JP2002047587A - Method for preventing corrosion of metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive and easily operable method for preventing corrosion of metal by which a firm coating layer is formed without requiring base preparation with high precision, crevice corrosion is not generated on the edge parts of the coating, and further, the coating is not made wasteful even at the time of maintenance. SOLUTION: In this method for preventing corrosion of metal the circumference of the metal as the object for corrosion prevention is coated with a corrosion preventive material composed of a metallic ribbon having a potential lower than that of the metal as the object for corrosion prevention, the metallic ribbon and the metal as the object for corrosion prevention are directly contacted, and the corrosion of the metal as the object for corrosion prevention is prevented by the sacrificial anode action of the metallic ribbon and the coating action of corrosive products.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for protecting a metal from corrosion, and more particularly to a method for protecting a metal from corrosion in the atmosphere where dry and wet conditions are repeated.

[0002]

2. Description of the Related Art
As a method for preventing corrosion of metals in the atmosphere, coating is generally used, but the coating is inferior in durability because the coating film is easily damaged by an external impact or the like. Also, in the case of repairing for maintenance, there is a problem that the site adjustment cost is high due to troublesome adjustment of the base and that maintenance is not easy.

In order to prevent corrosion of the outer surface and the flange portion of the steel pipe, a method of covering with a heat-shrinkable tube and a method of covering with a paste-like rust preventive have been adopted. However, in the method of coating with a heat-shrinkable tube or a paste-like rust inhibitor,
When exchanging the gasket of the flange, it is necessary to remove the coating for anticorrosion, which not only requires much work, but also has many problems such as the inability to reuse the removed material.

[0004] As described above, in the conventional corrosion prevention of metals, it is important to bring the coating for corrosion protection into close contact with the object when performing repair or the like in terms of maintenance.
It was necessary to carefully adjust the substrate of the surface of the anticorrosion target, and it took time to remove the unnecessary coating. Further, there are also problems such as crevice corrosion easily occurring at the end of the coating, and the coating cannot be reused.

Further, Japanese Patent Application Laid-Open No. 2000-129473 proposes a method of preventing the inner surface of a metal tube from being corroded by using fine particles such as particles as an anticorrosive material. However, in this method, it is difficult to directly attach the anticorrosion target having a complicated shape to the outer surface of the anticorrosion target. Further, even when the inside is filled with minute pieces, electrical conductivity with the anticorrosion target is remarkably deteriorated, and the absolute mass of the anticorrosion material to be filled increases, which is uneconomical.

Japanese Patent Application Laid-Open No. 11-323580 describes a curled galvanic anode made of a zinc alloy. The galvanic anode has a thickness of 0.05 to 0.3 mm and a width of usually 2 mm. 〜１０10 mm. However, even when such a galvanic anode is filled inside as an anticorrosion material, the electrical conductivity with the anticorrosion target is not always sufficient, as described above, and the absolute mass of the anticorrosion material to be filled is not sufficient. To increase.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to form a strong coating layer without requiring high-precision substrate adjustment, to prevent crevice corrosion from occurring at the end of the coating, and to provide a coating at the time of maintenance. An object of the present invention is to provide an inexpensive and easy-to-install metal corrosion protection method that does not waste metal.

[0008]

As a result of the study, the present inventors have found that a metal ribbon having a lower potential than the anticorrosion target metal is covered or filled with the metal ribbon, and the metal ribbon and the anticorrosion target metal are filled. It has been found that the above object can be achieved by directly contacting with.

The present invention has been made on the basis of the above findings, and comprises an anticorrosion material comprising a metal ribbon having a lower potential than the anticorrosion target metal, covering the periphery of the anticorrosion target metal, and forming the metal ribbon and the anticorrosion target. An object of the present invention is to provide a method for preventing corrosion of a metal, wherein the metal is brought into direct contact with the metal ribbon to prevent corrosion of the metal to be protected by sacrificial anodic action and corrosion of a corrosion product.

The present invention also relates to an anticorrosion material comprising a metal ribbon having a lower potential than the anticorrosion target metal, filling the interior of the anticorrosion target metal and bringing the metal ribbon into direct contact with the anticorrosion target metal. An object of the present invention is to provide a method for preventing corrosion of a metal, wherein the corrosion of the metal to be protected is prevented by a sacrificial anode function of a metal ribbon and a coating function of a corrosion product.

[0011]

Embodiments of the present invention will be described below. FIG. 1 is an explanatory diagram showing an outline of the metal corrosion prevention method of the present invention. In the figure, 1 is a metal to be protected,
2 indicates a metal ribbon, and 3 indicates a protective layer.

The anticorrosion target metal 1 is made of an iron-based alloy, a copper alloy, an aluminum alloy or the like, and particularly targets the inner and outer surfaces of the steel pipe in the atmosphere, a flange portion, and a pipe covered with a heat insulating material. You.

The metal ribbon 2 is an anticorrosion material having a lower potential than the anticorrosion target metal 1 and covers the periphery of the anticorrosion target metal 1 or fills the inside of the anticorrosion target metal 1.

The metal ribbon 2 having a lower potential than the metal 1 to be used here is preferably a galvanic anode material for cathodic protection, and more specifically, one made of zinc, aluminum, magnesium or an alloy thereof. It is.

For example, as a magnesium alloy, JI
SH 6125 and the like. As the aluminum alloy, Al / 1 to 10% by mass Zn / 0.1 to 6
Mass% Mg / 0.01 to 0.04 mass% In / 0.5 to
1 mass% Si or the like. As the zinc alloy, Zn / 0.
2 to 0.7 mass% Al / 0.03 to 0.14 mass% Cd
System. Also, pure zinc (purity 99.99% by mass) is preferably used.

However, in the present invention, since the metal 1 to be protected and the metal ribbon 2 are in close contact with each other, they need not necessarily have the same electrochemical properties as the galvanic anode material for cathodic protection. In zinc alloys, Zn, Cu, Ti,
A material containing at least one selected from Mg and Al in a total amount of 1% by mass or less is also applicable.

The shape of the metal ribbon 2 is 1 to 20 mm in width.
It is desirable that the length be 100 to 1000 mm and the thickness be 0.1 to 1 mm.

By firmly adhering the metal ribbon to the anticorrosion target metal, conduction between the anticorrosion target metal and the metal ribbon can be ensured even with simple substrate adjustment, and the anticorrosion action of the low-potential metal ribbon can be obtained. Can be. Therefore, even if there is a gap between the metal ribbon and the anticorrosion target metal, the anticorrosion effect can be maintained. Further, even when the metal ribbon is to be removed at the time of maintenance, each ribbon is independent of a small strip, so that the ribbon can be easily removed, and the remaining ribbon can be reused even when it is fixed again.

Usually, crevice corrosion occurring at the end of the coating or filling portion is caused by an oxygen concentration cell. In the present invention, since the filling material is composed of a low-potential metal ribbon, the metal ribbon has a sacrificial anode. And wear out,
Crevice corrosion does not occur in the metal to be protected.

In the present invention, as shown in FIG. 1, a protective layer 3 may be formed around the metal ribbon 2 in some cases.
It is preferable to cover with. The protective layer 3 is generally and effectively made of an insulating organic material. In addition, by using a metal material having at least a surface of the same kind of metal as the metal ribbon in the form of a wire net or a tape, the metal ribbon can be easily attached to a corrosion-resistant metal having a complicated shape.

Further, in the present invention, the metal ribbon may be disposed between the metal to be anticorrosion and the heat insulating material to have both the anticorrosion effect and the heat insulating effect.

In the present invention, even if the surface treatment of the anticorrosion target metal is incomplete, the metal ribbon having a low potential is pressed against the anticorrosion target metal, so that electrical conduction can be ensured. Even after the melting of the metal ribbon at the contact portion has progressed, the bulk ribbon can be brought into contact by pressure bonding.
In addition, even if electrical conduction is no longer obtained, dissolved products of the metal ribbon, for example, magnesium hydroxide (when a magnesium-based metal ribbon is used), aluminum hydroxide (when an aluminum-based metal ribbon is used), Since it is covered with zinc hydroxide and basic zinc carbonate (when a zinc-based metal ribbon is used), the anticorrosion effect can be maintained by its chemical inhibitory effect and environmental barrier effect.

Further, by using a metal ribbon as the anticorrosion material, not only is it easy to remove the anticorrosion material when removing it, but also the effective use of the anticorrosion material can be achieved.

Further, since the metal ribbon is used as the anticorrosion material, the shape can be kept within a certain range, and it can be directly attached to the anticorrosion target having an arbitrary shape.
In addition, even when a protective cover is required, the workability is excellent such that it is only necessary to cover with a wire mesh or the like. Then, even when the inside of a steel pipe or the like is filled, the electrical continuity with the anticorrosion target is maintained even under bad conditions, so that the anticorrosion effect is not reduced. Furthermore, since an appropriate gap is formed, the mass of the anticorrosion material to be filled can be reduced, so that economic anticorrosion is possible. As described above, JP-A-2000-1
Such an effect cannot be obtained by the method disclosed in Japanese Patent No. 29473. This is because Example 1 and Comparative Example 1
It is clear from the comparison with.

As described above, the anticorrosion method of the present invention is an effective anticorrosion method having both simplicity and effective use of resources.

[0026]

EXAMPLES Hereinafter, the present invention will be specifically described based on examples and the like.

Example 1 and Comparative Example 1 Assuming that the inner surface of a steel pipe was filled with an anticorrosive material, copper plates were placed at both ends of a box having a predetermined size as shown in FIG. The AC impedance between the copper electrode plates when zinc ribbon (Example 1) and zinc particles (Comparative Example 1) were filled as materials was measured. The results are shown in FIG. The zinc ribbon had a shape of 0.1 t × 5 W × 500 Lmm and a composition of purity 99.9.
A 9% by mass zinc test material was used, and zinc particles having a shape of about φ2 to 4 mm and a composition of 99.99% by mass zinc were used. In addition, tap water was injected into the box filled with the test material assuming a severe corrosive environment, and the gap in the test material was filled with the tap water.

As is clear from the results shown in FIG. 3, in Example 1 in which the zinc ribbon was filled, the impedance was low over the entire measurement frequency range and the phase difference was not changed. It can be seen that On the other hand, in Comparative Example 1 in which zinc particles were filled, capacitive impedance was recognized in a high frequency range, and 0.1H
The impedance in the low frequency range below z is 10 ^{5 of the} first embodiment.
It is very high, more than double, and the gap is not in an electron conducting state.

Since the impedance of 0.1 Hz or less is considered to be a value corresponding to the DC resistance between the two electrodes, the impedance has a very large effect on the electrolytic protection action of zinc. Ideally, the zinc and copper plates must be in an electrically conductive state, that is, low impedance indicating electronic conductivity,
As the anticorrosion material for the inner surface of the steel pipe, the granular material as in Comparative Example 1 does not have sufficient anticorrosion action, and it is understood that a ribbon-like material having a certain length as in Example 1 is suitable.

Such a difference in impedance is caused by a large number of contact points having a small contact area in the case of the granular shape as in Comparative Example 1. Example 1 needs to pass
In the case of such a ribbon shape, it is considered that the strip pieces are intricately entangled, so that one ribbon is in contact with a plurality of ribbons and also serves as an electric wire.

The weight of the zinc ribbon required for filling the inside in Example 1 was 80 g, whereas the weight of the zinc particles required for filling the inside in Comparative Example 1 was 350 g. This indicates that the mass of the anticorrosion material can be significantly reduced by using a zinc ribbon as the material required for anticorrosion.

Example 2 As shown in FIG.
, Three SGP steel pipes (thickness: 3.8 mm) 1 having a nominal diameter of 50A are driven into the steel pipe, and two steel pipes each having a composition of Al /
2.5 mass% Zn / 1.5 mass% Mg / 0.02 mass%
An aluminum alloy-based metal ribbon 2 of In / 0.2 mass% Si and a zinc-based metal ribbon 2 having a purity of 99.99 mass% were each filled to a height of 100 mm.

On the other hand, the same metal ribbon 2 was surrounded by a thickness of 10 mm on the outer surface at a height of 100 mm from the ground, and its outer periphery was covered with a protective layer 3 made of resin. The shape of the metal ribbon used here is 0.1 mm in thickness, 3 mm in width, and 200 mm in length.

The steel pipe was exposed to the air and subjected to a corrosion protection test for about one year. Tap water and seawater were occasionally sprayed during the test to promote corrosion. In addition, as a comparison, a corrosion prevention test was performed on the untreated (non-corrosion-proof) steel pipe under the same conditions.

Observation of the surface after the end of the test revealed that the corrosion-free steel pipe had red rust on the entire surface, and that the corrosion of the ground was remarkable on both the inner and outer surfaces. As a result of the wall thickness measurement, the corrosion-resistant steel pipe was found to have a maximum thickness reduction of 1.2 mm at the ground edge, whereas the corrosion-resistant steel pipe with an aluminum alloy-based metal ribbon or zinc-based metal ribbon had a reduced wall thickness. I was not able to admit.

[Embodiment 3] As shown in FIG. 5, a metal mesh formed by galvanizing a metal ribbon 2 based on pure zinc (purity 99.99% by mass) with respect to a flange 1 fixed by bolts and nuts 6 is formed. It was covered with a protective layer 3, fixed with a fixing band 5, and exposed to a saltwater-applied factory site for half a year. The shape of the metal ribbon is 0.1mm thick, 5mm wide,
It is 500 mm in length. As a comparison, a non-corrosion protected flange was similarly exposed.

As a result, the corrosion-free flange was completely corroded around the bolt gap and the flange connection, whereas the flange covered with the zinc-based metal ribbon was
Although covered with zinc corrosion products, no evidence of corrosion was observed.

[Embodiment 4] As shown in FIG. 6, a test piece 8 for corrosion evaluation (JIS standard SS400, 20 × 5) was provided on a part of a pipe 1 covered with a heat insulating material 7 in a factory.
(0 × 1 mm) was attached to the interface between the pipe 1 and the heat insulating material 7 with six test pieces. Three of the specimens were covered with a pure zinc (purity 99.99% by mass) -based metal ribbon 2 to examine the difference in corrosion state from other specimens.

As a result of the exposure test for about one year, the non-corrosion-proof piece
Almost the entire surface was covered with red rust, and an average corrosion rate of 0.11 mm / y was observed. On the other hand, the test piece covered with the pure zinc-based metal ribbon was entirely covered with a white product, and no generation of red rust was observed.

[0040]

As described above, according to the anticorrosion method of the present invention, even if the surface treatment of the anticorrosion target metal is incomplete, a metal ribbon having a low potential is pressed against the anticorrosion target metal. The anticorrosion effect can be maintained by the electrolytic protection effect of the ribbon, the chemical inhibitor effect by the dissolved product, and the environmental barrier effect.

When a metal ribbon is used as an anticorrosion material, when the anticorrosion material is removed, it is easy to remove the anticorrosion material.
It is possible to effectively use the anticorrosion material and reduce the cost.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of a metal corrosion prevention method of the present invention.

FIG. 2 is a perspective view of a test apparatus used in Example 1 and Comparative Example 1.

FIG. 3 is a graph showing frequency impedance characteristics of Example 1 and Comparative Example 1.

FIG. 4 is a schematic cross-sectional view showing a method for preventing metal corrosion in Example 2.

FIG. 5 is a schematic cross-sectional view showing a method for preventing metal corrosion in Example 3.

FIG. 6 is a schematic cross-sectional view illustrating a method for preventing metal corrosion in Example 4.

[Explanation of symbols]

 1: Corrosion protection metal 2: Metal ribbon 3: Protective layer 4: Soil 5: Fixed band 6: Bolt / nut 7: Insulation material 8: Test piece

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tsugio Minami 417-16 Nakaarai, Ageo City, Saitama Prefecture Inside Nakabo Tech R & D Laboratories Co., Ltd. (72) Inventor Shuichi Yamazaki 656- Kamakurabashi, Ageo Village, Ageo City, Saitama Prefecture 1 Mitsui Kinzoku Co., Ltd. Rolling Division (72) Inventor Kazuo Ikeda 656-1 Kamakurabashi, Ageo-mura, Ageo-shi, Saitama F-term in the Rolling Division Mitsui Metals Co., Ltd. 4K060 AA02 BA13 BA41 EA11 FA09

Claims (8)

[Claims] An anticorrosive material comprising a metal ribbon having a lower potential than the anticorrosion target metal, covering the periphery of the anticorrosion target metal, and directly contacting the metal ribbon with the anticorrosion target metal,
A method for preventing corrosion of a metal, wherein the corrosion of the metal to be protected is prevented by a sacrificial anode function of the metal ribbon and a coating function of a corrosion product. 2. An anticorrosion material comprising a metal ribbon having a lower potential than the anticorrosion target metal, filling the inside of the anticorrosion target metal, and bringing the metal ribbon into direct contact with the anticorrosion target metal,
A method for preventing corrosion of a metal, wherein the corrosion of the metal to be protected is prevented by a sacrificial anode function of the metal ribbon and a coating function of a corrosion product. 3. The method according to claim 1, wherein the periphery of the metal ribbon is covered with a protective layer. 4. The method according to claim 1, wherein the metal ribbon is made of zinc, aluminum, magnesium or an alloy thereof.
The method for preventing corrosion of metals according to 2 or 3. 5. The metal ribbon has a width of 1 to 20 m.
The method for preventing corrosion of metals according to any one of claims 1 to 4, wherein m, length is 100 to 1000 mm, and thickness is 0.1 to 1 mm. 6. The method according to claim 1, wherein the anticorrosion target metal is an iron alloy, a copper alloy or an aluminum alloy. 7. The method for preventing corrosion of a metal according to claim 1, wherein the metal to be protected is covered with a heat insulating material. 8. The method according to claim 3, wherein the protective layer is an insulating organic material or a metal material having at least a metal of the same type as the metal ribbon on the surface.