JP2012207251A - Electric protection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric protection method capable of controlling the amount of polarization in a range suitable for electric protection without using a reference electrode when carrying out electric protection.SOLUTION: The electric protection method is carried out by supplying electric current to a steel from an anode in a manner of controlling the amount of polarization calculated by subtracting the electric potential Eof the steel from the natural potential Ethereof within a prescribed range. The method includes calculating the natural potential Eof the steel and the instant-off potential Ethereof using the polarization curve of the anode, and carrying out the supply of current in a manner of controlling the amount of polarization within a prescribed range while setting the potential difference Vbetween the anode and the steel measured immediately after cutting off the current supply.

Description

  The present invention relates to an anticorrosion method for performing anticorrosion of a steel material by supplying current from the anode material to the steel material.

  Steel materials (such as iron pipes and reinforcing bars) arranged in water, soil, or concrete structures are originally protected from corrosion by forming a passive film on the surface. However, in environments where a large amount of chlorine is present, such as coastal areas and areas where anti-freezing agents are frequently used, the passive film may be partially destroyed by contact with the steel. There is. And the iron ion in steel materials elutes from the part where the passive film was destroyed, and promotes corrosion (oxidation) of steel materials. Such corrosion of the steel material reduces the strength of the steel material itself and may cause cracks in the concrete structure due to the expansion of the volume of the corroded portion in the concrete structure, and may cause the concrete to peel off.

  As described above, the partial corrosion of the steel material causes a potential difference between the corroded region (anode portion) and the non-corroded region (cathode portion) of the steel material. As a result, a corrosion current is generated by the flow of electrons from the anode portion to the cathode portion, and the elution of iron ions from the anode portion further proceeds.

  As a method for preventing the progress of such corrosion, for example, there is an electro-corrosion prevention method for supplying current (anti-corrosion current) to a steel material in a concrete structure through concrete from an anode material formed using a material such as titanium. Are known. The electro-corrosion prevention method is a method of preventing a corrosion current from being generated by supplying an anti-corrosion current to a steel material, thereby eliminating a potential difference generated between the anode part and the cathode part.

  In the cathodic protection method, in order to obtain an effective anticorrosive effect, the current supplied (or the voltage applied between the anode material and the steel material), that is, the amount of the anticorrosive current is managed. The supply current is managed by managing the polarization amount of the steel material when the current is supplied and the depolarization amount of the steel material after the supply current is cut off within a predetermined range. Further, depending on the environment in which the steel material is disposed, the instant-off potential of the steel material may be managed in addition to the polarization amount and the depolarization amount. The polarization amount, depolarization amount, and instant-off potential of the steel material are calculated by measuring the potential of the steel material with reference to a reference electrode disposed in the vicinity of the steel material so that a good anticorrosive effect can be obtained. In addition, the anticorrosion current is supplied (see Patent Document 1).

Japanese Unexamined Patent Publication No. 7-70774

  However, as described above, in the method using the reference electrode, when the reference electrode reaches the end of its life or is damaged, the amount of polarization cannot be measured, so the reference electrode needs to be replaced. Thus, the replacement work takes time and cost. In particular, when exchanging the verification electrode embedded in the concrete structure, it is necessary to remove the concrete near the embedded verification electrode and replace the verification electrode, and then backfill with concrete again. It takes a lot of work and cost.

  Then, this invention makes it a subject to provide the cathodic protection method which can manage the amount of polarization and a depolarization amount in the range suitable for cathodic protection, without using a collation electrode, when performing cathodic protection.

The cathodic protection method according to the present invention includes an anode material potential measurement that measures an instant-off potential of an anode material with respect to a supply current density in the cathodic protection method for performing steel corrosion prevention by supplying current from the anode material to the steel material. a step, in a state where a potential difference is stable between the anode material and a steel material not current to the steel is supplied, and V _ac measuring step of measuring the potential difference V _ac between the anode material and a steel material, the current V _ac-io measurement step of measuring the potential difference V _ac-io between the anode material and the steel material immediately after the supply current is cut off after the potential difference between the anode material and the steel material is stabilized by supplying The anode material potential E _a-corr when the supply current density measured in the anode material potential measurement step is 0 mA / m ² , and between the anode material and the steel material measured in the V _ac measurement step. The natural potential E _c-corr of steel is calculated by subtracting the potential difference V _ac Out, from the potential E _a-io of anode material which has been measured by the anode material potential measuring step with respect to the supply current density immediately before interrupting the supply current in said V _ac-io measurement step, in V _ac-io measuring step calculating the measured anode material and the potential difference V _ac-io steel by subtracting the potential E _c-io between steel, self potential E _c-corr steel calculated at, steel potential E _c It is characterized in that a current is supplied to the steel material so that the amount of polarization calculated by subtracting _-io falls within a predetermined range.

The cathodic protection method according to the present invention includes an anode material potential measurement that measures an instant-off potential of an anode material with respect to a supply current density in the cathodic protection method for performing steel corrosion prevention by supplying current from the anode material to the steel material. After cutting off the supply current from the process and the state where the potential difference between the anode material and the steel material is stabilized by supplying the current, between the anode material and the steel material when the potential difference between the anode material and the steel material is stabilized V _ac ′ measurement process for measuring the potential difference V _ac ′ of the steel sheet, and after supplying the current to the steel material to stabilize the potential difference between the anode material and the steel material, immediately after cutting off the supply current, V _ac-io measurement step for measuring the potential difference V _ac-io between the anode material potential E _a-corr 'when the supply current density measured in the anode material potential measurement step is 0 mA / m ² from the the steel the V _ac 'anode material measured by the measuring step The potential difference V _ac calculated the 'depolarization potential after E _c-corr steel by subtracting the' between the anode material potential to supply a current density immediately before interrupting the supply current in said V _ac-io measuring step By subtracting the potential difference V _ac-io between the anode material and the steel material measured in the V _ac-io measurement process from the potential E _{a-io of} the anode material measured in the measurement process, the potential E _{c- io} is calculated, and current is supplied to the steel so that the amount of depolarization calculated by subtracting the potential E _c-io of the steel from the post-repolarization potential E _c-corr 'of the steel is within a predetermined range. It is characterized by that.

According to such a configuration, the natural potential E _{c-corr of} the steel material, the post-repolarization potential E _c-corr ′ of the steel material, and the potential E _{c-io of the} steel material (immediately after the anticorrosion current is interrupted) without directly measuring using the reference electrode The amount of polarization and the amount of depolarization can be calculated without using a reference electrode.

In addition, by setting the potential difference between the anode material and the steel material (hereinafter also referred to as the instant-off voltage between the anode material steel materials) V _ac-io measured immediately after the supply current is cut off, the polarization amount and the depolarization amount can be set. It becomes possible to set to a predetermined range. Specifically, by setting the instant-off voltage V _ac-io between anode material steel, the anode material potential measuring step with respect to the supply current density corresponding to the instant-off voltage V _ac-io between anode material steel The measured potential E _a-io of the anode material can be obtained, and the potential E _c-io of the steel material can be calculated as described above. Such a steel material potential E _c-io corresponds to an instant-off potential of the steel material measured with reference to the reference electrode. That is, by setting the instant-off voltage V _ac-io between the anode steel materials, a potential corresponding to the instant-off potential of the steel material can be calculated. Therefore, based on the calculated natural potential E _c-corr of the steel material and the post-repolarization potential E _c-corr ′ of the steel material, the instant-off voltage V _ac− between the anode steel materials is adjusted by adjusting the current supplied to the steel materials. By setting _io , the amount of polarization and the amount of depolarization can be set within a predetermined range. As a result, by measuring the instant-off voltage V _ac-io between the anode steel materials, it is possible to manage the polarization amount and the depolarization amount that are optimal for cathodic protection without using a reference electrode.

Also, by measuring the instant-off voltage V _ac-io between the anode steel materials, the potential E _c-io corresponding to the instant-off potential of the steel material can be obtained without using a reference electrode. In addition to this, even if it is necessary to manage the instant-off potential of the steel material (that is, the potential E _c-io of the steel material) within a predetermined range, the potential E _c-io of the steel material can be set without using the reference electrode. It can be managed within a predetermined range.

  The polarization curve of the anode material is prepared by arranging a reference electrode in an environment where a steel material to be subjected to cathodic protection is provided, and measuring the instant-off potential of the anode material with reference to the reference electrode. It is preferable.

  According to such a configuration, the polarization curve of the anode material is created by measuring the potential of the anode material using the reference electrode disposed in the environment where the steel material that actually performs the anticorrosion is embedded. In addition, it is possible to obtain a polarization curve corresponding to the environment (such as the temperature and the amount of chloride in the concrete structure) where the actual anticorrosion is performed. As a result, there is a large difference between the polarization amount and depolarization amount measured using the reference electrode in the environment where the cathodic protection is actually performed, and the polarization amount and depolarization amount calculated using the polarization curve. Can be suppressed. For this reason, even after the reference electrode embedded together with the steel material ceases to function due to its life, etc., it is possible to calculate the polarization amount and the depolarization amount corresponding to the environment in which the anticorrosion is performed. Similarly, the amount of polarization and the amount of depolarization can be managed.

  As described above, according to the present invention, the amount of polarization and the amount of depolarization can be managed in a range suitable for the anticorrosion without using a reference electrode when performing the anticorrosion.

The flowchart figure which showed the flow of the cathodic protection method which concerns on 1st Embodiment. The figure which showed the example of the polarization curve of the anode material in the cathodic protection method which concerns on 1st and 2nd embodiment. The flowchart figure which showed the flow of the cathodic protection method which concerns on 2nd Embodiment. The figure which showed the polarization curve produced in the Example.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2.

<First Embodiment>
In the cathodic protection method according to the present embodiment, when the cathodic protection is performed by supplying current from the anode material to the steel material disposed in water, soil, or in a concrete structure, the polarization amount of the steel material is predetermined. The current is supplied to the steel material so as to be in the range. Below, the case where the electric corrosion protection of the steel materials embed | buried in a concrete structure is performed is demonstrated along the flowchart shown in FIG.

<Installation of anti-corrosion equipment>
When carrying out the anti-corrosion of the steel material in a concrete structure, an anode material is embedded in the concrete structure and a reference electrode is embedded in the vicinity of the steel material. At this time, the anode material and the steel material are connected to a power supply device that adjusts the voltage between the anode material and the steel material through a conductor, and the conductor is connected to a voltmeter that measures a potential difference between the anode material and the steel material. Connected through. On the other hand, the reference electrode and the steel material are connected to a voltmeter that measures a potential difference between the reference electrode and the steel material through a lead wire, and the reference electrode and the anode material have a potential difference between the reference electrode and the anode material. It is connected to a voltmeter to be measured via a conductor.

  The mode of embedding the anode material is not particularly limited. For example, in the case where an anode material formed in a planar shape is used, the anode material arranged so as to cover the area where the anticorrosion is performed is embedded with concrete. It can be set as an aspect. Or, in the case of using a strip-shaped anode material, a plurality of grooves having a shape corresponding to the anode material are formed on the surface of the concrete structure, and after placing the anode material in each groove, the embodiment is embedded with concrete. can do. As yet another aspect, in the case of using a rod-shaped anode material, a plurality of holes are formed from the surface of the concrete structure toward the steel material side, and the anode material is inserted into each hole and then embedded with concrete. It can be set as an aspect. As a material for forming the anode material, a commonly used material can be used, and a titanium material or the like can be used.

  The reference electrode serves as a reference when measuring the potential of the anode material and the steel material. Specifically, the potential difference between the verification electrode and the anode material is measured as the potential of the anode material, and the potential difference between the verification electrode and the steel material is measured as the potential of the steel material. As the reference electrode, a commonly used one can be used. For example, a saturated silver-silver chloride reference electrode, a copper copper sulfate reference electrode, a lead reference electrode, or a manganese dioxide reference electrode can be used. Further, since the reference electrode is embedded in the concrete structure, the internal electrolyte is absorbed in the concrete structure, and therefore, the reference electrode does not exhibit a stable potential when used over time. For this reason, the lifetime of the verification electrode is generally about 20 years.

<Management of polarization during the reference electrode usage period>
After the anode material and the reference electrode are embedded in the concrete structure as described above, when the electric protection is performed by supplying current from the anode material to the steel material using the power supply device, the polarization amount of the steel material is within a predetermined range. The current is supplied so that When the polarization amount is within a predetermined range, the corrosion current generated in the steel material can be effectively eliminated. The amount of polarization means the amount of change in the steel material potential when a current is supplied to the steel material. Specifically, the polarization amount is the steel material potential (hereinafter referred to as the natural potential of the steel material) in a state where no current is supplied to the steel material (before current supply or after the supply current is cut off and the steel material potential is stabilized). This is the amount of change in how much the electric potential has changed to the lower side.

In the present embodiment, the polarization amount of the steel material is calculated based on the reference electrode during the period until the reference electrode embedded together with the steel material that is actually subjected to the anticorrosion reaches the end of its life (hereinafter referred to as the reference electrode use period). . Specifically, in a state where no current is supplied to the steel material, the natural potential of the steel material is obtained by measuring the potential of the steel material with reference to the reference electrode. Furthermore, after the electric current is supplied to stabilize the electric potential of the steel material, immediately after the electric current is interrupted, the electric potential of the steel material is measured with reference to the reference electrode, so that the instant-off potential of the steel material (the electric potential E _{c-io of} the steel material described later) Equivalent). Then, the polarization amount of the steel material is calculated by subtracting the instant-off potential of the steel material from the natural potential of the steel material.

  In other words, during the reference electrode usage period, the amount of polarization is calculated as described above. Therefore, the supply current to the steel material is adjusted based on the natural potential of the steel material to be measured (that is, by the power supply device). By adjusting the voltage generated between the anode material and the steel material and setting the instant-off potential of the steel material, the amount of polarization can be set within a predetermined range. Thereby, it can manage so that the amount of polarization may become a predetermined range by measuring the instant-off electric potential of steel materials.

<Creation of polarization curve>
In this embodiment, the instant-off potential of the anode material with respect to the supply current density is measured during the reference electrode usage period (anode material potential measurement step). Specifically, the instant-off potential of the anode material with respect to the supply current density is measured using the reference electrode embedded as described above, and a polarization curve is created (polarization curve creation step). Such a polarization curve shows the change in the instant-off potential of the anode material with respect to the change in the supply current density (current density per unit area of the area where the anode material is embedded) when current is supplied from the anode material to the steel material. It represents. The instant-off potential of the anode material is the potential of the anode material measured immediately after the supply current is cut off after the current is supplied to the steel material to stabilize the steel material potential. In this embodiment, the supply current density is changed by adjusting the power supply device, the change in the instant-off potential of the anode material with respect to this change is measured with reference to the reference electrode, and the change in the instant-off potential of the obtained anode material Is graphed with respect to the change in the supply current density to create a polarization curve as shown in FIG. In other words, the polarization curve of the anode material becomes a curve in which the instant-off potential of the anode material changes to the noble side as the supply current density increases.

Moreover, the shape of the polarization curve of the anode material produced as described above varies depending on the environment in which the steel material is actually subjected to anticorrosion. For this reason, it is preferable to create a plurality of polarization curves in accordance with changes in the environment in which the steel material that is actually subject to cathodic protection is embedded. For example, it is preferable to create a plurality of polarization curves according to a change in temperature or a change in the amount of chlorine component during the use period of the verification electrode. By creating a plurality of polarization curves in this way, as will be described later, when calculating the polarization amount of the steel material using the polarization curve of the anode material, the polarization curve corresponding to the environment in which the electric protection is actually performed is selected. Can be used. As a result, it is possible to suppress the occurrence of a large difference between the potential of the anode material read based on the polarization curve and the potential of the anode material measured using the reference electrode at the site where actual corrosion protection is performed. it can. As a result, as will be described later, the natural potential E _c-corr of the steel material obtained by using the polarization curve and the potential E _c-io corresponding to the instant-off potential of the steel material are used as the reference electrode at the site where the actual corrosion protection is performed. It is possible to suppress a large deviation from the potential measured by using.

<Management of polarization after the reference electrode usage period has elapsed>
As described above, the reference electrode in the concrete structure reaches the end of its life due to use over time, and does not function properly. For this reason, after the verification electrode usage period has elapsed, the amount of polarization cannot be obtained using the verification electrode. Therefore, after the reference electrode usage period has elapsed, the amount of polarization is obtained by the method described below, and current is supplied so that the amount of polarization falls within a predetermined range.

Specifically, the current is not supplied to the steel material, and the potential difference between the anode material and the steel material is stable (before the current supply or after the supply current is interrupted and the influence of the supply current disappears) _Vac measurement step of measuring the potential difference V _ac between the anode material and the steel material in step 3), and after stabilizing the potential difference between the anode material and the steel material by supplying current, the anode immediately after the supply current is cut off From the value measured in the V _ac-io measurement process that measures the potential difference V _ac-io between the metal and steel, the polarization amount of the anode material created in the polarization curve creation process is used to calculate the amount of polarization. The amount of polarization is calculated by calculating a necessary natural potential E _c-corr of the steel material and a potential E _c-io (potential immediately after the anticorrosion current is cut off) corresponding to the instant-off potential of the steel material.

The natural potential E _c-corr of the steel material after the use period of the reference electrode is the potential of the anode material when the supply current density in the polarization curve of the anode material is 0 mA / m ² (hereinafter also referred to as the natural potential of the anode material) E It is calculated by subtracting, from _a-corr , a potential difference between the anode material and the steel material measured in the V _ac measurement step (hereinafter also referred to as a potential difference before polarization between the anode material steel materials) V _ac . That is, the natural potential E _c-corr of the steel material is calculated by the following equation (1).

“E _c-corr ” = “E _a-corr ” − “V _ac ” (1)

The natural potential E _c-corr of the steel material calculated as described above corresponds to the natural potential of the steel material measured during the verification electrode usage period. Further, the potential difference V _ac before polarization between the anode material and the steel material is a voltage generated between the anode material and the steel material, and can be measured by a voltmeter connected to the anode material and the steel material. On the other hand, the natural potential E _a-corr of the anode material based on the polarization curve is a state in which no current is supplied to the steel material during the use of the reference electrode (before the current is supplied, or the supply of current is interrupted). This corresponds to the potential of the anode material that can be measured after the influence disappears.

The steel material potential E _c-io corresponding to the steel material instant-off potential is determined based on the polarization curve with respect to the current density immediately before the supply current is cut off in the V _ac-io measurement step (current density before interruption). The potential difference between the anode material and the steel material (hereinafter referred to as the anode material steel material) measured in the V _ac-io measurement process from the potential of the material (hereinafter also referred to as the polarization potential of the anode material according to the polarization curve) E _a-io It is also calculated by subtracting V _ac-io . That is, the instant-off potential E _c-io of the steel material is calculated by the following equation (2).

“E _c-io ” = “E _a-io ” − “V _ac-io ” (2)

The instant-off voltage V _ac-io between the anode material and the steel material is a true voltage generated between the anode material and the steel material. Then, the instant-off voltage V _ac-io between the anode material and the steel material is obtained by stabilizing the voltage generated between the anode material and the steel material by supplying a current to the steel material, and then immediately after the supply current is cut off. It is measured by a voltmeter connected to the. Further, the instant-off voltage V _ac-io between the anode steel materials adjusts the supply current density when supplying current to the steel materials (that is, adjusts the voltage generated between the anode materials and the steel materials by the power supply device). It is possible to set by. The supply current density is preferably about 5 to 30mA / m ^2. On the other hand, the polarization potential E _a-io of the anode material based on the polarization curve corresponds to the true potential of the anode material that can be measured when the current is supplied to the steel material during the reference electrode usage period.

  Since “true voltage” and “true potential” are concrete between the anode material and the steel material and between the anode material and the reference electrode, the measured voltage and potential are It is not a true voltage or potential because it is affected by electrical resistance. However, since the influence of concrete can be eliminated by cutting off the supply current as described above, the voltage and potential measured immediately after the supply current is cut off become the true voltage and potential.

As described above, from the natural potential E _{c-corr of} the steel obtained using the polarization curve of the anode material, the potential E _{c-io of} the steel obtained using the polarization curve (corresponding to the instant-off potential of the steel) The amount of polarization is calculated even after the reference electrode usage period has elapsed. That is, after the reference electrode usage period has elapsed, the polarization amount of the steel material is calculated by the following equation (3).

Polarization amount = “E _c-corr ” − “E _c-io ” (3)

In other words, since the instant-off potential of the steel material cannot be measured and grasped after the reference electrode usage period has elapsed, the steel material is applied to the steel material based on the natural potential E _c-corr of the steel material calculated from the equation (1). By adjusting the supply current (that is, adjusting the voltage generated between the anode material and the steel material by the power supply device) and setting the instant-off voltage V _ac-io between the anode material steel materials, the polarization amount of the steel materials can be reduced. It can be set to be within a predetermined range. Thus, by measuring the instant-off voltage V _ac-io between the anode steel materials, the polarization amount is managed so as to be in a predetermined range.

  As a standard for the setting range of the amount of polarization when performing anticorrosion (corrosion prevention standard), it is generally possible to adopt a standard established by the Electrochemical Corrosion Protection Method Design and Construction Guidelines (draft) published by the Japan Society of Civil Engineers. Specifically, it is preferable to manage the amount of polarization of the steel material to be 100 mV (that is, the potential of the steel material is lower than −100 mV). In other words, it is preferable to manage such that the amount of change in potential from the natural potential of the steel material when current is supplied to the steel material is 100 mV or more. By managing the supply current so as to achieve such a polarization amount, it is possible to effectively prevent the corrosion current from flowing through the steel material, and to obtain a good anticorrosion effect.

In addition, when the instant off potential of the steel material and the corresponding electric potential E _c-io of the steel material become excessively negative (by over-corrosion), these are within a predetermined range. The instant-off voltage V _ac-io between the anode material and the steel material is set. For example, when a steel material is disposed in a prestressed concrete structure, hydrogen is generated on the surface of the steel material due to excessive corrosion prevention, which may cause embrittlement (hydrogen embrittlement) of the steel material. When such an adverse effect occurs, the instant-off potential of the steel material and the potential E _c-io of the steel material corresponding to the reference values specified by the Society of Civil Engineers (draft) published by the Japan Society of Civil Engineers For this, it is preferable to set the instant-off voltage V _ac-io between the anode steel materials by adjusting the amount of supplied current so that it is more noble than −1000 mV vs CSE.

Second Embodiment
Hereinafter, a second embodiment of the present invention will be described.

  The anticorrosion method according to the second embodiment is the first implementation in that the current is supplied to the steel material so that the depolarization amount of the steel material after the current supplied to the steel material is cut off is within a predetermined range. Different from form. Therefore, below, a different point from 1st Embodiment is demonstrated and description is abbreviate | omitted about a common structure.

<Management of the amount of depolarization during the reference electrode usage period>
After the anode material and the reference electrode are embedded in the concrete structure as described above, when a current is supplied from the anode material to the steel material using the power supply device to perform the anticorrosion, the depolarization amount of the steel material is a predetermined amount. Supply current so that it is within the range. When the depolarization amount is within a predetermined range, the corrosion current generated in the steel material can be effectively eliminated. The depolarization amount means a change amount of the steel material potential after the current supplied to the steel material is interrupted. Specifically, the amount of depolarization is the amount of change in how much the potential of the steel material that has changed to the base side by supplying current changes to the noble side after the current is cut off.

In the present embodiment, the amount of depolarization of the steel material is calculated based on the reference electrode during the reference electrode usage period. Specifically, after supplying the current to stabilize the potential of the steel material, immediately after cutting off the current, the potential of the steel material is measured with reference to the reference electrode, and thereby the instant-off potential of the steel material (the potential E of the steel material described later). equivalent to _c-io ). Furthermore, after the supply current is cut off from a state where the potential of the steel is stabilized by supplying a current, the potential after the repolarization of the steel is measured by measuring the potential of the steel when the potential of the steel is stabilized based on the reference electrode. Ask for. Then, the amount of depolarization of the steel material is calculated by subtracting the instant-off potential of the steel material from the post-repolarization potential of the steel material.

  That is, during the reference electrode usage period, the depolarization amount is calculated as described above, and therefore the supply current to the steel material is adjusted based on the measured potential after depolarization of the steel material (that is, By adjusting the voltage generated between the anode material and the steel material by the power supply device, the instant-off potential of the steel material is set to manage the depolarization amount within a predetermined range.

<Creation of polarization curve>
Also in this embodiment, the instant-off potential of the anode material with respect to the supply current density is measured (anode material potential measurement step). Specifically, a polarization curve of the anode material is created during the use period of the verification electrode by the same method as in the first embodiment.

<Management of the amount of depolarization after the reference electrode usage period has elapsed>
Similar to the first embodiment, after the reference electrode reaches the end of its life and the reference electrode usage period has elapsed, the amount of depolarization cannot be determined using the reference electrode. Therefore, after the verification electrode usage period has elapsed, the depolarization amount is obtained by the method described below, and current is supplied so that the depolarization amount falls within a predetermined range.

Specifically, after cutting off the supply current from a state where the potential difference between the anode material and the steel material is stabilized by supplying current, the anode material and the steel material when the potential difference between the anode material and the steel material is stabilized. V _ac 'measuring step for measuring the potential difference V _ac ' between the anode material and the steel material immediately after the supply current is cut off after the electric current is supplied to stabilize the potential difference between the anode material and the steel material. Steel material necessary for calculating the amount of depolarization using the polarization curve of the anode material created in the polarization curve creation step from the value measured in the V _ac-io measurement step for measuring the potential difference V _ac-io between The amount of depolarization is calculated by calculating a potential E _c-corr ′ after repolarization and a potential E _c-io corresponding to the instant-off potential of the steel material.

The potential E _c-io of the steel material according to the present embodiment is calculated by the same method as that of the first embodiment, and is calculated by the following equation (5) that is the same as the equation (2) in the first embodiment. Is done.

“E _c-io ” = “E _a-io ” − “V _ac-io ” (4)

The post-depolarization potential E _c-corr ′ of the steel material after the reference electrode usage period has elapsed is the potential of the anode material (natural potential of the anode material) E _a when the supply current density in the polarization curve of the anode material is 0 mA / m ^2. _-corr 'is calculated by subtracting the potential difference between the anode material and the steel material measured in the V _ac ' measurement process (hereinafter also referred to as the potential difference after repolarization between the anode material steel materials) V _ac '. is there. That is, the post-depolarization potential E _c-corr ′ of the steel material is calculated by the following equation (4).

“E _c-corr '” = “E _a-corr '” − “V _ac '” (5)

The post-depolarization potential E _c-corr ′ of the steel material calculated as described above corresponds to the post-depolarization potential of the steel material measured during the reference electrode usage period. The potential difference V _ac ′ after depolarization between the anode steel materials is a voltage generated between the anode materials and the steel materials, and can be measured by a voltmeter in which the anode materials and the steel materials are connected. On the other hand, the natural potential E _a-corr ′ of the anode material based on the polarization curve corresponds to the potential when the potential of the anode material is stabilized after the supply current is cut off during the use period of the verification electrode. Note that the natural potential E _a-corr ′ of the anode material based on the polarization curve in the present embodiment is equal to the natural potential E _{a-corr of the} anode material based on the polarization curve in the first embodiment.

As described above, the electric potential E _{c-io of} the steel material obtained using the polarization curve from the post _- depolarization potential E _c-corr 'of the steel material obtained using the polarization curve of the anode material (instant-off potential of the steel material) The amount of depolarization is calculated even after the verification electrode usage period has elapsed. That is, the depolarization amount of the steel material is calculated by the following equation (6).

Depolarization amount = “E _c-corr '” − “E _c-io ” (6)

In other words, since the instant-off potential of the steel material cannot be measured and grasped after the reference electrode usage period has passed, the steel material is based on the post-repolarization potential E _c-corr ′ of the steel material calculated from the equation (5). By adjusting the current supplied to the battery (that is, adjusting the voltage generated between the anode material and the steel material by the power supply device), the instant-off voltage V _ac-io between the anode material steel materials is set, thereby restoring the steel material. The extreme amount can be set within a predetermined range. Thus, by measuring the instant-off voltage V _ac-io between the anode steel materials, the depolarization amount is managed to be within a predetermined range.

  In general, the standard set by the Japan Society of Civil Engineers can be adopted as the standard for the range of depolarization when performing anti-corrosion (corrosion prevention standard). Specifically, it is preferable to manage so that the depolarization amount of the steel material is 100 mV (that is, the potential of the steel material is lower than 100 mV). In other words, it is preferable to manage such that the amount of change in potential from immediately after the supply current to the steel material is interrupted until the potential of the steel material becomes stable is 100 mV or more. By managing the supply current so as to achieve such a depolarization amount, it is possible to effectively prevent the corrosion current from flowing through the steel material and to obtain a good anticorrosion effect.

Similarly to the first embodiment, when an adverse effect occurs due to over-corrosion, the supply current amount is adjusted so that the potential E _c-io of the steel material falls within a predetermined range, and instant-off between the anode steel materials is performed. It is preferable to set the voltage V _ac-io .

  As described above, according to the cathodic protection method of the present invention, when performing cathodic protection, the amount of polarization and the amount of depolarization can be managed within a range suitable for cathodic protection without using a reference electrode.

That is, since the natural potential E _{c-corr of} the steel material, the post-repolarization potential E _c-corr 'of the steel material, and the potential E _c-io of the steel material can be obtained without directly measuring using the verification electrode, the verification electrode The amount of polarization and the amount of depolarization can be calculated without using.

Further, by setting the instant-off voltage V _ac-io between the anode steel materials, the polarization amount and the depolarization amount can be set within a predetermined range. Specifically, by setting the instant-off voltage V _ac-io between the anode steel materials by adjusting the supply current amount, the polarization curve is obtained from the supply current density corresponding to the instant-off voltage V _ac-io between the anode steel materials. Based on the above, the potential E _a-io of the anode material can be obtained, and thereby the potential E _c-io of the steel material corresponding to the instant-off potential of the steel material can be calculated as described above. That is, by setting the instant-off voltage V _ac-io between the anode steel materials based on the calculated natural potential E _c-corr of the steel material and the post-repolarization potential E _c-corr 'of the steel material, It becomes possible to set the depolarization amount within a predetermined range. Thereby, by measuring the instant-off voltage V _ac-io between the anode steel materials, it is possible to manage the polarization amount and the depolarization amount that are optimum for the anticorrosion without using the reference electrode.

Moreover, by setting the instant-off voltage V _ac-io between the anode steel materials, the potential E _c-io corresponding to the instant-off potential of the steel material can be obtained without using a reference electrode. In addition to this, even when it is necessary to manage the instant-off potential of the steel material within a predetermined range, the potential E _{c-io of} the steel material (that is, the instant-off potential of the steel material) is set to a predetermined value without using the reference electrode. Can be managed to a range.

  In addition, by creating a polarization curve of the anode material using a reference electrode arranged in a concrete structure in which steel material that is actually subjected to electrocorrosion is embedded, the environment where the anticorrosion is actually carried out (temperature and concrete structure) A polarization curve corresponding to the amount of chloride in the product can be obtained. As a result, there is a large difference between the polarization amount and depolarization amount measured using the reference electrode in the environment where the cathodic protection is actually performed, and the polarization amount and depolarization amount calculated using the polarization curve. Can be suppressed. For this reason, even after the reference electrode embedded together with the steel material ceases to function due to its life, etc., it is possible to calculate the polarization amount and the depolarization amount corresponding to the environment in which the anticorrosion is performed. Similarly, the amount of polarization and the amount of depolarization can be managed.

  In addition, the holder which concerns on this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of this invention. Further, the configurations and methods of the plurality of embodiments described above may be arbitrarily adopted and combined (even if the configurations and methods according to one embodiment are applied to the configurations and methods according to other embodiments). Of course, it is of course possible to arbitrarily select configurations, methods, and the like according to various modifications described below and employ them in the configurations, methods, and the like according to the above-described embodiments.

  For example, in the above-described embodiment, a reference electrode is embedded together with a steel material in a concrete structure that is actually subjected to cathodic protection, and a polarization curve created using the reference electrode is used. However, the present invention is not limited to this. Instead, for example, create a specimen of a concrete structure with a reference electrode embedded, and create polarization curves for each environment (pH and chloride content in the concrete structure) that is different from the environment where the actual corrosion protection is performed. And you may select and use the polarization curve corresponding to the environment which actually performs anti-corrosion from such a plurality of polarization curves.

In the above embodiment, the natural potential E _{a-corr of the} anode material is obtained using the polarization curve, but the present invention is not limited to this, and the supply current density measured in the anode material potential measurement step is not limited thereto. The natural potential E _{a-corr of the} anode material may be obtained from the relationship of the instant-off potential of the anode material. That is, the natural potential E _{a-corr of the} anode material may be obtained from the value of the supply current density and the corresponding instant-off potential value of the anode material without creating a polarization curve.

<Example 1>
1. Test specimen A specimen (size: 135 × 76) in which an anode material made of titanium mesh (manufactured by Sumitomo Osaka Cement Co., Ltd.) and a reinforcing bar (a deformed reinforcing bar with a diameter of 13 mm) was embedded in mortar (specified in JIS R 5201). × 100 mm) was produced. The anode material and the steel material are embedded along the longitudinal direction of the test body. The distance between the anode material and the steel material is 50 mm. And the lead collation electrode (made by Nippon Corrosion Co., Ltd.) was embed | buried in the position between the reinforcing bars and the anode material. Furthermore, the anode material and the reinforcing bar were connected by a DC power supply device (potential galvanostat HA-151A manufactured by Hokuto Denko Co., Ltd.).

2. Measurement of pre-polarization potential difference V _ac between anodic steel materials One month after preparing the test specimen, before supplying electric current to the reinforcing bars, a voltmeter (FLUKE 8062A) was used to pre-polarization potential difference V between the anodic steel materials. _ac was measured. The measurement results are shown in Table 1 below.

3. Preparation of Polarization Curve After measuring the pre-polarization potential difference V _ac between the anode material steel materials, current was supplied to the reinforcing bar at a current density of 5 mA / m ² per installation area of the anode material to stabilize the potential of the anode material. Thereafter, 24 hours after the supply of current was stopped, the change in the instant-off potential of the anode material with respect to the change in the current density was measured in the same manner as in the above embodiment, and a polarization curve was prepared. The obtained polarization curve is as shown in FIG.

4). Measurement of instant-off voltage V _ac-io between anode steels After that, supply current to the rebar at a current density of 5 mA / m ² , and voltmeters the instant-off voltage V _ac-io between anode steels after 7 days. It measured using. The measurement results are as shown in Table 1 below.

5. Calculation of Polarization Amount From the obtained polarization curve, the instant-off potential (natural potential of the anode material) E _a-corr of the anode material when the current density was 0 mA / m ² was read. Further, the instant-off potential of the anode material when the current density was 5 mA / m ² (the potential at the time of polarization of the anode material according to the polarization curve) E _a-io was read. The natural potential E _a-corr of the anode material and the polarization potential E _a-io of the anode material according to the polarization curve are as shown in Table 1 below.
Natural potential E _a-corr obtained anode material, and the polarization before the potential difference V _ac between anode material steel using the equation (1) of the above embodiment were calculated spontaneous potential E _c-corr steel. Further, the potential E of the steel material immediately after the supply current is cut off using the expression (2) in the above embodiment from the polarization potential E _a-io of the anode material according to the polarization curve and the instant-off voltage V _ac-io between the anode material steel materials. _c-io was calculated. And the amount of polarization was computed using (3) Formula of the said embodiment. Each calculation result is as shown in Table 1 below.

<Comparative Example 1>
1. Measurement of natural potential of reinforcing bar with reference electrode as reference In the specimen of Example 1, one month after the specimen was prepared, it was verified using a voltmeter (FLUKE 8062A) before supplying current to the reinforcing bar. The natural potential of the reinforcing bar was measured with reference to the electrode. The measurement results are as shown in Table 2 below.

2. Measurement of Reinforcing Bar Instant-Off Potential Current was supplied to the reinforcing bar at a current density of 5 mA / m ² , and the reinforcing bar instant-off potential was measured after 7 days. The measurement results are as shown in Table 2 below.

3. Calculation of polarization amount The polarization amount was calculated by subtracting the instant-off potential of the reinforcing bar from the natural potential of the reinforcing bar. The calculation results are as shown in Table 2 below.

<Summary>
When Example 1 and Comparative Example 1 are compared, it is recognized that the amount of polarization calculated using the polarization curve and the amount of polarization calculated based on the reference electrode are approximate values. That is, as in the present invention, the amount of polarization is calculated using a polarization curve, and the amount of polarization is managed, and the same management as in the case of managing the amount of polarization calculated using a reference electrode as in the prior art. It is recognized that can be done.

<Example 2>
1. Measurement of potential difference V _ac after depolarization between anode steel materials After supplying current to the reinforcing bar at a current density of 5 mA / m ² in the test body of Example 1, the potential difference between the anode material and the steel material was stabilized. The potential difference V _ac ′ after depolarization between the anode steel materials after the lapse of 24 hours after the supply current was cut off was measured using a voltmeter (FLUKE 8062A). The measurement results are as shown in Table 3 below.

2. Measurement of instant-off voltage V _ac-io between anode steels After that, supply current to the rebar at a current density of 5 mA / m ² , and voltmeters the instant-off voltage V _ac-io between anode steels after 7 days. It measured using. The measurement results are as shown in Table 3 below.

5. Calculation of the amount of depolarization From the same polarization curve as in Example 1, the instant-off potential (natural potential of the anode material) E _a-corr ′ when the current density was 0 mA / m ² was read. Further, the instant-off potential of the anode material when the current density was 5 mA / m ² (the potential at the time of polarization of the anode material according to the polarization curve) E _a-io was read. The natural potential E _a-corr ′ of the anode material and the polarization potential E _a-io of the anode material according to the polarization curve are as shown in Table 3 below.
The potential of the steel material immediately after the supply current is cut off using the equation (4) of the above embodiment from the polarization potential E _a-io of the anode material according to the obtained polarization curve and the instant-off voltage V _ac-io between the anode material steel materials. E _c-io was calculated. Also, the natural potential E _a-corr of anode material ', and pre-polarization between anode material steel potential difference V _ac' was calculated spontaneous potential E _c-corr 'steel from using (5) of the above embodiment. And the amount of depolarization was computed using (6) Formula of the said embodiment. Each calculation result is as shown in Table 3 below.

<Comparative example 2>
1. Measurement of natural potential of rebar with reference electrode as reference In the specimen of Example 1, after supplying current to the rebar at a current density of 5 mA / m ² and stabilizing the potential difference between the anode material and the steel material, The natural potential of the steel after 24 hours had passed after the supply current was cut off was measured using a voltmeter (FLUKE 8062A) with reference to the reference electrode. The measurement results are as shown in Table 4 below.

2. Measurement of Reinforcing Bar Instant-Off Potential Current was supplied to the reinforcing bar at a current density of 5 mA / m ² , and the reinforcing bar instant-off potential was measured after 7 days. The measurement results are as shown in Table 4 below.

3. Calculation of depolarization amount The depolarization amount was calculated by subtracting the instant-off potential of the reinforcing bar from the natural potential of the reinforcing bar. The calculation results are as shown in Table 4 below.

<Summary>
When Example 2 and Comparative Example 2 are compared, it is recognized that the depolarization amount calculated using the polarization curve and the depolarization amount calculated with reference to the reference electrode are approximate values. That is, when the depolarization amount is calculated using the polarization curve as in the present invention, and the depolarization amount is managed, the depolarization amount calculated using the reference electrode as in the conventional case is managed. It is recognized that similar management can be performed.

Claims (5)

In the anticorrosion method for performing the anticorrosion of steel by supplying current from the anode material to the steel,
Anode material potential measurement process for measuring the anode material's instant-off potential with respect to the supply current density, and the anode material and the steel material in a state where the potential difference between the anode material and the steel material is stable when no current is supplied to the steel material. V _ac measurement step for measuring the potential difference V _ac between the anode material and the steel material after supplying the current to stabilize the potential difference between the anode material and the steel material, and immediately after cutting off the supply current V _ac-io measurement process for measuring the potential difference V _ac-io of
From the potential E _a-corr of the anode material when the supply current density measured in the anode material potential measurement step is 0 mA / m ² , the potential difference V between the anode material and the steel material measured in the V _ac measurement step. Calculate the natural potential E _c-corr of steel by subtracting _ac ,
From the potential E _a-io of anode material which has been measured by the anode material potential measuring step with respect to the supply current density immediately before interrupting the supply current in said V _ac-io measuring step, measured in V _ac-io measuring step The potential E _c-io of the steel material is calculated by subtracting the potential difference V _ac-io between the anode material and the steel material,
From the natural potential E _c-corr steel calculated above, the polarization amount is calculated by subtracting the steel potential E _c-io is characterized by performing the supply of current to the steel to a predetermined range Electrocorrosion protection method. In the anticorrosion method for performing the anticorrosion of steel by supplying current from the anode material to the steel,
An anode material potential measuring step for measuring the instant-off potential of the anode material with respect to the supply current density, and after the supply current is cut off from a state where the potential difference between the anode material and the steel material is stabilized by supplying current, V _ac 'measurement process to measure the potential difference V _ac ' between the anode material and the steel material when the potential difference between the steel material and the steel material is stabilized, and the potential difference between the anode material and the steel material is stabilized by supplying current to the steel material. And a V _ac-io measuring step for measuring a potential difference V _ac-io between the anode material and the steel material immediately after the supply current is cut off.
From the potential E _a-corr ′ of the anode material when the supply current density measured in the anode material potential measurement step is 0 mA / m ² , between the anode material and the steel material measured in the V _ac ′ measurement step. By subtracting the potential difference V _ac ', the post-repolarization potential E _c-corr ' of the steel material is calculated,
Measured in the V _ac-io measurement step from the potential E _a-io of the anode material measured in the anode material potential measurement step with respect to the supply current density immediately before cutting off the supply current in the V _ac-io measurement step. The potential E _c-io of the steel material is calculated by subtracting the potential difference V _ac-io between the anode material and the steel material,
The current is supplied to the steel so that the amount of depolarization calculated by subtracting the potential E _c-io of the steel from the post-repolarization potential E _c-corr 'of the steel is within a predetermined range. Electrocorrosion protection method. Using the anode material potential with respect to the supply current density measured in the anode material potential measurement step, a polarization curve of the anode material is prepared, and the anode material potential E _a-corr when the supply current density is 0 mA / m ^2. 2. From the polarization curve, the potential E _a-io of the anode material with respect to the supply current density immediately before cutting off the supply current in the V _ac-io measurement step is obtained from the polarization curve. The method of cathodic protection described. Using the anode material potential with respect to the supply current density measured in the anode material potential measurement step, a polarization curve of the anode material is prepared, and the anode material potential E _a-corr when the supply current density is 0 mA / m ^2. 3 is obtained from the polarization curve, and the potential E _a-io of the anode material with respect to the supply current density immediately before the supply current is cut off in the V _ac-io measurement step is obtained from the polarization curve. The method of cathodic protection described.   The polarization curve of the anode material is prepared by arranging a reference electrode in an environment where a steel material to be subjected to cathodic protection is provided, and measuring the instant-off potential of the anode material with reference to the reference electrode. The cathodic protection method according to claim 3 or 4.

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