JP2008156671A - Corrosion prevention process for concrete, and concrete structure obtained by performing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corrosion prevention process for concrete, in which a stable and homogeneous corrosion preventive current is obtained over a long period, and a steel inside the concrete which is in the range where an anode metal layer is formed is prevented from corrosion, and to provide a concrete structure obtained by performing the same. <P>SOLUTION: In a corrosion prevention process for concrete, the surface of a concrete structure is as it is or turned to a rough surface, an anode metal layer A being a layer of a metal having a standard electrode potential lower than that of a steel inside the concrete is formed thereon, a terminal is installed thereon, further, an anode metal layer B is simultaneously formed thereon, and the steel and the anode metal layer are connected with the terminal. In the corrosion prevention process, the anode metal layer A and the anode metal layer B are obtained by thermal spraying. In the corrosion prevention process, the thermal spray metal is a zinc-aluminum pseudo alloy. In the corrosion prevention process, the thickness of the anode metal layer A is 100 to 200 μm and/or the thickness of the anode metal layer B is 50 to 150 μm. Also disclosed is a concrete structure obtained by performing a corrosion prevention process for concrete. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a corrosion prevention method for protecting a steel material inside a concrete structure from corrosion for a long period of time. In particular, the anode is a metal layer having a lower standard electrode potential than the steel material on the surface of the concrete structure. A concrete anticorrosion method capable of effectively and uniformly obtaining an anticorrosion current by forming metal layers above and below the terminals, and a concrete structure obtained by carrying out the same.

  In general, a concrete structure is one in which a steel material is embedded in the concrete, and the concrete and the steel material in the concrete work together against an external force.

Typical deterioration factors of concrete structures include neutralization, salt damage, frost damage, alkali aggregate reaction, chemical erosion, fatigue, and the like.
As described above, the problem of the durability of the concrete structure is often not only the durability of the concrete itself but also the problem of the durability (corrosion resistance) of the steel material inside the concrete used together.

  The corrosion of steel inside concrete depends on the location environment due to the neutralization of concrete, the salt contained in concrete, and the influence of chloride ions, sulfide ions, and nitride ions entering the concrete from the outside. May proceed in a relatively short period of time.

  Conventionally, as a method of preventing corrosion of steel materials in concrete, (1) a method of coating an organic anticorrosive paint on the surface of a concrete structure and blocking external deterioration factors, (2) by an external power source, A method of energizing between the steel material inside the concrete, which is the cathode material, and the anode material installed on the surface of the concrete structure, (3) a method using the galvanic anode method utilizing the difference in metal standard electrode potential, etc. Has been implemented.

In particular, the cathodic protection method using the galvanic anode method is characterized in that a special apparatus is not required, maintenance is easy, and long-term anticorrosion properties are excellent.
The galvanized anode method is typically a kerf embedding method, a kerf embedding covering method, a zinc plate mounting method, a galvanic anode member mounting method, etc. There is a problem that it is difficult to construct in a complicated or narrow place and the workability is poor.
As a method for solving this problem, there has been proposed a method in which a metal or an alloy having a standard electrode potential lower than that of a steel material in the concrete is sprayed on the surface of the reinforced concrete structure, and this sprayed coating layer is attached as an anode member. (See Patent Document 1 to Patent Document 5)

JP 05-331922 A JP-A-06-002174 Japanese Patent Laid-Open No. 06-116766 JP-A-10-245280 JP 2005-015835 A

  In the galvanic anode method, the anode member needs to be electrically connected to the steel material inside the concrete. The method of spraying a metal or alloy having a lower standard electrode potential than the steel material on the surface of the concrete structure uses a sealing treatment material to fill the voids in the sprayed coating layer of the conductive material, and sprays the conductive material. In the method of connecting a metal plate as a terminal to the end of the coating layer, electrical connection with a conductive material has been made without special consideration for the size, shape, attachment position, and the like.

  However, with this method, corrosion occurs at the edge of the terminal for a long period of time, so that the anticorrosion current cannot be supplied for a long period of time. There was a problem that could not be expected.

  The present inventor examined the problem of the corrosion prevention method for concrete structures by the galvanic anode method using the sprayed coating layer, and in order to reliably protect the steel material in the concrete in the range where the sprayed coating layer was formed, As a result of studying a method for obtaining a highly stable and homogeneous anticorrosion current, the present invention has been completed.

  That is, according to the present invention, an anode metal layer A, which is a metal layer having a lower standard electrode potential than the steel material inside the concrete, is formed on the surface of the concrete structure, a terminal is installed on the anode metal layer A, and a concrete layer is further formed thereon. A concrete anticorrosion method in which an anode metal layer B, which is a metal layer having a lower standard electrode potential than an internal steel material, is formed, and the steel material and the anode metal layer inside the concrete are connected using the terminals. This is a concrete anticorrosion method in which the surface of a structure is roughened, and an anode metal layer A, which is a metal layer having a lower standard electrode potential than the steel material inside the concrete, is formed thereon, and the anode metal layer B A corrosion protection method for the concrete formed by forming a surface protective layer on the metal, and the anode metal layer A and the anode metal layer B are used for thermal spraying of a metal having a lower standard electrode potential than the steel material inside the concrete. The concrete is a corrosion prevention method for the concrete, wherein the metal having a lower standard electrode potential than the steel material inside the concrete is a zinc-aluminum pseudoalloy, and the thickness of the anode metal layer A is It is a corrosion prevention method for the concrete having a thickness of 100 to 200 μm, and the thickness of the anode metal layer B is a corrosion prevention method for the concrete having a thickness of 50 to 150 μm. .

  By adopting the concrete anticorrosion method of the present invention, a long-term stable and homogeneous anticorrosion current can be obtained, and the steel material in the concrete in the range where the anode metal layer is formed can be reliably anticorrosive. It becomes possible.

Hereinafter, the present invention will be described in detail.
In the present invention, “parts” and “%” are based on mass unless otherwise specified.
Moreover, the concrete in this invention may contain a mortar.

  In the present invention, the steel material in the concrete is used as a cathode, the metal layer formed on the surface of the concrete structure is used as an anode, and electricity is passed between the cathode and the anode to prevent corrosion of the steel material in the concrete.

  In the present invention, an anode metal layer which is a layer of a metal having a lower standard electrode potential (hereinafter referred to as an anode metal) than the steel material inside the concrete is formed on the surface of the concrete structure.

  The anode metal layer is formed in two layers on the surface of the concrete structure so as to sandwich a terminal described later.

The anode metal layer is preferably formed by spraying the anode metal.
Specifically, a porous metal film layer is formed by laminating an amorphous metal-like scaly anodic metal melted at the nozzle tip of a metal spraying device or the like.

  Examples of the anode metal include aluminum, zinc, an aluminum alloy, a zinc alloy, and a zinc-aluminum pseudo-alloy.

  The aluminum alloy or zinc alloy is obtained by mixing at least 50% or more of aluminum or zinc alloy and mixing at least one or more metals such as Cr, Si, Fe, Ni, and Sn, and Zn or Al. Alloy.

  An anode metal layer formed of aluminum or an aluminum alloy is preferable because the surface of aluminum itself is oxidized to form a stable and dense sprayed coating layer, so that it is less consumed.

The zinc-aluminum pseudoalloy is a pseudoalloy containing zinc and aluminum at a ratio of Zn: Al = 85: 15 to 30:70 (mass ratio).
The zinc-aluminum pseudo-alloy is a state in which zinc and aluminum do not form an alloy composition, and zinc fine particles and aluminum fine particles are irregularly overlapped to form a zinc-aluminum alloy in appearance.

The anode metal layer formed of the zinc-aluminum pseudo-alloy has a blister shape and has continuous pores in the anode metal layer, so that the metal surface area is relatively large, and is most preferable in terms of obtaining good anticorrosion performance. .
The anode metal layer of the zinc-aluminum pseudo-alloy can be formed by arc spraying using a low-temperature spraying method such as a low pressure arc spraying method using a zinc and aluminum spraying wire.
For example, the diameter and feed rate of the aluminum wire and zinc wire are adjusted so that the volume ratio of metal aluminum and metal zinc is 1: 1, and the zinc-aluminum pseudoalloy is sprayed by arc spraying to form the anode metal layer. Can be formed.

Examples of the metal spraying method for the anode metal include a gas spraying method, a gas spraying method, an arc spraying method, and a plasma spraying method, and any of these methods can be used. Formula spraying is preferred.
A room temperature arc type thermal spraying device is a method in which low-temperature air or inert gas is injected at a high speed, a metal wire is melted in a decompression section generated by the injected air flow, and the molten metal is injected with a high-speed jet air current. It is possible to deposit blister metal on the ground surface of the base while rapidly supercooling and atomizing. The film thickness that can be sprayed at one time is usually about 70 μm, and the film thickness can be increased by spraying a plurality of times.

The anode metal layer forms two layers of AB so as to sandwich the terminal.
The anode metal layer A is formed on the surface of the concrete structure, and the anode metal layer B is formed on the surface of the terminal and the anode metal layer A.
The thickness of the anode metal layer A is not particularly limited, but is preferably 100 to 200 μm. If the thickness is less than 100 μm, the amount of metal forming the anode is small and the cost for the anticorrosion period may be high, and if it exceeds 200 μm, there is a high possibility that cracking or peeling will occur due to thermal strain during thermal spraying. There is.
The thickness of the anode metal layer B is not particularly limited, but is preferably 50 to 150 μm. If the thickness is less than 50 μm, the amount of metal forming the anode is small, and the cost for the anti-corrosion period may be high. If the thickness exceeds 150 μm, there is a high possibility that cracking or peeling will occur due to thermal strain during thermal spraying. There is.

In the present invention, a terminal is installed between the upper and lower anode metal layers.
For example, it is preferable to install the terminal directly above the steel material inside the concrete so as to be as close as possible to the steel material inside the concrete.

  The material of the terminal is not particularly limited as long as it is a material having electrical conductivity, and metals, ceramics, organic conductors, or the like can be used.

The shape of the terminal used in the present invention is not particularly limited, and a plate shape, a line shape, and a dot shape can be used.
The length of the terminal is preferably longer, but the smallest angle among the angles formed by the metal layer surface and the position farthest from the terminal among the steel materials inside the corrosion-prevented concrete, the shortest straight line connecting the terminals, and the metal layer surface. The length is preferably 10 to 90 degrees.

  Although the terminal installation method is not particularly limited, it is preferable to install the terminal directly above the steel material inside the concrete, and it is possible to install the terminal after confirming the position of the reinforcing bar by means of reinforcing bar exploration before installation.

  In the present invention, before forming the anode metal layer by thermal spraying, in order to improve the adhesion strength between the anode metal layer A and the concrete surface, the surface of the concrete structure and the terminals and the anode metal layer B In order to improve the adhesion strength, the terminal surface is preferably roughened with, for example, a rough surface forming agent.

  Although it does not specifically limit as a rough surface formation agent, For example, the epoxy resin, polyamide resin, etc. which disperse | distributed silicon carbide etc. are mentioned.

  Furthermore, in the present invention, in order to prevent the anode metal layer from deteriorating, it is preferable to protect the surface by using, for example, a sealing material.

  The sealing material is not particularly limited as long as the hole of the anode metal layer can be filled and the surface can be protected. For example, vinyl resin, butyral resin, etc. can be used.

  In the present invention, an anode metal layer is formed on the surface of the concrete structure, a terminal is installed, an anode metal layer is further formed, and when the anode metal layer and the steel material inside the concrete are connected via the terminal, Electricity flows between the anode metal layer and the steel material inside the concrete, and the steel material inside the concrete is protected against corrosion.

In the present invention, the effect can be confirmed by measuring the natural potential.
When a metal having a lower standard electrode potential is electrically connected to the steel material inside the concrete, the natural potential of the steel material itself inside the concrete is lowered. Therefore, the effectiveness of the anode electrode layer can be determined from the numerical value by measuring the natural potential.
The measurement of the natural potential was performed using a copper reference electrode with three points right next to the steel material inside the concrete on one side (side surface) of 150 mm × 530 mm perpendicular to the sprayed surface. Further, the instant off potential and the off potential 24 hours after stopping the energization were measured to calculate the amount of repolarization.

Ecse = EM-800
Ecse: Value measured with a lead verification electrode (mV)
EM: Saturated copper sulfate electrode standard conversion value (mV)

Depolarization amount (mV) = [Eio (mV)] − [Eof (mV)]
Eio: Instant off potential Eof: Off potential after 24 hours

  Hereinafter, the present invention will be further described based on experimental examples of the present invention.

Experimental example 1
A D19 deformed steel bar with a length of 600mm is placed so that both ends are out of the concrete 35mm each so that it is perpendicular to the 150x150mm face of the 150x150x530mm rectangular concrete specimen. Thus, a molded body was produced by using the steel material inside the concrete.
The formed body was cured outdoors for 4 weeks, and a concrete test body imitating a concrete structure was prepared.
One surface of 150 mm × 530 mm of the prepared specimen was used as the sprayed surface.
After applying a rough surface forming agent to the sprayed surface by air spraying, adjust the diameter and feed rate of the aluminum wire and zinc wire so that the volume ratio of metal aluminum and metal zinc is 1: 1, and arc spraying A 150 μm anode metal layer A was formed by spraying a zinc-aluminum pseudoalloy by the method.
On the anode metal layer A, a plate-like terminal made of stainless steel and having a size of 40 mm × 40 mm and a thickness of 2 mm was installed at the center in the longitudinal direction of the sprayed surface so that both ends protrude by 5 mm.
A rough surface forming agent is applied to the installed plate-like terminal surface, and, similarly to the anode metal layer A, a 100 μm anode metal layer B is formed, and a sealing agent is applied to the surface by air spraying. It was applied and sealed.
A conductive wire is electrically connected to one end of the steel material inside the concrete using a crimp terminal and a wood screw, and the other end of the conductive wire is a plate-like plate installed between the anode metal layers AB via a crocodile clip. Connected to the terminal to create a corrosion protection circuit.
Water is placed on a plastic bat of 600mm x 160mm and 20mm in depth about 10mm, and the surface opposite to the sprayed surface is placed in contact with water, so that the steel inside the concrete does not come into direct contact with water. The test body was supplied with water for 2 weeks or more and left in a corrosive environment. Thereafter, the natural potential was measured, and after a predetermined period, the corrosion state of the interface between the terminal and the anode metal layer was visually confirmed.
The natural potential is measured at three measurement points (1, 2, and 3) equidistant from the edge of the steel material inside the concrete on one side (side) of 150mm x 530mm perpendicular to the sprayed surface. Measurements were made using a copper reference electrode. Further, the instant off potential and the off potential 24 hours after stopping the energization were measured to calculate the amount of repolarization. The results of the natural potential measurement are shown in Table 1, and the results of the corrosion situation are shown in Table 2.

<Materials used>
Rough surface forming agent: Commercial product made of epoxy resin, polyamide resin, and silicon carbide

Experimental example 2
Adjust the diameter and feed rate of aluminum wire and zinc wire so that the volume ratio of metal aluminum to metal zinc is 1: 1, and spray zinc-aluminum pseudoalloy by arc spraying method to a thickness of 150 μm On the formed anode metal layer A, a plate made of stainless steel, 30 mm x 30 mm, thickness 2 mm is used as a terminal, and the end of the sprayed surface is arranged so that the end is about 5 mm. The test was performed in the same manner as in Experimental Example 1 except that the anti-corrosion circuit was formed by applying the sealing agent with air spray and sealing. The results are also shown in Table 1.

Experimental example 3
One side of the test body 150mm x 530mm is the sprayed surface, and it is made of stainless steel, with a 30mm x 30mm, 2mm thick plate as the terminal, and is placed so that the end of the sprayed surface is about 5mm in the longitudinal direction. In addition, the aluminum wire and the zinc wire are adjusted to have a volume ratio of 1: 1, and the diameter and feed rate of the aluminum wire and the zinc wire are adjusted, and the zinc-aluminum pseudoalloy is sprayed by an arc spraying method. The same operation as in Experimental Example 1 was conducted except that the anode metal layer A having a thickness of 100 μm was formed and the natural potential was measured. The results are also shown in Table 1.

Experimental Example 4
The experiment was performed in the same manner as in Experimental Example 1 except that the anode metal layer A and the anode metal layer B having thicknesses shown in Table 3 were formed. The results are shown in Table 3.

  By forming anode metal layers on the upper and lower sides of the terminal of the present invention, it is possible to obtain a stable and homogeneous anticorrosion current in the anticorrosion method for a galvanic anode type concrete structure, mainly in the civil engineering and construction industry. Suitable for repairing concrete structures such as offshore structures and revetment structures and improving durability.

Claims (8)

  On the surface of the concrete structure, an anode metal layer A, which is a metal layer having a lower standard electrode potential than the steel material inside the concrete, is formed, and a terminal is placed on the anode metal layer A. Furthermore, the standard is higher than the steel material inside the concrete. A concrete anticorrosion method in which an anode metal layer B which is a metal layer having a low electrode potential is formed, and a steel material inside the concrete and the anode metal layer are connected using the terminals.   The method for preventing corrosion of concrete according to claim 1, wherein the surface of the concrete structure is roughened, and an anode metal layer A which is a metal layer having a lower standard electrode potential than the steel material inside the concrete is formed thereon.   The concrete anticorrosion method according to claim 1 or 2, wherein a surface protective layer is formed on the anode metal layer B.   The concrete according to any one of claims 1 to 3, wherein the anode metal layer A and the anode metal layer B are formed by thermal spraying of a metal having a lower standard electrode potential than the steel material inside the concrete. Anticorrosion method.   The method for preventing corrosion of concrete according to claim 4, wherein the metal having a lower standard electrode potential than the steel material inside the concrete is a zinc-aluminum pseudoalloy.   The thickness of the anode metal layer A is 100-200 micrometers, The anticorrosion construction method of the concrete as described in any one of Claims 1-5.   The thickness of the anode metal layer B is 50-150 micrometers, The anticorrosion method of concrete as described in any one of Claims 1-6.   A concrete structure formed by performing the concrete anticorrosion method according to any one of claims 1 to 7.