JP3968438B2 - Method for forming organic film by light treatment - Google Patents

Description

The present invention relates to a method for surface modification of a metal substrate and a product thereof. More specifically, the present invention relates to an improvement in adhesion of an organic film formed on a metal substrate and an anticorrosion property by the organic film, The present invention relates to a method for forming a novel metal film that can remarkably improve the adhesion and anticorrosion properties of an organic film by extremely reducing bond defects when bonded to an oxide film.
The present invention provides, for example, an organic film on a metal substrate made of iron, steel, stainless steel, nickel-base alloy, copper, aluminum, and alloys thereof to form an organic film to improve the corrosion resistance. In the technical fields of film formation methods and surface modification methods, novel organic film formation methods, surface modification methods and their high anticorrosion properties that can significantly improve the adhesion and corrosion resistance of organic coatings on metal substrates Useful for providing metal products.

  Up to now, for example, as a method of forming a homogeneous metal oxide thin film without cracks, in the prior literature, when forming a metal oxide prepared from a solution containing a metal salt and an unsaturated organic compound solvent, In order to remove the organic compound solvent, ultraviolet rays are used (Patent Document 1). In another document, in order to obtain a good photocatalytic hydrophilic coating, it has been proposed to irradiate ultraviolet rays when removing dirt caused by water-repellent silicon (Patent Document 2). In another document, a method of irradiating ultraviolet rays of 250 nm or less is proposed as a method for making etching difficult in a semiconductor manufacturing apparatus (Patent Document 3). However, in these methods, it is not considered at all to form an organic film having high adhesion selectively with the base metal oxide.

  In other literatures, a method of irradiating these with ultraviolet rays has been proposed as a surface modification method for a substrate of silicon, germanium, tin, titanium, and zirconium and a method for producing an organic thin film (Patent Document 4). However, in this method, for example, when a nanoscale oxide film is formed on iron, steel, stainless steel, nickel-base alloy, copper, aluminum, and alloys thereof, the surface was modified by irradiation with ultraviolet rays. Nothing is envisaged later on to form organic thin films containing hydroxamic acid groups that selectively complex with oxides.

  In another document, a method of producing a metal oxide thin film by applying a solution containing an organic acid metal salt and an organic metal complex on a substrate and then irradiating with ultraviolet rays is proposed (Patent Document 5). . However, in this method, when the metal oxide film is formed on the metal ingot, or before the oxide film is formed and stabilized or before it is crystallized, the surface is effectively irradiated with ultraviolet rays. Nothing is said about forming an organic film for the purpose of improving anticorrosion properties after modification.

  In another document, as a method for flattening the surface of a silicon wafer at an atomic level and improving the dielectric breakdown characteristics of an oxide film, a technique of irradiating ultraviolet rays in a hydrofluoric acid aqueous solution is proposed (Patent Document 6). . However, this method is completely different from semiconductors, for example, when organic molecules bind to oxide films formed in the atmosphere on iron, steel, stainless steel, nickel-base alloys, copper, aluminum, and their alloys. There is no assumption about reducing the bonding defects, and no irradiation with ultraviolet rays in the atmosphere is assumed.

Further, in other documents, it is clear that when ultraviolet rays are irradiated to suppress the occurrence of pitting corrosion, strong ultraviolet rays of 8 mW / cm ² or more are effective, and 1.4 mW / cm ² or less are not very effective. (Non-patent Document 1). However, in this case, ultraviolet irradiation is effective for improving the adhesion and the like of the organic film formed on the metal substrate, and for example, the anticorrosion property of the organic film is extremely improved even with an ultraviolet intensity of 1.1 mW / cm ^2. Nothing is supposed about being effective.
Japanese Patent Laid-Open No. 2002-97018 Japanese Patent Laid-Open No. 11-50006 Japanese Patent Laid-Open No. 9-232538 JP 2001-246243 A JP-A-11-256342 JP-A-8-330198 Electrochimica Acta, 32, 1987, 1739

  Under such circumstances, in view of the above prior art, the present inventors, when forming an organic film on the base metal, have strong adhesion to the air oxide film or passive film on the base metal and anticorrosion. As a result of intensive research with the goal of establishing a technology for forming an organic film with the property, a metal oxide film is formed on a metal ingot, or an oxide film is formed and stabilized or crystallized. Aiming at the front, when forming an organic film containing hydroxamic acid groups for the purpose of improving the anticorrosion after irradiating with ultraviolet rays and surface modification, it has been found that the adhesion and anticorrosion of the film are significantly improved, Based on this finding, the present invention has been completed.

The present invention does not require a special environment such as a large device, an expensive device, or a vacuum, and can easily and in an atmosphere, for example, an ultraviolet lamp of 1.1 mW / cm ² , which is weaker and more economical than the conventional one. It is an object of the present invention to provide a novel organic film forming technique that can be used to impart extremely high corrosion resistance to an organic film.

The present invention for solving the above-described problems comprises the following technical means.
(1) A method for forming an organic film that improves the adhesion and anticorrosion properties of an organic film formed on a metal substrate, and 1) removes an air oxide film or hydroxide on the metal substrate to form a metal ingot. 2) After that, when the metal oxide film and / or hydroxide film is spontaneously formed, or before a passive film is formed in an aqueous solution and stabilized or crystallized in air, it is exposed to ultraviolet light. 3) Next, the adhesion and corrosion resistance of the organic film are improved by forming an organic film having a hydroxamic acid group on the metal substrate. Method for forming a film.
(2) The method according to (1), wherein the metal ingot is exposed by removing the air oxide film or hydroxide on the metal substrate by cathode reduction or mechanical polishing.
(3) The method according to (1) above, wherein the metal ingot is exposed, and thereafter, when an oxide film and / or a hydroxide film is naturally formed, ultraviolet irradiation is performed.
(4) The method according to (1) above, wherein the surface modification is performed with a natural oxide film formed by irradiating with ultraviolet rays in the process of solidifying the molten metal by air cooling or water cooling during metal production.
(5) The method according to (1), wherein a metal is passivated to form a flat surface at an atomic level, and the surface is irradiated with ultraviolet rays before the surface is completely crystallized.
(6) The method according to (1) above, wherein the metal substrate is immersed in an organic solvent containing an organic molecule having a hydroxamic acid group to form a self-assembled film.
(7) The method according to (1) above, wherein the surface of the metal ingot is irradiated with ultraviolet light having a wavelength of 150 to 400 nm so as to have an ultraviolet intensity of 0.5 to 50 mW / cm ² .
(8) The method according to (1) above, wherein an organic film containing a hydrophobic group as a terminal group and hydroxamic acid as a bonding group with a substrate is formed.
(9) A metal is passivated by the method according to any one of (1) to (8) to form an organic film having a hydroxamic acid group on a metal substrate having a flat surface at an atomic level. A metal product for anticorrosion characterized by improving the adhesion and anticorrosion properties of the organic film.
(10) The metal product according to (9), wherein the organic film has a long-chain alkyl group as the other terminal group.
(11) The organic film has a structure in which an oxide film or a passive film on a metal substrate and a hydroxamic acid group, which is a bonding group between the metal substrate of the organic film, are selectively complexed and bonded. (10) Metal product as described.

Next, the present invention will be described in more detail.
The organic film forming method of the present invention includes (1) removing the air oxide film and hydroxide on the metal substrate to expose the metal ingot, and (2) then surface-modifying by irradiating it with ultraviolet rays. (3) Next, an organic film is formed on the metal substrate. (4) The adhesion and corrosion resistance of the organic film are improved by the above (1) to (3). .
In the present invention, the metal oxide is exposed by removing the air oxide film or hydroxide usually present on the metal surface by cathodic reduction or mechanical polishing in an acidic aqueous solution or neutral aqueous solution. Thereafter, when the metal oxide film and / or hydroxide film is naturally formed, or before a passive film is formed in an aqueous solution and stabilized or crystallized in air, that is, within 24 hours after film formation. The irradiation with ultraviolet rays is preferably performed within one hour. In this case, as the ultraviolet ray to irradiate, for example, 254 nm, 1.1 mW / cm ² , which has hitherto been considered to be ineffective, can be used. Modification is performed. Then, the modified metal surface is immersed in an anticorrosive organic molecule, preferably, for example, an organic solvent containing an anticorrosive organic molecule having a hydroxamic acid group, and left for 1 to 24 hours. During this immersion, hydroxamic acid groups are selectively combined with metal oxides or hydroxides by complex formation to form a self-assembled film.

  This film is evaluated for corrosion resistance or adhesion to potential fluctuations in a neutral solution such as an aqueous boric acid solution. For example, when the film is formed in a 1 mM organic solvent, when the film is formed on the surface not subjected to ultraviolet treatment, most of the organic molecules are detached from the surface by several potential scans, and the anticorrosion property is completely lost. However, it has an unprecedented high anticorrosion property that shows 6 times higher anticorrosion property by irradiating weak UV light for 1 hour, and maintains 2 times higher anticorrosion property even if it is scanned more than 20 times. Bring sex. These can be easily obtained by using an inexpensive ultraviolet lamp in the atmosphere without using a special environment such as a particularly large apparatus, expensive apparatus or vacuum.

Examples of the substrate used in the present invention include, but are not limited to, iron, steel, stainless steel, nickel-base alloy, copper, aluminum, and alloys thereof. The present invention can be applied to an air oxide film naturally formed on a metal metal or a passive film formed chemically or electrochemically, and is not particularly limited to metals and alloys. Moreover, in this invention, a metal base means the to-be-coated metal base material which forms an organic membrane, The form etc. are not restrict | limited in particular. In the present invention, as the ultraviolet rays, for example, even a weak ultraviolet lamp having a wavelength of 254 nm and an intensity of 1.1 mW / cm ² significantly improves the anticorrosive property of the organic anticorrosive, but the range is preferably, for example, It has an ultraviolet wavelength of 150 to 400 nm and an ultraviolet intensity of 0.5 to 50 mW / cm ² at 50 mm from the light source.

  The organic molecule includes a hydroxamic acid group that selectively forms a complex with an oxide, preferably a hydrophobic group such as a long-chain alkyl group as a terminal group, and a hydroxamic acid as a bonding group with a substrate. Examples of the organic molecules include, but are not limited to, organic substances that can be used in the same manner as long as the substance contains a functional group that is firmly bonded to an oxide or hydroxide. That is, as the organic anticorrosive used in the present invention, a hydroxamic acid group that selectively forms a complex with an oxide and / or hydroxide on a base metal is one of the bonding groups to the base, Those having a hydrophobic group such as an alkyl group as the other terminal group are preferred, but are not particularly limited thereto, and any organic anticorrosive having the same effect can be used in the same manner. In the present invention, an organic film having improved adhesion and anticorrosion properties is formed by immersing the surface-modified metal surface in an organic solvent containing anticorrosive organic molecules.

According to the present invention, 1) When an organic film is formed on a metal substrate, it is possible to significantly improve the corrosion resistance of the organic film by irradiating a weak ultraviolet ray of 1.1 mW / cm ^2, which has not been effective in the past. 2) Corrosion protection can easily be improved by 6 times or more compared to the surface of the sample not irradiated with ultraviolet rays. 3) For example, 1 mM low concentration hydroxamic acid anticorrosive agent-ethanol which immediately loses its anticorrosive properties when not irradiated with ultraviolet rays. A strong anticorrosive film can be formed even in a solution. 4) Even if a film is formed in a low concentration anticorrosive solution, the anticorrosive effect can be strongly expressed, thereby reducing the consumption of the anticorrosive. The special effect of being able to suppress more than 2 times is produced.

  Next, although an example and a comparative example explain the present invention concretely, the present invention is not limited at all by these examples.

After the iron sample was electrochemically cathode reduced in 0.1 M borate buffer aqueous solution for 30 minutes to remove the air oxide film, the iron sample was taken out into the air and immediately separated from the ultraviolet lamp by 5 cm, and an ultraviolet ray of 254 nm was obtained. Was irradiated for 1 hour. The ultraviolet intensity on the sample at this time was 1.1 mW / cm ² . The sample was immersed in a 1.0 mM (n) -dodecane hydroxamic acid-ethanol solution for 1 day. Next, the sample on which the anticorrosive film of (n) -dodecane hydroxamic acid was formed was subjected to potential circulation (cyclic voltammogram, CV) between −1050 to 150 mV (SCE) in a 0.1 M borate buffer aqueous solution, and the number of cycles. And the maximum current density in each cycle was measured, and Fig. 1 (d) was obtained. A cyclic voltammogram was also measured for an untreated sample that had been left in the air for a long time, and FIG. 1A was obtained. As shown in FIG. 1, the sample irradiated with ultraviolet light for 1 hour shows a current density of about 1/10 at the first cycle number, compared to the untreated sample without the ultraviolet irradiation and without the anticorrosion film. The current density was ½ even at the 20th time, and high corrosion resistance and adhesion could be confirmed.

Comparative Example 1
The sample that had been left in the air for a long time was immersed in a 1.0 mM (n) -dodecane hydroxamic acid-ethanol solution for 1 day. Next, the sample on which the anticorrosive film of (n) -dodecane hydroxamic acid was formed was potential-circulated in a 0.1 M borate buffer aqueous solution between −1050 and 150 mV (SCE), and the maximum current in each cycle was measured. 1 (b) was obtained. In this case, the current density of the sample at the first cycle was slightly smaller than that of the untreated sample (FIG. 1 (a)), but the corrosion resistance was almost completely lost after the fifth cycle. From this comparative example, it can be seen that 1 hour of ultraviolet irradiation is extremely effective in improving adhesion and corrosion resistance.

After the iron sample was electrochemically cathode reduced in 0.1 M borate buffer aqueous solution for 30 minutes to remove the air oxide film, the iron sample was taken out into the air and immediately separated from the ultraviolet lamp by 5 cm, and an ultraviolet ray of 254 nm was obtained. Was irradiated for 4 hours. The ultraviolet intensity on the sample at this time was 1.1 mW / cm ² . The sample was immersed in a 1.0 mM (n) -dodecane hydroxamic acid-ethanol solution for 1 day. Next, the sample on which the anticorrosive film of (n) -dodecane hydroxamic acid was formed was potential-circulated between −1050 and 150 mV (SCE) in a 0.1 M borate buffer aqueous solution, and the maximum current density in each cycle was measured. 1 (c) was obtained. In this sample, the anticorrosive property of 6 times or more is recognized in the first cycle as compared with the case of not irradiating ultraviolet rays. In addition, it was found that this sample did not lose the anticorrosion film even at the 20th cycle, maintained at least twice the anticorrosion property, and had good adhesion.

After iron is electrochemically cathodic reduced in 0.1M borate buffer solution for 30 minutes to remove the air oxide film, this iron sample is taken out into the air and immediately separated from the ultraviolet lamp by 5 cm to 254 nm ultraviolet light. Irradiated for 1 hour. The ultraviolet intensity on the sample at this time was 1.1 mW / cm ² . The sample was immersed in a 1.2 mM (n) -dodecane hydroxamic acid-methanol solution for 10 hours. Next, the sample on which the anticorrosive film of (n) -dodecane hydroxamic acid was formed was potential-circulated between −1050 and 150 mV (SCE) in a 0.1 M borate buffer aqueous solution, and the maximum current density in each cycle was measured. FIG. 2C was obtained. This sample shows a current density of about 1/7 or less at the first cycle number compared to an untreated sample without ultraviolet irradiation and no anticorrosion film, and maintains a current density of 40% or less even at the 20th cycle. It was confirmed that it has high anticorrosion and adhesion.

Comparative Example 2
The sample that had been left in the air for a long time was immersed in a 1.2 mM (n) -dodecane hydroxamic acid-methanol solution for 10 hours. Next, the sample on which the anticorrosive film of (n) -dodecane hydroxamic acid was formed was potential-circulated between −1050 and 150 mV (SCE) in a 0.1 M borate buffer aqueous solution, and the maximum current density in each cycle was measured. FIG. 2 (b) was obtained. In this case, at the first cycle number, the sample shows the same current density as that of the sample irradiated with ultraviolet rays for 1 hour (FIG. 2 (c)). In the second round, the current density reached 3 times higher, and the corrosion resistance and adhesion were remarkably lost.

As described above in detail, the present invention relates to an organic film forming method for improving the corrosion resistance of a metal substrate. According to the present invention, a method for significantly improving the adhesion and corrosion resistance of an organic film is extremely simple. Can be provided. According to the present invention, even a weak ultraviolet ray of 1.1 mW / cm ^2, which has been considered to be ineffective in the past, can bring about a significant improvement in corrosion resistance. The anticorrosion property can be easily improved by 6 times or more compared with the sample surface not irradiated with ultraviolet rays. For example, a strong anticorrosive film can be formed even in a 1 mM low-concentration hydroxamic acid anticorrosive-ethanol solution, which immediately loses anticorrosive properties when not irradiated with ultraviolet rays. Even if a film is formed in a low-concentration anticorrosive solution, the anticorrosive effect can be strongly expressed, thereby suppressing the consumption of the anticorrosive more than twice.

The change of the maximum current density in the cyclic voltammogram for the hydroxamic acid self-assembled film formed in iron and 1.0 mM anticorrosive-ethanol solution in 0.1 M borate buffer aqueous solution with cycle number [(a), (B): no ultraviolet irradiation, (c), (d): ultraviolet irradiation]. The change in the maximum current density in the cyclic voltammogram for the hydroxamic acid self-assembled film formed in iron and 1.2 mM anticorrosive-methanol in 0.1 M borate buffered water with cycle number [(a), ( b): No UV irradiation, (c): UV irradiation].

Claims (11)

  An organic film forming method for improving the adhesion and corrosion resistance of an organic film formed on a metal substrate, wherein (1) the metal oxide is exposed by removing the air oxide film and hydroxide on the metal substrate. (2) Thereafter, when a metal oxide film and / or a hydroxide film is naturally formed, or before a passive film is formed in an aqueous solution and stabilized or crystallized in the air, it is irradiated with ultraviolet rays. (3) Next, by forming an organic film having a hydroxamic acid group on a metal substrate, the adhesion and anticorrosion properties of the organic film are improved. Method for forming a film.   The method according to claim 1, wherein the metal ingot is exposed by removing an air oxide film or hydroxide on the metal substrate by cathodic reduction or mechanical polishing.   The method according to claim 1, wherein the metal ingot is exposed, and then the ultraviolet ray is irradiated when the oxide film and / or the hydroxide film is naturally formed.   The method according to claim 1, wherein surface modification is performed with a natural oxide film formed by irradiating with ultraviolet rays in the process of solidifying molten metal by air cooling or water cooling during metal production.   The method of claim 1, wherein the metal is passivated to form a flat surface at the atomic level and is irradiated with ultraviolet light before the surface is completely crystallized.   The method according to claim 1, wherein the metal substrate is immersed in an organic solvent containing an organic molecule having a hydroxamic acid group to form a self-assembled film. The method of Claim 1 which irradiates the surface of a metal ingot with the ultraviolet-ray with a wavelength of 150-400 nm so that it may become the ultraviolet intensity of 0.5-50 mW / cm < ² >.   The method according to claim 1, wherein an organic film containing a hydrophobic group as a terminal group and hydroxamic acid as a bonding group with a substrate is formed.   The metal film is passivated by the method according to any one of claims 1 to 8 to form an organic film having a hydroxamic acid group on a metal substrate having a flat surface at an atomic level, and adhesion of the organic film And a metal product for anticorrosion characterized by having improved anticorrosion properties.   The metal product according to claim 9, wherein the organic film has a long-chain alkyl group as another terminal group.   The organic film has a structure in which an oxide film or a passive film on a metal substrate and a hydroxamic acid group, which is a bonding group between the metal film and the metal substrate, are selectively complexed and bonded. Metal products.

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