JPH0619339B2 - Highly sensitive polarization measuring method and apparatus for coated metal - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method and an apparatus for highly sensitively measuring a corrosion reaction of a metal coated with a coating material, a lining material or the like by an external polarization method.

[Prior Art] An external polarization method is known as a method for measuring the corrosion reaction behavior of a coating metal coated with a coating material or a lining material (hereinafter referred to as a coating metal) (for example, Japanese Patent Publication No. 53-316). That is,
DC voltage is applied to corrosive metal in arbitrary corrosive liquid while maintaining a certain magnitude or increasing / decreasing linearly at a certain speed. At this time, change in flowing current or change in electric potential is measured and polarization resistance is measured. , Corrosion current, polarization curve (potential-current curve), electric resistance or electric double layer capacity of the coating film, electric capacity of the coating film, etc. Further, instead of the magnitude of the above-mentioned constant value and the linear increase / decrease, a method of applying an AC wave, a pulse wave or a DC + pulse wave is also known.

As a device for measuring the corrosion reaction behavior of the coated metal, a so-called external polarization device, potentiostat (constant potential electrolysis device), galvanostat (constant current electrolysis device), coulostat (constant electric quantity electrolysis device), current interface There is a raptor method electrolysis device and the like. Now, as a typical example of these devices, a basic configuration circuit (block diagram) of a potentiostat is shown in FIG. In the measurement cell container 1, a corrosive liquid 2, a counter electrode C, a standard electrode R (or referred to as a reference electrode), and a coating metal W that is a measurement electrode are provided. The coating metal W is grounded, the reference electrode R is grounded to one input a of the DC differential amplifier (operational amplifier) 4, and also via the potentiometer 5. The counter electrode C is connected to the output d of the DC differential amplifier 4 via the ammeter 6. Further, one input b of the DC differential amplifier 4 is grounded via the DC power supply 7. Further, in order to operate the DC differential amplifier 4, a DC voltage + 15V and -1 obtained by rectifying a commercial power supply.
5V is supplied and the zero volt line is grounded.

Now, the operation of the potentiostat will be described with reference to FIG. For example, with respect to the reference electrode R, the potential (R
The potential of W or the potential difference between R and W when viewed from −0.
Assuming that the voltage is 5V, if the voltage of the DC power supply 7 is set to + 0.5V, the input value of the DC differential amplifier 4, that is, the potential difference between a and b becomes approximately 0 volt. In this state, the coating metal is electrolyzed in the vicinity of the potential of the natural electrode, and at this time, the electrolytic current (current value detected by the ammeter 6) flowing through the coating metal W becomes approximately zero amperes. Then, the voltage of the DC power supply 7 +0.5
When a certain voltage E is applied to V (or E is increased or decreased at a certain speed), a current I is detected by the ammeter 6, and from the relationship between E and I, the coating film is Values such as the polarization resistance near the lower metal surface, the polarization curve, the corrosion current, the electric resistance of the electric double layer container, or the coating film can be calculated.

[Problems to be Solved by the Invention] As the electric resistance of the coating film on the metal increases, the corrosion reaction behavior of the metal surface under the coating film (eg, polarization curve, corrosion current,
When behaviors such as polarization resistance and electric double layer capacity; these are hereinafter referred to as corrosion reaction behaviors) are measured, noise enters the external polarization measuring device and the coating metal, and it becomes difficult to satisfactorily detect this corrosion reaction behavior. Therefore, conventionally, a filter circuit for noise removal or a noise removal simulation solution using a computer is known, but there are drawbacks such as a decrease in response speed or an extremely complicated solution technology. It is not a method to raise the measurement sensitivity sufficiently. In addition, the actual measurement site is not necessarily in a good environment like a laboratory, but is easily affected by humidity and grounding. Therefore, even if a coating material that is supposed to have excellent corrosion resistance is developed or put into practical use, its corrosion resistance cannot be sufficiently grasped, and a satisfactory evaluation value cannot be selected or standardized. Therefore, establishment of a method and an apparatus for highly sensitively detecting and measuring the corrosion reaction behavior of the coated metal is strongly desired.

It is an object of the present invention to provide a method and device for sensitively measuring the corrosion reaction behavior of coated metals.

[Means for Solving Problems] A method for measuring a highly sensitive polarization of a coated metal according to the present invention is a coating material,
When measuring the corrosion reaction behavior of a coating metal coated with a lining material by the external polarization method, a battery is used as the power source of the external polarization device connected to the measurement system including the coating metal, and the external polarization device is used. While maintaining the insulation resistance of 10 ¹³ Ω or more with respect to the ground and the battery, the corrosion reaction behavior of the coating metal in the measurement system including the coating metal is measured by an external polarization device.

The high-sensitivity polarization measuring device according to the present invention is a device for measuring the corrosion reaction behavior of a coating metal coated with a coating material, a lining material or the like by an external polarization degree, and a coating metal electrode, a reference electrode and a counter electrode are made into a conductive solution. A measuring cell that is immersed, an external polarization device that measures the corrosion reaction of the measuring cell by an external polarization method, a battery that is an electrode of the external polarization device, a first metal container that houses the external polarization device, and a battery A second metal container for housing the external polarization device and the first metal container, or a space between the first metal container and a ground point outside thereof is maintained at a resistance of 10 ¹³ Ω or more. Between the first insulating material, the battery and the second metal container, or the second
It is characterized in that it is composed of a second insulating material which holds a resistance of 10 ¹³ Ω or more between the metal container and a ground point outside thereof.

[Operation] An insulation resistance of 10 ¹³ Ω or more is interposed between the external polarization device and the battery with respect to the ground (earth), and
By using a battery as the power source of the external polarization device, noise can be reduced and measurement can be performed with high sensitivity even in the case of measurement of coating metal with high insulation resistance.

EXAMPLES Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 shows a circuit diagram of the external polarization device (potentiostat). As shown in FIG. 2, a corrosive liquid 2 which is a conductive solution, a counter electrode C made of an inert material such as platinum, a standard electrode R (or a reference electrode such as a silver-silver chloride electrode) in a measurement cell container 1 And the coated metal W that is the measurement electrode. And this measuring cell container 1 and these 1, 2,
The container 10 made of metal (generally made of steel plate) that houses the side constant system 3 that collectively refers to C, R, and W is insulated by an insulation resistance R ₁ that is equal to or greater than the internal resistance (10 ¹³ Ω) of a potentiostat described later. There is. If the insulation resistance R ₁ is expected to decrease due to humidity, dirt, etc., the insulation resistance R ₂ is maintained so as to have a resistance of 10 ¹³ Ω or more with respect to the ground A.

When measuring corrosion in seawater, etc., the container 10
Cannot be used. In such a case, the container 10 and the resistors R ₁ and R ₂ may not be used.

The signal lines from the respective electrodes C, R, W of the measurement system pass through the holes provided in the container 10 and the container 100, and inside the metal (preferably steel) container 100 that houses the potentiostat (excluding the power supply). Be introduced to.

In the container 100, the coating metal W is the zero volt line Z.
Is connected to A ₁ point, the reference electrode R is connected a direct current differential amplifier is connected to one end a of the input terminal of the (operational amplifier) 4, and the point A ₂ of zero volts line via a potentiometer 5 ing. The counter electrode C is connected to the output terminal d of the DC differential amplifier 4 via the ammeter 6.
Further, one of the input terminals b of the DC differential amplifier 4 is connected to the point A ₃ of the zero volt line Z via the DC power supply 7. The zero volt terminal of the DC differential amplifier ₄ is connected to the point A4 of the zero volt line Z. Thus, the point A ₁ ,
A ₂ , A ₃ , and A ₄ are connected to a common zero-volt line Z, which is insulated from the potentiostat container 100 by an insulation resistance R ₃ . By setting this resistance to be equal to or higher than the input resistance of the potentiostat (10 ¹³ Ω), the corrosion reaction behavior of the coated metal coated with a normal or special highly anticorrosive paint can be measured with high sensitivity. (Conventionally, in the conventional method for measuring a coated metal disclosed in JP-A-57-80551, etc., the conductor 101 and the potential difference diameter between the reference electrode R and one a of the input terminals of the DC differential amplifier 4 are used. It suffices to insulate the conducting wire 102 tangent to 5 with the insulation resistance of 10 ¹³ Ω or more with respect to the zero volt line Z. However, the present inventors have eliminated noise,
In order to measure with higher sensitivity, the value of R ₃ which has not been noticed by the method disclosed in JP-A-57-80551 is set to 1
It has been found that it is necessary to set it to 0 ¹³ Ω or more. ) However, the container 100 and the zero volt line Z are connected to each other by 10 ¹³
It is difficult to hold with a resistance of Ω or more. That is, all the electric circuit components in the container 100 are
If the insulation resistance of 0 ¹³ Ω or more cannot be achieved, use this container 1
The resistance of the insulation resistance R ₄ between 00 and the ground A may be kept at 10 ¹³ Ω or more.

The operation of the potentiostat is the same as the conventional one. For example, with respect to the reference electrode R, the potential (R
The potential of W or the potential difference between R and W when viewed from −0.
Assuming that the voltage is 5V, if the voltage of the DC power supply 7 is set to + 0.5V, the input value of the DC differential amplifier 4, that is, the potential difference between a and b becomes approximately 0 volt. In this state, the coating metal is electrolyzed in the vicinity of the potential of the natural electrode, and at this time, the electrolytic current (current value detected by the ammeter 6) flowing through the coating metal W becomes approximately zero amperes. The voltage of the DC power supply 7 + 0.5V
When a certain constant voltage E (or E is increased or decreased at a certain speed) is applied, a certain current I is detected by the ammeter 6, and the relationship between E and I causes the coating metal W to be covered. Values such as polarization resistance near the metal surface under the covering film, polarization curve, corrosion current, electric double layer capacitance or electric resistance of the covering film can be calculated.

Next, the output signal 103 of the potentiometer 5 and the output signal 104 of the ammeter 6 are output from the output meter 10 such as a recorder, a calculation circuit, and a display meter.
5 is input so that a desired value relating to the corrosion reaction behavior can be found.

From a DC power supply (battery) 106 composed of a primary battery or a secondary battery, a power supply 107 for an ammeter 6, a power supply 108 for a DC differential amplifier 4, a power supply 109 for a DC power supply 7 for electrolysis of coated metal, and a potentiometer 5 Power supply 110 and output meter 105
A DC voltage is supplied as the power supply 111. And
This battery 106 is a battery container 11
It is insulated with an insulation resistance value R ₅ of 2 and 10 ¹³ Ω or more.
If this resistance is insufficient, the container 112 and the ground A are insulated by an insulation resistance R ₆ of 10 ¹³ Ω or more. Conventionally, the power source for operating the potentiostat is a commercial power source (AC 100V or AC 2
00V) itself or this commercial power source is used after being converted into a DC voltage through a rectifier circuit. However,
There is also a portable type for easy use in the field. In this case, a dry battery is used as the power source, but since it is not intended for high-sensitivity measurement as in the present invention, the zero volt line Z No particular consideration is given to maintaining high insulation between the ground and other parts.

In this example, the potentiostat was used as the external polarization device, but galvanostats, coulostats, current interrupter electrolysis devices, and other types of external electrode devices can also be used with the same configuration and high sensitivity. Measurement becomes possible.

As described above, the present invention holds the resistance between the external polarization device and the ground and the resistance between the battery and the ground with the insulation resistance of 10 ¹³ Ω or more. Be held in an external polariser insulation resistance resistance of more than 10 ¹³ Omega between ground can be realized by holding at R ₃ and at least one of 10 ¹³ Omega more insulation resistance R _4. Further, maintaining the resistance between the battery and the ground with an insulation resistance of 10 ¹³ Ω or more means that at least one of R ₅ and R ₆ is 10 ¹³ Ω.
It can be realized by holding with the above insulation resistance. Furthermore, if necessary, R in the resistance between the measurement system and ground.
_At least one of ₁ and R ₂ is held with an insulation resistance of 10 ¹³ Ω.

If the insulation resistance of the resistors R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ is set to 10 ¹³ Ω or more, for example, a person only approaches these measurement systems, external polarization devices, or batteries. Induced by the measurement value, the measurement is not satisfactory. That is, since the electric resistance of the coating film is extremely high, the electrolysis current becomes extremely small, and is susceptible to induction. Similarly, at the time of measurement operation, you must always touch the switches and knobs installed in the device. However, this is also difficult because of induction. In view of this, in the embodiment shown in FIG. 2, the automatic operation is possible although not shown. And
Containers 10, 100, 112 to protect the entire device from induction
Was used as a magnetic shield box.

FIG. 1 schematically shows the structure of a high sensitivity measuring apparatus according to an embodiment of the present invention. Further, a partial cutaway perspective view of a part of this embodiment is shown in FIG.

The measurement system S including at least the measurement cell container, the corrosive liquid, the counter electrode, and the reference electrode is connected to the input resistance (10 ¹³
It is supported by insulating materials G ₁ and G ₂ having an electric resistance of Ω) or more, and is housed in a container K ₁ made of a steel plate or the like having a magnetic shield function. On the other hand, an external polarization device P such as a potentiostat, a galvanostat or a coulostat, an output device Y such as a recorder, a calculation circuit, a computer or a display meter, and the polarization device P and the output device Y are automatically operated. A programmer / commander T (for this invention, P, Y, and T are collectively referred to as an external polarization system) for this purpose is housed in an internal container K ₂ made of steel or polymer resin, and the internal container K ₂ is supported by insulating materials G ₃ and G ₄ having an electric resistance of 10 ¹³ Ω or more, and is further housed in a container K ₃ such as a steel plate having a magnetic shield function. Further primary battery,
A so-called battery Q such as a secondary battery was supported by insulating materials G ₅ and G ₆ having an electric resistance of 10 ¹³ Ω or more, and this was stored in a container K ₄ made of a steel plate having a magnetic shield function. Further, the electrode wires connecting the external polarization device P and the measurement system S, that is, the counter electrode wire C, the reference electrode wire R, and the coated metal electrode wire W in FIG. 1 are provided in the containers K ₁ , K ₃ and K _Z. Insulation is maintained by passing through these holes and making no contact between these electrode wires and these containers. Similarly, the DC power supply lines D ₁ , D ₂ and D ₃ from the battery Q are also connected to the container K ₂ ,
Insulation is maintained by avoiding contact with K ₃ and K ₄ . Then, the containers K ₁ , K ₃ , and K ₄ are grounded.

As described above, in the present embodiment, the measurement system, the external polarization system, and the DC power source are all insulated with respect to the ground with high insulation of 10 ¹³ Ω or more. Insulation materials G ₁ , G ₂ , G ₃ ,
G ₃ ′, G ₄ , G ₄ ′, G ₅ and G ₆ are made of glass,
Alternatively, it may be made of plastic such as Teflon (registered trademark), and for example, a cylindrical shape having a diameter of 30 mmφ and a height of 50 mm may be used.

Further, when fixing this columnar insulating material, an adhesive is used, or when it is made of plastic, the container K _{3 and} this insulating material are fixed with screws (screws) as shown in FIG.

In addition, when the insulation resistance of the insulating materials G _{1 to} G ₆ may decrease due to moisture on the surface thereof (adhesion of water due to increase in humidity), a compressor A that sends dry air is used to Dry air is injected into the container (however, the insulation is not deteriorated), and air is blown out from the hole of the container through which various conductors are passed, so that the vicinity of the hole is also kept highly insulated.
Alternatively, if a desiccant is put in each container and kept at a low humidity, it is possible to keep a higher insulation.

The difference between the conventional method (using a commercial power supply and not considering insulation) and the method of the present invention will be described with measurement examples. The external polarization method used here is disclosed in Japanese Patent Publication No. 53-43425.
According to JP-B-53-43426 and JP-B-53-316, the corrosion reaction characteristics of the coated metal are measured, and the magnitude of the noise at that time (the magnitude of the noise relative to the average value of the measurement signal including the noise Ratio). An example is shown in Table 1. In addition, Table 2 shows the results of testing the range of insulation resistance that can be measured when the noise level is within 0.5% with the samples in Table 1. Samples are painted steel sheets for automobiles (3 coats,
3 bake; coating system of three layers of electrodeposition, intermediate coating and top coating; film thickness (total 90 μm), measurement area (12.5 cm ² )). The insulation resistance was maintained at 10 ¹⁴ Ω or higher in all cases.

From Tables 1 and 2, it was found that in this example, at least 20 times higher sensitivity was obtained as compared with the conventional method. Further, if a noise removal filter or the like is used, a highly sensitive and accurate measurement value can be obtained.

As an application of the present invention, if it is described with reference to FIG. 1, it is possible to perform measurement without setting the measurement system S in the container K ₁ to a high insulation resistance of 10 ¹³ Ω or more, for example, a salt spray test. It can also be combined with conventional corrosion testers such as machines and wet / wet alternator testers, and can also measure the behavior of coated metals in actual seas, rivers and ponds. However, in this case, since the noise is included, the sensitivity is lowered. However, although it cannot be measured by the conventional method, it can be measured by the method of the present invention. In the polarization measurement of the sample placed inside the salt spray tester or the sample placed in the sea or river, the corrosive liquid is connected to the ground, so the zero-volt line Z and the ground are highly insulated. In the conventional method, which does not, the current flows through the ground, and the current flowing through the sample cannot be measured.

[Effects of the Invention] Metal corrosion reaction covered with paint, lining material, etc.
It became possible to measure even when the coating film resistance was 10 ¹¹ Ω or more.

[Brief description of drawings]

FIG. 1 is a block diagram of a high-sensitivity measuring device by the external polarization method. FIG. 2 is a circuit diagram of the potentiostat. FIG. 3 is a partial cutaway perspective view of the apparatus shown in FIG. FIG. 4 is a sectional view showing fixing of the insulating material. FIG. 5 is a circuit diagram of a conventional potentiostat. S ...... measurement system, P ...... external polariser, Q ...... Batteryi, K _3, K ₄ ...... metal _{container, G 1, G 2, ~} , G 6 ...... insulating material.

Claims (7)

[Claims] 1. When measuring a corrosion reaction behavior of a coating metal coated with a paint, a lining material or the like by an external polarization method, a battery is used as a power source of an external polarization device connected to a measurement system including the coating metal, Further, the corrosion reaction behavior of the coating metal in the measurement system including the coating metal is measured by the external polarization device while the insulation resistance of the external polarization device and the battery is maintained at 10 ¹³ Ω or more with respect to the ground. Sensitive polarization measurement method for coated metal. 2. The method for measuring high-sensitivity polarization of a coated metal according to claim 1, wherein the measurement system including the coated metal is kept at an insulation resistance of 10 ¹³ Ω or more with respect to the ground. A highly sensitive polarization measuring method for a coated metal, which comprises measuring a corrosion reaction behavior of the coated metal. 3. An apparatus for measuring the corrosion reaction behavior of a coating metal coated with a coating material, a lining material, etc. by an external polarization method, wherein a coating cell, a reference electrode and a counter electrode are immersed in a conductive solution. , An external polarization device that measures the corrosion reaction behavior of the measurement cell by the external polarization method, a battery that is the power source of the external polarization device, a first metal container that houses the external polarization device, and a second metal that houses the battery A container made between the external polarization device and the first metal container, or between the first metal container and the grounding point outside the first insulating material, which holds a resistance of 10 ¹³ Ω or more; A second insulating material that holds a resistance of 10 ¹³ Ω or more between the battery and the second metal container or between the second metal container and a ground point outside thereof. High-sensitivity polarization measuring device for coated metal. 4. The high-sensitivity polarization measuring apparatus for coated metal according to claim 3, wherein the first insulating material or the second insulating material is glass. Sensitivity polarization measurement device. 5. A high sensitivity polarization measuring device for coated metal according to claim 3, wherein the first metal container or the second metal container is made of a material having a magnetic shield function. Characteristic high-sensitivity polarization measuring device for coated metal. 6. A high-sensitivity polarization measuring device for coated metal according to claim 3, further comprising a third metal container for accommodating the measuring cell. High-sensitivity polarization measuring device. 7. A high-sensitivity polarization measuring device for coated metal according to claim 3, wherein a control means for automatically operating the external polarization device is provided in the second metal container. Highly sensitive polarization measuring device for coated metal.