JPH06249820A - Estimation of corrosion-proof electric potential - Google Patents

Abstract

PURPOSE:To obtain a corrosion-proof electric potential estimation method for measuring or estimating the correct true corrosion-proof electric potential. CONSTITUTION:As for the corrosion-proof electric potential estimation method for a corrosion-proof objective article 1 in which an outside electric power source 4 whose negative side is connected with the corrosion-proof objective article 1 such as a buried pipe buried under the ground 5 and whose positive side is connected with an opposed electrode 3 buried in the ground 5 is installed, and electric corrosion-proof operation is carried out by suppllying electric corrosion-proof current from the ground 5 side to the corrosionproof objective article 1 side, the electric current which is formed by rectifying the full waves of the sine wave alternating current is used as the corrosion-proof electric current, and the electric potential between the corrosion-proof objective article 1 and the ground surface 50 is measured. Then, the dc component and the ac component of the electric potential are detected, and the sum of the dc ocmponent and constant times of the ac component is estimated as the corrosion-proof electric potential of the corrosion-proof objective article 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating the anticorrosion potential of a buried pipe or the like which has been subjected to anticorrosion, and more specifically,
The negative electrode side is connected to the anticorrosion target embedded in the soil, and the positive electrode side is provided with an external power source connected to the counter electrode provided in the soil, and the anticorrosion current is supplied from the soil side to the anticorrosion target side. The present invention relates to a method for estimating the anticorrosion potential of an anticorrosion target.

[0002]

2. Description of the Related Art Currently, as a corrosion protection measure for buried pipes, galvanic protection is applied together with the formation of coating, which is very effective for the maintenance of conduits. In cathodic protection, as an important index for judging the anticorrosion effect, the anticorrosion potential, which is the potential between the soil around the buried pipe and the buried pipe, has a predetermined value (E ≦ −8).
Whether or not it is within the range of 50 mV _vs. Cu / CuSO ₄ ) is the criterion. In measuring or estimating such an anticorrosion potential, a collation electrode 6 is provided on the soil surface 50, and a cable having the other end connected to the buried pipe 1 is provided so that a DC potential difference (apparent anticorrosion potential) between the two is provided. ), The measured value is compared with the above value to make the determination. When such a method is adopted, IR loss due to soil resistance and anticorrosion current is present when measuring the apparent anticorrosion potential. Therefore, the apparent anticorrosion potential (measured potential) is measured lower than the true anticorrosion potential (potential between the soil in the vicinity of the buried pipe and the buried pipe), which is unsafe as if it had a sufficient anticorrosion effect. A side evaluation takes place. Therefore, for the purpose of removing this anticorrosion current component, the external power supply, which is a direct current power source, is temporarily turned off (corrosion protection current is zero, that is, IR loss is zero), and the potential change is taken on the graph to obtain the instant immediately after the OFF operation. The true anti-corrosion potential is estimated from the potential shown in.

[0003]

However, this method requires an operation or device for temporarily turning off the external power source, and when a large number of external power sources are installed on one corrosion protection line, It is necessary to turn off all of them simultaneously (on the ms order), which is difficult to implement.
Therefore, an object of the present invention is to obtain a method for estimating the anticorrosion potential that can measure or estimate the true anticorrosion potential more accurately while the external power supply is kept in the operating state.

[0004]

The characteristic means of the method for estimating the anticorrosion potential according to the present invention for achieving this object is to use a current having a value of 0 periodically as the anticorrosion current, and The potential between the surfaces at the moment when the anticorrosion current takes a zero value periodically is estimated as the anticorrosion potential of the anticorrosion target. The action and effect are as follows.

[0005]

That is, in the anticorrosion structure of the present application, a current that takes a zero value periodically is adopted as the anticorrosion current. And
In the measurement of the anticorrosion potential, the potential between the ground surface and the buried pipe is measured as usual. However, the measurement is made at the time when the anticorrosion current becomes zero. Therefore, at this point, since there is no anticorrosion current itself, there is no IR loss between the ground surface and the vicinity of the buried pipe, which has been a problem in the past, and as a result, the measured potential represents the true anticorrosion potential. It has become a thing.

[0006]

Therefore, when each of the external power supplies for supplying the anticorrosion current is adopted and the anticorrosion potential is measured by the method of the present invention, an arbitrary power supply is maintained while the current supply state of the external power supply is maintained. It has become possible to measure the "true potential" at a point.

Further, a current obtained by full-wave rectifying a sine wave alternating current is used as the anticorrosion current, and a direct current component and an alternating current component of the potential are detected by a direct current voltmeter and an alternating current voltmeter, respectively. Assuming that the anticorrosion potential at the time when the anticorrosion current becomes 0 is obtained, the apparent output of the anticorrosion potential measurement side has a direct current component and an alternating current component corresponding to the period of the anticorrosion current as shown in FIG. Can be
The cycle in which the anticorrosion current becomes 0 and the cycle in which the potential shows the maximum value (noble value) match, and the DC component measured value is a constant multiple of the AC component measured value (actual AC voltage amplitude range This is the true anti-corrosion potential if you add it by adding the value obtained by converting the output value).

[0008]

Embodiments of the present application will be described with reference to the drawings. FIG. 1 shows a situation of a buried pipe 1 as an anticorrosion object to which the method of the present application is applied.

First, the structure of cathodic protection will be described. With respect to the buried pipe 1 as an anticorrosion target, the counter electrode 3 is installed in the soil 5 in which the buried pipe 1 is buried, and the negative electrode side is connected to the buried pipe 1 across the buried pipe 1 and the counter electrode 3, An external power supply 4 whose positive electrode side is connected to the counter electrode 3 is provided. The anticorrosion current supplied from the external power supply 4 is a full-wave rectified sine wave alternating current as shown in FIG. Here, since a normal commercial power source is used as the power source, the frequency of the anticorrosion current is 120 Hz. The anticorrosion current takes a value of 0 periodically and flows from the counter electrode 3 to the buried pipe 1 through the coating defect portion 2 in the soil 5.

When measuring the anticorrosion potential, a DC and AC voltmeter 7 is provided between the verification electrode 6 provided on the soil surface 50 and the buried pipe 1, and the potential difference between them is measured. It Further, in the method for measuring the anticorrosion potential of the buried pipe 1 of the present application, that is, from the measurement potentials measured by these voltmeters 7, the DC component potential E _DC and the AC component potential E
_AC is measured, and the value obtained from the following equation based on these values is estimated as the true anticorrosion potential E _T. E _T = E _DC + constant × E _AC Here, the constant is the actual voltage amplitude of the measured alternating current (E _DC
Amplitude above) / Output value of AC voltmeter Hereinafter, the measurement procedure will be described step by step. A full-wave rectified commercial current (sine wave AC 60 Hz) is supplied as an anticorrosion current from the external power source 4. This anticorrosion current has a point at which the current value instantaneously becomes zero (120 per second).
Times). Therefore, the potential of the buried pipe 1 also includes an AC component that changes at 120 Hz (see FIGS. 2 and 3). In this state,
When the potential is measured using the voltmeter 7 at the "specific point" of the buried pipe 1, the measurement result as shown in FIG. 3 is obtained. In the figure, the DC component is E _DC , and the AC component is E _AC . Using these measured values (DC component E _DC and AC component E _AC ), E _T (true potential) is obtained, and the anticorrosion potential is estimated.

[Other Embodiments] In the above-mentioned embodiment, an anticorrosion current using a full-wave rectified current is adopted, and the measured anticorrosion potential at the time when this current takes 0 value is estimated as the true anticorrosion potential. However, this is not necessarily limited to the sinusoidal waveform. That is, a current that takes a 0 value periodically is used as the anticorrosion current (however, the anticorrosion current needs to flow from the soil side to the buried pipe side), and the anticorrosion current is the potential between the buried pipe 1 and the soil surface 50. The potential at the instant when the zero value is taken periodically may be estimated as the anticorrosion potential of the buried pipe 1.
Therefore, the waveform can be arbitrarily set, and it is possible to employ a waveform that suddenly becomes a zero value at the time of measurement, or vice versa. Further, as the anticorrosion target, various objects such as the underground pipe 1 and the underground buried structure can be considered. Further, instead of including a DC voltmeter and an AC voltmeter 7, as shown in FIG. 4, a transient memory device (7 for outputting a potential between the buried tube 1 and the reference electrode 6).
0) may be provided and the true anticorrosion potential may be obtained from the output curve. Further, in detecting the anticorrosion potential, as shown in FIG.
A waveform analyzing device (7a) such as T is provided, and by this device, the potential at a specific moment when the anticorrosion current becomes 0 value is estimated (7b).
May be estimated by

It should be noted that although reference numerals are given in the claims for convenience of comparison with the drawings, the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a view showing a configuration of an anticorrosion structure and a measurement state of an anticorrosion potential.

FIG. 2 is a diagram showing an anticorrosion current.

FIG. 3 is a diagram showing detected anticorrosion potentials.

FIG. 4 is a diagram showing an example of measurement by a transient memory device.

FIG. 5 is a diagram showing a measurement example by a waveform analyzer such as FRA or FFT.

[Explanation of symbols]

 1 Anticorrosion target 3 Counter electrode 4 External power supply 5 Soil 50 Soil surface

Claims (2)

[Claims] 1. An external power source (negative electrode side is connected to an anticorrosion target (1) buried in soil (5) and positive electrode side is connected to a counter electrode (3) provided in said soil (5). 4) is provided, which is a method for estimating the anticorrosion potential of an anticorrosion target (1) which is galvanically protected by supplying an anticorrosion current from the soil (5) side to the anticorrosion target (1) side. Using a current that takes a zero value periodically,
At the potential between the anticorrosion target (1) and the soil surface (50),
A method for estimating an anticorrosion potential, which estimates the electric potential at the instant when the anticorrosion current takes a value of 0 periodically as the anticorrosion potential of the anticorrosion target (1). 2. A current obtained by full-wave rectifying a sinusoidal alternating current is used as the anticorrosion current, and a direct current component of the potential between the anticorrosion target (1) and the soil surface (50) is measured by a direct current voltmeter. Is detected by an AC voltmeter, and the potential at the instant when the anticorrosion current periodically takes a value of 0 is determined from the measured value of the DC component and the measured value of the AC component.