JPS6322257B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method and an apparatus for measuring the polarization characteristics of a metal surface under a coating of a coated metal having a coating such as a coating. Generally, painted metal always corrodes. That is, corrosive media such as water and oxygen that have penetrated the coating film reach the metal surface beneath the coating film and undergo an electrochemical reaction. Therefore, the reaction rate and type of reaction vary depending on the type of coating film, the type of metal, the type of metal surface, the environment in which the coated metal is placed, etc. Conventionally, the method of determining the corrosion resistance of painted metal has often relied on visual inspection, and it has become a practical method of judgment based on the magnitude of rust occurrence, rust area, etc. observed on the painted metal surface. There are many. However, the development of paints with better anti-corrosion performance, better metals for coating, prediction of accidents due to corrosion, determination of when to repaint, etc. are highly desired items from an industrial perspective. In order to satisfy these requirements, relying on the conventional visual judgment method described above is extremely difficult. This is because, if we consider the point at which rust is observed on painted metal, a paint film defect occurs (for example, the paint film is destroyed), and corrosion reaction products of the metal under the paint film (red rust of iron, etc. are mainly caused by This merely indicates that iron hydroxide (iron hydroxide) is exposed to the surface of the paint film through the defect; in reality, corrosion has progressed before that point. Nevertheless, it is questionable whether it is an industrially effective method to judge rust appearing on the surface of a paint film. For example, if we consider the type of corrosion in which pores form in the metal under the paint film, it is often the case that the metal under the paint film becomes pore-formed quickly before the paint film is destroyed. This type of example can be seen especially in recent implementation methods such as thick film painting or lining. On the other hand, in addition to determining the corrosion status of the metal under the paint film, it is also important to understand the rate of deterioration of the paint film itself. For this reason, conventionally, the ion permeability of the peeling membrane,
Measurements such as water vapor permeability, oxygen permeability, dielectric loss rate, etc. are being carried out. However, these values do not necessarily correspond to the actual corrosion and anticorrosion performance of coated metals. Therefore, it is preferable to measure the properties of the coating film in its practical painted state, and these obtained (film properties mentioned above)
By linking this value with the corrosion reaction of the metal under the coating film, it seems possible to evaluate the corrosion resistance of coated steel sheets, which has industrial value. In view of the above-mentioned current situation, the inventor has made earnest efforts to
We have been working on research and development of evaluation methods. That is, the present inventors have worked on the idea of making the contents of Japanese Patent No. 960239 even more effective, for example. In other words, the above patent is 1
This method detects the relationship between the potential and current when the coated metal is polarized at one speed, excluding only the coating film resistance component. That is, in the potential-current relationship, the resistance value of the coating film is assumed to be constant. However, it has been found that there are some paint films for which it is difficult to say that the electrical resistance of all painted films remains unchanged depending on the magnitude of polarization. Based on this fact, the present invention aims to measure the polarization characteristics near the surface of the steel under the coating on a steel plate coated with a high-resistance coating, as well as to measure the polarization characteristics near the steel surface under the coating. The purpose of this study is to examine whether it is possible to evaluate the corrosion resistance of steel plates. The first feature that led to the completion of the present invention is that conventionally, the potential of the sample is increased or decreased at a certain speed in the constant potential electrolysis method.On the other hand, in the constant current method, the potential of the sample is increased or decreased at a certain speed. However, in the present invention, polarization is performed at two or more different speeds. The second characteristic is that if the polarization speed is k, then even if k is changed, the coating film alone will have v/k
The value of (v is the voltage applied to the sample...in the case of constant current electrolysis) or i/k (i is the current applied to the sample...in the case of constant potential electrolysis) does not depend on k, but it depends on painted metal. I discovered that. The third characteristic is that as a result of evaluation using conventional methods, the corrosion resistance is poor (for example, blistering occurs, rust is observed, the rust-preventive pigment is not effective, or the paint film is in poor condition at first glance). For coated metals that are determined to be normal (such as holes penetrating the metal beneath the coating film), only the coating film exhibits the second characteristic described above. In other words, even if k is changed, the value of v/k is k
does not depend on The fourth characteristic is that normally painted metal depends on k, but as painted metal deteriorates, k
By tracking this dependence, it is possible to know the deterioration rate of painted metal, which can be applied to predicting the deterioration of painted metal and monitoring painted metal. Specifically, the first invention is a method for measuring the difference in current when two or more linearly varying voltages having different speeds are applied to a coated metal, and a coated metal having a coating film and a counter electrode. is immersed in a solution, and with a non-energizing interval of one fixed time or more sufficient to return the coated metal and the opposite electrode to their original non-energized state, a completely different rate of voltage change is applied to each energizing time. Intermittently apply any of various DC voltages or currents that linearly change in a positive or negative direction, and apply any of the respective electrolytic currents or voltages that flow between the coated metal and the counter electrode during each of the energization times. Find each division value by dividing the time change per unit time by the voltage change rate of the corresponding energization time above, and use one of the division values as a reference value, and divide the reference value, other division values, and The purpose of this method is to measure the external polarization characteristics of the metal surface under the coating film of coated metal, which is characterized by extracting the difference and determining the relationship between the difference and the application time of the DC voltage. The second invention is a method of measuring the difference in potential when two or more linearly changing currents having different speeds are applied to coated metal,
The painted metal and the counter electrode are immersed in a solution, and the DC current that changes linearly in a positive or negative direction at two or more different speeds at intervals of at least 1 minute is applied to the coated metal and the opposite electrode at intervals of at least 1 minute. is applied, the time change in the potential of two or more electrodes of the coated metal is divided by each of the above speeds, and the relationship between the difference and the polarization time is measured. The purpose is to measure the external polarization characteristics of the lower metal surface. Furthermore, a third invention provides a measurement cell comprising at least a coated metal and a counter electrode immersed in a solution;
means for detecting an electrode potential difference between the coated metal and the counter electrode, means for applying and maintaining a potential substantially the same as the electrode potential difference between the coated metal and the counter electrode, and having two or more different speeds; and a means for generating a direct current potential that can be changed linearly and positive or negative and applying it between the coated metal and the counter electrode; an applying means capable of applying an electric current between the coated metal and the counter electrode; a device that measures changes in electrolytic current flowing between the coated metal and the counter electrode; dividing the two or more measured values by each of the above-mentioned speeds, and A device for storing and extracting the difference between two or more values divided by mutually corresponding times in the different positive electric times,
The present invention proposes a new device characterized by comprising a device for recording the relationship between the difference and the energization time. Further, the fourth invention provides at least a measurement cell formed by immersing a coated metal and a counter electrode in a solution;
DC current generating means having three or more different speeds and capable of changing linearly and positively or negatively; and controlling means capable of operating the DC current generating means at intervals of one minute or more. , a device for measuring the potential change of the painted metal; a device for dividing the two or more measured values by the respective speeds and storing the same; and extracting the difference between the two or more divided values; A device for measuring the difference between two or more electrolytic potentials when a coated metal is polarized at two or more different applied current speeds is provided, comprising a device for recording the relationship between the difference and the polarization time. This is what we are trying to provide. As described above, the present invention appears to be extremely similar to the conventional constant-potential electrolysis method and the device related to the method, which is a potentiostat, as well as the conventional constant-current electrolysis method and the device related to the method, which is the galvanostat. Although it is common knowledge that the present invention is characterized by changes in current and voltage when a voltage and current are applied to a sample at an arbitrary time or at a predetermined rate at regular intervals, unlike conventional methods, To measure the rate of reaction between the sample and solution (corrosion rate, etc.), change over time, etc. to make the sample a material with better corrosion resistance, or to predict the life of the sample and prevent accidents due to corrosion. It is not intended to be used when exchanging samples in advance. That is, even though the present invention has the same purpose as the conventional one,
The measured values obtained, the method used to obtain them, and the equipment used for the method are extremely novel. The first meaning of conventional methods and devices is that it is known to polarize metals at two or more different speeds, and attempts are made to determine the performance and properties of metals based on the speed dependence. is also publicly known. In other words, when the same sample or samples are polarized at different rates, the difference in polarization is the difference in reactivity between the sample and corrosion at each polarization rate, and it is clear that each sample is polarized at different rates. This is the difference between the results of different states of the sample during polarization. The second method is to obtain information on how much the sample has changed over time, including the difference between two or more polarizations at regular intervals or for a certain period of time, and is the same as the second meaning above. It is. The third method is to measure the amount of change in the sample or the content of the change, similar to the above, although a combination of the first and second methods may be implemented. However, in the present invention, the details of which will be shown in Examples described later, in the constant potential method, the obtained electrolytic current is divided by the rate of applied voltage, and two or more different applied voltage rates are used. Similarly, the electrolytic current obtained at each speed is divided by each speed, and the difference is correlated with the voltage application time to obtain information about the metal surface under the coating film. be. On the other hand, the same applies to the constant current method; in the above example, the value obtained is the electrolytic current, but in this method, the only difference is that it is the potential. That is, the present invention is to remove the value due to the coating film by dividing the current and potential obtained by polarizing the coated metal by the polarization speed, and as a result, the value near the metal surface under the coating film, The objective is to obtain information on the so-called corrosion and anticorrosion reactions of metals under coatings. Next, among the present invention, the constant potential electrolysis method, that is, the first
The basic idea of the invention will be explained using FIG. Figure 1 is related to the constant potential method.
A high input resistance converter with a counter electrode C and a high input resistance converter between the C and R.
AMPI and arithmetic unit AMP2 are interposed, and an ammeter A is connected to the above W, while a voltmeter V, an applied voltage scanning generator Vt, and a DC voltage generation/holding mechanism.
Equipped with Vo. Figure 1B shows the actual circuit configuration. In the figure, 1 is a measurement cell, which is placed in a solution such as an aqueous corrosive solution, an organic solvent, or a mixture thereof (it does not have to be a commonly used electrolyte solution). It is made by dipping the counter electrode C and the painted metal W. The counter electrode C and the coated metal W form a closed circuit via a solution, with the first DC voltage power source 2a, the second DC voltage power source 3a, the ammeter 4a, and the ON state of the switch 5a. On the other hand, the voltmeter 6a is connected to the counter electrode C and the painted metal W. 7a is a division circuit, which is connected to the ammeter 4a and the subtraction circuit 8a. On the other hand, 9a, 10
a is a memory circuit, and the former memory circuit 9a is the above C-
The latter storage circuit 10a is the division circuit 7a that stores the time change of the current flowing between C and W, and the time change of the current flowing between C and W is stored as a mark of the first DC power supply 2a. This circuit stores the value divided by the acceleration, and there is no need to temporarily store it in the former storage circuit 9a, so the basics of its operation will be described below without providing the storage circuit 9a. Now, when the switch 5a is opened and turned off, the value on the voltmeter 6a becomes the potential difference between C and W, that is, the difference between the natural electrode potentials of the counter electrode C and the painted metal W in the solution. Assuming that this is Vo, the second DC voltage power source 3a is adjusted so that the same voltage -Vo, which has a different polarity from this Vo, has the magnitude of the second DC power source 3a. Next, when the switch 5a is turned on, a potential difference -Vo, which is opposite to the potential difference Vo between C and W, is applied between C and W, so that the current in the ammeter 4a becomes approximately zero. (This state will hereinafter be referred to as the state of electrolysis at the natural electrode potential of the coated metal).
After this state is established, the first DC voltage power supply 2a described above
is operated to linearly change the voltage with an applied acceleration of _k1 , and at the same time, the above-mentioned divider circuit 7a and memory circuit 10a are operated. With the above operation, C-
A current flows between W, and the time change of the current is constantly divided by _k1 via the ammeter 4a, and the resulting value is stored in the memory circuit 10a as a time change. Then a predetermined time (hereinafter referred to as polarization time)
After the polarization is completed, the switch 5a is turned off, and the first and second DC voltage power supplies 2a, 3a and the divider circuit 7a are returned to their original states, and at the same time, the value obtained by the above operation is stored in the storage circuit 10a. I'll keep it. By the above operation, the painted metal has returned to its natural state (electroless state), and after keeping it in this state for more than 1 minute, the natural electrode potential of the painted metal is restored again using the second DC voltage power supply 3a as above. electrolysis, and set the value of the ammeter 4a to approximately zero. Next, the first DC power supply 2a linearly applies a DC voltage between C and W at an applied voltage speed of _k2 . The electrolytic current at that time is inputted to the dividing circuit 7a via the ammeter 4a, and the value is constantly divided by _k2 , and the time change of that value is stored in the memory circuit 10a, and the polarization is continued until a predetermined polarization time. do. Next, the difference between the value divided by k ₁ and the value divided by k ₂ is calculated by the subtraction circuit 8a while synchronizing the elapsed polarization time, and the result is measured. Alternatively, without storing the value of the time change divided by k ₂ , synchronize the time change of the value divided by k ₁ first with the elapsed time (polarization time) of the value divided by k ₂ . Even if the subtraction circuit 8a calculates the value while doing so, the result will be the same as above. That is, even in a method in which only the first polarized value is stored and the next polarized value is not stored, the same value is obtained. Next, among the present invention, the constant current method, that is, the second
The basic idea of the invention will be explained using FIG. In Fig. 2A, 1 is a measuring cell, which is equipped with a painted metal W, a reference electrode R, and a counter electrode C. A high input resistance converter AMPI and a computing unit AMP2 are interposed between C and W. An amplifier AMP1' and a voltmeter V' are interposed between them, an ammeter A' is connected to W via a variable resistor _r1 , and an applied voltage scanning generator Vx' is provided. Figure 2 (b) shows the actual circuit configuration. What is different from Figure 1 (b) is the
The DC voltage power source 2a is the DC current power source 2' in FIG.
Similarly, in FIG. 2, the second direct current power source 3a is the zero current generator 3'a, and the divider circuit 7a, memory circuit 10a, and subtraction circuit 8a each calculate and store the time change of current. The division circuit 7a, memory circuit 10a, and subtraction circuit 8 in FIG.
a is only for calculating and memorizing the potential,
For this purpose, in FIG. 2, the output of the voltmeter 6a is simply connected to the divider circuit 7a. Therefore, the basic measurement operation is the same as that shown in FIG. 1 described above. However, in Fig. 1, the second
Although the magnitude of the DC potential power supply is set to -Vo, in FIG. 2, in order to make the current between C and W zero, a zero current generator 3'a is used which applies -Io to make it zero.
With the above configuration, in Fig. 1, polarization was performed at an applied voltage rate of k ₁ or k ₂ , but in Fig. 2, polarization is only performed at an applied current rate of k' ₁ , k' ₂ , and the basic operation is as follows. Since the content is similar to that explained in FIG. 1, the explanation will be omitted. Next, the third device, which is a device for carrying out the first invention,
The embodiment of the second invention will be described in detail. As mentioned above, it is necessary that the electrode potential of the counter electrode C itself is stable in the solution and that the potential of the counter electrode C itself is stable and difficult to change even if a current flows between the counter electrode C and the coated metal W. When measuring the metal W, for example, a silver-silver chloride electrode or a calomel electrode may be used as the counter electrode C. That is, the electrical resistance of the coating film is extremely high, the electrolytic current is extremely small compared to uncoated metal, and the polarization of the counter electrode itself has little effect. However, in order to perform more accurate measurements and detect corrosion and anticorrosion reactions on metal surfaces under coatings, it is sometimes necessary to further stabilize the counter electrode itself. Therefore, in the following embodiments, at least the counter electrode C serves only as an electrode that receives current flowing in and out of the coated metal W, and in order to prevent the influence of the polarization of the counter electrode itself from being added to the measured value, The measurement cell was equipped with a reference electrode, and the signal from the reference electrode was used. That is, the first
The first invention includes a measuring means for setting in advance the error current caused by the electrode potential difference between the counter electrode C and the coated metal W to approximately zero, while the second invention includes a Equipped with a detection means that can stably measure the electrode potential difference with the painted metal W, suppressing at least the influence of the polarization of the counter electrode itself as much as possible,
The measurement signal is the polarization current of the coated metal. Next, FIG. 3 is a block diagram of an apparatus for automatically measuring the external polarization characteristics of the metal surface under the coating of coated metal according to the present invention by a constant potential electrolysis method, and FIG.
This is a wiring diagram. Hereinafter, the order of operation and each block will be explained while comparing FIG. 3 and FIG. 4. First, the measurement cell 1 includes a coated metal plate W having a film or coating made of an inorganic substance, an organic substance, or a mixture thereof on the surface, a reference electrode R exhibiting a stable electrode potential such as a calomel electrode, a silver-silver chloride electrode, and the like. Counter electrode C made of non-corrosion-resistant metal such as platinum
was immersed in a 3% NaCl corrosive solution, and the electrode potential and electrolytic current of the painted metal plate W were measured and calculated twice with an interval of 1 minute or more, and the difference was synchronized with the measurement time. The polarization characteristics of the metal surface under the coating can be measured using it. Next, the electrode potential measuring means 2 measures the resistance between the coated metal W and the reference electrode R (the electrical resistance of the coating film in the immersion liquid +
The above-mentioned standard is passed through the high input resistance converter 3 which has an input resistance sufficiently higher (usually 10 ¹³ Ω or more) than the liquid resistance + the interfacial resistance called polarization resistance of the counter electrode surface and the metal surface under the coating film. connected to electrode R;
It is a voltmeter whose other end is grounded, and measures the electrode potential of the coated metal W while minimizing the input of the electrolytic current generated by the applied voltage described below. Specifically, the output of the converter 3 is connected to the resistor
DC amplifier AMP and resistor R ₂ are grounded through R ₁ and measure the potential difference across the resistor R ₁ .
are connected in parallel, one end is used as the output side of the converter 3 and the other end is used as the output signal of the voltmeter, and the amplification degree can be changed by the ratio of resistors R ₁ and R ₂ . It's summery. Furthermore, the measurement preparation means 4 that enables electrolysis at the natural electrode potential of the painted metal W in the solution includes a servo mechanism 5 whose one end is connected to the electrode potential measurement means 2 and whose other end is grounded, and a compensation It includes a signal supply means 6, a switch 7, and a first computing device 8.
Further, to explain in detail using FIG. 4, first, the input side of the arithmetic unit 8 is connected to the high input resistance converter 3
and potentiometer P ₁ of the compensation signal supply means 6
and the output side of the means is grounded via the closed state of the switch 7 (connection between c and d). The output side of the calculator 8 is connected to the counter electrode c, and calculates the output (electrode potential signal) a of the high input resistance converter 3 and the output (compensation potential signal) b of the compensation signal supply means 6. , the above painted metal W
The error current caused by the electrode potential difference between the electrode C and the counter electrode C is made approximately zero. Further, the servo mechanism 5 includes a comparator 9, a servo motor 10, and a comparison signal supply means 11, forming a negative feedback circuit. Specifically, the input side of the comparator 9 is the DC amplifier of the electrode potential measuring means 2 described above.
It is connected to the output of the AMP and also to the comparison signal supply means 11, while the output side is a normally open contact L ₁
The output (potential signal) Va of the electrode potential measuring means 2 and the output (comparison signal) of the comparison signal supply means 11 are connected to the servo motor 10 via
The output, which is the signal of the difference, is compared with Va.
By turning on (closed) the normally open contact _L1 , an input signal is input to the servo motor 10 to drive the motor. The potentiometer P1 of the above-mentioned compensation signal supply means ₆ and the potentiometer P2 of the above-mentioned comparison signal supply means 11 are linked to the drive of the servo motor ₁₀ . The supply means 6 is a potentiometer _P1
, a DC power supply E ₁ , and distribution resistors R _{3 and R 4} are connected in parallel, and the switch 7 is connected in the closed state (c-
The output voltage (compensation signal) a of the means 6 is connected to the first arithmetic unit ₈ through the potentiometer P1.
is input to the first arithmetic unit 8 while being constantly compensated for by the drive of the servo motor 10. On the other hand, the potentiometer P ₂ of the comparison signal supply means 11 is connected to the DC power supply E ₂ and the distribution resistor R ₅ ,
R ₆ is connected in parallel with the distribution resistor R ₅ ,
The branch point of _R6 is grounded, and the potentiometer _P2 is connected to the above-mentioned comparator 9 to input the comparator signal -Va. Then, normally open contact L ₁ is turned on (closed)
By doing so, the inputs Va and -Va of the comparator 9 are compared, and the servo motor ₁₀ is driven so that the above-mentioned potentiometer P2 is displaced so that the difference becomes approximately zero, and at the same time the above-mentioned The potentiometer _P1 of the compensation signal supply means 6 is also displaced, and the potential difference between a and b of the first arithmetic unit 8 becomes approximately zero, and as a result, the servo motor 10 is stopped. With the above configuration, preparation for measurement is performed, and the output of the first computing unit 8 described above becomes approximately zero, and as a result, the electrolytic current between the counter electrode c and the coated metal W described above becomes approximately zero. This preparation state is the state in which the coated metal W is electrolyzed at its natural electrode potential. Hereinafter, this state will be referred to as the first preparation state. Next, a power supply 12 that applies a DC voltage having a positive or negative linear gradient to the painted metal W is constructed by connecting a potentiometer P ₃ , a DC power supply E, and distribution resistors R ₇ and R ₈ in parallel. Therefore, the output example of potentiometer _P3 is the open contact side e of the switch 7 mentioned above,
It is connected to the branch point of the distribution resistors R ₃ and R ₄ of the compensation signal supply means 6 via the common contact c, and the branch point of the distribution resistors R ₇ and R ₈ is grounded. . With the above configuration, a DC voltage with a positive or negative slope is outputted from the DC voltage application power supply 12 by the displacement of the potentiometer _P3 , and if the switch 7 described above is connected between ce and e, the above compensation is achieved. Superimposed on the output voltage of the signal supply means 6,
It can be input to the input b side of the first computing unit 8, and as a result, the superimposed voltage is applied to the counter electrode c via the computing unit. The device 13 for measuring the electrolytic current flowing through the branches of the coated metal then comprises a DC amplifier 14 and a multi-stage resistor 15. For details, see DC amplifier 1.
4 is connected in parallel with resistor R ₉ , and its input side is connected to the painted metal W and is grounded via multistage resistor 15 . That is,
The multistage resistor 15 is a normally closed contact with the resistors _R10 to _R13 .
L ₂ and the normally open contacts L ₃ to _{L 5} are each connected in series and the whole is connected in parallel so that an appropriate voltage drop can be obtained by switching the contacts, and the resistors R ₁₀ to The degree of amplification of the output voltage of the DC amplifier 14 can be changed by changing the resistance value of R ₁₃ and the resistance value of the resistor R ₉ described above. Therefore, the electrolytic current flowing between the counter electrode c and the coated metal W is converted into voltage and detected. Next, after the above-described first preparation state, the output of the DC voltage applying power source 12 can generate a DC voltage at a speed having a positive or negative linear slope, so that the potentiometer P ₃ is adapted to be displaced at a constant speed by a synchronous motor 16, and this displacement speed kx (V/sec) is controlled by a displacement control means 17. As described above, if the synchronous motor 16 is driven to apply a DC potential (V/sec=kx) with a positive or negative potential gradient to the painted metal W using the counter electrode c, the corresponding painted metal The electrolytic current change of W receives an appropriate voltage drop by the multi-stage resistor 15 of the electrolytic current measuring device 13, is input to the DC amplifier 14, is amplified, and is then output as a measurement signal.
The output voltage is input to the dividing circuit 18 and divided by the displacement speed kx of the DC voltage applying power source 12 described above. Specifically, the division circuit 18 is connected to the DC amplifier 1
9. Equipped with a multi-stage resistor 20 and a DC amplifier 1
9 is connected in parallel with the resistor R ₁₄ , and its input side is connected to the electrolytic current measuring device 13 and grounded via the multistage resistor 20 . Further, the output side is connected to a switch 21.
The multistage resistor 20 is a normally closed contact with resistors R ₁₅ to _{R 18}
L ₆ and the normally open contacts L ₇ to L ₉ are each connected in series, and the whole is connected in parallel so that an appropriate voltage drop can be obtained by switching the contacts, and the resistor R ₁₅ The change in the electrolytic current described above is divided by the displacement speed kx using the resistance value of ~ _R18 and the resistance value of the resistor _R14 . That is, the time change i-t of the electrolytic current i is always divided by kx, and that value is always used as the output of the DC amplifier 19. This can be obtained by setting a suitable resistance value. Next, the time change of the value output by the division circuit 18 is determined by the switch 21 (connected between f and g),
and is stored in the first storage circuit 22 through the closed state of the normally open contact _L10 . Specifically, when a direct current voltage is linearly applied positively or negatively to the coated metal W by the counter electrode C at the speed kx, the coated metal W
The time change of the electrolytic current flowing through the circuit is divided by the value kx, and the resulting time change is stored in the first memory circuit 2.
2. When the polarization is completed for a predetermined period of time, the normally open contact _L10 is opened to stop the memorization and end the measurement. Then, a signal is sent from the control device 33 via the dotted line shown in FIG. 3 to wait for one minute or more until the next measurement and to return each means circuit switch to its original state. For example, the switch 7 is switched to the connection between c and d, and the output voltage of the DC voltage applying power source 12 is set to zero.
The potentiometer _P3 is returned to the starting state via the synchronous motor 16. With the above configuration, from the first preparation state described above, the coated metal W can be polarized with the applied velocity kx, and the electrolytic current it at that time is divided by k.
The value of t/k is now stored in the storage circuit.
This is hereinafter referred to as the first measurement. Note that the first storage circuit 22 is a storage type synchroscope,
Alternatively, there are many methods, such as connecting many ordinary hold-type digital voltmeters in parallel.
Details are omitted. Next, after the first measurement is completed, the same operations and configuration as described above up to the first preparation state are repeated for one minute or more, and the potentiometers P ₁ and P ₂ are automatically controlled by the servo motor 10. adjusted to
The electrolytic current flowing between the counter electrode C and the coated metal W is always approximately zero. In other words, it is in a state where it is electrolyzed at the natural electrode potential of the coated metal. Hereinafter, this will be referred to as the second preparation state. Next, after waiting for more than one minute, the switch is connected between ce and e as described above, and the synchronous motor 16 is driven at the speed k'x,
While displacing the potentiometer _P3 at a speed of kx, the normally closed contact of the multistage resistor 20
L ₆ is open, normally open contact L ₇ is closed, and resistor R ₁₆ is grounded. Further, the switch 21 is switched to the connection between f and h, and the switch 24 is connected between j and l, the normally open contact _L11 is closed, and the first memory circuit is connected to a similar second memory circuit. 23, the value obtained by dividing the time change (i'-t) of the electrolytic current by the applied acceleration (k'x) is always stored in the same way as described above. The state measured with this configuration is hereinafter referred to as the second measurement. However, the second measurement is particularly different from the first measurement described above because the displacement control means 17
The displacement speed of the potentiometer _P3 , which is controlled by , has become k'x. When the painted metal W is polarized for a predetermined time, the normally open contact _L11 is opened to stop the memory in the second memory circuit 23, and the switch 7 is connected between c and d. the potentiometer so that the output voltage of the DC voltage applying power source 12 becomes zero.
_P3 is returned to the starting state by the synchronous motor 16 mentioned above. With the above configuration, the memory circuits 22 and 23 store potential changes over time (originally, this time change is a value obtained by dividing the time change in the current flowing through the painted metal W by a predetermined value, but as described above, In this embodiment, the electrolytic current measuring device 13 is configured to convert DC current into DC voltage and output it.)
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kx and i'-t/k'x are stored. Next, the first memory circuit 22 and the second memory circuit 23 connect to the difference detector 2 via the normally open contacts L ₁₂ and L ₁₃ .
4 and are respectively connected to the recording device 25. Specifically, the difference detector 24 includes a second computing unit 26 and a voltmeter 2.
7, and the input of the second arithmetic unit 26 is
The first memory circuit 22 via the normally open contact _L12 .
and the second memory circuit 23 via the normally open contact _L13 , and the output thereof is grounded via a voltmeter 27. On the other hand, the output of the voltmeter is connected to the recording device 25, such as an ordinary pen recorder, oscilloscope, synchroscope, or the like. Next, the normally open contacts L ₁₂ and L ₁₃ are closed, and the first memory circuit 22 and the second memory circuit 2 are closed.
3 are operated simultaneously and are input to the second computing unit 26 while being temporally synchronized, the difference between m and q of the computing unit 26, specifically, the first
i-t/kx stored in the memory circuit 22 and i′- stored in the second memory circuit 23 mentioned above.
If the difference (△i/k) from t/k'x is detected by the second arithmetic unit 26 and its output is recorded in the recording device 25 via the voltmeter 27, then
The desired external polarization characteristics of the metal surface under the coating film of the coated metal can be obtained. On the other hand, the switch 28 is connected between j and n to close the normally open contact L ₁₄ , and at the same time the above-mentioned second measurement is started, the i-t/kx stored in the above-mentioned first memory circuit is , by sequentially closing the normally open contact L ₁₂ and sending it to the second computing unit 26,
The above △i/k is the same as above, the recording device 25
will be recorded in the second storage circuit 22.
becomes unnecessary. However, two or more of the above displacement speeds
Measure kx and calculate the difference △ at each value of kx
It cannot be said that it is suitable for detecting and recording i/kx.
This can be achieved by repeatedly using the first memory circuit 22 and the second memory circuit 23. For example, k ₁ in the first measurement, k ₂ in the second measurement, and k 2 in the third measurement.
k ₃ and k ₄ in the fourth measurement, the values at k 1 and k ₂ are stored in the first storage circuit and the value at k ₂ in the second storage circuit, respectively, and it/t/ at k ₃ at the third measurement is stored. k ₃ is stored in the first storage circuit. While removing the value of i-t/k ₁ , or before the third measurement, i-t/k ₁
The value of is set to zero and stored in the first storage circuit. Then, the difference between it/k ₃ in the first storage circuit and it/k ₂ in the second storage circuit is recorded by a recording device. Then, similarly, the object of the present invention can be achieved by sequentially switching the values obtained with k ₂ to zero and storing the value of k ₄ . Alternatively, as many memory circuits as the number of kx required may be provided. FIG. 3 also shows a control device 33 that controls each of the above-mentioned devices, circuits, contacts, and switches, performs synchronous operation of the memory circuits 22 and 23, starts, stops, and speed controls the synchronous motor, etc. At least the connection of the control signal of the control device 33 is shown by dotted lines, but since the basics of its operation have been described above, the following description will be omitted. Next, an embodiment of the fourth invention, which is an apparatus for implementing the second invention, will be described in detail. FIG. 5 is a block diagram of an apparatus according to the present invention for automatically measuring external electrode characteristics of a metal surface under a coating film of a coated metal by a constant current electrolysis method, and FIG. 6 is a wiring diagram thereof. While comparing Figures 5 and 6, as well as the aforementioned Figures 3 and 4,
The operation order and each block will be explained. First, the measurement cell 1 and the provision of a solution, a counter electrode C, a coated metal W, and a reference electrode R in the measurement cell 1 have been described above (the embodiment has already been explained using FIGS. 3 and 4). Similarly, a high input resistance converter 3, a switch 7, a first computing unit 8, a DC voltage applying power source 1
2. The synchronous motor 16 and the displacement control means 17 are the same as those shown in FIGS. 3 and 4, so details of individual operations and blocks will be omitted. th and 4th
Only the portion related to the second invention will be explained in detail. The painted metal W is grounded via a current control variable resistor 29 and directly connected to the high input resistance converter 3, and the output of the high input resistance converter 3 is connected to the input of the first computing unit 8. a, and the output of the first arithmetic unit 8 is connected to the counter electrode C. On the other hand, the input b of the first arithmetic unit is c-d of the switch 7.
grounded through a connection between the That is, the inputs a and b of the first arithmetic unit 8 are closed by the current control variable resistor through the ground, and the output of the first arithmetic unit 8 becomes zero. Therefore, no current flows between the counter electrode C and the coated metal W, and electrolysis occurs at the natural electrode potential of the coated metal W described above. Next, the above switch is connected between ce and the potentiometer of the DC voltage applying power source 12 mentioned above.
When P ₃ is driven at the speed of the synchronous motor 16 using the displacement control means 17, the output voltage of the DC voltage applying power source 12 is applied between the counter electrode C and the coated metal W. However, since the above-mentioned current control variable resistor 29 is connected between the painted metal W and the ground, voltage application control between the counter electrode C and the painted metal W is not performed, and the voltage applied between the counter electrode C and the painted metal W is not controlled. The current application is controlled between That is, the speed at which a linear current is applied between the counter electrode and the painted metal W is k'i (A/sec), and the linear potential change rate of the output voltage of the DC voltage applying power source 12 is k'v (mv/mv/sec). min), electrical resistance value r' (Ω) of the variable resistor 29 for current control.
Then, k′i is expressed by the following equation. k′i=k′v/r′×60×1000 (A/sec) Therefore, by changing the driving speed of the potentiometer _P3 and the value of the current control variable resistor 29, the above A positive or negative linear current change can be given between the counter electrode C and the painted metal W, and therefore, in order to give the above-mentioned positive or negative linear voltage change between the counter electrode C and the painted metal W, the above-mentioned DC voltage application power supply 12 and synchronous motor 1
6 displacement control means 17 was used, but it can be said that it is extremely convenient because the same means can be used. Next, a voltmeter 30 is installed between the reference electrode R and the painted metal W in order to track the change in electrode potential of the painted metal W when a linear current change is applied between the counter electrode C and the painted metal W. It is being Specifically, the reference electrode R is connected to the input of the DC amplifier 32 via a high input resistance converter 31 having an input resistance sufficiently higher (usually 10 ¹³ Ω or more) than the resistance between the painted metal W and the reference electrode R. connected to S, one of the sides, and
The t side, which is one of the other inputs of the DC amplifier 32, is connected to the painted metal W. With the above configuration, when a current is applied between the counter electrode C and the painted metal W, the potential change between the reference electrode R and the painted metal W can be detected as the output of the DC amplifier. can. Next, the output y of the voltmeter 30 is now a point in FIG. 6, which corresponds to a point in FIG. 5, and the output y is connected to the input of the above-mentioned divider circuit 18. The switch 21, the first memory circuit 22, the second memory circuit 23, and the difference detector 2 shown in FIG.
4. The configuration, connection, and operation details of each recording device are the same as those explained using FIGS. 3 and 4 above. That is, the points in FIGS. 5 and 6 are the same as the points in FIGS. 3 and 4. The content of the explanation of the embodiment using FIGS. 3 and 4 is that "a voltage is applied to the painted metal W, the current is detected as a response signal, and the current is converted to a voltage", and the voltage is It is used to detect and record the division and the difference between the two signals.
The content of the explanation of the embodiment using FIGS. 3 and 6 is that "a current is applied to the painted metal W, a voltage is detected as a response signal," and the voltage is sent to the points shown in FIGS. 3 and 4 above. It's going to happen. As mentioned above, the configurations of the second invention and the fourth invention often use the same means and circuits, but the basic signal types are different from those of the second invention.
In one invention, the opposite is true. However, the operations of dividing the signal by the polarization speed, detecting the difference between two or more speeds, and recording the difference are the same. however,
The units of the recorded values are different. Next, an embodiment that combines the third invention and the fourth invention, which is an apparatus for carrying out the first invention and the second invention, will be described. FIG. 7 is a block diagram of an apparatus for automatically measuring the external polarization characteristics of a metal surface under a coating of a coated metal, which constitutes the entirety of the present invention. Since the contents of the measuring cell 1 to the control device 33 having the configuration shown in FIG. 7 have been described above, the details will be omitted below, but the feature of this embodiment is that changeover switches 34 to 39 are provided. By connecting each switch to the v side in the figure, the third invention similarly connects each switch to i.
By connecting to the side, it becomes a block diagram of the fourth invention. That is, if each of the above switches is set to the v side, the block diagram shown in FIG. 3 is obtained, and if it is set to the i side, the block diagram shown in FIG. 5 is obtained. Therefore, details of this embodiment will be omitted. As described above, the measurement method can be easily changed by switching the switch. Next, an example of an experiment conducted using the above device will be explained. [Experiment example] In the experiment, a painted steel plate is made up of a ``paint film'' and a ``near the steel surface,'' and the corrosion of the painted steel plate is assumed to be the discharge of a local battery generated near the steel surface. Therefore, it was assumed that the polarization characteristics near the steel surface are firstly related to the corrosion state, and secondly can be expressed by the difference between the polarization characteristics exhibited by the coating film and the polarization characteristics exhibited by the coated steel plate. Here, if the electrical equivalent circuit of the coating film is a parallel circuit of a resistance component and a capacitance component, then in current scanning as shown in FIGS. 14 and 15, V/k-
In potential scanning, the t relationship and the i/k'-t relationship are curves that do not depend on the scanning speed (k: A/sec...k': V/sec). On the other hand, near the steel surface, the resistance of the electrolytic reaction changes as the polarization increases, as shown in Figure 16.
The relationship should depend on the scanning speed. Assuming that the "paint film" and "near the steel surface" are electrically connected in series, the coated steel sheet has a V/V measured at various scanning speeds using the current scanning method.
The kt relationship is simply the sum of the coating film component that does not depend on the scanning speed and the component near the steel surface that depends on the scanning speed. In other words, the V/k ₁ -t relationship obtained at two current scanning speeds k ₁ and k ₂ and the V/k ₂ -t
If we take out the difference in the relationship, V/k due to the coating film
The t relationship is canceled out and η/k due to the vicinity of the steel surface
- Only the difference in the t relationship is obtained. (η is the overvoltage applied near the steel surface) Based on the above assumptions, the scanning speed dependence of the polarization curve of the peeling coating film and the coated steel plate using the current and potential scanning method was investigated. In the experiment, a steel plate (JISG3141: SPCCB) was degreased with xylene and then painted with a doctor blade as a coated steel plate sample. The release coating is made of polyethylene plate or tin steel plate (GISG3303SPTE)
It was obtained by peeling off the painted material. As the paint, a glass flake-containing paint and a cyanamide hergon-based air-drying paint were used. The polarization device includes a corrosion rate meter (CRM, Nippon Paint Co., Ltd., AT-
101 model), and the current and potential were recorded on a three-pen recorder. The etchant was a 3% NaCl solution. The experiment was conducted under the conditions described below. Sample: (A): A paint containing glass flakes in a synthetic resin was applied to a tin plated steel plate by airless spray painting to a film thickness of approximately 3000μ, dried in a natural environment, and then painted on the tin plated steel plate using the mercury amalgam method. The film was peeled off to obtain a peel-off coating. (B): JIS-K- on steel plate (JIS.G.3141, SPCCB)
5325-1 cyanamide hergon undercoat red rust color paint was air sprayed to a film thickness of approximately 100μ, dried in a natural environment, and made into a coated steel plate. (C): A coated steel plate was prepared in the same manner as Sample B using a paint composition of Sample B that did not contain any antirust pigments. Solution: Immersion liquid (corrosion liquid) in the measurement cell is 3%
The temperature of NaCl and the immersion liquid was kept at 40°C. Polarization rate: per minute for constant potential method
It increased linearly at rates of 500mV, 50mV, and 10mV. On the other hand, in the constant voltage method, 3.9, 8.7, 17.5, and
The current was varied linearly at a rate of increase of 35.0×10 ^-10 A. However, the direction in which the current is applied is generally the direction that makes the steel surface under the coating where the reduction reaction occurs more negative, and the current is applied in the direction from the corrosive liquid to the steel surface under the coating through the coating. I let it flow. The first experimental example was about a peel release coating (sample A), and the measurement cell shown in FIG. 8 was used.
Specifically, two glass cells No. 1 and No. 2 made of glass each having an electrode and an opening for introducing a solution fix the peeling coating film in a sandwich shape with packing so that there is no liquid leakage, and The naked steel plate W and the above solution were placed in one chamber, and the reference electrode R (silver-silver chloride electrode), counter electrode C (platinum plate) and the above solution were placed in the other chamber, and the temperature was maintained at 40°C. The reaction between the release coating film and the solution (for example, the period during which the water absorption rate due to penetration of the solution into the coating film and the dissolution rate of water-soluble substances from the coating film are approximately constant; in this example, it is left to stand for 4 days) Next, after setting the current between C and W to approximately zero (a state in which W is electrolyzed at its natural electrode potential as described above), the potential of W is changed at the polarization rate described above, and the current change detected at that time is The relationship between and time was measured. The results are shown in Figure 9, which is a diagram of the relationship before detecting and recording the difference when polarizing at two or more speeds as described above. An example of a coating film containing glass flakes is shown as the polarization characteristics of a peel-release coating film.This is an example when potential scanning is performed.The i/k'-t relationship is
It could be considered that it does not depend on the scanning speed k'.
However, this curve was different from the electrical equivalent circuit that was initially assumed, in which the capacitance and resistance components were simply connected in parallel. The same was true for current scanning. At potential change rate kx (500, 50, 10mV/min),
The relationship between dividing the current change and the polarization time (up to 4 minutes in this example) is as shown in the figure.
Even if kx is within the range of 50 times, it is almost the same, and now kx
= 10 mV/min polarization rate as the reference, and the other 2
When the i/kx-t relationship at the two speeds is subtracted and recorded, it is shown in FIG. 10, and the difference is extremely small.
That is, the polarization characteristics of peel-release coatings cannot be measured by the method and apparatus of the present invention. As mentioned above, this is a feature of the present invention. For example, when paint film blisters are observed on a painted metal plate as a practical problem, considering the paint film blisters, A solution exists between the film and the metal, which is very similar to the presence of a solution between W and the peeling film in Fig. 8, and the steel plate W in Fig. 8 has glass cell No. .Reacts with the solution on the 1st side,
It is susceptible to corrosion. Therefore, the ninth
As shown in Fig. 10, if the polarization rate is not substantially dependent, the metal under the coating is in a state where it is easy to corrode.
Moreover, it can be said that the commonly observed coating film abnormality has occurred. Although this test is not shown, even if a sample in which paint film blistering is observed on a painted steel plate is measured in the same manner as in this experimental example, as shown in Fig. 10,
Δi/kx is extremely small, which is consistent with the fact that the result is almost independent of the polarization rate. Further, in the above example, the potential was changed and the current change flowing at that time was detected, but the same result could be obtained by applying a current and detecting the potential change. Next, in the second experimental example, sample B (painted steel sheet containing anti-rust pigment) and sample C (painted steel sheet without anti-rust pigment in the coating film) were each tested using the constant current method.
Apply current linearly at a rate of kx (3.9, 8.7, 17.5 and 35.0×10 ^-10 A/sec), measure the potential change at that time, and divide by each of the above kx,
It was detected by correlating it with the polarization time. The cross section of the measurement cell is the same as that shown in FIG. 8 above, and is shown in FIG. 11. In this example, since a painted steel plate was used, the experiment was conducted without injecting a solution into the cell (glass cell No. 1) on the back side of the painted steel plate. A painted steel plate was used as the sample electrode W, and the reference electrode R and counter electrode C were the same as in the above example. The obtained results are shown in Figure 12,
It is shown in FIG. FIG. 12 shows an example of polarization characteristics of a painted steel plate. This is the polarization characteristic in current scanning of a steel plate coated with cyanamide hergon-based air-drying paint that was immersed for about a month at a set temperature of 35°C. B is a steel plate coated with a paint containing a rust preventive pigment, and C is a steel plate coated with a paint that does not contain a rust preventive pigment. 1st
Curve C in Figure 2 shows kx of 3.9 to 35.0 (×10 ^-10 A/
sec), and the results were not dependent on the scanning speed.
On the other hand, in B, scanning speed dependence is clearly observed. Although C depended on the scanning speed at the initial stage of immersion, it had become negligibly small at this point. This scanning speed dependency is related to the overvoltage near the steel surface as shown in equation (1). And △(V/k)≡V/k ₁ - V/k ₂ = η/k ₁ - η/k ₂ (1) η: Overvoltage near the steel surface Its dimension is (V/A x sec.) This can be said to represent the resistance change near the steel surface. If the polarization resistance near the steel surface is small and the overvoltage near the steel surface reaches only a few mV in the current scanning range, the polarization resistance can be regarded as constant, so △(V/
k) becomes zero. On the other hand, the polarization near the steel surface is
When reaching 10 mV, the polarization resistance changes as a function of the current, so the Δ(V/k) value becomes a value that meshes with it. C in the figure is the former case,
B in the figure is considered to be the latter case. As described above, the Δ(V/k) value is related to the magnitude of polarization resistance. Incidentally, when comparing the corrosion resistance of coated steel plates B and C, it has been confirmed that B is better. As shown in Figure 13, kx
=35.0×10 ^-10 Based on the applied acceleration of A/sec,
When the difference from other speeds is measured and recorded, sample C is almost independent of the applied acceleration and shows almost no difference.
On the other hand, sample B depends on the applied acceleration. This fact agrees extremely well with the results of visual observation from various commonly performed immersion tests. For example, sample C has rust and paint blistering, while sample B has extremely good corrosion resistance, with no rust or paint blistering, which is consistent with the dependence of △V/kx on kx in this experimental example. do. Considering the above results, as shown in FIG. 10, it is clear that the release coating film does not depend on the polarization rate, and this makes the meaning of the present invention even more effective. In other words, when a coated metal is polarized with various polarization speeds and the difference is determined, the i/kx-t (first
(2nd experimental example) or V/kx-t (2nd experimental example) relationship is canceled out, and the difference only in the i/kx-t or V/kx-t relationship due to the metal surface under the coating is canceled out. will be obtained. In addition, it is also possible to use the error to calculate the corrosion rate of metal under the paint film, and even calculate the composition of paint (manufacturing new types of paint).
It can also be used as data for predicting the lifespan of a specified painted metal by examining or quantifying it.
This provides an extremely effective evaluation method and device. In addition, as shown in the examples, it is also a device that automatically performs the above experimental examples, and does not rely on individual sensory evaluations as in the past, suppressing individual errors. We can provide equipment that can also be used for monitoring. In addition, the present invention
The present invention is not limited to the apparatuses of the above experimental examples and examples, and various modifications can be made within the scope of the claims. Next, an example of digital measurement will be described in detail. Although the above-mentioned embodiments are about the analog measuring method and apparatus, the digital processing apparatus will be explained using the block diagram of FIG. 17. The points indicated by symbols in Fig. 17 are the same as the symbols in Figs. 3, 4, 5, and 6 described above, but below, the points indicated by symbols are explained using Fig. 4 described above. An apparatus for applying a potential change to a sample and measuring a change in the current flowing at that time, as shown in FIG. 17, will be described. FIG. The change in the current flowing through the sample described above is converted into a potential change at the point in FIG. 4, and this change is input to the first A/D converter 101 in FIG. 17, where it is converted from analog to digital. On the other hand, the value of the speed kx of the potential change rate applied to the sample described above is set by the change rate setting device 102, and the set value is set in the second A/
A D converter 103 converts analog to digital values. Next, for each unit time, the above 1A/
The output value of the D converter 101 (hereinafter referred to as Da),
The output value of the second A/D converter 103 (hereinafter kxa
), the first
The gate 104 is opened and the two digital values are simultaneously sent to the first arithmetic circuit 105. This first
The arithmetic circuit has a function of calculating Da/kxa, opens the second gate 106 immediately after the calculation is performed, and simultaneously stores the calculated value and the unit time in the first holding circuit 107. . The unit time is defined as zero, the start time of applying a potential to the sample at the rate kx of the potential change rate, and at the same time as the start time, a signal from the control device 33 is applied to the time control circuit 10.
8 is activated. This time control circuit 108 reads the number of oscillations of the oscillator 109 and calculates the amount of time elapsed due to changes in the integrated value of this number.The above-mentioned unit time is also determined by this time control circuit 108. Set. For example, if the opening/closing interval of the first gate 104 is 1 second, the first gate is open for 0.1 seconds and remains closed for the remaining 0.9 seconds. In addition, the second gate 106 described above
The opening/closing interval is the same time as above, but since the calculation time in the first calculation circuit 105 is not zero, at least the calculation time is the same as that between the first gate 104 and the second gate 106. Time difference. On the other hand, a signal from the time control circuit 108 causes the first holding circuit 107 to output the Da/kxa.
The value of is stored for each unit time, but it is necessary to also store the elapsed time for each unit time in the first holding circuit while correlating it with the value of Da/kxa for each unit time. . Therefore, the elapsed time of the time control circuit 108 is input from the third gate 110 to the first holding circuit 107 every unit time. With the above configuration, the current change when the potential of the sample is linearly changed at a rate of change of kxa is held in the first holding circuit with the elapsed time every unit time. Figure 18 is a model diagram that graphically represents this change, and shows one measurement example where the above kxa is 100 mV/sec, the unit time is 1 second, and 1 digital value is 1.000 × 10 ^-9 ampere. . Now, when the current is applied for 10 seconds and the electricity is not applied for 5 seconds, the changes over the 10 seconds are shown in the table below.
1. In the first holding circuit 107, the table -
The unit time in 1 and the value after the first calculation are held in correspondence. Next, if a different potential change rate kxb is measured after 5 seconds in the above example, the first arithmetic circuit 105 calculates the
The value Db and the elapsed time are held in a second holding circuit 111 different from the one described above. However, if the elapsed time in this case is the time from when the potential change is applied to the sample at the rate kxb above, then the change after 15 seconds in the example in Figure 18 will be as shown in Table 2. , the unit time in Table 2 and the value after the first operation are held in the second holding circuit 111 in the same way as above. Furthermore, when measuring at another potential change rate kxc, the change after 30 seconds in Figure 18 is the same as above, and the change after 30 seconds in Table 3 corresponds to the unit time and the value after the first calculation. The value of the third holding circuit 112 is
will be retained. As described above, each holding circuit holds the current change measured at each potential change rate and the measurement time in correspondence with each other. In this way, if at least the number of times the potential change rate kx is measured and the number of holding circuits are the same, a measured value at each kx can be obtained. Next, using the signal from the control device 33 described above,
The values held in each holding circuit are taken out every unit time and the difference between each potential change rate is determined. Now, in the above embodiment, based on the value held in the third holding circuit 112, the first holding circuit 107, the second holding circuit 107,
111. First, the first holding circuit 1
A signal comparing the values of 07 and the third holding circuit 112 is sent from the control device 33 to the time control circuit 10.
8 to the first holding circuit 107 and the third holding circuit 112, and at the same time, the time control circuit 108 sends a signal to open the fourth gate 113. As a result of the above, the second arithmetic circuit 114 and the first and third holding circuits 107 and 112 are connected at the same time. Furthermore, the fourth gate 113 is opened and closed every unit time, and the second arithmetic circuit 114
Subtract with and find the difference for each unit time,
It is recorded on the digital recorder 115 along with the elapsed time. Alternatively, it may be converted back into an analog value by the digital/analog converter 116 and recorded in the analog recorder 117. One example of the above embodiment is
Tables 4 and 5 are obtained from the values in Tables 1 to 3 above. Table-4, Table-5
As mentioned above, the 1.0 digital value of is 1.000×10 ^-9 ampere in this embodiment, and the result recorded in the analog recorder 117 is shown in FIG. FIG. 19 shows measurements made using a constant potential method, with the vertical axis representing current A and the horizontal axis representing voltage obtained by multiplying potential sweep rate (V/sec) by time (sec).

【table】

【table】

【table】

【table】

【table】

[Table] As detailed in the above example, the method for measuring the external polarization characteristics of the metal surface under the coating in a coated metal according to the present invention involves placing the coated metal having a coating and a counter electrode in a solution of a measurement cell. At least three types of DC voltages or currents varying linearly at different rates of change in voltage or current are applied one after another between the coated metal and the counter electrode with a certain de-energized interval between each. Apply the DC voltage or current intermittently and measure the change in the electrolytic current or electrolytic voltage that occurs between the coated metal and the counter electrode due to the applied DC voltage or current, and apply the measured value to the corresponding corresponding voltage for each of the application times. after dividing by the above rate of change, the divided value at the specified rate of change and at least 2
At least two or more subtracted values obtained by mutually subtracting the respective division values at other change rates of the species or more are compared with each other in a relationship corresponding to the respective application times. An apparatus for carrying out a method for measuring external polarization characteristics of a metal surface under a coating film in a coated metal includes a measurement cell formed by immersing a coated metal having a coating film and a counter electrode in a solution;
a means for eliminating the potential difference between the painted metal and the counter electrode; a means for generating direct current or current that changes linearly with at least three or more different voltage or current change rates; At least three types of direct current voltages or currents that vary linearly at different rates of change of voltage or current are applied intermittently one after another between the coated metal and the counter electrode with a certain de-energized interval between each. a means for measuring a change in the electrolytic current or electrolytic voltage generated between the coated metal and the counter electrode due to the DC voltage or current applied by the applying means; A circuit that divides by the corresponding rate of change for each application time, a division value of the division circuit,
A circuit for subtracting the difference between the division value at a specific rate of change and each division value at at least two or more other rates of change, and at least two or more subtraction values obtained by the subtraction circuit, and calculation means for calculating the measured value of the measuring means, which has a circuit that stores the relationship in correspondence with the application time, and therefore, it is possible to apply coating on coated metal using the simple method and simple structure as described above. This method has the advantage that the external polarization characteristics of the metal surface under the film can be easily and reliably measured.

[Brief explanation of the drawing]

1, A and B are circuit diagrams schematically showing a measuring device using the constant potential method of the present invention; FIG. 2, A and B are circuit diagrams showing an outline of the measuring method using the constant current method of the present invention; Figure 3 is a block diagram embodying Figure 1, Figure 4 is a concrete circuit diagram of Figure 3, Figure 5 is a block diagram embodying Figure 2, and Figure 6 is a concrete circuit diagram of Figure 5.
7 is a circuit diagram showing the entire measuring device that combines FIGS. 3 and 5 into one, FIG. 8 is a sectional view of one measurement cell, and FIGS. 1st
Figure 0 is a characteristic diagram of the experimental results measured with the cell in Figure 8, Figure 11 is a cross-sectional view of another measurement cell, and Figures 12 and 13 are characteristic diagrams of the experimental results measured with the cell in Figure 11. , Figures 14 and 15, and Figure 16
The figure is a characteristic diagram related to the experiments in Figures 8 and 11,
FIG. 17 is a block diagram of an apparatus for digitally processing the measuring method of the present invention, and FIGS. 18 and 19 are characteristic diagrams of experimental results measured with the apparatus of FIG. 17. DESCRIPTION OF SYMBOLS 1... Measuring cell, W... Painted metal plate, R... Reference electrode, C... Counter electrode, 2... Electrode potential measuring means, 3... High input resistance converter, 4... Measurement preparation means, 5... Servo mechanism, 6... Compensation signal Supply means, 7... Switch, 8...
1st computing unit, 9... comparator, 10... servo motor,
11... Comparison signal supply means, _P1 to _P2 ... Potentiometer, _R1 to _R6 ... Distribution resistor, 13... Measuring device,
14... DC amplifier, 15... Multistage resistor, 16... Synchronous motor, 17... Displacement control means, 18... Division circuit, 19... DC amplifier, 20
...Multi-stage resistor, 21...Switch, 22...First memory circuit, 23...Second memory circuit, 24...Difference detector, 2
5...Storage device.

Claims (1)

[Scope of Claims] 1. A coated metal having a coating film and a counter electrode are immersed in a solution of a measurement cell, and at least three or more types of DC voltages or currents are applied, each of which varies linearly at a different rate of change of voltage or current. is applied intermittently between the coated metal and the counter electrode with a certain non-current interval between each, and the electrolytic current or electrolysis generated between the coated metal and the counter electrode due to the applied DC voltage or current is After measuring the change in voltage and dividing the measured value by the corresponding rate of change for each application time,
At least two or more subtracted values obtained by mutually subtracting the division value at a specific rate of change and each division value at at least two other rates of change correspond to each of the above application times. A method for measuring external polarization characteristics of a metal surface under a coating film in a coated metal, characterized in that the characteristics are compared with each other based on the relationship. 2. A measuring cell comprising a coated metal having a coating film and a counter electrode immersed in a solution, a means for eliminating the potential difference between the coated metal and the counter electrode, and at least three or more different voltage change rates. A means for generating a DC voltage that varies linearly, and at least three types of DC voltages that vary linearly at different rates of change of voltage generated by the generating means, each with a fixed non-energizing interval between each. a means for applying an electrolytic current intermittently between the coated metal and the counter electrode one after another; a means for measuring changes in electrolytic current generated between the coated metal and the counter electrode due to the DC voltage applied by the applying means; A circuit that divides the measured value of the measuring means by the corresponding rate of change for each application time, and a division value of the division circuit that is at least two or more different from the division value at a specific rate of change. The above-mentioned device has a circuit for subtracting the difference between the respective division values at other rates of change, and a circuit for storing at least two or more types of subtraction values obtained by the subtraction circuit in a relationship that corresponds to each of the above-mentioned application times. 1. A measuring device for measuring external polarization characteristics of a metal surface under a coating film in a coated metal, comprising a measuring means and a calculating means for calculating a measured value. 3. A measurement cell comprising a coated metal having a coating film and a counter electrode immersed in a solution, a means for eliminating the potential difference between the coated metal and the counter electrode, and at least three or more different voltage change rates. A means for generating a current that varies linearly, and at least three types of direct current that vary linearly at different rates of change of current generated by the generating means, each with a fixed non-energizing interval between them. means for intermittently applying a direct current between the coated metal and the counter electrode, and a means for measuring changes in electrolytic voltage generated between the coated metal and the counter electrode due to the direct current applied by the applying means, and at least a circuit that divides the measured value of the measuring means by the corresponding rate of change for each application time; The above measurement has a circuit for subtracting the difference between the respective division values in the rate of change of and a circuit for storing at least two or more subtracted values obtained by the subtraction circuit in a relationship corresponding to the respective application times. and a calculation means for calculating the measured value of the means.