JP7306077B2 - Physical property evaluation method and apparatus - Google Patents

Description

The present disclosure relates to a physical property evaluation method and apparatus.

BACKGROUND ART Conventionally, physical properties such as corrosion resistance of coating films have been evaluated using electrochemical methods (see, for example, Patent Document 1).

JP 2016-050915 A

By the way, speeding up of various evaluation processes using an electrochemical method is desired in material development, process control in painting factories, and development of vehicle rust prevention quality. On the other hand, when elucidating the mechanism of electrochemical reactions in more detail, it may be effective to slow down the measurement speed in the electrochemical measurement process. Under these circumstances, there is a demand for development of a technique capable of appropriately adjusting the measurement speed of the electrochemical measurement process according to the purpose of measurement.

An object of the present disclosure is to provide a physical property evaluation method and apparatus capable of appropriately adjusting the measurement speed.

In order to solve the above problems, the physical property evaluation method according to the first technology disclosed herein is a method for evaluating the physical properties of a film-like measurement object using an electrochemical method, a step of contacting the surface of the object to be measured with the electrolytic solution; a step of arranging a first temperature adjusting means for adjusting the temperature of the surface side on the surface side of the object to be measured; a step of arranging a second temperature adjusting means for adjusting the temperature of the back side on the side of the back side; adjusting the level and difference between the set temperature of the first temperature adjusting means and the set temperature of the second temperature adjusting means; and adjusting the permeation rate of the electrolytic solution into the measurement object by adjusting the level and difference between the temperature on the surface side and the temperature on the back side of the measurement object by adjusting the The object to be measured is a coating film of a coated metal material provided with a coating film on a base material, the electrolytic solution is arranged so as to be in contact with the surface of the coating film, and the second temperature control means comprises: Arranged on the back side of the coating film via the base material, making the temperature of the surface side of the measurement object higher than the temperature of the back side, and making the temperature of the back side of the measurement object higher than the outside temperature is also reduced, and the physical property is the corrosion resistance of the coating film, and a voltage is applied between the front surface side of the coating film and the back surface side of the coating film while increasing the voltage, and when the coating dielectric breakdown occurs The corrosion resistance of the coating film is evaluated based on the voltage value of .

Fluid moves from a high energy, hot location to a low energy, cold location. According to this configuration, by setting the temperature of the surface side of the object to be measured which is in contact with the electrolyte solution to be higher or lower than the temperature of the back surface side, the temperature of the electrolyte solution is lower than when the front surface side and the back surface side have the same temperature. It is possible to accelerate or delay the permeation speed to the object to be measured. That is, by adjusting the level and difference between the temperature on the front side and the temperature on the back side of the object to be measured, the permeation rate of the electrolytic solution into the object to be measured can be adjusted. The measurement speed of the electrochemical measurement process can then be adjusted accordingly.

In the first technique, the temperature on the front side of the object to be measured is made higher than the temperature on the back side.

According to this configuration, it is possible to accelerate the permeation speed of the electrolytic solution into the object to be measured, so that the measurement speed in the electrochemical measurement process can be increased, and the electrochemical evaluation process can be speeded up.

In the first technique, a step of disposing a first temperature adjusting means for adjusting the temperature of the surface side on the surface side of the object to be measured; and adjusting the height and the difference between the set temperature of the first temperature adjustment means and the set temperature of the second temperature adjustment means, the measurement object and adjusting the level and difference between the temperature on the front surface side and the temperature on the back surface side.

According to this configuration, it is possible to more accurately adjust the temperatures on the front side and the back side by using the first temperature adjustment means and the second temperature adjustment means. As a result, the temperature difference between the front surface side and the back surface side can be adjusted more accurately, so that the permeation rate of the electrolytic solution can be adjusted more accurately, which in turn increases the measurement rate in the electrochemical measurement process. It can be adjusted with high precision.

A second technique is characterized in that, in the first technique, the first temperature adjusting means adjusts the temperature of the electrolytic solution.

According to this configuration, by adopting the means for adjusting the temperature of the electrolytic solution itself as the first temperature adjusting means, it is possible to easily adjust the temperature on the surface side.

In the first technique, the object to be measured is a coating film of a coated metal material provided with a coating film on a base material, and the electrolytic solution is disposed so as to contact the surface of the coating film, The second temperature control means is arranged on the back surface side of the coating film with the base material interposed therebetween.

According to this configuration, it is possible to appropriately adjust the measurement speed of the electrochemical measurement process for the coating film of the coated metal material. Thus, the evaluation speed of the electrochemical evaluation process of the coating can be adjusted.

In the first technique, the physical property is the corrosion resistance of the coating film, and a voltage is applied while increasing the voltage between the front surface side of the coating film and the back surface side of the coating film, and the coating film is subjected to dielectric breakdown. Corrosion resistance of the coating film is evaluated based on the voltage value when it is applied.

As a method for evaluating the corrosion resistance of a coating film, for example, a voltage is applied between the base material of the coated metal material and the coating film surface, and the voltage value when the coating film breaks down (hereinafter referred to as "insulation voltage"). Based on, a method for evaluating the corrosion resistance of the coating film can be used. Since the insulation voltage indicates the quality of the insulation related to the corrosion resistance of the coating film, the corrosion resistance of the coated metal material can be evaluated by measuring this voltage. By applying increasing voltage between the substrate and the coating film surface, the insulation voltage can be detected with higher accuracy. According to this configuration, in the process of evaluating the corrosion resistance of such a coated metal material, it is possible to adjust the measurement speed and thus the evaluation speed.

A third technique is characterized in that, in the first or second technique, the base material of the coated metal material is a steel plate for automobile members.

According to this configuration, it is possible to adjust the evaluation speed in the corrosion resistance evaluation process of the painted metal material for automobile use.

A fourth technique is characterized in that, in any one of the first to third techniques, the coating film is an electrodeposition coating film.

According to this configuration, it is possible to adjust the measurement speed in the measurement of the corrosion resistance of the electrodeposition coating film.

A fifth technique is characterized in that, in any one of the first to fourth techniques, the first temperature control means is a rubber heater, and the second temperature control means is a Peltier element.

According to this configuration, by adopting a rubber heater and a Peltier element as the first temperature control means and the second temperature control means, respectively, it is possible to perform temperature control on the front side and the back side of the object to be measured with higher accuracy. can.

A physical property evaluation apparatus according to a sixth technique disclosed herein is an apparatus for evaluating the physical properties of a film-like measurement object using an electrochemical method, and is in contact with the surface of the measurement object. an electrolytic solution placed in the , an electrode placed in contact with the electrolytic solution, and the electrode and the back side of the object to be measured are electrically connected to each other, and the electrode and the back side of the object to be measured are electrically connected to each other; a power source that applies a voltage between the object to be measured and a first temperature adjusting means that is arranged on the surface side of the object to be measured and adjusts the temperature of the surface side; and a second temperature adjusting means for adjusting the temperature of the electrolytic solution by adjusting the level and difference between the set temperature of the first temperature adjusting means and the set temperature of the second temperature adjusting means. It adjusts the permeation rate into the object to be measured, the object to be measured is the coating film of a coated metal material having a coating film on a base material, and the electrolytic solution is the coating film. The second temperature adjustment means is arranged to contact the surface, the second temperature adjustment means is arranged on the back surface side of the coating film via the base material, and the set temperature of the first temperature adjustment means is adjusted to the second temperature adjustment means , the set temperature of the second temperature control means is lower than the ambient temperature, the physical property is the corrosion resistance of the coating film, and the power supply supplies electricity to the electrode and the base material. is electrically connected, a voltage is applied between the electrode and the substrate while increasing it, and the corrosion resistance of the coating film is evaluated based on the voltage value when the dielectric breakdown of the coating film occurs. Characterized by

According to this configuration, by setting the temperature of the surface side of the object to be measured which is in contact with the electrolyte solution to be higher or lower than the temperature of the back surface side, the temperature of the electrolyte solution is lower than when the front surface side and the back surface side have the same temperature. It is possible to accelerate or delay the permeation speed to the object to be measured. That is, by adjusting the level and difference between the set temperature of the first temperature adjusting means and the set temperature of the second temperature adjusting means, the permeation speed of the electrolytic solution into the object to be measured can be adjusted. The measurement speed of the electrochemical measurement process can then be adjusted accordingly.

In the sixth technique, the set temperature of the first temperature adjustment means is higher than the set temperature of the second temperature adjustment means.

According to this configuration, it is possible to accelerate the permeation speed of the electrolytic solution into the object to be measured, so that the measurement speed in the electrochemical measurement process can be increased, and the electrochemical evaluation process can be speeded up.

A seventh technique is the sixth technique, further comprising a container for containing the electrolytic solution, and wherein the first temperature adjusting means is arranged on the outer circumference of the container and adjusts the temperature of the electrolytic solution contained in the container. wherein the second temperature adjusting means is a Peltier element arranged on the back side of the object to be measured.

According to this configuration, by adopting the means for adjusting the temperature of the electrolytic solution itself as the first temperature adjusting means, it is possible to easily adjust the temperature on the surface side. Further, by adopting a rubber heater and a Peltier element as the first temperature adjusting means and the second temperature adjusting means, respectively, it is possible to more accurately adjust the temperatures of the front side and the back side of the object to be measured.

In the sixth technique , the object to be measured is a coating film of a coated metal material having a coating film on a base material, and the electrolytic solution is arranged so as to contact the surface of the coating film. The second temperature control means is arranged on the back surface side of the coating film with the base material interposed therebetween .

According to this configuration, it is possible to appropriately adjust the measurement speed of the electrochemical measurement process for the coating film of the coated metal material. Thus, the evaluation speed of the electrochemical evaluation process of the coating can be adjusted.

An eighth technique is characterized in that, in the sixth or seventh technique, the base material of the coated metal material is a steel plate for automotive parts.

According to this configuration, it is possible to adjust the evaluation speed in the corrosion resistance evaluation process of the painted metal material for automobile use.

A ninth technique is characterized in that, in any one of the sixth to eighth techniques, the coating film is an electrodeposition coating film.

According to this configuration, it is possible to adjust the measurement speed in the measurement of the corrosion resistance of the electrodeposition coating film.

In the sixth technique , the physical property is corrosion resistance of the coating film, the power supply is electrically connected to the electrode and the substrate, and the electrode and the substrate are electrically connected to each other. The corrosion resistance of the coating film is evaluated based on the voltage value at which dielectric breakdown occurs in the coating film.

According to this configuration, in the process of evaluating the corrosion resistance of the painted metal material, it is possible to adjust the measurement speed and, in turn, the evaluation speed.

As described above, according to the present disclosure, by making the temperature of the surface side of the measurement object in contact with the electrolyte higher or lower than the temperature of the back surface side, can also accelerate or delay the permeation rate of the electrolytic solution into the object to be measured. That is, by adjusting the level and difference between the temperature on the front side and the temperature on the back side of the object to be measured, the permeation rate of the electrolytic solution into the object to be measured can be adjusted. Thus, the measurement speed of the electrochemical measurement process can be adjusted appropriately according to the measurement purpose.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the corrosion resistance evaluation apparatus and corrosion resistance evaluation method which concern on Embodiment 1. FIG. FIG. 4 is a diagram showing a change in voltage applied between an electrode and a steel plate (one-dot chain line) and a change in current flowing between the electrode and the steel plate due to the application of the voltage (solid line). 4 is a graph showing an example of the correlation between the insulation voltage and the number of coating film blistering cycles. 1 is a diagram for explaining the principle of a corrosion resistance evaluation method according to Embodiment 1; FIG. It is a graph which shows the relationship between temperature and saturated water vapor amount. FIG. 10 is a diagram for explaining the principle of the corrosion resistance evaluation method according to Embodiment 2; 4 is a graph showing the relationship between insulation voltage and temperature difference in Examples.

Hereinafter, embodiments of the present disclosure will be described in detail based on the drawings. The following description of preferred embodiments is merely exemplary in nature and is in no way intended to limit the disclosure, its applicability or its uses.

(Embodiment 1)
<Corrosion resistance evaluation device>
The corrosion resistance evaluation apparatus 1 (physical property evaluation apparatus) according to the present embodiment uses an electrochemical method to determine the electrodeposition coating film 5 (film-like measurement object, coating film) of the coated steel plate 2 (coated metal material). This is a device for evaluating the corrosion resistance (physical properties) of steel.

As shown in FIG. 1, the corrosion resistance evaluation apparatus 1 includes an electrode 6, a container 7, an electrolytic solution 8, a rubber mat 9, a power source device 10 (power source), an information processing terminal 11, and a rubber heater 21 (first and a Peltier element 31 (second temperature adjustment means).

-electrode-
The electrode 6 is for applying a voltage between the front side and the back side of the electrodeposition coating film 5 which is the object to be measured. Specifically, for example, a carbon electrode, a platinum electrode, or the like can be used as the electrode 6 . The shape of the electrode 6 is not particularly limited. The electrode 6 is arranged on the surface side of the electrodeposition coating film 5 with a slight distance from the surface.

-Electrolyte-
The electrolytic solution 8 is arranged between the surface of the electrodeposition coating film 5 and the electrode 6 so as to be in contact with both. The electrolytic solution 8 increases the electrical conductivity between the coated steel plate 2 and the electrode 6 and also serves as a corrosive factor for the coated steel plate 2 . Any electrolytic solution such as an aqueous solution containing a supporting electrolyte can be used as the electrolytic solution 8 . Specific examples of supporting electrolytes include sodium chloride, potassium chloride, magnesium sulfate, potassium nitrate, calcium phosphate, and potassium hydrogen tartrate.

-Containers and rubber mats-
A container 7 is arranged on the surface of the electrodeposition coating film 5 of the coated steel plate 2 via a rubber mat 9 for preventing liquid leakage. The electrolytic solution 8 is accommodated in the container 7 . The electrode 6 is arranged in a state of being immersed in the electrolyte 8 . Further, as described above, the electrode 6 is arranged slightly apart from the surface of the electrodeposition coating film 5, so that the space between them is filled with the electrolytic solution 8. As shown in FIG.

－Power supply equipment－
The power supply device 10 is electrically connected to the electrode 6 and the steel plate 3 that is the base material of the coated steel plate 2 . The power supply device 10 plays a role as a power supply section that applies a voltage between the electrode 6 and the steel plate 3, and also plays a role as a current detection section that detects a current flowing between the two. As the power supply device 10, specifically, for example, a commercially available high voltage power supply and an ammeter may be used in combination. Also, a controllable potentiometer/galvanostat or the like may be used as a voltage/current application method.

－Information processing terminal－
The information processing terminal 11 is communicably connected to the power supply device 10 . The information processing terminal 11 functions as a control section that controls the voltage applied between the electrode 6 and the steel plate 3 by the power supply device 10 . The power supply 10 also serves as a determination section that evaluates the corrosion resistance of the coated steel sheet 2 based on the voltage value when the electrodeposition coating film 5 breaks down due to the voltage application by the power supply 10 . As the information processing terminal 11, specifically, for example, a general-purpose computer equipped with a display, a keyboard, and the like can be used.

－Rubber heater－
The rubber heater 21 is arranged on the outer periphery of the container 7 and is temperature adjusting means for adjusting the temperature of the electrolytic solution 8 contained in the container 7 . The rubber heater 21 is not particularly limited, and a commercially available one can be used. By adopting the rubber heater 21 as the first temperature adjusting means, the temperature of the electrolytic solution 8 can be easily adjusted with high accuracy, and the temperature on the surface side of the electrodeposition coating film 5 can be easily adjusted with high accuracy. can be done. The rubber heater 21 is fixed so as to be in contact with the outer peripheral surface of the container 7 using, for example, double-sided tape, fasteners, or the like. A temperature sensor and a temperature controller (not shown) are electrically connected to the rubber heater 21 . The temperature sensor is immersed in the electrolyte 8 in the container 7 . Then, the temperature controller controls the temperature of the rubber heater 21 to adjust the temperature of the electrolytic solution 8 .

－Peltier element－
The Peltier element 31 is arranged on the back side of the electrodeposition coating film 5 via the steel plate 3 and the chemical conversion film 4 . Specifically, the Peltier element 31 is arranged so as to be in contact with the back surface of the steel plate 3 , and adjusts the temperature of the back surface side of the electrodeposition coating film 5 by adjusting the temperature of the steel plate 3 . The Peltier element 31 is not particularly limited, and a commercially available one can be used. By employing the Peltier element 31, the temperature of the steel plate 3 can be easily adjusted with high accuracy, and the temperature of the back side of the electrodeposition coating film 5 can be adjusted easily with high accuracy. A temperature controller (not shown) is electrically connected to the Peltier element 31 . A temperature controller controls the temperature of the Peltier element 31 to adjust the temperature of the steel plate 3 .

<Corrosion resistance evaluation method>
The corrosion resistance evaluation method (physical property evaluation method) according to the present embodiment is a method for evaluating the corrosion resistance of the electrodeposition coating film 5 using an electrochemical technique, and can be performed using, for example, the above-described corrosion resistance evaluation apparatus 1. can. The corrosion resistance evaluation method according to this embodiment includes a preparation process, a temperature adjustment process, a measurement process, and an evaluation process. A detailed description will be given below with reference to FIGS. 1 to 4. FIG.

≪Preparation process≫
- Preparation of test piece -
First, a test piece of coated steel plate 2 (coated metal material) as an evaluation object is prepared. In this embodiment, the coated steel plate 2 includes a steel plate 3 as a base material, a chemical conversion film 4 formed on the surface of the steel plate 3, and an electrodeposition coating film 5 (measurement object). That is, the steel plate 3 is arranged on the back side of the electrodeposition coating film 5 .

The steel plate 3 is a steel plate for manufacturing home electric appliances, building materials, automobile parts, or the like, and more preferably a steel plate for automobile members. Specifically, for example, a cold-rolled steel sheet (SPC), a galvannealed steel sheet (GA), a high-strength steel sheet, a hot stamp material, or the like can be used, and SPC or GA is more preferable.

The chemical conversion coating 4 has a role of suppressing direct contact of corrosive factors with the steel sheet 3 and suppressing rust by making the surface of the steel sheet 3 into an alkaline environment by reacting with the chemical conversion coating 4 itself. It also has a role of improving the adhesion between the electrodeposition coating film 5 and the steel plate 3 . Specifically, for example, a chromate chemical conversion film, a zinc phosphate film, or the like.

The electrodeposition coating film 5, which is the object to be measured, has high throwing power and uniformity, and exhibits high corrosion resistance after the baking process, thereby serving to protect the steel plate 3. Specifically, for example, an epoxy resin-based paint, an acrylic resin-based paint, or the like can be used.

- Preparation for measurement -
After preparing the test piece of the coated steel plate 2, the corrosion resistance evaluation apparatus 1 is prepared for measurement.

Specifically, for example, first, the container 7 is placed on the surface of the electrodeposition coating film 5 of the coated steel plate 2 via the rubber mat 9 . A rubber heater 21 is arranged around the container 7 . Also, a Peltier element 31 is arranged so as to come into contact with the back surface of the steel plate 3 of the coated steel plate 2 . Further, the wire to which the electrode 6 of the power supply device 10 is not connected is connected to the steel plate 3 of the coated steel plate 2 .

Next, the container 7 is filled with the electrolytic solution 8 . Thereby, the electrolytic solution 8 is brought into contact with the surface of the electrodeposition coating film 5 . Then, the electrode 6 connected to the power supply device 10 is immersed in the electrolytic solution 8 and held above the surface of the electrodeposition coating film 5 in a non-contact state. A temperature sensor connected to the rubber heater 21 is also immersed in the electrolytic solution 8 .

≪Temperature adjustment process≫
In this state, the difference between the set temperature of the rubber heater 21 and the set temperature of the Peltier element 31 is adjusted. Thus, the difference between the temperature on the surface side and the temperature on the back side of the electrodeposition coating film 5 is adjusted. Details of the temperature adjustment will be described later.

≪Measurement process≫
A voltage is applied between the electrode 6 and the steel plate 3 by the power supply device 10 under the control of the information processing terminal 11 . At this time, the voltage applied by the power supply device 10 is gradually increased over time, that is, applied while gradually increasing, as indicated by the dashed line in FIG. Thereby, the insulation voltage can be detected with higher accuracy. The sweep speed of the applied voltage is specifically, for example, in the range of 0.1 to 10 V/s, more preferably 0.5 to 2 V/s.

Then, the power supply device 10 detects the current flowing between the electrode 6 and the steel plate 3 when voltage is applied. In FIG. 2, changes in current are indicated by solid lines. As shown in FIG. 2, almost no current flows between the two until the voltage value _V1 is reached at time _t1 even if the applied voltage is increased. However, when the voltage value V ₁ is exceeded, the current amount increases sharply, and the current amount reaches the threshold value A1 at the voltage value V ₂ (time t ₂ ).

This can be considered as follows. That is, until the voltage value reaches _V1 , the corrosive factor in the electrodeposition coating film 5, that is, the blocking performance of the electrolytic solution 8 is maintained, and the amount of current is suppressed. On the other hand, the increase in the applied voltage promotes penetration of the electrolytic solution 8 into the electrodeposition coating film 5 . Then, as indicated by reference numeral 12 in FIG. 1 , the electrodeposition coating film 5 is gradually destroyed by permeation of the electrolytic solution 8 , and the electrolytic solution 8 eventually reaches the surface of the steel plate 3 . As a result, the electrical conductivity between the electrode 6 and the steel plate 3 increased abruptly, and the amount of current increased abruptly. That is, when the electrolyte 8 reached the surface of the steel plate 3, the dielectric breakdown of the electrodeposition coating film 5 occurred, and it can be considered that the blocking performance was lost.

≪Evaluation process≫
Assuming that the voltage value _V2 when the current amount reaches the threshold _A1 is the insulation voltage, the time _t2 at which the insulation voltage _V2 is reached corresponds to the period until the corrosion factor reaches the steel plate 3 .

Generally, in coated metal materials, corrosive factors such as salt water permeate the coating film and reach the base material to generate rust, that is, start corrosion. Therefore, the corrosion process of painted metal materials can be divided into the process until rust occurs and the process in which rust develops. It can be evaluated by obtaining the corrosion rate). Since the time _t2 at which the insulation voltage is _V2 corresponds to the period until the corrosion factor reaches the steel plate 3, the insulation voltage _V2 indicates the quality of the insulation related to the corrosion resistance of the coating film. There is a correlation with the suppression period.

The corrosion inhibition period can be experimentally measured separately by accelerated corrosion tests such as combined cycle tests and salt spray tests. Therefore, the correlation between the corrosion inhibition period and the insulation voltage is experimentally obtained in advance, and based on this correlation, the corrosion inhibition period of the test piece is obtained from the measured insulation voltage of the test piece, thereby obtaining the coating. Corrosion resistance of the film can be evaluated.

Specifically, FIG. 3 shows an example of the correlation between the number of cycles in which coating film blistering occurs, which indicates the corrosion suppression period, and the insulation voltage _V2 , obtained by a combined cycle test, which is a corrosion acceleration test. The object of evaluation was to form a zinc phosphate film as the chemical conversion film 4 on the surface of the SPC as the steel plate 3, and then form an electrodeposition coating film with an epoxy resin-based paint as the electrodeposition coating film 5 on the surface. is a coated steel plate 2 formed with In the combined cycle test, the test piece was subjected to salt spray (8 hours), drying (8 hours), and wetting (8 hours) as one cycle for 24 hours. The number of cycles in which (rust) was formed, that is, the number of cycles in which blistering of the paint film occurred was determined as the corrosion suppression period. The insulation voltage was measured by the above-described method under an environment of an outside temperature of 23° C. and an outside humidity of 30%, with the set temperatures of both the rubber heater 21 and the Peltier element 31 set to 23° C. FIG.

In FIG. 3, the four points indicated by S1 to S4 are the coated steel sheets 2 with the electrodeposition coating film 5 having thicknesses of 5 μm, 7 μm, 10 μm and 15 μm, respectively, and are baked at 150° C. for 20 minutes. The three points S5, S6, and S3 are the coated steel plate 2 with the electrodeposition coating film 5 having a thickness of 10 μm, and the baking conditions are 140° C./15 minutes, 140° C./20 minutes, and 150° C./20 minutes, respectively. It shows what was made. As shown in FIG. 3, the above points follow the regression line even if the film thickness of the electrodeposition coating film 5 and the baking conditions are changed, and the coefficient of determination R2 is 0.83. It can be said that there is a high correlation between the number of cycles in which blistering occurs in the coating film as the suppression period and the insulation voltage _V2 .

Thus, as the corrosion resistance of the electrodeposition coating film 5, the corrosion suppression period of the test piece is obtained from the measured value of the insulation voltage _V2 of the test piece based on the above correlation, and the corrosion resistance of the electrodeposition coating film 5 is calculated. can be evaluated.

The current amount threshold _A1 may be set to the extent that a rapid increase in the current amount can be detected. Specifically, it is preferably 0.5 mA or more, for example. Also, it is more preferably 1 to 50 mA, particularly preferably 5 to 15 mA.

<Features>
In the corrosion resistance evaluation method according to the present embodiment, by adjusting the level and difference between the set temperature of the rubber heater 21 and the set temperature of the Peltier element 31, the temperature on the front side and the temperature on the back side of the electrodeposition coating film 5 are adjusted. It is characterized by adjusting the height and difference of The temperature adjustment step will be described in detail below.

As described above, the electrolytic solution 8 placed in contact with the surface of the electrodeposition coating film 5 permeates into the electrodeposition coating film 5 from the surface side.

At this time, for example, if the set temperature of the rubber heater 21 is made higher than the set temperature of the Peltier element 31 , the temperature of the electrolytic solution 8 becomes higher than the temperature of the steel plate 3 . Then, the temperature of the surface side of the electrodeposition coating film 5 in contact with the electrolytic solution 8 becomes higher than the temperature of the back side of the electrodeposition coating film 5 in contact with the steel plate 3 . Thus, a temperature gradient is generated in the electrodeposition coating film 5 such that the temperature decreases from the front side to the back side.

Here, the fluid moves from a high energy, hot location to a low energy, cold location. Therefore, when the temperature gradient is generated inside the electrodeposition coating film 5 as described above, the temperature of the electrodeposition coating film 5 of the electrolytic solution 8 increases as shown by the arrow in FIG. The rate of penetration into the interior is accelerated. Since the time _t2 until the insulation voltage _V2 shown in FIG. 2 is reached is shortened, the measurement speed of the insulation voltage _V2 is improved, and the corrosion resistance evaluation process can be speeded up.

Conversely, if the set temperature of the rubber heater 21 is made lower than the set temperature of the Peltier element 31, the temperature of the electrolytic solution 8 becomes lower than the temperature of the steel plate 3. As a result, a temperature gradient occurs inside the electrodeposition coating film 5 such that the temperature increases from the front side to the back side. As a result, the permeation speed of the electrolytic solution 8 inside the electrodeposition coating film 5 can be reduced compared to the case where no temperature gradient occurs. For example, when comparing the corrosion resistance of a plurality of electrodeposition coating films 5, the permeation rate of the electrolytic solution 8 is too high to begin with, depending on the film quality of the electrodeposition coating film 5, making it difficult to observe the difference between these measurement objects. Sometimes. In such a case, it may be effective to reduce the permeation rate of the electrolytic solution 8 into the electrodeposition coating film 5 .

Then, even if either the set temperature of the rubber heater 21 or the set temperature of the Peltier element 31 is higher, the rate of acceleration or decrease of the permeation rate can be increased by increasing the difference between the two.

In this way, by adjusting the level and the difference between the temperature on the surface side and the temperature on the back side of the electrodeposition coating film 5, the permeation rate of the electrolytic solution into the inside of the electrodeposition coating film 5 can be adjusted. Thus, the time _t2 to reach the insulation voltage _V2 can be shortened. Then, the measurement speed of the measurement step in the corrosion resistance evaluation method can be adjusted as appropriate.

(Embodiment 2)
Other embodiments according to the present disclosure will be described in detail below. In the description of these embodiments, the same reference numerals are given to the same parts as in the first embodiment, and detailed description thereof will be omitted.

The corrosion resistance evaluation method and evaluation apparatus according to the present embodiment, in the above-described temperature adjustment step, particularly set the temperature of the rubber heater 21 higher than the temperature at which water vapor in the electrodeposition coating film 5 begins to condense, and the Peltier element The set temperature of 31 is set lower than the temperature at which water vapor in the electrodeposition coating film 5 begins to condense.

In general, the saturated water vapor amount a (T) [g/m ³ ] contained in the atmosphere is the mass (g) of water vapor that can exist in a space per unit volume (1 m ³ ), and is calculated by the following formula (1). be done.

a(T)=(217×e(T))/(T+273.15) (1)
However, T is temperature [°C] and e(T) is saturated water vapor pressure [hPa]. e(T) can be approximately determined by the following formula (2).

e(T)=6.1078×10^[7.5T/(T+237.3)] (2)
FIG. 5 shows the relationship between the saturated water vapor amount and the temperature calculated by the above formula (1). For example, consider an environment with an outdoor temperature of 25° C. and an outdoor humidity of 30%. At this time, the amount of saturated water vapor contained in the outside air is about 23 g. Then, since the outside air humidity is 30%, the outside air contains about 7 g (=23 g×0.3) of water vapor. Then, when the outside air temperature is lowered to, for example, 0°C, the amount of saturated water vapor at a temperature of 0°C is about 5g from FIG. .

The set temperature of the rubber heater 21, that is, the temperature of the electrolytic solution 8, is set higher than the temperature at which water vapor in the electrodeposition coating film 5 begins to condense, and the set temperature of the Peltier element 31, that is, the temperature of the steel plate 3 is set to the water vapor of the outside air. lower than the temperature at which it begins to condense. Then, the water vapor contained in the air present on the surface side of the electrodeposition coating film 5 is condensed and liquefied on the back surface side of the electrodeposition coating film 5 . Then, in the electrodeposition coating film 5, in addition to the temperature gradient, flows of water vapor and liquid water are formed as indicated by arrows in FIG. Thus, the permeation of the electrolytic solution 8 is greatly promoted.

In particular, if the set temperature of the rubber heater 21 is higher than the outside air temperature, the amount of water vapor contained in the air existing on the surface side of the electrodeposition coating film 5 can be increased. can increase the flow of water vapor and liquid water from the back side to the back side. Thus, the permeation of the electrolytic solution 8 into the electrodeposition coating film 5 can be further promoted.

Note that even when the set temperature of the Peltier element 31, that is, the temperature of the steel plate 3, is lowered to, for example, 0° C. or lower, at a temperature higher than the temperature at which the liquefied water actually starts to solidify, the liquefied water does not liquefy. The water becomes supercooled and does not solidify. Then, when the set temperature of the Peltier device 31 is lowered below the temperature at which the liquefied water starts to solidify, the liquefied water starts to solidify. If the liquefied water solidifies, it is considered difficult to accelerate the permeation of the electrolytic solution 8 into the electrodeposition coating film 5 . Therefore, the set temperature of the Peltier element 31, that is, the temperature of the steel plate 3, can be set to a temperature higher than the temperature at which the liquefied water begins to solidify. The temperature at which liquefied water begins to solidify may vary depending on various conditions such as measurement conditions.

As described above, according to the corrosion resistance evaluation method and evaluation apparatus according to the present embodiment, it is possible to greatly accelerate the permeation rate of the electrolytic solution 8 into the electrodeposition coating film 5 . As a result, the measurement speed of the electrochemical measurement process can be improved, and the evaluation process using the electrochemical technique can be speeded up.

(Other embodiments)
In the above embodiment, the first temperature control means is a rubber heater, and the second temperature control means is a Peltier device. is not limited to For example, either one of the first temperature adjusting means and the second temperature adjusting means may be provided to increase or decrease the temperature of either the front side or the back side of the electrodeposition coating film 5 . Also, both the first temperature adjusting means and the second temperature adjusting means may be rubber heaters or Peltier elements. A Peltier element may be used as the first temperature control means, and a rubber heater may be used as the second temperature control means. A hot plate or the like may be used as the heating device instead of the rubber heater. In place of the electrolytic solution 8, a rubber heater or a Peltier element is arranged on the surface of the electrodeposition coating film 5 outside the container 7 as the first temperature control means to heat the surface side of the electrodeposition coating film 5 itself. Alternatively, it may be cooled.

In the above-described embodiment, the voltage is gradually increased over time in the measurement step, and the detected insulation voltage is _V2 . However, the measurement method is not limited to this configuration. Specifically, for example, the change in the amount of current is observed while a constant voltage is applied, and the corrosion resistance of the electrodeposition coating film 5 is evaluated based on the time _t2 from the start of measurement until the amount of current reaches the threshold value _A1 . You may adopt the method etc. which do.

In the above-described embodiment, the coated steel sheet 2 to be evaluated can be configured to have a multilayer film of two or more layers as a coating film. Specifically, for example, in addition to the electrodeposition coating film 5, a configuration in which an intermediate coating film is provided on the surface of the electrodeposition coating film 5, or a configuration in which a top coating film or the like is further provided on the intermediate coating film. It can be a multilayer film. The intermediate coating film has a role of ensuring the finish and chipping resistance of the coated steel plate 2 and improving the adhesion between the undercoat film and the topcoat film. Moreover, the top coat film secures the color, finish, and weather resistance of the coated steel plate 2 . These coating films are specifically, for example, paints made of base resins such as polyester resins, acrylic resins and alkyd resins, and cross-linking agents such as melamine resins, urea resins and polyisocyanate compounds (including block bodies). Formed by By adopting this configuration, for example, in the manufacturing process of automobile parts, etc., parts can be removed from the manufacturing line for each coating process and the quality of the coating film can be checked.

In the above embodiment, instead of the container 7 and the rubber mat 9, a conductive solid containing the electrolytic solution 8 may be used. The conductive solid substance may be a solid substance that can take an arbitrary shape according to the shape of the object to be evaluated while containing the electrolytic solution 8, and that has conductivity. Specifically, for example, solid materials containing sodium chloride, potassium hydrogen tartrate, distilled water, and oils such as oleic acid and linoleic acid are preferred for solid raw material powders composed of gliadin, glutenin, starch, and the like. At this time, the mixing ratio of each component is, in volume ratio, 30 to 50% solid raw powder, 10 to 30% sodium chloride, 10 to 30% potassium hydrogen tartrate, 10 to 45% distilled water, and 3 to 15% oil. %. By adopting this configuration, it is possible to measure a test piece that does not have a flat surface, specifically, for example, an edge portion of the coated steel plate 2, a curved surface, etc., without being restricted by the shape of the test piece. . When a conductive solid material is used, as described above, the first temperature control means such as a rubber heater, a Peltier element, or the like is arranged on the surface of the electrodeposition coating film 5, and the surface side of the electrodeposition coating film 5 itself is heated. Heating or cooling is effective.

In the above embodiment, as the physical property evaluation method and the physical property evaluation device according to the present disclosure, the corrosion resistance evaluation method and the corrosion resistance evaluation method of the electrodeposition coating film 5 of the coated steel plate 2 were described as examples, but it is limited to this. do not have. That is, the physical property evaluation method and physical property evaluation apparatus according to the present disclosure can be widely used for physical property evaluation of film-like measurement objects using an electrochemical method. Specifically, for example, it can be used for evaluation of oxidation-reduction characteristics by cyclic voltammetry measurement of a film-like object to be measured.

Examples that were specifically carried out will be described below.

<Test piece>
In Examples 1 to 5, the configuration of the test piece was the same.

Specifically, SPC was used as the steel plate 3, and a test piece (approximately 50 mm square) of the coated steel plate 2 having the chemical conversion film 4 and the electrodeposition coating film 5 formed on the surface was prepared. The chemical conversion coating 4 was a zinc phosphate coating, and the chemical conversion treatment time with zinc phosphate was 120 seconds. The electrodeposition coating film 5 was formed using an epoxy resin-based coating. The baking conditions for the electrodeposition coating were 150° C.×20 minutes. The thickness of the steel plate 3 was 2 mm, and the thickness of the electrodeposition coating film 5 was 10 μm.

<Corrosion resistance evaluation test>
The corrosion resistance of the electrodeposition coating film 5 was evaluated using the test piece and the corrosion resistance evaluation apparatus 1 shown in FIG.

Specifically, an acrylic resin cylinder having an inner diameter of 20 mm, an outer diameter of 22 mm, and a height of 60 mm was used as the container 7 . A silicon rubber heater (manufactured by Hakko Denki Co., Ltd., standard type, A type with double-sided tape) was attached as a rubber heater 21 over the entire circumference and height of the outer peripheral surface of the container 7 . A temperature sensor (thermocouple (K type) molded type, manufactured by Three High Co., Ltd.) was connected to the rubber heater 21 , and the sensor portion at the tip of the temperature sensor was immersed in the electrolytic solution 8 . As the rubber mat 9, a commercially available silicon rubber sheet (thickness: about 0.5 mm, 30 mm x 30 mm) with holes having a diameter of 18 mm was used. A rubber mat 9 was placed on the surface of the electrodeposition coating film 5 , and a container 7 attached with a rubber heater 21 was arranged so as to cover the holes of the rubber mat 9 . The container 7 was filled with a 5% by mass sodium chloride aqueous solution as the electrolytic solution 8 . As the electrode 6 , a commercially available rod-shaped carbon electrode (about 5 mm in diameter and about 30 mm in length) was immersed in the electrolytic solution 8 . A thermomodule (LVPU-70 manufactured by Bicks Co., Ltd.) was arranged as a Peltier element 31 on the back side of the steel plate 3 . A high-voltage power supply (Model 2220, manufactured by Trek Japan Co., Ltd.) and an ammeter (DME1600, Kikusui Denshi Kogyo Co., Ltd.) were connected to the electrode 6 and the steel plate 3 as a power supply device 10 . A temperature controller (Double Thermo 100 manufactured by Hakko Denki Co., Ltd.) was connected to the rubber heater 21 to control the temperature. A temperature controller (VTH-1000 manufactured by Vicks Co., Ltd.) was connected to the Peltier element 31 to control the temperature. The set temperatures of the rubber heater 21 and the Peltier element 31 are as shown in Table 1.

For the test pieces of Examples 1 to 5, the voltage value of the electrode 6 with respect to the steel plate 3 was increased from 0 V at a sweep rate of 1 V / s using the high-voltage power supply in an environment with an ambient temperature of 25 ° C. and an ambient humidity of 30%. The insulation voltage _V2 was measured. The results are shown in FIG.

As described above, the time t ₂ at which the insulation voltage is V ₂ corresponds to the time until the corrosion factor reaches the steel plate 3 . Then, even for the same object to be measured, when the permeation speed of the electrolytic solution 8 becomes faster, the time _t2 becomes shorter and the insulation voltage _V2 becomes smaller. Conversely, when the permeation speed of the electrolytic solution 8 slows down, the time _t2 increases and the insulation voltage _V2 increases. That is, for the same object to be measured, the insulation voltage _V2 decreases as the permeation speed of the electrolyte 8 increases.

From the results of Examples 1 to 4, as indicated by the regression line L1 in FIG. increased, the insulation voltage _V2 decreased, that is, the permeation rate of the electrolytic solution 8 increased.

Further, from the results of Example 5, it can be seen that when the temperature of the Peltier element 31 is lowered to −0.5° C., which is lower than the temperature at which water vapor in the atmosphere begins to condense (approximately 7° C. under this test environment), FIG. As indicated by the arrow P1, it was found that the insulation voltage deviated from the regression line L1 of the results of Examples 1 to 4 and greatly decreased. When the temperature of the Peltier element 31 is lowered to −0.5° C., water vapor in the atmosphere condenses near the interface between the steel plate 3 and the electrodeposition coating film 5 , and the electrolytic solution 8 permeates into the electrodeposition coating film 5 . is thought to have been greatly promoted. By increasing the temperature difference between the Peltier element 31 and the rubber heater 21 while keeping the temperature of the Peltier element 31 lower than the temperature at which water vapor in the atmosphere begins to condense, the insulation voltage is reduced as indicated by the straight line L2 in FIG. , that is, an increase in the permeation speed of the electrolytic solution 8 is considered to be observed.

The present disclosure is useful in the field of physical property evaluation methods and apparatus.

1 Corrosion resistance evaluation device 2 Painted steel plate (painted metal material)
3 Steel plate (base material)
4 Chemical conversion film (substrate)
5 Electrodeposition coating film (object to be measured)
6 electrode 8 electrolyte 10 power supply (power supply)
21 rubber heater (first temperature control means)
31 Peltier element (second temperature control means)
V ₂ insulation voltage (voltage value when the coating film dielectric breakdown)

Claims (9)

A method for evaluating the physical properties of a film-like measurement object using an electrochemical technique,
a step of contacting the surface of the measurement object with an electrolytic solution ;
a step of arranging a first temperature adjusting means for adjusting the temperature of the surface side on the surface side of the object to be measured;
arranging a second temperature adjusting means for adjusting the temperature of the back side of the object to be measured on the back side;
The level and difference between the set temperature of the first temperature adjusting means and the set temperature of the second temperature adjusting means are adjusted to adjust the level and difference between the temperature on the front side and the temperature on the back side of the object to be measured. By adjusting the permeation rate of the electrolytic solution into the measurement object,
The object to be measured is a coating film of a coated metal material having a coating film on a base material,
The electrolytic solution is placed in contact with the surface of the coating film,
The second temperature control means is arranged on the back surface side of the coating film via the base material,
making the temperature on the front side of the object to be measured higher than the temperature on the back side,
lowering the temperature of the back side of the object to be measured below the ambient temperature;
The physical property is the corrosion resistance of the coating,
Applying an increasing voltage between the surface side of the coating film and the back side of the coating film, and evaluating the corrosion resistance of the coating film based on the voltage value when the coating film breaks down.
A physical property evaluation method characterized by: In claim 1 ,
The physical property evaluation method, wherein the first temperature adjustment means adjusts the temperature of the electrolytic solution. In claim 1 or claim 2 ,
A physical property evaluation method, wherein the base material of the coated metal material is a steel plate for automotive parts. In any one of claims 1 to 3 ,
A physical property evaluation method, wherein the coating film is an electrodeposition coating film. In any one of claims 1 to 4 ,
The first temperature adjusting means is a rubber heater,
The physical property evaluation method, wherein the second temperature control means is a Peltier device. A device for evaluating the physical properties of a film-like measurement object using an electrochemical method,
an electrolytic solution placed in contact with the surface of the object to be measured;
an electrode placed in contact with the electrolyte;
a power source electrically connected to the electrode and the back side of the object to be measured and applying a voltage between the electrode and the back side of the object to be measured;
a first temperature adjusting means arranged on the surface side of the object to be measured and adjusting the temperature of the surface side;
a second temperature adjusting means arranged on the back side of the object to be measured and adjusting the temperature of the back side;
By adjusting the level and difference between the set temperature of the first temperature adjustment means and the set temperature of the second temperature adjustment means, the permeation rate of the electrolytic solution into the measurement object is adjusted,
The object to be measured is a coating film of a coated metal material having a coating film on a base material,
The electrolytic solution is placed in contact with the surface of the coating film,
The second temperature control means is arranged on the back surface side of the coating film via the base material,
The set temperature of the first temperature adjustment means is higher than the set temperature of the second temperature adjustment means,
The set temperature of the second temperature adjustment means is lower than the outside air temperature,
The physical property is the corrosion resistance of the coating,
the power source is electrically connected to the electrode and the substrate;
Applying an increasing voltage between the electrode and the substrate, and evaluating the corrosion resistance of the coating film based on the voltage value when the dielectric breakdown of the coating film occurs.
A physical property evaluation device characterized by: In claim 6 ,
A container containing the electrolytic solution is provided,
The first temperature adjusting means is a rubber heater that is arranged on the outer periphery of the container and adjusts the temperature of the electrolytic solution contained in the container,
A physical property evaluation apparatus, wherein the second temperature adjustment means is a Peltier device arranged on the back side of the object to be measured. In claim 6 or claim 7 ,
A physical property evaluation apparatus, wherein the base material of the coated metal material is a steel plate for automotive parts. In any one of claims 6-8 ,
A physical property evaluation apparatus, wherein the coating film is an electrodeposition coating film.

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