JPS61108954A - Probe for measuring coat film - Google Patents

Abstract

PURPOSE:To detect and evaluate the deterioration of a coat film precisely and simply by forming a sponge-like electrode arranged on a surface opposed to the coat film so as to be a projected surface, and a vessel for storing conductive gell impregnated in the electrode. CONSTITUTION:When a coat film measuring probe is abutted upon a surface to be measured on the coat film 2, the probe is contacted with the surface to be measured from its center part without fail because the sponge-like electrode 11 on the leading end part of the probe body 8 is formed like a projected surface, and even if an air bubble is generated between the coat film 2 and the electrode 11, the air bubble is pushed out to the external periphery. Thereby, the electrode 11 is completely and tightly adhered to the surface to be measured of the coat film 2 and fixed by magnetic adsorbing force between a magnet 15 and a ground metal 1. The conductive gel 3 is impregnated into the electrode 11 and adhered to the whole surface to be measured. The change of pressure in the gel tank which may be generated when the electrode 11 is pressed or pealed against/from the surface to be measured is buffered by the expansion/contraction of bellows 9. Since the probe body 8 is fixed by the magnet 15 at the time of measurement, the probe body 8 can be fixed on any position and the impedance of the coat film can be measured simply and precisely.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a coating film measurement probe, and in particular, electrochemical measurement of the deterioration of coating films applied to metal surfaces for purposes such as rust prevention and aesthetic finishing. The present invention relates to a coating film measurement probe suitable for quantitative detection and evaluation.

[Technical background of the invention]

Generally, when detecting and evaluating the deterioration of a coating on a metal surface, an electrochemical evaluation method using a configuration as shown in the conceptual diagram of FIG. 5 is implemented. As shown in the figure, in the evaluation, a measuring electrode 4 such as A1 foil is brought into contact with a coating film 2 to be evaluated coated on a base metal 1 via a conductive gel 3. Next, an alternating voltage is applied between the base metal 1 and the measurement electrode 4 using a current power source 6 via an ammeter 5. The voltage applied at this time is read by a voltmeter 7 connected between the base metal 1 and the measuring electrode 4.

Generally, the coating film 2 has a very high electrical resistance in a normal state after coating, and has a DC resistance of 10 8 Ω-art or more. When the coating film 2 is normal, the electrical equivalent circuit of the coating WA2 is represented by a parallel circuit of a resistance Rf and a capacitance Of as shown in the equivalent circuit diagram of FIG. On the other hand, when the coating film 2 deteriorates, this resistance Rf
As the impedance decreases, the impedance changes from a simple equivalent circuit as shown in FIG. 6 to a complex impedance having multiple time constants. However, at the initial stage of deterioration, it is possible to treat it as a parallel circuit of a resistor Rf and a capacitor Cf.

The impedance Z (jω) of the coating film 2 can be determined from equation (1) based on the voltage and current measured through the configuration shown in FIG.

Z(jω)−e(jω)/i (jω) (1) where ω is the angular frequency, e(jω) is the voltage, and i(jω) is the current. In addition, another indicator of deterioration, tan
δ can be determined from equation (2).

tan6-I2ml/1Zel-(2) where Zm is the imaginary part of impedance, and Ze is the real part of impedance. Incidentally, the real part is the phase component when impedance is obtained by pure resistance. As the coating film deteriorates, the resistance Rf in FIG. 6 decreases, and when the same AC voltage e(jω) is applied, i'(jω) increases and the impedance Z(jω) decreases. Similarly, as resistance Rf decreases, 17el decreases and ta
nδ increases. By measuring the impedance or tan δ of the paint film 2 in this manner, deterioration of the paint film can be detected.

Changes in impedance before and after the paint film 2 deteriorates are shown in the characteristic diagrams of FIGS. 7 and 8. Incidentally, FIG. 7 is a plot of the absolute value of impedance versus frequency (logarithm), and is generally referred to as a Bode diagram. Compared to the impedance curve a of an undegraded paint film, as the paint film deteriorates, the impedance decreases markedly on the lower frequency side as shown in the curve. Therefore, when detecting deterioration only from the absolute value of impedance, it is more effective to measure at a lower frequency.

On the other hand, FIG. 8 shows the impedance as a real part and an imaginary part, which is generally expressed as a complex diagram in a form called a Nyquist diagram. As the coating WA2 deteriorates, the semicircle of the impedance locus d becomes smaller and the circle becomes deformed compared to the normal case (curve C). The degree of deterioration of the paint film can be estimated from this shape.

[Problems with background technology]

As described above, deterioration of the coating station 12 can be detected from the results of measuring the impedance of the coating film 2 through the configuration shown in the conceptual diagram of FIG.

However, in order to perform accurate measurements using this method, it is necessary to place the measurement electrode 4, such as aluminum foil, on the coating film 2.
It is necessary to keep it in close contact with the For this reason, conventional measures have been taken to reduce measurement errors by applying conductive gel 3 to the surface to be measured.

However, when the surface to be measured on the coating film 2 corresponds to a ceiling surface or a concave surface, bubbles M are generated in the conductive gel 3, as shown in FIGS. 9(a) and 9(b). This tends to lead to a situation where it is extremely difficult to remove the generated Qi aM. In this case, the conductive gel 3 is not present on the entire surface of the coating film 2 to be measured, and the measurement area between the measurement electrode 4 and the coating film 2 is not constant. This causes an error in the impedance measurement result, making it impossible to measure the original impedance of the paint film 2, and making it impossible to accurately detect the deterioration of the paint film 2.

[Purpose of the invention]

Therefore, an object of the present invention is to provide a coating film measurement probe that solves the problems of the prior art described above and makes it possible to accurately and easily detect and evaluate the deterioration of a coating film applied to the surface of a metal structure. There is something to do.

[Summary of the invention]

In order to achieve the above object, the present invention provides a coating film measurement method comprising a sponge-like electrode disposed in a convex manner on a surface facing the coating film, and a container containing a conductive gel to be impregnated into the sponge-like electrode. It provides a probe.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a coating film and a measurement probe according to an embodiment of the present invention, with FIG. 1(a) showing a sectional view and FIG. 1(b) showing a bottom view. On the other hand, FIG. 2 is an explanatory diagram showing a state in which the coating film impedance of a concave portion of the coating film is measured using the coating film measurement probe shown in FIG. 1.

Now, as shown in FIG. 1, a perforated plate 10 to which a bellows 9 is attached is disposed inside the probe body 8, and a sponge-like electrode 1 whose outer surface (measured surface side) is convex is disposed at the tip.
1 is attached.

Furthermore, an air vent hole 12 is provided above the hollow 9 of the probe body 8, and a gel injection port 13 for injecting the conductive gel 3 is provided on the side surface.

The conductive gel 3 is injected into a gel bath consisting of a sponge-like electrode 11, a porous plate 10, and a bellows 9 through an injection port 13. The conductive gel 3 is coated with copper I! as a lead wire. 14 are connected. By the way, as the conductive gel 3, 3% saline solution and 3% thickener (carboxyl methyl cellulose, etc.) can be used.The lower end of the probe body 8 can be coated with the probe body 8 when measuring the coating film impedance. A magnet 15 is attached for fixing to the membrane.

The operation of this configuration will now be explained with reference to the explanatory diagram of FIG. 2. When the coating film measurement probe configured as shown in FIG. The surface side is always contacted from the center, and even if air bubbles are generated between the coating film 2 and the sponge-like electrode 11, they are pushed out to the outer periphery. Therefore, the sponge-like electrode 11 is finally
is in close contact with the entire surface of the coating film 2 to be measured, and is fixed by the magnetic attraction force between the magnet 15 and the base metal 1. The conductive gel 3 has soaked into the sponge-like electrode 11 and adheres to the entire surface of the coating film to be measured. Furthermore, changes in the pressure within the gel bath that occur when the sponge electrode 11 is pressed against or peeled off from the surface to be measured are buffered by the expansion and contraction of the bellows 9.

Since the probe body 8 is fixed by the magnet 15 during measurement, it can be securely fixed on any slope, vertical surface, or ceiling surface, making it possible to easily and reliably measure the coating film impedance.

Now, the results of measuring the paint film impedance of the epoxy thick film paint using the paint film measurement probe of this example are shown in Table 1 below. As is clear from Table 1, the measurement results are almost the same as those obtained when aluminum foil electrodes are used, and the coating film measuring probe of this example works effectively in measuring coating film impedance.

Table 1. Coating film of epoxy thick film paint In the above embodiment, the shape of the sponge-like electric wire IN+11 was circular, but as shown in FIG. 3(a).

By making the electrode shape square or rectangular as shown in the explanatory diagram (b), it becomes possible to measure the impedance of the coating film, for example, in the case of a curved surface where the entire surface of the electrode would not be in close contact with a circular electrode.

Further, the material of the sponge-like electrode 11 may be a polyurethane sponge or a rubber sponge.
In either case, it adheres sufficiently to the coating film 2 and enables effective impedance measurement.

FIGS. 4(a) and 4(b) show cross-sectional views of coating film measuring probes according to other embodiments and other embodiments of the present invention, respectively. Figure (a) exemplifies a configuration in which the pressure change in the conductive gel bath that occurs when the sponge-like electrode 11 is brought into close contact with the surface to be measured is buffered by the expansion and contraction of the thin rubber membrane 16 attached to the upper part of the porous plate 10. It is something. On the other hand, FIG. 2B shows an example of a configuration in which pressure changes in the conductive gel tank are buffered by a damper 18 equipped with an extremely low pressure spring 17.

〔Effect of the invention〕

As described above, according to the present invention, when measuring the paint film impedance, it is possible to measure the paint film impedance regardless of whether the paint film surface to be measured is a slope, a vertical surface, a ceiling surface, or a concave or convex surface. In addition, 1. It is possible to prevent the generation of air bubbles within the measurement surface even in areas where air bubbles are likely to occur when applying the adhesive gel, and to accurately measure impedance for detecting paint film deterioration. This makes it possible to obtain a coating film measurement probe that enables the following.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are a cross-sectional view and a bottom view of a coating film measurement probe according to an embodiment of the present invention, and FIG. An explanatory diagram showing a state in which paint film deterioration is electrochemically evaluated. Figures 3 (a) and (b) are explanatory diagrams showing other examples of electrode shapes. Figures 4 (a> and (b) are FIG. 5 is a conceptual diagram showing a well-known method for electrochemically evaluating paint film deterioration, and FIG. 6 is an explanatory diagram showing another embodiment of the present invention and another example. Figure 7 is a characteristic diagram showing changes in frequency dependence of impedance due to deterioration of the paint film, Figure 8 is a characteristic diagram representing Figure 7 on a complex plane, Figure 9 (a) , (b) is an explanatory diagram showing problems when using A1 foil electrodes. 1... Base metal, 2... Paint film, 3... Conductive gel, 8... Probe body , 9...be0-110...
- Porous plate, 11... sponge-like electrode, 14... lead wire, 15... magnet. Applicant's agent Kiyoshi Inomata Figure 1 (α) Cb) Figure 3 (0L) (b) Figure 4 (α) (b) Figure 5 Figure 6 f

Claims (1)

[Claims] 1. A coating comprising a sponge-like electrode disposed in a convex manner on a surface facing the coating film, and a container containing a conductive gel to be impregnated into the sponge-like electrode. Membrane measurement probe. 2. The coating film measuring probe according to claim 1, characterized in that a magnet is arranged around the sponge-like electrode. 3. The coating film measurement probe according to claim 1, wherein the container is configured to absorb the pressure of the conductive gel. 4. The coating film measuring probe according to claim 3, wherein the container has a bellows shape.