KR20130045484A - Intermittent cathodic protection method for concrete structure, intermittent cathodic protection system for concrete structure and intermittent cathodic protection system for nuclear structure - Google Patents

Abstract

The intermittent electrical system 100 for a concrete structure according to the present invention includes a cathode part 10 connected to the reinforcing steel bars in the concrete structure, an anode part 20 and a cathode part 10 in contact with an exposed surface of the concrete structure, and It includes a DC power supply 30 for supplying a direct current so that the anode portion 20 is a cathode and an anode electrode, respectively. The DC power supply 30 is characterized in that to supply the reference current value in the reference interval time. This prevents the reduction of adhesion strength at the reinforcement-concrete interface and prevents penetration of corrosion factors (chlorine ions).

Description

INTERMITTENT CATHODIC PROTECTION METHOD FOR CONCRETE STRUCTURE, INTERMITTENT CATHODIC PROTECTION SYSTEM FOR CONCRETE STRUCTURE AND INTERMITTENT CATHODIC PROTECTION SYSTEM FOR NUCLEAR STRUCTURE}

The present invention relates to a method and system for cathodic protection. In particular, the present invention relates to an electric method and system for performing an electric method by applying an intermittent current to the concrete structure.

Since almost all metal materials used in industry are extracted from ore while being reduced to metal state, metal materials used in industrial structures or buildings are inevitably caused to corrode or oxidize with the surrounding environment over time. do. Since most of these corrosion occurs due to the electrochemical reaction caused by the movement of electrons, it is called electrochemical corrosion. The metal structure becomes a corrosion cell as corrosion progresses, causing a corrosion potential, and a constant corrosion current flows into the metal material. In particular, nuclear power plants located by the sea are always exposed to corrosion due to sea winds, and sufficient anticorrosive performance is required.

There are several ways to prevent corrosion of reinforcing steel reinforcement and to recover dropped concrete sections. One method is to recover the dropped concrete sections with repair mortar. However, when repairing in this way, there is a problem that the salinity in the concrete is not completely removed, causing corrosion of the reinforcing bars, thereby easily dropping off the repair site. As another method, it is known to perform external power protection (Cathodic protection) using a titanium anode network or a conductive surface coating material.

In general terms means the removal or suppression of one or more conditions of corrosion. The electric method is a method of controlling corrosion of a facility or structure by artificially controlling the potential or current of a facility or structure that requires a method. There is cathode protection (cathodic protection) to cathodic the object. The anode method is used in a limited way because the corrosion is accelerated if the potential control is not precisely made, and the cathode method is mainly used.

Cathode protection is a method of preventing corrosion by artificially lowering the potential of an anticorrosive object, and is classified into a sacrificial anode method and an external power supply method according to a method of applying an anticorrosive current. The sacrificial anode method cathodes the anticorrosive object by electrically connecting a metal with high ionization tendency in the electrolyte to act as an anode, and the external power method connects the negative electrode of a DC power supply or rectifier to the anticorrosive object. By connecting the positive electrode (+) to the positive electrode member, an anticorrosive current is obtained.

The electric method of supplying low current (5-20mA / m2) continuously for the life of the structure and the electric method of supplying high current (250-750mA / m2) temporarily for 6 to 8 weeks has already been studied. Widely used electrical methods (L. Bertolini, B. Elsener, P. Pedeferri, R. Polder, 2004, Corrosion of steel in concrete-Prevension, Diagnosis, Repair.Wieley-VCH and J. Broomfield, 2006, Corrosion of Steel in concrete-Understanding investigation and repair, E & FN Spon An imprint of routledge London and New York).

However, due to the characteristics of the electric method, the adhesion strength decreases due to the continuous hydrogen generation at the reinforcement-concrete interface, and furthermore, problems such as deterioration of the properties of concrete due to the long-term application of the electric method have been reported.

An intermittent electrical method and system for a concrete structure according to the present invention aims to solve the following problems.

First, it is intended to provide an electric method and system having an optimal current value and supply time in supplying DC current to a concrete structure including a nuclear power structure.

Second, in the electric method, it is to minimize the generation of hydrogen at the reinforcing-concrete interface to prevent the reduction of adhesion strength at the reinforcing-concrete interface and to prevent the deterioration of concrete properties.

Third, through the intermittent current supply chlorine ion (Cl ^-) that corresponds to the corrosive factors and to maximize the protection of the concrete penetrated.

The problem of the present invention is not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

In the intermittent electric method for the concrete structure according to the present invention, the anode of the DC power supply device 30 is connected to the reinforcing bar of the concrete structure, and the anode portion of the anode of the DC power supply device 30 is in contact with the exposed surface of the concrete structure. (20) and the step of supplying a current of the reference current value between the positive electrode portion 20 and the reinforcing bar in the DC power supply 30 as a reference interval time.

The reference current value is preferably 50 mA / m ² to 100 mA / m ² . Furthermore, it may be more preferable that the reference current value is 50 mA / m ² to 60 mA / m ² .

The reference interval time is preferably 2 hours to 4 hours every 24 hours. Furthermore, it may be more preferable that the reference interval time is 3 hours every 24 hours. However, the time for which the current is applied may be a continuous time, a time having a constant interval, or a time having a time interval set by the user according to the environment of the electrical system object.

In the aspect of the electric system, the intermittent electric system for the concrete structure according to the present invention includes a cathode part connected to the reinforcing steel bars, an anode part contacting the exposed surface of the concrete structure, and a cathode part and an anode part, respectively. It includes a direct current power supply for supplying a direct current to be a positive electrode. The DC power supply is characterized by supplying a reference current value at a reference interval time. The current value supplied by the DC power supply device or the time supplied is the same as described above.

The intermittent electrical method and system for a concrete structure according to the present invention uses the average current of 50 to 100 mA / m2 to perform the electrical method intermittently at a high risk of corrosion. This prevents the reduction of adhesion strength at the reinforcement-concrete interface and prevents penetration of corrosion factors (chlorine ions).

In particular, in case of nuclear power plants with high risk of corrosion due to sea wind, the electric system is operated intermittently only at high risk of salt, contributing to the improvement of corrosion resistance and life extension of the structure.

The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a structural diagram schematically showing an electric method or system configuration in which the present invention is used.
2 is a cross-sectional view showing a cross section of a concrete structure to which the present electric system is applied to a concrete structure.
3 is a schematic structural diagram of an experimental apparatus for verifying the effect of the present invention.
Figure 4 is a graph showing the experimental results for showing the effect of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, A, B, etc. may be used to describe various components, but the components are not limited by the terms, but merely for distinguishing one component from other components. Only used as For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

As used herein, the singular forms "a,""an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is to be understood that the present invention means that there is a part or a combination thereof, and does not exclude the presence or addition possibility of one or more other features or numbers, step operation components, parts or combinations thereof.

Hereinafter, an intermittent electrical method and system 100 for a concrete structure will be described in detail with reference to the drawings.

Prior to the detailed description of the drawings, it is to be clear that the division of the components in the present specification is only divided by the main function of each component. That is, two or more components to be described below may be combined into one component, or one component may be provided divided into two or more for each function. Each of the components to be described below may additionally perform some or all of the functions of other components in addition to the main functions of the components, and some of the main functions of each of the components are different. Of course, it may be carried out exclusively by. Therefore, the presence or absence of each component described through this specification should be interpreted functionally, and for this reason the configuration of the components according to the intermittent electrical system 100 for the concrete structure of the present invention is the object of the present invention It should be clearly clarified that this may differ from FIG. 1 to the extent that can be achieved.

1 is a structural diagram schematically showing a configuration of an electric method to system 100 in which the present invention is used.

The electric method used in the present invention is a cathode method for supplying external power. The negative electrode method is a method of supplying a current to the positive electrode portion 20 and the negative electrode portion 10 of the DC power supply device 30 that supplies a DC current from the outside. 1, the electrons supplied to the cathode unit 10 to reduce the oxygen (O _2), iron (Fe ^{+ 3)} ions, and decomposing water to produce hydrogen (H _2). In the anode portion 20, water is decomposed to produce coral, chlorine (Cl), and iron (Fe) is oxidized.

Between the cathode part 10 and the anode part 20 denoted by C means concrete. The concrete contains moisture so that the ions move as shown.

When the current supplied from the DC power supply device 30 is 1V, hydrogen starts to be generated, and when the supplied current is about 1.13V or more, the generated hydrogen is proportional to the strength of the current. In the conventional electric method, a large amount of hydrogen is generated because a method of continuously supplying a current or using a method of flowing a high current for a predetermined period of time. The generated hydrogen reduces the adhesion strength of the reinforcing-concrete interface and degrades the concrete properties itself. On the other hand, chlorine ions generated (Cl ^-) are also serve to promote corrosion by acting as a corrosion factor.

2 is a cross-sectional view showing a cross section of a concrete structure to which the present electrical system 100 is applied to a concrete structure.

A cathode current is applied to the concrete reinforcing bar 5 to form the cathode part 10, and the anode part 20 is formed on a surface exposed to the outside of the concrete structure. The anode 20 is formed on the concrete surface by contacting a metal such as titanium to the concrete surface or by applying a conductive paint. Since the anode portion 20 should be an insoluble anode, a platinum anode, a titanium anode, a titanium-based platinum plating anode, etc., which have low consumption rate, are used.

Although not shown in Figure 2, the insoluble anode portion is installed, the current flow power supply device is installed to perform the electric method. When the external power source is AC power, the AC power is changed to DC power through the rectifier.

Connect to (+) pole of external DC power source in insoluble anode part, connect (-) pole to reinforcing steel of concrete structure, supply anti-corrosive current to supply electron and polarize to cathode method.

Anti-corrosive objects are consumed by the current supplied to the insoluble anode connected to the positive pole, and electrons (electro-negative electrons) are supplied to the concrete structure (reinforcement), which is the anticorrosive object, through the (-) pole to negatively polarize the potential to the anticorrosive potential. Corrosion is prevented.

The key idea of the present invention is to intermittently adjust the current value to be supplied and when the current is supplied. This minimizes the generation of hydrogen and prevents the penetration of chlorine ions, a corrosion factor.

The following table presents the conditions of the conventional electric method and the electric method proposed in the present invention. Of course, the conditions of the present invention shown in Table 1 below are just preferred examples.

Type I is 5 to 20mA (the unit area to which the current value is applied is m ² ) and the electric system is installed and the current is continuously applied.Type II is the high current value of 250 to 750mA when the degree of corrosion is severe. This is a method of intensively applying current in a specific period. The problem arises as described above in that Type I is applied with a constant current, and Type II is applied with a high current for a certain period or for a relatively long time. This is because hydrogen occurs continuously (Type I) or rapidly (Type II).

In contrast, an embodiment of the present invention (Intermittent) is a method of applying a current of 50 to 100mA for 3 hours on a 24-hour basis. The timing of three hours may vary depending on the actual need for electricity. For example, when using a structure such as an aid structure exposed to sea breeze as the object of the anticorrosion, it is preferable to adjust the time for which the current is applied by applying a current at the time when the sea breeze becomes strong. Or if the structure is exposed to seawater it is preferable to adjust the time so that the electric method is performed at the time of exposure to seawater.

In the intermittent electrical method for the concrete structure according to the present invention, the anode of the DC power supply device 30 is connected to the reinforcing steel bars inside the concrete structure, and the anode portion of the anode of the DC power supply device 30 is in contact with the exposed surface of the concrete structure. (20) and the step of supplying a current of the reference current value between the positive electrode portion 20 and the reinforcing bar in the DC power supply 30 as a reference interval time.

The reference current value is preferably 50 mA / m ² to 100 mA / m ² . Furthermore, it may be more preferable that the reference current value is 50 mA / m ² to 60 mA / m ² .

The reference interval time is preferably 2 hours to 4 hours every 24 hours. Furthermore, it may be more preferable that the reference interval time is 3 hours every 24 hours. However, the time for which the current is applied may be a continuous time, a time having a constant interval, or a time having a time interval set by the user according to the environment of the electrical system object.

In terms of the electrical system, the intermittent electrical system 100 for the concrete structure according to the present invention is a cathode part 10 connected to the reinforcing steel bars inside the concrete structure, the anode portion 20 in contact with the exposed surface of the concrete structure And a direct current power supply device 30 for supplying a direct current such that the cathode portion 10 and the anode portion 20 become cathode and anode electrodes, respectively. The DC power supply 30 is characterized in that to supply the reference current value in the reference interval time. The current value and the time supplied by the DC power supply device 30 are the same as described above.

Furthermore, the above-described method or system can be introduced into a nuclear power plant structure with high corrosion concern by sea wind or the like. This can improve the corrosion resistance of the nuclear power plant structure, and extend the service life.

3 is a schematic structural diagram of an experimental apparatus for verifying the effect of the present invention. DC power supply (Power supply) formed the positive electrode portion 20 by the titanium mesh on both surfaces of the concrete mortar, and formed the negative electrode portion 10 in the center of the mortar.

The experiment proceeded as follows. (1) Prepare a mold having a diameter of 50 mm and a height of 100 mm and a reinforcing bar having a diameter of 10 mm with an exposure length of 50 mm. (2) Cement: Water: Sand = 1.0: 0.4: 2.5 The mortar is added to the prepared mold and the rebar is placed in the center of the mold. At this time, 3% NaCl of the cement amount is used with dissolving water. (3) After curing in plastic wrap for 28 days. (4) After curing, the titanium mesh is crimped around the specimen surface. (5) Connect cathode to rebar and anode to mesh using power supply. (6) Conventional methods continue to supply 20 mA / m ² of current from 12 hours after installation until the end of the test, and to stop the current pressurization only when the corrosion potential is measured. (7) In the case of the Intermittent method, a current of 50 mA / m ² is supplied for 3 hours out of 12 hours after 12 hours of installation. Corrosion potential is also measured in the same way.

Figure 4 is a graph showing the experimental results for showing the effect of the present invention. Two controls were used to compare with the present invention. One is a non-treated control and the other is a conventional control using the conventional method of continuously supplying a current of 20 mA / m ² .

(1) If no treatment is done, the corrosion threshold potential is recorded below -350mV, indicating that the corrosion continues to diffuse. (2) When applying Conventional CP, the area of -210-230mV is maintained and the corrosion is restored. (3) In the case of the embodiment of the present invention (Intermittent CP), the initial 24 hours by applying the electric method only maintained the area of -210-230mV like the conventional CP, but after the end of the electric system, -270-300mV However, the method was maintained by maintaining the corrosion threshold potential.

The embodiments and drawings attached to this specification are merely to clearly show some of the technical ideas included in the present invention, and those skilled in the art can easily infer within the scope of the technical ideas included in the specification and drawings of the present invention. Modifications that can be made and specific embodiments will be apparent that all fall within the scope of the present invention.

100: Intermittent electric system for concrete structure
10: cathode part 20: anode part
30: current flow power supply device

Claims (11)

In the electrical method for a concrete structure using an external power source,
Connecting the cathode of the DC power supply to the reinforcing bars in the concrete structure, and connecting the anode of the DC power supply to the anode contacting the exposed surface of the concrete structure; And
And intermittently supplying a current of a reference current value between the anode part and the reinforcing bar in the DC power supply unit at a reference interval time. The method of claim 1,
The reference current value is 50mA / m ² to 100mA / m ² intermittent electrical method for the concrete structure, characterized in that. The method of claim 2,
The reference current value is 50mA / m ² to 60mA / m ² intermittent electrical method for the concrete structure, characterized in that. The method of claim 1,
The reference interval time is an intermittent electrical method for the concrete structure, characterized in that every 24 hours to 2 hours to 4 hours. 5. The method of claim 4,
The reference interval time is an intermittent electrical method for the concrete structure, characterized in that 3 hours every 24 hours. In the electrical system for the concrete structure using an external power source,
A cathode part connected to the reinforcing steel bars in the concrete structure;
An anode portion in contact with an exposed surface of the concrete structure; And
It includes a DC power supply for supplying a direct current so that the cathode and the anode is a cathode and an anode, respectively,
The DC power supply device is an intermittent electrical system for a concrete structure, characterized in that for supplying a reference current value at a reference interval time. The method according to claim 6,
The reference current value is 50mA / m ² to 100mA / m ² intermittent electrical system for the concrete structure, characterized in that. The method of claim 7, wherein
The reference current value is 50mA / m ² to 60mA / m ² intermittent electrical system for the concrete structure, characterized in that. The method according to claim 6,
The reference interval time is an intermittent electrical system for the concrete structure, characterized in that every 24 hours 2 to 4 hours. 10. The method of claim 9,
The reference interval time is an intermittent electrical system for a concrete structure, characterized in that 3 hours every 24 hours. An electrical system for an aid structure that performs the electrical system using the intermittent electrical system according to any one of claims 1 to 5.

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