JP3234884B2 - Metal corrosion protection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion method for preventing rust and corrosion on a metal surface.

[0002]

2. Description of the Related Art Conventionally, metal anticorrosion methods include an electrolytic anticorrosion method,
There are various types such as coating and coating of inorganic and organic substances such as metals and polymers. For example, the most widely used coatings at present are those that clean the surface of a metal and wet and dry the coating.

[0003]

None of the anticorrosion methods had a life equivalent to the service life of the equipment, and there was no complete anticorrosion method in that sense. The service life of the equipment can be as long as 100 years, for example, taking the four cross-links as an example, but the life of the paint is only a few years, and it is necessary to repeatedly apply the paint until the life of the equipment. In addition, this repainting involves scaffolding, removing old paint and rust, and then repeatedly painting the paint several times, which requires considerable expense. The paint blocks water and oxygen to prevent corrosion without contacting the metal surface, but water and oxygen penetrate through very small gaps and penetrate various materials for a long period of time. To reach the metal surface and cause corrosion. However, it is almost impossible to make this water and oxygen not completely reach the metal surface for many months, and thus it is not a complete anticorrosion method. In addition, in such a method, when a defect occurs in a part, a local battery is formed in the part, and a corrosion reaction may remarkably proceed, which is a major drawback. In addition, local batteries are also caused by minor defects in the implementation.

[0004] In view of the drawbacks of the conventional anticorrosion method, the present inventors have invented an anticorrosion method in which a corrosion reaction does not occur even in the presence of water.

[0005]

The present invention is characterized in that a substance for passivating the surface of a metal is contained in an aqueous gel of a polymer having a three-dimensional network structure, and the substance is brought into contact with the surface of the metal. And a method for preventing corrosion of metals.

[0006]

The conventional anticorrosion method is a method of preventing both air and water from coming into contact with a metal, whereas the above-described method of the present invention is a method of preventing invasion of the atmosphere but using water. . A substance obtained by mixing a substance for passivating the surface of a metal with an aqueous solution of a monomer capable of gelation and adding an appropriate catalyst to the mixture is used. When the aqueous gel was brought into contact with a metal, the surface was passivated by hydroxide ions and the like, and corrosion was prevented. The polymerized aqueous gel contains a large amount of water but has a low dissipative property such as hydroxide ions, so it is effective to maintain the passivated metal surface, and is a uniform and strong passive film. Is generated, so that a local battery cannot be formed. In the anticorrosion method of the present invention, the presence of oxygen is also preferable because it promotes the formation of a passive film.

[0007] Metals to be protected from corrosion include iron, nickel, chromium, copper and the like and alloys thereof. In particular, the effect on iron is remarkable, a passive film is easily formed and the film is stable.

The substance to be contained in the aqueous gel is an alkali metal, an alkaline earth metal hydroxide, an alkali metal borate, water glass, an amine, etc., which dissolves in water to passivate the metal surface. . Phosphates, chromates, nitrites, etc. which promote the above-mentioned passivation may be added.
Its pH ranges from 9 to 13, preferably from 10 to 13. Of these substances, calcium hydroxide and water glass are particularly preferred because they form a stable passive film.

The aqueous gel is obtained by converting an aqueous gellable monomer solution into a polymer having a three-dimensional network structure using a suitable catalyst. In general, a substance for passivating the surface of a metal is mixed and added to an aqueous monomer solution, and a catalyst is allowed to act on the substance to be contained in a polymer gel having a three-dimensional structure.

Examples of the gellable monomer include a polyvalent metal derivative of acrylic acid such as magnesium acrylate, calcium acrylate, zinc acrylate or a mixture thereof, or a double bond in one molecule with acrylamide. Examples thereof include a mixture with two or more crosslinking agent monomers.
Thus, 100 parts of these monomers are usually added to 200 parts of water.
Parts to 1900 parts.

As a catalyst for gelling the monomer aqueous solution, it is convenient to use, for example, the following redox catalyst in order to complete the reaction quickly at room temperature. A mixture of sodium thiosulfate and potassium persulfate or ammonium persulfate; a mixture of dimethylaminopropionitrile and potassium or ammonium persulfate; a mixture of ferrous sulfate with potassium or ammonium persulfate; The ratio of the catalyst used depends on the type of the monomer and the catalyst, the temperature, and the like, but it is generally preferable that the compounding is performed so that gelation is completed within about 20 minutes. For example, in the first embodiment, the solution gelled at a liquid temperature of 20 ° C. within several minutes.

Examples of the crosslinking agent monomer having two or more double bonds include methylene, ethylene or propylene bisacrylamide, hexahydro 1.3.5 triacryl-S-triazine, N allyl acrylamide, N allyl methacryl amide, Ethylene or propylene bismethacrylamide, diacrylamitodimethylether and the like can be mentioned. Acrylic amide 100 used
The range is 5 to 30 parts, preferably 10 to 20 parts, per part. Acrylic acid calcium, magnesium,
In the case of a divalent or higher valent metal salt such as zinc, 2
Since it has two or more double bonds, the crosslinking agent is not necessarily required.

The ratio between the substance for passivating the surface of the metal and the components other than the substance varies depending on the material and the like, but is 5 to 7%.
It is about 0 parts to 100 parts. The more the substance to be passivated, the more advantageous from the viewpoint of anticorrosion, but if too much, the strength of the gelled substance becomes weak. Since the gelled material is used in contact with the surface of the metal, it preferably has some strength. However, it is essential that this gelled product contains a large amount of water, and this is significantly limited in this respect. The compressive strength of the gelled material without addition of a substance that passivates the metal surface is at least 0.1 kg / c per strain-corrected cross-sectional area.
m are ^two or more, generally compressive strength is increased by moderate substance added.

The gelled product of the present invention contains a large amount of water, but has a water permeability of 10 ⁻⁸ cm / s or less due to a three-dimensional network structure, and is substantially impermeable.

In the present invention, an aqueous solution of a monomer containing a substance for passivating the surface of the metal and an aqueous solution of a catalyst may be mixed, applied to the surface of the metal, and gelled before use. The mixed solution to be gelled may be impregnated into a cloth or the like to be gelled, and this may be wound around a metal body for use. In some cases, a large cover made of a material having no or low water permeability is formed in a portion where corrosion protection is required, such as a joint, and the mixture is gelled by putting a mixture between the cover and the metal body to prevent corrosion. The mixed solution may be injected into the soil to form a gelling layer around the buried metal body to prevent corrosion. In some cases, a gel layer is formed on wet ground, and a metal tank or the like is placed on top of it to protect the bottom surface. The gelled product of the present invention may not have sufficient strength, and a protective layer may be formed with a plastic sheet or the like so as to cover the gelled product.

It is important that the gel is not dried. A cover may be used for this purpose. From such a point, the present anticorrosion method is preferably used for anticorrosion in a place where water is always present and in a high humidity.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Several embodiments according to the present invention will be described below, but it is needless to say that the present invention is not limited to these embodiments.

This is a first embodiment. The following are the two components used. Solution A: 9.5 parts of acrylamide, 0.5 parts of methylenebisacrylamide, 0.4 parts of dimethylaminopropionitrile, 45 parts of water, and 65 parts of calcium hydroxide.
Solution B: 0.5 part of ammonium persulfate, 45 parts of water.

The above solution A and solution B were mixed, and rust was completely dropped in a beaker. The thickness was 2 mm, the width was 15 mm, and the length was 30 mm.
Was poured over the steel plate (SS41) into which a gel layer having a thickness of 10 mm was formed. The gel time was 12 minutes.

Put this in running tap water,
Examination was performed after a lapse of years, but no rust was observed. For comparison, an iron plate that was not coated with gel was rusted shortly after being put in tap water, and one hour later the entire surface was covered with rust.

This is a second embodiment. A liquid mixture of the liquid A and the liquid B having the same composition as the first embodiment is 10 mm thick and 50 mm on a side.
A 5 mm gelling layer was formed on each square piece of iron, nickel and chromium.

The test piece was placed in the sea, and after 3 months, the gelled layer was removed, but no rust was observed in any case. For the purpose of comparison, each test piece was also placed in the sea, but after three months, thick rust was observed on all the test pieces.

This is a third embodiment. The following are the two components used. Liquid A: 30% magnesium acrylate aqueous solution 40
Parts, potassium thiosulfate 0.6 part, water 10 parts, calcium hydroxide 15 parts. Solution B: 2 parts of potassium persulfate and 20 parts of water.

A weir is made of concentric foamed polyethylene having a thickness of 50 mm on both sides of a joint portion of an iron pipe water pipe having an inner diameter of 100 mm, and a polyethylene anticorrosion tape is wrapped around both outer peripheries to allow water to enter the joint portion. No state. A small hole was made in the upper part of the cover, and the mixture of the above-mentioned liquid A and liquid B was injected to fill the space between the tube and the cover and gelled.

This pipe was buried in soil of about 1 m in depth and dug up after one year to examine it. No rust was observed on the joint surface, the bolt and the nut surface. Rust was observed at various points in the joints of the sample in which the mixed solution was not injected for comparison.

This is a fourth embodiment. The following are the two components used. Solution A: 9.5 parts of acrylamide, 0.5 part of methylenebisacrylamide, 0.4 part of dimethylaminopropionitrile, 45 parts of water, and 40 parts of calcium hydroxide.
Solution B: 0.5 part of ammonium persulfate, 45 parts of water.

In a basement, an iron tube constantly humid at 100% is polished, and a cotton cloth impregnated with a mixture of the above-mentioned liquid A and liquid B is wound thereon to form an anticorrosion layer having a thickness of 5 mm. I made it.

Examination after one year showed no rust under the anticorrosion layer. Rust was generated on the entire non-corrosion protected portion of the same iron pipe.

This is a fifth embodiment. The following are the two components used. Solution A: 9.5 parts of acrylamide, 0.5 parts of methylenebisacrylamide, 0.4 parts of dimethylaminopropionitrile, 45 parts of water, and 15 parts of calcium hydroxide.
Solution B: 0.5 part of ammonium persulfate, 45 parts of water.

Two holes having a depth of about 500 mm were dug in the ground. Both bottoms of this hole were always wet with groundwater. The mixed solution of the above solution A and solution B was added to one of them to form a 50 mm thick anticorrosive aqueous gel layer. Another hole was filled with tar sand, and a 50 mm-thick anticorrosive layer was similarly formed. Tin oil cans were respectively inserted into these two holes, and the bottoms were brought into contact with the anticorrosion layer.

When the two petroleum cans were examined after standing for one year, no rust was observed on the bottom of the petroleum can on the anticorrosive water-based gel, whereas the bottom of the petroleum can on tar sand was completely rusted. Had occurred.

[0032]

The method for preventing metal corrosion according to the present invention described above has the advantage that the coexistence of water and oxygen, which has been the most detested from the viewpoint of conventional corrosion protection, is no longer a problem, and the penetration of carbon dioxide gas can be prevented by the gel. It is an excellent method with the following properties: it forms a passivation film on the metal surface as long as there is a substance that passivates the surface of water and the metal. It is something.

Continued on the front page (73) Patent holder 597155789 Maruishi Kogyo Co., Ltd. 1-2-34 Toyosu, Koto-ku, Tokyo (74) The above six agents 100073483 Patent Attorney Noboru Yakuho (73) Patent holder 591054299 Osamu 1-33-1-3 Nakazawa, Asahi-ku, Yokohama-shi, Kanagawa Prefecture (74) One of the above agents 100073483 Patent Attorney Noboru Yakuwa (one outsider) (72) Inventor Yuji Furutari Nittamae, Iwaki-shi, Fukushima 5-9-9 (72) Inventor Keiichi Hosokawa 1222 Mimamatsu Mansion, 1222 Toriyamacho, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Minami Miyazaki 157, 157 Karijuku, Nakahara-ku, Kawasaki-shi, Kanagawa 12-11 72) Inventor Hideo Wakisaka 2-42-1, Kokubuminami, Ebina-shi, Kanagawa Prefecture (72) Inventor Naoto Shiina 3-105, Wakabadai, Asahi-ku, Yokohama-shi, Kanagawa 1105 (72) Inventor Yukichi Toshima Shibuya-ku, Tokyo 3-60-3 Sasazuka (72) Inventor Shoji Asakura 24, Nakazawa-cho, Asahi-ku, Yokohama-shi, Kanagawa Prefecture Examiner Tomoko Hirono (56) References JP-A-1-240690 (JP, A) JP-A-60-59081 (JP, A) JP-B-49-45700 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00-22/86

Claims (1)

(57) [Claims] 1. A method for preventing corrosion of a metal, comprising adding a substance for passivating the surface of a metal to an aqueous gel of a polymer having a three-dimensional network structure and bringing the substance into contact with the surface of the metal.