JPH09304326A - Corrosion speed measuring method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure corrosion speed highly precisely by measuring respective partial voltage values of constant currents among three electrodes, including a sample electrode and finding a partial voltage resistance value of the sample electrode based on an operation result excluding partial voltage value factors of solution resistance among the respective partial voltage values and a constant current value. SOLUTION: An AC constant current (i) is made to flow between a sample electrode 27 and a counter electrode 29 by an AC circuit 47. A voltometer 41 measures a sample- side partial voltage value Va between a collation electrode 28 and the sample electrode 27 and a voltometer 42 measures a fourth electrode side partial voltage value Vb between the collation electrode 28 and the fourth electrode 30. A ratio station 43 automatically sets a ratio α of solution resistance of the sample electrode side and the forth electrode side respectively based on the partial voltage values Va , Vb , and the partial pressure value Vb is multiplied by the ratio α so that the factor of the solution resistance partial voltage value is excluded. Secondly, a subtractor 44 subtracts the partial voltage value Vb ×2 from the partial voltage value Va and a divider 45 divides Va -αVb by the AC constant current (i) fed from the constant current circuit 27, so that a partial electrode resistance γ1 is found. With this constitution, highly precise corrosion speed can be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion rate measuring method and apparatus for measuring the corrosion rate of, for example, an iron pipe.

[0002]

2. Description of the Related Art In a cooling system of a building or a plant, an iron pipe is often used as a pipe for circulating the cooling water. The cooling effect is reduced by clogging with mud and the like, and corrosion is caused by these. Since the life of the iron pipe due to corrosion greatly affects the life of the building or plant itself, it is important to know the progress of corrosion of the iron pipe.

For this reason, a corrosion rate measuring device and a conductivity meter are used for water quality control. Among them, the corrosion rate measuring device detects the progress of corrosion of cooling water pipes of buildings and plants, thereby suppressing corrosion. Manage the injection of agents. In addition, the conductivity meter detects the concentration and pollution of the cooling water and controls the blowing of the cooling water to prevent the blockage of the pipes, and is also used for the quality control of industrial wastewater and sewage water.

FIG. 8 shows a conventional three-electrode type corrosion rate measuring device. In the figure, 1 is a sample electrode such as an iron pipe, 2 is a counter electrode, 3 is a reference electrode provided between the counter electrode 2 and the sample electrode 1. An AC power supply 4 is connected between the sample electrode 1 and the counter electrode 2, and a voltmeter 5 as a voltage measuring circuit is connected between the sample electrode 1 and the reference electrode 3.

Next, the operation of this corrosion rate measuring device will be described separately for the AC constant current method and the AC constant voltage method. First,
In the AC constant current method, among the sample electrode 1, the counter electrode 2, and the reference electrode 3 immersed in the solution, a constant current as shown in FIG. AC power supply 4
9B, the voltage generated between the sample electrode 1 and the reference electrode 3 at this time is measured by the voltmeter 5, and the polarization resistance is obtained as the ratio of these voltage and current.

On the other hand, in the AC constant voltage method, the voltage input from the AC power source 4 between the sample electrode 1 and the reference electrode 3 is as shown in FIG.
As shown in (a), it changes to positive and negative with a constant amplitude,
The current flowing between the counter electrode 2 and the sample electrode 1 is controlled as shown in FIG. Then, the polarization resistance is obtained as the ratio of these voltage and current.

FIG. 11 shows a conventional four-electrode type conductivity meter. It consists of four electrodes 11, 12, 13,
14, an AC power supply 15 for flowing a constant current therebetween is connected between the electrodes 11 and 14, and a voltmeter 16 as a voltage measuring circuit is connected between the electrodes 12 and 13. .

In this conductivity meter, the electrodes 11 and 1 are
An AC constant current is passed from the AC power supply 15 between the four electrodes, and the voltage obtained between the electrodes 12 and 13 at this time is measured by the voltmeter 16. Then, the ratio of these voltage and current is obtained,
The cell resistance is multiplied by this ratio to obtain the solution resistance. Then, the dielectric constant is determined as the reciprocal of this solution resistance.

The three-electrode type is often used industrially in measuring the corrosion rate, but when the corrosion rate is measured by the polarization resistance method, the solution resistance indicates the type and state,
This solution resistance causes an error in measuring the corrosion rate, because it varies depending on the shape and arrangement of the electrodes. As a method of eliminating such a cause of measurement error, there is the following countermeasure. (A) Conductivity of the solution is measured with a conductivity meter, and the measured solution resistance value is used for correction. (B) In the two-electrode system, the distance between the sample electrode and the counter electrode is reduced, and in the three-electrode system, the space between the sample electrode and the reference electrode is narrowed to reduce the solution resistance.

[0010]

Since the conventional corrosion rate measuring method and the conventional corrosion rate measuring apparatus are configured as described above, in order to measure the corrosion rate with high accuracy, the measurement error of the corrosion rate due to the solution resistance should be considered. Need to be eliminated. However, in the countermeasure shown in (a) above, a conductivity meter must be prepared separately, and the operator must perform a correction calculation based on the measurement results, which is costly when configured as a corrosion rate measuring device. However, there is a problem in that the size increases and the size increases.

Further, in the countermeasure described in (b) above, the measurement voltage between the electrodes becomes unstable because the space between the electrodes is narrowed or the spaces between the electrodes are clogged due to the deposits on the electrodes. There is a problem that it is necessary to frequently perform maintenance of the electrodes.

The present invention has been made in order to solve the above-mentioned problems, and it eliminates the need for a conductivity meter and narrows the gap between electrodes due to the measurement error due to the solution resistance of the measured corrosion rate. Can be removed without
It is an object of the present invention to obtain a corrosion rate measuring method and a corrosion rate measuring device capable of accurately measuring a corrosion rate.

[0013]

According to a first aspect of the present invention, there is provided a corrosion rate measuring method, wherein at least three or more electrodes including a sample electrode made of the same material as the metal to be measured are immersed in a solution, and A partial pressure value measuring process of measuring each partial pressure value between the three electrodes including the sample electrode when a constant current is applied between the sample electrode and the counter electrode farthest away; Assuming that the ratio is equal and constant to the ratio of each partial pressure value measured in the partial pressure value measurement process, the solution resistance component based on the solution resistance value is calculated based on the ratio by the calculation performed between the partial pressure values. Based on the solution resistance element excluding process of excluding the pressure value element, the calculation result of the solution resistance element excluding process, and the constant current value flowing between the sample electrode and the counter electrode, the polarization resistance value of the sample electrode. And a polarization resistance calculating process for obtaining

According to a second aspect of the present invention, there is provided a corrosion rate measuring method, wherein a partial pressure on the sample electrode side between the reference electrode and the sample electrode when a voltage is applied between the sample electrode and the counter electrode in the three-electrode system. Value, and a partial pressure value measuring step of measuring the counter electrode side partial pressure value between the reference electrode and the counter electrode, and the sample electrode side partial pressure value and the counter electrode side partial pressure measured by the partial pressure value measuring step. Assuming that the ratio of the solution resistance value between the sample electrode and the reference electrode and the solution resistance value between the reference electrode and the counter electrode is equal and constant, the sample electrode side partial pressure Value and the counter electrode side partial pressure value is calculated, and the solution resistance element excluding step of excluding the solution resistance partial pressure value element by the solution resistance value based on the ratio, and the solution resistance element excluding step Based on the calculation result and the constant current value flowing between the sample electrode and the counter electrode, It is obtained so as to include a polarization resistance calculation process for obtaining the polarization resistance of the charge electrode.

In the corrosion rate measuring method according to the third aspect of the present invention, a sample electrode made of the same material as the metal to be measured, a counter electrode, a reference electrode provided between the sample electrode and the counter electrode, and a fourth electrode are provided. A sample electrode side partial pressure value between the reference electrode and the sample electrode when immersed in a solution and a constant current was applied by applying a voltage between the sample electrode and the counter electrode, and the first electrode Partial pressure value measuring step for measuring the fourth pole side partial pressure value between the four poles and the reference electrode, the sample pole side partial pressure value and the fourth pole side partial pressure measured by the partial pressure value measuring step Assuming that the ratio with the pressure value is equal and constant to the ratio between the solution resistance value between the sample electrode and the reference electrode and the solution resistance value between the reference electrode and the fourth electrode, the sample electrode Calculation is performed between the side partial pressure value and the fourth pole side partial pressure value, and the solution resistance partial pressure based on the solution resistance value is calculated based on the ratio. The solution resistance element elimination process for eliminating the element, and the polarization resistance value of the sample electrode based on the result of the calculation performed in the solution resistance element elimination process and the constant current value flowing between the sample electrode and the counter electrode. It is provided with a required polarization resistance calculation process.

According to a fourth aspect of the present invention, there is provided a corrosion rate measuring device, wherein at least three or more electrodes including sample electrodes made of the same material as the metal to be measured are immersed in a solution,
A voltage application circuit for applying a voltage between a counter electrode farthest from the sample electrode to flow a constant current, and a partial pressure value measuring circuit for measuring each partial pressure value between the three electrodes including the sample electrode. A ratio setting circuit for multiplying one of the partial pressure values measured by the partial pressure value measuring circuit by the ratio obtained from the partial pressure value measured by the partial pressure value measuring circuit, and the ratio A subtraction circuit that obtains the difference between the one partial pressure value multiplied by the ratio by the setting circuit and the other partial pressure value, and the constant that flows the value obtained by the subtraction circuit between the sample electrode and the counter electrode. And a division circuit for dividing by the value of the current.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1. FIG. 1 is an explanatory diagram showing a mounted state of a corrosion rate measuring device that realizes the corrosion rate measuring method according to the first embodiment of the present invention. In the figure, 21 is a corrosion rate measuring device, 22 is an electrode part, 23 is a cable connecting the corrosion rate measuring device 21 and the electrode part 22, 24 is a tank, and 25 is a solution stored in a tank 24.

FIG. 2 is a cross-sectional view showing the structure of the electrode portion 22 provided with three electrodes used in the three-electrode system, in which 23a is a cable connecting the corrosion rate measuring device 21 and the sample electrode 27. , 23b is a cable connecting the corrosion rate measuring device 21 and the reference electrode 28, and 23c is a cable connecting the corrosion rate measuring device 21 and the counter electrode 29. The sample electrode 27 is made of, for example, the same material as the material of the pipe whose corrosion rate is to be measured. The reference electrode 28 and the counter electrode 29 are made of the same material as the sample electrode 27 or a material such as gold, silver, platinum, and stainless steel, which is resistant to corrosion. The reference electrode 28 is arranged so as not to disturb the electric field distribution generated when a current is passed between the sample electrode 27 and the counter electrode 29. Reference numeral 31 is a resin protective cylinder, and 32 is a molded portion that protects the connecting portions of the cables 23a, 23b, 23c and the respective electrodes.

FIG. 3 is a cross-sectional view showing the structure of an electrode portion 22 having four electrodes used in a four-electrode system. In FIG. 3, the same or corresponding parts as those in FIG. 2 are designated by the same reference numerals. The description is omitted. In the figure, 23d is a cable connecting the fourth pole 30 arranged between the reference electrode 28 and the counter electrode 29 and the corrosion rate measuring device 21. 4th pole 3
For 0, the same material as the sample electrode 27 or a material such as gold, silver, platinum, and stainless steel, which is not easily corroded, is used. The reference electrode 28 and the fourth electrode 30 are arranged so as not to disturb the electric field distribution generated when a current is passed between the sample electrode 27 and the counter electrode 29.

FIG. 4 is a block diagram showing the structure of the corrosion rate measuring device. In the figure, reference numeral 41 denotes the potential (hereinafter referred to as the sample electrode side partial pressure value) generated between the sample electrode 27 and the reference electrode 28. A voltage measuring device (divided voltage measuring circuit) 42 for measuring, a voltage measuring device (divided voltage) for measuring a potential (hereinafter, referred to as a fourth divided voltage value) generated between the reference electrode 28 and the fourth electrode 30. (Value measurement circuit), 43 is a ratio setter (ratio setting circuit) for multiplying the ratio α between the sample electrode side partial pressure value and the fourth electrode side partial pressure value to the fourth electrode side partial pressure value, and 44 is the sample electrode side Partial pressure value and the ratio setter 43
A subtractor (subtraction circuit) for obtaining the difference from the value obtained in
Is the value obtained by the subtractor 44, and is used as the sample electrode 27 and the counter electrode 29.
A divider (division circuit) that divides by the current i flowing between
6 is a signal holding circuit for holding and outputting the value obtained by the divider 45, and 47 is an AC constant current for applying an AC voltage between the sample electrode 27 and the counter electrode 29 to flow an AC constant current i. Circuit (voltage application circuit).

FIG. 5 is an electrical equivalent circuit in the electrode portion 22 shown in FIG. 2, and FIG. 6 is an electrical equivalent circuit in the electrode portion 22 shown in FIG. In the electrical equivalent circuit shown in FIG. 5, RW1 and RW2 are solution resistances that cause a measurement error of the corrosion rate, RW1 is a solution resistance between the sample electrode 27 and the reference electrode 28, and RW2 is a reference electrode 28 and the counter electrode 29. The solution resistance between and.

E1 is the material of the sample electrode 27, the type of solution,
Corresponding to the state, the corrosion potential generated at the interface of the sample electrode 27, E3 is the corrosion potential generated at the interface of the reference electrode 28, and E2 is the corrosion potential generated at the interface of the counter electrode 29.

R1 is the polarization resistance of the sample electrode 27 to be measured, r3 is the polarization resistance of the reference electrode 28, and r2 is the polarization resistance of the counter electrode 29.

Va is a partial pressure on the sample electrode side generated between the sample electrode 27 and the reference electrode 28 when an AC constant voltage i is applied by applying an AC voltage between the sample electrode 27 and the counter electrode 29. Value, V
Similarly, b is a potential generated between the reference electrode 28 and the counter electrode 29 (hereinafter referred to as counter electrode side partial pressure value).

In the electrical equivalent circuit shown in FIG. 6, RW1
Is the solution resistance between the sample electrode 27 and the reference electrode 28, and RW2 is the solution resistance between the reference electrode 28 and the fourth electrode 30. RW
3 is a solution resistance between the fourth electrode 30 and the counter electrode 29.

E1 is the material of the sample electrode 27, the type of solution,
Depending on the state, the corrosion potential generated at the interface of the sample electrode 27, E3 similarly the corrosion potential generated at the interface of the reference electrode 28, E4 similarly the corrosion potential generated at the interface of the fourth electrode 30, and E2 the same. Is the corrosion potential generated at the interface of the counter electrode 29.

R1 is the polarization resistance of the sample electrode 27 to be measured, r3 is the polarization resistance of the reference electrode 28, and r4 is the fourth pole 30.
, And r2 is the polarization resistance of the counter electrode 29.

Va is a partial pressure on the sample electrode side generated between the sample electrode 27 and the reference electrode 28 when an AC constant voltage i is applied by applying an AC voltage between the sample electrode 27 and the counter electrode 29. Value, V
Similarly, b is a fourth pole side partial pressure value generated between the reference pole 28 and the fourth pole 30.

Next, the operation of measuring the polarization resistance value of the sample electrode 27 and determining the corrosion rate using the electrode portion 22 having the four electrodes shown in FIG. 3 will be described. The sample electrode side partial pressure value Va between the reference electrode 28 and the sample electrode 27 when the alternating constant current i is passed between the sample electrode 27 and the counter electrode 29 by the AC constant current circuit 47, the reference electrode 28 and the fourth electrode Fourth between pole 30
The pole-side partial pressure value Vb is represented by the following equations (1) and (2) from the electrical equivalent circuit shown in FIG. The sample electrode side partial voltage value Va is measured by the voltage measuring device 41, and the fourth electrode side partial voltage value Vb is measured by the voltage measuring device 42. In this case, the voltage measuring device 41 measures the sample electrode side partial pressure value Va immediately before the polarity is reversed. In addition, the voltage measuring device 4
2 also measures the fourth pole side partial pressure value Vb immediately before the polarity is reversed.

[0030]

[Equation 1]

[0031]

[Equation 2]

From the shape of the electrode portion 22 and the arrangement of each electrode, the ratio α of the solution resistance RW1 between the sample electrode 27 and the reference electrode 28 and the solution resistance RW2 between the reference electrode 28 and the fourth electrode 30 is α.
Is determined from the electrode arrangement and the like, and is constant as shown in equation (3). The ratio α may be set in the ratio setter 43 based on the electrode arrangement or the like, or the ratio setter automatically calculates from the sample pole side partial pressure value Va and the fourth pole side partial pressure value Vb. It is also possible to ask.

[0033]

(Equation 3)

In equations (1) and (2), the solution resistance RW
1. Since the voltage drop due to RW2, that is, the solution resistance partial pressure value is included, the change in the solution resistance according to the type and state of the solution is caused by the sample electrode side partial pressure value Va and the fourth electrode side partial pressure value. This will act as an error component on the corrosion rate measurement result obtained using the value Vb. Therefore, the element of the solution resistance partial pressure value is excluded from the sample electrode side partial pressure value Va and the fourth electrode side partial pressure value Vb. This is the solution resistance element elimination process. In the solution resistance element elimination process, first, the solution resistance R is applied to both sides of the equation (2).
Multiply the ratio α obtained from W1 and RW2. In this case, the operation of the ratio setter 43 is as follows:
b will be multiplied by the ratio α. Next, the equation (2) in which both sides are multiplied by the ratio α is subtracted from the equation (1) to eliminate the element of the solution resistance partial pressure value. As a result, the following equation (4) in which the element of the solution resistance partial pressure value is eliminated is obtained.

[0035]

(Equation 4)

In this case, the subtractor 44 operates as a ratio α from the sample electrode side partial pressure value Va measured by the voltage measuring device 41.
The fourth pole side partial pressure value Vb multiplied by is reduced.

Next, the polarization resistance r1 at the sample electrode 27 is obtained from the equation (4). The process of obtaining the polarization resistance r1 is the polarization resistance calculation process. As a result, the polarization resistance r1 is obtained by the following equation (5).

[0038]

(Equation 5)

In order to realize this polarization resistance calculation process, the divider 45 calculates Va-αVb obtained by the subtractor 44 with respect to Va-αVb.
The division is performed using the AC constant current i supplied from the AC constant current circuit 47.

E1-E3 and E3-E4 in the equation (5)
Is a potential measured between the sample electrode 27 and the reference electrode 28 when a current is not applied between the sample electrode 27 and the counter electrode 29, and a potential measured between the reference electrode 28 and the fourth electrode 30. You can easily know as. Therefore, the arithmetic processing performed by the divider 45 for realizing the polarization resistance calculation process of the equation (5) is performed by taking the values of E1-E3 and E3-E4 into consideration to calculate the polarization resistance r1 with high accuracy. It becomes possible to measure.

However, when the same material is used for the sample electrode 27, the reference electrode 28, and the fourth electrode 30, E1 = E3 = E4
Therefore, the equation (5) is represented by the following equation (6), and the elements of E1-E3 and E3-E4 disappear, so that the polarization resistance r1 can be accurately measured.

[0042]

(Equation 6)

When a material having excellent corrosion resistance such as a noble metal is used for the reference electrode 28 and the fourth electrode 30, E3 =
Since E4 = 0, the equation (5) is represented by the following equation (7), and the arithmetic processing performed by the divider 45 for realizing the polarization resistance arithmetic process of the equation (7) is E1. By performing the calculation in consideration of the value, it is possible to accurately measure the polarization resistance r1. The corrosion potential E1 generated at the interface of the sample electrode in this case is measured by measuring the potential between the sample electrode 27 and the reference electrode 28 in a state where no current is passed between the sample electrode 27 and the counter electrode 29. You can easily know.

[0044]

(Equation 7)

FIG. 7 shows the above E when determining the polarization resistance r1.
A block showing a configuration of a corrosion rate measuring device provided with a correction circuit 52 for performing correction when the value of 1-E3, E3-E4 or the value of E1 has to be taken into consideration when the divider 45 performs calculation. It is a figure. The correction circuit 52 uses the values obtained by the divider 45 to determine the corrosion potentials E1 and E generated at the interface of each electrode according to the material of each electrode, the type of solution, and the state.
Correction is made based on the measured values of E3 and E4 and the constant alternating current i flowing between the sample electrode 27 and the counter electrode 29.

Although the case of the 4-electrode type has been described above, the case of the 3-electrode type using the electrode portion 22 shown in FIG. 2 is similar to the 4-electrode type except that the fourth pole 30 is not provided. is there. In the case of this three-electrode type, the electrical equivalent circuit of the electrode portion 22 is as shown in FIG. 5, and therefore the sample electrode side partial pressure value Va and the counter electrode side partial pressure value Vb are expressed by the following equation (8). ,
It is represented by equation (9).

[0047]

(Equation 8)

[0048]

[Equation 9]

In the case of the three-electrode type as well as the four-electrode type, the ratio α of the solution resistance RW1 and the solution resistance RW2 is determined by the electrode portion 22.
When the shape and arrangement relationship of each of the electrodes is determined, it becomes a constant. This ratio α is the ratio between the sample electrode side partial pressure value Va and the counter electrode side partial pressure value Vb, assuming that there is no corrosion potential or polarization resistance of each electrode, in other words, between the counter electrode 29 and the sample electrode 27. It is a voltage division ratio between electrodes.

When the same material is used for each electrode, E1
= E2 = E3, r1 = r2 = r3, and therefore equation (8) is simplified to equation (10) below, and equation (9)
Is simplified to equation (11).

[0051]

(Equation 10)

[0052]

[Equation 11]

By multiplying both sides of equation (11) by the ratio α, equation (1)
0), the elements RW1 · i and RW2 · i of the solution resistance partial pressure value are excluded from Va-αVb, and the elements of the solution resistance partial pressure value are excluded from the equation (12). )
Is obtained. This is a solution resistance element elimination process in the case of the three-electrode type.

[0054]

(Equation 12)

In this case, the voltage measuring device 4 is operated by the subtractor 44.
The counter electrode side partial pressure value Vb multiplied by the ratio α is subtracted from the sample electrode side partial pressure value Va measured in 1.

Next, the polarization resistance r1 at the sample electrode 27 is obtained from the equation (12). The process of obtaining the polarization resistance r1 is the polarization resistance calculation process. As a result, the polarization resistance r1 is obtained by the following equation (13).

[0057]

(Equation 13)

In order to realize this polarization resistance calculation process, the divider 45 calculates Va-αVb obtained by the subtractor 44 with respect to Va-αVb.
The division is performed using the AC constant current i supplied from the AC constant current circuit 47.

In this case, the correction circuit 52 shown in FIG. 7 performs a correction process for multiplying the division result obtained by the divider 45 by the value of 1 / (1-α) obtained from the ratio α. To do.

On the other hand, when a material having excellent corrosion resistance such as a noble metal is used for the reference electrode 28 and the counter electrode 29, E2 = E
Since 3 = 0 and r2 = r3 = 0, the formula (8) is simplified to the formula (14) shown below, and the formula (9) is replaced by the formula (15).
It is simplified to.

[0061]

[Equation 14]

[0062]

(Equation 15)

Multiplying both sides of expression (15) by the ratio α, expression (1
Subtracting each side from 4), elements RW1 · i and RW2 · i of the solution resistance partial pressure value are excluded from Va-αVb, and the elements of the solution resistance partial pressure value are excluded from the equation (16). )
Is obtained.

[0064]

(Equation 16)

In this case, the voltage measuring device 4
The counter electrode side partial pressure value Vb multiplied by the ratio α is subtracted from the sample electrode side partial pressure value Va measured in 1.

Next, the polarization resistance r1 at the sample electrode 27 is obtained from the equation (16). The process of obtaining the polarization resistance r1 is the polarization resistance calculation process. As a result, the polarization resistance r1 is obtained by the following equation (17).

[0067]

[Equation 17]

In order to realize this polarization resistance calculation process, the divider 45 calculates the value of Va-αVb calculated by the subtractor 44 as follows.
The division is performed using the AC constant current i supplied from the AC constant current circuit 47.

In this case, the corrosion potential E in equation (17)
1 can be easily known as a potential measured between the sample electrode 27 and the reference electrode 28 when a current is not applied between the sample electrode 27 and the counter electrode 29. Therefore, the calculation process performed by the divider 45 for realizing the polarization resistance calculation process of the equation (17) is a division of (Va-αVb) / i, but the value of E1 / i is subtracted from this division result. The correction process enables accurate measurement of the polarization resistance r1.

Therefore, the correction circuit 52 shown in FIG.
The value obtained from No. 5 is used as the corrosion potential E generated at the interface of the electrode depending on the material of the sample electrode 27, the type of solution, and the state.
The correction process is performed using 1 and the alternating constant current i flowing between the sample electrode 27 and the counter electrode 29.

As described above, according to the first embodiment, in the measurement of the polarization resistance by the four-electrode type, the sample electrode side partial pressure value Va and the fourth electrode side partial pressure value Vb are measured to obtain these values. Since the ratio α is a constant, the subtraction process of Va−αVb is performed to eliminate the element of the solution resistance partial pressure value due to the solution resistance,
The configuration is such that the polarization resistance r1 of the sample electrode 27 is obtained. Also,
When it is necessary to consider the corrosion potential due to the difference in the material of each electrode at this time, the correction circuit 52 performs the correction process. Therefore, it is possible to perform accurate corrosion rate measurement with reduced measurement error due to solution resistance without using a conductivity meter and without narrowing the interval between the electrodes of the electrode section 22.

Further, in the measurement of the polarization resistance by the three-electrode type, the sample electrode side partial pressure value Va and the counter electrode side partial pressure value Vb are measured, and the ratio α between them is a constant, so Va−αVb
In this configuration, the polarization resistance r1 of the sample electrode 27 is obtained by eliminating the element of the solution resistance partial pressure value due to the solution resistance by performing the subtraction process of. When it is necessary to consider the corrosion potential due to the difference in the material of each electrode at this time, the correction circuit 52 performs the correction process. Therefore, it is possible to perform accurate corrosion rate measurement with reduced measurement error due to solution resistance without using a conductivity meter and without narrowing the interval between the electrodes of the electrode section 22.

The above embodiment also has the following features as a method and apparatus.

A ratio multiplication process of multiplying one of the divided pressure values by a ratio of each divided pressure value measured in the divided pressure value measurement process, and one of the ones multiplied by the ratio in the ratio multiplication process. Since the solution resistance element excluding step includes a subtracting step of removing the solution resistance partial pressure value element by the solution resistance value by obtaining the difference between the partial pressure value and the other partial pressure value, the solution by the subtracting step is configured. The polarization resistance in which the measurement error due to the resistance partial pressure value element is reduced can be obtained, and the corrosion rate can be accurately measured.

A predetermined calculation is performed based on the subtraction result of the solution resistance partial pressure value element obtained in the subtraction process and the constant current value flowing between the sample electrode and the counter electrode to obtain the polarization resistance value at the sample electrode. Since the polarization resistance calculating step for obtaining the above is provided, it is possible to obtain the polarization resistance in which the measurement error due to the solution resistance partial pressure value element is reduced by the subtraction step and the polarization resistance calculating step, and it is possible to obtain accurate corrosion. Can measure speed.

The subtraction result obtained by removing the solution resistance partial pressure value element obtained in the subtraction process and the corrosion potential generated at the interface of each electrode according to the material of each electrode including the sample electrode, the type of the solution, and the state And a constant resistance value flowing between the sample electrode and the counter electrode, a predetermined calculation is performed to configure a polarization resistance calculation step for obtaining a polarization resistance value in the sample electrode. Even if it is different from other electrodes or the material of each electrode is different, the measurement error due to the solution resistance partial pressure value element is reduced and the polarization resistance of the sample electrode considering the corrosion potential of each electrode is calculated. Therefore, the corrosion rate can be measured with high accuracy.

Ratio multiplication by multiplying either the sample electrode side partial pressure value or the counter electrode side partial pressure value by the ratio of the sample electrode side partial pressure value and the counter electrode side partial pressure value measured in the partial pressure value measurement process. Solution resistance element elimination step of eliminating a solution resistance partial pressure value element from a step and a subtraction step of obtaining a difference between the one partial pressure value and the other partial pressure value multiplied by the ratio in the ratio multiplication step. And performing a predetermined calculation between the subtraction result of the subtraction process and the constant current value flowing between the sample electrode and the counter electrode,
Since the polarization resistance calculation step for obtaining the polarization resistance value of the sample electrode is provided, the measurement error due to the solution resistance partial pressure value element is reduced by the subtraction step and the polarization resistance calculation step in the three-electrode system. The polarization resistance can be obtained, and the corrosion rate can be accurately measured.

Ratio multiplication by multiplying either the sample electrode side partial pressure value or the counter electrode side partial pressure value by the ratio of the sample electrode side partial pressure value and the counter electrode side partial pressure value measured in the partial pressure value measurement process. Solution resistance for eliminating a solution resistance partial pressure value element by a solution resistance value from a step and a subtraction step of obtaining a difference between the one partial pressure value and the other partial pressure value multiplied by the ratio in the ratio multiplication step. The element exclusion process, the subtraction result of the subtraction process, a predetermined calculation is performed between the sample electrode, the reference electrode, and the corrosion potential generated at the interface of the counter electrode and the constant current value flowing between the sample electrode and the counter electrode. Since it is configured to include a polarization resistance calculation process for obtaining the polarization resistance value at the sample electrode,
In the electrode type, even when the material of the sample electrode is different from other electrodes or the material of each electrode is different, the measurement error due to the solution resistance partial pressure value element is reduced and the corrosion potential of each electrode is reduced. It is possible to obtain the polarization resistance of the sample electrode in consideration, and it is possible to accurately measure the corrosion rate.

The ratio of the partial pressure value on the sample electrode side and the partial pressure value on the fourth electrode side measured in the partial pressure value measurement process is determined by either one of the partial pressure value on the sample electrode side and the partial pressure value on the fourth pole side. The step of multiplying by the ratio and the step of subtracting the difference between the one partial pressure value multiplied by the ratio in the ratio multiplying step and the other partial pressure value to obtain the solution resistance partial pressure value element by the solution resistance value. A polarization resistance calculation process for obtaining a polarization resistance value of the sample electrode by performing a predetermined calculation based on the solution resistance element elimination process to be eliminated and the subtraction result of the subtraction process and the constant current value flowing between the sample electrode and the counter electrode. In the four-electrode system, the polarization resistance in which the measurement error due to the solution resistance partial pressure value element is reduced can be obtained by the subtraction process and the polarization resistance calculation process, and the corrosion can be performed with high accuracy. Can make speed measurements

The ratio of the sample electrode side partial pressure value and the fourth electrode side partial pressure value measured in the partial pressure value measurement process is determined by either one of the sample electrode side partial pressure value and the fourth electrode side partial pressure value. From the ratio multiplication step of multiplying by and the subtraction step of obtaining the difference between the one partial pressure value and the other partial pressure value multiplied by the ratio in the ratio multiplication step, the solution resistance partial pressure value element by the solution resistance value And the result of the subtraction process, the corrosion potential generated at the interface of the sample electrode, the reference electrode, and the fourth electrode, and the constant current value flowing between the sample electrode and the counter electrode. And a polarization resistance calculation process for obtaining a polarization resistance value in the sample electrode, the sample electrode material is different from other electrodes in the four-electrode system, Solution resistance partial pressure While reducing the measurement error due to element it is possible to obtain the polarization resistance of the sample electrode in consideration of the corrosion potential of each electrode, it is possible to measure the accurate corrosion rate.

A correction circuit for correcting the value obtained by the division circuit based on the measured value of the corrosion potential generated at the interface of each electrode including the sample electrode and the value of the constant current flowing between the sample electrode and the counter electrode. Since it is configured so that even if the material of the sample electrode is different from other electrodes or the material of each electrode is different, the polarization resistance of the sample electrode corrected by the corrosion potential of each electrode Therefore, it is possible to accurately measure the corrosion rate.

[0082]

As described above, according to the first aspect of the invention, at least three or more electrodes including a sample electrode made of the same material as the metal to be measured are immersed in the solution to form the sample electrode and the sample. Each partial pressure value between the three electrodes including the sample electrode when a constant current is applied between the pole and the farthest counter electrode is measured, and the ratio of each solution resistance value between the three electrodes is equal to each partial pressure value. Assuming that the ratio is equal to and constant, the solution resistance partial pressure value element due to the solution resistance value is excluded by the calculation performed between the respective partial pressure values. Then, since the polarization resistance value of the sample electrode is obtained based on the result of the calculation and the constant current value flowing between the sample electrode and the counter electrode, the solution resistance partial pressure at the time of measuring the corrosion rate. The error due to the value element can be reduced, and the corrosion rate can be accurately measured.

According to the invention of claim 2, the sample electrode side partial pressure value between the reference electrode and the sample electrode and the counter electrode side partial pressure value between the reference electrode and the counter electrode are measured and measured. The ratio of the sample electrode side partial pressure value and the counter electrode side partial pressure value is equal and constant to the ratio of the solution resistance value between the sample electrode and the reference electrode and the solution resistance value between the reference electrode and the counter electrode. It is assumed that the calculation is performed between the sample electrode side partial pressure value and the counter electrode side partial pressure value to eliminate the solution resistance partial pressure value element due to the solution resistance value, and the calculation result and the sample electrode Since the polarization resistance value at the sample electrode is obtained based on the constant current value flowing between the counter electrode and the counter electrode,
It is possible to obtain the polarization resistance in which the measurement error due to the solution resistance partial pressure value element is reduced, and it is possible to accurately measure the corrosion rate.

According to the third aspect of the invention, the sample electrode made of the same material as the metal to be measured, the counter electrode, the reference electrode provided between the sample electrode and the counter electrode, and the fourth electrode are immersed in the solution. , A sample electrode side partial pressure value between the reference electrode and the sample electrode and a fourth electrode side partial pressure between the fourth electrode and the reference electrode when a constant current is applied between the sample electrode and the counter electrode The partial pressure value measuring step of measuring the value and the ratio of the measured partial pressure value on the sample electrode side to the partial pressure value on the fourth electrode side are the solution resistance value between the sample electrode and the reference electrode and the reference value. Assuming that the ratio with the solution resistance value between the pole and the fourth pole is equal and constant, the solution resistance is calculated between the sample electrode side partial pressure value and the fourth pole side partial pressure value. A solution resistance element elimination process for eliminating the partial pressure value element, a result of the calculation performed in the solution resistance element elimination process, and the test result. Since it is configured so as to include a polarization resistance calculation process for obtaining the polarization resistance value of the sample electrode based on the constant current value flowing between the pole and the counter electrode, the measurement by the solution resistance partial pressure value element in the four-electrode system is performed. The polarization resistance with reduced error can be obtained, and the corrosion rate can be accurately measured.

According to the invention described in claim 4, when at least three or more electrodes including a sample electrode made of the same material as the metal to be measured are immersed in the solution, the sample electrode is most distant from the sample electrode. A voltage application circuit for applying a voltage between the counter electrode and a constant current, a partial pressure value measuring circuit for measuring each partial pressure value between the three electrodes including the sample electrode, and the partial pressure value measurement The ratio obtained from each of the partial pressure values measured by the circuit, a ratio setting circuit for multiplying one of the partial pressure values measured by the partial pressure value measuring circuit, and the ratio by the ratio setting circuit A subtraction circuit for obtaining the difference between the one divided voltage value and the other divided voltage value, and the value obtained by the subtraction circuit is divided by the value of the constant current flowing between the sample electrode and the counter electrode. Since it is configured to include a division circuit that That measurement errors reduced polarization resistance can be obtained of, there is an effect that can be measured in accurate corrosion rate.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a mounted state of a corrosion rate measuring device that realizes a corrosion rate measuring method according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a structure of an electrode portion of the corrosion rate measuring device according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a structure of an electrode portion of the corrosion rate measuring device according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a corrosion rate measuring device according to the first embodiment of the present invention.

FIG. 5 is an electrical equivalent circuit diagram of a sample electrode, a reference electrode and a counter electrode of an electrode portion of the corrosion rate measuring device according to the first embodiment of the present invention.

FIG. 6 is an electrical equivalent circuit diagram of a sample electrode, a reference electrode, a fourth electrode and a counter electrode of the electrode part of the corrosion rate measuring device according to the first embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a corrosion rate measuring device including a correction circuit according to the first embodiment of the present invention.

FIG. 8 is a conceptual configuration diagram showing a conventional three-electrode type corrosion rate measuring device.

FIG. 9 is a waveform diagram showing the voltage and current of each part of the circuit obtained by performing the conventional AC constant current method.

FIG. 10 is a waveform diagram showing the voltage and current of each part of the circuit obtained by performing the conventional AC constant voltage method.

FIG. 11 is a circuit diagram showing a conventional conductivity meter.

[Explanation of symbols]

 21 Corrosion Rate Measuring Device 25 Solution 27 Sample Electrode 28 Reference Electrode 29 Counter Electrode 30 4th Electrode 41, 42 Voltage Measuring Device (Partial Pressure Value Measuring Circuit) 43 Ratio Setting Device (Ratio Setting Circuit) 44 Subtractor (Subtraction Circuit) 45% Calculator (division circuit) 47 AC constant current circuit (voltage application circuit) 52 Correction circuit E1, E2, E3 Corrosion potential RW1, RW2 Solution resistance r1, r2, r3 Polarization resistance

Claims (4)

[Claims] 1. At least three or more electrodes including a sample electrode made of the same material as the metal to be measured are immersed in a solution, and a constant current is applied between the sample electrode and a counter electrode farthest from the sample electrode. A partial pressure value measuring process of measuring each partial pressure value between three electrodes including a sample electrode, and a ratio of each solution resistance value between the three electrodes is a ratio of each partial pressure value measured by the partial pressure value measuring process. A solution resistance element excluding process of excluding the solution resistance partial pressure value element due to the solution resistance value based on the ratio by performing calculation between the respective partial pressure values assuming equal constant, and the solution resistance element exclusion Based on the result of the calculation of the process and the constant current value flowing between the sample electrode and the counter electrode, a polarization resistance calculation process for obtaining a polarization resistance value of the sample electrode that is inversely proportional to the corrosion rate is provided. Characteristic method of measuring corrosion rate. 2. A sample electrode made of the same material as the metal to be measured, a counter electrode, and a reference electrode provided between the sample electrode and the counter electrode are immersed in a solution, and the polarization resistance of the sample electrode is inversely proportional to the corrosion rate. In a corrosion rate measuring method of measuring a value and measuring a corrosion rate of the metal to be measured in the solution based on the measured polarization resistance value, in the case of applying a voltage between the sample electrode and the counter electrode, A sample electrode side partial pressure value between the reference electrode and the sample electrode, and a partial pressure value measuring step of measuring the counter electrode side partial pressure value between the reference electrode and the counter electrode, and the partial pressure value measuring step. The ratio between the measured partial pressure value on the sample electrode side and the partial pressure value on the counter electrode side is equal to the ratio between the solution resistance value between the sample electrode and the reference electrode and the solution resistance value between the reference electrode and the counter electrode. And, assuming that the sample electrode side partial pressure value and the counter electrode A solution resistance element excluding step of excluding a solution resistance partial pressure value element based on the solution resistance value based on the ratio, and a result of the operation of the solution resistance element excluding step. A method for measuring a corrosion rate, comprising: a polarization resistance calculation process for obtaining a polarization resistance value at the sample electrode based on a constant current value flowing between the sample electrode and the counter electrode. 3. A sample electrode made of the same material as the metal to be measured, a counter electrode, and a reference electrode and a fourth electrode provided between the sample electrode and the counter electrode are immersed in a solution to form the sample electrode and the counter electrode. Sample electrode side partial pressure value between the reference electrode and the sample electrode when a constant current is applied by applying a voltage between
Partial pressure value measuring step of measuring a fourth pole side partial pressure value between a pole and the reference electrode, the sample pole side partial pressure value and the fourth pole side partial pressure measured by the partial pressure value measuring step Assuming that the ratio with the solution resistance value between the sample electrode and the reference electrode and the solution resistance value between the reference electrode and the fourth electrode is equal and constant, the sample electrode A solution resistance element excluding process of performing an operation between the side partial pressure value and the fourth pole side partial pressure value to eliminate the solution resistance partial pressure value element due to the solution resistance value based on the ratio, and the solution resistance A polarization resistance calculation step for obtaining a polarization resistance value of the sample electrode inversely proportional to the corrosion rate based on the result of the calculation performed in the element exclusion process and the constant current value flowing between the sample electrode and the counter electrode. A method for measuring corrosion rate, characterized in that 4. A voltage is applied between the sample electrode and a counter electrode farthest from the sample electrode when at least three electrodes including the sample electrode made of the same material as the metal to be measured are immersed in the solution. A voltage application circuit for supplying a constant current, and a voltage division value measurement circuit for measuring each voltage division value between the three electrodes including the sample electrode,
A ratio setting circuit for multiplying a ratio obtained from each of the divided voltage values measured by the divided voltage value measuring circuit to any one of the divided voltage values measured by the divided voltage value measuring circuit, and the ratio setting circuit. A subtraction circuit for obtaining a difference between the one partial pressure value and the other partial pressure value multiplied by the ratio, and the constant obtained by flowing the value obtained by the subtraction circuit between the sample electrode and the counter electrode. A corrosion rate measuring device, comprising: a division circuit that divides the current value.