JP2006257532A - Method for measuring potential of corrosion-prevented body by cathodic protection, device for measuring potential, cathodic protection method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for precisely measuring a potential having an ohmic drop subtracted of a corrosion-prevented body by an impressed current system of a cathodic protection. <P>SOLUTION: The method is directed at measuring the potential of the corrosion-prevented body by the impressed current system of the cathodic protection. The cathodic protection device has a power source 2 for preventing corrosion, an anode 3 connected to an anode terminal 21 of the power source 2, a cathode of the corrosion-prevented body 5 connected to the cathode terminal 22 of the power source 2, wherein the power source 2 passes an electric current with a controlling pulse wave between the corrosion-prevented body 5 and the anode 3 while controlling the current by repeating turning it on and off. The potential measurement method includes measuring the potential of the corrosion-prevented body 5 just while the controlled pulse current is switched off. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for measuring a potential of an object to be protected in an external power source type of anticorrosion, an anticorrosion method, and an apparatus.

  When an external power source type anticorrosion is applied to an object to be protected placed in a corrosive environment, it is necessary to know whether or not the object to be protected is appropriately protected. Grasping of the achievement status of the anticorrosion is often performed by determination based on the anticorrosion potential or the anticorrosion current density, and various standards have proposed the anticorrosion achievement potential.

  By the way, it is possible to measure the corrosion protection potential of corrosion-protected bodies placed in corrosive environments with high electrical conductivity (low resistance) such as in seawater, so it is possible to grasp the status of corrosion prevention. However, for an object to be protected placed in a corrosive environment with low electrical conductivity (high resistance) such as soil, concrete, or fresh water, the ohmic drop (IR drop) during energization is added to the electrode potential. Therefore, since it is difficult to accurately measure the anticorrosion potential, there is a problem that the anticorrosion achievement status cannot be accurately grasped. Moreover, the to-be-protected object placed in such a corrosive environment with low electrical conductivity is often invisible or coated on the surface, and the surface area of the to-be-protected object can be accurately obtained. Therefore, even if the total anticorrosion current can be measured, it cannot be converted into a current density, and determination based on the anticorrosion current density becomes difficult.

  Instead of the judgment based on the anticorrosion potential and the anticorrosion current density, the potential value (instant-off potential) immediately after transition from the energization (on) state of the anticorrosion to the off (off) state, and a sufficient amount of time after the off time It has been widely used to obtain the anti-corrosion achievement status from the difference between the instant-off potential and the off-potential (shift value), and has been adopted in industrial standards and the like (the following non-patent document 1) reference). In calculating the shift value, the biggest problem is the measurement of the instant-off potential. The permissible amount of time until reading with respect to the off-potential that changes every moment is not clear, and therefore the reading value varies greatly among individuals. Further, as described in Non-Patent Document 2 below, measurement using a high-speed recording medium such as an oscilloscope has also been proposed, but it is unsuitable for on-site measurement and has not been put to practical use.

  On the other hand, as disclosed in Patent Documents 1 and 2 below, by using an AC component included in the anticorrosion current of the DC power supply device, the ohmic drop error is removed from the potential of the object to be protected detected by the reference electrode, and the anticorrosion potential obtained. A technique for performing anticorrosion based on the above has been proposed.

  However, these techniques have the disadvantage that the measured ohmic drop depends on a smoothing circuit built into the power supply circuit. Moreover, when the electrochemical time constant which exists in an interface with the soil under low moisture and the steel in concrete is small, it is easy to produce an error in a measured value.

National Association of Corrosion Engineers International Recommended Practice Standards (NACE, RP), 0169-2002, Section 6 (6.2.2.2.1.3, 6.2.3.1, 6.2.4) Japan Society of Materials Science, Corrosion and Corrosion Division Committee, "Theory and Application of Corrosion and Corrosion Learned through Experiments", 1999, p219-220 Japanese Utility Model Publication No. 63-19323 JP-A-9-268387

  The present invention has been made in view of the above-described problems, and provides a method for measuring the potential of a corrosion-protected body, a method for preventing corrosion, and a device capable of accurately measuring the potential of the corrosion-protected body in the external power source type of corrosion protection. The purpose is to provide.

  The present invention relates to a method for measuring the potential of an object to be corroded in an external power source type electric corrosion protection, and is capable of electrically connecting an anode to an anode terminal of a power source and capable of conducting to an anode terminal of the power source using the object to be corroded as a cathode. The current to be supplied from the power source is energized between the anode and the subject to be corroded while being repeatedly turned on / off by a control pulse wave, and is synchronized with the controlled pulse current being turned off. The object is achieved by providing a method for measuring the potential of an anticorrosive to measure the potential.

  Further, the present invention is a potential measuring device for carrying out the above-described method for measuring a potential of an object to be protected according to the present invention, wherein an anticorrosion current supplied from an anticorrosion power supply is supplied from the power supply based on a control pulse wave. A control unit that controls the on / off of the anticorrosive current, and a potential measurement unit that measures the potential of the corrosion-protected body connected to the cathode terminal of the power source in a synchronized manner when the controlled pulse current is off. The above object is achieved by providing a potential measuring device.

  In addition, the present invention provides an anticorrosion method for performing anticorrosion by setting an anticorrosion applied voltage with the potential of the above-mentioned anticorrosive body measured by the above-described method for measuring the potential of the above-described anticorrosive body as a control potential, The above objective has been achieved.

  Further, the present invention is an apparatus for carrying out the above-described cathodic protection method of the present invention, based on an anticorrosion power source, an anode communicatively connected to the anode terminal of the power source, and a control pulse wave. A control unit for controlling on / off of the anticorrosion current supplied from the power source, and a potential measuring unit for measuring the potential of the cathode connected to the cathode terminal of the power source in a conductive manner in synchronization with the controlled pulse current being turned off. The object is achieved by providing an electro-corrosion protection device.

  The present invention also relates to a method for measuring a cathode potential used when cathodic protection is performed by an external power supply system, wherein the anode is connected to the anode terminal of a power supply that outputs the AC without rectifying and smoothing the input AC. And connecting to the cathode terminal of the power source as a cathode to be protected, and energizing between the anode and the to-be-protected body with the power source, and an output zero cross corresponding to the alternating current The above object is achieved by providing a cathode potential measuring method for measuring the cathode potential in synchronization with each other.

  In addition, the present invention provides an anticorrosion method for setting the anticorrosion applied voltage using the potential of the corroded body measured by the above-described method for measuring the potential of the corroded body of the present invention as a control potential, and performing anticorrosion. The goal has been achieved.

  An apparatus for carrying out the above-described electrocorrosion protection method of the present invention, wherein the input AC is rectified and output without being smoothed, and the anode connected to the anode terminal of the power supply in a conductive manner And an electric corrosion protection device comprising a potential measurement unit that measures the potential of the object to be protected connected to the cathode terminal of the power source in a conductive manner at the time of zero crossing of the output corresponding to the alternating current. The above-mentioned purpose has been achieved.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to measure the potential of the body to be corroded while removing the ohmic drop while performing the electrical corrosion protection on the body to be corroded in a high resistance environment, and to effectively perform the electrical corrosion protection based on the potential. be able to.

  Hereinafter, the present invention will be described based on preferred embodiments thereof.

  FIG. 1 schematically shows a first embodiment of the cathodic protection device of the present invention. In FIG. 1, the code | symbol 1 has shown the cathodic protection apparatus.

  As shown in FIG. 1, the cathodic protection device 1 of the present embodiment includes an anticorrosion power source 2, an anode 3 connected to the anode terminal 21 of the power source 2 so as to be conductive, and a power source 2 based on a control pulse wave. A control unit 4 that controls on / off of the supplied anticorrosion current, and a potential measurement unit that measures the potential of the to-be-protected body 5 connected to the cathode terminal 22 of the power source 2 in synchronization with the controlled pulse current being turned off. 6 is provided.

  The anti-corrosion power source 2 and the anode 3 are selected according to the corrosive environment in which the anti-corrosion body 5 and the anti-corrosion body 5 are arranged.

  The control unit 4 includes a control pulse signal generation unit 41 that generates a pulse wave serving as a control signal, and an anticorrosion current pulse generation unit 42 that controls on / off of the anticorrosion current. The control pulse signal generator 41 is preferably a pulse generator or the like. The anticorrosion current pulse generator 42 includes a transistor 42 a connected to the output of the control pulse signal generator 41, and a field effect transistor (FET) that controls the current flowing between the anode terminal 21 and the anode 3 of the power supply 2. ) 42b and a photocoupler 42c that connects the transistor 42a and the FET 42b in an insulated state, and the anticorrosive current supplied from the power source 2 based on the pulse wave generated by the control pulse signal generator 41 is provided. ON / OFF control.

  The potential measurement unit 6 holds the potential of the reference electrode 61 disposed in the vicinity of the object to be protected 5 and the value of the potential (instant-off potential) of the object to be protected 5 in synchronization with the controlled pulse current being turned off. Circuit. As the potential holding circuit, a peak hold circuit (negative peak hold circuit), a sample hold circuit, or the like is used. The reference electrode 61 is selected according to the object to be protected and the corrosive environment in which the object to be protected is disposed.

  Next, the measurement of the potential of the body 5 to be protected in the above-described anticorrosion apparatus 1 and the electrocorrosion method using the potential will be described.

  First, as shown in FIG. 1, the cathodic protection device 1 is set, and the anode 3 is connected to the anode terminal 21 of the anticorrosion power source 2 via the control unit 4 so as to be conductive, and the power source 2 with the corroded body 5 as a cathode. The cathode terminal 22 is connected to be conductive.

  Next, with the control pulse wave generated from the control pulse signal generation unit 41, the current supplied from the power source 2 is energized between the anode 3 and the to-be-protected object 5 while being repeatedly turned on / off, and the controlled pulse The potential measurement unit 6 measures the potential (electrode potential) of the corrosion-protected body 5 in synchronization with the current being turned off.

  The ON / OFF time ratio of the controlled pulse current is preferably 40 or more, and more preferably 40 to 200. When the ON / OFF time ratio of the pulse current is within such a range, it is practically possible to measure the instant-off potential without being aware of turning off the anticorrosion current. In consideration of the fact that the electrochemical time constant at the interface may be very small and the measurement cable may be long in steel materials in low moisture soil or concrete, the pulse current off time 0.1 to 10 ms is preferable. Further, the on time of the pulse current is preferably 4 ms to 2 s in consideration of increasing the on / off time ratio as much as possible. The pulse current is preferably a rectangular wave.

  Then, the anticorrosion applied voltage of the power source 2 is adjusted / set using the potential of the to-be-protected body 5 measured by the potential measuring method of the to-be-protected body 5 as a control potential, and the anticorrosion is continued. The adjustment and setting of the anticorrosion voltage of the power supply 2 can be performed manually or can be automated by an electric control circuit.

  Thus, according to the method for measuring the potential of the object to be protected according to the present embodiment, even if the object to be protected is placed in a high-resistance environment, the object to be corroded is subjected to the anticorrosion and the ohm drop is removed. 5 accurate potential measurements can be repeated. Therefore, by controlling so that the potential of the obtained object to be protected becomes the control potential (corrosion protection potential), it is possible to stably perform the electrocorrosion protection with high corrosion resistance.

  FIG. 2 schematically shows a second embodiment of the cathodic protection device of the present invention. In FIG. 2, the same reference numerals are given to portions common to the first embodiment. Therefore, the description in the first embodiment is appropriately applied to a portion that is not particularly described.

  As shown in FIG. 2, the cathodic protection device 1 ′ of the present embodiment can be electrically connected to the anticorrosion power source 2 ′ that rectifies and outputs the input alternating current without being smoothed, and the anode terminal 21 of the power source 2 ′. A potential measurement unit 6 ′ that measures the potential of the corrosion-protected body 5 connected to the anode 3 connected to the cathode and the cathode terminal 22 of the power source 2 ′ in synchronism with the zero crossing of the AC, and a transformer of the power source 2 And a zero-cross detector 7 for detecting the alternating zero-cross.

  The rectifying element used in the rectifying circuit provided in the power supply 2 'is preferably a silicon element in which a dead zone is clearly shown at zero cross potential, and an element such as a diode or a thyristor is used. For example, a full-wave rectifier circuit in which silicon diodes as shown in FIG.

  The potential measuring unit 6 ′ synchronizes the potential of the verification electrode 61 arranged in the vicinity of the corrosion-protected body 5 and the potential of the corrosion-protected body 5 connected to the cathode terminal 22 of the power source 2 ′ at the time of the zero crossing of the alternating current. And an electric potential measuring circuit for measuring. For this potential measurement circuit, a sample hold circuit or the like is used for the purpose of synchronously measuring the potential.

  Next, a description will be given of the measurement of the potential of the object to be protected in the above-described cathodic protection device 1 'and the method of cathodic protection using the potential.

  First, as shown in FIG. 2, the cathodic protection device 1 ′ is set, and the anode 3 is connected to the anode terminal 21 of the anticorrosion power source 2 so as to be conductive, and the corroded body 5 is used as a cathode to the cathode terminal 22 of the power source 2. Connect to allow continuity.

  Next, while the power source 2 ′ is energized between the anode 2 and the object 5 to be protected, the potential measurement unit 6 ′ synchronizes with the detection output from the zero cross detection unit 7 and synchronizes with the zero cross of the AC. The electrode potential of the anticorrosive body 5 is measured.

  Then, the anticorrosion applied voltage of the power source 2 is adjusted / set using the potential of the to-be-protected body 5 measured by the potential measuring method of the to-be-protected body 5 as a control potential, and the anticorrosion is continued. Adjustment and setting of the anti-corrosion voltage of the power source 2 can be performed manually, or when a thyristor is used in the rectifier circuit, it can be automated by adjusting the ignition position.

  Thus, according to the method for measuring the potential of the object to be protected according to the present embodiment, even if the object to be protected is placed in a high-resistance environment, the object to be corroded is subjected to the anticorrosion and the ohm drop is removed. 5 accurate potential measurements can be repeated. Therefore, effective anticorrosion with high anticorrosion property can be stably performed by applying the anticorrosion applied voltage to the to-be-protected body 5 with the anticorrosion potential of the obtained to-be-protected body as a control potential.

  As a preferred embodiment of the apparatus for carrying out the method for measuring the potential of the object to be protected in the external power supply type electric corrosion prevention, the present invention is based on the control pulse wave in the electric corrosion prevention apparatus 1 of the above embodiment. A control unit 4 that controls on / off of the supplied anticorrosion current, and a potential measurement unit that measures the potential of the to-be-protected body 5 connected to the cathode terminal 22 of the power source 2 in synchronization with the controlled pulse current being turned off. 6, and the potential measurement device can be incorporated into an anticorrosion circuit in an existing external power supply type anticorrosion method to measure the potential of the object to be protected and to prevent corrosion.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Example 1]
To measure the potential of the carbon steel in tap water under cathodic protection (the anticorrosion material), sets the cathodic protection device of FIG. 1, while flowing a corrosion current at a current density of 350mA / m ^2, on / off time ratio The anticorrosion current was switched at = 50 (ms) / 1 (ms). A platinum-plated titanium electrode was used as the anode, and a saturated gypsum electrode (SCE) was used as the reference electrode. FIG. 3 shows the result of measuring the waveform of the potential value (vs. SCE) of the object to be protected at that time with an oscilloscope. The pulse-like peak corresponds to the potential value when the current is off. The potential of the carbon steel at the time of off was about −0.72 V (vs. SCE). The potential value synchronized with the OFF time is held (HOLD) through the potential holding circuit built in the potential measuring unit 6 so that the potential of the corrosion-protected body at the time of OFF is sufficiently stably measured by a low-speed digital voltmeter. I was able to.

[Example 2]
In order to measure the potential of the reinforcing steel (corroded body) in concrete under cathodic protection, set the cathodic protection device of FIG. 1 and on / off time ratio = 100 (ms) while passing a current of 1.2 A. The anticorrosive current was switched at / 1 (ms). The anode was an iridium oxide-coated oxide electrode, and the reference electrode was a manganese dioxide electrode. 4A and 4B show the potential waveform at that time and the potential value held by the potential holding circuit built in the potential measuring unit 6. These figures are measured under the same experimental conditions but are recorded with different time widths. (A) is a short time recording in accordance with the off time width, while (b) is recorded with a time width including three times of switching. The instant-off potential of the body to be protected was not affected by switching and showed a constant value, which was −1.28 V (vs. MnO ₂ ).

Example 3
In the concrete structure to which the anticorrosion different from that of Example 2 is applied, the anticorrosion device of FIG. 2 is set, and the reinforcing bars in the concrete are synchronized with the vicinity of the point where the AC voltage is 0 V (zero crossing). Then, the potential of the body to be protected was measured. The potential of the body to be protected was −362 mV (vs. MnO ₂ ). FIG. 5 shows the results of measuring waveforms of various parameters at that time with an oscilloscope. The potential of the corrosion-protected body measured in synchronization with alternating zero crossing coincided with the potential of the corrosion-protected body when the corrosion-proof current was zero.

  INDUSTRIAL APPLICABILITY The present invention is suitable when an external power source type electric corrosion protection is applied to an object to be protected placed in a corrosive environment, particularly in a corrosive environment having low electrical conductivity such as soil, concrete, and fresh water.

It is a figure which shows typically 1st Embodiment of the cathodic protection apparatus of this invention. It is a figure which shows typically 2nd Embodiment of the cathodic protection apparatus of this invention. It is a figure which shows the measurement result of the anticorrosion potential in the Example of this invention. It is a figure which shows the measurement result of the anticorrosion potential in the Example of this invention. It is a figure which shows the measurement result of the anticorrosion potential in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1 'Electrocorrosion protection apparatus 2, 2' Power supply 21 Anode terminal 22 Cathode terminal 3 Anode 4 Control part 41 Control pulse signal generation part 42 Corrosion prevention current pulse generation part 42a Transistor 42b Field effect type transistor 42c Photocoupler 5 Corrosion object (cathode)
6, 6 'Potential measurement unit 7 Zero cross detection unit

Claims (8)

A method for measuring the potential of an object to be protected in an external power source type electric protection,
The anode is connected to the anode terminal of the power source so as to be conductive, and is connected to the cathode terminal of the power source so as to be conductive as an anticorrosive body, while the current supplied from the power source is repeatedly turned on and off by the control pulse wave. A method for measuring the potential of an object to be protected in electrocorrosion, in which an electric current is passed between an anode and the object to be protected, and the potential of the object to be protected is measured in synchronization with the controlled current being turned off.   The method for measuring a potential of an object to be protected in cathodic protection according to claim 1, wherein an on / off time ratio of the pulse wave is 40 or more, an on time is 4 ms to 2 s, and an off time is 0.1 ms to 10 ms. An electric potential measuring apparatus for carrying out the method of measuring an electric potential of an object to be protected in electrocorrosion according to claim 1 or 2,
A controller for controlling on / off of the anticorrosion current supplied from the anticorrosion power source based on a control pulse wave, and the off of the anticorrosion current in which the potential of the to-be-protected object connected to the cathode terminal of the power source is connected. An electric potential measuring device including an electric potential measuring unit that measures in synchronization with time.   An anticorrosion method for performing anticorrosion by setting an anticorrosion applied voltage using the potential of the anticorrosive body measured by the method for measuring the potential of the anticorrosive body in electrocorrosion according to claim 1 or 2 as a control potential. An apparatus for carrying out the cathodic protection method according to claim 4,
An anti-corrosion power source, an anode connected to the anode terminal of the power source so as to be conductive, a control unit that controls on / off of the anti-corrosion current supplied from the power source based on a control pulse wave, and a conduction to the cathode terminal of the power source An electric corrosion protection device comprising: a potential measuring unit that measures the potential of the corrosion protected object connected in synchronization with the controlled anticorrosion current being turned off. A method for measuring the potential of an object to be protected in an external power source type electric protection,
The anode is connected to the anode terminal of the power source that rectifies and outputs the input alternating current without being smoothed, and is connected to the cathode terminal of the power source so as to be conductive with the subject to be protected as a cathode. A method for measuring the potential of an object to be corroded in electrocorrosion, wherein the potential of the object to be corroded is measured in synchronization with zero crossing of an output corresponding to the alternating current while energizing between the anode and the object to be corroded.   An anticorrosion method for performing anticorrosion by setting an anticorrosion applied voltage with the potential of the anticorrosive body measured by the potential measurement method for an anticorrosive body in electrocorrosion according to claim 6 as a control potential. An apparatus for carrying out the cathodic protection method according to claim 7,
An anticorrosion power source that rectifies and outputs an input alternating current without being smoothed, an anode connected to the anode terminal of the power supply in a conductive manner, and an anticorrosive body connected to the cathode terminal of the power supply in a conductive manner And an electric potential measuring unit that measures the electric potential in synchronization with the zero crossing of the output corresponding to the alternating current.

Images