JP2000192265A - Protection monitoring electrode and protection monitoring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to measure a protection state from above the ground in spite of the defect within the spacing of the protective coating overlap parts of protective coating steel products. SOLUTION: A blind cylindrical member having a hole 11 simulating the size of the spacing 16 in the protective coating overlap parts has a diametrally expanded second hole 12 communicating with the hole 11. A protection monitoring electrode 6 disposed with an electrode 61 in the bottom of the second hole 12 or near the same and a reference electrode 62 is embedded near the protective coating steel products 1 under the ground. The protection state of the protective coating steel products 1 is monitored by measuring the direction and current density of the current flowing to the electrode 61 and the potential between the potential between the electrode 61 and the reference electrode 62.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion monitoring electrode and a method for monitoring an anticorrosion state in a gap of an anticorrosion coating overlapped portion of an anticorrosion coating steel buried in the ground and subjected to cathodic protection.

[0002]

2. Description of the Related Art Cathodic protection, in which a metal structure is protected by passing a cathodic (cathode) current through a metal structure, is generally used. The cathodic protection includes an external power supply method (also referred to as an external power method) and a sacrificial anode method. (Also referred to as galvanic anode method). FIGS. 5A and 5B are diagrams illustrating two methods of cathodic protection, wherein FIG. 5A illustrates the external electrode method and FIG. 5B illustrates the sacrificial anode method.

In the external electrode method, as shown in FIG. 5A, for example, a commercial power supply is rectified into a DC power supply 3a, an insoluble electrode (a counter electrode 2a shown in the drawing) is used as a positive electrode, and the corrosion-protected body 1a is used as a negative electrode ( A current flows from the positive electrode to the negative electrode as a cathode). In this case, the output voltage value is adjusted so that the value of the supplied current becomes an appropriate value. In the sacrificial anode method, as shown in FIG.
For example, a current generated as the sacrificial anode 2b of zinc, aluminum, magnesium alloy or the like is melted is supplied to the anticorrosion target 1a. In this case, the resistance value of the output adjuster 3b, which is a variable resistor for output adjustment, is adjusted to adjust the current value to be supplied.

FIG. 6 is a view for explaining a conventional method for measuring the anticorrosion potential. In FIG. 6, 1 is an anticorrosion coated steel material buried underground, 2 is a counter electrode or a sacrificial anode, 3 is a DC power supply or output regulator, 4 is a pseudo member, 5 is a reference electrode, 7 is normally closed, Open switch, 8 is ammeter, 9 is voltmeter, 1
Reference numeral 3 denotes a steel material exposed portion. Conventionally, an anticorrosion-protected body buried in the ground and subjected to electrolytic protection (corrosion-protected coated steel material 1 in this example)
As the anticorrosion control method, an anticorrosion potential for measuring a potential difference between an anticorrosion target buried in the ground and a reference electrode 5 disposed on the ground surface has been used.

As a method for measuring the anticorrosion potential, a detection method based on an ON potential or an OFF potential is generally used. In this method, a small pseudo member 4 made of the same material (in this case, steel) as the anticorrosion coated steel material 1 is buried near the anticorrosion coated steel material 1 in the ground, and in a normal state (at the time of non-measurement), the pseudo member 4
Is short-circuited to the anticorrosion-coated steel material 1 via the normally closed switch 7 and the ammeter 8, and the switch 7 is opened to cut off the short-circuit state at the time of measurement, and the pseudo member 4 and the reference electrode at this moment (within 100 ms) 5 is measured, and this is used as the anticorrosion potential of the anticorrosion-coated steel material 1. Japanese Patent Application Laid-Open No. 6-265511 discloses an invention in which the potential of the reference electrode 5 is set as close as possible to the potential where the anticorrosion-coated steel material 1 is buried, and the anticorrosion potential is accurately measured.

FIG. 7 is a diagram for explaining the types of defects that occur in the anticorrosion-coated steel material. (A) of the figure shows a part of the anticorrosion coating 15 of the steel material 14 having a damaged portion, and the steel material exposed portion 13 in a state where the anticorrosion coating 15 of the damaged portion is completely removed.
(B) shows a gap in the overlapping portion of the anticorrosion coating, for example, the end of the heat-shrinkable tube provided at the welded joint portion of the anticorrosion coated steel pipe is turned up to form a gap 16, and from this gap 16, the ground is formed. This is the case where the water inside flows in and corrodes inside. In the case where the defect of the anticorrosion-coated steel material is the exposed steel material 13 shown in FIG. 7A, the anticorrosion current flows into the exposed steel material 13 as shown in FIG. Therefore, the conventional method for measuring the anticorrosion potential is considered to be an effective method for controlling the anticorrosion of the anticorrosion-coated steel material with respect to the defect having the steel material exposed portion 13.

[0007]

However, the object to be protected is an anticorrosion-coated steel material. Further, as a defect of the anticorrosion-coated steel material, a gap between the anticorrosion coating as shown in FIG. When there is a gap of about 20 mm), groundwater flows in many cases. Electrical conductivity can be obtained when groundwater is present, but the size of the gap greatly changes the electrical resistance value of the gap. That is, when the gap is small, the electric resistance is large, so that the anticorrosion current does not flow much into this gap. Further, there is a stray current starting from the electric railway in the ground, and the stray current flows out from a gap of the anticorrosion coating. Therefore, the anticorrosion current flowing into the gap is small,
Since the stray current flows out, the steel inside the gap often corrodes. However, until now, there has been no method for externally measuring the corrosion state of the steel inside the gap. In other words,
The conventional anti-corrosion management technology is based on the steel exposed portion 13 shown in FIG.
However, this method can be applied only to a defect in which the anticorrosion coating 15 on the surface is completely open. Therefore, as shown in FIG.
Is partly peeled off, and the anticorrosion coating 15 at the part where the part is peeled off
It was not even possible to measure the corrosion protection potential for a defect in which the steel surface 17 communicated with the outside through the gap 16 between them.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an anticorrosion monitoring electrode which can be applied to a defect inside a gap of an anticorrosion coating overlapping portion of an anticorrosion coating steel material. And an anticorrosion monitoring method.

[0009]

SUMMARY OF THE INVENTION An electrode for monitoring corrosion protection according to the present invention is an electrode for monitoring the state of corrosion protection of a steel material buried underground and subjected to cathodic protection. A bottomed cylindrical member having a hole simulating the size of the gap of the portion, wherein an electrode and a reference electrode are disposed inside the hole of the bottomed cylindrical member, near the anticorrosion coated steel material. It is buried and configured to measure the direction and current density of a current flowing through the electrode and the potential between the electrode and a reference electrode.

The method for monitoring corrosion protection according to the present invention is a method for monitoring the state of corrosion protection of a corrosion protection coated steel material buried underground and subjected to cathodic protection. A bottomed tubular member having a hole simulating the thickness thereof, wherein an anticorrosion monitoring electrode in which an electrode and a reference electrode are disposed inside the hole of the bottomed cylindrical member is embedded near the anticorrosion coated steel material. The anticorrosion state of the anticorrosion-coated steel material is monitored by measuring a direction and a current density of a current flowing to the electrode and a potential between the electrode and a reference electrode.

First, in the present invention, a bottomed tubular member, an electrode disposed inside a hole provided in the bottomed tubular member and made of the same material as the anticorrosion-coated steel material, and a reference electrode It is characterized by using an anticorrosion monitoring electrode having the following.
In the hole of the bottomed cylindrical member, the resistance of the current flowing in and out through this hole is adjusted in advance by simulating the size of the gap between the anticorrosion-coated overlapping portions of the anticorrosion-coated steel material. Therefore, this hole is a current resistance adjusting portion. Next, an electrode for measuring the anticorrosion potential and a reference electrode are disposed inside the hole. The anticorrosion monitoring electrode is buried in the vicinity of the anticorrosion-coated steel material, and by measuring the potential between the electrode and the reference electrode, the anticorrosion potential of the anticorrosion-coated steel material can be measured. At this time, the electrode is short-circuited to the anticorrosion-coated steel material at the time of non-measurement, the short-circuit state is opened at the time of measurement, and the potential between the electrode and the reference electrode at the moment of the open state is measured. Can be measured with accuracy.

Secondly, according to the present invention, by using the anticorrosion monitoring electrode formed of a bottomed cylindrical member, it is possible to estimate a change in the quality of the inflowing water in the gap of the anticorrosion coating, thereby enhancing the anticorrosion monitoring. That is, quick anticorrosion measures can be taken. In this case, the anticorrosion monitoring electrode is installed so as to face upward, and the inside of the hole is preliminarily gelled with an electrolytic solution or an electrolytic solution equivalent to the specific resistance of groundwater or soil near the installation site of the anticorrosion-coated steel material. It is filled with a sol (hereinafter referred to as an equivalent electrolytic solution). By filling the inside of the hole with the equivalent electrolytic solution in this way, the change in the water quality of the inflowing water in the gap of the anticorrosion coating can be known from the change in the measured anticorrosion potential. Therefore, in order to sufficiently fill the inside of the hole with the equivalent electrolytic solution, the bottomed tubular member has a second hole having an enlarged diameter communicating with the hole, and the second hole of the second hole has a large diameter. It is preferable that the electrode and the reference electrode are disposed at or near the bottom to provide an anticorrosion monitoring electrode.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of a corrosion protection monitoring method according to an embodiment of the present invention, and FIGS. 2 to 4 are diagrams showing the configuration of a corrosion protection monitoring electrode.

First, the configuration of the anticorrosion monitoring electrode according to the present invention will be described. The anticorrosion monitoring electrode 6 basically has a hole 11 in a bottomed cylindrical member 10 as shown in FIG. 2, and an electrode 61 and a reference electrode 62 provided at or near the bottom of the hole 11. It is. The hole 11 simulates the size of the gap 16 of the anticorrosion coating overlapping portion, and the hole diameter D and the hole length L are adjusted according to the size of the gap 16. Since the size of the gap 16 is usually about 0.5 to 20 mm in the case of a corrosion protection coated steel pipe, the hole diameter and the like are determined so as to match the size of the most frequent gap among them.

The bottomed cylindrical member 10 is made of a plastic material (for example, acrylic resin) which is a general insulating material. The electrode 61 is made of steel of the same material as the anticorrosion-coated steel material 1. The reference electrode 62 is preferably made of a material having high corrosion resistance. 63 and 64 are connection cables connected to the electrode 61 and the reference electrode 62, respectively.

The anticorrosion monitoring electrode 6 is preferably configured as shown in FIG. FIG. 4 is a sectional view of FIG. FIG. 1 shows an anticorrosion monitoring electrode 6 of this configuration example. The bottomed tubular member 10 of the anticorrosion monitoring electrode 6 shown in FIGS. 3 and 4 has a first hole 11 in which a hole diameter D and a hole length L are adjusted, as in FIG. There is an enlarged second hole 12 communicating with the hole 11. The electrode 61 and the reference electrode 62 are attached to the bottom plate 13 that covers the second hole 12, and the electrodes 61 and 62 are insulated from each other by, for example, epoxy resin. As described above, the first hole 11 constitutes the resistance adjusting portion for the anticorrosion current, and the second hole 12 serves as an electrode chamber. The electrode chamber 12 is filled with an equivalent electrolytic solution. The anticorrosion monitoring electrode 6 is installed at a position near the anticorrosion-coated steel material 1 in the ground such that the opening 11a at the tip thereof is on the upper side in the vertical direction.

First hole 1 constituting anticorrosion current resistance adjusting section
1 is manufactured to have a hole diameter simulating the gap so that the hole diameter becomes the same as the electric resistance value of the gap 16 of the corrosion protection coating overlapping portion of the anticorrosion coating steel material. This is because when excavating an old anticorrosion coating buried pipe, the gap between the anticorrosion coating overlaps is actually measured (about 0.5 to 20 mm), and the most frequent values The value, minimum value, etc. are determined in advance. When the first hole 11 is manufactured, a value to be adopted is determined according to use conditions, customer specifications, and the like, and a gap having the adopted value is manufactured with a simulated hole diameter and length. I am trying to do it.

Since the anticorrosion current resistance adjusting section (that is, the first hole) 11 is installed in such a position that the opening 11a at the tip is on the upper side in the vertical direction, it is possible to conduct electricity with the soil. At the time of burial,
It is desirable to cover or plug with a net made of insulating material or sponge (so that moisture can pass freely). Then, the second hole 12 constituting the electrode chamber is filled with an equivalent electrolyte.

The electrode chamber, ie, the second hole 12, has a space that can be filled with a predetermined volume of an equivalent electrolyte. Further, an injection hole having a horizontal hole may be provided in the electrode chamber 12 so as to easily inject the same electrolytic solution. An electrode 61 and a reference electrode 62 that are electrically insulated from each other are provided at the bottom of the electrode chamber 12, and external connection cables 63 and 64 are wired to the electrodes 61 and 62, respectively. Electrode 63 and reference electrode 6
The shape and arrangement of the electrodes 4 are not particularly limited. The electrode shape may be rectangular, or the electrodes 61 and 62 may be arranged on the inner peripheral surface near the bottom surface of the second hole 12.

When the anticorrosion monitoring electrode 6 is buried in the ground, at least an equivalent electrolyte is injected into the electrode chamber 12 so that the entire electrode 61 and the reference electrode 62 are filled with the equivalent electrolyte. It is installed with the opening 11a facing upward.
By injecting the equivalent electrolyte, each electrode of the electrode 61 and the reference electrode 62 disposed in the electrode chamber 12 is connected to the underground soil through the electrical resistance of the equivalent electrolyte and through the first hole 11. As a result, it becomes possible to detect a change in the water quality of the inflow water in the covering gap.

The electrode 61 is made of the same material as the anticorrosion-coated steel material 1. The electrode 61 provided in the electrode chamber 12 into which the equivalent electrolytic solution is injected at the time of installation and made of steel of the same material as the anticorrosion-coated steel material 1 undergoes corrosion after installation, and the corrosion state progresses with time. The corrosion state of the electrode 61 is the same as the corrosion state generated in the steel inside by the flow of water from the gap 16 of the anticorrosion coating overlapping portion of the anticorrosion coating steel material 1 which is actually buried in the ground and subjected to electrolytic protection. (To simulate the corrosion state).

The reference electrode 62 is made of, for example, lead, zinc, platinum,
Made of molybdenum, tungsten, etc. Since this reference electrode 62 is used as a reference electrode for measuring the anticorrosion potential, similarly to FIG. 5, even if it is installed in the electrode chamber 12 into which the equivalent electrolyte is injected, it does not corrode for a long time. Made of material. In addition, by disposing the reference electrode 62 together with the electrode 61 in the electrode chamber 12, when the anticorrosion monitoring electrode 6 is buried, the reference electrode 62 is installed near the anticorrosion-coated steel material 1. A true potential measurement that does not include the IR loss due to the corrosion protection current and soil resistance to the corrosion protection coated steel material 1 can be performed.

Next, a method for measuring the anticorrosion potential will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes an anticorrosion-coated steel buried underground, 2 denotes a counter electrode or a sacrificial anode, 3 denotes a DC power supply or an output regulator, and 2 and 3 denote an external electrode method or a sacrificial anode method described with reference to FIG. Indicates that any of the above-mentioned cathodic protection may be used. Reference numeral 6 denotes an anticorrosion monitoring electrode configured as described above, and reference numeral 7 denotes a switch which is normally closed and opened during operation. Reference numeral 8 denotes an ammeter, 9 denotes a voltmeter, and 16 denotes a gap in the anticorrosion coating overlapping portion shown in FIG.

In the normal state (when not measuring), the electrode 6
1 is short-circuited to the anticorrosion-coated steel material 1 via the normally closed circuit of the switch 7 and the ammeter 8. In addition, the anticorrosion monitoring electrode 6
Is installed near the anticorrosion-coated steel material 1. Then, the direction of the current flowing to the electrode 61 is measured. If the current flows into the electrode 61, it is determined that corrosion has been prevented, and if the current has flowed out, corrosion has occurred and it is determined that the corrosion has not been prevented. Also, the current density is measured to monitor that the anticorrosion current is flowing effectively. At the time of measuring the anticorrosion potential, the circuit of the switch 7 is opened to cut off the short-circuit state, and at the moment (within 100 ms) when the open state is reached, the potential difference between the electrode 61 and the reference electrode 62 is measured. This is determined as the anticorrosion potential of No. 1. Normally, when the anticorrosion-coated steel material is mild steel, the potential is -850 m based on the copper / copper sulfate electrode.
If it is kept below V, a corrosion prevention current flows to prevent corrosion.

The anti-corrosion current flowing from the counter electrode or the sacrificial anode 2 to the anti-corrosion coated steel material 1 flows into the electrode chamber 12 through the anti-corrosion current resistance adjusting portion comprising the first hole 11, and the first hole 11 Since the anticorrosion current resistance is adjusted by simulating the size of the gap 16 as shown in FIG. 7B, even if such a defect is present inside the gap of the anticorrosion coating overlapping portion, as described above. By measuring the current direction, the current density, and the anticorrosion potential, the anticorrosion state of the defect can be accurately monitored.

[0026]

As described above, according to the present invention,
A bottomed cylindrical member having a hole simulating the size of the gap of the anticorrosion-coated overlapping portion of the anticorrosion-coated steel material, which is disposed inside the hole of the bottomed cylindrical member and has the same material as the anticorrosion-coated steel material. And an electrode comprising a reference electrode and an anticorrosion monitoring electrode, the anticorrosion monitoring electrode is buried in the vicinity of the anticorrosion coated steel material, the direction and current density of the current flowing through the electrode, and the distance between the electrode and the reference electrode. Since the electric potential is measured, the anticorrosion potential can be measured even for a defect inside the gap of the anticorrosion coating overlapped portion. In addition, by putting an equivalent electrolytic solution into the hole or the second hole having an increased diameter communicating with the hole, the same corrosion state as a defect inside the gap of the anticorrosion coating overlapping portion can be detected by the anticorrosion monitoring electrode. It can be reproduced, and the corrosion state of the defect inside the gap can be detected from the ground.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a corrosion prevention monitoring method of the present invention.

FIG. 2 is a diagram showing a configuration example of an anticorrosion monitoring electrode.

FIG. 3 is a diagram showing another configuration example of the anticorrosion monitoring electrode.

FIG. 4 is a sectional view of FIG. 3;

FIG. 5 is a diagram illustrating two methods of cathodic protection.

FIG. 6 is an explanatory view of a conventional anticorrosion potential measuring method.

FIG. 7 is an explanatory diagram showing types of defects generated in the corrosion-resistant coated steel material.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 anticorrosion coated steel material 2 counter electrode or sacrificial anode 3 DC power supply or output regulator 4 pseudo member 5 reference electrode 6 anticorrosion monitoring electrode 7 switch 8 ammeter 9 voltmeter 10 bottomed tubular member 11 first hole (corrosion prevention current resistance) (Adjustment part) 12 second hole (electrode chamber) 16 gap of anticorrosion coating overlapping part 61 electrode 62 reference electrode

Continuing on the front page (72) Inventor Hiroshi Kajiyama 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Shozo Hatanaka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Incorporated F term (reference) 4K060 AA02 AA03 BA13 CA04 CA06 CA15 EA12 EB01 FA07

Claims (5)

[Claims] 1. An electrode for monitoring the anticorrosion state of a corrosion protection coated steel material buried in the ground and subjected to cathodic protection, comprising a hole simulating the size of a gap in a corrosion protection coating overlapping portion of the corrosion protection coating steel material. A bottom tubular member, wherein an electrode and a reference electrode are disposed inside the hole of the bottomed tubular member,
An anticorrosion monitoring electrode, which is embedded near the anticorrosion-coated steel material and configured to measure the direction and current density of a current flowing through the electrode and a potential between the electrode and a reference electrode. 2. An electrode provided inside a hole provided in the bottomed tubular member is made of the same material as the corrosion-resistant coated steel material. The hole of the bottomed tubular member has a resistance against corrosion current. An adjusting portion, wherein the bottomed tubular member has an enlarged second diameter communicating with the hole.
The corrosion prevention monitoring electrode according to claim 1, wherein the electrode and the reference electrode are provided at or near the bottom of the second hole. 3. A method for monitoring the anticorrosion condition of a corrosion-resistant coated steel material buried in the ground and subjected to cathodic protection, comprising a hole simulating the size of a gap of the corrosion-resistant coating overlap portion of the corrosion-resistant coated steel material. A bottom cylindrical member, wherein an anticorrosion monitoring electrode in which an electrode and a reference electrode are disposed inside the hole of the bottomed cylindrical member is buried in the vicinity of the anticorrosion-coated steel material, and the direction of a current flowing through the electrode is A method for monitoring the anticorrosion state of the anticorrosion-coated steel material by measuring a current density and a potential between the electrode and a reference electrode. 4. The anticorrosion monitoring electrode is installed so that the hole faces upward, and an electrolyte or an electrolytic solution having a specific resistance equal to that of groundwater or soil in the vicinity of the installation site of the anticorrosion-coated steel material is previously installed inside the hole. The anticorrosion monitoring method according to claim 3, wherein a gel or sol of the electrolytic solution is contained. 5. The electrode is short-circuited to the anticorrosion-coated steel material at the time of non-measurement, the short-circuit state is set to the open state at the time of measurement, and the potential between the electrode and the reference electrode at the moment of the open state is set. The anticorrosion monitoring method according to claim 3 or 4, wherein the measurement is performed.