Al in 0.02M cerium nitrate, an aqueous ethanol solution containing 0.2 wt% of sodium molybdate as a _{1wt% BTSE, 10% H 2} O , and additives. The sample is heat-treated at 100 ° C. for 1 h. The corrosion current density of the treated material in a 3.5 wt% NaCl solution is less than 0.001 μA / cm ² (below the detection limit), and the pitting potential is +100 mV.

Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment. In particular, the pitting potential is shifted to the noble side by 700 mV or more, and it can be seen that the pitting resistance is significantly improved. Film analysis confirmed that Mo was incorporated in the cerium oxide (or hydroxide). It can be estimated that the presence of Mo causes the pitting potential to be significantly shifted to the noble side.

The Al was treated with an aqueous ethanol solution containing 0.1 M cerium nitrate, 1 wt% BTSE and 10% H ₂ O. The sample is heat-treated at 100 ° C. for 1 h. The corrosion current density of the treated material in a 3.5 wt% NaCl solution is less than 0.001 μA / cm ² (below the detection limit), and the pitting potential is −26 mV. Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment. The pitting potential is further shifted to the noble side as compared with Example 1 in which the concentration is low.

In this example, lanthanum nitrate was used in place of cerium nitrate used in Example 1. The sample is heat-treated at 100 ° C. for 1 h. The corrosion current density in the 3.5 wt% NaCl solution of the treated material is less than 0.001 μA / cm ² (below the detection limit), and the pitting potential is −250 mV. Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment.

This example is the case where yttrium nitrate is used instead of the cerium nitrate used in Example 1. The sample is heat-treated at 100 ° C. for 1 h. The corrosion current density in the 3.5 wt% NaCl solution of the treated material is less than 0.001 μA / cm ² (below the detection limit), and the pitting potential is −220 mV. Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment. When considered together with the case of Example 4, it can be seen that the corrosion resistance is improved by using a rare earth.

This example is the case where BTESPT was used instead of BTSE which is a coupling agent used in Example 1. The sample is heat-treated at 100 ° C. for 1 h. The corrosion current density of the treated material in a 3.5 wt% NaCl solution is less than 0.001 μA / cm ² (below the detection limit), and the pitting potential is −26 mV. Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment.

In this example, γ-APS was used instead of BTSE which is a coupling agent used in Example 1. The sample is heat-treated at 100 ° C. for 1 h. The corrosion current density of the treated material in a 3.5 wt% NaCl solution is less than 0.001 μA / cm ² (below the detection limit), and the pitting potential is −420 mV. Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment.

In this example, acetic acid was used in place of H ₂ O which is a hydrolyzing agent used in Example 6. The sample is heat-treated at 100 ° C. for 1 h. The corrosion current density of the treated material in a 3.5 wt% NaCl solution is less than 0.001 μA / cm ² (below the detection limit), and the pitting potential is -155 mV. Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment.

In this example, hydrogen peroxide is added as a reaction promoter in place of sodium molybdate, which is an additive used in Example 2. The sample is heat-treated at 100 ° C. for 1 h. The corrosion current density in the 3.5 wt% NaCl solution of the treated material is less than 0.001 μA / cm ² (below the detection limit), and the pitting potential is −15 mV. Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment.

[Regarding the galvanized steel sheet in one-step process]
(Comparative example 2)
The corrosion current density of the untreated galvanized steel sheet is 10.21 μA / cm ² , and no pitting potential is detected.

0.02M cerium nitrate were treated galvanized steel sheet in an aqueous ethanol solution containing 1wt% BTESPT and 10% _{H 2} O. The sample is heat-treated at 100 ° C. for 1 h. The corrosion current density in the 3.5 wt% NaCl solution of the treated material is 0.35 μA / cm ² . No pitting potential is detected. Since the corrosion current density is lower than that of Comparative Example 2, it can be said that the corrosion resistance is remarkably improved by this treatment.

[Regarding Co in one-step processing]
(Comparative example 3)
The corrosion current density of untreated Co is 7.05 μA / cm ² and no pitting potential is detected.

0.02M cerium nitrate were treated Co ethanol aqueous solution containing 1wt% BTESPT and 10% _{H 2} O. The sample is heat-treated at 100 ° C. for 1 h. The corrosion current density in the 3.5 wt% NaCl solution of the treated material is 0.18 μA / cm ² . No pitting potential is detected. As compared to Comparative Example 3, the corrosion current density is lowered, so it can be said that the corrosion resistance is remarkably improved by this treatment.

[Regarding Ni in One-Step Process]
(Comparative example 4)
The corrosion current density of untreated Ni is 3.42 μA / cm ² and no pitting potential is detected.

0.02M cerium nitrate were treated Ni ethanol aqueous solution containing 1wt% BTESPT and 10% _{H 2} O. The sample is heat-treated at 100 ° C. for 1 h. The corrosion current density in the 3.5 wt% NaCl solution of the treated material is 0.21 μA / cm ² . No pitting potential is detected. As compared to Comparative Example 4, since the corrosion current density is reduced, it can be said that the corrosion resistance is remarkably improved by this treatment.

Table 2 shows an example and a comparative example (electrochemical evaluation) in the case of the two-stage treatment.

　〔二段処理のＡｌに関して〕

[Regarding Al in Two-Step Processing]

In this example, after being immersed in a 0.02 M cerium nitrate solution as the first treatment, Al was immersed in an ethanol solution of 1 wt% BTSE (water as a hydrolyzing agent) in the second treatment. After the second stage treatment, the sample is subjected to heat treatment at 100 ° C. for 1 h. The corrosion current density in a 3.5 wt% NaCl solution is less than 0.001 μA / cm ² (below detection limit), and the pitting potential is −235 mV. Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment.

In this example, after immersing in an aqueous solution in which 1 wt% hydrogen peroxide is added as a reaction accelerator in 0.02 M cerium nitrate solution as the first stage treatment, ethanol of 1 wt% BTSE (water as a hydrolyzing agent) in the second stage treatment The solution was immersed in Al. After the second stage treatment, the sample is subjected to heat treatment at 100 ° C. for 1 h. The corrosion current density in a 3.5 wt% NaCl solution is 0.001 μA / cm ² or less (below the detection limit), and the pitting potential is -18 mV. Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment. The addition of hydrogen peroxide causes many hydroxyl groups to be introduced on the surface of the cerium oxide to be formed, and the BTSE is arranged more and more orderly, so the pitting potential is considered to be largely shifted to the noble side. .

This example is the case where cerium chloride is used instead of the cerium nitrate used in Example 14. After the second stage treatment, the sample is subjected to heat treatment at 100 ° C. for 1 h. The corrosion current density in a 3.5 wt% NaCl solution is less than 0.001 μA / cm ² (below the detection limit), and the pitting potential is −22 mV. Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment. In the case of chloride, the same corrosion control effect as in the case of nitrate is obtained.

In this example, after immersing in an aqueous solution obtained by adding 0.4 wt% sodium tungstate as an additive to 0.02 M lanthanum sulfate solution as the first stage treatment, 1 wt% BTESPT (water as a hydrolyzing agent) for the second stage treatment Al was immersed in an ethanol solution. After the second stage treatment, the sample is subjected to heat treatment at 100 ° C. for 1 h. The corrosion current density in a 3.5 wt% NaCl solution is less than 0.001 μA / cm ² (below detection limit), and the pitting potential is 35 mV. Compared to Comparative Example 1, the corrosion current density is lowered and the pitting potential is shifted to the noble side by several hundred mV or more, so it can be said that the corrosion resistance is remarkably improved by this treatment. It has been confirmed that lanthanum oxide containing tungsten is formed on Al.

(Comparative example 9)
This comparative example is a case where it was changed to hydrogen peroxide solution immersion instead of the cerium nitrate immersion of the one-step process of Example 13. This is because hydrogen peroxide forms an oxide having a thickness greater than that of the natural oxide film on the Al surface. After the second stage treatment, the sample is subjected to heat treatment at 100 ° C. for 1 h. Although the corrosion current density is slightly lower than Comparative Example 1, the pitting potential is hardly changed, and the corrosion resistance improvement as in this Example is not observed. This indicates that the formation of the rare earth oxide has higher corrosion resistance than the formation of the Al oxide.

(Comparative example 10)
This comparative example is a case where Al is held at a constant temperature and humidity and an oxide and a hydroxide are formed on the surface in the one-step process as in Comparative Example 9. After the second stage treatment, the sample is subjected to heat treatment at 100 ° C. for 1 h. Although the corrosion current density is slightly lower than Comparative Example 1, the pitting potential is hardly changed, and the corrosion resistance improvement as in this Example is not observed. This indicates that the formation of the rare earth oxide has higher corrosion resistance than the formation of the Al oxide.

Table 3 shows the immersion test results when each treatment was applied.

　比較例１１～１４は、それぞれＮｏ．１、５、６および７（表１のＮｏ．）の処理を施した試料の浸漬試験結果を示す。いずれの場合も７日以降で孔食が発生している。

The comparative examples 11 to 14 are respectively No. The immersion test result of the sample which performed the process of 1, 5, 6 and 7 (No. of Table 1) is shown. In any case, pitting occurs after 7 days.

In Examples 19 to 30, each of the Nos. 2 to 9 (No. in Table 1) and No. 2 The immersion test results of the samples subjected to the treatments of 21 to 24 (No. in Table 2) are shown. In any case, pitting corrosion is not observed and exhibits good corrosion resistance.

In any of the examples, only one rare earth compound and one silane coupling agent are used, but similar results can be obtained by mixing a plurality of compounds. For example, not only cerium nitrate, but also a mixture of cerium nitrate and yttrium nitrate, a mixture of cerium nitrate and cerium chloride. In addition to BTSE, a mixture of BTSE and BTESPT is also effective.

The effects of the present invention will be described below.

According to the present invention, corrosion resistance, in particular, the resistance to holes, is achieved by providing an intermediate layer of an oxide or hydroxide composed of a rare earth element between a metal and a silane coupling layer, with respect to the metal. It can be realized to provide a surface that is excellent in corrosion resistance and still has the function of the metal surface.

Further, according to the present invention, an inorganic-organic organic compound is formed by forming an oxide or hydroxide of a rare earth on the metal surface of the transition metal and their alloys and further treating the upper layer with a silane coupling agent. By forming the composite laminated film, it is possible to provide a surface which is excellent in corrosion resistance, particularly pitting resistance, and which has the function of the metal surface as it is. Although this is a technology developed with a thin film in mind, it can of course also be used to improve the corrosion resistance of thick bulk materials.

1: Metal substrate, 2: Intermediate layer, 3: Silane coupling layer.

Claims (15)

It has a structure in which an intermediate layer and a silane coupling layer are laminated in this order on the surface of a metal substrate, and the intermediate layer is an oxide of one or more metals selected from the group consisting of Ce, La and Y or An anticorrosive coating structure characterized in that it is formed of a hydroxide. The anticorrosion film structure according to claim 1, wherein the intermediate layer contains one or more kinds of elements selected from the group consisting of Mo, W and V. The anticorrosion film structure according to claim 1, wherein the surface has a gloss of the metal substrate. The anticorrosive coating structure according to any one of claims 1 to 3, wherein the metal base is formed of a transition metal or a plated steel of cobalt or zinc. The anticorrosion film structure according to any one of claims 1 to 3, wherein the metal base is formed of aluminum, cobalt, nickel or iron or an alloy thereof. A metal member having the anticorrosive coating structure according to any one of claims 1 to 5. The metal base is immersed in an aqueous solution containing a salt of one or more metals selected from the group consisting of Ce, La and Y, and then treated with a liquid containing a silane coupling agent and an organic solvent. Anticorrosion treatment method. The said organic solvent is alcohol, The anti-corrosion treatment method of Claim 7 characterized by the above-mentioned. What is claimed is: 1. A method of corrosion prevention treatment comprising treating a metal substrate with a solution containing a salt of one or more metals selected from the group consisting of Ce, La and Y and a silane coupling agent. The method according to any one of claims 7 to 9, wherein the salt is a nitrate, a sulfate, a chloride or an acetate. The method of corrosion prevention treatment according to any one of claims 7 to 10, wherein the metal base is formed of a transition metal or a plated steel of cobalt or zinc. A treating agent for forming an anticorrosive film on the surface of a metal substrate, comprising a nitrate, a sulfate, a chloride or an acetate of a rare earth element, and a silane coupling agent. The surface treatment agent according to claim 12, further comprising hydrogen peroxide and molybdate, tungstate or vanadate. A treating agent for forming an anticorrosive film on the surface of a metal substrate, which is a two-component set stored separately, comprising an aqueous solution containing a salt of one or more metals selected from the group consisting of Ce, La and Y And a liquid containing a silane coupling agent and an organic solvent. The surface treatment agent according to claim 14, wherein the aqueous solution further contains hydrogen peroxide and molybdate, tungstate or vanadate.

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