JPH06324014A - Probe for measuring paint film impedance - Google Patents

Abstract

PURPOSE:To measure the paint film impedance of an equipment dipped in a liquid. CONSTITUTION:An electrode 10 for measurement is allowed to contact a paint film 2 which exists in a liquid such as water and is energized to measure the impedance of the paint film 2. In this case, guard electrodes 15 which are formed in cylindrical shape and whose one edge part contacts the paint film are laid out in the radius direction in multiples. Leak current generated at a part in contact with the electrode 10 for measurement flows to the guard electrode 15, thus preventing it from flowing to the electrode 10 for measurement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating impedance measurement suitable for electrochemically detecting and evaluating deterioration of a coating applied to a metal surface of a device immersed in a liquid such as water. For probes.

[0002]

2. Description of the Related Art Electrical equipment installed outdoors is coated for corrosion protection and aesthetic purposes, but if the coating film is left to deteriorate, the coating film will eventually peel off or the underlying metal will corrode. Therefore, it is necessary to perform maintenance such as repainting at an appropriate time. Therefore, the degree of deterioration of the coating film is quantitatively diagnosed by utilizing the fact that the electric resistance value of the coating film decreases and the impedance of the coating film changes as the coating film deteriorates.

As a device for measuring such coating film impedance, the device shown in FIG. 5 has been conventionally provided. That is, this is a coating film 2 on the surface of the base metal 1.
A measurement electrode 4 made of aluminum foil or the like is applied to the electrode via a conductive gel 3, a voltage is applied between the base metal 1 and the measurement electrode 4 using an AC power supply 5, and a current is measured by a current measuring device 6. In addition to measuring the current, the voltage measuring device 7 measures the applied voltage. Then, the coating film impedance for each frequency is calculated from the measured current value and voltage value, and a Bode diagram or a Nyquist diagram is created to determine the degree of deterioration of the coating film 2.

On the other hand, in recent years, a method of using a coating film deterioration measuring probe shown in FIG. 6 has been considered in order to improve the measurement accuracy. The coating film impedance measuring probe 8 contains a measuring electrode 10 having a spherical convex surface on the lower surface, which is made by containing a conductive gel in a sponge in a substantially cylindrical plastic body case 9 having an open lower surface. Is configured. Further, a tin foil 11 that contacts the measuring electrode 10 (conductive gel) is provided on the inner wall surface of the main body case 9, and the tin foil 11 is connected to the connection terminal 12.

On the other hand, a male screw portion 9a is formed on the outer peripheral portion of the main body case 9, and a holding ring 14 having a magnet 13 on the lower surface is screwed into the male screw portion 9a. At the time of measuring the coating film impedance, the coating film impedance measuring probe 8 is fixed on the coating film 2 by the magnet 13 of the pressing ring 14, so that the measuring electrode 10 is brought into close contact with a certain area of the coating film 2. It has become.

[0006]

By the way, some of the devices provided with this type of coating film 2 are placed in a liquid such as water rather than in the atmosphere. The coating film impedance measuring probe 8 described above has no problem in use in the atmosphere, but was not suitable for measuring the impedance of the coating film 2 immersed in water. That is, when the conventional coating film impedance measuring probe 8 is used, in addition to the current flowing through the coating film 2 in a predetermined area which is in contact with the measuring electrode 10 in water, the coating film 2 in the peripheral portion of the measuring electrode 10 is also used. The current (leakage current) flowing through the water will also be measured. Since the diagnosis of the coating film deterioration is performed based on the impedance with respect to a certain area of the coating film 2, if the measured current value includes the leakage current around the measuring electrode 10, it is meaningless to measure. Therefore, it becomes impossible to accurately diagnose the deterioration of the coating film.

When water enters the measuring electrode 10, the conductive gel contained in the sponge of the measuring electrode 10 leaks out from the measuring electrode 10 and diffuses into the water, so that the liquid is not contaminated. There is a problem that the conductivity of the liquid is increased.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a coating film impedance measuring probe capable of measuring the coating film impedance of a device immersed in a liquid.

[0009]

The probe for measuring coating film impedance of the present invention measures the deterioration of the coating film by bringing the measuring electrode into contact with a coating film existing in a liquid such as water and applying electricity thereto. In this configuration, a plurality of guard electrodes, which are formed in a cylindrical shape and one end of which is in contact with the coating film, are arranged in the radial direction around the measuring electrode.

Around the measuring electrode, a plurality of circular projections are formed in a cylindrical shape at one end thereof in the radial direction, and a guard electrode is arranged so that these projections come into contact with the coating film. It is characterized by

Further, a plurality of annular projections, which are formed in a cylindrical shape, are formed at one end of the measuring electrode in the radial direction, and the groove between the projections is made of a conductive rubber. It is also possible to insert a ring and configure the guard electrode to contact the coating through this contact ring.

In this case, a contact ring made of a light metal such as an aluminum alloy may be inserted into the groove between the protrusions via a spring so that the contact ring contacts the coating film.

[0013]

According to the coating film impedance measuring probe of the present invention, the guard electrode can be brought into close contact with the coating film in the peripheral portion of the measuring electrode. Therefore, even if this probe is used in a liquid, leakage current generated in parts other than the part in contact with the measurement electrode flows to the guard electrode and is prevented from flowing to the measurement electrode. It is possible to accurately measure the coating film impedance of a constant area portion.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The coating film impedance measuring probe according to the present embodiment has a columnar shape, and has a probe main body case 9 and a measurement electrode 10 loaded in the lower portion of the main body case 9. The measuring electrode 10 is connected to a lead wire 16a penetrating the body case 9, and is connected to the current measuring device 6, the voltage measuring device 7 and the AC power supply 5 via the lead wire 16a. A male screw portion 9a is formed on the outer periphery of the main body case 9, and the same plastic fixing ring 17 as that of the main body case 9 is screwed onto the male screw portion 9a. A cylindrical guard electrode 15 made of light metal such as aluminum is provided under the fixing ring 17.
Are multiply arranged in the radial direction, and these guard electrodes 15 are connected together between the current measuring device 6 and the AC power source 5 via a lead wire 16b that is collectively connected in the fixed ring 17 and has an insulating coating. . Further, each guard electrode 15 has a length in the axial direction that comes into contact with the coating film 2, and can be in close contact with the coating film 2 together with the measuring electrode 10 in which a sponge contains a conductive gel.

The coating film impedance measuring probe constructed in this manner is installed on the surface of the coating film 2 on the base metal 1, and the guard electrode 15 together with the measuring electrode 10 is brought into close contact with the surface of the coating film 2. . In this state, a voltage is applied between the base metal 1 and the measurement electrode 10 and the guard electrode 15 by using the AC power supply 5, and measurement is performed by the current measuring device 6 and the voltage measuring device 7.

Table 1 shows the case where the guard electrodes 15 having a thickness of 1.5 mm are arranged in a radial triple manner at intervals of 2 mm on the outer peripheral portion of the measuring electrode 10 having a diameter of 17 mm, and the case where no guard electrode is arranged. The coating film impedance value measured in water is shown.

[0017]

[Table 1]

According to this embodiment, since the guard electrode 15 is multiply provided around the measuring electrode 10, the leakage current generated in the portion other than the portion in contact with the measuring electrode 10 flows to the guard electrode 15. Of the conductive material contained in the sponge of the measurement electrode 10 because water does not enter the main body case 9 because the flow of water to the measurement electrode 10 is blocked and the guard electrode 15 is in close contact with the coating film 2. Gel is the measuring electrode 10
It does not leak out and diffuse into the water. Therefore, Table 1
As is clear from the above, according to the present embodiment in which the guard electrode 15 is provided, the current measuring device 6 and the voltage measuring device 7 can accurately measure the coating film impedance of the constant area portion in contact with the measuring electrode 10. You can

FIG. 2 shows another embodiment of the guard electrode 15 arranged on the outer peripheral portion of the main body case 9. The guard electrode 25 is formed of a light metal such as aluminum in a cylindrical shape, and is formed in a comb shape below the guard electrode 25. A large number of protrusions 25a are formed. Also in the guard electrode 25 configured in this manner, as in the above-described embodiment, the leakage current generated in a portion other than the portion in contact with the measurement electrode 10 is passed to the guard electrode 15 and does not flow to the measurement electrode 10. You can

In FIG. 3, the lower portion of the guard electrode 35 is formed into an annular shape to provide a plurality of protrusions, and a cylindrical contact ring 18 made of a conductive rubber is inserted into a groove 35a formed between the protrusions. It is arranged. According to this configuration,
Due to the elastic force of the contact ring 18, the guard electrode 35 can be brought into close contact with the surface of the coating film, such as unevenness and curvature.

In FIG. 4, the spring 20 is embedded in the groove 45a provided in the lower portion of the guard electrode 45, and the contact ring 19 made of a light metal such as aluminum is inserted and fitted in the lower portion thereof. Thus, the guard electrode 45 is closely attached according to the surface condition of the coating film.

The spring 20 embedded in the groove 45a may be a spiral spring over the entire annular groove 45a, but a small diameter spring is inserted in each of the groove 45a. May be.

According to the coating film impedance measuring probe shown in FIGS. 3 and 4, the elastic force of the contact ring 18 or the elastic force of the spring 20 allows the coating film to be surely brought into close contact with the curved surface. Highly accurate impedance measurement is possible even in water.

[0024]

As is apparent from the above description, the coating film impedance measuring probe of the present invention can bring the guard electrode into close contact with the coating film in the peripheral portion of the measuring electrode. Even when used inside, it is possible to prevent leakage current generated in parts other than the part in contact with the measurement electrode from flowing to the guard electrode and flowing into the measurement electrode, and to apply the coating on the part of a certain area in contact with the measurement electrode. The membrane impedance can be measured accurately.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a coating film impedance measuring probe according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

FIG. 3 is a sectional view showing another embodiment of the present invention.

FIG. 4 is a sectional view showing another embodiment of the present invention.

FIG. 5 is a sectional view showing a conventional example.

FIG. 6 is a sectional view showing another conventional example.

[Explanation of symbols]

Reference numeral 1 is a base metal, 2 is a coating film, 9 is a body case, 10 is a measuring electrode, 15, 25, 35 and 45 are guard electrodes, 17 is a fixing ring, 18 and 19 are contact rings, and 20 is a spring.

Claims (4)

[Claims] 1. A method for measuring impedance of a coating film existing in a liquid such as water by bringing the measuring electrode into contact with the coating film and energizing the coating film to measure the impedance of the coating film. A coating film impedance measuring probe, wherein a plurality of guard electrodes each having a cylindrical shape and one end of which is in contact with the coating film are arranged in a radial direction. 2. A method of measuring the impedance of a coating film existing in a liquid such as water by bringing the measuring electrode into contact with the coating film and energizing the coating film to measure the impedance of the coating film. For coating film impedance measurement, which is formed in a cylindrical shape, and a plurality of annular projections are formed in the radial direction at one end thereof, and a guard electrode is arranged so that these projections contact the coating film. probe. 3. The impedance of the coating film is measured by bringing the measuring electrode into contact with a coating film existing in a liquid such as water and energizing the coating film. , A plurality of annular projections are formed in a radial direction on one end of the cylindrical shape, and a contact ring made of conductive rubber is inserted into the groove formed between the projections. A coating film impedance measuring probe, characterized in that a guard electrode is arranged so as to come into contact with the coating film via the. 4. A cylindrical electrode is formed around a peripheral portion of the measuring electrode, and a plurality of annular projections are formed at one end thereof in the radial direction. A spring is provided in a groove formed between the projections. The probe for coating film impedance measurement according to claim 3, wherein a contact ring made of a light metal is inserted through the contact ring, and a guard electrode is arranged in contact with the coating film through the contact ring.